Diagenetic Processes in Aquaculture Ponds Showing Metal Accumulation on Shrimp Gills

The gill is the organ by which many toxic metals are taken up crustaceans. Iron known to precipitate at its surface, a phenomenon recently observed in some tropical aquaculture ponds. present study uses field approach understand better environmental conditions and ecological processes involved this deposit. Because shrimp exposed reduced products originating from organic waste accumulated sediment, spatial variation pH, redox potential concentrations of dissolved pore water were investigated these Total carbon, acid volatile sulfide pyrite also analyzed solid phase. Fe 2+ waters showed high variability between ponds within same pond with 1,193 μmol l –1 . Behaviors , Mn Co similar. Four geochemical environments identified, based on their physico-chemical characteristics. Highest for sediment occurred slightly acidic suboxic conditions. When became anoxic, H 2 S produced reacted and/or form pyrite. pH increased, concentration free rose 736 With neutral conditions, metal could be controlled precipitation as oxides hydroxides. production suggested existence possible process acidification two crop periods through sulfuric acid. This increase age cause accumulation after 30 years activity.