LABORATORY TEMPERATURE SELECTION IN SYMBIODINIUM CAN ENHANCE CORAL THERMAL RESILIENCE
Temperature increases of only 1 °C above summer maxima can cause coral bleaching. This breakdown in the endosymbiosis between coral and their Symbiodinium can cause considerable coral mortality. As coral bleaching tolerance is dependent on their symbionts, the human-assisted acceleration of evolutionary processes in Symbiodinium has been proposed as a strategy to enhance coral thermal resilience. We report an adaptive response in cultured Symbiodinium after only ~150 generations of thermal selection at 31 °C, a 4°C increase from the control temperature; the 31°C selected Symbiodinium outperformed the wild-type at 31°C, with higher growth rates, photosynthetic performance and lower extracellular reactive oxygen species production. At ambient temperature the performance of the selected-type was similar to that of the wild-type across most traits, indicating limited costs of thermal selection. Coral recruits of three Acropora species were subsequently inoculated at 27°C with both the selected and wild-type symbionts. Once symbiosis had established, a proportion of each was moved into 31°C. We observed species-specific differences in performance under elevated temperature. At 31°C, recruits harbouring the selected-type symbionts bleached slower than those infected with the wild-type cells, had greater photosynthetic capacities and exhibited similar growth to recruits harbouring selected and wild type symbionts at 27°C. Inoculation of corals with laboratory selected Symbiodinium may provide a highly valuable approach to enhance coral fitness in our warming oceans.
Chakravarti, L. J., James Cook University/Australian Institute of Marine Science/ARC CoE for Coral reef studies, Australia, firstname.lastname@example.org
Willis, B. L., James Cook University/ARC CoE for Coral Reef Studies, Australia, Bette.email@example.com
Leggat, B., James Cook University/ARC CoE for Coral Reef Studies, Australia, B.Leggat@jcu.edu.au
van Oppen, M., University of Melbourne/Australian Institute of Marine Science, Australia, firstname.lastname@example.org
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