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Dramatic Improvements in Beach Water Quality Following Gull Removal
Citation:
Converse, R., J. Kinzelman, E. Sams, E. Hudgens, A. Dufour, H. Ryu, J. Santo-Domingo, C. Kelty, O. Shanks, S. Siefring, R. Haugland, AND Tim Wade. Dramatic Improvements in Beach Water Quality Following Gull Removal. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 48(18):10206-13, (2012).
Impact/Purpose:
Seagulls were shown to be important contributors to fecal contamination at a Great Lakes Beach.
Description:
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 (FIB) and potentially pathogenic bacteria were measured before and during gull control using culture methods and qPCR. Harassment by dogs was an effective method of gull control, and average daily gull populations fell from 665 before to 17 during intervention. Enterococcus and E. 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 up to a 38% and 30% decrease in Enterococcus and E. coli densities, respectively. A significant reduction (p<0.001) in potential pathogens was also observed during gull control. Potentially pathogenic bacteria were detected on 82% of days prior to gull control and not at all following gull control. This study demonstrates that gull removal is a highly successful beach remedial action to improve microbial water quality.