Fecal indicator bacteria are abundant in wet sand at freshwater beaches

Potential fecal contamination of sand in the wave-washed zone of public bathing beaches is overlooked in beach monitoring programs. Activity in this zone can bring pathogens to the sand surface or into the water, presenting a health risk to sensitive populations. On a unit weight basis (colony forming units per 100g), the mean summer abundance of the fecal indicator bacteria enterococci and Escherichia coli was 3-38 times higher in the top 20cm of wet-sand cores than in the water column at six freshwater bathing beaches. E. coli were 4 times more abundant than enterococci in water but counts were similar in the sand. A correlation (r=0.60) existed between E. coli counts in the water and in the top 5cm of sand only, whereas no relationship existed between enterococci abundance in water and sand. In general, enterococci were most numerous in the 5-10cm sand stratum and E. coli in the 0-5cm stratum. These preliminary data show that wet freshwater beach sand is a reservoir of fecal indicator bacteria. Enteric pathogens may also be present in beach sand.