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Study shows Great Lakes losing important part of food chain

A Wisconsin researcher says the decline of some tiny but important species continues in the Great Lakes.

There have already been some signs that zooplankton and other invertebrates are declining in the lakes. Now, University of Wisconsin Superior has the first batch of numbers collected for a special project with the Environmental Protection Agency.

During springs and summers from 2001 to 2005, a university team traveling on an EPA research vessel collected biological samples in all five lakes.

Mary Bacer, project director, highlights one species that seems to be in more trouble. She says one of the more important things is diporia, small shrimplike animals that live down in the sediment.

Scientists had been noting decline in Lakes Michigan Huron for several years and the data confirms that the organism are continuing to go down in numbers.

Balcer says only Lake Superior seems relatively immune to the decline in diporia. She says elsewhere, scientists believe that the greater presence of zebra mussels may be affecting the tiny animal.

Balcer also reports other problems, including a sizable decline in zooplankton in the middle of the water column in Lake Huron and a possible drop at similar locations in Lake Michigan.

Balcer says in Lake Huron, these problems low in the food chain may be affecting fish. She says commercial and sport fishermen are very concerned about the size and quality of the lake trout and salmon they've been getting over the last few years."

Balcer says as more monitoring data comes in over the next year, natural resource agencies around the lakes will have to make several decisions about what kinds of fish to stock and whether to curtail some stocking programs.