Crayfish connections: Linking ecology and hydrogeology in Alabama’s Black Prairie using crayfish distribution patterns

Abstract

Abstract Floodplain ecosystems host diverse surface‐water habitats (e.g., lotic, lentic, ephemeral) and groundwater features that support high levels of species diversity. Our understanding of species–habitat relationships within these complex ecosystems, however, remains incomplete, potentially hindering conservation efforts. Understanding associations between burrowing crayfish and habitat features of floodplains is particularly valuable because crayfish, through burrowing, play an important role in establishing aquatic‐terrestrial connections which enhance local biodiversity. Species of crayfish that persist in floodplains must burrow deep enough to access shallow groundwater. Consequently, burrow presence may indicate a preference for specific surface and subsurface habitat characteristics. The primary goal of our study was to evaluate specific habitat attributes as predictors of burrowing crayfish presence/absence, and our secondary goal was to evaluate species‐specific habitat associations with respect to the same environmental variables. We evaluated burrowing crayfish presence/absence and crayfish species composition with respect to groundwater depth, flood frequency (standing surface water), soil characteristics, and tree size in the Bogue Chitto Creek catchment, Dallas County, Alabama, U.S.A. Active burrows were expected at sites with access to water (a shallow water table) and at sites with environmental variables more conducive to burrow stability (fine‐grained soils and mature trees). Species composition was predicted to vary with groundwater depth and flood frequency. Groundwater depth was the primary driver of burrowing crayfish presence/absence in our system; active burrows were more likely to be present in areas with relatively shallow groundwater depths. Within occupied sites, differences in crayfish species composition were significantly associated with the degree of flooding during the 1‐year study period. Species associated with a high dependence on surface waters were collected alongside species dependent on burrowing to access groundwater, suggesting that the environmental features of floodplains satisfy a diverse set of requirements. In particular, sites offering a mosaic of accessible groundwater depths and floodplain pools may provide critical habitat for diverse assemblages of burrowing crayfish species. Our study revealed a strong association between the presence/absence of active crayfish burrows and the depth to groundwater, a result that supports using burrowing crayfish as indicators of accessible groundwater. This will be increasingly important in the context of how climate change might influence water availability and local species diversity.