Geochemical environments at the water-sediment interface in aquaculture ponds showing metal accumulation on shrimp gills

The gill is the organ by which many toxic metals are taken up by crustaceans. Fe2+ is known to precipitate at its surface, a phenomenon recently observed in some tropical aquaculture ponds. The present study uses a field approach to understand better the environmental conditions and ecological processes involved in this deposit. Because shrimp are exposed to reduced products originating from organic waste accumulated in the sediment, spatial variation in pH, redox potential and concentrations of dissolved metals in pore water were investigated in these ponds. Total organic carbon, acid volatile sulfide and pyrite were also analyzed in the solid phase.