Award: OCE-1459200

Phytoplankton are central components controlling carbon cycling in the marine environment so shifts in their population distribution and abundance can have a large impact on biogeochemical cycling and global climate. As phytoplankton population dynamics are driven by the relative rates of cell growth and loss, interactions with other members of the planktonic community can directly influence both of these rate processes. Deciphering the nature and relative importance of these interactions will help to illuminate mechanisms that drive bulk measurements of phytoplankton loss and is necessary to inform models for the accurate prediction of phytoplankton population dynamics and ultimately, biogeochemical cycling and shifts in global climate. This project studied the relative importance of mortality process—via grazing by predators and infection by viruses— for the globally distributed, coccolithophore, Emiliania huxleyi, which forms massive blooms in the ocean and plays a large role in global carbon cycling due to its ability to photosynthesize and produce calcium carbonate biominerals that sink to the deep ocean.Like all phytoplankton, the abundance and distribution of E. huxleyi is driven by processes that stimulate growth and expedite mortality. Ultimately grazing and viral lysis processes may have contrasting influence on the structure and function of the marine food web and biogeochemical cycles. Our work showed that both processes are persistent in natural populations with zooplankton grazing generally proceeding virus-induced mortality which progresses at later stages of the bloom, but that these two processes are actually coupled to a larger degree than previously thought and this leads to enhanced export fluxes of phytoplankton into the deep ocean. The enhanced export and sinking was found to stimulated by enhanced production of sticky exopolymers during virus infection which serves to both aggregate phytoplankton and dense cell biominerals into rapidly sinking particles and serve as particulate food matter for larger grazers which in turn produce fecal pellets with high sinking rates. Research activities and findings reveaed how host physiology impacts of virus infection on unicellular photoautotrophs and how it impacted organism-organism interactions to regulate cell fate in the environment. Our work has revealed that specific physiological and phenotypic characteristics have a pronounced impact on how viruses and grazers interact with unicellular photoautotrophs. They have also revealed intriguing aspects of the reverse--how the presence of viruses and grazers can impact inherent phenotypic characteristics of cells with implications for the carbon cycle. Lastly, our work showed how physical circulation processes can set the stage for biological and ecosystem responses, namely by stimulating or repressing host losses via virus infection and grazers. This physical-biological coupling has profound impacts on ecosystem response. The project supported the research activities and traning of four graduate students, two postdocs, technical personnel, and six undergraduate students with most personnel participating in field research studying phytoplankton populations in the Norwegian coastal waters and in the Western North Atlantic. Graduate student, postdoc and technical personnel all helped to train undergraduate students in their work. Broader impact and outreach efforts created, developed, and disseminated the "Tools of Science"video and resource series on the process of science. Five videos (each ~5-7 min), entitled ?Testable Questions?, ?Collaborations?, ?Sampling?, ?Proxies? and ?Mathematical Models? are now completed and are freely available for viewing at the ?Tools of Science?You Tube Channel. Each highlight various scientific practices through real research investigations during the North Atlantic Virus Infection of Coccolithovirus (NA-VICE)research expedition that Bidle led in the North Atlantic in 2012. The videos are open access and are designed to be incorporated into both middle and high schools, as well as undergraduate classes. The collective series of videos are geared on the NGSS Science and Engineering Practices and enabling teachers nationwide to convey these concepts in their teaching using real ocean-based science. Ongoing efforts continue to train and integrate ToS into classrooms across New Jersey and nationally, as well as providing a platform for other researchers to participate highlight concepts and videos of their own. Last Modified: 08/15/2019 Submitted by: Kay D Bidle