Incorporating Sand Dynamics into Beach Water Quality Science and Policy

Water quality monitoring and science at nearshore/beach areas is largely limited to microbial/bacterial contamination of water. However, recent research has found that the sand at beaches can be more contaminated than the water itself. Given that most beachgoers spend more time in the sand than the water, they are potentially exposing themselves to higher concentrations of microbes than previously thought. Dynamic exchange of microbes between water and sand has been observed in marine and freshwater systems across the world. Microbes are often deposited from the water, into the sand at the beach during intermediate wave events. When wave energy is high enough, these accumulated microbes can be washed out of the sand and back into the water in a process deemed resuspension. This is in addition to the microbes in the sand that come from humans, wildlife, and waste materials. Within the sand, microbes can move around via spaces between sand grains and may also form biofilms attached to sand grains. When beachgoers play in the sand or the water, they expose themselves to the bacteria contained in it. This may lead to compromised health conditions, including respiratory, gastroenteric, and ear infections. By focusing monitoring and research efforts on water quality at the expense of sand conditions, we may be unintentionally putting beachgoers in danger with our existing protocols. The good news is, researchers are beginning to understand how sand and water interact to form the microbial community at beaches. Collaborative field and numerical modeling studies have characterized the impacts of sand on beach health, and there has been a shift in scientific focus to the entire beach system, or “beachscape”, rather than just the water. The political realm is also beginning to get involved, with discussions of including sand impacts and dynamics in recreational water guidelines currently underway. The issue of recreational water quality is the epitome of a one health challenge – microbial communities are impacted by human and environmental factors, wildlife usage, and even meteorological conditions. These microbial communities can then feed back to the human system by infecting beachgoers from both the water and the sand. In terms of human health, the paramount goal is to minimize the chance of infection in beachgoers, which will lead to increased visitation at beaches as well as social and economic gains for nearshore areas via tourism. By broadening research foci to the entire beachscape, we can better understand what may make the system dangerous to beachgoers, and we can improve beach management for human, economic, and environmental health. A recurring issue in natural resources is the disconnect between research and policy outcomes. The prospective inclusion of sand as a source of microbial contamination at beaches in future beach health guidelines is a concerted and encouraging attempt to bridge that disconnect. Though policy discussions are ongoing, there is promise that research into sand-water interactions will influence human health, environmental health, and policy outcomes as they relate to marine and nearshore systems.