Benthic-Pelagic Coupling and Structural Complexity of Coral Reefs in the Northern Bali Strait: Implications for Coastal Ecosystem Resilience

Abstract

This study examines benthic-pelagic associations in neritic environments by evaluating habitat structural heterogeneity, macrobenthic biodiversity, and pelagic community status at Grand Watudodol (GWD) in the northern Bali Strait. Utilizing Line Intercept Transect (LIT) protocols and volumetric filtration methods alongside in situ hydro-oceanographic monitoring, community ecological indexes were quantified across biological zones. The empirical results revealed a live hard coral cover of 41.55%, classifying the ecosystem status as moderate. The benthic matrix showed high architectural diversity, with branching Acropora, massive corals, soft corals, and sponges. Conversely, the pelagic zone demonstrated a community structure imbalance, suggesting potential environmental enrichment indicated by a high abundance of the diatom Skeletonema sp.. Statistical correlation analysis revealed that this pelagic microalgal accumulation was positively associated with vertical water clarity and calm surface current velocities (0.06 m/s), which may prolong the residence time of terrestrial nutrients. While current physicochemical parameters largely meet national environmental standards, chronic pelagic nutrient loading may pose long-term ecological risks of substrate smothering. Ultimately, these findings indicate a potential ecological shift, showing that long-term reef resilience requires expanding beyond localized physical marine protection to a comprehensive ridge-to-reef management framework that can mitigate terrestrial organic inputs.