Reproductive histology and energetics in Acropora hyacinthus in response to the 2019 Moorea bleaching event.

The French Polynesian island of Mo’orea experienced a severe mass bleaching event in 2019 accompanied by widespread coral mortality. At the most heavily impacted sites, Acropora hyacinthus individuals that were resistant to bleaching were observed alongside colonies that bleached but showed signs of symbiont recovery shortly after the bleaching event. Fragments of healthy A. hyacinthus colonies five months post-bleaching were sampled for energetic assays and histological measurements. Despite healthy appearances in both resistant and recovered corals, recovered colonies had significantly reduced energy reserves compared to resistant colonies. In addition, compound effects of stress on reproduction were observed: recovered colonies displayed both a lower probability of containing gametes and lower fecundity per polyp.