Aquaculture impacts on the water quality and plankton community in a mangrove ecosystem in Brazil

摘要

Mariculture has become an important source of human food and its production is likely to expand well in Brazil for the foreseeable future. However, mariculture has caused direct and indirect negative impacts on the coastal ecosystem. To assess the impacts caused by a shrimp culture farm at the Goiana mangrove area the water and plankton community were studied. Samples were obtained from May/1997 to January/1999, before and after the farm implantation. Mariculture facilities reduced around 20% of the mangrove area. An intensive mixture of the marine and freshwater fluxes occurred in the system, dominating the marine. The dissolved oxygen was under saturation at low tide, indicating a polluted area, and saturated at the river mouth, due to the marine influence. High overall nutrient concentrations indicated a eutrophic area. Primary productivity increased from 1997 (～14 mgC h~(-1) m~(-3)) to 1999 (～25 mgC h~(-1) m~(-3)). Chlorophyll-a was also high (～15 mg m~(-3)) and presented the same pattern. The marine eurihaline plankton dominated the area. The plankton biomass varied from 86.28 mg.m~(-3) (May/97) to 3086.29 mg.m~(-3) (January/98). Phytoplankton average density was 53,278,000 cel L~(-1) and the zooplankton 40,542 ind m~(-3). Failure to acknowledge the life-support function of mangroves is one explanation of the uncontrolled expansion and intensification of shrimp aquaculture in Brazil, which has led other countries to self-pollution and disease problems.