Copper accumulation by two bivalve molluscs: Salinity effect is independent of cupric ion activity

Abstract

Oysters ( Crassostrea virginica) and soft shell clams ( Mya arenaria) were exposed to two different total copper concentrations (10 μg liter −1 and 30 μg liter −1) and two different cupric ion activities (10 −10 m and 10 −9 m) under high salinity and low salinity conditions. Cupric ion activities were adjusted by adding nitrilotriacetic acid (NTA) to the experimental media. Copper accumulation by both species was inversely related to salinity and positively associated with total copper and cupric ion activity. This salinity effect was proportionately greater for lower copper concentrations and activities and it was concluded that salinity would, therefore, be an important influence on metal accumulation in the natural environment. The salinity effect was still apparent when the cupric ion activity was held constant indicating that the effect is, at least in part, independent of the copper speciation in the medium.