Sea Surface Temperature Anomaly and Reef Fish Community Turnover Across Indo-Pacific Coral Triangle Sites: A 15-Year Monitoring Study

This study investigates relationship between sea surface temperature anomaly severity and reef fish community species turnover, functional diversity loss, and trophic structure shifts over 15 years at Indo-Pacific monitoring sites within the context of marine ecology and coral reef conservation biology, an area of growing scientific importance given its implications for marine protected area network design, reef fish community recovery prioritization, and thermal resilience reef management. Using standardized 25m x 4m belt transect fish census paired with remotely sensed sea surface temperature anomaly from NOAA Coral Reef Watch degree heating week products, we examine bleaching-driven coral structural complexity loss reducing habitat heterogeneity and cascading into reef fish species richness and functional group loss, particularly herbivores and corallivores in 84 monitoring sites across the Coral Triangle (Indonesia, Philippines, Papua New Guinea) with annual belt transect surveys 2006-2021 (n=1,512 site-year observations) drawn from Indo-Pacific Coral Triangle spanning Indonesian, Philippine, and Papua New Guinean reef systems at 2-18 m depth. Results indicate that each additional 4 degree heating weeks of thermal anomaly is associated with a 12.4% reduction in reef fish species richness relative to baseline, with trophic corallivore specialist groups showing 48.4% decline in high-anomaly sites (p < 0.001), with 12.4% species richness loss per 4 DHW thermal anomaly; 48.4% corallivore decline at high-anomaly sites as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to marine ecology and coral reef conservation biology and carry actionable implications for the design of programs and policies targeting marine protected area network design, reef fish community recovery prioritization, and thermal resilience reef management.