Macroalgal community structure and composition in intertidal zone of Sarangan Beach, Gunungkidul, Indonesia

Abstract

The intertidal zone of Sarangan Beach is characterized by rocky substrates and it has high macroalgae biodiversity. However, based on previous research, limited research was conducted at the location on the changes of macroalgae community structure. This research aims to study the structure and composition of macroalgae communities in the intertidal zone of Sarangan Beach and the physicochemical factors that affect its growth. Data was collected in September 2023, during the maximum low tide. The data collection was done by systematic sampling method using 60 plots 1x1 m2. The physicochemical parameters were measured and observed i.e. water and air temperature, pH, salinity, light intensity, and substrate type. The results showed 23 species of macroalgae were found in the intertidal zone of Sarangan Beach, consisting of 8 species of Chlorophyta, two species of Phaeophyta, and 13 species of Rhodophyta. The highest abundance was shown by Ulva lactuca, followed by Sargassum crassifolium and Kappaphycus alvarezii, while the lowest was Gracilaria spinulosa. The structure of the macroalgae community consists of moderate diversity (H’=1.97) with high uniformity (E=0.63) and low dominance (C=0.27). This is influenced by physicochemical parameters, especially water and air temperature, pH, and substrate condition.