It is not every day that the ocean reveals a new chapter of its history.
On June 25, China's Ministry of Ecology and Environment released the findings of a two-year study on a rare coral blue hole discovered in the Huangyan Island lagoon within the South China Sea. Researchers confirmed that this is the first coral blue hole of its kind to be explored and officially documented in China, making it one of the rarest structures of its origin worldwide.
Preliminary radiocarbon dating indicates that this natural formation took shape at least 3,200 years ago. Unlike most known blue holes, which formed in limestone, this one emerged through the natural growth of a coral reef—a distinction that makes it of exceptional scientific interest.
The expedition was conducted by experts from the South China Institute of Environmental Sciences under the Ministry of Ecology and Environment, in collaboration with the Guangxi Laboratory on the Study of Coral Reefs in the South China Sea and other scientific institutions. The study utilized underwater dives, remotely operated vehicles (ROVs), drones, and environmental analysis via environmental DNA (eDNA) technology.
The results were striking.
Researchers documented an immense level of biodiversity both within and around the blue hole. Over two years of fieldwork, 165 species of hard corals and 184 species of fish were recorded, while eDNA analysis identified more than 2,700 marine species in the surrounding waters. Residents include the green sea turtle, which is one of the region's protected species.
Yet, the most valuable discovery may not lie in the number of species found.
Scientists refer to such blue holes as the ocean's natural archives.
Layers of sediment, the chemical composition of the water, and coral deposits preserve data on sea-level fluctuations, climate change, and the evolution of reef ecosystems over millennia. Consequently, these structures allow researchers to reconstruct the ocean's history far more deeply than modern observations alone permit.
What does this discovery contribute to the resonance of our planet?
Blue holes serve as a reminder that the ocean preserves not only life, but also the memory of its existence.
Recorded within layers of coral, sediment, and seawater are thousands of years of our planet's history—a chronicle that scientists are only just beginning to decode.
Perhaps the ocean is the greatest living book on Earth.
Each expedition reveals only a few new pages.
And the more carefully we learn to read them, the more profoundly we understand not just the ocean, but the history of life itself.
