Microbiological quality and environmental factors of estuarine area of Iguape Bay Marine Reserve (Bahia) for cultivation of native oysters

ABSTRACT: The objective was to verify the microbiological quality of water used in oyster cultivation in Iguape Bay, Bahia, and its correlation with environmental factors and tidal variations. Thirty six samples of surface water were collected from three oyster cultivation areas, totalizing 12 collections. The concentrations of total and thermotolerant coliforms were determined using the multiple tube test - Most Probable Number (MPN.100 mL-1). The environmental variables assessed in the water samples were: pH, temperature, salinity, turbidity, rainfall and tidal. Total coliforms and thermotolerant coliforms MPN values ranged from <1.8 to 1,600 MPN.100 mL-1 and from <1.8 to 350 MPN.100 mL-1, respectively. The oyster cultivation areas presented good microbiological quality of surface water. The influence of environmental factors on microbial density was obtained as a positive correlation with rainfall and negative correlation with temperature and turbidity. Considering the data from this study, there was an increase of the population of coliforms in the rainy season and spring tide. Thus, it is necessary to carry out microbiological and environmental monitoring of water intended for aquaculture because it promotes safe and sustainable production of oyster, since the quality parameters can suffer weather influences and seasonal variations.