Award: OCE-1829636

Marine viruses are abundant, diverse, and infect microorganisms at the base of the global ocean food web. Precisely because of the diversity of viruses and their microbial hosts, it remains difficult to identify which virus-microbe interactions disproportionately contribute to the turnover of populations, carbon, and nutrients. This NSF Biological Oceanography project led by Joshua Weitz (Professor of Biology at the University of Maryland) set out to understand how viruses impact mortality and the regeneration of nutrients in complex ocean microbial communities. Specifically, in collaboration with Prof. Matthew Sullivan (The Ohio State University) and Prof. Steven Wilhelm (The University of Tennessee-Knoxville) this project enabled a multi-year effort to probe complex dynamics between viruses and their microbial hosts spanning laboratory to research expeditions to the Sargasso Sea. In doing so, the core intellectual merit focused on team efforts to characterize how feedback between viruses and bacteria leads to unexpected and complex dynamics at the community scale and emergent patterns at the ecosystem scale. First, we developed methods to scale-up from pairwise interactions of viruses and bacteria to explore the predictability of community-scale dynamics. Through a combination of mathematical modeling and laboratory experiments, the project developed methods to compare expectations of pairwise models to community models. Then, through iterative comparison to experimental time series, we learned how much of community dynamics are predictable and when higher-order interactions may be needed to reconcile the mechanisms underlying coexistence of complex communities of viruses and bacteria. Second, through multiple expeditions to the Sargasso Sea, the team probed the ways in which viral lysis of microbial hosts can enhance community productivity. We identified multiple emergent phenomena at the study site, including structure in the giant virus community, mechanisms linking viruses to oxygen production peaks, and temporal niche partitioning for limiting nutrients. These findings leveraged the analysis of metagenomic and metatranscriptomics data, providing insights into the diversity of the virus and microbial communities and their associated activity. The analysis of virus-microbe dynamics were enabled by the development of computational models and simulations; software was released through open-access GitHub repositories. The contributions within and between disciplines was facilitated by the contributions of multiple undergraduate and graduate students. Two REU students were supported in the project. In addition, three Ph.D. students from biology and physics were partially supported by this grant. One student graduated with a Ph.D. in Physics with a research focus on the ecology of virus-host interactions in the oceans and then initiated a job in industry as a data scientist. In total, 6 new peer-reviewed articles were published as a direct result of support enabled by this project with more publications entering the preprint phase by the time of project close-out. The research discoveries in this project directly facilitated a series of efforts that resulted in broader impacts. Notably, project efforts were interrupted by the SARS-CoV-2 pandemic. Given the computational expertise of the group, multiple members of the Weitz group leveraged their training in virus dynamic modeling in service of providing early modeling-based analysis of the threat, developing response and scenario tools, and translating model findings into public-facing risk assessment dashboards used by millions of individuals to understand the risk associated with indoor transmission. In addition, Weitz leveraged methods developed in this project to complete a graduate textbook and series of computational laboratory guides on Quantitative Biosciences (Princeton University Press, 2024). Finally, Weitz and his research group have also been active in presenting their research in US universities, at international institutions, as part of disciplinary conferences (like the Aquatic Virus Workshop series), to conferences focusing on other disciplines, as part of international training courses (including in the US, Italy, Brazil, and France) and to the general public. Last Modified: 01/29/2024 Submitted by: JoshuaSWeitz