Macroinvertebrate Diversity of Submerged Detroit River Coastal Wetlands

Abstract

Urban rivers face sustained anthropogenic pressures limiting biodiversity. Yet, urban waterways such as the Detroit River are important habitat in supporting regional diversity. The Detroit River is a Great Lakes Area of Concern where conservation and restoration efforts prioritize improved biological and habitat integrity in the connecting channel. This study explores benthic macroinvertebrate in submerged aquatic vegetation across five mainstem channel wetlands and two tributary sites of the Canadian wetlands to describe spatial patterns and diversity. We first examine inter-wetland differences between five mainstem wetlands by hierarchical cluster analysis, NMDS and PERMANOVA, identifying two mainstem groups: one comprising of two middle reach wetlands (Detroit River Marshes and Grass Island), the second showed similarities among wetlands across all reaches (Turkey Creek, River Canard and Peche Island). The latter groupings shared similar habitat characteristics, deeper and finer grain-sizes, and functional feeding group characteristics - low abundances of shredders. Second objective, we perform an intra-wetland comparison for Turkey Creek and River Canard to analyze for differences along tributaries. At neither River Canard nor Turkey Creek we observed significant tributary influence on mainstem communities but had found the Turkey Creek tributary communities significantly differed from the channel communities. Diversity metrics and Hilsenhoff Biotic Index illustrate strained benthic communities across the river. We had also found water quality to be consistently moderately degraded. Our findings differ from prior analyses within emergent vegetation that indicate variable water quality conditions between mainstem and tributary and non-impaired macroinvertebrate communities.