Lack of evidence for the oxidative stress theory of bleaching in the sea anemone, Exaiptasia diaphana, under elevated temperature

Abstract To survive in nutrient-poor waters corals rely on a symbiotic association with intracellular microalgae. However, increased sea temperatures cause algal loss—known as coral bleaching—often followed by death. Some of the most compelling evidence support ‘oxidative stress theory bleaching’ comes from studies that exposed corals, cultures their endosymbionts, or model Exaiptasia diaphana to exogenous antioxidants during thermal stress. Here, we replicate these experiments using E. addition ascorbate + catalase, catechin, mannitol under ambient and elevated along an antioxidant-free control. In absence antioxidants, bleached no change reactive oxygen species (ROS) levels associated microalgal cells. Ascorbate catalase treatments rescued anemones bleaching, although ROS antioxidant temperature conditions. While bleaching was not changes net for symbionts, it is evident our findings excess connected phenotype were successful mitigating effects cnidarians. This understanding may assist applied research aims reduce impact climate reefs.