Episodic coral growth in China’s subtropical coral communities linked to broad-scale climatic change

Abstract

Evidence from the fossil coral record has shown that coral assemblages were able to extend their geographical range to higher latitudes during past global warming events. In the face of future global warming scenarios, we investigate the potential for China's subtropical coral communities to act as a refuge for corals as ocean temperatures continue to warm. Using uranium-thorium dating to chronologically constrain the age of dead corals, we reveal two distinct periods of coral growth between 6.85 and 5.51 ka B.P. and 0.11 to -0.05 ka B.P. (relative to A.D. 1950). The former coincides with the mid-Holocene Warm Period when temperatures in South China were similar to 1-2 degrees C warmer than present. Very few ages (13%) were obtained for the similar to 5.6 k.y. that followed. An increased frequency of corals with Th-230 ages dated to the past century suggests an increase in abundance coinciding with rising global temperatures. Nevertheless, modern monitoring programs have reported a recent dramatic decline in coral cover over the past 34 yr attributable to human influences. Our results suggest that although coral communities existed around the subtropical islands of Daya Bay (southeast China) in the past, their continued presence in the region largely depends on appropriate management of the adjacent coastline and coupled ocean-atmosphere conditions similar to those experienced in the mid-Holocene.