Corals Spin Tiny Whirlpools to Breathe at Night

Corals have no brain, no muscles and no way to swim somewhere better. So when the sun goes down and their oxygen supply cuts off, they do something nobody knew about until 2014: they spin.

Daylight is when coral polyps get their oxygen, courtesy of the algae living and photosynthesizing inside their tissue. Once the sun sets, that supply shuts off, leaving each polyp dependent on whatever oxygen happens to be dissolved in the water nearby. For an animal rooted permanently in place, that's a real problem.

The fix: thousands of hairlike cilia beating in coordinated patterns, carving tiny, fast-spinning whirlpools that pull oxygen-rich water toward the coral's surface. Researchers only discovered this a decade ago. Captured on camera with glowing, oxygen-sensitive nanoparticles, the swirls look almost choreographed.

A paper the team published in May 2026, in the journal Science, dug into how a creature with no central nervous system pulls off something this coordinated, and what happens to the system as water heats up. Hotter water carries less dissolved oxygen to begin with, so the coral's demand rises just as supply shrinks, and the cilia beat harder to compensate. The harder they beat, the more oxygen the beating itself burns. Past about 37 degrees Celsius (98.6 Fahrenheit) the cilia begin to slow. Past 39 degrees Celsius (102 Fahrenheit) they stop moving entirely, and the coral dies.

Corals have been running a precise engineering operation on their own surfaces this whole time. Science just hadn't looked closely enough to see it.

Read the full story at Quanta Magazine, August 5, 2026

Hot Take: Scientists have been staring at coral for over a decade and only just noticed it was doing its own CPR every single night. Make it make sense.