Reproductive resilience: pathways to gametogenic success in Montipora capitata after bleaching.

Abstract

Thermal bleaching, or the loss of symbiotic algae that provide most energetic resources for the coral host, is an increasing threat to reefs worldwide and is projected to worsen with climate change. While bleaching is a well-recognized threat, the impact on the process of reproduction in bleaching survivors is not well resolved, despite being central to coral resilience. Montipora capitata can survive bleaching while completing a full gametogenic cycle, offering an ideal system to study gametogenic resilience and physiological tradeoffs. We experimentally bleached fragments of M. capitata colonies and followed their gametogenesis and physiological responses for 10months (six time points). All bleached colonies produced gametes at the same time as controls, suggesting that reproductive processes were energetically prioritized. However, proteomic analysis revealed tradeoffs and delays in activating key physiological processes earlier in gametogenesis in areas such as skeletal growth and reproductive hormone synthesis. Tradeoffs during the gametogenic cycle, likely a direct response to thermal bleaching, resulted in smaller oocytes from bleached colonies, potentially indicating decreased transfer of parental resources to gametes. While gametogenesis is likely to continue in this species, it is unknown how the fecundity, synchrony of spawning, viability and success of future offspring may be impacted by future bleaching events.