Study of the bacterial content of ring-billed gull droppings in relation to recreational water quality

Ring-billed gull populations of eastern North America have grown dramatical ly in the past 30 years. To assess the possible impact of these populations on recreational waters, gull droppings collected at three colonies were ex amined for fecal coliforms, Aeromonas spp., Campylobacter spp., Pseudomonas aeruginosa, Salmonella spp. and Staphylococcus aureus. The samples were al so analyzed for Shigella spp. and Yeusinia spp. The samples were collected every two weeks from late April to mid-July. The measured concentrations we re compared on the basis of colony, age class and sampling date by analysis of variance (ANOVA) and Fisher's LSD multiple range test. In general, ther e was little difference in bacterial content as a function of age groups, c olony or sampling date. On the basis of the documented ratios between the v arious pathogens and total coliforms in the droppings, the limit of 200 fec al coliforms per 100 mi of water used for recreational water quality in Can ada provides an acceptable level of protection with respect to contaminatio n by gulls. However, we must qualify these findings by stating that they re flect the situation that existed at the time of sampling, that they apply t o a small number of pathogenic microorganisms, and that they do not take in to account soil or sand contamination at beaches. (C) 2000 Elsevier Science Ltd. All rights reserved.