Effect of environmental factors on microbiological quality of oyster farming in Amazon estuaries

Abstract

The objective of this study was to assess the effect of environmental factors on the microbiological quality of water and oyster flesh (Crassostrea gasar) farmed in two Amazon estuaries in Pará, Brazil. The estuaries were located in the Nova Olinda community in Augusto Corrêa (site 1) and the Lauro Sodré community in Curuçá (site 2). Physicochemical water parameters (the rainfall, salinity, temperature and pH) were evaluated over a one-year period. A total of six liters of water and 720 oyster samples from oyster farms were used to analyze coliforms, Escherichia coli, coagulase-positive staphylococci, molds, yeasts and Salmonella spp. The rainfall and salinity were the environmental factors that most strongly influenced the microbiological quality of the water and oyster flesh. The mean total and thermotolerant coliforms were higher in the farming water from site 2 (Curuçá) than from site 1. The oyster flesh from site 1 (Augusto Corrêa) had higher mean levels of total and thermotolerant coliforms, coagulase-positive staphylococci and molds and yeasts than that from site 2. E. coli was absent from the water and oyster flesh of both sites. Salmonella spp. was found in 38.33 % of oyster flesh with no significant differences across sites and seasonal periods. The water quality was considered good for farming bivalve mollusks. However, the presence of Salmonella spp. in the oyster flesh compromised the sanitary quality and represents a threat to public health. Therefore, depuration facilities and microbiological monitoring are required.