Isolation and identification of the fecal pollution indicators Enterococcus spp. from seagrass Thalassia testudinum at La Parguera Puerto Rico and the use of enterococci for microbial source tracking

The occurrence and persistence of the fecal contamination indicators Enterococcus spp. were studied in La Parguera, southwestern Puerto Rico, as an initial step in microbial source tracking (MST). The scientific literature suggests that different enterococcal species are associated to specific homeothermic hosts. Results from this study indicate birds as the main sources of fecal pollution in the area and suggests a E. gallinarum - cattle egret association. Precipitation may be a major factor in enterococcal occurrence. There are also reports that indicate that enterococci might survive for extended periods of time in sediments and in the phylosphere of vegetation. Potential non-point sources of enterococci may cause an overestimation of the enterococci that suggest fecal pollution as well as an obstacle for MST. In consequence, the association and survival of enterococci in the seagrass Thalassia testudinum, was evaluated. It was found that T. testudinum is able to host enterococci. However, overtime persistence of enterococci in this ecosystem was not evident. During the development of this study, high numbers of false positive enterococci were found while using standard methods for the isolation of enterococci from the environment. A protocol using Enterococcosel Broth followed by two confirmation tests was examined as a potential approach to be used in monitoring coastal waters of Puerto Rico. The method presented is economically viable, but still needs improvement. A re-evaluation of the current methods for fecal contamination assessment in our coastline is suggested.