Simple transfer functions for calculating benthic fixed nitrogen losses and C:N:P regeneration ratios in global biogeochemical models.

Bohlen, Lisa, Dale, Andy W. and Wallmann, Klaus (2012) Simple transfer functions for calculating benthic fixed nitrogen losses and C:N:P regeneration ratios in global biogeochemical models. Open Access Global Biogeochemical Cycles, 26 (GB3029). DOI 10.1029/2011GB004198.

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Empirical transfer functions are derived for predicting the total benthic nitrate loss(LNO3) and the net loss of dissolved inorganic nitrogen (LDIN) in marine sediments,equivalent to sedimentary denitrification. The functions are dynamic vertically integratedsediment models which require the rain rate of particulate organic carbon to the seafloor(RRPOC) and a proposed new variable(O2-NO3)bw (bottom water O2 concentration minus NO3-concentration) as the only input parameters. Applied globally to maps of RRPOC and(O2-NO3)bw on a 1° x 1° spatial resolution, the models predict a NO3- drawdown of 196 Tg yr-1 (LNO3)of which 153 – 155 Tg yr-1 is denitrified to N2 (LDIN). This is in good agreement with previous estimates using very different methods. Our approach implicitly accounts for fixed N loss via anammox, such that our findings do not support the idea that the relatively recent discovery of anammox in marine sediments might require current estimates of the global benthic marine N budget to be revised. The continental shelf (0 – 200 m) accounts for >50% of global LNO3 and LDIN, with slope (200 – 2000 m) and deep-sea (>2000 m) sediments contributing ca. 30% and 20%, respectively.
Denitrification in high-nitrate/low-oxygen regions such as oxygen minimum zones is significant (ca. 15 Tg N yr-1; 10% of global) despite covering only 1% of the seafloor. The data are used to estimate the net fluxes of nitrate (18 Tg N yr-1) and phosphate(27 Tg P yr-1) across the sediment-water interface. The benthic fluxes strongly deviate from Redfield composition, with globally averaged N:P, N:C and C:P values of 8.3, 0.067 and 122, respectively, indicating world-wide fixed N losses (by denitrification) relative to C and P. The transfer functions are designed to be coupled dynamically to general circulation models to better predict the feedback of sediments on pelagic nutrient cycling and dissolved O2 distributions.

Document Type: Article
Additional Information: WOS:000309415000001
Keywords: Benthic denitrification; Oxigen Minimun Zone; Benthic fluxes
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R05
OceanRep > SFB 754 > B5
OceanRep > SFB 754
OceanRep > SFB 754 > B1
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2011GB004198
ISSN: 0886-6236
Projects: SFB754, Future Ocean
Date Deposited: 05 Oct 2012 06:01
Last Modified: 23 Sep 2019 23:27

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