Effects of a Changing Earth on Predicting Microbial Dynamics and Human Health Risks in the Beach Water/Sand Continuum

Humans may be exposed to microbial pathogens at recreational beaches via environmental sources such as water and sand. Although infectious disease risk from exposure to waterborne pathogens, and the fecal indicator bacteria (FIB) used to monitor water quality are active areas of research, sand is a relatively unexplored reservoir of pathogens and FIB. Sand and water at beaches experience continuous exchange of microorganisms, and these habitats provide unique advantages and challenges to pathogen introduction, growth, and persistence. Models of FIB and pathogen fate and transport in beach habitats can aid prediction of the risk of infectious disease from recreational water use, but filling knowledge gaps is necessary for accurate modeling. Climate change predictions estimate an increase in global temperatures of 2.5 – 10° F, sea level rise, and intensification of storms and precipitation in some regions. Other global change factors like population growth and urbanization may exacerbate predicted impacts. These changes can alter microbial population dynamics in beach habitats, and may consequently affect the assumptions and relationships used in numerical models. We discuss literature on microbial population and transport dynamics in sand/beach habitats, with an emphasis on how climate change and other anthropogenic influences (e.g., land use, urbanization) should be considered when using and developing models.