Impact of Bioreef Block Application on Coral Fish Community Structure in Tanjung Seloka Waters, Kotabaru, South Kalimantan Indonesia

The Tanjung Seloka Sea waters, located in Pulau Laut Selatan District, Kotabaru Regency, South Kalimantan, serve as one of the selected locations for the application of Bioreef Block technology by PT State Electricity Company (Persero) East Kalimantan Development Unit. This innovation functions as a substrate for coral planula larval attachment and provides shelter for reef fish, utilizing Fly Ash and Bottom Ash as environmentally friendly construction materials. The objective of this study was to analyze the structure of the coral fish community associated with the Bioreef Block in the Tanjung Seloka waters. Data collection was conducted using the Underwater Visual Census (UVC) method. Research variables included fish species abundance, diversity, evenness, dominance, and water quality parameters such as temperature, salinity, pH, dissolved oxygen (DO), current velocity, brightness, and depth. In-situ measurements were carried out to obtain accurate environmental data. Findings indicated a notable increase in fish abundance and species richness following the installation of Bioreef Block. The target fish group was dominant, comprising 10 groups, followed by one major group and one indicator group, resulting in a total abundance of 3,160 individuals. Despite a low diversity index (H'), which suggests environmental stress, the high evenness index (E') reflects a stable fish community. Favorable environmental parameters also supported the success of the Bioreef Block in enhancing reef fish habitat and sustainability.