Boston Harbor Mussel and Lobster

Boston Harbor and Massachusetts Bay
MWRA Environmental Quality Department

Since 1992, MWRA has monitored winter flounder, lobster, and blue mussel (see monitoring locations). Mussels feed by filtering particles out of the water, and can concentrate (bioaccumulate) toxic materials from the water in their tissues. Mussels are collected from relatively pristine sites and then transferred to cages which are placed near Deer Island and in the Inner Harbor for up to 60 days, to permit bioaccumulation of contaminants.

BLUE MUSSEL

PAH levels in mussels have decreased and PCBs, pesticides are well within guidelines.

For this study, mussels from relatively clean areas in Gloucester and Sandwich were put in cages and placed on moorings for one to two months at the Inner Harbor near the New England Aquarium, and Deer Island Flats. Upon retrieval, the mussels were analyzed for lead, mercury, PCBs, PAHs, DDT, and ten other pesticides. PAHs in mussels have decreased since the early 1990s.

LOBSTER

Lobster meat shows little contamination, but the tomalley (hepatopancreas) exceeds FDA guidelines for PCBs.

Parts per billion, wet weight
Actual range of annual averages		FDA Limit
PCBs	10.8 - 39.8	2,000
DDT	0.7 - 6.0	5,000
Mercury	70 - 280	1,000

MWRA checks lobsters caught near Deer Island for signs of disease, and tests the tail and claw meat for contaminants. The hepatopancreas (tomalley) is also tested for these, and for lead, cadmium, copper, nickel, silver, zinc, chromium, and PAHs. The levels of contaminants in lobster meat are well below the FDA limit for human consumption, but there are consumer advisories against eating tomalley.

Although PCB levels are extremely low in MWRA discharges, PCBs break down very slowly and therefore persist in the environment. Because they are potential carcinogens, industrial PCBs were phased out of production beginning in 1971. However, concentrations of PCBs have increased in lobster tomalley annually since 1993. Possible explanations are a change in location where the lobster are foraging to a more polluted area, or an increase in age of the lobsters being tested.

Blue mussels being retrieved
for bioaccumulation testing

PCBs in lobster hepatopancreas (tomalley), 1992-2000. From 1993-1999 there was an upward trend in PCB levels in lobster caught in the harbor.