Organic nutrients and excess nitrogen in the North Atlantic subtropical gyre.

Landolfi, Angela , Oschlies, Andreas and Sanders, R. (2008) Organic nutrients and excess nitrogen in the North Atlantic subtropical gyre. Open Access Biogeosciences (BG), 5 . pp. 1199-1213. DOI 10.5194/bg-5-1199-2008.

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To enable an accurate estimate of total excess nitrogen (N) in the North Atlantic, a new tracer TNxs is defined, which includes the contribution of organic nutrients to the assessment of N:P stoichiometric anomalies. We measured the spatial distribution of TNxs within the subtropical North Atlantic using data from a trans-Atlantic section across 24.5° N occupied in 2004. We then employ three different approaches to infer rates of total excess nitrogen accumulation using pCFC-12 derived ventilation ages (a TNxs vertical integration, a one end-member and a two-end member mixing model). Despite some variability among the different methods the dissolved organic nutrient fraction always contributes to about half of the TNxs accumulation, which is in the order of 9.38±4.18×1011 mol N y−1. We suggest that neglecting organic nutrients in stoichiometric balances of the marine N and P inventories can lead to systematic errors when estimating deviations of nitrogen excess or deficit relative to the Redfield ratio in the oceans. For the North Atlantic the inclusion of the organic fraction to the excess nitrogen pool leads to an upward revision of the N supply by N2 fixation to 10.2±6.9×1011 mol N y−1.

Document Type: Article
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-5-1199-2008
ISSN: 1726-4189
Projects: Future Ocean
Date Deposited: 03 Dec 2008 16:51
Last Modified: 06 Jul 2012 15:06

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