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  • Thanks to the Monterey Bay Aquarium for partnering with us

  • on this episode of SciShow.

  • They hope you have a plank-ton of fun watching!

  • [♪ INTRO]

  • Right now, there are incredible creatures in the ocean

  • with the power to reshape the planet's atmosphere.

  • After all, they've done it before.

  • And you've probably never even seen them,

  • unless you've looked at seawater under a microscope.

  • I'm talking, of course, about phytoplankton,

  • the microscopic critters that almost all life in the oceans

  • (and arguably, on land) depends upon.

  • Phytoplankton is a catch-all category for all the tiny aquatic

  • organisms that can turn sunlight into food via photosynthesis.

  • And there are all kinds of different organisms included in it,

  • from cyanobacteria to whip-tailed dinoflagellates

  • to armored diatomswhich look amazing

  • under a microscope, by the way.

  • Diatoms are essentially algae that build little houses of glass

  • or, silica, to be precise.

  • And they come in a stunning diversity of forms.

  • In fact, if you've ever spread diatomaceous earth

  • around your garden or your house,

  • you were sprinkling fossilized diatoms!

  • There are also coccolithophores, which can look

  • kind of like a soccer ball covered in frisbees thanks to

  • their teeny-tiny shells made of calcium carbonate.

  • In fact, England's famous White Cliffs of Dover contain

  • the fossilized remains of countless coccolithophores.

  • And in today's ocean, the smelly compounds they produce

  • help give the sea its unmistakable scent—a smell birds

  • like albatrosses use to find their meals.

  • The compounds that make those smells also can travel

  • up high into the atmosphere to help clouds form and grow,

  • making them more reflective and helping to keep us

  • down here a lot cooler.

  • And dinoflagellates are also very cool -

  • don't want to leave them out.

  • They have two tail-like flagella that help them swim around,

  • and many can produce their own light

  • which makes for some really magical effects.

  • But, too many of them in one place can create a harmful algal bloom

  • —a phenomenon you might have heard referred to asred tide”.

  • Which is just one example of how these super teeny creatures

  • can have a big impact on the rest of useven us landlubbers.

  • No matter what form phytoplankton take,

  • they are unbelievably important to all life on Earth.

  • First off, they're the foundation of the marine food web,

  • underpinning everything from anchovies to whales.

  • In fact, with a wee bit of help from seaweed and aquatic plants,

  • they manage to support life in the ocean despite being outweighed

  • by roughly five to one by organisms that don't make their own food.

  • And if that's not enough, they're also atmosphere-altering machines.

  • They consume about as much carbon dioxide as all of

  • the world's forests and other plants combined, pulling roughly

  • eleven gigatons of carbon from our atmosphere every year.

  • Which is especially impressive when you consider that

  • by mass, there's about 450 times as much plant life on land.

  • Plus, phytoplankton account for more than half

  • of the planet's yearly oxygen production.

  • But even more importantly, they're kind of the reason

  • we have oxygen in the atmosphere at all.

  • Back about 2.5 billion years ago, near the boundary

  • between the Archean and Proterozoic eons,

  • the Earth was a very different place.

  • There were green seas and orange skies.

  • And the atmosphere was likely a mix of gases like

  • ammonia and methane that would immediately kill us.

  • Then, cyanobacteria evolved and ran rampant,

  • pumping out a huge amount of oxygen in what's now called

  • The Great Oxidation Event.

  • All that oxygen helped turn the ocean and skies blue,

  • and likely jump-started the evolution of complex life.

  • Then, around 540 million years ago, phytoplankton did it again,

  • exploding in numbers and bringing us up to more or less

  • the levels of oxygen in the atmosphere today.

  • Paleontologists think the boom may have occurred

  • thanks to nutrients weathered out of rocks by giant,

  • continent-sized glaciers.

  • Or, a more recent idea is that it happened

  • because the plankton evolved a more efficient internal machinery

  • related to photosynthesis.

  • Either way, this set the stage for life to fully spread

  • throughout the ocean and onto the land.

  • Since then, they've calmed down on the

  • reshaping the entire planetfront

  • and adopted more of a stabilizing role.

  • For example, paleontologists think the evolution

  • of calcifying plankton balanced ocean chemistry

  • and helped protect the seas from mass extinctions.

  • Before about 80 million years ago,

  • the ocean was not a super stable place to be.

  • Changes in the chemistry of the atmosphere from events

  • like volcanic eruptions often caused deadly swings in seawater pH.

  • Then, some lineages of planktonincluding those

  • ball-like coccolithophoresfigured out how to make shells

  • of calcium carbonate.

  • Soon, they took over the open ocean.

  • And over a relatively short period of time, so many

  • of their shells sank to the depths of the oceans that

  • they created a vast, thick layer of calcium carbonate ooze

  • on the seafloor.

  • That ooze acts as a chemical buffer in the ocean

  • —a natural braking system on runaway acidity.

  • See, the shells are solid at a more neutral pH,

  • but as the water gets more acidic, they start to dissolve,

  • releasing carbonate ions.

  • Those chemically react with the surrounding water to push

  • an acidic pH back towards neutral.

  • Now, there had been a minor version of this in the shallows

  • thanks to mollusks and other large shelled organisms.

  • But it took phytoplankton to make it ocean-wide.

  • And the end result was more stable ocean chemistry,

  • which meant marine life became less vulnerable

  • to things like volcanic eruptions.

  • Even today, this chalk layer is helping buffer the acidifying effects

  • of all the carbon dioxide that we humans are pumping

  • into the atmospherethough, there's only so much it can do.

  • When we consider everything that lives in the ocean,

  • from majestic whales to bountiful coral reefs, these little,

  • unassuming phytoplankton are easy to overlook.

  • But if you look at the history of the Earth,

  • it doesn't take long to realize that though they are small,

  • they are also mighty.

  • And they deserve as much fascination, love,

  • and protection as any other living thing on this planet.

  • Thank you again to the Monterey Bay Aquarium

  • for partnering with us on this episode of SciShow.

  • The Aquarium's mission is to inspire conservation of the ocean.

  • So give them a follow on their social media accounts

  • (they're very good at it), and visit their website

  • at montereybayaquarium.org, or if you are nearby, swing on by

  • - it is a beautiful and amazing place.

  • They're there to kelp, and hope to sea you soon.

  • [♪ OUTRO]

Thanks to the Monterey Bay Aquarium for partnering with us

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