Spatial and temporal variability of thermal stress to China’s coral reefs in South China Sea

Abstract

Coral bleaching, caused by elevated sea surface temperature (SST), is occurring more frequently and seriously worldwide. Due to the lack of field observations, we understand little about the large-scale variability of thermal stress in the South China Sea (SCS) and its effect on China's coral reefs. This paper used 4-km high resolution gap-filled SST (FilledSST) data and thermal stress data related to coral bleaching derived from Coral Reef Temperature Anomaly Database (CoRTAD) to quantify the spatial and temporal characteristics of chronic thermal stress and acute thermal stress to China's coral reefs in SCS from 1982 to 2009. We analyzed the trend of SST in summer and the thermal stress frequency, intensity and duration during this period. The results indicate that, as a chronic thermal stress, summer mean SST in SCS shows an average upward trend of 0.2 A degrees C/decade and the spatial pattern is heterogeneous. Waters of Xisha Islands and Dongsha Islands of the northern SCS are warming faster through time compared to Zhongsha Islands and Nansha Islands sea areas of the southern SCS. High frequency bleaching related thermal stress events for these reefs are seen in the area to the northwest of Luzon Island. Severe anomaly thermal stress events are more likely to occur during the subsequent year of the El Nio year for these coral reefs. Besides, the duration of thermal stress varies considerably by anomaly year and by region.