March 7, 2022 — The crab pots are piled high at the fishing docks in Newport, Oregon. Stacks of tire-sized cages fill the parking lot, festooned with colorful buoys and grimy ropes. By this time in July, most commercial fishers have called it a year for Dungeness crab. But not Dave Bailey, the skipper of the 14-meter Morningstar II. The season won’t end for another month, and “demand for fresh, live crab never stops,” Bailey says with a squinting smile and fading Midwestern accent.
Most marine animals don’t breathe air, but they need oxygen to live, absorbing it from the water as they swim, burrow, or cling to the seafloor. But lately, bouts of dangerously low oxygen levels—or hypoxia—have afflicted parts of the North American west coast, affecting critters from halibut to sea stars. These “dead zones” cause ecological disruption and economic pain for fishers like Bailey, who can’t sell crabs that have suffocated in their traps.
The phenomenon offers a preview of what climate change holds for many other parts of Earth’s oceans, which are already stressed by human impacts. As seawater warms, it holds less oxygen. Warmer surface water also acts like a cap that prevents the gas from mixing from the atmosphere down into the deep. And rising air temperatures can shift weather patterns in ways that worsen the problem.
It’s a subtle but significant change. While well-oxygenated water contains about eight milligrams of oxygen per liter, hypoxic water holds less than two and can sometimes approach zero. Overall, the world’s oceans have lost up to two percent of their total oxygen content over the last 50 years, and scientists estimate that they could lose another two to four percent over the next century. By 2100, some amount of climate-related oxygen loss could affect more than three-quarters of the ocean’s area, inflicting widespread damage to marine ecosystems and the billions of people who depend on them.
