UBC Theses and Dissertations
Assessing intertidal marine non-indigenous species in Canadian ports Choi, Francis Ming Pong
The establishment of non-indigenous species in natural ecosystems is a growing concern at global, national, and regional scales. Over 100 known marine non-indigenous species (NIS) are found along the Pacific and Atlantic coasts of Canada. It is widely believed that commercial shipping activities associated with international ports (e.g. ballast water discharge, hull fouling) could expose native communities to a variety of NIS. Thus, harbours are recognized as critical entry points for NIS and, pending establishment, can serve as invasion hubs for secondary dispersal vectors (e.g. recreational boats). The aim of this study was to characterize intertidal NIS distributions among ports on the Pacific and Atlantic coasts of Canada and to determine if commercial shipping activities (ballast water discharge, vessel arrivals) can be directly linked to the observed patterns of established NIS. Sixteen major international ports in Canada were surveyed for species composition and abiotic conditions, including both environmental and anthropogenic factors. Species diversity for both NIS and native species were found to be significantly different between the Pacific and the Atlantic intertidal communities. Although both NIS and native species had higher diversity on the Pacific coast, the Invasion index, a novel measurement of the degree of invasion developed in this thesis, demonstrated that the Atlantic coast was actually more invaded by NIS than the Pacific. No direct link was found between commercial shipping activities and the distribution patterns of established intertidal NIS in Canadian ports. Instead, NIS distributions were found to be strongly related to salinity, sediment type, human population, aquaculture and latitude on the Pacific coast and human disturbance at docks, latitude and salinity on the Atlantic coast. In contrast to what was previously suggested, these results demonstrated that ballast water discharge and vessel arrival frequency were not detected as the main variables towards NIS establishment success. However, this study highlighted the importance of environmental conditions and local anthropogenic vectors in the establishment of NIS in new regions. Future research in conservation and management of invaded communities should include environmental conditions and the risk posed by anthropogenic activities, in addition to commercial shipping, when characterizing invasion dynamics.
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