Thermal photo-physiological responses of massive heat-resistant coral Porites lutea under fish predated versus non-predated conditions

Abstract

Abstract. Ricot M, Jeetun S, Joggee S, Kaullysing D, Taleb-Hossenkhan N, Bhagooli R. 2023. Thermal photo-physiological responses of massive heat-resistant coral Porites lutea under fish predated versus non-predated conditions. Indo Pac J Ocean Life 7: 38-47. Fish predation on corals leading to polyp and tissue loss has been identified as a significant stressor to corals and is often associated with reduced growth, reproduction, and even mortality. However, how climate change-driven ocean warming may impact such a biological stressor is yet to be thoroughly understood. This study aimed to assess elevated temperature’s effects on the photo-physiology of fish-predated and non-predated parts of the thermally resistant coral Porites lutea (Quoy & Gaimard, 1833). The objectives were to assess the photo-physiological parameters such as effective quantum yield at photosystem II (FPSII), relative maximum electron transport rate (rETRmax), maximum photo-chemical quenching (NPQmax), photosynthetic efficiency (?), photoinhibition (?) and Ik at fish bite-affected (BA) and non-affected (NA) coral parts at temperatures of 28°C and 32°C under low-light (10 µmol quanta m-2s-1) and moderate-light (110 µmol quanta m-2s-1) conditions for a duration of 48hr. FPSII, rETRmax and NPQmax were not negatively affected by fish predation conditions. Under moderate light, the rETRmax increased in the non-predated condition at 28°C but not at 32°C while the NPQmax exhibited a more pronounced increase at 32°C compared to the 28°C treatment. The absence of significant declines in FPSII and rETRmax accompanied by a significant increase in NPQmax at 32°C is indicative of a lack of photo-inhibition and an active quenching of energy in a non-harmful way at PSII. No significant interactions of temperature and predation condition and light and predation condition were found, indicating that short-term exposure of 2 days to an elevated temperature of 32°C and moderate light intensity of 110 µmol quanta m-2s-1 did not result in any exacerbated negative photo-physiological impacts of fish predation in P. lutea. These findings suggest that both fish-predated and non-predated conditions in P. lutea are equally tolerant to the tested elevated temperature level. Thus, ocean warming events may not differentially impact their photosynthetic activities.

Photo-physiological responses and thermal tolerance of regionally endemic/rare and morphologically different corals of the Western Indian Ocean

“…Yet, lethal coral bleaching has been increasing in frequency, severity, and geographic scope over the past decades, and thus it is anticipated that this trend will continue (Grottoli et al 2014;Hughes et al 2017) which therefore increases the fragility of reefs (Goldberg and Wilkinson 2004) leading to biodiversity loss (McClanahan et al 2021) and rapid community structural changes (Tebbett et al 2023). To date studies on corals of Mauritius have looked at bleaching and mortality of corals under thermal stress (Bhagooli and Taleb-Hossenkhan 2012;Bhagooli and Sheppard 2012;Bhagooli and Kaullysing 2019;Bhagooli et al 2021b,c;Fai et al 2023;Jeetun et al 2023;Ricot et al 2023). However, rare and endemic corals' responses to thermal stress in the Mauritian waters is almost uncharted.…”