Turf Algae Monitoring on Artificial Reefs Using Underwater Photography and ImageJ

Coral reefs are vital ecosystems that support marine biodiversity and protect shorelines, but face increasing threats from human activities. Artificial reefs have emerged as a restoration tool to enhance ecological functions and provide habitats for benthic organisms. Turf algae, which are among the first to colonize artificial reefs, play a critical role but can inhibit coral recruitment and biodiversity when their growth becomes excessive. This study introduces a data-driven methodology for monitoring turf algae cover, applied at Damas Beach, East Java, using underwater photography and the ImageJ software. The measured turf-algae cover ranged from 12.0% to 33.9% across reef units. Turf algae were higher on sediment-free surfaces, consistent with sediment burial likely associated with lower early algal colonization. These results demonstrate that an ImageJ-based photo-analysis workflow can quantify turfalgae cover consistently and support long-term monitoring of artificial reefs.