Structure and seasonal variation of coastal prairie stream benthic invertebrate communities across a precipitation gradient
Carvallo, Fernando R.
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Predicted changes in precipitation patterns associated with climate change are expected to impact flowing water ecosystems. We used a natural climate gradient to enhance our understanding of how impacts will occur. We surveyed nine streams in the Texas Gulf Coastal Prairie that were distributed across a semi-arid to mesic rainfall gradient. A suite of characteristics including benthic invertebrate community characteristics, flow conditions, and water quality variables were assessed monthly in each site to relate precipitation regime to stream structure and function. Precipitation regime was observed to be a master variable. As annual rainfall increased, the flow environment became more stable within seasons and predictable across seasons. Invertebrate community composition was significantly influenced by rainfall and correlated flow variables. Mesic sites were dominated by slower growing taxa without adaptions for desiccation resistance and strong dispersal. Sites with higher low flow pulse percentage (associated with more arid sites) were dominated by taxa with the ability to exit the water. Mesic sites displayed greater seasonal variation in composition and species richness than semi-arid sites, whereas the communities in semi-arid sites were strongly shaped by flow conditions in the weeks prior to sampling. These observations demonstrate how small changes in rainfall can drive large changes on ecosystem structure and function and suggest that climate change may have sweeping impacts on the lotic fauna of the Texas Gulf Coastal Prairie.
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Carvallo, Fernando Rafael