Field note - N/A

Abstract. Kaullysing D, Jogee SY, Mundil SP, Soondur M, Gopeechund A, Ricot M, Jeetun S, Chinta T, Chockalingum J, Mungur D, Kowal B, Kristnama L, Gunness V, Balgobin A, Fakun ZR, Munbodhe V, Nohur MB, Ramdhun D, Ramsurrun LK, Rase S, Seetohul TK, Mattan-Moorgawa S, Ramah S, Bhagooli R. 2023. Variations in photo-physiological responses of shaded and non-shaded mangrove, Rhizophora mucronata tree parts from Mauritius Island, western Indian Ocean. Indo Pac J Ocean Life 7: 71-78. This study assessed and compared the photo-physiological responses of the tree parts of juvenile and adult mangrove, Rhizophora mucronata, under shaded and non-shaded conditions in the northern coast of Mauritius Island. Chlorophyll a fluorescence of mature (dark) leaves, young and mature propagules, lichen, buds, and sepal of adult R. mucronata trees, and of mature and young (pale) leaves of juveniles under natural shaded and non-shaded conditions was measured using a field-portable Diving Pulse-Amplitude-Modulated (D-PAM) fluorometer. Commonly used chlorophyll fluorescence parameters such as Fv/Fm, rETRmax, NPQmax were calculated. The tree parts of adult and juvenile R. mucronata showed considerable variations in their photosynthetic responses. Fv/Fm of adult tree leaves was 30% higher in shaded condition as compared to non-shaded condition. The combined effect of mangrove tree parts and conditions (shaded; non-shaded) resulted in significant differences in mean values of Fv/Fm (three-way ANOVA, p<0.001). Leaves of adult trees had 52% higher rETRmax in shaded condition. While a significant difference (p<0.001) was noted in the mean rETRmax values of various tree parts, the shaded and non-shaded conditions did not have any significant effect on rETRmax (p>0.05). Non-shaded parts of R. mucronata, including the leaves, exhibited higher NPQmax values as compared to shaded conditions. Mean NPQmax varied significantly among mangrove parts (p<0.001), between tree stage (p<0.001) and between conditions (p<0.05). These findings revealed differences in the photosynthetic activities of various mangrove parts of juvenile and adult trees under shaded and non-shaded conditions, a first attempt for the tropical island of Mauritius.

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.

Abstract. Munbodhe V, Jeetun S, Ricot M, Jogee S, Kaullysing D, Bhagooli R. 2023. Photo-physiological responses and thermal tolerance of regionally endemic/rare and morphologically different corals of the Western Indian Ocean. Indo Pac J Ocean Life 7: 100-107. Intensification in climatic variations is causing major alteration in ecosystem functionalities and an overall decline in reef biodiversity. Underlying the ongoing cumulative threats and the vulnerability to biodiversity loss in the reefs, this study aims to determine the photo-physiological response and the thermal tolerances of the morphologically different coral species namely, Porites lutea, Porites cylindrica, Acropora hyacinthus, Galaxea fascicularis, Seriatopora hystrix including the two regionally endemics of the Western Indian Ocean, Acropora branchi and Pocillopora indiania. Coral fragments from three colonies per species were collected from the south and southeast of Mauritius Island and treated at 27°C, 30°C and 32°C for 19 hours. Using a diving Pulse-Amplitude-Modulated (D-PAM) fluorometer, the effective quantum yield at photosystem II (FPSII) was recorded from the coral fragments initially and following 3, 6 and 19 hours of treatment. This experiment determined the thermal threshold of the understudied A. branchi and P. indiania, and detected the unexpectedly enhanced thermal tolerance of S. hystrix and G. fascicularis. Overall, it provides a preliminary insight into potential thermal stress tolerance in some Mauritius corals and has shown that these corals might have strategized to enhance their thermo-resilience while others are still struggling to withstand such stresses. These findings on the thermal resilience of regionally endemic/rare and morphologically different coral species are essential for further reef conservation efforts and the selection of coral species for reef restoration.

Abstract. Jogee SY, Jeetun S, Ricot M, Taleb-Hossenkhan N, Mattan-Moorgawa S, Kaullysing D, Riemann P, Blanc L, Casareto BE, Suzuki Y, Bhagooli R. 2023. Photo-physiology of healthy-looking and diseased/health-compromised hard corals from Mauritius Island, Western Indian Ocean. Indo Pac J Ocean Life 7: 27-37. The spatial photo-physiological responses of in hospite zooxanthellae in hard corals, including coenosarc and polyps, healthy-looking and affected parts in four coral diseases, namely Brown Band, Black Band, Skeletal Eroding Band and White Band on the coral Acropora muricata, and two health-compromised conditions such as the Pink Pigmentation Response and its differentiated morphology, the Pink Line Syndrome, on the coral Porites were investigated using the Imaging-PAM fluorometry. A significantly lower Fv/Fm was observed in case of Black Band, White Band, Brown Band and Pink Pigmentation Response affected parts compared to the healthy-looking parts. The Fv/Fm had the highest decline in Brown Band disease. Both the polyps and coenosarc had significantly lower Fv/Fm in White Band and Brown Band diseased parts compared to their healthy-looking parts. The rETRmax did not change significantly between diseased/health-comprised parts and healthy-looking parts. NPQmax declined significantly in White Band, Black Band and Pink Pigmentation Response cases. ? and ? generally did not tend to be affected in diseased/health-compromised conditions. The photo-physiology of in hospite zooxanthellae was least affected in Pink Line Syndrome. These findings suggest that diseased/health-compromised parts of corals behave differently in terms of their photo-physiology in different diseased and health-compromised coral conditions in important reef-building corals species such as A. muricata and Porites species, with important implications for the productivity and thus adaptive management of coral reefs in a globally warming ocean.