Jeju’s Soft Corals Collapse Again as Heat and Extreme Weather Intensify

The soft coral gardens off South Korea’s Jeju Island are beginning to collapse again, reviving fears that repeated environmental shocks could erode their ability to recover.

Ko Myeong-hyo remembers the corals as vibrant and full of life when she began diving around Jeju six years ago to harvest seafood for sale. After two years of rising temperatures and harsher weather, she watched the coral gardens slump and turn white. “Watching the coral garden collapse and turn white, it was so disorienting,” she said. “I was afraid the whole sea might be collapsing.”

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Watching the coral garden collapse and turn white, it was so disorienting.

The Paran Ocean Citizen Science Center, a group of divers that monitors the island’s UNESCO-listed soft corals, says the slumping phenomenon has appeared again this year. Roughly half of one cluster near the uninhabited islet of Beomseom has struggled in recent months.

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I was afraid the whole sea might be collapsing.

Soft corals lack the rigid calcium carbonate skeletons that support hard corals. They rely on internal fluid pressure to remain upright, and environmental changes can cause them to sag or collapse. Researcher Kim Taihun warned that repeated large-scale slumping could leave the corals progressively less able to recover. Kim and Korea Institute of Ocean Science and Technology researcher Anna Beate Jöst documented Jeju’s 2024 slumping event in a May article in Scientific Reports.

Kim said this year’s event resembled the 2024 episode but could worsen if high water temperatures continue through September. He also said El Niño could bring typhoons and heavy rain. Researchers cite the Korean peninsula’s record heatwave, heavy rain in the south and water flowing from China’s Yangtze River as possible factors affecting the corals through temperature and salinity changes. The Korea Heritage Service said it would continue long-term research, while the Oceans Ministry said it planned a detailed investigation into the damage.

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If another large-scale 'slumping' happens, corals partially recover and then a lot break off and deteriorate again, and that keeps repeating, their capacity to recover just keeps declining.