NSF Award
2416286
Plankton significantly alter elemental and energy cycling in the ocean, as well as maintain marine food webs and impact ecosystem health. To optimally predict plankton stocks and activity, there is a need for understanding factors that control them and how they are altered by anticipated environmental changes. B-vitamins, specifically vitamin B1 and related compounds, need to be externally supplied to key plankton for them to survive in the surface ocean yet have not received sufficient attention in part due to uncertainty about supply and demand in-situ. This study tackles the question: What processes are crucial in supplying B1/vitamers to seawater? To address this question, culture-based experiments and recently developed chemical analyses are conducted to estimate the amount of vitamin B1 and related compounds that come from bacteria themselves but also viral infection of bacteria in the surface ocean. In addition, fluxes of these compounds are evaluated with respect to temperature, an influential variable on biology that is predicted to change in the future surface ocean. Interdisciplinary training for two PhD students at collaborating institutions is supported by this project, as well as the training of undergraduates from underrepresented groups recruited as summer research interns. In collaboration with the NCSU Science House, whose staff are experts in pedagogical methods and learning assessment, lesson plans related to the ‘life and death’ of marine plankton are developed to introduce young students from middle school and early high school in rural or low-income regions of NC to marine plankton, their global importance, and connections between nutrients and activity of plankton.<br/><br/>Bacterioplankton and phytoplankton are cornerstones of the marine food web and impact oceanic elemental cycling, productivity, and ecosystem health. Most marine bacterioplankton and key phytoplankton lineages rely on exogenous vitamin B1 (thiamin; B1 herein) or vitamers (B1-related compounds) to survive. B1 & vitamers must come from cells, presumably via cell secretion/release and mortality, but the relative importance of these processes as well as the importance of certain taxa as sources and impact of environmental change (especially temperature) on flux are unknown. This project assesses the release of B1/vitamers by representatives of key de novo B1-producing bacterioplankton (picocyanobacteria and heterotrophic bacteria) in axenic cultures and in the context of temperature change. Moreover, tests are carried out to study whether viral infection and lysis results in unique B1/vitamer flux compared to release by model bacterioplankton alone and to assess how temperature change alters these processes – reaching beyond consideration of temperature as only an abiotic degradative factor. Overall, results of these laboratory experiments provide flux data enabling: the first estimation of in-situ fluxes in the surface ocean, tests of genome-based prediction of high vitamin providing bacterioplankton, and linkage of flux data to fundamental biochemical and physiological measurements (biomass, growth rate, lysis rate) useful for ocean models predicting biochemistry, community composition, and productivity.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
