Impact of Storm Water Outfalls on Sediment Quality in Corpus Christi Bay, Texas

To determine the quality of sediments and extent of contaminant impacts, a Sediment Quality Triad (SQT) study was conducted at 36 sites in the Corpus Christi Bay system, Texas. Fifteen of the 36 sites were located near storm water outfalls, but 13 other sites (i.e., industrial and domestic outfalls, oilfield produced water discharges, dredging activity) and 8 reference sites were also evaluated. Sediment samples were collected and analyzed for physical-chemical characteristics, contaminant concentrations (metals, PAHs, PCBs and pesticides), toxicity (amphipod and mysid solid-phase tests, and sea urchin fertilization and embryological development porewater tests) and a benthic index of biotic integrity (BIBI) comprised of 10 independent metrics calculated for each site. This large data matrix was reduced using multivariate analysis to create new variables for each component representing overall means and containing most of the variance in the larger data set. The new variables were used to conduct the correlation analysis. Toxicity was significantly correlated with both chemistry and ecological responses whereas no correlations between the benthic metrics and sediment chemistry were observed. Using the combined information from the SQT, four of the five most degraded sites were storm water outfall sites. Although estuaries are naturally stressful environments due to salinity and temperature fluctuations, this ecosystem appears to have been compromised by anthropogenic influences similar to what has been observed for other heavily urbanized bay systems along the Texas and Gulf coast.