Environment: Mother Superior's Secrets

The underwater exploration was at first plagued with problems, including poor visibility and bursting collection sacks. But after the first two days exploration and sampling went more smoothly. Exulted Long: "We've got rock formations that will knock your socks off !" The investigations planned for the Sea-Link will ultimately involve 27 scientists. Some will survey the spawning habits and conditions of lake trout. Others plan explorations to the wrecks of five ships thought to have sunk between 1880 and 1918 for relics of shipboard life. Because of low water temperatures and the relative lack of oxidation, "the Great Lakes provide excellent preservation, even of shoes and leather," says Kenneth Pott, curator of the Lake Michigan Maritime Museum.

A major focus of the expedition is pollution. Although concentrations of many contaminants have been markedly reduced in the Great Lakes (Superior is the cleanest), toxic chemicals like PCB remain a problem. Researchers plan to devote 16 dives to studying the nepheloid, a cloudy, particle-laden 6-in. layer of water just above the lake floor that seems to trap, and then rerelease, pollutants. "We had thought that bottom sediments were sort of permanent sinks for contaminants attached to particles," explains Steven Eisenreich, a professor of environmental engineering at the University of Minnesota. "Now we're finding out that under certain conditions these particles get recycled."

A clue to how pollutants travel may lie hi the giant furrows (up to 3 ft. deep and 20 ft. across) that stretch for miles along the lake floor. Scientists think that the trenches, similar to those on ocean bottoms, are carved by currents of water that can also disperse toxic material. Other investigators will concentrate on collecting two shrimp like organisms in the food chain, including Ponto-poreia hoyi, that dwell on the sediment and may ingest toxic chemicals.

Scientists hope that findings from the Sea-Link will point to solutions for some of the Great Lakes' continuing problems. With the expedition only a third over, researchers were already counting it a success. Richard Cooper, a marine biologist at the University of Connecticut and the scientific director of the project, declares that before the last dive, "we expect Mother Superior to yield up more of her secrets. We're finding things that will rewrite the book on ecology in the Great Lakes." --By Anastasia Toufexis. Reported by J. Madeleine Nash/Marquette