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| Titel |
Living (Rose-Bengal-stained) benthic foraminiferal faunas along a strong bottom-water oxygen gradient on the Indian margin (Arabian Sea) |
| VerfasserIn |
C. Caulle, M. Mojtahid, A. J. Gooday, F. J. Jorissen, H. Kitazato |
| 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 ; 12, no. 16 ; Nr. 12, no. 16 (2015-08-25), S.5005-5019 |
| Datensatznummer |
250118072
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| Publikation (Nr.) |
 copernicus.org/bg-12-5005-2015.pdf |
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| Zusammenfassung |
| Rose-Bengal-stained foraminiferal assemblages (> 150 μm)
were analysed along a five-station bathymetric transect across the core and
the lower part of the oxygen minimum zone (OMZ) on the Indian margin of the
Arabian Sea. Sediment cores were collected using the manned submersible
Shinkai 6500 during the RV Yokosuka cruise YK08-11 in the post-monsoon season (October 2008) at
water depths ranging from 535 to 2000 m, along a gradient from almost anoxic
to well-oxygenated (0.3 to 108 μM) bottom waters. Stained
benthic foraminifera were investigated from two different size fractions
(150–300 μm and > 300 μm). Stained foraminiferal
densities were very high in the core of the OMZ (at 535 and 649 m) and
decreased at deeper sites. The faunas (> 150 μm) were
dominated (40–80 %) by non-calcareous taxa at all stations. These were
mainly species of Reophax and Lagenammina but also included delicate monothalamous taxa
(organic-walled "allogromiids", agglutinated saccamminids, psammosphaerids
and tubular forms). These new data from the Indian margin are compared to
previous studies from the Murray Ridge, the Pakistan margin and the Oman
margin. The fact that similar species were found at sites with comparable
bottom-water oxygen concentrations but with very different surface water
productivity suggests that, within the strongly developed Arabian Sea OMZ,
bottom-water oxygen concentration, and not the organic flux to the sea
floor, is the main factor controlling the species composition of the
foraminiferal communities. Several foraminiferal species (e.g.
Praeglobobulimina sp. 1, Ammodiscus sp. 1, Bolivina aff. dilatata) were confined to the core of the OMZ. These species are
presently known only from the Arabian Sea. Because of their association with
extremely low oxygen concentrations, these species may be good markers for
very low oxygen concentrations, and could be used to reconstruct past OMZ
variability in the Arabian Sea. |
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