Coral diseases and associated photosynthetic responses around Rodrigues Island, Western Indian Ocean
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Abstract. Jogee SY, Anasamy M, Jeetun S, Ricot M, Ramkalam M, Korimbocus A, Kaullysing D, Nascimento B, Casareto BE, Suzuki Y, Wijayanti DP, Bhagooli R. 2025. Coral diseases and associated photosynthetic responses around Rodrigues Island, Western Indian Ocean. Indo Pac J Ocean Life 9: 100-110. The coral reefs of Rodrigues Island are among the most biodiverse ecosystems in the Western Indian Ocean (WIO) but are increasingly threatened by coral diseases. While disease prevalence has been documented, its physiological impacts remain poorly understood. This study assessed the photo-physiological responses of four reef-building coral species (Montipora sp., Platygyra sp., Acropora sp., Favia sp.) affected by Black Band Disease (BBD), Skeletal Eroding Band (SEB), White Band (WB), and White Syndrome (WS). Coral fragments containing both diseased and visually healthy tissues were collected from four sites and analyzed in situ using a Junior-Pulse-Amplitude-Modulated (PAM) fluorometer. Parameters measured included maximum quantum yield (Fv/Fm), maximum relative electron transport rate (rETRmax), maximum non-photochemical quenching (NPQmax), initial slope before saturation (?), post-saturation slope (?), and minimum saturating irradiance (Ik), derived from rapid light curves. Diseased tissues generally exhibited reduced photosynthetic performance, with BBD in Montipora sp. and SEB in Favia sp. showing the most pronounced declines in Fv/Fm and ?, along with altered ? and NPQmax values. In contrast, WB and WS had limited or non-significant effects on the measured parameters. These results highlight disease and species-specific vulnerabilities, indicating that some coral-algal symbioses are more susceptible to functional impairment. In the context of climate change, disease-driven stress could accelerate reef degradation, especially in isolated islands like Rodrigues. Integrating photo-physiological monitoring into routine reef health surveys can enhance early detection of functional decline, guide species-targeted restoration, and strengthen adaptive management strategies to safeguard the resilience of Rodrigues’ reefs and other WIO coral ecosystems.