Development and application of seawater nutrient proxies in deep-sea corals

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Reconstruction of nutrient concentrations in past intermediate and deep waters is a critical goal in paleoceanography. Such information will allow calculation of intermediate/deep water mass mixing ratios in areas of active advection (e.g., the Atlantic), and when combined with radiocarbon dating will yield ventilation rates, which are thought to be an important control on atmospheric CO2. Past nutrient distributions can also yield information about productivity and remineralization in areas of more sluggish circulation. This award supports refinement and application of paleo-proxies for the nutrient phosphate (P/Ca) and the quasi-nutrient barium (Ba/Ca) in the solitary deep-sea coral D. dianthus. The research will produce a regional proxy calibration for the Southern Ocean using live-collected corals, and will then analyze fossil specimens to determine the evolution of endmember Southern source water nutrient content since the Last Glacial Maximum. They will also reconstruct the history of nutrient concentrations at mid to deep water depths in the NW Atlantic over the past 30ky using dated fossil corals from the New England seamounts. The research will provide a new, quantitative assessment of nutrient distribution in the past ocean. This work is part of a larger collaborative effort involving scientists from CalTech and Imperial College, London, who will provide both sample material and complementary data. Broader impacts include funding of a female PhD student as well as outreach efforts in association with the well-established COSEE (Center for Ocean Sciences Education Excellence) program at Rutgers University.