Abstract: A four-season survey of intertidal macroalgae resources at eight sites in the Guangdong-Hong Kong-Macao Greater Bay Area was conducted from September 2020 to August 2021 to better understand the distribution and diversity of intertidal macroalgae biological resources in the Greater Bay Area. The variations of diversity and community structure of intertidal macroalgae across the four seasons were analyzed. A total of 91 species in 53 genera from three macroalgae phyla were recorded, including nine genera and 19 species of Chlorophyta, 36 genera and 59 species of Rhodophyta, and eight genera and 13 species of Ochrophyta. Seasonal pattern of macroalgae species were spring > winter > summer > autumn, with uneven seasonal distribution. Most of them were warm temperate seaweeds. A total of 14 species were classified as the dominant populations, with significant seasonal variations. The average annual biomass of macroalgae was 2800.65 g·m^-2, with a seasonal pattern of spring (7914.89 g·m^-2) > winter (2266.44 g·m^-2) > summer (653.12 g·m^-2) > autumn (368.13 g·m^-2), and a vertical pattern of low-tide zone (7075.98 g·m^-2) > mid-tide zone (1112.60 g·m^-2) > high-tide zone (213.37 g·m^-2). The vertical distribution was different across sites in each season. Diversity indices showed significant seasonal differences. The macroalgae species in the Greater Bay Area were abundant and with huge biomass. The species richness and biomass displayed significant seasonal and regional variations.

Key words: Guangdong-Hong Kong-Macao Greater Bay Area, macroalgae, intertidal zone, biodiversity, seasonal variation, dominant species.