Spirorbis tube worms are common epibionts on brown algae in the Baltic Sea. We made experiments with Spirorbis in the Kiel Outdoor Benthocosms at CO₂ and temperature conditions predicted for the year 2100. The worms were able to grow tubes even at CO₂ levels favouring shell dissolution but did not survive at mean temperatures over 24° C. This indicates that Spirorbis worms will suffer from future excessive ocean warming and from ocean acidification fostering corrosion of their protective tubes.