Collaborative Research: Nutrient Cycling in the Benguela Upwelling System during the Pliocene Epoch

Marine life depends on nutrients transported from the deep ocean into sunlit surface waters. There, nutrients fuel the growth of the microscopic organisms that support ocean food webs. This transport process is called “upwelling” and primarily occurs in four coastal regions off western North and South America and Africa. Together, these regions provide up to 20% of the global fish catch. Changes in ocean circulation may alter delivery of vital nutrients to the surface with consequences for marine ecosystems and food security. This research addresses how nutrient upwelling changed during past geologic periods of ocean warming and cooling by studying ancient ocean sediments from the Benguela region off southern Africa. A novel technique will measure nitrogen preserved in sediment microfossils to understand past nutrient sources. The project will train one graduate and six undergraduate students. A partnership with the Museum of Science, Boston will provide firsthand opportunities for the public to engage in the scientific process. Major uncertainties exist concerning how ongoing ocean temperature and circulation changes could affect the Benguela upwelling system and the critical fisheries it sustains into the future. To address these uncertainties, the research team will measure the nitrogen isotopic composition of foraminifera-bound organic matter to reconstruct the sources of nitrate to the Benguela upwelling system and the intensity of upwelling from three legacy scientific ocean drilling sites in the Benguela region. This approach will be applied to two time-slices, the Late Pleistocene glacial cycles and the mid-Pliocene warm period, to encompass broader ranges in ocean temperature and circulation than are present in the observational record. These new data will be integrated with existing reconstructions of ocean temperature and productivity to reveal the Pliocene-to-present upwelling history in the Benguela region and, more broadly, improve our understanding of how Eastern boundary upwelling systems respond to oceanographic change. 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.