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Quantifying the total wetted surface area of the world fleet: a first step in determining the potential extent of ships’ biofouling


Ships’ hulls can transport aquatic nuisance species, but there is little quantitative information about the magnitude of vessel biofouling on a global or regional scale. There does not exist a robust method to estimate the wetted surface area (WSA) of a particular fleet of ships, especially across the diversity of possible vessel types. An estimate of the total WSA of ship arrivals into a port or region is essential to determine the potential scope of biofouling and to inform management strategies to reduce the future invasions. Multiple statistical models were developed so commonly available ships’ parameters could be used to estimate the WSA for a given set of fleet data. Using individual ship characteristics and publicly available data from  ~120,000 active commercial ships in the world fleet, the method results in a total global minimum WSA estimate of approximately 325 × 106 m2. The size of the global fleet employed here is greater than the commonly cited vessel number of approximately 80,000–90,000, as we include ships <100 gross tons. Over 190,000 vessels were initially identified, representing a WSA of 571 × 106 m2, but active status of only 120,000 vessels could be confirmed. Reliable data were unavailable on the operating status of many additional and especially smaller vessels. This approach, along with a contemporary and comprehensive estimate of global WSA, when combined with knowledge of the different operational profiles of ships that may reduce biofouling (port residence times, steaming speeds, extent of antifouling coatings, cleaning frequency, etc.), can inform current numerical models and risk assessments of bioinvasions.

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This work was supported by the University of Maryland Center for Environmental Science (funding agreement 2012–38) and the U.S. Maritime Administration (MARAD). We thank Carolyn Junemann (MARAD) for guidance and programmatic support and Mark Minton (Smithsonian Environmental Research Center) for his advice with shipping data. We appreciate advice from Rich Everett (U.S. Coast Guard) and the data provided from the National Ballast Information Clearinghouse. This work was supported by Diane Lysogorski, Section Head of NRL Code 6136 and Director of the Center for Corrosion Science and Engineering—Key West, Florida. Finally, the reviews of this manuscript by Stephanie Robbins-Wamsley, Diane Lysogorski, Edward Lemieux (Branch Head, Code 6130), Barry Spargo (Acting Superintendent, Chemistry Division, Naval Research Laboratory), Jim Carlton, and three anonymous reviewers improved it—thank you.

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Correspondence to Cameron S. Moser.

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Moser, C.S., Wier, T.P., Grant, J.F. et al. Quantifying the total wetted surface area of the world fleet: a first step in determining the potential extent of ships’ biofouling. Biol Invasions 18, 265–277 (2016).

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  • Aquatic nuisance species
  • Hull fouling
  • Invasive species
  • Wetted surface area
  • Global fleet
  • Non-indigenous species