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| Titel |
Benthic foraminifera: key members of benthic communities within the Arabian Sea OMZ |
| VerfasserIn |
Andrew Gooday, Kate Larkin, Ana Aranda da Silva |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047549
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| Zusammenfassung |
| Foraminifera are one of the few eukaryotic taxa able to tolerate severe oxygen depletion and
are a consistently important component of benthic communities in hypoxic settings. Dense
populations are often found in oxygen minimum zones, stratified basins and fjords,
where strong sea-floor oxygen gradients are combined with a rich food supply. The
mechanisms that allow foraminifera to flourish in these extreme conditions are not well
understood, but include ultrastructural and physiological adaptations, as well as the
presence of prokaryotic symbionts. Foraminiferal assemblages in hypoxic settings are
dominated by a few species that play a key role in ecosystem functioning, including the
processing of labile organic carbon. Many of the species that are tolerant of severe
hypoxia are multichambered calcareous forms, but there is increasing evidence
for the presence of agglutinated and organic-walled species in OMZs and other
oxygen-depleted habitats. This contribution will provide a brief overview of foraminifera
from cross-margin transects in the Arabian Sea off Oman, Pakistan and India. Foraminiferal
assemblages from the core regions of these OMZs (400 m off Oman, 300 m off
Pakistan, 500 m off India) exhibited some common features as well as differences.
They were dominated by calcareous taxa, notably Uvigerina ex. gr. semiornata and
Bolivina aff. B. dilatata in the >300-μm and finer fractions, respectively. Other
calcareous species were present below the OMZ core, e.g. Globobulimina spp.
and Chilostomella spp. On all three margins, agglutinated foraminifera were fairly
common where oxygen levels were lowest. Species of Reophax were present in all
areas and Bathysiphon spp was common off Oman and Pakistan. Monothalamous
(single-chambered) taxa were also common at 400 m on the Oman margin possibly
reflecting the somewhat higher oxygen levels on the western side of the Arabian
Sea. Experimental studies and biomarker analyses on the Pakistan margin have
revealed something of the functional role of these protists. Trophic responses appear
to be species-specific with the calcareous species Uvigerina ex. gr. semiornata
playing a very active role in the processing of labile organic carbon derived from
photosynthetic production. In contrast, agglutinated species (including Reophax
spp.) appear to be either unselective or to ingest bacteria rather than algal remains. |
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