Date of Award


Degree Type


Degree Name



Great Lakes Institute for Environmental Research

First Advisor

MacIsaac, Hugh

Second Advisor

Bailey, Sarah


Arctic, Ballast water, Biological invasions, Conservation Biology, Hull fouling, Marine ecology




Ships' ballast water and hull fouling are leading transport vectors of aquatic nonindigenous species (NIS) globally, yet very few studies have examined the magnitude of these vectors in the Arctic. A combination of climate warming, resource exploration, and expanded Arctic shipping is expected to increase the risk of introducing NIS to the Arctic via ship vectors. Therefore, a formal assessment of the current risk levels associated with these vectors is warranted. I conducted a vector-based risk assessment to identify ports at relatively high risk of ballast-mediated invasions and the responsible vessel pathway. Churchill appears to be at greatest invasion risk from ballast water discharged by international merchant vessels. I subsequently collected ballast water and hull fouling samples from 32 and 13 ships, respectively, at Churchill and quantified colonization pressure (CP) and total propagule pressure (total PP) associated with each vector. I evaluated relative arrival potential of invertebrates via ballast water by comparing CP, total PP, and the relationship between CP and total PP in vessels from Europe destined for the Arctic with those bound for Atlantic Canada and the Great Lakes. Arrival potential of invertebrates in ballast water of Arctic ships may be lower than that of Atlantic ships but similar to that of Great Lakes ones. Furthermore, I determined the relative importance of ballast water and hull fouling as transport vectors of NIS to the Canadian Arctic by comparing CP, total PP, number of NIS, and total abundance of all NIS for invertebrates transported by each vector. Hull fouling appears to be the more important transport vector of NIS. Finally, to better understand ship-mediated dispersal mechanisms, I examined temporal changes in characteristics of species assemblages entrained by ballast water using datasets from other, previously studied Canadian systems with large sample size. Rank-abundance distributions and CP:total PP patterns varied widely by voyage route (Pacific vs. Atlantic), taxonomic group (invertebrates, diatoms, and dinoflagellates), and ballast water management (control vs. exchanged). Results of this dissertation can help direct research and management efforts at high-risk ports as well as the vector and vessel pathways that pose the greater risk given limited managerial resources.