The use of mangrove wetland as a biofilter to treat shrimp pond effluents: preliminary results of an experiment on the Caribbean coast of Colombia

The potential benefit of integrating mangrove and shrimp farms to protect ponds against erosion, to enhance the productivity of supply water and also to treat pond effluents has been pointed out previously. Agrosoledad, a 286‐ha shrimp farm located on the Caribbean coast of Colombia, was constructed behind a 1‐km‐wide mangrove area. Farm effluents are partially recirculated through a 120‐ha mangrove wetland used as a biofilter. A 3‐month study compared the concentrations of suspended solids and inorganic nutrients in the supply canal, the pond drainage and the biofilter. Suspended solids increased in pond drainage compared with supply water, but they were drastically reduced in the biofilter. In contrast, dissolved inorganic nitrogen and phosphorus concentrations were not different in supply water and pond drainage, but they increased in the biofilter because of the presence of a large marine bird community. Additionally, a significant decrease in dissolved oxygen and pH was observed in the biofilter. The study demonstrated the efficiency of the system to eliminate suspended solids from the effluent. However, nutrient dynamics showed that the possible use of mangrove wetlands as biofilters for effluent treatment will be less predictable than expected.