Award: OCE-1237108

This project funded the collection, processing, and analyses of hundreds of samples of 210Po and 210Pb activity in both the dissolved and particulate phase along the two transects: EPZT in the Eastern Pacific between Peru and Tahiti, and GEOVIDE in the North Atlantic and Arctic beteen Portugal and Newfoundland, Canada. Along both transects, samples were collected at specific stations and the activity of the radionuclides was measured on both particle (small and large) and in the water column. This data could tell us about the partitioning of the natural radionuclides in these various oceanic environments. This radionuclide pair is interesting for two reasons: first, the fact that the grandparent (210Pb) is much longer lived than the grand-daughter (210Po), means we can use the deviations from secular (radioactive) equilibrium of this pair to determine the export of particles from the surface ocean. Second, 210Po is the only natural radionuclide that bioaccumulates and so it can trace the behavior of organic material through the ocean, and the known half-life means we can understand the timing of partioning, uptake, export, and dissolution/remineralization. In fact, we connected the activity of the radionuclide to the respiration rate of the water column using the oxygen utiiization rate, so we could consider how quickly or slowly organic matter was being respired by bacteria in the top 200m or so of the surface ocean. The transects were chosen due to their diverse conditions, from shallow coastal settings, to areas with upwelling, areas over ocean spreading centers, the deep, open ocean, and the shallow seas and basins of the Arctic. Understanding the cycling of 210Po and 210Pb in these areas can provide insight into the behavior of other particle-reactive elements, but also the fate of organic matter in the ocean. And together, the isotopes can tell us about the magnitude and efficiency of the sequestration of arbon from the atmopshere via the biological pump. As climate change due to increasing carbon in the atmopshere is one of the biggest threats facing the planet, this research aims to understand some of the temporal and spatial variability in the surface ocean's ability to take carbon dioxide from the atmosphere and shuttle it to depth where it is stored for hundreds to thousands of years. This project was crucial in training a future oceanographer, and the results and insights from this project were described in undergraduate and graduate classes at Queens College, in the City University of New York. Queens College is the most diverse college in the country and the School of Earth and Environmental Sciences serves a unique population of urban and often under-priveleged students. In addition, most fo the students at Queens College are first generation Americans, and getting them interested and involved in understanding the environment around them (and specifically the ocean) is one of the major impacts of this project. We feel that we have managed to meet both the Intellectual Merit and Broader Impacts goals set forth in our proposal and will continue to share the knowledge gained through this project through presentations at conferences, peer-reviewed journal articles, and coursework and public lectures at Queens College. Last Modified: 07/02/2018 Submitted by: Gillian Stewart