A Great Lakes mystery: The case of the disappeari...(id an amino acid and a hydrocarbon she s...)

"We are just beginning to interpret these data, but they give us a better idea of how pollutants affect them," Seplveda said. "If nothing else, our results suggest that seemingly insignificant levels of pollution could significantly harm animals like Diporeia."

The project should help address suggestions by some researchers that Diporeia and/or invasive zebra and quagga mussels may be capable of bioaccumulating or affecting levels of pollutants in a way that might intensify their harmful effects, Seplveda said.

The project also should deepen understanding of exactly how the invasive mussels hurt Diporeia, Hook said. Researchers have looked into, but have yet to determine, the extent to which the mussels outcompete the crustaceans for food, contaminate their surroundings with their effusive waste material, or influence the transmission and spread of diseases.

Regardless of the reason, Diporeia's decline has already had some measurable negative effects on various fish species. Alewives, an important prey fish that provides Chinook salmon well over 80 percent of its food, have declined in growth rates, condition - measured as the ratio of weight to length - and caloric density since Diporeia populations began declining, said Charles Madenjian, research fishery biologist with the United States Geologic Survey.

"Alewives used to regularly reach 10 inches in length," Madenjian said. "Now we're lucky to find one that breaks 8 inches."

Diporeia previously supplied 50 percent of the food source for the commercially important lake whitefish and now supply only about 5 percent. Since the crustacean's decline began in the 1990s, growth rates and the condition of lake whitefish have substantially fallen off, Madenjian said.

If Diporeia's decline proves to have similar negative consequences upon other species and continues to worsen, the most severe effects may be fo
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