Community Composition of Aquatic Invertebrates along Dissolved Oxygen Gradients in Lake Huron Coastal Wetland Wet Meadows
Wetlands are an ecotone between terrestrial and aquatic environments and therefore support a diverse and unique flora and fauna. Macroinvertebrates make up a substantial portion of the biodiversity. The relationship between aquatic invertebrate community composition and the association with submergent and emergent macrophyte biomass is relatively well documented. However, the constraints imposed by conditions in wet meadow zones – areas that are intermittently flooded but whose soils are typically water-saturated and anoxic are less well understood. I investigated the relative importance of dissolved oxygen along the water depth gradient and its influenced on invertebrate community composition in comparison to the uniform vegetation found in the wet meadow zones of 10 wetlands in Lake Huron of the Laurentian Great Lakes.In 2017, I evaluated macrophyte community composition, sampled zoobenthos and fishes, and recorded diel dissolved oxygen trends along multiple transects in 10 coastal wetland wet meadows varying in geomorphology and exposure to agricultural activity in the contributing watersheds. The duration of hypoxia (DO < 4.0 mg/L) was a negative function of water depth along 30-m transects varying from 30-100 cm deep within each wet meadow site. Differences in the environmental factors were reflected in the relative abundance of oxygen-sensitive zoobenthos, being greater in areas that experienced a shorter duration of diel hypoxia and anoxia. However, overall invertebrate community composition was most greatly influenced by the major environmental differences between ecoregions and among wetlands within ecoregions. Thus, wet meadow community composition can be inferred from synoptic benthic samples collected from a wetland without concern for biases related to sampling depth.
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