Effects of Salinity on Species Richness and Community Composition in a Hypersaline Estuary

Salinity is often considered one of the most influential environmental factors affecting estuarine communities. This is particularly true for low-inflow estuaries, which typically experience limited freshwater input for long periods of time. Disturbance events related to hypersalinity (> 35) occur commonly in Baffin Bay, TX, and have been linked to changes in fish and macrofauna abundance. Here, we use a long-term fishery-independent dataset collected by the Texas Parks and Wildlife Department (1983-2019) to determine the extent to which salinity affects the fish and invertebrate communities (i.e., species richness, spatial distribution, and community composition) in the Baffin Bay complex. Increased salinity had a negative effect on species richness of communities captured in two gear types (gill net and bag seine) and across seasons (fall and spring) based on generalized linear models. Species richness was also explored spatially using optimized hot spot analyses. The location of hot and cold spots of species richness varied within each salinity bin (< 35, 35-50, > 50) for both bag seine and gill net samples. However, more well-defined hot spots were apparent where salinity was > 50. Multivariate analyses used to explore changes in community composition across salinity bins revealed differences between salinity regimes for both gear types. SIMPROF tests also yielded groups of species with similar responses in abundance across salinity bins, which could be used to identify indicator species. These results could aid resource managers as they incorporate environmental factors such as salinity into ecosystem-based fisheries management strategies. In addition, understanding drivers of community composition and species distribution will be needed when responding to extreme hypersalinity events.