RENEE MONTAGNE, HOST:
Let's talk populations. The last big census put the U.S. population at about 309 million. Now we're going to hear about one that accounts for trillions. It's a census of microorganisms that live in the oceans, providing food for most everything that swims and making a good amount of the oxygen we need to breathe. NPR's Christopher Joyce reports.
CHRISTOPHER JOYCE, BYLINE: Charles Darwin sailed to the New World in the 19th century and returned to Europe with a menagerie of curious creatures. And that's what an international team of scientists on a 110-foot sailing vessel have done now, except the creatures are mostly invisible to the naked eye. The expedition was called Tara, after the name of the schooner. It took three years and employed scores of scientists. They found over 35,000 different kinds of organisms - plankton, bacteria, viruses and krill - many unknown to science. Their work fills five papers in the journal Science. Journal editor Marcia McNutt says it's time the world took notice of what we can't see in the ocean.
MARCIA MCNUTT: How can we save the whales if we don't save the krill? There's something about the tragedy of the commons here.
JOYCE: Oceans are dumping grounds for the world's garbage. Climate change is making them warmer and more acidic. The Tara expedition was designed to measure what's out there and how it might be affected by a changing ocean. To do that, they siphoned up ocean water and used DNA probes to identify the organisms in that water. That enabled them also to understand how these organisms behave - eat, reproduce, interact. Team scientist Eric Karsenti, from the European Molecular Biology Laboratory, says they were surprised by how much these tiny organisms interact with each other, often in symbiotic relationships.
ERIC KARSENTI: It's not only survival of the fittest, but it's also how everybody collaborates with everybody else that makes life evolve.
JOYCE: They also discovered communities of organisms caught up in big eddies, like whirlpools. These eddies carry these little living ecosystems with them across the oceans. The researchers also found these microorganisms to be exquisitely sensitive to temperature changes. In effect, the oceans already are warming due to climate change. Steve Palumbi, a marine biologist at Stanford University, says all this is good reason to pay more attention to these microbes.
STEVE PALUMBI: Anything that goes on in that region of life, that bottom layer, these tiny things makes a big difference to how the planet functions.
JOYCE: They're the wide bottom of the oceanic food chain, and they also make our atmosphere breathable by emitting oxygen as part of their life cycle.
PALUMBI: Anywhere between 1-in-4 and 1-in-2 breaths we take, that oxygen comes directly out of the ocean. And that's mostly coming from these tiny little microbes.
JOYCE: Palumbi says this scientific bite at the oceanic apple will take years for scientists to digest. But he notes that the Tara scientists have made the unusual gesture of giving anyone in the world access to their data in the hope that many hands will make quick work of it. Christopher Joyce, NPR News.
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