Evaluation of fecal contamination by seagulls in an urban estuarine environment using microbiological and molecular approaches

Wild birds are important non-point sources of fecal contamination of surface waters, as they have been reported to excrete large amounts of fecal indicator bacteria and occasionally harbor enteric pathogens, such as Campylobacter and Salmonella. Hundreds of waterfowl frequent the sandflats within Talbert Marsh, a constructed wetland in Orange County, CA, on a daily basis for nesting and feeding purposes. The focus of this study was on the role of seagull fecal contamination as a potentially important contributor to the non-point sources of fecal contamination into Talbert Marsh waters, which eventually flow into the recreational surf-zone at Huntington Beach. Using traditional microbiological methods, Salmonella, Campylobacter, F+ coliphages, and bacterial indicators were isolated from Talbert Marsh seagull feces and/or estuarine waters. Genotypic methods, including PCR, RT-PCR, reverse line blot hybridization, PFGE, and nucleotide and amino acid sequencing, were employed on subsets of frozen suspensions of isolates for further characterization and to determine genetic relatedness. There is some limited evidence supporting the idea that seagull feces deposited on the sandflats of Talbert Marsh did impact the surrounding estuarine waters. A subset of isolates were relatively similar in both nucleotide and amino acid sequence and therefore may have come from the same population. Overall however, it is unlikely that pathogens from seagull feces in Talbert Marsh pose a significant health risk to swimmers in the ocean waters at Huntington Beach. Multiple adverse health outcomes have been linked to exposure to marine recreational water of poor microbiologic quality and identifying sources of fecal contamination as human or animal in origin is becoming a more important tool in decision making to manage fecal contamination of these waters.