As you take in your next breath of air, you can thank a form of microscopic marine life known as plankton.
They are so small as to be invisible, but taken together, actually dwarf massive creatures like whales. Plankton make up 98 percent of the biomass of ocean life.
"This invisible forest generates half of the oxygen generated on the planet," Chris Bowler, a marine biologist, tells Guy Raz, host of weekends on All Things Considered.
And, as climate change alters the temperature and acidity of our waters, this mysterious ocean world may be in jeopardy.
It's Bowler's mission to learn as much as possible about plankton — before the tiny creatures disappear. Bowler is the scientific coordinator of an around-the-world voyage named the Tara Oceans expedition. Aboard an 118-foot schooner, a team of marine scientists culled the world's waters for 21/2 years, studying plankton.
"By understanding the plankton communities, which are associated with areas that are more or less polluted, or more or less acidic, we hope that we'll get a feel for what sort of organisms prefer which kinds of conditions," Bowler says.
So as the oceans change in the future, he says, "we will be able to sort of see — predict which of these species are likely to go extinct, which ones are likely to migrate, which ones are likely to take their place."
Though the main voyage has ended, the work has only just begun. The biggest catch so far? Discovering up to a million new species of microorganisms.
"That's sort of a reflection of our ignorance of ocean life," Bowler says. "Particularly the microscopic world, which is difficult to study."
The expedition brought home around 27,000 samples, "a snapshot of the state of the oceans at the beginning of the 21st century," Bowler says.
"It's certainly going to be at least 10 years before I think we've gotten to the bottom of these samples," he says.
By then, he says he hopes they will start to develop a picture of how the oceans might look after a hundred years or more of climate change.
"It's going to be a continual discovery process, I think," he says.