Impact of Diatom Evolution in the Oceans

Although molecular clocks suggest that diatoms evolved over 200 Ma ago, this result has been largely ignored because of the lack of diatoms in the geologic fossil record with most studies therefore focused on diversification during the mid-Cenozoic 30 Ma ago where abundant diatom fossils are found. Much of the older fossil evidence has likely been destroyed by dissolution during diagenesis, subducted or is concealed deep within the Earth. I will provide evidence on diatom evolution and speciation in the geological record. We are using the isotopic silicon composition of fossil sponge spicules and radiolarians to track the timing and magnitude of dissolved Si drawdown following the origin of diatoms. The origin of the diatoms likely lead to the reorganization of the distribution of carbon and nutrients in seawater, changing energy flows and productivity in the biological communities of the ancient oceans.