Coral reefs are under threat by ocean warming leading to the death of the endosymbiotic Symbiodinium with consequent bleaching. Several experiments proved Symbiodinium capacity for warming adaptation. We assessed the cost of adaptation to warmer conditions in Red Sea isolated Symbiodinium adriaticum long-term adapted to ambient (26 ºC) and warming (32 ºC) temperatures. Temperature adaptation’s trade-offs were tested in population growth, photosynthetic performance and oxidative stress. Ambient adapted cultures reached higher growth rates, but warming adapted strain showed a higher optimum growth temperature. Production of intracellular reactive oxygen species (ROS) was similar in both strains at low and medium temperatures. However, at 32 ºC, warming adapted strain kept the same levels of reactive oxygen species as in lower temperature treatments, clearly showing a better capacity to cope with thermal stress. Photosynthetic performance was measured using the maximum photochemical quantum yield (Fv/Fm). Ambient adapted strain showed a significant decrease in photosynthetic performance in all treatments above 26 ºC along the experiment, whereas Fv/Fm values were more stable for warming strain. We demonstrated that warming adapted strain seems to cope better with thermal stress and its main consequence, ROS production, by keeping same production levels or not affecting its removal capacity, although reducing maximum growth rate. We also exposed the two adapted strains to UVB radiation to analyze whether warming adaptation could represent a cost facing multiple stressors.

Primary Presenter: Isabel Armelles Vicent, King Abdullah University of Science and Technology (KAUST) (isabel.armellesvicent@kaust.edu.sa)

Authors:

Isabel Armelles, King Abdullah University of Science and Technology (KAUST), Red Sea Research Center (RSRC)  (isabel.armellesvicent@kaust.edu.sa)

Ananya Ashok, King Abdullah University of Science and Technology (KAUST), Red Sea Research Center (RSRC)  ()

Manuel Aranda, King Abdullah University of Science and Technology (KAUST), Red Sea Research Center (RSRC)  ()

Carlos Manuel Duarte, King Abdullah University of Science and Technology (KAUST), Red Sea Research Center (RSRC) and Computational Bioscience Research Center (CBRC)  ()

Susana Agusti, King Abdullah University of Science and Technology (KAUST), Red Sea Research Center (RSRC)  ()