Focused flows to natural nurseries in Texas estuaries

Freshwater inflow has been altered throughout the world and becoming an increasingly important issue as human demands conflict with ecological needs. Estuaries require freshwater inflow to maintain specific conditions that benefit its communities, and in particular infauna and epifauna. Nursery habitats within estuaries are vital to growth and survival of juvenile species. Nursery habitat provides specialized conditions such as lower salinity, increase food availability, and refuge from predation. The goal of this study was to use two long-term datasets were used to determine the spatial impacts of wet and dry conditions on infauna collected in sediment cores and epifauna collected in trawls within three Texas estuaries. Estuaries were divided into segments to determine spatial response to changes in environmental conditions. Segments in the upper reaches of the estuaries, closer to freshwater inflow, had greater abundance of juvenile Blue Crab, Gulf Menhaden, Brown Shrimp, and White Shrimp. Infauna and epifauna abundance was 38 – 60 % greater in more marine segments in Lavaca-Colorado and Nueces Estuaries, but infauna abundance doubled in segments closer to freshwater inflow in Guadalupe Estuary. Epifauna abundance increased by 25 – 35 % during dry conditions in the upper reaches, whereas wet conditions decreased epifauna abundance by 30 %. Dry conditions decreased infauna abundance by half in the upper reaches of Guadalupe Estuary. Greater abundance of smaller individuals in the upper reaches indicates these areas serve as nursery habitats. Altering the freshwater inflow to nursery habitats can degrade estuary health by decreasing infauna and epifauna abundance and richness. Establishing environmental flows that focus on the needs of the upper reaches in estuaries will ensure the protection and maintenance of nursery habitat even when fresh water is scarce during droughts.