Old New Nitrogen

摘要

The availability of nitrogen limits primary production in many parts of the ocean, creating a tight link between the fluxes of nitrogen and carbon through marine ecosystems. This coupling between the nitrogen and carbon cycles is often quantified in terms of "new nitrogen," or nitrogen added to the biologically active pools in the upper ocean by processes such as vertical mixing, river runoff, atmospheric deposition, and nitrogen fixation. On page 244 of this issue, Ren et al. (1) introduce a powerful approach for characterizing the history of the oceanic nitrogen cycle and the role of new nitrogen in supporting primary production by measuring the nitrogen isotopic composition of the shells of plank-tonic foraminifera.