Recovery of a symbiotic octocoral Sinularia heterospiculata after heat stress exposure

Abstract

ABSTRACT Extending our knowledge about the bleaching and recovery processes in octocorals can offer valuable insights to predict future reef responses to continuing climate change. The octocoral Sinularia heterospiculata was exposed to a heat stress (32°C) for 2 days and then recovered within 205 days. The coral’s response was assessed by measuring total lipids, chlorophylls , carotenoids, and relative endosymbiont density. During the bleaching period, the coral lost half of its dinoflagellate symbionts; during the recovery period, it could completely restore their population. Photosynthetic activity of dinoflagellate symbionts was reduced after 1 week of recovery. However, the level of lipids was stable. The contents of chlorophyll b after the 2-day bleaching period increased relative to their proportion in the endosymbionts, which may be associated with the chlorophyll repackaging and absorption of more light. The content of carotenoids increases, which is probably associated with the complementary function of carotenoids as antioxidants.