Wednesday, June 6, 2007 - 2:45 PM
265

Macroinvertebrate responses to zebra mussel (Dreissena polymorpha) colonization of stream substrates

Alyson A. Olesen and Reuben R. Goforth. Fisheries & Wildlife, Michigan State University, 13 Natural Resources, East Lansing, MI 48823

Zebra mussels (Dreissena polymorpha) quickly spread throughout the Great Lakes soon after being introduced to Lake St. Clair.  They are now abundant in many inland lakes, as well as lake-outlet streams and large rivers.  The effects of dreissenid introductions on native aquatic communities have been extensively studied in lake habitats.  However, unintentional spreading of dreissenids will undoubtedly continue in other aquatic ecosystems and it is important to understand how lotic taxa may respond to such introductions.  I conducted an in-stream study of native stream macroinvertebrate responses to simulated dreissenid colonization using shells adhered to ceramic tiles.  I also conducted a laboratory experiment to determine if a prevalent taxon in the stream samples, hydropsychid larvae (Trichoptera), exhibited substrate preference in the presence of live vs. dead dreissenids.  My results suggest that several macroinvertebrate taxa exhibited positive preference for the dreissenid mussel shells, particularly hydropsychid caddisflies.  This suggests that benthic communities of small streams are likely to become altered in response to spreading of dreissenids into these ecosystems.  Given that such macroinvertebrate responses have led to significant food web changes in lentic ecosystems, there is great need for management plans to both prevent and respond to future introductions in lotic ecosystems.

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