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Urban Runoff Impact on the qPCR Signal of Enterococci and Other Alternative Fecal Indicators in a Tropical Beach
Citation:
MOLINA, M., S. Hunter, E. M. WHITE, Y. L. Lee, M. J. CYTERSKI, AND R. G. ZEPP. Urban Runoff Impact on the qPCR Signal of Enterococci and Other Alternative Fecal Indicators in a Tropical Beach. Presented at US EPA National Beach Conference, Huntington Beach, CA, April 20 - 22, 2009.
Impact/Purpose:
The overall objective of the proposed study is to evaluate the loadings, fate and transport of bacterial contaminants from agricultural non-point sources in surface waters through the use of DNA-based technology that can quantify and track fecal contamination back to its source.
Description:
In order to effectively control inputs of contamination to coastal recreational waters, an improved understanding of the impact of both point and non-point sources of urban runoff is needed. In this study, we focused on the effect of non-point source urban runoff on the enterococci qPCR signal in a tropical marine beach. The relationship between qPCR enterococci, presence of 16S-rRNA based markers, and biogeochemical and climatic parameters (e.g., storm events) was also investigated. Waist deep samples were collected at a beach in Luquillo, Puerto Rico from June to October, 2008. Samples, from three sites along a transect perpendicular to the shoreline, were processed for enterococci densities (EPA Method 1600) and qPCR. Automated equipment collected hydrometeorological and biogeochemical variables on a 24 hour basis. Culturable enterococci and qPCR signals peaked following the first strong rain episode. Late in the rainy season, both qPCR and culturable enterococci showed similar spatial trends with higher signals observed on the west side of the beach, which was impacted by runoff from a nearby contaminated wetland. Dissolved organic carbon concentrations were also higher on the west side, likely due to increased runoff from more frequent storm events. Data collected during this study were also used to identify relationships between different measurements of enterococci and to relate these measurements to changes observed in weather and biogeochemical properties. Culturable and qPCR densities were not linearly correlated indicating that outputs from each methodology cannot be explained by the same environmental variables. Preliminary results suggest that urban runoff influences the relationship between the qPCR signal and culturable measurements of enterococci.