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UBC Theses and Dissertations

Ecology and diversity of marine viruses on the Canadian Arctic Shelf, Arctic Ocean Payet, Jérôme Patrice


Viruses are the most abundant, ubiquitous and diverse biological entities in the world’s oceans. Through infection and lysis, viruses play critical roles in shaping marine microbial assemblages, with consequences for ecosystem functioning and biogeochemical processes. Despite their global-scale importance in oceanic processes, relatively little is currently known about the distribution, ecological roles and diversity of marine viruses. Furthermore, this existing knowledge is largely limited to temperate and lower latitude ecosystems, leaving the role of viruses in polar waters relatively unexplored. The Canadian Arctic Shelf (CAS) is a heterogeneous and productive marine ecosystem within the Arctic Ocean that plays a key role in carbon cycling. Emerging data suggest that the microbial assemblages on the CAS are active and diverse and can respond rapidly to changes in environmental conditions. This dissertation addresses a knowledge gap regarding marine viruses in polar waters by examining ecology and diversity of marine viruses on the CAS. Toward this end, multiple approaches such as flow cytometry and epifluorescence microscopy, experimental incubations and filtration, molecular techniques (polymerase chain reaction, denaturing gradient gel electrophoresis fingerprint analysis, cloning and sequencing) and statistical analyses were used to investigate 1) spatio-temporal variations in viral distribution and abundance, 2) significance of lysogenic and lytic viral infections and their impacts on host mortality and carbon cycling, 3) patterns in the genetic structure of T4-like viruses (Myoviridae) and phycodnaviruses (Phycodnaviridae), two virus families infecting bacteria and eukaryotic phytoplankton, respectively and 4) phylogenetic diversity and richness of T4-like viruses and phycodnaviruses. Together, the results of these studies have demonstrated that viruses are abundant, active and diverse components of the CAS microbial assemblages, and are strongly coupled with environmental conditions and microbial abundance, productivity and composition. In addition, these studies indicate that viruses are significant agents of microbial mortality on the CAS, and can influence energy fluxes and carbon cycling. Overall, this dissertation has increased our understanding of the marine viruses in arctic environments. Moreover, the results stress the need to include viruses in models when studying the influence of climate changes on biogeochemical cycles in the Arctic Ocean.

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