Avaliação da contaminação microbiológica em praias de macromaré: uma proposição de metodologia

Abstract

The coastal environment suffers a gradual environmental impact caused by anthropic actions that is increasingly accelerated, beaches are no exception. Brazilian legislation minimizes the risks that bathers and other beachgoers may face. The objective of this research is to evaluate the levels of microbiological contaminants in different microhabitats commonly neglected by regulatory bodies. Our study site is located on Olho D’água beach, close to the mouth of the Pimenta River, in the capital of Maranhão. The microhabitats Sea Surface Water (SW), Interstitial Water (IW) and Sediment (S) were evaluated for six months (low and high rainfall). We used the chromogenic substrate method to detect total coliforms, E. coli and Enterococci; and the molecular method (PCR) to identify the species and virulence genes of Vibrio spp.. For abiotic data, we analyzed temperature, salinity, pH and rainfall. The data were subjected to permutational multivariate analysis of variance in a Bray-Curtis and Jaccard dissimilarity matrix. For microorganisms from the coliform and enterococci groups, the results were significant during the period of high rainfall, with contamination levels in SW, IW and S above those established by Brazilian legislation. For Vibrio spp., the results were insignificant between periods and microhabitats. Thirty strains were identified with some recurrent species in both periods. Abiotic parameters do not appear to have influenced the dynamics of Vibrio spp., with the exception of rainfall. It is necessary that the sediment is taken into account in health quality bulletins, as it acts as a hot spot for pathogenic microorganisms. Both methodologies were efficient in detecting possibly pathogenic microorganisms, however, they must be used, as one complements the other and so that the real risk that microhabitats may pose to beach users can be ascertained.