A Great Lakes mystery: The case of the disappeari...(rthcoming although it is difficult to pr...)

Hook said he believes the initial step in taking action is to pinpoint causes.

"The first thing we can do is find out more precisely why they are declining," he said. "If we guess, any management decision we make could be counterproductive."

Zebra and quagga mussels were almost certainly spread to the Great Lakes from Europe or East Asia in the fresh water ballasts of oceangoing vessels, beginning in the late 1980s, Nalepa said. People need to be aware of the risks of spreading harmful invasive species and such ballasts should be more tightly regulated or possibly banned, he said. In one simple preventive measure, boats exchange their freshwater ballast for salt water ballast in the open ocean, thereby killing any freshwater species present.

The study by Seplveda used a process called gas chromatography to separate metabolites and matched them with known chemicals on a national database. Researchers identified 76 metabolites among lake-dwelling animals and 302 among the control and atrazine laboratory populations. Results from the two comparative analyses suggest that fatty acids and hydrocarbons are important to the animal's survival or may be interfered with by particular stressors.

Diporeia put on much of their weight during the spring bloom of diatoms, algal plankton they feed upon, during which energy capture and storage are particularly paramount. This leaves them vulnerable to disruptions in food or their ability to store it, a process in which fatty acids play a key role, Seplveda said.

The four-year grant includes researchers from three major universities - Purdue, University of Michigan and the State University of New York - as well as two federal institutions, Hook said.

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