Distribution and photo-physiology of bleached and non-bleached Sarcophyton sp. in Rodrigues reefs, Mauritius

Abstract. Ramkalam MK, Korimbocus AM, Jogee SY, Gerzer F, Nundlall Y, Chatoolsingh D, Anansamy M, Kaullysing D, Casareto BE, Suzuki Y, Reimer J, Wijayanti DP, Nascimento B, Bhagooli R. 2025. Distribution and photo-physiology of bleached and non-bleached Sarcophyton sp. in Rodrigues reefs, Mauritius. Indo Pac J Ocean Life 9: 163-171. Soft corals are key contributors to reef ecosystems, especially where hard coral cover is declining, yet their responses to bleaching stress remain poorly understood in the Indian Ocean. This study investigated the distribution and abundance of soft corals, alongside the photosynthetic performance of bleached and non-bleached Sarcophyton sp. around Rodrigues Island, Republic of Mauritius. Field surveys were carried out using Line Intercept Transects (LIT) across four sites: Ti Trou, Plateau Benitiers, Var Brulee, and Pate Reynieux, revealing significant variations in the soft coral communities. For healthy and bleached Sarcophyton colonies, chlorophyll fluorescence was measured using a JUNIOR Pulse-Amplitude-Modulated (J-PAM) to assess the photo-physiology (Y(II), rETRmax, NPQmax). Results showed that soft corals flourished at shallow southern sites (65.00±0.26% and 51.67±4.72%) with lower levels of nitrate and phosphate. The photo-physiological analyses showed that healthy Sarcophyton sp. had higher Y(II) (0.509±0.004) and rETRmax values (15.23±4.2) compared to bleached Sarcophyton sp. (Y(II); 0.163±0.05, rETRmax; 0.97±0.42), while NPQmax values remained similar (healthy looking; 0.09±0.02, bleached; 0.06±0.008). The retention of quenching activity suggests that even bleached the Sarcophyton samples still had some protective mechanisms hence the possibility of remaining symbionts. These findings demonstrate the physiological plasticity and resilience of Sarcophyton sp., which may contribute to adaptation and resilience to stress conditions and contributes to shifts in reef communities.