Factors influencing faecal contamination in coastal marinas M.D. Sobsey*, R. Perdue**, M. Overton** and J. Fisher** * University of North Carolina, Dept of Environmental Sciences & Engineering, Chapel Hill, NC 27599-7400, USA (E-mail: sobsey@email.unc.edu) ** North Carolina State University, Raleigh, NC 27695, USA Abstract Recreational pleasure and fishing boats are potential sources of human faecal contamination because the sanitary wastes from boat occupants may be discharged into the surrounding water. The impacts of such faecal contamination from boats is potentially high in marinas where boats are often kept and occupied for varying periods of time. The nature and extent of such faecal contamination from boats in marinas of different design and use is still inadequately understood. In this study the levels of faecal coliform (FC) bacteria were measured in the waters of a confined and an open water marina over a 6 d period encompassing a holiday weekend. Levels of FC rose with increasing occupancy by boats and boaters during the study period and then declined again. FC levels were higher in waters of a confined or basin marina than in waters of an open or unconfined marina. In both confined and open water marinas, FC levels were highest in water samples collected near boats but they also became elevated on occasion in water samples taken a distance of 305 m from boats. Concentrations of FC in marina waters exceeded the standards and guidelines for shell-fishing and primary contact recreation waters. Therefore, greater consideration of human health risks from enteric microbes in marina waters and shellfish is recommended. Keywords Boats; faecal coliforms; faecal contamination; marinas; pollution Introduction Faecal contamination of coastal waters used for primary contact recreation, shell-fishing and other beneficial purposes by human sewage and other wastes is a continued public health concern worldwide. Outbreaks of enteric and other infectious diseases have been attributed to bathing in, and eating molluscan shellfish from, faecally contaminated coastal waters. These concerns have led to efforts being made to develop guidelines and standards for allowable levels of faecal contamination in coastal waters and to identify and control point and non-point sources of faecal contamination potentially impacting these waters. Guidelines and standards for faecal contamination of recreational and shell-fishing waters typically are based on allowable concentrations of indicator bacteria such as thermo- tolerant (faecal) coliforms, Escherichia coli and enterococci. Considerable attention has focused on controlling fixed sources of faecal contamination in coastal waters such as sewage effluent discharges, combined sewer overflows, on-site wastewater treatment systems and runoff from land during precipitation events. Most pro- grams to monitor and manage the sanitary quality of coastal waters are directed at these sources of faecal contamination. Often overlooked and less subject to regulations are the many boats and other vessels plying coastal waters (e.g. pleasure or recreational boats and fishing boats). In many coastal areas large numbers of pleasure and commercial boats are kept in marinas and the human waste sanitation facilities on these boats are often overlooked, ignored or poorly regulated. Some studies have attempted to document the extent of faecal contamination from boats in marinas. However, no studies have attempted to determine the levels of faecal contamination impacting marina waters in relation to the design and hydrological features of the marina, and the potential faecal Water Science and Technology Vol 47 No 3 pp 199–204 © 2003 IWA Publishing and the authors 199 Downloaded from http://iwaponline.com/wst/article-pdf/47/3/199/424036/199.pdf by guest on 25 April 2021