Biogeochemistry of Jurujuba sound concerning phosphorus dynamics, Rio de Janeiro, Brazil

Guanabara Bay stands out as one of the most polluted coastal areas of Brazil, highly eutrophicated, surrounded by industries and a non planned urbanized area. The concentrations of nutrients in this area vary greatly, generally presenting higher levels in the inner portions. The present study proposes to evaluate the trophic levels of this area not only through the water column, but also through the composition of sedimentary organic matter. Results revealed unquestionable effects of eutrophication as hypoxia in bottom waters, and phytoplankton blooms in the surface, with chlorophyll-a values up to 40.58 mu g.L super( -1), and oxygen contents as low as 0.86 mg.L super( -1). Surprisingly, concentrations of dissolved nutrients were mostly characteristic of oligotrophic environments. Dissolved inorganic phosphorus varied between 0.09 and 3.98 mu M. Ammonium varied between 0.78 and 3.84 mu M. In the sediments, inorganic phosphorus varied between 1.61 and 15.80 mu mol.g super( -1) and organic phosphorus presented maximum and minimum values of 10.06 and 1.52 mu mol.g super( -1), respectively.