SUBLETHAL EFFECTS OF HEAVY-METAL CONTAMINATED SEDIMENTS ON THE BIVALVE MACOMA-BALTHICA (L)

Sublethal effects of estuarine sediments containing high levels of heavy metals were studied using the marine bivalve M. balthica. Burrowing behavior was inhibited in all contaminated sediments compared to the control. The time required for 50% of the population to burrow (ET50) ranged from 0.17 h in the control to 4.8 h in the most contaminated substrate. A comparison of linear regressions of the concentrations of individual metals in the sediments vs. the burrowing response times showed the regressions for Hg and Cd to be significant (P < 0.05 and < 0.001, respectively). An active threshold avoidance response by burrowed M. balthica was also demonstrated as clams showed a significant (P < 0.05) avoidance of the sediment containing the highest metal levels. Both behavioral responses were considered useful sublethal tests to assess the impact of polluted sediments.