Lipidomic and physiological changes in the coral Acropora aspera during bleaching and recovery.

Heat stress and other factors cause the loss of endosymbiotic dinoflagellates by corals, and is known as coral bleaching. Coral reef bleaching is a global environmental problem. To better understand corals' responses and adaptability to stressful conditions, we applied a lipidomic approach in combination with cytometry and microscopy to study the coral bleaching of Acropora aspera under heat stress (32 °C) and subsequent recovery. For eight days of bleaching, the coral lost 50% of its symbiont population and 100% after a week of recovery. It took 126 days to fully recover the symbiont population, content of chlorophyll a and reserve lipids. There were degradations in symbionts' thylakoids and disruption of thylakoid lipid homeostasis. Variations in the content of phosphatidylinositols involved in apoptosis and autophagy and changes in the molecular profile of glycosylceramides that may be involved in the sphingosine rheostat were observed. However, upon A. aspera bleaching, the loss of symbionts was compensated by increased mucociliary nutrition. An increase in the content of hydroxylated ceramideaminoethylphosphonates for membrane stabilization and a decrease in ether phosphatidylethanolamines for providing protection from oxidative stress may have been used as adaptation mechanisms by the coral host. Thus, the coral undergoes physiological and biochemical changes during heat stress that are aimed at mitigating the adverse destructive effects, which may be key to successful recovery.