how healthy is the marine ecosystem of the Bays?

he Bays system supports a rich and diverse ecosystem of normal plant and animal communities,but signs of stress are evi- dent. Stress results from multiple causes,including overfishing and contamination. The highest levels of contamination are T nearshore—sources include rivers,the atmosphere,sewer overflows,treatment plants,and past use of disposal areas. and shellfish beds is a concern along An overview of the Bays system North Essex At the southern end of the Gulf of most of the Bays’ coastline. The chief Ocean Sanctuary Maine,the / sources of this contamination are sewer Figure 15. system extends from the New Hamp- pipe overflows,stormwater runoff,and Resources and stressors shire border to the tip of Cape Cod, leaks from septic systems. Treatment in Massachusetts and encompassing about 1650 square miles. plants are a relatively minor source of Cape Cod Bays Stellwagen Bank A strong southward coastal current contamination. National Marine and a large flow of water from the Merri- Levels of toxic contaminants in the Sanctuary South Essex mack River produce an average flow water are highest near the and, Ocean Sanctuary 1 south through the Bays,exiting to the except for a few pollutants like polychlo- open Atlantic (Figure 15). Strong tide and rinated biphenyls (PCBs),generally meet IWS St wind effects produce circulation patterns water quality standards throughout the FA ellwag that are highly variable from day to day. Bays. However,the sediments near en MBDS urban shorelines like , B Shipping Lane ank Rich resources and multiple stressors Salem ,and Broad Sound have sig- The beaches,wetlands,rocky shores, nificant levels of contamination. and deep offshore waters of the Bays In sediments,as in the water column, Legend provide important habitat for many plant contaminant levels decrease with dis- Federal Marine and animal communities including com- tance from shore except at former waste Sanctuary mercially important species of fish and disposal sites in . State Ocean shellfish,and rare or endangered animals Contamination in offshore sediments is Sanctuary Stat e Area of Critical and birds. not high enough to cause detrimental Environmental Concern Cape Cod Bay There are a variety of environmental ecological effects,according to National Barrier beaches CapeMarine Cod Bay Sanctuary stressors in the Bays system:historical Oceanic and Atmospheric Administra- Ocean Sanctuary Cape Cod Bay Industrial discharges whale hunting and ongoing commercial tion standards. In fact,monitoring has Area of fishing; disappearance of habitat such as shown that the bottom-dwelling animal Sewage treatment plant Critical outfalls salt marshes; dams that hinder fish communities are typical of the Gulf of Environmental migration and spawning; commercial New MWRA outfall site Concern Maine ecosystem. ( shipping and boating activities; and pol- Former Mass Bay Disposal Sit e, Toxic organic compounds and metals or Foul Area ( FA) Sanctuary) lution. have many sources. Three examples Former Industria l Waste Site (IWS) illustrating this are chlorinated pesticides Many sources of pollution, past and (especially DDT and its breakdown prod- Present Mass. Bay Disposal Site (MBDS) present ucts),PCBs,and mercury. DDT was Average ocean current direction Bacterial contamination of beaches banned in 1972 and PCBs were phased Multiple sources of toxic contaminants to Distribution of silver in surface sediments Winter flounder liver disease rates the Bays

Presen t Annual Loading : MWRA Primar y Treatment 0.18 Broad Sound

44% Future Outfall site Deer Island Flats 22% 0.15 1.18 0.23 43% Chlorinated Pesticides PCBs Mercury 1.82 14% Total = 20.7 kg/year Total= 51 kg/year Total = 358 kg/year 8.9 0.42 Legend 2.7 0.27 Nantasket Beach Atmosphere Rivers MWRA 5.5 5. 7 Other Treatmen t Plants Other sources

Future Annual Loading; MWRA Secondar y Treatment 0.32

Eastern Cape Cod Bay 0.51 2% Chlorinated Pesticides PCBs Mercury Total = 8.8 kg/year Total = 27 kg/year Total = 332 kg/year 0.69

Estimated existing inventories in Massachusetts Bay Chlorinated PCBs (kg) Mercury (kg) Pesticides (kg) 2 Water 39 47 300 Figure 17.Sediment silver concentrations (measured as parts Figure 18.Flounder liver disease is high in and Broad Sound, and Sediment 430-1520 510-1800 40,000-80,000 per million of the mud fraction of sediment) decrease with distance low in Cape Cod Bay. The percentage of flounder showing early liver disease decreases from the coast. Cape Cod Bay has somewhat higher silver concentra- with distance from Boston Harbor—flounder at the new outfall site may be affected by tions than more northern locations; this may reflect sediment resus- toxic pollutants from the coastal sources or from old waste disposal sites. Improved Figure 16. Annual inputs (loadings) of chlorinated pesticides pension and transport by currents to Cape Cod Bay (data from Both- treatment, continued source reduction, and improved dilution and dispersion at the new and PCBs to Massachusetts Bay are small compared to the existing ner et al. 1993). location will minimize flounders’ exposure to the contaminants (PAHs,pesticides, and inventory accumulated from past sources. The source of mercury is PCBs) thought to cause this disease (data from Mitchell et al. 1996). primarily atmospheric. Secondary treatment will reduce the quantities contributed by MWRA. The area of the pie charts reflect the relative amounts of present vs. future loads. (Annual loading data from chusetts Bay. The amounts of silver extends from the Harbor to Cape minant-related liver disease is at very Mitchell et al. 1997, Massachusetts Bay estimates of existing PCBs and chlorinated pesti- Cod Bay (Figure 17),with higher concen- low levels in Cape Cod Bay compared to inventory from data by Shea, 1993, 1996 in prep.; Bothner et al. 1993. Estimates based on model in Shea 1995). cides entering the Bays will trations in parts of Cape Cod Bay than in the area close to Boston Harbor. continue to decrease in the other offshore waters. Because the Har- future,and are slowly degrad- bor apparently was the source,these sil- Future decreases in contamination out of production beginning in 1971. ing in the environment. ver concentrations correspond quite well As MWRA’s contribution of toxic pol- These contaminants can bioaccumulate to the modeled dilution of the effluent lutants continues to decrease due to in marine mammals and fish. Historical contamination signals dispersed into Massachusetts Bay from source reduction and treatment improve- Figure 16 shows that the present MWRA’s monitoring program has the existing Harbor outfalls (Figure 12a). ments,the existing gradient of pollutants inputs to Massachusetts Bay from all revealed that past sewage discharges Despite the pattern of silver (and other in the Bay should gradually lessen. In sources combined of PCBs and chlori- into Boston Harbor have contributed sewage tracers not shown),the contami- addition,moving the effluent discharge nated pesticides are a small fraction of contaminants to broad areas of Cape nants are not causing significant impacts to the new outfall site (see page 9) will the amounts that have accumulated Cod Bay as a result of tidal flushing. Past on the health of marine life in Cape Cod reduce the concentration of dissolved from past inputs,when the chemicals inputs of sewage and sludge in Boston Bay. Bottom-dwelling animal communi- contaminants reaching Cape Cod Bay were being used in large amounts. Sec- Harbor contained silver,which was his- ties in the Bay are typical for the Gulf of from Boston. ondary treatment will greatly reduce torically discharged in large amounts by Maine as a whole. Data gathered on win- MWRA’s contribution of PCBs to Massa- the photographic industry. A gradient of ter flounder (Figure18) show that conta-