Water depth and lake-wide water level fluctuation influence on α- and β-diversity of coastal wetland fish communities

Abstract

Abstract Coastal wetlands in the Laurentian Great Lakes are critical habitats for supporting fish diversity and abundance within the basin. Insight into the coupling of biodiversity patterns with habitat conditions may elucidate mechanisms shaping diverse communities. Within coastal wetlands, water depth as well as fluctuations in lake-wide water levels over inter-annual timescales, both have the potential to influence fish communities. Water level fluctuation can influence fish habitat structure (e.g., vegetation) in Great Lakes coastal wetlands, but it is unclear how water depth and lake-wide water level fluctuations affect fish community composition and diversity. Using β dissimilarity indices and multivariate ordination techniques, we assessed fish community structure among bulrush (Schoenoplectus acutus)-dominated wetlands in Saginaw Bay, Lake Huron, USA. We examined whether community structure was related to wetland water depth at the time of sampling and whether fish communities were more similar among years with similar Lake Huron water levels. Results suggested relatively high levels of both spatial (among wetlands) and temporal (among year) community dissimilarity that was driven primarily by species turnover. Thus, variability in water depths among wetlands and in Lake Huron water levels among years likely both contribute to regional fish diversity. Further, fish abundance and alpha diversity were positively correlated with wetland water depth at the time of sampling. Both climate change and anthropogenic water level stabilization may alter the magnitude and timing of water level fluctuations in the Great Lakes. Our data suggest that these changes could affect local fish community composition and regional fish diversity.