FISHERY BULLETIN: VOL. 84, NO. 1 



Table 1.— PHC (petroleum hydrocarbon) and PCB (polychlorinated biphenyl) 

 levels in northwestern Atlantic Arctica islandica. 



chlorobiphenyls (C1 3 -C1 7 ), as well as total PCB. PAH 

 values are presented as individual compounds (e.g, 

 napthalene) or as homologous series (SN). Table 3 

 lists the mean trace metal concentrations and stan- 

 dard deviations; data are presented on a dry weight 

 basis to simplify comparisons with other studies. 



DISCUSSION 



PCB levels observed in this survey ranged from 

 2 to 30 ng/g (ppb) wet weight (Table 1). These values 

 are in general agreement with other data reported 

 for PCB levels in other coastal bivalves (Giam et al. 

 1976; Goldberg 1978; Gadbois 1982), but are lower 

 than those (to 400 ppb) reported for estuarine spe- 

 cies (Goldberg 1978; MacLeod et al. 1981; O'Connor 

 et al. 1982; ERCO 1983). However, we have found 

 little data on PCB levels in offshore molluscs nor any 

 other data on PCB levels in A. islandica for compari- 

 son. None of the A. islandica levels approach the cur- 

 rent 2 ppm (= 2,000 ppb) U.S. Food and Drug Ad- 

 ministration (FDA) "seafood action limit" for human 

 consumption. 



In spite of the wide geographical range sampled, 

 PCB levels were relatively uniform with only an 



order of magnitude difference between the high and 

 low values. Clearly the Georges Bank (station 379) 

 and remote Nova Scotia (stations 367, 335, 349) 

 ocean quahogs were minimally contaminated, with 

 their levels (2-5 ppb) reflecting the global PCB trans- 

 port phenomena. The ocean quahogs in the near- 

 shore New York Bight, Rhode Island Sound, and 

 Buzzards Bay were more contaminated, with values 

 up to 25 ppb. It is not surprising as previous biogeo- 

 chemical studies in the western North Atlantic have 

 clearly shown that several major urban pollutant 

 sources influence the nearshore environment. For 

 example, inputs of PCBs are specifically known to 

 occur in the New York Bight, from esturine fluxes 

 and via direct ocean dumping (Boehm 1983b) and 

 in Buzzards Bay, MA, from industrial inputs to the 

 New Bedford Harbor region (Weaver 1982). Some- 

 what surprising were the elevated levels at some sta- 

 tions on the outer New Jersey shelf (12-16 ppb) and 

 in the Hudson Canyon area (20 ppb). Offshore trans- 

 port of PCB material towards these stations via 

 riverine fluxes followed by southerly transport along 

 the New Jersey shore and down-canyon transport 

 of ocean-dumped material are possible modes of 

 transport to these stations (Boehm 1983b). 



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