Seasonal variation in the toxicity of sediment-associated contaminants in Corpus Christi Bay, TX.

Seasonal variation in pore water and sediment-water interface (SWI) toxicity at two sites of suspected contamination was investigated using sea urchin embryological development (Arbacia punctulata) and copepod hatching success (Schizopera knabeni). Site S1, located inside a marina, was fine-grained and S2, located near a neighboring stormwater outfall, was sandy. Both sites were cored in summer and winter, along with reference sites of equivalent grain sizes. Whereas the muddy contaminated site displayed a slight decrease in sea urchin toxicity from summer to winter, pore water from the sandy contaminated site exhibited an increase in sea urchin toxicity. The sandy sites displayed slight toxicity increase to copepod hatching success in winter, which occurred in the SWI of S2 and in the pore water from the reference site, R2, where it coincided with sedimentation. Cu was the most prevalent metal in the sediment samples. Although Cu concentration increased in the whole sediments and pore waters from summer to winter, its concentration in overlying SWI exposure decreased from summer to winter. Organic compounds exhibited opposite behavior, with smaller variety identified in the winter pore water samples, but more chemicals detected in the SWI samples in winter.