The trouble with the bubble

摘要

As is the case for gardens, forests and fields, the availability of fixed nitrogen (such as nitrate and ammonia) can limit the productivity of our seas. Ocean-ographers are therefore interested in the relative magnitudes of sources and sinks of fixed nitrogen as dynamic controls of ocean fertility. The trajectory of the oceanic nitrogen inventory has been a long-debated and contentious topic: direct rate measurements of biologically mediated nitrogen fluxes suggest that the ocean is currently being depleted of this resource, whereas geochemical evidence indicates a steady-state, balanced nitrogen budget~1.