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| Titel |
The effect of carbonate chemistry and light levels on calcification and photosynthesis in the larger benthic foraminifera Operculina ammonoides |
| VerfasserIn |
Shai Oron, Sigal Abramovich, David Evans, Jonathan Erez |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101186
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| Publikation (Nr.) |
 EGU/EGU2015-286.pdf |
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| Zusammenfassung |
| We present data on metabolic measurements and growth experiments conducted on
Operculina ammonoides, a symbiont bearing larger benthic foraminifera (LBF) of the family
Nummulitidae, which is the closest living descendant of the Eocene Nummulites. The large
size, the high abundance and wide distribution of Nummulitids and other LBF make them a
vital archive for ancient and recent oceanic environments. LBF are also an important
component of the ocean tropical and subtropical benthic ecosystem, where they have a
significant contribution to primary production, and are major calcium carbonate producers.
Their symbiosis, calcification physiology, and ecological response to environmental changes
are poorly understood. The present study is part of an ongoing research effort focused on
those topics.
Calcification, respiration and symbiont photosynthesis were measured during long-term
experiments that included manipulation of carbonate chemistry parameters and light levels.
The experiments were done with large number of individuals (1500 in total) divided into
incubation groups of 60-100.
Diurnal and nocturnal data was obtained, along with cumulative incubations on a time span of
a few days. The metabolic rates were estimated from measurements of dissolved oxygen,
total alkalinity and pH before and after the incubations. This technique does not interfere with
the experimental populations and allow a series of measurements to be performed on the
same specimens.
In all experiments, both for the diurnal cycles and for the long incubations, we observed
significantly higher photosynthesis rates than respiration (positive O2 budget) for the
holobiont. This oxygen excess has increased with light intensity, suggesting a significant
growth of the symbionts within their host. Calcification was enhanced during the day
compared to the night but did not increase with light intensity or with photosynthesis. In
normal seawater, higher calcification rates were observed during the cumulative incubations
despite lower alkalinity and pH values that developed in the closed systems. However,
in the carbonate chemistry incubations, calcification rates increased linearly with
carbonate ion concentration and initial pH levels. Photosynthesis did not show any
trend with pH, calling into question the direct coupling between photosynthesis and
calcification.
These data suggest that symbiosis and calcification in O. ammonoides is quite different
from what is known for hermatypic corals but similar to Amphistiginiids that were studied
previously. Internal carbon cycling and the dependence on light intensity may affect both the
structure of foraminiferal shells and their isotopic and chemical composition, which serves
for paleoceanographic reconstructions. |
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