Episodic atmospheric nitrogen deposition to oligotrophic oceans

PHYTOPLANKTON production is generally thought to be limited by nitrogen availability over large regions of the ocean, particularly oligotrophic areas. The largest source of nitrogen to these regions is transport from deep waters. Atmospheric deposition is also a source of nitrogen to the oceans 1 ,2 but previous assessments of these inputs, based on calculations of annual deposition 3,4 suggest that they are of minor importance for oceanic production. Using a nine-year record of nitrogen deposition, we re-evaluate here the contribution of atmospheric nitrogen inputs to the ocean and show that these can contribute to an important proportion of 'new production' during episodic events. Furthermore, as human activities such as fossil-fuel burning contribute significant quantities of inorganic nitrogen to the atmosphere 5,6 we suggest that the atmospheric input of nitrogen to the oceans is a route whereby these activities might directly influence (by increasing) oceanic productivity.