"I propose to develop and apply a novel method for the integrated reconstruction of past changes in carbon cycling and climate change. This method will be based on combining a well-established sensitive paleoclimate proxy with a recent discovery: the stable carbon isotopic composition (δ13C) of marine dinoflagellates (algae) and their organic fossils (dinocysts) reflects seawater carbonate chemistry, particularly pCO2. Biological (culture) experiments will lead to new insights in dinoflagellate carbon acquisition, and enable quantification of the effect of carbon speciation on dinoflagellate δ13C. The rises in CO2 concentrations during the last century, and at the termination of the last glacial period will be used to test and calibrate the new method. The δ13C of fossil dinoflagellate cysts will subsequently be used to reconstruct surface ocean pCO2 and ocean acidification during a past analogue of rapidly rising carbon dioxide concentrations, 55 million years ago. My research will shed new light on processes such as ocean acidification and the marine carbon cycle as a whole. Past analogues of rapid carbon injection can aid in the quantification of climate change and identification of vulnerable biological groups, critical to identify ‘tipping points’ in system Earth. The study of dinoflagellate carbon isotopes comprises the initiation of a new research field and will provide constraints on ocean acidification in the past and its consequences in the future."