Diatoms are the most important group of photosynthetic eukaryotes

http://www.cns.fr/spip/Phaeodactylum-tricornutum,463.html

Diatoms are the most important group of photosynthetic eukaryotes

The oceans of our planet are Earth’s largest ecosystem. About 50% of the primary productivity is attributable to them. The most important photosynthetic eukaryotes are the diatoms; they contribute about 40% of the primary marine production, and thus produce almost 1/4 of the oxygen we breathe. Although they form only a small part of the photosynthetic biomass, in some regions of the ocean, they can fix the same amount of carbon per day as a forest of terrestrial plants.