Midwest Fish & Wildlife Conference 2019

AUTHORS. Zachary Johnson, Ashley Moerke, Mary Markel – Lake Superior State University

ABSTRACT. Great Lakes coastal wetlands are an important ecosystem that is often being altered by human activity. One way to measure the effect disturbances may have on wetlands is by examining functional diversity of aquatic macroinvertebrate assemblages. Over a 7-year period (2011-2017), macroinvertebrate assemblages across 26 wetland sites in the St. Marys River were assessed to determine if macroinvertebrates in wetlands exposed to high wave action exhibited different traits than protected wetlands. Of these 26 sites, 13 were in close proximity and exposed to a dredged freighter shipping channel (exposed sites), and 13 were located away from the channel or otherwise protected by a barrier or embayment (protected sites). We hypothesized that exposed sites would be dominated by macroinvertebrates with disturbance-associated traits whereas barrier sites would possess a composition reflecting more stable environmental conditions. Macroinvertebrates were collected from four vegetation zones, identified following Great Lakes Coastal Wetlands Monitoring Program protocols, and assigned traits (functional mode of existence and voltinism) using the USEPA’s Freshwater Biological Traits Database. Trait composition of macroinvertebrate assemblages in exposed and protected sites varied by vegetation type, with Schoenoplectus zones possessing higher wave action, and Typha and Phragmites zones generally receiving less wave action. In nearly all vegetation zones, mutlivoltinism and disturbance-resistant functional mode of existence was higher in protected than exposed sites, which was counter to our expectations and inconsistent with current ecological theory concerning macroinvertebrate assemblage response to wave action-induced disturbances. Further analyses are needed to understand the drivers of invertebrate trait composition in St Marys River wetlands.