Alexander Macadam - AIMS@JCU

Alexander Macadam

Recipient of an AIMS@JCU Scholarship

College of Science and Engineering

Alexander Macadam

College of Science and Engineering
Genomic prediction of heat tolerance in selectively-bred corals

Alex grew up in Devon, UK, where he spent his weekends at the beach searching for critters in the inter-tidal pools. As soon as he was old enough, Alex took the opportunity to learn to dive. This is where his fascination with coral reefs began. Alex perused a Bachelors (Hon) degree in Marine Biology at Swansea University and continued on to a Masters by Research. After graduating, Alex spent a year travelling, before securing a job as Research Coordinator at a research station in Norway. After several years in the Arctic, Alex was drawn back to the reef. For the past two years, he has been working at AIMS in several roles, including Experimental Research Technician with the Assisted Gene Flow project and Field and Lab Technician with the Water Quality team. Now, Alex is continuing his research journey at AIMS by pursuing a PhD examining genomic predictions of heat tolerance in selectively bred corals.

Genomic prediction of heat tolerance in selectively-bred corals

2022 to 2025

Project Description

This project will aim to identify the key underlying genomic drivers underpinning phenotypic trait variation in inter and intra- population offspring. Growth, survival, and temperature tolerance of offspring will be assessed across multiple life stages produced using selective breeding methods. A comparative genomic meta-analysis will be performed using bioinformatic/computational tools to investigate the genomics of heat tolerance of reefs globally, but with a particular focus on the Great Barrier Reef. Functional genomic datasets from across a range of species (oysters, corals, etc) will be queried to determine candidate genes associated with natural and adaptive heat tolerance. Genomic outputs will help us to quantify the feasibility, benefits, and risks of selective breeding by feeding into models of adaptive potential.

Project Importance

Tropical coral reefs are under threat from a range of stressors including environmental change caused by global warming, disease and other anthropogenic stressors. The future of coral reefs will greatly depend on the capacity of foundation coral species to adapt to changing conditions and for the development of restoration techniques that enhance this adaptive potential, like those proposed under selective breeding. Understanding the genetic basis of enhanced heat tolerance using an experimental design that incorporates selective breeding methods combined with an ‘omics and modelling approach will provide critical insight into how and the speed to which corals may be enhanced to respond to a rapidly changing climate. Genomic and transcriptomic techniques can identify genes that underly these enhanced phenotypes, and will inform applied modelling and management actions such as spatial planning and novel restoration techniques.

Project Methods

Gravid coral colonies will be collected from five reefs across a temperature gradient of the GBR and brought back to AIMS at the National Sea Simulator (SeaSim) to be reproductively crossed to produce offspring of mixed genetic background, inter and intra-population crosses. Once eggs and sperm are collected and fertilised to produce a number of different crosses, offspring (both larvae and post-settlement juveniles) will will be exposed to 27°C (ambient) and elevated temperatures (32-35.5°C) to assess their performance and determine if selective breeding can enhance targeted traits. Tolerance to heat stress will be assessed by measuring survival, growth, bleaching, and photosynthetic efficiency. Juveniles will be inoculated with either wild type or artificially heat-evolved symbionts prior to heating. Coral taxa x Symbiodiniaceae pairings will be examined for their fitness, thermal tolerance, trade-offs and stability. Coral-symbiont pairings with enhanced performance will be subjected to genomic and transcriptomic analyses to reveal the underlying genomic architecture of these phenotypic traits measured in these early life-stages. Genomic and transcriptomic analyses of the hybrid crosses will be compared to purebred crosses infected with a natural Symbiodiniaceae strains as controls. These genetic analyses will include, shallow-whole genome sequencing to extract single nucleotide polymorphism data to identify variants, and potentially genes, associated with heat tolerance and the corresponding physiological traits measured (survival, growth, bleaching).

Project Results

Preliminary results show that hybrid (mixed north and central parents) corals have either improved or equal survival at heat when compared to purebred central corals. These promising results show that assisted gene flow by selective breeding is a favourable intervention for reef restoration, however, in-situ survival of hybrid corals must be assessed to validate the technique.


Climate change,
Commercial use,
Controlled Environment,
Coral reefs,
Field based,
Management tools,
Manipulative experiments,
Molecular techniques,
Natural disturbance,
Ocean warming,
Quantitative marine science,
Remote Sensing