Transport of enterococci and F+ coliphage through the saturated zone of the beach aquifer

Enterococcus exceedances related to environmental variability at New Jersey ocean beaches

Microbial pollution at ocean beaches is a global public health problem that can be exacerbated by excessive rainfall, particularly at beaches adjacent to urban areas. Rain is acknowledged as a predictive factor of Enterococcus levels at NJ beaches, but to date no study has explicitly examined the link. Here, five beaches (156 observations) in Monmouth County, NJ, with storm drain outflows present were sampled for Enterococcus and water quality during dry and wet periods. Hypotheses included (1) beaches differ in Enterococcus levels, (2) Enterococcus is present year-round, and (3) Enterococcus exceedances could be modeled based on environmental parameters. Beaches showed significantly different median Enterococcus levels, with site SEA2 (Neptune Blvd. in Deal, NJ) lower than others and site SEA4 (South Bath Ave. in Long Branch, NJ) higher than the other sites. Elevated Enterococcus levels were detected at water temperatures from 6.5 to 22.2 °C. Multiple linear regression models identified rainfall (+), water temperature (+), and water level (-) as related to Enterococcus concentrations levels at these beaches. For the purpose of simulating the efficacy of different monitoring strategies, a hindcast model of Enterococcus abundance based on historic rainfall, water temperature, and water level data was produced. Results indicated that once-per-week sampling detected ~14% (e.g., 1/7) exceedance events, while sampling during summer alone detected ~ 50% of annual exceedance events. Models of Enterococcus exceedance based on readily available environmental time series have the potential to supplement and improve Enterococcus monitoring at NJ beaches.

The microbial dimension of submarine groundwater discharge: current challenges and future directions

Despite the relevance of submarine groundwater discharge (SGD) for ocean biogeochemistry, the microbial dimension of SGD remains poorly understood. SGD can influence marine microbial communities through supplying chemical compounds and microorganisms, and in turn, microbes at the land–ocean transition zone determine the chemistry of the groundwater reaching the ocean. However, compared with inland groundwater, little is known about microbial communities in coastal aquifers. Here, we review the state of the art of the microbial dimension of SGD, with emphasis on prokaryotes, and identify current challenges and future directions. Main challenges include improving the diversity description of groundwater microbiota, characterized by ultrasmall, inactive and novel taxa, and by high ratios of sediment-attached versus free-living cells. Studies should explore microbial dynamics and their role in chemical cycles in coastal aquifers, the bidirectional dispersal of groundwater and seawater microorganisms, and marine bacterioplankton responses to SGD. This will require not only combining sequencing methods, visualization and linking taxonomy to activity but also considering the entire groundwater–marine continuum. Interactions between traditionally independent disciplines (e.g. hydrogeology, microbial ecology) are needed to frame the study of terrestrial and aquatic microorganisms beyond the limits of their presumed habitats, and to foster our understanding of SGD processes and their influence in coastal biogeochemical cycles.