Surficial sediment samples were analyzed from 162 locations within five estuaries - Charleston Harbor, Winyah Bay, Leadenwah Creek, Savannah River, and St. Simons Sound - in coastal areas of South Carolina and Georgia states in a survey of sediment toxicity performed in 1993 and 1994.
All samples were tested for toxicity with a battery of complimentary laboratory bioassays. The laboratory bioassays consisted of amphipod survival tests in solid-phase sediments, microbial bioluminescence (Microtox™) tests of organic solvent extracts, and sea urchin fertilization and embryo development tests of porewaters. Some samples also were tested in copepod reproduction and cytochrome P-450 RGS bioassays. Chemical analyses for a suite of trace metals, organic compounds, and sedimentological factors were performed with portions of most samples.
The concentrations of some trace metals exceeded background levels, exceeded some effects-based guidelines concentrations, and showed strong correlative associations with toxicity.
The concentrations of many individual and classes of polynuclear aromatic hydrocarbons (PAHs) also were elevated in samples that were also determined to be significantly toxic.
The concentrations of chlorinated organic compounds [e.g., polychlorinated biphenyls (PCBs)] were elevated in a few samples. Results of cytochrome P-450 RGS assays showed strong correlations with the concentrations of high molecular weight PAHs and PCBs.
Toxicity tests performed with invertebrates and Microtox™ often indicated strong correlations with mixtures of potentially toxic substances, the composition of which differed among estuaries and toxicity tests.
The concentrations of substances such as copper and high molecular weight PAHs showed evidence suggesting they could have contributed to toxicity.
The concentrations of ammonia were sufficiently elevated only in a small minority of samples to contribute substantially to toxicity.
Overall, most samples (with some notable exceptions) from this survey area were somewhat less contaminated and toxic than samples from other U.S. estuaries. The spatial extent of toxicity was somewhat lower than the nationwide averages, as estimated with data from over 20 large estuaries studied nationally.
These data, however, agreed well with observations from similar chemical analyses and toxicity tests performed by NOAA for the Environmental Monitoring and Assessment Program (EMAP) - Estuaries in the Carolinian province, which includes all five of these estuaries.
