Prochlorococcus, the most abundant photosynthetic organism in the ocean, was long seen as a free-floating “loner”. MIT researchers have now shown that it also forms biofilms, communities of cells attached to particles. The study was published in Nature Communications.
The cells switch between the two states, and genetically identical cells can be in either. Attached cells grow more slowly, produce more chlorophyll and release almost twice as much organic carbon as free-floating ones.
Analysing DNA from seawater samples and the Tara Oceans database, the team found attached Prochlorococcus in every sample, from the surface down to 1,000 metres.
If these cells sink, they could carry about half a billion tonnes of carbon a year to deeper waters, an estimate the authors describe as rough. The microbe may therefore play a bigger role than thought in removing carbon from the atmosphere.
