Size Scaling of Contaminant Trace Metal Accumulation in the Infaunal Marine Clam Amiantis umbonella

Size scaling of the accumulation of four trace metals was examined in the infaunal clam Amiantis umbonella in Kuwait Bay. In clams of varying shell length (2.5–5 cm), soft tissue growth in A. umbonella from a contaminated site was inhibited compared with clams from a less contaminated reference site. Body burdens of all four metals were positively correlated with clam soft tissue wet weight, but for Cd, Cu, and Pb, correlations were stronger in clams from the contaminated site (r² = 0.6–0.9, p < 0.001) than the reference site (r² = 0.2–0.3, p < 0.002). Scaling factors for the accumulation of Cd, Cu, and Pb in the soft tissues of A. umbonella from both sites were not significantly different than 1, indicating that clams accumulated these metals in proportion to growth with little regulation. The scaling factor of Hg in clams from the contaminated site also was 1 but was 0.5 and 2.4 for high and low Hg accumulating subpopulations of clams from the reference site, respectively. The greater retention of Hg with respect to growth in clams from the reference site than from the contaminated site requires further investigation to determine differences in Hg bioavailability at the two sites and the form of Hg these clams accumulate.