Collaborative Research: Measuring Ocean Productivity from the Diurnal Change in Oxygen and Carbon

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The rate of primary production in the ocean is fundamental to the ocean's food web and the movement of carbon from surface waters to the deep ocean, known as the biological pump. Yet spatial and temporal variations in primary productivity are poorly known because the effort required for the current method of measuring primary productivity is significant, limiting its application, and the method has biases that are difficult to quantify. Using a novel combination of approaches, the investigators will estimate daily primary productivity in the ocean at three ecologically distinct sites. The research will significantly improve understanding of primary productivity variations and their impact on the ocean's biological pump, which will benefit the broader ocean community involved in carbon cycle modeling and benefit society via the impact of ocean primary productivity on atmospheric carbon dioxide uptake and future climate change. The research results will be incorporated into both undergraduate and graduate course curricula and outreach talks at the two institutions. There will be active undergraduate student participation in the project at both Oregon State University and the University of Washington.Within the last decade, an in-situ primary productivity method based on measuring the isotopic composition of dissolved oxygen (O2) gas has gained traction within the oceanographic community because it yields a primary production estimate from a simple water sample collection. This method has yielded basin-wide snapshots of primary productivity based on underway sampling of the surface ocean by ships of opportunity. However, accurate estimates of oxygen/particulate organic carbon (O2/POC) produced during primary productivity are needed to convert oxygen-based primary production rates to carbon production. In this project, daily in-situ rates of primary production in the surface ocean at three ocean sites will be estimated from continuous measurements of diurnal cycles in the oxygen/argon dissolved gas ratio and POC and compared to simultaneous in vitro primary productivity estimates. Variations in the O2/POC produced during primary production will be determined. Autonomous float-based estimates of primary production based on measurements of diurnal cycles in O2 and POC will be validated using ship based measurements. Estimates of primary production based on autonomous measurements resulting from this research have the potential to revolutionize our knowledge on the spatial and temporal variations in primary productivity in the ocean.