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| Titel |
Climatic forcings on algal cell size through the Cenozoic |
| VerfasserIn |
B. Hannisdal, J. Henderiks |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026804
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| Zusammenfassung |
| Marine phytoplankton constitute the base of the marine food chain and are fundamental
components in biogeochemical cycles. A better understanding of both the mechanisms and
the rates of climatic adaptation by marine phytoplankton remains a critical challenge in
predicting future impacts of climate change. Using coccolithophores (a prominent group of
calcifying unicellular algae) as an example, we explore why different species respond
differently to environmental change, and determine what climatic parameters drive changes in
cell size over geological time scales. We use comprehensive time series of coccolith
size – a proxy for cell size – over the Cenozoic, targeting the ancestry of extant
taxa that have revealed distinct physiological responses in culture experiments. We
employ a novel, information-theoretic method to quantify the relative influence
of different environmental variables on coccolith size. This model-free technique
detects the significance and relative strength of the causal influence of multiple
climatic forcing variables (including non-linear relationships), while correcting for
possible common causal interactions among the forcings. Our analyses suggest
that the macroevolutionary size decrease within the Reticulofenestra lineage (the
ancestry of today’s most prolific bloomer Emiliania huxleyi) primarily reflects a
physiological adaptation to CO2 limitation. In contrast, macroevolutionary size
variability within the Coccolithus lineage (the ancestry of Coccolithus pelagicus and C.
braarudii), while influenced by long-term trends in ocean temperature, is not affected by
changes in CO2. Improved understanding of such heterogeneity within ecosystem
functional groups, including taxon-specific climatic adaptation strategies, will be of
fundamental importance to the assessment of future climate change impact and mitigation. |
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