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One of the most important omens for the future of the lakes is the sharp reduction in the amount of phosphorus dumped into them. A 1972 U.S.-Canadian agreement lowered the levels of phosphates that municipalities were allowed to dump into the water, and most towns along the shores and on rivers emptying into the lakes are well on their way toward meeting those requirements. The significant exception is the city of Detroit; it continues to dump three times the permissible levels into the Detroit River, which flows into the western end of Lake Erie. One of the largest sources of the harmful phosphates was common laundry detergent, but the levels have now been lowered by law in every state and province bordering the lakes except Ohio. The result has been not only the lessening of unsightly deposits of suds along rivers and beaches, but also a slowdown of eutrophication, the nutrient-induced aging process that eventually chokes lakes with algae and other plant growth.
Even contamination from DDT, which some scientists had predicted would take hundreds of years to be washed out of the Great Lakes, is only 10% of what it was ten years ago. Says Wayland Swain, director of the EPA's Large Lakes Research Laboratory in Grosse He, Mich.:
"Even in Lake Erie we now expect DDT to disappear completely in a rather short time. In fact, it is now difficult to find it anywhere in the lake except in the sediment."
Large game fish are making a comeback. Virtually wiped out by overfishing, pollution and the eellike sea lamprey (an ocean predator that apparently first migrated from the Hudson River into the lakes after man had opened the way with the Erie Canal, the native lake trout is again being pulled from the lakes by sports fishermen, who now can also catch coho and chinook salmon from the Pacific Ocean. Still, despite the fact that the waters are cleaner and the lamprey has been contained by a concerted attack on its breeding ground, the game fish population can be sustained only by frequent replanting. Says K.H. Loftus, of the Ontario Ministry of Natural Resources: "The real criterion of the rebound of the lakes will be when the fish that were eliminated are back taking care of themselves.
That's the sign of a healthy lake, but it's yet to happen except in a few very isolated localities."
Toxic substances in the lakes are now the environmentalists' major concern The levels of such chemicals as mirex (an insecticide), PCBs and mercury are still too high to allow the resumption of commercial fishing, and Canada publishes a guide that warns sports fishermen which fish are unsafe to eat. Says Leila Botts, chairman of the Great Lakes Basin Commission
"As we learn more about the problems of he Great Lakes, we discover that it's not as easy as it first appeared when we assumed that if we'd just get industry and the municipalities to clean up their acts, we'd have clean water. Now we've largely done that, and we discover that there are dangerous toxic substances in the lakes we didn't even know about before."