Study finds robust corals are primed against bleaching

6 November 2018

Our study found that robust corals possess a unique capacity to generate the essential amino acid, histidine, which appears to help these corals cope with the effects of climate change.

A study led by ANU and James Cook University has found that robust reef-building corals are the only known animals to make an amino acid that could make them less susceptible than other corals to bleaching and climate change.

Amino acids, the building blocks of life, are crucial for repairing tissue or growing new tissue.

Corals can be divided into two major groupings: robust and complex. Using advanced genomic techniques, the research team found that the robust group, which includes several brain and mushroom corals, shares a key physiological advantage over complex corals.

Dr Hua Ying from ANU and Professor David Miller from the ARC Centre of Excellence for Coral Reef Studies at James Cook University led the study, which was supported by the Great Barrier Reef Foundation and Bioplatforms Australia.

"Our study found that robust corals possess a unique capacity to generate the essential amino acid, histidine, which appears to help these corals cope with the effects of climate change," said Dr Ying from the ANU Research School of Biology.

Generating amino acids is costly for animals, so they usually only generate 11 of the 20 required for life. The remaining nine amino acids are called the essential amino acids because they must be supplied by the animal's diet. Corals' diet includes tiny drifting animals known as zooplankton.

"When global warming causes corals to bleach, they expel their resident microalgae called Symbiodinium - which help provide corals with essential amino acids and also most of the energy needed to build their hard skeletons - and then they are suddenly dependent on their diet to meet this nutritional requirement," Dr Ying said.

"The advantage that robust corals have over other types of corals is that they can make at least one of the essential amino acids without the need of acquiring them from Symbiodinium. In turn, this might give robust corals extra protection against bleaching compared with complex corals like branching staghorns, at least in the short term."

Until now, scientists did not know why some corals only host a specific Symbiodinium type and others are less particular.

"Our research suggests that robust corals are potentially less choosey about which species of microalgae can take up residence in the coral tissue. The ability to host a broader range of Symbiodinium types could facilitate more rapid acclimation to higher temperatures," Professor Miller said.

The study, published in the prestigious journal Genome Biology, is part of the Sea-quence project, which is an initiative of the ReFuGe 2020 consortium.

ReFuGe 2020 (short for Reef Future Genomics) is a collaboration of the Great Barrier Reef Foundation, Australian Institute of Marine Science, Great Barrier Reef Marine Park Authority, Bioplatforms Australia, James Cook University, King Abdullah University of Science and Technology, University of Queensland and ANU, supported by Rio Tinto, Bioplatforms Australia through NCRIS, the Fitzgerald Family Foundation and the Australian Government.