After a three-week period, Mytilus from polluted Station 2 had accumulated 
significantly higher levels of Ni and Cu than had Mytilus from the clean Bay 
stations (Figure 3-5). Similarly, Station 2 values after three weeks were 
significantly higher than values from control animals sacrificed at time zero. 
However, levels remained the same in all animal groups after one additional 
week of exposure. 
DISCUSSION 
Currently, Mytilus edulis is being used as an indigenous biological monitor 
for a variety of materials including petroleum hydrocarbons, chlorinated 
hydrocarbons, and transuranics, in addition to trace metals in coastal waters of 
the United States (5). Similar activity is underway in the United Kingdom and 
Germany as well. Because of its ubiquitous distribution, Mytilus edulis is being 
considered as an international monitoring organism. 
To date, the use of Mytilus edulis appears to be limited to that of an 
indigenous monitor. We are not aware of an approach similar to that reported 
here where Mytilus is used as an introduced biological monitor. 
The results indicate that Mytilus as an introduced species does reflect 
elevated levels of metals previously observed in the polluted section of 
Narragansett Bay, in the sediments and the indigenous mollusc, Mercenaria 
mercenaria. Nickel and copper were concentrated to significantly higher levels 
in Mytilus introduced into the polluted section of the Bay compared to those 
introduced in the clean lower Bay, and those held in our laboratory 
flow-through system. Lead levels were observed to be higher in animals from 
collecting Station 2, than in either collecting Station 3 or the laboratory; 
however, statistical significance was not established due to the small data set. 
Cadmium, chromium, vanadium, and zinc were not reflected at higher levels in 
Mytilus from the polluted area. 
With one exception, that being in the case of Cd, these results reflect those 
reported by Phelps and Myers (5) for Mercenaria collected in the same parts of 
Narragansett Bay. In that study, Mercenaria from the polluted area were shown 
to concentrate to higher levels, but not depurate, Cd, Pb, Ni, and Cu compared 
to lower Bay animals. No differences were observed in levels of V and Zn 
between the two groups of Mercenaria before or after depuration. Thus, 
Mytilus edulis , when used as an introduced monitor, is demonstrated to reflect 
metal levels observed in the major resident or indigenous species in three out of 
the four metals of note. 
Higher metal accumulations were established after three weeks of 
monitoring by Mytilus introduced in the polluted section of the Bay for Ni and 
35 
