Release ofEscherichia colifrom Foreshore Sand and Pore Water during Intensified Wave Conditions at a Recreational Beach

Abstract

Foreshore beach sands and pore water may act as a reservoir and nonpoint source of fecal indicator bacteria (FIB) to surface waters. This paper presents data collected at a fine sand beach on Lake Huron, Canada over three field events. The data show that foreshore sand erosion as wave height increases results in elevated Escherichia coli concentrations in surface water, as well as depletion of E. coli from the foreshore sand and pore water. E. coli initially attached to foreshore sand rather than initially residing in the pore water was found to be the main contributor to elevated surface water concentrations. Surface water E. coli concentrations were a function of not only wave height (and associated sand erosion) but also the time elapsed since a preceding period of high wave intensity. This finding is important for statistical regression models used to predict beach advisories. While calculations suggest that foreshore sand erosion may be the dominant mechanism for releasing E. coli to surface water during intensified wave conditions at a fine sand beach, comparative characterization of the E. coli distribution at a coarse sand-cobble beach suggests that interstitial pore water flow and discharge may be more important for coarser sand beaches.

Recreational water monitoring: Nanofluidic qRT‐PCR chip for assessing beach water safety

“…Pore water samples had the highest E. coli levels (4.9–5.8 log copies/250 ml), showing that the pore water may act as a reservoir and nonpoint source of E. coli for surface waters (Vogel, O’Carroll, Edge, & Robinson, ). Generally, in our environmental samples, E. coli was not consistently associated with waterborne pathogens both across all 24 environmental samples ( R 2 = .005, p = .87) and in the 15 waterborne pathogen‐positive samples ( R 2 = .07, p = .33, Figure a), potentially indicating that E. coli is a poor health risk indicator for recreational waters—a pattern previously reported (Jang et al, ; Odonkor & Ampofo, ).…”

Influence of instantaneous and time‐averaged groundwater flows induced by waves on the fate of contaminants in a beach aquifer

“…Water exchange across the SWI can deliver large quantities of dissolved and particulate constituents including nutrients, organic matter (OM), trace elements, and microbial bacteria to a beach aquifer subsequently modifying the geochemical conditions [ McLachlan and Turner , ; Beck et al ., ; Anschutz et al ., ; Santos et al ., ; Whitman et al ., ]. As a result, a beach aquifer can be an important reaction hotspot with the interacting water exchange, flow and geochemical processes impacting the transport, fate, and ultimate flux of terrestrially derived and coastal‐derived constituents to coastal waters [ Slomp and Van Cappellen , ; Charette and Sholkovitz , ; Anwar et al ., ; McAllister et al ., ; Vogel et al ., ]. For instance, a beach aquifer can be an important biogeochemical reactor for regenerating inorganic nutrients (nitrate [ ], ammonium [ ], and phosphate [ ]) through mineralization of marine‐derived OM and also for controlling the exit conditions for terrestrially derived groundwater nutrients [ Spiteri et al ., ; Charbonnier et al ., ; Anwar et al ., ].…”

“…For instance, a beach aquifer can be an important biogeochemical reactor for regenerating inorganic nutrients (nitrate [ ], ammonium [ ], and phosphate [ ]) through mineralization of marine‐derived OM and also for controlling the exit conditions for terrestrially derived groundwater nutrients [ Spiteri et al ., ; Charbonnier et al ., ; Anwar et al ., ]. The interacting exchange, flow, and geochemical processes can also affect the accumulation and persistence of fecal contaminants in beach sediments including their potential to trigger a recreational water quality advisory [ Alm et al ., ; Whitman et al ., ; Vogel et al ., ]. Further, these interacting processes affect the persistence and morphology of nonaqueous phase organic liquid (NAPL) contaminants in beach sediments, with particular interest being the longevity of crude oil which can remain trapped in beach sediments long after an accidental oil spill occurs [ Li and Boufadel , ].…”

Impacts of a Changing Earth on Microbial Dynamics and Human Health Risks in the Continuum between Beach Water and Sand

“…Under controlled experimental conditions within a wave flume, only 60% of FIB were removed by waves with M values of up to 10 cm, suggesting that very large waves would be necessary to completely clear out the FIB reservoir from sand. Vogel et al (2016) also suggests that FIB are transferred to surface waters during high intensity wave events. In addition, FIB are also more rapidly mixed offshore, leading to lower concentrations in adjacent surface water and less potential for them to re-associate with beach sand; as discussed in section 5 (Cruising: Transport).…”