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| Titel |
Uptake of phytodetritus by benthic foraminifera under oxygen depletion at the Indian margin (Arabian Sea) |
| VerfasserIn |
A. J. Enge, U. Witte, M. Kucera, Petra Heinz |
| 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 ; 11, no. 7 ; Nr. 11, no. 7 (2014-04-10), S.2017-2026 |
| Datensatznummer |
250117355
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| Publikation (Nr.) |
 copernicus.org/bg-11-2017-2014.pdf |
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| Zusammenfassung |
| Benthic foraminifera in sediments on the Indian margin of the Arabian Sea,
where the oxygen minimum zone (OMZ) impinges on the continental slope, are
exposed to particularly severe levels of oxygen depletion. Food supply for
the benthic community is high but delivered in distinct pulses during
upwelling and water mixing events associated with summer and winter monsoon
periods. In order to investigate the response by benthic foraminifera to
such pulsed food delivery under oxygen concentrations of less than 0.1 mL L−1 (4.5 μmol L−1), an in situ isotope labeling experiment
(13C, 15N) was performed on the western continental slope of India
at 540 m water depth (OMZ core region). The assemblage of living
foraminifera (>125 μm) in the uppermost centimeter at this depth is
characterized by an unexpectedly high population density of 3982 individuals 10 cm−2 and a strong dominance by few calcareous species. For the
experiment, we concentrated on the nine most abundant taxa, which constitute
93% of the entire foraminiferal population at 0–1 cm sediment depth.
Increased concentrations of 13C and 15N in the cytoplasm indicate
that all investigated taxa took up labeled phytodetritus during the 4 day
experimental phase. In total, these nine species had assimilated
113.8 mg C m−2 (17.5% of the total added carbon). Uptake of nitrogen by the
three most abundant taxa (Bolivina aff. B. dilatata, Cassidulina sp., Bulimina gibba) was 2.7 mg N m−2 (2% of the
total added nitrogen). The response to the offered phytodetritus varied
largely among foraminiferal species with Uvigerina schwageri being by far the most important
species in short-term processing, whereas the most abundant taxa Bolivina aff. B. dilatata and
Cassidulina sp. showed comparably low uptake of the offered food. We suggest the
observed species-specific differences are related to species biomass and
specific feeding preferences. In summary, the experiment in the OMZ core
region shows rapid processing of fresh phytodetritus by foraminifera under
almost anoxic conditions. The uptake of large amounts of organic matter by
few species within four days suggests that foraminifera may play an
important role in short-term carbon cycling in the OMZ core region on the
Indian margin. |
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