Abstract:
Anthropogenic turbidity is a major stressor in the Anthropocene, altering coral reefs by reducing light availability, reshaping resource distribution, and diminishing visibility. Fishes, sensitive to these changes, offer critical insights into ecosystem health through their behavioural and energetic responses. The coral reefs of Kolombangara Island, Solomon Islands, shaped by freshwater discharge from over 80 rivers, form a natural turbidity gradient, providing a model system to study how turbidity-driven changes in visibility—used as a proxy for sediment load—reshape Energy Seascapes through the analysis of fish movements.
Combining feeding preference analyses with measurements of field metabolic rates (FMR), we investigated how resource use and energetic demand shift along this gradient. Stereo-video tracking, Overall Dynamic Body Acceleration (ODBA), and three-dimensional Behavioural Change Point Analysis (3D BCPA) were applied to functionally distinct species, including facultative and obligate corallivores, an excavating herbivore, and a detritivorous grazer. Our results reveal species-specific patterns in resource use among butterflyfishes, with specialists showing reduced foraging selectivity under turbid conditions, relying on less-preferred substrates, while generalists maintained resource flexibility. Energetic trade-offs emerged, with elevated FMR in turbid environments, particularly for specialists facing reduced prey detectability.
We demonstrate how turbidity-induced changes disrupt both resource use and energy dynamics, with specialists more vulnerable due to limited foraging plasticity. Early behavioural and metabolic shifts may occur before visible habitat degradation, positioning fishes as sensitive indicators of ecosystem health. Mapping Energy Seascapes offers a framework for early warning signals, informing conservation strategies, and enhancing predictive models of coral reef resilience under global change.