Invertebrates associated with residual ballast water and sediments of cargo-carrying ships entering the Great Lakes

Abstract

Most ships entering the Great Lakes carry cargo and declare “no-ballast-on board” (NOBOB) status. Approximately 250 of these vessels annually load Great Lakes’ ballast water when they offload inbound cargo and then discharge this water (which has now mixed with residual water previously present in the tanks) when they load outbound cargo. This procedure potentially allows nonindigenous species present in ballast residuals to invade the Great Lakes. We collected residual sediment, water, and associated organisms from 38 NOBOB ships entering the Great Lakes. We recorded seven established Great Lakes’ nonindigenous species, including some discovered since ballast water exchange was implemented. Occurrences of species not yet invaded indicate that this vector provides further opportunity for invasion. Collectively, NOBOB vessels appear to constitute a greater risk than ballasted vessels, as they make up a greater proportion of the traffic entering the lakes (~90%), and they do not undergo ballast exchange. Invertebrates in residual water appear to have a greater opportunity for discharge than those in sediments, although most in the water fraction have already invaded this system. Invertebrate numbers in residual freshwater ballast could be dramatically lowered if these vessels flushed with open-ocean water prior to entering the Great Lakes.

Biological invasions and natural colonisations: are they that different?

“…Within three years of the formation of volcanic Long Island, Papua New Guinea, 20 invertebrate species were found (Thornton 2001). In comparison, meiobenthic assemblages found within residual sediment and ballast water of ships range from an unknown number of species from 6 Classes, including 12 nematode genera (Radziejewska et al 2006), to 33 taxa from six ships (Gray et al 2007) and 147 taxa from 32 ships (Duggan et al 2005). The point we make is that there are no hard data to demonstrate that the number of species being dispersed by people is greater than that of species dispersing naturally, and such data would be highly beneficial.…”

Marine dinoflagellate cysts in the ballast tank sediments of ships entering the Laurentian Great Lakes

“…The NOBOB ships must flush their tanks with saltwater if they have not previously conducted an open-ocean exchange since last ballasting, and must also maintain on-board records demonstrating an active sediment reduction program. Duggan et al (2005) also suggested that use of saltwater flushing by NOBOB ships would reduce the invasion risk from invertebrates. Until more effective permanent solutions are implemented, the use of saltwater flushing by NOBOB ships is a reasonable approach to reduce the potential for non-indigenous species introductions into the Great Lakes.…”

“…Once in the Great Lakes these NOBOB ships discharge their residual water and sediment into the Great Lakes during the off-loading of inbound cargo and the loading of outbound cargo. These NOBOB ships represent a greater risk for introductions into the Great Lakes than ballasted ships (Duggan et al 2005).…”

“…The residual sediment and water found in ballast tanks of NOBOB ships contain a variety of live organisms, and resting stages, cysts, spores, and eggs of algae and invertebrates (Duggan et al 2005). Resting stages of many algae may remain viable in sediments for decades or even centuries (Sicko-Goad et al 1986) and can germinate under favorable environmental conditions.…”

Invertebrates and their dormant eggs transported in ballast sediments of ships arriving to the Canadian coasts and the Laurentian Great Lakes

“…Invertebrate species may be present in ballast tanks as active or dormant stages (e.g., dormant eggs, resting eggs, statoblasts, and cysts; Cá ceres 1997; Bailey et al 2005;Duggan et al 2005). The effect of MOE and saltwater flushing on active and dormant stages of invertebrates has been assessed in a number of studies with varying results (Gray et al 2007;Humphrey 2008;Briski et al 2010).…”