Assessing the potential for “assisted gene flow" to enhance heat tolerance of multiple coral genera over three key phenotypic trails (RRAP_ECT2.1; Years 1+2)

Updated: 2026-06-30

This data was collected as part of the Reef Restoration and Adaptation Program (RRAP). Year 1 heat stress experiments were conducted on adult Acropora kenti (formerly A. tenuis), A. tersa (formerly A. hyacinthus "neat"), and Goniastrea retiformis as well as larvae and recruits generated from A. kenti and A. tersa adults (i.e., broodstock). Year 2 heat stress experiments were conducted on A. tersa larvae and recruit offspring groups. Year 1 and 2 experiments were collectively run between 01 November 2020 - 01 April 2022. The overall aim was to further our understanding about the potential benefits of using thermal history provenancing-informed selective breeding to generated offspring with enhanced resilience. Mass coral bleaching and mortality events have increased in frequency over the last 30 years. Genetic interventions like assisted gene flow may speed up adaptation in reefs with less heat-tolerant corals by increasing the frequency of heat tolerance-associated genetic variants. To investigate, we generated reproductive crosses of corals from reefs along a thermal gradient on the Great Barrier Reef, comparing fitness traits in intra-region and inter-region offspring from three species (Acropora kenti, A. hyacinthus, and Goniastrea retiformis). Juveniles were inoculated with three heat-tolerant symbionts: Durusdinium trenchii, a heat-evolved Cladocopium goreaui strain, and “wild” symbionts from northern reef sediments. Survival, growth, colour change, and effective quantum yield of photosystem II (YII) were measured across larvae, juveniles, and adults at elevated and ambient temperatures. Results showed higher survival in some inter-region crosses compared to intra-region crosses from central reefs in larvae and juvenile corals, though enhancement varied by species. Heat-tolerant parents did not always produce heat-tolerant offspring and larval heat tolerance did not consistently persist to juveniles. Parent genetic background influenced survival more than innoculated symbiont. These findings underscore the complexity of heat tolerance acquisition in early coral life stages.