The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone

Glock, Nicolaas, Schönfeld, Joachim, Eisenhauer, Anton, Hensen, Christian, Mallon, Jürgen and Sommer, Stefan (2013) The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone Biogeosciences (BG), 10 . pp. 4767-4783. DOI 10.5194/bgd-9-17775-2012.

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Abstract

The discovery that foraminifera are able to use nitrate instead of oxygen as energy
source for their metabolism has challenged our understanding of nitrogen cycling in
the ocean. It was evident before that only prokaryotes and fungi are able to denitrify.
Rate 5 estimates of foraminiferal denitrification were very sparse on a regional scale.
Here, we present estimates of benthic foraminiferal denitrification rates from six stations
at intermediate water depths in and below the Peruvian oxygen minimum zone
(OMZ). Foraminiferal denitrification rates were calculated from abundance and assemblage
composition of the total living fauna in both, surface and subsurface sediments,
10 as well as from individual species specific denitrification rates. A comparison with total
benthic denitrification rates as inferred by biogeochemical models revealed that benthic
foraminifera account for the total denitrification on the shelf between 80 and 250m
water depth. They are still important denitrifiers in the centre of the OMZ around 320m
(29–56% of the benthic denitrification) but play only a minor role at the lower OMZ
15 boundary and below the OMZ between 465 and 700m (3–7% of total benthic denitrification).
Furthermore, foraminiferal denitrification was compared to the total benthic
nitrate loss measured during benthic chamber experiments. Foraminiferal denitrification
contributes 1 to 50% to the total nitrate loss across a depth transect from 80 to
700 m, respectively. Flux rate estimates ranged from 0.01 to 1.3 mmolm−2 d−1. Fur20
thermore we show that the amount of nitrate stored in living benthic foraminifera (3 to
705 μmolL−1) can be higher by three orders of magnitude as compared to the ambient
pore waters in near surface sediments sustaining an important nitrate reservoir in Peruvian
OMZ sediments. The substantial contribution of foraminiferal nitrate respiration
to total benthic nitrate loss at the Peruvian margin, which is one of the main nitrate sink
25 regions in the world oceans, underpins the importance of previously underestimated
role of benthic foraminifera in global biochemical cycles.

Document Type: Article
Additional Information: WOS:000322242700024
Keywords: Santa-Barbara Basin
Research affiliation: OceanRep > SFB 754 > B6
OceanRep > SFB 754 > B7
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > SFB 754
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.5194/bgd-9-17775-2012
ISSN: 1726-4170
Projects: SFB754, Future Ocean
Expeditions/Models:
Date Deposited: 13 Dec 2012 11:45
Last Modified: 11 Aug 2014 11:09
URI: http://eprints.uni-kiel.de/id/eprint/19736

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