Coral Reef Karstification Plays Vital Role in Sea-Air CO2 Exchange

Strategic Insights -

Researchers from Guilin University of Technology have made a groundbreaking discovery in the field of marine science. A 878.22-m coral reef sequence from the Xisha Islands, South China Sea, has provided valuable insights into the mechanisms of coral reef karstification, a process that plays a crucial role in sea-air CO2 exchange. The study reveals that karstification processes, including their signatures, primary controls, and implications for marine carbonate dissolution in global carbon cycling, have been influenced by sea-level changes and climate conditions.

Key Takeaways:

  • The coral reef sequence from the Xisha Islands, South China Sea, has provided a unique window into the mechanisms of coral reef karstification, dating back to the Middle Miocene epoch (19.6 Ma).
  • Petrological and geochemical analyses of the coral reef sequence revealed distinct karstification characteristics, including higher surface porosity, yellowish-brown to black impregnations, and micritic cements.
  • The study found that karstification in the coral reef sequence was dominated by non-selective dissolution and recrystallization processes, which occurred at the mixing zone in meteoric water systems during prolonged subaerial exposure.
  • The findings suggest that sea-level changes and climate conditions control coral reef karstification intensity, and dissolution during karstification may significantly modify ocean alkalinity and dissolved inorganic carbon.
  • The researchers concluded that karstification signatures varied across geological epochs, implying different controlling mechanisms.
  • The study highlights the importance of coral reef karstification in global carbon cycling and the need for further research to understand its mechanisms and implications for future climate scenarios.

Statistics:

  • The coral reef sequence from the Xisha Islands, South China Sea, spans 878.22 meters.
  • The study focused on the karstification characteristics of the coral reef sequence from the Mean Age of 19.6 million years ago to the present.
  • The researchers found that the surface porosity of the coral reef sequence ranged from 15-40%, with a mean of 25%.
  • The study revealed that the coral reef sequence underwent significant karstification during the Late Miocene (12.6-10.2 Ma) and the Pleistocene (2.2-1.8, 1.1-0.89, 0.29, and 0.2 Ma) epochs.
  • The researchers detected shifts in the 87Sr/86Sr ratio, Mn content, and Mn/Sr ratio, which indicate changes in karstification processes across different geological epochs.

Sources:

  • Yang Yang, Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, College of Earth Sciences, Guilin University of Technology, Guilin, People's Republic of China.
  • Kefu Yu, Bin Xiong, Wei Jiang, Shendong Xu, Rui Wang, Tianlai Fan, Guilin University of Technology.
  • Frontiers in Marine Science, 2025, 12. (Frontiers in Marine Science - http://www.frontiersin.org/Marine_Science). The publisher for Frontiers in Marine Science is Frontiers Media S.A.
  • Characteristics and primary controls of coral reef carbonate karstification in the South China Sea since the Miocene. Frontiers in Marine Science, 2025, 12.
  • https://doi-org.sdpl.idm.oclc.org/10.3389/fmars.2025.1619169