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Reductions in Gull Populations Improve Beachwater Quality.
Citation:
Converse, R., J. Kinzelman, E. E. HUDGENS, E. A. SAMS, A. P. DUFOUR, AND T. J. WADE. Reductions in Gull Populations Improve Beachwater Quality. Presented at American Society for Microbiology General Meeting, San Francisco, CA, June 16 - 19, 2012.
Impact/Purpose:
The objective of this study was to characterize changes in water quality at a recreational beach after gull control measures were enacted.
Description:
BACKGROUND. Gulls are often cited as an important source of fecal pollution to surface waters, and fecal indicator bacteria (FIB) concentrations have been shown to be significantly correlated with gull populations. However, it is unclear whether gull contamination poses a risk to beachgoer health, and few studies have measured the extent to which gull removal and control can improve water quality. The objective of this study was to characterize changes in water quality at a recreational beach after gull control measures were enacted. METHODS. Gulls were chased from a popular Lake Michigan beach by specially trained dogs, and water quality before and after the reduction in gull populations was compared. Enterococcus and E. coli were enumerated by membrane filtration (MF) and quantitative polymerase chain reaction (QPCR), and culture-based analyses were used to detect a suite of waterborne pathogens. RESULTS. Gull harassment by dogs was an effective method of gull control, and daily gull counts fell from over 2500 before intervention to 66 during intervention. Before the introduction of gull control, culturable pathogens (E. coli 0157 and Salmonella) were detected on three of eleven study days. No pathogens were detected during the nine study days gulls were excluded from the beach. There was a significant 10-fold reduction in culturable FIBconcentrations during the period of gull control (p