Abstrac—

Intensive algal sampling was conducted from 2017 to 2019 in coastal waters of Wuzhizhou Island (South China Sea, China). In total, 183 species of marine macrophytes, 9 species of Cyanobacteria and 2 species of seagrasses were found. The collection of benthic macroalgae was comprised of 63% of Rhodophyta, 12% of Phaeophyceae, and 25% of Chlorophyta. Among macrophytes, the largest number of species was found on hard substrates (123 species), 83 species were epiphytes, and 16 species grew on artificial substrates. In addition, 4 species of red algae were found on mollusk shells. The largest number of macroalgal species (150 species or 82% of all collections) was found at the end of the dry seasons. Species compositions of macroalgae during both the dry and rainy seasons were not significantly different. Over 50% of the species of macroalgae were common during both seasons. There were more algae found only in the dry season than those found only in the rainy season. In the upper and middle intertidal zone, macrophytes formed mono- and bidominant communities of algal turf and crust algae; in the low intertidal and upper subtidal zones, mosaic polydominant algal turf communities were observed.