June 26, 2012: FB2-Seminar

15 c.t., lecture hall, western shore building

Abstract: 

The marine N inventory is maintained by the coupling between marine N2 fixation and denitrification. The stronger the coupling the closer the balance. This paradigm implies that factors that limit N2 fixers ability to respond to N deficits may be re- sponsible for declining N inventories; While, the spatial proximity of N sources and sinks promotes stabilizing effects over N variability. Using a biogeochemical ocean cir- culation model, we here show instead that a close spatial association of N2 fixation and denitrification removes the stabilizing feedbacks on the N inventory and, because of stoichiometric constrains, leads to net N losses. Contrary to current theory, a bal- anced N inventory requires a regional separation of the two processes brought about by factors that reduce the growth of diazotrophs, such as iron, and affect the fate of the fixed nitrogen remineralization. In light of our findings we suggest a re-evalutaion of the stabilizing feedbacks suggested for reconstructing past, evaluating present and predicting future marine N inventory imbalances.