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- Henderiks, Jorijntje, et al.
(author)
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Phytoplankton size : Climatic adaptation and long-term evolution
- 2010
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Conference paper (other academic/artistic)abstract
- Marine phytoplankton, such as diatoms and coccolithophores, constitute the base of the marine food chain and are a fundamental component in biogeochemical cycles. The overall ecological success of marine phytoplankton, but also its taxonomic diversity and size distribution, determines the efficiency by which fixed carbon is transferred to higher trophic levels and into the deep ocean- and sedimentary carbon reservoirs. Therefore, we need a better understanding of the mechanisms and rates of adaptation within phytoplankton to evaluate marine ecosystems under present-day and future climate scenarios of rapidly rising ocean temperatures and lowering of ocean pH (‘ocean acidification’). The likely response of coccolithophores, the most prominent group of calcifying algae, in particular has provoked controversy.We have hypothesized that species-specific responses to climatic perturbations within extant members of this group are due to differences in the mechanism and rate of climatic adaptation inherent to their respective evolutionary lineages (Henderiks, J. and Rickaby, R.E.M., A coccolithophore concept for constraining the Cenozoic carbon cycle, Biogeosciences 4: 323-329, 2007). The Cenozoic ancestors of all extant coccolithophores have experienced much higher levels of CO2 and lower ocean pH than today, according to proxy reconstructions over the past 60 million years. However, we show that different lineages display different levels of variation in coccolith shape and cell size, and that this could indicate that some species are more adaptable to climatic change than others. The observed geological trends in algal cell size also have implications for long-term feedbacks in the Cenozoic carbon cycle.
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