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| Titel |
The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone |
| VerfasserIn |
N. Glock, J. Schönfeld, A. Eisenhauer, C. Hensen, J. Mallon, S. Sommer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-15), S.4767-4783 |
| Datensatznummer |
250018343
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| Publikation (Nr.) |
 copernicus.org/bg-10-4767-2013.pdf |
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| Zusammenfassung |
| The discovery that foraminifera are able to use nitrate instead of oxygen as
an electron acceptor for respiration has challenged our understanding of
nitrogen cycling in the ocean. It was thought before that only prokaryotes
and some fungi are able to denitrify. Rate estimates of foraminiferal
denitrification have been very sparse and limited to specific regions in the
oceans, not comparing stations along a transect of a certain region. 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, 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 probably account for the total denitrification in shelf
sediments between 80 and 250 m water depth. The estimations also imply that
foraminifera are still important denitrifiers in the centre of the OMZ
around 320 m (29–50% of the benthic denitrification), but play only a
minor role at the lower OMZ boundary and below the OMZ between 465 and 700 m
(2–6% of total benthic denitrification). Furthermore, foraminiferal
denitrification has been compared to the total benthic nitrate loss measured
during benthic chamber experiments. The estimated foraminiferal
denitrification rates contribute 2 to 46% to the total nitrate loss
across a depth transect from 80 to 700 m, respectively. Flux rate estimates
range from 0.01 to 1.3 mmol m−2 d−1. Furthermore we show that the
amount of nitrate stored in living benthic foraminifera (3 to 3955 μmol L−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 regions in the world
ocean, underpins the importance of the previously underestimated role of
benthic foraminifera in global biogeochemical cycles. |
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