DNA damage in mussels at sites in San Diego Bay

Identification and assessment of introduced and other toxicants is crucial to any comprehensive study of contaminants within the marine environment. The relationship between DNA single-strand breaks and the exposure of marine organisms to environmental contaminants was examined at sites in San Diego Bay, CA. A comprehensive assessment of the extent and consequences of marine environmental contamination in the area of Naval Station San Diego was conducted in the summer of 1995. The study addressed contamination sources, distributions, concentrations, transport, sediment-water exchange, biological effects, and degradation. The biological effects portion of the study (this paper) included contaminant bioaccumulation, organismal growth, and the determination of DNA single-strand breaks using the Comet assay. DNA damage was determined in hemocytes collected from deployed and resident mussels, Mytilus edulis, at six stations in and around the Naval Station San Diego. Deployed mussels were exposed on station for approximately 30 days in plastic mesh bags, placed 1 m above the bottom. Hemocyte samples were collected on days 0, 12, and 32. It was found that stations exhibiting the extremes of contaminant exposure, both highest and lowest concentrations, were easily identified using growth and DNA damage measurements. Sediment chemistry and bioaccumulation data indicated, Hg, Cu, and Zn, to be the most notable contaminants. The Comet assay, and in particular germ cell DNA damage determinations, were found to respond rapidly to station contaminants. Results from this study and an earlier 1993 study suggest that the non-sediment associated effects observed at one station may have been the result of the photoactivation of accumulated PAHs.