Controls on nitrogen fixation in the subtropical North Atlantic Ocean and the Mediterranean Sea

Over most of the global ocean, fixed nitrogen (N) is the primary limiting nutrient to phytoplankton. The marine N reservoir undergoes large natural fluctuations from N loss in suboxic regions (denitrification) and N addition by N2 fixing organisms. Our current understanding of how susceptible the marine N cycle may be to future increases in N through atmospheric deposition and N loss due to ocean deoxygenation/ denitrification is incomplete. Changes to these processes may potentially alter the marine N inventory with implications to global primary productivity in the future.

My project aims to explain the controls on N2 fixation in the low latitude ocean, specifically the Atlantic basin which has high N2 fixation rates due to being well-oxygenated with a high Fe supply from Saharan dust. However, sustained N2 fixation requires dissolved phosphorus (P). I am specifically investigating how tightly dissolved N/P nutrient ratios control N2 fixation by focusing on the subtropical North Atlantic Ocean and Mediterranean Sea. 

Research questions

- How do dissolved N/P nutrient ratios impact N2 fixation in the North Atlantic ocean?

- How important is N2 fixation in the Mediterranean?

- How will climate change affect global N2 fixation rates and what are the implications to the marine N inventory?

Supervisors

Dr Robyn Tuerena, SAMS

Prof Raja Ganeshram - The University of Edinburgh

Funder

NERC

University

The University of Edinburgh