Evaluating Oceanic Nitrogen Fixation using Spatial Variations in the Natural Isotopic Composition of Nitrate in the Subsurface Waters of the Subtropical N. Atlantic

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ABSTRACT OCE-9902450Recent studies have suggested that nitrogen fixation may play a central role in controlling the oceanic inventory of combined nitrogen, primarily nitrogen in the form of dissolved nitrate in the deep ocean. As a macronutrient limiting primary production in much of the ocean, nitrogen not only plays a critical role in maintaining the ecology of the sea but also in regulating the capacity of the ocean to drawn down atmospheric carbon dioxide and fix it into organic form. In this study, the PIs will use the isotopic composition of nitrate to evaluate and quantify the importance of N2 fixation in supplying combined nitrogen to the oligotrohpic central North Atlantic. This isotopic approach will complement ongoing efforts to measure the rates of oceanic nitrogen fixation directly.