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| Titel |
The PhytoSCALE project: calibrating phytoplankton cell size as a proxy for climatic adaptation |
| VerfasserIn |
Jorijntje Henderiks, Andrea Gerecht, Bjarte Hannisdal, Lee Hsiang Liow, Trond Reitan, Tore Schweder, Bente Edvardsen |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083176
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| Zusammenfassung |
| The Cenozoic fossil record reveals that coccolithophores (marine unicellular haptophyte
algae) were globally more common and widespread, larger, and more heavily calcified before
34 million years ago (Ma), in a high-CO2 greenhouse world. We have recently demonstrated
that changes in atmospheric CO2 have, directly or indirectly, exerted an important long-term
control on the ecological prominence of coccolithophores as a whole [1]. On closer
inspection, this macroevolutionary pattern primarily reflects the decline in abundance and
subsequent extinction of large-celled and heavily calcified lineages, while small-sized species
appear to have been more successful in adapting to the post-34 Ma “icehouse” world.
Coccolith size (length) is a proxy for cellular volume-to-surface ratios (V:SA), as
determined from fossil coccosphere geometries. Algal V:SA provides physiological
constraints on carbon acquisition and other resource uptake rates, affecting both
photosynthesis and calcification, and is therefore considered to be a key indicator
of adaptation. As a general rule, small cells have faster growth rates than large
cells under similar environmental conditions, giving small species a competitive
advantage when resources become limiting. Our research aims to bridge the gap
between short-term experimental observations of physiological and phenotypic
plasticity in the modern species Emiliania huxleyi and Coccolithus pelagicus, and
time series of the long-term phenotypic variability of their Cenozoic ancestors.
Single-clone growth experiments revealed significant plasticity in cell size and coccolith
volume under growth-limiting conditions. However, the range in coccolith size
(length) remained relatively constant for single genotypes between various growth
conditions. With these new data we test to what extent the size variation observed in the
fossil time series is a reflection of anagenetic changes (i.e. evolution of an ancestral
species to a descendant species without split of lineage), or changes in the frequency
and distribution of closely related species of different size and different ecological
preferences.
[1] Hannisdal, B., Henderiks, J., and Liow, L.H.: Long-term evolutionary and ecological
responses of calcifying phytoplankton to changes in atmospheric CO2, Global Change
Biology, 18(12), 3504-3516, 2012. |
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