Abstract. Mundil SP, Jogee SY, Kaullysing D, Bhagooli R. 2023. Prevalence and thermal photo-physiological responses of Skeletal Eroding Band (SEB)-affected Acropora muricata from Mauritius Island. Indo Pac J Ocean Life 7: 48-53. The threat to coral reefs due to coral diseases has been on the rise since the late 1990s, and the effects of climate change-driven global warming and coral diseases have yet to be thoroughly investigated. This study aimed at investigating the prevalance of Skeletal Eroding Band (SEB), a coral diease resulting from the ciliate Halofolliculina corallasia, in Acropora muricata, at two sites namely Flic en Flac and Belle Mare around Mauritius Island and the thermal photo-physiological responses, in terms of effective quantum yield at photosystem II (?PSII), of SEB-affected and non-affected A. muricata, measured with a Diving-Pulse Amplitude Modulated (D-PAM) fluorometer. Affected colonies were identified using underwater field guides and their prevalence was estimated using a random swim method. The prevalence of SEB was highest at Belle Mare during late summer with a prevalence of 24.44 ± 1.93%. The thermal stress experiment consisting of 6 aquaria with 3 at 27? and 3 at 32? were set up with both SEB-affected and non-affected A. muricata for a duration of 19 hours. Both SEB-affected and non-affected A. muricata were influenced by high ttemperatures. The SEB-affected samples exhibited a higher susceptibility to 32? treatment as the ?PSII declined to almost zero after 6 hours of exposure. These findings suggest that the region of Belle Mare may be potentially at risk if exposed to high temperatures for extended periods and may lose up to 25% or so of its A. muricata cover during future thermal severe bleaching events.