China Discovers Rare Coral Reef Blue Hole in South China Sea
China has announced the discovery of its first coral reef growth structure-type marine blue hole, a globally rare geological formation located in the lagoon of Huangyan Dao (Scarborough Shoal) in the South China Sea. The finding, revealed on June 25 by the Ministry of Ecology and Environment (MEE), offers a valuable new window into marine geology, paleoclimate, and biodiversity.
According to the MEE, the Huangyan Dao Blue Hole was identified in August 2025 during an ecological survey conducted by scientists from the South China Institute of Environmental Sciences and Guangxi University. The discovery marks only the second marine blue hole found in China’s territorial waters, following the Sansha Yongle Dragon Hole, a limestone dissolution-type formation in the Paracel Islands.
What Makes This Blue Hole Unique
Marine blue holes are deep, circular sinkholes in the ocean, often appearing bright turquoise or emerald green. They are classified into two types: limestone dissolution, formed when submerged caves collapse, and coral reef growth structure, created through the natural expansion and cementation of coral reefs over millennia. The latter is far rarer.
“Marine blue holes are rare geological and geomorphological units on Earth,” said Pei Xiaofei, MEE spokesperson, at a press conference. “Due to their deep blue waters and unique cave structures, they are highly attractive natural landscapes, often called the ‘Eyes of the Ocean.’” Pei noted that blue holes serve as “natural archives” of geological evolution, historical climate records, and biodiversity changes, as reported by Xinhua News Agency.
The blue hole has a mouth area of approximately 1,491.7 square meters, a maximum diameter of 56.3 meters, and a depth of 16.6 meters, with a funnel-shaped internal structure. Radiocarbon-14 dating indicates it formed at least 3,200 years ago, according to the MEE’s 2025 Survey Report on Huangyan Dao Blue Hole.
A Biodiversity Hotspot
The waters surrounding the blue hole host exceptional marine life. The survey recorded 165 species of hard corals, 184 species of fish, and detected over 2,700 marine species through environmental DNA sampling. Green sea turtles, a Class I nationally protected species in China, were observed inhabiting the area.
Pei Xiaofei emphasized that the discovery underscores the ecological significance of the Huangyan Dao ecosystem. “In September 2025, the Chinese government established the Huangyan Dao National Nature Reserve. The results of this survey demonstrate the positive outcomes of ecological protection in the waters of Huangyan Dao,” he said, according to Global Times.
Scientific and Geopolitical Dimensions
The Huangyan Dao Blue Hole is expected to provide critical insights into the geological evolution of the South China Sea. Its sediment layers may contain high-resolution records of climate change over the past three millennia, including monsoon patterns, sea-level fluctuations, and typhoon activity.
However, the discovery also carries geopolitical significance. Huangyan Dao, known as Scarborough Shoal internationally and Panatag Shoal in the Philippines, is a triangular reef formation located approximately 230 kilometers off the Philippine coast. It is claimed by both China and the Philippines and has been a flashpoint in the South China Sea disputes.
As the South China Morning Post noted, Beijing has used a combination of law enforcement patrols and scientific expeditions to solidify its control over the contested waters. The establishment of the Huangyan Dao National Nature Reserve in September 2025 and the bilingual publication of the blue hole report are viewed by analysts as part of this broader strategy.
Chinese state media, including People’s Daily, framed the discovery purely in terms of scientific achievement and ecological protection, making no mention of territorial disputes.
Looking Ahead
The MEE has announced plans for further research focusing on the blue hole’s formation mechanism, ecological evolution patterns, and its contribution to the region’s high biodiversity. The full report, published in both Chinese and English, suggests an openness to international scientific collaboration, though access to the site may be complicated by its location in disputed waters.
For now, the Huangyan Dao Blue Hole stands as a remarkable scientific find — a rare natural archive that could deepen our understanding of the South China Sea’s environmental history while also highlighting the complex interplay between science, conservation, and sovereignty in one of the world’s most contested maritime regions.