Ocean deoxygenation driven by climate change is already detectable and will likely be widespread by 2030 or 2040, according to a study by the U.S. National Center for Atmospheric Research, published last week in the journal Global Biogeochemical Cycles.

“Since oxygen concentrations in the ocean naturally vary depending on variations in winds and temperature at the surface, it’s been challenging to attribute any deoxygenation to climate change,” said NCAR oceanographer Matthew Long. “This new study tells us when we can expect the impact from climate change to overwhelm the natural variability.”

That impact adds up to “significant impacts on marine ecosystems,” he said, with some stretches of ocean nearly uninhabitable for some species.

“While some ocean critters, like dolphins and whales, get their oxygen by surfacing, many, including fish and crabs, rely on oxygen that either enters the water from the atmosphere or is released by phytoplankton via photosynthesis,” Grist explains. “But as the ocean surface warms, it absorbs less oxygen.” That “eventual suffocation” would ultimately “affect the ability of ocean ecosystems to sustain healthy fisheries.”