THE EFFECT OF BIOTIC AND ABIOTIC FACTORS ON THE DIVERSITY OF REEF FISH IN THE BATU ANJIR CORAL REEF ECOSYSTEM

Abstract

Coral reef ecosystems are important habitats for reef fish, whose existence is strongly influenced by the interaction of biotic and abiotic factors. Changes in environmental conditions such as temperature, salinity, and water quality, as well as food availability and interspecific competition, can determine the level of reef fish diversity. The purpose of this study was to analyze the influence of biotic and abiotic factors on the level of reef fish diversity in the Batu Anjir Coral Reef ecosystem, thus providing a basis for conservation efforts and sustainable management of marine resources. This study used qualitative methods by analyzing satellite imagery, water quality measurements, and marine biota surveys to assess the influence of biotic and abiotic factors on the Batu Anjir coral reef ecosystem. The results showed a significant decrease in live coral cover, water quality that largely met quality standards but with indications of mild pollution, and moderate reef fish diversity with the dominance of several species. PCA analysis confirmed that optimal physical-chemical environmental conditions play a significant role in supporting biota abundance, although other factors such as habitat complexity and human activities also influence. The results of the study indicate that the condition of the Batu Anjir coral reef ecosystem experienced a 33.88% decline in live coral cover between 2015, 2020, and 2025, shifting the ecosystem status to the "Moderate" category. Reef fish diversity is still classified as moderate, with a total of 40 species from 15 families (4,257 individuals), dominated by plankton-eating fish, invertebrates, and predatory fish. PCA analysis showed that most environmental factors, such as pH, DO, salinity, brightness, and depth, were positively related to fish diversity, while current speed contributed negatively.