HR: 1330h
AN: NB33R-01    [Abstracts]
TI: Comparison of Grazing Intensity & Diets of Native and Invasive Amphipods in Lake Erie
AU: * Duggan, J P
EM: umbraone@msn.com
AF: EASTERN MICHIGAN UNIVERSITY, 316 MARK JEFFERSON, YPSILANTI, MI 48197 United States
AU: Francouer, S N
EM: sfrancoeu@emich.edu
AF: EASTERN MICHIGAN UNIVERSITY, 316 MARK JEFFERSON, YPSILANTI, MI 48197 United States
AB: Echinogammarus ischnus, an invasive amphipod originating from the Ponto Caspian Basin, was first discovered in the Detroit River in 1995 and has migrated through the lower Great Lakes displacing the native amphipod, Gammarus fasciatus. Both amphipods seek food and refuge by inhabiting substrata encrusted with zebra mussels and/or filamentous macro-algae. The filamentous green alga Cladophora, along with its epiphytic communities, are an important food source and refuge from predators and physical stresses. We examined the gut content of both amphipod species to determine their preferred food in their natural habitats, and conducted a laboratory experiment to determine each amphipod's grazing effects on algal biomass. Gut analysis was completed by taking grab samples from 4 study sites located along the western shore of Lake Erie every two weeks July through September, 2004. Amphipods were separated by species and preserved in 90% alcohol for later dissection. Algal taxa from amphipod guts were identified and enumerated using brightfield microscopy. In the lab experiment, algal biomass prior to and after two weeks of amphipod grazing was determined using ash-free dry mass and chlorophyll-a. Preliminary results indicate that E. ischnus and G. fasciatus exert approximately equal grazing pressure on the Great Lakes food web.
DE: 4815 Ecosystems, structure and dynamics
DE: 9901 NABS Student Award - Basic Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly