That’s right, a bacterium called Prochlorococcus marinus, is the most plentiful photosynthesizing biomass on Earth.
There are a billion billion billion (or trillion trillion) Prochlorococci in all the world’s oceans. They’re not a plant (though they have chlorophyll like plants). They’re definitely not terrestrial.
Prochlorococcus is so small that you could lay 100 of them end-to-end and they would be the width of a human hair!
This important organism was first described by scientists in 1992.
Prochlorococcus is very important to the Earth’s ecosystem. It makes up the base of the food chain in the oceans.
They may account for 20% of the global production of oxygen (1 out of every 5 breaths you take are from Prochlorococci), and they take up to 25% of the carbon dioxide from the atmosphere.
Prochlorococcus is the smallest of the photosynthetic organisms on Earth. It is also “possibly (the) most plentiful genus on Earth,” meaning that there are more Procholorococci than any other organism on Earth.
Photosynthesis is when organisms with chlorophyll (green pigments) take the sun’s energy and produce food for themselves. Usually you think of plants photosynthesizing, but in this case it’s bacteria. In the process oxygen is released as a waste product. In the case of the ocean, oxygen is released from a water molecule.
Procholorococci live in subtropical waters (between 40 degrees N and 40 degrees S) that are nutrient poor (called oligotrophic). They are mainly found in the sunlit surface waters (euphotic zone) of the ocean, which goes down to 656 feet (200 m).
Procholorococci have been around for 3.5 billion years!
Not bad for an organism you probably never heard of until today!
For more information on Procholorococcus visit these websites:
Encyclopedia of Life article on Procholorococcus
PBS article on “Without These Ancient Cells, You Wouldn’t Be Here”