3 - International Joint Commission

smallest by volume and also the shallowest. It is divided into three basins.
The western basin, into which the Detroit River flows, is very shallow but has
the most important fish spawning and nursery grounds. It is downstream
from the Canadian chemical companies on the St. Clair River, downstream
from Detroit, and has Toledo on its shores. Thus, this part of Lake Erie is
the most likely to be affected by chemical contamination. Limnologically,
Lake Erie is different from the other four, deeper and essentially oligotrophic
Great Lakes. Lake Erie is mesotrophic and approached a eutrophic status
in the 1960s. It has a high nutrient load, relative to its volume. Combined
with its shallow depth and high biological productivity, it processes
contaminants differently from the other four lakes. The greater productivity
in Lake Erie may has several possible consequences: the biomass may dilute
the chemicals: the organic-rich suspended particulates may compete for toxic
metals and hydrophobic organic chemicals: the sedimentation and burial
rates are higher; and photochemical and biological degradation of chemicals
is perhaps greater. The rapid flushing of the lake (see Table 1) also accounts
for the lower concentration of contaminants in the water column. The net
result is that although loads of chemicals such as PCBs to the lake are
similar to Lake Ontario (Strachan and Eisenreich, 1988). the bioaccumulation
of these chemicals has been less.
Lake Erie has been heavily contaminated by metals. It is probably the
second most heavily contaminated with metals of the Great Lakes (after Lake
Michigan) based on overall concentrauons (Rossmann, 1984). The relative
occurrence of dissolved metal concentrations was highest in Lake Erie
(Rossmann and Barres, 1988). Lake Erie also had the highest total
concentrations of the greatest number of metals.
2.5.1 Water and Suspended Solids
Data on toxic chemical concentrations in water Lake in Erie are shown
in Table 10. Rossmann (1984) reviewed the available data on total and
dissolved lead in Lake Erie water. For water collected at unrecorded depths,
the 1974 and 1980 medians were at the minimum detection level (5 to 10
ppb) (n = 6). There were no trends in total lead in epilimnion water, taken at
depths of less than 5 m. Mean concentrations in 1967, 1973, 1975, 1978
and 1979 ranged from 0 to 9 ppb. These early data and those in Table 10