Seeding reefs with heat tolerant corals could enhance reef resilience under climate change. Selective breeding is an intervention that might be used to generate heat tolerant corals for reef restoration. We estimated thermal thresholds for gravid colonies of two Acropora species from Moore Reef and Davies Reef on the Great Barrier Reef using the Sea Simulator In A Box experimental system on AIMS research vessel, the Cape Ferguson. Rankings of photochemical efficiency thermal thresholds were used to select broodstock and selectively breed offspring in the National Sea Simulator. We then tested the heat tolerance of the offspring using the laboratory facilities at AIMS. The collected data was analysed to evaluate: 1) whether a rapid heat stress assay can be used to identify heritable heat tolerance in coral populations and 2) whether there is a trade-off between coral heat tolerance and fecundity that could impact the efficacy of selective breeding.

In the last 30 years, more than 2,000 research papers have been published on the impact of temperature stress on coral reef organisms. We conducted a systematic review of the literature to objectively examine what is known about the potential for natural adaptation of corals to increased temperatures and the effect sizes of assisted evolution efforts that have been documented to date. To identify relevant studies, we conducted a literature search (October 27, 2022) using the ISI Web Of Science database and search engine with the following strings to identify relevant peer-reviewed publications: Title = coral, Topic = bleach AND adapt, heat AND adapt, temperature AND adapt, acclimat AND adapt, acclimat AND bleach, acclimat* AND temperature, temperature AND bleach, assisted AND evolution, assist AND gene AND flow, assisted AND migration, gene AND edit, selective AND breed. The initial search returned 2,397 papers that met the above criteria. These papers were examined to assess if the study included the following elements: (1) a heat stress condition under laboratory or field conditions, (2) samples from any life history stage of a coral holobiont (excluding host-tissue extractions that were cultured in the lab, separated from the exoskeleton, or papers based solely on cultures of isolated symbionts or microbes and ignoring the coral holobiont), and (3) data reported for at least one coral species in the order Scleractinia from a tropical environment. In the end, 562 publications included all three elements. In some instances, multiple publications were found to report different aspects of the same heat stress experiment, but these were treated as independent experiments given that there was no duplication of data. Included in this collection is the R code for mapping products presented in the publication, which built on the source dataset Marine Ecoregions Of the World (MEOW).

Wild coral colonies of Acropora tenuis were collected throughout the Great Barrier Reef and transferred to the Australian Sea Simulater (SeaSim). Corals were spawned, and produced purebred and hybris crosses, see Quigley & van Oppen (2022) and Dixon & Kenkel (2019) for full details of spawning and reproductive crossing. Larvae produced from these crosses were sampled for gene expression and assayed using RNAseq before being exposed to control and heat stress for 36 hours (27 and 35.5 °C) in replicates of n=6 (“post” exposure samples). Separate cohorts of each larval cross not used in the heat trials were then induced to settle and exposed to four symbiont treatments. These replicates were sampled for RNAseq for each of the crosses prior to the heat stress at time 0 and 56 hours at 27°C and 35.5°C treatments. For survival measurements, individual larvae were counted within net-wells in replicate plates within each temperature treatment. Each larval survival measurement represents a discrete sample measurement. The unit of measure is the number of individual replicate wells containing larvae. Juvenile replicates RNAseq samples were taken in each of the crosses after 58 days at 27 and 32°C. Survival measurements represent individual juvenile survival. Each represents a discrete sample measurement. The unit of measure is the number of individual replicate juveniles per replicate well, per replicate plate, per replicate tank for each temperature and symbiont treatment. Larval survival was counted from 0 to 56 hours at 27°C and 35.5°C. Juvenile survival was counted at 0 and after 58 days at 27 and 32°C treatments. Larvae were assayed for RNAseq at 0 and 56 hours, and juveniles only at 58 days. Experimental metadata of detailed replicates for larval treatments are found on the github repository in file J19188meta.csv. For“pre”, and “post-ambient” there were 33 larval replicates. For “post-hot” there were 30 replicates. Each replicate represented 10 pooled larvae. Each of the 11 crosses was replicated 3 times within each of those 3 treatment groups. There was a total of 96 larval samples. Experimental metadata for juvenile data is found on the github repository in file J19234meta.csv. Of the juvenile samples, 119 werein ambient conditions with 27 in the heat treatment. Each of the 10 crosses was represented in the juvenile dataset 12-18 times. Thesymbiont treatments had 29 samples in C1, 38 samples in D1, 43 samples in SED, and 36 in SS1. There was a total of 146 juvenile samples. Derived statistics presented are defined as independent observations of n= independent larval or juvenile survival based on the number

Phenotypic variation in the heat tolerance of reef-building corals was measured across the Great Barrier Reef under the Reef Restoration and Adaptation Program’s Genetic Basis of Coral Traits project. This dataset encompasses measurements of experimental acute heat stress responses for 768 colonies of Acropora spathulata from 14 reefs, along with associated field metadata, environmental variables, and scripts used to analyse variation in heat tolerance traits.

The data set consists of whole transcriptome sequences (RNA) and physiological responses of 60 corals to an acute heat stress experiment. These data provide new insight into the genetic mechanisms that underlie recovery from heat stress in coral and highlight the role of transcriptional plasticity in the resilience of coral to increasing disturbances. Coral samples were collected on November 29th from Bundegi Reef in the Ningaloo Reef Marine Park, part of the Ningaloo Coast World Heritage Area. Samples were collected on SCUBA, total RNA was isolated, sequenced and analysed using DeSeq2.0 (Love et al., 2014).

Acropora tenuis colonies were collected from three thermally distinctive reefs and reproductively crossed to create 85 offspring lineages. Experiments in heat tolerance were performed in adult and early life stages: larval and settlement. The experiments aimed to understand acquired heat tolerance via outcrossing of offspring phenotypes by comparing five physiological responses: photosynthetic yields bleaching necrosis settlement survival Heat stress experiments were conducted at the larval, settlement and adult stages. Statistical analysis was undertaken for each experiment to examine the differences in larval survival, percentage of settled larvae, and differences in the photophysiologial responses of adults.

Mass coral bleaching and mortality events have increased in frequency over the last 30 years, with ocean temperatures projected to reach bleaching thresholds annually by 2050. 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, but the effectiveness of the intervention across species and life stages remains uncertain. 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 (same region) and inter-region (different 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, to assess symbiosis impacts on heat tolerance. Survival, growth, colour change (proxy for bleaching), and effective quantum yield of photosystem II (YII) were measured across larvae, juveniles, and adults at elevated (32 °C, 35.5 °C) and ambient (27.5 °C) 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. Furthermore, heat-tolerant parents did not always produce heat-tolerant offspring, and larval heat tolerance did not always persist to the juvenile stage. Parent genetic background influenced survival more than symbiont treatment. These findings underscore the complexity of heat tolerance acquisition in early coral life stages. See Macadam et al (2025) for full details - https://doi.org/10.1016/j.biocon.2025.111155

This study whether corals from the warmer reef produced more thermally tolerant hybrid and purebred offspring compared with crosses produced with colonies sourced from the cooler reef and whether different symbiont taxa affect heat tolerance. Juveniles were infected with Symbiodinium tridacnidorum, Cladocopium goreaui and Durusdinium trenchii and survival, bleaching and growth were assessed at 27.5°C and 31°C. The experiment focused on familial crosses produced from (n=3) parents from a warm far northern reef (WW1, WW2, WW3), one cross with a warm dam and cool sire (WC) and one cross with a cool dam and warm sire (CW). Larvae from each cross were allowed to settle, and grown on plugs for 11 days. Juveniles were exposed to one of three treatments of the following Symbiodiniaceae taxa cultured at the Australian Institute of Marine Science Algal Culture Facility: S. tridacnidorum (monoclonal SCF022.01), C. goreaui (monoclonal SCF055-01.10) and D. trenchii (heterogeneous SCF082) as described in Quigley et al. (2014) All inoculated juveniles were subsequently kept at 27.5°C for 8 days and symbiosis establishment was visually confirmed over this period under a microscope. Plugs were then randomly divided across treatment tanks, and half from each symbiosis-establishment treatment were placed into 31°C treatment tanks without ramping, totalling six tanks (three replicate tanks at 27.5°C and three replicate tanks at 31°C). Juvenile survival, bleaching and growth were assessed through image analysis, starting on the first day of exposure to 31°C, with five time points measured and analysed at 1, 9, 35, 49 and 70 days of heat exposure. Juveniles were scored as highly pigmented (3=D6), pale (2=D4), bleached (1=D1, translucent tissue), or dead (0, missing or bare skeleton with or without algal or cyanobacterial overgrowth) Statistical analyses completed in R using generalisezd linear models and percent change in the bleaching score and juvenile area were calculated for each individual juvenile across host genetic background and symbiont type. See Quigley et al (2020) for full details.

Interspecific hybridisation increases genetic diversity and has played a significant role in the evolution of corals in the genus Acropora. In vitro fertilisation can be used to increase the frequency of hybridisation among corals, potentially enhancing their ability to adapt to climate change. Here, we assessed the field performance of hybrids derived from the highly cross-fertile coral species Acropora sarmentosa and Acropora florida from the Great Barrier Reef. Following outplanting to an inshore reef environment, the 10-month survivorship of the hybrid offspring groups was intermediate between that of the purebred groups, although not all pairwise comparisons were statistically significant. The A. florida purebreds, which had the lowest survivorship, were significantly larger at 10 months post-deployment compared to the other three groups. The four offspring groups harboured the same intracellular photosymbiont communities (Symbiodiniaceae), indicating that observed performance differences were due to the coral host and not photosymbiont communities. The limited differences in the performance of the groups and the lack of outbreeding depression of the F1 hybrids in the field suggest that interspecific hybridisation may be a useful method to boost the genetic diversity, and as such increase the adaptive capacity, of coral stock for restoration of degraded and potentially genetically eroded populations.

Phenotypic variation in the heat tolerance of reef-building corals was measured across the Great Barrier Reef under the Reef Restoration and Adaptation Program’s Genetic Basis of Coral Traits project. This dataset focuses on measurements of experimental acute heat stress responses for 583 colonies of Acropora hyacinthus from 17 reefs, along with bleaching responses for an additional 60 colonies at 1 reef. Data includes physiological response variables, field collection metadata, host genomic cluster assignments, Symbiodiniaceae ITS2 variants, environmental predictor variables, as well as scripts used to analyse variation in heat tolerance traits.