Response of holosymbiont pigments from the scleractinian coral Montipora monasteriata to short-term heat stress

Abstract

Heating the scleractinian coral, Montipora monasteriata (Forskȃl 1775) to 32ЊC under Ͻ650 mol quanta m Ϫ2 s Ϫ1 led to bleaching in the form of a reduction in Peridinin, xanthophyll pool, chlorophyll c 2 and chlorophyll a, but areal dinoflagellates densities did not decline. Associated with this bleaching, chlorophyll (Chl) allomerization and dinoflagellate xanthophyll cycling increased. Chl allomerization is believed to result from the interaction of Chl with singlet oxygen ( 1 O 2 ) or other reactive oxygen species. Thermally induced increases in Chl allomerization are consistent with other studies that have demonstrated that thermal stress generates reactive oxygen species in symbiotic dinoflagellates. Xanthophyll cycling requires the establishment of a pH gradient across the thylakoid membrane. Our results indicate that, during the early stages of thermal stress, thylakoid membranes are intact. Different morphs of M. monasteriata responded differently to the heat stress applied: heavily pigmented coral hosts taken from a high-light environment showed significant reductions in green fluorescent protein (GFP)-like homologues, whereas nonhost pigmented high-light morphs experienced a significant reduction in water-soluble protein content. Paradoxically, the more shade acclimated cave morph were, based on Chl fluorescence data, less thermally stressed than either of the high-light morphs. These results support the importance of coral pigments for the regulation of the light environment within the host tissue.

Mechanisms of Thermal Tolerance in Reef-Building Corals across a Fine-Grained Environmental Mosaic: Lessons from Ofu, American Samoa

“…Indeed, data from Ofu show that significant gains in thermal tolerance can be achieved within roughly a week of preconditioning (Bay and Palumbi, 2015). Similarly, studies from other regions and on other coral taxa have revealed significant gains in thermal tolerance after days of preconditioning (Brown et al, 2002;Dove et al, 2006;Middlebrook et al, 2008;Bellantuono et al, 2012b). For example, Middlebrook et al (2008) showed that gains in thermal tolerance in A. aspera can occur in as little as 48 h of preconditioning.…”

“…More recently, focus has shifted toward understanding the plasticity of thermal tolerance in corals, and numerous studies have identified a direct link between thermal preconditioning and bleaching susceptibility from both field observations (Castillo and Helmuth, 2005;Maynard et al, 2008;Thompson and van Woesik, 2009;Castillo et al, 2012;Shuail et al, 2016) and experimental manipulation (Brown et al, 2000(Brown et al, , 2002Dove et al, 2006;Middlebrook et al, 2008;Bellantuono et al, 2012b;Bay and Palumbi, 2015). For example, Acropora, Pocillopora, and Porites from the Great Barrier Reef showed lower rates of bleaching during the 2002 bleaching event than the 1998 event, despite more intense conditions during the 2002 event (Maynard et al, 2008).…”

Locally accelerated growth is part of the innate immune response and repair mechanisms in reef-building corals as detected by green fluorescent protein (GFP)-like pigments

“…A downregulation of particular FP-encoding transcripts was previously reported, for instance, in response to heat stress, strong irradiation, bleaching and translocation (Dove et al 2006;Leutenegger et al 2007a;D'Angelo et al 2008;Bay et al 2009). The distinct response of several FP genes to various changes in the environmental conditions suggests that further biomarker assays can be developed that employ these pigments as the urgently needed intrinsic markers of coral health (D'Angelo et al 2008).…”

Different thermal sensitivity of the repair of photodamaged photosynthetic machinery in cultured Symbiodinium species

“…Thus, corals that harbor Symbiodinium where PSII repair is thermally sensitive are more susceptible to photoinhibition and, accordingly, more prone to coral bleaching under elevated seawater temperature. However, it should be noted that the sensitivities of photoinhibition and coral bleaching are not determined only by the properties of the Symbiodinium species, because host factors, such as the production of host pigments (34,35) and the colony morphology of corals (36), also have the potential to influence these sensitivities. Recent studies have demonstrated that thermally induced photoinhibition is strongly associated with coral bleaching caused by photobleaching of photosynthetic pigments in individual Symbiodinium in corals (21,26).…”