STEIMLE ET AL.: ORGANIC AND TRACE METALS IN OCEAN QUAHOG 



by Wenzloff et al. (1979), was not apparent from the 

 present data or from the studies summarized in Table 

 4. Results of other studies involving whole body anal- 

 ysis (Table 4) suggest that Cd, Ni, and Zn could also 

 be high on Georges Bank; otherwise, the values pre- 

 sented do not support any consistent latitudinal 

 trends. 



Results indicate, however, on a local level, elevated 

 trace metal levels were also usually associated with 

 known areas of inputs, eg., waste dumpsites or ad- 

 jacent to heavily industrialized coastal areas, such 

 as the New York Bight apex (station 29), or natural 

 depositional areas where trace metals from unknown 

 sources are apparently accumulating, ag, the "Mud 

 Patch" (stations 181, 237). 



The uptake and accumulation of trace metals by 

 marine organisms are known to be affected by a 

 number of variables. These variables include season, 

 age, size, temperature, and interactive effects of 

 several metals (Phillips 1977), and can be sources of 

 some of the variability shown between the results 

 of studies in the same area. Methodology is another 

 source of variability between the results of each 

 study, especially when intercalibrated results with 

 standards are not available It is interesting to note 

 that an expected close correlation between trace 

 metal levels in the sediment and in A. islandica 

 tissues was not evident in at least one study (Rey- 

 nolds 1979), suggesting that the water and food or 



other suspended material could be the primary 

 source of contaminants to this filter-feeding species. 

 In conclusion, a set of measurements of several 

 organic and seven trace metal contaminant levels in 

 the commercially valuable ocean quahog have been 

 obtained from a wide range of northwestern Atlan- 

 tic locations. This set can be used as a base to moni- 

 tor long-term changes in the assimilated levels and 

 distributions of these compounds in this species and 

 the risk to its health of future use as food. The levels 

 found were well below the FDA seafood action limit, 

 but elevated values were associated with impacted 

 coastal habitats and possibly waste dumpsites. 



ACKNOWLEDGMENTS 



This study would not have been possible without 

 the generous cooperation of the Northeast Fisheries 

 Center's Resource Survey Group, specifically Thom- 

 as Azarovitz, Charles Byrne, Donald Fletcher, Mal- 

 colm Silverman, and others, who supplied us with 

 the samples from annual clam assessment surveys. 

 We also express our thanks to John B. Pearce and 

 John O'Reilly for their support, and to Catherine 

 Noonan, Maureen Montone, and Michele Cox for 

 their assistance in preparing the manuscript. The 

 paper was improved significantly from the comments 

 of Donald Gadbois, Richard Greig, Carl Sindermann, 

 Robert Reid, and unidentified reviewers. Funding for 



Table 4.— Comparison of mean trace metals levels {^g g 1 dry wt.) in Arctica islan- 

 dica of the northwest Atlantic. 



'Original wet weight data converted into dry weight by multiplying by 8. 



139 



