journals.uchicago.edu
Habitat context mediates macroinvertebrate responses to Zebra Mussel (Dreissena polymorpha) shell deposits | Freshwater Science
Abstract The Zebra Mussel Dreissena polymorpha (Pallas, 1771) has invaded surface waters throughout North America, and it alters benthic habitats by depositing dense layers of shells. Although these shell deposits can increase habitat complexity in some systems, they may also lead to habitat homogenization, particularly in streams with coarse substrates. We sought to understand how these shell deposits may affect macroinvertebrate assemblages in the Rouge and Huron watersheds (Michigan, USA; August 2017). We examined whether shell deposit density is related to macroinvertebrate community diversity and relative abundance and if those relationships might differ between rural and urban streams, noting changes in taxa sensitive to habitat structure, such as Ephemeroptera and Trichoptera (mayflies and caddisflies). In one rural stream, the % abundance of specific mayfly and caddisfly families decreased with increasing shell density, suggesting a localized negative response to shell-induced substrate changes. However, this pattern was not consistently observed across other rural streams, indicating that site-specific factors may mediate these effects. Regardless, shell deposits in urban streams, where baseline habitat complexity is often low, may offer structural refuge and benefit specific invertebrate taxa. Our findings highlight the context-dependent nature of Zebra Mussel relationships with stream invertebrate community metrics and suggest that the ecological consequences of shell deposits may vary with stream habitat characteristics.
