Dramatic Improvements in Beach Water Quality Following Gull Removal Reagan R. Converse,* ,† Julie L. Kinzelman, ‡ Elizabeth A. Sams, † Edward Hudgens, † Alfred P. Dufour, § Hodon Ryu, § Jorge W. Santo-Domingo, § Catherine A. Kelty, § Orin C. Shanks, § Shawn D. Siefring, § Richard A. Haugland, § and Timothy J. Wade † † U.S. Environmental Protection Agency, 104 Mason Farm Rd., Chapel Hill, North Carolina 27514, United States ‡ City of Racine Health Department, 730 Washington Ave., Racine, Wisconsin 53403, United States § U.S. Environmental Protection Agency, 26 West Martin Luther King Dr., Cincinnati, Ohio 45268, United States * S Supporting Information ABSTRACT: Gulls are often cited as important contributors of fecal contamination to surface waters, and some recreational beaches have used gull control measures to improve microbial water quality. In this study, gulls were chased from a Lake Michigan beach using specially trained dogs, and water quality improvements were quantified. Fecal indicator bacteria and potentially pathogenic bacteria were measured before and during gull control using culture methods and quantitative polymerase chain reaction (qPCR). Harassment by dogs was an effective method of gull control: average daily gull populations fell from 665 before to 17 during intervention; and a significant reduction in the density of a gull-associated marker was observed (p < 0.001). Enterococcus spp. and Escherichia coli densities were also significantly reduced during gull control (p < 0.001 and p = 0.012, respectively for culture methods; p = 0.012 and p = 0.034, respectively for qPCR). Linear regression results indicate that a 50% reduction in gulls was associated with a 38% and 29% decrease in Enterococcus spp. and E. coli densities, respectively. Potentially human pathogenic bacteria were detected on 64% of days prior to gull control and absent during gull intervention, a significant reduction (p = 0.005). This study demonstrates that gull removal can be a highly successful beach remedial action to improve microbial water quality. ■ INTRODUCTION Fecal contamination of beaches results in numerous health and aesthetic concerns for recreators, and beach advisories posted when fecal pollution is detected can result in local daily economic losses of up to $100 000. 1 Identification of the dominant source(s) of fecal pollution is a first step toward improving microbial water quality and reducing beach advisories. Gulls (Larus spp.) are often cited as an important source of fecal contamination to surface waters and beach sand, 2-8 and conservative estimates show that a single gull can shed 4.8 × 10 9 Escherichia coli (E. coli) cells and 2.1 × 10 8 Enterococcus spp. cells daily. 9-11 As a result, fecal indicator bacteria (FIB) densities in surface waters are significantly and positively correlated with gull populations, 12,13 and water quality criteria exceedances are more common at beaches with large gull communities. 14,15 Human pathogens have also been detected in gull fecal samples. 16-20 Salmonella spp. infections have been reported in nearly 9% of gulls and Campylobacter spp. infections in nearly 16%. 16 E. coli O157 has also been identified in the feces of gulls that frequent landfills. 17 To date, there is no direct evidence of transmission of these pathogens from gulls to swimmers at beach sites, and the risk from gull contamination to beachgoer health is poorly understood. With gull populations increasing dramatically in urban areas, 21 gull population control measures have been undertaken at some beaches and gull feeding and roosting sites in hopes of reducing beach closures and potentially protecting beachgoer health. 15,22 These measures include projection of gull distress calls, shotgun noises, use of monofilament nets, introduction of predators such as falcons, and pyrotechnics. 23 Although the efficacy of each technique varies, the introduction of gull control measures has coincided with FIB reductions at an inland reservoir. 22 However, it was unclear whether the removal of gulls had a statistically significant effect on FIB densities or the presence of potential pathogens. Received: June 11, 2012 Revised: August 21, 2012 Accepted: August 22, 2012 Published: August 22, 2012 Article pubs.acs.org/est © 2012 American Chemical Society 10206 dx.doi.org/10.1021/es302306b | Environ. Sci. Technol. 2012, 46, 10206-10213