No abstract

The South China Sea in the Central Indo-Pacific is a large marine region that spans an area of more than 3 million km2 bounded by the coastlines of ten Asian nation states and contains numerous small islands. Although it abuts the western border of the Coral Triangle, the designated centre of maximum marine biodiversity, the South China Sea has received much less scientific and conservation attention. In particular, a consolidated estimate of the region's scleractinian reef coral diversity has yet to emerge. To address this issue, we assemble a comprehensive species distribution data set that comprises 16 reef areas spread across the entire South China Sea. Despite containing less than 17 % of the reef area as compared to the Coral Triangle, this region hosts 571 known species of reef corals, a richness that is comparable to the Coral Triangle's based on a standardised nomenclatural scheme. Similarity profile analysis and non-metric multidimensional scaling demonstrate that most areas are compositionally distinct from one another and are structured according to latitude but not longitude. More broadly, this study underscores the remarkable and unexpected diversity of reef corals in the South China Sea.

The highest concentration of Malaysian coral reefs is found in the coastal area of Semporna, eastern Sabah, which is located just within the boundaries of the Coral Triangle, the area of maximum marine species diversity. The Semporna reefs consist of five major geomorphological reef types, which include lagoonal reefs inside a proto-atoll, fringing reefs, continental patch reefs, a barrier reef and a reef capping an oceanic island. Surveys were carried out in this area to compare the species richness patterns of the scleractinian coral families Agariciidae, Euphylliidae, and Fungiidae from nearshore to offshore reefs. In total, 44 species of Fungiidae, 31 Agariciidae and 15 Euphylliidae have been observed, including 12 new records for Sabah and 4 records that are so far considered endemic to northeast Borneo. Based on coral species compositions for each site, multivariate analyses suggest the distinction of two main groups that reflect a difference in reef exposure, with a gradient in increasing coral diversity from the exposed barrier reef to the relatively sheltered nearshore reefs. Some reefs have been damaged by blast fishing, a threat still prevalent in the area. Nevertheless, the high coral species diversity is remarkable, and to date, Semporna holds the record for the highest species richness of Fungiidae, which surpasses records from other areas in the Coral Triangle.