Aguiar, V. M. C., Abuchacra, P. F. F., Baptista Neto, J. A., 2013. 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. Jurujuba is a small sound located at the eastern board of Guanabara Bay and comprises a local fishing community, which makes it economically important. 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 μg.L−1, and oxygen contents as low as 0.86 mg.L−1. Surprisingly, concentrations of dissolved nutrients were mostly characteristic of oligotrophic environments. Dissolved inorganic phosphorus varied between 0.09 and 3.98 μM. Ammonium varied between 0.78 and 3.84 μM. In the sediments, inorganic phosphorus (IP) varied between 1.61 and 15.80 μmol.g−1 and organic phosphorus (OP) presented maximum and minimum values of 10.06 and 1.52 μmol.g−1, respectively. Biopolymers characterized the sediments as hypertrophic, with high levels of proteins (PRT) and carbohydrates (CHO), therefore, confirming the conditions of eutrophication in this environment, despite the low levels of dissolved nutrients. PRT:CHO<1 characterized Jurujuba sound as a detrital-heterotrophic system, corroborating the contents of organic matter as high as 28.78%.
