Global coral reefs have entered a distinctive human-dominated era, the Anthropocene, characterized by more frequent severe global coral bleaching events and regional-scale coral habitat degradation. Coastal areas around the world are usually densely populated regions that are under increasing pressure from urbanization, intensifying land use, and industrial development. Compared with remote, pristine coral reefs, inshore reefs are at higher risk of degradation due to a combination of natural and direct human impacts.

The South China Sea (SCS), a marginal sea in the western Pacific, has numerous fringing reefs and non-reef coral communities distributed around near shore islands and along the mainland coast of southern China. The northern SCS has been defined as one of the “highly impacted regions” in the world. Coral habitats in this region have experienced significant declines in coral cover and biodiversity during recent decades.

Direct evidence of acute and chronic disturbance on most inshore coral assemblages is limited. Long-term, periodical surveys and historical baseline data essential for effective management are lacking, especially in the SCS and the vast majority of coral reefs over the Indo-Pacific .

Recently, researchers led by Prof. Chen Tianran from South China Sea Institute of Oceanology, Chinese Academy of Sciences, and Professor Zhao Jianxin from the University of Queensland, Australia, have made the latest progress in the study of coral reef dynamics in the northern South China Sea. The study was published in Science of the Total Environment.

 Using high-precision uranium-thorium (U-Th) dating technology, they reconstructed a ~100-year-long history of extensive coral loss, changes in coral community structure, and a shifting baseline. The data were collected at Weizhou Island, northern SCS, which has highly disturbed inshore coral habitats that are typical globally. According to their U-Th dates, major coral mortalities around Weizhou Island have occurred since the 1950s, with increasing frequency and severity since the 1980s. Prior to this collapse, the local coral community structure sustained remarkable long-term stability over millennia. The timing of the Acropora loss and massive coral mortalities coincides with multiple acute and chronic, natural and anthropogenic disturbance events.

“Finding new, efficient, and cost-effective restoration technologies is an urgent research need” said Prof. CHEN, “but priority should be given to directly addressing the causes of degradation and effectively controlling chronic disturbances before attempting to restore reef ecosystems.”

Fig.  U-Th age structures of (a) all dead coral samples（Image by SCSIO）

Information:

TianranChen^*#, ShuLi^*#, JianxinZhao, YuexingFeng. Uranium-thorium dating of coral mortality and community shift in a highly disturbed inshore reef (Weizhou Island, northern South China Sea). Science of The Total Environment,2020,752, 15 January 2021, 141866.

https://www.sciencedirect.com/science/article/pii/S004896972035395X

Contact

CHEN Tianran 

South China Sea Institute of Oceanology, Chinese Academy of Sciences

E-mail:chentianran@scsio.ac.cn