231 Distribution and diet of the invasive ponto-caspian hydroid, cordylophora caspia in southern Lake Michigan: Potential effects on fish prey availability

Tuesday, May 19, 2009
Ambassador Ballroom
Nadine C. Folino-Rorem , Biology Department, Wheaton College, Wheaton, IL
Matthew J. Duggan , Biology Department, Wheaton College, Wheaton, IL
Anne Parry Macdonald , Biology Department, Wheaton College, Wheaton, IL
Emily K. Mindrebo , Biology Department, Wheaton College, Wheaton, IL
Martin B. Berg , Department of Biology, Loyola University, Chicago, IL
Invasive species in the Great Lakes can alter benthic invertebrate community structure and function.  An often over-looked Ponto-Caspian invasive species is the colonial hydroid, Cordylophora caspia.  Cordylophora grows prolifically on hard substrata including docks, pilings and dreissenid mussel shells attached to docks and offshore shipwrecks in southern Lake Michigan. The purpose of our research was to assess the potential ecological impact of Cordylophora by documenting the distribution and predatory effects of this hydroid. Cordylophora colonies were found at seven of eight Chicago harbors and two of four offshore sites.  Colonies consume zooplankton (mussel larvae, cladocerans, copepods) and benthic macroinvertebrates (nematodes, annelids, harpactacoids and chironomids).  Gut analyses suggest that prey consumption differs between dock and benthic offshore habitats.  Chironomids are more frequently consumed at offshore wreck versus near shore dock sites.  Laboratory feeding experiments using Daphnia, nematodes and chironomid larvae indicate that prey behavior in conjunction with prey size were important factors for the hydroid’s ability to capture and consume prey.  The prevalence of Cordylophora in southern Lake Michigan, the prey consumed, and aspects of prey capture are of interest because prey items such as chironomids are important for larval, juvenile and benthivorous fish.
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