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| Titel |
Recent benthic foraminifera in the oxygen minimum zone at the Western Indian margin, Arabian Sea |
| VerfasserIn |
Marie Zahnert, Annekatrin J. Enge, Markus M. Moeseneder, Ursula Witte, Michal Kucera, Petra Heinz |
| 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 |
250049626
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| Zusammenfassung |
| Live benthic foraminiferal communities from the western Indian margin oxygen minimum
zone (OMZ) incubated for four days with labeled algae material in a spreader experiment
have been studied. The OMZ in this area extends between 180-1200 m water depth
with oxygen values 125 μm) and compared. In the center of the
OMZ 475 living individuals/10 cm3 were found, but only 44 living individuals/10
cm3 at the lower part of the OMZ. Samples were taken during the intermonsoon of
2008 (October-November). The faunas show a clear difference between the two
sampled depths. In 813 m water depth, Epistominella rugosa, Bolivina dilatata
and Trifarina occidentalis dominate the assemblages. These taxa thus appear to
be adapted to the very low bottom-water oxygen values (0.027-0.049 ml/l in the
OMZ core) and the extremely high input of organic carbon due to phytoplankton
blooms during monsoon season in the upwelling area. High surface abundances,
especially of calcareous species (>95 %), the appearance of some calcareous infaunal
taxa (e.g. Praeglobobulimina, Chilostomella, Fursenkoina, Globobulimina) and a
lower diversity are recognized in the sample from the central part of the OMZ.
This may result from specific physiological adaptations of the fauna to persistent
almost anoxic conditions and the nearly absence of predators and competition. The
lower part of the OMZ (1155 m) with oxygen values between 0.46–0.53 ml/l is
dominated by Bolivina dilatata, Epistominella exigua and Bolivina pacifica. This
depth shows higher diversities and low abundances with an increased agglutinated
fraction (>40 %). There is an obvious relationship between species distribution and
the strength of the OMZ. This relationship most likely results from differences
in the persistence of suboxic to anoxic conditions as well as the preferences of
individual species for amount and/or type of organic flux. This first comparison of
recent benthic foraminiferal faunas in the OMZ at the Western Indian margin extend
our knowledge about ecological demands of foraminiferal communities in oxygen
poor sediments and may help to reconstruct oxygen depleted conditions in the past. |
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