Benthic Sargassum composition and community characteristics in the intertidal zone of Hainan Island, China

Sargassum is one of the most important economic algae in Phaeophyta. It has broad prospects for development and application in industry, agriculture, food, medicine and ecological restoration, and plays an important role in maintaining the marine ecosystem. In recent years, however, environmental degradation, offshore farming and overharvesting have changed the ecosystem structure and threatened the Sargassum resources. To understand the composition and characteristics of Sargassum in Hainan, we conducted an annual field survey of four bays around Hainan Island, including Haiwei, Qinglan, Lingshui and Sanya. Results indicated that 16 species of Sargassum were collected in the intertidal zone of Hainan Island, belonging to two subgenera, three sections, and S. polycystum was the dominant species at all stations throughout the year. Lingshui and Sanya had the highest biodiversity index, followed by Qinglan and Haiwei. The community similarity between Qinglan and Lingshui was the highest, followed by Haiwei and Sanya. The biodiversity index of Sargassum was the highest in summer, followed by late spring and autumn, and the lowest in winter.