Impact of storm-water outfalls on sediment quality in Corpus Christi Bay, Texas, USA

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, Texas, USA, system. Fifteen of the 36 sites were located near storm-water outfalls, but 13 other sites (i.e., industrial and domestic out falls, oil field-produced water discharges, and dredging activity) and eigh t reference sites were also evaluated. Sediment samples were collected and analyzed for physical-chemical characteristics, contaminant concentrations (metals, polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], and pesticides), toxicity (amphipod and mysid solid phase and sea urchin pore-water fertilization and embryological development tests), and a benthic index of biotic integrity (BIBI) composed of 10 independent metric s calculated for each site. This large data matrix was reduced using multiv ariate analysis to create new variables for each component representing ove rall means and containing most of the variance in the larger data set. The new variables were used to conduct the correlation analysis. Toxicity was s ignificantly correlated with both chemistry and ecological responses, where as no correlations between the benthic metrics and sediment chemistry were observed. Using the combined information from the SQT, four of the five mos t degraded sites were storm-water outfall sites. Although estuaries are nat urally stressful environments because of salinity and temperature fluctuati ons, this ecosystem appears to have been compromised by anthropogenic influ ences similar to what has been observed for other heavily urbanized bay sys tems along the Texas and Gulf coast.