MIP: Abundance, Dynamics, and Diversity of Viruses in the Northwestern Sargasso Sea

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Viruses are ubiquitous, abundant, and dynamic components of marine communities. The majority of marine viruses are phage (viruses that infect bacteria). Viruses influence global carbon and nutrient cycles, regulate the composition of marine bacterial communities, and play a major role in horizontal gene transfer. Recent studies have revealed an enormous diversity of viruses in the oceans; however, most in-depth studies of viral diversity have focused on a single sample a snapshot in space and time. Since bacterial and viral communities are dynamic in nature (rapid infection, production, decay), snapshots of diversity are inadequate for describing the microbial ecology of marine systems. This project will examine the abundance, diversity, and dynamics of viruses over a depth profile at Hydrostation S in the northwestern Sargasso Sea during a two-year period. Viral abundance with depth will be determined monthly by direct microscopic counts, and changes in the composition of the viral community will be monitored using molecular methods (pulsed-field gel electrophoresis, hybridization against microarrays, and PCR for specific phage genes). Multivariate analyses will be performed using available microbial and biogeochemical data from this site to determine which parameters correlate with changes in viral abundance and community composition. Rates of virus production and decay, as well as the impact of viruses on the bacterial community, will be determined. Finally, this project will examine the ecology of the marine single-stranded DNA Microphage, a newly described viral group found to be abundant in the Sargasso Sea. The goal of this project is to produce a comprehensive dataset on the spatial and temporal variation of the viral community at this site and determine if there are recurring (and thus predictable) patterns in viral abundance and diversity. This project is of scientific importance because of the critical roles viruses play in biogeochemical cycling and gene transfer in marine ecosystems. Despite their abundance and importance, the diversity and dynamics of marine viral communities are not well-understood. The data from this project will be analyzed in conjunction with the parameters measured by the Oceanic Microbial Observatory and the Bermuda Atlantic Time-series Study. This will successfully expand the scope of the time series to include viruses and provide a context in which trends in the viral data can be analyzed. Data will be disseminated through release into public databases and the creation of a website with details of viral sampling techniques and results from the northwestern Sargasso Sea. This grant will support the training of one graduate student and three undergraduate students. Graduate and undergraduate students will also be trained through the integration of a viral ecology segment into the summer Microbial Oceanography course offered annually at the Bermuda Institute of Ocean Sciences. K-12 students will be involved through the creation of a Marine Microbiology patch program for Cadette Girl Scouts (ages 11-14), where participants will learn about microbiology, issues affecting the oceans and the biology within it, and possible career options as a marine scientist.