As phytoplankton provide the carbon and the energy for all higher trophic levels in the oceans, future changes in phytoplankton productivity and species composition will also impact the entire ecosystem. In view of their pivotal role in ecosystem functioning and biogeochemistry, the responses of diatoms to ocean acidification have gained increasing attention. Even though responses seem to species specific, diatoms have been regarded as potential winners of ocean acidification. In the recent years, also the effects of multiple stressors (i.e. the combination of changes in carbonate chemistry, temperature as well as light and nutrient availabilities) have been investigated. Under these more realistic environmental settings, the future fate of marine diatoms looks grimmer. During the talk, our current understanding of diatom responses to climate change will be presented. Special emphasis will be put on our recent findings from the polar environment.