The oceans represent a source of food, livelihood, and biogeochemical cycling that impacts our everyday lives. On the latter, the oceans absorb human-released carbon dioxide from the atmosphere, having, in effect, approximately halved the climate change impact of these gases. Critical to this ocean ?ecosystem service? are the floating organisms, or plankton, that are comprised of microbes and viruses, which effectively serve as a biological carbon pump on a grand scale. This is because it is these plankton that determine whether the ocean-absorbed atmospheric climate gases are incorporated into biomass and disposed to the deep sea or remineralized and released back into the atmosphere. For this reason, ocean scientists have long studied the organisms that drive the ocean carbon pump to better understand how the oceans will impact climate and the nutrient and energy flows that underpin much of how the Earth System works. In 2008, an ambitious, international project -- the Tara Oceans Expedition -- was launched to systematically study viruses, microbes, and small plants and animals throughout the world?s oceans. 

This NSF-funded project focused on understanding the viruses, and their larger ecosystem roles throughout the Global Ocean. Using methods developed to be portable enough to function on a sailboat (the ?Tara? research vessel) and systematic enough to allow for global sampling, we discovered via sequencing over 200,000 new virus species, which predominantly infect bacteria. Because virtually every one of these viruses were new to science, we developed machine learning approaches to classify them. With this Global Ocean virus catalog, we then identified the most abundant viruses so that they could be studied in the laboratory, as well as in the field. Laboratory experiments of some of the most abundant viruses revealed complex mechanisms of resistance, and how virus infections change under nutrient limitation. Genome sequencing revealed viruses directly encoded genes for photosynthesis, as well as cycling of carbon, nitrogen, and sulfur -- which directly implicates viruses in the very biogeochemical cycles for which the oceans are so important. Most unexpectedly, ecological modeling revealed that of all the plankton community members, viruses best predict the flux of carbon from surface to deep waters in the oceans. This means that viruses likely play an even bigger role in ocean food webs and nutrient cycling than previously realized, and the findings have spurred the field towards new experiments to better understand this.

Beyond the science, which resulted in over 15 research articles including several ?top tier? in Science, Nature, and Cell, this award supported several efforts that will have long-standing impact. First, the Global Ocean Virome dataset developed here serves as a critical resource for researchers around the world that want to study viruses in the oceans. Second, this award supported world-class training and research experience to dozens of undergraduates, graduates, and postdocs, as well as several ?viromics workshops? for workforce training efforts that impacted more than 100 trainees from around the world. Third, students and postdocs were trained in a new generation of ?big team science?, as well as how to communicate in public-facing venues including with the press corps and a science museum. Lastly, to best communicate this novel view of the impact of viruses in natural ecosystems, we collaborated with the Center of Science and Industry (COSI), which is a science museum and research center in Columbus, Ohio, to design and multi-year exhibit showcasing the role, impact, and diversity of viruses in the oceans. The exhibit is set to open to the public in December 2021, and will share the excitement of ?Tara Oceans? science in a way that will impact a large fraction of the >250K annual COSI visitors.

Last Modified: 11/30/2021
Modified by: Matthew Sullivan