Field measurements and modeling of dilution in the wake of a US navy frigate.

A field measurement and computer modeling effort was made to assess the dilution field of pulped waste materials discharged into the wake of a US Navy frigate. Pulped paper and fluorescein dye were discharged from the frigate's pulper at known rates. The subsequent particle and dye concentration field was then measured throughout the wake by a following vessel using multiple independent measures. Minimum dilution of the pulped paper reached 3.2 x 10(5) within 1900 m behind the frigate, or about 8 min after discharge. Independent measures typically agreed within 25% of one another and within 20% of model predictions. Minimum dilution of dye reached 2.3 x 10(5) at a down-wake distance of approximately 3500 m, or roughly 15 min. Comparison to model measurements were again within 20%. The field test was not only successful at characterizing wake dilution under one set of at-sea conditions, but was successful at validating the computer model used for assessing a wide range of ships and conditions.

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.