DAVID GREENE, HOST:
Every night all over the world, trillions - yeah, I said trillions - of tiny creatures swim up from deep in the ocean to the surface to eat. And scientists believe that daily migration might be mixing up the water. Let's hear about this new research from NPR's Rebecca Hersher.
REBECCA HERSHER, BYLINE: I'm not talking about, like, goldfish or something. These animals are less than a centimeter long - things like krill and little types of shrimp. So the idea that as they're swimming along, somehow their swimming generates enough energy to turn the oceans - it's a little hard to believe - so hard that most oceanographers who study what mixes up the ocean think it's silly.
JOHN DABIRI: The general consensus today would be that animals have nothing to do with ocean mixing.
HERSHER: John Dabiri is notably not an oceanographer. He is an engineer at Stanford. And he noticed that oceanographers were assuming something about these little creatures.
DABIRI: About 10 years ago, there were even papers being published saying that it was physically impossible for these tiny organisms to have an effect, but all of those papers made the assumption that the flow they create would only be as large as the individual animals.
HERSHER: Small swimmers leaves small wakes, basically. But, he thought, what happens when they gather in big groups? Might they be more powerful? So they tested it. Dabiri put a bunch of tiny shrimp in an 8-foot-tall tank and used light to attract them upwards in a big group, mimicking the daily migration that happens with ocean creatures.
DABIRI: As these animals start swimming upward, each of them kicks a little bit of fluid backwards. Think of Newton's law - for every action, there's an equal and opposite reaction.
HERSHER: A shrimp kicks upward; water goes down. Another shrimp kicks, and another and another.
DABIRI: And then pretty soon, you have this vertical stampede upward of these shrimp, and you're getting rushed downward a distance much larger than the individual animals could kick the water.
HERSHER: They found the jet of water behind the swarm of shrimp is pretty powerful - slower than a rip current, but faster than the mixing caused by things like wind. That's surprising. Even more surprising - all these little creatures may be affecting our lives, too. Oceans soak up carbon dioxide from the atmosphere, carbon dioxide that would otherwise cause the planet to warm even more. And the churning from those little animals might play an important role in that process. Rebecca Hersher, NPR News.
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