Spatial–temporal distribution of dissolved inorganic nutrients in the hypersaline Araruama Lagoon, Rio de Janeiro, Brazil

Abstract

Hypersaline systems are sensitive, mainly because of severe osmotic pressure. In these conditions, the introduction of inorganic dissolved nutrients can pose severe impacts on the water quality, leading to eutrophication, and in extreme episodes can cause fish mortalities. Most of the research on trophic processes in the water column of coastal environments focuses on temporal variation, but in extensive systems like Araruama Lagoon in Rio de Janeiro, Brazil, spatial variations may be important as well. The main goal of this work was to evaluate the spatial–temporal variation of trophic processes in Araruama Lagoon in the years 2010 and 2011. The State Environmental Agency (Rio de Janeiro) collected water samples from 52 sites during five campaigns, where water quality was analyzed. Contour maps were prepared to allow the interpretation of natural processes. Rainfall information was included to allow the evaluation of interactions between anthropic and climatic factors. It was concluded that the water quality was severely affected by an atypical summer precipitation that occurred in 2010, which was shown to influence the system until the winter of 2010. Furthermore, despite the large volume of the lagoon, nutrients originating from domestic effluents seem to promote unexpected negative environmental impacts.