THE IMPACT OF SEDIMENT RESUSPENSION ON MERCURY CYCLING AND THE BIOACCUMULATION OF METHYLMERCURY INTO BENTHIC AND PELAGIC ORGANISMS

Abstract

Sediment resuspension provides a potential mechanism for transferring Hg and MeHg from the sediment to filter feeding organisms and the pelagic food chain, and has been found to enhance Hg methylation. The study objective was to determine the effect of resuspension and clam density on Hg cycling and MeHg bioaccumulation into clams and zooplankton. Two, month-long mesocosm experiments were conducted. The Clam/No Clam Experiment compared resupension with clams (HDC1) versus without clams (NC). The Clam Density Experiment compared resuspension with a high-density population of clams (HDC2) compared with a low-density population of clams (LDC). In addition, a Hg stable isotope was added as a tracer to examine the complex trophic dynamics in the mesocosms. Results from the experiments suggest that clam density did not affect MeHg bioaccumulation into biota over the duration of the experiments. However, high clam density increased net production of MeHg in the water column.