Typha invasion associated with reduced aquatic macroinvertebrate abundance in northern Lake Huron coastal wetlands

Aquatic macroinvertebrates are a critical component of wetland nutrient cycling and food webs, with many fish and wildlife species depending upon them as food resources; but little is known about how invasion by dominant macrophytes may alter community dynamics. We examined the impacts of Typha invasion on aquatic macroinvertebrate communities in three northern Great Lakes coastal wetlands by comparing community composition between stands of native emergent marsh and those dominated by invasive Typha. Typha invaded zones were associated with shallower and cooler water than native emergent zones, and we detected decreased aquatic macroinvertebrate density and biomass in invaded zones. After accounting for the positive effect of plant species richness on macroinvertebrate abundance, we observed Typha invaded coastal zones had less total macroinvertebrate and insect biomass than native zones across all levels of plant richness. Our results suggest that Typha invasion reduces habitat quality for aquatic macroinvertebrates by homogenizing structural diversity and reducing water temperatures, which in turn may negatively impact predatory organisms by decreasing food resources. We recommend experimental tests of Typha management treatments to identify techniques that may promote structurally diverse and biologically rich Great Lakes coastal wetlands.