After a three-week period, M. edulis from polluted Station 2 had accumulated 

 significantly higher levels of Ni and Cu than had M. edulis 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, M. 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, M. edulis is being 

 considered as an international monitoring organism. 



To date, the use of M. edulis appears to be limited to that of an 

 indigenous monitor. We are not aware of an approach similar to that reported 

 here where M. edulis is used as an introduced biological monitor. 



The results indicate that M. edulis 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 M. edulis 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 

 M. edulis from the polluted area. 



With one exception, that being in the case of Cd, these results reflect those 

 reported by Phelps and Myers (4) for M. mercenaria collected in the same parts of 

 Narragansett Bay. In that study, M. 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 M. 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 M. edulis introduced in the polluted section of the Bay for Ni and 



35 



