Tiny Hairs That Help Corals Breathe May Malfunction in Warming Oceans
Several new studies have uncovered this long overlooked aspect of coral physiology that could be the key to the animals’ fate in a changing climate.
Corals, complex organisms forming colonies, require oxygen to survive. Tiny, hair-like cilia on their surface perform a frantic dance of survival, an invisible process discovered in 2014. Corals lack a consistent oxygen supply and cannot relocate to seek it. During the day, corals receive ample oxygen from symbiotic algae, but at night, the only oxygen source for coral polyps is the surrounding water.
Cilia then generate fast-moving water vortices to circulate oxygen to the coral's outer tissues and keep them free of sediment. A 2026 study in Science delves into how these cilia generate and regulate this process and what happens when water warms. Warmer water carries less oxygen, prompting corals to increase cilia activity. However, above a certain temperature, the system becomes counterproductive, using up the oxygen the coral tissues can absorb, potentially leading to suffocation.
Biologists are now exploring the physiological and hydrodynamic forces at play, aiming to understand bleaching patterns, coral diseases, and mass die-offs. These cilia, previously thought to be passive "brooms" that move mucus and waste, are now known to interact with the slow-moving boundary layer of water near corals, generating turbulence to deliver sufficient oxygen.
The study highlights the importance of cilia as a potential more direct indicator of coral health, potentially explaining why some corals bleach while others don't.
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