Carbon dioxide is released when the calcium carbonate “armor” of the photosynthetic alga Emiliania huxleyi forms, but Ehux can trap as much as 20 percent of organic carbon derived from carbon dioxide in some marine ecosystems. Its versatility in either contributing to primary production or adding to carbon dioxide emissions makes Ehux a critical player in the marine carbon cycle. The Ehux genome sequence has now been compared with other algal sequences.