Impacts of shrimp farming cultivation cycles on benthic assemblages and chemistry of sediments

There is a growing concern, both locally and worldwide, for the recognition of the finite and fragile nature of the coastal ecosystems in which shrimp farming often takes place. Attempts to fully control and regulate shrimp farming activities and their potential adverse impacts in many countries have been so far unsuccessful. The aim of this study was to evaluate the spatial and temporal impacts of semi-intensive shrimp farming based on multiple lines of evidence using an asymmetrical design. Significant differences were observed between impact and control areas for the water column and sediments. Concentrations of nutrients, Zn and Cu were significantly higher in impact than control areas. In general, the level of contaminants was highest during the harvesting period and in sites nearby the discharge of effluents. Abundance and richness of benthic assemblages were at least one order of magnitude smaller in impacted areas than in controls. The structure of the benthic assemblages was significantly different at these two treatments. The combined use of biological and chemical data showed to be efficient to provide precise answers regarding the extent of impacts caused by shrimp cultivation in coastal ecosystems. The results provide the basis for a better understanding of impacts of this activity and can subsidize the development of better management practices for coastal areas.