An international research team has calculated the costs and benefits of calcification for phytoplankton and the impact of climate change on their important role in the world's oceans.Single-celled phytoplankton play an important role in marine biogeochemical cycling, in marine food webs and in the global climate system. Coccolithophores are a particular group that cover themselves with calcium carbonate shields, known as coccoliths. Some wrap themselves in an impenetrable coat of coccoliths, some make coccoliths in the form of sharp spikes, some use them as parasols against the sun and some form funnel-shaped light collectors.But this requires a lot of energy — and the price for the artful armour could rise further due to global change. With the help of a new model, the researchers analysed the energetic costs and benefits of calcification. The results, published in the current issue of the journal Science Advances, suggest that the ecological niche for calcifying algae will become narrower in the future.