Links between high fecal indicator bacteria levels and rain, wind, and tides at Connecticut beaches

Abstract

Swimming beaches along Long Island Sound (LIS) throughout Connecticut (CT) provide recreational value, but water quality issues can inhibit public coastal access. Swimming advisories or beach closures are instituted when enterococci concentrations, the fecal indicator bacteria for saltwater beaches, exceed 104 MPN/100 mL. Understanding the environmental conditions coinciding with high enterococci concentrations is important. Some CT beaches preemptively close based on precipitation volume, but other factors can be influential. We hypothesize that high enterococci events are more likely with rain, onshore winds, and flood to high tidal stages. Enterococci and precipitation data for 74 CT beaches spanning 2003–2021 are accessed from the online Sound Health Explorer (SHE). Companion NOAA wind and tide data come from the nearest airport and tidal calculation station, respectively. Binary categorical analysis indicates rainy (wet) conditions account for 67 % of the high bacteria events (HBEs). Onshore winds and flood/high tides also individually are present for 67 % of the events. Combined categorical analysis indicates the wet, onshore wind, flood/high tide combination is the most prevalent (30 %). These findings point to adding winds and tides to online beach water quality sites such as SHE for retrospective analysis, highlighting their potential for triggering additional bacterial sampling to support management actions, and provides further context for understanding water quality patterns.