Species-specific interactions between algal endosymbionts and coral hosts define their bleaching response to heat and light stress |
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Authors: | Abrego David Ulstrup Karin E Willis Bette L van Oppen Madeleine J H |
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Institution: | AIMS@JCU and ARC Centre of Excellence for Coral Reef Studies, School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia Australian Institute of Marine Science, PMB 3 MC, Townsville, Queensland 4810, Australia. |
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Abstract: | The impacts of warming seas on the frequency and severity of bleaching events are well documented, but the potential for different Symbiodinium types to enhance the physiological tolerance of reef corals is not well understood. Here we compare the functionality and physiological properties of juvenile corals when experimentally infected with one of two homologous Symbiodinium types and exposed to combined heat and light stress. A suite of physiological indicators including chlorophyll a fluorescence, oxygen production and respiration, as well as pigment concentration consistently demonstrated lower metabolic costs and enhanced physiological tolerance of Acropora tenuis juveniles when hosting Symbiodinium type C1 compared with type D. In other studies, the same D-type has been shown to confer higher thermal tolerance than both C2 in adults and C1 in juveniles of the closely related species Acropora millepora. Our results challenge speculations that associations with type D are universally most robust to thermal stress. Although the heat tolerance of corals may be contingent on the Symbiodinium strain in hospite, our results highlight the complexity of interactions between symbiotic partners and a potential role for host factors in determining the physiological performance of reef corals. |
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Keywords: | Symbiodinium coral bleaching heat stress photosystem II oxygen consumption and respiration xanthophylls |
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