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| Titel |
Extremely heat tolerant photosymbiosis in a shallow marine benthic foraminifera |
| VerfasserIn |
Christiane Schmidt, Danna Titelboim, Janett Brandt, Raphael Morard, Herut Barak, Abramovich Sigal, Ahuva Almogi-Labin, Michal Kucera |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250134447
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| Publikation (Nr.) |
 EGU/EGU2016-15175.pdf |
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| Zusammenfassung |
| Thermal stress leads to the loss of algal symbionts (bleaching) in many shallow marine
calcifiers including foraminifera. The bleaching threshold often occurs at water temperatures,
which are likely to be exceeded in the near future due to global warming. Preadaptation
represents one mechanism allowing photosymbiotic organisms to persist under warmer
conditions, providing the tolerance can be carried to new habitats. Here we provide evidence
for the existence of such adaptation in the benthic foraminifera Pararotalia calcariformata
recently discovered in the eastern Mediterranean. We identify its symbionts as a consortium
of diatom species dominated by Minutocellus polymorphus. We show that in the field, the
foraminifera retains its pigments at a thermally polluted site, where peak water temperatures
reach 36∘C. To test whether this tolerance represents a widespread adaptation, we conducted
manipulative experiments exposing populations from an unpolluted site to elevated
temperatures for up to three weeks. The populations were kept in co-culture with the more
thermally sensitive diatom-bearing foraminifera Amphistegina lobifera. Reduced
photosynthetic activity in A. lobifera occurred at 32∘C whereas photochemical
stress in P. calcariformata was first observed during exposure to 36∘C and chronic
photoinhibition (but not mortality) first occurred at 42∘C. Survivorship was high
in all treatments, and growth was observed under thermal conditions similar to
summer maxima at the thermally polluted site (35-36∘C). The photosymbiosis in P.
calcariformata is unusually thermally tolerant for a photosymbiont-bearing eukaryote. The
thermal tolerance of this photosymbiosis is present in a natural environment where its
thermal threshold is never realized. These observations imply that photosymbiosis
in marine protists can respond to elevated temperatures by drawing on a pool of
naturally occurring pre-adaptations. It also provides a perspective on the massive
occurrence of symbiont-bearing foraminifera in the early Cenozoic hothouse climate. |
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