UBC Theses and Dissertations

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UBC Theses and Dissertations

Drivers of viral diversity and community compositional change over spatial and temporal scales in coastal British Columbia Gustavsen, Julia Anne


Marine viruses are ubiquitous, abundant, and genetically diverse in natural waters. They play key roles in nutrient and carbon cycles. The composition of marine viral communities changes seasonally and repeats annually, and such patterns can be driven by their hosts in response to environmental changes. Moreover, environmental parameters can also directly affect the viral community through the decay of viruses, and differences in viral infectivity under different conditions. Marine viral communities show changes over time and space, but the mechanisms that drive compositional changes and maintain high diversity are largely unexplored. Determining factors affecting viral community composition and structure is essential to explain how viral diversity is maintained. This dissertation will assess the diversity of marine viral communities, and the role of the environment and putative viral hosts in driving this diversity. The relationship between environmental parameters and the diversity of viruses and their putative hosts was explored in coastal seawater samples along a transect and over a 13-month time series at a nearshore location. I used PCR amplification to target ecologically-important double-stranded DNA (T4-like myoviruses) and single-stranded RNA (picorna-like) viruses, as well as their putative bacterial (16S rRNA gene) and eukaryotic (18S rRNA gene) hosts were examined. These were interpreted in the context of nutrients, salinity, and temperature. I observed patchiness in the distribution and diversity of viral communities across space and time (Chapter 2). Chapter 2 greatly increased the known genetic diversity of marine picorna-like viruses with 145 operational taxonomic units (OTUs) occurring within previously seen phylogenetic clades. In Chapter 3 there were temporal shifts in dominance of phylogenetically-related viruses and most viral OTUs were ephemeral. In Chapter 4, I demonstrated that nutrients, salinity, and temperature drive the co-occurrence of viruses and their putative hosts. Finally, in Chapter 5, I revealed that specific viral and protistan taxa were associated with controlling species composition and the demise of a phytoplankton bloom. Altogether, this dissertation advances the understanding of the phylogenetic structure of viral communities over time, the drivers of host-virus relationships, and the dynamics of viral and microbial communities during blooms by assessing multiple groups of viruses and microbes.

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