Sarangan beach has high biodiversity of macroalgae. Macroalgae has an important role as primary producer for herbivorous marine animals, potentially as biomonitoring, and pollutant bioremediation. As benthic organisms, macroalgae grows attached rocky or reef substrate in intertidal zone. These research aimed to study the macroalgal abundance in Sarangan Beach and influence factors of it. This study is important for local government as a reference to manage and develop the coastal areas of Gunungkidul. Sampling was conducted in 2012-2013 start from determination of the sampling point with line transect then collect data using quadrat plots 100 x 100 cm2 size, seawater nutrient analysis, species identification, and data calculation. The results showed that there were 14 species of Chlorophyta, 4 species of Phaeophyta, and 17 species of Rhodophyta. Enteromorpha intestinalis has a highest abundance, then Ulva fasciata, and Cladophora catenata. Analysis of correlation and regression showed that nutrient levels doesn’t affect the macroalgal abundance in Sarangan Beach. Based on result, the limiting factor of macroalgal abundance in Sarangan Beach is substrate.
Keywords: Abundance, Macroalgae, Sarangan Beach, Substrate