-------
-------
Excerptsfrom the Report on Algae (USEPA 1982).
Excerpts were taken from the Report on Algae to provide summaries and conclusions
regarding the major topical areas covered. The full Report on Algae was originally
published and distributed by USEPA Region V in January of 1982. This report was
prepared as a supporting technical reference document for the Environmental Impact
Statement on the Moose Lake-Windemere Sanitary District's proposed wastewater
treatment system. Complete copies of the Report on Algae are available from the
Project Monitor.
2.3.5. Summary of Blue-Green Algal Toxicity
Three genera of freshwater blue-green algae, Anacystis, Anabaena and
Aphani zomenon, are most commonly associated with toxin production and have
been reported to produce several different types of toxins. The toxicological
and pharmacological properties of the toxins as well as their chemical identi-
ties are not well understood. In addition, very little is currently known
about the physiological and/or ecological factors and interactions that lead
to toxic episodes.
There is well documented evidence, however, that blue-green algae can
produce toxic effects in animals and livestock. Livestock and wildlife
poisonings occur most frequently in lakes, reservoirs, and ponds in temperate
climates. Toxic blooms usually occur between late spring and early autumn.
Toxic effects in animals can occur only through ingestion of contaminated
water. A variety of toxic effects have been documented in the laboratory and
from observations of livestock and wildlife populations and include convul-
sions, gastrointestinal disorders, respiratory disorders, liver failure, and
death. There are, however, no documented or reported cases of human mortality
associated with toxic strains of freshwater blue-green algae.
Although more than 12 species belonging to 9 genera of freshwater cyano-
phytes have been implicated in cases of animal poisoning, toxic strains of the
three most common bloom forming species, Microcystis aeruginosa, Anabaena
H-l
-------
flos-aque, and Aphanizomenon flos-aque have been responsible for the majority
of the documented episodes. (In the literature, Anacystls is used synonymosly
with the genus Microcystijs.) The poisonings attributable to Anabaena^
flos-aque have been more dramatic in terms of the number of animals affected,
but toxic strains of Micrpcyst1s aeruglnosa appear to be more widely dis-
tributed geographically.
To date, twelve different toxins have been identified from strains and/or
blooms of the three most common toxlgenic species. The toxins differ In their
reaction time and their chemical structure. Several of the toxins are very
fast-acting and are suspected of being alkaloids. Some have a pronounced
latent period following ingestion and are suspected of being peptides. The
available evidence also indicates that a single bloom may contain several
different toxins simultaneously.
Investigations into the nature and occurrence of toxic blooms of blue-
green algae indicate that such blooms have a highly variable and mosaic
nature. The development of toxic blooms Is unpredictable and usually occurs
in short-lived pulses. They infrequently recur in the same body of water in
subsequent years. The fact that bloom toxicity is so varied and unpredictable
makes any bloom potentially dangerous and suspect at all times, even though
the majority are actually nontoxlc.
There have been several documented episodes of toxic blue-green algae
blooms in southern Minnesota. Toxic blooms are rare, however, In the northern
part of the state.
H-2
-------
3.3. Summary of the Causes of Swimmers' Itch
Swimmers' itch can be cercarial related or blue-green algae related. Man
is not a host or "carrier" of the schistosome which causes the cercarial
dennatitus form of swimmers itch. Therefore human waste (excrement) can not
be responsible for the presence of this more severe type of swimmers' itch.
However, the blue-green algae blooms which are 'responsible for the less
serious form of dermatitus can in part be caused by an influx of nutrients
from human waste.
H-3
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4.0. PHYTOPLANKTON COMMUNITY STRUCTURE AND EVIDENCE OF PUBLIC HEALTH PROBLEMS:
MOOSE LAKE, MINNESOTA
Four lakes in the Moose Lake-WIndermere Sanitary District were inves-
tigated to gather baseline information on phytoplankton community structure
and on existing water quality. The objective of this investigation was to
evaluate the relative abundance of blue-green algae in the four lakes and to
assess potential problems associated with blooms of blue-green algae. A
secondary purpose was to determine If cercarial dermititus (swimmers' itch) is
a problem in the Moose Lake area. The Moose Lake-Windermere Sanitary District
is located in eastern Minnesota between Minneapolis and Duluth. The four
lakes that were studied are Island, Sturgeon, Rush, and Passenger Lakes
(Figure 4-1).
The description and evaluation of the phytoplankton community structure
was based on lake sampling and water quality data analysis. Information on
blue-green toxicity events and swimmers' itch outbreaks was gathered in inter-
views with local physicians and veterinarians as well as with state health
officials.
4.1. Phytoplankton Community Structure
4.1.1. Description of Phytoplankton Community Structure
Phytoplankton community structure is determined primarily through inter-
actions Involving physical-chemical factors, zooplankton, and fish.
Typically, the dominance of a phytoplankton community by a particular species
will shift during the course of a year. That is, a particular phytoplankton
species may form the greatest proportion of the algal community biomass
(weight of living matter) only at certain times of the year when the interac-
tions taking place within the water body favor that particular phytoplankton.
As the aquatic ecosystem changes during the year, numerous interactions occur
that may, in sequence, favor other phytoplankton. For example, in eutrophic
lakes diatoms may be the dominant phytoplankton in the spring because they are
favored by high silicate concentrations, high light peneration, and cool water
temperatures present at that time of the year. In early summer as silicate
H-4
-------
Figure 4-1. Locations of mid-lake sampling stations
for phytoplankton, nutrient, temperature,
dissolved oxygen and chlorophyll data.
H-5
-------
concentrations decrease, green algae may become dominant because of increased
water temperatures and increased nutrient availability. As water temperature
reaches the late summer peak, and as dissolved nitrate levels decrease follow-
ing uptake by green algae and by rooted aquatic plants, blue-green algae may
become dominant. In late summer blue-green algae hold an advantage over other
algal species when levels of phosphorous are high compared to nitrogen because
blue-greens alone can fix atmospheric nitrogen into a useful nutrient form.
In addition, blue-green algae use their unique gas vacuoles to remain in
position at the water surface and take advantage of the diminished sunlight as
well as shade out other algae found deeper in the water column.
Algal groups such as blue-greens, diatoms, or greens are characterized as
dominant based on biovolume measurements micrometers cubed per millillter
3
Gum /ml). Biovolume Is a parameter which generally reflects biomass. It is
expressed in this Report as a volume of plankton per unit volume of water and
is therefore indicative of visible accumulations of living matter.
Phytoplankton samples were collected from Island Lake (6 stations) and
Sturgeon Lake (4 stations) on four sampling dates during late summer and early
autumn. Passenger and Rush Lakes were sampled on three dates during the same
period at one station in the middle of each the lakes. Phytoplankton samples
were taken in each instance at one meter below the surface, at raid-depth, and
at one meter from the bottom. The sampling station locations are shown in
Figure 4-1. Algal identification was taken at least to the genus level and to
the species level where possible. Phytoplankton dimensional measurements were
made of the most numerous phytoplankton species found. Measurements for other
less numerous phytoplanktons were taken from unpublished species lists for
Minnesota lakes (by letter, Nancy Holm, Liranological Research Center, Univer-
sity of Minnesota) and from Wetzel (1975). The list of phytoplankton volumes
used to calculate biovolumes in this investigation is Included in Appendix
A-3. Chlorophyll a_ samples were collected concurrent with phytoplankton
sampling on two dates at the same sample locations and depths. Secchi disk
depth was measured at all sample sites and on all sample dates.
Island Lake
Phytoplankton biovolume (abundance) and the percent composition
(dominance) of major phytoplankton groups for Island Lake at the surface,
H-6
-------
mid-depth, and bottom depths are depicted in Figure 4-2. From 26 August to
September 9 there was an overall decrease In algal density and a dramatic
shift In algal dominance. The decrease in algal density was due primarily to
the decline of the large dinoflagellate, Ceratium hirundinella, which had an
3
estimated volume of 75,000 um per organism. Over this same time period a
3
large blue-green species, Anabaena macrospora (45,000 Aim per organism) and
another blue-green, Aphanizorcenon flos-aquae (2800 >um per organism) grew in
3
number while a smaller blue-green, Phormidium mucicol_a (10 .urn per organism)
decreased in number. Thus, although the total blue-green algae cell number
per ml remained relatively constant from 26 August to 9 September, because of
the shift from small blue-green algae species to large-sized blue-green algae
species and declines in other phytoplankton (the dinoflagellates declined from
77% to less than 1% of the phytoplankton biovolume), blue-green algae in-
creased from 16% to 94% of the total phytoplankton biovolume. For the re-
mainder of September, blue-greens were 'dominant in Island Lake, with the
blue-green abundance reaching a peak around the September 14 sampling date
(Table 4-1).
Throughout the sampling period (26 August to October 5) Island Lake
consistently had the highest phytoplankton density of the four lakes inves-
tigated. High blue-green algal and other phytoplankton densities in Island
Lake also contributed to poor water clarity. Island Lake had the lowest
Secchi disk readings of the four lakes. The changes in the average Island
Lake Secchi disk readings were followed closely by the changes in phytoplank-
ton abundance (Figure 4-3a and b).
Sturgeon Lake
Changes in phytoplankton abundance and dominance in the water column for
the four Sturgeon Lake sampling dates are shown in Figure 4-4. The total
phytoplankton biovolume in Sturgeon Lake was lower than in Island Lake but
blue-green algae were still the dominant phytoplankton group throughout the
month of September. The dominant blue-green species was Anacystis spp.
Diatoms were an important component of the phytoplankton community in Sturgeon
Lake on all four sampling dates and were found at all depths but never
accounted for more than 24% of the phytoplankton biovolume. Based on Secchi
disk readings, water clarity was observed to be much greater in Sturgeon Lake
than in Island Lake (Figure 4-3a).
H-7
-------
ISLAND LAKE
Oft
10ft
20ftJ
Oft
9ft-
26 AUGUST 1981
bio volume in Jim x 10
t 35 79 11 13 15 17 19
9 I I
12% blue-green
25Z blue-green
11-
T^.121 blue-green
19ft1
14 SEPTEMBER 1981
biovolume in jun^ x 10^
1 35 7 9 U 13 15 17 19
98Z blue-green
98Z blue-
green
13ff
18ftJ
Figure 4-2.
98Z blue-green
9 SEPTEMBER 1981
biovolume in JHB x 10
1 35 7 9 11 13 15 17 19
i t t
9AZ blue-green
95Z blue-green
92Z blue-green
30 SEPTEMBER 1981
biovolume in unr* x 106
1 35 7 9 U 13 15 17 19
942 blue-green
94Z blue green
Abundance and dominance of major phytoplankton forms based
on biovolume data. Derived from plankton counts made on
samples taken from Island Lake on four sampling dates.
Depths of samples are approximately as shown.
H-8
-------
3 4
Table 4-1. Blue-green algal biovolumes Gum x 10 /ml) of four lakes in
the Moose Lake area and four lakes from southern Minnesota (the
Minneapolis-St. Paul area). Blue-green algae genera listed are
those most commonly associated with incidences of blue-green
algae toxicity in North America.
Location/
Date
Island Lake
26 August 1981
9 September 1981
14 September 1981
30 September 1981
Sturgeon Lake
27 August 1981
9 September 1981
15 September 1981
5 October 1981
Passenger Lake
10 September 1981
15 September 1981
1 October 1981
Rush Lake
10 September 1981
15 September 1981
1 October 1981
Anabaena spp.
61
671
1336
92
30
41
74
30
0
14
5
30
27
0
Anacystis spp.
17
7
11
8
58
102
66
48
18
14
2
0
24
4
Aphani zomenon
f]os-aquae
67
169
466
358
0
1
0
1
0
0
0
0
0
0
Sampling
Depth
Surface
Surface
Surface
Surface
Cedar Lake, MN
9 September 1974 14
Lake Harriet, MN
22 July 1974 41
Lake of the Isles, MN
22 July 1974 476
Lake Calhoun, MN
26 August 1974 232
169
297
460
544
2 meters
2 meters
Surface
Surface
H-9
-------
>,*»
I.JO
J.K>
1.50
1.10
J.JO
).20
1.10
5 l.oo
2 '"
2.IW
:«.»
: ,.»
J.*o
I 2.30
5 J.JO
3 1.19
' 1.00
,.»
>.»
I.JO
i.w
1.50
I.W
i.x
WATER CLARITY
(SECCHI DISK MEASUREMENTS)
26 ».,u.c
~\I 1
X> I Oec. J Oct
Figure 4-3a. Average Secchi disk values for the project area lakes
versus time. Data are from 19.81 field surveys.
PHYTOPIANKTON ABUNDANCE
(BIO-VOLUME ESTIMATES FROM CELL COUNTS)
10 -
90
l«l
200 .
1000 -
1500 -
2000 -
I
10
Sne.
Figure 4-3b. Average phytoplankton biovolumes for the project area lakes
versus time. Plotted data are representative of the
photic zones of the lakes,as only samples from just below
the surface of the water were taken into the averages.
-------
STURGEON LAKE
27 AUGUST
biovolume In urn x 10
I 35 79 11 13 15 17 19
Oft
9ft
19ft
76Z blue-green
69Z blue-green
73Z blue-green
9 SEPTEMBER
biovolume in um x 10
1 35 7 9 11 13 15 17 19
Oft
84Z blue-green
90Z blue-green
69Z blue-green
15 SEPTEMBER
biovolume In )m3 x 106
1 35 7 9 11 13 15 17 19
Oft
5 OCTOBER
biovolume in um^ x 10
1 35 7 9 11 13 15 17 19
13ft1
Oft
86Z blue-green
33Z blue-green
12ft.
75Z blue-green
22ftJ
87Z blue-green
69Z blue-green
Abundance and dominance of major phytoplankton forms based
on biovolume data. Derived from plankton counts made on
samples taken from Sturgeon Lake on four sampling dates.
Depths of samples are approximately as shown.
fMl
-------
Passenger Lake
Passenger Lake had low phytoplankton biovolumes (Figures 4-3b and 4-5)
and low blue-green algae biovoluraes (Table 4-1) compared to Island and Stur-
geon Lakes. Although Passenger Lake had the highest cell count per milliliier
of all four lakes (Appendix A) the phytoplankton that accounted for these h:!gh
numbers (Ochromonas spp; 4500 cells/ml) was a small golden-brown algae (40 Jim
per organism). For the three sampling dates, two phytoplankton groups w«-re
dominant, the golden-brown algae and the cryptomonads. Based on the the
findings of lower biovolumes in Passenger Lake than in Sturgeon Lake, deeper
Secchi disk readings in Passenger Lake would be expected. This was not cb-
served (Figure 4-3a). The lower (shallow) Secchi disk readings in Passenger
Lake may have been due to increased light scattering caused by the high number
of phytoplankton cells, by color due to dissolved organics, by suspended
solids brought into the photic zone (surface layer) from bottom sediment
resuspension, or by sediments carried into the Lake from the surrounding
watershed.
Rush Lake
Rush Lake had the lowest phytoplankton abundance (Appendix A-2), and had
blue-green biovolumes similar to Passenger Lake. Consequently, a relatively
small blue-green biovolume could dominate the overall phytoplankton communily
(Figure 4-6). Other groups that were important in terms of the the biovolun.e
percentages of Rush Lake included cryptonomads and dinoflagellates. Cell
sizes in the phytoplankton samples were small (less than 1000 jura per
organism) except for the dinoflagellate, Ceratium hirundinella. Large phyto-
plankton can have a significant impact on biomass concentrations even at low
densities. For example, in the 10 September mid-depth sample the total cell
density was 748 cells/ml, and although Ceratium was found at only 5 cells/ml,,
it represented 38% of the total phytoplankton biomass (Appendix A-l and Figure
4-5). The low phytoplankton biovolumes in Rush Lake are associated with th*
highest (deepest) Secchi disk readings of the four lakes investigated. Based
on the survey data of September 1981 it appears Rush Lake had the greates1:
water clarity of the four studied lakes (Figure 4-3a).
H-12
-------
PASSENGER LAKE
10 SEPTEMBER 1981
biovolume in urn x 10
35
9 11 13 15 17 19
Oft
16ft -
ry^v5\ ^ IX blue-green
cryptophyte.
7Z ocher
I'Z blue-green
36Ti cryptophyte
40Z euglenoid
Oft
14ff
15 SEPTEMBER 1981
biovolume in
1 35 7
> x 10
9 U 13 13 17 19
1 OCTOBER 1981
biovoluae in )im^ x 10"
1 35 7 9 11 13 15 17 19
Oft
iZ blue-green
^39Z cryptophyte
32% golden brown
8t other
^12Z blue-green
44Z cryptophyce
36Z golden brown
27% euglenoid^
14Z blue-green
59Z cryptophyte
6ft.
28ft-l
L4Z bluegreen
42Z cryptophyte
Z golden brown
17Z golden brown
blue-green
60Z cryptophyte
L5Z other
18Z blue-green
cryptophyte.
12ftJ / 2SZ golden brown
Figure 4-5. Abundance and dominance of major phytoplankton forms based
on biovolume data. Derived from plankton counts made on
samples taken from Passenger Lake on three sampling dates.
Depths of samples are approximately as shown.
H-13
-------
RUSH LAKE ,
10 SEPTEMBER 1981
biovoluroe In tun x 10
1 35 7 9 11 13 15 17 19
Oft
16ft
34ft J
18Z other
35Z blue-green
472 dlnoflagellate
Ulother
10Z blue-green
77Z cryptophyte
Oft
14ft
28ft J
15 SEPTEMBER 1981
bio volume in
1 35 7
m-' x 10
9 11 13 15 17 19
1 OCTOBER 1981
biovolume in jim x 10
3 5
9 11 13 15 17 19
Oft
71Z blue-green
41Z other
59Z blue-green
6ft
16Z other
9Z blue-green
75Z cryptophyte
nit
12Z blue-green
49Z dinoflagellate
39Z other
22Z other
;-/J 50Z blue-green
28Z cryptophyte
.31Z.other
blue-green
572 dinoflagellate
Figure 4-6. Abundance and dominance of major phytoplankton forms based
on biovolume data. Derived from phytoplankton counts made on
samples taken from Rush Lake on three sampling dates. Depths
of samples are approximately as shown.
H-14
-------
Chlorophyll a was another parameter measured in the four lakes. Chloro-
phyll a is a general indicator of the total phytoplankton biomass but does not
differentiate between specific groups and does not always correlate well to
water clarity. Table 4-2 lists chlorophyll _a concentrations for the 8 Septem-
ber and 15 September sampling dates. In general, chlorophyll a_ concentrations
in Island Lake samples were higher than in Sturgeon, Rush, or Passenger Lake
samples. Higher chlorophyll ja concentrations may also have resulted in the
observed green appearance of Island Lake's water compared to the other three
lakes. This characteristic has been reported by a number of lakeside resi-
dents and may be enhanced by the presence in Island Lake of suspended clay
matter which scatters (back-reflects) light. The presence of clayey soils in
the watershed of Island Lake is discussed in Section 4.1.2. below.
Table 4-2. Chlorophyll a_ concentrations Gug/1) for Island, Sturgeon,
Passenger, and Rush Lakes.
SEPTEMBER 8
Surface Mid-depth Bottom
Island
Is-1
Is-2
Is-3
Is-4
Is -5
Is-6
Sturgeon
St-1
St-2
St-3
St-4
Passenger
Rush
37
28
28
32
32
36
10
3
9
8
11
20
34
26
33
24
28
29
11
9
8
8
6
10
28
19
24
8
14
21
10
11
9
7
28
4
SEPTEMBER 15
Surface Mid-depth Bottom
19
30
39
9
26
29
10
45
33
32
40
20
26
12
28
22
6
16
8
10
8
9
8
7
8
14
9
13
8
8
16
53
13
H-15
-------
4.2. Physician and Veterinarian Interview Report
A survey of medical practitioners was conducted to determine whether any
human, pet or livestock health problems had been diagnosed in the drainage
areas of Island, Sturgeon, Passenger or Rush Lakes since 1979. Personal and
H-16
-------
telephone interviews were conducted with local medical and veterinary clinics;
state, county, and local health and water agencies; and experts. All respon-
dents were asked to consult their records and to poll their staffs on medical
problems that might be attributed to water pollution in the study area. They
were requested to document cases involving toxic effects attributable to
blue-green algae, bacterial and viral infections, and outbreaks of cercarial
dermatitus (swimmers' itch). An explanation of symptoms exhibited by humans,
pets and livestock after exposure to toxic strains of blue-green algae, and of
swimmers' Itch was provided to all survey participants. A phone number was
left with each respondant and they were encouraged to contact USEPA if they
wished to provide additional information.
None of the agencies, clinics, or experts polled had records of or were
aware of any medical problems associated with water contaminated by blue-green
algae, or due to the presence of bacteria or virus originating from human
waste in the study area (Table 4-4).
The Minnesota Department of Natural Resources1 (MDNR) Water Monitoring
and Control Unit (WMCU) is responsible for issuing permits for applying copper
sulfate to provide emergency control of cercarial dermatitus (swimmers' itch),
rooted aquatic plants and phytoplankton growth. No permits have been issued
for copper sulfate applications on Island, Sturgeon, Passenger or Rush Lakes
during the past twenty years (By telephone, Howard Krosch, Supervisor WMCU,
MDNR 10 November 1981).
Instances of animal illness or death attributed to blue-green algae are
rare in the northern portion of the state of Minnesota. Occasional toxic blue
green algae blooms have been recorded In southern and western Minnesota,
typically reappearing in two to three year intervals (By telephone, Howard
Krosch, WMCU, MDNR 18 November 1981). There have been no documented domestic
animal deaths attributable to blue-green algae in northern Minnesota near the
Moose Lake area (Personal communication, Dr. Clarence Stowe, Large Animal
Clinic - University of Minnesota, 9 November 1981).
Conversely, cercarial dermatitus (swimmers' itch) is reported to be
common in lakes throughout Minnesota (By telephone, Gene Jordan, Minnesota
State Department of Health, 5 November 1981). However, none of the state or
H-17
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H-19
-------
county agencies surveyed had records of any outbreaks of swimmers' Itch In Is-
land, Sturgeon, Rush or Passenger Lakes (Table 4-4). Most patients treated
for swimmers' Itch in the Moose Lake area probably contracted it while
swimming In Moose Head lake (By telephone, Doctors Raymond Chrlstensen and
Kenneth Etterman, 12 November 1981). Local citizens have not reported
occurences of swimmers' itch on Sturgeon, Rush or Passenger Lakes. One
instance of swimmers' itch occurring on 4 July 1981 was reported by a home
owner on the south shore of Island Lake (Personal communication, Harold
Westholm, November 1981). No reoccurences have been reported.
H-20
-------
T S
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-green algae, blo-volune
iflagellate, bio-volume
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ital blovolume) x 10* /ml.
L dink depth (meters)
2-SSS-g
MM M a M
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>tal blovolume) x 10* /ml.
L dlflk depth (meters)
2. tif il-g
J3 M M M M a.»
(S N *^ O Ox O I
-< IM 1A «> j
O BO O O »M M 1
ITI (S «SI M 1
M
r*
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«- Ki **« O 1
tn o ^ o co o i
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cr> in o o >*> o *n
! 1 1 1 1 f !
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I ! i ! ! 1 1
|.
f * * r;*o "»
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O 3 > J V
S 0 0 1 « " t
> ~, 0 . B
V J> o i >-
«» 0 > J< fi
« »5 1 B 3 JB
M A * 0 « -
S "3 -SS-iS S
5 e-S= .25"
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j: s xc »-c ~ c.
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i i i i : i i
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'PASSENGER LAKE
-green algae, bio-volume
itononad, bio-volume
len brown algae, bio-volume
lenoid, bio-volume
>r phytoplankton, bio-volume
itai blovolume) x 10* /ml.
L disk depth (meters)
- mfc.'o3*'^'O
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ti & O ^ *
*- » e o. i
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H-21
-------
Table A-3.
Phytoplankton Measurements
CTANOPHTTA
Anabaena
tp
CRY?TOPHYTA
acuta.
CRYSOPHYTA
ip
Octviomaruu
Utogttna. ip
PYRKHOFHTA
EUCtEHOPHYTA
BACILLARIOPHY7A
Navxcula
CHLOROPHTTA
45,000
9,000a
1,000
2,800
300a
10a
70
1000b
1100
soo
500*
550*
40
450
75,000
14003
3200*
1800
3000*
2000*
690*
2000b
840a
250"
300a
620a
150a
650*
5003
university of Minnesota aeasureaents/unpublished
bWetz*l. p 319, 1975
H-22
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Appendix I
Methodology for Population Projections
en
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Methodology for Population Projections
The available census data on popula-
tion within the Townships is for year-round residents only. Thus, esti-
mates of the peak population (seasonal plus year-round) are derived by
assigning an average household size for seasonal dwellings to the number of
seasonal dwellings and combining the result with the projected number of
year-round residents. Because of the large proportion of seasonal dwellings
in Windemere Township and the documented historic variability in the growth
of the year-round population versus the growth in the total number of
housing units, a population based projection would have to incorporate
subjective assumptions concerning the change in the ratio of seasonal to
permanent residents over time.
Accurate population projections are essential for designing cost
effective wastewater treatment facilities. Thus, the peak population is of
greatest importance because the wastewater treatment facilities must be
designed to accommodate the maximum anticipated wastewater flow for the
1-1
-------
life of the facilities. A housing unit based projection that is developed
from historic data yields a total housing unit projection that can be used
to estimate the total population, i.e., year-round as well as seasonal
residents.
To determine the population of an area when the number of housing
units is known requires two assumptions: the average household size and
the ratio of seasonal to permanent residents at the end of the projection
period. In this report, a slight decrease in the household size of year-
round residents was forecasted because of the documented trend toward
smaller households and the high median age in the project area which un-
derscores the attraction of the local region as a retirement area. Site
specific information on the average household size of seasonal dwelling is
not readily available. In one study conducted by the University of Wis-
consin Recreation Resources Center, an average household size of 3.0 was
found for seasonal dwellings in a similar rural lake area (University of
Wisconsin Recreation Resources Center 1979). Accordingly, the seasonal
population projections assume a household size of 3.0 during the planning
period. A slight decrease in the proportion of seasonal dwellings to
year-round dwellings also is assumed based on the trend apparent during the
1970s when the growth rate for permanent dwellings exceeded the growth rate
for seasonal dwellings. In spite of these household size assumptions, and
their potential for error, the total projected population, as derived from
the housing unit projections, should not result in significant error if the
total housing unit growth rates occur as projected. For example, if in the
year 2000 the actual number of housing units equals the total number pro-
jected, but there are fewer permanent residents than expected, the pop-
ulation on an annual basis should not vary significantly because the summer
season population will be larger than estimated while the average winter
season population is less.
Projections for Windemere Township
The housing unit projections were made by the "growth rate" method,
based on an extrapolation of past growth rates. This method was used
because it more closely models actual changes than any of the other me-
1-2
-------
thods. The "share" method was not used because it is not suitable for
jurisdictions in counties where there is a fluctuation in subcounty pop-
ulation growth rates, i.e., if some places are growing while others are
losing. The "ratio-trend" method was not used because of the historical
variability in the ratio between Windemere Township's population and Pine
County's population. Additionally, the use of the "growth rate" method
provides for several different projections based on different assumptions
concerning future growth. The different projections can then be comapred
with other factors such as the amount of buildable land, land values,
public services availability, etc. in determing the most reasonable pro-
jection for the facility planning or "service area".
The growth rate method is the only method by which the increase in the
number of housing units can be projected directly. One problem with the
growth rate method, though, is that the projection results from exponen-
tially applying the average annual growth rate to the previous year's
population. If the study area experienced unusually rapid growth in the
last decade, the exponential application of the average annual growth rate
can lead to an unrealistically high projection. Housing unit projections
were initially developed for Windemere Township based on four different
assumptions concerning future growth (Table 1-1 ; Figure 1-1 ).
Table 1-1. Housing Unit Projections, Windemere Township, 1980 to 2000.
Assumptions 1980 1990 _2000_
1. Straight average: growth rate for the
projection period remains constant at
the 1960 to 1980 average - 919 1,565 2,673
2. Trend rate: growth rate for the pro-
jection period changes at the same
rate as the 1960 to 1980 change 919 1,349 1,883
3. Rate slowdown: growth rate from 1980 to
1990 equals the 1970 to 1980 growth rate
and rate from 1990 to 2000 is onehalf
1970 to 1980 growth rate 919 1,286 1,614
4. Rate change slowdown: growth rate from
1980 to 1990 equals one-half the 1960
to 1980 growth rate and rate from 1990
to 2000 equals one-half the 1960 to 1980
growth rate. 919 1.201 1.375
1-3
-------
The exponential aspect of the growth rate method is apparent when the
projections are depicted on a graph (Figure 1-1 ). Assumptions 1 and 2 for
Windemere Township result in growth taking place at a rate exceeding that
experienced in the Township in the last decase. Assumption 3, although
termed a "rate slowdown," essentially is a straight-line projection.
Assumption 4 for Winderaere Township was the projection that was determined
to be most realistic. This projection assumes that growth will continue in
the Township from 1980 to 1990 at a rate similar to the growth experienced
from 1960 to 1980. After 1990, the projection assumes that the growth rate
will decrease as the area approaches "saturation."
Rural recreational areas such as the Island Lake and Sturgeon Lake
portions of Windemere Township are attractive to development because of the
amenities associated with lakefront property. As the first tier of lake
contiguous lots becomes fully developed, it is not unusual for growth rates
to decrease because property in the second tier (backlots) or on outlying
lots ie in less demand. There are a total of 151 homes on the platted land
areas adjacent to Island Lake at present, and the first tier of these
lake shore lots can accommodate an estimated 185 to 200 homes. Given this
situation, is expected that most of the available lakefront lots around
Island Lake will be developed in the next 10 years while in the second half
of the planning period (1990 to 2000) total growth around the Lake will
level off because developable lots will only be available in the second
tier (backlots). Assumption 4 appears to represent the possibility that
growth will continue, but not at the extremely high rates that were experi-
enced in the 1960s and 1970s.
The housing unit projection for Windemere Township was dissaggregated
so that the number of housing units within the subareas could be projected
(Table 1-2 ). The housing unit projection for the subareas within Winde-
mere Township assumes that after 1990, more of the Township growth will
take place in ED 503 as the supply of lakefront lots around Island and
Sturgeon Lakes becomes depleted. The housing unit projections indicate a
year 2000 total of 214 and 282 housing units around Island and Sturgeon
Lakes, respectively, and 1,375 housing units within Windemere Township.
The housing unit projections were further disaggregated according to sea-
sonal and permanent units based on survey information obtained from the
1-4
-------
2500-
2000-
2 1500-
o
z
m
o
1000-
500 -
I
1960
straight average
1970
I
1980
trend rate
rate slowdown
rate change slowdown
1990
I
2000
Figure i-i.Windemere Township housing units actual growth 1960 to 1980
and projected growth 1980 to 2000
1-5
-------
MLWSD and the I960 census (Table 1-3). The seasonal to permanent pro-
jections also assume that permanent residences will form a greater pro-
portion of the total after 1990 as a result of increased numbers of retired
residents living in the area on a year-round basis. Information from the
1970 and 1980 census1 support this assumption. Between 1970 and 1980, the
number of year-round residents in Windemere Township increased by 79.1%
while the number of housing units increased by 56.6% (US Bureau of the
Census 1981). This is an indication that some housing units that were
previously used on a seasonal basis are now being occupied on a year-round
basis.
Table 1-2. Housing unit projections within Windemere Township, 1980 to
2000 (US Bureau of the Census 1982).
Location
ED 504
Island Lake
Sturgeon Lake
Outlying Areas
ED 503
Windemere Township
1980
397
151
197
49
522
919
1990
519
197
260
62
682
1,201
2000
564
214
282
68
811
1,375
Note: The disaggregated projections assume that growth from 1980 to 1990
is spread evenly between the subareas. Because the amount of developable
land in ED 504 is limited, the year 2000 projection assumes that the per-
centage of the population is ED 504 decreases from 43% to 41% by the year
2000.
Table 1-3. Seasonal and permanent housing unit projection within Windemere
Township, 1980 to 2000.
1980
1990
2000
Location
ED 504
Island Lake
Sturgeon Lake
Outlying Areas
ED 503
Windemere Township
Permanent
138
64
42
32
269
407
Seasonal
259
87
155
17
253
512
180
84
55
41
351
531
339
113
205
21
331
670
223
103
72
48
446
670
Seasonal
341
111
210
20
365
705
Note: The split between seasonal and permanent housing units was determined from MLWSD
records and 1980 census data. The 1990 projections assume the same proportion of
seasonal to permanent residents as in 1980. The year 2000 projection assume an
increasing proportion of permanent residents as a result of increased demand by
retired people for year-round residences and a lower demand for seasonal resi-
dences.
1-6
-------
Appendix J
Water Quality Tables and Figures
CO
a
o
w
1
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Table J-l. Sampling program and schedule for surface water sampling in
Island, Little Island, Sturgeon, Rush, and Passenger Lakes,
Pine County MN.
Lake
Island
Little Island
Sturgeon
Rush
Passenger
Sampling Dates
26 August 1981
09 September 1981
14 September 1981
30 September 1981
03 February 1982
27 August 1981
09 September 1981
15 September 1981
05 September 1981
04 February 1982
10 September 1981
15 September 1981
01 October 1981
10 September 1981
15 September 1981
01 October 1981
Parameters
d/t; Sd; b
d/t; Sd; b; chl
d/t; Sd; b; chl
d/t; Sd; b
d/t; P^
03 February 1982 d/t; P
d/t; Sd; b
d/t; Sd; b; chl
d/t; Sd; b; chl
d/t; Sd; b
d/t; Pt
d/t; Sd; b, chl
d/t; Sd; b; chl
d/t; Sd; b
d/t; Sd; b; chl
d/t; Sd; b; chl
d/t; Sd; b
Number of
Stations Sampled
6
6
6
6
2
4
4
4
4
2
1
1
1
1
1
1
Parameter Key:
d/t = Dissolved oxygen and temperature at 2-foot depth
intervals from the surface
Sd = Secchi disk depth at each station
b = biovolume of phytoplankton at surface, mid-depth,
and above the lake bottom
chl * chlorophyll zi (corrected for breakdown products) at
surface, mid-depth, and above the lake bottom
P « Total phosphorus at surface (under the ice) and above the
lake bottom
J-l
-------
Field investigations were conducted in the project area in 1981 during
the periods of 24-27 August; 7-15 September; 28-30 September; and 1-5
October. During these sampling periods, prevailing wind directions were
easterly; westerly changing to southerly and then back to northwesterly;
easterly; and widely variable, respectively.
Table Jrr2-.
Peak daily air temperature and prevailing sky cover as re-
corded at the Duluth International Airport during the four
sampling visits made to the Moose Lake Area (NOAA 1981).
Date
Peak Daytime
Temperature, °F
Prevailing Daytime
Sky Cover
24 August
25 August
26 August
27 August
07 September
08 September
09 September
10 September
11 September
12 September
13 September
14 September
15 September
28 September
29 September
30 September
01 October
02 October
03 October
04 October
05 October
65
63
68
59
65
67
81
77
77
77
78
65
55
46
44
42
40
48
50
47
48
Overcast
Overcast
Overcast
Overcast
Overcast
Clear
Clear
Overcast
Clear
Clear
Clear
Scattered Clouds
Overcast
Overcast
Overcast
Overcast
Overcast
Clear
Overcast
Overcast
Overcast
J-2
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Appendix K
Letter to Citizen's Advisory Committee
-------
-------
RECEIVEDFEB021982
Rte. 2, Box 140-B
Island Lake
Sturgeon Lake. lln. 55783
372-3169
Jan. 25, 1982
Mr. Gregory Dean Evenson
Chairman
Citizens Advisory Committee
Moose Lake, Winn. 55767
Dear Mr. Evenson:
You requested Ideas from the Citizens Advisory Committee on Jan. 7,
1982 at the meeting which concerned the Draft Report ^n Algae.
Here are my Ideas.
First of all and most Importantly I am open minded to what this
study Is Investigating concerning the 4 lakes of Windea-.ere Town-
ship. It appears that this study must be enacted to satisfy fede-
ral and state regulations. From what I have gathered by talking to
PCA and WAPORA people, from public meetings, and personally obser-
ving Finney doing field work I feel that WAH^RA Is doing a profess-
ional job. However, this work needs to be monitored by Windejcere
Citizens.
The jewels of Wlndemere Township our lakes must have truly been
that as observed by the native American Indians, early explorers
and the early hardy Scandinavian pioneers.
The logging, fires, and land clearing was especially hard on Island
Lake due to the heavy clay soil comprising the bulk of the water-
shed. The pioneers knew that the land around Island Lake would be
many times more productive than the relatively sterile jack pine
outwasb plain around Rush Lake.
The heavy farmland clearing around Island Lake must have contri-
buted greatly to it's eutrophicatlon. As a casual observer around
Island Lake since the late 1940's I have noticed contributing factors
to eutrophication.
In the HEi Section 8, T. 4 5 R« 18 was located a barnyard directly
on the lakeshore with pig pens going right out into the lake. , At
loast two other farms in that Quarter Section had barnyards that
drained into the lake. In Section 4 at the end of the present
Twilight Lane Holsteins contently grazed along the lake following
a fence that went out into the lake to take a drink. There were
other barnyards in Sec. 3 and 4 that contributed runoff, as in Sec-
tions 9 and 10.
K-l
-------
Mr. Even son
Island Lake has walleyes that grow at 2 times the State average.
As being a young fishing partner of Ted Anderson who learned
techniques and spots from him. and in turn showed him spntSjI can
attest to having caught almost numerous quantities of these tasty
fish from 6 to 11 pounds. It Is my unscientific opinion that the
land clearing and barnyard nutrient enrichment has been a factor
in good fish growth.
Fowever, land use around Island Lake is changing or has changed to
chiefly residential- recreational use.
I had occasslon to observe when the bulk of the initial cabin and
homesite developoent took place along the lake she re. In Sections
3,4 & 9 some filling took place on swampy shoreline. In Sections
3 and 9 seme steep clay banks were graded with heavy equipment in
the Fall. The following Spring beavy rainfall washed large aaounts
of clay into the lake. For a time the water along that shore was
of a reddish-brown opague color due to clay particles suspended in
the water. Each additional developed lot contributes some erosion
therefore affecting nutrient balance in the lake*
Of course, inadequate septic tank drainfield systens have added
their share of pollutants.
I recall Island Lake as always having "dog days'* or algae bloom
in August or Sept. in the late 19*0' s and the 1950' s when kids
such as nyself were told not to go swimming. However, It seems
that the blooms are more severe now and I don't let my kids go
swimming in "(Jog days11.
A weed came into the lake in the 19J>0' s which we called hair weed,
which I believe is milfoil. A truly noxious type of weed as it
choked cut less noxious valuable shoreline and submerged weed beds.
In la-te Summer large matts of floating "hair weed" would make
rowing a boat difficult in shallow areas. The weed is still here
but seems to get chopped up by the large number of power boats on
the lake today.
In summary I think that this Draft Report ^n Algae is helping to
bring scientific biological investigation to the factors and core
problems affecting the eutrophication of these 4 lakes in Pine
County, Let us hope that the remainder of the studies will allow
us to become better informed citizens to study the alternatives
available for the protection of our "jewels" for our children.
Sincerely,
C
-------
Appendix L
Paleollmnological Investigation
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ONSITE WASTE TREATMENT AND LAKE EUTROPHICATION:
ANALYSIS WITH DATED LAKE SEDIMENTS
112 2
S. R. MeComas , J. C. Laumer , P. Garrison , and D. Knauer ,
, Inc., Suite 490, 35 E. Wacker Drive, Chicago, IL 60601
Lake Management Consultants, Inc., 166 Dixon Street, Madison, WI 53704
ABSTRACT:
Three seepage lakes in north central Minnesota were studied to evalu-
ate the relative impacts of onsite waste treatment systems and other nu-
trient sources on lake trophic status. Island and Sturgeon Lakes, having
extensive shoreline development served exclusively with onsite systems,
were compared to a third lake (Little Island Lake) having no shoreline
residential development. Interpretation of sediment core results indicated
all three lakes had phosphorus concentrations, chlorophyll degradation pro-
ducts, and diatom communities indicative of predominant land uses in their
watersheds. The present trophic condition for Island Lake was established
after the turn of the century (with conversion of forest lands to agricult-
ural use) and prior to development of a large lakeshore community. Stur-
geon Lake has a relatively small watershed and phosphorus concentrations in
the sediment core appear to have been influenced in the last 40 years by
one farmstead located on the lakeshore. Little Island Lake had the highest
chlorophyll and phosphorus sediment concentrations of the three lakes.
Little Island Lake is shallow, and macrophytes represent a chlorophyll and
phosphorus sink. Relatively minor changes in all three lakes' trophic
status have occurred since the 1950s, the period when lakeshore development
began to increase exponentially around Island and Sturgeon Lakes.
L-l
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INTRODUCTION
An increase in lake eutrophication by wastewater discharge from
municipal sewage treatment plants has been veil documented (Edmundson 1970,
Megard 1972, Larson 1975). Few studies have shown the effects of nutrient
inputs associated with onsite waste treatment systems on lake eutrophi-
cation. Typically, the first type of wastewater treatment serving lake-
shore residences is onsite. Lakeshore homeowners may correlate increasing
lake eutrophication symptoms with additional development of lakeshore lots
and the increase in onsite systems. They assume the input of partially
treated wasteflows from onsite systems is the primary factor for water
quality degradation. But, from the literature, the actual role of onsite
systems in lake eutrophication is unclear.
The literature describes a range of possibilities in regard to the
importance of nutrient inputs from onsite systems. Water chemistry data
and nutrient budget calculations for a number of lake watersheds in the
northern United States indicate septic tank/drainfield systems contribute
generally less than 30% of the total phosphorus or nitrogen load to the
aquatic system (Kerfoot and Skinner 1980, Jones and Lee 1977, USEPA 1979a,
1979b, 1979c, 1979d, 1979e, 1981, 1982). Typically, agricultural land use
in the watershed dominates the phosphorus load (Dillon and Klrchner 1974).
However, estimates using total phosphorus may overestimate the importance
of nutrients in runoff since not all of the total phosphorus component is
biologically available (Logan et al. 1982). Phosphorus associated with
septic tank effluent entering the groundwater flow field is typically in
the dissolved form and therefore, biologically available. Some studies
indicate that the potential for relatively high dissolved phosphorus inputs
from onsite systems (Brandes 1974, Viraraghaven and Warnock 1976) and Lee
(1976) suggests groundwater inputs could be especially significant to lake
water quality when water influx is dominated by seepage.
In this study, we examined stratigraphic characteristics of lake
sediment to determine changes in lake trophic indicators (including organic
matter, chlorophyll, diatoms, and phosphorus) covering a time period from
the settlement of the watersheds by non-Indians to the present. Sediment
1-2
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cores were taken from three seepage lakes in north central Minnesota. Two
of the lakes, Island and Sturgeon, have residences with onsite systems
around them, and currently are documented to have blue-green algae as the
dominant late summer phytoplankter (USEPA 1982). The third lake (Little
Island), is contiguous to Island Lake and has had only one house in its
watershed in the last 100 years and no visual signs of blue-green algae
blooms. Other than onsite systems, no wastewater treatment flows or other
point sources enter these lakes. It is assumed the major pathways for nu-
trient introduction into these lakes have always been groundwater, atmos-
pheric deposition, runoff in the direct drainage area, and internal nu-
trient recycling. Hydrologic and watershed parameters for all three lakes
are presented in Table 1.
It was hypothesized that if septic tanks played a major role in the
eutrophication of Island and Sturgeon Lakes, an increase in the eutrophic
indicators in the sediment core should be correlated with the onset of
intense development around both lakes (circa 1950). Little Island Lake
would be expected to have relatively unchanged indicators through this time
period because no onsite systems are situated on its shore. Alterna-
tively, if nutrient inputs from septic tanks played a minor role in the
eutrophication of the two developed lakes, the trends of the trophic indi-
cators for all three lakes should have some degree of consistency.
METHODS
In March 1982, two cores of 60 cm length were taken from each of
Island, Sturgeon and Little Island Lakes using a plexiglass piston corer
with a 11.25 cm inside diameter. One core was extruded in the field in 2
cm sections for determination of sedimentation rates using Cesium-137
dating (Eberline Laboratories, Inc., West Chicago, IL). The other core was
sectioned into 3 cm sections for determination of diatom composition,
chlorophyll degradation products, phosphorus fractions, and organic matter.
The samples were stored in sealed plastic bags and frozen until analyzed.
L-3
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Table 1. Lake and watershed parameters for Island, Sturgeon, and Little
Island Lakes. Information was obtained from recent lake surveys
conducted by WAPORA, Inc. and Minnesota Department of Natural
Resources, Fisheries Section.
Number of onsite systems
Length of shoreline (km)
Ratio onsite systems/km
of lake shore
Watershed area (ha)
Lake surface area (ha)
Ratio watershed/lake surface
Mean Depth (m)
Mean Secchi disk (m)
Chlorophyll _a (ug/1)
Total phosphorus, winter
values (mg/1)
Average Carlson Trophic
Status Index
Current lake trophic status
Island
151
10.1
1151
211
5.5
3.4
1.4 (n=24)
29 (n=35)
Sturgeon
197
12.9
560
686
0.8
6.9
2.4
8
(n=24)
0.04 (n=4) 0.02 (n=4)
eutrophic meso-eutrop.
Little Island
0
1.7
294
17
17.3
1.6
0.9
NA
0.03 (n=2)
eutrophic
L-4
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Percent moisture was determined by measuring weight loss of sediment
after a least 24 hours of dessication at 105° C. Organic matter was deter-
mined after weight loss on ignition at 550° C for one hour. Pigment anal-
ysis was performed on wet sediment using the procedure of Vallentyne
(1955). Pigments were extracted with 90% acetone containing 0.5% dimethy-
lanaline as suggested by Wetzel and Manny (1978) and reported as sedimen-
tary pigment degradation unit (SPDU)/gram dry weight. The sediment phos-
phorus tractions of apatite phosphorus, nonapatite phosphorus, and organic
phosphorus were determined following the methods outlined by Williams et
al. (1976a). All concentrations have been reported on a dry sediment
basis. The diatom preparation, identification, and enumeration was con-
ducted following the methods of Bradbury (1975) .
RESULTS AND DISCUSSION
Sedimentation Rates
Counting the activity of radioactive Cesium (Cesium-137) in lake
sediments can be used to determine recent lake sedimentation rates. Ce-
sium-137 is found in lake sediments as a result of nuclear weapons testing
and subsequent atmospheric contamination by the isotope. Testing first
began on a small scale in 1946 but increased in 1957 with the peak activity
occurring in 1963-1964. Because a 6 to 12 month delay typically occurs
between deposition of Cesium-137 in the watershed and delivery to the lake,
the maximum peak recorded in lake sediments is assumed to be 1965 (Ritchie
et al. 1973).
The recent sedimentation rate in both Sturgeon Lake and Island Lake is
estimated to range between 0.41 - 0.44 cm year (Figure 1). At this
sedimentation rate, a 1 cm segment would represent about 2.5 years. The
sedimentation rate is not as easily defined in Little Island Lake, but
because of the nature of the increase of Cesium-137 activity at 5 cm, the
sedimentation rate is estimated to be 0.29 cm per year (J. B. McHenry,
personal comm.). A 1 cm segment would represent about 3.45 years. Extra-
polating sedimentation rates to the bottom of the core represents a time
period of around 1835 for Island and Sturgeon Lakes, and around 1775 for
Little Island Lake.
L-5
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Although the sedimentation rate varies within a lake basin, Davis and
Ford (1982) found sediment arriving in the deep basin of a lake is well
mixed due to resuspension and reposition and qualitatively representative
of much of the basin. The sediment cores collected in this study were from
the deepest part of the lake basins. The Island and Little Island Lake
watersheds are located in clayly glacial till. One-half of Sturgeon Lake's
watershed is in glacial outwash sand and the other half is in the clayey
glacial till. Cores from all three lakes were taken in the clayey glacial
till.
Organic Matter and Chlorophyll Degradation Products
In the Sturgeon Lake core, organic matter (Figure 2) and sedimentary
chlorophyll degradation product (Figure 3) profiles showed little change
over time. Organic matter ranged from 19 to 23 percent while chlorophyll
ranged from 6 to 12 SPDU/gram dry weight. Organic matter was relatively
unchanged in the lower part of the core although there was a slight in-
crease above 12 cm (1955). Chlorophyll degradation products increased
slightly above 6 cm (1965) .
In the Island Lake core, organic matter (Figure 2) and sedimentary
chlorophyll degradation product values (Figure 3) are typically higher than
Sturgeon Lakes values. Organic matter ranged from 20 to 30 percent and
tends to decline slightly from the bottom to the top of the core. Since
the 1950s (above 12 cm) the % organic matter in the cores from Island and
Sturgeon Lakes is similar. Sedimentary chlorophyll degradation products
in the Island Lake core ranged from 14 to 30 SPDU/gram dry wt. The highest
value was at the bottom of the core. From 30 cm to 17 cm (1910-1940)
chlorophyll decreased somewhat. Since about 1940 (17 cm) chlorophyll
increased (especially in the top surficial segment) but has not exceeded
levels observed in the middle of the core.
In the Little Island Lake core, organic matter (Figure 2) and sedimen-
tary chlorophyll degradation product (Figure 3) values are generally grea-
ter than either Sturgeon or Island Lakes values. The organic matter pro-
file shows a declining trend from the bottom to the top of the core and
values range from 30 to 41 percent. The chlorophyll degradation products
L-7
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Figure 2
% VOLATILE SOLIDS
10
E
o
15-
30-
CL
LU
45-
60^
1960
1945-
1907
ISLAND
STURGEON
LITTLE
ISLAND
L-8
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Figure 3
CHLOROPHYLL
(SPDU/gr. dry wt.)
o
E
o
15-
30-
Q.
LJJ
Q
45-
60^
STURGEON
ISLAND
LITTLE
ISLAND
L-9
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were unusually low at 19 cm (1915-1920). In 1918, the Moose Lake Forest
Fire burned much of the lake's watershed and may have had an impact on the
chlorophyll values. Prior to 1918, chlorophyll values were declining. The
next core segment after 1918 (at 16 cm) shows chlorophyll values returning
to pre-1918 levels. Chlorophyll in the surficial core segment increased
dramatically compared to the underlying 3-6 cm segment, but is comparable
to values at the bottom of the core.
Although chlorophyll degradation product concentrations in the sur-
ficial sediments increase sharply for both Sturgeon and Island Lakes, there
are parallel increases in Little Island Lake. No reasons for the increases
are speculated on but, because they occurred in all three lakes, they can
not be attributed strictly to onsite systems. Little Island Lake has no
onsite systems on its shoreline.
Diatoms
In the Sturgeon Lake core a total of 97 diatom taxa were identified.
Melosira ambigua and Fragilaria construens v. venter were dominant species
(Figure 4). From 60 cm up to 37 cm (1835 - 1890), _F. construens v. venter
represented 20 to 40 percent of the diatom community. At 37 cm (1890),
coinciding with a decline in the logging industry and an increase in farm-
ing in the region (Pine County 1947), F. construens v. venter strongly
declined and M. ambigua, a planktonic diatom, increased. Between 17 cm and
7 cm (1940 - 1965) the percentage of littoral species increased (especially
Achnanthes spp. , Eunotia jge_c_tinalis, and E^_ incisa) while M._ ambigua de-
clined. Grouping eutrophic diatom indicators together indicates a trend
toward eutrophic conditions starting in the 1960s. However, the continued
presence of Cyclotella bodanica and the high level of Melosira ambigua
indicate the lake's trophic status has not changed drastically during the
time period covered by the sediment core. Similarly, the percent of eutro-
phic indicators above the fern level is comparable to the percent repre-
senting the 1890s.
In the Island Lake core a total of 118 diatom taxa were identified.
The dominant species are Melosira ambigua, M. italica, and Tabelaria fenes-
tjrata (Figure 5). These species are representative of mesotrophic-type
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conditions (Davis and Larson 1976) and give the mesotrophic indicator
species a majority of the diatom community percentage. However, above 20
cm (1935), M. italica dramatically decreases in abundance while M. ambigua
remain high. Also at about 1935, Cocconeis pjlacentula, Melosira granulata,
and Fragilaria crotonensis either first appeared or Increased In abundance,
resulting in an increase in the percentage of eutrophic indicators.
In the Little Island Lake core a total of 107 diatom taxa were identi-
fied. The diatom stratigraphy is much different compared to the other two
lakes. Most of the species identified are not associated with the pelagial
community. Although no single species dominates the community like Me-^
losira ambigua does in Island and Sturgeon Lakes, Fragilaria construens v.
venter and Melosira binderana were common (Figure 6). The diatom strati-
graphy showed few changes throughout the core. Starting at about 20 cm
(1916) there was a gradual but definite increase in the abundance of
Achnanthes lancelata, Cocconeis placentula, Fragilaria capucina, and Na-
vicula cryptocephala. All four species have been found in eutrophic lakes
or ponds (Jorgensen 1948, Stormer and Young 1970).
Changes in the diatom community have been interpreted in a qualitative
context with indicator species assigned to one of three categories; eutro-
phic, mesotrophic, and other. The "other" category includes species asso-
ciated with benthic conditions or species that have no specific trophic
affiliation. Assignments to a category were made with the usual assump-
tions and limitations that have been expressed by other authors (Bradbury
1975, Kalff and Knoechel 1978, Harris and Vollenweider 1982).
In Sturgeon Lake, the percent of eutrophic indicator diatoms has
increased twice since the 1920s. The second increase, starting in the
1960s, coincides with the onset of rapid residential development around the
lake. However, the percent of eutrophic indicators found after 1960 is
still less than what was found in segments representing the early 1900s.
Island Lake showed an increase in eutrophic indicators that dates to the
1930s. However, onsite systems probably were insignificant nutrient
sources in the 1930s. It was not until the end of that decade that elec-
tricity became available in the area for well pumps and it was not
L-13
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until the 1940s that most cabins installed indoor plumbing (Don Classen,
City clerk, pers. coram.). Until the decade of the 40s, nearly all lake-
shore residences were seasonal and used privies for waste treatment.
Because of the minimal water use in residences that have privies and be-
cause the privy pit is usually in unsaturated soils, there was probably
little nutrient input from the seasonally used privies. Coinciding with
the increase in eutrophic indicators for Island Lake in the 1930s was a
peak in agricultural land use intensity (USDA Census records) and a severe
drought lasting several years which lowered both groundwater levels and
lake levels (David Ford, MDNR, pers. comm.) A drought would have affected
the lake similarly whether onsite systems or agricultural land use were the
impetus for an increase in eutrophic diatom indicators. But, based on
literature values for loading rates (USEPA 1980) and on land use character-
istics in the watersheds, the agricultural component would contribute a
much higher phosphorus load than onsite systems. Little Island Lake has
the most diverse diatom community (based on average Shannon-Weiner values).
Although Little Island Lake had the highest percentage of eutrophic indi-
cators, it also had the highest percentage of littoral or benthic species.
Because Little Island Lake now has a large macrophyte community covering
30% of the surface area (MDNR 1975, unpublished) the consistancy of benthic
and littoral species in the core indicates Little Island Lake has been
shallow and productive, probably predating the earliest sediment core date
of 1775.
Phosphorus
Phosphorus in the sediment cores was fractioned into three categories;
apatite phosphorus (A-P), nonapatite inorganic phosphorus (NAI-P), and
organic phosphorus (org-P). Apatite phosphorus represents phosphorus
present in the crystal lattices of apatite grains and generally is of
detrital origin (Williams et al. 1976a). Nonapatitic inorganic phosphorus
consists of phosphorus not associated with A-P or org-P, and orginates
naturally, (i.e. by chemical weathering in the watershed) or from anthropo-
genic sources (i.e. fertilizers, septic tank drainfields, etc). Organic
phosphorus includes all phosphorus associated with organic molecules or
more specifically with carbon atoms by C-O-P or C-P bonds and may be an
indicator of lake productivty.
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(WO) Hld3Q
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In Sturgeon Lake, the apatite-P Is relatively constant throughout the
length of the core (Figure 7). NAI-P increases above 15 cm (1945) but
decreases at 5 cm (1970). Org-P is also fairly constant throughout the
length of the core with a slight increase above 5 cm (1970). Of the 3
lakes, Sturgeon Lake has the highest total phosphorus concentration in sur-
ficial sediments.
In Island Lake, total phosphorus was highest at the bottom of the core
and declined until about the 43 cm segment (1875) (Figure 7). It was
somewhat steady from 43 cm to 35 cm and then increased to a peak of about
1.25 mg/g near the middle of the core, the 25 to 30 cm segment, (circa
1910). NAI-P makes up the largest percentage of the three phosphorus
fractions and increases above the 7 cm mark (1965). The Org-P and A-P
fractions were relatively constant throughout the sediment core.
Historically, Little Island Lake had high total phosphorus values in
the sediments except for the period of 1915-1920. Otherwise the three
phosphorus fractions were relatively constant, only slightly increasing
since the 1940s. The organic phosphorus levels are higher than the other
two lakes indicating Little Island may be more productive.
An increase in sedimentary phosphorus concentrations in Sturgeon Lake
beginning in the 1950s coincides with increased housing development.
However, if these phosphorus trends were related to onsite system use, a
phosphorus decline In the sediment core from 1970 to 1980 would not be
expected. The explanation may be tied to a farmstead adjoining the shore-
line. On the northeast shoreline lies one farm house, a barn, and a pas-
ture sloping toward the lake. The current owner of the property purchased
the farm acreage In 1947 and immediately thereafter expanded dairy and crop
operations. The owner has stated that prior to 1947 there was not much
farming activity on this acreage. The owner retired in 1970 and since that
time there has been no active farming. The phosphorus increase and decrease
in the core correlates over time with the reported changes in this farming
operation. In a small watershed, without other major nutrient sources,
this potential source of phosphorus could be significant. Most of the
phosphorus in the 15 cm to 5 cm segment is in the NAI-P fraction. Since
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org-P and chlorophyll degradation products in this segment did not show
parallel increases, this increased phosphorus did not increase phytoplank-
ton productivity, although the percent of eutrophic indicators did in-
crease.
The rapid conversion of forested land to agricultural use in the
Island Lake watershed may have been responsible for the phosphorus in-
creases following the 1890s. The Hinckly Forest Fire of 1894 which burned
much of the region apparently did not burn Island Lake's watershed, but did
hasten the conversion of the lumbering economy to an agricultural economy
in the area. Farmlands extended to the lake until at least the early
1920s, when the land was subdivided for development. After the 1950s, the
phosphorus profile in Island Lake decreased until 1970, when it increased
slightly. Housing units around the lake have increased in number ex-
ponentially since the 1950s, and numbers of planktivorous fish have in-
creased dramatically since 1970 as well. It is speculated that there may
be a link with fishing pressure, an increase in planktivorous fish, and a
decrease in zooplankton: resulting in increased phytoplankton and sediment
phosphorus in the lake after 1970 (Table 2).
The phosphorus profile for Little Island Lake has been relatively
constant except for the -short segment where there was a sharp phosphorus
decline and recovery. A similar change in chlorophyll was observed over
this short segment. Extrapolating from the Cesium-137 derived sedimen-
tation rate, this segment of lowest phosphorus and chlorophyll concentra-
tion was dated 1915-1920, and corresponds to the time of the Moose Lake
Fire (1918). A 1918 U.S. Forest Service map indicated that most of Little
Island Lake's watershed burned, a small portion of Island Lake's watershed
burned, and none of Sturgeon Lake's watershed burned in this fire.
The high total phosphorus and high org-P fractions indicate Little
Island Lake has always been productive. The primary vestibule of pro-
ductivity is macrophytes. The bottom sediments are of a peaty composition
with a high organic matter content.
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Addressing the Hypothesis
Because the increase in eutrophication indicators in Sturgeon and
Island Lakes is not readily correlated with an increasing number of onsite
systems (circa 1950), onsite systems do not appear to be the predominate
cause of eutrophication in Island or Sturgeon Lakes. The results from the
sediment core analysis somewhat support the alternative hypothesis that
sediment core profiles from all three lakes follow similar trends. All
three lakes are limnologically distinct; however, similar trends are found
in all three lakes in the respect that sediment core profiles have reflect-
ed the impact of significant events in the watershed. If onsite tank
systems had an impact on the lakes through nutrient enrichment, the effects
were masked by contributions from other sources.
Analysis of the sediment core from Shagawa Lake, Minnesota shows that
distinct changes in trophic status could be attributable to point source
wastewater discharges from a small municipal wastewater treatment plant
(Bradbury 1975, 1978). This study did not show evidence of those types of
changes correlated with the increasing introduction of the diffuse waste-
water flows from onsite systems. The basic trophic trends in all three
lakes appear to have been established prior to the time period covered by
our sediment cores. In addition, unpublished MDNR fishery records (1938,
1955, 1967, 1970, 1975, 1979) cover the period when development was rapidly
increasing around Sturgeon and Island Lakes and indicate Secchi disk depth
readings have changed less than 1 meter for Sturgeon and Island Lakes since
1938 (Table 2).
Based on our results of the sediment core data for the three seepage
lakes in north central Minnesota, the predominant characteristics of the
lake's watersheds have an overriding influence on their trophic status.
The contribution of onsite systems to eutrophication in Island or Sturgeon
Lakes appears to be low and this should be a consideration in determining
the effectiveness of sewering these lakes to remove the nutrient input
associated with onsite systems.
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Acknowledgements
This project was funded by USEPA as part of an Environmental Impact
Statement for determining wastewater treatment alternatives in the Moose
Lake, Minnesota area. Mr. J. Novak was project monitor. We thank M.
Brookfield for performing the diatom analysis and E. Dahlen, R. Kulb, and
R. Wedepohl for field assistance. We appreciate the review and comments
made by J. Lens sen. We thank Mrs. D. Jackson-Hope for typing the manu-
script.
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Table 2,
Summary of data from Minnesota Department of Natural Resources
fisheries lake surveys.
Date
House Count
Sturgeon Island
Secchi Disc
Measurement
Sturgeon Island
PlanktIvor cms
Fish
Sturgeon Island
1982 -- 2.4
1979-80 208 169 2.3
1975 170 2.4
1970 128
1967 120 110 2.9
1954-55 81 35
1938 2.4
1.4
1.3 57
2.0 18
1.4
1.7 47
1.1 30
__
189
20
57
37
*~
Planktivorous fish include yellow perch, bluegill, pumkinseed, and
black crappie. Values represent number of fish caught per set and
includes trapnets and gillnets.
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-Supplemental Information-
and means of sediment parameters from
sediment cores.
Little
CaCO
(%)
Organic Matter
%
Chlorophyll
{SPDU/g. org. matt.)
Total Phosphorus
(mg/g dry wt . )
Organic Phosphorus
(mg/g dry wt . )
Inorganic Phosphorus
(mg/g dry wt . )
Apatite Phosphorus
(mg/g dry wt . }
Nonapatite Inorganic P.
{mg/g dry wt . )
Island Lake
0.7-3.3
1.7
20.8-29.4
25.6
57.4-102.0
79.4
0.80-1.72
1.07
0.21-0.52
0.34
0.44-1.20
0.73
0.08-0.24
0.15
0.29-1.05
0.58
Sturgeon Lake
0.7-1.9
1.3
19.0-22.9
20.4
32.6-54.8
40.7
0.80-1.50
0.95
0.15-0.40
0.27
0.39-1.18
0.68
0.22-0.37
0.27
0.15-0.92
0.41
Island
0.8-1.
1.2
29.8-41
36. £
31.0-1.
83.3
0.54-1
1.12
0.26-C
0.51
0.28-C
0..61
0.04-C
O.OS
0.24-C
0.52
Lake
8
.1
2.3
.32
.64
.72
.14
.63
aNote that chlorophyll breakdown products are presented herein on
a gram of dry organic matter basis.
1-22
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oligotrophic and eutrophic lakes. Ann. Rev. Ecol. Syst. 9:475-495.
Kerfoot, W.B. and S.M. Skinner, Jr. 1981. Septic leachate surveys for
lakeside sewer needs evaluation. J. Water Poll. Cont. Fed. 53:
1717-1725.
Lee, D.R. 1976. The role of groundwater in eutrophication of a lake
in glacial outwash terrain. Intern. J. Speleol. 8:117-126.
Lee, D.R. 1977. A device for measuring seepage flux in lakes and
estuaries. Limnol. Oceanogr. 22:140-147.
Viraraghavan, T. and R.G. Warnock. 1976. Groundwater quality adjacent
to a septic tank system. J. Am. Water Works Assn. 68:611-614.
Williams, J.D.H., T.P. Murphy, and T. Mayer. 1976. Rates of
accumulation of phosphorus forms in Lake Erie sediments. J. Fish.
Res. Board Can. 33:430-439.
Williams, J.D.H., J.-M. Jaquet, and R.L. Thomas. 1976. Forms of
phosphorus in the surficial sediments of Lake Erie. J. Fish. Res.
Board Can. 33:413-429.
L-23
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Traffic Data
, i:
?t-*F.±. >/:.>^ -- ..X* v; '. 2^ :-..'
\r- ' if." =';-. .-^Vr~^;>:-y^-«*^-^-r>-;=.~--^- .....>._".-,.r - j- ,>
/ " *'.'" "' :-- .".''»-" * :.' Q ' -
J--;. -rj'--?^*.->-,-.-} '.*;-;''..;; - ^r .- ;'.;_:'
1^'- -'^ ?/? :"' 2*9 zf?- ' :"
.''. i&vV"" ""': :---:-;;;-" -y '^Q' :~' "~2sd~J.
Figure M-l. 1979 average annual daily traffic in northwestern Pine
County (MOOT). Traffic volume on the state highway is
for 1978.
Figure M-1.
o
H
H-l
M
H
t
£
M-l
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Energy Data
Figure N-l.Unit price for residental energy during the period from April 1980
to March 1981 (Minnesota Energy Agency 1981).
Fuel Type
Location
Region 3
Region 7E
Minnesota
Use
Space heating
Non-space heating
Space heating
Non-space heating
Space heating
Non-space heating
Natural Gas
(per 1,000
cubic feet)
$3.70
4.42
3.33
3.85
3.51
4.10
Electricity
(per Kelo
watt hour)
4.72C
5.46
4.70
5.53
3.64
5.21
Fuel Oil
(per gallon)
$1.22
1.17
1.16
LP Gas
(per gallon)
71. 1C
74.7
69.8
The basis for heating values of the fuels are:
Natural gas: 1,000 BTU per cubic feet
Electricity: 3,412 BTU per KW hour
Distillate
Composite (fuel oil): 138,690 BTU per gallon
Propane: 91,500 BTU per gallon
cd
*j
Q
60
M
0)
53
a
I
N-l
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I
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United States
Environmental Protection
Agency
Region 5
Water Division 5WFI-12
230 South Dearborn Street
Chicago, Illinois 60604
Official Business
Penalty for Private Use
$300
Postage and
Fees Paid
Environmental
Protection
Agency
EPA-335
Third Class
Bulk
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