THE ESTUARINE CLAM RANGIA-CUNEATA (GRAY) AS A BIOMONITOR OF HEAVY-METALS UNDER LABORATORY AND FIELD CONDITIONS

Accumulation of copper, chromium, cadmium, and lead by Rangia cuneata (Gray, 1831) was investigated under laboratory and field conditions. B ioaccumulation rates and concentrations of metals in tissues and the e xposure water were determined in the laboratory for calculation of bio concentration factors (BCF). The BCF ratios ranged between 0 and 422 w ith significant correlations between exposure time and tissue metal co ncentration for each metal. Field exposures were conducted below two i ndustrial outfalls that contained some of the metals. High concentrati ons of the metals were found in the sediments, low concentrations in t he water, and intermediate concentrations in the tissues of R. cuneata . No significant relationships were found between exposure time and ti ssue concentrations during the field exposures. However, in most cases a significant increase in tissue burden of the metals occurred after the 40 d exposures, indicating that R. cuneata accumulated the most bi oavailable forms of the metals under natural conditions. In addition, laboratory-retained clams demonstrated that gametogenesis could be inh ibited, thus avoiding seasonal variations in body weight and percent g onadal biomass that affect survival and metal uptake.