It's impossible to overestimate how critical the oceans are to the overall health of life on Earth. For one thing, tiny marine plants called phytoplankton provide up to 85 percent of the world's oxygen, according to EarthSky.org. But the oceans don’t just give us good stuff like oxygen; they take away bad stuff, like carbon dioxide. A 2011 international study led by the University of East Anglia in Norwich, England, estimated that the oceans absorb 27 percent of the CO2 produced by the fossil fuel combustion.