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© Stephan BORENSZTAJN / Caroline THALER / IPGP / CNRS Photothèque
Bryozoans are reef-building multicellular organisms less than a millimetre in size that have calcium carbonate skeletons. These tiny animals, which live in colonies at all latitudes, play a major role in regulating the climate by storing the CO2 dissolved in seawater in their mineral structure. This is the tip of the skeleton of a colony of bryozoans of the species Cellaria fistulosa. Each organism lives in a sort of calcium carbonate chamber with openings, the main one of which enables the animal to filter seawater and feed. Around a dozen such cavities are visible: those at the top are still in the process of being made. This surprising shape is the random result of the gradual growth of the colony. Researchers are trying to gain a better insight into the ability of bryozoans to resist environmental disturbances in a context of ocean acidification.