United Stales
Environmental Protection
Agency
Office of
Toxic Substances
Washington DC 20460
Substances
oEPA
The Impact of
Inorganic Phosphates in
the Environment
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THE IMPACT OF INORGANIC PHOSPHATES IN THE ENVIRONMENT
FINAL REPORT
NOVEMBER, 1978
Prepared By
Justine Welch
Office of Toxic Substances
U. S. Environmental Protection Agency
Washington, D. C. 20460
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NOTICE
The report has been reviewed by the Office of Toxic
Substances, EPA, and approved for publication. Approval
does not signify that the contents necessarily reflect
the views and policies of the Environmental Protection
Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for
use.
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TABLE OF CONTENTS
Page
Conclusions 1
I. Introduction 2
II. Consequences of Nutrient Enrichment 3
Effects at Speci fi c Si tes 3
General Effects on Aquatic Plants, Zooplankton and the
Food Chain 12
Toxic Effects of Blue-Green Algae 14
Effects on Fi sh 20
Effects in Flowing Waters 24
III. Significance of Phosphorus in Eutrophication 27
IV. Critical Phosphorus Concentrations 36
V. Effects on Human Populations 44
Water Treatment Problems 44
Industrial Water Supplies 48
Toxic Algae 50
Property Values 51
Commercial Fishery 54
the Fish 54
the Industry 64
Effects on Sport Fishing and Other Forms of Recreation .. 66
VI. The Extent of the Eutrophication Problem 69
Appendi x 76
Literature Cited 79
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TABLES
Pat
TABLE 1 - Death-Inducing Algae 18
TABLE 2 - Mean Values for Relevant "Trophic Indicator
Parameters" for Gravenhurst Bay During the
Pre- and Post-Phosphorus Removal Years 33
TABLE 3 - Summary of Six Case Histories Showing Property
Value Increases with Water Quality Improvement 53
TABLE 4 - Order of Yield of Principal Commercial Species of
Fish Caught in Lake Erie in Selected Years from
1 908-1 975 56
TABLE 5 - Average Combined Annual United States and Canadian
Production of Major Commercial Fishes from Lake
Erie for Specified Time Periods, 1879-1975 57
TABLE 6 - Summary of Fish Species in Lake Erie Suffering
Recent Decimations 58
TABLE 7 - Trophic Status of Wisconsin Lakes 74
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FIGURES
Page
FIGURE 1 - Reversal of Cultural Eutrophication in
Lake Washington, Seattle 6
FIGURE 2 - Recovery of Lake Washington 7
FIGURE 3 - Vollenweider's (1968) Initial Phosphorus
Loading Curves 38
FIGURE 4 - Vollenweider's (1975) Permissible and
Dangerous Phosphorus Loading Rates 40
FIGURE 5 - Vollenweider's (1976) Latest Phosphorus
Loading Curves 41
FIGURE 6 - Larsen and Mercier's (1976) Relationship
Depicting Critical Phosphorus Loading Levels.. 42
FIGURE 7 - Dillon's (1975) Definition of Critical
Phosphorus Levels 43
FIGURE 8 - Relative Importance of Selected Water
Quality Problems in the United States 72
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Conclusions
The evidence contained in this report indicates that (a) excessive
nutrient concentrations are associated with undesirable changes (eutro-
phication) in aquatic ecosystems, including excessive production of
aquatic plants, depletion of dissolved oxygen, disappearance of cold
water fish, and appearance of nuisance algal species; (b) excessive
phosphorus is most frequently responsible for these undesirable changes
in lakes; (c) lakes and reservoirs respond more severely to excessive
phosphorus concentrations than do flowing waters, and do so at lower
phosphorus concentrations; (d) phosphorus may at times be the limiting
factor in estuaries but is not usually the limiting factor in coastal
waters; (e) critical phosphorus levels which lead to eutrophication have
not been clearly defined because of the variation in the response of
surface waters to phosphorus caused by differences in residence times,
mixing, sunlight penetration, etc., although some guidelines for phosphorus
loadings and concentrations have established; (f) eutrophication has
adversely affected human populations through increased water treatment
costs, decreased property values, changes in the commercial fishery and
reduction of the aesthetic and recreational values of affected lakes.
Eutrophication caused by excessive phosphorus levels is a problem
which occurs in most of the states, although the sources of excessive
phosphorus vary substantially even within states, and has the potential
to become more widespread. While phosphorus-caused eutrophication has
not yet impacted all of the nation's surface waters, there is a clear
potential for expansion of the problem without proper remedial and
protective actions.
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I. Introduction
Phosphorus problems in the environment are related to the fact
that phosphorus is an essential plant nutrient. Under certain con-
ditions, phosphorus enrichment can induce radical changes in aquatic
ecosystems that impact human populations using the affected resource,
This report characterizes the environmental problem associated with
phosphate enrichment of surface waters. The problem can be defined
as eutrophication, a term which describes the enrichment of surface
waters with nutrients (primarily nitrogen and phosphorus) and the
accompanying effects. It occurs naturally, with nutrients derived
from decaying organic matter or phosphate deposits, or artifically,
the product of excessive nutrient release from agricultural,
industrial, or urban activities. Whatever the source, nutrient
loadings are, in part, responsible for the productivity of surface
waters. Phosphorus is, most often, the nutrient responsible for the
eutrophication of freshwater lakes, and usually the nutrient which
is easiest to control.
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II. Consequences of Nutrient Enrichment
Effects at Specific Sites
Nutrients, along with other factors such as temperature and light,
control the productivity of water bodies and to a large extent, the
species composition and structure of aquatic communities. Special
examination of several in-lake studies will illustrate some of the
changes which occur during the eutrophication of lakes.
Schindler et^ aK (1971 and 1973) studied the effects of enrich-
ment with known quantities of nutrients on a small, unproductive lake
(lake 227) previously undisturbed by human activity. They added phos-
phorous (as NaHPO, or H,P(L) and nitrogen at levels which increased
the loading by a factor of five. Fertilization took place for 17-21
weeks during the ice-free periods of 1969 through 1972. Phytoplankton
standing crops, as measured by chlorophyll ^content, increased in
response to fertilization. At mid-summer, 1968, prior to fertilization,
chlorophyll ^concentrations did not exceed 3 ug/1 . After fertilization,
epilimnetic chlorophyll a^ levels in August ranged from 9-24 ug/1 in
1969, 48-92 ug/1 in 1970, 6-40 ug/1 in 1971, 30-70 ug/1 in 1972
(Schindler and Fee, 1974). Chlorophyll a_maxima were dramatically
higher after fertilization. Phytoplankton species also changed as a
result of nitrogen and phosphorus fertilization. In 1968, the year
prior to fertilization, pigmented flagellated algae (cryptophytes and
chrysophytes) were dominant throughout the summer. After fertilization,
chlorophytes, especially Scenedesmus, became the dominant group
(Schindler, 1977), and blue-green algae (cyanophytes) became more
abundant than before fertilization. No floating algal blooms were
present during the first summer of fertilization, but during the
second summer (Schindler, 1971), cyanophytes appeared in large
numbers for the first time.
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Langford (1948) and Smith (1969) studied the response to fertili-
zation of lakes in another part of tKe Canadian Precambrian Shield.
In both of these studies, the quantitative growth response of algae
to nutrient inputs was similar to that found by Schindler et_ al.
(1971). Algal species responses differed, however. While Schindler
e_t_ aj_. saw an increase in Chlorophyta, Langford (1948) found diatoms
of the genera label!aria. Fragilaria. and Melosira most responsive and
Smith (1969) found increases in populations of the blue-green algae,
Anabaena and Anacystis, and the green alga Spirogyra. The ratio of
the various nutrient inputs, particularly N:P, is probably responsible
for the varying response of phytoplankton groups (Schindler, 1977).
Vanderhoef et_ a_l_. (1974) studied the phytoplankton nutrient con-
centrations at fourteen sites in Green Bay, Lake Michigan. The open
end of the bay was dominated by diatoms (Fragilaria, Melosira,
Tabellaria, Asterionella), but, as nutrient levels increased in the
inner portions of the bay, blue-green algae predominated. Microcystis
was favored in areas where both nitrogen and phosphorus were available.
However, with the depletion of nitrogen relative to phosphorus levels,
Aphanizomenon, a nitrogen-fixing alga, appeared to out-compete
Microcystis.
A similar study was conducted in Provo Bay, Utah Lake, by
Brads haw et_ a_l_. (1973). Nutrient concentrations decreased from 1.2
to 0.1 mg/1 phosphorus and 0.7 to 0.1 mg/1 nitrogen with movement out
of the bay. Biochemical oxygen demand (BOD), algal standing crop
(cells/liter) and chironomid larvae numbers were much higher in the
bay than outside the bay where dilution of nutrients occurred.
Turbidity caused by the presence of algal cells was higher in the bay
than in the lake.
Lake Washington, Seattle, is a well-documented case illustrating
the consequences of eutrophication, as well as an example of the
effects of the nutrients in sewage effluents, and lake recovery
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following sewage diversion (Edmondson 1968, 1970, and 1977). During
the period between 1941 and 1963, treated sewage effluent entered the
lake in increasing amounts. In 1957, the total phosphorus loading was
between 100,000 and 108,000 kg, 42 percent (42,000 kg) of which was
derived from sewage effluent. By 1959, 11 secondary treatment plants
3
were operating, their effluent amounting to more than 23,200 m per
day. In 1962, total phosphorus inputs to the lake amounted to 231,000
kg of which 65 percent (150,000 kg) was contained in sewage effluent.
By the early 1950s, Lake Washington was beginning to show signs of
eutrophication, relative to conditions in 1933. Winter phosphorus
concentrations had nearly doubled. The appearance of Oscillatoria
rubescens, a colonial blue-green alga, in 1955, and oxygen depletion
of the hypolimnion warned water quality managers of the continued
deterioration of the lake. In 1958, a program to divert the sewage
effluent to Puget Sound was funded by public vote. By 1963, one
»
third of the sewage had been diverted, and effluents at this time
3
totaled about 75,600 m per day. Diversion was 99 percent complete by
1967. Figures 1 (Odum, 1971) and 2 (Edmondson, 1977) illustrate the
important change in physical, chemical, and biological indicators.
Transparency and diatom species diversity declined rapidly during the
1950s, while phosphate phosphorus and the percent of eutrophic species
in the diatom community increased. During and after sewage diversion,
these indices reversed their direction in response to decreased
nutrient income (Odum, 1971). In this case, secchi disk transparency
was a measure of algal standing crop rather than suspended silt.
Before diversion the mean summer transparency decreased from 2.1 m in
1950, was lowest in 1963 (1 m), but had increased to 2.8 m by 1969
(Edmondson, 1969 and 1970), 2.1-5.2 m in the late winter of 1972, and
5.7-7.5 m in the late winter of 1975 (Edmondson, 1977). Summer
phytoplankton peaks, as measured by chlorophyll a_ content, increased
more than 10 times between 1950 and 1964. Oxygen production, a
measure of primary production, increased from 4.48 g/m in 1957 to a
high of 6.95 g/m in June, 1966 fEdmondson, 1969). Oscillatoria
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YEAR
1960
1968
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1.9
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70
60
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TRANSPARENCY ^
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- PHOSPHATE
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DIATOM SPECIES
DIVERSITY
DIATOM SPECIES
COMPOSITION
%EUTROPHIC x-*'
FORMS X
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7
FIGURE 1. REVERSAL OF CULTURAL EU-
TROPHICATION IN LAKE WASHINGTON, SEATTLE.
NUMBERED EVENTS ARE AS FOLLOWS: 1. ELEVEN
SEPARATE SEWAGE PLANTS DISCHARGING TREATED
SEWAGE INTO THE LAKE. 2. FIRST NOTICEABLE
BLOOM OF NUISANCE ALGAE (OSCILLATORIA).
3. FIRST DETECTED OXYGEN DEPLETION IN BOTTOM
WATER (HYPOLIMNION) DURING THE SUMMER.
4. METRO GOVERNMENT SEWAGE PROJECT LEGIS-
LATION PASSED (1960). 5. FIRST STEP IN SEWAGE
DIVERSION (1963). 6. SECOND STEP IN SEWAGE
DIVERSION (1965). 7. ALL SEWAGE DIVERTED
(1967). THE TRENDS IN FOUR WATER QUALITY
INDICES (TWO PHYSICAL AND TWO BIOLOGICAL)
ARE SHOWN.
(ODUM, 1971). (GRAPH BASED ON EDMONSON,
1968, AND STOCKNER AND BENSON, 1967).
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100%
50%
I I
1963
I I
1970
I I I I
1974
FIGURE 2. RECOVERY OF LAKE WASHINGTON. MEAN VALUES FOR TOP TEN METERS.
THE VALUE FOR 1963 {IN PARENTHESES) IS SHOWN AS 100%. A=TOTAL PHOSPHORUS
FOR WHOLE YEAR (PERCHLORIC ACID DIGESTION; 65.7 jug/I). B=DISSOLVED INORGANIC
PHOSPHATE PHOSPHORUS, JANUARY-MARCH (55.3 xig/l). C=CHLOROPHYLL, JULY-
AUGUST (34.8 jug/I). D=NITRATE NITROGEN. JANUARY-MARCH (423 jug/I). E=CARBON
DIOXIDE, JANUARY-MARCH (4.05 mg/l). NOTE THAT THE WINTER VALUES ARE FOR A
SLIGHTLY DIFFERENT TIME FROM THOSE PUBLISHED EARLIER (EDMONDSON, 1970).
SEWAGE DIVERSION STARTED IN 1963 AND ENDED IN 1968. WINTER PHOSPHATE
PHOSPHORUS CAN EXCEED THE ANNUAL MEAN FOR TOTAL PHOSPHORUS WHEN THE
LATTER DECREASES DURING THE SUMMER AS IN 1974 (EDMONDSON, 1977).
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dominated in the mid-1960s, but has been seen only rarely since 1972
(Edmondson, 1977).
Wastewaters were also diverted from the lower Madison, Wisconsin,
lakes (Lake Waubesa and Lake Kegonsa). Sonzogni et_ a]_. (1975) sum-
marized the data available before and to 15 years after diversion.
Soluble phosphorus levels in winter were above 0.3 mg/1 P for the
years measured before and immediately after diversion in 1958. By
1960, soluble phosphorus levels were below 0.2 mg/1 and in 1972 below
0.05 mg/1. Other nutrients also decreased during this period. Algal
communities were dominated (99 percent of the algae) by the blue-green
alga Microcystis just before diversion (1955-57). Shortly after
diversion, Microcystis decreased to 25 percent to 90 percent of the
total number of algae, and the community became more diverse. Although
the lakes still experience summer algal blooms, they are composed of
non-blue-green algae that generally do not form an obnoxious scum along
the lake surface and shore.
The situation in lakes the size of the Great Lakes is complicated
by the multitude of perturbations on the lakes' ecosystem. Overfishing,
introduced species, pollution, and eutrophication have, in combination,
had remarkable effects on the biota of the Great Lakes. While it is
sometimes difficult to distinguish the effects of individual per-
turbations, some of the lakes' responses are those which typically
accompany increased nutrient loadings.
Hartman (1972) summarized the changes occurring in Lake Erie
over the past 50 years. Cultural eutrophication has been the direct
cause of changes in the density and diversity of the phytoplankton com-
munity and the depletion of oxygen levels. It has also been a
significant contributing factor in the changes occurring in the
composition of fish and benthic species. The western basin of Lake
Erie has been particularly affected by increased nutrient loadings,
due to its shallow depth and proximity to the major urban and
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industrial centers of Detroit, Michigan and Toledo, Ohio. This basin
has been considered an important spawning and nursery ground for fish
since it contains many shoals and rocky- reefs. Nutrient loadings
have increased in the lake over the past 50 years. Although the data
are scanty, Beeton (1969) estimated that total nitrogen and phosphorus
concentrations had increased by factors of 3 and 2 respectively
between 1930 and 1958. More recently, a five-fold increase in the
soluble phosphorus concentrations of the lake was reported between
1950 and 1961-62 (Verduin, 1969) and a 50 percent increase between
1961-62 and 1967-68 (TWPCA data cited by Verduin, 1969).
Phytoplankton have responded directly to the increased nutrient
loadings with changes in species composition and increased biomass.
Between 1928 and 1958, the plankton of the western basin of Lake Erie
was dominated by diatoms. By 1969, increasing numbers of flagellates,
blue-green and green algae as well as nuisance growths of Cladophora
were reported during the summer and fall (Anon., 1969). Cladophora
is a filamentous alga which attaches to lake bottoms near shore and
to depths of 5 m. Wave action and currents frequently break the alga
loose, forming dense floating mats which, when they sink and decompose,
add significantly to the biochemical oxygen demand of the sediments.
Frequently the mats wash ashore and produce foul odors and attract
insect pests as they decompose. Davis (1964) reported that the density
of phytoplankton sampled at a water filtration plant near Cleveland,
Ohio, increased from an average of about 400 cells/ml in 1920-1937 to
900 cells/ml in 1944-48 and to 1500 cells/ml in 1956-63. In the late
1960s and early 1970s the length of the spring and fall algal
abundance maxima were noticed to have increased considerably and the
summer and winter minima had become less pronounced. Hartman (1972)
cited the work of Davis, who studied the changes in plankton species
occurring in the central basin of the lake. Between 1920 and 1949,
the spring phytoplankton maxima were usually dominated by the
oligotrophic diatom Asterionella; since then, Melosira, a diatom
typical of more nutrient-rich waters, has been the dominant form.
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The fall pulses have shown a progression from Synedra and Meloslra
before 1947, to the mesotrophfc diatom Fragilaria, the green alga
Pediastrum, and the eutrophtc blue-green algae Anabaena and Aphanizomenon.
As recently as 1970, the fall pulses were dominated by a succession of
blue-green algae, Anabaena, Microcystis and Aphanizomenon (Hartman,
1972).
Summer oxygen depletion has been severe in parts of Lake Erie.
The western basin usually remains unstratified throughout the summer,
owing to the mixing action of winds and currents in this shallow
basin. Oxygen depletion in the hypolimnion of the central basin has
increased in severity. While first noticed in 1930 as an isolated
2
area, the zone of oxygen depletion had increased to 3,600 km in
1959, 6,600 km2 in 1970 and peaked in 1973 at 11,600 km2. In 1973,
the anoxic region covered 94 percent of the hypolimnion and 70 per-
cent of the entire basin (Great Lakes Water Quality Board, 1976).
Moderately low oxygen levels (2-5 mg/1 ) were reported in the deep
eastern basin as well (Hartman, 1972).
Oxygen depletion, a result of increased nutrient loadings, has
presumably been responsible for the devastation of the benthos of
Lake Erie. Before 1953, the benthos of the western basin was
dominated by nymphs of the mayflies ("Canadian soldiers") Hexagenia
rigida and H. 1imbata occulata before 1953. During the summer of
1953 populations were nearly exterminated during a period of oxygen
depletion which resulted after 28 days of hot, calm weather. By 1961,
Hexagenia populations had decreased in size to less than 1 percent
of their former abundance (Carr and Hiltunen, 1965). The period
from 1930 to 1961 saw an increase in species typical of eutrophic,
oxygen-poor waters in the western basin; sludge worms, midge larvae
(Chironomus) and tubificids (Limmodrilus) became dominant in the
benthos (Beeton, 1969; Verduin, 1969; Carr and Hiltunen, 1965; Veal
and Osmond, 1968).
10
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Oxygen depletion has been a factor contributing to the enormous
change in fish populations in the lake over the past 60 years; other
perturbations, including intensive exploitation, temperature increases,
construction of dams, land drainage, introduced species, and toxic
pollutants were also important. Populations of lake trout, lake
herring, sturgeon, whitefish and blue pike were intensively over-
fished, causing a rapid decline in abundance; however, decreased
oxygen levels have apparently precluded the recovery of these popu-
lations (Hartman, 1972). Increased algal growth and deposition of
organic sediments on the lake bottom are suspected as factors in the
decline of species such as walleye, blue pike, sauger, lake herring,
and whitefish that require rocky gravel shoals for spawning (Beeton,
1969). A more complete discussion of the change in the commercial
fishery of Lake Erie is contained in Section V.
Eutrophication of Lake Erie has had little effect on species such
as gizzard shad, goldfish, channel catfish, emerald shiners, brown
bullhead, carp, and white bass. These species spawn at shallow depths,
usually less than 5 feet, and have short incubation periods (less
than 5 days). These two factors tend to minimize the effects of
low oxygen levels that are detrimental to cold water bottom spawners.
The freshwater drum is one fish that has capitalized on the reduction
of competition and predation resulting from eutrophication and other
stresses. Since 1950, survival of the young-of-the-year has increased.
Unfortunately, freshwater drum has almost no value to commercial
fishermen and sports anglers (Hartman, 1972).
11
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General Effects on Aquatic Plants, Zooplankton and the Food Chain
AS seen in the preceding examples, increased algal biotnass and
productivity are the typical responses to increased nutrient loading,
but the specific biotic changes which accompany eutrophication are
variable, complex, and difficult to predict. The changes in the
phytoplankton community normally occurring during cultural
eutrophication were summarized by Prescott (1968). The cyanophytes
(Aphanizomenon, Microcystis, and Anabaena) typically dominate the
plankton, during late summer and early fall blooms, and diatoms, such
as Asterionella, Fragilarta, Tabellaria, and Men'dion, also become
more abundant, especially in the spring. Chlorophyte genera such as
Oocystis, Treubaria, Golenkinia, Tetrallantos and Ermosphaera,
characteristic of oligotrophic lakes, are replaced in eutrophic waters
by Pediastrum, Botryococcus braunii, Coelastrum microporum and
Scenedesmus spp. These generalizations are supported, in part, by
the previously cited studies of Schindler (1971), Schindler et al .
(1971), Langford (1948), Smith (1969), and Vanderhoef et_ al_. (1974).
In general, phytoplankton community diversity decreases as
lakes become more eutrophic. Community diversity (H1) is commonly
measured by the Shannon-Wiener method which incorporates the number
of species present as well as the distribution of individuals among
species (i.e., evenness). Phytoplankton diversity is significantly
correlated to the evenness component but not to the number of species.
Oligotrophic lakes, although low in productivity, are more diverse
than eutrophic lakes. Poor nutrient conditions favor no one species,
and overproduction of algae does not occur. Eutrophic lakes, on the
other hand, tend to become dominated by one or two algal species. Other
species may be reduced in number by adverse environmental conditions,
or by biological interactions such as competition, grazing, parasitism,
and antibiosis ("Porter, 1977).
12
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High phytoplankton production is sometimes associated with a
decrease in the production of aquatic macrophytes. Jupp and Spence
(1977), for example, noticed that Aiiabaena spp. were particularly
effective in reducing the amount of light available for Potamogeton
.filiformis and other macrophytes in Lock Leven. They suggested that
high phosphorus levels (O.Q5 mg/1) in the lake during the summer
months were responsible for the dense phytoplankton growths, which
in turn, may have been responsible for the reduction in macrophyte
biomass. Light attenuation and/or pH increase were thought to be the
causative factors.
Changes in the zooplankton during eutrophication are not as
well documented as phytoplankton changes. Macroconsumers (Calanoida and
larger Cladocera) dominate in oligotrophic lakes where nannoplankton
(less than 50u) are in the majority. These grazers are filter feeders,
which consume large numbers of diatoms, small green algae, and nanno-
flagellates. The colonial and filamentous cyanophytes and green algae
("net phytoplankton"), characteristic of eutrophic waters, have
defenses against zooplankton grazing; e.g., clogging of filter feeding
apparatus. The zooplankton inhabiting these waters are usually
microconsumers, utilizing algae indirectly by the way of the
associated bacteria and detritus (Porter, 1977 and Pederson et al .,
1976). Smith (1969) and Gentile 0971) reported a decrease in the
number of zooplankton during blooms of blue-green algae. A greater
proportion of algal productivity is used for food in oligotrophic lakes,
and the zooplankton food supply is used less efficiently as the trophic
state advances towards eutrophy (Hillbricht-Ilkowska, 1972). Welch
£t a]_. (1975) showed that net plankton was utilized less than 10 per-
cent as much as the smaller plankton.
These observations are of major importance in studying the
impact of eutrophfcation on the food chain in eutrophic waters. An
increase in phytoplankton primary production is not necessarily reflected
13
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in a proportionate increase in zooplankton secondary productivity.
Often the increased phytoplankton biomass ts not available to higher
trophic levels because blue-green algae are not utilized by herbivores,
Increased blue-green algal growth provides an energy source to the
decomposers or to a different component of the secondary trophic
level (e.g., zoobenthos).
Changes in the composition of higher trophic levels can be
expected to occur as the result of changes in the phytoplankton
community. Bottomfeeding fish are able to capitalize on their
increasing food stocks. In this manner, the trophic structure of
nutrient-enriched waters has completely changed from the phytoplankton-
zooplankton-carnivorous fish food chain of oligotrophic waters
(Pederson e_t aj_., 1976).
Toxic Effects of Blue-Green Algae
Those species which thrive in eutrophic waters are endowed with
mechanisms enabling them to prosper, sometimes at the expense of
other species. Some blue-green algae typical of eutrophic waters,
e.g., Anabaena, are able to fix atmospheric nitrogen. When dis-
solved nitrogen becomes scarce relative to other nutrients (the
case with sewage-enriched waters), the growth of other algae may be
limited; the blue-greens are able to proliferate by deriving
nitrogen from the atmosphere. Shapiro (1973) has also found that
C02 and phosphorus uptake kinetics favor the dominance of blue-green
algae over green algae.
*
Blue-green algae appear to influence phytoplankton species as
well as other levels of the food chain, Keating (1977) found that
blue-green algae from a eutrophic pond produce extracellular metabo-
lites which influence the succession of algal species. Macronutrients
and light determine the level of productivity and, to some extent,
major dominant groups; algae are adapted for optimal growth at
14
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specific nutrient concentrations and light intensity (Vollenweider,
1968). Other factors, including micronutrients and temperature patterns
determine which species will dominate. Extracellular metabolites
are thought to influence the seasonal succession of dominant
organisms within a eutrophic lake. Keating found that cell-free,
axenic filtrates of each dominant blue-green alga produced only
positive or neutral effects on the growth of the succeeding dominant
organism and only negative effects on the growth of its immediate
predecessor. These results suggest a very novel method which may be
of use, after further development, in the management of the nuisance
blue-green algal blooms typical of eutrophic water.
Earlier studies also showed the influence of some blue-green
algal metabolites on other phytoplankton groups. Gentile (1971)
summarized the earlier reports which showed that waters containing
blooms of Microcystis, Oscillatoria. Anabaena inhibited the growth
of other test algae.
While some blue-greens may indirectly impact herbivores by
reducing their food resources, some also directly influence other
trophic levels by the production of toxins. The toxin may be pro-
duced by the alga, or by the bacteria which appear in association
with the alga, or released by the alga upon decay (Gorham, 1960).
Gentile and Maloney (1969) isolated a toxic strain of Aphanizomenon
flos-aquae from Kezar Lake, New Hamphire. They used bioassays to
investigate the effects of the toxin from lysed cells on several zoo-
pi ankters. Bosminia longirastris would be expected to be killed by a
bloom containing 1 x 10 algal cells/ml, while elimination of Daphnia
catawba would require 4 x 10 cells/ml (Gentile, 1971). Daphnia
catawba could not be cultured with healthy cells of this algal even
when adequate food sources were provided. Gentile (1971) supposed
that Daphnta ingestton of the small filaments of the toxic algae
was responsible. Prescott (]96B) reported on an extrametabolite of
15
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Microcystis sp., another typical eutrophic cyanophyte, which inhibits
the growth of Daphnia and Cyclops. Mills and Wyatt 0974) found that
some strains of blue-green algae were toxic to the ostracod Cyprinotus^
incongruens, which typically inhabits the benthic habitat of inland
littoral zones. Additional evidence exists to support claims of
toxicity of some blue-green algae to zooplankton (Gentile, 1971).
Fish kills in eutrophic waters have been attributed to toxins as
well as oxygen depletion produced by blue-green algal blooms. Sawyer
et_ aj_. (1968) reported on massive fish kills occurring after copper had
been used to control blooms of Aphanizomenon flos-aguae in Lake
Winnesquam and Kezar Lake, New Hampshire. Toxin from the killed
algal cells was thought to be the primary cause of the fish mortality,
although copper may have acted synergistically to enhance sensitivity
to the toxin. In laboratory assays algal extracts were toxic to
mummichogs (Fundulus heteroclitus) and sheepshead minnows (Cyprinodon
variegatus) by intraperitoneal injections (LDnQO = 0.5 mg algal extract/
kg). Golden shiners (Notemigonus crysoleucas) were sensitive to con-
centrations of the toxin which would normally occur during a bloom
(Gentile and Maloney, 1969). Sawyer et_ al_. (1968) demonstrated the
toxicity of a natural population of Ap_. flos-aquae from Kezar Lake
to sunfish (Lepomis gibbosus), guppies (Lebistes reticulatus) and
white suckers (Catostomus commersoni), despite high (? 6 mg/1 ) con-
centrations of dissolved oxygen.
Two common species of Microcystis produce extrametabolites toxic
to Gambusia, the mosquito fish fPrescott, 1968). Carmichael and
Gorham (1977) and Carmichael e_t a_l_. (1975) reported that goldfish
were susceptible to a toxic strain of Anabaena flos-aquae if the
toxin was ingested. The toxin was apparently not able to enter the
fish through the gill membrane. Table 1 lists other algal species
thought to be toxic to some fish species and Schwimmer and
Schwimmer (1968) summarize the literature from the late 1800's.
16
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Terrestrial animals, including livestock and water fowl, have
been poisoned by drinking water containing high concentration of some
blue-green algae. While toxic blooms have been reported from most
regions of North America, they appear to be of particular importance
in eutrophic lakes and sloughs in Western Canada (Carmichael et al.,
1977). Anabaena flos-aquae, Aphanizomenon flos-aquae, and Microcystis
spp. have often been implicated in dramatic and serious poisonings
(Gorham, 1964a). In the fall of 1952, Storm Lake, Iowa, experienced a
series of toxic blooms of Anabaena flos-aquae. The algal poison was
blamed for the deaths of 5000 to 7000 Franklin's gulls, 560 ducks, 400
coots, 200 pheasants, 2 hawks, 50 fox squirrels, 18 muskrats, 1 skunk,
1 mink, 15 dogs, 4 cats, and 2 hogs (Rose, 1953). Gorham (1964b)
reported than an endotoxin from a strain of Microcystis aeruginosa
was toxic in laboratory experiments to sheep, rabbits, and calves, but
ducks were resistant. Carmichael and Gorham (1977) and others
(Carmichael et^ al., 1975) have reported on toxicity tests using toxic
strains of Anabaena flos-aquae on pheasants, mallards, calves, and
laboratory rats and mice. Small amounts (18-1200 ml) of a 20 mg dry
wt/ml (minimum lethal dose in a mouse by intraperitoneal injection=60
ml) algal suspension was toxic to most species in a short time (several
minutes to several hours). In another experiment, Carmichael et al.
(1977) concluded that the toxin from one toxic bloom of Anabaena
flos-aquae paralyzed the respiratory muscles of calves and probably
other livestock. They estimated that a 60 kg calf consuming 1.2 1 of
a concentrated bloom of toxic A_. flos-aquae (Type a_, strain NRC-44-1)
would die. Mackenthun and Ingram (1967) stated that, rather than
death, Microcystis may produce illness, characterized by decreased
milk production in cattle. Table 1 lists the algal species most often
implicated in livestock poisonings.
Most blooms are not directly toxic; of 11 species of blue-green
algae which dominate eutrophic blooms, Gorham (1964a) found only two
toxic species. Genetic factors determine the potential for toxin
production (Gentile, 1971). Environmental factors, such as light
17
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Table 1. Death-iducing algae (after Prescott, 1968).
Ducks
Algal Species Birds Sheep Cattle Fish White Mice
Anabaena flos-aquae + + + +
Anabaena circinalis +
Anabaena limnetica +
Anabaena Scheremetievi +
Anabaena inaequalis +
Anabaena Nadsonii +
Aphanizomenon flos-aquae + + + +
00 Aphanothece nidulans +
Aphanothece cyanea +
Gloeotrichia echinulata +
Lyngbya Birgei +
Microcystis toxica + +
Microcystis aeruginosa + + + +
Nodularia spumigena + + +
Scenedesmus sp +
Chorella sp +
Gonyaulax catenella* +
Cymodimium brevis* +
and other spp
*Marine species, blooms most often related to availability of vitamins.
-------
intensity, temperature, pH, and available inorganic nutrients
govern the dominance of the species and strain of algae as well as the
production of toxin, if any. In addition, the stage in the life cycle
of the algae (e.g., spore production) governs when the toxin is produced
and, possibly, released CGorham, 1964a).
Carmichael and Gorham 0977) produced evidence demonstrating that
biological factors, i.e., the presence of certain toxin-depressing
bacteria, influence the toxicity of Anabaena flos-aquae cultured in
the laboratory. The relative abundance of toxic and nontoxic strains
of the alga was another factor. They estimated that for an Anabaena
bloom to be toxic to livestock, it should consist predominantly of
A_. flos-aquae and be composed of 80-90 percent toxic filaments. For a
bloom to be toxic, the toxin must be present in sufficient quantity and
in a suitable form, as well as consumed by susceptible species and in
sufficient amounts for deaths to occur. Dilution, adsorption, or
destruction of the toxin may render it harmless before effects on
aquatic or terrestrial species are felt (Gorham, 1964a). These
variables make accurate predictions of the toxicity of algal blooms
difficult.
It can be concluded, from the foregoing studies, that blue-green
algae common in eutrophic lakes and ponds can be toxic to other
members of the aquatic and terrestrial community. The nature of this
interaction is variable and needs more study (Gentile, 1971). It is
difficult to adequately assess the hazard of toxic algae, as it relates
to eutrophication. It has been established that several algal species,
common in eutrophic lakes and ponds can be toxic to some animals. From
the evidence available, it would appear that toxic algae in eutrophic
waters are an infrequent problem. Animal poisonings from toxic algae
occur infrequently, according to Schwimmer and Schwimmer (1968) who
found only 65 episodes reported in the literature between 1878 and 1962,
although they appear to be a periodic problem in Alberta and
19
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Saskatchewan (Carmichael ejt aj_., 1977). On the basis of reported
frequency, toxic blooms appear to be of slight significance. On the
other hand, some toxic blooms may go unreported in the scientific
literature because of the difficulty in culturing the algae, identifying
causative agent, and obtaining a sample of the transient toxic bloom.
In addition, animal losses are more easily attributed, by the farmer,
veterinarian or pollution biologist to better known and better under-
stood causes (Schwimmer and Schwimmer, 1968). On the basis of the
evidence available, it is difficult to classify the significance of toxic
blooms as anything but slight. However, we should be aware that as the
frequency and extent of algal blooms increases with accelerated
eutrophication, the frequency of occurrence of a toxic strain of the
cyanophytes typical of such blooms may also be increased (Gentile,
1971). Carmichael and Gorham (1977) believe that since cyanophyte
blooms are potentially toxic all blooms are suspect, even though
most may actually be nontoxic.
Effects on Fish
Eutrophication is accompanied by changes in fish communities as
well. Moderate enrichment of lakes and ponds is a standard management
technique in some parts of the country, designed to increase the pro-
duction of favorable game species. However, with uncontrolled or
excessive nutrient enrichment, some fish populations suffer. In 1972,
an international symposium was held in Canada to explore the changes
in salmonid and associated communities in oligotrophic lakes (SCOL)
resulting from the separate and combined impact of eutrophication,
exploitation, and introduced species (see J. Fish. Res. Bd. Canada
29:6). A similar symposium was held in 1976 concerning percids
(PERCIS) (see J, Fish Res. Bd. Canada 34:10). Col by et_ aj_. (1972)
summarized the findings in SCOL lakes related to eutrophication and
Leach et_ aj_. (1977) summarized the work in PERCIS lakes. While
there was no SCOL nor PERCIS lake impacted solely by eutrophication,
salmonid and percid communities were considered to have certain
20
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characteristic responses to nutrient enrichment; for salmonids:
initial increased growth and increased incidence of parasitism and
later, possible introgression, reduction of natural reproduction,
and predictable species dominance; for percids: growth and biomass
increase to a threshold level followed by decrease, increased
parasitism, changes in food habits, distribution and spawning habits.
In several eutrophic SCOL lakes, some salmonid species enjoyed
increased growth rates: the coregonines of the Bodensee (Coregonus
wartmanni and C_. macrophthalamus) and the Schliersee. In the
Bodensee, abundance of C_. wartmanni ("Blaufelchen) increased as a
result of eutrophication, because of the increased amount of available
food (Numann, 1972). Northcote (1972) reported on similar effects on
kokanee (Oncorhynchus nerka) in Kootenay Lake. Percids responded to
cultural eutrophication with an increased growth rate in the young
and/or adult fish. This was true for walleye, blue-pike and Eurasian
perch in North American and European lakes, but additional evidence
suggests that at some point in the trophic continuum, the growth rate
of percids will peak, then decline (Leach e_t aj_., 1977).
The incidence of parasite infestations increased in salmonids and
percids in several SCOL and PERCIS lakes, possibly as a result of
eutrophication. Nutrient enrichment may have enhanced the growth of
the parasite populations by contributing to the greater abundance of
macrophytes, necessary for the completion of the life cycle of the
snail-fish-bird type parasite. For example, Eurasian perch mortality
in the Bodensee was blamed on the parasite Diplostomum valvens.
while periodic small year classes of coregonines have been blamed on
increased infection by Taenia (Numann, 1972). Rainbow smelt
mortalities in Lake Erie have been attributed to the microsporidean
Lugea hertwigi, which infests 90 percent of the lake's smelt popu-
lation (Dechtfar, 1972). The incidence of Lymphocystis sp. infestation
of walleye was greater in the more eutrophic sections of Lake of the
Woods (Schupp and Macins, 1977).
21
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Introgression may occur if the segregative mechanisms between
closely related species are destroyed. It has been suggested that
eutrophication may cause introgression by destroying the spawning grounds
of one species, causing it to spawn in another area which is also used
by a closely related species. Blue pike and walleye hybridization may
be a result of this (Regier et_ a]_., 1969), but the process is not
clearly understood.
Reproduction of many salmonids has been adversely affected by
the oxygen depletion and siltation of spawning grounds accompanying
eutrophication. At the same time, unaffected species, like perch, have
become more abundant due to the reduction in competition or predation.
Species that use shoals of lakes or lake bottoms for spawning and
whose eggs have long fncubation periods are particuarly adversely
affected. Christie (1972) suggested that lake trout populations
in Lake Ontario suffered from increased growth of Cladophora,
a response to nutrient enrichment. Decomposition of Cladophora
caused oxygen depletion fatal to overwintering eggs. Since the
intensification of eutrophic symptoms, burbot no longer make winter
spawning runs to the deepest part of the Bodensee, but spawn in
the sublittoral zone (Numann, 1972). Percids in Lake Constance, too,
have changed their distribution and spawning habits in response to
oxygen deficits, decreased transparency, and organic matter
deposition (Hartmann and Numann, 1977). Some evidence exists which
suggests that reproduction of coregonines in the Bodensee (Numann,
1972), blue pike in Lake Erie (Smith, 1972c) and whitefish in the
Bay of Quinte (Christie, 1972) suffered as a result of oxygen
depletion.
The succession of fish species in the Great Lakes was studied by
Smith (1972c) who noticed that fish families and species within
families declined and disappeared in the same order from different
lakes, or regions of lakes, during periods of rapid changes in water
22
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quality. Other influences, e.g., marine species and commercial fish
preference, seemed to have no impact on the sequence, indicating a more
subtle control of species dominance. The stresses accompanying
eutrophication appear to act first on those species close to the
southern end of their range and temperature preference. Susceptibility
of percid species to the effects of progressive nutrient enrichment
depends on the following factors: (a) ability to migrate to
suitable habitat when preferred habitat becomes unfavorable
(Colby et_ al_. (1972) suggested that eutrophication tends to increase
the vulnerability of sedentary discrete stocks to other stresses such
as commercial exploitation); fb) ability to switch prey species when
preferred food items become unavailable, and significantly,
(c) reproductive behavior. Lake-spawning walleye and sauger, which
broadcast their eggs on the lake bottom, would be most susceptible to
organic matter deposition resulting from nutrient enrichment. Yellow
perch, however, lay their eggs in ribbons which float upwards from
their attachment on the bottom Cor macrophyte), ensuring aeration
even when the mud-water interface is anaerobic (Leach et^ al_., 1977).
Smith (1972c) found that salmonines (Atlantic salmon, lake
trout) wet*e the first species to suffer, followed by coregonines
(lake herring, whitefish), then percids (sauger, blue pike, walleye,
yellow perch), eventually followed by centrarchids and cyprinids
(Smith, 1972b). Eutrophication is related to the disappearance of
lake trout in the southern portions of Saginaw and Green Bays,
before the sea lamprey became well established (Colby et_al_., 1972).
Increased yellow perch abundance in Lake Ontario may be related to
the proliferation of invertebrate food items associated with
Cladophora (Christie, 1972). However, nutrient enrichment may
not necessarily lead to an increase in fishing yield because the
added nutrients may flow through energy compartments not utilized
by harvestable fish species.
23
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Changes in the benthos as a result of eutrophication may have
a direct effect on fish populations. Colby e^ al_. (1972) suggested
that the sequence tn fish populations reflects the ability of the
fish to use the changing benthic species, i.e., from Mysis and
Pontoporeia to mayflies, to chironomids and oligochastes. Oxygen
depletion is suspected to cause the change in benthic invertebrates.
The diet of percids apparently reflects the change in benthic species;
in several PERCIS lakes, large food items such as Hexagenia and
amphipods were replaced by small items like chironomids (Leach et_ al_.,
1977) as eutrophication advanced.
Effects in Flowing Waters
The preceding discussion illustrates the typical biotic responses
occurring during eutrophication: increased algal production, decreased
algal community diversity, reduction in populations of benthic
organisms and fish which require high oxygen levels, and radical changes
in species composition at all levels of the food chain. These
responses imply a severe stress on the aquatic ecosystems affected.
It should be emphasized that eutrophication problems are not confined
to lakes or freshwater. The magnitude of disturbances associated
with a given nutrient loading rate is a function of the rate of flow
of the receiving water, as well as (among other factors) the relative
proportion of nutrients available and needed for algal growth.
Swiftly flowing waters rarely develop eutrophication problems, even
though their nutrient load could produce algal blooms in a lake with a
long detention time. (Reservoirs on nutrient rich rivers experience
eutrophication problems for this reason.) A flow rate above 0.3 m/sec
will probably prevent the most intense phytoplankton growth seen in
lakes (Gleisberg e_t al_., 1976). The short retention time of flowing
waters is not conducive to the proliferation of phytoplankton.
Stream enrichment is usually manifested by increased periphyton growth.
24
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Recycling of nutrients from the sediments is less likely in flowing
waters than in lakes; the sediments may be periodically scoured from
the river during periods of high flow. High sediment loads in flowing
waters reduce the depth of light penetration and, consequently, the
volume of the euphotic zone.
The slower moving portions of a river or estuary, however, like
a lake which receives the nutrient load of a stream or river, may
experience algal blooms and other problems associated with nutrient
enrichment. Several tributaries of the Chesapeake Bay are exhibiting
classical signs of eutrophication, resulting from nutrient enrichment
from domestic sewage. The Potomac River near Washington, D. C., and
the Back River, which receives sewage wastes from Baltimore, are good
examples of slow moving waters subjected to nuisance algal growths
resulting from nutrient enrichment ("Jaworski ejt a]_., 1972a and 1972b;
Pritchard, 1972). The Patuxent estuary, while still healthy, doubled
in productivity in the 1960s; Cory (1974) anticipated similar problems
in this area as well, if present trends continue.
Enrichment problems in the Chesapeake Bay appear to be limited,
at the present time, to tributaries. Taft and Taylor (1976) studied
phosphorous levels in the open waters of the Bay and found levels
below that suggested by Ketchum (1969) as a maximum value for unpol-
luted coastal waters (2.8 ug at P/l) and close to those obtained
in studies conducted in 1938 and 1964.
Estuaries are naturally nutrient rich and highly productive
bodies of water. The circulatory pattern within estuaries accounts
for their high retention of nutrients and consequent high productivity.
Surface layers of less saline waters flow toward the ocean while more
dense, saline waters flow generally landward. The nutrients tend
to be cycled within the estuary and are moved slowly seaward with ocean
water (Cronin and Mansueti, 1971).
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Nevertheless, in excess, nutrients can cause problems in
estuaries, as well as in lakes and rivers. The symptoms of nutrient
enrichment of estuaries are similar to those of lakes (Barlow et_
al., 1963). First, algae respond to increased nutrient concentration
with increased growth. Their respiration and decomposition by
bacteria leads to oxygen depletion of the deeper waters. Although
some atmospheric oxygen can be incorporated into bottom waters,
particularly in shallow estuaries through wind mixing, the increased
organic load puts added demand on oxygen levels, particularly during
calm and/or warm periods. Decreased oxygen levels stress estuarine
organisms, especially the sedentary benthos. Commercially and
ecologically important benthic animals, as well as their predators,
suffer. The elimination of preferred phytoplankton prey species,
resulting from changing nutrient levels, could potentially have a
devastating effect on the motile larvae of many species of crustaceans
(crabs, shrimp), molluscs (oysters, clams) and fish (Hobbie, 1970).
Increasing algal concentrations can create surface scums over portions
of the estuary, obnoxious odors, and beach foulings (Schofield and
Krutchkoff, 1974; Sawyer, 1965).
In particular, Perkins and Abbot (1972) and Waite and Mitchell
(1972) reported that nutrient-rich sewage effluents were responsible
for the intense growth of the benthic algae Enteromorpha and 111va
in some coastal plain estuaries. Decompositions of these algae on mud
flats may lead to the elimination of oxygen in the surface layer
of the mud flat, the production of hydrogen sulfide, and the
consequent destruction of several important mollusc and polychaete
species. Trent et_ al_. (1976) blame eutrophication and other factors
for the reduction in populations of blue crabs, oysters and shrimp
in a developed marsh along the Gulf Coast of Texas. When compared
to the adjacent undeveloped marsh, the developed area had higher
nutrient and phytoplankton concentrations, lower oxygen levels, and
smaller populations of important crustaceans and molluscs. Another
26
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factor contributing to oxygen depletion in the developed marsh was
the creation of small canals, which prevented large scale mixing of
the water with the atmosphere. Cope!and and Robbie (1972) mention
that nutrient enrichment from urban, agricultural and industrial
sources temporarily ruins the oxygenated habitat used by benthic
organisms (e.g., clams, snails, marine worms) in the Pamlico River
Estuary, North Carolina. Nitrogen is probably the limiting nutrient
in this estuary, but phosphorus additions, they speculate, could
lead to dominance of nitrogen-fixing blue-green algae, thus making
nitrogen available to other forms, as well. The increasing
frequency of algal blooms, as well as occasional incidence of
anaerobic conditions in late summer, are the effects of nutrient
enrichment in this estuary (Hobbie, 1974). Flemer (1972) warns of
similar problems in the Chesapeake Bay if present nutrient loading
trends are not reversed.
III. Significance of Phosphorus in Eutrophication
Phosphorus is the key element controlling the rate of
eutrophication of most lakes. It is one of about 20 nutrients which
is needed for algal growth. Any of the nutrients will become
limiting, according to Liebig's law of the minimum, if it is present
in the smallest quantity relative to the amount needed for growth.
Phosphorus is the limiting nutrient in most freshwater lakes, but
other nutrients can also become limiting if phosphorus is over-
supplied.
Furthermore, of the nutrients which limit plant productivity,
phosphorus is the easiest to control. Large amounts of other
nutrients, particularly nitrogen and carbon, can enter lake from the
atmosphere or from other natural sources; because anthropogenic
sources of phosphorus are so important, phosphorus is easier,
relative to other nutrients, to control. Phosphorus controls in
27
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productive systems, where another nutrient is limiting, may reduce
productTvTty if phosphorus loadings can be reduced to the point where
it is, in fact, limiting.
Oligotrophic lakes are usually phosphorus-limited. Many sewage
enriched lakes are nitrogen limited because greater quantities of
phosphorus have been supplied relative to nitrogen, resulting in a
decrease in the N:P ratio. Coastal waters are usually nitrogen-
limited (Ryther and Dunstan, 1971); estuaries may be limited by
phosphorus, nitrogen, or another nutrient, or even light (Thayer,
1974). On rare occasions, carbon, .limitation has been demonstrated
but only in hypereutrophic systems, or eutrophic lakes with very low
alkalinity.
Numerous studies have shown that phosphorus levels have a
positive effect on algal growth. The research can be divided into
two areas: in situ lake examinations and laboratory bottle tests
using lake water.
Miller et_ aj_. (1974) conducted algal assays on waters from 49
lakes across the United States and determined the factor limiting
algal growth in each. The lakes were chosen to represent a wide
variety of water qualities and geographic locations. Additions of
nitrogen (1.00 mg nitrogen/1 as NaNOo) and phosphorus (0.05 mg
phosphorus/1 as KgHPO^) were made, separately and in combination,
to flasks containing a culture of Selenastrum capricornutum Printz
and lake water. Additions of the limiting nutrient stimulated algal
productivity as measured by dry weight. Phosphorus was limiting in
most (72 percent) of the lake waters, nitrogen was limiting in 16
percent), and another unidentified nutrient was the limiting factor in
6 percent. The authors then related the limiting nutrient to the
28
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relative productivity of the lake water sample. On the basis of
algal dry weight production in the control assays, the lake
waters were divided into four categories: (1) low productivity
(0.00-0.10 mg dry wt/1), (2) moderate productivity (0.11-0.80 mg
dry wt/1), (3) moderately high productivity (0.81-6.00 mg dry wt/1),
and (4) high productivity (6.10-20.00 mg dry wt/1). There was an
inverse relationship between the relative productivity and the
percentage of lakes in each group which were phosphorus limited;
i.e., phosphorus was limiting in 83 percent of the low productivity
lake waters, 75 percent of the moderate productivity lake waters,
and 50 percent of the high productivity lake waters. These results
suggest that algal productivity is associated with phosphorus levels,
and nitrogen, or some other nutrient, is more likely to be the
limiting factor of lake waters with high concentrations of ortho-
phosphate.
Gakstatter et_ al_. (1975) arrived at similar results using water
from lakes in the National Eutrophication Survey. Many of the lakes
selected in the eastern United States were receiving sewage treatment
plant effluent and most (80 percent) were considered to be eutrophic.
Algal assays were conducted on waters from the lakes east of the
Rocky Mountains to determine the limiting nutrient of each. Phosphorus
was limiting in 67 percent of the lakes; nitrogen in 30 percent; and
another unidentified nutrient in 3 percent. The authors concur with
Miller et^ al_. (1974) that nitrogen is more likely to be the limiting
factor in lake waters with high concentrations of phosphorus.
Sewage effluent contains much lower N:P ratios (2 to 5:1 by weight)
than are normally found in natural waters (15:1 by weight). Municipal
effluents containing high concentrations of phosphorus could provide
phosphorus in sufficient quantity to make another nutrient, possibly
nitrogen, limiting.
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Whole lake studies have provided a clear picture of algal
growth stimulation by phosphorus loadings. Schindler ejt al_. (1971)
studied the result of the addition of a single dose of phosphorus and
nitrogen, to a small undisturbed lake (lake 227) in Ontario. Poly-
ethylene tubes were used to isolate water columns within the lake.
The tubes receiving phosphorus, in combination with nitrogen and/or
carbon, were found to have the highest phytoplankton standing crop,
as measured by chlorophyll a_, within 20 days following enrichment.
Phosphorus appeared to be the primary stimulus for phytoplankton
growth. Nitrogen and carbon may have produced additional algal
growth stimulation when an adequate supply of phosphorus was
available. Additional experimentation with the addition of only
phosphorus and nitrogen to the whole lake indicated that eutrophication
was induced despite the naturally low carbon levels.
Langford (1948) and Smith (1969) also studied lakes in the
Canadian Precambrian Shield (central and eastern regions). They, too,
found that algal growth was limited by phosphorus concentrations.
Schindler et_ al_. (1971) hypothesized that phosphorus limits algal
growth in most lakes of this geological area as well as in the
Great Lakes, which receive over half their drainage from land under-
lain by Precambrian Shield. Their hypothesis is supported by data
showing the similarities in phytoplankton, benthic algae and zoo-
plankton communities of the Great Lakes and small lakes in the
Precambrian Shield.
Schindler and Fee (1974) and Schindler (1975) reported on
another whole lake experiment conducted in the Experimental Lakes
Area of northwestern Ontario (Lake 226). The two basins of the lake
were completely separated by a nylon coated vinyl sheet which extended
across the narrow portion of the lake. Nutrient additions equiva-
lent to 3.2 g of nitrate nitrogen and 6.1 g sucrose per square meter
of surface area per year were made to the epilimnia of both basins
30
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2
in twenty equal weekly doses. Phosphorus (_0.60 g/m yr of phosphate
phosphorus) was added concurrently to one of the basins. The basin
recetvtng all three nutrients was covered by a bloom of the blue-green
alga Anabaena spiroides within two months. The basin receiving only
nitrogen and carbon remained similar to its prefertflization state in
terms of phytoplankton standing crop and species composition. Lake
304 (Schindler and Fee, 1974; Schindler, 1975; Schindler, 1977) in the
experimental lakes area was also divided into two basins; one was
2
used as a control, and to the other was added phosphorus (0.40 g/m /yr
? 2
as H3P04), nitrogen (5.2 g/m /yr as NH^Cl), and carbon (5.5 g/m /yr as
sucrose). Phytoplankton responses were similar to lake 227, exhibiting
large (three-fold) increases in algal standing crop and domination by
green and blue-green algae after two years of fertilization. During
the third year, the lake was fertilized only with carbon and nitrogen
simulating the removal of phosphorus during tertiary treatment.
Chlorophyll levels and algal composition returned to the prefertili-
zation state within one to two years. These two experimetns indicate
that phosphorus was the limiting nutrient in the two lakes and efforts
to control excess phosphorus loadings to such lakes would appear to
prevent eutrophication.
Municipal waste treatment facilities have long been implicated as
a source of phosphorus in surface waters. The following research
shows that sewage effluent stimulates algal growth; the component
in sewage responsible for increased productivity is phosphorus in
almost all cases where lakes receive the effluents.
Edmondson has studied the deterioration of water quality of
Lake Washing: .1, Seattle, and its improvement following sewage
diversion to Puget Sound. Although sewage effluent contains
nutrients other than phosphorus, Edmondson's study (1970) concluded
31
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that summer chlorophyll content in the lake was related to phosphorus
concentrations of the previous winter (a time of nutrient maxima in
some lake waters), and was not related to nitrate or CCL content.
While the other nutrients were important, they were supplied in excess
of need. Following complete sewage diversion in 1968, the winter
phosphorus concentration had decreased to 28 percent of the maximum
reached in 1963. The nitrogen concentration decreased to a lesser
extent (to 80 percent of that in 1963) because of higher N:P ratios
(by weight) in the contributing tributaries (19.9-35.2) than in the
sewage effluent (0.52-3.67) (Edmondson, 1969).
Edmondson (1970) concluded that phosphorus was more important
than nitrogen, based on surface water content of the two nutrients
during the spring growth of phytoplankton. In 1933, before the lake
became sewage enriched, nitrate was left over after phosphorus had
been nearly depleted by growing phytoplankton populations. The N:P
ratio was close to 15 (by weight). In 1962, however, after many years
of enrichment with phosphorus-rich sewage effluent, nitrate was
exhausted before phosphate, and the N:P ratio was decreased. Following
sewage diversion phosphorus, once again, was depleted before nitrate,
and the N:P ratio increased (Edmondson, 1969).
Similar observations were made by Michalski et_ a]_. (1975) in a
study of the effects of phosphorus removal facilities for the sewage
treatment plan at Gravenhurst Bay, Ontario. Improvements in mean
Secchi disk visibility, chlorophyll a_ level, N:P ratio and phyto-
plankton quantity accompanied decreases in the total phosphorus con-
centrations in the euphotic zone and the total phosphorus loadings '
(Table 2). Secchi disk visibility and phytoplankton quantity were
significantly correlated (p£0.05) to mean total phosphorus in the
euphotic zone, while a similar relationship with other nutrients
(N, $102) could not be made. There were indications that N and SiO?
32
-------
Table 2. Mean Value for relevant "trophic indicator parameters" for Gravenhurst Bay during the
and post-phosphorus removal years 1969 through 1971 and 1972 through 1973, respectively.
Data for total phosphorus, inorganic nitrogen, N: P, chlorophyll a_ and phytoplankton
stocks are based on samples collected through the euphotic zone (Michalski et_ aj_., 1975)
00
Total phosphorus loadings
(g P/rrT . yr)
Secchi disc visibility
(m)
Total phosphorus
(ug P/l)
Inorganic nitrogen
N:P
Chlorophyll a_
(ug/1)
Phytoplankton
a) Quantity ,
(A.S.U./ml)
b) Species
Pre-phosphorus removal conditions
1969/1970/1971
2.37
2.5
43.3
70.6
11.4
10.8
2,717
Asterionella formosa
Aphani zomenon flos-aquae
Anabaena spp.
Post-phosphorus removal conditions
1972/1973
0.40
3.2
33.0
141.0
17.1
7.6
1,424
Asterionella formosa
Aphanizomenon flos-aquae
Anabaena spp.
Synura uvella
Dinobryon spp.
Chroococcus spp.
1
Area! Standard Units
-------
were limiting algal growth when phosphorus concentrations were very
high, prior to advanced treatment. In further support of phosphorus
control of eutrophication in Gravenhurst Bay, when phosphorus removal
was temporarily interrupted, water quality problems returned. In late
1975, a new sewage treatment plant was brought into operation; for
the first six months of its operation Cfrom November to April) removal
efficiency was about 40 percent as compared to 90 percent removal at
the old plant. The following June a bloom of Aphanizomenon flos-aquae
was present, chlorophyll ^concentrations increased to pre-1971 levels
and transparency was reduced from 3-5 m in the previous year to less
than 1 m. Later in the summer, three months after efficient phosphorus
removal was once again operating, the degradation of water quality was
reversed (Dill ion et_ aj_., 1977).
Similarly, Lake Erie's western basin has recently shown a reduction
in near-shore phytoplankton densities following a decrease in phos-
phorus loadings (Nichols et_ al_,, 1977). Plankton samples were collected
weekly at the Union Water Treatment Plant in Kingsville, Ontario
between 1967 and 1975. Phytoplankton biomass had decreased steadily
since 1971, so that by 1975 there had been a 42 percent reduction over
the mean biomass calculated for 1967-1970. Phosphorus loadings to the
lake began to decline in the early 1970s as a result of phosphorus removal
at sewage treatment plants, legislation banning phosphate detergents and
reductions in industrial discharge. Phosphorus concentrations decreased
40 percent from an average of 62 mg/1 in 1967-1970 to 37 mg/1 in 1976.
The role of phosphorus in eutrophication is more complicated in
flowing waters, particularly estuaries. Flowing waters with a heavy
sediment load are often limited by light, rather than a nutrient.
Pomeroy et_ a]_. (1972) contended that phosphorus limits primary produc-
tion only in the most sediment-free estuaries; no estuary in the
southeastern United States has shown evidence of phosphorus limitation.
The upper part of the Cheasapeake Bay is vastly influenced by the
Susquehanna River and is phosphorus limited tPritchard, 1972). A
34
-------
series of dams and reservoirs along the lower course of the Susquehanna
trap much of the sediments it carries, so that the river water is
relatively clear at the point where it joins the Bay. Algal blooms,
particularly Anacystis sp.. have, since 1968, appeared more frequently,
lasted longer, and covered more area in the upper bay. The lower
portion of the Cheasapeake Bay is probably not phosphorus limited
throughout the year; the limiting nutrient may change from nitrogen to
phosphorus to a vitamin, depending on the season. Fournier (1966) found
that phosphorus limited production in September, trace metals and
nitrogen in October, and nitrogen in late March, April and May. The
shallow estuaries near Beaufort, North Carolina also appeared to be
limited by nitrogen and phosphorus, although nitrogen is probably the
primary limiting nutrient (Thayer, 1974). Although Knudson and Belaire
(1975) stopped short of defining the limiting nutrient in a Texas bayou
(a shallow, tidal stream,), their algal assays confirm the biostimu-
latory effect of a secondary sewage effluent as compared to tertiary
effluent with the phosphorus removed. Their study was in response to
repeated fish kills caused by oxygen depletion resulting from the
respiration of dense algal blooms. Anoxic conditions could also have
resulted during periods of low rainfall and slight mixing of fresh
and saline waters. Waite and Mitchell (1972) found that both phosphorus
and nitrogen stimulated the growth of the estuarine benthic alga Ulva
lactuca.
A controversy erupted a few years ago over whether carbon or
phosphorus limited algal growth in freshwater- Because of the vast body
of literature accumulated since then which supports phosphorus limita-
tion, it is generally agreed at the present time that phosphorus load-
ings are the principal causative factor in the overproduction of
phytoplankton. In most lake systems, enough carbon and nitrogen can
invade from the atmosphere to allow eutrophication to proceed in pro-
portion to phosphorus loadings (Schindler, 1977). The role of carbon
and nitrogen in eutrophication is still not completely understood,
however.
35
-------
While phosphates induce eutophication problems in surface waters,
their availability in terrestrial systems has helped to increase crop
production and, in some cases, can benefit water quality. Fertile land
is better able to support the vegetatfve cover that can reduce soil
erosion and nutrient loss from land to water- Nevertheless, agricul-
tural runoff continues to be a major source of phosphorus in surface
waters.
IV. Critical Phosphorus Concentrations
Eutrophication is well understood in a qualitative sense; phos-
phorus content is associated with trophic state, standing crop, and
productivity in most fresh waters. Nevertheless, definition of the
critical phosphorus concentrations in surface waters has been attempted
only recently. Variables including flow rate, depth, turbidity and the
concentrations of other nutrients determine the effect that phosphorus
will have. The threat of eutrophication resulting from phosphorus is
lessened in flowing, turbid, or deep waters, and in waters where phos-
phorus is not the limiting nutrient.
No national criterion on total phosphorus has been established by
EPA to prevent eutrophication (U.S. Environmental Protection Agency,
1976a). Some guidelines are available which define, in a general sense,
the levels at which phosphorus is expected to become a problem.
Obviously, these guidelines are not steadfast rules for all conditions
since there are natural conditions which would require consideration of
more or less stringent levels. Insufficient evidence exists to
establish universally safe phosphorus concentrations or loads,
according to Lee (1977).
Mackenthun (1973, p. 176} suggested that, to prevent nuisance
aquatic growth, total phosphorus in flowing waters should not exceed
100 ug/1 at any point; 50 ug/1 P should not be exceeded at the point
where streams enter a lake or reservoir. Vollenweider's (1968, p. 65)
36
-------
survey of the limnological literature allowed him to suggest a danger
level of 20 ug/1 total phosphorus in lakes. Sawyer (1947) determined a
critical level of inorganic phosphorus (10 ug/1 P) at the time of spring
overturn that would cause nuisance algal blooms in summer. For estua-
ries, Ketchum (1969) cited Yentsch's unpublished work which suggested
that a value of 2.8 ug-at P/l (86.8 ug P/l) as the appropriate upper
limit of unpolluted water. Ketchum1s own values of 2.55 ug-at P/l in
winter and 1.7 ug-at P/l in summer are based on oxygen supply in photo-
synthesis and oxygen demand, and are meant to be conservative danger
signals in evaluating the eutrophication of estuaries.
Many researchers have attempted to define the impact that various
loadings of phorphorus have on water quality. The available models
range in complexity from Vollenweider's (1968) single nutrient loading
concept to the multi-nutrient simulation models described by Chen et al.
(1975). There is some question as to whether or not complex ecosystem
models are really required for decisions made on the control of phos-
phorus loadings (Tapp, 1976). Lake phosphorus models are far better
developed than estuarine or stream models. Although the models are
still evolving, a cursory review of the more simple lake models is
warranted. These particular models have been used to describe the
effect of varying phosphorus loadings on a large number of lakes.
Vollenweider (1968) was the first to attempt to define the
relationship between phosphorus loading rates and lake trophic status.
Using data from North American and European lakes, he initially plotted
2
annual total phosphorus loading (g/m /Vr) against mean depth. He
empirically defined permissable loading levels (those which maintain
a lake in an oligotrophic state) and dangerous loading levels (those
which promote eutrophication) based on the known trophic state (as
determined by knowledgable limnologists) and relative loading levels
of each of the lakes. As shown in figure 3, deep lakes are capable
of assimilating higher loadings within a given trophic state than
are shallow lakes.
37
-------
10
oo
oo
CM
E
Q
O
00
-------
More recently Vollenweider 0975) refined his Initial model to
include hydraulic residence time as well as depth [Figure 4). This
model relates annual phosphorus loads to the mean depth divided by the
hydraulic residence time. Tolerance loadings were empirically estab-
lished based on the case where the mean depth divided by the retention
time was less than 1. This solution was used to project the tolerance
line throughout the commonly occurring ranges of mean depth divided by
retention time. The upper line was called the dangerous limit; it was
two times the permissible limit, the lower line. With this model,
identical loadings may promote eutrophic conditions in lakes with a
small mean depth to hydraulic residence time ratio, or oligotrophic
conditions in lakes where that ratio is large. Vollenweider (1976)
3
further refined the model using average inflow concentration (mg/P/m )
versus water residence time. Figure 5 illustrates the inflow concen-
tration and residence time associated with certain oligotrophic,
mesotrophic and eutrophic lakes and the permissible and dangerous
phosphorus loading levels.
Closely related to Vollenweider's latest model is that of Larsen
and Mercier (1975, 1976). Their approach is derived from a mass
balance model of phosphorus and related the average incoming phos-
phorus concentration to the phosphorus retention coefficient. Figure
6 illustrates this relationship; it is fitted with lakes of known
trophic condition. The upper curve in figure 6 represents the
transition from a mesotrophic state to eutrophic; the lower,
oligotrophic to mesotrophic. Larsen and Mercier selected in-lake
total phosphorus concentrations of 10 and 20 mg/1 to establish
permissible and dangerous loadings.
Dillon (1975) also used the mass balance approach and defined a
relationship between mean depth and a factor derived from the total
annual phosphorus loading 0-), the phosphorus retention coefficient
(R) and the water residence time (/). Figure 7 illustrates this
relationship along with permissible and dangerous loading rates.
39
-------
-^ 10.0.
-S
LU
Q
<
O
_i
00
D
cc
o
I
0.
CO
O
X
a.
O
D
2
2
_
b
0.1
0.01
II 1
1 1
1 III
DANGEROUS _J
"EUTROPHIC"
// /
L,Q)=0.20
L(0)=0.15
L(0)=0.10
'OLIGOTROPHIC"
I 1 1 1 II III
1 1 1 1 1 1 III
1 1 1 1 1 1 1
0.1
1.0
10.0
100.0
'1
MEAN DEPTH (m) /MEAN HYDRAULIC RETENTION TIME (yrs.)
FIGURE 4. VOLLENWEIDER'S (1975) PERMISSIBLE AND DANGEROUS PHOSPHORUS LOADING RATES.
-------
1000
n
.E
a
01
g
UJ
o
z
U-
o
<
EC
UJ
100 -
?V
0.1
10
100
1000
Figure 5. VOLLENWEIDER'S (1976) LATEST PHOSPHORUS LOADING CURVES.
-------
<
CC
LLJ
o
z
o
o
CO
ID
CC
o
I
Q.
CO
O
I
a.
O
O
<
LU
100.0 -
10.0
0.0 0.1
PHOSPHORUS RETENTION COEFFICIENT (Rexp)
FIGURE 6. LARSEN AND MERCIER'S (1976) RELATIONSHIP DEPICTING CRITICAL PHOSPHORUS
LOADING LEVELS. Rexp = 1 -OUTFLOW LOAD
INFLOW LOAD
-------
-p.
oo
0.01
10.0
MEAN DEPTH (METERS)
100.0
FIGURE 7. DILLON'S (1975) DEFINITION OF CRITICAL PHOSPHORUS LEVELS.
L = PHOSPHORUS LOADING; R = PHOSPHORUS RETENTION COEFFICIENT;
f> = HYDRAULIC FLUSHING RATE
-------
Dillion and Rigler (1975) approached the problem of defining
critical phosphorus loads from a slightly different point of view.
They were able to predict the in-lake spring phosphorus concentration
using phosphorus loading, lake morphometry and hydraulic budget
information. The spring phosphorus concentration determines the amount
of chlorophyll a^ and transparency. Permissible phosphorus loadings
could then be determined, depending on the chlorophyll ^concentrations
desired in the lake.
Additional simple models, as well as complex simulations, exist
for the prediction of safe phosphorus levels. The examples cited here
illustrate the major thrust in simple models. It is obvious that the
impact of phosphorus loadings on surface waters is difficult to pre-
dict universally due to the variability of aquatic systems and the
plethora of factors affecting phosphorus availability and ecosystem
response.
V. Effects on Human Populations
Besides the radical effects of eutrophication on aquatic
communities, human populations using lake resources are also directly
affected. Nuisance algal blooms destroy the recreational and aesthe-
tic values of lakes, decrease the value of lakeshore property, and
increase the costs of water treatment. Eutrophication has had an
impact on the commercial fishing industry in Lake Erie. The following
sections contain discussions of these problems.
Mater Treatment Problems
Increased algal growth, characteristic of eutrophication, can
cause several water treatment problems, including shortened filter
runs, objectionable tastes and odors, and occasional severe clogging
of intake screens. These problems lead to increased water treatment
costs related to the use of greater quantities of chemicals for
44
-------
adequate treatment, such as alum, lime and activated carbon, and
cleaning of water intake screens. A decrease in the volume of water
available to consumers, because of clogged intake filters, is also a
consideration. According to a 1967 survey of state sanitary engineers,
56% of the total municipal surface water supplies of the United States
are affected by water treatment problems associated with eutrophication
(Task Group Report, 1967). Silvey et_ a]_. (1972) list Anabaena,
Aphanizomenon, and Oscillatorta as the species causing most taste and
odor problems; they are also often associated with eutrophic conditions.
Water treatment costs are sometimes difficult to relate to water
quality. Generally, chemicals for water treatment are used in quan-
tities determined by historical practice or "eye ball" criteria. Moni-
toring of raw water and the use of appropriate amounts of chemicals for
treatment are rare practices (Elly, 1977). An additional consideration,
which may mask or eliminate the costs of water treatment, is the plant
design. Intake pipes can be designed or situated in areas to avoid the
problems associated with eutrophic waters. Several documented cases of
water treatment problems and design .avoidance associated with
eutrophic waters are contained Tn the literature as follows.
Eutrophication of Lake Erie has been an important cause of in-
creased treatment costs in Cleveland, Ohio. Taste and odor have been
perennial problems for many years I requiring the additional use (and
I » ~
cost) of activated carbon and other chemicals. The problems result from
increased algal growth causing anoxic conditions in the hypolimnion and
the consequent release of some chemicals (iron, manganese) from the
sediments (Elly, 1977).
Serious problems occured in the summers of 1966 and 1967 at the
Crown Filtration Plant in Cleveland (Potos, 1968). Prevailing southerly
winds pushed surface waters to the northern shore of the lake, causing a
shift in the thermocline. In the north, the thermocline became deeper
while ft rose in the south. As a result, the water intake drew from the
45
-------
hypolimnion instead of the epilimnion. Dissolved oxygen in the hypolim-
nion was very low, and peak iron, manganese, and phytoplankton concen-
trations existed. Sediment release of nutrients, iron, and manganese is
assumed to have occured under anoxic conditions. Since the hypolimnion
was still in the euphotic zone, the phytoplankton responded to the
nutrient release. Genera linked to musty taste and odor production were
found in water samples: Chlorella. Fragilaria, Melosira. and Mongeotia.
The algae and/or mineral content of the water were responsible for the
taste and odor problems, while a broken intake, allowing the entry of
more turbid water, aggravated the problem. Chlorine demand of the raw
water increased three to five times the normal value, due in part to the
high concentrations of reduced iron and manganese. But heavy chlorina-
tion accentuated the taste and odor problems, requiring heavy doses of
alum to correct. Vertical extension of the intake pipe has been recom-
mended (Potos, 1968), while control of the eutrophication problem
resulting from excess nutrient loadings has also been advised (Elly,
1977).
In August, 1974, the sand filters at Cleveland's Division Avenue
Water Filtration Plant became clogged by massive amounts of the
filamentous alga Oedogonium. The shutdown lasted for three days,
leaving some of the 400,000 residential, commercial, and industrial
users without water. Increased quantities of chlorine, carbon, alum,
and permanganate were required immediately before the plant shutdown,
while massive amounts of chlorine were used to declog the filters. The
probable cause of the bloom of Oedogonium has been attributed, in part,
to local nutrient buildup in the eutrophic near-shore waters (Elly,
1977).
An earlier report (Poston and Garnet, 1964) identified several
phytoplankton species which cause additional problems in Cleveland.
Shortened filter runs, particularly during late winter and early spring,
have occurred due to large phytoplankton populations composed primarily
of Melosira, and also Tabellaria. Asterionella, Cyclotella and
46
-------
Stephanodicus. Taste and odor problems are frequently caused by
Apham'zomenon.
The overall increase in water treatment costs in Cleveland has
risen from $4.50 per million gallons treated in 1968 to $9.00 in 1975.
These figures reflect only the treatment costs associated with producing
potable water. Costs related to inflation, fluoridation, wages and
operating expenses were excluded. According to Elly (1977), the chief
engineer has attributed the increase to increased taste and odor pro-
blems related to the rate of eutrophication of Lake Erie and changes in
the chemicals used and chemical suppliers.
Poston and Garnet (1964) investigated water treatment problems
related to algae on Lake Michigan and Lake Erie. They concluded that
Tabell aria is the phytoplankton causing the most severe problems with
shortened filter runs in Lake Michigan. Taste and odor problems on Lake
Michigan were caused primarily by Dinobryon and Uroglenopsis, while
Anabaena, a blue-green algae, presented the biggest taste and odor
problem in Lake Erie. Activated carbon, although expensive, is used
successfully to overcome taste and odor problems in the water supplies
of larger municipalities. Treatment problems related to algal growth
have been minimized on the Great Lakes by locating the water intakes at
depths and sites to avoid such problems.
The incidence of taste and odor problems in drinking water, as well
as treatment costs, appears to increase as reservoirs age. Elly (1977)
reports that costs at the Lima, Ohio water treatment plant decreased
following a change in source from an old reservoir to a new reservoir in
1958. The older reservoir developed algal and taste and odor problems
not found in new reservoirs. Prevention of these problems has been
attempted by draining unused reservoirs and burning the highly organic
bottom sediments.
47
-------
Gizzard (1976) reported that the 20-year-old Occoquan Reservoir,
which serves 600,000 customers in northern Virginia, is exhibiting
classic signs of cultural eutrophication. Periodic taste and odor
problems arise from the release of metabolic end-products from algae and
the decay of organic matter. The onset of taste and odor problems
coincides with peak production of the blue-green algae, Anabaena,
Microcystis and Aphanizomenon. Large quantities of copper sulfate are
used in the reservoir to control algal growth. Usually, alternate water
sources are used when reservoirs develop algal blooms (Owens and Wood,
1968).
Water treatment problems relating to Cladophora, a filamentous alga
that responds to eutrophic conditions, are few, according to a recent
review of the problem (Neil, 1975). Intakes for municipal water sup-
plies are generally located in deep waters, well above the lake bottom,
yet at depths where surface accumulations of Cladophora are not a
problem; the intakes are designed to avoid the problem. Poston and
Garnet (1964), however, reported that Cladophora has caused clogging on
intake screens in southern Lake Michigan for several years.
Not only do algae or their products taint water supplies, but some
are responsible for causing objectionable tastes in fish flesh. Tabachek
and Yurkowski (1976) found that several species of Oscillatoria, a blue-
green algae common to eutrophic waters, produced geosmin which is
thought to be responsible for a muddy flavor in fish. This was espe-
cially damaging to the fish farming industry in the prairie lakes of
Manitoba.
Industrial Mater Supplies
Reports on the impact of eutrophication on industrial water sup-
plies are uncommon. Taylor et_ aj_. (1977) described eutrophication-
related problems in the operation of the power plants located on the
highly eutrophic man-made cooling lake, Lake Brauning, outside of San
48
-------
Antonio, Texas. Condenser fouling resulted from the growth of peri-
phytic algae, which is enhanced by eutrophic conditions. Periphytic
algae grow and accumulate on the walls of the condenser, decreasing heat
transfer efficiency. Shock chlorination is the normal control practice;
concentration up to 1 mg/1 for 1/2-1 hour are used about 3 times per
week. The total annual cost for this treatment is low ($10,077 in
1974), indicating that periphytic fouling is not a serious problem even
with highly eutrophic water supplies.
Condenser fouling can also occur as the result of carbonate species
deposition, usually in the form of calcite or dolomite. Changes in pH,
resulting from the diurnal cycles of respiration and photosynthesis of
dense phytoplankton populations, are responsible (Taylor e_t al_., 1977).
Fouling of water intake screens is a common problem in power
plants, according to Taylor e_t al_. (1977). Costs of routine maintenance
and cleaning generally increase as eutrophication progresses. Nuisance
species, such as filamentous algae, carp and shad, are the principle
problem. A natural shift in the dominant phytoplankton from the
nuisance filamentous Chlorphyceae to Diatomaceae corrected intake screen
fouling at Lake Brauning.
In Ontario, Cladophora has been a problem with a number of major
, t
generating plants which use surface intakes. At Lakeview, near Toronto,
continuing Cladophora problems have required the extension of dikes to
ensure a clear water-intake screen. The Ontario Hydro Nuclear Station
at Pickering on Lake Ontario also uses a surface intake. Continued
clogging of water lines and occasional shut downs, costing $40,000 in
lost revenues for each occurence, required the installation of heat
exchangers at a cost of $2.7 million. Removal of Cladophora and other
trash (up to 5.6 cubic meters) from intake screens is a daily chore
during certain seasons (Neil, 1975).
49
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Problems with the treatment of eutrophic lake water for bioler and
feed water were reported by Taylor et_ aj_. (1977). Removal of organics
and suspended solids, associated with phytoplankton growth which inter-
fere with the ion exchange process of demineralization, is the principle
problem. In 1975, total costs for the treatment of boiler feed water
amounted to $2.14 to $3.13 per 1,000 gal.
Toxic Algae
Some of the algae that respond to eutrophic conditions are toxic to
some aquatic and terrestrial animals. A summary of the hazard to
domestic animals is contained in Section II. Livestock poisonings are
not a common occurrence, even in eutrophic waters, and no data are
available on the economic losses associated with toxic algal blooms.
Toxic algae pose little hazard to humans. Most disorders may be
classified as gastrointestinal, respiratory, and dermatological.
Microcystis, Anabaena and Aphanizomenon are involved most often.
Gentile (1971) refers to cases of human intoxication by blue-green algae
in the Ohio River basin; Saskatchewan, Canada, and Wisconsin. Gorham
(1964b) and Schwimmer and Schwimmer (1968) cited several cases of
gastroenteritis associated with involuntary ingestion of toxic blue-
green algae. Public health problems associated with contaminated water
supplies are considered negligable because any toxins present would be
rapidly inactivated during treatment (Gorham, 1964b). For Microcystis
and Anabaena flos-aquae, Gorham (1964b) estimated that the minimum
lethal oral dose for a 150-lb man is one to two quarts of a thick,
smelly, paint-like suspension. He quickly discounted any danger of
voluntary ingestion, but recognized a potential problem with involuntary
ingestion. According to Gorham, toxic algal blooms apparently can be
considered nuisances and perhaps economic hazards, but not public
health problems. Gentile (1971) does not refute this, but warns that,
with acceleration of eutrophication and increased use of surface waters
5C
-------
for recreation and municipal purposes, the potential for health hazards
to result from toxic algal blooms might increase.
Property Values
It is a common assumption that the value of lake shore property
is depressed along eutrophic lakes; this assumption is difficult to
prove or quantify. Neil (1975) summarized a study by Ormerod (1970)
concerning the relationship between algae and real estate values along
the north shore of Lake Erie's eastern basin. Ormerod's analysis made
use of real estate figures derived from assessment value and multipliers
based on the relationship between actual sales dollars and assessed
value. His findings show that lake frontage with algae averaged 80 to
85% of the value of clean frontage. Property values declined steeply
with the initial accumulation of small amounts of algae, but as algal
growth increased, the rate of decline of real estate value leveled off.
This study suggested that eutrophication has caused a significant
decline in the value of property located over much of the lower Great
lakes and perhaps Lake Michigan. If a depreciation of even 10% were
applied to lake shore property values, the cost of eutrophication could
be considered "staggering".
Dornbusch et_ a]_. (1975) described a method to assess the impact of
water pollution abatement on property values. Their method can also be
used to predict the benefits, in relation to property values, of pro-
jected water quality improvements, or the costs of not improving water
quality. They compared the property values in 17 areas before and after
the correction of water pollution problems. Six of the selected areas
had been affected primarily by eutrophication-related problems; reduc-
tion of nutrient loadings in each area improved water quality. In each
of the selected areas, water quality improvements were associated with
increased property values, even when inflation costs were factored in.
The amount of increase varied with the type and size of water body,
visual and physical access to the water body, distance of the property
51
-------
from the shore, the orientation of the community toward the water, and
the improvements perceived by the community. With comparable improve-
ments in water quality, a greater increase in values was seen with
property near large lakes with good or unlimited public access, while a
smaller increase was seen in the value of property bordering small
rivers with very limited public access.
The six areas investigated with eutrophication problems were Lake
Washington, Seattle (2 sites); Green Lake, Seattle; San Diego Bay;
Brown's Lake, Wisconsin; and Lake Minnetonka, Minneapolis. Table 3
contains a summary of the problems at each area, abatement procedures,
and the property value increase.
In an earlier study, Dornbusch and Barrager (1973) measured pollu-
tion abatement benefits for single family waterfront residences at four
of the same 17 sites, including one site (San Diego Bay) impacted by
excessive nutrient loadings. Sale prices and calibrated local tax
assessments were compared before and after pollution abatement. Pro-
perty values increased from 4.2 to 8.2% after water pollution control in
the Bay, depending upon the distance (from 2000 to 100 feet) from the
water.
52
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Table 3. Summary of six case histories showing property value increases with
water quality improvements. (From Dornbusch et^ al_., 1975)
en
CO
Study Area
Lake Washington I
Lake Washington II
Green Lake
San Diego Bay
Brown's Lake
Lake Minnetonka
Principal
Land Use
residential
residential
residential
residential
residential
residential
commercial
Water Quality
Problems
1,2,3,7
1,2,3,7
2,3,4,7
1,2,5,6
4,5,6,7
1,2,3,7
Cause of ^
Pollution
1,4
1,4
2
1,4,7
1,5,6
1,4
Abatement
Procedure
sewage
diversion
sewage
diversion
dredging
dilution
sewage
diversion
sewage weed
harvest
sewage
diversion
Mean Property 3
Value, Increase
13.9
14.7
8.0
7.0
17.4
4.0
1
Water Quality Problems: 1. low dissolved oxygen 2. algal blooms 3. decreased water clarity 4. rooted
aquatic vegetation 5. declining fish populations 6. high fecal coliform counts
7. phosphorus.
'Cause of Pollution: 1. Cultural eutrophication 2. Nctural eutrophication 3. Man-made impoundment
4. Nutrients from sewage 5. Nutrients from nonpoint sources 6. septic tanks
7. other
Percentage change in real property values.
-------
Commercial Fishery - The Fish
Phosphate-induced eutrophicatton has, in some areas, induced
changes in fish populations to the extent that populations of com-
mercially valuable fish have been adversely affected. Destruction
of oxygen regimes in the hypolimnfon is especially detrimental to species
of fish and shellfish which are part of the benthic environment, either
as adults or embryonic stages.
Radical changes have occurred in the Great Lakes fishery over the
past 80 years which can be partially attributed to eutrophication.
Other stresses, including over-exploitation, toxic pollutants, chemical
contaminants, tributary damming, marsh drainage, siltation, temperature
increases and the introduction of new species, have also contributed to
the change. Smith ("unpublished manuscript) stated that of the factors
impacting fish population declines in the Great Lakes, "cultural eutro-
phication has apparently exerted the environmental stress that has been
most closely associated with the terminal decline of many of the
species to near extinction or extinction."
The Lake Erie fishery was chosen for an extensive evaluation for
several reasons. Not only does an extensive body of data exist to
define the extent of eutrophication in the lake (see section II) and the
commercial catch, but Lake Erie has traditionally been the most produc-
tive, and most diverse fishery of all of the Great Lakes. Annual
production from 1915-1965 averaged close to 50 million pounds and often
equaled the production of the other four Great Lakes combined, and
usually at least one third of the total Great Lakes catch. Apparently
the diversity of habitats and the shallow, warm character of the lake
have been responsible for the high productivity (Applegate and Van
Meter, 1970). It was felt that if eutrophication had any impact on a
commercial fishery, the impact would be most obvious with Lake Erie.
It should be emphasized that nutrient enrichment of other waters has
also had a detrimental effect on commercially important fish and
54
-------
shellfish (Perkins and Abbott, 1972; Newmann, 1972, Trent et aK, 1976;
Schneider and Leach, 1977; Ryther, 1954).
The other four Great Lakes have been impacted by nutrient enrich-
ment less than has Lake Erie. Their fishery statistics reflect the
important impact that marine invaders (sea lamprey and alewife) have had
on important commercial fish species. Populations of these invaders
were abundant in Lake Erie because suitable spawning sites were not
available for lamprey, and predators were able to check alewife abun-
dance (Smith, 1972a). Nevertheless, Smith (1972a) related deteriorating
water quality in Lake Ontario with declines of important commercial
species-lake trout, whitefish, lake herring, deepwater ciscos, burbot,
and deepwater sculpin, and warned of the similar danger in the deepwater
regions of the Upper Great Lakes as well. Smith (1972a) attributes the
loss of Lake Erie's valuable species to the vast amounts of waste added
to the lake as a result of industrialization. Oxygen depletion in the
central basin has made this large portion of the lake uninhabitable for
many fish and fish-food species, reducing fishery productivity in this
area. Tables 4-6 summarize the change and causes for change in Lake
Erie's fishery from the 1800s.
The size of many animal populations is subject to wide, natural
fluctuations. Commercial fishery statistics reflect natural variations
in fish population size but are subject to market factors as well.
They are not necessarily true indicators of abundance. Poundage landed
is a more accurate reflection of abundance for the more valuable fish;
but fish with little or no value in the market place will not be
fished for as heavily. State restrictions and bans resulting from
chemical contamination also limit the poundage landed of certain species.
Because of natural fluctuations in population size and price fluctuations,
it is difficult to accurately relate landings to abundance of even the
more valuable fish without a perspective of several years. Analysis of
many years of commercial catch statistics can be a valuable tool for
measuring the change in fish populations over time. Several good
55
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Table 4- Order of yield of the principal commercial species of fish caught in Lake Erie in
selected years from 1908-75 . ("Suckers" include both white and redhorse species;
catches of "channel catfish" usually include some bullheads before 1952).
Order
of yield
1
2
3-
<
5
6
7
8
9
10
19082
Lake herring
Slue pike
Carp
Walleye
Northern pike
Sauger
Yel low perch
Lake whi tef ish
Suckers
-
19153
Blue pike
Lake herring
Carp
Sauger
Lake whi tef Ish
Yel low perch
Wai leye
Freshwater drum
Suckers
-
1920
Lake herring
Blue pike
Carp
Sauger
Yel low perch
Whitefish
Freshwater
drum
Suckers
Walleye
Channel cat-
fish
1930
Blue pike
Yel low perch
Freshwater
drum
Whitefish
Carp
Wai leye
Suckers
Sauger
Lake herring
White bass
Blue pike
Whitefish
Yel low perch
Walleye
Freshwater
drum
Carp
Suckers
Lake herring
Sauger
White bass
1950
Blue pike
Wai leye
Yel low
perch
Freshwatei
drum
Whitefish
Carp
White bass
Channel
catf i sh
Lake
herring
Suckers
960 1
el low V
perch
melt I
reshwater
drum
White
Bass
Carp
966
e 1 1 ow
perch
mel t
:Carp
Freshwater
drum
Whi te bass
1
Walleye
Channe 1
catfish
Suckers
Coldf Isf
Bull
head
Walleye
Channe 1
catfish
Suckers
Goldfish
Bui Iheads
1975
Smelt
Ye 1 1 ow
perch
Whi te bass
Carp
Freshwater
d rum
Channe 1
catfish
Wat leye
Bui Iheads
0,.- .,;- 4
Sunf ish
Adapted from Applegate and Van Meter, 1970.
Ranking of yields of all but lake herring inferred In part from descriptive reports (Canadian landings not reported for majority of species).
3
Ranking of fourth through ninth species based largely on U.S. records; reports of Canadian landings of sauger. freshwater drum, and suckers lacking.
"-.5u;-,f.-,..Jh ca-:or.t ir, CMr.acUcr, waters only.
-------
Table P. Average combined annual United States and Canadian production (thousands ol pounds) ol iiiajor (,bu..i.-rciui
fishes' from Lake Erie for specified time periods 1879-1975 (after Hartman, 1973).
T3
0
U
O.
i
1879- I9066
I9IO-19I66
1920-I9296
1930-1934
1935-1939
1940-1944
1945-1949
1950-1954
1955-1959
1960-1964
1965-1969
1970-1975
c
o
0>
Ol
01 >-
(TJ *-»
.
1,052
77
39
39
31
22
25
14
14
4
1
Northern
Pike
1,356
1,250
77
62
29
37
21
12
14
2
2
6.28
en
c
0) u
ro U
-1 X
25,625
27.201
14.126
764
1,070
283
6,067
475
128
8
rg
L.
4>
at
to
to
3,700
3,656
2,437
1,943
1.414
878
567
354
21
1
--
jr
VI
u
SL
2,402
2,945
1,675
2,094
2,696
4,058
4,701
2,297
749 ;
19
5
2'
01
u
m
10.7977
9,277
11,292
14.623
18,526
13,517
12.509.
13,535
10,078 ''
3
0)
u>
i
_««-
1,756
1,577
2.113
3,515
3.779
5.807
7,566
10,267
1.484
941
146
0)
o.
1
a
2,791
3.017
5,356
12,382
6.444
3.869
4;245
6,784
19,540
20,219
26.662
17,428
IF
in
--
k
--
--
890
4,345
13.508
13,489
13,410
Freshwater
drum
1,061
2,499
2,367
2.381
3.359
3,624
3,965
3.492
4,020
5.770
3,465
1,224
in
1/1
ra
ca
o
611
383
360
447
655
553
701
3,485
5,092
4. Ill
2.439
2,619
U
0)
u
D
CO
1,350
1,120
1,090
1.462
980
628
506
661
413
333
224
151
O
-------
Table 6. Summary of Fish Species in Lake Erie Suffering Recent Population Decimations (From
Hartman, 1972, 1973; Applegate and Van Meter, 1970; Smith, 1977C).
Suspected Contributing Cause of Population Decimation
CD
CM
c:
o
tn
oo
Species
Lake Trout
Sturgeon
Northern Pike
Lake Herring
Whitefish
Sauger
Blue Pike
0 >>
r- X
+-> 0
CJ CO
^ S- QJ
S-
C/>
Related to Eutrophication
o *>
X
X
X
X
X
X
.^ > ^>-}
n3 >^J
+j n3 o^
r- -!-> C
1 O 3 'r-
$- r -Q E
QJ Q. -1- E
> x s- to
o uj 1 a
X
X X
X
X
X
X X
X
t- o
OJ =3-r-
CL) -t-^ 4-*
CD rO fO
(d S_ 3
JT C CL) +>
W -r- Q- O
t. ns E 3
(« S- CD r
S Q 1 U-
X
X
X
X
X
CO
M
-o
X
X
Resulting from both erosion and accumulating organic material produced by nutrient enrichment.
?
"Of particular importance in regard to availability of or access to suitable spawning grounds.
-------
historical summaries of the Lake Erie fishery are available (Applegate
and Van Meter, 1970; Hartman, 1972 and 1973) while the raw data on
volume and value of fishery products are summarized annually since
1970 by the National Marine Fisheries Service, and previously by the
Bureau of Fisheries of the Fish and Wildlife Service. A recent GAO
report (Government Accounting Office, 1977) contains a table (Table 3,
App V) which summarizes the Lake Erie catch statistics by species since
1879. The Appendix contains a list of the common and scientific names
of fish species mentioned in the report.
Prior to a recognized phosphate-induced eutrophication problem in
Lake Erie, severe changes were evident in the fish community. Popula-
tions of several valuable species suffered decimations prior to 1930.
Over-exploitation of the fish stock and elimination of suitable stream
spawning grounds, or access to them, are usually blamed for the initial
decline of these populations. Environmental degradation resulting from
phosphate-induced eutrophication has further contributed to the biolo-
gical extinction of some populations and has prevented the comeback of
others in Lake Erie.
Lake trout populations in Lake Erie were decimated by overfishing
in the late 19th century. The probably small population of slow-
growing, late-maturing, long-lived fish could be expected to be elimi-
nated by the fishing pressure of the turn of the century. The complete
elimination of the species, however, was after 1937 (Smith, 1972c) and
probably due to the destruction of suitable habitat for growth and
reproduction. Nutrient enrichment, contributing to the destruction of
summer oxygen regimes and siltation of spawning grounds, is the probable
explanation for the biological extinction of lake trout in Lake Erie.
Lake trout are currently being stocked in Lake Erie in small numbers
(Zarbock, 1977), but there is no evidence that the population is sus-
taining.
59
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Sturgeon populations declined rapidly between 1895 and 1919, and
steadily after that time. The sturgeon is considered a rarity in the
lake today. When the fish was abundant, little of the flesh was
marketed; the roe was important for caviar, the bladder used in the
manufacture of isinglass, and the carcass for oil. Large numbers were
simply destroyed by fishermen because the large, powerful fish frequently
caused heavy damage to fishing gear- Since sturgeon mature very slowly
(some spawn for the first time at age 20), over-exploitation is the
probable cause of their initial decline. Other factors, however, have
also contributed: destruction of the bottom habitat by industrial,
agricultural and domestic pollutants, and the damming of tributaries and
drainage of marshes, with the consequent obstruction of spawning runs.
Smith (1968) noticed that even with fishing pressure aleviated by
partial protection, Lake Erie's population has continued to decline.
He blames the inhibited recovery on the continued pollution of shallow
spawning areas and eutrophication (S.H. Smith, personal communication).
The third abundant species eliminated in Lake Erie was the lake
herring or cisco, whose numbers decreased markedly in 1925 and never
recovered, except for a brief comeback in 1945-46. It has been com-
mercially extinct since 1957. Landings of 10 to 50 million pounds were
recorded in the 10 years prior to the collapse. Overfishing and possibly
environmental change may have interacted to produce the sharp decline in
lake herring stocks in the 1920s. The subsequent reduction in the mid-
1960s was more likely a result of environmental stress (e.g. the high
oxygen demand at the mud-water interface where the eggs'incubate), as
evidenced by the slow growth of the fish shortly before this time
(Smith, 1968 and unpublished manuscript). Beeton and Edmondson (1972)
proposed that overfishing was not the major cause for the population
declines of lake herring. Rather they stated that pollution or eutro-
phication, or both, was probably responsible for the destruction of
suitable habitat in parts of the lake, tending to concentrate populations
in smaller areas where exploitation could continue.
60
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Northern pike, the fifth most abundant species landed in Lake Erie
in 1908, is also now commercially extinct. Destruction of natural
spawning grounds, due to the construction of dams in the early 1900's,
and drainage of marshes for farmland1is the most likely cause for the
collapse. Enrichment of shallow spawning areas can be expected to keep
the population low (S.H. Smith, personal communication).
Whitefish and blue pike, too, have been impacted by eutrophication.
Annual whitefish catches fluctuated between 1 and 7 million pounds from
1915 to 1954, and have gradually declined to 1-10 thousand in the past
10 years. Intensive exploitation is a significant factor in the decline,
but environmental conditions, especially temperature and oxygen levels
were undoubtedly important in recent decades. The whitefish require
cold, well-oxygenated bottom waters in summer, and silt-free lake
spawning areas for successful reproduction. Like the lake trout, it is
at the southern end of its zoogeographical range, and even natural
temperature cycling could have had a severe impact on the success of
some year classes. Nutrient enrichment, especially in the western and
central basins of Lake Erie, has eliminated suitable whitefish habitat
through the depletion of summer oxygen regimes, as well as the sedimen-
tation of decaying algae on spawning sites. Only remnants of the
population remain in the deep eastern basin, which is least affected by
eutrophication and intensive fishing.
Blue pike landings also declined precipitously in the late 1950s.
That population, while extremely important in the Lake Erie fishery,
naturally experienced wide fluctuations in harvest, ranging from 2 to 26
million pounds annually in the years from 1915 to 1957. Since that
date, blue pike have declined to less than 1000 pounds in the last
decade, and are apparently now biologically extinct (Hartman, 1973;
Nepszy, 1977). Although subjected to intensive exploitation., the rapid
decimation of the population implies an additional severe stress. The
first recordings of oxygen depletion in the central basin coincided
with the blue-pike decline of the late 1950s. Blue-pike were most
61
-------
plentiful in this basin which was also their major spawning area (Smith,
1972c). Nepszy (1977) suggested that summer oxygen depletion in the
central basin may have forced the blue pike to concentrate in the more
suitable waters of the eastern basin, where they may have been more
vulnerable to exploitation. He believed that exploitation and habitat
destruction at critical times were the most serious stresses on the blue
pike population, while rainbow smelt may have been another factor. The
final blow may have resulted from hydridization with the walleye (Regier
et_ al_., 1969).
With the elimination of large populations of valuable fish, the
fishery began in 1960 to depend more heavily on yellow perch, walleye,
and smelt. Since that time, walleye and yellow perch populations have
been declining. Landings of walleye peaked at 16 million pounds in the
late 1950s, but fell precipitously in the 1960s, averaging 1.4 million
pounds annually between 1960 and 1964, and 0.9 million pounds annually
between 1965 and 1969. Since 1970, landings have not exceeded 252,000
pounds and in 1975 walleye production had been reduced to 2 percent of
that in the peak year of 1956 (Schneider and Leach, 1977). Increased
Canadian fishing pressure and catch efficiency with the use of sonar,
nylon gill nets and ship-to-shore radio are blamed for the rapid decline
in walleye catches. Populations in the western and central basins have
also been impacted by the depletion of summer oxygen levels in the
hypolimnion, siltation of spawning areas and losses in valuable benthic
food organisms (e.g. Hexagem'a) (Schneider and Leach, 1977). During the
years of peak walleye production the bulk of the walleye catch came from
the western and central basins while the contribution from the eastern
basin was a small but consistent portion of the total catch. After the
population decline and fishing bans in the western and central basins,
the small, but persistent production from the eastern basin came to make
up the bulk of the walleye catch. According to Schneider and Leach (1977)
exploitation and nutrient loadings were the most important factors in
the decline of walleye populations in the western basin. Smelt, intro-
duced into an inland lake in Michigan in 1912, may also have caused
62
-------
additional stress on walleye populations (Reiger e_t al_., 1969), but
alewife and sea lamprey populations were too sparse to impact walleye
(Schneider and Leach, 1977). Strong walleye year classes in 1970
and 1972 indicate that the environment still allows reproduction to
occur. According to recent evidence, walleye stocks are apparently
recovering; commercial fishing bans in Ontario, Ohio and Michigan due to
mercury contamination may be partially responsible (Nepszy, 1977).
Yellow perch has regularly been an important species in the Lake
Erie fishery. After decimations of the whitefish, lake herring, and
blue pike populations, it became far more important. Since 1955, yellow
perch has dominated the annual landings; their numbers reached an all-
time high in 1969 with 33 million pounds landed but declined to 10
million in 1975. The last highly succesful catch was in 1965, and in
1976, Ohio reported the lowest catch in the past 15 years (Zarbock,
1977).
Smelt was the most abundant fish in the commercial catch from Lake
Erie in 1975. In the 15 years before that time it ranked second, behind
yellow perch. Smelt is harvested primarily in Canadian waters; there is
evidence that this area of the lake is preferred habitat. Smelt has
been used for farm-animal food, but its value for human consumption is
increasing. S.H. Smith (personal communication) noted that developments
in the U.S. industry, eg. trawling and advanced processing plants, would
do much for the U.S. smelt fishery.
White bass is expected to become a more important resource as the
abundance of high-value species declines. Sheepshead (freshwater drum)
populations are currently underexpolited because market acceptance of
this species has been limited. Sheepshead are estimated to exceed all
other fish species in biomass, but there may be greater numbers of
shiners and gizzard shad. Channel catfish has supported a relatively
stable fishery. A good market for live catfish exists but there is some
evidence that populations are being fished too heavily. Low market
63
-------
demand has impaired exploitation of populations of coarse fish such as
carp, goldfish, suckers, and bullheads, yet the carp may rank second in
biomass in the western section of the lake where it thrives in enriched
waters.
Commercial Fishery - The Industry
Data contained in the Fishery Statistics of the United States
(National Marine Fisheries Service) and a review by Applegate and Van
Meter (1970) were used to analyze the changes in the Lake Erie fishery
in the past 25 years. Several striking trends in the fishery are obvious,
The combined Canadian and United States production from Lake Erie
he changed little over the past quarter century. Fluctuations in the
tonnage landed are considered normal. On the other hand, the amount of
fish taken from Canadian waters has increased remarkably, while the
current United States catch has declined to less than one-third of its
catch in the early 1950's. American fisherman caught 55% (25.5 million
pounds) of the fish taken from Lake Erie during the period from 1950-
1955; the same figure for 1970-1975 is 21.2% (8.82 million pounds).
There are several explanations for the decline in the American fishery.
The rapid expansion of the Canadian fishery around 1950 is one explana-
tion for the increase in percentage taken by Canadian fishermen.
Although not easily documented, declining catches in U.S. waters may be
an indication that the preferred habitat of the most important fish is
in Canadian waters. There is some evidence that suggests this might be
true for smelt. Less restrictive regulations on harvest methods in
Ontario and lower labor costs have fostered a sizeable smelt fishery
there (W.L. Hartman, personal communication).
While the cause of the decline in the U.S. fishery is unclear, it
is obvious that the fishery is not nearly as important as it was 25
years ago. The dollar value of the catch decreased along with the
tonnage and the marketability of the fish species in the late 1960s but
64
-------
since then the value has doubled ($2.7 million in 1976), even though the
poundage has remained about the same. In Lake Erie, low value species,
usually discarded from the catch, comprised 37% of the catch-by-Weight
in haul seines and 26% of that in trap nets in 1969. It has been
estimated that an additional 2.8 million pounds could have been harvested
from the lake if a suitable market for these fish existed (Zarbock,
1977). Yellow perch, although important, was long considered of
secondary value when compared to species such as walleye, whitefish, and
blue pike. With the elimination of the more valuable species, producers
have come to rely heavily on yellow perch to remain in business. Smelt
are largely taken only in Canadian waters; the increase in their value
for human consumption has done little for American fishermen. Sheeps-
head (freshwater drum) have traditionally been considered a noxious fish
and are usually sought by fishermen only when other, more valuable
species are unavailable. Because of difficulties in marketing the fish
for human consumption, sheepshead is one of the most underexploited
major populations in the lake. The development of new markets for this
abundant fish would help fishermen economically and perhaps benefit the
more desirable walleye, yellow perch, and white bass; it is felt that
sheepshead compete for space with these species. Fishing effort for
white bass, once thought an incidental species, is expected to increase.
The market for channel catfish has been stable for the past 20 years and
the price paid for the landed fish is stable, as well. Carp, goldfish,
suckers and bullhead are in low demand and the market is subject to
unstable prices (Applegate and Van Meter, 1970). The less desirable,
low-priced species are marketed for pet food processing but can no
longer be used as food for captive fur bearing animals (e.g. mink)
because of PCB contamination.
The impact of the declining Lake Erie fishery in the U.S. is
reflected by the number of people and vessels employed in catching fish.
From 1950 to 1962, the industry employed between 1,132 and 855 (mean,
963) regular, part-time, and casual fishermen. The total gross tonnage
of fishing vessels ranged from 1,620 to 1,214 (mean, 1388) for the same
65
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period. Since that time, the average number of fishermen decreased to
392, and average total vessel gross tonnage decreased to 488 for the
years 1970-1972. In Ohio and Pennsylvania, the number of plants engaged
in the processing and wholesale manufacture of fish products decreased
by the early 1970's to less than half (mean, 33) of the number operating
in the 1950's (mean, 73), but the number of people employed in these
activities remained fairly constant.
Applegate and Van Meter (1970) warn that unless markets for the
medium and low-value fish can be found, U.S. fishermen on Lake Erie are
destined for bankruptcy. Yellow perch, although abundant, will not be
able to keep the industry solvent. The loss in the fishery resource
attributable to eutrophication alone is impossible to quantify in dollar
value. It cannot be denied, however, that eutrophication of Lake Erie
has had a very significant effect on the U.S. fishing industry and is at
least partially responsible for its decline. While the significance of
eutrophication in past fishery depletions remains to be quantified,
Smith (1972a) recognized the importance of favorable water quality to
the maintenance of sustaining fish stocks in the future. Fishery
restoration programs in the Great Lakes will futile unless adequate
measures are taken to create the proper water quality conditions neces-
sary for the maintenance of fish stocks. Eutrophication is one of
several threats to the success of fishery restoration programs in the
Great Lakes.
Effects on Sport Fishing and Other Forms of Recreation
Sport fishing trends are far more difficult to follow because of
the paucity of uniform regional data. Because of the recent growth of
sport fishing, more interest is being expressed in a standarized system
for sport fishing data within the Great Lakes region. Of the data
available, as reported to the Great Lakes Fishery Commission by state
and provincial agencies, yellow perch comprised 60% of the total sport
catch in the Michigan waters of Lake Erie in 1975, and 47% of the sport
66
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catch in Canadian waters of the lake in 1976 (Zarbock, 1977). Walleye
and smallmouth bass made up 13% and 10% of the sport catch, respectively,
in the Canadian waters of Lake Erie in 1976, and were the most sought
after fish. White bass, freshwater drum and sunfish were also caught.
There is no available information on the impact that nutrient
enrichment has had on the sport fishery. Traditionally, however,
nutrient enrichment has been a standard management technique in parts of
Europe, Asia and Africa where the production of commercial fish in small
lakes and ponds is important. The addition of limited amounts of
fertilizer is supposed to increase the productivity of the ecosystem and
ultimately result in a larger carrying capacity of harvestable fish. In
the United States, fertilization of lakes and ponds is usually employed
for the production of sport fish and primarily in the southeast where
the soils and lakes are infertile. Fertilization of lakes and ponds
outside of this area is not a widely accepted practice. The problems
associated with intentional fertilization, i.e. nuisance algal blooms
and oxygen depletion resulting from algal respiration and/or decom-
position, are the same as those associated with cultural eutrophication
(Bennett, 1971). In many areas where artificial fertilization has been
attempted salmonid (trout) and coregonine (ciscos and whitefish) fishes,
which require cold, well-oxygenated water, have been eliminated. Many
of the changes resulting from artificial fertilization are harmful to
the most valuable sport fish (Tanner, 1960). Bennett (1971) recommends
the use of artificial fertilization only in waters draining infertile
soils.
Neil (1975) made some attempt to measure the effect of Cladophora
on the recreational value of the lower Great Lakes. Cladophora is a
filamentous alga whose growth is dependent upon nutrient enrichment.
Cladophora affects beach and water uses when it is loosened from its
attachments on rocks by wind and waves and washed up on the beach.
Small dipterous flies and odors are associated with the drying and
decaying algae. Many beaches along the lower Great Lakes are affected,
67
-------
and if the beaches are not cleaned, many are not used. A survey of
shore-line state parks was conducted, and estimates for clean-up opera-
tions related to Cladophora problems ranged up to $14,400 per park per
year. Additional costs associated with swimming pool construction and
shoreline improvements necessitated by eutrophication problems cannot be
determined.
Data are not readily available on the number of sports fishermen,
boaters, and swimmers affected by eutrophication, or their economic
importance. Stroud 0977) estimated that sport fishing in the Great
Lakes alone put approximately $149 million into the economy in 1975.
An obvious trend has been the increase in the number of people enjoying
water-based recreation requiring clean, unpolluted water.
Concurrently, there has been an increase in the amount of money
people are willing to spend to protect or improve local water quality.
One indication is the Clean Lakes Program which was established by PL
92-500 and authorized $300 million in matching funds to community
projects for lake restoration and pollution control. Close to 56 pro-
jects have been funded so far, at a total cost to local communities of
about $15 million. In the early 1960's, voters in Seattle, Washington,
elected to use an estimated $120 million in public funds to divert
sewage away from Lake Washington in an effort to improve the trophic
status of the lake (Edmondson, 1973). The diversion of industrial and
municipal wastes from Lake Sammamish, Washington cost $3 million (Welch,
1977). Many thousands of dollars are spent annually by private citzens
or local governments to correct eutrophication problems. The amount
that citzens are willing to spend on remedial projects such as weed
harvest and copper sulfate treatments is some indication of how much a
clean lake is worth. It was estimated that for Lake Sebasticook, a lake
in Maine plagued with nuisance algal problems, $40,000 (1965) dollars
would be required for annual copper sulfate treatment to control the
algae (Anon, 1965). Mackenthun 0973) estimated that annual losses from
nutrient-induced aquatic plant growths or their control have amounted to
68
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$14 million for 17 western states. It is unfortunate that similar
figures are not available on a nation-wide basis. These examples are
good-indicators of the importance of clean water to lake-shore communi-
ties.
VI. The Extent of the Eutrophication Problem
The preceding sections have delineated the impact of eutrophica-
tion. For complete evaluation, the magnitude of the eutrophication
problem should be assessed. Three major indices can be used for this
evaluation: the National Eutrophication Survey, the annual National
Water Quality Inventory, and the National Commission on Water Quality.
Each of these reports involves one Cor several) scheme(s) for classi-
fying the trophic condition of lakes. There is a wide diversity in the
schemes available. While no attempt has been made in this report to
evaluate the different schemes, it should be recognized that lack of a
uniform classification system interferes to some extent with an attempt
to estimate the scope of the eutrophication problem. Nevertheless, the
information to follow is the best available means of evaluating the
extent of the problem. Another caution is necessary. The following
evaluation makes no attempt to differentiate between cultural and
natural eutrophication. While the vast majority of eutrophication
problems are related to human activities, high natural phosphate levels
and low anthropogenic loadings make natural eutrophication a problem in
some areas. For example, Florida and Vermont reported in the 1975
National Water Quality Inventory (U.S. Environmental Protection Agency,
1975) that natural eutrophication would prevent them from meeting 1983
goals of fishable and swimmable waters. Both states also recognize the
significance of anthropogenic sources of phosphorus.
The National Eutrophication Survey was initiated in 1972 by EPA to
identify and characterize lakes receiving municipal sewage effluent; it
was later expanded in scope to include lakes receiving non-point source
contributions. The data are not necessarily representative of the
69
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conditions of all lakes and reservoirs in the United States. Consequently,
they have only limited value for quantitative analysis of the extent of
eutrophication, but they can be used as a guide in determining-the scope
of the problem.
Potential eutrophication problems could be expected if median total
phosphorus concentrations in a lake exceeded 0.025 mg/1 or if annual
phosphorus loadings exceeded a critical level as defined by Vollenweider
(1968). Data from 298 lakes in 22 states east of the Mississippi were
used for this assessment. Most (73%} of the lakes for which data were
available exceeded the 0.025 mg/1 total phosphorus level. The majority
of these lakes (85%) were impacted by sewage effluents. Other nutrient
sources, however, were equally important in most of the lakes. More
than 74% of the 234 lakes for which loading analysis was completed
received less than half of the total phosphorus load from municipal
waste. Using Vollenweider's model, 83% of 156 lakes received total
annual phosphorus loadings at rates characterized as eutrophic. Sewage
enriched lakes had a greater incidence of eutrophication (82%) than
lakes impacted from only non-point sources (30%) (U.S. Environmental
Protection Agency, 1975).
Omernik (1977) mapped the nutrient concentrations found in 928
stream sites sampled as part of the National Eutrophication Survey.
Only sites impacted solely by non-point sources were considered. The
map shows a remarkable concentration of areas exceeding the "safe"
phosphorus level for flowing waters (>.l mg/1 as total P) in central
California and the Great Plains (North and South Dakota, Nebraska,
Kansas, Oklahoma, Iowa, southern Minnesota, Illinois, Indiana and Ohio).
In fact most (38) of the contiguous United States contained at least one
area with stream phosphorus concentrations exceeding the safe limit, and
all but one of the states approached (0.071-0.1 mg/1 total P) the safe
level. In an accompanying report, Omernik (1976) found significantly
higher nutrient content in streams draining agricultural watersheds
versus streams draining forested watersheds. Omernik's map shows how
70
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widespread nutrient enrichment is in streams impacted only by non-point
sources, but it gives no indication of water quality problems resulting
from enrichment. If we were to exclude the areas receiving high natural
phosphorus loadings (e.g. central Florida) and add the streams impacted
by point sources, the areas experiencing high levels are likely to be
even more extensive. Unfortunately, the data needed for this analysis
have not been compiled.
The National Commission on Water Quality, established by PL 92-500
section 315, attempted to assess the range of water pollution problems
throughout the United States and how point source controls would affect
them. The country was divided into 13 regions on the basis of the
principal geologic, soil, and vegetation types. A total of 41 sites
were selected within the regions on the basis of available environmental
data. Hater quality problems existed at most of the locations selected
for study, but most areas contained both polluted and non-polluted
sections, and a number of sites with relatively minor water quality
problems were analyzed. Some areas.were affected by both point and non-
point source pollutants.
Twenty-two (54%) of the 41 sites reported major problems with high
nutrient levels (nitrate nitrogen> 0.9 mg/1, total P>0.1 mg/1) and the
symptoms of eutrophication. Ten additional sites reported sufficiently
high nutrient levels, but algal blooms were limited by turbidity or flow
velocity. The majority of sites with major nutrient-enrichment problems
were impacted primarily by municipal wastewater discharge. High
nutrient levels and eutrophication problems were considered significant
in 5 of the 13 regions: Midwest, Great Lakes, Middle Atlantic/South/Gulf,
Southern Plains, and Central Valley. Nutrients and eutrophication
problems were of moderate significance at sites in the Northern Plains,
Columbia Plateau, Hawaii, Great Basin and Southwest Desert, Colorado
Plateau, Upper Ohio, New England and Puerto Rico (Figure 7). (National
Commission on Water Quality, 1976).
71
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ALASKA
1
PACIFIC
NORTHWEST
COLUMBIA
PLATEAU
NORTHERN PLAINS MIDWEST
PRESENT WATER QUALITY PROBLEMS
SCALE
Significant
Moderate
Minor
GREAT LAKES
SO. CALIF. BIGHT
GREAT BASIN
& S.W. DESERT
COLORADO
PLATEAU
SOUTHERN
PLAINS
KEY
NEW ENGLAND
UPPER OHIO
MID ATL.. SO., GULF
PUERTO
RICO
PUERTO RICO
STUDY
AREA
| DISSOLVED OXYGEN
[NITROGEN & PHOSPHORUS (NUTRIENTS)
TURBIDITY
TOTAL DISSOLVED SOLIDS
A-M GEOGRAPHIC REGIONS f""3 COLI FORM BACTERIA
Note: Assesment studies wero conducted on specific river reaches
or water bodies within each shaded area.
FIGURE 8. RELATIVE IMPORTANCE OF SELECTED WATER QUALITY PROBLEMS IN THE UNITED STATES.
(NATIONAL COMMISSION ON WATER QUALITY, 1375).
-------
The most recent National Water Quality Inventories (1975 and 1976)
contain information which can be used to assess the extent of the
eutrophication problem. The annual Inventory is mandated by section
305(b) of the Federal Water Quality Act Ammendments of 1972. It sum-
marizes state reports which describe the water quality of all navigable
waters within the state.
The 1975 Inventory (U.S. Environmental Protection Agency, 1975)
reports that high (P concentration not specified) phosphorus and nitro-
gen loadings, indicative of a potential eutrophication problem, were
mentioned as a problem in 43 of the 52 state reports. The 43 states
reporting high nutrient levels were distributed across the country;
relatively fewer southern and southwestern states reported problems in
comparison with the Great Lakes, central, western, middle Atlantic, and
northwestern states. Ten states reported lower nutrient levels and
decreasing eutrophication potential; 28 states reported no change in
nutrient levels; five states, however, reported worsening eutrophication
potential. Despite nutrient and other water quality problems, most (23)
of the 32 states attempting an overall evaluation reported good water
quality overall.
The 1976 state reports indicate that high nutrient concentrations
are still a problem in many states. Maryland, Vermont, and Florida cite
high levels of phosphorus and nitrogen as the most serious water quality
problem (U.S. Environmental Protection Agency, |976b).
Other states have attempted to classify the trophic status of their
lakes, as mandated by Section 314(a) of PL 92-500. State reports for
Wisconsin and Michigan contained readily usuable information for this
assessment.
In Wisconsin, Uttomark and Wall (1975) classified 98% of the lakes
equal to or greater than 100 acres in size. They developed a "Lake
73
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Classification Index" based on several observable parameters indicating
eutrophication, including oxygen level of the hypolimnion, transparency,
history of fish kills and recreational use impairment by excessive
aquatic plant growth. Each lake was assigned "penalty points" which
increased with the degree to which undersirable characteristics were
exhibited. According to this index, 30% of the lakes analyzed were
oligotrophic, 50% were mesotrophic and 20% were eutrophic. In comparison
with the National Eutrophication Survey, which surveyed 42 of the same
lakes, the LCI is more optimistic, as shown in Table 7 (Wisconsin
Department of Natural Resources, 1976).
Table 7. Trophic Status of a Set of Wisconsin Lakes, as determined
by Uttormark and Hall (1975) and the National Eutrophicat-Ton"
Survey (U.S. Environmental Protection Agency, 1975)
Uttormark & Wall NES
Lake Type # of Lakes % # of Lakes %
2 5
5 12
35 83
01 igotrophic
Mesotrophic
Eutrophic
5
16
21
12
38
50
42 42
Michigan (Michigan Department of Natural Resources, 1976)
surveyed 15% of the lakes more than 50 acres in size, representing
nearly half of the state's total combined lake surface area. Trophic
status for each of the 286 lakes was determined using two methods,
depending on the degree of study. If a lake met three of the following
criteria, it was considered eutrophic:
1. Clinograde oxygen curve during stratification.
2. Dissolved oxygen ^0,5 mg/1 1 meter off the
bottom during stratification.
3. Secchi disc transparency<2m.
4. Chlorophyll a >10 ug/1 .
74
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5. Organic nitrogen >0.8 mg/1,
6. Total inorganic nitrogen>0.3 mg/1 CNH3 t N03)
7. Total phosphorus >0.10 mg/1,
Alternatively, citzens participated in a Self-help Water Quality
Monitoring Program for some lakes and considered a lake eutrophic if
the secchi disk transparency was less than 2 meters, or the chlorophyll
a concentration greater than 10 ug/1 . National Eutrophication Survey
criteria were used in NES lakes. Of those surveyed, lakes in more
heavily populated areas were more likely to be found eutrophic: 24.6%
were considered eutrophic in the upper Peninsula, 27.4% in the northern
portion of the lower Peninsula and 56.4% in the southern portion of the
lower Penisula. Based on these data, 39.5% (776) of the large (>750
acres) lakes in Michigan are eutrophic, although small sample size and
purposeful selection of problem lakes may bias this extrapolation.
75
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APPENDIX
The Appendix includes the scientific names and some colloquial
names given to the fishes mentioned in this report. The names are
listed alphabetically under the common name adopted by the American
Fisheries Society CAPS) (1970). The asterisk denotes European fishes not
included in the AFS publication.
Common Name
Alewi fe
Atlantic salmon
*Blaufelchen
Blue pike
Bullhead, including:
Brown bullhead
Yellow bullhead
Black bullhead
Burbot
Carp
Channel catfish
Cisco (lake herring)
Deepwater cisco
*Eurasian perch
Fourhorn sculpin (deepwater
sculpin)
Freshwater drum (sheepshead)
Gizzard shad
Goldfish
Lake sturgeon
Lake trout
Lake whitefish
Mummichog
Northern pike
Rainbow smelt [smelt)
Sauger
Scientific Name
Alosa pseudoharengus
Salmon salar
Coregonus wartmanni
Stizostedion vitreum glaucum
Ictalurus nebulosus
Ictalurus natalis
Ictalurus melas
Lota lota
Cyprinus carpio
Ictalurus punctatus
Coregonus artedii
Coregonus johannae
Perca fluviatilus
Myoxocephalus quadricornus
Aplodinotus grunniens
Dorosma cepedianum
Carassius auratus
Acipenser fulvescens
Salvelinus namaycush
Coregonus clupeaformis
Fundulus heteroclitus
Esox lucius
Osmerus mordax
Stizostedion canadense
76
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APPENDIX (cont.)
Common Name
Sea lamprey
Sheepshead minnow
Shiners, including:
Emerald shiner
Golden shiner
Smallmouth bass
Sockeye salmon (kokanee)
Suckers, including:
Quill back
Norther redhorse
Silver redhorse
Golden redhorse
White redhorse
Sunfish
Walleye (yellow pike, pickerel)
White bass
Yellow perch
Scientific Name
Petromyzon marinus
Cyprinodon variegatus
Notropus spp. and Notemigonus spp.
Notropus atherinoides
Notemigonus crysoleucas
Micropterus dolomieui
Qncorhynchus nerka
Catostomidae
Carpoides cyprinus
Moxostoma marcolepidotus
Moxostoma anisurum
Moxostoma erythrurum
Moxostoma commersoni
Lepomis spp.
Stizostedion vitreum v'treum
Morone chrysops
Perca flavescens
77
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87
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA- 560/1-7.8-003
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
The Impact of Inorganic Phosphates in .the
Environment.
5. REPORT DATE
November 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Justine L.. Welch
S. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Toxic Substances
401. M Street, -S.W.
Washington/DC "20460.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same ..as 9
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report reviews the literature ;concerning .. the- con-sequences -of nutrient enrichment
:he significance 'of phosphprus in fiutrophication, critical phosphorus concentrations, the
Effects 'of. eutrdphicatipn oft human .populations, and th'e extent'-wf ttie -eutrophication
problem in the United.States.. The evidence contained in this report indicates that (a)
excessive nutrient concentrations'are associated.with undesirable changers (eutrophieatipn)
in aquatic plants','depletion of dissolved oxygen, disappearance of'cold water 'fish, and
appearance of nuisance .algal species;' (b) excessive phosphorus is most frequently respon-
sible, for these, undesirable changes in lakes; (c) lakes and reservoirs respond more
s^er.ely to ex'cessiye phosphorus concentrations 'than do flowing waters, and do so at lower
phosphorus concentrations; (d.) .phosphorus may at tildes be the limiting factor in estuaries
Dut ^Ls not'usually the limiting factor in coastal waters; (e) critical phosphorus levels
rfiich. lead-to -eutraphicatiori have ;.not been.-clearly, defined because.-of the variation--in
the response of surface waters to.phosphorus caused by differences, in. residence times,
nixing, sunlight penetration, etc:," although some guidelines for phosphorus loading's and
concentrations -have-established; (f). eutrophication-has- adversely affected human popula-
tions through increased'.water treatment costs, decreased property values'-, chariges"in the
commercial, fishery- and.'reduction ,of the aesthetic and recreational values- of -affected
Lakes.
17.
KEY WORDS ANp QOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TEAMS
c. COS.ATI field/Croup
Phosphorus.
Phosphates, inorganic
Eutrophication
Nutrients
Limnology
Economic Impact
Nutrient Enrichment
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
93
20. SECURITY CLASS (Thij page)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLBTE
PRINTING OFFICE: 1979 0-620-007/3739
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