Nitrogen cycling in deep-sea sediments of the Porcupine Abyssal Plain, NE Atlantic

Brunnegard, J., Grandel, S., Stahl, H., Tengberg, A. and Hall, P. O. J. (2004) Nitrogen cycling in deep-sea sediments of the Porcupine Abyssal Plain, NE Atlantic Progress in Oceanography, 63 (4). pp. 159-181. DOI 10.1016/j.pocean.2004.09.004.

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Rates of transformation, recycling and burial of nitrogen and their temporal and spatial variability were investigated in deep-sea sediments of the Porcupine Abyssal Plain (PAP), NE Atlantic during eight cruises from 1996 to 2000. Benthic fluxes of ammonium (NH(4)) and nitrate (NO(3)) were measured in situ using a benthic lander. Fluxes of dissolved organic nitrogen (DON) and denitrification rates were calculated from pore water profiles of DON and NO(3), respectively. Burial of nitrogen was calculated from down core profiles of nitrogen in the solid phase together with (14)C-based sediment accumulation rates and dry bulk density. Average NH(4) and NO(3)-effluxes were 7.4 +/- 19 mumol m(-2) d(-1) (n = 7) and 52 +/- 30 mumol m(-2) d(-1) (n = 14), respectively, during the period 1996-2000. During the same period, the DON-flux was 11 +/- 5.6 mumol m(-2) d(-1) (n = 5) and the denitrification rate was 5.1 +/- 3.0 mumol m(-2) d(-1) (n = 22). Temporal and spatial variations were only found in the benthic NO(3) fluxes. The average burial rate was 4.6 +/- 0.9 mumol m(-2) d(-1). On average over the sampling period, the recycling efficiency of the PON input to the sediment was similar to94% and the burial efficiency hence similar to6%. The DON flux constituted similar to14% of the nitrogen recycled, and it was of similar magnitude as the sum of burial and denitrification. By assuming the PAP is representative of all deep-sea areas, rates of denitrification, burial and DON efflux were extrapolated to the total area of the deep-sea floor (>2000 m) and integrated values of denitrification and burial of 8 +/- 5 and 7 +/- 1 Tg N year(-1), respectively, were obtained. This value of total deep-sea sediment denitrification corresponds to 3-12% of the global ocean benthic denitrification. Burial in deep-sea sediments makes up at least 25% of the global ocean nitrogen burial. The integrated DON flux from the deep-sea floor is comparable in magnitude to a reported global riverine input of DON suggesting that deep-sea sediments constitute an important source of DON to the world ocean. (C) 2004 Elsevier Ltd. All rights reserved.

Document Type: Article
Keywords: nitrogen cycling autonomous benthic landers seasonality burial denitrification DON flux deep-sea sediments NE Atlantic Porcupine Abyssal Plain diffusive benthic fluxes eastern north pacific organic-carbon seasonal deposition early diagenesis shelf sediments oxygen-demand pore-water goban spur in-situ
Research affiliation: Kiel University
Refereed: No
DOI etc.: 10.1016/j.pocean.2004.09.004
ISSN: 0079-6611
Date Deposited: 24 Jan 2012 06:58
Last Modified: 09 Oct 2012 03:57

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