Variable PSII functioning and bleaching conditions of tropical scleractinian corals pre-and post-bleaching event

Abstract

Mattan-Moorgawa S, Rughooputh SDDV, Bhagooli R. 2017. Variable PSII functioning and bleaching conditions of tropical scleractinian corals pre-and post-bleaching event. Ocean Life 1: 1-10. This study compared pre-bleaching and post-bleaching conditions of eight reef-building corals, Acropora cytherea, Acropora hyacynthus, Acropora muricata, Acropora sp., Pocillopora damicornis, Pocillopora eydouxi, Galaxea fascicularis and Fungia sp., in terms of visual coloration (non-bleached (NB), pale (P), partially bleached (PB) and bleached (B)) and chlorophyll fluorescence yield at photosystem II (PSII)). A total of twenty colonies from twelve stations along four transects were surveyed at Belle-Mare, Mauritius, from October 2008 to October 2009, and compared to the CoralWatch Coral Health Chart. PSII functioning, measured as Fv/Fm, were recorded in coral samples using a pulse-amplitudemodulated (PAM) fluorometer. Physico-chemical parameters (sea surface temperature, dissolved oxygen, salinity and pH) were recorded in situ. An increase in SST up to 31.4ºC in February 2009 triggered the bleaching event observed in May 2009 at the site. Acroporids showed the first sign of bleaching and paling as from January 2009 when mean SST was at 30ºC. Branching coral (P. eydouxi) and solitary coral (Fungia sp.) exhibited only 15% of their colonies showing paling by April 2009. A. cytherea, A. hyacynthus, and A. muricata showed varying bleaching conditions [Pale (P), Partially-bleached (PB) and Bleached (B)] at onset of the bleaching event whilst Acropora sp. showed only a paling of its colonies. Post-bleaching data indicated a differential recovery in visual coloration and PSII functioning among the corals. P. eydouxi and Fungia sp. showed no bleaching conditions throughout the study. P. damicornis and G. fascicularis indicated a quick coloration recovery from P to NB after the bleaching event, although their maximum quantum yield at PSII did not show significant changes in P and NB samples. A. muricata recovered faster than A. hyacynthus and A. cytherea in terms of PSII functioning. A differential recovery was observed post-bleaching event among the eight coral species, in terms of recovery of color and PSII functioning. The order of recovery was as follows: massive-like/ solitary corals > branching and semi-bulbous corals > tabular corals.

Differential responses of effective quantum yield to acute thermal stress in scleractinian corals including pre- and post-transplanted Acropora muricata

“…Thick-tissued massive and encrusting corals have a more effective photo-protective capacity as they retract their tissue and self-shade better than thintissued corals (Brown 1997;Hoegh-Gulberg 1999). A study on the differential bleaching observations and postbleaching PSII functioning recovery showed paled P. damicornis and G. fascicularis, displayed no significant changes in fluorescence quantum yield while bleached A. muricata recovered faster than A. cytherea post-bleaching (Mattan-Moorgawa et al 2018). Bleaching susceptibility was significantly different among corals ascribed to each growth form, whereby a much higher proportion of branching, tabular and submassive corals bleached, compared to encrusting, massive and free-living corals.…”

“…Similarly, overall live coral cover showed a noticeable decreasing trend between 2007 and 2009, while algal cover increased significantly at most sites (Bhagooli et al 2021a;Bhagooli and Kaullysing 2019). A study done during the 2010 bleaching event revealed differential recovery of different corals under variable bleaching conditions at Belle Mare, stating that there was no significant change in the PSII functioning of the pale colonies of Pocillopora damicornis and Galaxea fascicularis post-bleaching while bleached A. muricata had a higher Fv/Fm and a faster recovery than A. cytherea (Mattan-Moorgawa et al 2018). Differential coral bleaching and photo-physiological responses among corals are not restricted to around Mauritius only but have also been reported at the Saya de Malha, Mascarene Plateau, Indian Ocean (Bhagooli et al 2021b).…”

Rare coral and reef fish species status, possible extinctions, and associated environmental perceptions in Mauritius

“…In 2010, six studied sites exhibited a 96-100% decline in coral cover (Bhagooli et al, 2021). However, several studies have documented intra-and inter-species variability in coral responses that suggest the potential for resistance and sanctuary from stress (Bhagooli & Taleb-Hossenkhan, 2012;Louis et al, 2016;Louis et al, 2020;Mattan-Moorgawa, Bhagooli, & Rughooputh, 2012;Mattan-Moorgawa, Rughooputh, & Bhagooli, 2018;McClanahan et al, 2005). The consequences of thermal and other stresses on the habitats and status of the rare and endemic corals is, however, undocumented.…”

Diplosoma simile (Ascidiacea: Didemnidae) distribution and its photosynthetic thermal stress responses from Mauritius: Implications for invasive or opportunistic behavior

“…Coral bleaching and reef degradation rates are escalating worldwide and locally, mostly due to increasing global temperatures and exposure to anthropogenic-related stressors (Mattan-Moorgawa et al 2012;Louis et al 2016;2020;Hughes et al 2017;Bhagooli and Kaullysing 2019;Bhagooli et al 2021a) and some reefs are predicted to be "locally extinct" (Sheppard 2003;Bhagooli and Sheppard 2012). It is generally considered that corals bleach, whereby they lose their zooxanthellae and/or the zooxanthellae photosynthetic pigments (Glynn 1993), and this disassociation between the coral animal and its dinoflagellate zooxanthellae occurs in most cases due to the zooxanthellae photosynthetic dysfunctioning under thermal and light stressors (Iglesias-Prieto et al 1992;Warner et al 1996;1999;Jones and Hoegh-Guldberg 1998;Bhagooli 2013).…”