Smartphone RGB Coral Health Analysis ImageJ Optical Characterization of Coral Bleaching

Abstract This report evaluates the efficacy of smartphone-based RGB color analysis and ImageJ workflows for assessing coral health and bleaching. Research indicates that specific indices, such as DeltaE76, provide strong correlations with physiological metrics, reaching average absolute values of 0.787. While consumer digital photography offers a scalable screening tool, significant evidence gaps remain regarding smartphone-specific validation and inter-device agreement. The principal recommendation involves adopting standardized acquisition protocols and reference-card normalization to ensure relative measurement reliability across heterogeneous datasets. Introduction Coral bleaching is primarily an optical and physiological phenomenon characterized by the loss of endosymbiotic algae and their associated pigments. This process increases the apparent reflectance of the coral skeleton, leading to the visible whitening of reefs globally. As traditional monitoring methods are often resource-intensive, there is a growing need for low-cost, accessible alternatives for large-scale assessment. Smartphone photography combined with open-source software like ImageJ/FIJI provides a unique opportunity to quantify coral health from online marine photographs. These tools allow citizen scientists and researchers to extract chromatic data that correlates with symbiont density and pigment concentration. This report examines the technical requirements and limitations of using such consumer-grade optical tools for professional coral reef monitoring in 2026. keywords: Coral bleaching, RGB analysis, ImageJ, low-cost monitoring, Red Sea, Marine conservation, Smartphone imaging, Optical Characterization