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Bleaching tolerance and adaptation

There is heated debate about whether corals can adapt quickly enough to cope with climate change.

AIMS is investigating whether corals have sufficient heritable variation in heat tolerance to adapt to climate change over the next several generations. We are also examining the direct adaptive response to selection in the laboratory.

Genetic adaptation occurs when heritable gene variants (such as genes that confer higher or lower heat tolerance) become more common or rare in a population over generations as a result of natural selection.

Bleaching resistance varies between and within coral species, and depends on many factors associated with the host and their algal symbionts, including:

  • the heat stability of certain membranes in the symbiont cell
  • the ability of the zooxanthellae to dissipate excess light energy
  • the density and dynamics of different symbiont types in coral tissues
  • the amount of photo-protective proteins and anti-oxidant enzymes that the coral can produce.

AIMS is investigating the genes underlying the variation of bleaching resistance in coral by comparing the gene products from corals in warm and cooler environments, and from heat-stressed and non-stressed corals.

Once AIMS has identified the genes underlying these variations, the distribution of gene variants in warm and cooler regions may point to those that confer the highest heat tolerance. This can be tested in aquarium-based studies using colonies with gene variants that are suspected or known to play a role in heat tolerance.

Our researchers are also investigating if and how coral parents pass their tolerance on to their offspring. Our research is revealing that temperature-tolerant parents have more tolerant offspring than coral parents less tolerant of high temperatures.

This information can help identify reef coral populations that are either sensitive to or tolerant of bleaching, which will contribute to risk mapping of coral reefs. It can also inform selective breeding of corals and assisted migration of tolerant corals into sensitive populations if this becomes necessary in the future.