Ecology and biology of aquatic viruses and their microbial hosts in a changing climate.

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Today a virus is most commonly thought of as a critical threat, particularly to human life. But viral infection is not unique to humans, nor does it always cause disease. We know that in the ocean viruses play a diverse role and have complex relationships with aquatic microorganisms. They can control algal bloom formation, drive processes such as nutrient flow through food webs and stimulate the sequestration of carbon. It is recognized that, collectively, viruses make an important contribution to global ecosystem function, to the health of aquatic habitats, and to buffering the effects of climate change. However, we still lack critical understanding of how climate change and the build-up of excessive nutrients (eutrophication) may affect the ecology of aquatic viruses, their microbial hosts, and the consequences of their interactions. In freshwater systems for example, including Canadian watersheds, rising temperatures and nutrient levels have driven an increase in harmful algal blooms (HABs) that threaten ecosystem health and reliant economies such as aquaculture and tourism. We need to understand the extent to which viruses control populations of these harmful algae and whether that ability might be diminished in a changing environment. Such understanding is essential for stakeholders and decision-makers to predict how the health and function of aquatic ecosystems may change in the future, and whether mitigation strategies are likely to be successful. This proposal will lay the foundations for a research program that will address these questions. It will investigate (i) the ecology and success of environmentally-important viruses and their hosts, and (ii) their co-evolutionary dynamics and adaptation to climate change and eutrophication. Experiments with select algae, bacteria and viruses as models will be linked to observations in the more complex natural environment in which they occur. The outputs of the work will improve ecosystem models of microbial interactions in aquatic environments and our understanding of the ecological role of aquatic viruses and their hosts in a changing climate. This research will also provide new knowledge on algal and bacterial biology during infection and improve our general understanding of viruses that vary in size, genomic structure and the mechanisms that they employ to kill their hosts. The use of state-of-the-art culturing facilities and analytical methods for microbiology and molecular biology to address the specific research questions of this proposal (in support of the overarching goals of the research program; i & ii) will allow us to bridge the gap between findings from the laboratory and field. Critically, the proposed program will also foster the development of future leaders, providing them with the knowledge and technical expertise to pursue successful careers in virology and ecology or engage in high-impact environmental consultancy at the interface of science and decision-making.