Composition and diversity of macroalgae community in the coast of Karang Bolong, Nusakambangan Island

Abstract

Abstract Karang Bolong Beach is a beach located at the eastern tip of the island of Nusakambangan Cilacap. Karang Bolong Beach has a substrate type in the coral and composite substrate (fragment coral, rock, and sand). Therefore, a lot of seaweed grows there. This research aims to determine the macroalgae community on different substrates at Karang Bolong Beach, Cilacap. This is done to explore and use seaweed as a source of bioethanol. The research method used was a survey method - sampling using transects with a random process. The research variables included the macroalgae community in terms of species diversity and abundance on different substrates. The main parameters observed were the number of species and the number of individuals for each species. Supporting parameters consist of current velocity, nitrate content, turbidity, depth, tides, salinity, temperature, and pH. The data obtained were analyzed using Primer-7 to determine the diversity and density of each macroalgae species. The results showed 11 species of macroalgae consisting of Amnasia glomerata, Caulerpa mexiana, Chaetomorpha crasa, Dictyota ciliolata, Eucheuma serna, Gracilaria arcuata. Gracilaria gigas, Laurencia subopposita, Padina australis, Rhodymenia sp., and Ulva rigida. On the coral substrate, there were eight species, and on the composite substrate, six species. Four of these species are found in both substrate types. The diversity of species on the coral substrate varies from low to moderate. The highest abundance on composite substrates dominated by Padina australis biomass with a weight of 431 g.m−2. On coral substrate dominated by Gracilaria gigas with a value of 275.33 g.m−2. The community is in an unstable condition due to ecological pressures.