Prevalence and distribution of fecal indicator organisms in South Florida beach sand and preliminary assessment of health effects associated with beach sand exposure Tonya D. Bonilla a, * , Kara Nowosielski a , Marie Cuvelier a , Aaron Hartz a , Melissa Green b , Nwadiuto Esiobu b , Donald S. McCorquodale a , Jay M. Fleisher c , Andrew Rogerson a,1 a Oceanographic Center of Nova Southeastern University, Dania Beach, FL 33004, USA b Department of Biological Sciences, Florida Atlantic University, Davie, FL 33314, USA c College of Osteopathic Medicine, Nova Southeastern University, Fort Lauderdale, FL 33328, USA Abstract Fecal indicator levels in nearshore waters of South Florida are routinely monitored to assess microbial contamination at recreational beaches. However, samples of sand from the surf zone and upper beach are not monitored which is surprising since sand may accumulate and harbor fecal-derived organisms. This study examined the prevalence of fecal indicator organisms in tidally-affected beach sand and in upper beach sand and compared these counts to levels in the water. Since indicator organisms were statistically elevated in sand relative to water, the study also considered the potential health risks associated with beach use and exposure to sand. Fecal coliforms, Escherichia coli, enterococci, somatic coliphages, and F + -specific coliphages were enumerated from sand and water at three South Florida beaches (Ft. Lauderdale Beach, Hollywood Beach, and Hobie Beach) over a 2-year period. Bacteria were consistently more concentrated in 100 g samples of beach sand (2–23 fold in wet sand and 30–460 fold in dry sand) compared to 100 ml samples of water. Somatic coliphages were commonly recovered from both sand and water while F + -specific coliphages were less commonly detected. Seeding experiments revealed that a single specimen of gull feces significantly influenced enterococci levels in some 3.1 m 2 of beach sand. Examination of beach sand on a micro-spatial scale demonstrated that the variation in enterococci density over short distances was considerable. Results of multiple linear regression analysis showed that the physical and chemical parameters monitored in this study could only minimally account for the variation observed in indicator densities. A pilot epidemiological study was conducted to examine whether the length of exposure to beach water and sand could be correlated with health risk. Logistic regression analysis results provided preliminary evi- dence that time spent in the wet sand and time spent in the water were associated with a dose-dependent increase in gastrointestinal illness. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Beach sand; Marine beach; Water quality; Interstitial water; Fecal indicator microorganisms; Enterococci; Fecal coliforms; Escherichia coli; Coliphage; Public health; Swash zone; Recreational beach; Exposure; Health risk 1. Introduction The numbers of fecal indicator organisms in shoreline water are enumerated to assess the level of fecal contamina- tion at recreational beaches, and hence the associated health risks of exposure to fecal-derived microbial patho- gens (USEPA, 1986; Pruss, 1998). Fecal indicator concen- trations in beach sand are not routinely measured despite the possibility that beach sand may act as an important 0025-326X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2007.04.016 * Corresponding author. Present address: Department of Infectious Diseases and Pathology, University of Florida, Gainesville, FL 32611, USA. Tel.: +1 352 392 4700x5839; fax: +1 352 392 9704. E-mail address: bonillat@mail.vetmed.ufl.edu (T.D. Bonilla). 1 Present address: Department of Biology, Marshall University, Hun- tington, WV 25755, USA. www.elsevier.com/locate/marpolbul Marine Pollution Bulletin 54 (2007) 1472–1482