Can a multi-metric bioassessment tool be used to assess faunal communities in tidal streams along the lower Texas coast?

Tidal streams are dynamic, transitional systems that provide key habitat to many ecologically and economically important species. Currently, the Texas Commission on Environmental Quality (TCEQ) monitors tidal streams in Texas using only physicochemical parameters and lacks a standardized biomonitoring protocol. To address this gap in management tools, a multi-metric index of biotic integrity (IBI) was created to assess the condition of tidal stream nekton and benthic macroinfauna assemblages along the lower Texas coast. By identifying biotic metrics that are differently sensitive to anthropogenic impairment, the IBI synthesizes complex biological data into a practical management tool. To create the IBI, 15 sites were classified as having high (reference) or low (test) anthropogenic impairment based on surrounding land-use land cover, watershed population density, and historical conventional parameter concentrations for each tidal stream. During 2020 and 2021, sites were sampled for nekton, via seine hauls, and benthic macroinfauna, via benthic cores. Water quality, conventional parameter, and habitat measurements were also assessed during these sampling periods. Results show distinction between reference and test communities based on multivariate analyses. IBI metrics were derived from historical IBI studies and community analyses based on their ability to discriminate between test and reference conditions. Selected metrics included abundance of certain nekton taxa, abundance and biomass of benthic macroinfauna taxa, measures of diversity, and faunal functional groups. Refinements to the IBI should consider further regionalization based on coastal climate zone, assessing multiple sites per stream along the upstream-downstream salinity gradient, and incorporating long- term monitoring data. Once validated, the tidal IBI will enhance the TCEQ’s monitoring and management program by providing a standardized protocol to evaluate the biological communities in tidal streams and identify areas most in need of management attention.