Trends in regional enterococci levels at marine beaches and correlations with environmental, global oceanic changes, community populations, and wastewater infrastructure

Lara E Tomenchok; Afeefa A Abdool-Ghany; Samir M Elmir; Maribeth L Gidley; Christopher D Sinigalliano; Helena M Solo-Gabriele

doi:10.1016/j.scitotenv.2021.148641

Trends in regional enterococci levels at marine beaches and correlations with environmental, global oceanic changes, community populations, and wastewater infrastructure

Sci Total Environ. 2021 Nov 1:793:148641. doi: 10.1016/j.scitotenv.2021.148641. Epub 2021 Jun 24.

Authors

Lara E Tomenchok¹, Afeefa A Abdool-Ghany¹, Samir M Elmir², Maribeth L Gidley³, Christopher D Sinigalliano⁴, Helena M Solo-Gabriele⁵

Affiliations

¹ Department of Civil, Architectural, and Environmental Engineering, University of Miami, Coral Gables, FL 33146, USA.
² Miami-Dade County Health Department, 1725 NW 167 Street, Miami, FL 33056, USA.
³ University of Miami, Cooperative Institute for Marine and Atmospheric Studies (CIMAS), Miami, FL 33149, USA; National Oceanic and Atmospheric Administration (NOAA), Atlantic Oceanographic and Meteorological Laboratory (AOML), Miami, FL 33149, USA.
⁴ National Oceanic and Atmospheric Administration (NOAA), Atlantic Oceanographic and Meteorological Laboratory (AOML), Miami, FL 33149, USA.
⁵ Department of Civil, Architectural, and Environmental Engineering, University of Miami, Coral Gables, FL 33146, USA. Electronic address: hmsolo@miami.edu.

PMID: 34328980
DOI: 10.1016/j.scitotenv.2021.148641

Abstract

An increase in the number of advisories issued for recreational beaches across south Florida (due to the fecal indicator bacteria, enterococci) has been observed in recent years. To evaluate the possible reasons for this increase, we reviewed weekly monitoring data for 18 beaches in Miami-Dade County, Florida, for the years 2000-2019. Our objective was to evaluate this dataset for trends in enterococci levels and correlations with various factors that might have influenced enterococci levels at these beaches. For statistical analyses, we divided the 20-year period of record into 5-year increments (2000-2004, 2005-2009, 2010-2014, and 2015-2019). The Wilcoxon rank sum test was used to identify statistically significant differences between the geometric mean of different periods. When all 18 beaches were collectively considered, a significant increase (p = 0.03) in enterococci was observed during 2015-2019, compared to the prior 15-year period of record. To better understand the potential causes for this increase, correlations were evaluated with environmental parameters (rainfall, air temperature, and water temperature), global oceanic changes (sea level and Sargassum), community populations (county population estimates and beach visitation numbers), and wastewater infrastructure (sewage effluent flow rates to ocean outfalls and deep well injection). In relation to the enterococci geometric mean, the correlation with Sargassum was statistically significant at a 95% confidence interval (p = 0.035). Population (p = 0.078), air temperature (p = 0.092), and sea level (p = 0.098) were statistically significant at 90% confidence intervals. Rainfall, water temperature, beach visitation numbers, and sewage effluent flow rates via deep well injection had positive correlations but were not significant factors. Sewage effluent flow rates to ocean outfalls had a negative correlation.

Keywords: Beach; Enterococci; Fecal indicator bacteria; Sargassum; Sea level rise; Temperature.

MeSH terms

Bathing Beaches*
Enterococcus*
Environmental Monitoring
Feces
Seawater
Wastewater
Water Microbiology

Substances

Waste Water