The potential use of mangrove forests as nitrogen sinks of shrimp aquaculture pond effluents: The role of denitrification

A generalized nitrogen budget was constructed to evaluate the potential rol e of mangrove sediments as a sink for dissolved inorganic nitrogen (DIN) in shrimp pond effluents, DIN concentrations were measured in pond effluents front three semi-intensive shrimp ponds along the Caribbean coast of Colomb ia between 1994-1995. Mean NH4+ concentrations in the discharge water for a ll farms were significantly higher (67 +/- 12 mu g/L) than in the adjacent estuaries (33 +/- 8 mu g/L), Average NH4+ concentrations in the pond discha rge over all growout cycles were similar, representing an approximate doubl ing in relation to estuarine water concentrations. In contrast, NO2 + NO3 c oncentrations were similar in both pond effluent and estuarine waters, Diss olved inorganic nitrogen loading of the ponds was similar, The estimated re duction of DIN in pond effluents by preliminary diversion of outflow to man grove wetlands rather than directly to estuarine waters would be greater th an or equal to 190 mg N/m(2) per d. Based on this nitrogen loss and dependi ng upon the enrichment rate, between 0.04 to 0.12 ha of mangrove forest is required to completely remove the DIN load from effluents produced by a 1-h a pond.