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Comparing rapid non-invasive imaging and destructive cellular analyses for coral bleaching quantification
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Comparing rapid non-invasive imaging and destructive cellular analyses for coral bleaching quantification

Conor Hendrickson, Peter Butcherine, Sophia Ellis, Amarah T. Fiori, Daniel Patrick Harrison and Brendan Kelaher
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Elsevier
27/04/2026
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Abstract

coral bleaching Climate change coral colour pigments Methods Hyperspectral imaging coral chart reef monitoring
Coral bleaching poses a significant threat to reef ecosystems. Monitoring the progression of bleaching is a critical component for management strategies to address this crisis. Here, a 65-day simulated bleaching experiment was used to compare the ability of common non-invasive bleaching metrics including, colour charts, RGB imaging and hyperspectral indices to predict tissue-based metrics (symbiont density, chlorophyll a, c2, peridinin, diadinoxanthin and total pigment concentrations, lipid peroxidation, superoxide dismutase, glutathione peroxidase and catalase activity) as the simulated bleaching summer progressed. The experiment had an orthogonal factor of temperature (3 levels: 0 °C-weeks (control), moderate heat-stress: 4 °C-weeks and high heat-stress: 6 °C-weeks) and a nested factor (tank). All the colour-based metrics showed similar and significant predictive performance for the concentration of key pigments (R2 = 0.38 – 0.49) and symbionts (R2 = 0.32 – 0.39). The colour metrics were poor predictors of oxidative stress biomarkers. Health chart scores and RGB metrics predicted tissue metrics equally to hyperspectral indices, suggesting that large-scale changes in reflectance occurred and the additional resolution of the hyperspectral camera did not benefit predictive performance. Despite this, imaging metrics offer additional benefits, providing information such as colony size, the spatial distribution of bleaching and improved cross-study comparability, particularly when using radiometrically calibrated hyperspectral data. As bleaching events and reef restoration efforts escalate, scalable and interoperable monitoring networks using the best available methods will be key for tracking coral bleaching and the outcomes of intervention efforts to protect reefs globally.

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