Plankton Portrait: Coccolithophores

Here’s a shout-out to some of the tiny little critters that make life in the ocean and on Earth possible! Yes, I said on Earth! Did you know every second breath you take is made possible by phytoplankton everywhere?

Thanks, plankton!

Plankton are marine or freshwater organisms that can’t swim. They don’t have to be small, (the giant man-of-war jellyfish is a plankton) but most of them are. Zooplankton (tiny animals) are often larval stages of fish and other big animals, but some, like copepods, stay small for their whole lives. Phytoplankton (tiny plants) take energy from the sun and produce nutrients, just like land plants.

I wanted to showcase the beautiful Emiliania huxleyi, a coccolithophore!

Close-up of a coccolithophore. The plankton forms the lithes around itself! (

It looks kind of like a golf ball, but is about 2,000 times smaller. You can’t even see it under a regular microscope; you have to cover them in gold foil and bounce electrons off to take E. hux.’s portrait. But unlike a golf ball, you can see E. hux. from outer space! Every year, coccolithophores form massive blooms known as the Sea of Milk. And the White Cliffs of Dover are white thanks to coccolithophores being smashed against the cliffs for centuries.

Giant coccolithophore bloom turns the deep blue a light teal (

But why exactly are coccolithophores so out of this world?

Like corals, coccolithophores produce a limestone structure. In coccolithophores, they’re known as lithes (cocco = sphere, lith = lithes, phore = bearing, so “coccolithophore” literally means “round plankton with lithes”).

Since their lithes are really heavy for their size, they sink carbon and organic material down to the bottom of the ocean. Dead coccolithophores and other dead critters sinking down provides food for deep-sea ecosystems and helps keep the oceanic carbon cycle going.

They also help buffer ocean acidification with their limestone lithes, which makes them an important indicator species for oceanic climate change. With more carbon dioxide in the ocean, some species of coccolithophores can’t properly form their lithes, like shown below. This scientific figure looks scary, but the up-and-down axis tells you what type of coccolithophore they used and the left-to-right axis says how much carbon dioxide was added (for reference, the current atmospheric concentration of carbon dioxide is just over 400 ppm)

Coccolithophores at different concentrations (parts per million) of carbon dioxide (

This will disrupt the carbon cycle and could have large effects on the ecosystem. So ocean acidification doesn’t affect only corals, but other critters too, including coccolithophores, lobsters, and even baby fish!

So let’s keep the coccolithophore love going and do our best to reduce carbon emissions! It’s the least we can do for these tiny giants that help keep human life afloat!