Biochemical and microbiological tools for the evaluation of environmental quality of a coastal lagoon system in Southern Brazil

This study aimed to evaluate the environmental quality of surface water of the Marica Lagoon System through physicochemical, biochemical and microbiological parameters, in order to assess its environmental quality. Marine influence over the system was evidenced by the salinity and temperature gradients, where the most distant point, in Marica Lagoon, presented the largest protein, lipid and biopolymeric carbon concentrations. Biopolymers, with predominance of lipids, presented a pattern that differs from the literature for coastal sediments. The concentration of thermotolerant coliforms characterised Marica Lagoon and Boqueirao Channel as unfit for bathing (60.0 and 66.3 cells. mL(-1), respectively). The bacterioplankton in the system proved to be predominantly heterotrophic, a consumer of organic matter, with fermentative, denitrifying and sulfate-reducing metabolism. No esterase enzyme activity was detected, despite the presence of active metabolism, measured by the electron transport system (average of 0.025 mu gO(2).h(-1). mL(-1)). The bacterial biomass (autotrophic, heterotrophic and coliforms), bacterial respiratory activity and biopolymer parameters evinced a spatial degradation pattern in the Marica Lagoon System, where the points with less water renewal are the most impacted.