Heat-resistant coral to fight bleaching

By Georgia Kelleher

14 May 2020

4 minute read

The Great Barrier Reef from the sky

Heat-resistant coral is being built to handle the heat in the Great Barrier Reef.

You’ve likely heard the saying “if you can’t handle the heat, get out of the kitchen”. But what if the kitchen is actually the ocean and you’re merely a piece of coral just trying to get by? You can’t get out – but it turns out you can get a little more resilient.

We’re part of a collaborative team of scientists that has successfully grown coral in a laboratory setting that is more resistant to increased seawater temperatures.

So why is it important that coral be built to handle the heat?

Heat-resistant coral has the potential to reduce the impact of reef bleaching. This bleaching can come as a result of marine heatwaves. As a result of climate change, marine heatwaves are becoming more common.

Speaking of current events

The coral-focused taskforce included researchers from our Synthetic Biology Future Science Platform (SynBio FSP), the University of Melbourne and Australian Institute of Marine Science (AIMS).

Our science lead, Dr Patrick Buerger, said coral reefs are in decline worldwide.

“Climate change has reduced coral cover, and surviving corals are under increasing pressure as water temperatures rise and the frequency and severity of bleaching events increase,” he said.

Bleached Coral

Bleached coral on the Great Barrier Reef. Credit: Chris Jones

How to create heat-resistant coral

So, how did they do it?  The first step to making coral more tolerant of temperature-induced bleaching is olstering the heat tolerance of its microalgal symbionts. These are tiny cells of algae that live inside the coral tissue and supply the coral with nutrients.

“Our novel approach strengthens the heat resistance of coral by manipulating its microalgae, which is a key factor in the coral’s heat tolerance,” Dr Buerger said.

The team then began isolating the microalgae from coral and culturing them in the lab. This was done using a technique called “directed evolution”. The final step in the process was to expose the microalgae to increasingly warmer temperatures. This occurred over a period of four years.

The process assisted the microalgae to adapt and survive hotter conditions.

“Once the microalgae were reintroduced into coral larvae, the newly established coral-algal symbiosis was more heat tolerant compared to the original one,” Dr Buerger said.

“The temperatures the microalgae were exposed to are comparable to the ocean temperatures during current summer heatwaves. Similar ones are causing coral bleaching on the Great Barrier Reef. This gave us insight into some of the mechanisms responsible for the enhanced coral bleaching tolerance,” he said.

Professor Madeleine van Oppen was the project lead for AIMS and the University of Melbourne.

“We found that the heat-tolerant microalgae are better at photosynthesis and they improve the heat response of the coral animal,” she said.

“These exciting findings show that the microalgae and the coral are in direct communication with each other.”

The future of coral

Our next steps? We need to further test the algal strains in adult colonies and across a range of coral species.

“In order to be effective, the tool must combine with conventional environmental conservation and determined action on climate change mitigation,” Dr Buerger said.

“Most importantly, we need to have conversations with the Australian public. And with the various groups that rely on the Reef for their livelihood before we move to the implementation stage.”

SynBio FSP Director Associate Professor Claudia Vickers said: “This breakthrough provides a promising and novel tool to increase the heat tolerance of corals and a great win for Australian science.”