EPA-660 3-74-034
DECEMBER 1974
Ecological Research Series
Eutrophication of Lake Tahoe
Emphasizing Water Quality
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
U.S. Environmental Protection Agency, have been grouped into
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facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
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2. Environmental Protection Technology
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4. Environmental Monitoring
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This report has been assigned to the ECOLOGICAL RESEARCH STUDIES
series. This series describes research on the effects of pollution
on humans, plant and animal species, and materials. Problems
are assessed for their long- and short-term influences. Investigations
include formation, transport, and pathway studies to determine
the fate of pollutants and their effects. This work provides
the technical basis for setting standards to minimize undesirable
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EPA-660/3-74-034
December 1974
EUTROPHICATION OF LAKE TAHOE
EMPHASIZING WATER QUALITY
Charles R. Goldman
Division of Environmental Studies/Institute of Ecology
University of California
Davis, California 95616
Research Grant No. 16010 DBU
Program Element No. 1BA031
Project Officer
Charles F. Powers
Eutrophication and Lake Restoration Branch
Pacific Northwest Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
For saie by the Superintendent "of "Documents, U.S. Government Printing Office
Washington, D.C. 20402 Stock. No. 5501-00996
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ABSTRACT
A 4 1/2-year study on the rate and factors affecting the cultural eu-
trophication of oligotrophic Lake Tahoe is reported. Primary produc-
tivity increased alarmingly during the investigation with a steady
shift in the seasonal maximum from early spring to late summer. Pro-
ductivity increased 25.6% from 1968 to 1971. Using the 1959-1960 data
from earlier studies, the increase to 1971 was 51%. Diatoms dominate
the phytoplankton population and the maximum zone of phytoplankton
photosynthesis may be as deep as 50-75 m. The extent of winter mixing
is important in the nutrient budget of the lake and bacteria associated
with stream-borne nutrients facilitate nutrient regeneration. The
littoral zone, although extremely important visually to the lake, con-
tributes only 10% of the total primary production. Great variability
in fertility of the lake has been investigated by synoptic studies and
aerial remote sensing. Highest productivity is found in the lake where
tributaries drain disturbed land. Nutrients associated with road
building, housing, and lumbering are now major causes of eutrophication
in Lake Tahoe. In special bioassay studies, it was found that NTA
stimulates primary productivity, drainage from a sewage land disposal
site continues to yield high levels of nitrate, and marinas may serve
as nutrient and sediment traps or as very eutrophic isolated systems.
The important cladoceran component of the zooplankton population has
virtually disappeared from the lake and predation by the introduced
zooplankter Mysis relicta and the kokanee salmon are suspect. Crayfish
ii
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are the dominant members of the benthic animal community which deserve
particular attention as scavengers of the littoral zone.
This report was submitted in fulfillment of Research Grant No. 16010
DBU under the sponsorship of the Office of Research and Development
Environmental Protection Agency. Work was completed as of December
1971.
iii
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CONTENTS
Page
Abstract 13-
List of Figures vi
List of Tables xii
Acknowledgements xv
Sections
I Conclusions 1
II Recommendations 5
III Introduction 9
IV Physical Characteristics 29
V Lake Water Chemistry 78
VI Phytoplankton Primary Productivity, Species Composition
and Abundance 104
VII Synoptic Surveys, Bioassays, Remote Sensing, Land
Disposal, and NTA Experiments 137
VIII Microbial Heterotrophic Growth in Lake Tahoe 228
IX Primary Production of Periphyton and Planktonic Algae
in the Littoral Zone of Lake Tahoe 240
X Zooplankton 262
XI Benthic Organisms 282
iv
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CONTENTS (Continued)
Page
XII Effects of Marinas and Ecology of a Tahoe Basin Stream 296
XIII References 316
XIV Publications, Manuscripts, Reports, and Theses 330
XV Appendices 336
v
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FIGURES
No. age
1 Bathymetric map of Lake Tahoe indicating the index
station and other locations. 10
2 Cooperative relationships between the UCD Limnology
Group and other agencies and institutions involved
in Tahoe basin studies. 22
3 Daily solar radiation at Lake Tahoe from mid-1967
through 1971. 31
4 Seasonal solar radiation at Lake Tahoe. 32
5 Seasonal Secchi disk transparency at the index station
of Lake Tahoe. 36
6 Downwelling spectral irradiance of Lake Tahoe. 41
7 Tristimulus values of the upwelling and downwelling
spectral irradiance of Lake Tahoe and Crater Lake. 43
8 Isotherms for the index station of Lake Tahoe from
mid-1967 through 1971. 48
9 Monthly (January-June) heat storage-depth profiles
at the index station of Lake Tahoe. 50
10 Monthly (July-December) heat storage-depth profiles at
the index station of Lake Tahoe. 51
11 Seasonal heat storage at various depths at the index
station of Lake Tahoe. 52
VI
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FIGURES (Continued)
No.
12 Seasonal temperature at various depths at the index
station of Lake Tahoe. 53
13 Annual temperature stratification cycle of Lake Tahoe. 57
14 Schematic diagram of the Lake Tahoe physical model. 60
15 Results of two typical physical model experiments. 62
16 Distribution of rock types in the Tahoe basin. 68
17 Grain-size distribution in cores from Lake Tahoe. 75
18 Total primary productivity at the index station of
Lake Tahoe from mid-1967 through 1971. 109
19 Primary productivity-depth curves at the index station
of Lake Tahoe from mid-1967 through 1971. 110-111
20 Representative vertical profiles of primary productivity,
temperature, light, and phytoplankton biomass at the
index station of Lake Tahoe.
21 Seasonal total primary productivity at the index station
of Lake Tahoe.
22 Annual primary productivity at Lake Tahoe between
1959 and 1971. 119
23 Seasonal phytoplankton biomass at the index station
of Lake Tahoe. 123
24 Seasonal variation of phytoplankton species at the
index station of Lake Tahoe. 126
25 Seasonal variation in numbers of the most dominant
phytoplankton species at the index station of Lake
Tahoe. 132-134
26 Primary productivity measurements at five stations
in Lake Tahoe during 1967. 143
vii
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FIGURES (Continued)
No.
27 Contour maps of primary productivity in the upper
15 m of Lake Tahoe, 1968-1971. 146-147
28 Deep water measurments of total iron, nitrate-nitrogen,
total phosphorus, and temperature at the mid-lake
station of Lake Tahoe. 155
29 Bioassay of nitrogen and phosphorus additions to Lake
Tahoe water. 156
30 Bioassay of nitrogen and iron additions to Lake Tahoe
water. 157
31 Bioassay of General Creek water additions to Lake Tahoe
water. 159
32 Bioassay of Upper Truckee River water additions to
Lake Tahoe water. 160
33 Bioassay of Incline Creek water additions to Lake
Tahoe water. 162
34 Bioassay of Taylor Creek water additions to Lake Tahoe
water. 164-165
35 Biostimulation of Lake Tahoe water from a 10% addition
of four of its tributaries. 166
36 Map of Lake Tahoe indicating the Upper Truckee River
transect study area. 169
37 Seasonal variation in stream flow and meteorological
conditions in the Upper Truckee River watershed during
the 1970-71 water-year. 175
38 The Upper Truckee River sediment plume for 29 March
1971 and values of suspended sediment, dissolved
inorganic carbon, and primary productivity. 177
39 The Upper Truckee River sediment plume for 12 April
1971 and values of suspended sediment, dissolved
inorganic carbon, heterotrophic activity, and primary
productivity.
viii
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45 Nitrate-nitrogen concentrations for eight creeks within
the Tahoe basin.
FIGURES (Continued)
No.
40 The Upper Truckee River sediment plume for 7 June 1971
and values of suspended sediment, dissolved inorganic
carbon, heterotrophic activity, and primary porductivity. 179
41 The Upper Truckee River sediment plume for the morning
of 20 June 1971 and values of suspended sediment,
dissolved inorganic carbon, heterotrophic activity,
and primary productivity. 180
42 The Upper Truckee River sediment plume for the afternoon
of 20 June 1971 and values of suspended sediment,
dissolved inorganic carbon, heterotrophic activity,
and primary productivity. 181
43 Multispectral photograph of the Upper Truckee River
sediment plume for the morning of 20 June 1971. 133
44 The Heavenly Valley Creek area indicating the site
receiving effluent spray. 198
50 Seasonal temperature, primary productivity, and
heterotrophic activity at the Upper Truckee River
station.
199
46 Nitrate-nitrogen and UV absorbance along Heavenly
Valley Creek. 204
47 Seasonal nitrate-nitrogen concentration at the three
sampling stations of Heavenly Valley Creek. 2Q6
48 Bioassay of Heavenly Valley Creek water additions
to Lake Tahoe water. 209
49 Bioassay of Heavenly Valley soil extract additions
to Lake Tahoe water. 211
231
51 Heterotrophic activity in the Upper Truckee River
transect area on 30 July 1971. 233
ix
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FIGURES (Continued)
No.
52 Heterotrophic bioassay of additions of nutrient-
stripped silt in combination with organic carbon,
nitrogen, and phosphorus to Lake Tahoe water. 234
53 Schematic diagram of a periphyton station. 243
54 Dominant species of periphyton found on glass
cylinders exposed in situ to periphyton invasion
for 14 weeks between 24 June and 30 September 1970. 246
55 Dominant species of periphyton found on glass
cylinders exposed in situ to periphyton invasion for
2-23 weeks between 1 October 1970 and 2 May 1971. 247
56 Periphyton rate of growth between 1 May and 15 July
1971. 249
57 Periphyton rate of growth between 28 March and 18
September 1968. 251
58 Periphyton production estimates for the littoral
zone of Lake Tahoe. 253
59 Phytoplankton productivity estimates for the littoral
zone of Lake Tahoe. 255
60 Total primary production of the littoral and pelagic
zones of Lake Tahoe. 257
61 Phytoplankton primary productivity-depth profiles at
various distances offshore of four littoral zone
stations. 258
62 Numbers of individual rotifer species at the index
station of Lake Tahoe from mid-1967 through 1971. 268
63 Numbers of individual copepod species at the index
station of Lake Tahoe from mid-1967 through 1971. 270
64 Numbers of individual cladoceran species at the
index station of Lake Tahoe from mid-1967 through
1971. 272
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FIGURES (Continued)
No.
65 Total number of zooplankton at the index station
of Lake Tahoe from mid-1967 through 1971. 274
66 Seasonal number of zooplankton at the index
station of Lake Tahoe. 278
67 Depth-distribution of the crayfish population at
various locations in Lake Tahoe. 284
68 Number of organisms found in benthos samples at
various locations in Lake Tahoe. 293
69 Benthos diversity per individual at various locations
in Lake Tahoe. 294
70 Map of Star Harbor indicating the sampling stations. 299
71 Iron, nitrate-nitrogen, and phosphate-phosphorus
concentrations at the Star Harbor sampling stations. 302
72 Iron, nitrate-nitrogen, and primary productivity
relationships in Star Harbor. , 303
73 Bioassay of Burton and Polaris Creek water additions
to Star Harbor water. 305
74 Bioassay of Burton and Polaris Creek water additions
to Lake Tahoe water. 306
75 Bioassay of Star Harbor water additions to Lake Tahoe
water. 307
76 Seasonal autotrophic and heterotrophic activity of
Taylor Creek. 312
77 Seasonal nitrate-nitrogen and phosphate-phosphorus con-
centrations along Taylor Creek. 313
XI
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TABLES
No. Page
1 Incident solar radiation at Lake Tahoe, 1967-1972. 34
2 Percent light transmission at the index station of Lake
Tahoe, 1969. 38
3 Percent light transmission at the index station of Lake
Tahoe, 1970. 39
4 Percent light transmission at the index station of Lake
Tahoe, 1971. 40
5 Tristimulus chromaticity coordinates, dominant wavelength,
excitation purity, and Munsell notation of the spectral
irradiance at various depths for Lake Tahoe on 25
February 1970. 45
6 Temperature at the mid-lake station of Lake Tahoe,
1969-1971. 49
7 Diatom species in a 90 cm core taken from mid-Lake
Tahoe. 73
8 Total phosphorus at the index station of Lake Tahoe,
1968-1971. 81
9 Nitrate-nitrogen at the index station of Lake Tahoe,
1968-1971. 82
10 Iron at the index station of Lake Tahoe, 1970-1971. 83
11 Water chemistry at the synoptic stations of Lake
Tahoe, 1968-1971. 85
xii
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TABLES (Continued)
No. Page
12 Particulate carbon at the index station of Lake
Tahoe, 1968-1971. 86-87
13 Nitrate-nitrogen at the mid-lake station of Lake
Tahoe, 1970-1971. 88
14 Total phosphorus at the mid-lake station of Lake
Tahoe, 1970-1971. 89
15 Silicate-silicon at the mid-lake station of Lake
Tahoe, 1971-1972. 91
16 Iron at the mid-lake station of Lake Tahoe, 1970-1971. 92
17 Oxygen at the mid-lake station of Lake Tahoe, 1969-1971. 93
18 Comparative water chemistry of various creeks in the
Tahoe basin, 1968. 94-95
19 Comparative water chemistry of various creeks in the
Tahoe basin, 1969. 97
20 Comparative water chemistry of various creeks in the
Tahoe basin, 1970. 98-99
21 Comparative water chemistry of various creeks in the
Tahoe basin, 1971. 100-101
22 Water chemistry of Incline and Third Creek transects,
1969. 103
23 Total primary productivity per year at the index station
of Lake Tahoe, 1959-1960 and 1968-1971. 115
24 A comparison of the nitrogen and phosphorus content of
surface water of Lake Tahoe in 1962 and 1968-1971. 120
25 Phytoplankton species found at the index station of
Lake Tahoe, including cell volumes. 130
26 A comparison of the mean primary productivity of the upper
15 m of water at the pelagic stations and the littoral
stations for the Lake Tahoe synoptics, 1968-1971. 149
xiii
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TABLES (Continued)
Ho. Page
27 Simple correlation coefficients for Upper Truckee
1fifi—187
River sediment plume variables. -100 xo
28 Chemical analyses of series 29500-29503 sewage
effluents. 216
29 Chemical analyses of series 39500-39503 sewage
effluents. 217
30 Effects of NTA and sewage effluent additions on Lake
Tahoe water. 221
31 Effects of NTA and sewage effluent additions on Castle
Lake water. 223
32 Effects of NTA and sewage effluent additions on Clear
Lake water. 225
33 Lake Tahoe periphyton species list, including cell
volumes. 241
34 Lake Tahoe zooplankton species list. 264-265
35 Organisms found in benthos samples from Lake Tahoe. 290—291
36 Nitrate, phosphate, iron, primary productivity, and
phytoplankton biomass at the Star Harbor sampling
stations. 301
xiv
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ACKNOWLEDGEMENTS
This research was supported from 1967 through 1971 by the Environmental
Protection Agency (16010 DBU). Additional support for our studies
was provided by the following agencies. The Swedish Natural Research
Council (Committee of Natural Resources) and the Fishery Board of
Sweden aided the crayfish studies of the late Dr. Sture A. Abrahamsson.
The geology studies were assisted by National Science Foundation grants
(GA-10686 and GA-13082) and a Sigma Xi Grant-in-Aid-of-Research. The
Atomic Energy Commission provided assistance for the geochronology
studies of lake sediments (AT [Q4-3]-34, Project 84) and our coopera-
tive studies with Dr. Osmund Holm-Hansen (AT [11-1] Gen 10, P.A. 20).
Our cooperative studies with Drs, Raymond C. Smith and John E. Tyler
on Tahoe optical properties were assisted by the National Science
Foundation (GA-19830). Remote sensing was provided by the Space Science
Division, NASA-Ames Research Center, Moffett Field, California. The
League to Save Lake Tahoe provided partial funds for the production
of a color film depicting the research program. Other studies were
aided by the National Science Foundation (GB-6422X and EB-19136) and
by an Environmental Protection Agency grant (WPD-48) to the Lake Tahoe
Area Council. Additional computer time was provided through the com-
puter center by a National Science Foundation grant (GJ-462) to the
computer center. The ongoing research is currently supported by a
Grant-in-Aid from the National Science Foundation's Research Applied
xv
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to National Needs (RAM) program (GI-22).
A great number of individuals helped with our research studies. We wish
to particularly acknowledge the assistance of Drs. Richard Armstrong
and Gerald A. Moshiri in the early development and direction of the
project and also the design of critical experiments and methods. The
major field operation was under the direction of Peter J. Richerson
during the summer of 1967, James E. Court from 1967 to 1968, and Robert
C. Richards from 1969 to 1971. The ecological and physiological cray-
fish studies were under the supervision of Drs. Sture A. Abrahamsson
and Gerald A. Moshiri, respectively.
Special thanks for phytoplankton and periphyton identification and
enumeration are due to Theodore Scalione, Anne Sands, and Robert
Thomson. Zooplankton identification and enumeration was provided by
Peter Richerson, Noel Williams, H. Michael Shepard, and Garth Redfield.
Frank Sanders sorted and identified the benthic organisms. Chemistry
procedures were developed by Dr. Richard Armstrong from 1967 to 1969
and modified by Dr. Dennis K. Fujita during 1970-1971. Dr. Hans W.
Paerl developed methods for the measurement of heterotrophic activity.
Computer programs for data analysis were developed by Evelyne de Amezaga.
R. Scott Altmann was in charge of the production of the Tahoe film.
Field and laboratory assistance was provided by Mr. Allen, Scott Altmann,
Mr. Andrews, David Bartlett, Denne Bertrand, Peter Biskup, Sid Cheong,
John Coil, Rod Ellis, Henry Fraczek, Gordon Godshalk, William Hart,
Bjord Idestrom, Larry Immer, Holly Jensen, Michael Johnson, Frank
Knowlton, Mr. Koney, Douglas Kubo, Robert Melville, Phil Moeller, Jack
Momii, Marc Monaghan, Donald Mull, Hans Paerl, Michael Perkins, Jon
Robbins, Frank Sanders, William Sholes, Mr. Shultz, Richard Sitts, Jon
Smaker, David Warren, Mr. White, Noel Williams, and Yen-ting Yang.
xv i
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Technical assistance was provided by Glenn Amandson, Pat Clancy, Peter
Hacker, Leonard Myrup, Jack Pangborn, George Parkhurst, Thomas Powell,
Freda Reid, Elisabeth Stull, and Lynn Whittig.
Evelyne de Amezaga, Denne Bertrand, and Uy Loi Ly assisted in data
reduction. Richard Armstrong, Alan Jassby, Barbara Jost, Jane Minabe,
Jeffrey Richey, Meryllene Smith, and Elisabeth Stull also assisted in
the preparation of various manuscripts. Robert Wrigley, Verne Oberbeck,
and William Quaide participated in the remote sensing program at Tahoe.
California Fish and Game, especially Alex Calhoun and Phillip Baker,
were very helpful in making arrangements for Dr. Sture Abrahamsson's
crayfish studies and the transport of live crayfish from the Tahoe basin
to Sweden. The Deep Seers Diving Club of Davis assisted with SCUBA in
the crayfish studies. Bolt Associates of Norwalk, Conn., kindly pro-
vided the air gun for seismic reflection profiles of the Tahoe sediments.
Assistance in preparation and review of the many sections of this re-
port was, in particular, provided by Evelyne de Amezaga and Denne
Bertrand. Thomas Powell, Leonard Myrup, Bob Wrigley, Jane Heltne-
Rundquist, Barbara Jost, Robert Leonard, Uy Loi Ly, Hans W. Paerl,
Garth Redfield, Robert Richards, Peter Richerson, and Noel Williams
also assisted in review of various sections. Meryllene Smith typed the
final report.
The support of the project by the Office of Research and Development,
Environmental Protection Agency, and the cooperation and assistance and
review of Dr. Charles Powers, grant project officer, are gratefully
acknowledged.
xvii
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SECTION I
CONCLUSIONS
1. Despite accelerated eutrophication over the last 15 years, Lake
Tahoe is still one of the most oligotrophic lakes in the world. Be-
cause of its clear waters, active photosynthesis extends to depths
of over 100 m. The depth at which maximum primary productivity
occurs may be as deep as 50-75 m, and attached plants live to depths
of over 100 m. The distribution of primary productivity with depth
evolves from a simple unimodal curve during winter and spring to a
biiaoclal curve In summer and fall.
14
2. Measurements of primary productivity with Carbon are by far the
most sensitive indicators of changing fertility in Lake Tahoe.
Based on about 6,200 samples, the annual productivity of Tahoe has
shown a steady and alarming increase from year-to-year over the
4 1/2 years covered in this report. The best available productivity
data cover the time interval from 1968 to 1971. During this period
productivity increased 25.6%. Using the 1959-1960 data, the in-
crease to 1968 was about 20% and to 1971 was 51%. Considering the
entire 1967-1971 period, the seasonal maximum of productivity has
shifted steadily from early spring in 1968 to late summer in 1971.
3. The lake has received increasing nutrient and sediment input from
a number of its influent tributaries as a result of accelerated road
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building and construction in the basin. Synoptic surveys of aereal
variation in fertility indicate the relatively high productivity of
the littoral zone and the steady increase in the productivity of the
pelagic zone relative to the littoral. Emerald Bay is the most
productive part of the lake proper and stations off Bijou, Incline
Creek, Dollar Point, and the Upper Truckee River gave particularly high
productivity values. Sediment plumes delineated by aerial photo-
graphy and simultaneously sampled for 'water truth' demonstrated the
importance of spring inflow to increasing the productivity of Tahoe's
surface waters. The more disturbed the watershed, the greater the
output of such algal growth-promoting nutrients as nitrogen, phos-
phorus, and iron. An abandoned land disposal site for sprayed
sewage effluent continues to yield high concentrations of nitrate to
Heavenly Valley Creek several years after application.
4. To the largely shore-based human population, the littoral zone is a
highly visible and important part of the lake. Despite the relatively
high fertility of Tahoe's littoral zone, it constitutes a small
percentage of the lake's area, because of its great depth and steep
contours. The littoral zone contributes only about 10% of the lake's
total primary production. To the organisms that inhabit the lake,
the littoral zone is highly important for food, cover, and repro-
duction.
5. Measurement of heterotrophic growth in Tahoe has been particularly
valuable in relation to sediment input. The bacteria are extremely
important in nutrient regeneration and their growth is consistently
stimulated by sediment. Even nutrient-stripped sediment provides a
substrata for bacterial growth.
6. The degree of winter mixing is particularly important in distributing
available nutrients, particularly nitrate, from the depths of
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Tahoe back into the euphotic zone. This is probably a key factor in
year-to-year variation in productivity.
7. Nitrogen, phosphorus, iron, silicon, and particulate and inorganic
carbon were measured routinely during the course of the study.
Phosphorus is more uniformly distributed than nitrate which forms a
distinct nitrocline. This gradient in nitrate concentration is
particularly valuable as a marker in determining the depth of winter
mixing. Ammonia is found at vanishingly low levels and deionized
water blanks were often higher than the lake water. Nitrate concen-
trations are generally as low as or lower than total phosphorus.
Near shore areas are typically higher than deep water stations in
both phosphorus and nitrogen and show greater seasonal variation.
Particulate carbon in lake waters averaged about 50 1-ig'l and
inorganic carbon about 10 yg'l with fairly high uniformity.
8. Significant stimulation of photosynthesis was observed in experiments
with additions of NTA at low concentrations. The response to NTA
additions was greatest in waters of low inorganic nitrogen content.
In addition to perhaps supplementing the direct nitrogen requirements
of the lake's natural phytoplankton populations, the chelation
properties of NTA may increase the availability of other necessary
and perhaps limiting trace elements.
9. There are over 160 species of phytoplankton in Lake Tahoe of which
112 are diatoms. Only 10 are centric forms and the rest are pennate.
Cyclotella bodanica and Melosira crenulata are dominant centric
diatoms while Fragilaria crotonensis is the most important pennate.
These three oligotrophic forms account for about 80% of the phyto-
plankton biomass throughout most of the year.
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10. The Lake Tahoe zooplankton community has undergone a transition in
dominance with the virtual elimination of cladocerans as a major
phytoplankton grazer. The cladoceran disappearance may be related
to introduction of two new predators. Mvsis relicta, the opossum
shrimp, has become well established and may be an important predator
on cladocerans. Oncorhynchus nerka, the land-locked red salmon
called "kokanee1,1 is also a major predator on cladocerans and may
have contributed to their disappearance from the plankton.
11. Marinas may serve as nutrient and sediment traps if their tribu-
taries are polluted. Because marinas have limited circulation,
they have their own special problems of eutrophication. The large
Tahoe Keys development at South Shore was found to be from 3.4 to
19.2 times more productive than the richest area of the lake.
Star Harbor at the north shore reduces the nutrient and sediment
load of its polluted tributaries and grows large quantities of
periphyton.
12. The single most important benthic organism is the California cray-
fish Pacifastacus leniusculus. These abundant scavengers are
important in grazing the littoral zone of Lake Tahoe and have
served as brood stock to re-establish an important industry in
northern Europe that has been gradually destroyed by a plague to
which the California crayfish is highly resistant.
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SECTION II
RECOMMENDATIONS
The following recommendations are based on the research included in
this report and are pointed towards the central objective of maintaining
the water quality and aesthetic values that have given Lake Tahoe its
international reputation as one of the clearest and most beautiful
lakes in the world. Recommendations are also directed towards the
research that still needs to be accomplished or data that will require
further evaluation and interpretation.
1. Reducing sediment yield from the watershed with its associated
nutrients should be a major component for planning, management, and
enforcement in the basin. Additional studies on erodibility,
weathering, and hydrology are particularly desirable. Water levels
in the lake should be maintained by the Water Master at a lower
level than the near flood stage conditions of maximum storage to
reduce beach and shore erosion. The physical process of wind
mixing in winter is of extraordinary importance to the economy of
the lake's nutrient regime and deserves continued attention.
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2. Atmospheric sources of nitrogen are important to Lake Tahoe and the
quantitative role of denitrification in the lake and on the water-
shed needs further clarification.
3. General monitoring of the chemical content of Tahoe's offshore
waters was the least productive of the Tahoe limnological research
efforts. Few chemical laboratories are able to routinely maintain
the precision necessary for reproducible results at the extremely
low levels encountered. Tributary and near shore waters require the
most attention, and nitrogen, iron, and, to a lesser degree, phos-
phorus are currently the nutrients most limiting to algal growth in
Tahoe.
4. Measurements of primary productivity in Tahoe together with measures
of heterotrophy remain the most important and sensitive indicators
of eutrophication in the lake. Without them, the basis for recog-
nizing the rate of eutrophication and point sources of greatest
fertilizing influence would be lost. These measures which began in
1959 provide a highly sensitive and important integration of the
biology, physics, and chemistry of the lake and should be continued
indefinitely in any ongoing research program at Tahoe.
5. Synoptic sampling combined with aerial photography has clearly
delineated the problem areas in the lake. Special attention should
continue to be given to the Upper Truckee River, Incline, Third,
Burton, and Taylor Creeks. Monitoring of General Creek should be
continued as a control for the more intensive studies on Ward
Creek before, during, and after its development.
6. Bioassay experiments emphasize the great importance of nitrogen and
iron and, to a lesser extent, phosphorus in the algal growth in-
Tahoe. Efforts should be directed toward keeping these nutrients
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at limiting levels in the lake.
7. NTA is a potent biostimulant for algal growth in Tahoe and should
- not be permitted in the basin.
8. Land disposal of treated sewage as it was practiced on the Heavenly
Valley Creek watershed should never again be permitted. This area,
years after disposal has ceased, continues to yield the highest
levels of nitrate of any drainage in the basin. Nitrogen in ground
water may prove of considerable importance in the basin and new
studies should be directed towards this problem. Nitrogen stripping
as ammonia in tertiary treatment may require further evaluation.
9- The role of bacterial regeneration of nutrients in the process of
eutrophication is becoming more clear. Continued research in this
area should be encouraged.
10. Periphyton, abundant in the littoral zone and along tributary
stream courses, has first access to stream-borne nutrients and
continues to be of importance to the economy of the lake. Alenough
contributing only about 10% of the primary productivity, attached
algae in the littoral zone provide the greatest visual evidence of
the lake's deterioration to the largely land-bound resident and
tourist. The dynamics of attached algal growth will require
continued study. The possibility that the resident crayfish
population provides a measure of control also merits further study.
11. The disappearance of some components of the zooplankton population
requires further attention. The quantitative trophic relation-
ships between bacteria, detritus, phytoplankton, zooplankton, and
fish need further elaboration. Studies directed toward Daphnia
predation by kokanee (Oncorhynchus nerka) and perhaps Mysis are
-------
necessary.
12. Marinas have a complicated relationship to the lake. They may
actually improve the water quality of polluted or sediment-laden
streams by serving to strip nutrients through periphyton and
planktonic algal growth and settle out sediment derived from
drainage. The construction phase is the most potentially damaging
and should be carefully evaluated and controlled.
-------
SECTION III
INTRODUCTION
Lake Tahoe lies at an altitude of 1898 m in the Sierra Nevada. It is a
2
large (499 km ), deep, subalpine lake, formed in a graben fault, with a
maximum depth of 501 m. The lake basin has steep sides, a flat bottom,
and very little shallow water for its size (Fig. 1). The average depth
of the lake is 313 m and its shoreline covers 113 km. Lake Tahoe is
particularly renowned among the lakes of the world for its great trans-
parency and the beauty of its deep blue color (Smith, Tyler, and
Goldman 1973). Mean monthly Secchi depth readings to 40 m have been
recorded in the winter months and the compensation depth (where photo-
synthesis equals respiration) is found at about 105 m. In this extra-
ordinarily clear lake the littoral zone extends to a depth of 100 m.
Because of its steep basin, this represents only 18.7% of the surface
area of the lake. This narrow band of shallow water has, however,
great importance to the many users of the lake and provides the main
visual evidence of water quality to the largely shore-bound populace.
Lake Tahoe is unquestionably changing and it has been towards quanti-
fying and slowing this change that the research reported here has been
directed. During the last few decades there has been a dramatic popu-
lation increase in the Tahoe basin and signs of accelerating eutrophi-
cation are now clearly discernible. In spite of the lake's great
volume for dilution, local nutrient sources are altering the productivity
9
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LAKE TAHOE
INCLINE CREEK
TRUCKEE RIVER
KILOMETERS
i r—I 1 r
24 6 8 10
UPPER TRUCKEE RIVER
Figure 1. Bath vine trie map of Lake Tahoe indicating the index station and
other locations. The contour interval is 50 m. The shaded
area indicates the littoral zone which extends to 100 m depth.
10
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pattern around the lake. Aerial photographs taken since 1967 show
spectacular local increases of turbidity due to the inflow of sediments
and nutrients from tributaries of disturbed watersheds. As the human
population,continues to increase in the Tahoe basin with a concommitant
rise in construction activities—lumbering, road building, housing de-
velopments—serious damage to the watershed of the lake has resulted.
This exposure of mineral soil to erosion and the resulting leaching out
of nutrients is causing a cultural eutrophication of the lake. Large
plumes of sediment from tributary streams and the appearance of luxuri-
ant growths of attached algae around the entire margin of the lake were
the first really visible signs of change. The first spring algal bloom
that was observed appeared off South Shore in 1969, thus providing the
residents and tourists alike visible evidence of a general increase in
fertility.
During the past 15 years Lake Tahoe has been the subject of intensive
limnological research with emphasis on the lake's primary productivity,
nutrient limiting factors, and the process of eutrophication (Goldman
and Carter 1965, Goldman and Armstrong 1969, Goldman 1972). Since 1959
measurements of primary productivity have been made in the lake as part
of a series of northern California lake investigations on nutrient
limiting factors (Goldman 1964). These investigations of photosynthe-
sis by phytoplankton have provided an important index of the fertility
of the lake and, perhaps of greatest importance, have established a
particularly valuable base line for determining the extent and rate at
which eutrophication is progressing. During the period from mid-1967
through 1971 the research program was greatly expanded with an FWQA
(now EPA) Grant #16010 DBU. The continued and expanded surveillance of
primary production within Lake Tahoe provides a quantitative evaluation
of long-term eutrophication trends in Lake Tahoe together with a better
understanding of the processes involved.
11
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RESEARCH PROGRAM
Since 1967 routine weekly to trimonthly sampling at the index station
located near the western shore of the lake (Fig. 1) has been made in-
volving measurements of primary productivity with the sensitive C
method, collection and enumeration of zooplankton and phytoplankton,
phosphorus, nitrogen, and particulate carbon concentrations. Data
collected at the index station has provided a nearly continuous record
of photosynthetic rates along with ancillary limnological information.
The value of this phase of the research increases as the data accumu-
lates, since it forms the basis for long-term analysis of the rate of
Lake Tahoe's eutrophication. There is strong evidence that the fer-
tility of the lake has increased by about 50% in the last decade and
by about 25% during the four years of study covered by this report.
One of the most valuable techniques of locating areas of high production
within Lake Tahoe developed during the studies is simultaneous collec-
tion, incubation, and analysis of samples taken during synoptic cruises.
The synoptic approach has greatly improved our evaluation of cultural
eutrophication, since it has enabled the investigator to accurately lo-
cate the. most important sources of nutrients before the entire lake has
undergone change. Contour mapping of synoptic primary production data
generally indicates a positive correlation between intensive land de-
velopment and higher production rates (Goldman, Moshiri, and Amezaga
1972).
Synoptic studies also clearly evidence the higher fertility of the lake
near areas of population build-up and where streams are delivering a
high nutrient load to the lake. Such areas of increased fertility have
been discovered at the south shore of the lake under the influence of
the Upper Truckee River drainage and high resident population, in Crystal
Bay where Incline and Third Creeks drain highly disturbed land, and near
12
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the outflow of the lake where there is both a high resident population
and fairly extensive areas of shallow water (Goldman and Carter 1965).
These studies continue to provide a feasible rationale for predicting
changes occurring in the lake as a result of watershed development with
associated natural and polluted drainage (see Section VII).
In investigations of the sources of eutrophicating substances, Lake
Tahoe's tributaries have been shown to be of paramount importance.
Their biostimulatory effect upon the lake has been documented using
the l^C-bioassay technique (Goldman 1963) in combined stream and lake
water cultures. In 1968 productivity measurements were routinely made
at the mouths of influent streams draining culturally disturbed regions
of the lake's basin (Upper Truckee River and Incline Creek). The re-
sults of these experiments are described in detail in Goldman and
Armstrong (1969) where it was shown conclusively that the lake is
heavily influenced by stream water from disturbed land areas. This in-
fluence was far greater than that observed off the mouth of a control
stream draining relatively undisturbed land (General Creek). The
measurements further indicate that it is primarily the nutrient loads
in the sediments carried by the streams from disturbed watersheds
which can be stimulatory to algal growth. One such measurement on 12
August 1969, following the disturbance of Third Creek during construc-
tion of a golf course, resulted in the highest stimulation ever en-
countered in similar experiments from a variety of tributaries in the
Tahoe basin (Goldman, Moshiri, and Amezaga 1972). Third Creek effluent
stimulated growth by 620% over controls. This quite dramatically re-
vealed the influence of drainage from freshly exposed soils on the
growth of algae in Lake Tahoe. Clearly these investigations substan-
tiate previous indications of considerable cultural eutrophication
occurring in Lake Tahoe's water from disturbed land areas. Further,
they have helped provide a basis for new zoning ordinances proposed by
the Tahoe Regional Planning Agency (see Section VII).
13
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A study of the bottom sediments of Lake Tahoe was undertaken in order
to evaluate the extent of sediment pollution of the lake resulting
from increased land disturbance within the Tahoe basin as well as to
determine the extent of areal variability in the sediment types. Ex-
amination of bottom surface sediments collected on a grid system cover-
ing the whole lake has revealed that there are two major types of sedi-
ment present: pollen-rich diatomaceous ooze typical of passive fluvial
erosion deposits and sediments resulting from rapid erosion and slumping
into deeper parts of the lake typical of exposed products of glaciated
rocks (Court, Goldman, and Hyne 1972). The types of pollen found in
bottom samples have been analyzed as well as their possible role as a
source of nitrogen and phosphorus to the lake (Richerson, Moshiri, and
Godshalk 1970). The studies also indicate that high concentrations of
suspended matter in tributaries result from erosion in areas of ex-
tensive land development (see Section IV).
Research was also conducted on two man-made marinas at Lake Tahoe. The
large Tahoe Keys marina at South Shore is about three times as produc-
tive as Lake Tahoe. It has been isolated from the lake, except for a
small channel to the lake, in a former swampy area. In the much smaller
Star Harbor, primary productivity was found to closely follow the con-
centration of iron during the year. Results showed a highly signifi-
cant positive correlation between iron concentration and primary pro-
ductivity. In bioassay culture experiments, additions of iron in con-
centrations of 25 pg-1 or more were found to definitely stimulate
the growth of algae in Star Harbor water. In biostimulation cultures
neither of the two streams flowing into the harbor significantly stimu-
lated productivity in the harbor, but both streams stimulated the pro-
ductivity of Lake Tahoe water. Although Star Harbor serves as a sedi-
ment and nutrient trap, its waters still have some biostimulatory
effect on the water of Lake Tahoe (Coil 1971) (see Section XII).
14
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Work has continued on the delineation of Lake Tahoe's morphometry-
Such studies are designed to reveal details of the geology and geo-
morphology of the Tahoe basin and have involved our cooperation with
T
geologists and geophysicists. Investigations using a large piston
corer for extraction of 6 m cores, a bottom sounding air gun for re-
cording the depth and extent of sediment layers, a magnetometer for
determination of basement rock fractures, submerged fault scarps, and
magnetic anomalies, and data taken from fathometer transects have re-
sulted in the production of a detailed bathymetric map of the basin
and in increased knowledge of its geological history (Hyne et al. 1972).
A submarine mountain (lake mount) rising 7.6 m above the lake floor has
been discovered and described by Goldman and Court (1968). Since the
initial studies, the lake mount has been more accurately located by
several transects over it to obtain a three-dimensional outline, and
formulae have been derived for computer application. Corrected slope
profiles were then used to plot an accurate contour map. Periodic
fathometer readings continue to be taken to further our explorations
of the bottom features of this unusual lake (see Section IV).
A cluster analysis was used in an investigation of the community ecology
of both the zooplankton and phytoplankton to determine the spatio-
temporal structure of the Tahoe plankton. These investigations re-
vealed that phytoplankton are more loosely clustered than the animal
portions of the community and support the notion that the phytoplankton
are a non-equilibrium assemblage in apparent violation of the competi-
tive exclusion principle (Richerson, Armstrong, and Goldman 1970). An
analysis of the summary statistics and other data indicated that spatial
heterogeneity was at least as important as temporal differences in
generating the observed diversity of phytoplankton.
.15
-------
Combined phytoplankton-zooplankton clusters showed that these two
portions of the community were structurally independent and consequen-
tly subtle differences in food preferences have no demonstrable effect
upon the diversity of the zooplankton (Richerson 1969). Phytoplankton
diversity was found to be positively associated with both high turnover
rates and zooplankton grazing. The model postulated is that zooplank-
ton reduce phytoplankton biomass but increase turnover rate, thus ad-
mitting more species to the assemblage. The disappearance during the
course of our investigation of an important zooplankter Daphnia rosea
may have important implications for phytoplankton grazing and fish food
supply in the lake.
The crayfish Pacifasticus leniusculus has been the subject of research
since 1968 in Lake Tahoe. The size, structure, density, seasonal and
diurnal migration, and reproductive characteristics of populations has
been determined (Abrahamsson and Goldman 1970, Goldman 1973). Field
and laboratory studies of crayfish diet and feeding habits have been
coupled with respiratory metabolism to establish the energy relation-
ships of the organism (Moshiri and Goldman 1969; Moshiri et al. 1970,
1971). Subsidiary studies were also initiated on their abundance and
characteristics in nearby Donner and Fallen Leaf lakes. As a result of
these studies, this crayfish is being introduced to Swedish lakes and
rivers by the Swedish Fishery Board to replace native species destroyed
by an epidemic. The crayfish research resulted not only in research
and publication concerning the physiology and breeding habits of
Pacifasticus but, perhaps more significantly, was instrumental in pro-
moting international goodwill and cooperation between Sweden and the
United States (see Section XI).
14
The C-bioassay technique described by Goldman (1963) has been used in
monthly experiments to determine nutrient deficiencies of the lake and
has demonstrated the relatively greater potential of nitrogen for"
16
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increasing the growth of Tahoe phytoplankton as compared with phosphorus.
Nitrate additions to cultures of Tahoe water were found to stimulate
phytoplankton growth. Additional phosphate research has indicated that
phosphorus concentrations are already adequate to support greater
standing crops of algae if additional nitrogen and iron are provided
(Goldman, Tunzi, and Armstrong 1969). Additional phosphate does pro-
vide for stimulation of algal growth with added nitrate so that nitrate-
phosphate supplies interact to promote added growth. Even when maximum
response to added phosphorus was obtained, the magnitude of response
was far less than that observed during incubation of pelagic lake water
with 1% additions of stream water. The stimulatory effect of stream
water cannot be attributed to the phosphorus content alone, since this
is seldom more than three times that of the lake itself. The stimula-
tory effect of streams is largely from nitrate and iron and is related
to some component, presumably a dissolved organic compound, of stream
water having a high absorbance in the ultraviolet (Goldman and Armstrong
1969). This water is peculiar to the Upper Truckee River which provides
about 40% of the-lake's inflow, and has a high bacterial activity as
measu
VII).
measured by C-acetate uptake (Paerl and Goldman 1972a) (see Section
Investigation of a former land disposal site at Lake Tahoe indicates
that nitrogen continues to leach from the area. Many years after the
spraying of secondary effluent ceased (see Section VII) Heavenly Valley
Creek, which drains the area, continues to be the most polluted stream
in the basin.
Sampling in 1968 of the rate of attached algal colonization on glass
cylinders has demonstrated the utility of this technique as an ex-
cellent means for the detection of enriched water masses. Data
gathered from periphyton samples indicate, as did the primary produc-
tivity information gathered from simultaneous synoptic cruise collection,
17
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accelerated growth in certain areas within the lake (Goldman, Moshiri,
and Amezaga 1972). Duplicate sets of glass cylinders were collected
from 79 stations around the lake shore. One set was used for biomass
determination (Armstrong, Goldman, and Fujita 1971) and the second set
was preserved for species identification and enumeration. The infor-
mation derived from these studies has produced an extensive list in-
cluding over 130 individual species of periphyton. The importance of
the shallow water production has been evaluated by Goldman and Amezaga
(1974) (see Section IX).
In 1962 a series of determinations of oxygen concentration at depths
from the surface to the sediment-water interface were initiated.
Measurements since then have revealed no evidence of oxygen depletion
at the sediment-water interface and only slight variations in concen-
tration with depth. With the acquisition of high quality reversing
thermometers and frames, a bimonthly sampling of oxygen and temperature
to a depth of nearly 450 m was instituted. The data derived from these
samples enabled computation of temperature and oxygen budgets with
greater accuracy and examination of the problem of vertical mixing with-
in the lake. The assemblage of this data provides a base line, thereby
facilitating the detection of changes accompanying future eutrophica-
tion. Interest in deep water limnology has increased through the
cooperative activities of the Marine Food Chain Group from Scripps
Institution of Oceanography at the University of California at La Jolla
(Holm-Hansen et al. unpublished) (see Sections IV and V).
Towards the end of four years of study our attention was directed
toward a consideration of the role of bacteria in Tahoe eutrophication.
We intensified our activity in this area since we recognized the prob-
able importance of bacteria associated with sediment entering the lake.
In conducting the heterotrophic study of Lake Tahoe we have been able
to plot the paths of certain water masses originating from polluted
18
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streams (Paerl and Goldman 1972a). By using an extremely sensitive
method for detecting the water mass originating from streams and
measuring their stimulatory effect on the lake bacterial populations,
we have been able to delineate the extent of a eutrophicating stream
flow. The procedure involved in these studies utilizes bacterial
14
uptake of trace amounts of C dissolved organic substrates which were
found to be an excellent measurement of heterotrophy. The microbial
14 - 14
incorporation of 2- C-acetate is monitored and converted to C-acetate
assimilation rates. This approach clearly demonstrates the hetero-
geneity of water masses, particularly those originating from disturbed
watersheds. This technique has enabled us to determine the relative
importance of individual inflows on the lake's fertility (Goldman et al.
1974).
To substantiate the fact that bacterial uptake, is, in fact, being
measured, autoradiographic techniques were employed to locate the
14 3
tracers among algal and bacterial populations. C and H autoradio-
graphic evidence indicates that bacteria were largely responsible for
14
C-acetate uptake during incubation while algal cells failed to show
acetate incorporation. This work has subsequently been extended by
use of the scanning electron microscope (Paerl 1974).
The year-round study of heterotrophy and primary production has shown
how these processes complement one another since both show similar sea-
sonal cycles. After monitoring changes in rates of heterotrophic up-
take of acetate for one year using monthly sampling on both a horizontal
(18 stations in Tahoe) and a vertical scale (0 to 105 m depth), in-
creases in both heterotrophic population and activity were found to
follow algal blooms both temporally and spatially. When the algal popu-
lation begins to decrease in activity, the heterotrophic population may
increase tenfold in assimilation rate of acetate and other organic com-
pounds. This, as well as increased creek inflow and siltation in the
19
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spring and summer months, is being linked with increased bacterial
cycling in the slowly warming water column (Paerl and Goldman 1972b) .
Siltation in itself appears to be extremely important with regard to
accelerating bacterial growth in Lake Tahoe. Autoradiographs and scan-
ning electron microscopy have shown that silt particles offer good sub-
strate and attachment sites for actively growing bacteria which further
suggests the importance of siltation in eutrophication (Paerl and
Goldman 1972b) (see Section VIII).
During the 1967-71 period of research, certain innovations and modifi-
cations of experimental procedures have been developed which greatly
facilitated the research and should prove particulary valuable to future
investigations. A method for measuring particulate carbon and the
carbon content of periphyton was developed which employs combustion of
samples in an induction furnace and measuring their carbon dioxide
content with an infrared carbon dioxide analyzer (Armstrong, Goldman,
and Fujita 1971). The refinement of the earlier synoptic approach has
enabled more precise productivity measurements and determination with.
greater accuracy of the areal variation in Lake Tahoefs fertility
(Goldman, Moshiri, and Amezaga 1972). A bacterial activity assay pro-
cedure has been developed by Paerl and Goldman (1972a) for detecting
water masses in Lake Tahoe. Autoradiography and scanning electron
microscopy have been utilized also to observe bacterial attachment to
substrates (Paerl and Goldman 1972b). Holm-Hansen and Paerl (1972)
have applied ATP methods to estimate microbial biomass and metabolic
activity. The transect work provided "water truth" for a remote sensing
study with NASA-Ames of the Upper Truckee River sediment plume (Goldman
et al. 1974).
20
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RELATIONSHIP OF EPA STUDY TO OTHER PROJECTS AND ONGOING RESEARCH
It is obvious from the previous pages of this report that a great deal
of the information presented here on the general limnology and the
eutrophication of Lake Tahoe has already been compiled and published.
It was also apparent that the significance of much of that work was
that it has provided the essential background of data to use as a
baseline for further study and to provide a cornerstone for policy
making decisions that are so necessary for the protection of the Tahoe
environment.
Of great importance to the U.C. Davis limnological studies described
in this report has been our interaction and cooperative research
efforts with many other groups, agencies, and individual scientists
working at Tahoe. Figure 2 indicates the cooperative relationships
between the University of California, Davis, Limnology Group and other
agencies and institutions involved in Tahoe basin studies, A series
of descriptions of these cooperative efforts follows which details the
extent of these interactions. The limnological work that was begun
with EPA funding is to a large degree being continued with different
emphasis through NSF-RANN support. The exact point where support from
the first ceased and the second began is of less importance than the
fact that the general continuity of research activity survived.
Environmental Protection Agency
Dr. Goldman has been involved in consultation on eutrophication research
with EPA-Corvallis and the EPA-WERL Group at Las Vegas. A report was
submitted to EPA on the effects of NTA on natural phytoplankton popu-
lations in Tahoe, Castle, and Clear Lake (Goldman and Fujita 1970).
Three years of Lake Tahoe and tributary stream water chemistry data
was provided the EPA-San Francisco office for its data bank. Robert
21
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Tahoe Research Group
NSF-RANN project
Environmental Protection
Agency
Tahoe Regional
Planning Agency
California Division of
Parks and Recreation
University of Southern
California
EUTROPHICATION PROJECT
Tahoe Limnology Group
EPA PROJECT
Scripps Institute of
Oceanography
(Various studies)
University of Tulsa,
Oklahoma
Dept. of Geol. Sci.
NASA - Ames
(Weaver and Arvesen)
Lake Plankton Group
(Myrup, Powell, Richerson)
UCD
Figure 2. Cooperative relationships between the University of California,
Davis, Limnology Group and other agencies and institutions
involved in Tahoe basin studies.
22
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Richards and Hans Paerl recently carried out a small study of the
effects of taconite disposal in Lake Superior for EPA using biological
assay techniques employed routinely in Lake Tahoe studies (1971). The
principal investigator provided expert testimony during the court
trial in Minnesota. Dr. Goldman visited Lake Baikal in the USSR with
an EPA-sponsored scientific exchange group led by Dr. John Buckley.
He was able to apply some of the Tahoe research technology to this lake.
NASA-Ames
;
Aerial photography and photo-interpretation services were available to
the Tahoe Limnology Group through the NASA-Ames group at Moffett Field,
California. The federal government has recently shown great interest
in the use of remote sensing in the study of environmental problems.
Cooperative studies involved the distribution of sediment plumes from
the Upper Truckee River (Goldman et al. 1974), and aerial spectrophoto-
metric determination of lake chlorophyll distribution (Weaver and
Arvesen). Distribution maps derived from photos are compared with
simultaneous "ground truth" measurements of physical and chemical param-
eters in the lake itself. The great potential for rapid and extensive
monitoring of lake conditions by aerial photography has required de-
tailed calibration by "water truth" studies in the lake (see Section
VII).
Tahoe Research Group (NSF-RANN)
This multidisciplinary research project has continued several aspects
of the EPA-supported work and involves integrated studies ranging from
nutrient release and erodability of soils in the basin to the attitudes
and policy preferences of decision makers. The research has as its
principal objective the identification and measurement of the impacts—
physical, biological, and social—of commercial and recreational
23
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development of the Lake Tahoe basin. One faction of this research in-
volves the correlation of water quality data from the limnological re-
search with terrestrial ecosystem disturbances in order to develop
causal relationships between terrestrial ecosystem disturbance and
water quality in Lake Tahoe. The RANN study is striving to quantify
the soil losses which contribute to the pollution of Lake Tahoe. The
primary productivity data, four years of which were developed with
EPA support, has already provided important information about the
sources, rates, and types of nutrient and sediment inflows. This has
made it possible to analyze and determine the sources of increased
productivity in the Tahoe basin.
State Division of Parks and Recreation
The University of California, Davis, agreed to provide assistance to
the Division of Parks and Recreation in establishing a public informa-
tion center at Lake Tahoe. This center has not yet been established,
but should eventually provide visual aids for conservation education
including scientific exhibits and photographic displays of the physical
and biological resources of the basin. Initial arrangements for this
cooperative effort were made through William Penn Mott, Director of the
Division. A 16 mm color conservation and science education movie of
Tahoe has been filmed and is in the final stages of preparation which
should be of great value in' public education.
Scripps Institute of Oceanography
Dr. 0. Holm-Hansen and his associates of Scripps Institute of Oceano-
graphy at La Jolla have utilized our research facilities on several
occasions for their collection of ATP, DNA, chlorophyll, and nutrient
samples. Our cooperative studies have covered various phases of
biochemical and physical limnology for comparisons with their
24
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oceanographic data. Lake Tahoe is now recognized by the Scripps ocean-
ographers as an excellent freshwater body for use in comparisons with
oceanographic findings. A joint paper on the chemical and biological
characteristics of a Lake Tahoe water column (Holm-Hansen et al.
unpublished) is being completed. Mr. Dale Kiefer, Dr. Tom Herman and
Dr. 0. Holm-Hansen also undertook a study of the areal and vertical
variation of chlorophyll using fluorometric procedures. Initial results
were interesting since an unsuspected layer of chlorophyll was dis-
covered between 300 and 350 m (Kiefer et al. 1972). The importance and
structure of this layer remains unknown, but will be the subject of
further study.
Mr. Peter Hacker of S.I.O. has utilized our research vessel and men on
several occasions to gain information for part of his doctoral disser-
tation on the changes in micro-structure of thermal stratification with
depth. Using a boomerang recording thermistor unit, he began the in-
vestigation of the extent of deep water mixing in Lake Tahoe (Hacker
1973) . He did detailed conductivity analyses and aided in the cali-
bration and interpretation of reversing thermometer data (see Section
IV).
Dr. E. Goldberg from S.I.O. has obtained several samples from sediments
located in deep (450 m) waters. These cores have been analyzed for
isotopes of lead to detect increases of this element in the sediments
from increased human activity (automobile exhaust) in the Tahoe basin
(Koide, Bruland, and Goldberg 1972).
Dr. Ray Smith of Dr. John Tyler's group at S.I.O. utilized our equip-
ment to supplement his determinations of the spectral quality of Lake
Tahoe water. Use of an alpha meter and spectroradiometer produced data
on percent light transmission and changing spectral qualities of the
water with increasing depth (Smith, Tyler, and Goldman 1973) (see
25
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Section IV).
University of Southern California
A separate grant proposal involving studies of sediment redistribution
within Lake Tahoe has been submitted to NSF-RANN by Dr. Bonn Gorsline
of U.S.C. This vork will require use of the University of California
research vessel and will be coordinated with stream and lake erosional
input studies by the Tahoe Limnology Group. A knowledge of sediment
movement after deposition in the lake is of particular importance with
respect to patterns of eutrophication that may result primarily from
nutrient release from sediments by heterotrophs. Greater under-
standing of lake currents and factors affecting changes in sandy beaches
of great recreational value will also result from these studies.
Geology of the Tahoe Basin
The almost complete lack of information concerning the geology below
the lake surface of Tahoe prompted this investigation. Previous work
has resulted in the construction of a bathymetric map of Lake Tahoe
from a precision depth recorder survey (Goldman and Court 1968, Hyne
et al. 1972). See Section IV for details of this work. Norman J.
Hyne (Dept. of Geol. Sci., Univ. of Tulsa), Paul Chelminski (Bolt
Associates, Norwalk, Connecticut), James E. Court (Dept. of Geology,
City College of San Francisco), Bonn S. Gorsline (Dept. of Geol. Scien-
ces, Univ. of Southern California), and Charles R. Goldman (Div. of
Environmental Studies, U.C. Davis) have all contributed to this work.
University of California, Davis
A proposal for the study of Lake Tahoe's heat budget by Drs. Thomas
Powell, Leonard Myrup, and Peter Richerson has been funded by NSF.
26
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These studies propose to describe the relation between a lake's changing
physical conditions and subsequent ecological effects. Such research
will include considerations of local atmospheric conditions, lake
currents, and wave motions among other environmental factors. The
sophisticated electronic monitoring equipment necessary for the deter-
mination of the Tahoe heat budget will be installed in our new labora-
tory (shortly to be constructed). In addition, the use of our SCUBA
equipment, divers, boats, and lab personnel will be required in the
installation, maintenance, and manipulation of the field sensors and
equipment utilized in their studies.
Lake Tahoe Area Council (LTAC) and Lake Tahoe Environmental Education
Consortium (LTEEC).
A project involving the eutrophication of streams and surface waters of
Lake Tahoe has been conducted for several years under the direction of
Dr. P. H. McGauhey of U.C. Berkeley for the LTAC. They have independent
laboratory facilities and funds, but have been assisted by Dr. Goldman
in the form of lab furniture and help with sampling in the lake and
planning initial phases of the research. Information dissemination of
EPA-sponsored research findings are now being assisted by the LTEEC with
the aid of a new, NSF funded, research coordination board.
League to Save Lake Tahoe.
The League has provided partial funds for the production of a 30 min.,
16 mm color movie, now nearing completion, depicting the nature and
extent of field and laboratory work at Tahoe, and the support program
for data analysis in Davis. Dr. Goldman and his associates have given
a number of slide talks to League meetings on the subject of Lake
Tahoe and related conservation issues. Dr. Goldman is currently serving
as a member of the Board of Directors. A small water use study for
27
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selected areas of the Tahoe basin was funded by the League in 1969 and
a report has recently been submitted.
Tahoe Regional Planning Agency (TRPA)
Dr. Goldman and his associates have had steadily increasing interaction
with the TRPA and Forest Service environmental planning at Lake Tahoe.
They have served on various technical committees of TRPA, assisted in
upgrading planned unit developments, and participated in TRPA public
hearings on regional planning. On 17-18 July 1972 a jointly sponsored
meeting on remote sensing was held at South Tahoe.
28
-------
SECTION IV
PHYSICAL CHARACTERISTICS
LIGHT
Methods
Solar radiation has been recorded directly and continuously since July
1967 with a pyrheliometer (Belfort Instruments, Baltimore, Md.). The
daily light curve recorded on the chart was then planimetered and the
total amount of langleys available that day at the surface of the lake
was computed. The instrument was calibrated with an Eppley unit.
Transparency was measured with both a Secchi disk (25.5 cm in diameter)
and with a photometer. A Rigosha submarine light meter was used in 1967.
In 1969 and subsequent years a submarine photometer (G.M. Mfg. Instrument
Corp., Model No. 268WA310) replaced the previous instrument. The deck
cell was used to correct for any changes in sky light intensity during
the course of the measurements. The surface value for transmitted light
was measured just below the air-water interface in order to eliminate
any possible increase in intensity due to reflection and scattering of
light at the surface caused by small waves. The percentage of surface
light transmitted at each sampling depth was calculated from the photom-
eter measurements. The extinction coefficient was computed from those
values.
29
-------
The Scripps spectroradiometer (Tyler and Smith 1966) was used to measure
absolute values of spectral irradiance for a comparison of the optical
properties of Tahoe and Crater Lake, Oregon (Smith, Tyler, and Goldman
1973). Principal features of the instrument include: a double Ebert
monochromator to minimize stray light within the instrument, a carefully
constructed and calibrated underwater collector, spectral sensitivity
from 350 to 750 nm, an accurate (5-10%) and precise (±2.5%) response,
a sensitivity (with 5 nm bandwidth) to energy levels down to 0.005
r\ -i
pW-cm -nm (less than 0.01% of the average noon surface spectral ir-
radiance in the blue region of the spectrum), and an absolute calibration.
The submersible spectroradiometer and experimental details for spectral
irradiance measurements have been discussed in detail by Tyler and Smith
(1966, 1970).
Beam transmittance was measured using a 1-m pathlength transmissometer
(Petzold and Austin 1968). Salient features of the instrument are: a
cylindrically limited and folded beam; fixed optical alignment; temper-
ature, fatigue, and drift stability; insensitivity to ambient light; and
a means of checking calibration while the instrument is submerged. This
instrument has less than a few tenths of one percent error due to forward
scattered light for the work reported by Smith, Tyler, and Goldman (1973).
Results
Solar Radiation -
The amount of solar radiation received on the surface of the lake varies
_2
from a minima of a few langleys (g cal-cm ) per day on dark days in the
winter months to maxima above 650 langleys per day. Figure 3 shows the
seasonal variation of solar radiation at Lake Tahoe in langleys per day
for each single day of the year and the total amount of solar radiation
that reaches Lake Tahoe each year. Deviations from the expected smooth
seasonal curve of solar radiation (Fig. 4), due to the seasonal
30
-------
800-
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 3. Daily solar radiation at Lake Tahoe from mid-1967 through
1971. The total yearly radiation in langleys is also
indicated.
31
-------
-------
variation of the path of the sun, reflect weather conditions at Lake
Tahoe. There were a few very dark days in 1968 in the winter and
summer months, with a summer low of 185 langleys on 31 July. No such
very dark days were observed in mid-summer days of the following years.
There were, however, half as many dark days in the winter of 1968 as in
the winters of the following years. For the first three months of 1968
there were 14 days with less than 200 langleys of incoming solar radi-
ation as compared to 31 days, 30 days, and 27 days for 1969, 1970, and
1971, respectively. In 1969, the winter minimum was observed on 21
January with 2.5 langleys for the day. The summer of 1969 shows less
light fluctuation from very cloudy days than the other three years. The
minimum in the winter of 1970 was reached on 14 January with 7.5 langleys
for the day. There was more total solar radiation for the first three
months of that year than for any of the other years. In 1971 the mini-
mum winter light recorded was 45 langleys on 13 January. The total and
mean monthly insolation and the total amount of solar radiation that
reaches the surface of the lake each year is given in Table 1. It shows
a steady decline from one year to the next in the total amount of solar
radiation that reaches the surface of Lake Tahoe.
The maximum solar radiation recorded on any one day for each of the four
years also shows a slow but steady decline in solar radiation since
1968. Each of these days was a clear day, without cloud cover for the
period of time immediately preceding or following the 21st of June.
Unfortunately this decline is roughly within the experimental error of
the instrument. If it is real, it may reflect an important increase in
air pollution or cloud cover.
Transparency -
First measurements of Secchi disk transparency at Lake Tahoe were re-
corded by Le Conte in 1883. Since then Lake Tahoe has had the reputation
of being among the clearest lakes of the world. Although many Secchi
33
-------
TABLE 1, INCIDENT SOLAR RADIATION AT LAKE TAHOE, 1967-1972
MEAN MONTHLY LANGLEYS PER DAY
1967
1968
1969
1970
1971
1972
MONTHLY
AVERAGE
1967
1968
1969
1970
1971
1972
JAN
—
210
138
157
191
184
176
JAN
—
6,510
4,270
4,875
5,940
5,690
FEE
—
269
210
296
300
276
270
FEE
—
7,545
5,872
8,300
8,410
7,998
MAR
—
410
430
445
373
398
411
MAR
—
12,712
13,323
13,805
11,565
12,340
APR
—
558
531
498
478
483
510
APR
—
16,725
15,920
14,940
14,341
14,500
MAY
—
621
637
611
488
597
591
TOTAL
MAY
—
19,250
19,755
18,930
15,130
18,500
JUN
—
650
548
496
617
580
578
LANGLEYS
JUN
—
19,510
16,425
14,865
18,500
17,410
JUL
—
604
627
616
607
596
610
PER MONTH
JUL
18,715
19,435
19,095
18,805
18,475
AUG
581
555
581
572
547
538
562
AUG
18,005
17,230
18,010
17,730
16,960
16,665
SEP
474
481
473
511
500
446
481
SEP
14,220
14,440
14,201
15,335
15,010
13,365
OCT
361
332
368
354
357
296
345
OCT
11,185
10,310
11,420
10,975
11,070
9,175
Nov
207
202
260
185
230
212
216
Nov
6,221
6,070
7,785
5,550
6,898
6,350
DEC
178
169
178
165
164
141
166
DEC
5,506
5,255
5,535
5,128
5,072
4,370
MEAN
YEARLY
LY/DAY
423
416
410
405
397
TOTAL
PER
YEAR
—
154,272
151,951
149,528
147,701
144,838
-------
disk records have been taken between 1959 and 1963 (Goldman and Carter
1965), Secchi disk readings have been taken more frequently since 1967
and on an all-year round basis, approximately every week in summer and
every two weeks in winter. Seasonal variation of Secchi disk trans-
parencies at the index station shows typically higher transparencies in
the early part of the year, lower in summer, and higher again in the
last part of the year. Most of the highest values occur early in the
year. For the half year of data recorded in 1967, the lowest Secchi disk
transparency recorded was 12 m on 25 August and the highest value of 31 m
was recorded on 1 November. On 8 February 1968 the highest value that
has ever been recorded at Lake Tahoe was a 43,25 reading. Other locations
in the lake during the same time period were also giving measurements of
Secchi disk transparency of over 40 m. On 31 July of the same year, the
lowest value for the year was recorded as 16.5 m.
On 15 March 1969, another high reading (40.4 m) was taken with the Secchi
disk at our index station. This was the maximum for the year, and a val-
ue of 15.5 m on 20 June was the minimum. In 1970 and 1971 the pattern
of seasonal variation of the Secchi disk measurements was somewhat al-
tered from the previous one. In 1970 a very low value of 17,0 m was
recorded on 19 January. This was the minimum for that year and the
maximum of 35 m was measured on 5 May. In 1971, the maximum of 35.25 m
was recorded on 12 February, a low of 20.5 m was read on 1 June, but the
minimum for the year (19 m) was measured on 29 November. Mean monthly
Secchi disk transparency values are shown in Figure 5 . These values
have been obtained by planimetering by month the area under the curve of
Secchi depth variation and dividing by the number of days in that month.
The greatest mean monthly Secchi disk recording was 37.4 m for February
1968, the lowest was 19.8 m for August 1967, followed by 20.2 m for
November 1971. The average daily Secchi disk transparency reading,
based on a whole year of data, was found to be 29.3 m for 1968, 27.8 m
for 1969, 29.0 m for 1970, and 27.6 m for 1971. It is doubtful that
35
-------
u
"t/S
25 10
UJ
X
t
S 20
CO
Q
X
O
£ 30
A(\
I I I ! I I I I I l i
• 1967
• 1968
o 1969
a 1970
LAKE TAHOE A 1971
MONTHLY AVERAGE
B
o
0 •
0 • ^--^ ° •
x. ° *.x"X ° • ° * i ''
0
i l l l 1 1 1 | 1 I I
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 5. Seasonal Secchi disk transparency at the index station of Lake Tahoe calculated
from monthly averages from mid-1967 through 1971. Each point is the average
for the month.
-------
this represents a significant change in the transparency of Lake Tahoe
over the four years in question.
Measurements of transparency obtained with the submarine photometer are
given in Tables 2-4. These are expressed as the percentage of surface
light transmitted at each sampling depth and are shown together with
the amount of cloud cover for each of our sampling days in 1969, 1970,
and 1971. A change in scale for photometer readings at low light in-
tensity is reflected by an increase in the number of decimal places
given in the results.
To move from these conventional measures of transparency to a higher or-
der of precision required the use of specialized equipment from the vis-
ibility laboratory at the Scripps Institution of Oceanography. The
Scripps' submersible spectroradiometer was used for a comparative study
of the optical properties of Lake Tahoe and Crater Lake, Oregon. Al-
though summarized below, this study appears in detail in Smith, Tyler,
and Goldman (1973). The remarkable clarity of the water, particularly
in the 400 to 550 nm range, is evident in Figure 6.
Color -
Of particular importance at Lake Tahoe is the color of the lake water.
Descriptions of the beauty of the "cobalt blue" waters of Tahoe are
legendary, yet we have no way of knowing whether or to what extent Lake
Tahoe has changed its color since the early descriptions of its color
and beauty. It is now possible, however, with a knowledge of the
spectral composition of the radiant energy upwelling from lake waters,
to make an objective evaluation of the color attributed to lake waters
in terms of the C.I.E. chromaticity coordinates. A detailed discussion
of color and its quantitative description is given in The Science of Color
(Optical Society of America 1953). An evaluation of color in terms of
the C.I.E. chromaticity coordinates requires: (1) A source of
37
-------
TABLE 2, PERCENT LIGHT TRANSMISSION AT THE INDEX STATION OF LAKE TAHOE, 1969,
DATE
% CUOUD
COVER
DEPTH (M)
0
2
5
ID
15
20
30
40
50
60
75
90
105
DATE
% CLOUD
COVER
IFPTH (M)
0
2
5
JD
15
20
30
40
50
CD
75
9D
105
16 JAN
50-100%
100.0
54.0
54,0
43,6
32.6
22,6
13.6
5.8
3.2
2.1
.36
.48
.37
8JUL
OS
100,0
78.3
59.8
39,1
27.8
18.9
10.1
5.7
3,8
2.5
.58
.'0
.14
1FEB
JOE
100,0
59,5
54,8
40.5
32.4
25.5
15.5
10.2
6,4
5.0
2,7
1,5
.78
15JUL
0%
100,0
85.0
72.5
50.0
36.2
17,2
7,1
4.0
2.6
1.2
,46
,34
,09
2 MAR
75-100%
1DO.O
75.3
64.7
47,0
40.0
32.9
17.5
11.3
7.1
3.5
2.2
1.2
.56
22Jut
0%
100.0
78,9
60,0
41,0
24.2
18.8
9.8
4.4
3.5
1.5
,46
,25
.11
15PIAR
OX
mo
68,2
54.5
44,3
36,4
26,1
16.1
9.8
5,7
4.3
1.5
.70
.31
24 Jut
1%
100.0
71.6
55.7
36.4
23.9
17,0
9,6
5,0
3.1
1,8
,75
.33
,15
30HAR
m
100,0
63.6
52.7
40.9
29,1
25,4
15.1
8.4
4,6
2,7
1.'!
,€5
,27
30JUL
0%
1)0,0
72,5
52.9
37.2
27.4
20,0
10.5
5.9
3.1
1,3
,72
,29
,15
13 .APR
0%
100,0
82.6
G6.3
50.0
3S.4
29.1
14,5
7,9
4,3
2,0
,78
,37
,19
5Au6
OS
100.0
80.4
62,0
41,3
30.4
22.8
12,8
7,5
4,3
2,3
,94
.'13
.18
19 APR
OS
100.0
78.3
60,9
45,6
35.9
27.2
17,'l
9.9
5.2
2.7
1.2
.49
.IS
14AuG
OS
100.0
80.4
63.7
'0.0
24.5
17,0
10.6
6,3
3,5
2,1
,93
,37
,18
25 APR
OS
100,0
91,2
73,6
54,9
39,6
28,6
13,4
6.5
3.3
2.2
.87
.33
.13
20Aus
02
100,0
72.3
49.4
36.1
27.5
20.5
11.6
6.4
3.4
2.2
.78
.35
9 MAY
(K
DO.O
92.5
78.8
61.2
52.5
43,8
12.1
7,9
4.1
2,0
,74
,28
,13
28AU6
0%
100,0
83.8
56,7
43.8
33,4
24,7
13,5
7,5
4.2
2.9
1,4
,67
,30
25 IVY
(K
1DO.O
87.8
75.6
51.2
28,0
21.0
8,9
3,6
2.4
,93
.43
,14
,052
3 SEP
Z?
100,0
15.9
14,5
11.3
13.1
11.6
8.2
5.5
3.2
1.3
.88
.42
.21
7JUN
5Z
100,0
70,4
52.4
32.0
20.4
11,2
6.3
2.7
1.3
.75
.26
.11
,042
9 SEP
UK
100,0
69,0
53.6
39.3
29.0
21,2
10,6
5.5
3.0
1.6
.65
.31
.15
20JUN
E
mo
80.0
67.0
52.2
28.7
?«.7
7.7
2,7
2,1
1.2
.55
,53
.11
15 SEP
35
100.0
63.2
55.8
44.2
38,9
27.4
9,5
4.4
3.2
1.4
.55
.32
.12
1JUL
OZ
100.3
78.?
47.0
33.6
18.5
12.4
5.3
3.5
2.3
,73
.47
.17
.070
23 SEP
0%
100.0
75.6
61.0
54.9
42,7
—
—
—
—
—
—
—
—
38
-------
TABLE 3, PERCENT LIGHT TRANSMISSION AT THE INDEX STATION OF LAKE TAHOE, 1970,
DATE
| CLOUD
CWER
DEPTH M
0
2
5
10
15
a
30
to
50
60
75
90
105
125
150
DATE
Z CLOUD
COVER
DEPTH (M)
0
2
5
ID
15
20
30
40
50
60
75
90
105
125
ISO
53 JAN
40-60*
mo
59.3
51.3
—
52,1
42.8
36.0
14.0
lfl.5
1.8
1.3
.57
.29
—
—
24JUL
0%
100.0
80,0
69.2
53.8
46.2
38.5
23.8
15.2
ID.ii
1.2
.58
.32
.19
.10
—
1DFEB
ICffi
100.0
71,1
66.7
60.4
48.0
36,9
20.4
11.1
2.7
1,4
.76
,56
,27
—
—
31JUL
ft
100.0
73.5
61.fe
44.1
36,8
36.3
21.9
14,0
8.5
5.4
1,0
.47
,29
,12
.054
23 FEE
0%
100.0
96.3
38.9
89.6
81.5
56,4
47.0
31,3
18.8
5.0
2,5
1.6
,35
—
—
11AUG
a,
100.0
72.0
60.3
45.6
36.3
33,5
21,6
14,1
8,4
5,9
,98
.39
,36
,13
,(fti
28FEB
JOB
100,0
100.0
100.0
35.7
64.3
32,7
9.4
6,7
3.7
2.1
1.3
,70
.32
—
—
]7Aus
60%
mo
65,8
57.5
45.2
35.6
30,1
24.6
15.8
10,2
6,5
3.3
.65
.32
.21
.U8J
IDMw
TIE
100,0
52.5
87.5
75.0
67,5
40.0
25,0
15.0
9.2
1.8
1,5
,97
.58
—
—
24AU6
0%
100,0
76,6
55.8
53,2
39.0
29.9
27.9
18,4
12.2
7.8
1.6
.75
.32
.25
,072
15 Am
90%
100.0
80.9
64.0
47.2
37.1
31.5
22,5
11.6
7.4
4.5
.90
,53
,25
—
—
2 SEP
OZ
100,0
79.0
67.7
50.0
38,7
32,2
28.7
18.5
11.6
7.2
3.4
--
.40
.IS
,050
2 MAY
m
100.0
76.4
58.3
47.2
38.9
33.0
27,9
18,0
11,2
6.7
3.5
.64
.35
.17
—
8 SEP
0%
100.0
75,8
61.3
45,2
37.1
39,4
24.3
15,0
9.4
5.6
1.2
.51
.27
.IB
.048
J3M»Y
60%
100,0
74.1
59,8
50.6
.35.7
30.4
22.0
14.5
8.2
5.6
2.8
,40
,36
.18
—
17 SEP
(K
100.C
66,0
52.8
46,3
40,4
32.4
20.9
11.3
7.4
1,6
.75
.32
.26
.11
,033
25 MAY
OK
100.0
75,0
61.4
47.7
39.8
34.1
21,4
13,3
7,4
4,3
.82
.36
,28
,11
,039
23 SEP
IB
100.0
70.2
56.1
38.6
37.5
28.1
15.4
8.8
5.4
2.6
.50
.40
.13
.074
.005
4JUN
ion
100.0
76.8
60.0
40.0
29.5
24.2
15,7
9.0
5,4
3.4
.58
.28
.20
.330
.028
20cr
(K
100.0
76.4
65.4
49.1
40,0
40.0
25.4
15.8
8.2
5,4
2,7
.40
.33
.13
,044
16JUN
50Z
100,0
71.1
48.2
38.6
36.1
31.3
20.2
14,3
8.7
5.2
2.8
.43
.27
,12
.047
14 On
OK
100,0
78,6
66.1
42.8
44.6
38.4
24.8
15.0
8.4
5.7
1.0
.41
.20
.12
.041
IJut
(K
100.0
mo
97.3
78.4
62.2
42.7
36.8
25.1
li.2
9.4
1.9
.86
,66
.30
.10
10 Nov
m
100.0
68.7
54.2
55,8
42,7
32.3
18,3
10.6
6.2
1.4
.55
.46
.]£
.062
.018
7JUL
(K
mo
67.2
55.2
SJ.7
35.2
35.1
22.1
14,6
3.6
5.5
1.1
.52
.36
.16
.038
6 DEC
OZ
100.0
54.4
45.3
47.6
33.8
26.0
13,1
7.3
4.0
.91
.40
.34
.IB
.053
.016
14JUL
(K
100.0
74.4
59.U
51.3
43.6
35.9
22.2
14.6
3,8
6.1
3.5
.34
.27
.12
.017
22 DEC
52
100,0
78.9
63.2
58.4
46.3
35.7
18.9
10.3
5.0
1.3
.63
.54
.32
.14
.059
20JU.
301
100.0
96.6
77.6
58.6
50.0
41.4
24.2
16.9
11.4
8.4
4.6
.71
.44
.18
.071
39
-------
TABLE 4, PERCENT LIGHT TRANSMISSION AT THE INDEX STATION OF LAKE TAHOE, 1971,
DATE
IGtouD
COVER
DEPTH (M)
0
2
5
10
15
20
30
40
50
60
75
90
105
125
ISO
DATE
COVER
DEPTH W
0
2
5
10
15
20
30
40
50
60
75
90
105
125
150
8 JAN
75%
100.0
71.9
84.0
6b.9
45.2
34.2
19.3
9.0
2.3
1.7
.74
.79
.35
.12
.028
UUL
0%
mo
65.7
55.7
45.0
40.0
33.3
23.3
14.0
7.8
4.5
2.0
.42
.19
.071
.020
21JAN
0%
100.0
72.7
51.4
5D.O
36.4
35.9
20.9
12.0
6.5
1.8
.80
.40
.42
.18
.005
8JUL
0%
100.0
69.1
58.2
45.4
35.4
37.8
28.7
14.5
8.4
4,9
2.5
.45
.22
,084
,033
3FEB
0%
100.0
74.5
51.7
45.8
34.0
27.6
22.3
11.3
7.0
3.8
.74
.34
.34
.13
.047
14JUL
0-20%
100.0
64.3
46.4
35.7
38.8
31,4
20.4
12,1
7.5
3.8
.58
.41
.18
.11
.027
12FEB
30%
100,0
75.6
63.5
'6.4
46.1
34.2
21.8
12.6
6.6
1.9
.87
.52
.46
.22
.083
22JUL
5%
100,0
70.7
55.2
41.4
31.0
25.9
21.7
13,1
6.7
3.6
,60
.21
,19
.069
.021
22FEB
KH%
mo
100.0
94.8
85.7
69.7
51.4
32.0
17.7
10.8
6.8
1.5
.88
.45
.20
.079
3Aue
60%
100.0
71.2
59.1
45.4
35,4
33.3
22.7
16,2
10,6
4,2
.70
,33
,28
,099
.032
7N/W
80%
100,0
71.6
49.1
39.5
32.1
29.4
26.6
18.0
U.O
5.9
3.1
.63
.31
.25
.11
UAuG
5%
100,0
70,9
60,0
45.4
40.0
29.1
23.8
13,6
7,6
4.0
1,6
.42
,19
,063
.023
17 MAR
0%
100.0
76.4
65.4
58.2
47,3
40.0
33.1
21,1
]2.0
8,2
4,5
,49
,36
.41
.16
17/te
0%
100.0
61.2
47.4
42.8
43.5
34,8
22.1
15.2
8.5
5,0
,85
,36
,26
,10
,036
2APR
75%
100,0
60.3
51.7
44,8
39,6
40,9
27.6
19.5
13.5
8,4
4.3
2.2
,52
.34
.12
24AUS
80%
100.0
51,2
52,5
42,8
33,8
27,9
20.4
10,5
6,2
3,7
.49
.38
,16
.052
.018
13 APS
100%
KE.O
64.5
58.1
60.8
51.7
42.2
26.0
16.2
10.1
6.1
1.5
.77
.47
.40
.15
2 SEP
85%
100,0
73.7
63,2
44.7
36.7
37.2
22.9
15.6
9.8
5.6
2.1
,37
.23
,064
,020
23 APR
5%
100.0
64.9
56.8
44,6
36.5
28.4
22,4
14.4
9.2
5.5
2.8
,58
,32
,22
.13
9 SEP
10%
100.0
78.9
68.4
55.3
44.7
3B.8
26.0
16.3
9.5
5.5
2.5
.45
,23
—
—
sn»Y
65%
100.0
77.2
64.4
42.8
33.8
26.0
24.1
14.6
7.2
3,6
.55
.51
.25
.088
.024
9Nw
80%
100.0
48.3
37.9
20.7
17.2
46.5
39.0
2.7
—
—
—
—
—
—
BMAY
80%
100.0
98.5
85.4
77.4
71.5
53.3
41,7
15,9
14,7
8.3
2.4
1.9
1.0
.48
.13
24 Nw
40-80%
100.0
67.4
56.7
38,0
25.6
22.4
8.3
4.9
IJUN
103%
100.0
53.0
51.1
53,4
38,9
27,5
14.5
8,0
2,0
1.1
.53
.44
.22
.090
,031
6 DEC
75-90%
100.0
63,4
45.5
30.9
20,3
11.5
5,5
2.8
—
—
—
—
—
—
—
14 JUN
0%
100,0
59.4
55.4
45.2
32.2
25,8
14.0
7.6
4.4
2.7
.48
.31
.15
.060
.011
IE DEC
0-5%
100,0
68.5
59,0
41.0
20.6
13.7
7.4
4,2
—
—
—
—
—
—
—
25 JUN
0%
100.0
67.8
55,4
41,1
35.7
28,6
25.9
15.2
8.2
4.4
,71
,25
.22
,082
.028
40
-------
i
I-
o
<
o
oc
DC
<
£
o
LU
o_
CO
O
a
1000
100
10
1.0 E
0.1
0.01
0.001
11.1 meters
LAKE TAHOE
25 FEBRUARY 1970
21.3 meters
350 400 450 500 550 600 650 700 750
WAVELENGTH m,t
Figure 6. Downwelling spectral irradiance of Lake Tatxoe. The elevation of the sun was between
40° and 42°. Data taken 25 February 1970 at the mid-lake station under clear, sunny
skies and a calm water surface.
-------
illumination, which defines the achromatic point on the chromaticity dia-
gram. We have chosen the C.I.E. coordinate svstem and standard source C,
an approximate representation of average daylight, which matches closely
our experimental conditions. (2) An appraiser, the human observer. We
have chosen luminosity data for the 1931 C.I.E. standard observer (Judd
1933). (3) An object which modifies the incident illumination by selec-
tive reflection and absorption. We shall evaluate how the waters of
Crater Lake and Lake Tahoe modify and reflect the incident illumination.
It is this modified and reflected light which, upon reaching the obser-
ver's eyes, constitutes the color attributed to the lake.
Using the up- and downwelling spectral irradiance data, Smith, Tyler,
and Goldman (1973) have calculated the tristimulus values of this radi-
ant energy for each depth (Optical Society of America 1953) . These
tristimulus values, when plotted on the C.I.E. chromaticity diagram
(Fig. 7), give the numerical specification of the colors, at different
depths, of the up- and downwelling illuminance of the lake waters.
The loci of the color specification objectively and graphically show
how the selective absorption and scattering of the indident radiant
energy, with increasing depth, alter the water color. The color seen
by an external observer would be closely approximated by the color cal-
culated for the near surface upwelling irradiance.
The principal value of the tristimulus values shown in Figure 7 is that
they provide an analytical tool for the objective comparison of lake
color. Two lakes cannot be juxtaposed for direct visual comparison nor
can a direct visual comparison be made for a single lake as its color
changes with time. However, the tristimulus values of different natural
waters can be compared and the changes for a single lake can be monitored
over a period of time.
Because of color constancy, the aesthetic pollution (the degradation of
42
-------
0.45
0.40
0.35
0.30
0.25
0.20
0.15 -
0.10
0.05
Crater Lake
Lake Tahoe
0.05 0.10 0.15 0.20 0.25
0.30 0.35
Figure 7. Tristimulus values of the upwelling (long, curved lines) and
downwelling (short lines) spectral irradiance of Lake Tahoe
and Crater Lake, labeled with the corresponding depth in meters,
A portion of the C.I.E. chromaticity diagram (Optical Society
America 1953) is also shown, with the loci of spectrally pure
wavelengths represented by the dots labeled from 410 to 495 nm,
based on standard source C as the achromatic stimulus.
43
-------
the natural appearance) in Lake Tahoe waters may be so gradual that it
could go unrecognized for some time. However, color constancy can be
greatly reduced by critical, analytical scrutiny. If a means is avail-
able to make a direct comparison of change in color, the observer is
likely to be startled by the amount of change he inadvertently tolerated.
One technique for making such a comparison (suggested by R. W. Austin,
personal communication) is to use the tristimulus values of the reflected
light from the lake waters to specify the reflected color in terms of the
Munsell system of color standards (Newhall, Nickerson, and Judd 1943;
Optical Society of America 1953). Each Munsell color standard is
labeled with a notation indicating its hue (H), value (V), and chroma (C) ,
in the form HV/C. In the Munsell color system, the hue notation of a
color indicates its relation to the spectral colors, the value notation,
indicates its lightness, and the chroma indicates the saturation or
purity of the color (Munsell Color Co. 1967).
Table 5 gives the tristimulus values for the up- and downwelling spectral
irradiance of Lake Tahoe for the depths where the irradiance measurements
were made. In addition, the dominant wavelength, purity, and Munsell
notation for each set of tristimulus values are given. With this infor-
mation, it is possible to objectively compare the differences in color
between two lakes and to see precisely how the appearance of color
changes as a function of depth in either lake. More important, the data
in Table 5 provide a basis for an objective evaluation of possible future
changes in appearance of Lake Tahoe.
It should also be noted that sunlight filtered through a layer of smog
would give a very different achromatic point. Since the appearance of
smog is increasingly frequent at South Tahoe, we must unhappily point
out that the appearance of the lake waters can be affected not only by
the pollution of the water itself, but also by the pollution of the air
above those waters. In future measurements, it may be necessary to
44
-------
Ln
TABLE 5, TRISTIMULUS CHROMATICITY COORDINATES (X,Y*Z), DOMINANT WAVELENGTH (\j), EXCITATION
PURITY/ AND MUNSELL NOTATION OF THE SPECTRAL IRRADIANCE AT VARIOUS DEPTHS FOR LAKE TAHOE,
LAKE TAHOE
25 FEE 1970
DOWNWELLING
UPWELLING
DEPTH
(METERS)
11,1
21,3
31,9
62,3
93,8
11,6
31,8
X
0,186
0,156
0,150
0,135
0,132
0,153
0,142
Y
0,262
0,207
0,189
0,137
0,113
0,163
0,146
z
0,552
0,637
0,661
0,728
0,755
0,684
0,712
Xd(m,)
485,5
481,9
480,7
477,1
475,2
472,3
472,8
PURITY
50,8
67,8
72,5
84,1
88,5
74,6
79,9
HV/C
l.OPB 1,3/6,2
1.5PB 1,3/7,1
-------
select clear, well ventilated days to accurately reproduce results of
light-related measurements.
TEMPERATURE
Methods
Vertical profiles of water temperature were obtained at the index station
on every sampling date as well as with collections from other areas in
Lake Tahoe. A bathythermograph (BT) was employed for all measurements
through April 1970. Accuracy of the BT was determined to be i" 0.25°C.
Readings were taken through a slide viewer calibrated by means of surface
temperature adjustment to that measured independently by a "bucket" ther-
mometer with 0.1°C divisions.
Because of increasing interest in the Tahoe temperature regime, measure-
ments were taken after April 1970 with a thermistor equipped with a 100 m
conductor (Martek TMS). The thermistor unit was calibrated before each
series of readings, if necessary, and checked against a surface reading
of the bucket thermometer. Accuracy was determined to be i 0.1°C. All
index station profiles were recorded between 1030 and 1130 hours.
Mid-lake deep water temperatures were taken with a series of reversing
thermometers (KAHLSICO). At each depth, two thermometers were employed
to give protected (ambient) and unprotected (depth-pressure) readings.
Before tripping the reversing thermometer frames, at least a ten-minute
wait was instituted to allow for thermometer equilibration. Readings
were taken after all thermometers had been retrieved and allowed to
come to ambient temperature. Protected thermometers with a range of
-2° to +16°C in 0.05°C divisions were used in deep sampling where tem-
perature variations were slight. In the upper 100 m of water where
temperature changes were expected to exceed that range, thermometers
46
-------
with a -2°C to +30°C scale in 0.1° divisions were used. All unpro-
tected thermometer scales were -2° to +30°C or +35°C in 0.1°C divisions.
Recalibration of these thermometers was done by the Scripps Institution
of Oceanography at La Jolla, California.
Results
Figure 8 illustrates the annual changes in isotherm configuration at the
index station for the study period from mid-1967 through 1971. Tempera-
ture values at the index station are given in Appendix A. Heat storage
depth profiles calculated from the index station temperature data are
shown in Figures 9,10. Seasonal heat storage and temperature curves for
several depths at the index station are shown in Figures 11,12. Tem-
perature values measured in deep water, down to 400 m, are given in
Table 6.
Although Lake Tahoe appears to follow similar patterns of thermal strat-
ification and mixing from year to year, it was not possible to demon-
strate a complete turnover with existing data until 1973 (Paerl et al.
1974) . Detailed examination of the upper 100 m show that stratification
and the depression of the 6°C isotherm from the surface to deeper depths
has occurred around 20 April each of the four years covered by this
report. Peak surface temperatures are usually reached in August and
the lowest surface readings occur in Feburary - March. The lake mixes
deeply and is nearly homothermous from the end of December to April or
May with most of the temperature change limited to the upper 70-80 m
(Table 6).
The irregular variations that occur from one sampling date to the next
are characteristic of Tahoe (Fig. 8). It is possible that these are
caused by long shore currents, a thermal bar, or upwelling of deeper
cold water which cause a rise in the isotherm levels especially evident
47
-------
.p-
oo
1967 1968
C.A.S.O,N.D.J.F.M,A ,M,,
1969
A,S.O,N,D,J.F
A.M.J.J.A.S.O N D
IOO
J'F'M'A'M'J'J'A'S'O'N'D'J'F'M'A'M'J'J'A's'o ' N'D
1970 1971
Figure 8. Isotherms (°C) for the index station of Lake Tahoe from mid-1967 through 1971.
-------
TABLE 6. TEMPERATURE (°c) AT THE MID-LAKE STATION OF LAKE TAHOE, 1969-1971.
DEPTH
M
0
50
100
200
300
WO
DEPTH
M
0
50
100
200
300
400
1969
Nov
13
9.32
8.73
4.96
4.64
OCT
16
13.21
7.51
5.36
1,86
4.69
4.64
DEC
17
7.42
7.39
5.28
4.66
4.62
4.61
Nov
17
9.57
9.23
5.44
4.87
4.69
4.64
1370
JAN
2
6.40
6.22
6,11
4.62
4.61
DEC
30
5.85
5.73
5.66
4.85
4.70
4.66
JAN
20
5.72
5.54
5.37
4.73
1971
JAN
25
5.21
5.03
4.98
5.00
4.78
4.70
FEB
5
5.29
5.25
4.95
—
FEB
10
5.44
4.91
4.87
4.78
4.68
4.66
FEB
25
5.64
5.12
4.96
4.94
4.67
4.62
FEB
24
5.25
4.89
4.88
4.87
4.74
4.68
MAR
13
5.97
5.03
4.95
4.81
4.65
4.62
MAY
10
6.99
5.23
4.92
4.76
4.70
4.67
APR
9
6.82
5.18
5.09
4.82
4.64
4.61
JUN
3
9.03
6.39
5.13
4.73
4.77
4.66
MAY
5
7.61
5.19
4.93
4.76
4.66
4.64
JUN
30
13.13
6.81
4.99
4,74
4.74
JUN
2
11.37
5.58
5.14
4.76
4.66
JUL
16
13.10
6.40
5.00
4.74
4.70
4.67
JUL
3
14.69
6.20*
5.34
4.84
—
AUG
4
20.35
6.33
5.05
4.74
4.70
4.67
AUG
3
13.82
6,48
5.38
4.85
4.70**
4.86**
AUG
26
19.66
—
5.03
4.75
4.70
4.66
SEP
9
17.73
6.95
5.56
4.95
SEP
14
18.10*
7.80
5.02
4.75
4.70
4.68
OCT
1
14.35
7.17
5.34
4.85
4.67
4.63
OCT
6
13.70*
6.87
5.03
4.75
4.69
4.68
OCT
5
14.11
—
5.34
4,84
4.68
4.64
DEC
8
6.60*
6.44
5.36
4,78
4.72
4,69
* TEMPERATURE AT THIS DEPTH MEASURED WITH A THERMISTOR,
** TEMPERATURE AT THIS DEPTH MEASURED AUG, 5, 1970.
-------
CALORIES-MONTH"1-cm"3
-4 -3 -2 -I
u
10
20
30
40
to
E
ieo
Q.
LJ
°70
80
90
100
110
I?O
\ FEB
JAN-*\ ^
1
i
\
—
—
\
Lake Tahoe \
~ Heat Storage \
Averaged 1967-70 i
- JAN. - JUNE 1
\
j
i
\
i
—
//MAR' .'' ' V
.'APRIL MAY / '•
\^ V I
I JUNE...--'/"
j/*"" /
/ /
/] (
(1 /
i/ 1
! 1
! !
1
* 1
I '
Figure 9. Monthly (January-June) heat storage-depth profiles at the index
station of Lake Tahoe calculated from 1967-70 temperature data.
50
-------
CALORIES-MONTH"'-cm"3
-4
-3
Lake Tahoe
Heat Storage 1
Averaged 1967-70 *
JULY -DECEMBER
Figure 10. Monthly (July-December) heat storage-depth profiles at the
index station of Lake Tahoe calculated from 1967-70 temper-
ature data.
51
-------
10
i
o
0
a
o
-2
-3
-4
LAKE TAHOE HEAT
STORAGE1. Averaged 1967-1970
Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Figure 11. Seasonal heat storage at 0, 33, 66, and 99 m at the Index station of Lake Tahoe
calculated from 1967-70 temperature data.
-------
J
M
~r
A
M
15
10
t_n
LO
LAKE TAHOE TEMPERATURE
AVERAGED 1967-1970
Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec
Figure 12. Seasonal temperature at 0, 15, 24, 27, 33, 45, 66, and 99 m at the index station
of Lake Tahoe calculated from 1967-70 temperature data.
-------
at greater depth. Measurements by Goldman and Bachmann (unpublished)
showed a 10 m displacement of the discontinuity layer by an internal
seiche. Year-to-year fluctuations in meteorology are responsible for
some of the variation observed.
Well-defined stratification occurred during two years when mid-summer
temperatures surpassed the 20°C mark. In 1967, stratification was
most pronounced in late August and the upper 12 m of water was almost
homothermous at 20-21°C. A similar situation appeared in late August of
1969 when the top 20 m was above 20°C and sharp stratification was evi-
dent below that depth. The intervening years have less well defined
periods of stratification, but all, except 1968, reach surface tempera-
tures above 20°C. The lower epilimnion temperatures present in 1968 may
account, in part, for the lower level of primary production that year
(Fig. 21). The influence of temperature on primary productivity is
further discussed in Section VI and comparison of their vertical profiles
is illustrated in Figure 20 for some days in 1969.
The significance and extent of winter mixing in Lake Tahpe cannot be
fully understood from the isotherm plots of the index station, Lake
Tahoe is generally considered to be a monomictic lake (mixing completely
once a year), but as with other lakes is influenced by variations in. the
weather. The assumption that the lake undergoes complete mixing each
winter was not shared by all and remained speculative until 1973. Data
on deep temperature and oxygen stratification (Table 6 and Table 17),
and chlorophyll and other organic and inorganic substances (Kiefer et a,l,
1972) indicate the total mixing of the entire water column to depths in,
excess of 450 m might be more complex than originally thought and possibly
not completed each year.
Following the completion of the present study, the question of how com-
pletely the lake mixed was examined in more intensive fashion. Vertical
54
-------
profiles of NCL-N have characteristically shown a severe depletion in
the euphotic zone. Using this nitrocline it was possible for Paerl
et al. (1974) to demonstrate beyond doubt that the severe winter of
1972-73 did cause a complete turnover of Lake Tahoe. The importance of
this finding can scarcely be over-emphasized and leads us to believe
that the lake will not completely mix during milder winters.
The principal investigator had previously noted an increase in the
maximum summer surface temperature (18°C in 1965 to 20°C in 1968) coin-
cided with increasing productivity of the surface waters and speculated
that surface warming could be due to a decreasing transparency of the
surface waters (Goldman, Moshiri, and Amezaga 1972). With the aid of a
meterologist (Dr. L. Myrup) and a physicist (Dr. T. Powell) he began in-
vestigating the possible consequences of an alteration of the heat
storage pattern within the lake.
A Decrease in the Heat Budget of Lake Tahoe, California-Nevada by
Cultural Eutrophication
The hypothesis that increasing pollution of the lake will ultimately lead
to cooler wintertime water and that, since the lake now approaches 4°C
in winter, the surface of the lake might even freeze in some future
winter has been investigated. This hypothesis has been tested by means
of a physical laboratory model which reproduces, in miniature, those
heat transfer processes which were selected as critical to this problem.
The model generates temperature profiles and heat budgets which are sim-
ilar to real-world lakes and oceans. A series of experiments have been
conducted with this model in which the thermal behavior of clear and
turbid water is compared. Without exception, the turbid waters become
cool relative to clear waters. The "turbidity cooling" mechanism pro-
posed here (i.e., that increased turbidity will cool systems which
closely resemble natural lakes) is plausible, but further, more closely
55
-------
controlled experimentation on the model associated with field studies
will be necessary before credible statements concerning the magnitude
of the effect can be made.
The annual temperature stratification cycle of Lake Tahoe is shown in
Figure 13. The lake is nearly isothermal during the winter months with
a temperature approaching 4°C (the point of maximum density of water).
In the summer months, the lake develops a three layer structure typical
of large lakes and oceans. The upper layer (epilimnion), with nearly
uniform temperature, is separated from the cool lower layer (hypolimnion)
by a region characterized by a large temperature gradient (thermocline
or discontinuity layer). This thermal profile is thought to be the
result of interaction between absorption of solar radiation, roughly
exponential with depth, and wind induced turbulence generated at the
surface of the lake which acts to produce the isothermal epilimnion.
A change in transparency of the lake has been documented by aircraft
photographs (Goldman et al. 1974) showing spectacular local increases
of turbidity due to inflow of sediment and nutrients from areas dis-
turbed by the many construction activities, of the basin. The augmented
nutrient supply has resulted in increased algal growth in the littoral
•
zones close to the sources of pollution (Goldman, Moshiri, and Amezaga
1972). A summer increase of temperature could then be accounted for by
increased absorption of solar energy by the increasingly turbid lake
waters. However, the additional heat content of the surface water,
gained at the expense of the deeper waters, would be more easily lost
through the increased evaporation and sensible heat transfer to the at-
mosphere during the fall than it would be if distributed throughout the
water column. The net effect of these processes, when the winter iso-
thermal period arrives, would be a cooler lake. If a cooling trend con-
tinued for several years, the winter lake temperature would fall below
that of the maximum density of water. Under these conditions, the
56
-------
0
WATER TEMPERATURE (°C)
,0 4 8 12
a.
Ul
o
^~ THERMOCLINE
100
Figure 13. Annual temperature stratification cycle of Lake Tahoe, winter
(A) and summer (B).
57
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coldest water would then be buoyant and would rise to the surface, and
the radiation loss to space during a clear, calm, winter night could
freeze the surface waters.
Although bays occasionally freeze, there is no record of a frozen Lake
Tahoe. Such a spectacular environmental modification would have pro-
found effects on the biota at all levels of the food chain, and there-
fore, the possibility deserves serious study. Some of the possible
ecological consequences of a freeze are the following:
1. Study of the plankton communities in Lake Tahoe (Richerson, Armstrong,
and Goldman 1970) indicates that roughly 80% of the biomass of phyto-
plankton is produced before the summer months. A large amount of
the total primary productivity of the lake occurs during the first
five months of the year while its vertical curve is "unimodal" and
the lake is unstratified (see Section VI). These phytoplankton
organisms form the base of the food chain in the lake. A layer of
ice followed by the inevitable heavy winter snows in the area would
block much of the light now reaching the winter plankton. Since the
resident phytoplankton require this light energy to live, it is
possible that a significant change in both biomass and productivity
would result from a frozen Tahoe. It is probable some species of
phytoplankton best adapted to frozen alpine lakes would become dom-
inant in place of the present three dominant species.
2. It is possible that the numbers of bacteria (detritus feeders)
would increase in proportion to the phytoplankton, since these
organisms are less affected by low light conditions. The place that
bacteria occupy in freshwater food chains has been little studied
and initial indications are that they may already play a significant
role in Lake Tahoe (Paerl and Goldman 1972a).
58
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3. Another undesirable effect is oxygen depletion, which might begin to
occur at the sediment-water interface if Lake Tahoe remained ice-
covered for extended periods of time in winter. This effect would
make itself felt directly on such members of the Tahoe food chains
as the sculpin, lake trout, and crayfish that utilize the lake
bottom. These organisms are adapted to cold, oxygen-rich waters.
Low oxygen conditions in winter could eventually result in reduction
of their numbers.
4. Perhaps the most important effect of a frozen Tahoe would be the
consequences of arresting the long winter circulation. Anaerobic con-
ditions at the sediment-water interface could then develop causing
insoluble ferric phosphate to be converted to soluble ferrous phos-
phate. Since the lake shows distinct iron and nitrogen limitations
(Goldman 1964), a spring bloom would almost certainly result from
the release of nutrients during what could amount to winter stagna-
tion in the deep waters of the lake.
Although ecosystem dynamics are still too primitive to discriminate
among these possibilities, or others for that matter, ecologists agree
that any radical change at the base of the trophic structure is likely
to make itself felt drastically throughout the whole food chain. Until
the biota adjust to the new regime, Tahoe residents and visitors could
expect a great change in the lake's organisms.
The physical model, shown schematically in Figure 14, consists of a Cubic
foot of water, heated from above by an ordinary 200 watt incandescent
light bulb. The light is contained within a parabolic reflector which
delivers 180 watts to the water surface. The surface waters are agitated
by a wire grid (28 gauge wire, 18 x 14 wires-in ) which is oscillated
in the vertical direction with a stroke of 0.79 cm at a frequency of
59
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Voltage
Amplitude and
Period Control
Agitation
Amplitude
and
Frequency
Con trol
Support Table
LAKE MODEL APPARATUS
Figure 14. Schematic diagram of the Lake Tahoe physical model.
-------
3.75 Hz. The turbidity level was controlled by adding calibrated amounts
of Nigrasin dye to the water. In the experiments reported here, a dye
concentration of 0.040 g-1 was used. The evaporation rate (latent
heat loss) and rate of sensible heat transfer to the air were controlled
by varying the ventilation of water surface. The physical model is re-
lated to experiments performed by Rouse and Dodu (1955) and Turner and
Kraus (1967). The experiment reported here differs from its predecessors
in that the thermocline is achieved by differential heating rather than
by artificially setting up a fresh-over-salt water stratification.
In designing this apparatus, the following processes were chosen to
model: (1) absorption of visible and infrared radiation at a rate de-
pendent on water turbidity and distance from the surface, (2) mixing of
heat by turbulence generated near the surface, and (3) removal of heat
from the water surface at a rate dependent on the ventilation. No
attempt has been made to achieve geometrical similarity with the Lake
Tahoe basin nor to model realistic generation of turbulence by shearing
motion or wave breaking. The hypothesis is that the heat budget is in-
sensitive to the mechanism by which the surface waters are mixed.
A series of experiments were performed in which the system parameters
(water turbulence level, light intensity, water turbidity, and ventilation
rate) are varied to resemble seasonal changes. At periodic intervals,
the water temperature profile and the water level are measured in order
to obtain the evaporation rate. Figure 15 shows results from a typical
pair of experiments in which the light was set at full intensity for one
i
hour and then turned off for an additional hour. All other parameters
were held constant during these experiments. In one run, clear tap
water was used on the working fluid and in another run, dye was added
to the water. The extinction depth D is defined by,
R(z) = R e'Z/D
o
where R(z) is the downward flux of radiation at depth a, R is the flux
61
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(Ti
S3
21
TEMPERATURE (0°C)
21.5 22 22.5
23.5
PHYSICAL LAKE MODEL
TEMPERATURE SOUNDINGS FOR
CLEAR WATER CASE
SOUNDINGS AT HALF-HOUR
INTERVALS
LIGHT TURNED OFF DURING
SECOND HOUR
CONSTANT VENTILATION
THROUGHOUT EXPERIMENT
WATER AT 2I°C INITIALLY
DEPTH AVERAGED TEMPERATURE
Figure 15. Results of two typical physical model experiments.
-------
which has been absorbed at the surface, and D is the depth at which R(z) =
R /e. D, a strongly wavelength dependent quantity, was measured in the
visible range (0.35-0.65 ji) by means of a photometer (Weston 594) soun-
ding. A value was estimated and averaged over all wavelengths by means
of a calorimeter technique. For the "clear" experiment, D = 100 cm in
the visible and 42.3 cm overall, including the strongly absorbing infra-
red portion of the input spectrum. For the "turbid" water, D = 6.99 cm
in the visible and 0.78 cm overall. In Figure 15, n temperature series
is presented made at half-hour intervals for "clear" water. The model
can be seen to develop the three layer temperature profile characteristic
of lakes and oceans during the late spring, summer, and early fall. The
companion "turbid" experiment was initiated at the same temperature
(21°C) and developed a similar temperature profile, but cooled steadily
relative to the "clear" experiment. The curves at the lower portion
of Figure 15 show the depth-averaged temperature for the two experiments.
At the end of the two-hour experiment, the "turbid" system was 0.54°C
cooler than the "clear" system.
In all the experiments a similar "turbidity cooling" effect was observed
for depth-averaged temperature. In experiments in which the ventilation
rate was low or zero, the surface waters of the "turbid" system warmed
relative to the "clear" system. The depth-averaged temperature after a
"seasonal" cycle, however, was cooler for the "turbid" system. An al-
ternative explanation of the decreased temperature of the "turbid" ex-
periment relative to the "clear" experiment shown in Figure 15 is that
the humidity changed from run to run and caused an increased evaporative
heat loss in the "turbid" experiment. Later studies, carefully controlled
for ambient humidity, show the same "turbidity cooling" effect, but with
a smaller magnitude. On the basis of the experiments reported here, the
hypothesis that turbid lakes will cool relative to clear lakes is plaus-
ible in the sense that the effect can be observed in a laboratory system
"similar" to real lakes. If the pollution of Lake Tahoe were to continue,
63
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it is possible that the lake will freeze. However, the crucial question,
namely, how long would the observed increases in surface turbidity have
to persist in order to freeze the lake, cannot be answered at this time,
because little is known concerning the relative magnitudes of the various
terms in the energy budget for both the model and the lake.
The next step in this study will be to establish the numerical magnitude
of the "turbidity cooling" effect for real lakes so that the effect of
a given increase of organic or inorganic turbidity can be predicted.
The following approaches are now being made to the problem: (1) An
automated limnological and meteorological station at Lake Tahoe which
will provide information needed to estimate the heat budget of Lake
Tahoe is being established. (2) A numerical model of heat transfer
processes in lakes is being formulated. (3) An improved version of the
physical model has been constructed which will be operated on a com-
puter-controlled basis. This model can be installed on an existing ro-
tating platform facility if it seems desirable to add rotation effects
to the model.
GEOLOGY
Lake Tahoe lies in a deep, graben basin which is steep-sided and flat-
bottomed. Its bathtub-like morphometry is interrupted on the sides by
several canyons which resemble, on a smaller scale, the submarine canyons
along the California coast. Several small lake mounts extend up from
the lake bottom. Although the basin morphometry had been contoured by
a U.S. Coast and Geodetic Survey using wire sounding in 1923 (Chart 5001),
a more accurate bathymetric map was produced in conjunction with the
present study by University of Southern California personnel in coopera-
tion with University of California, Davis investigators.
The geological history of the Lake Tahoe basin is complex and the
64
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underwater geology was relatively unknown until the present studies were
undertaken. Lake Tahoe lies in a deep basin formed both by tectonic and
volcanic processes and subsequently modified by glaciation and sedimen-
tary deposition. The basin is the southernmost in a series of tectonic
depressions (grabens) that ran southeasterly from Mt. Lassen (Batemann
and Wahrhaftig 1966). Sierra Valley to the north and Carson Valley to
the east are dry basins formed in this manner.
Man has influenced the sedimentation rate at Tahoe on two major occasions.
During the Comstock mining days many areas of the basin were logged.
More recently the explosive building development in the basin has in-
creased the sediment load greatly wherever new roads and houses have
gone in. The sediment increase through development from the Upper
Truckee River was estimated at twice the natural rate in the late 1960's
(State of California Resources Agency 1969).
Methods
Investigation of the subaqueous geological features involved use of
equipment for surface sounding and sediment sampling. Subsurface sounding
and sediment coring was also included for detection of hidden geophysical
features. Navigation on all across-lake runs and locations of piston
cores and other bottom samples was accomplished by sextant triangulation
on lakeshore landmarks.
A bathymetric map was constructed from a precision depth-recorder survey
using a Gifft recorder and EDO transducer, seismic reflection profiles,
and lead-line soundings from U.S. Geodetic Survey chart 5001. Supple-
T>
mental soundings were taken with a recording Raytheon DE-721A Fathometer
Depth Sounder. Continuous seismic reflection data of the extent of sub-
surface layering and sediment thickness were recorded by a Bolt Associates
PAR model 600 air gun with a 1 cu. in. chamber firing 1400 psi, a model
65
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1011 hydrophone streamer, and a model PA-7 preamp/fliter. A sound velo-
city of 1463 m-sec in water and 1524 m-sec~ in sediments was used for
depth and sediment thickness computations, respectively. Fault lines
and other subsurface features such as volcanic intrusions were detected
by towing a Varian rubidium magnetometer behind the boat which was wired
to shipboard recording instruments.
Core subsamples for textural analysis were wet-sieved through a 62 P
Tyler sieve to separate the sand + gravel fraction (>62 p) from the silt
+ clay fraction (<62 y) . The sand 4- gravel fraction was further separated
by courser sieves, dried, and weighed in pre-tared aluminum dishes. The
silt + clay fraction was filtered through pre-weighed GFA filters, oven-
/
dried, and weighed. Separation of clay from the heavier silt was done
by gravity settling and decantation of clay five times. Organic matter
(chiefly pollen) flocculation problems were alleviated by H_0? solubili-
zation. Clay was classified as particles less than two microns to
facilitate X-ray diffraction analysis. Silt fractions (2-62 y) were
air-dried and weighed in pre-tared aluminum dishes.
X-ray diffraction analysis of clay fractions was done on a G.E. XRD-5
unit. Four patterns were run for each sample with the following treat-
I | _j_
ments; Mg saturated, solvated with glycerin, K saturated, and heated
to 500°C. Sands were stained with sodium cobaltinitrate and amaranth
for feldspar detection and examined microscopically to estimate mineral
components. To aid in identification of mineral grains, selected samples
were examined with a petrographic microscope.
Organic carbon in the top 0-2 cm of several cores was detected gasometri-
cally. Samples were burned in a LEGO induction furnace and the C0«
released was measured with a Beckman infrared analyzer. Pollen and dia-
tom frustule content in cores was estimated by microscopic examination
of discrete subsamples. Diatom species and abundance were also determined
66
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for one complete mid-lake core. Age of core sediments by carbon dating
was done by the Age Determination Laboratory of Isotopes, Inc.
Results
Quaternary History -
About 2 million years ago, volcanisms and tectonics closed the basin
at the northwestern edge and began the formation of geological features
as we know them today. Pleistocene glaciers along the south, west, and
northern shores scoured and eroded basin topography from basin crests
to the lake shore. The formation of Emerald Bay, Cascade Lake, and
Fallen Leaf Lake indicate the extent to which glaciation reached the
lower elevations. Less visible today, but highly significant to Tahoe
basin topography, was the work of glaciers at the northwestern edge of
the basin and intermittent ice-damming of the Truckee River outlet. On
several occasions, the lake level rose as much as 250 m above its present
elevation and glacial outwash deltas built up to a corresponding lake
level. When the outlet ice dam eroded away or broke, a rapid lowering
of the lake level brought about catastrophic slumping of the once-submer-
ged deltas down the steep western and southern shores and some deltaic
debris were carried out over the central lake floor (Hyne et al. 1972).
This event apparently occurred several times during and at the end of
three glacial periods.
Interglacial periods were characterized by a comparatively slow deposi-
tion of a well-layered "rain" of suspended fine sediments which "ponded"
in depressions around the mid-lake bottom topography. Today only
scattered tops of the slump deposits, covered by a thin layer of fine
sediments, remain above the relatively flat central lake floor.
Terrestrial Geologic Features -
Rocks of t'l.e Tahoe basin are divided into four major categories (Fig. 16),
67
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ROCK TYPES
fej GRANITIC
0 VOLCANIC
£3 GLACIAL DEPOSITS
H METAMORPHIC
El LAKE BEDS
CONTOUR INTERVAL
600 FT
BOUNDARY OF
LAKE TAHOE
DRAINAGE BASIN
Figure 16. Distribution of rock types in the Tahoe basin.
68
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Granodiorite is the most abundant granitic bedrock and predominates
along the mid-western lake shore, around the southern end of the basin
at high elevations, and along most of the eastern side of the basin.
Metamorphic rocks occur as roof pendants in the granitics at isolated
high elevations on the east, south, and west sides of the basin. Vol-
canics occur primarily along the north and northwestern shores and at
the remote south end of the basin. Recent volcanism (Holocene) is evi-
denced by the well-preserved cinder cones near Tahoe City.
Quaternary sediments, the fourth category, are glacier and lake bed de-
posits laid down or distributed during the pre-Wisconsin and Wisconsin
periods of the Pleistocene glaciation. Four glaciations within that
period affected the Lake Tahoe area. The Hobart, Conner Lake, and
Tahoe glaciations (Birkeland 1964) are thought to have produced most of
the present day relief above and below the lake surface. The more
recent Tioga glaciation played a lesser role in formation and redistri-
bution of-deltaic slump deposits along the western and southern shores.
Pleistocene glaciation was limited to the western Sierra Nevada side of
the basin and a rain shadow produced by the mountains kept the eastern
shore and Carson Range from experiencing glaciation.
Bathymetry -
The sub-surface relief of Lake Tahoe in Figure 1 indicates that the
basin is steep-sided and fairly flat-bottomed. Two large shelf areas
occur at the south end and on the northwest shore. Numerous canyons
and gullies bisect the bottom contours. Some of these can be traced to
the mouths of present day streams, but others show no link with terres-
trial drainage patterns.
The east and west sides are fault scarps with slopes averaging about 30C
although the fault lines are neither evident from seismic reflection
profiles nor visible from land because of the glacial outwash cover.
69
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The northern subsurface relief at North Stateline Point and Crystal Bay
exhibit spectacular ridges of bedrock T,dLth slopes approaching nearly
45° and ponded sediments between them. The North Stateline bedrock
trends northwesterly some 5 km before disappearing under central lake
floor sediments.
The southern shore is characterized by a wide, shallow shelf which drops
off rapidly after passing about 5-m depth at a slope of about 11°. Slump
mounds occur all down the slope to the relatively flat central lake floor
which is dotted with numerous high energy slump "lake mounds" (Goldman
and Court 1968; Hyne, Goldman, and Court 1973). These mounds number at
least 15 of significant size; the largest approaches 130 m in height
and has a slope of 17°. The tectonic origin of these mounds from the
times of glacial ice dam breakage appears to be supported by the nature
of sediments surrounding the base of such mounds. The sediments are
neither upbent nor downbent which indicates deposition after the mound
formation. Volcanic origin is ruled out because magnetic field varia-
tions between the mounrJs and adjacent sediments are nearly non-existent.
Further evidence of the mound origins is revealed by piston cores. About
1 m is fine-grained turbidite characteristic of interglacial and Holocene
depositional periods. Below that level, the sediment is a chaotic jumble
of clay to cobble-sized fractions. The similarity of these mounds to
the size and structure of off-shore oceanic mounds and abyssal hills of
abyssal plains is striking (Menard 1964).
Geophysical Data -
Neither total sediment thickness nor maximum number of layers was record-
ed during the r-tudies due to equipment limitations. However, indica-
tions are that central lake floor sediments are much more than 400 m
thick in some areas, because no signs of bedrock were detected by seismic
reflection equipment over a large portion of the mid-lake bottom. The
70
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well-layered surface sediment extends to only 40 m and alternate layers
of jumbled, chaotic and level, well-layered sediments continue downward
to the detection limit. Hyne et al. (1972) have estimated that the
depositional rate is at least 12 cm-1000 years .
Heavier glaciation of the western and southern portions of the basin has
resulted in a larger deposit of sediments along the western bottom than
is found below the eastern shore. The sediments also dip westward,
indicating more extensive faulting along the western edge of the graben.
The bottom from Sugar Pine Point to Dollar Point is a chaotic jumble of
slump blocks. Seismic reflections of the southern edge of the lake basin
indicate the presence of two or possibly three major deltaic sediment
surfaces buried beneath the present delta. This supports the possibility
that the three glaciations affecting Lake Tahoe basin topography con-
structed consecutive glacial outwash deltas which slumped and were buried
by subsequent deltas.
Carbon dating of sediments has revealed that rapid deposition character-
ized the earliest stages of Tahoe basin formation. A core from mid-lake
had an age of about 7000-8000 B.P. from the 250-580 cm depth. Volcanic
ash layers above it date from around the time of the Mount Mazama
eruptions (6000-7200 B.P.). The top 25 cm of the core was dated at about
2060 B.P. About 30 cm of Tecent sediments was lost during the coring
operation for which no dates are available, possibly accounting for the
age of the uppermost core sample.
Surface Sediments -
Investigation of mineral and biogenic components of the surface sediment
at 40 sites reveals two main sediment types in Lake Tahoe. One is an
organic ooze of postglacial origin, slowly deposited in flat-lying beds,
homogenous in composition, containing a high proportion of diatoms and
pollen and chloritic intergrades, and derived mainly from granitic rocks.
71
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The granitic rocks predominate over about 70% of the basin (McGauhey et
al. 1963). The other type is non-organic in origin with an inhomogenous
texture, chaotic organization, rapid deposition during glaciation, high
in vermiculite, mica, and montmorillonite. Its source is from both
granitic and volcanic rocks. Pollen is absent or rare. Differentiation
of the two sediment types was clear. Most samples were organic ooze
composed of 50-90% diatoms and pollen. The non-organic sediment sites
contained less than 10% organic material. Most of these sites were on
the northwestern side of the basin and at lake mound locations.
It is notable that neither diatom species nor size variation was signifi-
cant throughout a single 90 cm core taken from mid-lake for microscopic
examination (Table 7). Curiously enough, there is a complete lack of
Fragilaria crotonensis throughout the length of the core. This diatom
is now the dominant type in Lake Tahoe, both in biomass and numbers.
Because of core top disturbance during sampling, it is not known if this
influx of a new dominant algal species is a current event or began in
recent geological time. This discrepancy may signal a subtle ecological
change in Lake Tahoe, but further samples will be needed for confirmation.
It is possible that a gradual increase in the lake nutrient level is
responsible. Hutchinson (1968, p. 483) notes that ]?. crotonensis is
readily able to utilize nitrate-nitrogen at the expense of other species.
Temperature, light, and species compositional changes may all have
played an important role in the change.
Sediments in the coarse fraction (>62 y) included many volcanics, notably
hypersthene, feldspar basalts, sphene, hornblende, and quartz. The fine
fraction (<62 y) included montmorillonite and mica from volcanic sources
and vermiculite and chloritic intergrades derived from the granitic rock
which is dominant over about 67% of the basin.
Six tributaries, also samples for mineral type, mirror their drainage
parent rock type in their sediment load. The Upper Truckee River,
72
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TABLE 7, DIATOM SPECIES IN A 90 CM CORE TAKEN FROM MID-LAKE TAHOE.
FAMILY: BACILLARIOPHYCEAE
ACHNANTMES CLEVEI
LANCEOLATA
tCLLLL
PERAGALLI
AMPHORA OVALIS
COCCONEIS DISCULUS
PLACENTULA
RUGOSA
CYCLOTELLA BQDANICA
OCELLATA
STELLIGERA
CYMBELLA GRACILIS
LANCEQLATA
VENTRICOSA
SINUATA
PROSTR
DlATOMA ANCEPS
DlPLONEIS ELLIPTICA
OCULATA
FINNICA
EPITHEMIA SOREX
TURGIDA
ZEBBA
EUTQNIA NAEGELII
IENEUA
FRAGILARIA INTERMEDIA
P1NNATA
CONSTRUENS VARBINODIS
LEPTOSTAURQN
FRUSTULIA RHOMBOIDES
GOMPHONEMA ACUMINATUM
HANTZSCHIA AMPHIOXYS
MASTOGLOIA SMITHII
MELQSIRA CRENULATA
HER ID ION C1RCULARE
NAVICULA AURORA
B6C1LUM
COCCINIFORMIS
EXIGUA
HUTICA
PSEUDOSCUTIFORMIS
PUPULA
RADIOSA
CAP1TATA
NlTZSCHIA FILL1FORMIS
AMPHIBIA
OPEPHORA MARTYI
PiNNULARIA BICEPS
AESTUAR1I
ABAUJENSIS
RHOICOSPHENIA CURVATA
RHOPALODIA GIBBA
STEPHANODISCUS ASTREA
SURIRELLA OVATA
RUMPENS
ULNA
INCISA
TABELLARIA FLOCCULOSA
TETRACYCIUS LACUSTRIS
73
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Incline, and Eagle Creeks flow over mostly granitic rock while Blackwood
and Watson derive their mineral content from volcanic sources. Glenbrook
Creek traverses both types of rock. Figure 17 illustrates the percentages
of coarse and fine mineral constituents found at major lake and stream
sampling sites.
Lithology of the sediments falls into four basic types:
1. Well stratified, flat-lying sediments in the deepest central floor
and "ponded" in depressions surrounding lake mounds. These are
usually composed of homogenous organic type sediments, rich in
diatoms and pollen, which result from slow deposition during inter-
glacial periods.
2. Contorted, jumbled layers exposed in lake mounds rising in relief
above the central floor. These sediments are texturally inhomogenous
and non—organic in type.
3. Deltaic deposits on the steep slopes and periphery of the central
floor. They occur chiefly on the western and southern shore in the
form of high energy slump features. They are inhomogenous, chaotic
and composed of coarser materials deposited rapidly in outwash deltas
during glacial times and redistributed by slumping when the lake level
fell rapidly.
4. "Bedrock" with little sediment cover is located in isolated spots
along the fault scarp at North Statelire Point and in Crystal Bay.
This type of granitic rock is also indicated by soundings off Emerald
Bay and Zephyr Point.
Explanation for the non-uniform distribution of the biogenic components
(pollen and diatoms) in the organic ooze possibly lies in their differing
hydrodynamic properties. Court, Goldman, and Hyne (1972) infer from
74
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Silt SgndS
Gravel
Weight percent
Figure 17. Grain—size distribution in cores from Lake Tahoe. Coarse-
grained samples (13, 23, 27, 31) reflect the steep, granitic
eastern side-wall.
75
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their analysis that diatoms are less transportable than pollen and less
subject to windrowing at high energy wave and current sites. Because of
this, pollen tends to accumulate at low energy sites and diatoms do not.
It is also suggested that pollen could be selectively destroyed in an
oxidizing environment, but this seems unlikely in Lake Tahoe because
of high dissolved oxygen contents measured at all locations and depths.
The apparent lack of diatoms and pollen in sediments from periods of
glaciation can be explained by lower lake and air temperatures which
reduced aquatic and terrestrial growth seasons and areas. The biogenic
materials produced were also heavily diluted by the tremendous increase
in lithogenic materials through accelerated erosion and weathering.
The apparent dominance of chloritic intergrades derived from granitic
sources in the organic ooze sediments is linked to previous glacial
action on the two prominent basin rock types. Glaciation was evidently
heavier in volcanic rock areas and, thus, more interglacial period
erosion of weathered material occurred in the granitic areas and led to
deposit of more chloritic minerals.
The present day surface sediment composition of Lake Tahoe has undoubted-
ly played an important role in selection of benthic flora and fauna and
their distribution on the bottom. Not only is the type of substrate
important, but the nutritive capabilities of the deposits may be critical.
This is discussed in the following chemical section (V) on the nutritional
effect of pollen to increasing primary productivity of Lake Tahoe
(Richerson, Moshiri, and Godshalk 1970).
The processes of erosion and sediment deposition by basin streams have
only recently come under intensive investigation. The State of California
Resources Agency conducted sedimentation and erosion studies in the
Upper Truckee River and Trout Creek watershed in 1967-1968. Accelerated
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erosion resulting in doubling of natural sedimentation rates was attribu-
ted to construction in developing areas on a relatively small percentage
of the total watershed (State of California Resources Agency 1969). Far
more dramatic sediment increases have been noted by Glancy (1971, 1973)
on five creeks in the Incline Village area in Nevada. Development areas
were estimated to yield 12-13 times more sediment than undisturbed areas
over two water-years ending 30 September 1971- These studies are con-
tinuing in order to provide a valuable quantitative assessment of sedi-
ment yields during the period of "healing" of large areas of nearly com-
pleted construction in the watersheds.
The U.S.G.S. is conducting streamflow and sediment studies on several
other major streams in the Tahoe basin. The most intensive study is
being conducted cooperatively with the Tahoe Research Group (under the
direction of Dr. Charles R. Goldman) in the Ward Valley watershed near
Tahoe City. Standard methods of water discharge and sediment measurement
and analysis are being combined with detailed research into the hydrogeo-
chemical processes in the watershed. The primary goals of the project are
to establish base water quality levels in Ward Creek prior to major recrea-
tional development, to relate development effects to possible changes in
water quality and to recommend methods of preserving water quality during
and after development.
The complete 1972-73 water-year of data has been compiled and is in the
process of analysis. Preliminary comparison of data from Ward and Incline
Creeks reveals that sediment concentrations in Incline were many times
higher than in Ward Creek under comparable flow conditions. Disturbance
by construction in Ward Valley is as yet minimal. The continuing applied
and basic research program of the Tahoe Research Group is providing up-
to-date assessment of changes in quantity and quality of sediments and
dissolved nutrients in Ward Creek as the terrestrial environment of the
valley is transformed from natural to developed. The ultimate intensity
of the development is as yet unknown.
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SECTION V
LAKE WATER CHEMISTRY
Water chemistry analyses at many locations reveal a remarkable seasonal
and areal uniformity in water quality for most parts of the lake. Near-
shore variations tend to be more pronounced, localized, and transient
especially in the vicinity of tributary stream inflows. Although 90-95%
of Lake Tahoe's surface and deeper waters remain of extremely high water
quality, inshore sampling reveals some disturbing increases in the con-
centration of important bio-stimulatory nutrients. See Section VII on
tributary-lake transects for further evidence of this condition.
INVESTIGATIONS
In general, water chemistry of the main body of Lake Tahoe is a much
poorer indicator of lake fertility than the phytoplankton and periphyton
communities that utilize the nutrients. If one were to base opinions as
to Tahoe's present and future condition strictly on these parameters,
one would be forced to the conclusion (as has already happened) that the
water quality has not deteriorated. The evidence presented in Sections
VI, VII, VIII, and IX of this report clearly evidence the fact that the
lake has already undergone a degree of cultural eutrophication and will
continue to increase in fertility at an unnaturally high rate until
population, vegetation, and land management controls stem the flow of
nutrients from its many disturbed watersheds. Sewage diversion was a
78
-------
major step in this direction. Drainage and vegetation control must now
follow.
Methods
A variety of methods has been used in the chemical analyses presented
in this section. Most of the standard methods are not of sufficient
sensitivity for working in the low parts per billion (or pg*l ) range
typical of Lake Tahoe's waters. Considerable attention in the research
program was directed towards modifying existing procedures to deal with
Tahoe's ultra-low levels. These chemical methods with their modifica-
tions are included as Appendix E of this report. Ammonia determina-
tions in Tahoe have been a particularly difficult problem. Current
levels have been near zero and it is difficult to get blanks as low in
ammonia as the lake water. For this reason, the ammonia determinations
for the lake have not been included in this report. Both nitrate and
phosphate methods were changed after 1968. Comparisons with the 1968
data are therefore less reliable than subsequent years.
Oxygen samples were collected in conjunction with the temperature and
water chemistry samples for our study of Lake Tahoe deep water limnology.
A series of three Van Dorn, non-metallic water samplers were placed on
the hydrographic wire two meters above each reversing thermometer
frame and tripped in sequence with the thermometers. Samples were
drawn off immediately upon sample retrieval into 125 ml Pyrex bottles
fitted with tapered, ground-glass stoppers and teflon stirring bars.
Each calibrated bottle (nearest 0.1 ml) was stoppered and then opened
for immediate addition of 1.0 ml of MnSO, and alkaline-iodide. Samples
were stored in a cool, dark chest and acidification and titration done
within 2-4 hours. The method used a micro-Winkler technique (Carpenter
1965) employing a 5-place micro-burette. All depths were sampled in
triplicate and oxygen results computed as the average of the three
79
-------
readings. Thiosulfate was standardized using 0.1 N KI03 taken from am-
poules which were run before, during, and after sample titrations.
The determination of total particulate carbon as a measure of seston
content in Lake Tahoe was carried out during the course of the study at
every index station and for most synoptics and other specialized studies.
A 2-liter sample was taken in opaque glass bottles at each sampling
depth and stored under refrigeration. The sample was split into 1-liter
aliquots and passed through a 25 mm Whatman GF/C glass-fiber filter
under 20 Ib. vacuum pressure. The glass-fiber filters were pre-combus-
ted in a muffle furnace at 550°C to remove any residual carbon contami-
nation. The duplicate filters were placed in aluminum weighing dishes
scribed with date, depth, and volume of sample and kept frozen until
induction furnace analysis (Armstrong, Goldman, and Fujita 1971). Care
was taken not to handle the filters or write on them since any oil or
ink would increase the carbon content of the filters dramatically.
Results
Synoptic and Index Stations -
Since most synoptic stations and the index station are taken in areas
of the lake where depths are at least 20-150 m, they represent chemical
conditions typical of most of the lake. Tables 8-10 provide water column
values for total phosphorus, nitrate-nitrogen, and total iron present
at the index station (depth 105 m) over the 1968-1971 period. Total
phosphorus concentration is usually well below 8 ug-1 (or ppb) from
0 to 150 m while nitrate-nitrogen levels are very low and range from
1 to 25 ug-1 . Total iron levels are also characteristically low and
typically remain below the 7 vig-1 level. The 14 ug'l measured at
75 m on 22 December 1970 probably represents a contaminated sample.
Trends in the average nutrient concentration in the water column at the
80
-------
TABLE 8, TOTAL PHOSPHORUS (MS/I) AT THE INDEX STATION OF LAKE TAHOE/ 1968-1971,
DEPTH
11
0
2
5
ID
15
20
30
40
50
60
75
90
105
DEPTH
:1
0
2
5
10
15
20
30
40
50
60
75
90
105
1968
FEE
20
1.7
—
0.7
—
1.5
—
—
—
1.8
—
—
1.2
—
1969
DEC
16
2.6
—
4.2
2,0
2.6
1.6
2,3
—
2.3
—
1.3
—
5.9
FEE
29
0.9
1.8
2.8
2.5
2,4
2.0
1,7
1.0
1.5
1.2
1.4
14
—
1970
JAN
19
2.9
—
3.4
3.2
2.2
2.2
3.7
—
2.0
—
2.1
—
2.1
fa
6
1,5
3.1
1.6
1.6
1.7
—
3.4
0.9
—
1.5
1.3
1.1
—
FEE
ID
2.9
—
2.8
2.8
1.8
5,2
3.0
—
6.6
—
5.4
—
3.7
fVw
13
1.7
1.9
1.4
1.4
1.2
1.7
1.7
—
1.6
1.6
1.9
1.1
0.5
FEE
28
5.2
9.1
3.9
4.2
5.2
5.2
5.2
5,2
4.6
5.2
4.3
4.9
—
MAR
26
1,9
1.7
1.5
1.4
1.4
1.4
1,6
1.6
1.8
1.2
1,2
—
—
APR
2
4.8
4.6
5.0
4.6
3.9
5.3
6.7
7,9
8.0
6.9
6.2
5.1
3.9
?IAY
1
1.5
2.4
2.2
1.6
1.6
—
1,1
1,1
1.6
1.6
1.5
1.6
—
JUL
1
6.8
—
6.7
6.2
—
6.0
6.2
6.3
3.5
6.6
7.6
8,8
10.2
JUN
5
1.9
1.9
2.1
1.9
—
1.9
1.9
—
1.7
—
—
2.7
—
JUL
24
5.0
4.9
4.4
4,5
4.2
3.8
3.7
2,9
2.7
3.0
3.7
4.1
5.1
JUN
12
1.4
1.5
1.6
1.6
—
1.9
1.6
—
1.5
—
1.4
2.2
1.8
AUG
11
7.0
3,7
4.7
2.5
2.5
4.0
3.7
9.6
7.0
6.8
12.0
12.2
13.4
JUN
26
1.8
1.9
1.8
1.6
1.8
1.8
1.9
—
1.6
—
1.6
1.7
1.7
SEP
2
6.1
5.7
6.3
6.0
5.2
5.2
5.4
4.8
4.7
4.4
4.2
4.3
4,1
JUL
11
1.5
—
2.0
1.9
2.2
2.0
—
—
1.7
—
2.0
2.0
2.3
Ocr
2
5.4
5.2
4.3
4.1
4.3
4.4
4.3
4.3
4.5
4.3
4.3
4.4
4.6
JUL
31
1.9
2.^
2.7
2.1
2.0
2.5
2.3
2.3
2.5
1.9
2.9
2.1
2.1
DEC
22
1.2
1,3
1.2
1.1
1.3
1.4
2.4
1.2
1.1
0.8
1.1
0.8
0.8
1969
JUL
24
3,9
—
—
2.9
—
8.2
6.9
—
2.6
—
—
—
7.2
1971
JUL
14
6.3
5.4
4.6
4.4
5.1
5.8
6.3
6.5
6.2
5.4
5.8
6.3
6.3
lev
24
2.6
—
4.9
2.0
2.6
2.6
2.0
—
2.6
—
2.6
—
1.6
AUG
17
3.3
3.5
3.3
3.1
2.3
2.0
2.4
2.6
2.9
2.8
3.2
3.3
3.5
-------
TABLE 9, NITRATE-NITROGEN (vg/i) AT THE INDEX STATION OF LAKE TAHOE, 1968-1971,
1968 I%9
DEPTH FEE FEE FEE MAR MAR "!AR JUN JUN JUN JUL JUL Jut Nov
M
0
2
5
ID
15
20
30
10
50
00
TIT
1J
90
105
DEPTH
1
n
2
5
10
15
20
30
40
50
60
75
on
rs
8
15.0
—
12,0
—
13.0
—
21.0
—
13.5
—
11,5
—
1969
DEC
16
1.1
—
0,9
1.1
1.1
0.9
1,1
—
1.1
—
1,6
—
3 **
20
11.0
—
11,0
—
11.5
—
11,5
—
12,0
12.0
12,0
—
1970
JAN
19
10.7
—
8.3
8.8
9.5
8.7
8.2
—
9.6
—
10.0
—
9.9
29
10.0
—
11.0
—
—
—
—
13.0
—
—
11,0
—
FEE
10
3.1
—
2.1
3.3
3.3
1.1
3.3
—
3,1
—
3,8
—
i -
s * _
6 13
13.0 —
— 13.0
—
11.0
_i_
— 13.0
11.0
—
9.0
— 11.0
10.0 10.5
— 10.0
FEE APR
28 2
11.8 6.7
11.6
12.1 1.6
11.6 —
11.7 5.0
12.1
11.9 5.0
12.3
13,1 5.2
12.7
11.3 5,9
15.1 —
15.1 5.1
26
10.0
—
12.0
—
—
13.0
—
—
11.0
—
10.0
6.0
JUL
1
2.8
—
2,1
?,7
—
1,7
3.6
5.2
1,6
1.7
2.1
2.7
5.7
5
8.0
9.0
—
11.0
—
—
10.0
—
—
—
19 f!
l£»U
—
23,0
JUL
21
3.0
1.2
2.1
1.7
1.6
2.1
1.5
2.0
1,8
1.7
1.8
2.5
3.5
12
19.0
—
—
23.0
—
—
21.0
—
—
16.0
11.0
12.0
AUG
11
3.2
3.0
2.6
2.8
3.0
2.5
2.6
2.8
2.3
2.9
2.9
2.8
2.9
26
20.0
—
—
12.0
—
—
11,0
—
—
9.0
9.0
8.5
SEP
2
1.7
1,6
1.8
1.6
1.1
1.1
1.5
1.6
1,1
1.3
1.3
0.9
0.5
11
15.0
—
21.0
23.0
25.0
19.0
—
—
23.0
—
iq n
.13 .U
20.0
23.0
OCT
2
6.2
5.9
5,3
5.0
5.5
5.8
5,1
1.7
1.2
1.1
3.8
3.6
3.7
31
12.0
12.0
13.0
13.0
12.0
13.0 ,
12.0
13.0
11.0
11.0
q n
J,U
13.0
26.0
1971
JUL
11
5.3
5.6
5.6
3.8
3.8
3.1
3.8
3.8
1.3
1.2
1.2
3.8
1.1
21
0.0
—
—
0.0
—
0.0
0.0
—
0.0
—
—
0.2
AUG
17
1,1
3.7
3.5
2.9
2.6
2.1
2.5
2.9
3.0
3.6
3.3
3.1
3.7
21
5.0
—
5.2
5.0
5.2
1.7
5.1
—
5.0
—
it =i
T. J
10.1
82
-------
TABLE 10, IRON (ug/i) AT THE INDEX STATION OF LAKE TAHOE/ 1970-1971,
DEPTH
M
0
2
5
10
15
20
30
40
50
60
75
90
105
1970
DEC
22
0
2
0
0
1
0
5
7
3
0
14
7
0
1971
>
JUL
14
2
1
1
1
1
1
1
1
1
1
1
1
1
AUG
17
2
2
1
2
2
2
2
2
2
2
2
2
2
82
-------
_
index station are discernable. Phosphorus levels were lower (<2 yg'l )
_i
and nitrate levels higher (10-20 yg-1 ) in 1968 than in later years.
Phosphorus values were from 2 to 5 yg'l and nitrate levels fell to
1-10 yg-l"1 in 1969- The pattern was similar in 1970. Phosphorus
levels were generally less in 1971 than the two previous years and
nitrate concentration remain low. Iron levels were similar in 1970
and 1971.
Lake-wide concentration levels of nitrogen and phosphorus are given in
Table 11. Chemical analyses during synoptic studies over the four-year
period indicate several interesting points: (1) Nitrate levels are
generally as low or lower than total phosphorus concentrations at all
locations. (2) Near-shore locations have slightly higher N and P levels
than deep water stations. (3) There is more year-to-year variation in
nutrient levels at the littoral stations.
The amount of total particulate carbon found in Lake Tahoe varies
seasonally by a surprisingly small amount (Table 12). Values in 1970
averaged around 50 yg C-l and ranged from 34 to 145 yg C-l . Appar-
ently, seasonal changes in seston form do not cause large variations in
carbon content throughout the water column.
Deep Water Chemistry -
A deep water station in mid-lake was sampled during 1970 and 1971.
Table 13 shows the depletion of nitrate-nitrogen in the euphotic zone
with high levels present from about 200 m down in January 1970. There
is evidence from the nitrate distribution that mixing may have occurred
in the late spring of 1971. The utility of using nitrate distribution
as evidence of deep mixing has been demonstrated by Paerl et al. (1974).
Total phosphorus is much more uniformly distributed with depth than ni-
trate (Table 14). In July 1970, however, it shows the same distribution
84
-------
TABLE 11. WATER CHEMISTRY (ug/i) AT THE SYNOPTIC STATIONS OF LAKE TAHOE, 1968-1971,
1
TOTAL PHOSPHORUS
NITRATE-NITROGEN
STATION LOCATION
INDEX OAHOE PINES)
GENERAL CREEK
RUBICON POINT
EMERALD BAY
CAMP RICHARDSON
TAHOE KEYS
SOUTH TAHOE
AL TAHOE
BIJOU
ELK POINT
PELAGIC (SOUTH SHORE)
ZEPHYR COVE
CAVE RXK
PELAGIC (SOUTH)
GLENBROOK BAY
PELAGIC (RIDLAKE)
PELAGIC (MIDLAKE)
PELAGIC (MIDLAKE)
SKUNK HARBOR
SAND HARBOR
INCLINE CREEK (EAST)
INCLINE CREEK (MOUTH)
INCLINE CREEK (WEST)
CRYSTAL BAY
NORTH STATELINE
PELAGIC (CRYSTAL BAY)
PELAGIC (NORTH STATELINE)
KINGS BEACH
CARNELIAN BAY
DOLLAR POINT
TAHOE CITY
PELAGIC (TAHOE CITY)
WARD CREEK
AVERAGE
1968
3.7
4.0
3.8
4.1
3.8
—
4.0
4.0
4.0
3.7
4.3
3.7
3.8^
—
3.8
4.5
4.1
3.9
3.9
3.8
3.8
3.8
3.8
—
3.7
—
4.0
—
3.7
3.6
4.4
—
—
3.9
1969
11.8
14.2
16.0
11,7
22.5
67.0
32.0
20.7
22.5
19.5
10.2
7.2
7.8
8.5
14.8
11.2
9.0
13.8
27.7
16.8
]7.2
9.3
11.5
11.3
31.5
11.3
10.8
14.2
13.8
11.2
9.0
13.4
17.0
15.1
1970
11.0
11.3
9.9
10.1
7.8
23.2
9.4
10.5
12.4
6.6
6.0
9.6
8.8
6.9
9.4
7.2
6.4
5.5
5.3
7.6
10.4
10.0
9.4
6.6
6.9
7.0
5.5
6.4
5.5
5.4
9.0
4.4
7.1
7.9
1971
3.3
3.6
3.4
17.1
8.1
24.4
14.5
13.2
12.8
4.2
2.4
2.6
3.6
2.5
3.8
2.6
2.3
2.0
3.6
4.3
8.7
10.8
U.7
7.5
8.1
8.6
2.4
4.2
4.6
3.3
3.5
2.9
3.3
5.6
1968
5.0
6.4
5.0
4.8
5.3
—
4.8
4,4
4.8
4.2
4.2
5.3
3.4
—
4.0
4.0
3.1
2.8
5.0
5.2
4.4
4.5
5.4
—
4.8
—
3.8
—
5.3
5.6
5.2
—
—
4.6
1969
4,5
3.2
2.2
1.3
2.2
2.0
2.2
2.0
3.8
2.5
3.2
2.5
3.0
2.5
5.0
2.5
2.5
3.8
5.0
3.2
3.5
3.5
6.2
5.8
7.5
5.8
4.0
2.5
2.8
3.5
2.5
3.0
2.2
3.5
1970
6.0
6.1
4.9
4.1
5.7
6.1
6.3
5.6
5.1
5.4
4.9
4.8
4.5
5.3
6.0
6.6
4.8
4.2
5.1
5.6
5.2
4.7
4.4
4.2
4.8
4.7
4.3
4.4
4.9
4.8
4.0
4.0
3.5
5.0
1971
2.0
2.3
2.3
4.5
6.2
14.4
8.2
5.3
3.5
2.6
2.3
2.4
2.8
2.1
3.1
2.3
2.3
2.3
2.6
4.6
7.0
7.6
7.3
5.3
3.5
4.8
2.3
3.5
2.3
3.1
3.2
2.3
2.4
3.7
1968 VALUES ARE BASED ON AN AVERAGE OF ONE SYNOPTIC, 1969 ON FOUR, 1970 ON SIX, AND 1971
ON ONE.
EXCLUDING EMERALD BAY AND TAHOE KEYS,
85
-------
TABLE 12, PARTICULATE CARBON (ug/i) AT THE INDEX STATION OF LAKE TAHOE, 1968-1971,
DEPTH
H
0
2
5
10
15
20
30
40
50
60
75
90
IDS
DEPTH
H
0
2
5
ID
15
20
30
10
50
60
75
90
105
DEPTH
H
0
2
5
Tfl
5
20
30
10
50
60
75
90
IDS
1968
SEP
11
68,3
44.4
13.3
34,2
30,6
10,6
37.3
38.1
35.2
32,0
55.5
31.1
36,9
1969
SEP
23
57,0
17,6
73.7
15.3
39.0
38.3
13,0
19,1
51,5
11,5
36.0
30,1
37,0
1970
AUG
11
11.5
33,0
36.5
39.0
16,0
37,5
15,5
39,0
19,0
15,5
59.0
65,5
17.0
SEP
17
50,7
39.2
29,9
28,7
27.9
19,0
20.7
23.2
31.7
26,8
28,5
31.0
38.5
OCT
ID
12.3
52.8
44.3
36,0
30.1
31.1
38.1
36.8
30.2
44.3
32.0
35.9
35.1
AUG
17
38.0
18.0
44.0
13.0
53,0
13,5
56,5
18.5
52,5
61,5
56,5
82,5
50,0
Ocr
19
56,7
32,1
37,8
27,3
29,0
28.3
21.3
23.8
19,2
37.9
36,3
35.8
30.0
OCT
22
38,0
11.3
15.1
10,8
31,1
18.7
19.1
15,8
17.?
19.8
53.0
12.2
11.9
AUG
21
35.5
27.9
30.0
27.9
19.0
22.1
37.2
31,5
41,3
58,0
63,0
39,2
13,8
DEC
1
87,5
22,5
65,0
37.5
10.0
55,0
10.0
12,5
12.5
20.0
15.0
75.0
70,0
OCT
28
36,0
33.1
38.8
36,0
35,7
36.8
32.1
37.9
39.6
13.0
11.7
12.6
40.7
SEP
8
67.0
17.0
57.5
55.5
60,0
19.5
58.5
61.5
17.0
51.0
63,5
52,5
51,5
DEC
7
10,0
37,5
25,0
27.5
27,5
62,5
17,5
25.0
37,5
17.5
62.5
25.0
27,5
Nov
12
37,1
32.2
37.0
35,1
35,8
39,6
35,8
31.1
37.5
31.6
31.3
31.9
37.1
SEP
18
63.0
51.5
61,0
53.5
55.0
55.0
68.5
59.5
61.5
75.0
60.5
76,0
79.0
DEC
22
72.5
55.0
15.0
55,0
55.0
37,5
77,5
50,5
37.5
10.0
35.0
15.0
15.0
Hov
23
66.2
66,0
39.5
36,0
39.5
86,0
18,0
31.1
10.0
37.0
31.1
31.0
36.0
SEP
23
59.5
53.0
58,5
60.0
60.5
19,0
51.5
53.5
51,0
58.5
19,0
11,0
13,0
1969
JAN
16
21,2
19,1
19,8
16.7
20.1
21.5
21,5
21,3
23,5
25,7
23,2
17,2
21.1
DEC
5
91,0
56.5
18,0
35.0
28,0
112,5
32,5
10.5
30.5
36.5
36.5
36.0
66.0
OCT
2
54,9
53,5
52.1
63.1
53.5
53.5
52,8
68,5
70,0
73,0
85,0
73,0
60,6
FEB
1
31.9
21.9
17.2
21.1
20,8
25.3
20,8
26,5
27,7
28,3
36,6
31.0
11.9
DEC
IB
57,5
62,5
75,0
56,5
H.O
120,0
35.0
65.0
50.0
10.0
16.0
35.5
11,5
OCT
11
31.5
37,0
33,5
28,0
30,0
13,0
16,5
11.5
16,5
H.O
11.5
18,5
31.5
FEB
15
25,1
31,1
21,5
20,8
32.5
66.2
13.1
11,9
15,6
10,7
13.0
39,3
68,8
DEC
26
17.5
33,0
21,5
29,0
21,0
123,0
33.5
17.5
33.0
33.0
59.5
28,5
29.5
New
10
76.0
19,0
50.5
56,0
61,0
83.0
77.0
83.0
92.0
89,0
90.0
73,0
75.0
MAR
2
53,8
10,8
29.8
21.9
31.7
11.8
13.7
65.3
27,2
11.7
38.1
32.9
31,9
1370
JAN
6
60.0
18,0
15.5
10,5
39,0
112,0
57,2
16,7
59.0
11,6
12.7
37.5
10.0
1371
JAM
8
67.5
83,0
74.5
87,5
77,0
61,0
73.5
78.5
74.5
72.0
92,0
100.0
88,0
MAR
15
51.2
61.4
66.7
54,3
56.4
32.4
37,9
24.0
24,6
45.8
36,6
42,8
39,2
JAN
30
36.5
32.0
25.0
31,0
26.0
27.5
32,5
65.0
29.0
32.0
39.5
26.5
32.0
JAN
21
71,0
74,0
116.0
70.0
58.5
66.5
72.0
76.5
57,0
118,0
73,5
91,5
68.0
HAR
30
37.6
21.9
35,6
36,9
40,0
27,2
24,0
36.0
33.8
82,0
74,2
70.0
77.6
FEB
ID
31.0
36.5
12,0
32.0
48.0
41.0
47.5
13.0
85.5
38,5
37.5
31,5
35,0
FEE
2
82,0
68.5
79.0
71,5
65.5
68.0
60.0
63.0
71.0
60.5
103.0
66.5
85,0
APR
25
21,1
20.1
23.9
39.3
40,7
36,9
36.5
33.6
11,2
29.6
32.7
26.3
33,3
FEB
23
53,5
39.0
15.0
39.5
42.5
62.0
39.0
13,0
1DO.O
63,0
53,5
13,0
63,0
FEB
12
69.5
12,0
50.0
29,5
45,5
11,0
44.0
76.0
67;5
56,5
47,5
41,5
28,5
["AY
9
43.4
41,0
45,7
42,7
50,1
53,9
58.6
57.0
53,8
65,2
62,6
81.4
20.8
FEE
28
62,2
78.6
47,0
18.5
19.0
51,6
37.3
68,2
44.0
—
62.0
62.6
50.1
FEB
22
60.0
65.0
58,0
61,0
88.5
54,5
54,5
40,0
43.5
51,5
58.0
17.0
60,0
MAY
23
52,0
49,4
53,7
65,2
78,3
71.2
71.6
73.0
73,7
82.1
69.1
77.5
90.2
Mw
10
15.5
11.0
50.0
19,0
62.2
38.5
37.3
41.7
82.1
54,4
55.0
37,9
34,5
MAR
7
65.9
70.6
52.1
55,1
57.5
59,9
57.5
50,8
53,5
52.1
47.7
57,2
46.7
86
-------
TABLE 32, CONT'D.
DEPTH
H
0
2
5
10
15
20
30
40
50
60
75
90
105
DEPTH
PI
0
2
5
10
15
20
30
10
50
60
75
90
105
DEPTH
H
0
2
5
10
15
20
30
10
50
60
75
90
105
3969
JUN
7
35,3
27.2
53,2
53.0
15.8
78,5
86.3
81,0
72,1
81,1
62.1
53,2
56,1
3970
MAR
23
37.5
30.5
35.0
31.5
25.5
35,0
47,5
55,0
50,0
37.5
93.5
35.5
31.0
1971
37
100.2
107,8
81,9
86,1
81,5
85,0
87,8
77,1
102.3
87.1
83,6
69.8
51,1
JUN
20
47.7
31,3
31,5
39,1
11,1
48,0
58.2
53,7
57,8
13,7
27.3
B.I
15,8
APR
2
55,5
53,0
13.5
13.5
11,0
57,0
35,0
16,5
55,5
50,0
59,5
18,0
31,0
APR
2
106,1
85,1
86,5
85,1
90.8
81.7
87,6
89,7
97,2
107,9
90.8
92,2
92,9
JUL
1
29.3
38.1
65,9
81.6
79.2
90.3
79.5
72.9
70,3
61,5
60,8
56,9
57.2
APR
35
58.0
53.3
52.6
57.0
56,0
53.0
50.2
51.9
66.5
55,5
19.3
55.0
28,1
APR
33
110,1
96,2
98.8
99,3
92,5
99,3
91.9
107.1
106.6
96.2
122.7
97.5
81,5
JUL
8
45.6
18,5
19,6
13,5
59,3
55,2
37,1
11,1
11,8
55,7
12,5
12,7
12,2
2
11,0
69,0
80,5
69,5
72,0
71,0
61,5
81,0
67,0
52,5
61,5
59,5
55,5
APR
23
72.5
82,2
69.6
92,9
91,0
81.0
104,0
85,1
81,4
71,8
89,6
62,2
71,1
JUL
22
57.8
H.8
55,0
19.1
17.9
11.3
50.2
26.3
23.9
30.8
23.1
39.8
23.1
PlAY
33
53,5
41,5
39,5
33,0
31,0
48,0
17.0
13,5
78,0
30.0
34,5
33,0
23,5
RAY
5
73,2
80,5
105,1
83,6
72.1
102.0
104.3
76.7
107,0
81.3
108,9
90.5
123,1
JUL
21
68,1
59,2
50,6
13,3
15,5
38.3
38,8
49.1
40,9
60,1
43,0
36,3
29.5
MAY
25
38.0
50,0
35.3
33.0
38.0
35.0
38.5
39.1
66.5
40.5
17.0
50.0
18.3
HAY
39
120,6
71.0
63.7
77.2
76.0
87,6
79,6
81,0
87,6
83,6
88.0
79.2
129.0
JUL
30
17,9
13,1
13,3
10,4
37,5
41,8
26,1
21,3
38.2
33,1
30.6
21,9
38,2
JUN
4
38,8
28.0
35,0
10,5
71,0
13,7
67,1
115.0
71,3
82,2
100.3
83,0
48.4
JUN
1
KW.O
86.0
30.5
96.5
92.0
153.0
117.0
89.0
67,5
55,0
62,0
15,0
41,0
AUG
5
72,7
52.7
56.2
12.8
13.5
36.1
17.1
18,3
56,0
47,1
37,1
57,6
51.0
JUN
16
36.0
26.0
29,0
36,0
42,5
29,5
37,5
56,5
47,5
16,0
53,5
15,0
10,0
JUN
11
80,5
93,3
79,7
98,3
88,4
.102,4
98.3
98,3
83.0
59.5
57.8
51.1
16.2
Aus
11
52,0
19,0
53.9
48.0
37,2
31,6
11,8
17.8
55.9
17.0
H.O
25.6
32.6
JUL
1
82,0
59,0
35,0
16,5
78.0
63,0
50,0
71.5
62.0
70.0
17.0
38.0
36,0
JUN
25
73,1
61,6
67,5
78,8
81.0
67,9
71.5
79,7
84.4
81.6
91,5
84.1
66,0
AUG
20
42.1
58.1
60.8
71,2
55.3
42.3
47,8
49,9
48.7
52.1
53,7
43,2
37.8
JUL
7
56.0
48.0
52.5
48.0
50.5
16.0
51.5
71.0
50.0
57.5
69.0
54.5
62.5
JUL
1
94.3
65,4
52,2
60,5
56,2
51,8
41,2
55,6
72,5
75.8
63.2
51,0
48,5
AUG
28
89.7
56,2
51,1
48,9
53.0
52.9
55.1
57.5
54.6
52,1
58,8
41,1
52,1
JUL
14
17.0
41.2
39,0
39.1
13.5
39,9
39,9
57.3
65,0
53,2
61,1
68,5
11.0
JUL
8
61.4
53,5
51,8
75.7
60.1
65.3
62.7
62.7
77.0
97,9
87.5
92,0
65,3
SEP
3
56.2
51,9
59,3
44,1
47,0
61.1
59.0
45.9
43,4
39,9
40,3
36,0
32.9
JUL
20
43.5
13,5
17,1
17,1
39,0
38,0
42,0
39,0
37,4
53,0
51,0
55,4
70.0
JUL
14
66,6
55,0
63,2
53.6
78,2
54,4
58,6
77,6
71,0
69,6
67.3
56.5
55.2
SEP
9
41,0
31.3
32.2
36.6
41,3
31,2
41,8
17,5
12,6
15.9
38,1
35,9
32,4
JUL
24
37.9
33,9
39.0
39.0
16.5
38.0
38.0
10.2
13.1
17.9
49.0
42.1
59.5
AUG
21
126.8
88.1
91.0
91.1
356.6
120,8
126.8
320.8
303,0
108,9
97,0
323.8
3D3.0
SEP
35
30,5
27,1
48,3
26.2
32.7
15.1
33.5
30.6
33.6
38,8
36,7
33,1
29,5
JUL
31
23.0
25.0
31,5
22,5
30,0
31,5
13,5
30,5
45,5
39,0
50,0
51.5
M,0
87
-------
00
CO
TABLE 13, NITRATE-NITROGEN (wg/0 AT THE MID-LAKE STATION OF LAKE TAHOE, 1970-1971,
1970 1971
DEPTH JAN FEE JUL AUG Nov JAN FEE I'kR MAY JUN JUL AUG AUG SEP OCT DEC
M 2 25 3 3 17 25 10 15 10 30 16 4 26 14 6 8
0
20
50
100
200
300
400
BOTTOM
8,0
8,2
7,9
8,3
16,6
20,7
18,8
29,4
3,6
6,1
4,4
6,2
7,3
6,6
—
14,4
9,6
5,8
3,0
3,3
11,0
8,0
14,9
16,6
2,5
3,0
4,5
3,0
11,5
3,5
9,5
18,5
2,0
2,0
3,1
3,3
11,0
13,1
21,8
17,7
5,0
5,2
4,0
7,5
8,1
10,0
19,0
15,5
3,8
2,3
5,0
4,7
11,9
19,8
11,4
22,0
8,0
7,9
8,0
8,0
8,2
19,3
15,2
23,9
5,5
4,2
4,0
12,8
10,7
13,2
14,3
14,1
5,4
0,9
0,8
1,1
1,7
2,8
—
—
4,8
5,0
4,3
3,8
4,8
5,0
5,3
4,8
3,9
3,7
2,4
3,0
3,7
3,9
4,1
4,1
1,8
2,5
1,5
2,4
10,3
15,4
8,3
8,6
11,0
11,4
7,5
10,0
13,5
20,1
17,5
35,8
3,3
3,0
3,0
3,9
8,6
11,8
J2-3
12,3
4,8
4,2
4,6
8,3
14,1
16,9
20,0
24,0
(450)
-------
CD
TABLE 14, TOTAL PHOSPHORUS (pg/i) AT THE MID-LAKE STATION OF LAKE TAHOE, 1970-1971,
1970 1971
DEPTH JAN FEB JUL AUG Nov JAN FEE MAY JUN JUL AUG AUG SEP Ocr DEC
n 2 25 3 3 J7 25 JO ID 30 16 4 26 14 6 8
0
20
50
100
200
300
CO
BOTTOM
(450)
2,1
2,9
2,1
4,3
3,7
3,0
3,4
3,6
2,3
7,0
4,3
4,4
4,2
4,6
3,8
9,2
7,4
8,3
6,5
6,8
10,7
11,8
17,5
23,8
8,5
4,5
3,5
5,5
5,4
7,0
6,5
0,5
2,6
2,6
3,3
4,6
3,7
3,0
6,9
5,0
1,6
2,4
3,3
3,3
1,8
1,8
2,2
2,2
5,7
2,0
2,9
10,0
3,7
4,8
2,4
2,5
2,1
2,0
1,8
2,1
1,8
2,0
1,7
0,9
3,5
2,3
1,9
1,8
2,3
4,5
—
—
5,4
4,4
3,5
3,5
3,1
3,5
2,4
2,5
3,5
3,2
2,3
2,4
2,9
3,3
3,3
3,5
7,2
19,5
2,1
4,0
9,5
2,7
2,7
24,6
9,5
6,2
.7,5
14,5
9,5
11,5
9,0
—
20,4
21,5
9,5
11,3
8,2
7,1
5,8
12,5
12,0
7,1
7,0
8,2
8,2
16,4
13,0
25,2
-------
as nitrate which may reflect a particularly long-term accumulation of
organic matter in the deeper waters that could result from a lack of
mixing the previous winter.
Silicate-silicon, which may in certain circumstances limit diatom
growth, is present in mg-1 concentrations and does not appear to be
greatly influenced by mixing (Table 15). Iron levels are generally
low, but some surprisingly high values appear in Table 16.
Oxygen samples collected over a two-and-one-half year period at a mid-
lake station indicate Lake Tahoe consistently maintains a high level of
oxygen concentration from the surface to bottom (Table 17). The range
of all values recorded was within 7-11.6 mg-1 and percent saturation
corrected for altitude always remained above 80%. Slight super-satura-
tion (100-110%) has occurred frequently at depths less than 150 m.
As with temperature (Table 6 ) seasonal oxygen trends are well—defined
and annual surface stratification occurs during the summer, but unlike
temperature, the highest values are seldom found .at the surface.
Lenses of highest oxygen concentration are usually located in or just
below the thermocline region from 50 to 100 m during spring and summer
months when corresponding surface values are lowest for the year.
These maxima are likely to reflect peaks of photosynthetic activity.
These upper-level variations appear to be dependent on both physical
and biological factors. Apparently, phytoplankton-zooplankton respir-
ation in combination with higher water temperatures leads to oxygen
removal at a rate faster than can be produced photosynthetically. This
results in a net oxygen loss in the upper 20-30 m of water from about
June to October.
Below 100 meters, the range of yearly variation is less, but still very
90
-------
TABLE 15, SILICATE-SILICON («»g/i) AT THE MID-LAKE
STATION OF LAKE TAHOE/ 1971-1972,
1971 . 1972
DEPTH JAN AUG SEP OCT DEC MAR
H 25 26 14 6 8 15
0
20
50
100
200
300
400
BOTTOM
(450)
5,2
3,8
3,5
5,0
5,0
4,4
3,4
5,0
6,9
6,6
6,6
6,4
6,7
6,3
6,7
7,4
5,8
5,7
5,8
5,6
5,6
5,6
5,6
5,8
6,4
6,5
6,5
5,6
8,5
7,4
6,5
6,1
6,1
6,4
6,2
6,4
6,4
6,4
6,2
6,6
5,6
5,6
5,6
5,6
5,9
5,8
5,6
5,7
91
-------
TABLE 16, IRON (wg/i) AT THE MID-LAKE STATION OF LAKE TAHOE, 1970-1971,
DEPTH
M
0
20
50
100
200
300
400
BOTTOM
(490)
1970
AUG
3
8
7
10
12
8
9
14
20
Nov
17
7
9
6
11
7
7
21
46
1971
JAN
25
0
28
16
10
126
0
4
55
JUN
30
6
4
3
4
6
8
-
-
JUL
16
1
1
1
1
1
1
1
1
AUG
4
2
1
1
1
1
2
1
2
SEP
14*
13
17
13
20
44
15
13
>232
>
OCT
6*
171
59
21
18
20
8
80
53
DEC
8*
68
5
8
59
10
1
18
38
*HlGH BLANK VALUES,
92
-------
vo
UJ
TABLE 17
DEPTH
M
0
20
50
100
200
300
400
BOTTOM
(150)
DEPTH
M
0
20
50
100
200
300
WO
BOTTOM
(450)
, OXYGEN
1969
MAR
1
9.30
9.27
9.26
9.24
9.27
9.24
9.23
9.29
1970
JUL
3
8.98
10.03
10.59
10.54
10.17
10.32
9.92
9,65
(mg/l) AT THE MID-LAKE STATION OF LAKE TAHOE, 1969-1971.
MAY
31
8.97
—
—
9.40
9,25
9.20
9.16
3.15
AUG
3
8.56
10.48
11.11
10.94
10.60
10.97
10,53
10.05
JUL
9
7.83
8.99
9.40
9.32
9.02
9.00
8.98
9.00
SEP
9
8.49
8.89
1D.68
10.75
10.26
9.90
9.79
9.54
JUL
25
7.51
8.67
9.63
9.22
8,96
9.27
8.83
8.41
OCT
IB
8.30
8.32
10.13
9.86
9.31
9.20
9.04
9.03
AUG
7
7.40
8.97
9.70
8.69
9.14
8.79
9.03
8.84
Nov
17
9.04
9.05
9.76
9.89
9.39
9.31
9.26
8.96
AUG
21
6.85
9.34
9,94
9.56
9.5.2
9,55
9,06
9.29
DEC
30
9.71
9.76
9.76
9.82
9.64
9,39
9.38
9,15
SEP
4
7.14
8.38
9.08
8.63
8,47
8.46
8.40
8.40
L971
JAN
25
10.31
10.27
10.29
10.28
10.20
10,08
9,93
9.72
SEP
19
8.07
7,74
10.27
9.91
9.65
9.64
9.71
9.43
FEE
10
10.09
10,06
9.98
10.00
9.63
9.56
9.44
9.43
Nov
11
8.38
8.44
8.51
9.44
8.92
8.96
8.87
8.73
FEE
24
11.33
11.28
11.33
11.36
11.44
10.98
10.74
10.64
DEC
17
8.98
8.98
8.97
9.17
9.05
9.01
8.93
8.71
MAY
ID
10.50
10.79
11,34
11.09
1D.8S
1D.91
10.82
11.21
1970
JAN
2
9.00
9.02
9.05
9.06
8.82
8.83
8.79
8.56
JUN
3
10.89
10,93
11.33
11.32
11.27
11.08
10.86
10.66
JAN
20
9.07
9.06
9.06
9.06
8.87
9,01
8.93
8.64
JUN
30
10.05
10.46
11,56
11.47
11.41
11.02
—
FEE
5
9.50
9.59
9.60
9.52
9.36
9.21
9.59
9.12
JUL
16
8.42
9.85
10.62
10.44
10.01
10.12
9.92
10.11
FEB
25
10.52
10.48
10.73
10.52
10.44
10.15
9.99
9.86
AUG
4
8.09
9.67
11.07
7.44
11.24
10.21
9.90
9.38
MAR
13
10.49
10.52
10.55
1D.52
1D.25
Ifl.lD
9.94
9.90
AUG
26
8.19
10.30
11.12
10.77
10.96
10.45
10.31
10.1E
APR
9
10.54
10.58
10.73
10.48
10.23
10.08
9.80
9.82
SEP
14
8.22
9.22
11.57
10.85
10.65
10.55
10.48
9.51
MAY
5
10.40
10.50
10.48
10.25
10.03
9.98
9.97
9.83
OCT
6
9.47
9.53
11.55
11.00
10.81
10.82
10.67
10.64
JUN
2
10.00
10.54
10.91
10.75
10.46
10.20
10.27
10.08
DEC
8
9.99
9.84
10.25
10.12
9.93
9.90
9.72
9.46
-------
TABLE 18, COMPARATIVE WATER CHEMISTRY (ug/i) OF VARIOUS CREEKS IN THE TAHOE BASIN/ 1968,
_ NORTH
FALIBI _ _ „ T ..... „ ___ r _____
10FEB
19 FEE
22 FEU
25FEB
17 MM
7APR
27 to
7*Y
21 HAY
28 »Y
7Jui
25Ju»
27Ju«
•
1JUL
NOj-N
%ll
mrN
%-N
NOj-N
Wj-N
TOTAL?
NOj-N
NV"
TOTAL F
%N
TOTAL P
TOTAL?
%*
%N
NOj-N
Wj-N
TOTAL F
NOj-N
IKj-H
TOTAL F
N05-N
%-N
TOTAL P
NOj-N
Itlj-N
TOTAL P
N03-K
NHi-N
TOTAL F
700,0
125,0
31,1
11,0
33,5
37,0
18,0
12,0
3,3
10,0
12.8
11,0
66.0
15.0
8.6
16,0
17.0
17.0
29.0
19.5
1.6
17,0
15,6
38.0
2.7
13.0
9.6
5.9
30,0
23,0
12.8
18.0
17.0
11.1
108.0
125.0
30.0
38.0
27.9
39.5
36.0
32.0
1.5
26.0
3.6
2.2
17.0
29.0
D.O
6.5
31,0
B.O
8.5
25,5
86,5
120.0
67.5
38.3
60.0
36.0
2.0
35,0
1.6
5,3
26,0
32.0
22.0
6.6
21,0 32.0 36.0 33.0
16.0 19.0 21,5 37.0
11,3 11.1 8.5 9.2
13.0 26.0 27.0 21.0 25.0 17.0 28.0
27.0 18,0 39.5 18.0 21.0 20,0 38.0
5.7 6,3 2.2 1.3 2.2 1.6 2.8
17.0 B.O 13.0 22.0 19.0 39.0 28.0 23.0 23,0 21.0 3S.O 68.0
20.5 36.0 18.0 17.0 12.0 11.0 18.0 15.0 17.5 15,0 — 20.0
7.6 1,9 3.1 1.6 12,1 3,0 2.7 1.2 11.5 1.1 3.2 19.8
-------
TABLE 18, CONT'D,
VO
DATE
9JUL
16JUL,
24 JUL
29JUL
5AUG
BAUG
25Auo
NUTRIENT
%fl
%-N
TOTAL P
NOj-H
%N
TOTAL?
NOj-fl
NHj-N
TOTAL?
NOyfl
MKj-N
TOTAL?
%N
%N
TOTAL?
N03-N
1%-tl
TOTAL?
NOj-fl
M4- M
TOTAL?
INCLINE
56.0
53.0
35.8
53.0
47.0
B.5
18.0
38,0
14.2
20.0
43,0
10.8
50,0
31.0
16.4
56.0
30.0
21.6
59.0
31,0
22.4
THIRD
55.0
29.0
E.8
63.0
26.0
7.2
58,0
35,0
10,8
31.0
40.0
10.3
44.0
29.0
14,4
32.0
30,0
F.6
30,0
32,0
8.0
GENERAL
16.0
19.5
8.2
14.5
37,0
7.9
21.0
39,5
30.7
30,5
25.5
1.1
85.0
32,0
8,8
7.0
26.0
31,7
12.0
26,0
10,5
UPPER
TRUCKEE
51,0
19.5
6.7
59.0
21,0
6,7
53.0
37,0
8.3
B.O
25,0
4,0
50,0
37.0
37.0
19.0
27,0
7.9
50.0
35.0
15.1
KURD
37.0
22.0
8.7
48.0
28,0
30.5
22.0
27.0
6.6
B.O
33.0
8.9
25.0
31,0
10.1
16.0
9.0
30.6
TAYLOR
37.5 .,
23.0
4.3
37.0
B.O
3.0
B.O
21.0
4.0
27.0
28,0
2.5
84.0
29.0
4.3
73,0
32.0
6.0
77.0
29.0
6.5
EDGEWOOD
14.0
32.0
B.8
33.0
22.0
14.8
31.0
14.0
7.3
21.0
25,0
7,4
40.0
32.0
14.5
41.0
30.0
16.8
41.0
36,0
8,5
MARLETTE GRIFF
50.0
22.0
23.5
52.0
26.0
B.O
21,0
19.0
6.8
50.0
32.0
17.2
41.0
24,0
20.4
36.0
28,0
19,6
FALLEN
BURKE LEAF BLACKFOOT
25.0
39.0
30.2
30.0
25,0
3.5
9,0
33.0
7,7
31.0
27.0
8,5
9.0
14.0
8.5
CASCADE
30.5
23.5
2.5
32,0
14.5
2.1
36.5
19.0
2.0
10.0
17.0
2.2
14.5
28.0
2.7
22.0
35.0
5.0
14.0
,30.0
5.3
EAGLE
32.0
16.0
3.8
30.0
21.5
2.6
8.0
26.0
2.5
67.0
27,0
1.7
88.0
33.0
2,7
95.0
35.0
4.2
99,0
31.0
4.5 -
KEEK
29.0
23.0
6.0
25.0
B.5
5.9
26;0
20.0
7.5
39.0
23.0
6.0
34.0
33.0
8.9
46.0
29.0
8.1
50.0
33.0
9.5
WTOON BLACKHOOD GLENBROOK BLISS
17.0 30.0
17.0 21.0
6.8 4.6
16.0
41,0
.11.2
53.2
32.0
3.8
100.0
31.0
6.4
62.0
28.0
8.3
59.0
20.0
7.5
SECRET
38.0
20.0
1.5
41.0
31.0,
12.1
37.0
26.0
9.7
10.0
44.0
7.9
63.0
2.0
U.8
58,0
29,0
14.4
58.0
31.0
B.I
TALLAC
37.0
28.0
3,7
20.0
23.0
4.7
39.0
30.0
4.2
33.0
28.0
5.1
39.0
31,0
7,3
37,0
27,0
8,0
HODDEN
10.0
21.0
9.8
17.0
26.0
8.0
76.0
27^0
5.8
86.0
27.0
6.6
76.0
26,0
6,6
NORTH
CANYON
12.0
33.0
B.I
-------
much in evidence. The information points to the possibility of large
vertical and/or horizontal water mass displacements, but it is diffi-
cult to speculate on the significance of this without more knowledge of
Lake Tahoe deep water current patterns. Further support of this idea
is gathered during periods of vertical mixing and general lake circu-
lation in the fall or early winter and in the spring when the most uni-
form oxygen values are evident from surface to bottom. On 2 January
1970, the lack of mixing below 200 m is as evident with oxygen as it is
with the nitrate already mentioned.
Although spring data are spotty, highest surface oxygen concentrations
occur then, but are soon replaced by lower values as the surface tem-
perature increases. It is noteworthy that the deepest samples taken
less than one meter from the bottom are always well oxygenated. The
lack of reducing conditions anywhere in Tahoe above the mud-water
interface has obvious significance in the lack of nutrient re-cycling
from sediments that have accumulated in the lake.
Chemistry of Tributaries -
A considerable effort went into measures of nitrate, ammonia, and
total phosphorus from the numerous tributaries in Lake Tahoe. The
work began in 1968 (Table 18), and continued in 1969 (Table 19), 1970
(Table 20), and 1971 (Table 21). The most obvious result of this
sampling is the evidence that streams such as Incline, Third Creek,
and the Upper Truckee River carry heavier nutrient loads than those
streams such as Ward Creek that drain more natural, undisturbed water-
sheds. The streams invariably are higher in phosphorus, nitrogen,
silicon, and iron than Lake Tahoe, and all contribute to the higher
fertility of the inshore waters (see Section IX).
The most polluted stream in the basin is Heavenly Valley Creek (see
Section VII). Nitrate-nitrogen values of over pg-1 reflect the former
96
-------
TABLE 19, COMPARATIVE WATER CHEMISTRY GJS/I) OF VARIOUS CREEKS IN THE
TAHOE BASIN/ 1969,
UPPER
DATE NUTRIENT TAYLOR WARD GENERAL TRUCKEE THIRD INCLINE MCKINNEY
JUN 7
JUN 17
JUN 30
JUL 1
JUL 28
AUGll
SEP 1
SEP 15
OcTl7
Nov25
DEC 202
NOj-N
N03-N
N03-N
N03-N
TOTAL
N03-N
TOTAL
N03-N
TOTAL
NOj-N
TOTAL
%-N
TOTAL
N03-N
TOTAL
NOj-N
TOTAL
NO^N
P
P
P
P
P
P
P
0,4
3,9
2,0
4,9
14,0
9,2
18,2
2,5
0,7
0,7
0,4
17,0
<1,0
18,9
<1,0
16,0
2,7
19,6
0,8
0,9
12,4
0,2
18,9
0,2
21,5
1,8
32,0
1,6
27,0
2,3
29,0
2,9
28,0
218,0
19
2
19
2
19
2
22
12
,6
,3
,6
,3
,6
,8
,3
,6
54,
<1,
36,
3,
0
0
5
4
84,0
8,
17,
4,
320,
291,
6
3
3
0
0
22,2
0,7
43,0
0,2
39,0
5,6
62.21
4.71
99,0
7,0
258,0
93,0
258,0
4,6
3,8
5,9
3,6
19,6
33,0
10,5
11,9
SAMPLED SEPT 17, 1969
2RAIN STORM SAMPLES
97
-------
TABLE 20, COMPARATIVE WATER CHEMISTRY (us/i) OF VARIOUS CREEKS IN THE TAHOE BASIN/ 1970,
DATE NtflniENT
8 JAN IOTAL F
%-N
16 JAN TOTAL P
1%-N
25 MAR TOTAL P
NOj-N
17 APR TOTAL F
1%-N
21 APR TOTAL F
1%-N
25 APS TOTAL P
%-N
6*Y TOTAL P
1%-N
VO
00 7 MAY TOTAL F
1%-N
21 MAY TOTAL P
1%-N
22 MAY 1%-N
3Jw TOTAL F
1%-N
FE
HJuN TOTAL?
1%-N
28 JUN" TOTAL P
1%-N
FE
28 JUN* TOTAL F
1%-N
6 JUL TOTAL P
NOyN
UWD
13.5
65.5
7.0
< 5.0
7,0
6.5
JD.O
16.5
10.0
ffi.5
3.3
11.1
16.0
5.0
lfl.5
10.0
36.0
30,
6.0
9.5
GENERAL TAYLOR
5.5
17.1
2.5
28.6
•= 5.0
5.0
< 5.0 < 5,0
7.5 7,0
<5,0 <5.0
7,5 9.0
13.1 21.5
1.1 5,6
5.0
7.5
28.5
a.
8.8 6.1
35,0 33.0
42. 22.
11.0 < 5.0
13,5 21.5
urrci*
TRUCKEE TROUT INCLINE
63.8
123.0
80,0
18.5
6.0 11.0
22.0 78.0
51.0
30.5
62.3
28.1
18,5 31.0
36,5 <0.0
1.6 11.7
6.3 15,6
21.0 33.0
9.5 20.2
20.5 51.0
88. 231.
15.8 35.5 11.5
19.0 11.0 150.0
207. 391. 382.
lfl.0 18.5 51.0
25.0 36.5 17.0
THIRD HEAVENLY sTnour McKimEY BLACKWOD TRUCKEE BURTON POLARIS WATSON CASCADE EAGU MEEKS MADDEN GLENBROOK CM SECOND TALLAC HILL
28.2 6,9 32,1
189.0 M0.2 180.0
150.0
7,0
31.0
17.0
11.8
5.3
11.1 16.9
ffll.O 98.0
35,0
13.0
11,7 55.2 8.8 0,3 12.4 5.2 5.2 11,1 1.0 1,6 1.3 1.0 3.3 2.6
6.1 25.5 7.2 7.0 8.8 0.9 3,2 1,6 0.7 2.9 1.6 1.1 0!l
31.0
33,1 66.0
50.0 313.0
316. 176.
35,0
18.0
390.
21.5
20.0
-------
TABLE 20, CONT'D,
*RD
B JUL" TOTAL P
NOj-N
FE
B. JUL' TOTAL F
%N
22 JUL TOTAL F
%-N
28 JUL TOTAL P
%H
4 Aus TOTAL P
NOj-N
FE
5 AJG TOTAL P
l%fl
12 Aus TOTAL P
NOj-N
26 Aus TOTAL P
%-N
8 SEP TOTAL F
NOj-N
17 SEP TOTAL P
NOyfl
23 SEP TOTAL P
%fl
230CT TOTAL?
NOj-N
6 Nmr TOTAL P
%-N
FE
10 DEC TOTAL F
%-«
8,0
9.2
12,
12.5
9.5
8.0
14,2
14.0
11.0
18.5
B.O
ID.
19.0
11.5
20.0
B.O
37.5
5,5
43,0
28.0
18.0
7.0
23.0
25.0
7.2
4.5
9.
12.5
12.5
B.O
20,0
16.0
U.O
23.0
5,5
9.
45,0
8.7
18,0
8.0
38.5
5.0
38.5
5.0
48,5
B.O
20.0
8.7
53.0
5.0
U.5
4,6
37.
20.0
21.0
4.0
18.3
15.
5.0
19.5
5.0
27.9
5,0
31.0
7,5
33.5
18.
26.5
37.0
5.0
25.5
25.0
7.0
27.5
5.0
27.0
30.0
30.0
8.1
10.7
21.
30,0
12,5
72,8
25,1
110.
9.0
37.1
12.0
47.3
7.0
55,0
9,0
34,5
115,
36.0
15.0
8.0
53.0
36.0
72.0
36.0
88.0
U.5
50,5
39.5
48.5
21,2
159.5
106.
35,0
69,0
8.9
28,3
85,
1B.5
31.8
18.0
10.5
B.O
19.0
16.0
15.5
97,
42.5
45.5
16.0
45.0
14,5
27.5
40.0
31.5
12.0
57.0
18.0
21.5
44.5
15.0
15.4
48,1
115,
17,4
12.3
107,
46,0
21,0
54.0
39.5
5E.O
28,0
59.5
15.0
Bl.
46.5
28.0
22.0
26.0
62,5
85.0
54,5
50,0
27,0
29,5
26.7
32.0
108.
63,5
45.0
21.2 9.1 2.6 6.6 62.2 8.0 26.9 5.9 3,1 2,7 4.6 6.0 17.0 '8.0 28.5
B.7 1B.6 68.4 3.8 0.5 8.1 18,2 28,6 2.7 15.1 10.5 B.3 79.8 6.0 8.1
68. 290. 20. 12. 8. ID. B, 40. 30. 15. 16. 36. 43. 18. 366.
26.0
21.0
30.0
54.3
44,0
220.0
117.0 12,0 3,0 7,5 3,5 8,0 67.0 20,0 4.0 4,0 3,5 9.5 50.5 53.0 3.5
186,0 100.0 48,5 6.5 5.0 B.5 30.5 59.0 9.0 42.5 14.5 18.0 58.5 6.0 12.5 36.5
76. 360. 18, 14, 9, 10, 16, 45. 38. 22. 20. 44. 44. 360. 12.
66.5
38.0
43.5
55.0
98.5
350.0
120.0
2120.0
30.0
58,5
20.3 4.8
29.0 5,2
139. 140.
38.0
34.5
* SWPLED ON THE SANE UTE AT DIFFERENT TUCS OF THE DAY.
-------
TABLE .21. COMPARATIVE WATER CHEMISTRY (vg/D OF VARIOUS CREEKS IN THE TAHOE
BASIN, 1971,
DATE NUTRIENT
2 JAN TOTAL P
1%-N
FE
21 JAN TOTAL P
%-N
28 JAN TOTAL P
%-N
1 FEE TOTAL P
%-N
20 FEB TOTAL P
%-N
1 MAR TOTAL P
%-N
28 MAR TOTAL P
%-N
FE
1 APR TOTAL P
%-N
22 APR TOTAL P
I%N
1 MAY* TOTAL P
%-N
FE
IflAY* TOTAL?
%-N
20 MAY TOTAL?
I%N
3 JUN TOTAL P
%-N
6 JUL TOTAL P
%-ii
FE
6 BUG TOTAL P
i%-H
FE
3 SEP TOTAL P
%-N
FE
SiOj-Si
18 Nw TOTAL P
%-ii
FE
SiOj-Si
18 DEC TOTAL P
%-«
SiOj-Si
"SAMPLED an SAME
HARD
7.7
23.8
0,
31,5
31.0
<2.0
13.0
13.0
6.0
18.0
5.7
25,7
32.
5.5
32.5
<5,0
12,5
2,2
11,2
18.
<5.0
25,5
<5.0
23.5
6,1
1.5
21.
6,1
3.6
6,
19,0
6,5
6,
(PPM) 7.1
27.0
31.5
8,
(PPM) 11.7
18.1
57.0
(PPM) 12.0
GENERAL
11.6
]£.9
126.
33.0
]2.0
31.5
10.5
36,0
13.5
5.0
6.0
<5,0
12.5
3.3
11.7
31,
< 5,0
11,0
•=5,0
10.0
2.6
12.6
17.
<5.0
29,2
<5.0
6.0
< 5.0
8,0
2.2
5,2
18,
1,5
1.1
1,
21.0
5.3
31.
10.1
23,5
6,5
22.
11.7
17,0
26,6
9,2
TAYUJR
8,1
31.6
1.
13.5
10.5
33.0
11.0
33,0
25.5
5.0
18,0
5,0
12.5
3,9
6.9
16,
<5.0
11.0
<5,0
8.0
1,2
6.5
12.
< 5.0
11.5
<5.0
9,5
<5.0
8,0
1,9
7,3
11.
5,2
5.9
11.
6.5
22.0
IS.
2.1
31.0
36,2
50,
1.8
19.7
16.6
1.7
UPPER
TRUCKEE
3.9
76.2
80.
13.0
-------
TABLE 21, CONT'D,
DATE MATSON TAHOE CITY GLENBROOK BLAOWOX CASCADE EDGEH
2 JAN 3.0 6.7 11,9 4,7
71.3 83.3 27.6 18.6
29. 112, 154. 102.
21 JAN
OOD HILL fees
4,8
20,8
121.
EASU ItaN COLD HOUSE* H
18.7
72.3
153.
g£CT/'' FIRST Ma*
3.3
68.5
38.
28 JAN
4Fas
20 FB
28 MAR
1APR
22 APR
4NW
4 toy"
20 BAY
3JUN
6JUL
6Aus
3SEP
ISNov
18 DEC
4.0
68.4
64,
2.5
62.7
31.
8.5
6.5
45.
9.5
7.2
11.
17.2
43.5
32.
J2.4
11.5
40.
10.4
6,2
58.4
324.
8.9
79.2
96,
58,6
292.0
97,
33,0
194.8
43,
62,4
24.0
82.
11.6
19,4
255.3
179.
14.9
209,0
192,
21.4
63.8
46.
15.6
45.8
9.
~ 360.0
13.0
102.
5,8
31.0
38,0
111.
9.8
12.1
110,0
9.9
5.8
82.2
163.
1.7
78.4
69,
36.4
28.7
40,
31.3
22,2
6.
13.3
5.5
32,
11.9
27.D
11.0
42.
12.2
8,3
23,3
11.8
1.3
13,3
15.
0.8
3.5
17,
6,1
3,2
10.
5,1
3,9
11,
4.6
11.6
4.
0.4
87.5 12.8
155.0 13.7
167. 100.
98.3 1.3
51.7 12,3
216. 30.
9.4 6.1
12.4 11.8
47. 19,
3.8
3.2
7.
44.6 30.1
22.0 7,0
80. 76,
6.8 4.2
12.0
36,3
5.6
3.3 10.8
39.5 63.3
37. 174.
0.9 2.9 20.3 6.7 13.0 46.9
37.9 80.4 65.6 48.6 31.7 40.3
«, 20. 230. 219. 214. W.
8.1 3.1 4.3
9.2 4.4 1.8
27. 12, 20,
6.9
7.2
8.
4.2 37,5 65.0
66.0 14,0 75.0
5. m. JOO.
0.5 6,1 6.1
'
5.4 10.6
36.6 164,5
1.7 9.9
"SVPLED ON SAFE DATE AT DIFFERENT TIMES OF DAY AND DIFFERENT UXATION IN THE CREEK,
101
-------
use of its watershed for land disposal of treated sewage from the
-South Tahoe treatment plant. The water from this drainage was de-
tectable well out into the lake (Goldman and Armstrong 1969) .
Transects along the course of two creeks in the disturbed Incline area
were also included during the 1969 program (Table 22). The increase in
both nitrate and phosphorus as one proceeds downstream towards the mouth
is particularly evident in Incline Creek. Third Creek showed high mid-
course values during the 24 November 1969 sampling.
102
-------
TABLE 22. WATER CHEMISTRY (pg/0 OF INCLINE AND THIRD CREEK TRANSECTS, 1969.
INCLINE CREEK TRANSECT
| g | I » £
5 d I -
P I O 3? 3- ^ -*•
DATE NUTRIENT .p JE J
O£t
-------
SECTION VI
PHYTOPLANKTON PRIMARY PRODUCTIVITY, SPECIES
COMPOSITION AND ABUNDANCE
PRIMARY PRODUCTIVITY
Introduction
The general emphasis in this study on measurement of primary productivi-
ty is based on the idea that rates of carbon fixation are a sensitive
indicator of eutrophication. The primary producers forming the base of
the food chain in the Tahoe ecosystem provide the best integration of
the complexity of physical, chemical, and biological indicators of
eutrophication and are the most sensitive indication of change in the
system known to the principal investigator.
14
Primary productivity was measured with the C method at the index
station for detection of the seasonal and long term trends. A synoptic
approach was used for determining the degree of areal variation and
productivity transects were run offshore for studies of the potential
as well as the immediate influence of certain disturbed and undisturbed
tributaries on near shore fertility. Tahoe is unusual among the lakes
of the world in having a euphotic zone that extends to at least 100 m
with one or two maxima occurring at great depths. The evolution
of the vertical profile of productivity in this remarkably clear lake
104
-------
has been an area of considerable investigation as has the trend of in-
creasing productivity over the four and one half years of study. The
question of degree and rate of eutrophication in Tahoe has been the
subject of both national and international concern. Considerable
attention is therefore given to this problem in the analyses of the
results of this portion of the investigation. The trend towards higher
rates of carbon fixation is very clear from the results presented here.
Methods
14
Measurements of primary productivity were made in situ with the C
method of Steemann Nielsen (1952) using the modifications of Goldman
(1963).
Samples taken at the index station (Figure 1) near the western shore of
Lake Tahoe, were collected weekly or tri-monthly depending on weather
conditions and personnel availability. From 28 July 1967 through
28 September 1967 samples were taken from depths at which "standard"
percentages of surface light ("total" light) was transmitted. These
corresponded to the depths at which 100%, 75%, 50%, 25%, 10%, 5%, and
1% of the surface light was transmitted. It was soon realized that:
1) sampling at irregular depths (meters) was a great inconvenience
overall, 2) significant amounts of primary productivity could still be
measured below the depth of the 1% light transmission, and 3) greater
density of measurements was needed in the region of greatest rate of
change of primary productivity with depth. The sampling was extended
first to ten fixed depths between 0 and 90 m, then to twelve depths
between 0 and 90 m on 1 November 1967. The euphotic zone was found,
however, to extend even beyond 90 m depths at certain times of the
year. The depth of 105 m w^s added on 1 May 1968 to the regular sampling
program at the index station. Since then, thirteen depths were sampled:
0, 2, 5, 10, 15, 20, 30, 40, 50, 60, 75, 90, and 105 m. A completely
105
-------
opaque PVC Van Dorn bottle was used to take each sample of water from
which subsamples for primary productivity and other measurements were
collected. Particular care was taken not to expose the samples to
surface light by filling each of the 13 duplicate 125 ml light glass
bottles in a dark container and keeping them in the dark during collec-
tion time. A dark bottle was also included for each depth as a measure
of non-photosynthetic carbon uptake. These were painted white to
14
avoid direct heating from solar radiation. Rapid addition of C sodium
carbonate solution from 20 ml glass ampoules was made with an auto-
matic syringe of 1 ml capacity calibrated by weight to deliver 0.50 ml
to the glass stoppered 125 ml bottles. In situ incubation of light and
dark bottles was from 1000 until 1400 hours. Immediately after incu-
bation the samples were transported to the lakeside laboratory in
• T>
insulated light proof containers and filtered through HA Millipore"-'
filters (0.45 - 0.02 ym pore size) of 30 mm diameter. The filtration
was done at low (10-15 mm Hg) vacuum within half an hour after the end
of the in situ exposure. Filters were air dried at least 24 hours.
Radioactivity measurements of filters were performed with an automatic
Nuclear Chicago D-47 gas flow counter (Nuclear Chicago Corp., Des
JS
Moines, 111., U.S.A.) equipped with an ultrathin micromir^ window- To
eliminate serious errors in calibration and counting,the efficiency of
counting was determined by gas phase analysis (Goldman 1968a). The
14
absolute activity of the C sodium carbonati
by the same method and was 4 to 5 yC per ml.
14
absolute activity of the C sodium carbonate solution used was measured
The total inorganic carbon content of the water was measured at each
depth from a subsample taken from the same Van Dorn sample as the C
sample. Initially inorganic carbon was determined through measurement
of pH, temperature, and alkalinity by standard acid titration techniques
(American Public Health Association 1965) and conversion using the table
of Saunders, Trama and Bachmann (1962). After July 1969, the inorganic
106
-------
12 Q
C available for photosynthesis was measured by means of a BeckmaiF
IR-215A infrared analyzer.
The results of the measurements were recorded on IBM data cards, in a
format to fit the standard computer program developed by the limnology
group at the University of California at Davis to compute all the prim-
ary productivity measurements made with the methods described above.
This program computes the mg of carbon fixed per cubic meter per hour
of incubation at each sampled depth, the mg of carbon fixed per hour
of experiment in the entire column of water under a square meter, the
mg of carbon fixed per day per cubic meter, and per day per square
meter of surface. In addition, the mg of carbon fixed under a square
meter in the entire column of water per calorie of light available at
the surface of the lake was computed. The program contains several
other optional features that were not used in the present study. An
IBM 7044 and later a Burroughs 6700 computer were used for data pro-
cessing. The Burroughs 6700 together with a Calcomp Digital Incremental
Plotter Model 563 were used for graphing Figures 18 and 19.
Other measurements taken at the index station in parallel with the pri-
mary productivity included light, Secchi depth, and temperature. Water
chemistry samples were taken at each depth from the same Van Dorn
sample whenever possible. Phytoplankton was also collected from the
same Van Dorn sample as primary productivity. Zooplankton samples were
taken in triplicate with a 150 m to 0 m vertical haul. For a specific
description and discussion of these measurements refer to Sections IV,
V, VI for phytoplankton and Section X for zooplankton.
Results and Discussion
Results of primary productivity measurements are given in Appendix B
The values of total primary productivity under a square meter surface
107
-------
-2 -1
for the day are shown in Figure 1,8. They vary between 42 mg C-m -day
on 25 April 1968 and 259 mg C-m~2-day~1 on 24 August 1971. The low value
of 25 April 1968 is due in part to some depths at which carbon fixation
in the dark bottle was higher than in the light bottle. Estimates of ex-
perimental error in integral photosynthesis have been given and discus-
sed by Goldman and Carter (1965). The mean value of primary productiv-
ity per cubic meter of water of the euphotic zone varies correspondingly
O -I _0 _]_
between 0.5 mg Om -day and 2.6 mg C'm -day . These values place
Lake Tahoe among the most oligotrophic lakes of the world. It is only
slightly more productive than the permanently frozen Lake Vanda in
Antarctica (Goldman 1968b).
Primary productivity-depth curves are shown in Figure 19. This figure
shows the results from measurements of about 6,200 samples taken from
28 July 1967 to 16 December 1971. Units are in milligrams of carbon
per cubic meter per hour of incubation time. This represents the mean
productivity per hour between approximately 10 a.m. and 2 p.m. on the
day that the samples were taken and incubated. Although primary pro-
ductivity was measured to a depth of 100 m, it is apparent on some days
primary productivity would have been found to be significantly greater
than zero at even greater depths. The euphotic zone (where net photo-
synthesis occurs) extends to at least 100 m depth for Lake Tahoe. It
is due in part to the remarkable transparency of the Lake Tahoe water,
which allows light to penetrate deeper than in most of the world's lakes
and in part to the ability of Lake Tahoe deep water phytoplankton to
efficiently utilize extremely low light intensity for photosynthesis.
The depth at which one percent of the light received on the surface of
a lake is transmitted is generally considered to be the depth of the
euphotic zone. This is often not the case in Lake Tahoe where values
of primary productivity significantly greater than zero are recorded
much below the depth of one percent light transmission. Some examples
of this for 1969 are presented in Figure 20. On 23 May, in particular,
108
-------
JFMflHJJflSOND
cc
D_ ,
JFMHMJJHSOND
Figure 18. Total primary productivity at the index station of Lake
Tahoe from mid-1967 through 1971.
109
-------
PRIMflRT PRODUCTIVITY MG C/MS.HOUR
il.'t 0.6"0.0 0.3 0.6 0.0 0.3 0.0 0.3 0.0 0.3 0.6 0.0 0.3 0.0 0.3 0.0 0.3 0.6 0.0 0.3 0.0 0.3 0.0 0.3 O.B 0-1 _0.0 3-'I
/ 1
28 JUL 2 RUG 9 BUG 14BUG 25BUG 2 SEP 7 SEP 14SEP 2! SEP * 28SEP ' 5 OCT ' 11OCT ' I80KT
0,0 0.3 0.0 0-3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 O-3 °-P "-"^ °-6
T
1968 ,
260CT "l NOV 4 8 NOV 4 15NOV * 1 DEC 8 DEC ' 2 JBN 17JBN ' 24JRN ' 8 FEB I4FEB 20FEB 29FF.B B M3R
CL:
IJLJ
I—
3..:
i—
CL.
l.i I
t 1
13MRH * 20MHR * 2SMHR * 2 RPR 11 flPR " lORPH 2SBPR f I Mflf / 3 nflf
«~
/ 16MBT
22HH1 /29MBT / 'i IIIN
0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0
0.3 0.0 0.3 0,6 0.0 0.3 0.60.0 0.3 0.0 0.3 0.0 0.3
12JUN /I9JUN /26JUN
*11JUL / 17 JUL \ 24JIJL
0 0.3 0.0 0
7 ~r
7 RUG j LZfllJG ( 21 HUG / 28RIJG /2 5F.H | 11 'i
1.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 ^1.0 0.3 0.0 0.3 0.0 0.3 _0,0 0.3 0.0 u.'l 0.0 0.3 0.0 0.3 (J.<
^
' 17SEP / 26SEP / I50CT / 190CT J 270CT f 2 NOV J 1 DEn /7 DEC J 16JBN / 1 FEB f 1SFEB /I MBR J 15HHR ^TltJHHR
0.0 0.3 0.0 0.3 0.0 0.3 OlO 0.3 0.0 0.3 0,0 0,3 Q.O 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 0.0 0.3 O.D 0,3 0.0 0.3
I3BPR /2SBPR J 9 MBY J 23MHT / 7 JUN \ 20JUN / 1 JUL J 8 JUL / 1SJUL f 22JUL / 24JUL 30JUL J 5 BUG / I4BUG
Figure 19a. Primary productivity-depth curves at the index station of Lake Tahoe from mid-1967
through 1971.
-------
PRIMflRY PRODUCTIVITY MG C/MS.HOUR
iooJ/ 20RUE J 28RUG * 3 SEP \ 9 SEP f 15SEP / 23SEP / 100CT /220CT / 26OCT / 12NOV / 23NOV J 5 DEC { 16DEC J 26DEC
19
6 JRN 1 19JHN / 30JRN J 10FEB f 23FEB / 28FEB f 10MBR /23MRR J 2 RPB / 15BPR / 2 HRY / 13MRY /25MHY / 16JUN
0.0
o-rt
cc
•\i \ }
1 JUL /7 JUL y'ltJUL J 20JUL. /~24JUL / 31 JUL \ 11 HUG / 17RUG / 24RUG | 2 SEP /8 SEP / 16SEP / 23SEP f~2 OCT
"^-, ' '^= X "N "'^ "'Vf "V
,97, 7 S )
.„ ^ I40CT ^ iONOV f 6 DEC f 22DEC / 8 JRN f 21JRN /3 FEB /12FEB /22FEB /7 MRR /17MRR /2 RPR ^l3RPR /23RPR
0.0
i
100 f S NRY / 19MHY / 1 JUN T 14JUN T 25JUN T 1 JUL T 8 JUL t 14JUL / 22JUL /3 BUG /11RUG /HRUG /24RUG
2 SEP /9 SEP /16SEP \ 23SEP / 5 OCT f 300CT / 9 NOV f 2HNOV / 6 DEC I I6DEC
Figure 19b. Primary productivity-depth curves at the index station of Lake Tahoe from mid-1967
through 1971.
-------
PRIMARY PRODUCTIVITY (mg C-m-3.hr-')
-. I. .1 .... L^ 1 L L
50 -
100-
0 100 0
.00 .30 .60
50 ^
1%
100 H
100
.00 .30 60
j U-
7^— LIGHT
PRIM'ARY PRODUCTIVITY
TEMPERATURE
8 JUL
-BIOMASS
10°
10 OCT
100 0 100 200
PHYTOPLANKTON BIOMASS (mg rrf3)
300
400
Figure 20. Representative vertical profiles of primary productivity, temperature, light,
and phytoplankton biomass at the index station of Lake Tahoe in 1969.
-------
one percent light was recorded at 60 m with a euphotic zone greater
than 105 m. On that day the maximum primary productivity of 0.40 mg
—3 —3 -1
C-m per hour (and 3.54 mg Om -day ) occurred at 50 m. Only 2.4
percent of the surface light reached that depth! This represents
_2
8.28 langleys of light (gm cal-cm ) available for photosynthesis at
-3 -1
50 m that day, and a photosynthetic efficiency of 0.41 mg C-m -ly
Similarly on 30 March 1969, at 1% light transmission there were 2.7
langleys of light available for photosynthesis which gives an efficiency
-3 -1
of utilization of 0.86 mg C'm *ly . These values of efficiency are
similar to those measured in Castle Lake, California (Goldman 1970b)
where the depth of the euphotic zone is only 30 m.
Maxima of primary productivity in Lake Tahoe are found at remarkably
great depths at times, as compared with other lakes. These correspond
quite often to times of high seasonal productivity. These deep maxima
are commonly found at 50 or 60 m, but occasionally as deep as 75 m
(Fig. 19 and Fig. 20). On 1 May, 19 June, and 26 June 1968 a maximum
occurred at 75 m.
The study of four and a half years of data, collected regularly with
relatively short intervals of time between sampling, made apparent an
extremely interesting pattern of seasonal change in the shape of the
primary productivity-depth curves, or "profile" of primary productivity.
Lake Tahoe productivity has two different, typical, profiles depending
on the time of the year. In winter and spring it is a unimodal curve
with one maximum. This single maximum appears near the surface of the
lake, sometimes in December, while there is very little light and over-
all primary productivity values are low. The maximum slowly descends
deeper into the lake as solar radiation increases and overall primary
productivity values increase. During this period the lake is homo-
thermal. The highest value of this maximum is reached at the very end
of the winter or in the first half of spring at 50 m or 60 m depth. It
113
-------
remains at that depth or sinks another 10 or 15 m until May or early
Juen when surface water temperatures increase significantly and strati-
fication sets in. At that time the simple curve of primary productivity
that had persisted through the last five or six months gives way to a
curve with two maxima. The two maxima appear first rather close to-
gether in the upper part of the water column. The upper maximum remains
in the first 20 m of water until November,while the second maximum re-
mains below 30 m and as already noted may occur as deep as 75 m. These
depths correspond to regions in the hypolimnion for the "deep" maximum
and in the epilimnion or in the vicinity of the discontinuity layer for
the upper maximum. This two-maxima shaped curve of primary productivity
and its relation to the thermocline is not unfamiliar in lakes and has
been previously described for Castle Lake (Goldman, Stull, and Amezaga
1973). As the surface water cools off in the fall and the upper 30 or
40 m of water becomes homothermal, more than two maxima might occur
temporarily. The lower maxima will eventually disappear as the light
intensity declines in fall and winter and the simple shaped, one maximum,
curve returns.
The upper 100 m characteristically undergoes gradual nitrogen depletion
during the spring and summer months. Although most index station
sampling was restricted to the upper 105 m (Table 9), deep water
sampling in 1969 and 1971 (Table 13) shows higher levels rather con-
sistently below 100 m. Paerl et al. 1974 have clearly demonstrated the
importance of winter mixing in 1973 to redistribution of the limited
nitrate supply. Further, the phytoplankton clearly reduce the nitrate
level in the euphotic zone.
Extremely low values of photosynthetic carbon fixation, a remarkably
deep euphotic zone with deep maximum, and the seasonal change in the
profile are all characteristics of the primary productivity of Lake
Tahoe that have prevailed through the course of the study; the preceeding
114
-------
work as well as the ongoing research program.
Careful examination of several consecutive years of measurements at
Lake Tahoe point out, however, other characteristics that may be indica-
tive of how long this particular stage in the life of the lake might be.
These characterize the long term trends of primary productivity that
only become apparent when we compare the total primary productivity of
one year with the next, and the relative time of occurrence of seasonal
maxima or minima.
The monthly total of-primary productivity and the yearly total primary
productivity were calculated for each year from the values of primary
productivity per day under a square meter of lake surface (Fig. 2l)•
These values were obtained by mathematical integration under the seasonal
curve shown in Figure 18 per month and per year. Verification of these
computer results was done by comparison with values obtained by hand with
planimetry of the area under the same curves. The results indicate that
there has been a steady increase in the primary productivity of Lake
Tahoe from year to year over the four years of most intensive study
(Table 23).
Table 23
Total primary productivity per year under a square meter surface at the
Lake Tahoe index station.
Year
1959-60
1968
1969
1970
1971
_O -1
mg -Om -year •L
38,958
46,685
50,525
52,467
58,655
Percent increase over
the previous year
20% since 1959-60
8.23%
3.84%
11.79%
115
-------
220-
T 180-
o
TJ
cvi
I
O
o>
140-
100-
60
01967
QI968
-A 1969
•1970
1971
/ \ X
V--A
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 21. Seasonal total primary productivity at the index station of Lake Tahoe from
mid-1967 through 1971. Each point is the average for the month.
-------
The difference between the 1971 and the 1968 values represents an in-
crease of 25.6 percent in total primary productivity at the index
station over a period of only four years.
Earlier measurements of primary productivity have been made since 1959
as part of a series of northern California lake studies (Goldman 1964)
The data collected monthly off Cave Rock (Fig. 1) between 4 June 1959
and 31 May 1960 were used for comparison with total annual productivity
—2 —1
of the recent years. Any value of mg C-m -day , that seemed to have
been an underestimate of the primary productivity for the day (if the
deepest sampling depth measured was above the depth of the euphotic
zone), was increased accordingly by assuming the compensation depth
to be at 100 m. This assumption was based on observations of the
vertical curves of primary productivity of the years 1968 through 1971
as reported above. These results were graphed and the area under the
curve was planimetered to give a comparative value of total annual
primary productivity for the year 1959-60. From 1968 through 1971 si-
multaneous measurements of primary productivity were made at the index
station and off Cave Rock on thirteen different dates. The averages of
these measurements from these two widely separated stations gave a ratio
of 0.9933. On this basis of less than 1% difference in the two stations,
the 1959-60 Cave Rock data is included in the plot of the change in
productivity at Lake Tahoe from 1959 through 1971. .This value was
-2 -1
35,326 mg C-m -year which would indicate an increase of about 32%
from 1959-60 to 1968 and an increase of 66% from 1959-60 to 1971! Two
of the single monthly measurements for 1959-60 indicated no measurable
primary productivity at all, due to very stormy conditions and very
low light intensity on these two days. To use a more representative
monthly value of primary productivity for these two months the zero
value was replaced by a three point average using the value of the
measurement before and the measurement following the particular day.
117
-------
The total primary productivity per square meter for the year was recal-
culated and found to be a conservatively high value of 42,590 mg
C-m"2-year"1. The mean of the low estimate and the high estimate of
-2 -1
primary productivity per year for 1959-1960 is 38,958 mg C-m -year
and was considered the best estimate for comparison with recent years.
This value indicates an increase of about 20% from 1959-1960 to 1968
and an increase of 51% from 1959-1960 to 1971 (Table 23)- The graph of
the annual primary productivity at Lake Tahoe between 1959 and 1971 is
shown in Fig. 22. The curve that seems to fit the 1968 to 1971 data
best was drawn through the four points and dotted back to the 1959-1960
value. The regression line (A) through the five data points and the
regression line (B) through the four points of the recent years are
also indicated.
We have examined a variety of relevant dependent variables including
weather, light, and water chemistry and find that this is not explainable
by the data we have on them. No change in these variables can account
for this increase in primary productivity. Our observed change in
annual incoming solar radiation, if it represents a real change rather
than instrument fatigue (see Section IV), should have had the opposite
effect on productivity of the lake and we should have seen a slight
decrease. A rough comparison of nitrogen and phosphorus values can be
made from the data collected in 1962 with that of the present (Table 24).
Although the sampling sites were different between 1962 and the other
year, and the analytical techniques used were not the same, the results
would certainly seem to suggest a higher nitrogen concentration in the
surface water of the lake in 1968, but these values dropped back the
following years to the range measured in 1962.
It appears likely that the overall fertility of the lake has gradually
continued to increase since 1959-60 (when less intensive data was
collected) and that production has taken rather long to peak out after
118
-------
80,000
7 0,000 J,
60,0 OOH
CVJ
i
u 50,000^
o>
E
40,000^
30,000
1958 I960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980
Figure 22. Annual primary productivity at Lake Tahoe between 1959 and 1971. The regression
line (A) through 1959-60 and 1967-71 and the regression line (B) through 1967-71
are also indicated.
-------
TABLE 24, A COMPARISON OF THE NITROGEN AND PHOSPHORUS CONTENT (pg/i) OF SURFACE
WATER OF LAKE TAHOE IN 1962 AND 1968-1971.
NOj-N 1%-N P(TOTAL)
1962
NUMBER OF SAMPLES
RANGE
MEAN
1968
NUMBER OF SAMPLES
RANGE
MEAN
1969
NUMBER OF SAMPLES
RANGE
MEAN
1970
NUMBER OF SAMPLES
RANGE
MEAN
1971
NUMBER OF SAMPLES
RANGE
MEAN
4
2.0-6.7
5
.
10
8.0-20.0
13.3
3
0.0-5.0
2.0
9
1.7-11.8
b.5
2
4.1-5.3
4.7
4 4
—
2 7.5
13 11
10.0-43.0 0,9-1.9
20.8 1.6
3
2.6-3,9
3.0
10
1.2-7.0
4.7
2
3.3-6.3
4.8
120
-------
sewage diversion began. This probably reflects continued loss from
existing septic tank leach fields, continued loss from a land disposal
site at South Shore (see Section VII) > the fact that erosion and leaching
have been increasing with the building boom, and finally, that the lake,
as often noted, is extremely efficient in recycling nutrients once they
enter the system.
Goldman and Armstrong (1969) comparing the average daily value for the
one year of data from June 1959 through May 1960 to that of the one
year of data from August 1967 through July 1968 speculated on whether
or not the higher 1967-68 data reflected the high spring runoff of 1967
or actually evidenced an alarming increase in fertility over the previous
eight years. We can now say with more assurance that, in view of the
three and one half years of data following their measurements, the pri-
mary productivity for 1967-68 most probably reflected both. The alarm-
ing increase in fertility that was observed over the previous eight
years was indeed a continuing trend in increasing fertility. The summer-
fall data of 1967 was, however, unusually high (as can be seen from
Fig. 18) and was probably influenced by the high spring runoff that year.
Careful scrutiny of primary productivity in Lake Tahoe is continuing
and it will be of great interest to see how long this trend will con-
tinue. With the large block of data now available a model can soon be
built which should enable us to predict with considerable confidence
alternative futures at different levels of development for the produc-
tivity and transparency of this unusual lake.
The mean primary productivity per day for each month of each year was
calculated from the monthly total which was obtained by integration.
Results are shown in Figure 21. The curve of mean monthly productivity
exhibits a steady shift in the seasonal maximum from one year to the
next. The maximum, or peak of primary productivity, was recorded in
121
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March 1968, in April 1969, then shifted further to May 1970, and fin-
ally to August in 1971. This corresponds in 1968 and 1969 to maximum
seasonal primary productivity occurring while the lake was not strati-
fied in the upper 120 m and while the profile of the primary productiv-
ity curve was unimodal with a maximum at a depth of about 50 m. In
May 1970, the seasonal maximum corresponded to the onset of stratifi-
cation and the onset of the two peaks in the profile. In 1971 the
seasonal maximum in August occurred when the lake was strongly strati-
fied and while the profile of the primary productivity curve was bi-
modal with two very accentuated peaks at about 10 m and 50 m (Fig. 19) •
Several factors have been considered that might have caused the shift
in seasonal maximum. The total amount of solar radiation per month
for the months preceding the maximum in 1968 was not greater in 1968
than in the following years nor was the amount of solar radiation in
March 1968 greater than in March of the following years (Fig. 4).
Similarly, for the following years, the months of maximum primary pro-
ductivity did not coincide with a month of unusually clear weather for
that time of year nor did it coincide with unusually clear weather on
the days when primary productivity was measured.
The curves of solar radiation (Fig. 3) show, however, that there were
fewer very dark days in the first three months of 1968 than the fol-
lowing years (see Section IV), thus allowing the biomass of the phyto-
plankton to keep increasing early in the year (Fig.23). It is inter-
esting to speculate on the causes of the subsequent shifts the following
years. Vie know now that in some years (March 1973, Paerl et al. 1974)
Lake Tahoe does mix all the way to the bottom (over 400 m). Some years,
however, the lake mixes only partially. Good profiles of temperature
below 135 m were not available until late in 1969 (see Section IV). How
early and how well Tahoe mixes may determine the time and the size of
the seasonal maximum of primary productivity through return of nutrients
i
122
-------
to
160
140-
120-
100-
80-
60-
p.
A -- -
A -- A
x
/
**A
\
1967
n n 1968
A A 1969
A
A
o
•D-
x\
""D
\
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 23. Seasonal phytoplankton biomass (mean for the euphotic zone) at the index station
of Lake Tahoe from mid-1967 through 1969. Each point is the average for the
month.
-------
(particularly nitrate) to the euphotic zone. The year 1968 might have
been a year when good growth conditions came early for the phytoplankton
which then depleted the nutrients from the euphotic zone early in the
season. Additional nutrients may not have been available from deeper
depths to sustain the population if there was not a complete overturn
in the late winter of that year. The unusually high population of zoo-
plankton in May, June and July of 1968 could also have grazed down the
phytoplankton population (see Section X). The year 1969 may have been
similar to 1968 but had many more dark days (31 versus 14) during the
first months of the year, which delayed the buildup of phytoplankton
and the maximum of primary productivity (see Section IV). This maximum
was, however, considerably greater than that of 1968. On the other hand,
1970, which saw the maximum of primary productivity occur in May at
the onset of stratification, might well have been a year when there was
moderately deep mixing in late winter. That year exhibits an initial
small peak of primary productivity in February when the "profile" of
productivity is unimodal and the water is not stratified in the upper
120 m. This was the time of year when the seasonal maximum of 1968 and
1969 occurred. The primary productivity dropped in March and April.
A second and higher maximum occurred in May suggesting new nutrients
were supplied in April to the euphotic zone.
The primary productivity curve for 1971 suggests good early conditions,
which created a small initial seasonal peak in February and March,
and perhaps complete or nearly complete mixing in the spring. Some
evidence for mixing is found in the nearly homothermous conditions
extending to 400 m (see Section IV, Table 6). Mixing may have re-
supplied enough nutrients to the euphotic zone to support a large
second seasonal peak of primary productivity during stratified summer
conditions when the depth profile of primary productivity is bimodal.
The shift in the seasonal peak of primary productivity was reflected
124
-------
in the phytoplankton biomass for the years 1968 and 1969 (Fig. ^23).
During these years all phytoplankton samples collected in parallel
with primary productivity depths were enumerated. In 1968 the mean
monthly biomass of the phytoplankton peaked in March. Its value was
still high in April and May and dropped drastically in June of that
year. In 1969 the phytoplankton biomass was highest in April, May and
June with the peak value in May and a drastic drop in July.
The shift in the seasonal peak was also followed closely by the number
of zooplankters. Their seasonal maximum occurred the month following
the highest phytoplankton biomass values and one or two months after
the maximum primary productivity.
In March 1968, at the time of the seasonal maximum of primary produc-
tivity, the phytoplankton biomass was dominated by the three diatom
species which were also dominant the rest of the year. Fragilaria
crotonensis had the highest biomass value followed by Cyclotella bodanica
and Melosira crenulata (Fig. 24 ). From 6 March 1968 through 2 April
1968, 78% of the total phytoplankton biomass was accounted for by these
three species. On 6 March 1968, when primary productivity was partic-
ularly high and had its maximum at a depth of 50 m, the bulk of the
phytoplankton biomass was also found at 50 m. The three dominant
species were the same diatoms as mentioned above, followed by the
chrysophycean Dinobryon sertularia.
On 25 April 1969,at the time of maximum primary productivity, 89% of
the biomass of the phytoplankton was accounted for by the three diatom
species. These were dominant throughout the year in 1969, and consisted
of Fragilaria crotonensis, Cyclotella bodanica and Melosira crenulata.
The fourth most abundant diatom species that day was Stephanodiscus
astrea. At 40 m depth where the local maximum occurred, the phytoplank-
ton was dominated by these same species.
125
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LAKE TAHOE 1966
JAN FEB IUR APR MAT JUNE JULY AUG SEPT OCT NOV DCC
Figure 24. Seasonal variation of phytoplankton species at the index
station of Lake Tahoe. Biomass variation of the three
dominant species (A), variation in number of three species
of Fragilaria (B), and variation in number of three flagellate
species (C) found in Lake Tahoe in 1968.
126
-------
In 1970, although we do not have all samples enumerated for that year,
it appears that the dominant phytoplankton at the time of maximum pro-
ductivity are Synedra radians, Melosira crenulata and Cyclptella
bodanica. Fragilaria crotonensis, which frequently dominates, was only
the fourth highest in biomass of the phytoplankton species.
We hope to be able to examine more closely in the near future the
samples of phytoplankton for the years 1970 and 1971 to see if the
change in time of occurrence of the maximum primary productivity
created further changes in dominance of species of algae. Those
species which are most efficient in utilizing available resources of
nutrients, light, and temperature would be expected to become the domi-
nant forms. There are major environmental variables at Tahoe which
cause the wax and wane of the phytoplankton. The obvious influence of
solar radiation, water temperature, and the amount of nutrient runoff
from the watershed are further modified by the amount of wind mixing
that occurs when stability is lowest. It may soon be possible to
predict the algal groxtfth in the lake by following critical winter and
spring parameters.
.PHYTOPLANKTON SPECIES COMPOSITION AND ABUNDANCE
Methods
From August 1967 through December 1971 a sample for phytoplankton enum-
eration was collected from the same Van Dorn sample each time primary
productivity was measured. The water was collected in a 125 ml glass
bottle and immediately fixed with neutral Lugol's solution. Preserved
samples were then brought back to the central laboratory at Davis where
preparation of slides, counting and data processing were done. The
Millipore filter method was used throughout this study. In this method,
127
-------
100 ml of the sample were filtered through AA Millipore gridded filters,
25 mm in diameter. The filters were then dried completely, trimmed and
cleared with cedarwood oil. Filters were mounted on slides slightly to
the left of the center, covered with coverslips and ringed with Hyrax.
The counting was done using a stage restriction mechanism with the
Wild M-40 inverted phase microscope. Black and white photographs of
each species were taken with a polaroid camera attachment on the micro-
scope. Photographs were collected in a book for future reference. A
biomass estimate of an "average" individual of each species was done by
approximating geometrically the volume of several individual cells,
calculating the average volume of an individual of the species and con-
verting it to fresh weight by assuming a density of one.
Raw counts were recorded directly on data sheets that have been speci-
ally designed for compatibility with the format required by computer
data cards and by our computer program for phytoplankton data reduction.
These special data sheets are such that no additional transcription or
other work is necessary before having computer cards punched. At the
same time these data sheets are sufficiently self-explanatory to be
kept as a very good original record of phytoplankton raw counts. A
computer program was developed that reduces all phytoplankton data and
prints out results of phytoplankton concentration and biomass at each
depth, total and average for the entire "integrated" column of water.
This is printed for each species, for each class and for the entire
phytoplankton population. Results of calculations of community diver-
sity, diversity per individual, and redundancy are also printed at
each depth where the phytoplankton has been sampled and for the entire
column of water. The expression for diversity adopted for this program
is the information measure of diversity used by Margalef (1958, 1965),
Goldman et al. (1968) and Goldman (1970b).
128
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Results and Discussion
There are over 160 species of phytoplankton in the waters of Lake Tahoe
of which 129 are found at the index station. The phytoplankton popu-
lation is composed mainly of diatoms of which there are 112 species.
The rest of the phytoplankton consists of eight species of Chlorophyceae,
three of Cyanophyceae, three of Chrysophyceae, two of Dinophyceae, and
one Cryptophycea. Ten of the Bacillariophyceae are centric diatoms,
the other diatoms are pennates. The name of each phytoplankton species
identified at the index station together with its mean cell volume is
given in Table 25.
All samples collected in parallel with the primary productivity at the
index station between 9 August 1968 and 13 May 1970 were identified
and enumerated. Samples from 22 additional dates in 1970 and 1971 were
carefully examined for this report. Thirteen different depths were
sampled for each date. Although some aspects of the results of 1970
and 1971 are considered, our main conclusions on the phytoplankton
population in Lake Tahoe will be drawn from the results of 1967, 1968,
and 1969 data.
The average number of cells per ml of the entire 105 m water column for
each species on each sampling day is given in Appendix C. The values
were obtained by examining 13 samples from 13 different depths between
0 and 105 m (except for early dates when the water column was sampled
to 90 m only; see previous subsection). The number of cells at each
depth were weighted according to depth and summed to obtain the overall
integrated value of the total number of cells for each species present
in the entire 105 m water column. This value divided by the number of
ml of water in the water column is the average number of cells per ml.
Some small flagellates were present in Tahoe, but because of difficul-
ties in identification and enumeration are not reported here. Total
129
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TABLE 25, PHYTOPLANKTON SPECIES FOUND AT THE INDEX STATION
OF LAKE TAHOE/ INCLUDING CELL VOLUMES
MCILLARIOPHYCEAE
CYr,|,DTFJ.iA ANTISUA
CYCLOTELLA OCELLATA
CYCLOTELLA STELLIGERA
HELOSIRA CRENULATA
tlELOSIRA GRANULATA
MELOSIRA VARIANS
ftLOSIRA UNDULATA
STEPHANODISCUS ASTREA
ACHNANTHES CLP/EI
ACHKANTHES EXIGUA
ACHNANTHFS f( FXELLA
ATHNAMTWFS IAIMOIATA
ArWNANTHFS ! INFARIS
ArHNANTWFS Nffll. II
flrjtJANTWFS PpRAGAI 1 I
AMPHIPRORA PALUDOSA
AMPHIPLEURA PELLUCIDA
flHPHORA OVALIS
ASTERIONELLA FORMOSA
COCCONEIS DISCULUS
COCCONEIS PLACENTULA
COCCONEIS RUGOSA
CYMBELLA CUSPIDATA
CYMBELLA GRACILIS
CYMBELLA LANCEOLATA
CYMBELLA VENTRICOSA
CYMBELLA SINUATA
CYMBELLA PROSTRATA
CYHATOPLEURA SOLEA
DlATOMA ANCEPS
DlATOMA HIEMALE
DlATOHA VULGARE
DlPLONEIS ELLIPTICA
DlPLONEIS OCULATA
DlPLONEIS FINNICA
EUNOTIA NAEGLII
EUNOTIA TENELLA
EUNOTIA TRIODON
EUNOTIA PERPUSILLA
EUNOTIA PECTINAUIS VENTRICOSA
EUNOTIA PECTINAUIS
EPITHEMIA SOREX
EPITHEMIA TURGIDA
EPITHEMIA ZEBRA
EPITHEMIA ARGUS
FRAGILARIA CROTONENSIS
FRAGILARIA INTERMEDIA
FRAGILARIA PINNATA
FRAGILARIA VAUCHERIAE
FRAGILARIA CONSTRUENS
FRAGILARIA LEPTOSTAURON
CELL VOLUME
635
1778
157
77
1209
1806
1301
170950
707
350
300
880
120
120
265
130
96000
1080
2500
180
500
503
25D
10000
1275
6000
1800
375
15750
37370
1000
1060
3600
1781
330
11100
510
590
2500
in
793
1750
5125
66000
11520
510
2500
175
276
2] 5
210
BttlLLARIOPHYCEAE (fONT.)
FRAGILARIA CAPUCINA
FRUSTULIA RHOMBOIDES
GOHPHONEMA ACUH1NATUM
GOHPHONEMU PARVULUM
GOHPHONEm CAPITATUM
GOHPHONEMA VE^^HICOSUH
HANTZSCHIA AIIPHIOXYS
GYROSiSm ATTENUATUM
HANNEA ARCUS
flASTOGLOlA SMITH1I
MERIDION CIRCULARE
NAVlgjLA AURORA
ffaVICULA BAC1LLUM
NAVICULA COCCONEIFORMIS
tlAVlCULA EX1GUA
HAVICULA FESTIVA
flAVlCULA HUTia
NAVICULA PSEUDCSCUTIFORMIS
NAVICULA PUPULA
HAVICULA RADIOSA
llAVICULA SCUTTEL01DES
HAVICULA CAPITATA
HAVICULA CUSPIDATA
NAVICULA COSTULATA
NEIDIUH HITCHCOCKIi
NEIDIUM AFFINE
NlTZSCHIA FILL1FORMIS
NlTZSCHIA AMPHIBIA
NlTZSCHIA SINUATA
NlTZSCHIA PALEA
OPEPHORA HARTY1
OPEPHORA AMERICANA
PlNNULARIA BICEPS
PlNNOLARlA AESTUAR11
PlNNULARIA SUBCAP1TATA
PlNNULARIA ABAUJENS1S
PlNNULARIA RUPESTRIS
RHOICOSPHENIA OJRVATA
RllOPALOlllA G1BBA
STAURONEIS PHOENCENTERON
STAURONEIS SMITHII
STAURONEIS ANCEPS
SURIRELLA OVATA
SYNEDRA AMPHICEFHALA
SYNEDRA MAZAMENSIS
SYNEDRA RADIANS
SYNEDRA RUMPENS
SYNEDRA SOCIA
SYNEDRA ULNA
SYNEDRA INCISA
TABELLARIA FBIESTRATA
TABELLARIA FLOCCULOSA
CELL VOLUME
-------
phytoplankton biomass at each depth on each sampling date is given in
Appendix D.
The ten most dominant species in number of cells and the ten most domi-
nant species in number of occurrences on a day were determined for each
year of the study, for all years from 1967 through 1971 and for the
three years from 1967 through 1969. This was done by comparing the to-
tal per year of the number of cells per ml of each species and ranking
the species in order of decreasing number from the species with the lar-
gest number of cells enumerated that year to the species with the smal-
lest number. Thirteen of the most dominant species on this basis have
been graphed on a logarithmic scale using the computer, and are shown in
Figure 25. The ten most dominant species for the years 1967-1969 were:
Fragilaria crotonensis
Melosira crenulata
Fragilaria pinnata
S tephanodiscus astrea
Cyclotella bodanica
Sphaerocystis schroeteri
Peridinium sp.
Dinobryon sertularia
Cyclotella ocellata
Kephyrion ovum
Three additional species were found to be among the ten dominant species
when numbers were summed over the five years, 1967 through 1971. These
were Synedra radians, Asterionella formosa, Navicula radiosa. Cyclotella
stelligera, an uncommon species in Lake Tahoe for the years 1967-1971,
is also presented in the graph. This species has been found in large
numbers in some recent midlake samples (1972-1973 unpublished data).
The dominant species listed above were also among those species that
occur the most frequently at the index station. Comparison of the
131
-------
OJ
FflRGILflfllfl P1NNHTR
SrCRfWOOJSOJS flSTFER 196''
CTCLOTELLH BOOWICR 1967
A-A/
J J R S 0 N D
Figure 25a. Seasonal variation in numbers of the 13 most dominant phytoplankton species
at the index station of Lake Tahoe from mid-1967 through 1971. Cyclotella
stelligera and the total phytoplankton number are also .shown.
-------
U>
SPHBOWCTSTIS SCHHOCTER! t9E?
DINDBBTON SEHTULFWIR 196?
CTCLOTELLfl OCELLBIfl
KEFHTBIOI* OVUH
Fxgure 25b. Seasonal variation in numbers of the 13 most dominant phytoplankton species
at the index station of Lake Tahoe from mid-1967 through 1971. Cyclotella
stelligera and the total phytoplankton number are also shown.
-------
U)
MWICU.R HOI05H
CTCLOTELLR S1EU»
Figure 25c. Seasonal variation in numbers of the 13 most dominant phytoplankton species
at the index station of Lake Tahoe from mid-1967 through 1971. Cyclotella
stelligera and the total phytoplankton number are also shown.
-------
seasonal variation in total phytoplankton population and the seasonal
variation in Fragilaria crotonensis (Fig. 25) shows the importance of
this species in the Lake Tahoe phytoplankton concentration. Three
species dominated the biomass of the phytoplankton. The pennate diatom
Fragilaria crotonensis formed by far the most important algal biomass
and easily outgrew the two centric diatoms Melosira crenulata and
Cyclotella bodanica (Fig. 24). These three species accounted for about
80% of the total biomass of the phytoplankton during most of the years
1968 and 1969. They were the dominant species during maxima of primary
productivity (see previous subsection) and showed similar seasonal vari-
ation. Optimum growth for other species, however, was achieved at
various other times of the year (Fig. 24). Some very clear successional
patterns can be observed. In 1968 F_. crotonensis peaked during the first
half of the year, followed by maxima of two other species of the same
genus after June (Fig. 24). Among the three important flagellates,
Kephyrion ovum was replaced in May 1968 by Dinobryon sociale, which was
in turn succeeded by Peridinium sp. (Fig. 24).
The mean monthly total phytoplankton biomass was evaluated by mathe-
matical integration (as per mean monthly primary productivity; see
previous subsection) for the data from August 1967 through December
1969 (Fig. 23). The biomass peaked in March-April-May 1968 following
the seasonal primary productivity maximum of April 1969. This lag be-
tween maximum primary productivity and biomass of the phytoplankton is
14
to be expected if the C method is actually a measure of the rate of
change of the biomass, i.e. the primary productivity is mathematically
related to the phytoplankton as the first derivative of the biomass
(Amezaga, Goldman, and Stull 1973). The phytoplankton data for Lake
Tahoe in 1968 and 1969 seems to nicely support this well-established
assumption.
The phytoplankton population, as indicated by mean monthly biomass,
135
-------
crashed in June of 1968 and in July of 1969- These months corresponded
to the seasonal maximum of numbers of zooplankton which were probably
grazing heavily on the phytoplankton and caused their decline. The
importance of the loss of Daphnia rosea from the system is discussed
in Section X and may well be related to the population shifts in phyto-
plankton observed.
136
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SECTION VII
SYNOPTIC SURVEYS, BIOASSAYS, REMOTE SENSING,
LAND DISPOSAL, AND NTA EXPERIMENTS
SYNOPTIC SURVEYS
Introduction
Culture experiments show that Lake Tahoe is deficient in available iron,
that the interaction between nitrogen and phosphorus is complicated,
and that the various tributaries of the lake differ greatly in their
stimulation of algal growth (see following subsection; Goldman and Arm-
strong 1969; Goldman, Tunzi, and Armstrong 1969).
The areal variation in productivity in the lake was first documented
during two synoptic studies in 1962 (Goldman and Carter 1965). Three
small synoptic surveys were done in 1967. Thirteen synoptic studies
covering a large number of stations were done between 1968 and 1971 and
are reported here.
The present study is directed toward identifying the major sources of
nutrients reaching Tahoe and the patterns of eutrophication they produce
in the lake. The synoptic studies proved to be a particularly useful
approach to the problem of identifying nutrient sources and evaluating
their effect on adjacent Tahoe waters. These investigations include
137
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primary productivity of phytoplankton and some examination of species
composition, biomass, and biotic diversity.
In addition, variation in periphyton growth and community over the
whole lake is reported in Section IX and variation in benthic inverte-
brate organisms and their diversity is covered in Section XI.
Synoptic studies have often been made at sea where oceanographic vessels
collect large numbers of samples in transects or over broad areas.
Such collections are limited in their coverage by the time required for
sampling each station and the slow speed of the vessels between stations.
Further, most of the marine synoptics cover days, weeks, or months so
that time and weather are important variables. Some improvement is
anticipated as automated sampling and aerial reconnaissance techniques
are improved, but the limitations indicated above still remain as
serious problems. Synoptics covering physical and chemical parameters
1 have been made in the Great Lakes (Ayers et al. 1958; Anderson and
Rodgers 1963; Saunders, Trama, and Bachmann 1962). Synoptic surveys of
two New Zealand lakes- for water chemistry, phytoplankton, and zooplank-
ton distribution were made by Fish and Chapman (1969). For primary
productivity measurements, shipboard incubation has long been used for
synoptic surveys at sea, and Sorokin (1959) used the technique in
Rybinskii reservoir in Russia over a period of seven days in June. He
found photosynthesis varied in different parts of the lake as much as
tenfold during this period.
Because of the photosynthetic variation from day to day, reflecting
changes in the composition of phytoplankton, nutrients, or weather, a
synoptic covering the shortest possible time period will have the
greatest precision for detecting variation in fertility within the
system. The synoptic approach we developed for Tahoe is probably unique
in covering the entire surface layers of a large lake in a single day
138
-------
without disrupting the natural light cycle of the organisms. The pro-
cedure includes a simultaneous in situ incubation of all the primary
productivity samples at a single location. This eliminates the un-
certainties associated with studies covering longer time periods with
various light conditions or the necessity of using the unnatural light
of deckboard incubation. It provides a nearly instantaneous measure of
phytoplankton productivity, composition, and biomass over the whole lake.
Methods
The synoptic approach has evolved from the first series of synoptics
done in 1962 to the 1968-71 series reported here. In 1962 eight stations
were incubated in situ with varying incubation time from station to
station. These were corrected to a daily value on the basis of a di-
urnal series of samples run simultaneously at an index station. In
1967 five different stations on three different dates were sampled
for comparison of primary productivity. Incubations were done in a ro-
tating incubator under constant artificial light at surface water tem-
perature. Samples for each station were taken at two depths where the
photometer measurements indicated 75% and 50% transmission of the
available surface light. The following paragraphs describe the methods
used in 1968 and subsequent years.
In the summer of 1968 three synoptic studies were conducted on 17 July,
12 August, and 2 September. Four were done in 1969 on 28 June, 31
July, 28 August, and 24 October. In 1970 synoptic sampling was ex-
tended to winter and spring sampling. The five synoptics that year were
done on 28 February, 2 April, 1 July, 24 July, and 2 October. Only
one synoptic study was done in 1971 on 14 July.
Thirty stations were selected for the initial design of large synoptic
surveys of 1968. Twenty-five of these stations were located along the
139
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shore around the lake and five stations in the middle of the lake. In
areas where it was desired to test for steep gradients in production,
three stations were located relatively close together, such as for
General Creek, Upper Truckee River, Cave Rock, and Incline Creek where
one station was chosen near the mouth of the creek and one on each
side. Some of these stations were eliminated in subsequent years at
locations where it was found that more than one station was not nec-
essary. Other stations were added in areas where the productivity
gradient was found to be greater than expected.
Two boats were used to collect all the water samples within about a six
hour time period. All the water samples were collected at night, be-
tween approximately 8:30 p.m. and 2:30 a.m., and stored in insulated
boxes, so that no photosynthesis or sample warming was taking place
and in order not to expose the organisms to surface light or otherwise
disrupt their normal diurnal rhythm. Four depths were sampled in 1968:
0, 5, 10, and 15 m. The 5-m depth sample was eliminated the following
years and replaced by a sample at 20 m. Water samples were collected
in 125 ml PyrejK bottles for measurements of primary productivity using
the 14C method as modified by Goldman (1963) (see Section VI). A
single light bottle and a dark bottle were used in 1968. Duplicate
samples for light bottles were taken the following years. Strengthen-
ing and improvement of the field gear became necessary as the number of
samples collected on a synoptic almost doubled. Phytoplankton and water
chemistry samples were collected at the same time. All samples were
returned to the index station located near Homewood on the west shore.
This is near out laboratory where regular in situ productivity measure-
ments are taken on a year round basis.
14
All primary productivity samples were rapidly injected with C solution
just before sunrise, lowered into the lake, and suspended at the same
depths from whence they were cqllected. The bottles were left to
140
-------
incubate all day and were returned to the laboratory for filtration at
sundown. Handling of the large number of samples collected during the
synoptic was therefore accomplished only before any photosynthesis had
occurred in the morning and after photosynthesis had ceased in the eve-
ning. This provided an equal incubation period for all samples so that
the primary productivity measurements for all stations were comparable.
A "standard" index station (see Section VI) was sampled on the day of
the synoptic incubation in order to make it possible to estimate synop-
tic primary productivity below 20 m for the entire lake.
Phytoplankton samples were collected for each station by pooling ali-
quots from each depth into one sample. The samples were fixed with
neutral Lugol's solution and returned to Davis for identification,
counting, and measurement of individuals for determination of their
(&
biomass. An inverted Wilcr microscope was used for this work.
The water chemistry samples for alkalinity determination were taken for
each station at the 5-m depth only, since no significant change with
depth down to 15 m was detected in Lake Tahoe. Carbon available for
photosynthesis in 1968 was calculated from the pH, alkalinity, and tem-
perature nomograph of Saunders, Trama, and Bachmann (1962). The more
rapid and sensitive method of infrared CO. analysis after combustion
with acid was used the following years.
Results and Discussion
In 1967 the variation in primary productivity was particularly high in
-2 -1
August and September. Results were not converted to mg Om -day ,
because samples were incubated under constant light which was not very
representative of the lake conditions. Crystal Bay and South Shore were
the highest stations in August and early September, respectively
141
-------
(Fig. 26). With the onset of winter storms and mixing, the variation
in stations disappeared in late September.
The 1968 synoptics provided a great deal more data than 1967. For each
synoptic at each station the primary productivity for the day, under a
square meter surface for the 15 m column of water, was calculated in
—2 —1 A
mg C-m 'day . Contour maps of primary productivity were constructed
from this data (Goldman, Moshiri, and Amezaga 1972). For the first
—2 —1
synoptic, the range of values was from 11.04 mg Om -day in a mid-
—2 —1
lake station to 78.52 mg C-m -day at the mouth of Incline Creek. For
-2 -1
the second synoptic, values ranged from 12.41 mg C-m -day in a mid-
-2 —1
lake station to 90.86 mg C-m -day at Tahoe City. For the third sy-
-2 -1
noptic, values ranged from 17.85 mg C-m -day at a midlake station to
-2 -1
84.07 mg C-m -day at the mouth of the Upper Truckee River.
—2 -1
Productivity values in mg C-m -day were also calculated in 1969 for
the 15-m water column at all stations except near Tahoe City where
bottom depth is 10 m. Results from the first synoptic on 28 June had
-2 -1
a range of 3.2 to 43.3 mg C-m -day . Highest values were measured
in Crystal Bay and the Kings Beach-Brockway area on the north end and
along the southeast shore from the Upper Truckee River inflow to Zephyr
Cove. Isolated high production areas occurred at Glenbrook Bay, mid-
lake south, and Emerald Bay. The average productivity per station was
-2 -1
20.02 mg C-m -day .
For the second synoptic, the range of values was 8.7 to 96.6 mg
-2 -1 -2 -1
C-m -day and the average per station was 40.91 mg C-m .day . The
second synoptic of 1 August indicated an overall productivity of the
upper 15 m of Lake Tahoe twice that of the first synoptic at the end of
June. The northern and eastern shore stations again exhibited high pro-
ductivity. High values were recorded for the first time at the mid-
lake station and midlake south stations. As expected, high values
142
-------
AB.- Agate Bay
SH.-Skunk Horbo
S.S-Sauth Shore
C.B.-Crystal Bay
M-L-Mid-Lake
STATIONS
Figure 26. Primary productivity measurements at five stations in Lake
Tahoe during three different sampling periods in 1967 at
the two depths where 75% and 50% light were transmitted.
143
-------
occurred at the south shore and Emerald Bay.
The third synoptic on 28 August indicated an increase in average pro-
—2 —1
ductivity per station to 48.37 mg Om -day , while the range of
e\ -I
values from 10.9 to 89.2 mg C-m -day did not differ appreciably from
earlier measurements that year. On that day, the highest value was
again recorded at Emerald Bay. The unique morphometric and limnological
conditions of Emerald Bay isolates it somewhat from the main waters of
the lake. Therefore, high measurements in Emerald Bay should not be
considered too critical when assessing the changes in the primary pro-
ductivity of the main Tahoe waters. The pattern of areal variation in
productivity of the third synoptic was similar to that of the second.
The 25 October synoptic values were lower with an average of 28.73 and
—2 —1
a range of 18.4 to 38.0 mg C-m -day . The decrease in the range of
station-to-station variation during this fall sampling indicates the de-
creased inflow from tributaries, which provides less potent localized
sources of nutrients capable of influencing the primary productivity
of the lake. There was no definite trend in the variation of produc-
—2 —1
tivity over the whole lake. Values above 30 mg C-m -day occurred
from Tahoe City on the northwestern shore to Sand Harbor on the north-
eastern shore. Similar values in the southern half of the lake were
found along the southeastern shore and at one location on the south-
western shore.
During 1970 a total of five synoptics were run. They produced a large
amount of data on both spatial and temporal changes in Lake Tahoe pri-
mary productivity by covering part of the winter and spring as well as
the summer. The seasonal variation in the average productivity for the
whole lake followed the same pattern as that of the productivity at the
index station (see Section VI, Fig. 21). The average was 42.9 mg
-2 -1
C-m -day (for the 20-m water column) in February. It was lower in
April, increased in July, was highest at the end of July (108.7 mg
144
-------
-2 -1
C'm -day ), and was still very high in early October (83.6 mg
—2 —1
Om -day ). Emerald Bay had the highest primary productivity values
of all stations on all synoptics, except on 2 April when productivity
was found to be slightly higher at Camp Richardson. The other stations
with unusually high primary productivity values were Dollar Point on
28 February, Bijou on 1 July, and off Incline Creek on 24 July and 2
October. The values were 62.5, 53.6, 86.4, 177.7, and 101.9 mg
-2 -1
C-m -day to a depth of 20 m, respectively.
A new station was sampled in Tahoe Keys (an enclosed marina) in 1970.
Values of primary productivity at that station were found to be 3.4 to
19.2 times larger than that of the highest value in the lake. The
lowest values of primary productivity were recorded at the midlake
station off State Line on 28 February, at Tahoe City on 2 April, at
Camp Richardson on 1 July and 24 July, and at Al Tahoe on 2 October.
-2 -1
The values were 17.8, 15.6, 25.2, 65.1, and 63.4 mg C-m -day , re-
spectively.
One synoptic survey covering the entire lake was conducted in 1971 on
14 July. The highest value of primary productivity for the stations in
—2 —1
the lake's main waters was 128.41 mg C-m -day measured off Incline
-2 -1
Creek. The value at Emerald Bay was 193.1 mg C-m -day . At Tahoe
-2 -1
Keys it was 127.34 mg C-m -day for the 5 m of water sampled there or
about four times as high as off Incline Creek. The lowest value on
-2 -1
that day was measured at the center of the lake (61.1 mg C'm -day ).
For each station, the average of all synoptics was calculated for each
year. A contour map of primary productivity in the lake was drawn based
on the average of all synoptics surveyed the same year (Fig. 27). Pri-
mary productivity values per square meter were standardized to a 15-m
water column for all years.
145
-------
1968
Figure 27a. Contour maps of primary productivity in the upper 15 m of Lake Tahoe in 1968-1971
based on the average of all synoptics surveyed the same year. Three synoptics
were run in 1968, four in 1969, five in 1970, and one in 1971.
-------
1970
Figure 27b. Contour maps of primary productivity in the upper 15 m of Lake Tahoe ir.
based on the average of all synoptics surveyed the same year. Three s?>
were run in 1968, four in 1969, five in 1970, and one in 1971.
-------
The overall primary productivity of the lake increased from 1968 to
1971 as did the primary productivity at the index station (see Section
VI). Quantitative evaluation of the overall increase from one year to
the next cannot be based, however, on the average synoptic values per
year since they are not all representative of the whole year or the
same time period (see Section VI).
Variations in areal distribution of primary productivity, however, are
very well documented by these synoptic contour maps. The range of
average values varied by fourfold in 1968 and 1969, from 14.9 mg
-2 1 -2 -1
C-m -day at a midlake station to 58.8 mg C-m -day at Tahoe City
—2 —1
in 1968 and from 12.4 mg C-m -day at the midlake station to 51.8 mg
—2 —1
C-m -day at Elk Point in 1969. The range of average values varied
-2 -1
by twofold in 1970 and 1971, from 33.9 mg C-m -day at Camp Richardson
—2 —1
to 68.6 mg C-m -day off Incline Creek in 1970 and from 45.7 mg
-2 -1 -2 -1
C-m -day at the center of the lake to 105.1 mg C-m -day off
Incline Creek in 1971. The spatial patterns of primary productivity
appear not to be random, but ordered. Primary productivity is often
high near shore and at the mouths of creeks. It is generally low at
stations near the middle of the lake.
A comparison of pelagic and littoral zone phytoplankton primary pro-
ductivity from 1968, 1969, 1970, and 1971 synoptic studies indicates a
steady increase in the fertility of the pelagic zone relative to the
littoral (Table 26). In 1968 the pelagic productivity per unit of
surface area was only 51% of the littoral. It increased to 78% in 1969
and 96% in 1970. Only one synoptic was conducted in 1971 in which
pelagic productivity was 90% of the littoral.
Two logical, but not unrelated explanations for this shift are proposed,
First, that the fertilized littoral zone water mixes into at least the
upper levels of Tahoe each winter, so that the pelagic euphotic zone
148
-------
TABLE 26, LAKE TAHOE SYNOPTIC SURVEYS, A COMPARISON OF THE MEAN PRIMARY
PRODUCTIVITY OF THE UPPER 15 M OF WATER AT THE PELAGIC STATIONS
AND THE LITTORAL STATIONS (EXCLUDING EMERALD BAY AND TAHOE KEYS).
1968
JULY 17
AUGUST 12
SEPTEMBER 2
AVERAGE
1969 '
JUNE 28
AUGUST 1
AUGUST 28
OCTOBER 25
AVERAGE
1970
FEBRUARY 28
APRIL 2
JULY 1
JULY 24
OCTOBER 2
AVERAGE
1971
JULY 14
MG C-M~
PELAGIC
16,24
20.30
23.83
20.J2
14.40
35.11
36.32
25,72
27.89
28.97
21.33
38.12
84.95
61.84
47.04
75.66
2,DAY-1
LITTORAL
28.94
43,24
46,42
39,53
20,96
40,50
50,78
29.83
35.52
30,55
21,68
41,76
89,38
62,86
49,25
83,81
PELAGIC
LITTORAL
51%
78%
96%
90%
149
-------
increased In fertility each, year relative to the consistently more
fertile littoral zone, whose nutrients are replaced more directly by
spring inflow. This inflow may be at least partially isolated from the
pelagic zone during the summer months by a thermal bar. This hypothesis
is supported by the steady increase in productivity at the index station
each year of the study (see Section VI) . The second explanation is that
the littoral periphyton have taken up a larger and larger amount of the
available nutrients each year leaving fewer for the littoral phyto-
plankton. A combination of these two explanations probably provides
the most likely cause of the increase in pelagic productivity relative
to that in the littoral zone.
Studies of the phytoplankton enumeration, biomass, and diversity for
the synoptic surveys of 1968 have been reported by Goldman, Moshiri,
and Amezaga (1972). These authors further investigated the significance
of the difference between shallow water and deep water productivity,
phytoplankton concentration, and diversity. The results of a student t^
test have been discussed by these authors.
The synoptic approach is very useful in studying cultural eutrophica-
tion as it enables the investigator to accurately locate sources of
nutrients before the entire lake has undergone change. Lake Tahoe
shows several areas of increased fertility. These are at the South
Shore under the influence of the Upper Truckee River drainage and
high resident population (Goldman et al. 1973, 1974), in Crystal Bay
where Incline Creek and Third Creek drain highly disturbed land, and
near the outflow of the lake (Tahoe City) where there is both a high
resident population and fairly extensive areas of shallow water. One
should note, however, the decrease from 1968 to 1971 in the high fer-
tility observed off Tahoe City relative to other areas. It might be a
direct consequence of the sewage treatment and effluent diversion from
the north end of the lake, which is currently disposed of in a volcanic
150
-------
cinder cone. Further, much, of the construction in the area was complete
by 1971 and surface erosion from disturbed building sites may be on the
decline.
Despite the lake's great volume for dilution of the annual inflow, local
nutrient sources are altering the productivity pattern around the lake.
A spring bloom of algae, which actually turned Tahoe's traditionally
blue water green, has already been observed at the south shore and
periphyton growth has become luxuriant around the entire margin during
the last decade. In August 1969 following extensive land disturbance
associated with construction of a golf course and a subdivision, Third
Creek was found to be extremely stimulating to growth of Tahoe algae.
In the experiment summarized in Figure 35(discussed in following sub-
section) , 10% of this stream water added to Tahoe's natural phytoplank-
ton population stimulated photosynthesis by over 600%. When compared
with controls, Incline Creek and the Upper Truckee River were also
notable lake fertilizers in contrast to relatively undisturbed General
Creek. This is not surprising since the Incline Creek drainage has
been recently subdivided for homes and drains a fertilized golf course
while the Upper Truckee River and some of its tributaries have also
suffered considerable disturbance. Further, this drainage was used for
some time as a land disposal site for treated sewage. The sewage is
now being exported out of the basin, but the land disposal site still
provides a drainage very high in nitrogen (see subsection on Land
Disposal).
Tahoe is unquestionably changing. The synoptic approach provides a
nearly instantaneous evaluation of conditions as they exist on a given
day. Close monitoring of wind and currents could add further to our
understanding of water transport in the lake as it affects the presence
and movement of more fertile water masses. In general, the primary
producers must be viewed as a more sensitive indication of increased
151
-------
fertility than chemical parameters, since any addition of nutrients to
the lake appear to move rapidly into the phytoplankton. We character-
istically find little or no measurable change in water chemistry (see
Section V, Table 11), while phytoplankton photosynthesis is showing
significant change. If the quality of our lakes is to be conserved,
synoptic studies can be a great aid in locating and defining the influ-
ence of nutrient sources. When combined with bioassays (see following
subsection), the relative stimulation capacity of various sources can
be quantified and corrective measures taken before accelerated eutrophi-
cation destroys the quality of the entire lake.
BIOSTIMULATORY EFFECTS OF NUTRIENTS ON LAKE TAHOE PHYTOPLANKTON
Introduction
Bioassays utilizing the carbon-14 method were part of the Tahoe research
program's evaluation of the contribution of chemical nutrients and
nutrients contained in natural tributary waters to algal growth rate
in the lake. Biostimulation by allochthonous sources and the implica-
tions of this to lake enrichment have been well documented for a number
of lakes, including Lake Tahoe (Goldman 1964), and recently by Likens
(1972). Considerable evidence has been gathered on the seasonal vari-
ation in biostimulatory effect caused by streams both under and away
from the influence of "cultural eutrophication". Although the role and
relative importance of nitrogen, phosphorus, iron, and micronutrients
has been rather well clarified, additional work is continuing as part
of the ongoing NSF-RANN project to extend our understanding of the com-
plex interaction of nutrient limitation in Lake Tahoe.
The rapid human population increase in the Tahoe basin and the corres-
ponding inhabitation and disturbance of several major watersheds appears
to be a major factor in increasing the seasonal effect of tributary
152
-------
biostimulation of the lake. Sedimentation to the lake is increased
over the natural levels by human activities (State of California
Resources Agency 1969) and eutrophication is occurring in Tahoe at an
accelerated rate (see Section VI). In addition, it should be noted
that nutrient interactions and species-specific requirements may change
the lake phytoplankton population if eutrophication is further accel-
erated. Studies indicate that nitrogen and, to a lesser extent, iron
and phosphorus are now the most important nutrients which are in low
supply and individually or in combination reduce or "limit" the growth
of Tahoe phytoplankton. One member of our limnology group once commen-
ted that limiting factors might best be defined as "what does not
happen in terms of what is not there" (Richard Armstrong personal com-
munication) .
Methods
Lake Bioassays For Nutrient Stimulation -
l^C bioassays were performed according to the procedures developed and
modified by Goldman (1963). Water from an offshore station was col-
lected for the bioassays in a clean, non-metallic, opaque Van Dorn
sampler from the depth of maximum primary productivity (20-50 m) and
held in an opaque carboy for sub-sampling. Acid-leached and distilled
water-rinsed 500-ml Pyrex screw-cap Erlenmeyer flasks were filled
after addition of C to the carboy. To each flask was added the nu-
trient solution(s) to produce the final desired concentration. Samples
were taken from the cultures for initial and final phytoplankton enum-
eration and identification as well as to determine nutrient concentra-
tions. C uptake measurements were made daily for a period of from
T>
5 to 7 days by filtering 50 ml subsamples on HA Millipore filters and
counting with an automatic, ultra-thin window, gas flow GM counter.
153
-------
Lake-Tributary Bioassays -
Methods were similar to the above except that freshly collected, un-
filtered stream water was added in 0.1, 1, and 10% concentrations to
the lake water. Cultures were usually run in triplicate and under
either a 12- or 24-hour light cycle in a rotating shelf incubator, with
temperature set at the in situ lake level. Water samples were collected
from the mouths of the Upper Truckee River, Third, Incline, and General
Creeks, and the upper, middle, and lower portions of Taylor Creek.
Results
Nutrient Biostimulation of Lake Water -
Concentrations of nutrients in Lake Tahoe are generally very low at all
depths (Fig. 28) and particularly in the euphotic zone at the depths
of greatest biological utilization. Nitrogen compounds range from 2
to 20 yg-l~ NCL-N and NH--N is frequently undetectable. Total phos-
J J _1
phorus is usually less than 5-10 yg-1 and iron is similar to nitrogen
in concentration. A recurring problem with nutrient measurements at
Tahoe is that the results are usually at or near the lower limit of
detection by the most sensitive methods available (Strickland and
Parsons 1968). A number of modifications of existing methods have been
developed which are included in Appendix E.
Although nitrogen is probably the most limiting nutrient in Lake Tahoe,
indications are that biostimulation of Tahoe phytoplankton by nitrogen
and/or phosphorus is complex (Fig. 29). Acting in concert, moderate
levels of addition of both nutrients will produce a greater stimulation
than either one added singly (Goldman 1972). This is also true for
additions combining nitrogen and iron (Fig. 30)- Increasing growth of
phytoplankton over control values is dependent upon the availability of
NO -N and also on the presence of Fe. This is especially significant
now that it has definitely been established that, at least during some
154
-------
0
20
50
100
200
300
400
bottom
jug- liter"1
10 15 20
25
TEMPERATURE
LAKE TAHOE
3 AUGUST 1970
OSPHORUS
NITRATE-NITROGEN
10
15
20
25
Figure- 28. Deep water measurements of total iron, nitrate-nitrogen,
total phosphorus, and temperature at the mid-lake station of
Lake Tahoe on 3 August 1970.
155
-------
600
5OO
4OOJ
0>
*•
o
3OO-
Ln
«
200
IOO
LAKE TAHOE 21-25 NOV. 1967
PHOSPHORUS-NITROGEN INTERACTS
32 4B 72
Hours of Incubation
92
Figure 29. Bioassay of nitrogen and phosphorus additions (yg/1) to Lake Tahoe water,
-------
Ln
8
TAHOE AUGUST 1968
N-Fe CULTURE
20N-5Fe
5N-5Fe
ON-5FB
20N-OFe
SN-OFe
CONTROL ON-OFe
2 3
SAMPLING TIME (DAYS)
Figure 30. Bioassay of nitrogen and iron additions (yg/1) to Lake Tahoe water.
-------
years, Tahoe mixes all the way to the bottom and returns relatively
nutrient-rich water to the photosynthetic zone to fuel the spring
phytoplankton blooms (Paerl et al. 1974).
Tributary Water Biostimulation of Lake Water -
Several of the streams flowing into Lake Tahoe have been used as exam-
ples of watersheds under the influence of different levels of human
activity. The amount of activity is in close agreement with the amount
of biostimulation that each watershed contributed per unit volume to
the lake.
Aside from some differences in natural geochemical input, erodibility
of watersheds as well as climatic, elevational, and vegetational vari-
ations, it is increasingly obvious that certain Tahoe watersheds are
more "polluting" (unnaturally biostimulatory) than others.
Although all streams contribute nutrients to the lake, General Creek is
a good example of a reasonably unpolluted stream which when added to
Tahoe does not exhibit a pronounced stimulatory effect (Fig. 31).
Seasonal variation is very low from winter to summer in comparison to
the Upper Truckee River (Fig. 32) even though the water chemistry
levels can vary (see Section V). The General Creek watershed has a
dense vegetative cover, usually carries low sediment loads even during
snowmelt periods, and flow levels are not as variable as many other
Tahoe streams. Despite some history of lumbering in its upper reaches,
it appears to be enriching Lake Tahoe at a natural rate and may be con-
sidered a fairly typical Tahoe tributary stream.
The Upper Truckee River (Fig. 32) also exhibits a small stimulatory
effect on the lake in the winter months, but produces very significant
algal stimulation in the spring during peak snow melt runoff. This is
noteworthy because the Upper Truckee River produces 30-40% of the total
158
-------
180-
8
8 lee-
140-
a
8
o
u
100-
60
Control
344 735 1086 1320 1735
ctsAnin cts/min cts/min cts/min cts/min
10 .11 I 10 .1 I 10 .1 I 10 .1
General Creelc-ll
19 Feb. 1968
Control
200- 548cpm 1207cpm 1433cpm 1718cpm
180-
8 160H
"o
8 140-
w
a
S 120-1
U
100-
80
60
B
General Creek - V
21 May 1968
1C I.
Subsamples approximately 24 hours apart
Figure 31. Bioassay of General Creek water additions to Lake Tahoe water.
General Creek was selected as the best example of an unpolluted
stream available. Low biost'mulation was observed in both
winter (A) and spring (B).
159
-------
468
Control
624 880 1050 1064
9O<"h ^O" °" oow iv»w iww^
*w| cts/min cts/min ctsAiln cts/mln cts/min
180-
0
8 160-
~o
§ 140-
U
a
% 120
4)
.M
«
QL
-------
tributary inflow to Lake Tahoe and the stimulatory effect of this river
is quite significant in terms of volume and area affected by the inflow-
ing water mass (Goldman et al. 1974). A doubling of primary productiv-
ity is apparent when lake water is diluted by 10% with Upper Truckee
water.
It should be noted that this condition is not limited to this large
stream. Incline Creek (Fig. 33) exhibits a similar pattern in bio-
stimulatory potency. It is very low or actually inhibits lake phyto-
plankton growth in the winter, but shows a large increase in bio-
stimulation by the end of May when peak flows predominate. The
"inhibitory" response exhibited may be simply dilution or lack of some
essential nutrients or initial light shock which organisms may suffer
when collected from below the surface of the lake.
Another tributary studied in more detail has been Taylor Creek (Fig. 34)
This stream while under the moderating influence of an upstream lake
(Fallen Leaf Lake) which regulates flow, clarity, and to some extent
nutrient input, nevertheless shows significant winter-summer changes
in biostimulation of the lake water phytoplankton and also produces
some variation in response with the location of creek water collection
for the bioassay. As with the other streams, Taylor Creek winter bio-
assays showed little or not positive response, especially from the
lower station. This was probably due to the nutrient stripping actions
of the stream periphyton community as the water passed toward the lake.
However, in the late spring during peak snowmelt, the stimulation at
all three stations was about 240% above the lake water controls, in-
dicating that even streams with moderating, influences such as lakes and
relatively undisturbed watersheds can have a biostimulatory effect upon
the lake. It should be remembered that although the Taylor Creek
watershed is not undergoing rapid development, a significant human pop-
ulation does exist upstream along Fallen Leaf Lake's shore and on a
161
-------
200-
180-
S
8 160-
*o
8 140-
I
S 120-
Control
402 907 1242 1552 1712
cts/min cts/min cts/min cts/min cts/min
Incline Creek-II
22 Feb. 1968
-X
Q_
U
80-
An-
-
i
.1
10
i
-
.1
10
p
1
—
.1
PI
10
_
.1
-
10
1
[
p
1 10
Control
200i
180-
0
8 160-
"o
§ 140-
0.
IS 120-
jj
«
I TOO-
U
80-
AD-
715cpm 1244cpm 161:
.1
i.
0
p
.1
1.
._.
10
.1
1.
c
10
pm 1825
.1
p
1.
fF
0
m 2283cpm
.1
__
1.
10
B
Incline Creele-V
28 May 1968
Subsamples approximately 24 hours apart
Figure 33. Bioa.ssay of Incline Creek water additions to Lake Ta.n,oe v?a.ter.
Stimulation was greatly increased from winter (A) to spring (B).
162
-------
seasonal basis when large numbers of hikers utilize its main tributary
as a route into the back country. The stream also is an important
spawning ground for the land-locked red salmon which die after spawning
and contribute to the stream's fertility (see Section XII).
When stream courses are altered, as was the case with Third Creek when
it was diverted to make way for a golf course during the Incline Village
development, a large nutrient release results. Figure 35 illustrates
the biostimulatory effect of this stream toLakeTahoe waters in com-
parison with three other streams following the rechannelization. This
represented the greatest amount of stimulation recorded from any stream
bioassayed in the basin and provides clear evidence of the serious na-
ture of major watershed manipulations in speeding the cultural eutrophi-
cation of the lake.
It is very probable that with major portions of sewage now being diver-
ted from the basin, the dramatic increase in in situ lake primary pro-
ductivity evidenced during the course of this study (see Section VI)
is largely due to mechanical disruption of the watershed associated
with soil exposure and vegetation loss resulting from construction of
new roads and subdivisions. Once the basin is "built up" to its
planned capacity, this kind of input should gradually decline. That
stabilization nutrient input takes considerable time is indicated by
the still potent fertilization from the Heavenly Valley Creek area which
was used as a land disposal site for treated sewage effluent (see Land
Disposal subsection).
LIMNOLOGICAL STUDIES AND REMOTE SENSING OF THE UPPER TRUCKEE RIVER
SEDIMENT PLUME IN LAKE TAHOE, CALIFORNIA-NEVADA
(This work is published in Remote Sensing of Environment, by Charles R.
Goldman, Robert C. Richards, Hans W. Paerl, Institute of Ecology
163
-------
CONTROL
CPM
o
6454 10,584 14,685 18,922 35,189
A
r=i- UPPER
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-
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— 1
1
10
.1
1
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-,
10
-,
.1
1
10
.1
1 0
g 120-
O
^~ IAA
LU IUU
Q_
CO
•< 80-
UJ
•^
-------
1931
CONTROL
(CPM)
5455 7358 12,312 20,894
240-
220-
200-
180-
160-
140-
i?n -
i-
_
~
-
r
"-
r-|
1
r 1
B
UPPER
o
o 220-
i —
5 200-
[5 180-
V)
•* 160-
iy
iS 140-
Q-
3
S i»n-
i-T
.-
-
r
-
MIDDLE
240-
220-
200-
180-
160-
140-
i?n -
-n
"I r-
-l
r-
_|-,
LOWER
.1110 I 110 I 110 I 110 1110
6 30 54 96 144
HOURS OF INCUBATION
Figure 34b. Bioassay of Taylor Creek water additions to Lake Tahoe water.
Significant increase in biostimulation was noted from winter
(A) to spring (B).
165
-------
740-
700-
«j 660-
1 620-
£ 580-
540-
I 500-
SJ 460-
o
£ 420-
-E 380-
S5 340-
o, 300-
2 260-
| 220-
o
o*
o 140-
<" 100-
60-
Incline
LAKE TAHOE
12 August 1969
Incline
Creek
Incline
VHIage
Upper
Trujtkee
River
Soft ft (jenero) 1
Shore Ci^ek
Contraf
10% STREAM WATER ADDED TO LAKE WATER
Figure 35. Biostimulation of Lake Tahoe water from a 10% addition of four of its tributaries
Highest biostimulation was measured by Third Creek following disturbance of its
watershed. General Creek, which drains an undisturbed area, was used as a control
-------
University of California, Davis and Robert C. Wrigley, Verne R. Oberbeck,
and William L. Quaide, Space Science Division, NASA-Ames Research Center,
Moffett Field, California).
Introduction
Accelerated eutrophication of Lake Tahoe, an oligotrophic subalpine lake,
has been evident from casual observation of algal growth in shallow
water and measured increases in primary productivity and algal biomass
of phytoplankton (free-floating algae) as well as periphyton biomass
(attached algae) (Goldman and Armstrong 1969; Goldman 1970a; and
Goldman, Moshiri, and Amezaga 1972). These authors also investigated
tributary streams, the major source of nutrient enrichment, and demon-
strated stimulatory effects of stream water on growth of the natural
phytoplankton population in Tahoe water. In addition, in situ sampling
of transects toward (the mouth of) the Upper Truckee River, the major
tributary, indicated the increases in both heterotrophic (bacterial)
activity and primary productivity as the stream mouth was approached
(Paerl and Goldman 1972a). These results, coupled with evidence of
recently doubled sediment contribution to the Upper Truckee River from
man-made disturbances on its watershed (State of California Resources
Agency 1969), point strongly to siltation as an increasingly important
and continuing cause of lake enrichment. (This is particularly true
now that treated sewage effluent is exported from most of the lake basin
and is considered less of a threat to water quality than it was in the
past).
The influence of major tributaries on lakes and rivers has long been
studied (Hutchinson 1957, p. 295). Water masses peculiar to an inflow-
ing river or stream have been traced and identified in the receiving
water body through measurement of various parameters. Movement of the
Rhine River through Lake Constance (Numann 1938), the Rhone through
167
-------
Lake Geneva (Dussart 1948), and the Colorado through Lake Mead (Anderson
and Pritchard 1951) are all cases in point. The biological influence
of tributaries on lake fertility has been evaluated by bioassay in a
number of Alaskan and Californian lakes (Goldman 1964). Temperature,
oxygen, light transmission, dyes, sediment load, conductivity, and
chemical and biological changes have all been utilized to some extent.
Few studies have, however, coupled the use of limnological field methods
with high resolution aerial photography to provide an overall view of
the process. In this study, simultaneous photography and water sampling
have provided a nearly instantaneous measure of variation in biological
productivity and physical changes in the lake under the influence of
its major tributary.
A joint study by Ames Research Center (NASA) and the University of Cali-
fornia, Davis was begun in early 1971 to document the influence of the
Upper Truckee River sediment plume on eutrophication of Lake Tahoe.
The study area is shown in Figure 36. The major objective was to deter-
mine if high resolution aerial photography could be used to correlate
location of the plume with biological, physical, and chemical conditions
measured in the water mass and indicate the value of photography in
defining plume limits. Another objective was to investigate the re-
lationship between siltation and the process of eutrophication. Lake
Tahoe is particularly appropriate for this study, because the water is
extremely clear and the plume varies seasonally in volume and intensity.
Spring snowmelt water entering the Upper Truckee River from the highly
urbanized South Lake Tahoe Valley area produces the most significant
sediment plumes observed in the lake.
Methods
Sampling Time Selection -
168
-------
1601 2345
KILOMETERS
Figure 36. Map of Lake Tahoe indicating the Upper Truckee transect
study area. The index, mid-lake, and 5d stations not shown
on Figures 38-42 are shown here. The thin line around the
lake periphery indicates 6 m depth.
169
-------
Observation of changing meteorological conditions in northern California-
Nevada and on-site reconnaissance was used to select sampling dates
during the 1971 runoff. Sampling was scheduled to include a variety of
runoff stages, encompassing low and peak flows. Past stream flow
records for the Upper Truckee River were combined with meteorological
data, primarily air temperatures, to predict runoff development. It
was also necessary to have favorable conditions for aerial photography
over water: clear skies, low windspeed (<10 kt) , and moderate sun angle
(30-50° above the horizon). The latter was accomplished by conducting
the photography during the early morning or late afternoon. Lack of
favorable conditions prevented sampling during May.
Field Methods -
While aerial photographs were being taken, samples for chemical analysis,
biological activity, and physical characteristics of the plume area were
collected along transects radiating from the Upper Truckee River mouth.
Shallow water samples were taken near the bottom, deep water samples
at 20 m. A fast boat usually made collection possible during a three-
hour period. Station location was achieved by sighting on-shore land-
marks and prominent bottom features. Samples were transported in dark-
ened ice chests to the laboratory. Additionally, on-site measurements
at the twenty stations usually included light transmission, temperature,
Secchi disk measurements, and field notes on visual conditions of the
water .
Primary (algal) productivity samples were transferred to 125 ml
14
bottles, injected with C-bicarbonate, and incubated in situ for four
hours at 2-m depth from a lakeside pier (Goldman 1963, Goldman and
Carter 1965). Morning samples were incubated the same afternoon. The
20 June afternoon samples were held overnight in the dark at lake sur-
face temperature and incubated the following morning.
170
-------
Heterotrophic (bacterial) activity samples were transferred in parallel
to 125 ml opaque Pyrex^bottles. Heterotrophic assimilation of 2- C-
acetate was measured by adding a trace amount (10 ng acetate•! ) of
carbon-14 labeled substrate to each water sample. Incubation was done
in a darkened incubator with rotator. Incubation temperatures were
held close to sampling temperatures. Assimilation rates were compared
throughout the sampling period. In earlier work (Paerl and Goldman
1972a), assimilation of acetate was shown to be largely due to bacteria
in Lake Tahoe and acetate concentrations in the lake (derived from
gas chromatographic analyses and kinetic plots) varied from 1 to 10
\ig acetate•! . (Micro-autoradiography was employed in the earlier
study to demonstrate bacterial uptake and absence of algal uptake of
^-^C-acetate at the substrate concentration used in experiments reported
here.)
Incubation of heterogenous samples taken at depths ranging from 0.5 to
20.0 m and differing environmental surroundings (light, temperature,
nutrients, etc.) do not give absolute in situ values of primary produc-
tivity and heterotrophic activity. The values are an index of the
ability of different phytoplankton and bacterial populations to respond
to stimuli under similar, measurable conditions. Both sets of samples
were filtered at low vacuum on 25 mm, 0.45 pm filters (HA Millipore^j
immediately after incubation. Air-dried filters were counted witli a
Geiger-Muller ultrathin window counter and sealer (Nuclear-Chicago—5,
db
calibrated with gas phase (Goldman 1968a), or a Beckman3^ LS-100 liquid
scintillation counting system.
The remainder of the water sample was divided into smaller containers
for determination of dissolved inorganic carbon (DIG), sediment content,
water chemistry, and phytoplankton identification and enumeration. Dis-
solved inorganic carbon, composed mainly of HCO , was determined
171
-------
Immediately by infrared analysis using NaHCO standards (Armstrong,
Goldman, and Fujita 1971). Water chemistry samples were immediately
analyzed or preserved by freezing. Phosphate, nitrate, and iron analy-
ses were done according to procedures for microgram quantities
(Strickland and Parsons 1968), with modifications by Fujita (see
Appendix E ).
Phytoplankton samples preserved in Lugol's solution were filtered
(0.45 ym) and the filters oil-cleared. Phytoplankton were counted by
species from a filter area large enough to allow less than 10% error in
/T>>
total count. A Wild-''inverted microscope equipped with an image-
splitting eyepiece for cell volume (biomass) calculations was used.
Primary productivity, phytoplankton numbers, biomass, and correlation
coefficients were computed using a Burroughs^ 6700 computer. Suspended
sediment samples were filtered through 47 mm, 0.8 ym filters (AA
Millipore—) and dried for 24 hours at 110°C. Filter weight, corrected
for an average loss on drying, was subtracted from the weight of the
filter with its retained sediment.
Photographic Coverage -
The Upper Truckee River sediment plume was photographed at each sampling
2
time to yield overlapping coverage about 20 km at a scale of 1:20,000.
Each photographic mission used a Kargl K3B camera of 225 mm x 225 mm
format and either a 305 mm or 210 mm focal length lens. Kodalr^ 2448
color film was developed to a positive transparency. On one mission,
multispectral and color photographs were taken simultaneously to evaluate
application of multispectral photography to sediment plume study. An
International Imaging Systems MK 1 multispectral camera recorded four
wavelength band images on different squares of the same 225 mm x 225 mm
negative. The scale was 1:42,000. Wrattefl^ 25, 57a, and 47b filters
were used on lenses photographing red, green, and blue wavelengths,
respectively, along with special infrared blocking filters. Only a
172
-------
R ;
Wratten 88a filter was used on the lens photographing near infrared.
Multispectral film was developed to a negative and positive transpar-
encies were used for sediment plume study.
Photographic analysis involved converting photographs into line drawings
and determining the extent of various units of differing visual con-
trast within the plume. Silt-laden river water entering the lake from
the Upper Truckee River contrasts strongly with clear lake water and
the shallow shelf bottom. As the river water intrudes further into the
lake, various water masses develop which change in position and visual
contrast with time. Their boundaries can usually be delineated with
little difficulty. They can be mapped as discrete areal units and
assigned density values representing degrees of contrast. Beyond the
shallow shelf (6 m), the bottom slopes precipitously. Contrasts are
still visible, but estimated density values are less accurate. Units
beyond the shelf are often extensions of near-shore plume units which
allow successful extrapolation. Four or five values of contrast
density were assigned in each plume study. Heavily silt-laden river
water was given a value of "1". Higher numbers were assigned as the
_visual contrast against the shelf bottom decreased. Contrast values
are valid only for relative comparisons at a given time and are only
generally similar for different sampling dates. In one case it was
necessary to assign the values "la" and "Ib", because two areal units
had similar values of contrast but differed in color. Line drawings
were superimposed on a modified U.S.C. and G.S. chart 5001 showing
sampling stations, shoreline, and the offshore shelf margin.
Results
Development of the Sediment Plume -
Four days were selected for study: 29 March, 12 April, 7 June, and
20 June. These represented a variety of snowmelt runoff stages during
173
-------
1971. On 20 June photographs and water samples were taken in both early
morning and late afternoon with photogrphic coverage by both color and
multispectral cameras in the morning. Daily streamflow data for the
Upper Truckee River and Trout Creek were supplied by the Water Resources
Division of the Gological Survey in Carson City (Fig. 37A) . The 29 March
and 12 April studies occurred during early stages of snowpack melting
while those of 7 June and 20 June bracket peak melt runoff. Also shown
are daily maximum and minimum air temperatures at Tahoe Valley airport
(Fig. 37B) and precipitation data taken at Tahoe City (Figs. 37C,D).
Tahoe City is not in the Upper Truckee River watershed, but it is the
only precipitation station in the Tahoe basin.
Figure 37A shows that from October 1970 to late March 1971, runoff is
3 —1
generally very low (daily average about 1 m •sec ). However, some
restricted periods of high runoff do occur. Runoff peaks on 25 November,
17 January, and 26 March were due to heavy rain and/or snow that melted
soon after falling.
Figures 37C,D show total precipitation at Tahoe City was high on 25
November and 26 March, but snowfall was low compared to other days.
This implies conditions of alternating rain and snow with most of the
precipitation as rain. On 17 January a total of 0.8 cm precipitation
fell despite no record of snowfall. Thus, isolated peaks in runoff
during low flow periods from October 1970 to late March 1971 were pro-
duced by heavy rains and rapidly melting snow. The 29 March study was
shortly after the day of maximum yearly precipitation at Tahoe City.
On 26 March, the precipitation consisted mostly of rain. It is likely
that this rain had a pronounced effect on plume formation three days
later.
Spring melting of the Tahoe basin snowpack produced large runoff in the
Upper Truckee River and Trout Creek from late March to late June
174
-------
UPPER TRUCKEE RIVER NEAR MYERS, CALIF
WATER YEAR 1971
8
;
2
0
30
20
"
10
°
-10
-20
25 NOV IT JAN
?6 MAR
2T JUN
DISCHARGE UPPER
TRUCKEE RIVER
AND TROUT CREEK
O STUDY DAYS
DAILY i
TEMPERATURE
--MAXIMUM
MINIMUM
^
*n
5r
*
TOTAL PRECIPITATION
£11
g
220
I 0
i
- , I1 I '
U > ill !
: ,,i :,!„,, J,L,h,i! ULi,
SNOWFALL
31 30 31 31 28 31 3.0 31 30 31 31 30
OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1970 1971
Figure 37, Seasonal variation in stream flow and meteorological conditions
in the Upper Truckee River watershed during the 1970-71
water year.
175
-------
(Fig. 37A). Diurnal fluctuations in runoff rate occurred due to insolation
and warmer daytime air temperatures followed by cooler night air temper-
atures. Figure 37B shows that when daily minimum temperatures consis-
tently exceeded freezing, runoff became large and flow variations
followed daily maximum temperature fluctuations. When daily maximum
temperatures exceeded 15°C, runoff neared its maximum. A major cooling
trend in late May reduced runoff more than 50% although daily minimum
temperatures did not drop.
There appears to be increasing sediment plume development associated
with increasing runoff of melting snowpack. This would be expected due
to increased displacement of lake water by turbid river water. Figures
38-42 show maps of each sediment plume outline and various units of
differing visual contrast densities within the plumes. The 29 March
and 12 April plumes are confined to the lakeshore east of the river
mouth and extend northerly to just beyond the shallow shelf edge. Both
plumes of 20 June, near maximum runoff, extended far into the lake
(>3 km) and along the eastern shore as far as Maria Bay, 8 km from the
river mouth (Fig. 36). We have no explanation for the fact that the
7 June plume occurred during high runoff, but had the smallest total
outlined area. It contained the largest extent of highly contrasted
areal units (density values 1 and 2) of all morning plumes. Total
mapped areas of morning plumes are not a strong function of runoff even
excluding the 7 June plume: a 40% increase in plume area occurred from
29 March to 20 June while runoff increased 400%. Multi-spectral photo-
graphs of the 20 June morning plume (Fig. 43) show much greater plume
area, especially to the north, than color photographs and indicate ob-
servational difficulties with color film.
Figure 43 also shows differing responses to the plume among the spectral
bands. Blue band response delineates the plume envelope well in both
shallow and deep water, but loses detail in dense plume areas; the
176
-------
o
N
3»d
500
METERS
SUSPENDED PRIMARY
SEDIMENT DIC PRODUCTIVITY
UT MOUTH
1A
16
1C
ID
2A
26
2C
20
3A
38
3C
3D
4A
4B
4C
4D
5A
56
5C
50
Mid Lake
Index
7.5
08
04
0.3
0.5
0.6
2.5
0.6
0.1
8.8
5.9
33.5
0.1
17.5
4.2
0.6
_
_
_
_
0.3
0.2
0.3
5.5
10.8
112
11.0
10.5
10.0
9.6
9.8
9.9
7.5
7.4
9.7
9.8
9.8
8.0
9.5
_
_
_
_
9.7
10.2
9.6
30
44
3
18
30
22
22
20
19
42
24
42
29
100
47
27
_
_
_
__
29
16
8
VISUAL PLUME DENSITY
Itl RIVER MOUTH
• SAMPLING STATION
SHELF MARGIN
rim SHORELINE
HI
i i
EZ3
E23
1 a/b (MOST DENSE)
2
3
4 (LEAST DENSE)
Figure 38. The Upper Truckee River sediment plume for 29 March 1971.
Values of suspended sediment (mg/1), dissolved inorganic
carbon (DIC) (mg/1), heterotrophic activity (yg acetate/m-Vhr
of assimilation), and primary productivity (mg C/m^/hr of
incubation x 10~2) are also given. These same values are also
given in Figures 39-42.
177
-------
o
N
2»d
500
METERS
1000
STATION
UT MOUTH
1A
IB
1C
ID
2A
2B
2C
20
3A
38
3C
30
4A
46
4C
40
5A
SB
5C
SO
Mid Lake
SUSPENDED
SEDIMENT
9.1
05
0.4
04
0.5
0.4
0.3
0.4
0.3
74
43
0.3
0.6
2.3
5.8
0.3
16
1.5
0.7
0.6
0.3
0.1
DIC
5.5
10.8
11.2
11.0
10.5
10.0
9.6
9.8
9.9
7.5
7.4
9.7
10.1
9.8
8.0
9.5
9.5
10.6
9.9
9.9
10.0
10.2
VISUAL PLUME
m RIVER MOUTH
• SAMPLING STATION
SHELF MARGIN
TTTT1 SHORE LINE
HETEROTROPHIC
ACTIVITY PR
150.6
57
5.3
5.5
2.2
21.2
75
8.6
3.3
169.9
152.6
4.4
4.8
50.4
48.2
5.3
95.5
5.9
8.2
4.4
3.5
-
DENSITY
ill (MOST DENSE)
EH 2
EHl 3
m <
PRIMARY
PRODUCTIVITY
12
15
12
6
2
11
14
61
20
9
25
16
19
16
22
6
6
5
9
5 (LEAST DENSE)
Figure 39. The Upper Truckee River sediment plume for 12 April 1971,
178
-------
0
N
500
METERS
STATION
UT MOUTH
IA
IB
1C
ID
2A
2B
2C
2D
3A
3B
3C
3D
4A
4B
4C
40
5A
5B
sc
50
Mid Lake
SUSPENDED
SEDIMENT
147
I.I
0.2
02
0.1
in
02
0.3
0.2
62
0.8
0.6
[12
1.6
1.0
04
0.7
0.6
0.5
0.4
0.2
06
V
m RIVER MOUTH
HETEROTR
DIC ACTIVIT
27
9.2
9.6
9.6
97
77
9.3
9.7
94
55
6.0
9.4
96
6.4
77
9.3
8.4
9.4
105
10.2
10.1
10.0
SUAL PLUME DENSITY
•
• SAMPLING STATION tgf''
SHELF MARGIN
rrm SHORELINE
5724
866
9.8
0.8
3.8
1 4 1
18
2.9
5.4
3277
241.7
22.6
10.8
324.4
148 4
9.7
3470
502
18.2
24.7
7.9
4.7
1 (M
2
3
4(1
PRIMARY
PRODUCTIVITY
15
19
44
33
33
6
54
30
36
36
6B
42
27
55
57
6
42
1 IMOST DENSE!
4(LEAST DENSE)
Figure 40. The Upper Truckee River sediment plume for 7 June 1971.
179
-------
N
500
METERS
1A
IB
1C
10
2A
2B
2C
20
3A
3B
3C
3D
4A
4B
4C
4D
5A
58
5C
50
Mid Lake
Index
SUSPENDED
SEDIMENT
2 1
6.1
03
0 1
8.9
05
02
0 1
0.7
0.5
0.2
04
2.6
04
0.2
0.3
0.1
0.0
HETEROTROPHIC
ACTIVITY
3.0
8.3
8.6
8.6
8.7
7.6
5.8
8.6
8.6
3.8
8.3
9.0
8.6
7.9
8.2
6.8 1
86
84
8.3
86
84
VISUAL PLUME DENSITY
PRIMARY
PRODUCTIVITY
19
13
16
21
19
9
16
33
32
20
9
17
35
20
16
9
13
9
24
m RIVER MOUTH
• SAMPLING STATION
SHELF MARGIN
ITTTTI SHORELINE
I (MOST DENSE)
5 ItEAST DENSE)
Figure 41. The Upper Truckee River sediment plume for the morning of
20 June 1971.
180
-------
500
METERS
UTM
IA
IB
1C
ID
2A
2B
2C
20
3A
3B
3C
3D
4A
46
4C
4D
5A
56
5C
50
Mid Lake
SUSPENDED
SEDIMENT
95
07
0.3
0.3
P.4
07
06
1.3
03
4.7
2.7
06
05
4.1
0.7
0.5
0.8
3.2
0.6
0.2
0.2
-0.1
0.2
90
9.0
9.0
90
9.2
90
9.2
60
7.9
86
87
85
8.6
9.1
VISUAL PLUME DENSITY
m RIVER MOUTH
• SAMPLING STATION
SHELF MARGIN
rrm SHORELINE
HETEROTROPHIC
ACTIVITY
2311.3
309
33.3
34.1
18.0
466
301
430
280
11831
623.8
664
19.6
2437.4
182.6
88.5
282.4
678.7
44.5
56.8
55.5
18.8
47.2
PRIMARY
PRODUCTIVITY
74
19
12
32
17
17
20
12
21
48
42
23
14
27
21
26
35
38
13
13
22
13
23
JSITY
1 [MOST DENSE!
m 2
WJ] 3
5 I LEAST DENSE I
Figure 42. The Upper Truckee River sediment plume for the afternoon
of 20 June 1971.
181
-------
effect appears to be a reduction of upwelling light by scattering and/or
absorption. Against the bright, shallow shelf, the green band shows
less reduction of upwelling light than the blue and provides some in-
terior plume structure. In deep water, denser plume areas appear bright
in green light against a dark background due to reflection from sus-
pended sediment. Reflection predominates in very dense plume areas in
the red band and provides more internal structure, but in somewhat less
dense plume areas sediment reduces upwelling red light creating a dark
area against the shelf. Thus, there is a gradation between reflection
and absorption which is dependent upon sediment concentration. No in-
frared light derives from either clear or sedimented areas due to a large
«
attenuation coefficient in water for this band and an apparent lack of
significant amounts of sediment at the surface.
Relationship Between Aerial Photographic Interpretations and Aquatic
Measurements -
Sediment plume density maps based on relative visual contrasts of ad-
jacent water masses are in good agreement with water property measure-
ments and field observations as detailed below.
Suspended sediment - Visually dense plume units near the river mouth
contain the most suspended sediment whereas less dense, more extensive
units contain less sediment (Figs. 38-42). Sediment from all plumes
consists primarily of silt-size mineral grains of feldspar, mica,
quartz, and hornblende in order of decreasing abundance according to
X-ray diffraction and microscopic analyses. These minerals comprise a
large portion of bottom sediments in this area of the lake (Court,
Goldman, and Hyne 1972). Combustible material (organic matter) is
generally present in amounts less than 20% in weight. Inspection of
filtered sediment residues revealed that samples from dense plume units
near the mouth are generally coarser grained than those from plume
units of lesser visual density. This indicates that dispersion of
182
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00
OJ
B
Figure 43. Multispectral photograph of the Upper Truckee River sediment plume for the morning
of 20 June 1971. Blue band (A), green band (B), red band (C), infrared band (D).
-------
sediment from the river mouth is, in part, a function of grain size and
implies that photographically defined units are units of differing sus-
pended sediment size as well as quantity.
Water chemistry, dissolved inorganic carbon (PIC) - In all plume
transects, except that of 29 March, there appeared to be a strong re-
lationship among increasing plume density, increasing suspended sedi-
ment, and decreasing DIG; Table 27 shows correlations at confidence levels
above 99.9%. The river mouth always had the lowest DIG. Values in-
creased in irregular fashion away from the mouth in a way highly depen-
dent upon plume configuration. At stations where isolated lenses of
turbid water occurred, LiIC was lower. This measurement appears to have
promise as a water mass marker where differences between river
(3-5 mg C-l~ ) and lake (8-10 mg C-l" ) are great enough.
tfater chemistry, nutrients - Three of the biologically more important
nutrients (nitrate, phosphate, iron) were sampled and analyzed from all
studies except the first two, which did not include iron analyses.
Results show that inflowing river water is consistently nutrient en-
riched relative to mid-lake and index station waters; iron by a factor
of 25, nitrate and phosphate by factors of 10. There is a spotty re-
lationship between nutrients and either plume density values, sus-
pended sediment, or DIG. Table 27 shows nutrients correlate well.with
these parameters for the first two studies, but only moderately or
poorly for other studies. Sample sites west of the plumes consistently
had nutrient contents similar to mid-lake. Samples from regions directly
influenced by inflowing river water had nutrient contents intermediate
between river mouth and mid-lake waters. Iron and phosphate concentra-
tions at almost all stations north and east of the river mouth increased
significantly from morning to afternoon on 20 June. Nitrate concentration
increased to a lesser extent. The greatest increases occurred at station
4b: from 18 to 40 yg'l iron, 17 to 32 yg-1 phosphate, and 6 to 10
184
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yg-1 nitrate. This nutrient change paralleled photographically ob-
served eastward movement of the plume.
Temperature and light measurements - Temperature readings were not
taken during March, but during all other morning samplings river mouth
temperatures were lower than any lake station. They increased during
the season from 3.0°C on 12 April to 8.8°C on 20 June while surface tem-
peratures in clear lake water increased from 5-6°C to 10-12°C. Plume
area surface temperatures directly northeast of the river mouth were
always intermediate between those of the mouth and clear water. Vertical
temperature gradients in this area indicate that simple density gradient
flow occurred. Dense plume units farther from the river mouth had near
surface temperatures approximately 1°C higher than clear water, sugges-
ting that solar heating of suspended sediment particles was responsible,
in part, for water mass warming. Temperatures in less dense plume units
along the shore east of the river mouth were consistently 2-3°C higher
than those in similarly shallow clear water to the west. This is con-
sistent with a solar heating mechanism. Such warming created a double-
valued function of temperature vs. other parameters and precluded good
simple correlations. Table 27 shows no consistent temperature correla-
tion with plume density, suspended sediment, or DIG for morning plumes.
The temperature of river mouth water reached 15.5°C during the afternoon
of 20 June, considerably higher than the morning (8.8°C) and higher than
any lake station at the time of sampling (12-15°C). Again, stations to
the northeast had temperatures intermediate between the river mouth and
clear water. Although some vertical mixing of river and lake waters
occurred, vertical temperature gradients indicate that river water in-
trusion took place primarily by surface flow over cooler, more dense
lake waters. Surface temperatures in tenuous plume units along the
eastern shore and beyond the shelf to the north were higher than temper-
atures in plume units nearer the mouth. The former approximate the
185
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TABLE 27, SIMPLE CORRELATION COEFFICIENTS FOR SEDIMENT PLUME VARIABLES-*-
DATE
29 INARCH 1971
(17 DEGREES OF FREEDOM)
12 APRIL 1971
(17 DEGREES OF FREEDOM)
VARIABLE SED, DIC
PLUME DENSITY UNITS -0,464
SUSPENDED SEDIMENT
DIC
PRIMARY PRODUCTIVITY
HOj-N
POj, P
No. CELLS • VomME"1
PLUME DENSITY UNITS -0.819 0,845
SUSPENDED SEDIMENT -0,907
DIC
HETEROTROPHIC ACTIVITY
PRIMARY PRODUCTIVITY
NOj-N
LIGHT PENETRATION
SURFACE TEMPERATURE
No, CELLS • VOLUME
HET, PPR % POk, FE
-0.712 -0.730
0,556 0,709
-0,686 -0,673
0,597
0,860
-0,891 -0,625 -0,844 -0.802
0.898 0.686 0,965 0,921
0.872 -0,540 -0,931 -0,892
0,733 0,893 0.898
0.570 '0.549
0,902
LIGHT TEMP, CELLS BIOMASS
o-
0,709
-0.603 0.448
0.630 0.462
-0.615 0.544
-0.604 -0,500
-0.645 0.610
0.457
0,630
PLUME DENSITY,UNITS -0,642 0.831 -0.818 -0.673 0,722
SUSPENDED SEDIMENT -0.873 0,783 -0,682 -0.704
7 JUNE 1971 DIC -0,928 -0.660 -0.580 -0,432 -0.574 0.733
(20 DEGREES OF FREEDOM) HETEROTROPHIC ACTIVITY 0,695 0.483 0.487 -0.819
PRIMARY PRODUCTIVITY _ -0,550
f«3 N 0,840 0,838
P04 P 0.842
FE
LIGHT PENETRATION
SURFACE TEMPERATURE
No. CELLS • VouwE"1
186
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TABLE 27, CONT'D,
DATE
20 JUNE 1971
NORN ING
(21 DEGREES OF FREEDOM)
20 JUNE 1971
AFTERNOON
(21 DEGREES OF FREEDOM)
VARIABLE SED.
PLUME DENSITY UNITS -0,766
SUSPENDED SEDIMENT
DIC
HETEROTROPHIC ACTIVITY
PRIMSRY PRODUCTIVITY
NOj-N
FVP
FE
LIGHT PENETRATION
SURFACE TEMPERATURE
No. CELLS • VOLUME"^
PLLME DENSITY UNITS -0.752
SUSPENDED SEDIMENT
DIC
HETEROTROPHIC ACTIVITY
PRIMARY PRODUCTIVITY
NOj-N
Pfy-P
FE
LIGHT PENETRATION
SURFACE TEMPERATURE
No. CELLS . VomME"1
DIC HET. PPR NOj PO^ FE LIGHT TEMP. CELLS BIOMASS
0.755 -0.619 -0.561 -0.730 0.655 -0,581
-0,981 0,416 0.493 0.599 -0.704 -0.579 0,624 0.811
-0,495 -0,513 -0.556 0.661 0.601 -0.660 -0.854
0.508 0.446 0.524 0.577
0.474 0.552 0.440
0.689 -0.447
-0.631 0.443 0.623
0.636 -0.515
-0.442 -0.544
~" is
0,776 -0.796 -0.695 -0.689 -0,456 -0,609 0.699 -0,620 -0.510 -0.576
-0.941 0.898 0,873 0.615 0.444 -0,713 0.469 0.538 0.890
-0.970 -0,791 -0.605 0.688 -0.489 -0.780
0.721 0.572 -0.723 0,472 0,682
0,683 -0.688 0,510 0.831
0.584 0,734 0,441 0.513 0,610 0.640
0.919 0.674
0,715 0,460 0,443
0,576
0.637
• DIRECT AND INVERSE RELATIONSHIPS ARE INDICATED BY POSITIVE AND NEGATIVE VALUES RESPECTIVELY. SIMPLE CORRELATION COEFFICIENTS NEAR
ZERO IMPLY NO CORRELATION WHEREAS SIMPLE CORRELATION COEFFICIENTS NEAR 1.000 OR-1.000 IMPLY HIGH DIRECT OR INVERSE CORRELATIONS,
RESPECTIVELY. PLUME DENSITY UNITS ARE SUCH THAT LOW NUMBERS CORRESPOND TO HIGH PLUME DENSITY, THUS, ANY RELATIONSHIP THAT WOULD
BE DIRECT IN TERMS OF PLUME DENSITY APPEARS AS AN INVERSE ONE IN TERMS OF PLUME DENSITY UNITS Al€> VICE VERSA, CONFIDENCE LEVELS
FOR CORRELATION COEFFICIENTS ARE INDICATED THUSLY: CbOX =% 95K, O.XXX =% 935, AND O.XXX = 99.9%. SIMPLE CORRELATION COEFFICIENTS
BELOW 9555 CONFIDENCE LEVEL HAVE BEEN OMITTED FOR CONVENIENCE.
187
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mouth temperature. Warming of distal plume units again points to solar
heating of suspended sediment. Correlations of temperature with a num-
ber of variables in Table 27 improved markedly over morning plumes
possibly because high mouth temperatures created less pronounced double-
valued functions.
Photometric measurements of light penetration were reduced to relative
values to compare penetration with visual plume density. Relative
values at each turbid water station were determined by dividing percent
light penetration at the deepest measurement by percent light trans-
mission at that depth in clear water. Such values consistently corre-
late well with plume densities, suspended sediment, and DIG (Table 27).
Clear water stations always had high relative light penetration values
(0.7-1.0), while stations in dense plume units (1 or 2) always had low
values (0.1-0.6). Stations with intermediate plume density values
(3,4, or 5) usually had relative light penetration close to clear water.
In many cases, such stations were indistinguishable. Similarly, plume
units 1 and 2 could not be distinguished one from another. It appears
color aerial photographs can be used more successfully than light pen-
etration values to distinguish various degrees of turbidity.
Secchi disk readings could be made only in clear water deeper than 20 m
or in very turbid shallow water. Disk readings could not be taken
where the bottom was visible. Stations beyond the shelf had lower
readings (18 to 34 m) than mid-lake stations (26 to 40 m).
Heterotrophic activity - It has been demonstrated that the influence
of the Upper Truckee River upon bacterial growth in Lake Tahoe is pro-
nounced (Paerl and Goldman 1972a). Growth has also been shown to in-
crease from winter to summer. This is well illustrated by Figures
-3 -1
39-42 where heterotrophic acetate assimilation in/ug acetate-m *hr
given for each station. Heterotrophic activity varied over two orders
188
-------
of magnitude and correlated excellently with plume density, suspended
sediment, DIG, and light penetration (Table 27). Plots of heterotrophic
activity vs. plume density units show a consistently strong relationship.
Increased photographic capability enhances the spatial relationship be-
tween measured microbial activity and photographically detected water
masses noted earlier (Paerl and Goldman 1972a). Although values were
low during April, the influence of the inflowing water was still readily
detectable. Assimilation values were higher at the river mouth, directly
north in the heart of the plume, and along the eastern shelf. June
transects show a similar strong relationship between heterotrophic activ-
ity and plume shape and density. Transect assimilation values were
higher. The double sampling on 20 June registered peak values during
the sampling period and showed a distinct shift eastward in the after-
noon.
Primary productivity - Phytoplankton carbon assimilation rates relate
to changes in plume density and configuration in a more irregular
fashion than does bacterial activity. Still, primary productivity in-
creased in areas influenced by the plume to the north and east of the
river, but remained low in clear water to the west. Higher values of
primary productivity were observed in 1968 northeast of the mouth during
synoptic studies (Goldman, Moshiri, and Amezaga 1972) . Correlations of
productivity with plume density, suspended sediment, DIG, and hetero-
trophic activity are good except for 29 March (Table 27). However,
there are usually one or two stations in each study that exhibit marked-
ly different primary productivity than expected based on plume density
and heterotrophic activity values. Discrepancies in primary productivity
are probably due, in part, to physiological factors rather than physical
conditions. For example, placement of phytoplankton from a turbid
water environment in clear water for incubation could cause anomalous
results since light values could be higher.
189
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Productivity was greater in March than April at all but two stations.
The plume was highly developed and evidently contained rain runoff from
the 26 March storm. It probably carried a-high nutrient load in melting
snows from lower altitude urban areas. The plume was well developed in
April, but higher productivity was limited to the immediate river mouth
area and a few areas to the northeast and east. Increased productivity
occurred at all stations on 7 June. Values were highest at the river
mouth and decreased sharply to the west and less sharply eastward; no
major discrepancies in primary productivity compared to plume density
and heterotrophic activity occurred. The morning sampling on 20 June
resulted in lower values of phytoplankton growth rate, but the pattern
was less distinct (note lower confidence levels for productivity vs.
sediment, DIG, and heterotrophic activity in Table 27). The afternoon
sampling resulted in high correlations between plume density, hetero-
trophic activity, and primary productivity. The morning and afternoon
studies confirmed that productivity as well as other indicative values
were illustrative of the plume's eastward shift during the afternoon.
This discovery is to some degree tempered by the fact that the incuba-
tion procedure differed (see Methods).
Phytoplankton - Except for studies on 20 June, correlations of the
number of cells per unit volume or biomass with other parameters were
almost non-existent. It is unclear why good correlations exist only on
20 June. The lack of consistent correlations emphasizes the differences
between measures of standing crop and measures of metabolic activity or
environmental conditions. Since biomass measurement required phyto-
plankton identification, it was possible to observe trends of various
species by station location and throughout the period of study. The
trends were not tested by simple correlations, but the observations
follow.
The largest biomass level for any of the studies was recorded on 29 March.
190
-------
There were distinct differences in phytoplankton community composition
between near and off-shore stations for that plume. The phytoplankton
community of each station was dominated by three or four diatoms which
were the major biomass contributors except in close proximity to the
river mouth. Cyclotella bodanica, Melosira crenulata, and Synedra
radians were usually the most abundant species. Synedra radians pro-
vided the single largest biomass component. Other diatoms such as
Asterionella formosa, Fragilaria crotonensis, and the chrysophycean
Dinobryon sertularia were abundant locally and together with Cryptbmonas
reflexa, Euglena sp., and some flagellates were responsible for most
differences in phytoplankton composition detected near the river mouth.
The greatest measured cell concentration and biomass occurred just to
the east of the inflow where the highest primary productivity was found
(Fig. 38).
Early April sampling revealed a similar phytoplankton composition with
Synedra, Cyclotella, and Melosira dominating. Asterionella appeared
again close to the river mouth, but Dinobryon, which had also been an
indicator of plume location, was much less prevalent. Cryptomonas,
Euglena, and the flagellates were not present. Melosira was more abun-
dant in the plume than at locations to the west. Samples to the north-
east and around the river mouth contained the largest biomass. Total
values were lower than those in March.
The 7 June sampling was marked by a definite decrease in dominance of
the major diatoms and by important but isolated appearances of the green
algae Staurastrum paradoxum and some other diatoms, such as several
species of both Achnanthes and Epithemia. There was a significant re-
surgence of Dinobryon and a very large increase in Peridinium sp. and
flagellates at most sampling locations. Asterionella formosa was present
in samples near the river mouth, but also occurred in many samples
within the plume influence to the east and north. Consistent with the
191
-------
higher primary productivity, there was a larger lumber of cells, but with
lower biomass than in April; the highest values of both occurred east of
the river mouth.
The two samplings on 20 June revealed a continuing trend toward greater
community diversity along with subsidence of previously abundant forms
and Staurastrum. Dinobryon became much more abundant and so did another
chrysophycean Kephyrion ovum. Flagellates were present in a fan-shaped
pattern north of the river mouth, but did not appear to the east or
west along the shoreline. In contrast to Asterionella, which again was
locally abundant in the plume, Dinobryon showed a general increase in
numbers with increasing distance away from the plume. Peridinium was
abundant at almost all stations. Many diatom species were present at
the river mouth, both in the morning and afternoon, possibly indicative
of the dynamic nature of the sampling area and mixing of water and
phytoplankton from both lentic and lotic environments. Cell numbers
and biomass increased in the afternoon and there was a distinct shift
of the phytoplankton population east of the river mouth during the day,
concurrent with visible evidence of plume movement. Total cell numbers
were lower than on earlier dates, but biomass decreased only slightly.
Discussion
Sediment plumes of the Upper Truckee River can be mapped for both po-
sition and density a considerable distance into Lake Tahoe by aerial
photography and simultaneous field collections of water truth data.
Several chemical and physical parameters correlate with mapped plume
positions and densities. Most importantly, biological measurements of
bacterial and phytoplankton activity clearly show the influence of the
plume. These measures of biological activity are particularly useful in
assessing eutrophication processes. Bacterial activity is strongly re-
lated to increasing plume density as the Upper Truckee River mouth is
192
-------
approached. It is suggested that suspended detrital material, issuing
from the river mouth, stimulates bacterial growth, because it simultan-
eously provides attachment surfaces for bacterial adhesion and a concen-
trated nutrient source. Bioassay experiments with nutrient-stripped,
sterile silt added to mid-lake water provided attachment surfaces and
showed striking amounts of stimulation over mid-lake water without silt
(Paerl and Goldman 1972b). These experiments were conducted with
similar final concentrations of organic and inorganic nutrients, thus
proving that surface area is of prime importance to promotion of bacter-
ial growth. In addition to surface area, the high nutritive content of
silt in the sampling area (nitrate, phosphate, organic carbon) further
boosts bacterial growth. Additional evidence of bacterial attachment
comes from micro-autoradiographic experiments showing bacteria actively
assimilating heterotrophic substrates while attached to silt (Paerl
and Goldman 1972b). It would appear that attached bacteria utilize
nutrients from silt as well as solution. An alternate explanation of
the heterotrophic activity-plume density relationship is that the bac-
teria attached to silt particles derive from the original soil. Hence,
good correlation between the two parameters would be caused by the fact
that soil bacteria are always attached to the silt. However, the above
experiment with sterile silt showed stimulation of mid-lake bacteria as
opposed to soil bacteria. Secondly, the bacteria continue to survive
and multiply in the lake environment so that any effect on the lake is
identical irregardless of their origin. Through mineralization, nutrients
are eventually available for later uptake by phytoplankton. In addition,
the hundred-fold change of heterotrophic activity caused by sediment
plumes raises the possibility that a minor biomass component, bacteria,
may have major effects on eutrophicating processes, namely breaking down
organic sediment to release nutrients for algal growth (Paerl and
Leonard unpublished).
The relationship between phytoplankton productivity and mapped plume
193
-------
density is less dramatic, but the correlation varies between 99% and
99.9% confidence levels except for 29 March. Lack of correlation on
that date is probably due to an hour's time lag between photographic
observation and beginning aquatic sampling; field notes indicate a
plume shift sufficient to change the character of the water mass at a
number of stations. Subsequent studies commenced aerial and aquatic
efforts simultaneously, albeit for other reasons. Phytoplankton utilize
dissolved nutrients and not those attached to silt as do heterotrophs.
In view of spotty correlations between plume density and dissolved nu-
trients, which may be caused by biological utilization (see below), it
is not surprising that primary productivity displays lower correlation
than heterotrophic activity with plume density.
Nutrients under plume influence owe their changes, in part, to biologi-
cal processes which utilize them. Lake Tahoe contains very low concen-
trations of nutrients and primary productivity has been proven to be
nitrogen and iron limited (Goldman and Armstrong 1969, Goldman 1964).
Biological utilization may well have contributed to the spotty correla-
tion with plume density. Changing concentrations of these nutrients
during 20 June may be linked to both increased inflow of nutrients from
the river as well as biological utilization.
Changes in phytoplankton diversity, cell numbers, and biomass were
indicative of the Upper Truckee River sediment plume. But while they
signaled the changing seasonal conditions in the lake, the relationship
of these phytoplankton characteristics to plume density is unclear.
Only during 20 June was there a strong correlation (Table 27) between
plume density units and total cell numbers or biomass. Unless inflow
brings in new species and/or greater numbers of phytoplankton, the
change in plume configuration is too rapid to produce a good correlation
between phytoplankton and plume density. However, it is clear from the
data that certain algal species are quite indicative of plume presence.
194
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Several types are either excluded from the area adjacent to the river
mouth or are more abundant than in other areas. It is apparent that
phytoplankton community changes, although useful indicators, taken alone
cannot define the effects that a tributary has on Lake Tahoe.
Good correlations between photographic and aquatic data imply that it is
reasonable to assign similar values to various water parameters in un-
sampled areas. The values can be assigned to mapped units with a cer-
tainty corresponding to the degree of correlation (Table 27). High
heterotrophic activity represents plume units of high density and the
activity of even the least dense units will be higher than clear water.
The data also suggests that the Upper Truckee River sediment plume prob-
ably causes higher than normal levels of primary productivity to extend
over much of the southeastern corner of the lake. Photographs show that
the sediment plume grows from early spring to reach its maximum size
during peak river discharge. The data indicate that primary productivity
followed a similar development and that the Upper Truckee River plume
has become a permanent influence on algal growth in the lake.
Spatial and temporal association of high biological activity with the
Upper Truckee River sediment plume is circumstantial evidence that the
sediment plume is the causative agent, but additional evidence must be
added to demonstrate a causal relationship. The strong relation between
plume densities, suspended sediment, and heterotrophic activity coupled
with the evidence for bacterial attachment to and nutrition by sediment
particles is strong evidence for stimulation caused by sediment particles.
The link between plume densities and primary productivity, while less
dramatic, is important because it measures actual algal growth rate in
the lake. Good correlations exist between primary productivity and
plume density; plume density is correlated with nutrients for the first
two and last studies, but biological utilization may have destroyed the
correlation for the other two as well as that between primary productivity
195
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and nutrients. Previous work (Goldman and Armstrong 1969) showed high
nutrient levels in Upper Truckee River water (such as were consistently
measured at the mouth station in this work) increased primary productivit
in the lake's water. Taken together, the two lines of evidence indicate
that the nutrients associated with the sediment plume are the causative
agents of increased primary productivity. Thus, both measures of bio-
logical productivity indicate that the sediment plume is the causative
agent of increased production.
Conclusions
Aerial photographs and simultaneous on-site water samples in Lake Tahoe
can be used to document temporal and spatial influences of the Upper
Truckee River sediment plume on a yearly or daily basis. DIG and
heterotrophic activity are highly correlated with photographic evidence
and appear to be especially promising methods of water mass delinea-
tion. Nutrients, sediment load, light penetration, temperature, phyto-
plankton community changes, and primary productivity can also be useful
when samples are numerous enough for correlation with photographic
records.
Relationships between the sediment plume and both primary productivity
and bacterial activity implicate sediment particles and associated
nutrients with more rapid nutrient utilization and growth by bacteria
and phytoplankton. Coupled with these findings, the sediment load in
the Upper Truckee River from man-made disturbances in its watershed is
increasing. It appears that land disturbance is contributing further
to accelerated eutrophication of Lake Tahoe.
Methods described here should be applicable to other situations where
tributary inflows to a river or lake are visibly different in clarity.
Collection of similar baseline limnological information is a continuing
196
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necessity for proper interpretation of tributary influences evidenced
by photographic data.
LAND DISPOSAL OF SEWAGE EFFLUENT
(This sub-section is to be published in Ecology by Michael A. Perkins,
Charles R. Goldman, Robert L. Leonard, Division of Environmental Studies
and Institute of Ecology, University of California, Davis).
Introduction
Heavenly Valley Creek is a small subalpine creek located in the Trout
Creek drainage system at the southern end of the Lake Tahoe basin (Fig.
44). This creek was sampled initially in April 1970, during a stream
survey designed to locate the source of high ultraviolet absorbance in
the waters emanating from the south shore region of the basin as reported
by Goldman and Armstrong (1969) .
Samples from Heavenly Valley Creek had much higher UV absorbance readings
than did those from other streams in the region sampled at the same time.
Chemical analysis of the samples indicated a nitrate—nitrogen (NO,.—N)
-1 •
concentration of 1.08 mg'l for Heavenly Valley Creek. This value was
unusually high for streams of the Tahoe basin, where NO,.-N values rarely
exceed the microgram per liter level (Fig. 45).
The high NO -N concentration and associated UV absorbance of Heavenly
Valley Creek warranted further investigation into land use practices
within the subdrainage. A conference with the United States Forest
Service revealed that the area to the immediate south of the creek was
one of two areas in the south shore region that had received surface
spraying of sewage effluent from the South Tahoe Public Utilities Dis-
trict (STPUD) plant. Area 1, located to the south of Heavenly Valley
197
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Figure 44. Heavenly Valley Creek area indicating the site receiving
effluent spray. The numbers (1-6) represent sample stations
along the creek. The location of the spring draining from
the spray area is designated by X.
198
-------
1000_
- 100_
•
M
%
z
o
WARD GEN TAY U T R TRT HVC INC 3rd
Figure 45. Nitrate-nitrogen concentrations for eight creeks within the Tahoe basin. Values
are means of 13 samples collected between January and June 1971.
-------
Creek, consisted of approximately 40.5 hectares (100 acres) which were
sprayed with secondary effluent from 1960 to 1965 (Fig. 44)- Area 2
(outside the study area shown in Fig. 44), located between Trout
Creek and the Upper Truckee River, consisted of approximately 58.3
hectares (144 acres) which were sprayed from 1966 to 1968. The efflu-
ent was derived entirely from residential and commercial service, in-
cluding gambling casinos in the Nevada Stateline area. No significant
industrial effluents or other sources of unusual toxic substances were
involved. Although Area 2 does not influence Heavenly Valley Creek,
its drainage does enter the Upper Truckee River and Lake Tahoe. After
April 1968 the facilities for exporting tertiary effluent out of the
basin to Indian Creek Reservoir, 45 km south, were completed (Gulp and
Moyer 1969).
A striking feature of the study site was the absence of large stands
of coniferous trees within the area which had received effluent spray.
Prior to effluent spraying, this area contained a moderately dense stand
of Jeffrey pine (Pinus jeffreyi) with sparse shrub cover. Most of the
pines died during the period of effluent treatment. The pines were
most likely killed by prolonged soil saturation. Normal summer soil
moisture conditions in the Tahoe basin range from field capacity in
late June, just after snowmelt, to extremely dry by September and often
through November before heavy snowfall. Boron in the soil may also
have reached toxic levels (2 mg-1 was found in the soil after pro-
longed spraying, Paul Zinke personal communication). After cessation
of spraying, the dead trees were cleared from the site and an attempt
was made to revegetate the area (U.S. Forest Service personal communi-
cation) .
This report is an evaluation of one aspect of the long term effects of
spraying treated effluent directly upon the forest floor in the Tahoe
basin. The secondary effluent, as it percolated through the soil
200
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profile, was partially stripped of its rich nutrient load through bio-
logical uptake and adsorption onto soil particles. A residual nutrient
load apparently remained within the soil profile to be leached in future
years. Five years after cessation of spraying onto Area 1, the release
of high levels of nutrients, particularly NO--N, into Heavenly Valley
Creek was still observed. These nutrients are eventually carried into
Lake Tahoe.
Methods
Six stations were selected at approximately 200 m intervals along
Heavenly Valley Creek in order to locate and further investigate the
source of the NO..-N and the substance responsible for the high UV ab-
sorbance. Water samples collected at these sites in 2-liter, acid-
rinsed, polyethylene containers were transported to the Davis laboratory
for analysis. If immediate analysis was not practical, the samples
were frozen and analyzed at a later date.
Nitrate-nitrogen was determined by the cadmium-reduction method of
Strickland and Parsons (1968). Phosphate-phosphorus, as total acid-
hydrolyzed phosphate, was determined by a modification of the single-
solution method of Murphy and Riley (1962) , using butyl acetate ex-
i I i I [
traction for low levels of phosphate. Na , Mg , and Ca were deter-
mined by atomic absorption spectrophotometry. Ultraviolet absorbance
was measured on filtered samples (Whatman GFC) at 200 nm in 1 cm quartz
cells in a Beckman DBG spectrophotometer.
Ground-water extractors were distributed within the study area to test
for nutrient differences between sprayed and unsprayed sites. An ex-
tractor consisted of a length of PVC tubing (6.5 cm diameter) fitted
with a porous ceramic cup at one end and a rubber stopper at the other
(Soil Moisture Equipment Co., Santa Barbara, Calif.). The extractors
201
-------
were placed in the ground to a depth of 120 cm and were then evacuated
through a tube in the rubber stopper. Ground water samples, drawn
through the porous cups from the soil, were collected from the extrac-
tors every two weeks and analyzed as described above. The area to the
immediate north of the creek, opposite Station 5, was chosen for the
unsprayed sample location since it was completely outside the influence
of the sewage spray (Fig. 44). The soil on either side of the creek
consisted primarily of coarse-textured, decomposed granite.
Lake water enrichment bioassays were set up to test the effect of
Heavenly Valley Creek water on photosynthetic carbon fixation. The
method used was a modification of that described by Goldman and
Armstrong (1969). C-carbonate (20 yc-ml~ ) was added to Lake Tahoe
water taken from a depth of 15-20 m. The water was then distributed
into 500-ml, screw-cap, culture flasks. Stream water from various
stations along the creek was introduced into the culture flasks to
make 0.1, 1.0, and 10.0% (v/v) additions. The flasks were incubated
at 18°C with a 14-hour light period. Fifty-milliliter subsamples were
taken at 24-hour intervals over a five-day period and filtered through
0.45 t 0.02 ym HA Milliporl^filters at low vacuum (<10 psi). The
filters were air dried and then placed on planchets for counting of
radioactivity in a Geiger-Mueller, ultra-thin window, gas flow system.
All controls (untreated lake water) and additions for each culture
period were run in triplicate. Replicate samples, expressed as counts-
per-minute, agreed within 10% for all culture periods.
To supplement the information gained from the stream water bioassays,
soil samples were collected from depths down to 45 cm in both the
sprayed and unsprayed areas. These samples were passed through a 2 mm
mesh sieve and then placed in a 4 cm diameter plexiglass column for
leaching with quartz-distilled water at a waterrsoil ratio of 5:1. The
soil-water extract obtained was added to Lake Tahoe water to make 0.1,
202
-------
1.0, and 10.0% (v/v) additions. Culture conditions were the same as
those outlined for the stream water additions.
Results and Discussion
Stream water samples taken along Heavenly Valley Creek in May 1970
revealed significant differences in both NO -N and UV absorbance between
Stations 5 and 6 (Fig. 46). More intensive sampling indicated that the
break occurred abruptly at a point in the creek fed by a small spring
draining from the south slope. The initial samples from this spring
had a NO,,-N concentration of 12.4 mg-1 and a UV absorbance which read
off-scale. Samples taken 5 m upstream and downstream from the spring
had respective NO -N concentrations of 0.02 and 0.35 mg'l and UV
absorbance values of 0.152 and 0.452. It was evident that the spring
was a major source of both the high NO -N concentration and the high UV
absorbance values in the creek.
The spring lies at the highest point along the creek receiving immediate
drainage from the sprayed area. Thus, it seemed likely that the excep-
tionally high NO--N concentration and UV absorbance of both the spring
and the creek could be attributed to the past treatment of the adjacent
area with sewage effluent.
A weir was placed across the spring and flow rate and nutrient output
were measured twice a month from February through June 1971. The flow
3 -1
rate remained fairly constant at about 0.045 m -min (0.026 cfs) until
3 —1
a thaw in April, at which time the rate increased to 0.076 m -min
(0.044 cfs), a level maintained throughout the remainder of the study
period. NOq-N output averaged 854 g-day during the period of low
-1
flow and 1818 g-day during the period of increased flow. Overall,
NO -N output ranged from 750 to 2198 g-day , with a mean value of 1336
g-day .
203
-------
K>
O
-P-
.8
.7
_ .6
r -5
O)
I .4
Z
I o
O
z
.2
O— — — O—
S T ATIO N 1
downstr earn
~f , N 0,-N
.
O —
u
.3
.2
.1
0
5 6
upstream
Figure 46. Nitrate-nitrogen and UV absorbance along Heavenly Valley Creek in May 1970. Note
the sharp drop in nitrate and UV absorbance between Stations 5 and 6.
-------
A downstream station, an upstream station, and the spring were sampled
periodically from July 1970 through June 1971 (Fig. 47). Nitrate
concentrations at the downstream station ranged from 0.25 to 3.75 mg
NCL-N-l"1 with a mean value of 1.25 mg-l~ (SD = 0.98). The concentra-
tion of NO_-N was always much lower at the upstream station with a
mean value of 0.038 mg-l"1 (range = 0.007-0.082 mg-l"1, SD = 0.007).
_i
On the average, there was an increase of 1.212 mg-1 from the upper
to the lower station. The nitrate concentration of the spring was
much greater and fluctuated widely. The mean value was 11.84 mg-1
over a range of 0.825 to 23.60 mg-l~ .
In order to calculate total nitrate loading of Heavenly Valley Creek
from the effluent spray site, including the spring and direct entry
into the stream channel below the spring, monthly water discharge from
Heavenly Valley Creek was estimated from Trout Creek records of the
U.S. Geological Survey taken above and below the confluence of the two
streams. The total nitrate load carried by Heavenly Valley Creek for
the period July 1970 to June 1971 was estimated to be about 6000 kg
(nitrate concentration data from Fig. 45). This amount of nitrate is
well over 20% of the average total nitrate carried into Lake Tahoe
annually by surface runoff (Goldman 1974); it is nearly 60 times more
nitrate-nitrogen than was carried by Ward Creek in water-year 1972-73
(Leonard and Coats 1974). (Values were adjusted for differences in
total water discharge between the two watersheds and water-years).
Annual average nitrate concentrations in Lake Tahoe as a whole are
still low (13 ug-l"1 in 1972-1973, Paerl et al. 1974), but may have
increased in the past 10-20 years (Goldman and Armstrong 1969) . In
addition, tributary enrichment with nutrients has caused highly visible
algal blooms in localized areas at the southern end of the lake
(Goldman et al. 1974).
205
-------
10000
1000_
z
o"
Z 100_
SPRING
UPSTREAM
I I I I
I I I
I I I I
N D | J
1970 1971
M
M
Figure 47. Seasonal nitrate-nitrogen concentration at the upstream, spring,
and downstream stations of Heavenly Valley Creek from April
1970 to June 1971.
206
-------
Phosphate levels were fairly low throughout the sampling period. There
appeared to be no discernible pattern among the values at the three
stations sampled indicating that the drainage from the spray area was
not significantly affecting phosphate concentration in the creek. The
mean values were: upstream, 0.019 mg-1 ; spring, 0.034 mg-1 ; and
_i
downstream, 0.023 mg-1
Cation analyses initiated in January 1971 revealed concentration pat-
terns similar to that of NO~-N which increased gradually through the
+
summer, fall, and winter and then dropped sharply in the spring. Na ,
i i i i
Mg , and Ca all showed a gradual increase through the winter months
followed by a decreased concentration in April, May, and June, reflecting
the dilution effect of spring snowmelt. The mean values at the down-
• -i -i i i
stream station were: Na , 2.34 mg-1 (range = 1.30-3.02 mg-1 ); Mg ,
1.14 mg-l~ (range = 0.26-1.43 mg-l~ ); and Ca , 3.01 mg-l~ (range =
1.28-3.90 mg-1"1).
Due to sampling difficulties, data on concentration of groundwater nu-
trients are sparse. The mean NO.—N concentration for 13 samples from
-1 ^ -1
the sprayed area was 3.99 mg-1 (range =. 0.65-7.8 mg-1 , SD = 2.33).
Six samples taken from the unsprayed area had a mean concentration of
0.49 mg-l~ (range = 0.04-1.00 mg-l~ , SD = 0.42). The mean concen-
tration was approximately eight times greater in samples from the sprayed
area. Concentration of Na in the samples from the sprayed area aver-
aged 451% higher than in samples from the unsprayed area, the mean
values being 14.93 and 3.31 mg-1 , respectively. There were no differ-
ences in the other elements included in the groundwater analyses which,
might be attributed to the sewage effluent.
At no time during the investigation of Heavenly Valley Creek was con-
spicuous periphyton growth noticed, a fairly common feature of many
streams in the Tahoe basin. This lack of abundant periphyton growth
207
-------
seemed inconsistent with the high nutrient levels in the creek, partic-
ularly in its downstream reaches where suitable sites for algal attach-
ment and other favorable environmental conditions existed. The pos-
sibility of algal inhibition by substances being released into the creek
via subsurface drainage from the sprayed area was suspected. The C-14
bioassays of the stream water and soil extract additions to Lake Tahoe
water were set up to test this possibility.
The data for the stream water additions compared to untreated controls
appeared to support the hypothesis that high concentrations of substances
present in Heavenly Valley Creek were inhibiting algal growth in the
stream itself. The various additions of downstream and spring water
were either slightly inhibitory, slightly stimulatory, or had no appar-
ent effect upon photosynthetic carbon-fixation by Lake Tahoe phyto-
plankton. The spring and downstream stations showed slight stimulation
only for the 0.1% addition while the 1.0 and 10.0% additions gave no
effect or slight inhibition. The addition of upstream water gave the
expected stimulatory response for the 0.1 and 10% additions (Fig. 48).
A one-way analysis of variance of the stream water additions indicated
that only the 10% upstream addition differed significantly from the
control and other additions (95% confidence level) showing a 22% increase
over the control.
Goldman and Carter (1965) and Goldman and Armstrong (1969) have shown
that algal photosynthesis in Lake Tahoe is relatively sensitive to
rather minute additions of inorganic nutrients, especially NO--N. Con-
sidering the amount of nutrients being added through the addition of
stream water, the lack of a stimulatory response was surprising. The
upstream additions had the least amount of added NO.,-N (0.1% = 0.015 mg,
1.0% = 0.15 mg, 10% = 1.5 mg) and gave the greatest stimulatory response.
The spring and downstream additions contained considerably more NO--N
and yet showed a stimulatory response only for the 0.1% additions
208
-------
K>
O
140
100
<-> 80
u.
O 60
Z 40
OL
01
0.
20
0.1 1.0 10
UPSTREAM
-fh;
0.1 1.0 10
SPRING
o.i i.o 10
D OWNST REA M
Figure 48. Bioassay of Heavenly Valley Creek water additions to Lake Tahoe water. Shaded
areas represent percent increase over an untreated lake water control.
-------
(Fig. 48). It is evident that some substance present in the spring
and downstream water, possibly the nitrate, is inhibitory to algal
growth and that its effect is negated and even reversed through dilution.
Nitrate is usually stimulatory at relatively low concentrations
(<50 ug-l~ ), but can be inhibitory at higher concentrations in lake
water algal cultures.
The soil extract additions from the sprayed area showed only slight
stimulation for the 1.0 and 10% additions from the upper horizon of the
soil profile (0-15 cm), the -increase relative to the control being 17
and 5%, respectively (Fig. 49). All additions from the lowest horizon
sampled (30-45 cm) resulted in significant inhibition of photosynthesis
as compared to the control, the lowest being the 10% addition which
gave a value 26% less than the control (Fig. 49), A"one-way analysis
of variance comparing the two depths sampled indicated that the 1.0 and
10% additions from the lower depth (30-45 cm) resulted in significant
inhibition of photosynthesis relative to equal additions from the upper
horizon (0-15 cm).
After 96 hours of incubation, all additions of soil extract from the
unsprayed area had resulted in significant increases in photosynthesis
relative to that of the control (Fig. 49). All additions from the un-
sprayed area were significantly more stimulating to photosynthesis than
were equivalent additions from the sprayed area.
V
A one-way analysis of variance comparing the two depths sampled within
the unsprayed area indicated that for equal additions only the 10%
addition varied significantly, the extract from the lower depth (30-45
cm) being 38% more stimulating to algal photosynthesis.
These results lend further support to our hypothesis that substances
present in the subsurface drainage from the sprayed area are inhibitory
210
-------
200t-
0.1 1.0 10
SPRAYED SPRAYED UNSPRAYED UNSPRAYED
0-15 cm 30-45 cm 0-30 cm 30 - 45 cm
Figure 49. Bioassay of Heavenly Valley soil extract additions to Lake Tahoe water, Shaded
areas represent percent increase over the control.
-------
to algal growth at the concentrations present in Heavenly Valley Creek.
These substances are probably related to the past treatment of the
area with sewage effluent.
Conclusion
The combined results of the chemical analyses and bioassay experiments
indicate that unique nutrient characteristics of the lower reaches of
Heavenly Valley Creek are related to the history of sewage effluent
spraying in Area 1 (Fig. 44). Exceptionally high concentrations of
NCL-N were released from the sprayed area into the stream. Cooper (1969)
has commented on the nutrient regulating effect of forest vegetation
by uptake and storage as well as by influencing the flow of water
through the soil profile. Bormann et al. (1968) have demonstrated the
increased nutrient output due to removal of forest vegetation and the
importance of vegetation in maintaining nutrient cycling within the
ecosystem. The results presented in this report are indicative of a
similar type of nutrient release which when coupled with the accumula-
tion of nutrients contained in sewage effluent can create a long term
potential for eutrophication of the receiving body of water.
Phytoplankton growth in Lake Tahoe has been shown to be most limited
by nitrate (Goldman and Carter 1965, Goldman and Armstrong 1969,
Goldman 1972). Goldman and Armstrong (1969) have also shown close cor-
relation between primary productivity and UV absorbance in lake waters
off the South Shore. They suggested that this UV absorbance may be due
to nitrate and/or dissolved organic matter (DOM), present in the water.
Although the data did not reveal a consistently strong, positive cor-
relation between nitrate and UV absorbance in the present study, there
was no doubt that the high UV readings were traceable to drainage from
the sprayed area. The UV absorbance noted by Goldman and Armstrong
(1969) and its correlation with primary productivity were in fact
212
-------
indicators of the enrichment of south Lake Tahoe water by drainage from
the two sprayed areas within the Trout Creek-Upper Truckee River
watersheds.
Because of the sensitivity of the coniferous soil-vegetation system to
unseasonal flooding and possibly to toxic substances in the effluent
and the sensitivity of the aquatic system to nutrient additions, large-
scale land disposal of secondary sewage effluent is inappropriate in
the Tahoe basin.
THE RESPONSE OF NATURALLY OCCURRING PHYTOPLANKTON POPULATIONS TO NTA
IN LAKE TAHOE, CASTLE LAKE, AND CLEAR LAKE, CALIFORNIA
Introduction
The mounting concern about the eutrophication of surface waters has
directed attention toward the high phosphate content of conventional
detergents, since phosphorus has long been considered a major limiting
factor in aquatic environments. High phosphate concentrations are often
found in very eutrophic waters. Limiting, factor work at the University
of California, Davis has identified a number of different limiting
factors in Alaska, New Zealand, and California lakes (Goldman 1964).
Molybdenum, for example, was found to be a limiting factor in Castle
Lake, California in combination with potassium and sulfur (Goldman 1960).
Clear Lake, the largest lake entirely within the boundaries of California,
is characterized by extremely high phosphate levels with nitrogen the
most limiting of the spectrum of stimulatory chemicals (Goldman and
Wetzel 1963). Lake Tahoe, long renowned for its remarkable clarity and
low nutrient-content, is primarily limited by iron (Goldman 1964) and
nitrogen (Goldman and Armstrong 1969) .
Because of the extensive limnological research that has been done with
213
-------
these three lakes, they were selected for bioassay experiments with NTA
which has been proposed as a phosphate substitute in the detergent in-
dustry. During the summer and fall of 1970, culture experiments with
natural lake populations were conducted to determine the influence of
NTA on algal growth. NTA in various forms for these experiments was
supplied by the E.P.A. Pacific Northwest Environmental Research Labor-
atory. Natural populations of phytoplankton were used exclusively in
these experiments without concentration. Both laboratory and in situ
culturing were employed.
Although NTA was banned in detergents for other reasons, it appears
likely that its eutrophicating potential in some California lakes might
have been just as great if not greater than the phosphate it was to
replace.
Methods
The carbon-14 bioassay techniques developed by Goldman (1963) were used
14
in this study. Solutions of Na_ CO- of known activity were carefully
premixed in the total culture medium prior to the addition of the NTA
14
solutions being tested. The following amounts of C were added to
each of the cultures:
Lake Tahoe 50.0 pc-l~ (50 subsample filtered daily)
Castle Lake 8.0 yc-1 (50 ml subsample filtered daily)
Clear Lake 5.4 yc-1 (25 ml subsample filtered daily)
Carefully washed and autoclaved 500-ml Pyrex^ culture flasks were
used in all experiments. Whether incubated in situ or in the laboratory,
well-mixed subsamples of each culture were filtered daily through HA
Millipore*^ discs of 30 mm diameter. The experiments lasted from 4 to 7
days. The radioactivity of the organisms retained on these filters
was measured with an ultra-thin window, automatic, gas-flow Geiger-
Muller counter.
214
-------
Nitrate determinations were made with the cadmium reduction method of
Strickland and Parsons (1968). Phosphorus was determined colorimetric-
ally as the blue phosphomolybdate complex, based on a method that
closely paralleled that of Murphy and Riley (1962). Total iron was
measured after conversion to the ferrous state with hydrochloric acid
and hydroxylamine. The red iron (Il)-bathophenanthroline complex ex-
tracted into isopentyl alcohol was measured colorimetrically. Dissolved
inorganic carbon concentrations were determined by the infrared analysis
method of Armstrong, Goldman* and Fujita (1971).
All experiments used dilutions from 5.00 mg Na«NTA-H90-l stock solu-
-1
tions (equivalent to 3.44 mg NTA-1 ). Series #29500 - 29503 and
#39500 - 39503 sewage effluents from the Corvallis laboratory pilot plant
were used in these experiments. Chemical analyses of these effluents
provided by the E.P.A. are given in Tables 28 and 2.9,
Exact details of the experimental procedures were sometimes modified
for the different tests. Therefore, a more detailed description of
each experiment identified by number is included below.
Lake Tahoe studies included one in situ and one laboratory incubation
experiment.
Lake Tahoe NTA Culture (LTC-IV-70), 27-31 July 1970 -
Water was collected 27 July at a depth of 20 m from the index station.
Chemical analyses of water collected at the same location on 24 July
-1 -1
for total phosphorus (3.8 yg P-l ), nitrate-nitrogen (2.1 yg N-l ) ,
and inorganic carbon (916 mg C-l ) were performed. After spiking with
NTA and sewage effluent solutions, the samples were incubated in the
laboratory at Lake Tahoe. Included in this study were 0.01% - 1.0%
dilutions of the NTA stock solution and series #29500 - 29503 sewage
215
-------
TABLE 28, CHEMICAL ANALYSES OF SERIES 29500 - 29503 SEWAGE EFFLUENTS
SUBSTANCE #29500 #29501 #29502 #29503
TOTAL C (mg/D
TOTAL ORGANIC C (mg/D
TOTAL INORGANIC C (mg/D
AMMONIA - N (mg/D
NITRITE - N (mg/D
NITRATE - N (mg/D
KJELDAHL - N (mg/D
ORTHOPHOSPHATE - P (mg/D
pH
TOTAL ALKALINITY (mg/D
BICARBONATE ALKALINITY (mg/D
DISSOLVED FE (wg/i)
'21
2
19
<1
<0,1
23,1
3
7,56
7,3
59
59
260
24
3
21
<1
<0,1
23,1
0,3
7,20
7,3
64
64
160
22
2
20
<1
<0,1
24
0,3
0,84
7,0
82
82
<100
?
2
?
<1
<0,1
24,2
0,1
0,60
7,3
82
82
<100
-------
TABLE 29, CHEMICAL ANALYSES OF SERIES 39500 - 39503 SEWAGE EFFLUENTS
NJ
SUBSTANCE
#39500 #39501 #39502 #39503
SECONDARY EFFLUENT TERTIARY EFFLUENT SECONDARY EFFLUENT TERTIARY EFFLUENT
+ OTA + OTA
AMMONIA - N (ug/i)
NITRITE - N (ng/i)
NITRATE - N (mg/i)
TOTAL P («g/D
ORTHOPHOSPHATE - P (mg/D
pH
TOTAL ALKALINITY (mg/i)
BICARBONATE ALKALINITY (mg/i)
TOTAL FE (wg/i)
OTA Gog/D
60
5
42
12
12
7,1
64
64
600
0,1
60
5
40
0,357
0,189
7,4
54
54
80
0,1
60
4
44,1
12
12
7,3
75
75
360
0.1
120
8
42
0,357
0,231
7,3
75
75
80
0,1
-------
effluents.
Lake Tahoe NTA Culture (LTC-V-70). 6-13 August 1970 -
Water was collected at the index station at a depth of 20 m on 6 August.
The results of chemical analyses performed on water samples collected
at the same place on three dates before and after 6 August are listed
below:
3 Aug. 11 Aug. 15 Aug.
Total Phosphorus (iag P-l~ ) 4.5 4.0
Nitrate (jig N-l"1) 3.0 2.5
Total Iron (yg Fe-l~ ) 7.0 —-
Inorganic Carbon (mg C-l ) 10.16
Culture flasks were incubated in situ for a seven day period and re-
moved for daily filtrations of 50 ml aliquots. Dilutions of the NTA
stock solution and series #29500 - 29503 sewage effluents from 0.01%
to 10.0% were studied.
Castle Lake tests also included one in situ and one laboratory incuba-
tion experiment.
Castle Lake NTA Culture (CASL-1-70), 27 Sept.-3 Oct. 1970 -
Water from a depth of 3 m was collected at the deep station (35 m) on
27 Sept. The following water chemistry data was obtained:
Nitrate - N <1. pg-l~
Soluble PO.-P <0.5 yg-l"1
Total P - 3.1 yg-l"1
Total Fe 37. ug-l~
_i
Inorganic C 3.4 mg-1
Nineteen culture flasks were prepared containing 0.01%-1.0% dilutions
of the NTA stock solution and sewage effluents #29500 - 29503. Cultures
were incubated in situ at Castle Lake for seven days and removed for-
daily subsampling of 50 ml aliquots.
218
-------
Castle Lake NTA Culture (CASL-2-70), 29 Oct.-4 Nov. 1970 -
On 25 Oct. water at a depth of 5 m was collected from the deep station.
Chemical analyses were performed for the following elements:
Soluble PO.-P 0.5 yg-l"1
^ _1
Total Fe 16. yg'l
Nitrate-N <1. yg-l"1
Inorganic C 4.1 yg-l
Eight different solutions were prepared in triplicate. Additions of
the NTA stock solution at the 0.2%-7.0% levels and sewage effluents
#39500 and #39502 at the 0.2% level were made. These samples were in-
cubated in the Davis laboratory for seven days.
All three Clear Lake experiments were incubated at the laboratory at
Davis under controlled light and temperature conditions for seven-day
periods.
Clear Lake NTA Culture (CLC-1-70), 17-23 Sept. 1970 -
Water was collected 15 Sept. at the raft station using a sampler which
isolated a continuous column of the top 3 m of water. Water chemistry
analyses and measurements of physical parameters yielded the following
results:
Soluble PO.-P 390. yg-l"1
Total soluble P 404. yg-l
Total P 431. yg-l"1
Total Fe 2.40 mg'l"1
Inorganic C 25.3 mg-l~
Nitrate - N 15. yg-l
pH 8.75
Temperature 20.8°C
Secchi dapth 0.33 m
Depth of 1% light transmission 0.92 m
Eleven different solutions were prepared in duplicate. These included
219
-------
0.1%, 1.0%, 5.0%, and 10.0% dilutions of the stock NTA solution and 0.2%
dilutions of the #29500 - 29503 sewage effluents.
Clear Lake NTA Culture (CLC-2-70), 13-19 Oct. 1970 -
Water was collected 3 Oct. at Corinthian Bay and stored nine days before
use. No chemical analyses were performed. Culture flasks were incubated
for two days at--v22°C in a fume hood under fluorescent lighting. They
were then transferred to an incubator at 17°C under improved lighting
conditons for the remaining five days. Sewage effluents from the #39500
- 39503 series were used.
Clear Lake NTA Culture (CLC-3-70). 29 Oct.-4 Nov. 1970 -
Water was collected at a depth of 0.5 m from the raft station on 27 Oct.
Sample collection followed by one week the first rainfall of the season.
The autumn bloom of Aphanizomenon which had initiated approximately
one month earlier was still in evidence. A marked increase in nitrate
concentrations over that of CLC-1-70 was observed.
Soluble PO.-P 303' Vg-1
4 -1
Total P 316. yg-1
Total Fe 2.62 ug-1
Nitrate - N 300. yg-1
Temperature 16.3 C
Results and Discussion
Lake Tahoe Cultures -
The bioassays of Lake Tahoe phytoplankton showed that NTA and the sew-
14
age effluents containing it generally stimulated C uptake (Table 30).
In the first experiment (LTC-IV-70) all additions of secondary and
tertiary effluents both with and without NTA were stimulatory. At the
end of the four day study, the cultures with effluents containing NTA
-3 -4 14
at the 2 x -10 % and 2 x 10 % levels showed more assimilated C
220
-------
TABLE 30, EFFECTS OF MTA AND SEWAGE EFFLUENT ADDITIONS ON LAKE TAHOE WATER
% STIMULATION^) OR INHIBITION(-) VS. CONTROL
(LAST DAY OF EXPERIMENT)
SUBSTRATE ADDED
2 x art
2 x IQ'%
2 x 10"2%
2x10"%
2 x 10"%
2 x 10"2%
2 x art
2x10^%
2 x 10"%
9 Y irr^j
L A -LU /o
2 x 10'%
2 x aD'3*
2 x 10"2%
2 x art
0.011
o-,a%
1.0%
10.0%
TERTIARY
EFFLUENT
TERTIARY
EFFLUENT + iW\
SECONDARY
EFFLUENT
SECONDARY
EFFLUENT + NTA
NTA STOCK
SOLUTION
-
LTC-IV-70
+59
+9
+117
+100
+13
+99
—
+14
+20
+62
+34
+27
+54
—
-10
+37
+37
—
LTOV-70
+12
+17
+36
+35
+16
+21
+61
-9
-35
+4
+24
+48
+57
+85
+21
+25
+58
+48
221
-------
than did those containing the same concentration of effluents without
_2
NTA. At the highest concentration of 2 x 10 %, the reverse situation
was observed with this level producing definite inhibition. Additions
of the NTA stock solution were stimulatory at the 0.1% and 1.0% levels
while the 0.01% (0.344 g NTA-l""1) showed no significant change from
control values.
The second Lake Tahoe experiment (LTC-V-70) also included additions of
NTA and sewage effluents at the 2 x 10~ % level. Incubation for this
test was carried out in situ over a seven day period. Additions of
tertiary effluents with and without NTA were all stimulatory to carbon-14
-4 -!„
uptake in the concentration range tested (2 x 10 % to 2 x 10 %). All
secondary effluent additions with NTA were also stiirulatory; lack of
stimulation was exhibited only by the two most dilute solutions of
secondary effluent which did not contain NTA. Additions of the NTA stock
14
solution at 0.01%, 0.1%, 1.0%, and 10.0% levels also increased C
uptake with greatest photosynthetic enhancement shown at the 1.0% level
of addition (34.4 yg'l"1 NTA).
Castle Lake Cultures -
Of all our experiments, the in situ Castle Lake culture (CASL-1-70)
produced the most significant stimulatory effects with NTA addition
(Table 31). All tertiary effluent additions gave positive responses,
but those which contained NTA were the most stimulating. For the
samples with secondary effluents added, only the ones with NTA were
14
stimulatory. The cultures responded with increased C uptake only to
the addition of the stock NTA solution at the 0.01% level. In the
range tested, the higher concentrations were not found to be stimulatory.
The second Castle Lake experiment (CASL-2-70) was incubated in a labora-
tory at Davis. All of the eight different cultures spiked with NTA
or secondary sewage effluents (#39500 and 39502) responded with increased
222
-------
TABLE 31. EFFECTS OF NTA AND SEWAGE EFFLUENT ADDITIONS ON CASTLE LAKE WATER
% STIMULATION (+) OR INHIBITION (-) VS. CONTROL
(LAST DAY OF EXPERIMENT)
SUBSTRATE ADDED
CASL-1-70 CASL-2-70
2 x 10 7, SECONDARY
2xlO~3% EFFLUENT -2.5
2 x 10"27= -32
2 x 10'1/? — +175
2x10'^ SECONDARY +1430
2xlO~3% EFFLUENT + NTA ^
2 x 10"27o +920
2 x lO'1^ — +140
2x10'^% TERTIARY +550
2xlO-3% EFFLUENT +890
2 x 10~2% +1320
L. X _LU Q/Q _„„
2x10'^ TERTIARY +1050
2xlO'3% EFFLUENT + NTA +m
2 x 10"2% +1430
Z X _LU 7o —
0,0]% f'JTA STOCK +1240
n 17 SOLUTION 91
U.I/o Z_L
0,2% — +7
0,6% — +33
1,0% +11 +35
3,0% — +20
7.0% -- +43
223
-------
C uptake over the control after seven days of incubation (Table 31)
The secondary effluents with and without NTA were more effective at
14
enhancing C assimilation than NTA alone.
Clear Lake Cultures -
All three Clear Lake NTA culture experiments were performed under light
and temperature-controlled conditions at Davis. Effects from the addi-
tion of NTA and sewage effluents were less noticeable and more variable
in. nutrient-rich Clear Lake water compared to Lake Tahoe or Castle Lake.
Variations in the results from these three experiments may be explained
on the basis of significant changes in phytoplankton and chemical compo-
sition of Clear Lake water during the period tested. Further, the
filamentous bluegreen algae (Aphanizomenon) clumps and therefore provides
more sampling error than the more dilute Castle and Tahoe populations.
Greatest positive responses to NTA were observed for the first Clear
Lake test (CLC-1-7Q) (Table 32). Additions of the 5.00 mg Na-NTA-H O-l"1
14
stock solution at 0.1%, 1.0%, 5.0%, and 10.0% levels stimulated C
assimilation as did the two sewage effluents containing NTA. The high-
est stimulation was exhibited by the medium containing the NTA solution
at the 1.0% level. At the end of the seven-day incubation period, the
NTA-free sewage effluents (#29500 and 29502) both showed slight inhibi-
tion at the 0.2% level although definite stimulation had been observed
for the first six days.
14
Because of the possibility of non-photosynthetic adsorption of C in
experiments of this type (Goldman and Mason 1962), both the 0.45 y
Millipore^--filtered lake-water plus 1.0% NTA solution and the unfiltered
14
autoclaved lake water plus 1.0% NTA solution were checked for C uptake
during the seven-day period. Carbon-14 uptake by these adsorption
controls was found to be negligible.
224
-------
TABLE 32. EFFECTS OF NTA AND SEWAGE EFFLUENT ADDITIONS ON CLEAR LAKE WATER
% STIMULATION (+) OR INHIBITION (-) VS. CONTROL
(LAST DAY OF EXPERIMENT)
SUBSTRATE ADDED
CLC-1-70 CLC-2-7Q
0.2% SECONDARY -2 +18
EFFLUENT
0.2% SECONDARY +40 +14
EFFLUENT + NTA
0.2% TERTIARY -3 +1
EFFLUENT
0.2% TERTIARY +41 +6
EFFLUENT + NTA
0.1% NTA STXK +22
007 SOLUTION ,-77
, z/o — +33
1.0% +50
2.0% — +9
4.0% — +5
5.0% +21
10.0% +34 0
225
-------
At the completion of the second Clear Lake test (CLC-2-70) all samples
showed stimulation of C uptake over the controls (Table 32). Highest
positive responses were found for the NTA stock solution at the 0.2%
level (+33%), 0.2% secondary effluent (+18%), and 0.2% secondary effluent
plus NTA (+14%). The culture flasks containing additions of the NTA
stock solution showed initial inhibition at the 4.0% and 10.0% levels.
After what appeared to be acclimatization periods of five and seven days,
respectively, the organisms in these cultures were able to assimilate
14
C as well as the controls. . In contrast, the more dilute NTA solutions
14
showed immediate accelerated rates to C assimilation.
The third Clear Lake test (CLC-3-70) was unique in that neither inhibition
nor stimulation could be attributed to the added NTA or sewage effluents.
No really definite trends were observed when compared to the control;
the variations observed were within the limits of experimental error.
The absence of a measurable effect suggests that an entirely adequate
supply of nutrients was present in the natural lake water. Except for
a twenty-fold increase in the nitrate-nitrogen concentration, all chem-
ical parameters measured were very similar to those for CLC-1-70.
This definitely suggests the involvement of nitrogen in the earlier
stimulation recorded and follows the upward shift in the nitrogen-to-
phosphorus ratio which preceded this experiment.
Conclusions
The experimental results reported here demonstrate the stimulatory
effect of effluents containing NTA on the photosynthetic activity of
natural phytoplankton populations. This is not surprising when one con-
siders that the three lakes assayed all tend to be nitrogen deficient,
at least during the period when these experiments were conducted.
Further, Lake Tahoe is a known iron deficient lake (Goldman 1964) which
may be affected by chelation. Chelation by NTA, which may suppress
226
-------
inhibitory levels of copper in Clear Lake, may be partly responsible for
the high stimulation by NTA in Clear Lake phytoplankton.
227
-------
SECTION VIII
MICROBIAL HETEROTROPHIC GROWTH IN LAKE TAHOE
THE REGULATION OF HETEROTROPHIC ACTIVITY BY ENVIRONMENTAL FACTORS AT
LAKE TAHOE (This section is based on a Ph.D. dissertation by Hans W.
Paerl).
Introduction and General Description
Studies of algal primary productivity on a spatial and temporal basis
indicate that Tahoe's extremely oligotrophic state is in delicate bal-
ance. The noted response to even minute additions of nutrient origi-
nating mainly from sewage influx and land disturbance has confirmed that
affected areas of Tahoe are assuming a more common trophic state, that
of normal oligotrophy or even mesotrophy. In these areas of the lake
proper, as well as man-made impoundments, noticeable changes in the rates
of primary productivity, or fixation of inorganic carbon, are currently
being detected (Goldman, Moshiri, and Amezaga 1972). With regard to the
microbial community as a whole, however, this is only part of the pic-
ture of community change. The biological, chemical, and physical param-
eters regulating, or limiting, the bacterial incorporation ^.nd breakdown
of organic carbon (heterotrophy) are also changing in certain areas .of
the lake. It was the objective of this study to differentiate between
predictable temporal fluctuations in heterotrophic activity in unaffected
sections of Lake Tahoe and fluctuations regulated to some extent by
228
-------
nutritive input attributable to man's activity in the watershed. Fur-
thermore, assessment of particular modes of bacterial stimulation were
considered as they relate to the sources of stimulation in the Tahoe
watersheds. Silts, composed of inorganic materials such as mica and
feldspar and particles of detritus (non-living organic particulate mat-
ter), are currently entering Lake Tahoe at accelerated rates. Distur-
bances associated with land development are largely responsible for this
accelerated nutrient input. At South Lake Tahoe where 40% of Tahoe's
surface runoff enters by way of Trout Creek and the Upper Truckee River,
silt discharge is substantial. Approximately 30,000 tons of sediment
was deposited by this river system in 1969 (State of California Resources
Agency 1969). A combination of bioassay methods in the laboratory with
in situ sampling in the Upper Truckee influx area of Lake Tahoe was used
to link siltation originating from this watershed with increased microb-
ial growth in the influx area. Methods of in situ sampling as well as
bioassays were developed to aid in the detection of stimulatory sources
and their influence on the waters of Lake Tahoe. The methods presented
here in published form (see literature cited) have potential application
to the full range of aquatic ecosystems from oligotrophic to eutrophic.
The stimulatory effects of several parameters (temperature, nutrients,
bacterial biomass) on heterotrophic activity in Lake Tahoe were measured
from 1970 through 1971 on an uninterrupted basis. Results from these
studies are summarized in a Ph.D. thesis (Paerl 1973a) and several pub-
lications which have resulted from the study. Abstracts of these pub-
lications are attached to this report (Paerl and Goldman 1972a, b;
Paerl 1973a; Holm-Hansen and Paerl 1972; Goldman et al. 1973, 1974),
Methods
All methods used in this research are included in the above publications
cited.
229
-------
Results and Discussion
Judging from heterotrophic responses to terrigenous as well as utogenic
(primary production) input it is quite clear that organic carbon is the
factor most limiting to heterotrophic growth. Because of the hetero-
geneity and imbalance of nutrients brought about by different kinds of
nutritive inflow, however, organic carbon is not limiting in all sec-
tors of the lake. For instance, inorganic phosphorus additions to mid-
lake water consistently increase rates of heterotrophic growth. This
indicates that in midlake and in deep waters there appears to be a
chronic shortage of phosphate which is limiting to a community deriving
its main energy source from organic substrates. A review of the nu-
trient concentrations (both organic and inorganic) indicates that it is
not unusual for inorganics to limit a heterotrophic community (Paerl
1973a).
Under nutrient conditions that prevail in most of Lake Tahoe, tempera-
ture parallels heterotrophic activity (Fig. 50). This is probably not
surprising since metabolic activity and growth have long been known to
be closely related to temperature changes. Respiration is also affected
by temperature changes (Zobell 1946). Zobell proposes that under the
influence of increased water temperatures, the amount of carbon fixed
by heterotrophic uptake may well be excreted as C09 through respiration.
In that case, no net increase in biomass would be noted. Zobell's hy-
pothesis could not be substantiated by the present studies. In fact,
some opposite results were obtained. Studies using ATP determinations
of bacterial biomass reveal that biomass increases virtually simultan-
eously with temperature increases while nutrient levels (inorganic as
well as organic) remain fairly constant. This suggests that some bac-
terial species in Lake Tahoe find increased temperatures advantageous in
terms of increasing their total biomass during the summer months. This
is mainly accomplished through changes in (1) bacterial diversity and
230
-------
18
16
14
12
•10
£.4
o
00
E
I .3
= •2
B
Prlm«ry
Productivity
Haterotrophic
Activity
-a—i—«—]—]—r
TiMt-Moiths
10
6 I
T>
Figure 50. Seasonal temperature (A), and primary productivity and
heterotrophic activity (B) at the Upper Truckee River
station from March to November 1971. All samples were
taken at 1.5 m depth.
231
-------
numbers, noticed in both direct and plate observations, and (2) changes
in cell size, observed T/ith the scanning electron microscope. Further-
more, under similar nutrient concentrations, bioassay experiments re-
peatedly gave higher rates of heterotrophy and accumulation of biomass
in cultures incubated at elevated temperatures. These cultures also
show rapid changes in bacterial morphology and diversity in response to
temperature change. Thus, the relationships between nutrient limitation
and heterotrophic response in terms of growth are very complex as water
temperatures change, presumably due to changes in cell size or growth
and diversity of species of bacteria.
Synoptic results of heterotrophic uptake assays are valuable in disting-
uishing seasonal patterns in heterotrophy regulated mostly by tempera-
ture from increased growth rates caused by nutritive input from the
watersheds. Since temperatures at the synoptic stations (Paerl 1973a)
were virtually the same during any one synoptic, the effect of variable
nutrient concentrations (involving a complex nutrient regime) could be
monitored. The synoptic data (Fig. 51) emphasize the impressive ferti-
lizing effect of the Upper Truckee River (Paerl and Goldman 1972a,
Paerl 1973a).
Heterotrophic Growth in Response to Siltation -
In areas receiving terrigenous input of particulate and dissolved nu-
trients, consistently higher rates of heterotrophy were noted as well
as increased bacterial biomass, when compared to mid-lake areas. The
stimulatory role of organic carbon and phosphorus as elucidated through
bioassay experiments (Paerl and Goldman 1972b) has been discussed
(Paerl 1973a) (Fig. 52). There is another factor stimulating bacterial
growth. This is the total surface area present on all organic and in-
organic particulate matter.
Earlier experiments have shown surfaces of sampling bottles to be highly
232
-------
assimilated
Visible outline of water mass from
aerial photographs
Figure 51. Heterotrophic activity (yg acetate-m~^-hr"^- assimilated) in the Upper Truckee
River transect area on 30 July 1971. Sampling stations are indicated by a small
cross. Acetate concentrations were 0.05 yg acetate*! . Note the visible outline
of the Upper Truckee River water mass as it enters the lake.
-------
225
x
J 150
w
I
75
UJ
. SILT-OC-N-P
SILT —OC —P
SILT-OC-N
LAKE WATER—OC — N — P
SILT —NO ADDITIONS
.-LAKE WATER-NO ADDITIONS
12
24 36
IxibatioN Tine-Hours
48
60
Figure 52. Heterotrophic bioassay of additions of nutrient-stripped silt in combination with
organic carbon (100 ug/1 as-glucose), nitrate (10 yg/1), and phosphorus(12 yg/1)
to Lake Tahoe water. Notice stimulatory effects of surface area in silt bioassays
having similar nutrient concentrations as lake water without silt.
-------
stimulatory to bacterial growth (Javornicky and Provesova 1963). Rodina
has also discussed the role of particulate material in the formation of
detritus, which he describes as a complex conglomeration of non-living
organic matter interlaced and covered with decomposers, mainly bacteria
and fungi (Rodina 1963). Because his study is based on light microscopy
observations, difficulties arose in distinguishing bacteria from detrital
matter. Paerl's own light microscopic observations (phase with oil im-
mersion) indicate the task of separating non-living from living particu-
late matter is extremely difficult and at times impossible for the
following reasons: (1) Staining techniques using erythrosin, methylene
blue, and acridine orange were not specific (i.e., stains did not selec-
tively stain living material). He observed mineral and organic parti-
cles, clearly non-living, that had incorporated or absorbed each of these
stains. (2) Shapes of suspended solids in the Upper Truckee inflow area
were very similar to bacterial shapes, and visual enumeration proved
fruitless. Scanning electron microscopy (SEM) revealed that morphologi-
cal distinction between detrital material and bacterial cells is subtle.
SEM observations indicate that the extent of association of bacterial
cells smaller than 1 ym with detritus is very difficult to quantify
using light microscopy. Both SEM and freeze-etch electron microscopy
observations of Lake Tahoe detritus show that associations of bacteria
with detrital material commonly occur, and have a significant influence
on estimates of total biomass (Paerl and Leonard unpublished). In con-
trast, others (Weibe, Johannes) with whom Paerl has discussed this prob-
lem have seen little association of bacterial cells with detrital mat-
ter vin the Atlantic Ocean. These workers used light microscopy obser-
vation in reaching their conclusions.
Autoradiography proved to be very helpful in giving direct evidence that
bacteria were associated with detritus in Lake Tahoe (for autoradiogra-
phic methods see Paerl and Goldman 1972a). Samples incubated with
14
2 - C-acetate for periods up to four hours showed localization of
235
-------
radioactivity around detrital particles. Metabolic inhibition of the
same water samples with 2, 4-dinitrophenol and subsequent incubation
with the C substrate reduced radioactivity by 80%. Such experiments
left little doubt that live organisms, which are too small to detect or
discriminate with light microscopy, were actively metabolizing organic
carbon on detrital particles. When acid-hydrolyzed (nutrient-stripped)
silts were added to mid-lake water samples, it was shown that bacterial
activity and biomass were notably increased (Paerl 1973a). By providing
a site for attachment or adherance even without nutritional value, silts
are able to stimulate bacterial growth in Lake Tahoe.
Autoradiographs performed on these "inert" silt additions showed again
that bacteria rapidly colonized such particles and soluble organic mate-
rials (in this case C-acetate) accumulated on particles. The role of
particulate material in stimulating bacterial growth in Lake Tahoe ap-
pears to be two-fold. A direct source of nutrition and attachment is
provided'by detritus and inorganic silts, since it has been shown that
particulate material originating from inflow sources contains apprecia-
ble amounts of carbon, nitrogen, and phosphorus. Secondly it appears
advantageous for bacteria to be attached to suspended material regardless
of its nutritive nature, because organics and inorganics adsorb to this
material.
The importance of this finding may be better amplified if Tahoe's oligo-
trophic nature is considered. In a low nutrient environment the growth
of organisms capable of extracting and utilizing dissolved nutrients in
trace concentrations is favored. One adaption has been found using SEM.
Electron micrographs show that bacterial cell size in Lake Tahoe is
very small compared to a more eutrophic lake such as Castle Lake, Cali-
fornia. Thus the increased surface-to-volume ratios of small organisms
is favored. In addition, a high incidence of bacterial attachment on _
suspended solids is evident (Paerl 1973b). In view of the capacity of
236
-------
this material to support bacteria utilizing dissolved substrates in trace
concentrations, they form a kind of "dinner plate" for bacteria capable
of adhering to particles. Much of the detritus of Tahoe is composed of
decaying remnants of algae as well as zooplankton and, of course, the
products of terrestrial erosion.
Results in Relation to Current Environmental Problems in the Tahoe Basin -
Regardless of various intricate and still poorly understood mechanisms
of nutrient release in Lake Tahoe, it should be stressed that bacteria
are greatly involved. They are essential cyclers of organic substrates,
nitrogen and phosphorus, acting upon these substrates and converting
them to biomass. Bacteria in turn eventually release nutrients through
death and autolysis. This is attributed to several limiting factors
halting growth as well as through zooplankton and protozoan utilization
of bacterial biomass (Sorokin 1966). An extremely important function
of bacteria in aquatic ecosystems as shown here is to reintroduce or-
ganic and inorganic materials into living matter, thereby keeping them
from rapidly piling up in the sediments largely unacted upon. Through
their characteristics of high surface-to-volume ratios, capability for
attachment, ability to take up a wide range of organic material, and
rapid reproductive rates, aquatic bacteria are quick to take advantage
of utilizable nutrients and either pass them on to higher levels of the
food chain or release inorganic nutrients through death. These re-
leased inorganic nutrients have been shown to be the factors limiting
algal growth in Lake Tahoe (Goldman and Armstrong 1969). It is there-
fore safe to assume that increases in algal and bacterial production go
hand-in-hand with the process of eutrophication. The excellent spatial
relationship of primary productivity and heterotrophic activity certain-
>
ly substantiates this. Pockets of Lake Tahoe currently being affected by
either high dissolved and/or particulate-nutritive input, as exemplified
by the Upper Truckee River inflow area, demonstrate this relationship.
There exists, however, a distinct advantage in using bacterial activity
237
-------
as an indicator of sources of eutrophication in the Tahoe watershed.
The means of bacterial stimulation, either due to sources of organic
nutrition or sources of surface areas for bacterial attachment, can be
directly related to particular sites of man's activity in the Tahoe
basin. Algal stimulation appears to be more generally related to soluble
levels. Soluble nutrient concentrations are more difficult to relate to
current routes of nutritive input, because mineralization and chemical
nutrient releasing processes have in some cases preceded the uptake of
these nutrients by algae.
An example of current eutrophication trends at Lake Tahoe should illus-
trate the distinct advantage in using heterotrophic activity as an in-
dicator. Approximately ten years ago, the input of nutrients from both
septic tanks and sewage treatment plants was conclusively shown to in-
crease the primary productivity of the lake (Goldman and Carter 1965) .
Algal growth response to this input of soluble nutrition proved to be
an excellent indicator. This data was instrumental in initiating sewer-
ing all of the Tahoe watershed and exporting treated sewage to another
watershed. Today, Tahoe is facing a distinctly different, and perhaps
less reversible, route of nutritive input. Land disturbance and result-
ant siltation of streams leading into Lake Tahoe has become a prime
threat to the lake's clarity. Silt plumes are evident year around in
the Upper Truckee-Trout Creek inflow area (approximately 40% of Lake
Tahoe's inflow source). During periods of heavy rainfall and snowmelt,
other tributaries downstream from areas of development in the Tahoe
basin also have silt plumes of varying intensity. Since silt addition
to Lake Tahoe water consistently stimulates bacterial growth rates by
offering both surface area for attachment as well as nutrition, a direct
relationship linking land disturbance to aquatic bacterial growth rates
can be measured. Interpretation of algal responses to siltation are
complicated by the fluctating transparency of water containing suspended
solids. Changes in transparency affect photosynthesis rates and thus
238
-------
primary productivity measurements in silty areas reflect integrated
effects of nutritional status and transparency of the water samples.
There appears to be a better relationship of bacterial activity to sedi-
ment content of Lake Tahoe water. The effects of siltation can be
measured at great distances from the immediate inflow area with the sen-
14
sitive C-acetate method. SEM observations on water samples taken from
areas affected by siltation are helpful, since particular types of sedi-
ment (of both organic and inorganic nature) can be directly linked to
sites of land disturbance through identification of either soil types
or organic matter originating from stream mouths. Differential bacter-
ial growth on sediments has been noted in samples obtained from the
Upper Truckee inflow area. This means that some sites of land distur-
bance (in morphologically identifiable soil or vegetation areas) play
a higher stimulation role to bacterial growth than others. In this
manner, disturbance areas of the Tahoe watershed, to which increased
bacterial growth in the lake is highly susceptible, can be "finger-
printed" morphologically. Such information-should prove valuable to
planning and environmental control agencies attempting to define and
control sites of land disturbance and erosion threatening the water
quality of Lake Tahoe.
239
-------
SECTION IX
PRIMARY PRODUCTION OF PERIPHYTON AND PLANKTONIC ALGAE IN THE LITTORAL
ZONE OF LAKE TAHOE
Introduction
Lake Tahoe has very little littoral zone for its size and only about 10%
of the lake's primary productivity is accounted for in the littoral zone.
The narrow band of shallow water has, however, great importance to the
lake's biota and provides the main visual evidence of water quality to
the largely shorebound populace. In the last decade there has been an
alarming increase in the growth of attached algae. Diatoms and green
algae flourish in the shallow waters of Lake Tahoe. Accumulation rates
of these algae were measured at offshore stations anchored to the bottom
with submerged floats holding a rack well above the bottom. Pyrex^
glass cylinders, attached to the rack and exposed to periphyton invasion,
were collected periodically and combusted in an induction furnace. Algal
biomass was measured in terms of organic carbon. In general, the peri-
phyton distribution in Lake Tahoe was found to be surprisingly uniform.
In all probability this results from the circulation of nutrient-rich
tributary water around the margins. Attached forms have the advantage
of more water contact than planktonic forms, since the water passes over
them rather than carries them along. Jnsightly masses of periphyton,
algae break loose and surface in the spring. Their decay may be instru-
mental in triggering blooms of planktonic algae. The phytoplankton
240
-------
TABLE 33, LAKE TAHOE PERIPHYTON SPECIES LIST, INCLUDING
CELL VOLUMES
PERIPHYTON SPECIES LIST COMPILED FROM MICROSCOPIC EXAMINATION OF LIVE AND PRESERVED
SAMPLES ON GLASS CYLINDERS AND ROCKS, WHERE CELL VOLUMES HAVE BEEN MEASURED THEY
ARE GIVEN IN (w3).
CHLOROPHYCEAE
SPHAEROCYSTIS SCHROETERI (268)
GEMINELLA ORDINATA
ULQTHRIX SP.
BULBOCHAETE SP,
PEDIASTRUM SCULPTATUM
TETRAS VAR. TETRADON
MOLJGEOTIA GENUFLEXA
ZYGNEHA (STERILE)
COSMARILJM SP. A
SP, B
EUASTRLJM B1DENTATUM
PLEUROTAENIUM SP.
STAURASTRUM NATATOR (4350)
EUGLENACEAE
EjJSLENASP.
DlNOPHYCEAE
PERIDINIUM PUSILLUM
CHRYSOPHYCEAE
DlNOBRYON SERTULARIA (900)
BACILLARIOPHYCEAE
CYCLOTELLA ANTIGUA (635)
EQDAMICA (4778)
MELOSIRA CRENULATA (1209)
VARIANS (1301)
STEPHANODISCUS ASTREA (707)
DlATOMELLA BALFOURIANA (660)
TABELLARIA FLOCCULOSA (2700)
DlATOMA ANCEPS (1000)
HIEMALE (MESODON) (1060)
VULGARE (3600)
OPEPHQRA AMERICANA
ASTERIONELLA FORMOSA. (480)
FRAGILARIA CAPUCINA (140)
CROTONENSIS (510)
INTERMEDIA (2500)
PINNATA (175)
CAPITELLATA (276)
SYMEDRA ACTINASTROIDES
ULM (19200)
ULNA SPATHULIFFRA
EUNOTIA TENELLA (590)
ACHNANTHES ClEYEl (350)
FLEXELLA (880)
(420)
BACILLARIOPHYCEAE (CONTO.)
ACHNANTHES MICROCEPHALA
PERAGALLI (430)
COCCONEIS PLACENTULA (503) -
AMPHIPLEURA PELLUCIDA (4080)
DlPLONElS ELL1PTICA 0781)
OCULATA (330)
FRUSTULIA RHOMBOIDES (7600)
MASTOGLOIA SMITHII (5184)
NAVICULA AURORA (14016)
EAcilUfi (2000)
COCCONEIFORMIS (980)
PUPULA (1000)
RADIOSA (1100)
NEIDIUM HITCHEXKIL (14800)
PlNNULARIA BICEPS (4980)
RUPESTRIS (18000)
GOMPHONEIS HERCULEANA (6831)
GOMPHONEMA ACUMINATUM (610)
PARVULUM 050)
AMPHORA OVALIS (2500)
CYMBELLA CUSPIDATA (10000)
PROSTRATA (15750)
S1NUATA (375)
VENTR1COSA (1800)
•EPITHEMIA ARGUS
SOREX (5125)
TURGIDA (66000)
ZEBBA (11520)
RHOPALODIA GIBM (8000)
DENTICULA (ELEGANS)
NlTZSCHIA LINEAR1S
(SIGMA?)
CYMATOPLEURA SOLEA (VAR?) (37370)
SJBISELLA (DIDYMA) (13000)
CYANOPHYCEAE
OSCILLATORIA TENUIS
ANABAENA (VARIABILIS?)
NOSTQC M1CROSCQPICLM
C&LDJ1EIX
LYUSBYA.
NEPHROCYTIUM AGARDHIANUM
TOLYPOTHRIX SP.
CRYPTOPHYCEAE
CRYPTQMONAS.
241
-------
population is very diverse with over 160 species. Eighty-six species
of periphyton have also been identified in the lake (Table 33). As ex-
pected, some of the periphyton also occur in the phytoplankton.
The substrata in the littoral zone varies from fine sand to boulders.
The surface water temperature ranges from 4.6°C in the winter to 19°C
in the summer. Levels of nitrate, total phosphorus, and iron are very
low all year round (less than 10 yg'l ). In contrast, levels of sili-
con, so important for maintaining diatom populations, are of the order
of 3 to 7 mg-l"1 SiCL-Si (see Section V).
There are only a few isolated beds of macrophytes (Anachous canadensis,
Myriophyllum sp., Potomogeton crispus) in the littoral zone of the lake
with an abundance of chara, the fungus Apostemidium gueriiisal, and
aquatic moss (Fissidens), together with luxuriant growths of filamentous
periphyton extending to depths of about 100 m (Frantz and Cordone 1967).
No attempt has yet been made to estimate the abundance or productivity
of these littoral zone plants. A large population of the crayfish
Pacifastacus leniusculus inhabit the littoral zone and may be effective
in grazing the periphyton crop (Goldman and Amezaga 1974).
Methods
In 1968, 79 periphyton sampling stations were located around the lake
(Goldman, Moshiri, and Amezaga 1972). In 1971 periphyton was studied
at 17 stations. Each offshore station consisted of a wooden rack an-
chored to the bottom of the lake in 10 m of water (Fig. 53). The rack
was held in place 5 m above the bottom by submerged floats. The
station location was determined by triangulation on terrestrial land-
. D
marks. Pyrcx1- glass tubing cylinders (40 mm length and 24 mm O.D.),
used as substrates for periphyton growth, were held by test tube holders
attached to the rack. Installation and retrieval of the cylinders was
242
-------
.£-
U>
Figure 53. Schematic diagram of a periphyton station, Submerged floats hold the station in
place 5 m above the bottom in 10 m of water.
-------
done by SCUBA. Four samples were collected for each growth period.
Three samples for total carbon measurement were placed in polyethylene
vials and kept frozen until analysis. The fourth sample was placed in
a glass vial filled with distilled water and fixed with Lugol's solution
for periphyton species identification and enumeration.
A rapid method for the estimation of the carbon content in periphyton
(Armstrong, Goldman, and Fujita 1971) was used to determine the amount
of organic carbon that accumulated on the cylinder during the growth
period. The method consists of combusting the sample in an induction
furnace and measuring the evolved carbon as CO with an infrared gas
analyzer.
Preparation of the sample for periphyton identification and enumeration
was initially accomplished by scraping the periphyton off the cylinder
into its glass vial container. Later in the study, removal of periphyton
from the cylinder was greatly facilitated by placing the glass vial con-
taining the cylinder in an ultrasonic cleaner for five minutes. The
sample was then shaken well to insure uniform distribution of the cells,
a subsample was settled in an Utermohl chamber, and identification was
done using a Wild M-40 inverted phase microscope.
Preliminary periphyton species identification was done from live samples,
using glass cylinders that had been exposed at locations around the lake
for 14 weeks between 24 June and 30 September 1970. The influence of
the substrate on species composition was investigated by comparing glass
cylinders and natural rock communities at several locations. Communities
from both fresh and preserved samples on glass cylinders were compared
at several locations to determine the effect of preservation.
Samples from some of the major tributaries to the lake were also examined
for species composition.
244
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Results
Periphyton Taxonomy -
Observations made on the cylinders incubated for 14 weeks during the
summer of 1970 are shown in Figure 54. One Chlorophycean species
(Mougeotia genuflexa) and six diatoms were found to be the dominant
species. Mougeotia genuflexa occurred at all stations. Cylinders off
the south-southwest shore of the lake were invaded by a relatively few
dominant species (three or four) in comparison to the other stations
(six dominant species), but their growth coverage was dense or very
dense. Emerald Bay, which is partially isolated from the rest of the
lake, had seven dominants. Fragilaria capucina was a dominant form
only off the Upper Truckee River mouth and in Emerald Bay.
Results shown in Figure 55 are based on observations made on four to
eight different samples at each station. These samples had been left in
the lake for lengths of time varying from 2 to 23 weeks (overwinter) be-
tween 1 October 1970 and 2 May 1971. A rating system was devised to
determine which species were dominant overall during the season at each
sampled location. At each of the stations, for each sample available,,
the dominant species (dominant in number of cells present) were given a
number of points in decreasing order of dominance (10 for the most dom-
inant, 9 for the next dominant, 8 for the next, etc.). The total num-
ber of points for each species was computed, and the species that were
most dominant during the season determined. The dominant species were
those species that received a total number of points 25% or greater of
the maximum total possible.
In winter, the number of dominant periphyton species remained substan-
tially unchanged from those in the summer, yet the species composition
changed almost completely (Fig. 55). The lake periphyton, in this
winter-spring period, was dominated by seven diatom species. Synedra
245
-------
SUMMER
1970
DENSE
LIGHT
ho
DENSE
MODERATE
[i Mougeotio genuflexa
$f^ Epithemio argus
Rhopolodia gibba
If^H Synedra ulna
jiE-E^ Cymbella verrtricosa
j Navicula aurora
Frogilario capuctna
LIGHT
DENSE
VERY DENSE
DENSE
DENSE
Figure 54. Dominant species of periphyton found on glass cylinders exposed in situ to peri-
phyton invasion for 14 weeks between 24 June and 30 September 1970. The percent
of the circle drawn represents the percentage of the slide that was covered by
periphyton (50, 90, 95, or 100%). The relative density of growth is also indicated,
-------
WINTER
1970-71
Synedru ociinastroides
Fragilaria crotonensis
Gomphonema parvulum
Cyclotella bodonica
Synedra ulna
Gomphoneis herculeana
Melosira crenulata
Figure 55. Dominant species of periphyton found on glass cylinders
exposed in situ to periphyton invasion for 2-23 weeks (over
winter) between 1 October 1970 and 2 May 1971.
247
-------
actinastroides was the most dominant at all stations. Fragilaria cro-
tonensis was the second most dominant species, which was also found
at all stations. The same pattern of low diversity (three or four
species) that was observed in the summer persisted in the winter along
the south-southwest shore. This zone is strongly influenced by the
Upper Truckee River (Paerl and Goldman 1972a).
Observations of natural communities growing on rocks and piers near the
offshore locations during our study of the shallower portion of the
littoral zone showed, in addition, a dominance of Ulothfix in many of the
areas around the lake and Gbmphonema in some of them. UldthriK is
present in a number of tributaries.
Our preliminary comparison of communities growing on glass cylinders and
communities growing on natural rocks seemed to evidence better blue-
green growth (Calothrix, Tolypothrix, Nostoc) on rocks and better green
growth (Mougeotia, Zygnema, Spirogyra) on glass, while diatoms grew well
on either substrate. Later study indicated that glass was readily col-
onized by a large variety of algae. It was felt that rather than the
substrate difference, differences in depth, current, and light were
primarily responsible for the observed difference in colonization. Fresh
samples were essential for accurate identification to the species level
and Lugol's solution was found adequate as a preservative for subsequent
enumeration.
Periphyton Production -
Periphyton growth around the margins of the lake was measured at the sub-
merged stations described in Methods. Since each was located offshore
at a depth of 10 m, the distance from the shore was quite variable. The
highest growth rates were recorded near stream mouths where human activ-
ity is greatest, except in the vicinity of the largest tributary, the
Upper Truckee River (Fig. 56)- The shallow shelf there necessitated
248
-------
1971
i i i i r i
01 2345 mg C-m"2-day"'
Figure 56. Periphyton rate of growth per day between 1 May and 15 July
1971 as measured by organic carbon increase over a 14-day
period. The increment of the circle radius indicates the
average growth per day for the 14-day period. The center of
the circle indicates station location.
249
-------
placement of periphyton stations 700 to 1200 m from the stream mouth to
avoid loss of stations. This remote placement was not necessary off
Ward Creek which, together with the Incline Creek location (partially
contained by Crystal Bay), showed the highest increments of growth. In
general, slower growth occurred in areas of least tributary influence
such as along the sparsely populated east shore.
Rate of growth of periphyton in 1968 varied from 0.094 mg OnT
north of Skunk Harbor between 20 July and 18 August to 2.228
mg C.m~^'day~l, 70 yards offshore north of Sand Harbor between 15 and 23
July. Periphyton growth was found to be a function of both the location
and the time of incubation period (Fig. 57). After completing a matrix
of 17 stations and five incubation periods in 1968, results were aver-
aged to give one average value of rate between 28 March and 18 September
-2 -1
1968 (Fig. 57). These results vary between 0:343 rag C-m -day north-
-2 -1
east of the Upper Truckee River to l.OlOmg C-m -day south of Tahoe
City.
The average daily amount of periphyton growth on the bottom of the entire
lake in 1968 was estimated by using the results from growth per day at
each station as measured in organic carbon per square meter. Each station
was chosen to be representative of a section of the littoral zone de-
limited by the shoreline, the depth of 100 m, and the distances halfway
to the next stations . The periphyton production for that section was
obtained by multiplying the surface area (determined by planimetry) by
the amount of production at the corresponding station. The sum of the
production of these sections gave the estimate of the total production
of periphyton per day for the lake. The carbon content of algae was est-
imated to be 13% of the total fresh weight of the algae. On that basis,
the average total fresh weight of periphyton added daily to the bottom
of the lake (by photosynthesis on the bottom surface only) was found to
be about 576.8 kg. This was an under -estimate of the average daily
250
-------
TAHOE PERIPHYTON 1968
O 28 March - I May
I May - 13 M.»
Roriods of incubation
18 July - 29 July
18 July —7 Aug.
(§20 July - 18 Aug.
16 Aug.— I Sept
28 Aug.— 13 Stpl
SCALE i . " .5mg nr'-day'1
Periods of incubation
, IBJune—17 July
18June—10 July
4 July— 18 July
10 July— 18 July
15 July— 23 July
ESTIMATED
AVERAGE PERIPHYTON
PRIMARY PRODUCTIVITY
PER DAY BASED ON DATA
COLLECTED BETWEEN
28 MARCH 81 18 SEPT.
Figure 57. Periphyton rate of growth per day between 28 March and 18
September 1968 as measured by organic carbon increase over
various time periods. The circle radius indicates the
average growth per day for the time of incubation. The
center of the circle indicates station location.
251
-------
bottom growth of periphyton, since no correction was made to account for
the irregularity of rock surfaces. Fox, Odlaug, and Olson (1969) found
in western Lake Superior that, "after forty-six days of regrowth on art-
ificially denuded rocks in Stony Point Bay, the growth level was approx-
imately eighteen percent of that occurring naturally." Assuming this
result valid for Lake Tahoe would have meant that there are about
147,397 kg (fresh weight) of periphyton in Lake Tahoe (about 147 metric
tons). For purposes of comparison, the biomass of planktonic algae was
calculated by averaging biomass per square meter for the three synoptic
dates, which resulted in an estimate of 2,180 metric tons in the upper
euphotic zone of the lake (Goldman, Moshiri, and Amezaga 1972).
The total production of periphyton per day for the entire littoral zone
of Lake Tahoe was also estimated for 1971 (with a better seasonal cov-
erage) in the same way as for 1968. This calculation was done for each
of the dates in 1971 for which we had data available from periphyton
cylinders left in the lake for a period of 14 days. The results plotted
against time are shown in Figure 58. The growth rate increased steadily
from early April until mid-May, leveled out through mid-June, and then
declined through mid-July. This follows closely both the seasonal light
curve and the influx of nutrients from the watershed.
Phytoplankton Productivity -
Phytoplankton productivity for the entire littoral zone of Lake Tahoe
14
was based on in situ C measurements made regularly at 12 depths be-
tween 0 and 100 m at our index station near Tahoe Pines (see Fig. 1) .
The phytoplankton productivity of the littoral zone relative to this
index station was estimated from 13 synoptic measurements of primary
productivity. Three synoptic surveys were done in 1968 and have been
reported by Goldman, Moshiri, and Amezaga (1972); four were done in 1969,
five in 1970, and one in 1971. They consisted of sampling 32 stations
at several depths during a single night and incubating the samples
252
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N3
Ln
250-
200-
I
? 150-
O
o>
100-
50-
PERIPHYTON PRODUCTION
-3.0
-2.5
-2.0
-1.5
- 1.0
-as
5"
•p
CM'
'E
6
o>
E
MAR
APR MAY
JUN
JUL
1971
Figure 58. Periphyton production per day estimates for the littoral zone of Lake Tahoe. The
left scale indicates the total production for the lake. The right scale indicates
the average production per square meter for the lake obtained by dividing the
total production value by the total surface area of the littoral zone.
-------
in situ during the following light period. Eight of these station lo-
cations are pelagic, one is our regular index station, and the others
are littoral. The average primary productivity for all 13 synoptics
was calculated for all littoral stations to give one littoral value of
—2 c
mg C-m and for all pelagic stations to give one pelagic value of
f\
mg Onf . The phytoplankton productivity of this littoral zone relative
to the index station was calculated as a percentage of the average pro-
ductivity of all littoral stations to the index station. The phytoplank-
ton productivity in the pelagic zone relative to the index station was
also calculated as a percentage. These estimated percentages were used
to compute the average primary productivity of the phytoplankton on any
day in the 12 layers of water in which the littoral zone had been divided
corresponding to each depth of the index station. The sum of the phyto-
plankton productivity of the 12 layers of water was estimated to be the
total phytoplankton productivity in the littoral zone that day. Results
from these computations made for the period of time that corresponds to
our periphyton production study are shown in Figure 59. The bimodal
phytoplankton productivity curve peaked out in early June with the second
peak occurring in August. This was in contrast to the periphyton biomass
production curve' (Fig. 58), which showed a single high plateau lasting
for over two months between April and June.
Primary Production of the Littoral Zone vs. the Pelagic Zone -
To compare the total primary production per day of the littoral zone of
Lake Tahoe to that of the pelagic zone, the total biomass production
per day of the periphyton (Fig. 58) was added to the total phytoplankton
productivity in the littoral zone (Fig. 59). The biomass'increments of
periphyton growth and the rate measures of phytoplankton productivity are
not strictly comparable. Combining them, however, should provide a good
approximation of total littoral production. This was done by planimeter-
ing the areas of two week periods under each curve (Fig. 58 and Fig. 59),
computing the corresponding mean value of carbon per day for each
254
-------
K3
On
Ui
12,000 -
10,000 -
T^ 8000 -
o
•O
6
o. 6000 -
4000 -
2000-
PHYTOPLANKTON PRODUCTIVITY
LITTORAL ZONE
MAR APR MAY JUN JUL AUG
1971
140
120
100
80
60
40
-20
o
•p
M'
i
E
6
o>
Figure 59. Phytoplankton productivity per day estimates for the littoral zone of Lake Tahoe,
-------
community, and adding up these values. The primary productivity per day
of the pelagic zone of the lake was computed by correcting the mean pro-
ductivity per cubic meter at the index station by the percentage that
the pelagic zone productivity represents and multiplying by the volume
of water in the euphotic zone (0 to 100 m) of the pelagic zone. Re-
sults are shown in Fig. 60- We shall use the term primary production
whenever we are referring to either biomass increments only or both
biomass increments and C measurements combined. We shall continue
14
to use the term primary productivity when referring to C measurements
only.
By comparing the primary production curve of the littoral zone of Lake
Tahoe with the pelagic productivity curve, we get a graphic impression
of the relatively small littoral area involved as well as its contri-
bution to the overall productivity of the lake. Only about 10% of the
lake's production is accounted for by the combined phytoplankton pro-
ductivity and periphyton production down to 100 m. Because of Lake
Tahoe's morphometry, the pelagic zone contributes an order of magnitude
more carbon to the lake in productivity than does the littoral zone.
Transect Measurements of Primary Productivity -
Primary productivity in the littoral zone was measured in 1968 with a
series of transects. Computer contouring was utilized to display vari-
ation in productivity offshore (Goldman and Armstrong 1969) . An
average of four transects were used to construct each of the vertical
profiles of phytoplankton productivity shown in Fig. 61• The Upper
Truckee River, which provides 40% of Lake Tahoe*s surface inflow, has
a highly productive phytoplankton population per unit volume near shore
decreasing steadily towards the pelagic zone. This decrease in pro-
ductivity per unit volume with depth is inverse to the productivity per
unit of surface area. The same is true for the Incline Creek transect
except that the fertility of this partially enclosed area (Crystal Bay)
256
-------
Ni
Ul
o
T3
O
o>
100,000 -
80,000 -
60,000 -
40,000 -
20,000 -
TOTAL PRODUCTION
LITTORAL ZONE
MAR APR MAY JUN
1971
PELAGIC
200-
150 -
100-
50-
LITTORAL
- 1000
-800
-600
-400
-200
JUL AUG
o
TJ
e
6
Figure 60. Total primary production per day of the littoral zone compared to the
total productivity of the pelagic zone of Lake Tahoe.
-------
PRIMARY PRODUCTIVITY 1968
Ul
00
0 5 1900 3000
1000 2500
DISTANCE FROM SHORE
t Meters)
0 100 450 1200
350 800
Figure 61. Phytoplankton primary productivity-depth profiles at various distances offshore
of four littoral zone stations. Each point represents an average of four
measurements taken on four different days between April and July 1968. The
insert graph shows the variation of the total (mg C'm -day~l) and average
(mg Om~3'day ) productivity as a function of the distance from shore.
-------
is more uniform and probably reflects the less significant volumes of
fertilizing inflows. General Creek has been used in our work as a con-
trol (Goldman, Moshiri, and Amezaga 1972) and the stream influence
disappears within a short distance from shore. The transect at Cave
Rock, along the sparsely settled east shore, shows very little variation
in fertility with depth. The steady rise in productivity per unit of
surface area simply reflects the steady increase in the photic zone
with increasing depth offshore.
Discussion
The littoral zone of Lake Tahoe is characterized by narrow extent and
a relatively small contribution to the overall algal productivity of
the lake. Still, it remains the most visible feature of the lake to
the largely landbound population and presented the first visible evi-
dence that eutrophication was occurring in the inshore areas. Further,
the food chain contribution of the littoral zones of deep lakes like
Tahoe and Baikal in the USSR may be much greater than these measures
indicate. The luxuriant growths of periphyton may reflect a restriction
of nutrient-enriched waters to the shallow zone of Lake Tahoe by a
thermal bar. The periphyton seem particularly sensitive to the spring
inflow of nutrients, warming temperature, and increasing photoperiods.
The most luxuriant growths of attached algae are usually to be found
in the vicinity of stream mouths, but most of the lake's inshore areas
are visibly green in spring and early summer. Occasionally, large mats
of decaying periphyton and associated bacteria break off and float to
the surface or are carried in from streams. Their decay is suspect of
triggering a secondary bloom of phytoplankton such as the large lens
of Scenedesmus that is usually observed near the mouth of the Upper
Truckee River in spring.
The diversity of the periphyton is similar throughout the year, although
259
-------
the species making up the summer and winter populations are quite dif
ferent. The lower diversity occurring to the east of the Upper Truckee
River mouth is accompanied by a high phytoplankton production. If one
accepts the theory that more eutrophic situations are less diverse,
this is a logical expectation.
The Upper Truckee River sediment plume extends well along the southeast
corner of the lake and appears to reduce periphyton growth through
shading or be dissipated and deflected east before it can fertilize
the southern stations. It does, however, greatly influence the phyto-
plankton and planktonic bacteria which thrive in the vicinity of the
plume (Goldman et al. 1973, 1974).
Because glass substrata are utilized, it seems likely that our estimates
of periphyton growth somewhat underestimate natural growth. An irregu-
lar substrate provides not only easier attachment, but a variable pro-
tection for periphyton growth. The heavy mats that break loose from
the wave zone following a spring storm are never duplicated on our
slides. Further, we have no real estimate of grazing by the variety
of organisms that utilize periphyton as food.
Although aquatic insect larvae and protozoans may graze the periphyton
community in Lake Tahoe, the California crayfish Pacifastacus leniusculus
is probably the most important benthic organism in Lake Tahoe (see
Section XI). Studies have shown a distribution of the P^ leniusculus
population between 0 and 60 m depth in Lake Tahoe with maximum densi-
ties occurring between 10 and 20 m (Abrahamsson and Goldman 1970).
This area of concentration is exclusively in the littoral zone of the
lake and may, because of its great abundance, have considerable in-
fluence on the ecology of the littoral zone.
The shallow water environment of the littoral zone of even a deep lake
260
-------
such as Tahoe is of great interest to the limnologist. Although the
water may remain relatively clear, it contains higher levels of nutrients
than the pelagic waters and has much greater contact with the substrata.
The organisms which frequent this zone have the first opportunity to
concentrate the nutrients into organic matter. This tends to reduce
the amount immediately available for a spring phytoplankton bloom and
in a sense buffers the system against loss of transparency. A better
understanding of stream and littoral zone periphyton productivity
should help to improve our understanding of the dynamics of shallow
and deep lakes alike.
261
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SECTION X
ZOOPLANKTON
Introduction
Historically zooplankton of Lake Tahoe have received relatively little
study and it was not until the early part of this century that any sig-
nificant interest was shown in the invertebrate fauna. Pioneer studies
by Ward (1904); Juday (1907); and Kemmerer, Bovard, and Boorman (1923)
were of a general survey nature. More recently a comprehensive list of
many invertebrate groups including zooplankton has been published by
Frantz and Cordone (1966) and Richerson (1969). Richerson, Armstrong,
and Goldman (1970) have completed the first intensive documentation of
zooplankton dynamics and community ecology.
The major objectives of the study reported here were to quantify seasonal
changes in abundance of pelagic zooplankton and relate these changes to
other limnological variations such as primary productivity, the wax and
wane of phytoplankton populations, and intra-specific interactions among
the zooplankton themselves.
About 25 species of free-living crustaceans and 14 species of rotifers
that have been identified compose the known zooplankton community of
Lake Tahoe (Table 34). Many of these animals were identified through
the efforts of previously mentioned investigators who sampled a broad
262
-------
spectrum of the. Tahoe environment. Our study concentrated sampling at
deep water pelagic stations (greater than 120 m) and did not normally
encounter the many benthic or littoral zone forms.
Three cladocerans were taken routinely. Daphnia rosea, D. pulex
(pulicaria of some taxonomists), and Bosmina longirostris were common.
Infrequently, Chydrous sp. was collected. Copepods taken consistently
included Epischura nevadensis, Diaptomus tyrrelli, and an occasional
cyclopoid. Apparently a new addition not reported from sampling by
earlier investigators is the harpacticoid copepod Bryocamptus zschokkei.
It was rare, but occurred in three samples in both 1970 and 1971.
Another rare crustacean in the pelagic collections was a member of the
order Ostracoda which was found on two occasions in the fall of 1970.
It should be noted that since the end of the current study, another
crustacean Mysis relicta, the opossum shrimp, has begun to appear spo-
radically in samples and undoubtedly has become established as a major
zooplankter in Lake Tahoe since its introduction in 1963 (Linn and
Frantz 1965). Collections of Mysis by presently used methods are not
representative of its true numbers because of its particular behavior
and swimming characteristics (net avoidance, strong diurnal migration
through considerable depths, large size, etc.).
The list of rotifers in Table 34 appears to be the most recent and com-
plete compilation of rotifers occurring in Lake Tahoe. Frantz and
Cordone (1966) did not include them. The concurrent study by Richerson
(1969) compiled a list which has been lengthened and revised. Eleven
genera and species and three unidentified forms are now known. Some
rotifer determinations were made by W. T. Edmondson (personal
communication).
263
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TABLE 34, LAKE TAHOE ZOOPLANKTON
A LIST OF PELAGIC AND BENTHIC INVERTEBRATES COMPOSING THE ZOOPLANKTON
COMMUNITY OF LAKE TAHOE COMPILED FROM THE WORK OF FRANTZ AND CORDONE (1966),
RlCHERSON (1969), AND THE TAHOE RESEARCH GROUP STUDIES, AN ASTERISK (*)
INDICATES PRESENCE IN THE 150 TO 0 M VERTICAL TOWS, CODE WORDS FOR COMMENTS
ARE: C=CCW3N, R=RARE, P=PELAGIC, B=BENTHIC, V=VERY.
PHYLUM: ROTIFERA
Cuss: MONOGONONTA
ORDER: PLOIMA
FAMILY: BRACHIONIDAE
EPIPHANES ? (ROTIFER I) * c,p
KELLICOTTIA LONGISPINA * VC,P
KEBAiaiA CQCHLEARIS * VR,P
KERATELLA QUADRATA * R/P
MONOSTYLA SP. * VR,P
NOTHQLCA (STRIATA TYPE) * R,P
NOTHOLCA (SQUAMULA TYPE) * C,P
FAMILY: GASTROPIDAE
ASCOMORPHA (AGILIS AMERICANA TYPE) * vc,p
CHROMOGASTER OVALIS * VC,P
FAMILY: LECANIDAE
LECAUE. SP. * VR,P
FAMILY: SYNCHAETIDAE
POLYARTHRA SP, * C,P
FAMILY: TRICHOCERCIDAE
TRICHOCERCA SP. * VR,P
UNIDENTIFIED ROTIFER I * c,p
UNIDENTIFIED ROTIFER II * C,P
PHYLUM: ARTHROPODA
CLASS: CRUSTACEA
SUBCLASS : ENTOMOSTRA^A,
ORDER: COPEPOD/V
SUBORDER: CALANOIDA
FAMILY: TEMORIQAE
EPIISCHURA. NEVADENSIS LILLJEBORG * vc,p
FAMILY: DIAPTOMIDAF
DlAPTOMUS TYRRELLI PoPPE » vc/p
264
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TABLE 34 (CONT'D)
SUBORDER: CYCLOPQIDA
FAMILY: CYCLOP IDAE
CYCLOPS VERNALIS FISCHER *? VR,B
ALBIDUS JURINE *? VR,B
SUBORDER: HARPACTICOIDA
FAMILY: CANTHOCAMPTIDAE
BRYOCAHPTUS ZSCHQKKEI * VR/B
ORDER: CLADOCERA
FAMILY: SIDIDAE
LATONA SETIFERA 0. F. MULLER R,B
FAMILY: DAPHNIDAE
DAJPUUA BOSEA_SARS * c/p
DAPHNIA ELLEX (PULICARIA) RICHARD * c/p
SlMOCEPHALUS SERRULATUS foCH R/B
FAMILY: BOSMINIDAE
BQSMINA LONGIRQSTRIS 0. F. FULLER * c/p
FAMILY: I^ACROTHRICIDAE
DREPANOTHRIX DENTATA EUREN. R,B
ILYOCRYPTUS ACUTIFRONS SARS R/B
EURYCERCUS LAMELLATUS 0, F. HULLER C,B
CAMPTOCERCUS RECTIROSTRIS SCHOOLER R,B
HAfiEA£ BftIRD R,B
ALONA AFFINIS LEYDIG C/B
AUONA QUADRANGULAR IS 0, F. MuLLER R/B
PLEUROXUS DENTICULATUS BIRGE R/B
CHYDORUS LATUS SARS *? R,B
CHYDORUS SPHAERICUS 0. F, MULLER *? R/B
ORDER: OSTRACODA
FAMILY: CYPRIDAE
CANDONA SP. *? VR/B
ORDER: ANIPHIPODA
FAMILY: TALITRIDAE
HVAI i FI A AZTECA SAUSSURE R/B
HYALLELA INERMIS S. I. SMITH
FAMILY: GAMMARIDAE
STYGQBROMUS HUBBSI SHOEMAKER C/B
SUBCLASS: IIALACOSTRACA
FAMILY: ^SIDAE
REL1CTA LOVEN * COMMON, BUT
NOT IN TOW, P
265
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Methods
Index station collections were made with a Clarke-Bumpus plankton sampler
with a 12.5 cm mouth, flow meter, and a No. 20 (80 p mesh opening) net.
Triplicate vertical tows from 150 m to the surface were taken usually
between 1030 and 1100 at a tow rate of about 50 m/minute. Samples were
rinsed from the cod-end bucket into jars and preserved in 5% formalin.
Flow meter readings taken before and after the tow allowed an estimate
3
of the water volume filtered. This volume was about 1.2 m per tow.
Periodic flow meter calibration was done according to the manufacturer's
recommendations (G. M. Mfg. and Equip. Corp., New York, N.Y.).
The entire sample, including rotifers, was counted under a dissecting
microscope at medium magnification (SOX or 45X) after the sample super-
natant was drawn off and the remaining 5-10 mis was allowed to settle in
a gridded Petri dish. Texts and references for identification included
Ahlstrom (1940, 1943), Beachamp (1932), Donner (1966), Edmundson (1959),
Gurney (1931, 1933), Humes (1955), Kincaid (1953), Marsh (1933), Pennak
(1953), and Voigt (1957). Cladocerans and copepods were enumerated by
life stages and identified to species when possible. Rotifers were
identified at least to genus. Counts from the three tows were averaged
after adjusting numbers according to the volume filtered. The data is
shown in Figures 62 to 65 as number of individuals per cubic meter. A
Burroughs 6700 computer together with a Calcomp Digital Incremental
Plotter Model 563 were used for graphing Figures 62 to 65.
Results
Rotifers -
Rotifers are a numerically important part of the Lake Tahoe zooplankton.
Populations of the four major genera, with a few exceptions, did not
show significant upward or downward trends during the study period, but
266
-------
they were subject to large fluctuations in numbers from one sampling to
the next. Conversion to biomass will eventually provide an important
analysis of their importance relative to larger forms of the zooplankton
(Figure 62).
Chromogaster ovalis, a small rotifer characteristic of unproductive
waters was very common and numerous throughout much of the year. Peak
_3
populations of about 200-m usually occurred in early winter and it
was abundant from late fall through the end of winter. It became rare
or nonexistent from June to October.
Ascormorpha (agilis americana type), a small raptorial rotifer, was com-
_3
mon (300-7000-m ) throughout 1967-69 except for a brief decline in the
fall of each year. In 1970 and 1971 the mid-summer decline occurred,
but the numbers remain*^ low for the rest of the year. There has also
been a noticeable downward trend in total numbers each consecutive year
since 1968.
Notholea (squamula type) population growth curves are variable in shape
from year to year with no consistent temporal pattern. Peak numbers of
_3
about 2500-m occurred in June of 1968 with lower peaks in June and
August of 1969 and from February to May in 1970 and 1971. Hutchinson
(1967) indicates that this is a cold water form.
Based on our sampling, Kellicottia longispina is the most dominant
pelagic rotifer in Lake Tahoe. It suffered population crashes in 1969,
but these did not recur in the next two years. Peak numbers (over
irsi
_0
_3
6000-m in 1968) were reached in June most years and usually persisted
until early winter. The population was seldom less than 10-50-m
These sedimentary feeders eat 10-12 y size particles and are recognized
as preferring the pelagic zone (Hutchinson 1967).
267
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oo
— l000' PQUflRTHflft
eHBOHOBBTEfl 1969
ROTIFER 1 19t
KEfWTELLft QUflOWTfi
A/LA
Figure 62. Numbers of individual rotifer species in a 150 to 0 m vertical tow at the index
station of Lake Tahoe from mid-1967 through 1971.
-------
Keratella quadrata, Polyarthra sp. and an unidentified rotifer also
periodically made significant contributions to the rotifer population.
Keratella, a strongly cyclomorphic pelagic form, tends to peak in
abundance in mid-summer, die back in the fall, and exhibit a secondary
peak in early winter. The 1971 data indicates Polyarthra may be under-
-3
going a decline in Lake Tahoe. Maximum concentration of about 1000-m
occurred in the early winter of. 1968. A mid-summer increase in 1969
and 1970 was bracketed by lower numbers in spring and fall. However,
in 1971 Polyarthra appeared only briefly in July. The unidentified
Rotifer I (Epiphanes?) has remained at low and fluctuating population
levels throughout the study and appears to have both summer and winter
peaks in abundance.
The other rotifers found and listed in Table 34 are as yet unidentified
so that quantitative evaluation of their role in the Tahoe plankton
community is not practical.
Copepods -
Although not extremely rich in number of species, the Lake Tahoe copepod
community constitutes the major zooplankton component. Counts of
adults, copepodites, and nauplii of the two major copepods Diaptomus
tyrelli and Epischura nevadnesis revealed that they were by far the
roost abundant zooplankton. Both forms appeared to be slightly increasing
in number with Diaptomus increasing most rapidly (Figure 63).
Epischura adult population levels were found to be about the same
_3
throughout the study period. Maximum density was near 200*m and
this peak was usually reached some time in mid or late summer. Rapid
population decline occurred in the fall and a low number of adults
persisted through the winter until the population increased, sometimes
dramatically, in April or May. The copepodites followed a similar
-3
pattern. Density in 1971 was near 1000-m at its peak. Nauplii were
269
-------
COPEPODfl
EPISCHURfl NHUPUl 1968
EPISCMLtflfi EGGS 1970
EPISCHUFW COPEPODITES
:> ID
Q
z
—• I
DIflPTOMUS EGGS
OIHPTOHUS NBUPL1I 1966
1000 DIflPTOMUS COPEPODITES
1967
DJflPTOMUS ROULTS
1969 {
Figure 63. Numbers of individual copepod species in a 150 to 0 m vertical
tow at the index station of Lake Tahoe from mid-1967 through
1971.
270
-------
present in maximum numbers from May to August and exhibited a short-
lived die-off in late winter. Eggs were most abundant in spring and
'summer when they reached concentrations of about 100-m
Diaptomus^ numbers appeared to be increasing in all three life stages
during the study period, but the egg number was found to be slightly
less. All three forms followed similar yearly patterns with lowest
_3
numbers occurring in the late winter when less than 10-m were found.
_3
Peak numbers occurred from May to October (100-500'm ). The numbers
counted in 1970 were fairly low, but were followed by an obvious
increase in 1971.
Cladocerans -
Perhaps the most striking phenomenon occurring in the Tahoe zooplankton
during the study period was the almost complete disappearance of the
cladoceran population. Both Daphnia and Bosmina began to decline sig-
nificantly in 1970 and were absent from all index station counts by
mid-1971 (Figure 64).
Bosmina adults were relatively abundant from 1967 to 1969 with a charac-
_3
teristic peak in abundance of 400-1000-m occurring each fall. Bosmina
-3
embryos and admits remained at low densities of less than 10-m in
_3
1969 until late summer. Embryos peaked in abundance at about 50*m , but
adults increased by nearly one hundred-fold in September. A steady
decline of both life stages followed. In 1970, embryos made only
sporadic appearances in winter and fall and adults occurred at low
levels throughout the year with no fall increase. In 1971, no embryos
were detected and adults gradually disappeared by June.
Daphnia followed a similar pattern of disappearance. Both embryos and
adults maintained fairly uniform numbers throughout most of 1967-69,
-3
ranging from about 5 to 700-m . That density level continued to May
271
-------
CLROOCERR
SJ
Figure 64. Numbers of individual cladoceran species in a 150 to 0 m vertical tow at the
index station of Lake Tahoe from mid-1967 through 1971.
-------
1970 and then a slow, steady decline continued to the end of the year.
Daphnia eggs which had not been counted separately until May of 1970
showed a similar rate of decline. Only one Daphnia adult was counted in
December of 1971!
As with rotifers, no attempt has been made to quantitatively evaluate
the significance of the other copepods, cladocerans and malacostracans,
and oscracods found infrequently in the samples.
Discussion
The Lake Tahoe zooplankton community appears to be undergoing a signifi-
cant change. Species dominance appears to be shifting, but it is not
yet clear whether or not total numbers of zooplankton are increasing.
The lake formerly contained a large pelagic cladoceran population con-
sisting mostly of Daphnia species and Bosmina longirostris. The data of
Figure 64 indicate that not only have cladocerans almost entirely dis-
appeared from the sampling area, but a progressive shift in time of
zooplankton peak abundance has taken place (Figure 65). Such an occur-
rence is not unknown and it has been attributed to different causes.
Predation by planktivorous fish (Anderson 1972, Brooks and Dodson 1965,
Galbraith 1967, Hrbacek et al. 1961, Hutchinson 1971, Reif and Tappa
1966, Relmers 1958, Wells 1970, Wong and Ward 1972) has often been
offered as an explanation for the disappearance of large cladocerans.
Interspecific competition for available food (Brooks and Dodson 1965,
Dodson 1970, Anderson 1970) or a change in the quality of the food
supply caused by increasing euthrophication have also been mentioned
(Bradshaw 1964, Beeton 1965, Brooks 1969, Zyblut 1970).
It is not yet clear what has led to the reduction of these large and
important zooplankters, but it is suspected that successful introductions
of both a large omnivorous zooplankter Mysis relicta and the
273
-------
TOTAL ZOOPLANKTON
Figure 65. Total number of zooplankton in a 150 to 0 m vertical tow at the index station
of Lake Tahoe from mid-1967 through 1971.
-------
planktivorous kokanee salmon Oncorhynchus nerka have been major factors
in the zooplankton species shift. Accumulation of population data on
both fish and Mysis should resolve the questions developed in this report.
The opossum shrimp Mysis relicta was introduced in 1963 to provide
forage for the Tahoe trout fishery (Linn and Frantz 1965). It has been
successfully introduced into other lakes (Furst 1965; Schumacker 1966;
Sparrow, Larkin, and Rutherglen 1964) and has caused changes in zoo-
plankton composition in some cases (Northcote 1972). Recent studies
by Lasenby and Langford (1972, 1973) have indicated that adult Mysis
can be voracious predators on Daphnia pulex, Bosmina, and the rotifer
Kellicottia. They found that Mysis played a dual role in the ecosystem
of Stony Lake, Ontario as a benthic detritivore by day which ascended
by night to feed on Daphnia and Bosmina. There was even some evidence
suggesting that Mysis were selective for the cladocerans, because there
was a striking lack of diatoms and rotifers in the opossum shrimps'
stomachs.
Mysis are known to be concentrated around the thermocline by night and
descend to the near bottom when light intensity becomes too high in
daylight (Larkin 1948; Mundie 1959; Beeton 1959, 1960; Wells 1960). Al-
though occasionally present in shallow waters, they were more commonly
found in deeper water where light from the surface does not produce a
negative phototactic reaction (Robertson, Powers, and Anderson 1968).
This diurnal cycle could occur year-round since temperature does not
appear to be as much of a barrier to their vertical movements as it was
once believed (Smith 1970). Juday and Birge (1927) observed them to
tolerate temperatures ranging from 0° to 21°C in the surface waters of
Trout Lake, Wisconsin. They have been kept in the Tahoe laboratory for
nearly a month at room temperature (15°C) with no special precautions
other than aeration. Daily short-term "high" temperature exposures in
the epilimnion do not appear to affect their ability to feed there at
night. It is entirely feasible that Mysis is at least partially
275
-------
responsible for the cladoceran disappearance, since their nocturnal
ascent brings them into the area of the thermoeline occupied by the
pelagic cladocerans.
The unintentional introduction of the planktivorous kokanee salmon
into Lake Tahoe in 1944 was followed by a series of kokanee fry plantings
from 1949 to 1955 and from 1964 to 1969. This established the kokanee
as an important member of the Tahoe fishery in the late 1960's (Cordone
et al. 1971). These investigators determined that all sizes of kokanee
are highly dependent upon zooplankton for food and observed that clado-
cerans and primarily Daphnia were found in 90 to 100% of the fish stomachs.
Copepods, of which Epischura nevadensis composed the largest percentage,
were present about 15% of the time.
The composition of kokanee food appears to be shifting away from an al-
most strictly cladoceran diet to one composed of several types of
zooplankton. In 1963 and 1964, cladocera occurred in fish stomachs
about 93% of the time, copepods 20%, and midge larvae 2%. In 1972,
percent frequency of occurrence was 10% cladocerans, 53% copepods,
44% midge larvae, and 16% mysids (T. Frantz personal communication).
Kokanee are facultative planktivores which will normally feed on the
larger daphnids when they are present, but will take other smaller
food sources when their preferred one diminishes (Brooks 1969) . Their
order of food preference is usually cladocerans, cyclopoids, and then
calanoid copepods.
The interaction of the two nearly simultaneous species introductions
into the Lake Tahoe ecosystem at different trophic levels may produce
a series of complex changes with ramifications throughout the food chain.
The changes in specific zooplankton abundance along with the increasing
chemical enrichment might conceivably influence the rate of eutrophica-
tion of Lake Tahoe by altering the grazing pressure on phytoplankton.
276
-------
Heavy predation usually has the effect of eliminating first the large
forms such as Daphnia which allow smaller forms such as Bosmina to
become dominant (Brooks and Dodson 1965, Hutchirison 1971). Apparently
predation by Mysis and kokanee salmon has nearly eliminated both Daphnia
and Bosmina, although other* limnological factors may also be important.
This is contrary to changes which .usually occur when lake planktivores
are selective of large size prey (Brooks 1968).
The removal of cladocera may bring about a shift in rotifers, although
no significant change has been noted to date. Rotifers in Tahoe do not
appear to have increased dramatically and some have even decreased
(Figure 62). The large total number of zooplankton observed in 1968
was mainly due to the predominance of the rotifers Kellicottia,
Ascomorpha, and Notholca (Figures 65, 66). The reason for this sudden
growth and decline is not understood. There is a slight increase in
copepods in 1970-71, possibly indicating that they are gaining a com-
petitive edge over the rotifers. This change may continue until balance
is restored between these two groups which filter feed on similar size
particles (Brooks 1968). Polyarthra, Ascomorpha, and Chromogaster seem
to be losing their place as dominant rotifers to Kellicottia populations.
The loss of the larger zooplankton which are more efficient filterers of
a wider size range of algae and particles (Burns 1968) could also lead
to a shift in phytoplankton dominance. Although it has not been demon-
strated in a large lake, Hrbacek (1962) has shown that a population of
Daphnia in fish ponds maintained water of greater transparency by being
more efficient at the removal of large and small phytoplankton than a
population of smaller herbivores which did not filter as rapidly or
remove the larger "net" phytoplankton (>50y). The implication of this
is obvious for Lake Tahoe. Reduced water clarity even in pelagic waters
is a strong possibility, because adequate numbers of large zooplankton
no longer exist to remove large phytoplankton.
277
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8000
10
IT
LJ
CC
LU
m
6000-
4000
2000
O 1967
D 1968
~A 1969
• 1970
• 1971
D.
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 66. Seasonal number of zooplankton at the index station of Lake
Tahoe from mid-1967 through 1971. Each point is the average
for the month.
278
-------
Removal of the most efficient phytoplankton grazers may also change the
diversity and stability of the Tahoe phytoplankton and might well cause
an increase in both large and small forms. Richerson (1969) believes
that the "grazing pressure" on Lake Tahoe phytoplankton was greatest
during late summer and fall particularly because of the presence of
Daphnia. He indicated that a high rate of phytoplankton turnover
existed at this time which supported a diverse zooplankton population.
It should be noted that these observations occurred before the reduction
in cladocerans. Brooks (1969) believes that "a shift in dominance from
large-bodied to small-bodied planktonic herbivores (as a result of size-
dependent predation) should cause a lake to become more eutrophic."
Margalef (1968) has theorized that eutrophic lakes tend to exhibit less
diversity and stability in their plankton assemblages. Therefore, a
loss in zooplankton diversity in Tahoe might well cause certain large
algal forms to become more dominant.
Because of the introduction of Mysis, two important changes in the food
availability may occur for the Tahoe fishery.
1) Mysis are providing a heretofore unavailable food source to
bottom feeding lake trout (Salvelinus namaycush) which are known
to feed on them when available (Rawson 1961).
2) If Mysis are predatory in Tahoe, they are removing the major
food source (cladocerans) for kokanee salmon (Oncorhynchus nerka)
while remaining fairly unavailable themselves as a pelagic food
source because of their diurnal, vertical movements to and from
the photic zone where kokanee normally feed.
The increasing occurrence of Mysis in lake trout stomachs is now sub-
stantiated. In 1970 none of the trout checked contained mysids (Frantz
and Cordone 1970), but in 1971 the frequency of mysids jumped dramatically
to 60% (T. Frantz personal communication). This should lead to an
increase in the number of lake trout in the fishery. They depend heavily
279
-------
on cladocerans and copepods when young and they are a strongly piscivor-
ous fish after attaining a length of 0.5 m. This predatory nature may
lead to the reduction in other game (white fish, rainbow trout) and
non-game fish (sculpins, minnows, suckers) in Lake Tahoe. It is also
possible that predation on crayfish, probably the most important benthic
detritivore, may become more severe.
If the second change in food availability occurs (it appears that clad-
ocerans are very rare now), then one is tempted to predict that kokanee
salmon numbers will decline from a lack of an adequate prime food
source. It is still a question whether they can succeed as facultative
planktivores feeding largely on pelagic zooplankton, but it has occurred
before (Northcote 1972).
It is interesting to note that as of September 1973, cladocerans were
not completely gone from Lake Tahoe because they were collected in
Emerald Bay. Daphnia may exist there because of reduced predation by
kokanee. The fish may not frequent the bay due to its shallow nature
or Daphnia may be less susceptible to predation because of the lower
transparency of the water there. Mysis may also find conditions less
ideal than the main lake because of the relative shallowness (63 m) of
the bay. There is also the possibility that they do not exist there
because fche very shallow (2.5 m) mouth may have acted as a barrier to
their horizontal migration. It is not known if Mysis are present in
Emerald Bay, although they were released there during the original
introduction in 1963-64 (Linn and Frantz 1965).
One of the most significant indications of change in zooplankton standing
crop in Lake Tahoe is the progressive shift in the peak zooplankton
abundance. Not only has the peak occurred at a later date each year
since 1968, but the curve has changed from bimodal to unimodal (Figure 66)
This change in curve configuration is apparently due to the disappearance
280
-------
of cladocerans which were most numerous in the fall. This is significant
especially in view of the primary productivity information presented in
Section VI that peak primary productivity is occurring later each year.
If Bosmina and Daphnia depend on specific algal and/or bacterial con-
ditions for growth, the temporal shift in primary productivity may delay
development of populations until other environmental conditions are
unfavorable. If the phytoplankton peaks are very close to the end of
the main algal growing period at Tahoe (just before light and temperatures
begin to decline), it is entirely possible that the physical and biotic
environment are limiting the growth of the cladoceran population. It is
suggested that this shift in production (both primary and secondary)
may be as important as kokanee or Mysis predation in elimination of the
cladocerans, but little evidence is available.
It appears that Lake Tahoe is losing some diversity in zooplankton species.
The large phytoplankton, without grazing pressure, may gain a competitive
interspecific advantage over smaller cells which are utilized by smaller
zooplankton. This could conceivably reduce the diversity of phytoplank-
ton species in the lake and water clarity. A similar process would be
true for zooplankton. With competition fot food lessened together with
an increase in fish predation on the remaining smaller sized zooplankton
community, Lake Tahoe may support fewer dominant species, but greater
numbers of those with a particular feeding advantage.
281
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SECTION XI
BENTHIC ORGANISMS
CRAYFISH
Introduction
The California crayfish Pacifastacus leniusculus is probably the most
important benthic organism in Lake Tahoe and has achieved considerable
international importance as an introduced species in European waters.
It is believed that the first introduction of P_. leniusculus into Lake
Tahoe took place in 1895 when 19 males and 37 females from the Klamath
River were introduced into the Truckee River in the vicinity of Reno.
In 1909 more crayfish were introduced "with the object of providing food
for the introduced varieties of fish as well as a table delicacy for our
citizens..." (La Rivers 1962). Three hundred and sixty crayfish, prob-
ably from coast streams in Oregon, were placed in the Truckee River, the
Carson River, and Washoe Lake. A third introduction in the water sys-
tems of Lake Tahoe was made in 1916.
From this information it may be concluded that there were no endemic
crayfish in Lake Tahoe. This theory is further supported by reports of
the diet of the Washoe Indians who lived around the lake during the sum-
mer (Downs 1966). Though they were clever fishermen and had no taboos
on food, there is no indication that they either ate or used crayfish as
bait which they should have if these animals were native to Lake Tahoe.
282
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The various introductions of _P. leniusculus to Lake Tahoe included cray-
fish from several different water systems. It is likely that the lake
received several subspecies including P_. trowbridgii (Stimpson), and P_.
klamathensis (Stimpson). This resulted in hybridization, and intergrade
forms of the subspecies of P_. leniusculus are now found in Lake Tahoe.
The P_. leniusculus in Lake Tahoe show a variety of color phases from
greenish-brown through blue and red. The majority are greenish-brown,
and it is not known whether the variability is genotypic or phenotypic.
Trapping studies of the distribution of the P_. leniusculus population
between 0 and 60 m depth (where 97.2% of the population resides) in Lake
Tahoe indicates that their maximum densities occur between 10 and 20 m
(Fig. 67). The lower density of crayfish at 0-10 m depth is probably
due to the high light intensity, as well as the scarcity of food mater-
ials caused by heavy wave action in the shallower areas of the lake.
High light intensity has been shown to inhibit primary production in the
upper water levels at high altitudes (Goldman 1963) and at high lati-
tudes (Goldman, Mason, and Wood 1963). Periphyton production may be
somewhat reduced in shallow waters from a .combination of high light in-
tensity and wave action. Strong wave action, particularly during cold
weather, has also been observed to cause appreciable mortality of cray-
fish in shallow areas of the lake. This may result directly by physical
injury of rolling rocks on the bottom, displacement, and perhaps in-
directly by reduction of its food supplies. Below the depth of 40 m the
crayfish population declines very rapidly, even if the bottom substrate
is very suitable for crayfish at this depth. A reason for the rapid de-
cline of the population below 40 m depth seems to be the inability of
the crayfish eggs to hatch in the cold water found below this depth dur-
ing the summer months.
283
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to , 100 , 140 IM lgtf 60 , 100 . >«» . HO
OFF COAST GUARD STATION [A S. STATELINE
June 1967-Jn" '"•"£ !• 26-27 Sept. 1967
40 Bti 920 wo 10 40 W
DEPTH - METERS
Figure 67. Depth-distribution of the crayfish population at various
locations in Lake Tahoe in 1967.
284
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Methods and Results
Utilizing population data obtained by SCUBA and trapping methods, the
crayfish population in Lake Tahoe during 1967 at depths from 0-40 m
(which includes 90% of the population) was estimated to include 55.5
million individuals. Based on an average weight of 20 grams per animal,
the standing crop of adult crayfish in this depth range was calculated
to be about 1,100,000 kg (Abrahamsson and Goldman 1970). Studies of
crayfish from different areas of Lake Tahoe have shown that there is a
large variation in the average body length of these animals. The area
off the Coast Guard Station has a very stony bottom which provides good
coyer against predation which results in high density, a shortage of
food, and a stunted crayfish population. The average body length was
found to be inversely related to the population density and is there-
fore greater in deep water (Abrahamsson and Goldman 1970). Furthermore,
there are local sources of pollution .in Lake Tahoe which may lead to
higher levels of productivity in certain areas (Goldman and Carter
1965). There are also substrate differences which may have -important
effects on the total population structure. The bottom material in
Crystal Bay, for example, consists of large stones scattered over a
plain sediment bottom, which has been receiving quantities of silt from
building activities on the Incline Creek drainage. This substrate pro-
vides little protection for the crayfish population and leads to a high
predation level, low density, abundance of food, and a greater average
length per animal. All these factors correlate positively with the low
population densities encountered in the deeper regions (Abrahamsson and s
Goldman 1970).
The percentage of mature crayfish within the total population increases
with an increase in the size of the animals up to a point where 80-100%
of the members of the population larger than 95 mm are sexually mature.
This indicates that almost all adult individuals of both sexes take
285
-------
part in reproduction every year. This was not found for Pacifastacus
by Miller (1960) nor for Astacus by Svardson (1949).
Aquaria observations have shown that spawning may, to a great extent,
be influenced by such factors as high population density, shortage of
cover, and lack of nutrition. Pleopod egg counts show that there is a
considerable variation in egg production, but there is a positive cor-
relation between body length of females and the number of eggs produced.
The average number of pleopod eggs of Lake Tahoe crayfish during 1967
was 110 eggs per female, based on a sample of 120 females (Abrahamsson
and Goldman 1970).
As already indicated, the maximum density of the P_. leniusculus popula-
tion in Lake Tahoe occurs between 10 and 20 m. This area of concentra-
tion is exclusively in the littoral zone of the lake and Pacifastacus
may, because of their great abundance, have considerable influence on
the ecology of the littoral zone.
Studies on juvenile stages in a number of Decapoda indicate that these
animals are strictly algal and detrital feeders (Blegvad 1914).
Pacifastacus is an omnivore and in addition to consuming plant and ani-
mal food, ingests a variety of detritus and probably a number of ben-
thic organisms including immature aquatic insects (Moshiri and Goldman
1969).
Immature periphyton communities in the littoral zone of Lake Tahoe dis-
play a high rate of productivity. As the community develops and the
density of growth reaches a maximum, an equilibrium may exist before
the winter decline. The mature periphyton community, without grazing,
only produces new cells to replace old and dead cells. The productivi-
ty may therefore decrease in a climax or equilibrium state (see Section
IX).
286
-------
It seems likely that the aquatic periphyton community is similar to a
terrestrial grassland community which maintains a higher productivity
when they are grazed by herbivores. The presence of a crayfish popu-
lation in the littoral zone of the lake may increase the productivity
of periphyton by grazing pressure and may provide an efficient recycling
of nutrients for both attached and free-floating communities which
would otherwise be restricted to the periphyton community (Goldman and
Amezaga 1974).
The possibility that the periphyton community is maintained in a more
productive state by the grazing of the Lake Tahoe crayfish population
seems consistent with the observations in the lake. The primary pro-
ductivity of Lake Tahoe is very high off Tahoe City. The standing crop
of crayfish is also most dense in this area of the lake which may re-
flect a combination of food supply and abundant cover (Abrahamsson and
Goldman 1970).
At present very few crayfish are removed from Lake Tahoe except by pre-
dation. If harvested efficiently, crayfish might provide one means of
permanent removal of organic matter from Lake Tahoe which is primarily
valued for its present low productivity. Further study is needed to
determine how great a sustained yield the lake could provide today.
Its steadily increasing fertility will probably cause a higher produc-
tion of crayfish in the future (Abrahamsson and Goldman 1970) .
International Importance of Crayfish Research at Tahoe
The importance of the species P_. leniusculus is not limited to its in-
fluence on the ecology of the littoral zone in Lake Tahoe. It has been
introduced into Sweden to rejuvenate the crayfish fishing industry there
since the indigenous Swedish crayfish population of Astacus astacus has
been steadily decimated by the fungus Aphanomyces astaci first noted
287
-------
there in 1907. Since then, this "crayfish plague" has devastated about
half the country's crayfish waters, with new areas being infected every
year. This has caused severe economic consequences for the fishery and
presently it is calculated that every year the fungus causes damage
estimated at tens of millions of crowns in Sweden (Abrahamsson 1973).
In 1960 under the suggestion of the Swedish general consul in San
Francisco, Erik von Essen, 100 Pacifastacus were introduced to an ex-
perimental lake outside Stockholm. These crayfish proved to be immune
to the fungus and survived, grew, and reproduced satisfactorily. This
motivated a more thorough ecological study of the species which was
begun by Dr. Sture Abrahamsson in Sweden. In 1967 and 1968, Abrahamsson
and Goldman (1970) studied Pacifastacus in .its natural habitat at Lake
Tahoe. A portion of the information obtained from this work has already
been included in this report. The results of their studies indicated
that P_. leniusculus was a suitable species for a large scale introduc-
tion into Sweden. In 1969, under supervision of the Swedish Fisheries
Board and the California Department of Fish and Game, about 60,000
adult crayfish were transferred from Tahoe to Sweden after first being
held in quarantine.
Because of the risk of transferring parasites and fish diseases when im-
porting adult crayfish, in subsequent years it was decided to stop im-
porting adult crayfish and to continue the restoration program with
Pacifastacus hatched in Sweden. This necessitated the development of
hatching techniques in Sweden. This work was begun in Sweden under the
direction of Dr. Abrahamsson with our continued cooperation. A high
degree of success in developing hatching technology was reported by Dr.
Abrahamsson just before his death following the First International
Crayfish Symposium held in Hinterthal, Austria in 1972. The parasite
and disease-free, hatched young continue to be released into lakes and
streams and it is hoped that it will eventually raise the production
288
-------
levels of the Swedish crayfish Industry to pre-plague levels.
Pacifasticus leniusculus has the advantage of being more cold water
tolerant than Astacus astacus and therefore can colonize more northern
lakes. This example of international cooperation has been greatly ap-
preciated in Sweden where crayfish assume great importance at summer
parties throughout the land.
The initial work with ]?. leniusculus at Lake Tahoe and in Sweden has
stimulated the initiation of aquaculture facilities for this species on
the Davis campus under the direction of Drs. Goldman and Graham Gall.
The experimental system is based on a water-recycling trout hatchery
where nutrient-rich trout culture effluent will be used to grow macro-
scopic hydrophytes as a forage plant for the crayfish. This work is
just beginning, but will extend and continue the work carried on during
the period of EPA support.
SYNOPTIC SURVEY OF OTHER BENTHOS
Methods
Thirty-nine locations were chosen, evenly distributed over the lake on
a grid, plus one station in Emerald Bay and one on the "lakemount".
Sampling was conducted between 1 August and 26 October 1968 and served
as the basis for a study of sedimentation in the lake (Court, Goldman,
and Hyne 1972; see Section IV). Only one sample, using a Shipek sampler,
was taken from each station so that a high degree of quantitative relia-
bility cannot be claimed for the collections. The sediment samples
collected varied in amount from less than one liter to more than four
liters, depending on the substrate, and were washed and sieved before
sorting. Lake water was used for the washing, and care was taken not
to cause a grinding of the organisms in the washing of the sand and
silt. Sieving was graded and fine enough to prevent the passage of even
289
-------
TABLE 35. ORGANISMS FOUND IN BENTHOS SAMPLES FROM LAKE TAHOE
CLASS
PROTOZA
TURBELLARIA
NEMATA
OLIGOCHAETA
OSTRACODA
COPEPODA
GENERA
TETRAMERIS
PHAGOCATA
DENDROCOELOPSIS
RHYNCHOSCOLEX
TRILOBUS
DORYLAIMUS
lOTONCHUS
PELOSCOLEX
LUMBRICULUS
LlMNODRILUS
HENLEA
ILYIOPRILUS
RHYNCHELMIS
IkPLOTAXIS
NAIDIUM (BREVISETA)
E I SEN I ELLA
AEOLOSQMA
(IMMATURE)
(NEWLY HATCHED)
(COCOONS)
(EGGS)
CANDONA
DIAPIQMIS OYRELLI)
EPISHURA
No. OF
STATIONS
ORGANISMS
PRESENT
3
20
1
1
8
8
8
19
3
4
2
5
3
1
1
1
1
3
H
9
2
26
1
1
%OF
TOTAL NO. TOTAL NO,
ORGANISMS ORGANISMS
7
7 .8
79
3
1
83 9.3
25
23
20
68 7.6
57
26
24
19
13
8
5
2
2
1
19
20
24
2
222 24.9
152
152 16.9
37
3
40
4.5
290
-------
TABLE 35, CONT'D,
MALACOSTRACA
AMPHIPODA
INSECTA (CHIRONOMIDAE)
INSECTA (PLECOPTERA)
ACARI
MOLLUSCA
GASTROPODA
PELECYPODA
TERRESTRIAL ARACHNID
MISCELLANEOUS
STYGOBROHUS
HYALELLA
(DECOMPOSED)
(UNIDENTIFIED)
ORTHOCLADIINAE*
PROCLADIUS
CHIRONOMUS (ATRITIBIA)
PHAENOPSECTRA
CAPINA
(TERRESTRIAL GNAT)
(MlDGE)
(LARVA)
(DIPTERA ADULT)
(UNIDENTIFIED)
LfEEBJJA
LlMNQCHARES
PARAPHQLYX
GYRAULUS
PISIDIUM
ARACHNIDA*
EGGS
COCOONS
'
30
9
2
2
6
2
1
1
3
1
1
i
i
i
2
1
1
1
2
1
9
1
TOTAL No, OF ORGANISMS FOUND
219
28
2
2
251
17
2
1
1
7
1
1
1
1
1
33
2
1
3
6
1
7
HA
1
18
3
21
892
28,2
-
3,7
.3
,8
,5
,1
2.3
*NOT IDENTIFIED TO GENUS .
291
-------
such small organisms as cladocerans and copepods. Following the wash-
ing, the samples were preserved in formalin in small vials. The vari-
ous organisms were then identified and enumerated.
Results and Discussion
Thirty-three different genera representing a total of twelve different
classes of animals were identified in the benthos samples (Table 35).
Two genera composed 46.6% of all identified organisms. The dominant
organism found in 30 of the 41 stations was Stygobromus (Amphipoda) .
A total of 219 of these were identified, which represented 27.5% of all
the identified organisms and 24.5% of all organisms found. The second
dominant organism found in 26 stations was Candona (Ostracoda). One
hundred and fifty two were found which represented 19.1% of the identi-
fied organisms.
The total number of organisms found in any one sample varied from 0 to
79 (Fig. 68)- Values of diversity per individual were computed for
each station and varied from 0 to 2.94 bits per individual (Fig. 69)-
Values of diversity per individual for our data on benthos were probably
more relevant than total number of individuals per sample, due to the
limited number and difficulty of obtaining samples of comparable size.
The results of the benthic survey are difficult to interpret, for there
does not appear to be a systematic pattern to either the distribution
of numbers of organisms or the distribution of biotic diversity. This
condition is especially evident when compared to the synoptic surveys
of primary productivity where the primary productivity rate increased
sharply near the mouths of some of the creeks (Goldman, Moshiri, and
Amezaga 1972; and Section VII of the present report). It is quite pos-
sible that the lack of pattern in the benthos data may be a result of
the lack of replicated samples and the small, variable sample sizes.
292
-------
LAKE TAHOE 1968 BENTHOS
TOTAL NUMBER OF INDIVIDUALS PER SAMPLE
DIAMETER SCALE
.F20INDIVIDUALS
Figure 68. Number of organisms found in benthos samples at different
stations in Lake Tahoe collected between 1 August and
26 October 1968.
293
-------
LAKE TAHOE 1968 BENTHOS
DIVERSITY
DIAMETER SCALE
^ = I BIT PER INDIVIDUAL
Figure 69. Benthos diversity per individual at different stations in
Lake Tahoe sampled between 1 August and 26 October 1968.
294
-------
However, the abundance and diversity of the benthic organisms may not
be functions of the same environmental property as the abundance, pro-
ductivity, and diversity of the phytoplankton. Algae are clearly assoc-
iated with the mouths of creeks and their productivity has been shown
to be stimulated by additions of creek water (Goldman and Armstrong
1969). The environmental factors that affect the benthos have not been
determined, and a lack of pattern in benthic numbers and diversity may
be an indication that nutrient enrichment is not a primary factor lim-
iting the abundance of various species of benthos.
295
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SECTION XII
EFFECTS OF MARINAS AND ECOLOGY OF A TAHOE BASIN STREAM
A LIMNOLOGICAL STUDY OF STAR HARBOR, A TAHOE MARINA
Introduction
The management of harbors and marinas has long been a problem for both
the shipping industry and for recreation. In heavily used waterways
there is increasing concern for navigation hazards, docking facilities,
and general traffic control and safety measures. However, in a lake
such as Tahoe, particular attention is directed towards water quality.
Noting Tahoe's clear waters, the public is particularly concerned with
the threat of eutrophication through increased use of the basin for re.c-
reation by a growing population. Sewage disposal systems have re-
placed most septic tanks and the bulk of the sewage is now being exported
out of the basin, even after tertiary treatment. Stricter building codes
are being enforced and many previously ignored questions concerning
water quality are being faced by state agencies, local government, and
land developers alike.
In the construction of on-shore developments, there is particular con-
cern for excessive land disturbances. Road building and tree removal
can cause severe erosion which releases nutrients and silt to the lake.
Another problem which is peculiar to harbor developments is water
296
-------
stagnation. This allows nutrients flowing in from the streams to ac-
cumulate in the harbor and allows for the buildup of large populations
of algae and sediment, which are eventually carried into the lake.
Star Harbor is a small land development, approximately 17 acres in size,
on the north shore of Lake Tahoe, one mile east of Tahoe City, California
(Fig. 1). Prior to construction, the area was a marsh at the mouth of
Burton Creek, which has a 3100 acre watershed. Another small stream
with a 900 acre watershed, which is primarily springfed, also empties
into the development site. During years of excessive snowmelt, Burton
Creek flooded into this marsh, carrying large amounts of debris and silt.
In the first phase of construction of Star Harbor, an impoundment was
built along the floodplain of the creek, creating a channel of quiet
water at the mouth of the creek 2.5 m in depth, to be used as an anchor-
age for boats belonging to the residents living in the condominiums
along the shore. The rest of the marsh was drained and a new creek was
constructed from the spring flows. Part of the drainage was diverted
along the east side of the property where it flows into one of the la-
goons_, while the major portion of the drainage was diverted along the
west side of the property to form a new creek, Polaris Creek, which is
now being used as a trout spawning channel because of its cold (12°C) ,
swiftly moving water. Now both streams flow into the main channel. Be-
tween March 1970 and September 1971 a limnological study was conducted
at Star Harbor as a M.S. thesis (Coil 1971). The purpose of this study
was to determine: (1) if the development causes any biostimulatory ef-
fects on algal growth in the lagoon and future harbor, (2) what the
level of nutrients is now entering the harbor from its tributary stream,
(3) if the harbor has any effect on the near-shore waters of the lake,
and (4) a possible water management strategy in order to minimize any
eutrophication in the lagoon and harbor and reduce the flow of nutrients
and sediment into the lake.
297
-------
Methods
Seven sampling locations were chosen: one in each of the two streams
which are tributary to the lagoon, four within the lagoon itself, and
one in the lake (Fig. 70). The following parameters were measured on a
monthly basis at each station:
Water Chemistry
Nitrate
Phosphate
Iron
Inorganic carbon
Phytoplankton (algae)
Numbers of individuals
Biomass (fresh weight)
Primary Productivity (the growth rate of algae) — utilizing the
sensitive carbon-14 method of measuring photosynthesis (Goldman
1963).
Physical Factors
Light
Temperature
Samples were collected at a 1-m depth at each station. Productivity
samples were incubated in situ and all other analyses were performed at
the limnology laboratory at Davis, California.
In addition to this regular sampling, biostimulation experiments were
performed by the addition of both stream water and harbor water to sam-
ples of Lake Tahoe water. Different concentrations of water were added
to the lake water to determine if there was any stimulation to algal
growth by the addition of water from Star Harbor. These experiments
give an indication of the consequences of mixing the now partially im-
pounded lagoon waters with the lake.
Results
Results of nine samples collected between 14 April 1970 and 21 January
298
-------
•JD
Figure 70. Map of Star Harbor indicating the sampling stations.
-------
1971 indicate that Polaris Creek (Station 2) carries the higher nutrient
concentrations of the two inflowing streams (Table 36). Primary pro-
ductivity was also highest in this stream while the actual algal biomass
was found to be lowest. This indicates that the high nutrient concen-
trations in the stream are able to support a small population of rapidly
growing algae and once the stream enters the harbor, a larger population
of algae is allowed to accumulate due to the extended residence time of
water in the harbor.
Figure 71 indicates that at the present rate of nutrient recharge into
the harbor, there is only limited nutrient removal by algae. There is
a notable decrease in nutrients due to dilution as the streams enter
the less-nutrient-rich harbor. Once in the lagoon there is neither a
significant increase nor decrease in nutrient content of the lagoon
waters until it reaches the lake (Station 7). However, this also in-
dicates that the harbor is not causing an increase in nutrients entering
the lake since: (1) the streams would carry their high nutrient load to
the lake regardless of the presence of the harbor, (2) sediment which
provides substrata for bacterial growth is settled out in the harbor,
and (3) the growth of planktonic and attached algae requires some loss
of nutrients from the water mass.
There was found to be a direct relationship between iron and the growth
rate of algae (primary productivity) in the harbor and an inverse re-
lationship between nitrate and primary productivity (Fig. 72). This
can be explained by the fact that as iron concentration increases, algal
growth rate also increases. An accompanying decrease in nitrate occurs
as it is utilized by the growing population. When the available iron
has been utilized, the growth rate decreases, allowing a subsequent
increase in nitrate. This cycle would seem to indicate that iron is
currently the nutrient most limiting the growth of algae in the lagoon.
In general, this is in agreement with the findings of Goldman (1964);
300
-------
TABLE 36, NUTRIENTS/ PRIMARY PRODUCTIVITY, AND PHYTOPLANKTON BIOMASS AT THE
STAR HARBOR SAMPLING STATIONS, VALUES ARE AVERAGES OF NINE SAMPLES
TAKEN BETWEEN 14 APRIL 1970 AND 21 JANUARY 1971,
(MG OM •DAY'-'-)
STATION
1
2
3
4
5
6
7
NITRATE
(ug/l)
13,4
40,7
23,2
24,1
22,5
29,9
9,3
PHOSPHATE
(MS/I)
22,1
71,0
45,2
46,0
42,0
41,4
10,8
IRON
(pg/i)
61.5
92,1
73,9
55,7
65,0
64,5
13,3
PRIMARY
PRODUCTIVITY
2,484
4,303
2.167
3.434
4,214
3,810
1,514
BIOMASS
(OF ALGAE)
162,5
82,3
107,7
100,6
116,8
117,0
90,4
301
-------
u>
o
ro
90
- 80
en
=L
— 70
-------
PRIMARY PRODUCTIVITY
I I I I I
MAY JUNE JULY AUG SEPT OCT NOV DEC JAN
0.0
Figure 72. Nutrient-productivity relationships in Star Harbor. A direct relationship was
found between iron and primary productivity and an inverse relationship between
nitrate and primary productivity.
-------
Goldman and Armstrong (1969); and Goldman, Tunzi, and Armstrong (1969).
A biostimulation culture begun on 30 October 1970 shows that neither
Burton Creek nor Polaris Creek stimulate algae growth in Star Harbor
(Fig. 73). However, both creeks exhibit high stimulation of Lake Tahoe
water with Polaris Creek being more stimulating than Burton Creek
(Fig. 74). When water from the harbor was added to lake water, a sig-
nificant stimulation also occurred (Fig. 75). This indicates that with
the present rate of nutrient input and population growth, there would
be a stimulation of primary productivity in the lake when the harbor is
opened. However, the stimulation will not be as dramatic as in the cul-
tures, due to dilution and current patterns in the lake, and is probably
no greater than the influence of the streams alone. The cultures show
that there is now a marked difference between the quality of water in
the Star Harbor lagoon and that of the lake. Since the lagoon is mainly
a mixture of Burton and Polaris Creek water, this finding was expected,
Conclusions
Iron has been found to be the nutrient most limiting the growth of algae
within Star Harbor. This knowledge provides a reference point for future
management of the system. In any attempt to control the growth of aqua-
tic plants it is first necessary to determine what natural factors are
limiting their growth. Once this has been achieved, a workable program
may be developed to accurately trace the sources of these factors. Once
knowledge is gained of the inputs to a system, the community "metabolism"
of these inputs may be studied with a greater understanding. In the case
of Lake Tahoe where there is an interest in preventing further accelera-
ted algal growth, an investigation of the inputs, one of which being
Star Harbor, is essential in describing a nutrient budget for the lake.
It is stressed here that since iron has been found to be the limiting
304
-------
O
O
o
O
o>
•>
O
CO
300
200
o
o>
°- 100
O.I 1.0 10.0 O.I 1.0 10.0
BURTON CREEK POLARIS CREEK
Percent Creek Water Added to Star Harbor Water
Figure 73. Bioassay of Burton and Polaris Creek water additions to Star
Harbor water. Additions of 0.1%, 1.0% and 10.0% did not
stimulate algal growth.
305
-------
800
o 700
.§ 600
0
c_>
o
o 400
o
| 300
CO
^ c(J()
05
o
Q_ 100
-
—
—
—
—
iliiii
1111111;
Illllll
111111
III!!!
O.I 1.0 10.0 O.I • 1.0 10.0
BURTON CREEK POLARIS CREEK
Percent Creek Water Added to Lake Water
Figure 74. Bioassay of Burton and Polaris Creek water additions to Lake
Tahoe water. Additions of 0.1%, 1.0% and 10.0% showed high
stimulation of algal growth with Polaris Creek more stimulatory
than Burton Creek.
306
-------
1200
1100
1000
§ 900
800
o>
O
c
o
o
3
E
700
600
500
C/5
- 400
300
200
100
O.I 1.0 10.0
Percent Star Harbor Water Added to Lake Water
Figure 75. Bioassay of Star Harbor water additions to Lake Tahoe water,
Additions of 0.1%, 1.0% and 10.0% showed significant
stimulation of algal growth.
307
-------
nutrient, future research should be concerned with tracing the source
of iron to the streams and implementing a program to reduce the flow of
iron to the harbor and hence to the lake. It has been shown in this
study that the streams flowing into Star Harbor have a bio stimulatory
effect on the water of Lake Tahoe, therefore it is essential that the
nutrient concentrations in the streams be reduced, thereby minimizing
primary productivity within the channels.
Plots of iron versus productivity in this study suggested linearity
within the ranges measured, but the regressions performed did not pass
through zero. It is suggested that a nonlinear model which would pro-
duce a sigmoidal curve would be more realistic. At low light intensi-
ties and low nutrient levels, the decrease in productivity would be
more pronounced, and at high light intensities and high nutrient levels,
the rate of increase in productivity would begin to slow down. Once a
point is found where productivity would be the lowest with available
light and lowest nutrients, a valuable reference point in a management
study could be the result.
EFFECTS OF SALMON DECOMPOSITION ON THE ECOLOGY OF A SUBALPINE STREAM
Introduction
Juday et al. (1932) observed that Pacific salmon carcasses are important
in resupplying the oligotrophic ecosystems that constitute the nursery
areas of young salmon. Nelson and Edmondson (1955) assumed that great
quantities of nitrogen, phosphorus, and other important elements are
liberated by the decay of spawned-out salmon in Karluk and Bare Lakes,
Alaska. Odum (1959) suggested that the reduction in salmon runs has
led to an impoverishment of nursery watersheds. Nikolskii (1963) found
that the death of sockeye salmon in Lake Dalnie, Russia, led to an
increase in phosphate of 10-20 mg-l~ . Krokhin (1967), Donaldson (1967),
308
-------
and Hall (1972) have demonstrated the vital role of migratory fishes in
maintaining phosphorus reserves in the headwaters of spawning areas.
Narver (1967) felt that a primary production maximum in a salmon-rich
bay of Babine Lake, British Columbia, might be explained by an increase
in micronutrients from carcass decomposition. Mathisen (1971) concluded
that the decline in primary productivity of the lakes of the Nushagak
District, Alaska, was probably due to a substantial reduction in the
salmon escapement in the lakes. Donaldson (1967) and Mathisen (1972)
have postulated that periphyton act as a reservoir for nutrients re-
leased by decaying salmon.
It would appear that mineralization of dead salmon may play an important
role in the nutrient cycles and energy flow of the nursery watershed.
The study reported here presents some evidence directly linking changes
in nutrients and production to salmon runs in Taylor Creek, California.
Changes in autotrophic and heterotrophic production and water chemistry
were followed and related to the spawning and decomposition of the land-
locked sockeye, or kokanee, salmon (Onchorhynchus nerka).
Methods
Study Area -
Taylor Creek is a short (8 km), forested stream of the Tahoe drainage
basin (Fig. 1). Its source is the outflow of Fallen Leaf Lake, which
spills over a small concrete dam and drains into Lake Tahoe. The
stream is uniform in size throughout its length, with no significant
feeder streams. Because of the stream uniformity and because the dam
blocks any further salmon migration into Fallen Leaf Lake itself, it
was assumed that any difference in upstream-downstream biological or
mineral activity might be attributed to the salmon decomposition.
Accordingly, phosphate, nitrate, primary production, and heterotrophic
activity were monitored at monthly intervals from 1 October 1970 through
309
-------
4 September 1971 at lower, middle, and upstream stations. In January
1971, ammonia and iron were also assayed.
Analytical Methods -
Autotrophic carbon uptake by free-floating phytoplankton was measured
with the 14C method (Goldman 1963). Heterotrophic activity was measured
using 2-14C-acetate uptake (Paerl and Goldman 1972a). Samples were
collected in the field, kept cool in the dark, and transported back to
the laboratory for analysis.
Water from each station was collected in polyethylene jugs and frozen
until analysis. Nitrate was measured by cadmium reduction (Strickland
and Parsons 1968), phosphate by ammonium molybdate (Murphy and Riley
1962) with sulfuric acid used for the hydrolysis of the particulate
fraction, iron by bathyphenanthroline (Strickland and Parsons 1968), and
ammonia by a hypochlorite method (Strickland and Parsons 1968). Fil-
tration was at a low vacuum through acid-soaked and rinsed GFC filters.
Estimates of daily streamflow were obtained from the U.S. Geological
Survey. Spawner abundance (escapement) estimates were provided by the
California Department of Fish and Game.
Results
Visual Observations -
The kokanee salmon started to ascend Taylor Creek in late September and
October 1970, with the bulk of the spawning in November and December.
The accumulation of salmon carcasses reached a peak in January 1971 with
decomposition completed by the end of March. At middle Taylor and
especially at lower Taylor Creek, a very heavy bloom of the periphyton
Ulothrix occurred in January and February 1971. Escapement was estimated
at 14,000 fish and the average stream flow from October through March
310
-------
was 30.2 cfs.
Productivity -
Figure 76 shows the patterns of stream-borne phytoplankton carbon fix-
ation in 1970-71. There was little difference between stations, with
_2 _]^
values averaging 1-4 mg C-m 'hr . In January 1971, the time of peak
carcass decomposition, there was a distinct downstream increase, with a
-2 -1
maximum at the lower Taylor Creek station of 13.8 mg C'm -hr
Coinciding with the downstream peak of productivity in January 1971 was
a peak of heterotrophic activity (Fig. 76), except the gradient was
spread over December and February. Heterotrophic activity at upper
Taylor Creek remained very low until June, when it surpassed the other
stations. This is a time of much pleasure boating, hiking, and other
recreational activity on Fallen Leaf Lake and its watershed. The
heterotrophic activity is probably a reflection of increased organics
in the lake water entering the stream. *
chemistry -
A limnological survey of the streams of the Tahoe drainage basin in
1969-70 revealed a peak of phosphate in Taylor Creek at the time of
salmon spawning. This peak was not seen in the1 other, salmon-free,
streams of the basin at that time (Goldman 1970c ) • This nutrient pattern
was maintained during the 1970-71 study reported here. Nitrate concen-
trations increased downstream to a February maximum of 19 yg'l
(Fig. 77). By May Taylor Creek was relatively homogenous with respect
to nitrate at about 5 yg'l . The same general pattern was shown by
phosphate concentrations (Fig. 77). Values are erratic and might be
attributed to difficulties in the analysis (cf . Chamberlin and Shapiro
1973). However, downstream maximums of about 14 yg'l were observed
during the time of decomposition, while upstream values were only about
5 yg-1 . The stream also became uniform for phosphate by late spring.
311
-------
CO
16
*•—%
^ 12H
o
B>
* 8
"s
X
12-
2 «•
I I
B
A- A .A........ A........
O'N'D'J'FMAMJ'JA'S
Figure 76. Seasonal autotrophic and heterotrophic activity of Taylor Creek between October 1970
and September 1971. At lower (0), middle (D), and upper (A) stations.
-------
20
16-
I 12-
*
5
^> 8"
ae
4-
A
"A..
< A--"-^
"A-..
"••A
B
16
•
4H
• -A
—D
' D ' j 'FM'A
1970
IHI
1971
J JAS
Figure 77. Seasonal nitrate-nitrogen and phosphate-phosphorus between
October 1970 and September 1971. At lower (0), middle (p) ,
and upper (A) stations in Taylor Creek.
313
-------
Higher concentrations of both nitrate and phosphate were maintained
after the peak of carcass decomposition, possibly due to slow release of
nutrients by periphyton. In January, ammonia concentrations were 6, 26,
and 29 pg-l~ at the upper, middle, and downstream stations, respect-
ively. Iron concentrations were at the limit of concentration of 15
yg-1 at all stations.
An approximation of the phosphorus available through the decomposition
of salmon carcasses may be calculated from the streamflow and escapement
estimates. Assuming an average wet weight of 1750 g per fish with
0.364% phosphorus (Donaldson 1967), yields 8.92 x 10 yg from a salmon
run of 14,000 fish. The water volume over the time of the residence
of the salmon in the stream (October through March) was 1.34 x 10
liters, given the average flow rate of 30.2 cfs. Dilution of the phos-
phorus from the fish in that volume of water gives a final concentration
_i
of about 7 yg-1 . The approximate difference between upstream and
downstream concentrations of phosphate was 10 yg'l , so it would be
possible for the salmon decomposition to have supplied the difference.
Periphyton would have sequestered an unknown amount of phosphate and
nitrate.
Discussion
That the sockeye salmon are indeed responsible for modifying the ecology
of Taylor Creek might be inferred from: (1) An increase of phosphate in
Taylor Creek coincident with the salmon run, which was not observed at
the same time in other salmon-free streams of the basin. (2) Carbon
fixation, bacterial heterotrophy, and periphyton activity was greatest
at the peak of salmon decomposition in mid-winter (an unusual time for
heavy blooms). Both metabolism and nutrient concentrations were
greatest downstream at this time. The only difference noted between the
upstream and downstream stations was the presence of salmon.
314
-------
(3) Calculations show that the decomposition of salmon was sufficient to
account for the difference between upstream and downstream phosphorus.
From the above, some aspects of the role of the kokanee salmon in the
mineral and energy flows of Taylor Creek are clear. The salmon migrate
up Taylor Creek from Lake Tahoe to spawn and die. The presence of the
energy-rich carcasses stimulates bacterial activity, leading to the
release of inorganic nitrogen, phosphorus, and presumably many other
macro- and micronutrients. The minerals released stimulate a mid-
winter bloom of phytoplankton and periphyton. The periphyton hold the
nutrients in the spawning stream to be released slowly after the final
decay of the salmon. Bacterial and algal stimulation in Tahoe by trib-
utary inflow is now well documented in Lake Tahoe (Goldman et al. 1974).
These nutrients may be important in maintaining the fertility of the
nursery area of the lake adjacent to the stream mouth where the smolts
develop, after hatching and migrating to the lake.
315
-------
SECTION XIII
REFERENCES
Abrahamsson, S. 1973. The crayfish Astacus astacus in Sweden and the
introduction of the American crayfish Pacifastacus leniusculus,
p. 27-40. In_ S. Abrahamsson (ed<), Freshwater crayfish. Proc.
First Int. Symp. Freshwater Crayfish, Austria, September 1972.
Abrahamsson, S. and C. R. Goldman. 1970. Distribution, density and
production of the crayfish Pacifastacus leniusculus Dana in Lake
Tahoe, California-Nevada. Oikos 21:83-91.
Ahlstrom, E. H. 1940. A revision of the rotatorian genera Brachionus
and Platyias with descriptions of one new species and two new
varieties. Bull. Amer. Mus. Natur. Hist. 77:143-184.
Ahlstrom, E. H. 1943. A revision of the rotatorian genus Keratella
with descriptions of three new species and five new varieties.
Bull. Amer. Mus. Natur. Hist. 80:411-457.
American Public Health Association. 1965. Standard methods for the
examination of water and wastewater. 12th edition. New York.
769 p.
Amezaga, E. de, C. R. Goldman, and E. A. Stull. 1973. Primary pro-
ductivity and rate of change of biomass of various species of
phytoplankton in Castle Lake, California. Verh. Int. Verein.
Limnol. 18:1768-1775.
Anderson, D. V. and G. K. Rogers. 1963. A synoptic survey of Lake
Superior. Great Lakes Res. Div., Univ. Mich., Pub. No. 10:79-89-
Anderson, E. R. and D. W. Pritchard. 1951. Physical limnology of Lake
Mead. Rep. 258, Problem NEL 2J1. U.S. Navy Electronics Lab.,
San Diego. 152 p.
316
-------
Anderson, R. S. 1970. Predator-prey relationships and predation rates
for crustacean zooplankters from some lakes in western Canada.
Can. J. Zool. 48:1229-1240.
Anderson, R. S. 1972. Zooplankton composition and change in an alpine
lake. Verh. Int. Verein. Limnol. 18:264-268.
Armstrong, R., C. R. Goldman, and D. K. Fujita. 1971. A rapid method
for the estimation of the carbon content of seston and periphyton.
Limnol. Oceanogr. 16:137-139.
Ayers, J. C., D. C. Chandler, G. H. Lauff, C. F. Powers, and E. B.
Henson. 1958. Currents and water masses of Lake Michigan. Great
Lakes Res. Div., Univ. Mich., Pub. No. 3. 169 p.
Bateman, P. C. and C. Wahrhaftig. 1966. Geology of the Sierra Nevada.
Geology of northern California. E. H. Bailey (ed.). Calif. Div.
Mines Geol. Bull. 190:107-172.
Beauchamp, P. de. 1932. Contribution a letude de genre Ascomorpha et
des processus digestifs chez les rotifers. Bull. Soc. Zool. France
57:428-449.
Beeton, A. M. 1959. Photoreception in the opossum shrimp, Mysis
relicta Loven. Biol. Bull. 116:204-216.
Beeton, A. M. 1960. The vertical migration of Mysis relicta in Lakes
Huron and Michigan. J. Fish. Res. Board Can. 17:517-539-
Beeton, A. M. 1965. Eutrophication of the St. Lawrence Great Lakes.
Limnol. Oceanogr. 10:240-254.
Birkeland, P. W. 1964. Pleistocene glaciation of the northern Sierra
Nevada north of Lake Tahoe, California. J. Geol. 72:810-825.
Blegvad, H. 1914. Food and condition of nourishment among the communi-
ties of invertebrate animals found on or in the sea bottom in
Danish waters. Rep. Dan. Biol. Sta. 22:41-78.
Bormann, F. H., G. E. Likens, D. W. Fisher, and R. S. Pierce. 1968.
Nutrient loss accelerated by clear-cutting of a forest ecosystem.
Science 159:882-884.
Bradshaw, A. S. 1964. The crustacean zooplankton picture: Lake Erie
1939-49-59; Cayuga Lake 1910-51-61. Verh. Int. Verein. Limnol.
15:700-708.
317
-------
Brooks, J. L. 1968. The effects of preysize selection by lake plank-
tivores. Syst. Zool. 17:273-291.
Brooks, J. L. 1969. Eutrophication and changes in the composition of
the zooplankton, p. 236-255. In Eutrophication: causes, conse-
quences, correctives. Nat. Acad. Sci., Washington, D.C.
Brooks, J. L. and S. I. Dodson. 1965. Predation, body size, and com-
position of plankton. Science 150:28-35.
Burns, C. W. 1968. The relationship between body size of filter-feeding
Cladocera and the maximum size of particle ingested. Limnol.
Oceanogr. 13:675-678.
Carpenter, J. H. 1965. The Chesapeake Bay Institute technique for the
Winkler dissolved oxygen method. Limnol. Oceanogr. 10:141-143.
Chamberlin, W. and J. Shapiro. 1973. Phosphate measurements in natural
waters - a critique, p. 355-366. In E. Griffith, A. Beeton, J.
Spencer, and D. Mitchell (eds.)» Environmental phosphorus handbook.
Wiley, New York.
Coil, J. A. 1971. Primary productivity and limiting nutrients in a
Lake Tahoe harbor. M.S. Thesis. Univ. California, Davis. 81 p.
Cooper, C. F. 1969. Nutrient output from managed forests, p. 446-463.
In Eutrophication: causes, consequences, correctives. Nat. Acad.
Sci., Washington, D.C.
Cordone, A. J. , S. J. Nicola, P. H. Baker, and T. C. Frantz. 1971. The
kokanee salmon in Lake Tahoe. Calif. Fish Game 57:28-43.
Court, J. E., C. R. Goldman, and N. J. Hyne. 1972. Surface sediments
in Lake Tahoe, California-Nevada. J. Sediment. Petrol. 42:359-377.
Gulp, R. L. and H. E. Moyer. 1969. Wastewater reclamation and export
at South Tahoe. Civil Eng. 39(6):38-42.
Dodson, S. I. 1970. Complementary feeding niches sustained by size-
selective predation. Limnol. Oceanogr. 15:131-137.
Donaldson, J. R. 1967. The phosphorus budget of Iliamna Lake,
Alaska, as related to the cyclic abundance of sockeye salmon.
Ph.D. thesis. Univ. Washington. 141 p.
Donner, J. 1966. Rotifers. F. Warne, New York. 80 p.
318
-------
Downs, J. F. 1966. The two worlds of Washo, an Indian tribe of
California and Nevada. Holt, Rinehart, and Winston, New York.
113 p.
Dussart, B. 1948. Recherches hydrographiques sur le lac Leman.
Ann. Sta. Centre Hydrobiol. Appl. 2:187-206.
Edmondson, W. T. (Ed.). 1959. Fresh-water biology. 2nd edition.
Wiley, New York. 1248 p.
Fish, G. R. and M. A. Chapman. 1969. Synoptic surveys of lakes Rotorua
and Rotaih. New Zeal. J. Mar. Freshwat. Res. 3:571-584.
Fox, J. L., T. 0. Odlaug, and T. A. Olson. 1969. The ecology of peri-
phyton in western Lake Superior. Part I - taxonomy and distribu-
tion. Water Resourc. Res. Cent., Univ. Minn., Bull. No. 14. 127 p.
Frantz, T. C. and A. J. Cordone. 1966. A preliminary checklist of
invertebrates collected from Lake Tahoe, 1961-1964. Biol. Soc.
Nev., Occ. Pap. No. 8. 12 p.
Frantz, T. C. and A. J. Cordone. 1967. Observations on deepwater
plants in Lake Tahoe, California and Nevada. Ecology 48:709-714.
Frantz, T. C. and A. J. Cordone. 1970. Food of lake trout in Lake
Tahoe. Calif. Fish Game 56:21-35.
Furst, M. 1965. Experiments on the transplantation of Mysis relicta
Loven. Rep. Inst. Freshwat. Res. Drottingholm 46:79-89.
Galbraith, M. G. 1967. Size-selective predation on Daphnia by rainbow
trout and yellow perch. Trans. Amer. Fish. Soc. 96:1-10.
Clancy, P. A. 1971. A reconnaissance of streamflow and fluvial sedi-
ment transport, Incline Village area, Lake Tahoe, Nevada. First
Progress Rep., 1970. Nev. Dep. Conserv. Natur. Resourc., Water
Resourc. Div., Water Resourc. Inform. Ser. Rep. 8. 28 p.
)
Clancy, P. A. 1973. A reconnaissance of streamflow and-fluvial sediment
transport, Incline Village area, Lake Tahoe, Nevada. Second
Progress Rep., 1971. Nev. Dep. Conserv. Natur. Resourc., Water
Resourc. Div., Water Resourc. Inform. Ser. Rep. 19. 37 p.
Goldman, C. R. 1960. Molybdenum as a factor limiting primary produc-
tivity in Castle Lake, California. Science 132:1016-1017.
319
-------
Goldman, C. R. 1963. The measurement of primary productivity and
limiting factors in freshwater with carbon-14. In M. S. Doty (Ed.),
Proc. conf. primary productivity measurement, marine and freshwater,
U.S. Atomic Energy Commission, Div. Tech. Inform., TID-7633:103-113.
Goldman, C. R. 1964. Primary productivity and micronutrient limiting
factors in some North American and New Zealand lakes. Verh. Int.
Verein. Limnol. 15:365-374.
Goldman, C. R. 1968a. The use of absolute activity for eliminating
serious errors in the measurement of primary productivity with
C. J. du Conseil 32:172-179.
Goldman, C. R. 1968b. Aquatic primary production. Amer. Zool. 8:31-42.
Goldman, C. R. 1970a. Is the canary dying? - The time has come for
man, miner of the world's resources, to surface. Calif. Med. 113:
21-26.
Goldman, C. R. 1970b. Photosynthetic efficiency and diversity of a
natural phytoplankton population in Castle Lake, California,
p. 507-517. In Prediction and measurement of photosynthetic pro-
ductivity. Proc. IBP/PP Tech. Meeting, Trebon, Czechoslovakia,
September 1969.
Goldman, C. R. 1970c. Limnological conditions in Fallen Leaf Lake
and its effluent stream in relation to Lake Tahoe. Report to the
Fallen Leaf Lake Protection Association.
Goldman, C. R. 1972. The role of minor nutrients in limiting the pro-
ductivity of aquatic ecosystems, p. 21-33. ^n G. E. Likens (ed.),
Nutrients and eutrophication. Amer. Soc. Limnol. Oceanogr. Spec.
Symp., Vol. 1.
Goldman, C. R. 1973. Ecology and physiology of the California crayfish
Pacifastacus leniusculus (Dana) in relation to its suitability
for introduction into European waters, p. 105-120. In S. Abrahamsson
(ed.), Freshwater crayfish. Proc. First Int. Symp. Freshwater
Crayfish, Austria, September 1972.
Goldman, C. R. 1974. Trophic status and nutrient loading for Lake
Tahoe, California-Nevada. Preliminary report to the North
American Project of the Organization for Economic Cooperation and
Development (OECD).
Goldman, C. R. and E. de Amezaga. 1974. Primary productivity of the
littoral zone of Lake Tahoe, California-Nevada. Proc. Symp. Limnol.
Shallow Waters, Tihany, Hungary, September 1973 (in press).
320
-------
Goldman, G. R. and R. Armstrong. 1969. Primary productivity studies
in Lake Tahoe, California* Verh. Int. Verein. Liinnol. 17:49-71.
Goldman, C. R. and R. C. Carter. 1965. An investigation by rapid
carbon-14 bioassay of factors affecting the cultural eutrophication
of Lake Tahoe, California-Nevada. J. Water Pollut. Contr. Fed.
37:1044-1059.
Goldman, C. R. and J. E. Court. 1968. Limnological studies of Lake
Tahoe, p. 60-66. Jin J. R. Evans and R. A. Matthews (eds.)» Geologic
studies in the Lake Tahoe area, California and Nevada. Annu.
Fieldtrip Guidebook Geol. Soc. Sacramento.
Goldman, C. R. and D. K. Fujita. 1970. The response of naturally
occurring phytoplankton populations to NTA in Lake Tahoe, Castle
Lake and Clear Lake, California. Report to the Federal Water Quality
Administration,.
Goldman, C. R., M. Gerletti, P. Javornicky, V. Melchiorri-Santolini,
and E. de Amezaga. 1968. Primary productivity, bacteria, phyto-
and zooplankton in Lake Maggiore: correlations and relationships
with ecological factors. Mem. 1st. Ital. Idrobiol. 23:49-127.
Goldman, C. R. and D. T. Mason. 1962. Inorganic precipitation of
carbon in productivity experiments utilizing carbon-14. Science
136:1049-1050.
Goldman, C. R., D. T. Mason, and B. J. B. Wood. 1963. Light injury
and inhibition in Antarctic freshwater phytoplankton. Limnol.
Oceanogr. 8:313-322.
Goldman, C. R., G. A. Moshiri, and E. de Amezaga. 1972. Synoptic
study of accelerated eutrophication in Lake Tahoe - a subalpine
lake, p. 1-21. In R. S. Murphy and D. Nyquist (eds.), Water pollu-
tion control in cold climates. U.S. Gov. Printing Office, Washington,
D.C.
Goldman, C. R., R. C. Richards, H. W. Paerl, R. C. Wrigley, V. R.
Obert/eck, and W. L. Quaide. 1973. Aquatic studies and remote
sensing of the Upper Truckee River sediment plume in Lake Tahoe.
NASA Tech. Mem. TM X-62,238. 28 p.
Goldman, C. R., R. C. Richards, H. W. Paerl, R. C. Wrigley, V. R.
Oberbeck, and W. L. Quaide. 1974. Limnological studies and remote
sensing of the Upper Truckee River sediment plume in Lake Tahoe,
California-Nevada. Remote Sensing Environ. 3:49-67.
321
-------
Goldman, C. R., E. A. Stull, and E. de Amezaga. 1973. Vertical patterns
of primary productivity in Castle Lake, California. Verb. Int.
Verein. Limnol. 18:1760-1767.
Goldman, C. R., M. G. Tunzi, and R. Armstrong. 1969. Carbon-14 uptake
as a sensitive measure of the growth of algal cultures, p. 158-
170. In E. J. Middlebrooks, T. E. Maloney, C. F. Powers, and
L. M. Kaack (eds.)» Proc. eutrophication-biostimulation assessment
workshop. Berkeley, June 1969-
Goldman, C. R. and R. G. Wetzel. 1963. A study of the primary produc-
tivity of Clear Lake, Lake County, California. Ecology 44:283-294.
Gurney, R. 1931. British fresh-water Copepoda. Vol. 1, Calanoida.
Ray Soc., London. 238 p.
Gurney, R. 1933- British fresh-water Copepoda. Vol. 3, Cyclopoida.
Ray Soc., London. 384 p.
Hacker, P. W- 1973. The mixing of heat deduced from temperature fine
structure measurements in the Pacific Ocean and Lake Tahoe.
Ph. D. Thesis. Univ. California, San Diego. 121 p.
Hall, C. A. S. 1972. Migration and metabolism in a temperate stream
ecosystem. Ecology 53:585-604.
Holm-Hansen, 0. and H. W. Paerl. 1972. The applicability of ATP
determination for estimation of microbial biomass and metabolic
activity. Mem. 1st. Ital. Idrobiol. 29 Suppl.: 149-168.
Hrbacek, J. 1962. Species composition and the,amount of zooplankton
in relation to the fish stock. Roz. Cesk. Akad. Ved. 72(10).
116 p.
Hrbacek, J., M. Dvorakova, V. Korinek, and L. Prochazkova. 1961.
Demonstration of the effect of the fish stock on the species com-
position of zooplankton and the intensity of metabolism of the
whole plankton association. Verh. Int. Verein. Limnol. 14:192-195.
Humes, A. G. 1955- The postembryonic developmental stages of a
freshwater calonoid copepod, Epischura massachusettsensis Pease.
J. Morphol. 96:441-472.
Hutchinson, B. P. 1971. The effect of fish predation on the zooplank-
ton of ten Adirondack lakes, with particular reference to the
alewife, Alosa pseuddharangus. Trans. Amer. Fish. Soc. 100:325-
335.
322
-------
Hutchinson, G. E. 1957. A treatise on limnology. Vol. I. Geography,
physics, and chemistry. Wiley, New York. 1015 p.
Hutchinson, G. E. 1967. A treatise on limnology, Vol. II. Introduction
to lake biology and the limnoplankton. Wiley, New York. 1115 p.
Hyne, N. J., P. Chelminski, J. E. Court, D. S. Gorsline, and C. R.
Goldman. 1972. Quaternary history of Lake Tahoe, California-Nevada.
Geol. Soc. Amer. Bull. 83:1435-1448.
Hyne, N. J., C. R. Goldman, and J. E. Court. 1973. Mounds in Lake
Tahoe, California-Nevada: a model for landslide topography in the
subaqueous environment. J. Geol. 81:176-188.
Javornicky, P. and V. Prokesova. 1963. The influence of protozoa and
bacteria upon the oxidation of organic substrates in water. Int.
Rev. Hydrobiol. 48:335-350.
Juday, C. 1907. Notes on Lake Tahoe, its trout and trout fishing.
Bull. U.S. .Bur. Fish. 26:133-146.
Juday, C. and E. A. Birge. 1927. Pontoporeia and Mysis in Wisconsin
lakes. Ecology 8:445-452.
Juday, C. W., H. Rich, G. I. Kemmerer, and A. Mann. 1932. Limnological
studies of Karluk Lake, Alaska, 1926-1930. Bull. U.S. Bur. Fish.
57:407-436.
Judd, D. B. 1933. 1931 I.C.I, standard observer and coordinate
system for colorimetry. J. Opt. Soc. Amer. 23:359.
Kemmerer, G., J. F. Bovard, and W. R. Boorman. 1923. Northwestern
lakes of the United States. Biological and chemical studies with
reference to possibilities in production of fish. Bull. U.S. Bur.
Fish. 39:51-140.
Kiefer, D. A., 0. Holm-Hansen, C. R. Goldman, R. Richards, and T. Berman.
1972. Phytoplankton in Lake Tahoe: deep-living populations.
Limnol. Oceanogr. 17:418-422.
Kincaid, T. 1953. A contribution to the taxonomy and distribution of
the American fresh-water calanoid Crustacea. Calliostoma Co.,
Seattle. 74 p.
Koide, M., K. W. Bruland, and E. D. Goldberg. 1973. Th-228/Th-232 and
Pb-210 geochronologies in marine and lake sediments. Geochim.
Cosmochim. Acta. 37:1171-1187.
323
-------
Krokhin, E. M. 1967. Effect of size of escapement of sockeye salmon
spawners on the phosphate content of a nursery lake. Fish.
Res. Board Can. Transl. Ser. No. 1186:31-54.
La Rivers, I. 1962. Fishes and fisheries of Nevada. Nevada State
Fish and Game Commission. Carson City, Nevada. 782 p.
Larkin, P. A. 1948. Pontoporeia and Mysis in Athabaska, Great Bear
and Great Slave lakes. Bull. Fish. Res. Board Can. 78. 33 p.
Lasenby, D. C. and R. R. Langford. 1972. Growth, life history, and
respiration of Mysis relicta in an arctic and temperate lake.
J. Fish. Res. Board Can. 29:1701-1708.
Lasenby, D. C. and R. R. Langford. 1973. Feeding and assimilation of
Mysis relicta. Limnol. Oceanogr. 18:280-285.
Le Conte, J. 1883-1884. Physical studies of Lake Tahoe. I, II, III.
The Overland Monthly 1:506-516, 1:595-612, 3:41-46.
Leonard, R. and R. Coats. 1974. Precipitation and water quality in
the Ward Valley watershed, Lake Tahoe basin, California. Third
Nat. Conf. on Fire and Forest Meteorology of the Amer. Meteorol.
Soc. and Soc. of Amer. Foresters. Lake Tahoe, California, April
1974.
Likens, G. E. (Ed.). Nutrients and eutrophication. Amer. Soc. Limnol.
Oceanogr. Spec. Symp., Vol. 1. 328 p.
Linn, J. D. and T. C. Frantz. 1965. Introduction of the opossum shrimp
(Mysis relicta Loven) into California and Nevada. Calif. Fish.
Game 51:48-51.
Margalef, R. 1958. Information theory in ecology. Gen. Syst. 3:36-71.
Margalef, R. 1965. Ecological correlations and the relationship be-
tween primary productivity and community structure. Mem. 1st.
Ital. Idrobiol. 18 Suppl.:355-364.
Margalef, R. 1968. Perspectives in ecological theory. Univ. Chicago
Press, Chicago. Ill p.
Marsh, C. D. 1933. Synopsis of the calanoid crustaceans, exclusive
of the Diaptomidae, found in fresh and brackish waters, chiefly
of North America. Proc. U.S. Nat. Mus. 82, Art. 18. 58 p.
324
-------
Mathisen, 0. A. 1971. Escapement levels and productivity of the Nushagak
sockeye salmon runs from 1908 to 1966. Fish. Bull. 69:747-763.
Mathisen, 0. A. 1972. Biogenic enrichment of sockeye salmon lakes and
stock productivity. Verh. Int. Verein. Limnol. 18:1089-1095.
McGauhey, P. H., R. Eliassen, G. Rohlich, H. F. Ludwig, and E. A. Pearson.
1963. Comprehensive study on protection of water resources of
Lake Tahoe basin through controlled waste disposal. Prepared for
the Lake Tahoe Area Council. Engineering-Science, Inc., Oakland,
California. 157 p.
Menard, H. W. 1964. Marine geology of the Pacific. McGraw-Hill,
New York. 271 p.
Miller, G. C. 1960. The taxonomy and certain biological aspects of
the crayfish of Oregon and Washington. M.S. Thesis. Oregon State
Univ., Corvallis. 216 p.
Moshiri, G. A. and C. R. Goldman. 1969. Estimation of assimilation
efficiency in the crayfish, Pacifastacus leniusculus (Dana)
(Crustacea: Decapoda). Arch. Hydrobiol. 66:298-306.
Moshiri, G. A., C. R. Goldman, G. L. Godshalk, and D. R. Mull. 1970.
The effects of variations in oxygen tension on certain aspects of
respiratory metabolism in Pacifastacus leniusculus (Dana) (Crustacea:
Decapoda). Physiol. Zool. 43:23-29-
Moshiri, G. A., C. R. Goldman, D. R. Mull, G. L. Godshalk, and J. A.
Coil. 1971. Respiratory metabolism in Pacifastacus leniusculus
(Dana) (Crustacea: Decapoda) as related to its ecology. Hydro-
biologia 37:183-195.
Mundie, J. A. 1959. The diurnal activity of the larger invertebrates
at the surface of Loc La lange, Saskatchewan. Can J. Zool. 37:
945-956.
Munsell Color Company. 1967. Munsell Book of Color. 12th ed. Baltimore.
Murphy, J. and J. P. Riley. 1962. A modified single solution method
for the determination of phosphate in natural waters. Anal. Chim.
Acta. 27:31-36.
Narver, D. W. 1967. Primary productivity in the Babine Lake system,
British Columbia. J. Fish. Res. Board Can. 24:2045-2052.
325
-------
Nelson, P. R. and W- T. Edmondson. 1955. Limnological effects of
fertilizing Bare Lake, Alaska. U.S. Fish Wildl. Serv. Fish
Bull. 56:413-436.
Newhall, S. M., D. Nickerson, and D. B. Judd. 1943. Final report of
the O.S.A. subcommittee on the spacing of Munsell colors. J. Opt.
Soc. Amer. 33:385-418.
Nikolskii, G. V. 1963. The ecology of fishes. 2nd edition. Academic
Press, New York. 352 p.
Northcote, T. G. 1972. Some effects of mysid introduction and nutrient
enrichment on a large oligotrophic lake and its salmonids. Verh.
Int. Verein. Limnol. 18:1096-1106.
Numann, V. 1938. Die Verbreitund des Rheinwassers in Bodensee. Int.
Rev. Hydrobiol. 36:501-530.
Odum, E. P. 1959. Fundamentals of ecology. Saunders, Philadelphia.
546 p.
Optical Society of America. 1953. The science of color. Crowell,
New York. 385 p.
Paerl, H. W. i973a. The regulation of heterotrophic activity by
environmental factors in Lake Tahoe, California-Nevada. Ph.D.
Thesis. Univ. California, Davis. 139 p.
Paerl, H. W. 1973b. Detritus in Lake Tahoe: structural modification
by attached microflora. Science 180:496-498.
Paerl, H. W. 1974. Bacterial uptake of dissolved organic matter in
relation to detrital aggregation in marine and freshwater systems.
Limnol. Oceanogr. (in press).
Paerl, H. W. and C. R. Goldman. 1972a. Heterotrophic assays in the
detection of water masses at Lake Tahoe, California. Limnol.
Oceanogr. 17:145-148.
Paerl, H. W. and C. R. Goldman. 1972b. Stimulation of heterotrophic
and autotrophic activities of a planktonic microbial community
by siltation at Lake Tahoe, California. Mem. 1st. Ital. Idrobiol.
29 Suppl.:129-147.
Paerl, H. W., R. C. Richards, R. L. Leonard, and C. R. Goldman. 1974.
Seasonal nitrate cycling as evidence for complete vertical mixing
in Lake Tahoe, California-Nevada. Limnol. Oceanogr. (in press).
326
-------
Pennack, R. W. 1953. Freshwater invertebrates of the United States.
Ronald Press, New York. 769 p.
Perkins, M. A., C. R. Goldman, and R. L. Leonard. 1974. Residual
nutrient discharge in streamwaters influenced by sewage effluent
spraying. Ecology (in press).
Petzold, T. J. and R. W. Austin. 1968. An underwater transmissometer
for ocean survey work. Scripps Inst. Oceanogr., Univ. Calif.,
Ref. Rep. No. 68-9. 7 p.
Rawson, D. S. 1961. The lake trout of Lac La Ronge, Saskatchewan.
J. Fish. Res. Board Can. 18:423-462.
Reif, C. B. and D. W. Tappa. 1966. Selective predation: smelt and
cladocerans in Harveys Lake. Limnol. Oceanogr. 11:437-438.
Reimers, N. 1958. Conditions of existence, growth, and longevity of
brook trout in a small, high-altitude lake of the eastern Sierra
Nevada. Calif. Fish Game 44:319-333.
Richerson, P. J. 1969. Community ecology of the Lake Tahoe plankton.
Ph.D. Thesis. Univ. California, Davis. Ill p.
Richerson, P. J., R. Armstrong, and C. R. Goldman. 1970. Contemporaneous
disequilibrium, a new hypothesis to explain the "paradox of the
plankton." Proc. Nat. Acad. Sci. 67:1710-1714.
Richerson, P. J., G. A. Moshiri, and G. L. Godshalk. 1970. Certain
ecological aspects of pollen dispersion in Lake Tahoe (California-
Nevada) . Limnol. Oceanogr. 15:149-153.
Robertson, A., C. F. Powers, and R. F. Anderson. 1968. Direct obser-
vations on Mysis relicta from a submarine. Limnol. Oceanogr. 13:
700-702.
Rodina, A. G. 1963. Microbiology of detritus in lakes. Limnol. Oceanogr.
8:388-393.
Rouse, H. and J. Dodu. 1955. Turbulent diffusion across a density
discontinuity. Hoville Blanche 10:522-532.
Saunders, G. W., F. B. Trama, and R. W. Bachmann. 1962. Evaluation of
a modified 14c technique for shipboard estimation of photosynthesis
in large lakes. Great Lakes Res. Div., Univ. Mich., Pub. No. 8.
61 p.
327
-------
Schumacher, R. E. 1966. Successful introduction of Mysis relicta
(Loven) into a Minnesota lake. Trans. Amer. Fish. Soc. 95:216.
Smith, R. C., J. E. Tyler, and C. R. Goldman. 1973. Optical properties
and color of Lake Tahoe and Crater Lake. Limnol. Oceanogr. 18:
189-199.
Smith, W. F. 1970. Tolerance of Mysis relicta to thermal shock and
light. Trans. Amer. Fish. Soc. 99:418-422.
Sorokin, Y. I. 1959. Determination of the photosynthetic productivity
of phytoplankton in water using C-14 (in Russian). Fiziol. Rast.
6:125-133.
Sorokin, Y. I. 1966. Carbon-14 methods in the study of the nutrition
of aquatic animals. Int. Rev. Hydrobiol. 51:209-224.
Sparrow, R. A. H., P. A. Larkin, and R. A. Rutherglen. 1964. Successful
introduction of Mysis relicta Loven into Kootenay Lake, British
Columbia. J. Fish. Res. Board Can. 21:1325-1327.
State of California Resources Agency. 1969. Sedimentation and erosion
in the Upper Truckee and Trout Creek watershed. Rep. Calif. Dep.
Conserv. - Div. Soil Conserv July 1969. 43 p.
Steemann Nielson, E. 1952. The use of radioactive carbon (^C) for
measuring organic production in the sea. J. du Conseil. 18:117-140
Strickland, J. D. H. and T. R. Parsons. 1968. A practical handbook
of seawater analysis. Bull. Fish. Res. Board Can. 167. 311 p.
Svardson, G. 1949. Stunted crayfish populations in Sweden. Rep. Inst.
Freshwat. Res. Drottingholm 29:135-145.
Turner, J. S. and E. B. Kraus. 1967. A one-dimensional model of the
seasonal thermocline. I. A laboratory experiment and its inter-
pretation. Tellus 19:88-97.
Tyler, J. E. and R. C. Smith. 1966. Submersible spectroradiometer.
J. Opt. Soc. Amer. 56:1390-1396.
Tyler, J. E. and R. C. Smith. 1970. Measurements of spectral irradi-
ance underwater. Gordon and Breach, New York. 103 p.
Voigt, M. 1957. Rotatoria. Die Radertiere Mitteleuropus. Borntraeger,
Berlin. 2 vol.
328
-------
Ward, H. B. 1904. A biological reconnaissance of some elevated lakes
in the Sierras and Rockies. Amer. Microscop. Soc. Trans. 25:
127-154.
Wells, L. 1960. Seasonal abundance and vertical movements of plank-
tonic Crustacea in Lake Michigan. U.S. Fish. Wildl. Serv., Fish.
Bull. 60:343-369.
Wells, L. 1970. Effects of alewife predation on zooplankton popu-
lations in Lake Michigan. Limnol. Oceanogr. 15:556-565-
Wong, B. and F. J. Ward. 1972. Size selection of Daphnia pulicaria
by yellow perch (Perca flavescens) fry in West Blue Lake,
Manitoba. J. Fish. Res. Board Can. 29:1761-1764.
ZoBell, G. E. 1946. Marine microbiology. Chronica Botanica, Waltham,
Mass. 240 p.
Zyblut, E. R. 1970. Long-term changes in the limnology and macrozoo-
plankton of a large British Columbia lake. J. Fish. Res. Board
Can. 27:1239-1250.
329
-------
SECTION XIV
PUBLICATIONS, MANUSCRIPTS, REPORTS, AND THESES
Published
Abrahamsson, S. and C. R. Goldman. 1970. Distribution, density, and
production of the crayfish Pacifastacus leniusculus Dana in Lake
Tahoe, California-Nevada. Oikos 21:83-91.
Armstrong, R. and C. R. Goldman. 1969. Determination of trace amounts
of molybdenum. Amer. Soc. Test. Mater., Microorg. Matter Water,
Spec. Tech. Pub. No. 448:116-124.
Armstrong, R., C. R. Goldman, and D. K. Fujita. 1971. A rapid method
for the estimation of the carbon content of seston and periphyton.
Limnol. Oceanogr. 16:137-139.
Arvesen, J. C., E. C. Weaver, and J. P. Millard. 1971. Rapid assess-
ment of water pollution by airborne measurement of chlorophyll
content. Amer. Inst. Aeron. Astron. Paper No. 71-1097. 7 p.
Court, J. E., C. R. Goldman, and N. J. Hyne. 1972. Surface sediments
in Lake Tahoe, California-Nevada. J. Sediment. Petrol. 42:359-377.
Goldman, C. R. 1967. The bad news from Lake Tahoe, California. Cry
Calif. 3(1):12-23.
Goldman, C. R. 1970. Is the canary dying? - The time has come for man,
miner of the world's resources, to surface. Calif. Med. 113:21-26.
Goldman, C. R. 1972. The role of minor nutrients in limiting the pro-
ductivity of aquatic ecosystems, p. 21-33. In G. E. Likens (ed.),
Nutrients and eutrophication, Amer. Soc. Limnol. Oceanogr. Spec.
Synp., Vol. 1.
330
-------
Goldman, C. R. 1973. Ecology and physiology of the California crayfish
Pacifastacus leniusculus (Dana) in relation to its suitability for
introduction into European waters, p. 105-120. ^n S. Abrahamsson
(ed.)> Freshwater Crayfish. Proc. First Int. Symp. Freshwater
Crayfish, Austria, September 1972.
Goldman, C. R. and R. Armstrong. 1969. Primary productivity studies
in Lake Tahoe, California. Verh. Int. Verein. Limnol. 17:49-71.
Goldman, C. R. and J. E. Court. 1968. Limnological studies of Lake
Tahoe, p. 60-66. In J. R. Evans and R. A. Matthews (eds.), Geologic
studies in the Lake Tahoe area, California-Nevada. Geol. Soc.
Sacramento Annual Fieldtrip Guidebook.
Goldman, C. R. and R. L. Leonard. 1972. The Lake Tahoe microcosm: an
ecosystem out of balance. Proc. West. Agr. Econ. Assoc. 44:251-
254.
Goldman, C. R., G. A. Moshiri, and E. de Amezaga. 1972. Synoptic study
of accelerated eutrophication in Lake Tahoe - a subalpine lake,
p. 1-21. In. R. S. Murphy and D. Nyquist (eds.), Water pollution
control in cold climates. E.P.A. U.S. Gov. Printing Office,
Washington, D.C.
Goldman, C. R., R. C. Richards, H. W. Paerl, R. C. Wrigley, V. R.
Oberbeck, and W. L. Quaide. 1973. Aquatic studies and remote
sensing of the Upper Truckee River sediment plume in Lake Tahoe.
NASA Tech. Mem. TM X-62,238. 28 p.
Goldman, C. R., R. C. Richards, H. W. Paerl, R. C. Wrigley, V. R.
Oberbeck, and W. L. Quaide. 1974. Limnological studies and
remote sensing of the Upper Truckee River sediment plume in Lake
Tahoe, California-Nevada; Remote Sensing Environ. 3:49-67.
Goldman, C. R., M. G. Tunzi, and R. Armstrong. 1969- Carbon-14 uptake
as a sensitive measurement of the growth of algal cultures, p.
158-170. ^n Proc. eutroph. biostim. assess, workshop, limnol.
invest, sess., Berkeley, California, June 1969.
Holm-Hansen, 0. 1972. The distribution and chemical composition of
particulate matter in marine and fresh waters. Mem. 1st. Ital.
Idrobiol. 29 Suppl.:37-51.
Holm-Hansen, 0. and H. W. Paerl. 1972. The applicability of ATP deter-
mination for estimation of microbial biomass and metabolic activity.
Mem. 1st. Ital. Idrobiol. 29 Suppl.:149-168.
331
-------
Hyne, N. J. , P. Chelminski, J. E. Court, D. S. Gorsline, and C. R.
Goldman. 1972. Quaternary history of Lake Tahoe, California-Nevada.
Geol. Soc. Amer. Bull. 83:1435-1448.
Hyne, N. J.,' C. R. Goldman, and J. E. Court. 1973. Mounds in Lake Tahoe,
California-Nevada: a model for landslide topography in the subaque-
ous environment. J. Geol. 81:176-188.
Kiefer, D., 0. Holm-Hansen, C. R. Goldman, R. C. Richards, and T.
Berman. 1972. Phytoplankton in Lake Tahoe: deep-living popula-
tions. Limnol. Oceanogr. 17:418-422.
Koide, M., K. W. Bruland, and E. D. Goldberg. 1973. Th-228/Th-232 and
Pb-210 geochronologies in marine and lake sediments. Geochim.
Cosmochim. Acta. 37:1171-1187.
Moshiri, G. A. and C. R. Goldman. 1969. Estimation of assimilation
efficiency in the crayfish, Pacifastacus leniusculus (Dana)
(Crustacea: Decapoda). Arch. Hydrobiol. 66:298-306.
Moshiri, G. A., C. R. Goldman, G. L. Godshalk, and D. R. Mull. 1970.
The effects of variation in oxygen tension on certain aspects of
respiratory metabolism in Pacifastacus leniusculus (Dana)
(Crustacea: Decapoda). Physiol. Zool. 43:23-29.
Moshiri, G. A., C. R. Goldman, D. R. Mull, G. L. Godshalk, and J. A.
Coil. 1971. Respiratory metabolism in Pacifastacus leniusculus
(Dana) (Crustacea: Decapoda) as related to its ecology.
Hydrobiologia 37:183-195.
Paerl, H. W. and C. R. Goldman. 1972. Heterotrophic assays in the
detection of water masses at Lake Tahoe, California. Limnol.
Oceanogr. 17:145-148.
Paerl, H. W. and C. R. Goldman. 1972. Stimulation of heterotrophic
and autotrophic activities of a planktonic microbial community
by siltation at Lake Tahoe, California. Mem. 1st. Ital. Idrobiol.
29 Suppl.:129-147.
Richerson, P., R. Armstrong, and C. R. Goldman. 1970. Contemporaneous
disequilibrium, a new hypothesis to explain the "paradox of the
plankton". Proc. Nat. Acad. Sci. 67:1710-1714.
Richerson, P., G. A. Moshiri, and G. L. Godshalk. 1970- Certain
ecological aspects of pollen dispersion in Lake Tahoe (California-
Nevada) . Limnol. Oceanogr. 15:149-153.
332
-------
Sanford, G. R., A. Sands, and C. R. Goldman. 1969. A settle-freeze
method for concentrating phytoplankton in quantitative studies.
Limnol. Oceanogr. 14:790-794.
Smith, R. C., J. E. Tyler, and C. R. Goldman. 1973. Optical properties
and color of Lake Tahoe and Crater Lake. Limnol. Oceanogr. 18:
189-199.
In Press
Goldman, C. R. and E. de Amezaga. Primary productivity of the littoral
zone of Lake Tahoe, California-Nevada. (Proc. Symp. Limnol.
Shallow Waters, Tihany, Hungary, September 1973).
Perkins, M. A., C. R. Goldman, and R. L. Leonard. Residual nutrient
discharge in streamwaters influenced by sewage effluent spraying
(Ecology).
In Preparation
Godden, D. B., T. M. Powell, L. 0. Myrup, and C. R. Goldman. Climatolog-
ical estimates of the energy budget of Lake Tahoe, 1967-1970.
Goldman, C. R. and E. de Amezaga. Vertical and temporal changes in
primary productivity in Lake Tahoe, California-Nevada, 1959-1971.
(Verh. Int. Verein. Limnol.).
Goldman, C. R., L. 0. Myrup, and T. M. Powell. Cultural eutrophication
and a decrease in the heat budget of Lake Tahoe, California-Nevada.
Hacker, P. W. and C. R. Goldman. Vertical temperature structure in
Lake Tahoe, California-Nevada. (Limnol. Oceanogr.)
Holm-Hansen, 0., C. R. Goldman, R. C. Richards, and P. M. Williams.
Chemical and biological characteristics of a water column in Lake
Tahoe, California. (Limnol. Oceanogr.)
Powell, T. M. Vertical turbulent transport in stratified regions of
lakes. (Verh. Int. Verein. Limnol.)
Richards, R. C., C. R. Goldman, T. Frantz, and R. Wickwire. Where
have all the Daphnia gone? - Decline of a major cladoceran in
Lake Tahoe, California-Nevada. (Verh. Int. Verein. Limnol.).
333
-------
Richey, J. E., M. A. Perkins, and C. R. Goldman. Effects of salmon
decomposition on the ecology of a subalpine stream.
Tilzer, M. M., C. R. Goldman,aand E. de Amezaga. The efficiency of
photosynthetic light energy utilization by lake phytoplankton.
(Verh. Int. Verein. Limnol.).
Williams, N. J. and C. R. Goldman. Some aspects of lake phytoplankton
community structure. (Verh. Int. Verein. Limnol.).
Williams, N. J. and P. J. Richerson. The importance of small scale
zooplankton patchiness on the structural and functional dynamics
of plankton communities. (Limnol. Oceanogr.).
Projected
Fujita, D. K., C. R. Goldman, J. F. Elder, and R. C. Richards. Aerial
dispersion of nitrogen stripped by tertiary treatment in the Lake
Tahoe basin.
Weaver, E. C., J. C. Arvesen, C. R. Goldman, and R. C. Richards. Air-
borne remote sensing of chlorophyll in Lake Tahoe, California.
Reports
Goldman, C. R. 1968. The carbon-14 bioassay technique for measuring
algal growth in laboratory and field. Algal Growth Potential
Task Force (FWPCA).
Goldman, C. R. 1970. Siltation and the eutrophication of Lake Tahoe,
California-Nevada. Lahontan Water Quality Control Board.
Goldman, C. R. 1970. Taconite tailings as a biostimulant for algal
growth in Lake Superior. Lake Superior Enforcement Conference
(FWQA).
Goldman, C. R. and D. K. Fujita. 1970. The response of naturally
occurring phytoplankton populations to NTA in Lake Tahoe, Castle
Lake and Clear Lake, California. (FWQA)
334
-------
Theses
Agee, B. 1974. An analytical model of the dynamics of Lake Tahoe
phytoplankton. M.S. Thesis. Univ. California, Davis. In
Preparation.
Coil, J. A. 1971. Primary productivity and limiting nutrients in a
Lake Tahoe harbor. M.S. Thesis. Univ. California, Davis. 81 p.
Hacker, P. W. 1973. The mixing of heat deduced from temperature
fine structure measurements in the Pacific Ocean and Lake Tahoe.
Ph.D. Thesis. Univ. California, San Diego. 121 p.
Paerl, H. W. 1973. The regulation of heterotrophic activity by envir-
onmental factors in Lake Tahoe, California-Nevada. Ph.D. Thesis.
Univ. California, Davis. 139 p.
Richerson, P. J. 1969- Community ecology of the Lake Tahoe plankton.
Ph.D. Thesis. Univ. California, Davis. Ill p.
335
-------
SECTION XV
APPENDICES
Appendix Page
A Lake Tahoe Temperature-Depth Profiles 337
B Lake Tahoe Primary Productivity-Depth Profiles 346
C Lake Tahoe Phytoplankton Species Numbers 357
D Lake Tahoe Total Phytoplankton Biomass-Depth
Profiles 372
E Lake Tahoe Water Chemistry Methods 379
336
-------
APPENDIX A
LAKE TAHOE TEMPERATURE-DEPTH PROFILES
Temperature (°C) vs. sampling depth at the index station of Lake Tahoe,
1967-1970.
337
-------
LAKE T»Hf)E (967 «» *«* TEMPEM T I'NE PHOFILES*****
OJ
Ul
00
DEPTH
(M)
0.
3.
6.
9.
12.
IS.
18.
21.
20.
27.
30.
33,
36.
39.
42.
45.
48.
51.
54.
57.
60.
63.
66.
69.
72.
75.
78,
SI.
B4.
87.
90.
93.
96.
99,
102.
105.
108.
llli
114.
ti7.
120.
123.
126.
12».
132.
135.
8/ 9
19.25
19.00
19,00
18.75
18.75
18.50
15.75
11.75
10.25
9.25
8.75
7.75
7.25
6.75
6.75
6.25
6.25
6.25
5.75
5,75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5,75
5.75
5.75
5.75
8/25
20.50
20.50
20.00
20.00
20.00
19.50
14.00
12.00
10.50
8.50
8.00
7.25
6.75
6.50
6.00
5.75
5.50
5.25
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
.75
.75
.75
.75
,75
.75
.75
.75
.75
,75
.75
.75
.75
.75
.75
9/ 2
20.00
19.50
19.50
19.00
19.00
18.50
15.00
13.00
12.00
.50
.50
.00
,00
.50
.25
.00
6.00
5.75
5.75
5,50
5.50
5.50
5.50
5.25
5,00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
9/ 7
19.00
18. 5U
18.00
17,50
11-00
16.50
12.50
10,50
10.00
9.00
S.50
8.00
7.50
7.00
6.50
6.50
6.00
6.00
6.00
5.75
5.50
5.50
5.25
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5,00
5,00
5.00
5.00
5.00
9/14
lB,r>o
17. SO
17.50
17.50
17.75
I7.no
17.00
14. GO
9.50
8.00
7.50
7.00
6.50
6.00
5.75
5.75
5.50
5.50
5.25
5.25
5.00
S.C'O
5.00
5.00
5.00
5.UO
5,00
5.UO
5.00
5.00
5-. 00
5.00
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
9/21
16. 50
16,50
16.50
16.50
16.25
16.25
16.25
16.00
10.00
9.00
7.50
7.00
6.50
6.25
6.25
6.00
5.75
5.50
5.50
5.50
5.50
5.25
5.00
5.00
5.00
5rOO
5.00
5.00
5.00
5.00
5. OP
4.75
.75
.75
.75
,75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
9/23
16.50
16.50
16.50
16.50
16.25
16.00
14.50
12.75
11.00
10.00
9.00
H.50
r.50
6,50
A. 00
6.00
5.75
5.50
5.50
5.00
5.00
5.00
5.00
5.00
5.00
4,75
4.75
.75
.75
.75
.75
.50
.50
.50
.50
.50
.50
.50
,50
,50
,50
,50
,50
.50
.50
,50
ll/ 1
11.50
11 .50
11 .50
11.50
1 1.50
11.50
11 .50
11 .50
11.25
11.25
11.25
11 .00
10.50
10.00
9.50
9.00
S.50
7.50
7.00
6.25
A. 25
6.00
5.75
5.50
5.25
5.25
5.00
5.00
5.00
5.00
5.00
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
4.75
4.75
4.75
11/15
10. bO
10. 50
10. 50
10. '30
1000
10. SO
lll.^S
10.35
10.25
10.25
10.25
10.25
10.10
•J.75
9.75
•Joo
'.25
9.2i
9.1)0
fl.'jO
a. oo
r.<>3
7.00
6.30
6,00
5.75
5.50
5.50
5.25
5.25
5.00
5.00
5.00
4.75
4. '5
4.fS
4.75
4.75
.75
.75
.75
.75
.75
.75
.75
.75
12/ I
4,5)
4. VI
<*.S-|
"•<>0
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'.75
'.7,
'.50
'.51
'.SO
'.5)
'.V)
7.25
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7.00
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6,75
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6.5J
6.25
6. 25
6.00
6.0.)
5.75
5.5!)
b.50
5.25
5.25
5.00
i.OO
5.00
4.75
4.75
4.73
4.75
4.7S
4.75
4.7-J
4.75
4.73
4.75
t.75
4.75
-------
LAKC TAHOE 1968 ««*»*TEMPERtTUPE PROFILES*****
DEPTH
(M)
0.
3.
6.
9.
12.
15.
18.
21.
24.
27.
30.
33.
36.
39.
42.
45.
48.
51.
54.
57.
60.
63.
66.
69.
72.
75.
78.
81.
84.
87.
»0.
93.
96.
99.
102.
los.
108.
Ill'
114.
117.
120'
123.
126.
129.
132.
135.
1/24
.75
.75
.75
.75
.75
.75
.75
.75
.50
.50
.So
.50
.So
.50
.50
.50
.So
.50
.50
.50
.50
.So
• So
• SO
.50
• 50
• So
• So
• So
• SO
.So
• So
• So
• So
• So
• So
• So
• So
.50
.50
.So
• So
• So
• So
.50
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?/ 8
5.00
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.50
.50
.50
.50
.50
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.50
.50
• SO
• So
.50
• So '
• SO
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.50
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.50
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.50
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• So
• 50
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• So
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• 50
• so
• 50
• 50
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.50
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.50
• 50
>/14 ,
.50
.50
.50
.50
.50
.50
.50
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.no 7. or 7.75 ft. 00 .75 9.50
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4.75 5.00 6.25 5.75 5.75 5.75
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4.5C 5.00 e.25 5.75 5.75 5.75
4.50 5.ot 6.00 5.75 5.75 5.75
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».50 .75 5.50 5.25 5.25 5.25
-------
LAKE TAHOE 1968 ***«*TEMPEKATURE PROFILES*****
DEPTH 6/12 6/19 6/26 7/ 4 7/U 7/17 //24 7/31 8/ ,' »>/12 y/ ? /?6 10/lb 10/19 10/27 ll/ 2 12/ 1
0.
3.
6.
9.
12.
15.
18,
21.
24.
27.
30.
33.
36.
39.
42.
45.
48.
51.
54.
57.
UO 60,
.p- 63.
O 66.
69.
72.
75.
78.
81.
84.
87.
90.
93.
96,
99.
102*
105.
108.
111.
114.
117.
120.
123.
129*
132.
135.
10.50
10.25
10.25
10.00
9.75
9.50
9.25
8.75
8.50
8.25
8.00
7.75
7.50
7.25
6.75
6.50
6.25
6.25
6.25
6.00
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
15.00
14.00
12.75
12.50
11.50
10.75
10.50
10.25
10.00
9.75
9.75
9.50
8.75
8.25
7.75
7.50
7.25
7.25
7.00
6,75
6.75
6.50
6.25
6,25
6,00
6.00
5.75
5.75
5.75
5.75
5.75
5.75
5.50
5.50
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
15.25
15.00
14.75
14.00
13.50
12.50
11.25
10.75
9.75
9.75
9.5a
8.75
8.25
8.00
7.50
7.00
6.75
6.75
6.50
6.25
6.25
6.00
5.75
5.75
5.75
5.75
5.75
5.75
5.53
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
15.50
15.25
15.25
15.00
14.50
13,50
13,00
12,00
10.75
10.00
9.25
8.75
8.50
8.00
8.00
7.75
7.50
7.25
7.00
6.75
6.75
6.75
6.50
6.50
6.25
6.25
6.00
5.75
5.7S
5.75
5.7s
5.7s
5.75
5.5Q
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5,50
5.50
5.5d
5.50
16.75
1«.50
15.50
14.25
13.25
12.75
12.25
12.00
11.25
10.25
9.75
9.23
8.50
8.00
7.5')
7..)')
6.75
6.75
6.50
6.50
6.25
6.25
6.00
6,00
5.75
5.75
5.75
5.75
5.'5
5.50
5.51
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5,50
5,50
5.50
5.50
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
16.00
15.75
15.25
14.75
14.75
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14. 25
13.00
(2.50
11.75
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9.75
8.75
8.50
8.25
8.00
7.50
7.25
7.25
7.00
6.75
6.50
6,50
6.25
6.25
6.?5
6.00
6.01
5.75
5.-75
5.75
5.75
5.50
5.5')
5.50
5.50
5.25
5.25
5.25
5.25
•5.25
5.25
5.25
5.25
5.2b
17,00
t • 00
1.50
1.25
1.00
7.50
7.00
7.00
6.75
6.50
6,50
6.25
•i.OO
4.00
5.75
5.75
•i.75
'•..50
5.50
5.50
s.25
5.25
5.25
S.25
5.25
S.25
5.00
5.00
s.on
5.00
s.oo
5.00
5.00
5.00
5.00
1-V.OO
18.75
11.75
17.50
15.50
13.50
13.00
11.50
10.50
10.00
9.50
"•00
H.75
«.50
K.PO
7.75
7.50
7.25
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7.00
6.75
6.50
6.50
6.25
6.25
6.25
6.25
6.00
6.00
6.00
6.00
6.00
5.75
5.75
5.75
5.75
5.75
5.75
5.75
S.75
S.75
5.75
5.75
S.75
5.75
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18.7')
1«. 50
18.00
17.bt>
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15.uO
13.50
12.50
11. ('0
10.50
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8.50
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7,/S
7.50
7.yb
7.0t;
6.75
6.b(
6 .
-------
LAKE TAHOE 1968 ****«TEMPERATI)RE PROFILES*****
DEPTH
CM)
0.
3.
6.
9.
12.
15.
18.
21.
24.
27.
30.
33.
36.
39.
42.
45.
48.
51.
54,
5?.
60.
63.
66,
69,
72.
75,
78.
81.
84,
87.
90.
93.
96.
99.
102.
105,
108,
111.
114.
117.
120.
123.
126.
129.
132.
135.
12/ 7 12/22
8.75 7,00
8.75 7.00
8.75 7.00
8.50 7.00
8.50 7.00
8,50 7.00
8.50 7.00
8.50 7,00
8,50
8.50
8.50
8.50
8.50
8.50
8.50
8.50
8.50
8.50
8.50
8.50
8.25
8.25
8.00
8.00
7.75
7,50
7,00
.75
.50
.25
.00
.00
.75
5.75
5.75
5.50
.75
.75
.75
.75
.75
.75
,75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.75
.50
,50
.50
.50
.50
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.00
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5.50 6.00
5.50 5.75
5.50 5.75
5.50 5.75
5.50 5.75
5.25 5.75
5.25 5.75
5.25 5.75
5.25 5.50
5.25 5.50
-------
LAKE TAHOE 1969 ***«*TEMPER*TURE PROFILES*****
DEPTH
(M)
0.
3.
6.
9.
12.
lb.
18.
21.
2«.
27.
30.
33.
36.
39.
42.
45.
48.
51.
54.
57.
LO 60.
-P- 63.
N> 66.
69.
72.
75.
78.
81.
84.
87.
90.
93.
96,
99.
102.
105.
108.
111.
114.
117.
120.
123.
126.
129.
132.
135.
1/16
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
2/ 1
4.75
5.00
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5,25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
2/15
5.00
5.00
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
3/ 2
5.00
5.00
5,00
5.0U
5.00
5.00
5.00
5.00
5.00
5.00
4.75
4.75
4.75
4.75
4.75
4.75
4.7b
4.75
4.75
4.75
4.7i
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
4.75
3/lb
5.25
5.25
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
3/30
5.50
5.50
5.25
5.75
5. 25
3.00
5.00
3.00
3.00
3.00
j. on
4.75
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0/13
•5.50
"3.75
5.75
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5.25
-3.25
5.25
5.25
5.25
5.25
5.25
5.25
•5.25
5.25
5.25
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
1/25
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5.75
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5.25
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5.00
4.75
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d.75
'1.75
4.75
4.75
4.75
0.75
a. 75
1.75
1.75
1.75
4.75
D.75
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4.50
4.50
4.50
d.50
4.50
4.50
4.50
1.50
4.50
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5/ 9
9.25
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8.00
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7. '10
6.75
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6.50
6.JO
6.10
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6..J-3
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5. '5
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5.50
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5.30
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5.25
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5.25
5.25
5.25
5.15
b.25
5.00
5.00
5.,)0
5. ,)0
5.00
5. 50
5.1)0
5. 10
5. 10
5 .i>0
5.')0
3/21
13.50
12.25
11.50
10.50
10.00
V.75
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9.50
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9.00
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8.75
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3.25
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6.75
6.75
6.75
6.75
6.75
6.75
6.75
6.75
6.75
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6.50
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6. '5
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6.75
6.75
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6.5n
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6. bo
6. in
.1/20
I •» . 5 0
11.1)0
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13.50
12. '30
1 1 . 5 U
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7.00
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5.25
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5.00
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1 '. .00
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6.50
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6.50
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i ft . 5 (
1 6.01
b.bi
'i.Ol
'l.Oi
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7.7b
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H.75
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7.00
6.7b
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6.50
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6.00
6.00
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l>.7b
b.7b
b.75
b.75
S.75
'...75
b.5o
5.50
5.50
5.50
S.50
b.5o
5.50
5.50
5.25
?>.2b
b.7b
5.75
7/22
19.75
19.00
Ifl. 75
1 7. bO
16.CO
11. bn
1 }.7b
1 i . (i 0
i 1 .bo
1 O.bO
9. '5
9.00
D.bO
n.bo
K.OO
7,75
7.'b
7. bo
7. bo
7.bO
7.25
7.*5
7. CO
7.00
7.00
7.00
6.75
6.75
6.75
6. bO
6.bO
6.50
6.50
«.bO
6. bO
6. bo
6.50
6. bo
6. bo
6. '30
6.50
6.2b
6.25
6.25
6.25
6.?5
7/30
20.50
70.50
20.00
19.00
16.50
15.50
l«.b»
13. 7b
12.75
12.00
11 .00
9.50
''.00
B.25
B.OO
7.75
7.50
7.2b
7.00
7.00
6.75
6. bo
6. bO
6.bO
6.50
6.50
o.bo
6. bo
6.2b
6.25
6.2b
6.00
#.00
6.00
6.00
6.00
6.00
6. on
6 . 00
6.00
5.7b
5.7b
5.75
5.75
b.7b
5.75
8/14
20. bO
20.25
20.00
20.00
19.75
19.00
15.50
15.00
13.00
11.75
10.00
9.25
8.50
B.OO
7.50
7.75
7.00
7.00
6.75
6.50
6.50
*.25
6.25
6.00
6.00
6.00
6.00
6.00
6.00
6.00
5.75
5.75
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
8/77
20.50
20. ?b
20.25
20.25
20.00
20.00
19.75
17.00
15.00
14.00
12.00
11.00
10.00
9.50
8.75
8.50
8.25
8. 00
B.OO
7.75
7.75
7.50
7.50
7.00
7.00
7.00
7.0.0
7.00
7.00
7.00
7.00
6.50
6.50
6.50
6.50
6.50
6.50
6.50
6.50
6.50
6.50
6.25
6.25
6.25
6.25
6.?5
-------
LAKE TAHOE 1969 *****TLMPENA F LIRE PKC1F I lES* ****
DEPTH
CM)
0.
3.
6.
9,
12.
15.
18,
21.
24.
27.
30.
33.
36.
39.
42.
45.
48.
51.
54.
57.
60.
63.
66.
69.
72.
75.
78.
81.
84.
87.
90.
93.
96.
99.
102.
105.
108.
111.
114.
117.
120.
123.
126.
129,
132.
135.
»/ 3
19.50
19.50
19.50
19.50
18,75
17.50
15.25
13.75
11.75
10.00
9.25
8.75
8.25
7.75
7.50
7.25
7.00
6.75
6.50
6.50
6.25
6.00
6.00
5.75
5.75
5.50
5.50
5.50
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5,00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
10/10
12.25
12.25
12.25
12.00
10.75
9,25
9,00
8.50
8.00
7.75
7.25
7.00
6.75
6.50
6.75
6.00
6.00
5.75
5.50
5.50
5.50
5.50
5.50
5.25
5.25
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5,00
5.00
10/22
11.50
11.25
11.00
11.00
11.00
11.00
11.00
11.00
11. on
11.00
11 .00
10.75
10.50
6.50
7.00
6.50
6.50
6.25
5.75
5.50
5.50
5.25
5.25
5.25
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5,00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
4.75
4.75
4.75
4,75
4.50
10/28
11.25
11. CO
11.00
11. CO
11.00
11. CO
11.00
11. CO
11. CO
11. CO
10.75
10. 5U
10.25
9.50
8.75
8.50
7.75
7.50
7.00
6.75
6.50
6.25
6.00
5.75
5.50
5.50
5.50
5.50
5.25
5.25
5.00
5. CO
5.00
5,00
5,00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
4.75
4.75
4.75
4.50
11/12
10.00
9.75
9.75
9.75
9.75
9.50
9,50
9.50
9.50
9.50
9.50
9.50
9.50
9.50
9.50
9.25
9.00
8.75
8.50
7.00
6.75
6.50
6.25
5.75
5.75
5.50
5.50
5.50
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
11/23
9.00
9.00
9.00
9. on
9.00
9.00
9,00
9,00
9,00
9,00
9.00
9.00
9,00
8.75
8.75
8.50
8,50
8.00
7.50
7 .00
6.75
6.50
6.25
6.00
6. '00
5,75
5,50
5.50
5.51
5.25
5.00
5.00
5.00
5.00
5.00
5.01
4.75
4.75
.75
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.50
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.50
• 50
I?/ 5
H.50
H.50
8.50
8.50
B.SO
1.50
H.50
H.50
H.50
H.50
8.50
0.50
H.50
H.50
H.50
H.50
H.50
H.50
7.75
7.50
7.00
s.75
6,50
6.25
4.00
5.75
5.50
5.50
5.25
5.25
S.OO
5.00
i.OO
•5,00
5.00
5.00
4.75
4.75
4.75
4.50
4.50
4.50
4.50
4.50
4.50
1.50
1»/16
7.25
7.25
7.?5
7.25
7.25
7.25
7.25
7.25
7.25
7.25
7.25
7 .0(1
7.00
6.75
6. f3
6.50
6.50
6.50
6.25
6.10
6.00
i.75
>.50
5.50
5.50
5.50
5.50
5.25
5.00
5.00
5.00
5.00
5.00
5.00
5.00
S.OO
5.00
5.00
5.00
5.00
5.00
5.00
5.00
4.75
4.75
4.75
12/26
S. V)
6. ) )
6.50
6.75
6.25
6. JO
6,0 rj
«..)•)
6.10
6.,)}
6. 10
6, J1
6.00
6.00
6.1)0
6.11
5.ri
5.7'J
5.50
5. >1
5.50
5.50
5.51
5.25
5.P3
5. ,) 0
3.:) 0
5. V)
5. 10
5.11
5.00
5.00
4.75
4.75
4.75
4,75
4.75
4.75
4.75
-------
L»KE TAHOE 1970 *****TLMHERM"Rf PPUTILES*****
DEPTH
(M)
0.
J.
6.
9.
12.
15.
18.
21.
24.
27.
30.
33.
36.
39.
42,
45,
48.
51.
54.
57.
60,
63.
66.
69.
72.
75.
78.
81.
84.
87,
90.
93.
96.
99.
102.
105.
108.
111.
114.
117.
120.
123,
126.
129.
132.
135.
I/ 6
6,00
6,00
6,00
6,00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6,00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6,00
6,00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6,00
6.00
6,00
6,00
6.00
5.75
5.75
5.50
5.50
5.50
5.50
5,50
5.50
5.50
5.50
1/19
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5,5o
5,50
5.50
5.50
5.50
5.50
5,50
5.50
5.50
5.50
5,50
5.50
b.50
5.50
5.50
5.50
5.50
5,50
5.50
5.50
5.50
5.50
5,50
5.50
5.50
5.50
5.50
5,50
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.25
5.00
1/30
5,50
5.50
5. 50
5.5o
5.50
5.5Q
5.50
5.5o
5.5o
5.5o
5.5o
5.5o
5.50
5.5o
b.bo
5.50
5.5o
5.5o
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.5Q
5.50
5.5Q
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5, SO
5.50
5.50
5.50
5.50
5.50
5.5o
5.50
5.50
2/10
5.25
5.2S
5.25
5.25
5.25
5.75
5.25
5.25
5.75
5.75
5.25
5.00
5.PO
5.00
5.00
5.00
5.00
5.PO
5.00
5.00
5.00
5.00
5.PO
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5,00
5,00
5.00
b.OO
5.00
5. CO
5.00
5.00
5.00
5.00
5.00
2/23
S'.bo
5.50
5.50
5.bO
5.50
5.50
5.50
5.5o
5.50
5.50
S.bO
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5.25
7/7H
5.7S
5.25
5.25
5.25
5.25
5.75
5.25
5.01
5.00
5.00
5.00
5.00
b.OO
b.OO
5.00
5.00
b.OO
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
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5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5,00
5.00
1/10
3.00
5.00
5.00
5.00
S.OO
5.00
S.OO
b.OO
S.OO
S.OO
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5.00
5.00
5.00
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5.00
5.00
5.00
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5.00
5.00
5.00
5.00
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s.oo
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5.00
5.00
5.00
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S.OO
s.oo
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
3/23
5.7b
S.50
5. So
5. So
5. So
5. So
5.50
5.50
S.25
5.25
5.25
S.?b
5.25
S.25
5.25
5.25
S.25
5.75
5.25
S.2b
5.25
S.25
5.25
5.25
5.25
S.75
5.25
5.25
5.25
5.75
5.25
5.75
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
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6. SO
5.75
5.50
b.25
5.25
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5.^5
5.03
5.03
5.00
5.30
3.33
5.00
5. Oil
5.03
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5.00
5.00
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5.00
5,00
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5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5; 00
5.00
5.00
5.00
5.00
5.00
5.00
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5.50
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3.S.-I
3.S.1
3.2S
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b.OO
3.00
5.00
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5.00
3.00
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3.00
5.00
5,30
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7.7'j
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7.50
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3.7b
6.53
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6.50
6.50
6.23
6.2J
6.?b
6.03
6.30
6.00
6.00
j.7b
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5.50
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'i.50
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''.75
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S.7b
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5.75
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3.7b
S.7b
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3.75
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S.7S
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3.75
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b.7b
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1 1 . i^b
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17. bO
17. !>0
17.J.5
1 1. bo
10. ?b
9.75
9.b,j
S. 1 b
6.00
7 .25
7.00
7.00
6.7b
6.75
6. bo
6.bO
6.2b
6.2'i
6.ZS
6.2b
ft. 00
6.00
6.00
6.03
6.00
6.00
b.7b
b.75
b.75
5.75
5.75
5./b
b.7b
5.75
b.7b
5.7S
5.75
5.75
5.75
b./5
5.75
5.75
7/ 1
15. 7b
15.00
11.00
13.25
17.7b
12. bo
H.75
10.75
9.5o
9.00
s.50
8.7.5
1.00
7.7b
7. bO
7.2b
7.00
7.00
6.75
6.50
6.30
6. bo
6.23
6.73
6,00
6.00
6.00
6.00
6.00
6.00
5.7b
5.75
5.75
b.7b
5.75
b.7b
5.75
b.75
5.75
5.7b
5.75
5.75
5.75
5.75
5.75
5.75
7/14
If.. 00
16.75
15.50
U.75
11.00
13.50
17.50
11.50
11 .00
10.25
9.00
f .75
P.. 25
6.00
7.75
V.50
7,00
7.00
7.00
*.75
t.50
6.50
*.50
6.25
6.25
6.00
6.00
6.00
6.00
6.00
5.75
5.75
5.75
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
b.50
5.50
5.50
5.50
5.50
7/70
20.00
18.25
16.75
16.00
15.00
13.75
12.25
11.00
10.50
9.75
9.00
8.50
8.75
8.00
7.75
7.50
7.75
7.25
7.00
6.75
6.75
6.50
6.50
6.50
6.50
6.25
6.25
6.25
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6,00
6.00
6 . 00
6.00
-------
LAKE T«HOE 1970 *****Tt:MPrRATURE. PROFILES*****
Ui
DEPTH
(M)
0.
3.
6.
9.
12.
15.
18.
21.
2*.
27.
30.
33.
36.
39.
42.
45.
86.
51.
54.
57.
60.
63.
66.
69.
72.
75.
78,
81.
84.
87,
90.
93.
96.
99.
102.
105.
108.
HI.
114.
117.
120,
123.
126.
12».
132.
135.
7/24
18,50
17.75
17.00
16.50
15.75
14.50
13.75
13.00
11.75
11.00
10.50
10.00
9.25
8.50
8.25
7.75
7.50
7.00
7.00
.75
.50
.50
.50
.25
.25
,00
.00
.00
.00
.00
.00
5,75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
7/31
17.25
16.75
16.00
16.no
15.75
15.50
14,75
13.50
11.25
10.00
8.75
8.25
8.00
7.50
7.25
7,25
7.00
7,00
7.00
.75
.75
.50
.50
.50
.25
.25
.00
.00
6.00
6.00
6.00
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
5.75
8/11
18.25
18.00
18.00
17.50
16.50
15.25
13.25
11.50
10.50
9.50
8.75
8,25
8.00
7.50
7.25
7.00
7.00
6.75
6.50
6.50
6,50
6.50
6.50
6.25
6.25
6.25
6.00
6.00
6.00
6.00
6.00
6,00
5.75
5.75
5.75
5.75
5.75
5.75
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
8/1?
18.75
18.50
18.25
17.75
16.50
14.50
12.50
10.75
10.00
9.00
8.25
7.75
7.25
7.00
7.00
6.75
6.75
6. 50
6.25
6.00
5.75
5.75
5.75
5.50
5.50
5.50
5.50
5.50
5.25
5.25
5.?5
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5,00
5.00
5.00
5.00
5.00
5.00
5.00
8/24
18.25
IB. 00
17.75
17.50
17.00
16.00
13.75
12. un
It .25
10.25
9.50
8.75
8.00
7.25
6.75
6.50
6. i>0
5.75
5.75
5.50
5.50
5.25
5.25
5.00
5.00
5.00
.75
.75
.75
.50
.50
.50
.50
.50
.50
.50
4.50
4.50
4,50
4,50
4.50
4.50
4.50
4.25
4. 25
4.25
9/ ?
IB. on
17.75
17.50
17.50
1 7.00
16.5(1
14.00
12.25
11. 75
11.00
10.00
9.00
8.00
7.50
7.25
7.00
6.75
6.50
6.25
6,00
6,00
5.75
5.75
5.75
5,75
5.5n
5.50
• 5.5C
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5.00
5.00
5.00
5.00
5.00
5. on
5. no
5.00
5.01
5.00
5.00
v/ a
16.75
16.75
14,75
1A.75
15,75
1 •> . 00
11.50
13.75
12.75
12.00
11.50
10.50
9.50
".75
H.OO
7.50
7.00
6.75
•S.50
*,50
6.50
6.25
IS. 00
«.oo
6.00
5.75
5.75
5.50
5,50
5.50
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5.00
5.00
5,00
ti.OO
b.OO
•5.00
5.00
5.00
5.00
9/17
15.50
15.50
15. ?5
15.25
15.00
15.00
11.75
l'J.50
13.75
12.50
10.50
9.50
9.00
8.00
7.50
7.00
6.75
6.50
6.25
6.00
6.00
6.00
5.75
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.25
5.25
5.25
5.25
5. 00
•>.oo
5.00
5.00
5.00
5.00
9/?j
14.00
14.00
13.75
13.75
13.75
U./5
13.50
13.25
12.25
11 .1)0
9. 50
floO
7.75
7.25
7. 00
6.75
6.50
6.25
6.25
6. )0
5.75
5.75
S.'iC
5. 50
5.5C
5.50
5.25
5.25
5.25
5.25
5.25
5.25
5.00
5.00
5.00
5.00
5.0C
b.OC
5.00
5.00
5.00
5.00
5.00
5.00
5.00
4.75
-------
APPENDIX B
LAKE TAHOE PRIMARY PRODUCTIVITY-DEPTH PROFILES
-3 -1
Primary productivity (mg C*m -hr ) vs. sampling depth at the index
_3
station of Lake Tahoe, 1967-1971. Total (mg Om ) and average
_3
(mg C-m ) productivity per hour of incubation and per day, and total
efficiency per calorie of light are also listed.
346
-------
LAKE TAHOE 196? *««**PKIMARY PRODUCTI VITY****»
-P-
--J
MILLIGRAM Ur CARBON PEK CUHlC METER PER HOUR
OEPTH 7/28 OFPTH »/ 2
CM) (M)
0. 0.11 0. 0.32
8. 0.64 3, 0.6H
15. 0.29 10. 0.6'
25. 0.38 20. 0.22
35. 0.25 35, O.M
bo. Oil? 61. 0.1')
70. 0.34 70. 0.29
hlTAL MG HfR SSUAHF. METER
25.57 ?3.4b
AVERAGE MG PER CUHIC METErt
0.37 0.33
TOTAL PHIMARf PRDOUCTIVlTY MG
****** 7.16. 4,>
AVERAGE Mb C/CUBIC METER. iJAY
*••*•* 3. )8
TOTAL EtFICItNCY (PER CALORIE
****** {) ( 6 4
JEPTH 9/28 OfPTH 10/ b
CM) (M)
0. 0.23 (I. 0.12
7. 0.3fl 5. 0.11
15. 0.20 10. 0.20
30. 0.1? 15. 0.22
50. 0.11 20. 0.27
62. 0.06 30. 0.11
89. 0.03 40. 0.42
DEPTH fl/ V
t»)
". 0.22
1?. 0.27
17. 0.29
25. 0.17
40. 0.32
in. 0,41
tn. o.2b
20.26
0.29
C/SauARl METER
164.92
2.36
OF L IU-H ) (X
0.47
DEPTH 10/11
(»)
0. 0.19
b. O.iS
10. 0.32
15. 0.24
•in. o.?t
Jn. n.16
40. o.!>7
brt . ij . 42
^n. o.oi
90. "0.1?
DEPTH
(M)
0.
7.
1?.
22.
37.
50.
80.
,;>AY
,0001 )
DEPTH
(M)
0.
•>.
10.
15.
20.
30.
40.
C f.
3D •
70 .
90 .
A/14
0.23
0.59
O.bO
0.27
0.21
0.31
0.18
23.82
0.30
21 3.4?
2.67
0*60
10/11
0.16
0. 16
0.2J
0.26
0.23
0.14
0.29
01 >
. J *
0.18
0.07
UFPTH
(M)
0.
7.
12.
?2.
17.
50.
80.
OI-PTH
CM)
0.
5.
10.
15.
70.
30.
40.
SO .
70 .
90 .
8/25
0.2f
O.i2
0.72
0.16
0.09
0.0'
0.02
14. 3'
0.18
******
******
10/26
0.02
0.72
0.36
0.32
0. J6
0, 10
0.19
n 1 f
u . e. i
0.18
0.0^
DEPTH
(M)
0.
5.
10.
24.
36.
bO.
70.
DEPTH
CM)
0.
2.
b.
10.
Ib.
20.
30.
4 0 •
^0 •
An
QU •
7 1
f j •
Jn
V(J fl
9/ 2
0.34
0.50
O.b2
0.20
0. 14
0.18
0.10
16.92
0,24
193.34
7.76
0 * ftb
a/ i
"0.01
0.05
O.lb
0.21
0.2«
0.34
0. 30
01 7
• it
0*34
0 t 31
0*14
0 • 0 .1
DEPTH
CM)
0.
4.
8.
17.
31.
43.
71.
DEPTH
(M)
0.
7.
5.
10.
15.
20.
30.
40"
50.
60*
75 *
90 .
<>/ 7
0.77
0.55
0.58
0.19
0.27
0.28
0.43
23.08
0.33
169.72
7.39
o * bv
ll/ 8
0.25
0.20
0.21
0.31
0.30
0.30
0.25
0 t ?6
o« 3 \
0« 1 9
0 • 1 ?
0*01
DEPTH
CM)
0.
3.
b.
8.
11.
Ib.
20.
23.
27.
38.
50.
57.
72.
82 .
DFPTH
CM)
0.
2.
5.
10.
Ib.
20.
10.
40 »
50.
60.
f t
I 3 .
90 .
V/14
0.24
0.43
0.56
0.61
0.68
0.64
0.37
0.26
0.21
0.44
0,46
0.32
0.15
0.16
29. 5«
0.36
222.17
2.71
Of t
» f J
11/15
0.23
0..23
0.21
0.30
0.30
0.30
0.21
0.18
0 . 1 H
0.15
0.08
0.05
OF.PTH
(M)
0.
5.
12.
24.
40.
52.
80.
DEPTH
(M)
0.
2.
b.
10.
15.
20.
30.
40.
50.
60.
75 .
90 .
9/21
0.09
0.47
0.60
0.2?
0.76
0.74
0.06
21.85
0.27
125.18
1.56
Of A
• DO
12/ 1
0.06
0.12
0.11
0. 18
0.2«
0.27
0.33
0. 26
0.21
0.14
0.04
0.04
TOTAL MG PER SflUAWE METER
11. «0 19. «6
AVERAGE Mb PER CUHIC METEH
0.13 U.22
UTAL PHIMARf PRODUCTIVITY MS
149. J3 132.94
AVERAGE MG C/CUBIC METEH?t)AY
1.68 l.dd
TOTAL EFFICIENCY (PER CALORIE
0.76 0,">T
20.09
0.22
C/S8UARL METER
******
******
OF LIGHT) (X
******
.DAY
.0001)
19. -,3
0.22
132.81
1.48
0.77
20.56
0.23
133.69
!.«»
0.81
21.00
0.23
142.24
1.58
0.86
19.58
0.22
1 09 . 85
1 .2?
0.79
16.03
0. 18
111.32
1 .24
1.17
15.83
0.18
137.08
1.52
0.80
-------
LAKE TAHOE 1967 *****PHIMARY PRODUCTIVITY*****
MILLIGRAM OF CARBON PER CUBIC METER PER HOUR
DEPTH
(M)
U.
2.
5.
10.
15.
20.
30.
40.
50.
60.
12/ 8
0.05
0.04
0.07
0.09
0.16
0.21
0.18
0.21
o.ia
0.11
-p-
oo
TOTAL MG PER SQUARE
».*2
AVERAGE MO PER CUBIC METER
0.16
TOTAL PRIMARY PRODUCTIVITY MG C/SOUARE METER. DAY
66.80
AVERAGE MG C/CUBIC METER. DAY
i.u
TOTAL EFFICIENCY (PER CALORIE OF LIGHT) ex .ooon
0.75
-------
LAKE TAMUE 1968 •••••PKIMANY PHUUUCTIvlTY«**«*
UJ
MILLIGRAM lit CAKBUN PER CUBIC METIK PtP HUllH
UtPTH I/ 2 1/17 1/21
IM,
0. 0.15 0,06 '0.02
•5. o.l» n.i>3 ii.oo
10. 0.31 O.Ot) 0.09
15. o.39 0.08 o.06
1 ">/ 9 b/16
(M)
0. 0.03 0.11 -0.01
2. 0.03 0.12 0.0"
lo. n.12 o.U o.ob
Ib. 0.11 1.29 0'0»
20. 0.19 o.cib 0.12
30. 0.27 0.30 0.1**
10. "0.0 3 0 • 2 b U « 1 V
bo. o.lo o.3b "o»04
60. 0.22 O.?b 0»19
^ b « 0.27 0.18 0 « 1 9
Vu. 0*o3 0.06 0*10
lob. 0.02 0.03 0.0**
TuTAl MG HER SUUAhE METER
13.86 21.10 1?-OU
AVERAGE Ml, PFH CUBIC MFTEK
0.12 0.23 Q.ll
rUTAl PRTHARY PRODUCTIVITY Mr,
107.85 201. If 136.70
AVERAGE MO C/CUUTC MFTF.R,OA»
0.90 1.92 1.30
TUtAI EFFiUfNCY (PER C»LURIF
0.34 0.62 0.39
2/ b 7/l«
0.02 0.01
0. O'* 0. Ob
o.oi n.o*
o.o7 n.16
o.lo o.lb
o.lb o.?7
0.24 n.37
0.2« n.32
0.32 n.30
0.26 o.?b
0.2J o.lb
0.13 n.OB
IH.IO i".9o
0.20 n.?2
C/SuuAHE MFIFH.
1 1 A. fef 1 3* . 4V
1 * 3 0 f • S 1
Of LlliHU '» .
(I • V f 1 . fr "
S/22 ^/?9
).01 .02
1.01 .02
) . 02 .0**
uui .0^
).U^> .0V
).U/ .11
J 1 1 J • 1 J
j t ^^> * 1 i?
J • if*1 * 2 1
0 • I V • /?6
o.?0
I'.l'
( 1 , ? *t
o.?3
n.l!>
n. j5
fl ( 1 0
o . t 2
- i j
r, . I J
n , ?0
("• • ? b
n • 1 *
(1 ( 0"
1C.17
0.1?
159,45
1.52
0.16
3/20
•0.04
0 . 02
0.02
0.07
O.H
0.2J
0.37
0.«2
0.41
0.36
0.13
0.11
21.82
0.24
1 6 S * t>6
1 • ttfl
0 t 69
// fl
0.21
0* 1ft
0*16
0.21
0.21
0,17
0 • 1 2
0« 1?
0 • 1 1
Oil?
0 * 1 fl
•T . 1 ft
™ 0 • U 3
13.46
0.13
101.74
0.97
0.33
3/26
0.04
Onl
» U J
0,02
0.07
0.11
0.10
0.37
0.51
O.bO
0.39
0.28
0.13
26.32
0.29
213*80
23 U
* JO
rt 77
0 • ' *
7/11
0.17
0.22
n 71
I) . c 1
0.24
0.24
1.22
01 '2
tie.
0 » 1 V
0 • 1 V
0 • 1 tt
»• 7
• 1 '
0 * 1 fl
0 • Ofl
17.6V
0.17
IbH.OS
1.51
0.46
4/ 2
0.07
o.io
0.13
0.17
0.21
0.25
0.35
0.32
0.39
0,32
0.17
o.oe
22.42
0.25
_
203* 03
n 9fc
/•CO
Iy&
t C "
7/17
0.17
0.11
«) M
i i °
0.15
0.31
0.2V
01 S
» * 3
0 » t i
0 1 1 1)
0 * 09
nt )
» 1 J
0* (J J
0 • t) 1
1?.V1
0.12
108. (12
1.04
0.31
4/11
0.03
•0. QO
0.02
0.05
0.10
0.12
0.20
0.26
0.34
O.bO
0.27
0.12
2?. 06
0.25
9 ft A V S
cO*t • c J
2 • Slfl
OQO
* TV
7/2fl
0.1V
0.22
01 1
• J i
0.70
0.60
0.35
0-> 7
« C J
0*10
0 * 00
0* 3 U
0 » 0 J
Ot 02
0 » 0^
20.VU
0.20
172.44
l.*4
0.51
4/1B
0.02
0.02
0.05
0.06
0.13
0.1V
0.29
0.31
0.25
0.24
0.17
0.02
16.83
0.19
ltd All
1 Ji • ot
* sn
I t J V
ntt y
• **€.
'"3\
0.48
0.47
Oft 1
• D J
0.53
0.25
0.17
0.10
0. 05
0.04
0.03
0.01
0 . 02
0.01
12.08
0.12
204.31
1.95
?.?0
4/25
0,00
•0.06
0.02
0.05
0.08
•0.23
0.10
0,37
0,29
0.41
0.24
-0.92
8,07
0.09
it y 'i4
*» F • J '
n. «7
nl IL
• 1 •?
fl/ 7
O.I/
0.22
0\ 2
. Jc
0.4V
n.34
0.28
6,H9
0.34
55.74
2.79
0,20
-------
LAKE TSHUE 1968 *»*.*PNIMARY PRODUCTIVITY*****
Ol
o
MILLIGRAM OF CARHUN PER CURIC METER PEP HUUN
DEPTH 8/ 7 fl/12 8/21
(M)
0. ** Otl5 0.04
2. ** 0.13 0>08
5. ** 0.38 0.11
15. ** 0.0« 0«17
20. ** 0.21 0«08
JO. 0.15 0.0' 0*15
00. 0.12 0.12 0«10
50. 0.10 0.11 0-08
60. 0.05 0.15 0*08
'5. 0.08 0.0? 0«04
»0. 0.04 0.07 -0.04
105, ******* 0.05 'O.O*
TOTAL MG PER SOUARE METER
5.16 13.84 6.56
AVERAGE MG PEN CUBIC METER
0.09 0.13 0.06
TOTAL PRIMARY PRODUCTIVITY MS
44.10 121.3? 47.56
AVERAGE MG C/CUHIC MF.TER.UAY
0.^3 1.16 o«45
TOTAL EFFICIENCY (PER CALORIE
0.16 0.37 0.27
8/28
0.01
O.OJ
0.0'
0.03
0.08
0.16
0.13
0.15
0.16
0.22
0.13
0.10
0.03
12.80
0.12
C/S8UARE
94.46
0.90
OF LIGHT)
0.36
«/ 2
0.19
0.15
n.18
0.21
n.18
n.ir
0.14
0.10
P.16
0.14
P. 11
0.06
0.02
1?.93
0.12
MFTER.
9A.B8
0.92
(X .
0.34
9/11
0.1?
0.21
0.27
0.43
0.42
0.48
0.15
0.14
0.18
0.14
0,08
0.06
0.04
18.50
0,18
DAY
127,94
1.22
0001)
0.50
9/17
0.07
0.13
0.18
0.27
0.28
0.32
0.19
0.17
0.17
0.14
0.10
0.05
0.03
15.78
0.15
110.82
1.06
0.46
9/26
0.08
0.10
0.15
0.24
0.30
0.28
0.20
0.14
0.18
0.13
0.08
0.04
0,03
14,56
0.14
105.70
1.01
0.50
10/15
0.08
0.08
0.12
0, 16
0.16
0.24
0.24
0.21
0.13
0.10
0,06
0.04
0.02
1?.90
0.12
8C..15
0.82
0.47
10/19
0.11
0.12
0.15
0.23
0.24
0.26
0.24
0.15
0.12
0.11
o.oe
0.05
0.02
13.8o
0.13
117.75
1.12
0.62
10/27
0.13
0.11
0.15
0.23
0.25
0.28
0.25
0,18
0,16
0.13
0.07
0.04
0.03
14.9Q
0.14
V3.94
0.89
0.62
ll/ 2
0.20
0.23
0.28
0.27
0.29
0.24
0.20
0.19
0.14
0.10
0.06
•o.oo
0.00
14.00
0.13
66. 78
0.83
1.40
12/ 1
0.20
0.18
O.i«
0, £0
0.21
0.22
0.16
0.16
0.10
0.06
0.03
0.01
0.60
10.76
0.10
58.39
0.56
0.88
12/ 7
0.09
0.10
0.14
0.18
0.23
0.29
0.31
0.28
0.26
0.15
0.11
0.04
0.01
17.80
0.17
100.44
0.96
0.94
-------
LAKE TAHUE 1969 •••••PKIMAHY PKUUUCTI V1TV*****
OJ
MILLIGRAM nf CAHHUN PEH CURIC METEK
DEPTH i/l* ?/ i 2/15
CM)
0. 0.14 0.06 0.25
2. n. 1 1 0. 07 0-28
5. 0*12 O.OB o.3i
1U. 0.20 0.13 (J.40
15, 0.35 0.21 0.40
20. 0.44 O.lV 0«40
JO. 0.52 0.25 (>.,J2
»o. o.47 n.?* 0.22
50. 0.32 0.20 0.16
60. 0.18 0.1* 0.0V
'5. 0.10 0.0* 0-06
VO. 0.03 O.nt 0-01
Iu5. 0.02 0.03 0.02
TUT41 MG HER SWUANE METEP
2U.23 I''.'',' ifl.«7
AVERAGE MO PFh CUHIC MFTFH
0.23 0.15 0-18
TUTAL PHIMAHY PHnilUC T I V I T f Mr,
130.81 11". 0* 133. hi
AVERAGE Mb C/tUHTC MFTEN.UAY
1.28 1.12 |.27
IUTAI. EFFICIENCY (PER CAUJHIF
l.l? 1.21 a. 31
l)EPTH 7/22 7/2» 7/30
IM)
0. O.OB 0.11 0.10
2. 0.22 0.25 o.ll
5. 0.29 0.36 u-21
10. 0.39 0.30 0-28
15. 0.28 0.2V 0-26
20. 0-21 0.20 0.16
30. 0.12 0.10 0.13
40. 0.10 0.11 0*08
5o. o. lo n.i 1 0-17
60. 0.16 0. 16 [, . 12
75. 0.07 0.06 0.11
TUTAL M(, HER SflUAHE METER
1«.3B 14. |3 11. |J
AVERAGE MI. PFK CIIHIC METF.K
0.1" 0.13 0-15
TUTAI. PRIMARY PNnilUC T I Vl T Y Mr,
12».95 113. H4 85.48
AVERAGE Mb C/CUBtC MFTEH.UAY
1.19 1.Q8 1.14
TUTAL IFFICIFNCY (PEB CALUHIF
0.39 o.35 0.26
3/ 2
0.03
0.03
0.06
O.ll
U.21
0.27
0.3V
0.3V
0.35
0.25
0.07
0.18
0.07
22.65
0.22
C/S.JUAHE
124.60
1.19
PER HOUR
1/15
n.Ol
o.OO
•o.ou
n.06
n.09
n.15
0.3<4
P. 43
r-. 54
0,44
n.27
n.12
n.ov
27.22
n.76
Mr IEH
19S.16
1 .H6
(If LIGHT) IX
o.vu
H/ b
O.OB
0.22
0.31
0.«5
0.33
0.24
o.l»
0.12
0.11
0.11
0.05
0.06
0.04
\'I.V/
0.14
C/SUUARE
112.3V
1.07
UF LIGHT
0.35
O.HO
P/l »
n,?l
n. 10
n.19
n.27
n.?4
n.19
0.22
n.iv
r.iv
n.13
n.17
n . 09
0. 05
17.26
n. 16
MrlER
12T.62
1.?2
) IX
0.43
3/30
0.01
0.01
0.02
0.05
0.10
0.15
0.30
0.6u
0.61
0.51
0.33
0. 14
0.09
31. 17
0.3U
.DAY
242.06
2.31
.0001 )
0.88
H/20
O.Oo
0. 16
0. 24
0.2V
0.24
0.22
0.11
0, 16
0.14
0.12
0.13
0 . 1 0
0. 08
15.31
0.15
.DAY
130.27
1.24
.0001 )
0.45
4/13
0.01
0,01
0.04
0.10
0.23
0.27
0.44
0.50
0.50
0.42
0.23
0.10
0.07
28. VB
0.26
211.91
2.02
0.81
8/20
0.0V
0. 13
0.21
0.25
0.29
0.3B
0.11
0.20
0.17
0.12
0.11
0.07
0. 0?
16. «0
0. 16
116.49
1.11
0.38
4/25
0.02
0.01
n.o3
0.07
0.17
0.28
n.5i
0.5V
0.46
0.3B
0.22
0.08
0.04
2H.64
n.27
26S.7«
?.53
0.83
V/ 3
0.10
0.11
(I. 19
0.14
0.11
0.28
0.19
0.12
•0.01
O.OB
0.02
0.03
«.15
0. 10
22?. 39
2.47
0.82
<;/ 9
O.ll
P.05
0, 10
0.12
0.13
0.22
n.32
0.40
0.55
0.41
P. 09
0. 10
o.ll
2«,94
n.?4
19-;, 93
t.«7
0.66
9/ 9
0.07
0.19
0.19
0.44
0.42
0.24
0.22
0.13
o.?o
0.10
0. 06
O.Ol
0.03
1^.42
0.15
104.77
1.00
0.42
•5/23
0.07
0.06
O.ll
0.19
0.33
0.30
0.3]
0.32
0.40
0.28
0.12
0.07
0.05
22.56
0.21
19S.51
1.86
0.57
9/15
0.15
9.27
0.3o
0.4?
0.29
0.24
0.13
0. 18
0.15
0.11
0.08
0.05
0.04
15.67
0.15
120.96
1.15
0.49
6/ 7
0.17
0.21
0.38
0.33
0.28
0.27
0.17
0.16
0.12
0.20
0.12
0.04
0.02
16.75
0. 16
134.26
1.28
n.43
9/23
0.11
****•*»
0.19
o.i a
0.28
0.20
0.09
0.19
0.15
0.12
0.06
0.06
0.03
13.15
n.13
93.10
0,89
0.30
6/20
(1.12
0.18
0.22
0.36
0.23
0.11
0.08
0.31
0,19
0.23
0.12
0.05
0.12
17.45
0.17
137,65
1.31
0.43
10/10
0.06
0.10
0.13
0.20
0.13
0.14
0.16
0.26
0.18
0.13
0.11
0* 06
0.03
11.87
0.13
9?. 11
O.bB
0.4B
7/ 1
0.08
0.18
0.15
0.19
O.lb
0.17
0.15
0.11
0.02
0.20
0.14
0.06
0,02
12.46
0.12
102.25
0.97
0.29
10/22
-0.00
0.07
0,17
0,22
0.27
0.23
0.27
0'.3U
0.31
0.22
0.1 J
0.11
0. 02
20.30
0. IV
122. if
1.17
0.69
7/ 8
0.07
0.26
0.30
0.40
0.38
0.22
0.12
0.15
0.09
0.12
0.12
0.03
0.02
14.75
0.14
162.34
1.55
0.67
10/28
0.06
0.05
0.08
0.16
0.19
0.25
0.17
0.22
0.06
0.14
0.08
0*03
0. 00
!?• 15
0.12
fa. 86
0.71
0.46
7/15
0.15
0. la
0.28
0.29
0.22
0.22
0.13
0.08
0.13
0.1V
n.12
0.07
0.02
14.69
O.ll
122.26
1. 16
0.36
11/12
0.04
0.07
0.06
0.17
0.19
0.20
0,24
0.16
0.15
0. 14
O.OB
0.03
0. 00
12.86
n.u
77. «5
0.7»
0.55
-------
LAKE. TAHOE 1969 o**««PRIMARY PHQOUCTIVlTY***«*
LO
Ln
N3
MILLIGRAM Of
OtPTH 11/23
(M)
0.
2,
5.
10.
15.
20.
30.
40.
50.
60.
'5.
105.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
It
06
09
21
24
30
35
17
06
17
12
04
CARBUN PER CUBIC METLR PER HUllH
I?/ 5 12/16 12/26
0
0
0
0
0
0
0
0
0
0
0
0
0
,
.
.
,
,
.
.
,
,
.
.
.
.
05
07
11
24
30
39
33
29
21
19
03
01
TUTAL MG PER SQUARE
AVERAGE
16.
MG
0.
27
PER
15
17
,
65
CUBIC
0
,
17
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
METER
13.
METER
0.
03
05
10
14
14
31
26
21
16
14
05
02
02
59
13
"0
0
0
0
0
0
0
0
0
0
0
0
0
11
0
.01
.06
.11
.23
.25
.16
.24
.It)
.14
.06
.04
• 00
.01
.52
.11
TUTAL PRIMARY PRODUCTIVITY MR C/SuUARE MFTER.QAY
114.05 107.72 61.21 76.76
AVERAGE MG C/CUBIC METER.DAY
1.09 1.03 0.77
0.73
TUTAL EFFICIENCY (PER CALURIE OF LIGHT)
0.77 0.60 0.63 0.55
(X ,0001)
-------
u>
Ul
LO
LA«i TAnOE
UtPTW
IM)
0.
2.
5.
10,
15.
20.
JO,
40.
iO.
60.
'5 .
»0.
lob.
125,
150.
Tul»i
TUlAI
I/ 6
O.u5
0,05
0.11
o.lt
0.19
0.2'
0.24
0.22
0.1'
0. 10
0. 10
0.05
0.04
KG HER
14.23
0.14
PRTHAfiV
11?. '6
1/19 1 /JO ?/10
0,04 0.0'
0.08 0-OV
0. 12 u.O'
0.1 ' 0.15
0 . ? 0 0 . I «
o.?6 o.2«
0,?B 0.33
0.21 0.20
0.13 0.22
0.0* 0-15
0.0" 0.05
•0.00 0-04
o.ol -0-01
SBUAKE Mf.Yt>
1?. )V ]5.ei
H CUH 1 C WF T f H
0.12 0.15
HKOyllCI IvI TY Mr,
69, H' 1 1 f . 80
0.15
0.1'
0.22
0.2'
0.20
0.35
0. 3u
0.24
0.15
o.ov
O.Oi
0.02
U.Oc
IS. (11
0.15
C /Vrf'J'i^S
1 Jo. no
K/7J
o.ol
".02
r.03
n , ov
0.12
A. 15
n . 3o
f.?'
0 , 7 '
n.?'
0.13
n, o5
1.03
1'. 13
n . fri
MF 1 «.i
1 1 • . «
• * *
?/20
0.04
0,06
0 0V
oil J
0.1'
0,1V
0. 10
0.22
0. IV
0.15
o.0«
0.02
0,01
12.60
".12
A ¥
" 1 , 5ij
3/10
0.00
0.01
0,04
0,04
0,00
0,13
0.18
0.26
0.24
0. IV
0. 1 1
0.06
0, 04
13.61
0.13
'4, '6
3/23
-0.00
0,02
o.ol
0.08
0,13
0.25
0.29
0.26
0.24
0.13
0, 08
0.01
16. 1 1
". 15
119.38
«/ 2
o.ol
•0,01
0, O6
0,05
n. 10
0,15
0,?6
r.?3
P. 18
n, 06
0.0»
0.02
11. S'
o.ov
12". 70
4/15
-0,00
0.00
•o.oi
0,02
0. 04
0, 10
0,16
0,20
0.27
0.19
0.1?
0.07
0.03
0.00
0.00
13.13
1,09
VS. 38
5/ 2
•o.oo
0.04
0.02
0.02
0.05
0,04
0.08
0, 16
0.17
0,36
0.14
o.lv
0.06
0.04
14,46
0.1?
115.86
S/13
0,04
0.00
0.06
0.05
0.05
0.20
0.16
0.26
0.28
0.26
0.25
0.18
0.15
20. 17
0.19
16*. 62
5/25
0.03
0.01
0.05
0.12
0.1'
0.2'
0.43
0.42
0.38
0.35
0. i4
0.21
0.11
0,05
•0.00
31. '2
0,21
258.26
6/16
0.08
0.11
0.02
0.14
0.19
0.20
0.21
0.19
0.16
0.18
0.16
0.09
0.03
0.04
0.03
16.92
0.11
130,63
7/ 1
0.00
O.OV
0.06
0,15
0.27
0.21
0.21
0.25
0.13
0.23
o, IB
o.U
0.0'
0.03
20.47
0,14
163.54
A»ES«GE MG C/CUHIC MFTFR.uAY
IU1.1
1.0'
Ef FICIF
0.96
0.6' 1 . 1 1
MCY (t>E" C«l UKIF
1.01 [,.'5
1 .21
Of llij-
1 .'0
' • 1
) I .t
/-. 7
1 . 'o
001 )
O.'l
1.14
n.B6
0.66
0.93
0.38
1.59
0.55
1.72
0.00
0.87
0.43
1.09
0.4V
UtPTK
(«)
0,
i.
5.
10.
15.
3fl!
«0.
50.
60.
'5.
v«.
1U5.
15il.
7/ 7
0.07
0.08
0.11
0.08
o. lo
0. 07
0.04
0.06
0.06
0.09
0.22
0.06
0.04
n. 0? •
7/|4
0.15
0.23
0.26
0.2'
1.?4
0.1'
0.14
0.11
0. IB
0.1'
0.22
0.2U
0.08
"20
o.io
n. 2V
0- 30
0.40
;.2'
0.15
0.10
()• 12
0.13
0-13
0.11
o.ov
«°1«1 •
7/^4
0.23
. 0.3V
0. 30
0.4 i
II. 30
0.31
o.ov
0.12
0. 15
O.U
0.2'
0.15
0. 10
?/ M " /
'•.?•> (>.
0,?6 (I,
r . &G t, €
O. 5u 0 .
«.M 0,
o.'l' 0.'
0.16 0 ,
f . ? 3 i; .
«,!« 0,
<* , ? 1 (.• .
0.14 0,
".12 0.
1 1
Jo
ib
4 I
5t>
it
15
11
lo
10
15
14
IV
•!/,/
0 . 2f>
0. Jt>
0. b j
O.'Ji
0. 31
0, 2 '
0. le
0.11
0. 10
0. 15
O.I'
0.13
0.1 1
•4/^1
T.20
0.2S
" . ?">
0. J'
D. 24
0,20
0. 10
0.16
o.io
0.15
0. 14
0. 10
7
1.64
IUTAI trriCIFNCY (PEB CAI UR1F OF cIOHT) IX ,0001)
0.2» 0.52 ,').47 0.5» «.»9 0,5»
20.66 10.78
0,20 0,19
165.68 149,59
1.58 1.4?
0,6* 0,50
1*.42 18,74 26.26 20,42 23.46 24.21 26,87
f-,16 0.18 0.25 fl,19 0.22 0,?3 n.2e
12".,66 132.28 1V9.97 147.32 168.32 175.98 1'4.0'
1.?0 1.2k 1,90 1,40 1,60 1.68 1.66
n,4» 0.4n 0,76 0.58 0.74 0.85 1.16
-------
LAKE TAHOE 1970 **««*PRIMAKY PHOOUCTIvlTV****«
U)
Ul
MILLIGRAM nr CARBON PER CUBIC METLR PER HOUR
DtPTH
(M)
0.
2.
5.
10.
15,
20.
30,
»0.
58.
60.
rs.
»0.
105,
I?/ 6
0.14
0.50
0.32
0.21
0.50
0.21
0.26
0.38
0.19
0.14
0.09
•0.07
0.01
12/22
0,0?
0.06
0.09
o.ie
0.26
0.30
0.40
0,49
0.29
0.09
0.10
0.04
0.04
TOTAL M6 PER S8UARE METER
18.16 20,26
AVERAGE MG PFR CUBIC METEH
0.17 0.19
TUTAL PRTMARY PRODUCTIVITY M6 C/SQUARE MfTER.DAV
147.84 121.54
AVERAGE MG C/CUBIC METER.DAY
1.41 1.16
TOTAL EFFICIENCY (PER CALURIE OF LIGHT) ex ,ooon
1.26 0.95
-------
LAKF TAHCH 1971 •*..»PKIMA«Y P«(UUUC T IV I T Y***««
UJ
.17
7.0, 0.37 0.30 0.75
10. C.«7 0,74 Ot35
40. o.4i 0.40 o.3H
bo. n.2B n. 11 o. i«
60. o.i9 o.?3 n . ? j
75. o.tl n.i? 0.14
»o. o.oi n.o9 n.o'
105. 0.02 1.06 o.ob
TOTAL MG PEH SUUAHF. Ml T[ X
21.19 2". in 21.25
AVERAGE MG PER CUHIC MUM
0.23 n. |9 0.20
TOTAL PRIMARY PHOUijC T 1 V I T y Mi,
133.0^ I?.4.fl7 13'. 0V
AVERAGE MG C/CDBTC MFTEH.JAY
1.27 1.19 1.31
TOTAL EFFICIENCY IPER CAI.IJRU
1 .M - 0.88 tt.H'l
>EPTH 7/1 7/8 7/14
(M)
0. 0.13 0.19 0.32
2. 0.13 0.40 0.9U
5. 0.11 0.35 O.J6
10. 0.16 0.43 0.42
13. 0.21 0.36 0.4V
20. P.?0 0.26 T.I"
10. 0.20 0.74 ,),?J
40. 0.30 0.22 n.21
•JO. 0.1« 0.73 ,1.7.6
SU. 0.36 o.?3 0.22
7b, 0.19 0.70 n.l'
90. 0.0* T.08 0.07
lili. 0.09 0.10 O.OH
r,)TAL MG PER SflUAHf METLK
22.00 23.12 24.97
AvEHAC.E Mii PEK CllblC METEr<
0.21 0.22 0.24
TOTAL PRIMARY PrtdUijC T I V 1 T Y MG
165.02 185. 1« 222.6'
Ai/LHAlU MG C/CU8IC METEK.OA*
1.57 1.76 2.12
TOTAL EFFICIEMCY fPfcR CALURIE
0.55 0.57 0.73
?/12
d.03
0.04
0,06
0.12
0.15
n.?2
n.30
0.39
0.39
0.33
0. 19
n. 1 1
0.04
23. nj
n.?2
C/^QUAHh.
1^3.54
1 .46
n t LIGHT
o.es
7/2?
0.19
n.43
n.7/
n.46
n. 36
n.3b
0.^3
0.20
0.16
0. 16
0.15
0.08
0.05
27, n
0.22
c/sau«RE
177.70
1.69
PER HOUR
2/22
0.07
0.05
0.09
n, 14
o.ia
0.27
0.4]
0. 45
0.33
0.20
0. 16
0.07
0.02
2?. IB
0.21
Mf TIR
I'll. 15
1.62
) (X
1 .42
«/ 1
0.58
0.63
0.91
0.60
0.3'
0.29
0.26
0.21
0.30
0.20
0.17
0.08
0.02
26.03
0.25
METER
201 .9?
1.92
f)F LIGHT) (X
0.60
0.71
3/ 7
0.01
0.03
0.03
0.09
0.09
0.14
0.2.1
O.»l
0.50
0.43
0.23
0.1?
0.13
?6.06
0.25
.PAY
160.6?
I.1)/
.0001 )
0.8 j
1/11
O.iS)
(!.>>?.
a . 5 1
0.6S
0. J?
0.24
0.25
O.?1
o.i a
0.23
0.20
0.13
0.05
25.73
0.25
• DAY
186.60
1.78
.0001)
0.79
3/1 1
•0.00
0.01
0.02
0.03
0.05
0.12
0.24
0.29
0.36
n.34
0.30
0.17
0.10
07.53
O.?l
160.08
t .52
o.ft?.
«/! /
n.?7
n.4B
n.56
0.5()
0. 35
n. \>
0. 15
0.20
0.?4
0.72
0. 19
0. 10
0.06
73.76
n.23
243-14
2.3?
O.A3
«/ 2
•0.01
0.02
0.01
n.o2
0.07
o.to
0.18
n.23
0.31
0.30
0.27
0.1?
0.08
19.15
0.19
147. H?
t ."I
n.62
H/24
0.48
0.4H
1, .69
0.71
fl.«7
n.i*
0.14
0.33
n.62
0.20
0.23
0.19
0. 10
i3.67
0.32
269.33
7.57
1.17
4/13
0.01
0.01
0.01
0.07
0.09
0.17
0.19
0. 25
0.31
0.30
0.25
0.24
0.07
21.28
0.20
145.07
1.38
0.77
*/ 2
0.16
0.22
0. 34
0.41
0,49
0.38
0. 30
0. 16
0. 14
0.1'
0.16
0. 10
0.03
21.52
0.20
182.73
1.7«
0.68
4/23
-0.02
0.06
0.01
0.05
0.09
0.13
0.7.1
0.22
0.31
0.29
0.25
0.17
0.09
19.81
0.19
154.lt
1.47
0.55
9/ 9
0.07
0.70
0.32
0.32
0.3'
0.37
0. 19
0.71
0.37
0.43
0.21
0.11
0.05
26.1'
0.25
183.62
1.75
0.69
5/ 5
0.04
0.01
0.02
0.05
0,04
0.08
0.15
0.20
0.2«
0.19
0.12
0.05
0.06
12.62
0.12
103.34
0.98
0.«7
9/16
0.33
0.37
0.37
0.43
0.51
0.43
0.15
0.24
0.27
0.27
0.15
0.09
0.02
24.48
0.23
m. «z
1.65
0.69
5/19
0.01
0.02
0.0?
0.03
0.10
n.i?
0.15
0.21
0.18
0.21
0.14
0.06
0.02
12.84
O.t2
105.27
1.00
0.34
9/23
0.21
0.3?
0.4?
0.5o
0.6]
0.53
0.18
0.7.0
0.21
0.30
O.t4
•0.01
0.01
23.96
0.23
167.59
1.60
0.71
6/ 1
0.12
0.14
0.18
0.20
0.36
0.42
0.50
0.32
0.22
0.09
0.07
•0.03
24.80
0.24
249.68
2.38
1.37
10/ 5
0.15
0.19
0.19
0.30
0.40
0.39
0.40
0.25
0.32
0.29
0.16
0.06
0.02
24.53
0.23
169.J6
1.61
0.79
6/14
0.11
0.10
0.18
0.34
0.27
0.20
0.40
010
• 3¥
0.34
0.?8
0.13
0.03
0.04
23.01
0.22
182.65
1.74
0.58
10/30
0.17
0.19
0.29
0.34
0.40
0.«2
0.28
0.29
0.22
0.25
0.10
0.02
0.03
21.49
0.20
12».3»
1.18
1.00
6/25
0.07
1.15
n.2l
0.23
0.24
0.24
n.20
nt 7
• £ t
0.21
1.18
0.16
0.06
1.07
1«.34
0.17
177.07
1.64
0.56
It/ 9
0.04
0.09
1.12
0.19
0.28
0.31
0.33
0.34
0.23
0.16
0.05
0.06
•o.oo
'11.13
0.17
i«r.46
1.40
0.97
-------
LAKE TAHDE 19M *«««*iJxiMARY PRODUCTIVITY*****
Ul
ON
MILLIGRAM Of CARBON
DEPTH
(Ml
0.
2.
5,
10.
15.
20.
30.
«0.
50.
60.
75.
90.
105.
11/24
0.06
0.11
0.17
0.30
0.39
0.44
0.48
0.30
0,20
0.14
0.08
0.04
0.02
12/ 6
0.04
n.io
0.21
0.30
0.44
0.49
0,47
0.32
0,20
0.11
0.05
0.03
-0.03
PE« CUBIC METER PER HOUR
12/16
0.06
0.08
0.14
0.29
0.33
0.50
0.55
0.46
0.30
0.16
0.07
0.02
0.01
TOTAL M<» PER SQUARE METER
21,34 20.84 24.19
AVERAGE MG PER CUBIC METER
0.20 0.20 0.23
TOTAL PRIMARY PRODUCTIVITY MG C/SOUARE METER.DAY
124.51 125.05 1*5.24
AVERAGE MG C/CUBIC METER.DAY
1.19 1.19 1.38
TOTAL EFFICIENCY (PER CALORIE OF LIGHT) ex ,oooi>
1.42 1.39 1.16
-------
APPENDIX C
LAKE TAHOE PHYTOPLANKTON SPECIES NUMBERS
Average number of individuals per milliliter for the entire 105-m water
column at the index station of Lake Tahoe for each phytoplankton species,
1967-1971.
357
-------
LAKE TAH"E 1 O67*.«. *">HYTnPL ANKTON**** •
AVERAGE NUMBER Qr TNtllvlm/ALS PER ML
DATE*
1 CYCLUHLLA ANTIGUA ""
' "nnTEn ""
« rJclnTf^
0 CYCHlTf LL
'
T MELUS1M VAPIANS
K MELOSIRA UNOULATA
9 STEPHAhUDlSCUS ASTRK*
10 ACHNANTrfES CLEVEI
11 ACHNANTHES ExlGUA
12 ACHNANTHES FLFXELL.A
13 ACHNANlHES I.ANCEDLATA
U ACHNANTHES LlNtARlS
15 ACHNANTHES NOLLII
U ACHNANTHES PERAGALL!
17 AHPHIPRQRA PALUDUSA
IB AWPHlPltgRA PELLUCIOA
19 AMPHCiRA :)VAI IS
?0 ASTER 1 fINEI LA FORMOSA
?1 cncCHNEIS DISCULUS
22 COCCllNfls PLAcENlUtA
23 cuccciNLi; HiiansA
24 CYHBLLLA CUSP1DATA
25 CYMBEILA GRACTUS
26 CYMRFILA LANCEOLATA
27 CYMBULA UENTRlCOSA
28 CYMRELLA SINUATA
W 29 CYMBELLA PROSTRATA
Ul 30 CYHATDPLEURA sOLEA
OO 31 nIATuHA ANC/PS
3? nIATOMA HIEMALE
33 DIATIIMA UHL6ARE
34 OIPUINEIS ELLIPTICA
35 DlPLUNLIs OCUtATA
16 OlPLONEIs FINNUA
37 EUNtlTIA NAEGEl.II
38 FUNOTIA TENELLA
39 EUNOTIA TRIODON
40 FUNHTIA pi RPUSILLA
41 F.UNCITIA pf.CTlNALlS tfENT.
4? EUNOTIA PICTINALIS
41 F.PITHFMIA SOSEX
44 FPITHFMA TURBID A
45 FPITHENIA ^EI^RA
46 f PI THE MI A ARGUS
47 FRAGHAHIA CROTONENSIS
4fl FRAGILAHIA INTERMEDIA
49 FRAGILAHIA pj[NNA™
si FRAG i L ARIA cuNSTRuE'is
52 FRAGILARIA LEpTOSTAUKON
53 FRAG I LAO I A CApUClNA
54 FRUSTULIA RHQM80IUES
55 GnMPHONLHA ACijHINAluM
56 GOMPHONEHA PARVULUM
57 GOMPHDNEMA CApITATUK
58 GOHPHONEHA VENTRICOSUM
59 HANTZSCHIA AHPHIOXYS
60 GYRDS1GMA ATTENUATUM
61 HANNEA ARCUS
62 HASTUGIUIA SMITHII
63 HERIDION CIRCULUHE
6« NAVICIILA AURORA
' 9> R
0,0'
*...,.°.
0.11
0.04
*******
0.01
0.21!
0.01
0.0ft
.**.****
0,0'
0.05*
0.06
*******
14/ e ?5/ 6
1.01 2.67
0.06*******
"•".. *;.6
0.59 0.76
0.09 0.02
0.01 0.1?
0.01 0.18*
O.S2 0.51
0. 05*******
0.?? 0.18
**************
*************
0.38 0.1B
0.01 *******
?/ 9 7/9
6.56 ?,26
0,07 0.06
f 0.21 0.23
3.27 1.93
1.21 0.13
****** 0.05**
0.76 0.19
14/ 9
5.00
O.Ol
0.11
1.66
2l/ o
7,9?
0.04
0.05
1.39
0.02 0.0f>
************
0.23
0.21
2«/ 9
5/11
'.67 9.05
0.03*******
n..5
*":;;**
0.10**
1.01
0.17
0,03************** 0.01*******
0.24 0.16 0.03 0.07 0,10
********************************..*»
...•I*.....1.....
1,04*******
0.37 0.35
0.09*******
0.23
0.04
0.11
0.03
...!:::.
0.14
0.05 0.0?
0.10 0.31
0.01 *******
2.61
';;;;•
*****
0.1 1*
0.1ft
0.02*
*****
......
11/10 1t)/l->
4.75 5.64
0.03*******
0.57 0.59
0.91 1.15
0.03 0.01
0.12*******
****** 0.04*
0.17 0.19
*************
0,03*******
..:::t...;:ii.
0.1?******* 0.06
0.01 0,16 0.09
0*0?**************
26/10
6.42
0.61
0.76
1.42
0.11
0.05
******
1.41
1/11
6.15
0.15
.!:"...
0.66
0.01
0.01
0.05
0.15
1.01 *******
o.ia o.oi
1.04 0.06
..!.".
0.29
0.19 0,03
0.19 0.06
0.07*********'
0/11 15/11
6.34 6,99
0.31 0.97
.;.....;;::.
c.97 i,:-r
0.06 0.07
0.01*******
0*01*******
0.10 0.30
0.02 0.01
0.07 0.34
0.04 0,02
0.23 0.64
0.03 0.04
0.02 0.14
0.07 0.12
>***. O.OI*
i/lie 8/12
".34 4.76
0.70 0.26
0*03*******
0.91 0.43
0.15 0.06
0.03*******
0.03*******
0.06 0.15
0.39 0.04
0.31 0.10
0, 02*******
0.55 0.26
0.01 0.01
0,o3*******
0,05 0.13
****** 0.04
*******
0.0'
0.05 0.09
0.0^ 0.05
0.07 0.06
0.0.1 0.06
0.02
0.01
0.08*******
0.04
0.16
0.06 0.04
0.20
0.09
0.14 0.11
0,10 0.03
0.45
0.11
J6.2"
11-17
0.65 1.12
12.43 42.79
17.86 11.64
1.13 0.73
72.54 11.2'
24.38 2'. 48
0.52
0.06
25.40
12.81
0.31
0.1»
24.38
15.75
1.63
0.17
12.60
1«.53
1.7?
0.?7
39.66
12.08
0.33 0.16
0.07 0.16
16.46 11.49
10.17 5.63
0.48
0.19
12.77
22.36
0.62
0.11
14.9n
12.55
0.42 0.47
0.13 0.27
11.65*******
11.35 13.12
0.84 0.12
0,43 0.02
15.52 18.96
28.53 5.38
0.0*
0.31 0.34
0,0'******* 0.01
0.01 0.14 0.1?
0.0*
0.09*******
0.40 0.24
0.06*******
0.21 0.31
O.tO 0.14
0.12
0.03
0.02
0.03
0.10
***** **
0.1'
0.04
0.12
0,0?
0.11
0.05
0.21
0.01
0,10
0.11
0.06*******
0,02*******
0,o6*******
0.01*******
0.06
0.08
0.02*
0.12
0.05
0.11
0.02
********
0.13
0,04
0.22 0.21
0.04 0.08
0.14 0.03
***** 0.04**************
0.03 0.13 0,05*******
0.04 0.04
A. 01 0.02
-------
LAKE TAHnE 1O67*****PHYTHPLANKTQM*****
Al
65 HAVICIJLA KACILLIIH
66 NAVlCULA CDCCHNE
67 NAVlCULA F.XIGUA
68 NAVICIILA FEStlVA
69 NAVICIILA HUTICA
70 NAVlCULA PSEUDOS
7] NAVlCULA PUPULA
72 NAVUUL4 HADInSA
73 NAVlCULA SCUTTLLOI atS
74 NAVICHLA CAPITATA
75 NAVlCULA CUSPIOATA
76 NAVlCUlA COSfLILATA
77 NEIDIUM HITCHCOCKII
78 NF1DIUM AFFI.'iF
79 N1TZSCHIA FJLLlFDltMIS
80 UlT/SCHlA AMPHIBIA
al NITZSCMIA SlNUATA
8? N1T7SCHU PALTA
83 6PEPKMRA MARTYI
84 ;PEPHL'RA AMERICANA
85 PINNUI ArtIA BICEPS
86 PlNNul.ArilA AEslUARlI
87 PlNNULARIA SURCAP1TA1A
88 PINNUIARIA AHAUjENSIb
89 PlNNUlArtlA BilpEStHIS
90 RHQIcnSi>H.r>4IA CURVATA
91 RHOPAUIOIA "HBRA
92 STAllRONEIS PHDEN
ij 93 STAIIhONLIS 5i4lth
in 94 STAIJRHNEIS ANcEP
VQ 95 SUKlRELLA IJVATA
96 SYNEDRA AHpHICEPHAH
97 SYNtDRA 1AZAMFNSIS
')8 SYNEDRA RADIANS
99 SYNEIJPA KIIMPENS
100 SYNFORA silcIA
101 SYNFj)RA IJLNA
102 SYNEliRA INCISA
103 TAljELlAHIA fl til s
104
105
106 TEIRACYCl.tlS LACUSTRIS
107 nlATHMlLLA
108 ACTINOCYCLU
1(19 CALONFIS Ft
110 CALON!IS 5P
111 RIUOULfHIA AUHITA
112 r.OMPHMNElS HERCllLtAlA
113 FLAKALO'HRIX
115 SPHAFROCYSIIS SC^«Qi--tl.rtI 2.64 4.7? 7.64 ]5.53 11.2r 6 • O7 39.77 57.9| 3«.^,6 16,85 43.65 60.35 65.22 9«.84 60"03 73,"36 9.~75
116 STAllHASfnUM PARAOUXrLI .............. 0.03************** 0.02************** 0.19************** 0.03************** 0 03******* 0 02
117 ROTRYnC'JCCUS IjRAUNII
118 nOCYSTIS NAEGELII
119 PEO!AST*i)« «A«RAISl
-------
LAKE TAHHE 1«68*****PHYTI]PLAHKTON*****
AVERAGE Nu»6TR Oi- INDIVIDUALS PER "L
DATE- 2/ 1 16/ 1 ?«/ 1 8/ 2 14/ 2 20/ 2 ?8/ 1 */ 3 13/ 3 20/ 3 26/ 3 2/4 lit 4 IB/ H 75 / 4 1/5 9/5
SPF'1 •
1 CYCLDTELLA ANTIGUA
? CYCLOTELLA Si>n4NIC«
3 CYCLUTELLA TCEL1.ATA
« CYCLOTELIA srF.I.LUEHA
5 MEL1SIRA CRFNUI.ATA
6 MELOSlRA GHANULflTA
7 MELOSlRA VAPIAMS
9 MELOSlRA UNO'lLAtA
9 STEPHANOOISCHS ASTHEA
10 ACHNANTHCS CI.EVFI
11 ACHNANTHFS FXIUUA
12 ACHNANTHES FLEXF.LLA
13 ACHNANTHES L»NCFOLATA
14 ACHNANTHFS LINFARIS
15 ACHNANTHES NOLLlI
16 ACHNANTHES PFRAGALLI
17 AMPHtPRORA PALUOOSA
IS AMPHIPLEURA PEI.LUCIOA
19 AMPHORA OVALIS
20 ASTERIQNELLA FORMOSA
21 COCCIINEIS OtSCULUS
22 COCCIINEIS Pl.ACfNTULA
23 C1CCHNEIS RU-iOSA
24 CYMBELLA CUSPIPATA
25 CYMBELLA GRAClLlS
26 CYMRELLA LANCEOLATA
27 CYMBELLA VEVTRICOSA
28 CYMBP.LLA SINUATA
29 CYMBELLA PRHSTRATA
30 CYMATOPLEURA SOLEA
32 OIATOMA HIEMALE 9,03**************************** 0.02******* 0.08 0.08************** 0.12 0.08 0.06 0.06 0.06
33 OIATOMA VULGARE »•.*«•*•*************.******•****•«..**.**••******•*.*«*,,****.««*.<************.*****».•*•*****.******...•».*..**.**««*
34 DIPLONEIS ELLIPTIC* o.O* 0.03 0.02 0.01 0.14 0.10******* 0.03 0.10 0.17 0402 o.02«******«****** 0.06 0.02*******
35 OIPL3NEIS OCULATA 0pOS 0-0, o,o5 0;10 Oi(,e otj0 0,0j«««t.«* g.^******* 0,o5 0,03 o,04 0,35 0,0? o>0j Og05
37 EUNOrlA hAEGELII .*..*.* o.Ot*******•*•***•*•****• 0.08**************************** 0.07 e.02*««***«**************«****«****««**
38 EUNOTIA TENELLA *.<.*.,***.....*,*..........«****.**....*. o.o6************** o.oi*********************************** 0.06*******
39 EUNOTIA TRIOOON *•**«•«I*************************** 0.02***********«•«*******«**«•*«•****«**«***«***«***«******»********•**»*•**•«***
40 EUNOTIA PERPUSILLA «******.*****.**.***•*****.•***«.«*•*•»*•.*.*«***.•.*.«..<*•.**...«**•*..***.*.«.*•**,.****.**..«.****«,<*«......*....
41 EUNOTIA PFCTINALIS VENT. ****.*..*****.**.*«***•.•*••.•*****•***«.*************•«*******•*•»****.***»*.*********•«*.*..****.**«*....**...«,.,.**
4? EUNOTIA PECTINALIS **•*«**•****.*•*•«••***********»*******•***.********«*«.«.****.***********.,**.*****,****....**.«***,*«,«•.*..,,,..»..»
41 EPITHEMIA SOREX 0.3B 0,H 0,09 0>()i 0,i4 0.42 fllli 0.33 0.14 8,53 0.07 0,0» 0,33 0,19 „ ,3 n ,4 „ 26
44 EPIThEMIA TIIRGIDA «*.*.*,**..*****,*.*« o.Ol*********************************** Q.|)6***********>** 0.08******* 0.0?****«*********
45 EPITHEMIA ZEBRA 0.14 0.04 0.07 0.15 0.05 0.13 0.1* 0.05 0.10 0.10 0.15 0.02 0.01 0.10 0.10 0.07*******
46 EPITHEMIA ARGUS ************«**********•********•*«*.**•**•*•**«***»****.*•«***•***•«•***•<***•*****,..«*****«•..****.*.«...,.<..*.,,.
«7 FRAGILARIA CROTONENSIS 3J.H 44.68 H4.95 81.12 101.20 111.39 117.1? 182.49 167.7i 155.7fl 134.52 162.17 133.25 165.47 112.19 124.13 137.49
48 FRAGILARIA INTERMEDIA *****•.*******•****»•**•*•••***«*•****•*********«**••***.<**•********•.****»**•******.**«*«*.*.*.*«.****.....««*«,*.<..
49 FRAGILARIA PINNATA 8,3! 3.86 5.87 8.21 6.60 5,65 3.65 12.98 7.24 4.65 6.07 3.37 5.9i) 12.50 6.28 4.10 4.29
50 FRAGILARIA VAUCHERIAE ........*.**..**«*•**•*.»,>««.«*.*.*•*.«.**.*.*.****..... 0.04**********»********** 0.08 0.06 0.02 0.26*******
51 FRAGILARIA CONSTRUCNS ..*...,*.....,*.,..*.....,..,*..*...,....,..,»..*......„....„...*..,......„...*„..„...,.,...,..».;.,.,..,.,,...„,
<52 FRAGILARIA LEPTOSTAURON «•«•«..•**.**.**.*************.«*.>**«•*.*********•**«**.*•*********<«*********«****,...**.*«...,«««.*»*.*.»,.«...,.«„
53 FRAGILARIA CAPUCINA ..»..„*..**..«.«**.****»»«...*.*.**...«.*»*.*.«...»*«.*,.....***....«.,4...»**,...*»»*»,*..».»..«*.»».«.t».«,,»t,«4t.»
54 FRUSTULIA RHOMBOIDES »••••*.*•**...****••.*•**••*****************•****••*****»**•*** (I.01*************************************************
55 GOMPHONEMA ACUMINATIIM o.o*> 0*01******* o.oi o.o? 0.06******* O.o2*********«******«*********** 0.08«***««***««*** 0,53.******
56 GOHPHONEHA PARvULUM o.O* 0.08 0.19 0.15 O.O7 0.17 0.37 n.12 0.25 0.41 0.32 0.11 0.09 0.46 0.38 0.61 0.10
57 GOMPHONEMA CAPITATUM *****.**•*****•*••***«•******•**•**•**•••**•**•>•**•**********»**•«***.***«•*»******•««..**..*«*..,*,.«,..,,,«,,.,.«....
58 GOMPHONEMA VENTRICOSUM **«**«.•*»*•••<••**•******••*«***•**«****»•*•**•*•*•*•***************•••»•**»«*******.**.**«*..,,.«,.,...,.„.....,,.,..
59 HANTZSCHIA AMPH10XTS «..*.....«...*...**»•......*......*.......•...*.*.**..«*...•*........»«....*»..»....*.*.....,...,,..,«.......... . ,,
60 GYROSIGMA ATTENUATUM 0.01**•*****•**•**•••**«**•••*••«*•*•*•**•«*****•***•*«*•********«*******«*«*••«***•••*»«..».*,*.«,«*...•«•••».««••
7.94
0.«7
2.2.
1.2?
0.0'
0.00
0.10
0.04
0.25
0.25
0.04
0.12
5.2?
0.26
2.56
0.9?
0.11
0.0?
0.02
o.io
0.01
0.14
o.in
0.05
6.94
0.64
'.15
2.37
*******
0.06
0.15
0.47
0.18
0.36
0.45
0.04
.4.93
2.53
7.22
2.89
0.19
(1.28
0.61
0.28
0.21
0.05
0.09
4.76
2.42
11.32
2.09
n.o2
0.14 .
0.86
0.09
0.43
0.19
0.06
4.42
2.44
9.?9
3.88
0.21
0.04
0.60
0.15
0.50
0.15
0.03
5.16
2.|7
13.7?
4.69
0-0*
0.31
0.50
0.1«
0.2?
0.31
0.10
5.08
?.73
,<.*
5.6]
0.04
n. lo
n.87
0.39
0.08*
1.6B
0.13
5.88
4.19
13. 28
3.«B
0.17
0.19
1.47
0.56
******
O.O'
0.16
6.62
2.58
22.79
j.74
1.76
?6.1-
8.10 7.04
0.16*******
0.44
1.01
0.51
n.06*
0.49
0.14
5.15
1.71
21.36
5.51
0.02
0.1 7*******
0.83 0.46
0.19
******
0.40
0.32
0.19
0.19
0.08*
0.09
0.06
0.01
4.24
1.40
13.24
5.08
0.01**
0.09
1.36
3.27
2.99
20.92
3.07 3.21 3.46
1.19 1.25 1.26
6.53 18.80 8.92
7.12 5.20 5.89 6.27
************ 0.05 0.05
0.03
2.44
0.34 0.47
*************
0.08 0.08
0.30 0.49
0.06
0.13
0.06 0.28 0.07
1.83 ?.07 1.30
0.34 0.26 0.25
0.18 0.01 0.02
0.11 0.28 0.34
0.13 0.10 0.33
61 HANNEA ARCUS
0.07
62 MAST08LOIA SMITHII fl.06*********************************** 0.08***********«»*«*******««««»***«***» 0.02 0.06******* 0 01*«****«
61 MEHIOION C1RCULARE .........*....*...*...•..*..**•..•* O.OI****************************************** 0.02******.*...*......,
64 HAVICULA AURORA ******* 0.06 0.05 0.02 0.08 0.07 O.O?************** 0.01 0.07 0.02 0.01 0.06******* 0
-------
LAKE TAHflE 1o*fl*****PHYTDPLANKTnN*****
AVERAGE NUMP.TR 0.- INDIVIDUALS PER ML
DATE- 2/ I 16/ 1 ?4/ 1 B/ 2 14/ 2 20/ 2 ?8/ ? A/ 3 I3/ 1 20/ 3 26/ 3 2/4 ll/ « IB/ 4 ?5/ 4 1/5 9/5
SPEC.
65 NAVICULA HA1ILLUM ***********..« n.o? 0.07*«**«*«************** 0.01 0.0? 0.06************** 0,01 0.10 0.14 0.02*******
66 NA1/ICULA CHCCHMTIRIRMIS ' "' " .....
6? NAVICULA FXIr.UA
6» NAVICULA FFSTIVA
69 NAVICULA MIITlCn
70 NAVICULA PSClinnSCUt IFIIK.
f\ NAVICULA PUPItLA
72 NAVICULA RAOtnSA
71 NAVICULA SC'ITTELnlur.S
74 NAVICULA CAPITiU*
75 NAVICULA CUSPICATA
!<< NAVICULA CD5IULATA
tJ NE1DIUM HItCHCDCI'II
f* NF.IDIUM Aff TNI
79 NUZ-.CHIA FHl.IFORMIS
«0 NITZSCHIA AMPHIBIA
81 NIT7SCHIA SMllJATA
8? NIIZ3CHIA P^lEH
83 OPEPHHRA HARIYI
84 fPEPHIRA AMERICANA
«5 PINNULARIA BICFPS
86 PINNULARIA AFSrilARII
87 PINNULARIA SHRC4PITATA
8B PINNIILASIA ArtAIJ.IFNSIS
«9 PINNULARIA RIIPfSTRIS
90 RHOICOSPHENIA ClIHVATA
91 RMOPALODIA r.lUB.I
9? STAUHONEIS PimFNCf
93 STAURONFIS S'lIIHII
S4 STAIIRONUS 1MCFPS
V5 SU«IRF.LI_A OVATA
96 SYNFDRA AMPHICFPHALA
97 SYNH1RA MAZ»«FNS!S
98 SYNFDRA HAUlrtNS
99 SYNEURA DUMPFNS
100 SYNfDRA SBC!/!
101 SYNEDRA ULNA
102 SYNEDRA INCI1A
103 TASfLtARlA FKNF5TRATA
tO« lAdELLARlA FIOCCULiJSA
105 TFIRACYCLUS tHA^iilNATUS
106 TETRACYCLUS LAC'ISTiflS
107 OIATHMELLA HAFO-IHI ANA
108 ACTINOCYCLUS FHRFNBF.RGI i
109 CALfNEIS FEN7L1I
1 10 CALflNEIS SPFrlnSA
1 t 1 HTOnul PHI A AMR I I A
11? GHH'MONEIS HF.RCilLEANA
113 tl AKALDTHRIX fiELATINUSA
114 SCtNFDESNUS 'JIIAORICAUDA
115 SPH'ERilCYStlS SCHRUETFRl
116 STAl:HASIRUH rAHAnOxUM
117 HnlSYOCHCCUS PRAIINII
HB nncYsiis NAFI-.ELII
119 PEOIASTRUM KAKHS1SLYI
1?0 ULniHRIX AE9IIAI. IS
121 ANAPAFNA SP.
12? MEK1SMOPH1IA FLF'iANS
123 POLYCYSTIS AFRlir.INUSA
124 DINCiHRYON SFRTllLARIA
125 KEPHYRII1H OVUM
126 MAL1AMONAS
127 " PEHIOINIUM SP.
12P CEHATIUM HlSIINnlNFLLA
129 CRYPTOMDNAS REFLEX*
0.01 0.03
0.06*******
0.1' 0.19
0.64 0.?5
0.02 0.02 0.06*******
0.03 0.02 0.10
0.09 0,12 0.06
0.20 0.29 0.25
0.10
0.06
0.39
0.01 0
0.20 1
0.1? '0
o.i' n
0.3? 0
.02 O.Ofl 0.01 ************** 0.02 0.01
.06 0,03 0.06 0.19 0,08 0,08 0,11
,26******* 0.06 0.11******* 0.14 0.20
.47 0.17 0.54 0.22 0.08 0.49 0.60
0.04 0.14
0.00 0,03
0.09 0.07
o.ai 0.57
0.08
0,11
0.18
0.17
0.0" 0.0?
0.0? 0.01
0.02*******
0.02 0.32 0.62
0.03 0.15 0.40
0.0? 0.01 0.11
0.46
0.37
0,06**
0.7? 1
0.67 r,
.22 1.6R 1.34 1.26 1,76 |.«1 2,06
,31 0.3A 0.72 0.20 1,66 0.29 1.33
************ 0.08***********************************
1.58 1.55
1.7H 1.06
0.01 0.03
0.78
0.71
0.17
0.1? 0.0«
0.14 (,.1)3
n.on o.o?
0.0? 0,14 0.0?
0,01 0.29 0.03
0.06******* 0.08
0.24
O.ol**
o.ofl o
***** 1)
.08 0.2? 0,04 0.11 0.01 0.06 0.26
.01******* 0.08******* 0.07 0.01 0,04
0.0? 0.05*
0.23
0.02
0.07
0.44 0.36
39. 51 jT.ag
+*******+***+*
**************
•.«! «.5l
***************
0.57 o.32 0.57
,4.?7 3.54 8.03
2.73 2.61 ?,58
14.03 ?«.?0 ?5.47
3.97 4.42 3.90
**********************
0,44
2.«2
1.91
21.51
2.70
0.2" 0
8,85 1
4.49 *
15.3? 15
2.?? 0
****************
, 0,44 0. 6 0,22 0. 3 0,15
.64 7.06 ].?« 2-'9 ?.33 1.75 j.]?
.06 3.3? 7.70 7.59 T. 11 7.53 13.78
,45 ?5.n6 9.78 11.13 6,65 3.63 7,2?
.35 ?.76 3,?5 1.50 1.92 4.12 3.80
*********************************************
0.04 0.03
..*.,.* ,.67
16.67 6.49
1.24 3,58
5.88 2.01
0.02
0-5'
38.31
1.02
3,99
*********************
-------
LAKE TAHflE 1 °6fl*****PHYTOPLANKTON*****
NUuBrp Of INDIVIDUALS PER ML
DATE
'.etc.
I rmnTELlA ANTIGUA
7 CYCLHTELIA RflPANKA
i CYCIOTELLA OCELLATA
4 CYfLHTELLA STELLIGERA
t MfL'ISlHA CRENULATA
6 "(LHSIRA GRANULAtA
T MlLflSIRA VAR1ANS
fl I'ELOSIRA UNOULATA
V SHPHANCDISCUS ASTREA
1C ACHNANTHFS CLEVEI
11 ACHKANTHES EXIGUA
i? HHMNTHES FLEXEULA
1J SChMNTHES LANCEOLATA
H ACHNANTHES LINEARIS
15 ACHNANTHES NOLLII
16 ACHNANTHES PERAGALLt
17 AMPHIPRORA PALUOOSA
16 AKPHlPLEuRA PFLLUCIOA
19 AMPHORA C1VALIS
20 ASTER10NFLLA FORMOSA
21 C1CCONEIS OISCULUS
22 COCCONEIS PIACENTULA
23 COCCONEIS RUGOSA
2« CYH8ELLA CUSPIOATA
25 CYMBELLA GRACILIS
26 CYMBELLA LANCEOLATA
27 CYMRELLA VENTRICOSA
28 CYMBELLA SINUiTA
W 29 CYMflFLLA PROSTRAT*
"^ 30 CYMATOPLEJRA SOLEA
Is* 31 DIATTMA ANCEPS
32 DIATOMA HICMALE
33 DIATOMA VULGARE
34 DIPLONEIS ELLIPTICA
35 nlPLONEIS OCULAIA
J6 DIPLONEIS FINNIC*
37 EUNDTIA NAEGELII
38 EUNHT1A TENELL*
39 FUNOTIA TRIODON
00 EUNOTIA PERPUSILLA
41 EUNOTIA PECTINALIS VENT.
«2 EUNOTIA PECTINALIS
43 EPITHEM1A SOREX
44 EPITHEMIA TURGIDA
45 EPIIHEHIA ZEBRA
46 EPITHEMIA ARGUS
47 FRAGILARIA CROTONENSIS
48 FRAGILARIA INTERMEDIA
49 FRAGILARIA P1NNATA
50 FRAGILARIA VAUCHERItE
51 FRAGlLARIA CONSTRUENS
52 FP.AGILARI* LEPTOST»URON
53 FRAGILARIA CAPUCIMA
54 FRUSTULIA RNOMBOIOES
55 GOMPNQNENA ACUMINATUM
56 GOMPHONEMA PARtfULUM
57 GOMPHONEMA CAPITATUM
58 GOMPHONEMA VENTRICOSUM
59 HANTZSCHIA AMPHIOXtS
60 GYROSIGMA ATTENUATUM
61 HANNFA ARCUS
62 MAS10GL01A SMITHII
63 MERIOION CIBCULARE
64 NAVTCULA AURORA
16/
22/
5/6 12/ 6 l9/ 6 26/ * «/ 7 ll/ 7 |7/ 7 24/ 7 31/ 7 7/8 12/ B ?!/ fl 2«/ 8 2/9
2.4' 4.28
1.31 I. 45
11,75 35.14
6.2' 8.03
0.0« 0,04
0.2" 0.08
2. 55 0.61
**************
0.49 0.00
0.09*******
0.31 0.10
3.05 2.65
0.26 0.43
8.16 4.87
4.81 4.25
0.03 0.04
0.12 0.13
O.OB 0.06
2.15
0.09
3.83
5.87
0.08
0.20
0.12
0.01 0.01*******
0.01 0.01
0.03 0.13
******* 0.03***************
**************
0,21 O.ll
0.0« 0.03
**************
**************
0*0^ 0*02
0.11 0.06*'
0,01*******
0.05 0.12
0.04 0.02
0.01 0.01
0.08*******
0,05
0.07
0.0?
0.75
0.18
2.00
0.1'
2.47
1.27 2.70
O.Ol*******
0.06
0.60
O.Ol
0.03
0.03
0.07
*************
0.05
0.10
0.05
O.Ol
0.09
0.0«
0.1"
0.27
?,27 1.2*1 1.38
0. 34 0<64 0.58
2.34 l.oi 1.13
1.72 3.17 3.79
0.01 0.01 0.12
0.16 0.0? 0.24
1.61 1.31 2.35
0.07*********************
0.03
0.1'
O.l1!
0.00
O.K
0.11
0.01
0.15 0.08 0.14
n.Oi******* 0.03
0.10 0.09 0.26
0.04******* 0.04*'
0,04 0.09********'
0.32 0.13 0.90
0.1? 0.17 0.25
0.58
0.42
0.73
4.31
0.98
0.44
3.69
0.08
0.06
0.45
0,01
0.37
1.96
0,06
0.91
2.63
0.08
0.22
1.38
0.03
0.04
0.06
0.03
0.19
****************
0.06 0.04
*************
0.40 0.29
0.38 0.20
0.01******* 0.08 0.02************** 0.04*******
0.02********************* o.Ol ************** 0.04
Q.Q7**************
0.02
O.ll
0.10******* 0.06
0.06
1.65 2.08
0.16*******
0.72 0.51
8.31 6.49
0.12 0.03
0.13 0.12
1.88 1.10
0.06 0.06
0.01 0.03
0.17 0.06
0.04*******
0.13 0.03
»«** 0.01
0.03 0.10
0.01 0.06
0.46 0.05
0.17 0.17
1.08
0.10
1.19
4.72
0.0'
0.01
0.21
1.38
0.17
1.17
i.ir
0.22
1.06
6.65 6.71
n. 01*******
0.02
0.27
1.70
0.02
0.15
1.22
0,09**************
0.01 0.01
0.15 0.19
0.04 0.08
0.03 0.02
0.25 0.08
0.04 0.03
0.06*******
0.13 0.06
0.04*******
0.25 0.17
0.17 0.15
0.02 0.02 0.04
0.01**************
0. 04*** ***********
0,08
0.04
0.10
0.13
0.12
0.23
0.06
0.02
0.01
0.03
O.«l
0.21
0.04 0.02
0. 06*******
0.02
0.01
**************
0.03**************************** 0.01******* Q«0&********************* 0.06 0.01
0.01
0.27
0.34
0.09
0.01
0.14
0.04
0*08
0.01
0.07
0.04
0.11 0.3'
O.Ol* ******
0.38 0.7.1 0.36 0.96
0.09 0.04 0.09 0.06
n.52
0.15
0.69 0*40
0.26*******
0.61
0.20
0.72
0.38
0.40
0.21
128.21 168.02 114.55 69.86 83.16 ]6.fl7 5.61 31.39 32.96 85.39 17.88 14.58 16.99 16.90 19.03 14,13 8.92
******************* 0.72 0,60************************************************************************************
6.17 3.37«******«»**««****«*»* 3,06 7.20 6.67 5.03 14.62 25.66 16.36 8.62 6.67 15.96 7.63 12.67
•****•*» o-02
0.37 0.05
**************
*•*******«**•* 0.QJ Q.,,3
0.13 0-19 0.12 0.07
0.04*********************
0* O3
0.21
0.01
o»o8 o»o6
0.17 o.2ft
0,02*******
0*0* 0*13************** O'lO
0.24 0.38 0,19 0.12 0*07
0*03****************************
0*0? 0*0*
0.15 0.51
0. 02*******
o.o'
0.26
0.06
***********************************
o.oi 0*0?*******
0.01
0*03 0*06**************************** 0.06*******
0,0?******* 0.04 0.02 0,03**************
************** 0.01 0.02******* 0*o2 0<1?
0.01********************* 0.03 O.Ot 0.06
******* o-07 0.01 0*02 0.02 0*Ql 0*10
0.01***********************************
0.02 O.Q3 0.03 0.24 0.08 0.13
O.Ot Q.oA******* 0*02 0.01*******
O.OB 0.0? 0.19 0.19 o.04*******
0.02*********************
0.09 0.14 0.13 0.13
0*04 0.02 0.02*******
0.01 0.19 0.01 0.06
-------
LAKE TAHHE 1*J6fl*****PHYTOPLANKTnN*****
65 NAVliUILA BACULUM
66 NAVICULA C1CCONEIFORMIS
67 MAV1CULA EXIGI "ITZSCHIA PALFA
6.1 'PtpHHRA MAHTYI
«4 'PfPt-ORA AMERICANA
Si PlhhULARIA BICEPS
86 PINMILARIA AESTUARII
87 PlNM'LARIA SUPCAPlT«TA
1)8 PINNIILARIA AHAUJENSIS
(19 PINM1LARIA RUPESTRIS
90 FMUICOSPHEN1A CURVATA
9! RHOS'ALnDIA GIBBA
V? RTJUHONEIS PHtlENcE
OJ 93 S1AUKONEIS SMITHII
ON 94 S'AIJHONEIS ANCEPS
(jj J'j 51IRIHELLA nVATA
96 SYNEIIRA AMPHICEPHALA
ir SYNF'DHA HAZAMFNSIS
98 SVM'IIRS RADIANS
99 SVMORA RUMPENS
1HO SYNtHRA SOCIA
101 SYfjFnRA hLNA
III? SYNEDRA INCtSA
1113 TAPKLLARIA FtNESTRAT
!0« TADFLLARIA FLHCCIILOSA
1U5 TflHACYCLUS EnARQlNAIuS
1116 TI1RACYCLUS LACUSTRIS
107 DlnTOHELLA BAFOURIANA
1UH ACIIMOCYCLUS FHRENRERGlI
t J9 CALIINEIS FEN71 1 I
HO CAI.HNEIS SPtCIOSA
\\\ M !()!)HLPH? A ANPI TA
112 GOHPUONETS KERCULEANA
1M FLAKALHTHRIx GELATINOSA
IH SCKMFOESMUS OUAORICAUDA
VI!) SI'HAEnnCYSTIS SCM
116 S rA'lHASTHUM PARAD
I 17 Hi)Ti»YDCIICCIIS BRAU
118 TUCYSTIS NAKGtLII
ii'j pr.ousrRun KA^HAISLVI
120 ill.OfHRK AEUUALtS
121 ANA^AENA SP.
12? MI-'SISMOPEIIIA ELEfiANS
123 PDLfCYSTTS AEBUGIH05A
124 nINi)RHY"N SERTULARI
12r> KCP^YHinN HVIIH
120 MALLAMQNAS
127 PCHIOINl'JH SP.
128 CEKATIUM HIHIIMDINELLA
129 C^YlTn^nNAS RLTLEXA
AVERAGE "UK
OATE
SPEC.
FORMIS
UllFOR.
IDES
A
4
II
*MIS
(
UI
IT«TA
ISIS
US
•>/ 5 5/6 12/ 6 1 9/ 6 26/ 6
0.07 Q,()2***********************************
o,on**************************** o.oi 0.1"
0.14 O.M 0.35 0.01 0.08 0.06 0.03
0.54 0.16 0.26 0.17 0.28 0.11 0>13
0.64 2,1' 0,03 0.05 0.02******* 0.11
0.05 0.26 0.02 0.04 0.05 0.02 0.04
************** 0.0ft 0.11 0.20******* 0.0R
************** 0*01 0.01******* 0.06 0.09
0.4* 0.02******* 0.02 0.01 O.OI 0.21
0.2ft 0.31************** 0.10 0.13 0.0*
0.2'******* 0-04 0.02 0.03 1.61 l-7«
16.99 6.7a 0.06 Q.7Q 0.65 0.13*******
«/ '
n.02
0.08
0.16
0.51
0.19
0.21
11/ 7
0.01
n.ll
0.1?
0.40
0.14
0.03
0,10*******
0.03
0.01
0.01
0.08
o.io
0.01
0.13
*******
0.28
*******
0.01
*******
0.26
0.03
0.11
*******
1.78
*******
17/ 7
0.10
0.03
0.19
1.27
0.13
0.?4
0.07
0.01
0.03
0.04
0.21
0,16»*
0.10
0.44
1.33
0.33
************************************************************************
************************************************************************
?4/ 7
0.10
0.13*
0.34
0.21
1.59
0.24
0.35
0.06
0.10*
0.21
0.06
0.34
*****
******
0.02
0.50
31/ 7
0.10
******
0.06
0.10
0.04
0.78
0.11
0.23
0.04
******
o.oi
0. 06
0.15
0.09**
********
0.10
0.76
7/ 8
0.03
o.ei*
0.09
0.13
0.14
0.92
0.40
0.28
0.10
0.03
12/ «
0.13
******
0.03
0,01
0.17
0.49
0.05
0.39
0.01
0.10
0.01*******
0.24 f. 19
*****
*****
0.01
0.06
0.35
0,22**************
0.10
1.76
******
0.10**
5.32
*****
3.63
0.03
n.oi
0.12
0.06
1,62
0- 17
0.83
4. 09
********************
?!/ « 2»/ 8
0.05 0.13
0.06*********
0.15 0.06
0.35
0.30
0.83
0.13
0.16
0.21
0.24
0.0?
*******
0.08
*******
*******
0.06
0.06
1 ,38
i.oo*
0.86
9.44
0.11
0.17
0.92
0.41
0.31
0.01
0.08
0.07
2/ 9
0.07
*****
o.oi
0.29
0.15
0.89
0.26
0.13
0.02
0.08
0,12
0. 10*******
0.30 0.12
0.06**
0.01
0.03
0.03
1.97
********
0.64
1.02
11.99
*****
0.03
o.ua
0.04
O'.Ol
0.97
*****
0.06
1.47
0.69
9.68
*********************
-------
IAKF TAHI1E |068-1949****«PHYTOPLANKTON*«*««
U)
1 CYCLOTELLA ANTIGUA
2 CYCLOTELLA P.UOANICA
3 CYCLUTELLA OCELLATA
4 CYCIOTELI.A STELLUERA
5 MELDSIRA CRENuLATA
6 HtLOSIRA GRANULATA
7 MELOSIRA tfARIANS
f) MELOSIRA UNnULATA
9 STEPHANODISCUS ASTREA
10 ACHNANTHES CLEVEI
11 ACHNANTHES EXIGUA
i? ACHNANTHES FLEXELLA
13 ACHNAUTHES LANCEULATA
u ACHNANTHES LINEAHIS
15 ACHNANTHES NOLLII
16 ACHNANTHES PCRAGALLI
17 AMPHIPRDRA PAtUOOSA
1A AHPHIPLEURA PF.LLUCIOA
19 AMPHORA OVALIS
20 ASTERIQNELLA FORMOSA
21 COCCONEtS DlSCUlUS
22 COCCUNEIS PLAcENTULA
23 COCCONEIS RUGOSA
2« CYMBILLA CJSPIDATA
25 CYMBILLA GRACILIS
26 CYMBELLA LANCEOLATA
27 CYMBEUA VENTRlCOSA
28 CYMBF.LLA SINUATA
29 CYMBELLA PROSTRATA
30 CYMATOPLEURA SOLEA
31 DIATOMA ANCEPS
32 OIATOMA HIEHALE
33 DIATOMA VULGARE
3« OIPLONEIS ELLIPTICA
35 DIPLONEIs UCULATA
36 DIPLONEIS FINNIC*
37 EUNOTIA NAEOELU
36 EUNOTIA TENELL*
39 EUNOTIA THIOOON
40 EUNOTIA PERPUSlLLA
»i EUNOTIA PECTINALIS VENT.
42 EUN01IA PECTINALIS
43 EPITHEMIA SOREX
4« EPITHEHIA TURGIDA
45 EPITHEHIA ZEBRA
46 FPITHEHIA ARGUS
47 FRAGlLARIA CROTONENSIS
46 FRAGI1ARIA INTERMEDIA
49 FRAGHARIA PINNATA
50 FRAGlLARIA VAuCHERIAE
.51 FRAGlLARIA CONSTRUE
52 FRAGlLARIA LEpTOSTAUROt
53 FRAGlLARIA CAPUCINA
54 FRUSTULIA RHOMBOIDES
55 GOMPHONtMA ACgMINATUM
56 GOMPHONEMA PARVULUM
57 GOMPHONEHA CApITATUN
5B GOMPHONEMA vENTRICOSUM
59 HANT2SCHIA AMPHIOXTS
60 GYROSIGMA ATTENUATUM
61 HANNEA ARCUS
6? MASTOGL01A SKITHII
63 MERIDION CIRCULARE
64 NAVKULA AURORA
AVERAGE NUuBfR Or INDIVIDUALS PER ML
OATt" lit 9 17/ 9 ?6/ 9 15/10 19/10 J7/10 2/U
•SPEC.
0.0********************** 0.08**************
:A 1.9= 0.74 2.98 1.99 1.81 3.30 2.97
'* 0.04 0.49 1.06 1,54 1,77 1.59 1.79
1 0.4* 0.23 0.39 0.92 1.27 0.59
\ ******************************************
1.07
0.01
r?EA 5.6n 1,66 6.08 5.40 5.83 4.49 2.7.1
0.01 0.11 0.04 0.13 0.17 0.06 0-06
************** 0.01 0.06 0.01 0.01 0.01
.A **************************** Q , 1 5**************
:*TA 0.21 0.66 0.81 0.49 0.49 0.37 0.4fl
15 1.1S 0.19 0.17 0.04 0.05 0.13 0.11
******* 0.13 Q.03********************* 0.17
•IOA 0.01 0.01 0.06 0.04 0.08 0.04
0.2" 0.06 0.38 0.34 0.60 O.?l
)SA ******* o.02******* 0.03 0.15 O.o3
• *««»**« 0.2* 0.55 0.46 0.47 0,88
IL* 0.19 0.10 0.21 0.77 0.47 0.12
0.19 0.06*****************************
1 0.11 0.04 0.01******* 0.04 0.19
******* "0.06 0.15 0.11 0.17 0.02
* 0.01 0.08 0.11 0.01 0.12 0,06
'A 0.33 0.17 0.22 0.28 0.19 0.15
0.0* 0.15 0.22 0.42 0.46 0.47
************** o.Ol************** 0.10
0.0? 0.01 0.01 0.06**************
0.06******* 0.06******* O.Ol*******
:A 0.02******* 0.01 0.12 0.12*******
************** 0.03 0.01******* 0.43
********************* o.Ol**************
0.0? o.Ol******* 0.06 0.03 0.0*
0.65 0.15 0*46 0.28 0.36 0.16
************** 0.01 0.06**************
0.35 0.17 0.10 0.15 0.0« 0.17
NSIS 9.83 9.9i> 11.20 H.04 33.03 31.27
DIA .»***.« 1.50 4.95 4.67 3.54 4.90
' _. 13.79 0,72 1.20 0.82 2.61 9.53
i*-NS ******* 0.01 0.02 0*09. 0.12*******
1/1?
0.03
1.99
1.06
1.67
0.03
1.72
0.16
0.03*
0.04
0.62
0.28
0.16
0.02 0.02
0.2" n.23
0,01*******
0.15 0.46
0.85 0.43
****** 0.01
0.01*******
0.04*******
0.09 0.10
0.25 0.11
0.39 0.41
0.01
0*04
0.04
0.06
0.21
0.01
0.03
0.31
0.01
O.lt
32.50
2.0"
5.80
0.01
7/1?
0.07*'
7.95
0.51
0.01
2.66
0.08
******
0.01
0.38
0.06
0.0.1
0.01
0.17
0.3S
0.21
0.99
0.05
0.01
0.01
0.05
0.1?
0.11
22/12
******
2.16
0.51
0.56
0.08
2.33
0.07
0.01*
0,02
0,26
0,02
0.0?
0.06
0.30
0.12
0.55
0.04
0.02
0.03
0.04
0.11
0.15
0.06 0,00 0.02
0.10******* 0.01
0.02**************
0.10
A. 09
0.07
n.os
0.31
0.03
0.24
41.83
3.08
5.11
0,01
0.05
0.10
0.17
0.0'
0.03
O.*1
0.04
0.16
59.09
1.94
1.95
0.00
0.04
0.01
0.14
16/ 1 I/ 2 15/ 2 Z/ 3 15/ 3 30/ 3 13/ 4
0.01 o.Ol**************************** 0.01
3.5o 2.95 2.41 H.75 2.07 1.93 2.06
1.35 1.90 1.64 1.09 0.69 1.44 1,09
2.09 6.32 6.33 9.14 V.85 10.60 11.16
0*02******* o.o3************** ******* 0*11
2.55 1.65 3.31 3.98 4.43 4.40 5.07
0.04 0.02 0.05 0*12 0.09 0.05 0,02
******************** 0.00 0.0? 0.05*******
0.01 0.02**************************** 0,02
0.14 0.13 0.22 0.09 0.15 0.11 0.12
0.01 0.03 0,07 C.05 0.04 0.11 0.01
0.15 0,19 0.17******* 0.05 0,11 0.00
0.54 0.40 0.19 0.30 0.49 0.78 1.17
0.08 0.03 0.04 0.01 0.08 0.14 0.17
0.43 0.20 0.33 0.25 O.lft 0.24 0.17
0.00******* 0.01******* 0.00 0.02 0*01
0*02********************* 0.00**************
0*00 0,02**************************** 0,00
0*04 0.02 0.01******* 0. 04**************
0.0« 0.07 0.10 0.00 0.06 0.03 0.04
0*14 0.05 0,16 0.02 0.03 0.02 0.11
0*04 0.02**************************** 0.02
0.04 0,02 0.01 0*01 0.02******* 0.01
0.02 0.04 o,03******* 0,04 0.71 0.03
0.04 0.01 0.05 o.Ol******* 0.01*******
0.02 0,02 0.06 0.02******* 0.06*******
0*02******* 0,01 0.00 0*01************** 0.04
0.04 0.03 0.05 0.02 o.Ol******* 0,02 0.02
0.14
0.03
0.15
«?.35
0.23
0.11
0.02
0.04
0*21 0.14 0.08 C.01 0.10 0.08 0.08
0*02********************* 0*05 O.OJ*******
0.13 0.08 0.03 0.09 0.01 0.07 0.10
441.51 46,41 50.43 54.37 6Z.31 119.47 188.58
0.03 0.14 0.09 0.04 0.06 0.21 0,03
0*58 0.31 0.76 (1.58 0.35 0.85 0.77
0*01 0.01 0.02 0.04 0.01 0.06 0.10
0*00********************* 0,00**************
'^UM 0*0* 0*03******* 0*10 Q.l7 O.o2
« 0.21 0.0* 0.34 0.06 0.13 0.30
O.o******** 0.21 0.10 0.08 0.06
0*0,4
0.19
0.05
0.0?**
0*04
0.03
0.12
0.12
0.15
0*01
0.13
0.02 0.02 0.03
*******************
0.04 0.01 0.03
0*»7 o.OZ******* o*01*********«***« 0*03
0.0? 0.07 0.04******* 0.04 0.07 0.03
0.04 0.03 0.00 0.01 0.0? 0.07*******
0*01 0.01 0,01********************* 0.00
0*03 0,05 0,01 0,03 0.01******* 0.01
-------
LAKF TAHflE 1«68-19*9*****PHYTOPLANKTQN*****
(_n
NAVICULA BACII.LIIM
NAVICULA COCCnNEIFORMI
NAVICULA EXIGIIA
NAVICIILA FESTIVA
NAVICULA MUTICA
NAVlCULA PSFUDUS
NAvICULA PUPUIA
NAVICULA RAOIOSA
NAVlCULA SCIITTELOIOEs
NAVICULA CAPITATA
NAVICULA CUSP1DATA
NAVlCULA COSTllLATA
NEIDIUM HtTCHcnCKII
NEIOICJH AFFINF
NITZSCHIA FlLLlFtlRMIS
NITZSCHIA AMPHIBIA
NITZSCHIA SINUATA
NITZSCHIA PALFA
CPEPHORA MARTYI
84 JPEPHURA AMERICANA
85 PINNULARIA BICEPS
PINNULARIA AESTIJARII
pINNULARIA SUBCAPlTATA
PINNUL'RIA ABAUJENSIS
PINNULARIA PupESTRIS
RHOICOSPHENIA CIIRVATA
RHOPALODIA GIBBA
STAURHNEIS PHnEN
STAURONEIS SMITHII
STAURtlNEIS ANcEpS
SJRlRFLLA DVATA.
SYNFDRA AMPHICEPHALA
SYNFDRA MAZAMFNSIS
SYNEpRA RADIANS
SYNFnRA RUMPLNS
SYNEORA SOCIA
SYNFnRA ULNA
SYNEDRA INClSA
TAflELLARl* FEhfE
TAflfLLARIA FLOCCULOSA
TETRACYCL1IS EH»RaIN4TIJS
TETRACYCLUS LACUSTRIS
DlATOMtLLA RAFOIINIANA
ACTINnCYCLUS EHRE
CALONFIS FENZLlI
CALONFIS SPECIOSA
RIOnUI.PHIA AURITA
GOMPHONEtS HtRCULEANA
fl.AKALOTHRlX GELATINJSA
SCtNEnESMUS JUAORICAUOA
SPHAEROCYSTIS SCH
STAURAS1K1IM PARAOOXUrt
BCTRYQCUCCUS RRAUNII
nDCYSTIS NAF.dfLII
PEOIASTRUM KAHRA1SLYI
ULOTHRIX AEOUALIS
ANARAENA SP.
MERISMDPEllI* ELFGANS
123 POLYCYSTIS AERIIGINIISA
124 nINOBRYON SFRTUL'RIA
125 KEPHYRIUN UVIJM
126 HALIAMONAS
127 PERIDINIUM SP,
128 CERATIUrt HlRUHUINELLA
129 CRYPTOHUNAS REfLtXA
65
66
67
60
69
70
7!
72
71
7*
75
76
77
78
79
80
81
fl?
83
86
87
88
89
90
91
92
93
9*
95
96
97
98
99
100
101
10?
103
10*
105
106
107
108
109
110
111
II?
113
11*
115
116
117
US
119
1?0
121
AVERAGE NUMBFR Or INDIVIDUALS PER ML
OATE» 11' 9 I7/ 9 ?6/ 9 15/10 19/10 27/10 2/H 1/12 7/1? 22/12
SPEC,
0.15 0.06 0.13******* 0.21 0.10 0.1* 1.18 0,1* 0.06
FORM IS ******* Q.O?********************************************************
0.1* 0.03 0.26 0.35 0.13 0.16 0.1* 0,22 0.18 0.05
*******.**.********** 0.08 0.18 0.06 0.05 n.03 0.0?*******
UTIfOH.
IDES
A
A
II
RMIS
A
RII
ITATA
NSIS
RIS
VATA
ENTERON
I
ALA
S
RAT*
LOSA
INATIJS
TRIS
UNA
NBErfGII
EANA
TINJSA
ICAUOA
OxUrt
Nil
SLYI
ANS
NOSA
RIA
iELLA
XA
0.1» 0.13*******
0.17 0.13 0.32
0.5* 0.52 1.10
*********************
O.?n 0.04 0.18
0.0« 0.*5 0.37
0.07******* 0.08
^»****** 0.03********
******* 0.02 0.02
******* 0.01 0.02*
************** 0*01
******* 0.01 0.25
0.0* 0.0*********
0.06 0.08 0.04
0.61 0.73 0.33
1.47 1.91 1.88
0.12 0.18 O.«0
0.09 0.07*******
0.22 0.38 0.60
0.53 0.53 0.41
*.72 4.44 7,?9
0.05 0.06 0.01
************* 0.02
0,01**************
************* 0.02
0.01******* 0.06*
0.21 0.01 0.06
*****.******** 0. 02
0.11 o.oi************** 0.0********
******* o.ll 0.17 0.08 0.10 0,10
].3'«****** 0.02
12.95 0.63 1.4*
0» I9 O-O4 0- ly
1.19 0.29 1.22
1.90 2.67 4.46
0.
0.
1.
0.
0.
0.
0.
4.
0.
o.
0.
0.
0.
0"
50
21
07
01
68
3*
01
05
01
03
0*
0«
********
0.
0.
0-
0>
0.
0-
0.
0-
n
0*
0'
0*
01
54
30
76
0.11 0.03 0.01*
0.28 0,20 0.08
1.22 0.91 0.*9
0.07 0.11 0.03
0.02******* 0,01
0.73 0.39*******
0.3* 0.16*******
?.37 0.99 O.*0
0.05 0.01 0.02
n. 01 **************
0.11 0.04 0.02
0.03 0.0" 0.08
16/ 1
0.07
0.01
0.1!
0*06
I/ 2 15/ 2
o.o********
0.10 0.03
0.0* 0.03
0.06 0.03
*************
0.15 0.08
0.33 n.21
0.07
0.02*
0.26
0.34
0.8'
0.01
0.03*
0.01
0.01
0.06 0.!)?**************
************ 0,01
0.0* 0.0? 0.00
O.OI 0.0' 0.01
0.02
0.00
0.06
********
0.26
0.34
0.31
0.01**
0.07
0.37
0.05
2/ 3 !5/ 3
(t,Q]*4*******
0.00*******
0.02 0.04
0.01 0.06
************
0*01 0*00
0.09 0.10
0.01 0*06
30/ 3
*****
0.02
0.06
0.03
0.05
0,02
0.13
0.20
0.02
13/ 4
0.05
0.09
0.01
0.02
0.04
0.04
0.10
0,16
0,00
*********************************
0.18 0.06 0.01 0.05 0.05
0.25 0.10 0.13 0.25 0.76
0.80
0, 0********
****** 0,04
0.05
0.02
0.00
0.0*
0,01
0.02
0.01
0.02
0. 06*******
0.06 0.02 0.02**************
0.12 0.08************** 0.03
rt.35 0'™ OM3
1.59 2.95 l.flfl
0.84 0.63 0. 37
0-«2
0.07
3.32
0-11
o-o'
0.02
1.41
0.1*
0.05
0.00
0.04
0-16
0.03
2.0*
0.07
o.o6 o.n
0*01 0.01
C*04 0.00
0*01 *******
0,00*******
0.01 0.01
0.03 0.0?
0.07 0.06
0.01 0.01
0.01*******
O'll O'l?
0.23*******
0.59 0.80
0,04******* 0»04
0.15
0.00
0,04*******
0,02 0,03
0,02*******
o, oft*******
0.10
0.02
0.03
0.04
0.33
0.12
0. 02*******
0-0*
1.43
0. 16
0.07
4.37
0.96
0,02*******
-------
L»Kf TAH1E |069*****PHYTnPLANKTON*****
AVERAGE NUBBrR 0- INDIVIDUALS PER HL
OATE» ?5/ 4 9/5 '3/ 5 7/6 •'O/ 6 1/7 8/7 IV 7 22/ 7 24/ 7 1Q/ 7 5/8 20/ 8 2U/ « 3/9 9/9 15/ 9
1 CYCI.1FEU.A ANTIrjttA ********************* 0.06******* Q.Ol************** 0.04******* 0.00******* 0.01 0.07******* 0.01 0.01
2 CYCI.HTELLA RtiriANICA 2.61 ' 2,5,5 1.55 2.19 1.53 1.12 1.57 0.56 3.39 0.32 1.61 n.o» 0.95 6.30 1.26 1,70 1.59
i CYCinrclLA C1CELLATA 0.66 O.ln 0.04 0.28 0.34 0.39 0-05 n.29 4.81******* 1.08******* 0.28 51.62 0.01******* 0.05
« CYCL1TF.LLA STELLIGERA 0.01*********************************** 0.00************«*****«********«******* 0.00****************************
•> "ELHSIR* CRtNULATA 1B.8« 15.'9 12.21 8.46 7.22 5.?8 2.59 1,04 18.7* 0.28 5.59 0.00 2.16 28.79 0-86 H.79 7.09
6 uEl'KSIRA GHANtJLATA ********************* |). 01 ********************* 0.09***************************«******* 0.61 ************** 0.03
f MftnsiRA VARIANS o.07........*......**»***.***.**«****"«**********«*********««.**.......**......*...*..*...*....*.....**...**..*****
a MEI..ISIRA UNDULATA .».»*»,*»***,«**.*«.****»».**.****••**********•*»****.**.«««***.«.«««.*.,«.*.**..,»,*,..».,«*,*..,.«,.«**,**,.*«»**«*»*
•> SFEPHANOOISCUS ASTREA 5>91 3.3,, 1.93 2.56 2.26 0.98 0.25 0.93 3.79 0.06 1.4o 0.01 0.73 3.77 0.65 1.61 1.78
10 ACHNANTHES CLFVEI 0.17 0.16 0.08 0.09 0.10 0.05 0.01 0.03 0.4?************** 0.01 0.01 0.39 0.06 0,08*******
11 ACHNANTHES FXTG'JA ********************* 0.01 O.Ol 0.00******* 0.02******* 0.03 0.01 0.00 0.02 0.00************** 0.02
12 ACHNANTHFS FLEXELLA ******* 0.02******* 0.00***.**** 0.02 0.00******* 0.04******* 0*05************** 0.09 0.0?******* 0.02
13 ACH1ANTHES I.ANCEOLATA 0.4r 0> 0, 0.07 0.14 0.23 0.17 0.11 0.17 0.22 0,07 0,22 0.01 0.02 0.62 0.06 0.19 0,12
11 ACHNMTMFS LIMEARIS o 05 o 06******* o 05 0.02 0.04 0,01 1.10******* 0,00 0,01 o oo***********************************
15 ACH,va,4THES NOLL 11 „ .0«..*...*..*•.*.**..****..*..***.**«.**«.*...***.*...........*...**.*..*.*.*.......*.*..*.**.*.*..*».*....***«...*
16 ACHNANTHES Pf-RAr,ALLf ********************* 0.02 0.02 O.Ol******* 0.01 0.01 0.10 0,02************** 0,05 0,01 0,01 0,02
17 AMPHlPRORA PALUIKISA .****,*....*...«.*.******....*,*..•*.****.•*•********..*,.**•*.*****.*..*****......**......*******...****.**.**«**•****
18 AHPHIPLEURA PEUUCtDA o.01 **************************** 0,01************** 0.0? 0,01 •..*****•**»•**••***•**.***.•«**«*•*•*•*•*••*••**
19 AMP'IflHA nvAl IS o.n 0.0? 0.05 0.03 0.00 0.04 0.01 0.03 0.00 0.02 0.02******* 0.07 0,10******* 0,03 0,09
20 ASTFR1QNF.LIA FORMOSA 0.9, 0.8, 0>01 ,,,37 0>87 0.02 0.00 0.07 0.11 0.03 O.H 0.48 0.10 0.20 0.01 0.04 0.13
21 COOcnNEIS OTSnULUS 0.03 0.05 0.02 0.03 0,00 0,05 0,05 0.00 0.0,6******* 0,01******* 0.04 0.24 0.01 0,01*******
22 cnccnuFls PLACE«ITULA 0,?1 0.17 o,]7 o.i9 o.o' o.is o.o? o.io 0.59 0.02 0.22 o.oo o.is o,7o 0,05 o.i? 1.04
23 COCCONEIS RIIGHSA 0.01****************************************** n.01•*****•**•****•***•****•*.****•**** 0.04******* 0.01 0.01
24 CYH1ELLA CUSPIDMA ************** o.01 ************** O.Ol******* 0,02 0,n6 0,01****************************************** 0,03
25 CYM6FLLA GRACIL1S o.01 ********************* 0.01 0*03 0.01 0.01 0.06******* 0*01 0*00******* 0.03******* 0.01*******
26 CYMRF.LI.A t-ANCfOLATA .0.04************** 0,03******* 0,01******* 0,00 0.?8 0,01 0.02************** 0.01 ************** 0,05
27 CYMBFLLA VF.NTRICUSA Oi(v, 0-i8 . , 02 0>17 Oi20 Ol?8 0.04 0>21 0-r1 0.02 0>28 0-04 0>03 Oi99 Oi07 Oi28 0.31
2fl CYMBFLLA 5INUATA 0-|, Q.O.J 0.05 0.02 0.0* 0.16 0,0? 0.09 0.14 0.00 0,04 o.OO 0.04 0.13 0.0« 0,03 0.12
29 CYMHELLA PRHSTRATA ************** 0*01 0.00********************* 0.01 0.04******* 0,02************** 0,01*********************
30 CYHATOPLFUR4 SOLCA .«.**..**...**...****.•**.***..*.** O.Ol******* 0.02*****«***********«***»*****«*******«*«*««**«****«******«*******
31 nlATIIMA ANCtPS o.oi******* O.Ol 0,02 0,02 0,o4******* 0,01******* 0,00 0.02 0,01******* ft.05 0.0? 0.02 0.05
32 DIATOM* HIEnAl.F. 0,26 0,12 0,04 o,02************** 0,0? o,04**************************** 0,03 0,04******* 0,01*******
J3 DlATHMA UJUSARE .,.....**.«..*..***...**.*..*....**.**.*.*.*.*....»*...*..**...**..**...*,.*.****.***.....«*.*..«*.....*..,***.* 0.45
34 DIPLHNEIS ELLIPTICA ************** 0,01 O.O'l 0.02 0,05 0,0?******* 0.0^******* o.Q2************** 0*07 0,01 0,06 0.08
35 DtPLONEIS OCULATA 0.10 0.05 0.03 0,07 0,02 0.05*.****** 0,03 0.04**************************** 0.03 0.01 0*00 0.02
36 OIPLONEIS FINNICA ******************************************************** 0,05********************************************************
37 EU'JQTTA NAEGELI! ************** o*03************** 0.01************** 0.04 O.Ol*********************************** 0,01 0,03
36 EUNHTIA TENF.LLA o,01******* 0*01 0,02 O.O7******* 0,01 0,02 o,1?********************* 0,01 0,18************** 0,06
39 FUN3TIA TRiaoON .I**********************************************************************************************************•*•**.*****
40 FUNOTIA PERPUSIUA ***.*.*,...*...,.......*.,****.**..**.*... o.Ot*************************************************************** 0.01
11 E'JNfJTIA PECTINALlSVENT, .**««***.********«**«****•*******.*****.******•«**•*»..«..*••********.•.*.**•*****••*.*««*«****.****..*..*..*******..*.
42 F.JNQTU PCCTINALIS **.**..*•**..***.**...<*.*.*.*«*.«***«»******.**•*....** 0.04******* 0.03********************* 0.01**************
43 EPITHEMIA SOREX 0o' 0-01 O.fl4«****«* 0-0» 0-0? o.04******* O'fll O'Ol******* O.Q2 0«07 O.fl3******* 0.01
56 GOMPHONEHA PAPVULUM 0,n 0.04 0.02 0.14 0.10 O.oS 0-10 0.08 0.37 0.02 O.O7 0.01 0.03 0.08 o.H 0.20 O.H
V GOMPHHNEMA CAPITATUH ******* 0.05 0,01 0,04 0,02 0,05 0.01 0.01 0.03***'************************* 0.04 n ni A ns n i\9
5« GQHPHOHEMA WENTRICOSUM ,...*...*»........*...»,...*.»*...«.****..**.,....«,**,.,.....»..,...,.,.».»«,,..»,....,»,,,...1..,**..**..».I.!..».!l»I
i9 HANTZSCHIA AHPHIOXYS ,.»*....*.*..*..*....,.,.,..*...*,...*.,.,..,».*. 9 oi******* 0.00*«**»«***»***«.***...«»*.... n m*....... n nt
60 GYROSIGMA ATTTNUATUH 0>01 0.01 *********•**•********««•***•*****«****************««*«*. 0.0«**««************..*«**..*i».........»...,*
61 HANNEA ARCUS 0.01******* 0.06 0.02 0,05 0.01 0,01 0.03************«« 0.01 0.OO************** o 01**«*«***«*«*«*
62 MASTOGLOIA SM1THH o,04************** 0.02 O.Ol 0.02******* j.02******* 0.00 0.10 0.01 0.04 0.07 0 OS n (17 n is
63 MERIOION CIRCULARS «•*«**•*•**•** o.Ol 0.08 0.00 O.Ol 0.01******* 0.03******* 0.02************** o 06*****«* n'OI nnl
64 NAVICULA AURORA 0.01 0.03 0.01 0.04 0.05 0.03 0.01 0.02 0.23************** 0.00 0,01 0.18 0 04 005 0 IB
-------
LAKE T*HHE 1969*****PHYTnPLANKTON*****
65 SAVICULA HAC1LLUM
66 NAVICIJLA COCCPNE
67 NAVICIJLA FXIGUA
6B NA1HCULA FESTIVA
69 NA'MCULA MUTKA
70 NAV Iflll A PSEUOUV
71 NAV ICIIL A PtlPUl A
72 NAVICULA RAHIOSA
7) NAVICULA SCUTTF.LUIDES
70 NAVICULA CAP1TATA
7b i.'AvTCULA CI'SPtPATA
76 NAVICULA cnSThLAIA
7H SYNF.HRA RADIANS
99 SYNEORA RUMPFNS
1'JO SYNEHRA SQCIA
101 SYKtHRA ULNA
10^ SYNCURA INClSA
10) lAuFLL^RlA FENE
104 TABELLAR1A FLUCCIlLUSA
IOS TETRACYCLUS CHARfitNAT
106 TFTRACYCLUS LACUSTRI&
107 OIAinwELLA RACUU
1011 AC1 INOCYCLUS l.HR
109 CALU-IEIS FfNZI.II
1 ID CALHNEIS SPECIOSA
111 BIljnULPHIA AIJRITA
1 1 3 Fl. AKA1.IJT HHI
111. .SCt:,<|FOF.SMUS
lib SPH«EKUCYST
116 STA'IRA.STRIIM PAhADUXUM
llfl IIUCYSTIS NAEOfLII
119 PEDIASTRlIM KA«RAISI YI
120 MLUTMK1X AE9UALIS
121 ANAHAENA SP
1?? MER1SMOPEUIA ELEGANS
123 pnu^CYSTIS
121 nlNH'tRYON S^RTULARIA
123 KEP'-IY!U(1N OVUM
126 MALLAKONAS
127 PERinlNIUM SP.
126 CERAUIIM HIRUIDINCLLA
129 CRY^rO.IONAS
AVERAGE NUMI
SPEC.
M
TFI1RMIS
CUTIfOR.
UIDES
A
TA
IA
I1RMIS
IA
A
A
S
ARII
PITA1A
EN5IS
IRIS
RVATA
CENTEPON
III
S
HALA
IS
STRATA
:ilLUSA
ifilNATUS
JSTRIS
JRlANA
ilNBlRGH
[
>A
FA
JLFANA
.ATINDSA
3RHAUOA
:HROEIF RI
iDUXUM
(UNIT
[I
MSI Y!
IS
:GANS
;iN(iSA
.ARIA
INELLA
.EXA
SrR Or INDIVIDUALS PER
• ?5/ a 9/5 '3/ 5
******* 0.07 0.04
0.01 0.14 0.12
0.01 0.05 0.04
ML
7/ 6
0.04
0.21
0.05
0.05**
0.20
0,08
0.0'******* 0.0?**************
0,0?************** 0.07 0.01
0.2o 0.12 0.01 0.11 0.01
0.27 0.05 0*09 0.04 0.06
0. 05 **************
1.01 0.7? 0.04
0.54 0.16 0.02
0.?9 0.02 0.01
******* p.03 0.01
.******* 0.03*******
0.01 0.03 0.0?
0.11 0.17*******
0.04******* 0.03
0.14 0.0?*******
0.17 0.02*******
*********************
******* 0.05 0.06
******* 0.07*******
0,27 0,67 0,01
0.00
0.05
0,11
0.04
0.01**
0.01
0.06
.0.04
0.05
*****
0,04*********
0,01*******
0.12
0.01**
0.01
0.01
0.02
0,10
0,10
0.39
0.07
*****
1/7 8/7
***** 0.04
0,?6 0.01
0.05 0.04
0.04 0.00
0.10 0.01
0.16 0.00
0.19 0.07
o.oo o.oi
0.03 0.01
0.11 0.17
0.08 0.11
0.00*******
***** 0,00
0,01*******
0,02 0,04
0,02*******
0.06 0.04 0,01
0..03******* 0.09
0.04**
0.11
0.08
0.78
*************
0,09 0«07
0,07 5.24
0,69 1.0'
(1.13
0.24
0.08
22/ 7 24/ 7
0.01 0.04
0.05 0.01
0.04*******
O.OI******* 0.00
0.09 0.0? 0.00
0.14 3.0? 0,07
0.20 0.11 A. 04
-.02
0.10
0.06
0.11
0,03
0.00
0.03
0.01 *******
0.04*******
0.03*******
0.0?*******
0.01 ********
O.OB 0.02
10/ ' !/ 8
0.01 0.00
0.04 0.01
0.01*******
20/ 8 2S/ fi 3/9
0.01 0.04 0.02
0.07 0.05 0.09
0.01******* 0.05
0.02 0.00 0.00
0.05**************
0.07 0.02 0.00
0.08 0.01 0,04
-0,01*******
0.01*******
0. 06*******
0,04*******
0.11
0.17
0.4?
0.07
0.01
0.00
0.04 0.01
0. 12*******
0.05 0.06
11.21 0.06
0.02 0.01
0.27*******
0.04 0,01
0*80*******
**********************************
0,32******* 0,07 0,04 0.09
p,14******* 0,00******* 0.00*******
0.02*
0,03
0.01
******
0.02*
0.05*
****** 0.00
0.0? 0.01
0.01 *******
0,23*******
*************
****** 21.12
0. 04 *******
0,00********************* 0,00
0.07 0.00
0.03*******
0.04*******
0, 1 I}*******
0.30 0.29
0.06 0.04
0.00*
0.06
0.00
0.10
0.45
0.11
9/ 9
0.09
0,05
0,07
0,04
0,09
0.13
0.23
0.01*
0.06
0,04
0.06
0.01
0.01
0.08
0.01
15/ 9
0.09
0.14
0.14
0.01
0.10
0.22
0.36
0.01
******
0.02
0,03
0.00
0.06
0,06
0,00
0,02
0.03
0,03
0.13
0.03
**************
0.04
****** o,03*******
0,05******* 0.01
0.11 0.19
0. 36*******
0.13
*******
0.02
0.06
0.01
0.00
0.01
0.02
0.02
0.08
2.58
-------
LAKE TAHnt 1°69-1970»**««PHYTOPLANKTON«****
AVERAGE NuMBrp Q. INDIVIDUALS PEP "L
DATE' 24/ 9 10/10 52/10 28/10 12/11 23/11 5/1? l«/l? 26/13 6/ l 19/ 1 30/ 1 10/ 2 23/ 2 ?8/ ? 10/ 3 23/ 3
t prr
1 CVCI OTEU A ANllGIJA
? CYC1.1TF.I.IA RnilANICA
3 CYCLIlTtllA (1CFUATA
1 CYCLOTII.LA STFU.IGERA
5 MFLISIRA CHENULATA
6 HlLflSlRA GBANIiLATA
7 MFLHSIRA VADKNS
fl MELOS1HA UNI'ILATA
i) sTEFHANmiisciis ASTKEA
10 ACHNANTHFS Cl F VFI
] 1 ACHNANTHE S FXIGdA
1? ACHNHNlHtS F|.FXFLL«
13 ACHNANIHFS L«"CFO|ATA
14 ACHNANTHFS LII»EARIS
IS ACHNANTHlS MniLI'
16 ACHNANTHlS PFRAfiAI.LI
17 AMCHIPRC1RA PHLUOOSA
IB AMPHIPLfL'HA PELIMIOA
19 AMPHORA DVALIS
20 ASTERIONEl.LA FURMOSA
xi cncciiNEls OISCULUS
2? CGCCDNE1S PLACFNtULA
23 COCCHNETS HIlr.fiSA
24 CYMHFLLA CUSPIOATA
25 CYMBELLA GRACHIS
26 CYMRILLA LA"4CEOI.ATA
27 CYMBFLLA VENTRICOSA
28 CYMBFLLA SINilATA
OJ ?9 CYMRELLA PRHSTRATA
ON 50 CY»»TOPLEURA SOLF.A
OO Jl OIATHMA ANCFPS
32 OIATOMA HlEMALf
33 UIATOMA VULliARF
34 DIPLONEtS ELLlpUCA
35 DIPLONEIS OCIIIATA
36 OIPLONE1S FIMNICA
37 EUNHTIA NAEGELIt
3B EUNOTIA TENEILA
39 EIINIITIA TRlnnnN
40 EUNHTIA PFRP'ISILLA
«i EUNHTIA PECTINALISVFNT.
47 EUNOTIA PECTINALIS
43 EPITHEM1A SnqEx
44 EPITHEMlA TURfilOA
45 EPITHEMlA ZF5RA
46 EPITHEMlA ARGUS
47 FRAlilLARlA CR010NENSIS
48 FRAGILARIA INTERMEDIA
49 FRAGILARIA PINNATA
50 FRAGILARIA VAIICHFRUE
51 FRAGILARIA CllNSTSUtNS
.52 FRAGILARIA' LFPTQSTAURON
53 FRAGILARIA CAPUCINA
54 FRUSTULM RHnwBOIOES
55- GOMPHONEMA ACUMINATUM
56 GOMPHONEMA PARVULUM
57 GOMPHONEMA CAPITATUM
58 GOMPHONEMA VENTRICQSUM
59 HANTZSCHIA AMPHIOXYS
60 GYROSlGMA ATTENUATUM
61 HANNCA ARCUS
62 MASTOGLOIA SMIIHII
63 MERIOION CIRCULARE
64 NAVICULA AURORA
o.oi*
1.90
16.30
*******
0.11
1.93
0.1'
0.11
*************
1.69 3.02
1.73
0.00
0.13
1.21
0.01
0.01
0.19
0.03*******
0,01 *******
0,0? 0.06
0."* 0-05
0.06
0.04
0.46
O.I'
0.01
0.01
0.0?
0.01
0.01
0.31
C.Ol
0.01
0.2S
0.08
0.03
0.05
0.06
0.0?
0.03
0,00**************************** 0.0?******* 0.08 0.05 0.02************** 0.04*******
3.49 4.44 l.SO 0.9* 3.61 2.19 1.79 79.53 |3.37 12.93 3.74 2.44 3.26 1.74
9.48 10.83
0. 00*******
0.0?
2.32
0.2?
0.03
0.02
0.06
0.3?
0.58
0.03
0.12
0.59
0.09
0.01
0.03
0.02
0.07
0.07
2.13
0.22
0.00
0.01
0.13
0.34
0.61
0.05
0,07
0.63
0.03
0.03*
0,04
0.11
13.45 6, S3 0-8" 9.02 3. So 3.26 195.01 27.40 41.61 19.16 14.57 10.87 6.90
0.05 0.04************ **************** 0*02 0.04***********************************
3.15 1,40 0.54 3.57 l.So 1.02 4.34 3.58 3.00 1.43 I.5B 1.63 2.24
0.39 0.13 0.11 n.14 0.12 0.05 0.33 0.33 0.37 C.07 0.11 0.03 0.05
0.01 0,02*********************************** 0.04 0.05******* o.O?**************
0.00 0.02******* 0.01***************************************************************
0.1? 0.04 0.00 0,01 0.03 0,04 0.03 0.00 0.07******* 0.01******* 0.02
0.62 1.99 2*0' S.35 4.16 4.63 4.61 9.13 14.03 13.85 10.19 17,30 32.24
0.22 0.29******* 0,41 O.P7 0.09 1.84 o.«3 0.55 0.1 fl 0.3fl 0.26 0.2*
0,02 0.02******* n,02+*****+ 0,01 0.13 0,04 0.01******* 0,0?**************
0.05 o.ll******* 0,08 0,07 0.02 0.07 o,05 0.15 0.04 0.04**************
0.30 0.51 0.03 0.53 0.00 0.19 2.39 0.36 0.86 0.52 0.21 O.OS 0.03
********************************** 0,01 0,00******* 0.04 0. 04 ******* 0.03 0*01
0, ]Q* ********************************** 0*03 0,03 0*06 0.02 0.04**************
0.03**************************** 0.03 0,01 0.04******* 0.02 0.01 0.04 0.04 0.02
o.os
0.17
64.40
0.10
2.89
0.0"
0.01
0.06
0.06
0.0'
0.0?
0.66
47.4J
0.07
0.17
0.02
0.09
0.06
0.09
0.07
0.5?
'1.88
0.41
0.17
0.45
39.95
0.33
0.07 0.15
0.03*******
0.10
0:01
0.09
0.04
0.03
0.0? O.O4 0*04 0,04 0.07******* 0*09 0.03 0,92 0*04*********************
0.46 0*?3 0*2* 0.42 0.17 0,22 0.9* 0.27 0,38 0-«1 0.16 0.05 0.10
19.31 l5.«l 25.24 50.18 44.?-, 39,21 45.97 50.16 52.67 67.72 6 1 . 2« 85.37 89.16
0.49 0.91 0*02 0.51********************* O.O/ 0,54******* 0.20 0.62 1.24
.,....,*...... **,*..*... o.O? *......*....*...... *.*....
0.24 O.OS o.O' 1.01 0.01 0.03 0.33 n.l« 0.13******* 0.03 0.08 0.04
0.02********************* o.OI******* 0.03 0.02 0.01 0.04 0.05******* 0.01
0.06 0.03 0.01 0.13******* 0.03******* 0.05 0.04 0.92 0.05 0.09 0.04
0.05 0.01 0.01 0.05*.*.... 0.01 0.34 0, i« 0.03 ^.10 O.'o9 S.'fll o'.O*
-------
LAKE TAHHE |069-1970****»PHYTOPLANKTnN*«***
65 NAVICULA RACILlUM
66 NAVICULA CUCCONEIFORMIS
67 NAVICULA FXI1UA
6« NAVICULA FESTtVA
69 NAVICULA HUTICA
70 NAVICULA pSflint'5
71 NAVICULA PUPIIlA
7? NAVICULA HAPIOSA
n NAVICULA SCUTTEL'IIUES
'4 NAVICULA CAPITATA
75 NAVICULA CUSPIOATA
76 NAVTCULA COSTULATA
77 NEIDIUN HITCHCIICKI I
7fl NElniUH AFFINC
79 NIT7SCHIA (ILL
flO NII7SCHIA AMPHIRU
^1 NII7SCHIA SlNUATA
fl? N1T7SCHIA PALEA
83 CPEPHORA MARTYI
84 '-PFPHHRA AMERICANA
85 PINNIJLARIA RICSPS
»6 PINNiJLARIA AFSIUARII
67 PINN-JLABIA SIIRCAPITA1A
Bfl PINNIJLARIA AHAlljFNilS
K9 PINNIJLARIA Ri
90 RHO-I cnSPHENI A CURVATA
91 RHUPALOOIA TIRB
92 STAIIRHNFIS PMOF
O^ V4 5TAURONEIS ANCt
VO 95 SUKIRELLA CVATA
96 SYNEORA SMPHICFPM4LA
97 SYNEnRA MA7AHENSIS
VH SYNFi)RA RADIANS
99 SYNEOR* R1IMPFNS
100 SYNEORA SOCIA
101 SYNFDRA ')| N»
102 SYNiORA INCISA
103 TA8FLLARI» rENFSFRATA
104 TAgflLAHIA FLDCCULUSA
105 TETRACYCLUS fMARGINATUS
106 TETRACYCLIJS I
107 OIATDMELLA RAFnilRIANA
108 ACTINOCYCLUS FHRE
109 CALONEIS FEN7L1I
110 CALMNEIS SPCCIOSA
111 BIDOULPHIA A'lBITA
11? COMPHONEIS HF.HCULEANA
113 ELAKALOTHRIX IF;IATINOSA
114 SCENfDESMUS
115 SPHAFROCYSTl!
116 STAURASTRUH PAUAOOXUM
117 ROIRYOCOCfU'i 8KAUNII
us nncvsris NAERELII
119 PEDIASTRUM
-------
LAKE TAHO.E 1070-1971»****PHYTOPLANKTON*****
AVERAGE NUuBFR Or INDIVIDUAL"; PC" «L
DATE" 2/ 1 15/ 4 2/5 13/ 5 |6/ 6 24/ 8 2/9 2l/ 1 3/ 2 12/ 2 22/ 2 23/ 1 5/10
1 CYCLdTELLA ANTIGUA SPEC> 0.0, 0.0, 0.02 0,02 o.OO**.**** 0.01****************»******************«******
2 CYCLOTELLA flflDANKA 3.49 5.4o 3.91 2.83 2.03 2.56 2.99 13.73 18.15 H.41 16.05 6.46 0.64
3 CYCLOTELLA OCElLATA 0.01**************************** 0.01***««*«**********«**«*«***«**««»«**«****** 0.40
4 CYCLOTELLA STElLIGERA .I*.*,.*..,...,................,.*.,.......,...........,,,.,....,.,....«...*..........*.*..
5 MELOSIRA CRF.NULATA 16.9' 52.50 15.46 23.41 8.63 0.92 2.5H 5,88 9.96 8.17 10.50 15.96 0.63
6 HELOSIRA GRANULATA |) o*************** 0.00****«»******** o.OI «*•»•****•**•«•***••«******••»***** 0.28
7 MELOSIRA VARIAXS *...**..*.****....... O.Ol..**.********* o.0«*******«**«*««**««»*»«**«»****»*«*« 0,01
6 MELOSIRA UNOULATA ..................... 0.05**.*****•****•*******•*•***«*«**••«•****.«*.************.**•***
9 STEPHANOOISCUS 4STREA 2.03 2.26 2.20 1.53 0.89 0.66 1.48 2.82 0.67 0.99 0.78 0.05 0.02
10 ACHNANTHES CI.F.VFI A************.*.**.** o.oi o.oo************** 0.03********************* n.oo o.oi
11 ACHNANTHES F.XIEHJA o.o?************** o.oo o.oo**************************** 0.02************** 0.06
12 ACHNANTHES FLEX^CLA ******* 0.02 0.02******* o.oo o.o5 o.o? 0.02******* o.o4 o.oo**************
13 ACHNANTHES LANCEOLATA o.o« 0.07 0.07 0.06 o.oo 0.17 0.35 0.02 o.o?*****«*«****** o.oi 0.37
14 ACHNANTHES LINEARIS ******* 0.02 0.02 otoo************************************************* 0.21 0.00
15 ACHNANTHES NOLLH *********«******».««. o.oo o.oo************************************************* 0.04
16 ACHNANTHES PFRAGALLl ............................ o 01*«***«*******«******************************************
17 AMPHIPRQRA PALUOHSA [[[
18 AHPHTPLEURA PELLUCID* •*****«*********>**•*****•*•****«********* o.04**************************** 0.05*******
19 AMPHORA OVALIS O.Ort 0.05******* 0.04 0.02 0.02 0.1?**************************** 0.03 0.00
20 ASTERIONtLLA FORMOSA 13.7? 16.17 9.27 7.77 1.28 5.90 5.0" 5,65 6.86 5,47 3.41 2.28 o.ll
21 COCCONEIS OISCULUS ............................ o.OO 0.00 O.OO******************************************
22 COCCONEIS PLACENTULA 0.2' 0.24 0.5o 0.09 0.0' 0.70 0.2' 0.02 0.01 0.06******* 0.01 0.18
23 COCCDNE15 RUGOsA O.C? 0.06******* 0.01 0.00 0.02****************************************** 0.06
24 CYMDELLA CUSPIDATA *.******•**************.*•*• o.Ot******* 0.10************** 0.04*********************
25 CYMBCLLA GRAClLIS to************************* o.OO************************************************* O.il
26 CYHBELLA LANCEDLATA 0.0^ 0.07 0.02 0.01 0.01 0.05 o.O9******* 0.01******* 0.06**************
27 CYHBELLA VENTRICOSA 0.21 1,11 0.12 O.OT 0.0« 0,06 0.17 0.05 0.01 0.05 0.0* 0.10 0.26
28 CYMBELLA SIN'IATA 0.04 0.08 0.01 0.03 0.01 O.oi 0.01 o.0?*******«******************** 0.01
39 CYMBELLA PROSTRATA ******* 0 00*********************************** 0 02***********************************
30 CYMATOPLEURA SGLEA ****•*«*»«*.*.*•*•*., o 01******«***««******«*«**»****«*****»*************«********«**«**
31 .OIATOMA ANCF.PS 0.01 0.02************** O.OI************************************************* 0.00
32 OIATOMA HIEMALE ******* o.OI************** O.Ol******* 0.0?***********************************«******
33 OIATOMA VULGARF. ******* 0.02 Q.Q3******* 0.00******* 0.37******************************************
34 OIPLONEIS ELLlP^lCA ******* Q,Q2******* 0.01 o.OO******* o.OI********************* 0,00 0.00 0,01
35 OIPLONEIS OCHLATA 0.03 0.03 0.03 0.03***************************************************************
36 OIPLONEIS FINNIC* >«**************.**.****.............,.....*...............................................
37 CUNOTIA NAESELII ................................... 0,02 o.oa******************************************
38 CUNOTIA TENELLA 0.02 o.o« o.oi******* 0,00******* 0.02*********************************** o.oo
39 EUNOTIA TRIODON 0.0?**•*.»..«.***.****»****»•*.*«*•***•.*****«*****•**.*«**«********.*.*.*.****..»..*..*
40 EUNQTIA PERPUSILLA [[[
41 EUNOTIA PECTINALIS VENT. .*****..*****.****«** o.oi***************************************************************
42 CUNOTIA PECTINALIS [[[
43 CPITHEMIA SOREX ******* 0.03 0.01 0.04 0.02********************* 0.02******* 0.03 0.01 0.08
44 EPITHEMIA TURGIOA ******* Q.OQ******* 0.01 0.02 0.02 O.O9 0.02 o.OI************** 0,05*******
45 EPITHEMIA ZEBRA 0.5' 0.36 0.31 O.ZT 0.ll 0.85 0.68 0.05 0.01******* 0.05 0.09*******
46 EPITHEMIA ARGUS [[[ Oi05
47 FRASH»RlA CROTUNENSIS 93.21 94.32 67.65 67.55 9.91 21.95 30.96 H.08 9.47 6.82 16.82 14.94 12.02
48 FRAGILARIA INTERMEDIA .......................................... 0.0***<***************************************
49 FRAGILARIA PINNATA 0*3? 0.68 0.11******* 0*06 0.38 o*24**************************** 0,07 0,97
50 FRAGILARIA VAUCHERIAE ******* 0.02*********************************** 0.00**************************** 0,00
51 FRAGILARIA.CONSTRUtNS 0.4? 0.04 0.01 0.14 0.01 0.06****************************************** 0 65
« FRAQILARIA LEPTOSTAURON ........*.....*..*.**,*•...............1..................*...,.**..*,..»»***,.*....,,.»I°,
53 FRAGILARIA CAPUCINA ....*............*[[[ 0 06
54 FRUSTULIA RHHMBOIDES ..*........*..........*.............*............ O.OO***********************************
55 QOMPHONEM* ACUMlNATUM *»*»..« g.gi********************* 0,04 OtO«*******************«***«*********«**«*«**«
56 GOMPHONEMA PARVULUM 0.03******* 0.07 0.03 O.Ol 0.07 0.15******* O.OI************** 0.00 0 05
57 GOHPHONEMA CAPITATUM .............. 0.03 O.Ol************************************************.*....** 001
58 OOMPHONEMA VENTRICOSUM **************************** 0.01************** 0.00 0.02************** n 01 n'ns
59 HANTZSCHIA AMPHIOXYS ........*............ Ot02..**..***.*.***.....«..*.*.....*I............*..........„....,
60 GYROSIGMA ATTENUATUM ..*[[[ . „.
-------
65 NAVICULA RACTL'JJM
66 NAVICULA COCCONEIFDRM1S
67 NAVICULA EXIflUA
OB NAVICULA FESTIYA
69 NAVICULA MUTICA
10 NAVICULA PSElllinsCUTIFOH
71 NAVICULA PUP'tl,A
77 NAVICULA HADItlSA
73 NAVICULA SCIlim (1
74 NAVICULA CAPITA!!
75 NAVICULA CUSP I DAT A
76 UAVICULA COSrULATA
77 NEIOIUM HITCHCOCK I I
7°, NEIOIUM AFF1NF
79 NIT7.SCHIA FILLIFIIRMIS
30 NirZSCHIA AMPHIRIA
HI NIT7SCHIA SINUATA
82 NITZSCHIA PALLA
83 JPEPKOR* .1AKTYI
84 t'PEPHDRA AMERICANA
85 PINNijLARIA RICEP.S
66 PINNHLARIA AESTIlARlI
BT PINN.ILARIA StIBCAPITATt
e» PINNIJLARIA AKAII.JENSIS
89 P!NNi|LAR)A RUPFSTRIS
90 RHIHCOSPHEHIA CIIRVATA
91 RHOPALgnU >!1RBA
92 STAURONEIS »HmN
OJ 93 STAIIHONCIS S'lIrHlI
^J 94 STAURONFIS ANC'PS
I—I 95 SURIRELLA OVATA
96 SYNEDRA AMPHICKPHALA
97 SVNEDRA HAZAMTNSIS
9°. SYNEORA RADIANS
99 SYNEDRH RUMPENS
100 SYNfORA SOCIA
101 SYNFORA ULNA
102 5YNEORA INCISA
103 TABCILARIA FFNLSTRATA
104 TAHFLLARIA FLHCCU10SA
105 TETRACYCLUS F-MARG!NATUS
106 TETRACYCLUS LACIISTRIS
107 OIATOMCLLA RArilURIANA
tos ACTINOCVCLUS EHRE
109 CALONE IS FfNZlH
110 CALONFI5 SPFClnSA
111 BIOOJLPHIA AURITA
\\? GOMPHONEIS HFRCIILF.ANA
H3 ELA
114 SCE
115 sPH
11* STAURASTHUrt PAHADOXUM
117 nOTRYOCOCCUS HRAUNII
llfl llOCVoTIS NAFr.n. II
119 PE01ASTRUM KAXHAISLYl
120 ULOTHRIX AEQUALTS
121 ANAHAENA SP.
122 HERISMOPEDU ELEOAIIS
123 POLYCYSTIS ATRunlNOSA
1?4 DlNOaRYON SERTi.lLARIA
125 KEPHYRIHN O'JilH
126 MALL A HOIAS
127 PEHIOINIUM SP.
128 CERATIU'1 HIOiJN
129 CKVPrOM')N4S REFLEXA
AVERAGE NUx
DATE
SPEC.
UTIFOH.
IDES
A
II
RMIS
A
RII .
ITATA
NSIS
RIS
VATA
1
ALA
S
'RATA
ILOSA
ilNATUS
;TRIS
IIANA
:NBERGII
i
t
ITINOSA
IICAUOA
IROETER!
10XUM
JNII
ISLYl
;
INOSA
>RIA
NELLA
EXA
RFR Or INDIVIDUALS PER M
« 2/4 15/ 4 2/5
0.01 0.05*******
0.01 0.05*******
0.01******* 0.03**
0.0ft 0.09 0.01
0.11 0.11 0.04
******* o.OI*******
***********************
0.07******* 0-.04
******* 0.00 0.02
0.04 0.10 0.04
0.44 1,26 3. 30
0.07 o.«2 2.72
L
13/ 5
0.00
0.02
*****
0.04
0.02
0.02
*****
0.02
0.01
0.02
?.06.
0.30
16/ 6 ?«/ a 2/9
0.01 0.02 0.07
0.00 0.05 0.09*
0.01******* 0.04
0.01 0.22 0.20
0.00 0.12 0.07
13,02**************
0.01 0.02 0.01
0,02**************
0.03 0.12 0.09
****** o.l 1 0«3<>
0.00 1.46 1.3A
21/ 1 3^ 2 12/ 2 22/ 2 23/ «
OiOi o.OI************** 0.01
**********************************
o.o?*****************************
0.01 0.00 0.91 O.Qfl 0.03
0,00 0.01 *********************
46.10 90.69 115.45 100,37 23.43
n.04************** o.03~*******
0.03************** 0.05 0,05
0,04 0.05 0.07 0.05 0.01
1.74 n.87 0.26 0.31 0.20
0.19 0.07 0,04 0.05 0.11
5/10
0.03
0.24
******
0.31
0.58
0.37
2.71
0.01
o.on
8.63
******
0.08
0,02
0.01
2.89
0.03
0.59
2.11
25.88
1.61
-------
APPENDIX D
LAKE TAHOE TOTAL PHYTOPLANKTON BIOMASS-DEPTH PROFILES
_3
Freshweight biomass (mg-m ) of the whole phytoplankton community vs.
sampling depth at the index station of Lake Tahoe, 1967-1971.
372
-------
LAKf TAhClE 1967 ***PHYTOPLANMUN*«*
FRFSH WilGNT HH'PASS OF Ttlf KMflLE PhYTPHI »NKTUI> COMMUNTTY
PER CURIC MITER
IEPTH
(V)
P.
12.
17.
2*.
4n.
en
j n •
7n
< '' .
V/ 6
21.09
16.61
411. is
37.13
3«. 29
6 U • 6?
DEPTH
(M)
C.
7.
12.
22.
60.
14/ 8
9.15
26.95
44.27
31.51
41.54
DEPTH ?5/ 8
(M)
0. 13.39
7. i?.78
12, 37.28
22. |8. 4*
37. A6.40
50. 153.9)
DEPTH 2/ 9
(M)
0. 17.|0
5. 19.86
13. 61.47
24. «2«86
3«. 1J8.27
50. 177.51
70. 118.81
DEPTH
(M)
0.
4.
8.
17.
31.
43.
71.
7/ 9
17.09
36.62
32.27
40.33
62.96
63.83
6u.47
DEPTH
^J
Co
IFPTH 5/in
(»)
P. 28.47
IP. 81.89
1',. 155. 3<<
2(i. ioe.1*
3f,. lib. 07
•ir. lot. 5"
9p. 81.19
DEPTH
(>-)
t .
11.
15.
20.
31.
5t.
9C.
11/10
25.98
2c.01
3t.47
37.62
3C.64
55.16
51.73
DEPTH
(M)
0.
lt>,
2C.
40.
70.
1B/10
?4.3«
13.1?
9.1«
P6.47
f>0.55
DtPTh 26/10
(P)
C. 26.51
1C. It.ei
15. 3C.93
20* 3<,S6
3C. 77.39
5(!. llc.52
9r> 102.68
DEPTH
(»')
c.
10.
15.
2C.
3C.
5n. i
-t\i , j
9C.
1/11
26.56
28.14
16.46
28.98
42.46
127.74
54.81
DEPTH
(M,
0.
10.
15.
20.
30.
t= «
3U *
90.
0/11
32.71
35.53
2*. 04
30,74
65.32
120.14
7V. 44
DEPTH 15/11
(")
0. 31.61
10. 26.49
1". 23.89
20. «].«5
30. 66.53
50. 94.00
90. 105.55
DEPTH 1/12
(M)
0. 53,21
10. 77.04
15. 7«,eo
20. 43.77
30. 94.76
50. 104.76
90. 129*19
-------
UJ
•^1
-p-
TAhOt 1967-1968 ***PHY T OPLAhiKTOiN*»*
FPFSH HllGHT HOMASS OF THF WHOLE PHY1 flHLANKTON COMMUNITY
HIILIGRAM PtP CUBIC HFTER
DEPTH
0.
10.
I*.
20.
30.
50.
90.
12-!.
DEPTH
(M)
0.
7.
10.
I1!.
20.
30.
An
50.
60.
71?.
'o.
10*.
12".
15ft.
6/17
•58.15
69.48
32.11
63,96
62.51
41.65
30.68
76/ 3
179.97
163.77
******
162.35
1*6.58
1M.90
175.13
116.04
2/ 1
80.26
89.41
68.15
85.36
78.50
86.20
66.90
2/ «
118.19
134. 5C
122.16
143.14
164.06
171.71
152.41
16/ 1
37.20
53-78
69.46
70.23
53.95
- 67.81
87.44
I!/ 4
63.11
73,54
102*04
92.67
111*41
162.50
177.94
2"/ 1
65.82
92.41
105.71
91.36
113. b7
103. «2
** * *
83.98
I*/ 4
147.93
141.90
122.63
176.45
162.46
174,20
719.52
O/ 7
85.13
106.14
83.90
86. g7
95-35
"7.21
117. p7
25/ 4
71.21
101.07
64.93
119.27
90.43
110.52
187,97
14/ 2
107.21
119.01
93.57
101.5?
117.78
100.89
148.20
I/ 5
66.26
66.25
85.52
97.52
121.58
74.05
195.62
2 1)/ 2
140.59
112.81
93.76
137.97
129.30
115.58
90.39
9/ 5
96.28
110.32
129. «7
153.65
166.Q5
117.17
193.77
189.02
-------
LAKE. TAhot 196* ***FhYTOPLANiatlN***
FRFSH WtlGKT fclljMASS (IF THE JKhdLt FhYl nPI AK'KTdK I llt-MI.'N! T Y
NFI LIBRAE PLP rtlWK MIHR
DEPTH
(M)
0.
IP.
in.
5P.
7*.
9r>.
I?1!.
15P.
12/ 6
?7.f.6
******
32.51
?1.
-------
OJ
--J
LAKl TAMflE 1968-1969 ***PHY TIlPL ANK t UN. **
FKFSH WtJGMT RItlMASS (if THF Wli(iLF. PHY1 f'HL ANKTON COMMUNITY
Mil I IGRAM PEP fUPlC
10.
1".
2P.
30.
40.
"JO.
6n.
7-!.
90.
10*.
12".
16/ 1
!/ 2
15/ 2
2/ 3
15/ 3
3Q/ 3
13/ 4
9/ 5
23/ 5
"3.97
37.05
"9.76
<4.07
32.13
91.75
31.37
32.29
"4. it
"0.33
38.5?
"7.61
56. 2*
60-01
4
55-81
59.24
7B.76
59.31
49.44
50.5)
59.29
63,21
b0.7o
57.75
41.66
6*. 10
69.08
14.76
41.59
sp.gn
6?,77
51.76
57.96
66.44
60.78
70-12
56.92
55.72
90.95
76-20
22-1?
50.30
127.85
49.66
60.85
51.75
66.27
66.93
37.06
46.34
77.35
45.92
86.38
98.43
21.92
67.66
ltie.87
79.95
53.08
96.99
60.95
9C.01
109.72
109.19
71.78
113.82
119.51
76.25
159.47
Ib3.b0
lbl.29
170.14
li>6« 1 1
131.68
1*6.20
114.22
73.89
168.22
i01.37
132.96
110.69
1*7.20
259.11
112.73
l?t>.80
2?V.96
139.86
773.76
177.87
144.95
113.1P
1 10-7"
76.31
173.9(1
93.75
40.92
62.61
57,07
155.73
179.56
166.87
61.82
166.69
293.73
198.36
219.71
163.32
54.74
75.80
11.57
35.75
35.22
44.93
76.25
105.51
63.00
108.79
110.34
125.38
l2?.26
DEPTH
r.
1C.
i*-.
70.
4p.
5C.
6P.
7".
12".
150.
7/ A
20/ 6
\l 7
«/ 7
15/ 7
24/ 7
20/ 6
26/ 6
?0.93
19.1,2
37.64
36.41
M.UO
74,29
115.94
83.27
2"7.66
213.04
157.83
2"7.74
138.80
11.89
7.38
21.24
15.64
26,27
33.78
97.94
146.63
181.16
165.79
100.50
702. 10
185.91
12.18
21-40
18.63
12.42
15.66
26.57
47. 3C
15.48
25.58
154.65
119.4?
127.53
12H.98
12,94
11.59
2J.28
20.24
25,24
17.47
1)5. *7
30.76
35.67
53.99
09.02
1 lil.49
119.48
10.4?
73-47
41.01
74.37
54.15
39.91
82-89
49.58
34.98
66.23
4.0?
47.40
65.25
420.06
558.21
13.45
72.61
54.7?
66,93
38.91
33.73
98,28
76.50
376.63
108.0?
89.51
9.14
6.78
******
45.90
******
52.25
40,73
66.89
72.51
194.35
******
82.57
40-46
27,06
26.76
14.59
24.37
37,34
56,52
8.24
38.19
00.58
152.85
114,47
99,23
S3. 02
12.64
******
ro-40
71-2P
17.24
44.10
"2-56
76.70
53.17
86.79
123.84
41-21
89.69
13.34
15.55
10.11
11.68
8.49
26.14
15.35
24.46
41.15
71.12
60.35
81.64
110.66
54.77
46.96
49.58
126.68
58.44
67.38
4Q.58
217.11
123.44
>2l.34
273.26
162.07
125*09
-------
L/lKt TAhnt l9r,«-t97U ** *PHYTi,PLANK TON* * •
FRrsH Wtllil'T MDMASS [If TH» Hhlll.K PHY TpHLAWM IIC COMMUNITY
HIIIIGRAH PtP CtlHlf:
DEPTH
CM)
P.
y •
* s
IP.
!*.
?P.
?P.
IP.
50.
60.
7«i.
9P.
10*.
1?«.
150.
3/ 9
3. (15
Si ^
• y .1
6.50
9.61
17.1?
19. k!
40.5?
13.73
72. t8
41.37
61.03
«0.66
16. 7!
******
******
9/ 9
6.70
e -j i.
J • 1Q
I 1.61
)5.25
)9.49
32.21
27.93
31.76
46.24
56.97
65. 17
75.66
96.35
******
******
IS/ '/
41.53
fla . 5H
1 1 .Od
43.56
}«-t.i
10^.5"
107.
-------
LAKE TAhni 19/0-1971 *»*PHYTuPl-ANKTOI»***
FRrSH WEIGHT HIOKASS DF THF WhOU PHYTpPLANnTON COMMUNITY
MlIIGPAP PEP CUPIt CITFR
DEPTH
00
2/
13/ 5
U/ 6
24/
'it 9
21/ 1
12/ 2
2V 4
5/10
p.
«;_
10.
?p.
30.
4f.
ftp.
7*.
9p.
17r.
150.
14.73
117.05
PI. 01
77.71
P2. 7P
105.53
72.67
98,67
14.63
71.55
P7.00
113.43
"fc.C?
72.34
159.36
87.82
77.45
56.54
135.10
91.95
61H.55
bli.23
717.52
124.67
e o . e j
49.94
96.85
33-89
58-50
17.97
15.86
14.66
40-27
22-54
33-66
55-12
45.57
40.91
38.38
7).o7
67.82
92.43
1.t<2
5.13
13.59
1.93
6.52
39.58
49.34
4'i.3l
35.23
46.29
31.77
61.22
8.14
22.40
20-36
31.54
46.01
49.67
40-94
41.60
53.83
64.89
104.20
66.60
152.47
106.12
171.80
134.55
203.80
194.62
169.39
133.01
189.50
124.40
215.76
119.69
14C.90
4«2«01
235.13
231.23
206.45
239.02
167. Q6
260.83
lVc-74
244.57
3*4.19
232.77
262-36
135.90
334.19
3/1.76
3U3.21
236.20
294.77
303.39
207.76
2t>0.44
206.67
266.36
205.76
302.92
250.12
4/0-7!
172-55
464.67
208. 5P
350-80
206-26
267.2?
2*2-90
)78.6P
236*94
242-l«
2?1»2*
3/4.60
309.64
131.85
67.47
70.65
56.49
91.90
449.49
91.59
Bfl.13
13B.45
116.74
41.08
41.86
31-79
68.67
42.52
75.65
66.76
76.32
126.31
51.28
46.16
86.79
50.23
88.78
63.28
-------
APPENDIX E
LAKE TAHOE WATER CHEMISTRY METHODS
NITRATE ANALYSES
Nitrate-nitrogen concentrations are determined by the method described
by Strickland and Parsons (1968). In this procedure, the nitrate ion is
reduced to nitrite ion by finely-divided particles of cadmium-copper
amalgam under mildly acidic conditions. A diazotization reaction between
nitrite (nitrous acid) and sulfanilamide followed by a coupling re-
action with N-(l-naphthyl)-ethylenediamine produces a red azo dye whose
absorbance is measured at 543 nm. The results of analyses are expressed
in terms of parts per billion of nitrate-nitrogen (i.e., micrograms of
elemental nitrogen present in the nitrate form per liter of solution).
Reagents
Concentrated Ammonium Chloride Solution -
Weigh 175.0 i 0.1 g analytical reagent grade ammonium chloride (NH.C1)
and dissolve in 500 ml of freshly deionized and distilled water. Store
in a clean, tightly-stoppered glass or polyethylene bottle.
Dilute Ammonium Chloride Solution -
Dilute 50.0 ml of the concentrated fl
ionized and distilled water. Store in a glass or polyethylene bottle.
Dilute 50.0 ml of the concentrated NH.C1 solution to 2000 ml with de-
4
379
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Sulfanilamide Hydrochlorjde Solution -
In a 500 ml volumetric flask, prepare a solution, of 50,0 t 0.5 ml analy-
tical reagent grade concentrated (12 M) hydrochloric acid dissolved in
approximately 300 ml of deionized and distilled water. Weigh 5.00 t
0.05 g sulfanilamide and dissolve it in the above dilute HC1 solution.
Dilute the mixture to exactly 500 ml with deionized and distilled water.
When stored in a tightly-stoppered glass or polyethylene bottle at room
temperature this solution remains stable indefinitely.
Concentrated Synthetic Seawater Medium -
Dissolve 620 1 1 g analytical reagent grade sodium chloride (NaCl), 200 t
1 g analytical reagent grade magnesium sulfate heptahydrate QtgSO,'7ELO),
and 1.00 - 0.01 g analytical reagent grade sodium bicarbonate (NaHCO-)
in 2000 ml of deionized and distilled water. Store in a glass or poly-
ethylene bottle.
Amalgamated Cadmium-Copper Filings -
Remove metal filings from analytical reagent grade cadmium sticks with a
coarse hand file. With a sieve, separate and discard the fraction that
passes through 0.5 mm openings. Stir approximately 90 g of cadmium
filings (enough for two reductor columns) with 400-500 ml of 2.X copper
sulfate pentahydrate (CuSO^-SE^O) solution until all blue color has dis^-
appeared and a suspension of metallic copper particles has formed in the
solution. At this point, decant and discard the suspension of fine par-
ticles. Rinse the copper-coated Cd filings with several portions of the
dilute NH^Cl solution to remove the fine particles which, if not removed
now, may restrict the flow of water samples through the reduction,
columns. Push a small plug of glass wool, or copper wool if available,
into the bottom of the reduction column. Partially fill the column with
dilute NH^Cl solution and slowly pour in, the slurry of Cur
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small plug of copper wool or glass wool to cover the filings, and wash
the column thoroughly with two or three 100-ml aliquots of dilute NH.C1
solution. Store the column filled with this solution to prevent the
filings from drying out. Wrap the column with opaque tape or foil to
prevent the exposure of the filings to light.
Properly prepared and handled columns will typically retain their effec-
tive reducing ability for at least six months, even if weekly batches
of 20 samples or more per column are analyzed. With time, however, col-
umns become physically obstructed and Cu-Cd filings become coated with
unreactive oxide or carbonate films causing a decrease in the overall
sensitivity of the method. When this occurs, the filings should be
emptied from the column and the filings should be washed by stirring
vigorously with approximately 150 ml of 0.5 M HC1 solution. Decant the
suspended particulate material and repeat the treatment with the HC1
two more times. Wash the clean filings thoroughly to remove the excess
acid and decant as much water as possible. Since some Cd dissolves
during this treatment, it is necessary to add additional fresh Cd filings
to replace it. Retreat the metal filings with CuSO. solution as described
above.
N-(l-Naphthyl)-Ethylenediamine Dihydrochloride Solution -
Weigh 0.500 1 0.005 g CIQE NHCH2CH2NH2•2HC1 (Eastman Organic Chemicals
#4835) and dissolve in 500 ml deionized and distilled water. Store in
a dark glass bottle completely wrapped with foil or opaque tape and re-
frigerate during storage. Check the color of this solution prior to use
and discard monthly or more frequently if a yellow-brown coloration
develops.
Standard Nitrate Solution (100 ppm nitrate-nitrogen) -
Oven-dry a sample of primary standard grade or analytical reagent grade
potassium nitrate (KNO ) to constant weight at 110 - 120°C. Weigh
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0.7218 t O.OOQ2 g KN03 after cooling in a desiccator to room tempera-
ture. Transfer the sample to a 1000-ml volumetric flask, dilute to
the mark with deionized and distilled water, and mix thoroughly. Store
in a tightly-sealed glass hottle. As needed, standard solutions of
lower nitrate-nitrogen concentration are prepared by quantitative dilu-
tion of this 100 ppm standard. For example, a 50 ppb nitrate-nitrogen
standard solution may be prepared by diluting l.QO jj O.Q1 ml (Class A
volumetric pipette) of the 100 ppm standard nitrate solution to 2000
ml with deionized and distilled water in a volumetric flask.
Procedure
I. Add 2.00 "t 0.05 ml concentrated ammonium chloride solution and
10.0 i 0.1 ml concentrated synthetic seawater medium to each 90.0
+ 0.5 ml sample in 125-ml Erlenmeyer flasks equipped with rubber
snap-caps. The ammonium chloride and synthetic seawater solutions
are most conveniently introduced via automatic pipettes capable of
the stated precision, while 100-ml polypropylene graduated cylinders
(which drain completely and cause negligible meniscus error due to
the hydrophobic nature of this plastic) allow adequate precision for
measuring sample volumes.
2. Prior to the introduction of the first sample, the cadmium-copper
reduction columns must be drained of the dilute ammonium chloride
solution contained in them and flushed with an additional 100-150 ml
of fresh dilute ammonium chloride solution. While rinsing the col-
umns, the flow rates should be equalized by adjusting the Teflon
needle valve at the base of each column. A flow rate of approximate-
ly 8 minutes per 100 ml is typical. Once established, the flow rates
must remain constant for all samples and standard solutions to ensure
the same reduction efficiency. Allow the rtnse solution to drain
to within 2-3 cm of the top of the bed of Cd-Cu filings and prepare
382
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to pour the standard and sample solutions through, the reducing col-
umns. Because of the potential danger of contaminating one sample
with the residue of the previous sample that has been passed through
the column, it is desirable to analyze samples of similar origin
and/or concentration in consecutive order.
3. Begin rinsing the column with approximately 5 ml of one of the sample
solutions and allow it to pass through the column. Such rinsings
should be collected in a flask or beaker and will be discarded. Re-
peat this rinsing process four or five more times with 5-ml aliquots.
The series of small successive rinses decreases the probability of
contaminating the remainder of the sample with the previous one.
Continue to rinse, adding all but approximately 55 ml of the solution.
When this last rinse has entered the bed of Cd-Cu filings, add the
remaining 55 ml of sample and begin collecting the effluent in a
50- or 100-ml polypropylene graduated cylinder containing 1.00 ml
of the sulfanilamide solution. (The presence of the sulfanilamide
at this point ensures improved reproducibility between trials while
also enhancing the sensitivity of the method by utilizing a greater
proportion of the unstable nitrous acid for the formation of the
diazonium intermediate).
4. Collect a total of 50.0 ± 0.5 ml of effluent (51.0 ml total including
the 1.00 ml of sulfanilamide solution originally pipetted into the
graduated cylinder), mix the solution, and transfer this back into
the original drained 125-ml Erlenmeyer flask where the diazotization
reaction is permitted to continue for exactly 5 more minutes.
5. Add 1.00 t 0.01 ml of N-(l-naphthyl)-ethylenediamine dihydrochloride
solution and mix well. Allow at least 20 minutes for color develop-
ment. Avoid excessive warming of the samples or illumination by
bright artificial light or sunlight as these factors are responsible
383
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for irregular color development and premature fading of the azo dye.
6. Measure the absorbances of the samples at 543 run between 20 minutes
and 2 hours after color development. Selection of cell pathlength
(1 cm, 4 cm, or 10 cm) will depend upon the nitrate concentrations
being measured. As a general rule, the longest pathlength cells
which give sample absorbance values less than about 0.6 - 0.8 should
be used. Because the absorbance scales of most spectrophotometers
are compressed for high readings (i.e., absorbances greater than about
0.4), more accurate measurements may be obtained by recording the
linear % transmittance values and converting later to absorbance
(sometimes called "optical density") by the use of a conversion
table such as the "Transparency to Optical Density Conversion Table"
(Chemical Rubber Co. 1971).
7. The reliability of the results from this method are dependent upon a
consistent reduction efficiency of each Cd-Cu column. To monitor
this important factor, a series of standards should be analyzed be-
fore and after every 10-15 samples. In addition, occasional repli-
cation (duplicate or triplicate) of samples is essential to provide
an estimate of overall precision of the method. A minimum of three
different concentrations of standard solutions should be used. The
most concentrated standard solution should have more ppb nitrate-
nitrogen than the most concentrated water sample to eliminate the
necessity of extrapolating the standard curve.
8. Prepare a standard curve of corrected absorbances versus ppb nitrate-
nitrogen, where A = A ^ , , -A, . ,
corr standard T»lank.
9. The absorbance readings of the samples are corrected for the nitrate
contamination of the deionized and distilled water in which the
384
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reagents are dissolved by the. following equation:
Acorr - Asample ' (l2/l02)Ahlank
The concentrations of nitrate-nitrogen corresponding to these cor-
rected sample absorbances are then read from the corrected standard
curve prepared in the previous step. A discussion of the signifi-
cance of these formulae is presented in the following section.
Blank Corrections for Nitrate Analyses
Non-zero absorbance values for reagent blanks, representing an apparent
.!
contamination by the analytical reagent grade chemicals and/or the de-
ionized and distilled water, are encountered in every type of analysis
involving a high level of sensitivity. Blank corrections are especially
critical for nitrate analyses of Lake Tahoe water since many of these
samples have nitrate-nitrogen concentrations below 5 ppb and occasionally
lake water samples exhibit uncorrected absorbances less than the blanks
themselves. Our experiences at Lake Tahoe indicate that these results
are explicable only if one assumes that the solid analytical reagent
grade chemicals contribute negligible amounts of nitrate-nitrogen and
that the deionized and distilled water are fully responsible for the con-
tamination. The blanks, standards, and lake water samples all contain
exactly the same quantities of reagent grade chemicals, but different
amounts of deionized and distilled water (102 ml for the blanks and stan-
dards, and only 12 ml for the lake water samples).
Since all of the standard samples and blanks contain the same reagents
and about 102 ml of deionized and distilled water (90 ml sample + 10 ml
synthetic seawater + 2 ml concentrated NH.C1 solution), the full value
°f \lank is sub-racted from each standard (AcQrr = Astandard - A^^) .
Since the 12 ml of reagent solutions added to each lake water sample
(synthetic seawater and ammonium chloride solutions) were prepared with
deionized and distilled water containing nitrate contamination, the true
385
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nitrate content of the samples may be obtained by eliminating the ef-
fect of the slightly contaminated deionized and distilled water by sub-
tracting (12/102) \lartk from each sample absorbance (AcQrr - Asample -
(12/102) A, , ). These corrected absorbances are then used to find
the true sample concentrations from the corrected standard curve. It
should be apparent that the factor (12/102) is used because only 12 ml
of the total sample (90 ml lake water + 12 ml reagents) contribute
water containing nitrate contamination. On the other hand, nitrate
standards contain 102 ml of nitrate contaminated water so the full
value of AblMk is subtracted from A8tandard.
Chemistry
Reduction of NO- by Cd-Cu Column -
3'-r-r * | •vrrt j r
H + NO- + /
Cd - Cd + 2 e
3 H+ + NO," + Cd - HNO- + Cd"1"*" +
3 2
(I)
Diazotization Reaction -
HN02
S02NH2
(II) (I) (III)
386
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Coupling Reaction (Dye Formation.) -
V
HC1
z:H2NH2 S02NH2
(IV) (III) (V)
(I) = nitrous acid
(II) = sulfanilamide hydrochloride
(III) = p-benzenesulfonamide diazonium chloride
(IV) = N-(l-naphthyl)-ethylenediamine
(V) = an azo dye
PHOSPHATE ANALYSES
Described here are three related methods for the analysis of dissolved
and particulate forms of phosphorus in natural waters. Depending upon
the type of preliminary sample treatment, the concentrations of differ-
ent forms of phosphorus may be determined:
1. Total phosphorus (including both dissolved and particulate fractions)
by acid hydrolysis of unfiltered samples.
2. Total dissolved phosphorus (including both inorganic and organic
compounds) by the analysis of acid-hydrolyzed, filtered samples.
3. Soluble orthophosphate by the analysis of filtered samples without
the acid hydrolysis steps.
Acid hydrolysis at 115-120°C releases a large proportion of the phospho-
rus present by converting it into soluble orthophosphate from particulate
387
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inorganic phosphate minerals, from dissolved and participate phosphorus
compounds, and from soluble condensed inorganic forms such as pyrophos-
phates, metaphosphates, and tripolyphosphates. The following hydrolysis
procedure is used:
1. Add 1.00 ml of 10.8 N H_SO, per 100 ml of water sample.
2. Autoclave the samples at 115-120°C for 15 minutes (total heating
time is approximately one hour including depressurization and cool-
ing cycles). If an autoclave is not available, heat the samples in
a pressure cooker at the boiling point for one hour.
3. Add 3-5 drops of phenolphthalein indicator solution to each sample
and carefully neutralize by adding about 1.00 ml of 10.8 N NaOH per
100 ml of water sample.
4. Continue with the procedure given below.
The following method is based on the reduction of a phpsphomolybdate com"
plex by ascorbic acid and is similar to the methods described in Murphy
and Riley (1962) and Strickland and Parsons (1968) , An intensely-colored
blue sol ("molybdenum blue") is produced whose absorbance at 675 nm
varies directly with the orthophosphate content of the sample.
Reagents
Unless otherwise specified, all chemicals should be analytic reagent
grade. All reagent bottles, filters, and glassware should be thoroughly
acid-leached with a dilute HC1 solution prepared from about 10-20 ml of
concentrated HC1 in 1000 ml of deionized and distilled water; detergents
should never be used to clean glassware used for phosphate analyses.
388
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Molybdenum-Antimony Reagent -
Introduce approximately 1500 ml of delontzed and distilled water to a
2000-ml graduated cylinder set aside for this sole purpose. Slowly and
cautiously add 244 ml of concentrated H2SO, while mixing well with a
magnetic stirrer. Allow the solution to cool for approximately one hour
and then add 21.00 1 0.01 g ammonium heptamolybdate tetrahydrate,
(NH4>6 Moy024'4H20 and 0.600 1 0.001 g antimony potassium tartrate,
K(SbO)C4H4.0g'l/2H20. Continue to mix until the solids have dissolved in
the sulfuric acid solution and when it has cooled to room temperature
dilute to the 2000-ml mark with deionized and distilled water. Mix
thoroughly and store the solution in a tightly-stoppered glass or poly-
ethylene bottle.
Ascorbic Acid Solution -
Dissolve 3.00 + 0.01 g of ascorbic acid in 100 ml of 95% ethanol; store
in the refrigerator. This solution is stable for at least one month.
An alternative is to dissolve the ascorbic acid in 100 ml of deionized
and distilled water. However, this aqueous solution must be prepared
fresh daily.
10.8 N H2S04 Solution -
Add 300 ml of reagent grade concentrated H2SO (36 N) to about 500 ml dis-
tilled water in a 1000-ml volumetric flask. Mix well and allow to cool
to room temperature. Dilute to the 1000-ml mark with distilled water
and mix again.
10.8 N NaQH Solution -
Weigh 432 1 1 g of analytical reagent grade NaOH and transfer the pellets
to a 1000-ml volumetric flask and add approximately 300 ml deionized and
distilled water. Mix cautiously by swirling the unstoppered flask to
dissolve the NaOH and then stopper the flask and cool the solution to
room temperature. Dilute to the 1000-ml mark and mix well. Store the
389
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solution in a tightly-stoppered polyethylene bottle.
Butyl Acetate -
"Purified" grade (J. T. Baker Chemical Co. or equivalent).
Standard Phosphate Solution (100 ppm phosphate-phosphorus) -
Oven-dry a sample of analytical reagent grade potassium dihydrogen ortho-
phosphate (KH2P04) to constant weight at 105-110°C. Weigh 0.4393 t
0.0002 gKH2PO^ and dissolve in a 1000-ml volumetric flask with deionized
and distilled water. Mix the solution thoroughly and store in a tightly-
stoppered glass bottle after adding a few drops of chloroform as a pre-
servative.
Phenolphthalein Indicator Solution -
Dissolve 0.10 g of phenolphthalein powder in 50 ml of 95% ethanol and
add 50 ml of deionized and distilled water.
Procedure for the Determination of High Levels of Phosphate
If the concentration of orthophosphate is greater than about 50 ppb
PO.-P, the absorbance of the blue phosphomolybdate complex may be ob-
tained by measuring the unextracted aqueous solution in 4-cm pathlength
cells at 675 nm. Below this concentration, increased sensitivity may
be gained by doubling the size of the sample and by extracting the blue
complex from the aqueous phase and concentrating it in a small volume of
butyl acetate (described in the next section).
1. To 100.0 t 0.1 ml of water sample in a 125-ml Erlenmeyer flask add
10.0 t 0.1 ml of the molybdenum-antimony reagent and 1.00 i 0,01 ml
of ascorbic acid solution and mix well after the addition of each
reagent.
390
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2. Wait a minimum of 30 minutes for the blue color to develop.
3. Measure the absorbances of the samples at 675 nm in 1-cm or 4-cm
pathlength cells. Cell pathlength should be selected so that the
majority of the sample absorbance values fall in the range from
about 0.2-0.6.
4. Duplicate standards having at least three different phosphate con-
centrations and spanning the full range of phosphate concentrations
anticipated in the samples should be prepared with each day's deter-
minations. Duplicate blank samples consisting of 100 ml deionized
and distilled water each must also be analyzed.
5. Prepare a standard curve of corrected absorbances plotted against
ppb phosphate-phosphorus, where A = A , , - A, ., ,
v* K v f f ' corr standard T>lank.
6. The absorbance readings of the samples are corrected for phosphate
contamination in the color development solutions added by the
following formula:
corr sample olank
The corrected absorbance is then read from the corrected standard
curve to obtain the concentration of phosphate-phosphorus in the
sample. The conversion factor (11/111) is used because only 11 ml
of the total sample (100 ml water sample + 11 ml reageats) contribute
deionized and distilled water with possible traces of orthophosphate,
while the blanks and standards contain 111 ml of the slightly con-
taminated deionized and distilled water. With care, phosphate blanks
having absorbances of 0.000-0.005 in 4-cm pathlength cells can be
obtained routinely.
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Procedure for the Determination of Low Levels of Phosphate
For orthophosphate concentrations below approximately 50 ppb phosphate-
phosphorus, the sensitivity may be enhanced by increasing sample sizes
to 200 ml (or more) and by extracting the blue complex into 10 ml of
butyl acetate. If absorbances greater than 1.0 are obtained even in 1-cm
pathlength cells, sample sizes may be decreased to 100 ml or 50 ml while
maintaining the same volume of butyl acetate. Solvent extraction using
butyl acetate is also an effective method of separating the blue phos-
phomolybdate complex from samples which exhibit high levels of turbidity.
1. To 200 - 2 ml of the water sample (measured with an acid-rinsed grad-
uated cylinder or a modified, rapid-draining pipette) in a separatory
funnel, add 20.0 ~t 0.1 ml of molybdenum-antimony solution and 2.00 1
0.02 ml of ascorbic acid solution. Mix thoroughly after adding each
reagent and allow 30 minutes for color development.
2. Carefully add 10.0 i 0.1 ml of butyl acetate to the separatory funnel
using an automatic pipette. Stopper the separatory funnel tightly
and shake vigorously for exactly 3.0 minutes. It is convenient to
extract two or more samples simultaneously. Extraction efficiency
is a function of the extent to which the aqueous and organic phases
mix together. Therefore, extraction time as well as shaking frequen-
cy and vigor must be identical for all samples.
3. Allow the aqueous and organic phases to separate. Drain off and
discard the lower aqueous phase. Collect the remaining butyl ace-
tate solution in a 15-ml centrifuge cone. Centrifuge the sample
for approximately 5 minutes to separate inadvertently-transferred
water droplets that may contribute to turbidity in the butyl acetate
phase.
392
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4. Transfer the butyl acetate solution into a 1-cm pathlength cell (or
larger) and measure the absorbance at 675 nm against pure butyl
acetate in the reference cell.
5. A minimum of three different phosphate standard solutions in dupli-
cate should be prepared with each day's determinations. They should
span the full range of phosphate concentrations found in the samples
analyzed. Two blank samples consisting of 200 ml distilled water
each must also be analyzed.
6. Prepare a standard curve of corrected absorbance vs. ppb elemental
P, where
7 . The absorbance readings of the samples are corrected for phosphate
contamination in the color development solutions added by the
following formula:
corr sample l^lank
The concentration of phosphate-phosphorus in the sample correspon-
ding to the corrected absorbance is then read from the corrected
standard curve. The factor (22/222) appears in the formula because
only 22 ml of the total sample (200 ml water sample and 22 ml re-
agents) are contributed by deionized and distilled water containing
possible traces of phosphate ion.
TOTAL IRON ANALYSES
The determinations of iron are complicated by the many varied forms in
which iron exists in water samples: colloidal and complexed ferric iron,
insoluble iron minerals (sand, clay, etc.), soluble ferrous iron re-
leased under anaerobic conditions, soluble and particulate organic iron
compounds, and insoluble ferric hydroxide. The procedure described here
provides a measure of the "biologically reactive iron" that is released
393
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by a preliminary treatment with hydrochloric acid. This treatment is
believed to release iron from each of the previously-mentioned sources
that is likely to be available to phytoplankton. The measurement of
the true total iron content of the sample would require a much more
vigorous acid digestion process involving complete dissolution of all
of the above sources by HC10, and HF.
Reagents
Bathophenanthroline Solution -
Dissolve 0.175 ± 0.001 g of analytical reagent grade bathophenanthroline
(4,7-diphenyl-l, 10-phenanthroline) in 250 ml ethanol. Then add 250 ml
distilled water and store in a tightly-stoppered polyethylene bottle
that has been thoroughly acid-washed. Although the solution is stable
indefinitely, great care must be taken to prevent contamination by dust,
residue on pipettes, etc. that may contain traces of iron.
Hydroxylamine Hydrochloride Solution -
Even analytical reagent grade NH^OH'HCl contains appreciable amounts of
iron which will cause high blank values in this procedure. Dissolve
20.0 ± 0.1 g of analytical reagent grade NH OH'HCl in 200 ml of deionized
and distilled water in an acid-leached separatory funnel (store funnels
filled with dilute HC1). Add about 5 ml of the bathophenthroline solu-
tion and mix. Then add 10 ml isoamyl alcohol and shake vigorously for 1
minute to extract as much of the red-orange iron complex as possible.
Extract 2 more times with additional 10 ml aliquots of isoamyl alcohol
until the extracts are colorless. Add 5 ml of bathophenanthroline and
repeat the extraction steps. Allow the final extraction mixture to
separate at least 10 minutes before draining the lower aqueous
Nl^OH-HCl solution into a clean polyethylene bottle. Store in the re-
frigerator.
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5 N Hydrochloric Acid Solution -
Dilute 210 I 5 ml of analytical reagent grade concentrated HC1 (specific
gravity = 1.19; concentration = 12 N) to 500 ml with deionized and dis-
tilled water in an acid-washed volumetric flask. Store the solution in
a clean polyethylene bottle.
Sodium Acetate Buffer Solution -
In a 2000-ml graduated cylinder (acid-washed), add 320 ± 2 ml glacial
acetic acid to about 500 ml deionized and distilled water. Add 1088 g
reagent grade sodium acetate trihydrate and add deionized and distilled
water to the 2000-ml mark. Store the solution in a clean polyethylene
bottle.
Isoamyl Alcohol -
Also called "isopentyl alcohol" or "3-methyl-l-butanol". Use analytical
reagent grade.
Standard Iron Solution (200 ppm Fe) -
Weigh out 1.4043 g analytical reagent grade ferrous ammonium sulfate
hexahydrate, FeSO,(NH ) SO -6H 0. In a clean 1000-ml volumetric flask,
dissolve the salt in about 100 ml distilled water and 20 ml concentrated
reagent grade HCl. Add distilled water to the 1000-ml mark and mix well.
Store in a clean, tightly-stoppered container.
Procedure
This procedure is applicable to the determination of up to 30-40 micro-
grams of Fe.
1. Mix the samples to resuspend solid material uniformly. With a clean -oi
pette (the tip of the pipette should be shortened approximately 2-3 mm
to allow particulate material to pass through the enlarged opening
395
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and promote rapid draining), measure an appropriate aliquot of the
samples into acid-washed Erlenmeyer flasks or reagent bottles.
Rinse the pipette with deionized and distilled water, allowing the
rinsings to drain into the flask. Use the following table as a guide
for the selection of sample sizes:
Separatory Funnel
ppb Fe Sample Volume Volume Cell Size
0 - 150 100 ml 200 - 250 ml 4 cm
150 - 500 50 ml 125 ml 1 cm
500 - 1000 25 ml 125 ml 1 cm
1000 - 4000 10 ml 125 ml 1 cm
2. Add 1.0 ± 0.1 ml of 5 N HC1 and 3.0 ± 0.1 ml NH2OH-HC1 solution to
each sample. Mix well and cover with a loosely-fitting glass
stopper or a rubber snap-cap.
3. Autoclave the samples at 115-120°C for 15 minutes (total heating
time is approximately one hour including depressurization and cool-
ing cycles). If an autoclave is not available, heat the samples in
a pressure cooker at the boiling point for one hour.
4. Cool the samples to room temperature. Add 5.0 1 0.1 ml sodium ace-
tate buffer solution to each sample with an automatic pipette and
mix well.
5. Then add 3.0 t 0.1 ml bathophenanthroline solution, mix, and allow
the color to develop for 10 minutes.
6. Transfer the sample quantitatively to a separatory funnel. Add
rinses with deionized and distilled water to the separatory funnel.
7. Add 10.0 ml of isoamyl alcohol by automatic pipette to the separatory
396
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funnel. Shake each funnel vigorously for exactly 2.0 minutes. It
is often most convenient to extract two or more samples simultan-
eously. Extraction efficiency is a function of the extent to which
the aqueous and organic phases mix together. Therefore, extraction
time as well as shaking frequency and vigor must be identical .for
all samples.
8. Allow the layers to separate and discard most of the lower aqueous
layer. Swirl the funnel to dislodge additional water droplets and
allow the phases to separate. Discard the lower aqueous layer and
the first milliliter of the alcohol layer. Collect the remainder
of the alcohol fraction in a 12-20 ml centrifuge .cone. Due to
traces of water, the alcohol extract is often turbid. The cones
should be centrifuged for about 5 minutes or until transparent be-
fore making absorbance measurements.
9. Within one hour of extraction, measure the absorbance at 533 nm
using isoamyl alcohol as the reference. Sample volumes and spectro-
photometer cells should be selected to obtain absorbance readings
in the range from about 0.2 to 0.6.
10. Standard iron solutions with at least 3 different Fe concentrations
spanning the range of Fe concentrations expected in the samples and
a blank are required. All. must be autoclaved along with the samples
3+ 2+
to assure complete reduction of Fe to Fe by the hydroxlamine.
Using aliquots identical in size to those of the samples and follow-
ing Steps 1 - 9 in the above procedure, prepare extracts from each
of the three standard solutions and one distilled water blank.
11. Prepare a standard curve of uncorrected absorbances versus ppb Fe.
12. Determine the iron concentration in each sample by finding the ppb Fe
397
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corresponding to the uncorrected sample absorbances. In our analy-
ses there is much evidence to support the idea that the reagents
and not the deionized and distilled water are fully responsible for
the iron contamination observed in the blank samples. The above
data treatment is therefore analogous to the more tedious process
of subtracting the blank absorbance from all of the standard absorb-
ances, constructing a standard curve of corrected absorbances versus
ppb Fe, subtracting the blank absorbance from all of the sample
absorbances, and finding the ppb Fe in each sample by comparing
corrected absorbances to the corrected standard curve.
AMMONIA (LOW LEVEL) ANALYSES
Ammonia concentrations are determined by a modified method utilizing the
blue indophenol reaction between ammonia, phenol, and hypochlorite at
high pH as reported by Solorzano (1969). Although the reaction has been
known since 1859 (Berthelot), it could not be applied to the determina-
2+
tion of ammonia in natural waters containing high concentrations of Ca
2+
or Mg . In this new procedure, calcium and magnesium interference is
eliminated by complexing with sodium citrate. Other advantages of this
method are the elimination of distillation or solvent extraction steps,
improved sensitivity over nesslerization methods, speed, stability of
blue coloration, and absence of reaction with other forms of nitrogen.
It is reported that .glycine, alanine, lysine, histidine, arginine,
tyrosine, glutamic acid, urea, and nucleic acids do not interfere. The
method is applicable in the range of ammonia concentrations from 0 to
500 ppb NH3~N with negligible departure from the Beer-Lambaert law. The
limit of detection is approximately 5 ppb NH_-N.
Reagents
Unless otherwise specified, all chemicals should be analytic reagent
398
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grade.
Phenol-Ethanol Solution -
Dissolve 50.0 - 0.1 g of analytical reagent grade phenol in 500 ml 95%
ethanol. Avoid chemical burns from phenol!
Sodium Nitroferricyanide, 0.5% Solution -
Dissolve 2.50 _ 0.01 g of analytical reagent grade sodium nitroferricya-
nide (also called sodium nitroprusside) in 500 ml freshly deionized
water. Storfe in a dark bottle wrapped with aluminum foil in the re-
frigerator; replace monthly.
Alkaline Citrate Solution -
Dissolve 200.0 _ 0.1 g analytical reagent grade trisodium citrate dihy-
drate and 10.00 3 0.05 g analytical reagent grade sodium hydroxide in
1000 ml of freshly deionized water.
Sodium Hypochlorite Solution (NaOCl) -
Use analytical reagent grade sodium hypochlorite solution. In an
emergency, commercial bleach such as Chlorox may be used if it is fresh.
Store this reagent in a dark bottle in the refrigerator.
Oxidizing Solution -
Mix 100 ml of sodium citrate-sodium hydroxide solution with 25 ml of
sodium hypochlorite solution (or other appropriate volumes in a 4:1
ratio). Prepare this mixture fresh daily.
Standard Ammonia Solution (50 ppm NHj-N) -
The standard solution may be prepared from either oven-dried (110°C),
analytical reagent grade ammonium chloride or ammonium sulfate. Weigh
0.3818 1 0.0002 g NH Cl or 0.4617 3 0.0002 g (NH^) SO , transfer to a
2000-ml volumetric flask, and dilute to 2000 ml with freshly-deionized,
399
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non-distilled water. Store in a clean tightly-stoppered bottle.
Procedure
1. Measure 50.0 - 0.5 ml of sample into a clean 125-ml Erlenmeyer
flask with a graduated cylinder or a modified, rapidly-draining
volumetric pipette.
2. Add 2.0 1 0.1 ml of the phenol-ethanol solution and mix.
3. Add 2.0 1 0.1 ml of the sodium nitroferricyanide solution and mix.
4. Add 5.0 ± 0.1 ml of the oxidizing solution. Mix thoroughly and
allow the blue color to develop for a minimum of two hours.
5. Measure the absorbances at 640 ran in 4-cm pathlength cells if the
solutions are yellow or yellow-green (ammonia concentrations from
• approximately 0 to 100 ppb NH_-N). Use 1-cm pathlength cells if
the solutions are blue (ammonia concentrations greater than approxi-
mately 100 ppb NH--N).
6. Prepare a series of standards from the stock NH.C1 solution. Select
at least 4 different concentrations covering the expected range of
values for the samples plus a blank. Treat these standard solutions
as in Steps 1-5. Prepare a standard curve of uncorrected absor-
bances versus ppb NH.,-N and determine the sample concentrations from
their uncorrected absorbances.
SILICON ANALYSES
Dissolved silicon is determined spectrophotometrically by the formation
of a yellow molybdosilicate complex according to the procedures described
400
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in Standard Methods for the Examination of Water and Wastewater (APHA
1971). Interference from orthophosphate and arsenate ions is eliminated
by the addition of oxalic acid. Contamination from silica in glassware
is minimized by the use of polyethylene sample and reagent containers;
polypropylene pipettes, graduated cylinders, and beakers; and freshly-
deionized, non-distilled water. The steps suggested for the conversion
of "molybdate-unreactive silica" to "molybdate-reactive silica" by a
one-hour digestion process with sodium carbonate have been eliminated,
because no significant difference between these two types of soluble
silicon has been found in samples of Lake Tahoe water. It has not been
necessary to resort to more sensitive or more involved analytical methods
that require the reduction of the heteropoly anion of molybdenum and
silicon to the blue form which exhibits strong electronic absorption
bands in the region from 650-800 run. Typical reducing agents required
for the latter procedures include solutions of copper (I), mercury (I),
iron (II), and tin (II) salts and benzidine.
Apparatus
1. Polypropylene beakers, 100 ml, with covers.
2. Polypropylene graduate cyclinders, 100 ml.
3. Graduated polypropylene pipettes; 1 ml (1) and 2 ml (2).
4. Clock or timer.
Reagents
6 N Hydrochloric Acid -
Mix 500 ml concentrated HC1 with 500 ml of freshly-deionized water.
Store in an acid-washed polyethylene bottle.
401
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Ammonium Molybdate Solution -
Dissolve 50.0 g reagent grade (NH4)6Mo7024'4H20 in deionized water.
Dilute to 500 ml. Adjust pH to 7.8-8.1 with reagent grade pellets of
NaOH. Store in a polyethylene bottle.
Oxalic Acid Solution -
Dissolve 50.0 g reagent grade H^O^I^O in deionized water and dilute
to 500 ml. Store in a polyethylene bottle.
Stock Silicon Standard Solution -
A 500 ppm SiO ~-Si solution is prepared by dissolving 5.0595 g reagent
grade sodium meta-silicate (Na-SiO^I^O; formula weight = 284.20) in
freshly-deionized water in a 1000-ml volumetric flask. Because of the
deliquescent nature of this solid compound, this solution must be stan-
dardized by gravimetric analysis to determine the silicon content via
the weight loss as volatile SiF, when aliquots of this concentrated
stock solution are treated with HF and heated to a constant weight at
1200°C. Store this stock solution in a polyethylene bottle.
Standard Silicon Solution -
For routine use, a more dilute standard solution is prepared. A 5 ppm
SiO_ -Si standard solution is prepared by pipetting 10.0 ml of the stock
Si solution into a 1000-ml volumetric flask and diluting to the mark
with fresh, deionized water. After mixing, the solution is transferred
to an acid -washed polyethylene bottle for storage. As needed, less con-
centrated standard solutions are prepared by dilution of this 5 ppm
standard.
Procedure
1. All beakers, cylinders, pipettes, etc. should be acid-washed, de-
ionized water-rinsed, and stored in a dust-free environment.
402
-------
2. Carefully measure a 50.0 ml sample into a plastic beaker using a
graduated cylinder.
3. In rapid succession, add 1.0 ml 6 N HC1 and 2.0 ml ammonium molyb-
date solutions using the plastic pipettes.
4. Mix well and allow the solution to stand for 5-10 minutes while the
yellow color develops.
5. Add 1.5 ml oxalic acid solution and mix thoroughly again.
6. Measure the absorbance of the yellow solution at a wavelength of
410 nm 5-10 minutes after the addition of the oxalic acid (the color
begins to fade significantly after approximately 15-20 minutes).
For concentrations below about 5 ppm SiO_ -Si, 4-cm pathlength cells
should be used.
7. If two people are available, it is most convenient for one person to
measure samples and develop the color while the second person
measures the absorbances at appropriate time intervals.
8. Prepare a standard curve of uncorrected absorbances versus ppm
SiO_ -Si from a series of four or more standards plus a blank
covering the range of concentrations expected in the water samples.
(These standards and blank are treated according to Steps 1-7).
From this curve, the sample absorbances are read directly and con-
verted to ppm SiO ~-Si. At least one sample, selected at random,
should be run in triplicate for each series of determinations to
provide an estimate of precision.
DISSOLVED OXYGEN ANALYSES
A modified version of the Winkler method is used to determine the
403
-------
concentrations of dissolved oxygen. This procedure is essentially the
one described by Carpenter (1965) with the only exception being the
addition of sodium azide to the sodium iodide-sodium hydroxide solution
(APHA 1971) to eliminate interferences from nitrite and ferrous ion
found in highly eutrophic waters such as Clear Lake.
Reagents
3 M Manganous Ion Solution -
Weigh 600 ± 1 g analytical reagent grade manganous chloride tetrahydrate
(MnCl2'4H 0) and dissolve in distilled water. Make u, to 1000 ml.
Manganous sulfate monohydrate (MnSO,-H 0) (516 t 1 g) may be substituted
for the former.
NaI-NaOH-NaN3 Solution -
Dissolve 600 1 1 g Nal(4 M), 320 ± 1 g NaOH, and 10.0 t 0.1 g NaN3 in
distilled water and make up to 1000 ml. The sodium azide (NaN~) is
2+
especially important where appreciable concentrations of Fe or N0_
are believed to be present in the water samples.
18 N Sulfuric Acid Solution -
Cautiously add 500 - 2 ml concentrated reagent grade H.SO, in small
portions to about 450 ml distilled water in a 1000-ml volumetric flask.
Mix well and allow to cool to room temperature. Add distilled water to
the 1000-ml mark and mix well.
1% Starch Solution -
Add 2.0 g soluble starch to 200 ml hot distilled water. Bring to a boil
with stirring and allow to settle. Pour off the clear supernatant
solution and preserve with 0.5 g salicylic acid.
0.14 N Sodium Thiosulfate Solution -
a.
Weigh 35.0 _ 0.1 g analytical reagent grade sodium thiosulfate
404
-------
pentahydrate (Na_S 0 *5H 0) and prepare 1000 ml of solution with dis-
Preser^v
a well-stoppered dark bottle.
tilled water. Preserve with 1 drop of carbon disulfide (CS ) . Store in
Ampoulated 0.01000N Standard KIO Solution -
Weigh 0.3567 g oven-dried (105-150°C) analytical reagent grade potassium
iodate (KICL). Transfer quantitatively to a 1000-ml volumetric flask
and dissolve in about 500 ml distilled water. Add distilled water to
the mark and mix thoroughly. This solution is then sealed into glass
ampoules of approximately 20-25 ml capacity which are broken open as
needed to standardize the sodium thiosulfate solution.
Apparatus
1. 125-ml nominal capacity sample collection bottles with tapered glass
stoppers. Bottles should be permanently labelled and their volumes
calibrated "to contain" by weighing both empty and filled with water
of known density. If a Teflon-coated magnetic stirring bar is to
be used in titrations, its volume must be subtracted from the bottle
capacity. After initial volume calibrations, stirring bars must
remain in their respective sample bottles.
2. Three rapid delivery pipettes for the addition of 1.00 ml of mangan-
ous ion solution, sodium iodide-sodium hydroxide solution, and
sulfuric ac±d solution. Calibrate to deliver 1.00 1 0.05 ml.
3. Microburette with 2.000 ml capacity (subdivided into 0.001 ml incre-
ments) for titration of liberated iodine with 0.14 N Na^S^O^
solution.
Procedure
405
-------
1, Collect the water samples in the calibrated bottles. Place the de-
livery tube from the water sampler at the bottom of the collection
bottle and thoroughly flush the air from the bottle by filling and
overfilling with about 3 bottle volumes, being careful at all times
to avoid excessive turbulence in the water stream. Replace the
tapered glass stopper without trapping any air bubbles inside of the
bottle.
2. Add 1.00 ml of the manganous ion solution and 1.00 ml of the Nal-
NaOH-NaN3 solution with the rapid delivery ]
glass stopper without trapping air bubbles.
NaOH-NaN3 solution with the rapid delivery pipettes. Replace the
3. Shake the bottle to disperse the precipitate uniformly. Allow the
precipitate to settle at least halfway to the bottom. At this
time, shake the bottles again and allow the contents to settle at
least two-thirds of the way to the bottom. If desired, samples may
be stored in this condition for several hours provided they are
kept cold and are stored in a dark location.
4. Add 1.00 ml of the H SO, solution, and mix with the magnetic stirrer
to dissolve the precipitate and release the I .
5. Titrate the iodine with 0.14 N sodium thiosulfate from the micro-
burette until the brown color lightens to a straw yellow. The tip
of the microburette should be submerged in the solution about 5 mm
with the magnetic stirrer in operation.
6. Add about 0.25 ml of the starch indicator (5 drops) and continue
the titration to the complete disappearance of the blue iodine-
starch complex.
7. Record the volume in tnilliliters of thiosulfate solution required
406
-------
for the titration. This volume is designated R in the calculations.
Standardization -
A clean sample bottle is required for this titration. Acid-rinsing a
previously-used bottle followed by several distilled water rinses will
remove traces of manganese. Pipette 10.0 ml of 0.01000 N KIO into the
bottle and nearly fill it with distilled water. Add 1.00 ml Nal-NaOH-
NaN0 solution and 1.00 ml H_SO. solution. Titrate the liberated iodine
o 24
as described in Steps 5-7. This volume is designated R . in the calcu-
s td
lations .
Reagent Blank -
A clean sample bottle is required here also. Pipette 1.00 ml of 0.01000
N KIO solution into the bottle and add approximately 100 ml of distilled
water. Add 1.00 ml of Nal-NaOH-NaN solution and 1.00 ml of sulfuric
acid solution and begin mixing with the magnetic stirrer. Then add 1.00
ml of the manganous chloride solution and titrate the liberated iodine
with sodium thiosulfate. Record the microburette reading (X ml) having
begun the titration at a reading of 0.000 ml. Then pipette another 1.00
ml sample of 0.01000 N KIO- into the previously-titrated solution and
again titrate to the new endpoint without refilling the microburette.
Record the final microburette reading (Y ml). The volume R, .., is ob-
tained by subtracting the volume difference between the first and
second endpoints from the volume required to reach the first endpoint:
Rblk = x ~ (Y - x) = 2X - Y
Calculations -
Dissolved oxygen (mg/1) =
(Rstd - W (Vb - Vreagent8) '
where R = ml of Na?S?0,, required for sample titration
R , = ml of Na0S000 required for standard titration
std z Z J
407
-------
R, ., = reagent blank volume
V. , ^ = ml of KIO- standard (10.0 ml)
lodate 3
N. , .. = normality of KIO. standard (0.01000N)
lodate 3 3
V, = calibrated volume of sample bottle (ml)
b
V ^ = volume of sample displaced by reagents = 2.00 ml
reagents v v j
eq. wt. 0 = 8000 mg/equiv.
D.O. = oxygen content of reagents added (0.026 mg/1)
reagents J°
800 (R - R^)
Dissolved oxygen (mg/1) = -7= - = - r — „,. - 0.026
oxygen (mg/1) = -7= - = - rj^ — „,. - 0.
(Rstd~Rblk) (Vb"2)
REFERENCES
American Public Health Association. 1971. Standard methods for the
examination of water and wastewater. 13th ed. New York. 874 p.
Carpenter, J. H. 1965. The Chesapeake Bay Institute technique for
the Winkler dissolved oxygen method. Limnol. Oceanogr. 10:141-143.
Chemical Rubber Co. 1971. Handbook of chemistry and physics. 51st
ed. R. C. Weast (ed.). Cleveland. 2364 p.
Murphy, J. and J. P. Riley. 1962. A modified single solution method
for the determination of phosphate in natural waters. Anal. Chlm.
Acta. 27:31-36.
Solorzano, L. 1969- Determination of ammonia in natural waters by the
phenolhypochlorite method. Limnol. Oceanogr. 14:799-801.
Strickland, J. D. H. and T. R. Parsons. 1968. A practical handbook of
seawater analysis. Bull. Fish. Res. Board Can. 167. 311 p.
408
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TECHNICAL REPORT DATA
(1 lease reail Inunctions on tin' reverse be/ore completing)
HI I'OHl NO. • 2.
TITLt ANU SUBTITLE
EUTROPHICATION OF LAKE TAHOE EMPHASIZING
WATER QUALITY
AUTHOR(S)
C. R. GOLDMAN
PERFORMING ORG MMIZATION NAME AND ADDRESS
INSTITUTE OF ECOLOGY
CALIFORNIA UNIVERSITY
DAVIS, CALIFORNIA 95616
1? <-TONSORING AGENCY NAME AND ADDRESS
U.S. ENVIRONMENTAL PROTECTION AGENCY
PAC. NW ENVIRONMENTAL RESEARCH LAB, NERC-CORVALLIS
200 SW 35TH STREET
CORVALLIS, OREGON 97330
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
1BA031
11. CONTRACT/GRANT NO.
16010 DBU
13. TYPE OF REPORT AND PERIOD COVERED
FINAL, 1967-1971
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A 4 1/2-year study on the rate and factors affecting the cultural eutrophication of
oligotrophic Lake Tahoe is reported. Primary productivity has increased alarmingly
with a steady shift in the seasonal-maximum from early spring to late summer. Produc-
tivity increased 25.6% from 1968 to 1971. Using the 1959-1960 data from earlier
studies, the increase to 1971 was 51%. Diatoms dominate the phytoplankton population
and the maximum zone of phytoplankton photosynthesis may be as deep as 50-7r; m. The
extent of winter mixing is important in the nutrient budget of the lake and bacteria
associated with stream-borne nutrients facilitate nutrient regeneration. The littoral
zone, although extremely important visually to the lake, contributes only 10% of the
total primary production. Great variability in fertility of the lake has been
demonstrated by synoptic studies and aerial remote sensing. Highest productivity
is found in the lake near tributaries which drain disturbed land. Nutrients associated
with road building, housing, and lumbering are major causes of eutrophication in Tahoe.
In bioassay studies NTA was found to stimulate primary productivity. Drainage from a
sewage land disposal site continues to yield high levels of nitrate, and marinas may
serve as nutrient and sediment traps or as eutrophic, isolated systems. Daphnia, an
important cladoceran component of the zooplankton population has virtually disappeared
from the lake and predation by the introduced zooplankter Mysis relicta and the
kokanee salmon are suspect.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
*Eutrophication, *primary productivity,
*synoptic analysis, *bioassay, *remote
sensing, *detergents (NIA), water pollution
sources, aquatic productivity, zooplankton,
discharge (water), periphyton, aquatic
bacteria, limiting factors, crayfish,
geomorphology, sediment transport
•OlSlHinuriON STATEMENT
RELEASE UNLIMITED
b.lDENTIFIERS/OPEN ENDED TERMS
Lake Tahoe,
California-Nevada,
Pacifastacus leniusculus
19. SECURITY CLASS (This Report)
20. SECURITY CLASS (This page)
c. COSATI Field/Group
05 C
21. NO. OF PAGES
408
22. PRICE
Form 222Q.) (9.73)
•;.- U.S. GOVERNMENT PRINTING OFFICE: 1975-697-828/79 REGION 10
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