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Chemical Contamination

Chemical contamination of the marine environment has become widespread as urban growth and population centers continue to expand within coastal watersheds. Types of contaminants entering the coastal environment from both point and non-point sources include suspended solids, organic debris, metals, synthetic organic compounds, nutrients, and pathogens. The coastal waters adjacent to the Sanctuary, particularly within Boston and Salem Harbors, are among the more contaminated coastal environments in North America for a number of trace metals, PCBs and petroleum hydrocarbons (Pearce, 1990). Contaminant sources include sewage and industrial discharges, combined sewer overflows, stormwater runoff, ground water inflows, in place sediments, seeps, and atmospheric deposition (Menzie-Cura, 1991). Additional chemical and nutrient loads flow into Massachusetts Bay from the north in the buoyant freshwater plumes associated with the Merrimack River and several other large river discharges from the southern coast of Maine (EPA, 1993).

Contaminated sediments exist at the Massachusetts Bay Disposal Site (MBDS) and the Industrial Waste Site (Foul Area), both of which lie just outside the western boundary of the Sanctuary. Analysis of sediment chemistry in at the MBDS indicate elevated concentrations of copper, lead,
zinc, chromium, total PAH and total PCB relative to samples from outside the general areas of disposal.(EPA, 1989). Despite the long-term, use for disposal of contaminated sediments and other debris, (including unknown amounts of low-level radioactive waste) at these sites, ambient water quality conditions generally comply with the EPA's chronic water quality criterion concentrations for most parameters. Mercury was found to be variable at the site, with elevated concentrations above the chronic criteria concentration (CCC) of 0.025 ppm and average copper concentrations were only slightly below the 2.9 ppm CCC (EPA, 1989). Yet despite this and numerous other sources of contamination, the Bays and waters surrounding the Sanctuary are not grossly or uniformly polluted, and remain highly productive habitat for a vast diversity of marine life, including several species of marine mammals.

There is a growing body of literature (see sections below) providing evidence of chemical contamination in the populations of marine mammals which commonly occur in the Gulf of Maine region, yet due to the highly migratory nature of most species, it is extremely difficult to determine how and where certain animals accumulate these contaminants in their bodies. Given the numerous and diverse sources of chemical loadings to the GOM and the apparent species/individual dependent nature of effects, it is likely that direct causative relationships to chemical exposure will remain illusive until directed research efforts can better describe the pathways, fate, and induced effects of pollutants on marine mammals (see Reijnders, 1988). And while there is little empirical data regarding chemical toxicity in marine mammals from this region, evidence from around the world is increasingly pointing to chemical pollution as a contributing cause to viral epizootics and other mass die-offs of marine mammals (Raloff, 1994, Rik de L. Swart, et. al. 1994, Kuehl, et. al., 1994).

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