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When corals bleach, what is the weakest photosynthetic link?

Funding: 2005: $58,000
2006: $38,000
2007: $38,000

Project Member(s): Ralph, P.

Funding or Partner Organisation: Australian Research Council (Other funds for ARC projects)
Australian Research Council (ARC Discovery Projects)

Start year: 2005

Summary: Coral bleaching threatens reefs around the world. Two hypotheses attempt to explain the impact of bleaching to the vulnerable photosynthetic apparatus of microalgae living within the coral host. These hypotheses suggest that an impact occurs at either Photosystem II or the dark CO2 fixation reactions, which leads to enhanced reactive oxygen production. This project will assess the impact of bleaching on a number of key Photosystem II component(s), as well as the dark CO2 fixation reactions. The project will also assess the capacity of the photosynthetic apparatus to acclimate to bleaching stress. The outcomes will provide critical information on the breakdown of the photosynthetic processes linked with coral bleaching.


Hill, R & Ralph, PJ 2008, 'Dark-induced reduction of the plastoquinone pool in zooxanthellae of scleractinian corals and implications for measurements of chlorophyll a fluorescence', SYMBIOSIS, vol. 46, no. 1, pp. 45-56.

Hill, R & Ralph, PJ 2008, 'Impact of bleaching stress on the function of the oxygen evolving complex of zooxanthellae from scleractinian corals', JOURNAL OF PHYCOLOGY, vol. 44, no. 2, pp. 299-310.
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Hill, R & Ralph, PJ 2005, 'Diel and seasonal changes in fluorescence rise kinetics of three scleractinian corals', FUNCTIONAL PLANT BIOLOGY, vol. 32, no. 6, pp. 549-559.
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Hill, R, Frankart, C & Ralph, PJ 2005, 'Impact of bleaching conditions on the components of non-photochemical quenching in the zooxanthellae of a coral', JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, vol. 322, no. 1, pp. 83-92.
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Ralph, PJ, Larkum, AWD & Kuhl, M 2005, 'Temporal patterns in effective quantum yield of individual zooxanthellae expelled during bleaching', JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, vol. 316, no. 1, pp. 17-28.
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Ralph, PJ, Schreiber, U, Gademann, R, Kuhl, M & Larkum, AWD 2005, 'Coral photobiology studied with a new imaging pulse amplitude modulated fluorometer', JOURNAL OF PHYCOLOGY, vol. 41, no. 2, pp. 335-342.
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Keywords: photosynthesis, coral, microalgae, physiology, coral bleaching,

FOR Codes: Marine and Estuarine Ecology (incl. Marine Ichthyology), Phycology, Living resources (incl. impacts of fishing on non-target species), Living resources (flora and fauna), Phycology (incl. Marine Grasses), Marine Flora, Fauna and Biodiversity, Marine biodiversity