There's concern that such a short circuit in the food chain could lead to declines in a number of fish, including perch, alewives, sculpin, bloater and smelt, with possible secondary effects on trout and salmon predators."

Data collected in the early 1990's indicated that the declines have been concentrated over a 5-mile-wide strip of lake bottom extending along the eastern Lake Michigan shore from near Chicago at the southern end to St. Joseph.

"Although amphipod populations declined by 60 to 90 percent in the early 1990's, there were still at least some of these animals left. When we picked through samples from the St. Joseph site in early November, we couldn't find a single amphipod. We just couldn't believe it," Nalepa said.

"During the 1980's, that site had 9,600 amphipods living on every square meter of lake bottom," Nalepa said. "Now, they're all gone. We're now wondering about how extensive this dead area might be. We hope that additional sampling planned for 1998 can provide the answers."

While other organisms are still present in the mud, they are not as readilyfed upon by fish as are amphipods. Prior to the zebra mussel's appearance in Lake Michigan, amphipods had relied on a rich crop of microscopic plants called diatoms for growth and survival.

For more information about amphipods and other trends in the benthic macroinvertebrate ,visit this "NOAA" site. To learn more about monitoring, visit GLNPO's Mysis and Diporeia Sled.

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Microscopic African creatures are making their way to the Great Lakes, joining the long list of exotics changing the Great Lakes ecosystem.

Daphnia lumholtzi, a type of zooplankton, is now moving this way, via the Mississippi River, said Phil Moy, a fisheries biologist for the U.S. Army Corps of Engineers in Chicago.

Zooplankton are microscopic animals that form the base of the food chain for many aquatic animals. Because zooplankton are a vital food supply for many newly hatched and even adult fish, the introduction of D. lumholtzi may negatively affect the fish communities of the waters it infests.

An electric barrier in progress by the U.S. Army Corps of Engineers for the Chicago Sanitary Ship Channel , to put a halt to the invading Eurasian gobie from the Mississippi ,is two or more years away, the barrier hugs the channel's bottom.

Even then, an electric barrier will not stop the African zooplankton called the Daphnia lumholtzi, Moy said.

This tiny barbed animal was first discovered in Texas inland lakes, said Rodney W. Horner, the aquatic nuisance species specialist for the Illinois Department of Natural Resources.

Daphnia lumholtzi is very different from other zooplankton . It is longer and has large spines on the head and tail. Including spine lengths, D. lumholtzi reaches almost 6 mm. Newly hatched fish consume a great deal of zooplankton.

"In all probability, it came in the ballast water and transferred into a gulf port," Horner said. "It's been marching up river ever since."

The animals' travels may be aided by a combination of barge bilge-water transfer and waterfowl.

The eggs of the Daphnia can be dried and carried on the feet of ducks, Horner said.

"I think the last identification of it was only 30 miles away" from the channel that joins the Mississippi system with the Great Lakes, Horner said.

While native Daphnia are important to the Great Lakes food web as the first food of many young fish, the barbs along the spine and tail of the African Daphnia suggests this creature won't have any effective enemies.

The overall effect of this zooplankton on the Great Lakes food web is uncertain.

for more information about Daphnia lumholtzi, and other exotics species visit Exotics and the Great Lakes.

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