Prof. Dr. Stefan Schouten

Marine microbiologist Stefan Schouten searches for chemical compounds that can divulge details about the climate in earlier times. ‘Ocean floors contain a kilometres-thick archive that, amongst other things, is full of information about the temperature during various periods in the past as well as the composition of the water and air above the ocean floor. We are working on techniques that will allow us to read that archive. Our approach is indirect. We do not literally look at the temperature but instead at “proxies”: substances that indirectly tell us something about the temperature or chemical composition of the atmosphere or the oceans.’

Bacterial culture

‘We mainly look at the different chemical compounds that occur in bacteria and other microorganisms. For example, we culture bacteria in the laboratory at different temperatures and then examine the influence of those temperatures on the fatty acids these organisms produce. Sometimes we think we have found a fantastic relationship between a fatty acid and the temperature while working in the laboratory, only to discover in the field that the reality in nature proves to be somewhat more complex.’

Collecting imperfect techniques

‘Ultimately, there is no such thing as the “ideal proxy” for the climate of the past. No metaphorical thermometer exists somewhere that directly reveals what the temperature in a certain period was. All the substances we investigate have their own shortcomings. However, when we examine a collection of, say, five imperfect substances and each of the five tells the same story, then we do have a valuable indication. Our work therefore revolves around finding many different points of reference. If we also subsequently try to recognise and understand the shortcomings of all those different substances, then will keep getting closer to recognising and understanding the climate of the past. Furthermore, our research also teaches us a lot about the current microbial life in the ocean. Because if one had to name a single unexplored field in marine research, then that would certainly be microbiology!’