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Perturbing Plankton in the Sea: Past and Future

The response of the marine forests i.e. the vast blooms of phytoplankton to future high levels of atmospheric CO2 is crucial to understanding whether the marine biological pump will amplify or hinder future global warming. Recent evidence from rapidly accumulating sediments implies that some species of phytoplankton, which make exquisite limestone shells, the coccolithophores are increasing their calcification in response to anthropogenic change. This observation appears at odds with the paradigm view that coccolithophores reduce the ratio of calcification to photosynthesis rates and tend towards malformation with increasing levels of atmospheric carbon dioxide and decreased pH. 

A large factor for the decreasing ratio, is that in addition to reduced calcification, there is an increase in carbon fixation with increasing carbon dioxide. Nonetheless, the complexity of the response to changing carbon conditions by different species of coccolithophore has already highlighted that these phytoplankton which calcify under physiological control inside the cell may not be sensitive to ocean saturation in the same way as organisms which mediate the nucleation of calcification under less physiological control upon templates. The converse to the calcification paradigm is whether coccolithophores may increase their photosynthetic efficiency as CO2 increases in the environment and how that would influence calcification response.

Listen to 'Climate on Earth and Mars' in our series of podcasts to hear Rosalind Rickaby explain more about her research into coccolithophores.


Rosalind Rickaby (University of Oxford)


Rosalind Rickaby is a young researcher at the University of Oxford, with a fellowship at Wolfson College whose academic background also includes a PhD from the University of Cambridge and a postdoctoral fellowship at Harvard University in the United States. Recently, Ros was recognised by the EGU for being an “Outstanding Young Scientist” and, won the Philip Leverhulme Prize in 2008 and has just been awarded the 2009 Rosenstiel Medal. 

Ros is fascinated by the jigsaw of complex interactions between the evolution of mineralising organisms, ocean chemistry, atmospheric composition and Earth’s climate. The extraction of chemical signatures from fossil shells of marine micro-organisms as a tool for constraining past ocean conditions and their influence on climate, on timescales ranging from hundreds to millions of years, is fundamental to her research. Seeking innovative alternative approaches to constraining past climates has increasingly directed my research towards an understanding of the physiological response of phytoplankton to the changing carbon cycle in the past and for the future.