Our l.i['iiii^ l^i'\oiiiri'\ — Aquatic Ecosystems 



24} 



70 72 74 76 78 80 82 84 86 88 90 

 Year 



Fig. 2. Conlaminant results from Lake Michigan lake trout, 

 1970-90. 



Great Lakes, and changes in fish tissue concen- 

 trations do not follow use patterns for reasons 

 that are not well understood. 



Lake Superior 



Total DDT and PCB concentrations in lake 

 trout from Lake Superior were the lowest of all 

 the Great Lakes and generally declined from 

 1977 to 1990 (Fig. 3). Dieldrin was always low 

 and varied little from 1977 to 1990. 

 Contaminant concentrations are lowest in Lake 

 Superior because of the low density of agricul- 

 ture and industry in the lake basin. 



Lake Huron 



Concentrations of total DDT and PCBs in 

 lake trout from Lake Huron were intermediate 

 between Lake Michigan and Lake Superior. 

 Similar trends of declining concentrations of 

 these chemicals were observed in Lake Huron 

 (Fig. 4). Dieldrin concentrations were similar to 

 Lake Superior but declined from a high in 1979 

 to a low by 1988. With the exception of the 

 Saginaw Valley, both agriculture and industry 

 are much less developed surrounding Lake 

 Huron than Lake Michigan, thereby resulting in 

 lower containinants in Lake Huron fish. 



Lake Ontario 



The contaminants in Lake Ontario fish are 

 relatively high (Fig. 5), second only to Lake 

 Michigan. Trends in total DDT concentrations 

 in lake trout from Lake Ontario were fairly con- 

 stant from 1977 to 1990. Total PCBs in lake 

 trout declined significantly from a high in 1977 

 to a low in 1990, a slower decline than in Lake 



Michigan. The relatively high contanunant con- 

 centrations in Lake Ontario fish are a result of 

 the highly urbanized, industrial, and agricultur- 

 al basin. In addition, it is the lowemiost of the 

 Great Lakes, receiving pollutants from 

 upstream through the Niagara River Dieldrin 

 concentrations in lake trout from Lake Ontario 

 reached a high in 1979 and then declined to a 

 low by 1988r 



Lake Erie 



Total DDT, PCB, and dieldrin concentra- 

 tions in Lake Erie walleye (Fig. 6) were lower 

 and more similar to concentrations in lake trout 

 in Lake Superior than those of other Great 

 Lakes. Total DDT and PCBs peaked in 1977 

 and declined to a low in 1982; no consistent 

 trend was noted for dieldrin. Low concentra- 

 tions of contaminants in Lake Erie were similar 

 to those in Lake Superior even though Lake Erie 

 is surrounded by the largest urbanized, industri- 

 al, and agricultural basin of all the Great Lakes. 

 Lake Erie, however, is the shallowest of all the 

 Great Lakes and contains the highest amount of 

 particulate matter Contaminants flush more 

 quickly through the shallow lake and are 

 removed from the water column as they adhere 

 to particulate matter and settle to the bottom. 

 These factors work together in reducing the 

 amount of contaminants available to fish in 

 Lake Erie. 



Contaminant Effects 



Reduced reproductive success in fish-eating 

 birds has been linked with DDT and PCBs 

 (Giesy et al. 1994). As the concentrations of 

 these contaminants have declined, populations 

 of fish-eating birds such as the bald eagle 

 {Haliaeetus leucoceplialus) are beginning to 

 recover in the Great Lakes basin. In lake trout, 

 PCBs are also linked to reduced egg hatchabili- 

 ty and may also be responsible for fry deformi- 

 ties and mortality (Mac et al. 1993). In spite of 

 reductions in PCBs in lake trout in all of the 

 Great Lakes, substantial natural reproduction 

 occurs only in Lake Superior (Mac and Edsall 

 1991). The role of contaminants and other fac- 

 tors in lake trout reproductive problems in the 

 other four Great Lakes is still under investiga- 

 tion. 



Another fish health problem associated with 

 toxic chemicals is found in Great Lakes harbors 

 and tributaries where heavy industry was locat- 

 ed (Baumann et al. 1991). Bottoin sediments in 

 these areas are heavily contaminated with poly- 

 cyclic aromatic hydrocarbons (PAHs). Presence 

 of liver tumors and other deformities such as lip 

 papillomas, stubbed barbels, or skin discol- 

 orations in bottom-feeding fishes, such as the 

 brown bullhead, have been linked to the 



77 78 80 82 84 86 88 90 

 Year 



Fig. 3. Contaminant results from 

 Lake Superior lake trout. 1977-90. 



Fig. 4. Contaminant results from 

 Lake Huron lake trout, 1977-90. 



77 78 80 82 84 86 88 90 

 Year 



Fig. 5. Contaminant results from 

 Lake Ontario lake trout, 1977-90. 



