Water quality, weather and environmental factors associated with fecal indicator organism density in beach sand at two recreational marine beaches

Abstract

Recent studies showing an association between fecal indicator organisms (FIOs) in sand and gastrointestinal (GI) illness among beachgoers with sand contact have important public health implications because of the large numbers of people who recreate at beaches and engage in sand contact activities. Yet, factors that influence fecal pollution in beach sand remain unclear. During the 2007 National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water Study, sand samples were collected at three locations (60 m apart) on weekend days (Sat, Sun) and holidays between June and September at two marine beaches — Fairhope Beach, AL and Goddard Beach, RI — with nearby publicly-owned treatment works (POTWs) outfalls. F+ coliphage, enterococci, Bacteroidales, fecal Bacteroides spp., and Clostridium spp. were measured in sand using culture and qPCR-based calibrator-cell equivalent methods. Water samples were also collected on the same days, times and transects as the 144 sand samples and were assayed using the same FIO measurements. Weather and environmental data were collected at the time of sample collection. Mean FIO concentrations in sand varied over time, but not space. Enterococci CFU and CCE densities in sand were not correlated, although other FIOs in sand were. The strongest correlation between FIO density in sand and water was fecal Bacteroides CCE, followed by enterococci CFU, Clostridium spp. CCE, and Bacteroidales CCE. Overall, the factors associated with FIO concentrations in sand were related to the sand–water interface (i.e., sand-wetting) and included daily average densities of FIOs in water, rainfall, and wave height. Targeted monitoring that focuses on daily trends of sand FIO variability, combined with information about specific water quality, weather, and environmental factors may inform beach monitoring and management decisions to reduce microbial burdens in beach sand. The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency.

Fecal Indicators in Sand, Sand Contact, and Risk of Enteric Illness Among Beachgoers

“…23–26 Culture-based tests of Enterococcus were performed by local laboratories within 6 hours of collection following EPA Method 1600 27 with some modifications (eAppendix 1, http://links.lww.com). Samples for the F + coliphage analysis were sent on ice at 4oC by overnight express and processed by a modification 28 of EPA Method 1601 29 to accommodate the analysis of sand instead of water samples (eAppendix 1, http://links.lww.com). Fecal indicator-organism concentrations are reported as qPCR calibrator cell equivalents per gram of dry weight sand for Enterococcus , Bacteroidales , fecal Bacteroides , and Clostridium spp.…”

“…Calibrator cell equivalents were calculated according to the comparative delta-delta cycle threshold method reported by Wade et al 20 Enterococcus measured by EPA Method 1600 27 are reported in colony-forming units per gram of dry weight sand, and F + coliphage as a most probable number per gram of dry weight sand following a modification 28 of Method 1601. 29 Results below detection and potential inhibition for qPCR-based data were handled as described previously. 20 …”

Sources and Persistence of Fecal Indicator Bacteria and Bacteroidales in Sand as Measured by Culture-Based and Culture-Independent Methods: a Case Study at Santa Monica Pier, California

“…M. Yamahara et al 2012). Wetting events such as wave height and one day prior rainfall were positively associated with cENT density in sand at a beach in RI and AL (Heaney et al 2014). Both field and laboratory studies have shown higher levels of cENT in dry sand samples after they have been subjected to natural or simulated tidal wetting (Halliday et al 2015; Yamahara et al 2009) which points to the possibility that drying and wetting cycles, as opposed to constant wetter conditions, result in rapid FIB growth.…”

“…Correlations were widely different between the May and October microcosms, with a fairly strong correlation in October (r 2 = 0.585) and overall (r 2 = 0.64) and no correlation in May (r 2 =−0.03). Generally, poor correlations have been observed in sand and sediments between cENT and qENT both in the field (Shah et al 2011; Heaney et al 2014) and in microcosms (Yamahara et al 2012; Rogers et al 2011). Stronger correlations can sometimes be explained by fresher fecal contamination (Haugland et al 2005).…”

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“…The origin of the strain of S. aureus that is contracted by marine mammals was most likely from terrestrial sources introduced into the marine environment via runoff (van Elk et al, 2012). fecal contamination on recreational beaches and coastal areas (Aranda et al, 2015;Heaney et al, 2014;Wade et al, 2003;US Environmental Protection Agency, 1986 and2004). A recent study examining the number of exceedances of enterococci on recreational beaches in Miami-Dade County, FL from 2000-2010 (Aranda et al, 2015) showed that beaches were only in exceedance of the allowable levels of enterococci 3% of the time.…”