Only 5 percent of the ocean has been explored, but that's enough for scientists to know there's trouble under water. The same fossil fuels polluting the air are also making the ocean more acidic.
"It has incalculable risks associated with it; it may overshadow global warming," marine biologist Sylvia Earle said.
Earle is one of the most respected marine biologists in the world. She's logged more than 6,000 hours underwater and was named by the Library of Congress as a living legend.
Earle founded an Alameda Company that builds submersibles to explore the ocean. She's also a fellow at the California Academy of Sciences.
When it comes to ocean research, Earle is the gold standard, and she says it's time the rest of us start paying attention
"We are messing around with the chemistry of the planet," she said.
At the moment, Earle is focusing on tiny organisms called prochlorococcus. Prochlorocuccus are greenish single cell creatures discovered by MIT professor Penny Chisholm. They're so tiny that a glass of ocean water could hold billions.
"Proclorococcus contributes 20 percent of the oxygen in the atmosphere," Earle said.
An incredible one-fifth of all our oxygen comes from the minute species critical to life as we know it.
"It does two important things, it generates oxygen and it takes up carbon, carbon dioxide, transforms that through photosynthesis to carbohydrates, that means food, food for life in the sea," Earle said.
But that fragile ecosystem is being damaged by excess carbon from cars, power plants and factories. The carbon turns the ocean more acidic, making it corrosive to shellfish and coral.
Scientists are not sure of the effect on prochorlorcoccus, but Earle says we can't wait to find out.
"The trend is clear, we are losing elements that keep us alive," she said.
Earle believes the key to saving the ocean is knowing what's happening. That takes exploration and education.
Earle is in her 70s, but she's not slowing down. She's launched an alliance called Mission Blue to ignite public interest and save critical ocean habitats.
"Now that we know, we can do better; we can take actions that will protect procholorococcus, that will protect the kelp forest, that will protect the ocean, that will actually protect human beings," Earle said.
Written and produced by Jennifer Olney