National Geographic : 1970 Dec
Lakes can be even more vulnerable than rivers. Witness Lake Erie, second smallest (after Ontario) and shallowest of the five Great Lakes. No body of fresh water in the country has received more attention than Erie, a lake dying of too much nourishment. "Lake Erie is suffering from eutrophica tion," I was told by Francis T. Mayo, Great Lakes Regional Director of the Federal Water Quality Administration. "That word comes from the Greek eutrophos, meaning 'well nourished.' A lake becomes overnourished as part of its normal aging process, but man ac celerates the process tremendously by pour ing in nutrients and industrial chemicals." When I asked if Lake Erie could be saved, he nodded. "It has to be saved. Nobody can afford to write it off." But salvation comes hard, I learned. Many industrial plants and municipalities around the lake must change their ways. The tribu taries that flow into the lake must be cleaned up-including the inflammable Cuyahoga River. Sewage plants must be upgraded, and agricultural runoff must be controlled. "Nitrates are very difficult to remove from sewage water," Mr. Mayo said. "About 80 percent of the phosphorus can be taken out chemically, though, and that should hold down algae. Once the pollution stops, Erie should begin to clean itself. Its flushing time is only three to five years-that's the time it takes to replace all its water." If three to five years seems long, consider Lake Michigan's flushing time: one century! The lake's only outlets are the slow-moving Chicago River and the Straits of Mackinac. Thus Michigan rates special concern from Mr. Mayo and his associates. The lake's pol lution load is light-by Erie standards, at least-but any pollution is bound to be there for a long, long time. Tahoe's Sewage Water Fit to Drink At an environmental conference in Wash ington last spring, I was given a glass of water to drink. I sipped with some misgiving, for it was the end product of a sewage plant. There was an amused glint in the eyes of Frank Sebastian (page 774) as he watched how slowly I tilted the glass. Mr. Sebastian is Senior Vice President of Envirotech, a Cali fornia corporation that makes, among other things, tertiary sewage-plant equipment. "It's purer than the water that comes from your faucets at home," he said comfortingly. The water-which tasted like any other 758 KODACHROMES BYJAMESP. BLAIR( N.G.S. Sexual trickery may lead to the downfall of the cabbage looper, a major farm pest. Entomologists at the University of California, Riverside, have learned that when the odor of the female moth is spread over whole fields, males become too con fused to mate. Oscilloscope (above) records this male moth's response to the female aroma. Fed eral and state governments are pushing develop ment of biological controls as alternatives to pesticides that threaten wildlife. How DDT can affect birds: Mallards at the U. S. Government's Patuxent Wildlife Research Center in Maryland were fed DDE, a breakdown product of DDT, in concentrations now common in the wild. They laid thin-shelled eggs, subject to hairline cracks (below). On an average, as this exhibit dramatizes, three eggs in a clutch of 12 were cracked or crushed by the mother. Eight others failed to develop, and only one hatchling, rather than the usual 9 to 11, emerged alive.