Bleaching in soft and scleractinian corals: Comparison of the physiology, genetics, and biochemistry of Symbiodinium

The symbiotic association of scleractinian corals with Symbiodinium has been well studied. Until now, very little attention has been given to the symbiotic associations of soft corals with Symbiodinium. Further, soft coral resistance to heat stress (one type of bleaching) has not been well described despite soft coral abundance exceeding that of scleractinian corals within some coral reefs. The aims of this thesis were to compare and contrast soft corals Sarcophyton ehrenbergi, Sinularia sp. and Xenia sp. to scleractinian corals Acropora hyacinthus, Favites complanata and Porites solida. The specific aims for each chapter were to: (1) establish the susceptibility of the different coral types to bleaching at elevated temperatures; (2) determine if resistance is related to different temperature tolerant Symbiodinium phytopigments; (3) ascertain Symbiodinium genotypes within each coral type (soft and scleractinian) and to determine if Symbiodinium genotypes are correlated with the tendency of hosts to bleach at higher temperatures; and (4) determine if Symbiodinium cell death arising from elevated temperatures is by apoptosis and/or necrosis.