First basin-wide experimental results on N-2 fixation in the open Mediterranean Sea

• Published in: Geophysical Research Letters
• Main Authors: Ibello, Valeria, Cantoni, Carolina, Cozzi, Stefano, Civitarese, Giuseppe
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: GEOPHYSICAL RESEARCH LETTERS 2010
• Subjects: North Atlantic
• Online Access: https://hdl.handle.net/11511/30095; https://doi.org/10.1029/2009gl041635

The Mediterranean Sea presents several biogeochemical anomalies compared to the global ocean. An unbalanced N budget, high nitrate/phosphate ratios in subsurface waters and low N-15/N-14 ratios in particulate and dissolved nitrogen suggest a significant occurrence of N-2 fixation. This study presents, for the first time, a basin-wide overview of direct measurements of N-2 fixation, with values in the North Atlantic for comparison, during late spring 2007. Very low N-2 fixation rates (0.052 +/- 0.031 nmols N l(-1) d(-1)) were observed in all sub-regions of the Mediterranean, in contrast to the higher values measured in the North Atlantic (0.300 +/- 0.115 nmols N l(-1) d(-1)). Higher phosphorus (inorganic or organic) concentrations were not associated with higher N-2 fixation rates. Low N-15/N-14 ratios in particulate organic nitrogen (from -2.10 to +4.11%), associated with low N-2 fixation rates, suggest that other N sources, such as atmospheric inputs, fuel the Mediterranean ecosystem. Citation: Ibello, V., C. Cantoni, S. Cozzi, and G. Civitarese (2010), First basin - wide experimental results on N-2 fixation in the open Mediterranean Sea, Geophys. Res. Lett., 37, L03608, doi:10.1029/2009GL041635.