Wallace, W. G. United States Geological Survey, wwallace@usgs.gov
Brown, C. G. USGS, clbrown@usgs.gov
Luoma, S. N. USGS, snluoma@usgs.gov

 
THE INFLUENCE OF ANIMAL SIZE AND EXPOSURE HISTORY ON THE SUBCELLULAR PARTITIONING OF Cd AND Zn IN THE BIBALVE POTAMOCORBULA AMURENSIS AND THE IMPLICATIONS FOR METAL TROPHIC TRANSFER
 
Recent studies indicate that metal trophic transfer may be predicted based on subcellular compartmentalization within prey and that it is the metal associated with the cytosol and intracellular organelles which is the most bioavailable to predators. Consequently, factors influencing metal partitioning may affect metal trophic transfer. The goal of the present study is to investigate how animal size and exposure history influence subcellular partitioning of Cd and Zn in Potamocorbula amurensis. A strong size dependence in subcellular metal partitioning appears to result from size dependent metal detoxification. Small clams had 10% Cd bound to metallothionein (MT) proteins and 2% Zn stored in metal-rich granules (MRG). Large clams had 35% Cd associated with MT and 16% Zn sequestered via MRG. Because of differences in bioavailability to predators of this detoxified metal (Cd-MT, Zn-MRG), it is estimated that when feeding on small vs. large clams Cd bioavailability would increase from 56% to 64% and that of Zn would decrease from 80% to 70%. Additionally, exposure history was also found to have an important role in controlling these processes. Clams from an historically contaminated site in San Francisco Bay had 26% more Zn associated with the biologically available fraction than clams from a relatively clean site. There was a similar relationship for Cd, though the difference was not as great (18%). These site specific differences in biologically available metal, in conjunction with differences in total metal body burdens translate into a 3.0x greater Cd exposure and a 2.0x greater Zn exposure for predators ingesting clams from the contaminated versus the clean site.
 
Day: Friday, Feb. 5
Time: 03:30 - 03:45pm
Location: Sweeney Center
 
Code: SS28FR0330S