Cenozoic plankton diversity dynamics and the impact of macroevolution on the marine carbon cycle.

The marine biological carbon pump is one of the most important mechanism to extract carbon from the atmosphere and export it to the deep-sea and the sediments, and thus take it out from the cycle for millions of years. Today, marine planktonic diatoms are the main element of that pump; however at the beginning of the Cenozoic they were too rare and not diverse enough to have much geochemical significance. Calcareous nannofossils and foraminifera on the other hand were already important components of the carbonate carbon pump; however they also contribute to the alkalinity pump which on shorter timescales have an adverse effect on carbon sequestration. In addition, heterotrophic, amoeboid protists, in particular polycystine radiolarians, are also known to contribute significantly to the carbon export to the deep-sea due to their role in forming rapidly sinking particles of aggregated organic material. We present new diversity reconstructions using the Neptune database (NSB) and case studies focussed on the Late Neogene and the Eocene-Oligocene transition using newly collected full-fauna/flora diversity data. We will then show how the diversity and abundance history of these groups changed throughout the Cenozoic, what the role of climate/oceanographic changes and competition on their evolution was, and, in the end, what consequences their evolution had on the marine carbon cycle.