Six thallus surface types of coralline algae with descriptions of two new records of Amphiroa beauvoisii and Neogoniolithon setchellii in Sanya reef, China

Coralline algae are globally distributed calcifying species and play critical ecological roles to marine ecosystems by contributing significantly to their structural complexity and diversity. Thallus surface types of historical samples in Sanya coral reef reserve were studied based on the scanning electron microscope (SEM) method. Our results show six thallus surface types within the study area: Corallina-type, Jania-type, Leptophytum-type, Phymatolithon-type, Pneophyllum-type, and Spongites-type. The Phymatolithon-type is the dominant surface type in Sanya reefs. Two new record species in the region are described: Amphiroa beauvoisii and Neogoniolithon setchellii. Although thallus surface types provide useful diagnostics characters for distinguishing coralline algae at tribe or subfamily level, species identification needs to refer to the reproductive features. This is the first surface study of coralline algae in the South China Sea. This result provides the baseline data needed for the monitoring and management of reef-building organisms of coral reef in China.