Date of Award
Great Lakes Institute for Environmental Research
MacIsaac, Hugh (GLIER)
CC BY-NC-ND 4.0
Transoceanic vessels entering the Great Lakes are required to undergo ballast water exchange to reduce the risk of transporting non-indigenous species. Ballast water exchange effectively reduces invertebrate density and richness in ballast; however, an alternative treatment is required for non-compliant ships. Sodium chloride brine was proposed to treat residual and incompletely-exchanged ballast water. Laboratory experiments were conducted to determine the minimum brine treatment to exterminate >95% of ballast water taxa. Invertebrate communities were exposed to a range of brine concentrations (15ppt to 115ppt) until complete mortality was reached. Biological evidence supports a one-hour exposure to 115ppt brine to treat ballast water. This treatment is broadly effective (>99.9%) regardless of treatment temperature, taxonomic group, or species' habitat salinity. A median of 0.00% (range 0.00-5.33) of individuals in ballast are expected to survive treatment, and the expected number of individuals released is within Canadian discharge standards. Before implementation, ship-scale trials are required.
Bradie, Johanna, "Brine-induced mortality of non-indigenous species in ballast water" (2009). Electronic Theses and Dissertations. 362.