If you live in a coastal area, you are probably familiar with colorful beach warning flags. Purple for stinging marine life, yellow to encourage caution in rough waves, and a green flag for the all-clear. Sometimes public health officials issue warnings against beach activity when there are high levels of fecal bacteria in the water. Contamination of water by exposure to human fecal bacteria is one of the most common forms of disease transmission, and there are many disease-causing microorganisms known as pathogens that can be in water if it has fecal contamination. Enterococci are a type of fecal bacteria known as an “indicator organism” for water quality – they are a normal part of the bacteria that everyone has in their gut, and therefore their presence in recreational water indicates that there might also be dangerous contamination in the water as well. These enterococci fecal indicating bacteria (abbreviated as FIBs) are routinely measured by beach managers and health officials, and there are strict guidelines about how many of these enterococci there can be in recreational water for it to be considered safe to swim or play in. When the levels in the swimming water exceed these guidelines, warnings are posted at the beach. Enterococci bacteria can also come from a variety of other animal hosts, not just humans, and they can sometimes even grow in the background of beach sand or seaweed wrack where they might not indicate any relationship to dangerous pathogen bacteria. Because of this complexity, the presence of enterococci bacteria are not perfect predictors of health risk at the beach, since the degree of health risk from elevated levels of enterococci at the beach depends upon what the sources of the enterococci are. Some sources are much less dangerous than others.
Threats that aren’t taken seriously can pose health risks for locals and beach vacationers, but, in a community driven by beach tourism and recreation, unnecessary closures can also hurt the local economy. The BEACHES project, funded by the Gulf of Mexico Research Initiative, is a multi-institutional collaborative research project including the University of Miami in cooperation with NOAA AOML that aims to better understand how children interact with the beach environment and how their behavior can affect their exposure to potential beach contamination such as harmful bacteria or chemicals that may be in the beach environment. By linking this with source tracking of potential contaminants at the beach, they are working toward reducing uncertainty of risk, and better educating the public about safe beachgoing practices and behavior.
Researchers on the BEACHES project are using genetic markers developed by AOML, and by their collaborators such as academic university partners and the US EPA, to identify sources of bacteria to assess their individual threat. Sources such as shrimp burrows, or decaying seaweed can cause heightened levels of enterococcus in the water but may pose little to no risk to humans, whereas enterococci from human or pet waste may indicate a higher-risk contamination. Considering where to sample for bacteria at a beach can also influence perceived risk. For example, public health institutions and beach managers traditionally test only the water in the swim zone for enterococci and do not address the sand or tidal zones, which is where most beachgoers spend the bulk of their time.
Understanding the nature of human behavior is also a key component to assessing the relative risk of exposure at the beach. The primary focus of the BEACHES project is documenting all the various ways children physically interact with the water, sand, and seaweed during a typical beach visit. This can include everything from grabbing a bucket of ocean water, to sitting in the surf zone, to building a sandcastle, or playing with seaweed, or enjoying a snack. Many children even put sand and/or seaweed on their hair or in their mouths. BEACHES scientists carefully video record the volunteer children while playing at the beach to analyze and count the various kinds of common behaviors that could expose children to contamination if the beach happened to be contaminated (such as by a sewage or septic leak, oil spill, chemical accident, etc). Behavioral scientists are evaluating survey data and videos to define activities that pose higher risk. Enterococci and the pathogens that it indicates can be transferred orally, so families who eat without proper handwashing or toddlers who get sand in their mouths can get sick even if they aren’t swimming. Likewise, contaminants from oil spills may linger on plants in the high-tide zones or form tiny pellets and tar balls in the swash zone where children explore.
The results of this project will aid beach managers in making more informed decisions about beach closures and activities, and empower individuals and families in making wise beachgoing decisions. The project will also launch a public education initiative to help families reduce risk and enjoy our beaches in good health.