Interannual and Seasonal Changes in the Benthic Algae Flora of Coral Reef in Xiaodong Hai (Hainan Island, China)

Intensive algal sampling conducted in 2016–2019 in the Xiaodong Hai locality (Hainan Island, South China Sea), yielded a total of 198 benthic macroalgal species and their taxonomic forms (54% reds, 20% browns and 26% greens) and 20 species of Cyanobacteria. The largest number of species belonged to the families Rhodomelaceae, Ceramiaceae and Corallinaceae (Rhodophyta); Sargassaceae and Dictyotaceae (Phaeophyceae); Cladophoraceae and Caulerpaceae (Chlorophyta). The majority (79%) of species inhabiting only the tropics or subtropics were previously recorded and 21% of the species were also inhabiting temperate latitudes. Cosmopolitan algae inhabiting from the tropics to Arctic or Antarctic waters amounted to 14%. The level of maximum similarity of macroalgal species diversity in different years was on average more than 70%, interannual species specificity was observed only in the group of dominating species in algal turf communities. The seasonal variability of floras was manifested in a significant decrease in species diversity from the dry season to the rainy and in the change of dominant species in algal turf communities.