Florida’s 825 miles of beaches are one of the state’s most alluring tourist attractions. The beaches’ relaxing waters, soft sands and stunning sunsets help attract more than 100 million tourists to Florida each year (that’s about five visitors per Florida resident!) In addition to being an integral part of the state’s economy, Florida’s beaches protect coastal developments from storms and shelter critical habitats for a variety of wildlife species.
In order to protect the economic and ecological vitality of beaches, as well as the public health of those who visit them, Florida’s coastal counties continuously monitor the quality of the beaches’ water. Health officials sample water at beaches once a week to determine whether water quality meets safety standards. These sample collections help municipalities create advisories and close beaches when necessary.
Ocean water quality is determined by measuring the number of disease-causing microbes in the water. However, most disease-causing microbes exist in very small amounts and are difficult and expensive to find in water samples. ‘Indicator organisms’ are used to help identify if disease-causing microbes may be present. In marine waters, the indicators are enterococci, a group of bacteria that commonly reside in the guts of animals, including humans. These intestinal bacteria make their way into the ocean water via feces.
“Microbes that are completely harmless to humans are naturally abundant in ocean water,” says Helena Solo-Gabriele, University of Miami College of Engineering (UMCoE) associate dean for research and professor in the Department of Civil, Architectural and Environmental Engineering. “However, fecal contamination – a major source of ocean water pollution – introduces other, more dangerous microbes into the ocean water. Beaches are closed when these microbes show up.”
Enterococci “indicator” microbes are usually present in the ocean water, but at relatively low – and safe – concentrations. During fecal contamination, however, the enterococci concentrations go up significantly, indicating the possible presence of disease-causing microbes. If the disease-causing microbes are ingested while swimming or enter the skin through a cut or sore, they can cause infections rashes or even diseases.
“Fecal pollution in beaches can come from many different sources, such as stormwater runoff, pets and wildlife, as well as human sewage,” says Solo-Gabriele. “The problem is identifying exactly where the pollution is coming from as each source carries its own threats to public health.” For example, in Key Biscayne, a Florida town on a barrier island across from the Miami metropolitan area, the concentrations of enterococci have been increasing over the past three years. However, nobody knows exactly why the levels are increasing.
Solo-Gabriele recently received funding from the municipal government of Key Biscayne to evaluate potential sources of enterococci at Key Biscayne Beach. The research project, titled, “Evaluating Potential Sources of Enterococci to Key Biscayne Beach,” will focus on assessing four potential sources: sewage from the Central District Wastewater Treatment Plant (CDWWTP), leaking sewers or septic tanks, local animals such as birds and dogs, and seaweed.
The project will involve careful analysis of CDWWTP’s records of discharge quality and quantity, as the wastewater treatment facility discharges effluent into the Biscayne Bay. Although the facility has been designed to limit the impact of treated sewage on nearby coastal waters, its proximity to Key Biscayne Beach, as well as its large discharge, makes it a suspect source of enterococci.
Untreated sewage, from both humans and animals, will also be considered as a potential source of enterococci. Malfunctioning septic tanks and leaking pipes can directly leak untreated sewage into the bay area, increasing enterococci levels in the ocean water. Additionally, seaweed, which is usually present at beaches, will also be investigated as it can retain moisture and provide enterococci with the nutrients they need to grow and reproduce.
Solo-Gabriele’s team will take measurements on all four sources throughout the entire year to, ultimately, assess possible relationships between environmental measures, and enterococci levels. “This information will be useful for Key Biscayne to take pro-active efforts to minimize enterococci exceedances at their beaches.”
“The state of Key Biscayne’s beaches greatly influences not only the region’s economy, but also the health of the surrounding environment and general public,” continues Solo-Gabriele. “Therefore, it is of utmost importance to identify the source of enterococci at Key Biscayne beach to better understand the risks associated with increasing enterococci levels.”
