Photoinhibition of Symbiodinium spp. within the reef corals Montastraea faveolata and Porites astreoides: implications for coral bleaching
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It is speculated that differences in coral bleaching susceptibility may be influenced by the genotype of in hospite Symbiodinium and their differential responses to bleaching stressors. Photoinhibition of photosystem II (PSII), damage to the D1 (psbA) PSII reaction centre protein and production of reactive oxygen species by in hospite Symbiodinium are likely precursors of coral bleaching. In order to assess whether photorepair rates of in hospite Symbiodinium underlie the bleaching susceptibility of their hosts, photoinhibition (net and gross), photoprotection and photorepair rates were assessed in a bleaching-‘tolerant’ coral (P. astreoides) and a bleaching-‘sensitive’ coral (M. faveolata) using non-invasive fluorometric techniques and by blocking de novo synthesis of psbA. Previous studies using such techniques have demonstrated that in vitro Symbiodinium types ‘sensitive’ to bleaching stressors had reduced rates of photorepair relative to ‘tolerant’ Symbiodinum types. Our measurements demonstrated that Symbiodinium in the more bleaching tolerant P. astreoides had higher photorepair rates than Symbiodinium in M. faveolata. Higher repair rates in P. astreoides resulted in lower net photoinhibition relative to M. faveolata, where both corals exhibited similar susceptibility to photodamage (gross photoinhibition). Photoprotective mechanisms were observed in both corals; M. faveolata exhibited higher antennae-bed quenching than P. astreoides at low-light intensities, but at and above light-saturating intensities, which are different for each coral species, P. astreoides displayed more efficient non-photochemical quenching (Stern–Volmer quenching) of chlorophyll fluorescence than M. faveolata. Increased NPQ by P. astreoides at E/Ek ≥ 1 was not driven by antennae-bed quenching. The ability of in hospite Symbiodinium in P. astreoides to mitigate the effects of photoinhibition under high light conditions compared with Symbiodinium in M. faveolata, and their high repair capacity following photoinhibition, may be a key factor to consider in future bleaching studies and may underlie the relative bleaching tolerance of P. astreoides compared to M. faveolata.
KeywordsHigh Light Electron Transport Rate Coral Species Coral Bleaching PSII Reaction Centre
The authors wish to thank Roberto Iglesias-Prieto, Susana Enríquez, Robin Smith and the staff of the Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autónoma de México for their generous time and logistical support. This work was supported by funding from the National Science Foundation (award 0825490 to A. Grottoli, and award 0825413 to M. Warner). All work undertaken in this study complied with the current laws of Mexico and the United States of America.
- Baker NR, Oxborough K (2005) Chlorophyll fluorescence as a probe of photosynthetic productivity. In: Panageorgiou GC, Govindjee A (eds) Chlorophyll a fluorescence: a signature of photosynthesis. Advances in photosynthesis and respiration, vol 19. Springer, The Netherlands, pp 65–82Google Scholar
- Cosgrove J, Borowitzka MA (2010) Chlorophyll fluorescence terminology: an introduction. In: Suggett DJ, Prasil O, Borowitzka MA (eds) Chlorophyll a fluorescence in aquatic sciences: methods and applications. Springer, Dordrecht, pp 1–17Google Scholar
- Falkowski PG, Raven JA (1997) Aquatic photosynthesis. Blackwell Science, MAGoogle Scholar
- Hennige SJ, Suggett DJ, Warner ME, McDougall K, Smith DJ (2008b) Unravelling coral photoacclimation: Symbiodinium strategy and host modification. In: Proceedings of the 11th international coral reef symposium, Ft. Lauredale, FLGoogle Scholar
- Obura DO (2001) Can differential bleaching and mortality among coral species offer useful indicators for assessment and management of reefs under stress? Bull Mar Sci 69:421–442Google Scholar
- West JM, Salm RV (2003) Resistance and resilience to coral bleaching: implications for coral reef conservation and management. Conserv Biol 268:43–53Google Scholar