Sea turtles are a flagship species, an umbrella species and a national key conservation species of Class I. They have an irreplaceable position in the history of biological evolution and play an important role in maintaining the balance of the marine ecosystem. There are five species of sea turtles distributed in China's waters, and the Chelonia mydas accounts for 87% and is the only sea turtle species that lays its eggs in China.

1. Discovered that the C. mydas population in the Xisha Islands is a separate geographic population with unique conservation value

The discovery that the C. mydas population in the Xisha Islands has a unique genetic composition and is an independent geographic population is of great value in enhancing the conservation status of China's sea turtle population and strengthening the protection of sea turtle habitats. Tracing the migratory path of released sea turtles by satellite, we found that the South China Sea area is an important habitat for China's C. mydas population, which provides scientific and technological support for the establishment of sea turtle sanctuaries and marine national parks, and demonstrates China's image as a responsible superpower in biodiversity conservation in the South China Sea.

2. Revealed that C. mydas are threatened by spawning ground pollution, over-utilization and other factors

We identified the hazardous level of heavy metal and microplastic pollution in the nesting sites of C. mydas in the Xisha Islands, as well as the direct impact on turtle hatching; we discovered that plastic pollution in the Xisha Islands mainly comes from the neighbouring countries in the South China Sea, which indicates that marine conservation requires the establishment of a transnational joint management mechanism; and we revealed the current state of pollution in the 13 historical nesting sites of turtles on Hainan Island, which provides an important basis for restoring the nesting sites and promoting the return of sea turtles to Hainan.

These findings provide guidance for the scientific management of C. mydas habitats and pollution prevention. We found that the sex ratio of C. mydas populations in the South China Sea is biased towards females, which is significantly affected by rising temperatures (the sex of sea turtles is controlled by temperature), revealing the importance of coping with climate warming for the protection of C. mydas.

We also uncovered the problem of illegal trade exacerbated by the massive demand for sea turtles in China's oceanariums and aquariums, and pushed government to strengthen the control over the use of public exhibition venues and rare and endangered marine species, to comprehensively prohibit the illegal trade of sea turtle products, and to promote the formulation and adjustment of relevant national laws, regulations, and policies. A detection system based on molecular markers of mitochondrial and microsatellite genes has been developed by our team, which can quickly determine the parentage of sea turtles and reveal the origin of their birthplace. This is important for controlling illegal breeding and combating illegal trade.