Ships' sea-chests: an overlooked transfer mechanism for non-indigenous marine species?

Historically, hull fouling associated with slow-moving, wooden-hulled vessels has been recognized as the primary transport mechanism responsible for the dispersal of non-indigenous marine species (NIMS) around the world and the fouling of hulls may have contributed significantly to the current patterns of bi-ogeographic distributions of many marine organisms (e.g., Carlton and Hodder, 1995). Over the past three decades however, ballast water has been identified as the primary causal mechanism and has been the focus of international concern (e. suggest that the attachment of organisms on the hulls of vessels remains a significant vector in modern times, possibly equal to ballast water, although further conclusive evidence is required. Currently , there is no concerted effort to evaluate the relative importance of these disparate mechanisms in the transfer of NIMS to new locations. The discussion of transfer mechanisms has identified that numerous locations within and on a vessel may afford distinct environments (e. discussed sea-chests (sea inlet boxes, or suction bays) as environments linked with hull fouling assemblages. Similarly, Gollasch (2002) has discussed the role of sea-chests in the transport of fouling organisms. Sea-chests provide a unique part of the vessel for the transport of marine organisms, dissimilar to ballast water and the exposed surface of the hull. Sea-chests are recesses built into a ships hull located beneath the waterline on the side and/or on the bottom near the engine room. They are designed to reduce water cavitation, and thus increase pumping efficiency when seawater is pumped aboard the vessel for engine cooling, ballast, and fire fighting purposes. The size, number and dimensions of sea-chests vary considerably with vessel size and type. As a general rule, the larger the vessel, thus increasing demand for ballast water, the greater the size and number of sea-chests. Sea-chests are protected by metal grates, which have holes (15–25 mm in diameter) or slots (20–35 mm width) to prevent foreign matter entering and damaging the ships pumps. These grates are held in place by a number of bolts, and therefore sea-chests are usually only accessible during dry-docking. In order to ascertain the extent to which sea-chests provide a unique habitat and contribute to the transport of NIMS, we undertook a preliminary investigation of the passenger ferry Spirit of Tasmania, which operates in southeastern Australia. The hull of the Spirit of Tasmania was surveyed for fouling at the Australian Defence Industries Limited dry-dock at Garden Island, Sydney, on …