Abundance and composition of heterotrophic prokaryotes in ballast water discharged into Canadian harbors

Abstract

Bacterial abundance and size was characterized in ballast and port water along the West and East coasts of Canada and on the Great Lakes during 2007 and 2008. Ballast water unexchanged at sea showed higher bacterial abundance than ballast water exchanged. On average, bacterial abundance in receiving port water was three-to-four-fold higher than that in ballast water. During 2007, bacterial community structure, as determined by fluorescence in situ hybridization, showed that the bacterial communities did not differ among ballast waters which had experienced different ballast operations. However, bacterial communities differed between ballast and port water, which implies that there is a potentially environmental risk from ballast water-distributed bacteria into Canadian harbors. With an increase of ballast water age, both the % Bacteria and the % Alpha-Proteobacteria in ballast water samples decreased.