5531 905R78117
LAKE MICHIGAN STUDY: SOME PRELIMINARY FINDINGS
JUNE 1978
Great Lakes National Program
Region V, U.S. EPA
Chicago, IL
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SUMMARY EVALUATION
The open waters of Lake Michigan are still slowly deteriorating. This
is evidenced by reduced silica concentrations in the epilimnion, in-
creased phytoplankton and zooplankton levels and the increasingly
frequent appearance of stephanodiscus and other species of phytoplankton
indicative of mesotrophic or eutrophic conditions. This enrichment has
reached a stage where the waters must be considered more mesotrophic
than oligotrophic. The enrichment now being observed is the result of
the high rates of loading to which the Lake was subjected during the
sixties and early seventies. It is known that it requires 10-20 years
for the open waters of the Lake to come into equilibrium with nutrient
loadings imposed upon it. Therefore, worsening conditions must be
expected in the near future. In the open lake waters, the benefits of
reduced phosphorus loadings will be to reduce the rate of eutrophication
and may be reflected in terms of degradation that does not occur rather
~> than actual improvement.
The abatement programs have produced positive improvements in local
nearshore areas. Several beaches in Lake County, Illinois and north
"N- Chicago have been reopened for public bathing, the incidence of taste
"; and odor problems at Chicago water intakes has decreased as a result of
~x the industrial abatement programs in the Calumet area. ^'' Further,
,/- cladophera is no longer the problem it was during the late sixties.
^J Average total phosphorus concentrations along the entire Indiana shore-
, _ line of Lake Michigan are the lowest in the entire southern basin. This
^ seems to reflect the benefits of the 1973 Indiana detergent phosphate
ban and phosphorus removal by municipal treatment which may have been
implemented in recent years. Productivity as measured by chlorophyll in
this nearshore zone, is lower than other similar areas, e.g., Green Bay
and the eastern shoreline near river sources. This is expected since
phosphorus generally controls phytoplankton production and standing
crops in temperate lakes.
Chloride concentrations are accumulating more rapidly over the last ten
years than ever before. The effects of higher chloride levels are not
known, but there is a conbern that higher chloride levels wil'l encourge
the growth of stephanodiscus and other filamentous algae. If this
occurs, it may affect the cost of water filtration plant operation where
plants draw their water from the nearshore zone.
Sulfate, which was increasing rapidly during the sixties, appears to
have leveled off with virtually no increase since 1970 in the southern
basin. This may be attributable to the discontinuation of sulfuric acid
pickling by the steel industry and to reduced use of high sulfur fuels.
The concentration of DDT in Lake Michigan fish has decreased steadily
since 1969. In 1976, it was down to approximately 10% of 1969 con-
centrations. This is the result of the ban on the use of DDT, and shows
that even a persistent compound such as DDT will disappear if its source
is eliminated. Figure 1.
\
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PCB concentrations were slightly lower in 1976 than in previous years
for all three species tested - coho salmon, brown trout, and chub. It
is not certain if this is the start of a downward trend or a random
perturbation of the data. PCB compounds are very similar to DDT. Their
manufacture in the United States has ceased and their use has been
restricted to sealed electrical components. Unfortunately PCBs were
used for a great many things whereas DDT was used almost exclusively as
a pesticide. This makes it far more difficult to eliminate the input of
PCB compounds to the lake. It is now estimated that 80% - 90% of the
PCBs reaching the lake come by way of atmospheric fallout. They get
into the atmosphere when materials containing PCBs are incinerated.
There is also evidence that PCB compounds escape from land fills through
gas vents. There is no question that the problem of PCB contamination
in Lake Michgian fish will eventually dissipate. It may have started
already, but it is likely to be a much slower process than the dis-
sipation of DDT which has gone down 90% in seven years.
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TROPHIC STATE
The definition of the trophic state of a lake is primarily a subjective
process. There is general agreement that eutrophication is an aging
process and that young or oligotrophic lakes are nutrient-poor and old
or eutrophic lakes are nutrient-rich. Figure 2 summarizes some of the
methods used to classify lakes.
Figure 3 characterizes the lake according to three criteria: Phyto-
pi ankton, chlorophyll a_, and total phosphorus. These criteria indicate
that the open waters of the southern basin are on the border between
oligotrophy and mesotrophy. The nearshore waters are clearly mesotrophic.
The open waters at the extreme southern end represented by Station 1
are definitely mesotrophic. The open waters in the transition area
between the northern and southern basins of the Lake represented by
Station 26 are still somewhat oligotrophic.
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10
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Water Supply Problems Taste and Odor-Fifter Clogging
Phytoplankton Species Change
Zooplankton Species Change
Benthos Species Change
Heavy Cladophora Growths
Dissolved Oxygen Problems
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PHOSPHORUS
Phosphate phosphorus is one of the major nutrients required for plant
nutrition and is utilized roughly in a ratio of 1 to 15 to 106 with
nitrogen and carbon. Since it is the most easily controlled of the
major nutrients needed for plant growth and usually in least supply,
regulation of phosphorus is the primary means for controlling eutrophi-
cation.
Phosphates enter the lake from several major sources, point source
discharges which include industrial, human and detergent contributions;
tributary sources which include land drainage and agricultural sources;
and atmospheric deposition.
This distribution of average total phosphorus concentrations in 1976 are
shown in Figure 4. The changes in total phosphorus concentrations from
inshore to offshore zones are consistent with important sources of total
phosphorus to the lake. Important sources of total phosphorus loading
to the lake are Green Bay, the northern suburbs of Chicago, the Benton
Harbor area, the Grand Haven-Muskegon area, and the Ludington-Manistee
area; conspicious by its absence is the Indiana Harbor area.
Changes in the expected pattern in the Calumet-Indiana Harbor, area may
be due to the detergent phosphorus ban in the State of Indiana. Near-
shore phosphorus concentration in Indiana waters are actually lower than
in adjacent open-lake waters. This is remarkable in view of the major
municipal discharges in the area some of which do not have adequate
treatment facilities. The ammonia data, Figure 5, clearly shows the
impact of these discharges. The fact that the phosphorus data does not
show a similar impact is very significant and a strong indication that
by controlling the sources of phosphorus we can slow or even reverse the
eutrophication process.
Dissolved reactive phosphorus concentrations in the lake are almost
invariably less than 2 ug/1 which is the limit of detectability of the
analysis. Dissolved reactive phosphorus is the form of phsophorus
actually used by phytoplankton for growth, Levels lower than 5 ug/1
indicate that there is no excess dissolved reactive phosphorus and that
the organisms are continuously recycling it. This supports the belief
that phosphorus is the controlling nutrient in Lake Michigan.
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MILWAUKEE
CHICAGO
FIGURE 4
VS. ENVIRONMENTAL
PROTECTION AGENCY
Lake Michigan
Total Phosphorous Distributk
in ug/1 -1976
GREAT LAKES NATIONAL PROGRAM
REGION V CHICAGO, ILLINOIS
SCALE
II
Id 20 30 40 50 MILES
I I I
10 5 0 10 nO 30 40 5r 60 70 80 KILOMETERS
I J 1 III I 1 1 1 I
Buffalo
Michigan City
Hammond
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. ENVIRONMENTAL
PROTECTION AGENCY
Lake Michigan
Ammonia Distribution
ug/1 in 1976
GREAT LAKES NATIONAL PROGRAM
REGION V CHICAGO, ILLINOIS
MILWAUKEE
SCALE
1° 5 ° 10 20 30 40 50 MILES
III I I L .I,... .J
10 5 0 10 20 30 40 50 60 70 80 KILOMETERS
III I I I I I I I I
CHICAGO
Hammond
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CHLOROPHYLL
Chlorophyll is the basic chemical compound in the photosynthetic process
used by all plants to convert sunlight and nutrients into organic matter
and oxygen. All algae contain chlorophyll and measuring this pigment
can yield some insight into the amount of algae in the water. Algal
production of chlorophyll varies from species to species and with
environmental and nutritional factors. Biomass estimates based on
chlorophyll measurements are relatively imprecise but form a major
method for estimation of productivity and algal biomass.
The average chlorophyll a concentrations are shown in Figure 6. The
maximum values occur nearshore south of the Green Bay outlet towards
Manitowoc Wisconsin and North from Michigan City, Indiana to Manistee,
Michigan.
Chlorophyll a concentrations along Indiana in the southernmost basin do
not attain the high values found near other major tributaries. This may
be linked to reduced phosphorus concentrations in the area resulting
from the detergent phosphorus ban in Indiana, from turbidity that
reduces photosynthesis of algae, or from possible toxic effects of
industrial discharges in the area.
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VS. ENVIRONMENTAL
PROTECTION AGENCY
Lake Michigan
Chlorophyl A
in ug/1 -1976
GREAT LAKES NATIONAL PROGRAM
REGION V CHICAGO, ILLINOIS
SCALE
'050 10 10
aO Mil tS
10 5 0 10 20 30 40 50 60 70 80 KILOMETERS
III I I I I J__l_iL.J
CHICAGO
Hammond
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SILICA
Silica is essential to diatoms which incorporate it into their exo-
skeleton. If other nutrients and light are available, diatom popu-
lations will increase causing a reduction in silica concentrations. If
this reduction becomes severe, the diatoms are less able to compete for
nutrients and other, less desirable, algae may become dominant. This
process appears to be occurring in Lake Michigan.
Figure 7 shows the vertical distribution of dissolved reactive silica at
Station 26 on eight days between May 26 and October 8, 1976. During
May, before stratification, the vertical silica distribution was virtually
constant with a surface concentration of 1.21 mg/1. As the season
progressed, the surface concentration of silica decreased steadily until
it reached 0.27 mg/1 in early August. Thereafter, it began to recover.
Concentrations in the hypolimnion, and particularly near the bottom,
increased steadily throughout the season reaching 2.76 mg/1 during
October. This clearly shows that silica settles toward the bottom with
diatomaceous organisms. The total silica in the water column remains
reasonably constant but the silica available in the epilimnion and the
photic zone, where virtually all of the photosynthetic activity takes
place, is greatly reduced.
Figure 8 compares the annual silica cycle in the surface waters at Lake
Michigan for the years 1954, 1965 and 1976. It shows that there has
been a significant decrease in silica available in surface waters since
1954. If this trend continues, it could lead to major changes in the
phytoplankton species which are dominant in the lake.
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Chloride
Chloride compounds are associated with many of man's activities. Salt
is used extensively for de-icing roadways in the winter. Industrial
processes result in the discharge of brines. Chlorine is added to
wastes to destroy bacteria and, recently, ferric chloride has been
added to municipal waste water plants to remove phosphorus. As a
result, the chloride ion can be used to measure cultural pollution,
the added impact that modern man is making on the Lake.
Before the extensive population growth and industrial development of
the Lake Michigan basin, chloride concentrations in Lake Michigan were
around 1.0 mg/1. (3) This represented an equilibrium concentration where
the natural sources of chloride balanced the outflow from the Lake.
These natural sources include weathering and erosion of rocks and soils,
and atmospheric aerosols. The concentration increased reaching 3.0 mg/1
by 1910. The 1962-3 offshore samples of the lake averaged 6.5 mg/1,
and the 1976 sampling of the entire Lake found an average of 7.9 mg/1.
Figure 9 shows the distribution of mean chloride during 1976; From
these observations, the rate of chloride accumulation over this period
is about 0.11 mg/l/yr.
This accumulation rate is approximately four times that estimated during
the period 1860 to 1910 (.025 mg/l/yr.), and greater than that estimated
for the period 1910 to 1960 (.07 mg/l/yr.).
Supporting information is provided by nearshore water intake records.
Nearshore time series data from three water filtration plants are shown
in figure 10. The average annual rates of increase over the different
time periods shown are 0.10 +_ .01 mg/1 at Milwaukee's Linwood Filtration
plant, 0.12 ±0.1 mg/1 at Chicago's South Water Filtration Plant, and
0.15 +_ .01 mg/1 at Grand Rapids Lakeshore Filtration plant. Close
inspection of these time series will show that the rate of accumula-
tion since the 1960's is greater than the average rate during1 previous
years.
Calculations of loading of chloride confirm the observed rates of
increase of chloride concentration in the open lake. During the
last 15 years the rate of increase ranged between 0.10 mg/1 and 0.13
mg/1. These increases in concentration correspond to loadings of
900,000 and 1,050,000 metric tons of chlorides per year. During 1975
chloride loadings from rivers were estimated to be 775,000 metric tons.
Point source estimates for direct discharge totaled 1609000 metric
tons (5) an The sum of these estimates,, 1,018,000 metric
tons/year, compares quite well with observed increases in lake con-
centrations.
Figure 11 compares 1963 chloride values with 1976 chloride values
for 11 different open lake segments. The mean rate of accumulation
over the thirteen year period is higher at the northern and southern
ends of the lake then in the middle of the lake (segments E and D}.
This is because of the abatement of brine discharges from the Frankfort-
Manistee area which caused higher concentrations during 1963. The
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nearshore zone at Frankfort-Manistee is the only area of the lake
where 1976 average chloride concentrations are less than 1963 con-
centrations. Figure 12 shows the distribution of chloride in Lake
Michigan with the highest concentrations in the Southern basin and
the Ludington Manistee area.
In 1972-1973, salts used for road deicing amounted to 445,000 metric
tons as chloride (7). Assuming that chlorides are conservative and
that ion exchange between chlorides and various soil types are minimal,
most of the chloride used for deicing eventually reaches the Lake.
This source of chloride could account for approximately 40% to 45%
of the total current load. Other factors affecting modern loadings
are the use of hydrochloric acid in steel manufacture, coagulation
with chloride salts for phosphorus removal at municipal treatment
plants and many industrial waste treatment processes which use
chloride salts as coagulants.
The accelerating accumulation of chloride in Lake Michigan may lead
to the current Lake chloride standards being violated in the next
decade. State governments will be faced with the choice of taking
action to reduce chloride loadings or altering their lake standards.
The State of Indiana has recently proposed raising their standard
from 10 mg/1 to 15 mg/1. Illinois has a standard of 12 mg/1.
Although there is no doubt that the current levels of chloride con-
centrations are far below the drinking water standard of 250 mg/1 set
by the United States Public Health Service which is based on ,taste
and not toxicity, there is the unpleasant possibility that future
increases in chloride levels may lead to fundamental, probably irre-
versible, changes in the lake's natural biological systems. The
extent, severity, and desirability of these changes and the chloride
levels at which they will occur are not known. The chloride levels
in Lake Erie are much higher than in Lake Michigan but the effects
have been masked by the massive eutrophication that has taken place
in that lake. The effects of increased chloride levels on a meso-
trophic lake where phosphorus imputs are controlled is a subject for
research which will be required for basic policy decisions.
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9
US. ENVIRONMENTAL
PROTECTION AGENCY
Lake Michigan
Chloride Distribution
in mg/1 - 1976
GREAT LAKES NATIONAL
REGION V CHICAGO, IUINOPS
SCALE
10 5 0 10 20 30 40 50 MILES
10 5 0 10 20 30 40 50 60 70 80 KILOMETERS
Soutli Haven LiLJ-. 1-1 1....J iL.JUnL 1
CHICAGO
MK higan City
Hammond
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PLANKTON
Plankton are the small animal (zooplankton) and plant (phytoplankton)
organisms that float or drift In the water at or near the surface and
are incapable of sustained mobility in directions counter to the water
currents. Diatoms are a major form of open water plankters and are
dominant in oligotrophic waters of the Great Lakes. Plankton are a
large part of the food chain base and as primary producers convert
inorganic heterotrophic nutrients to organic matter. They use the
energy of sunlight to metabolize inorganic nutrients and convert them to
complex organic materials. Zooplankton and other herbivores graze upon
the phytoplankton passing along the stored energy to higher organisms
which in turn use the zooplankton as food.
Information of phytoplankton and zooplankton populations and species
distribution has application in several areas. The kind of species and
relative percentage of total population is important in characterization
of a lake trophic status. These organisms are sensitive indicators of
pollution and by their presence of absence can indicate toxic exposure
to cultural discharge sources. Plankton often are a source of taste and
odor problems and if present in large numbers increase costs of treat-
ment at water filtration plants. Plankton blooms can permanently alter
the habitat and cause extreme fluctuations in dissolved oxygen con-
centrations which can adversely effect living conditions for fish and
other higher forms of aquatic life. Zooplankton are part of the food
chain, feeding on bacteria and phytoplankton and are in turn consumed by
fish. Since phytop.lankton are the base of the food chain and widespread
change in their composition can have a great impact on all of the biota
in the lake.
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SULFATE (S04=)
Sulfate is a conservative ion which reflects sulfur inputs to the lake.
Biochemical and chemical reactions in a well-aerated system such as
Lake Michigan have little affect on the concentration of sulfate in
the water. Thus it is useful in tracking man's impact on the environ-
ment.
Rising levels of sulfate in the nearshore zones create concern because
additions of sulfide (S~) from industrial sources demand large amounts
of oxygen. This is because of the rapid oxidation of sulfide to sulfate
and increased populations of sulfur-reducing bacteria.
Sulfate has many sources. Weathering and erosion of sulfur-containing
minerals and soils remove sulfur from the watershed to the Lake. Human
activities add sulfates via waste discharges from petrochemical, chemi-
cal, metal mining and refining, metal working and fabricating, and the
pulp and paper processes.
The standard for sulfate in public water supplies, which is based on
taste and laxative effects, is 250 mg/1, much higher than levels presently
found in Lake Michigan.
The concentration of sulfate in Lake Michigan was increasing more rapidly
than any other ion between 1900 and 1960 based on data compiled and
published by Beeton. This data indicated an average rate of increase
of 0.14 mg/l/yr. A comparison of the 1963 data with the 1976 data for
open lake waters shows an average accumulation rate of 0.08 mg/l/yr
(Figure 12). A close examination of this figure indicates that thts
increase may have leveled off completely in the early seventies. Averages
of data collected in the southern basin varied between 20 mg/1 and
22.7 mg/1 with an overall average of about 21 mg/1. This compares with
the 1976 average of 21.1 mg/1 in the southern basin (Figure 13).
The water intake data (Figure 14) shows average rates of increase of
0.09 mg/l/yr at Milwaukee, 0.18 mg/1 at Chicago south water filtration
plant, and 0.31 mg/l/yr at Grand Rapids. Close examination of the
Chicago data shows a leveling off around 1970 although this is not
evident in the Milwaukee or Grand Rapids data.
Monitoring of the Calumet area during 1965-1969 shows a dramatic
decrease in sulfate loadings due to changes in steel making processes
and effluent treatment. The change from pickling steel with sulfuric
acid to hydrochloric acid and the use of deep well disposal for spent
acids is a factor in this apparent decrease in sulfur accumulation at
the southern tip of the lake. Another factor may be the reduced use
of high sulfur fuels in the Chicago metropolitan area.
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Gladstone
13
US. ENVIRONMENTAL
PROTECTION AGENCY
Lake Michigan
Sulfate Distribution
in mg/1 -1976
GREAT LAKES NATIONAL
REGION V CHICAGO,
SCALE
utli H.n.'ii 10 5 0 10 20 30 40 50 MILES
|_J_J MJ, nj....,..!, , ,..i... J
10 5 0 10 20 30 40 50 60 70 80 KILOMETERS
Ml I I__L_. ' I III
CHICAGO
Hammond
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