Protists, Engines of the Carbon Cycle

Protists, the phytoplankton (single celled plants) and protozoa (single celled animals), account for over 90 percent of the biomass of all living organisms in the ocean. Protists are arguably the most important organisms in the oceans. They are the base of the food web on which essentially all other marine life depends. In addition they play a major role in the global carbon cycle taking up about 50% of the carbon dioxide produced by living things, including humans, and produce about 50% of the oxygen we breathe. Some species produce chemicals, which when ventilated to the atmosphere, promote the formation of clouds.

SEM of the silica skeleton of the silicoflagellate, Dictyocha speculum
Image: Fiona Scott