Stressing out reef life earns marine researcher a nod from the PM

Australian scientists said they have discovered a detached coral reef on the Great Barrier Reef that exceeds even the height of iconic buildings like the Empire State Building and the Eiffel Tower.

In tanks across the world, marine researcher Christopher Cornwall’s​ team deliberately stressed coral and algae species, by slowly making the water more acidic. The work, recreating what’s happening in our oceans because of climate change, earned him the Prime Minister’s emerging scientist prize.

Reefs – from the famous coral ecosystems to forests of kelp – are facing an uncertain future, said the Victoria University research fellow. Human-made greenhouse gas emissions are affecting the oceans in two ways.

The additional carbon dioxide in the air is absorbed by the ocean, affecting the pH balance of the water, which is slowly becoming more acidic. Species that surround themselves with calcium carbonate skeletons struggle to maintain a stable internal environment. It’s this effect that Cornwall is mimicking in his tanks.

The increased temperatures, caused by our use of fossil fuels, are also a problem. Marine heatwaves stress out species such as coral and kelp. During these events, marine life can die in a matter of weeks, and it can take up to a decade for the ecosystem to recover, Cornwall said, if it recovers at all.

Although these events are depressingly frequent in Australia, they’re also occurring here as well. “I like to think of Australia as a canary in a coal mine,” he added.

Chris Cornwall has been recognised for his research mimicking the effects of more acidic oceans.
Chris Cornwall has been recognised for his research mimicking the effects of more acidic oceans. MONIQUE FORD/STUFF

During a stint at the University of Western Australia, Cornwall wanted to understand if marine species could adapt, to see which might survive in a more acidic ocean.

In his first round of tank experiments, he introduced coral and algae and slowly made the water more acidic over a week. He then left them for a year, but most species stopped growing. None recovered.

Next, Cornwall wanted to understand what would happen if the shift occurred across multiple generations. For this, he chose coralline algae – “the pink stuff on the rocks”. These only take six weeks to reproduce, but are a crucial species for many reefs.

“They emit a chemical cue into the water that tells kina and paua larvae: ‘Come back to this reef, this is where you need to live’,” he added. “Without that coralline algae, we don’t have paua, we don’t have kina.”

The research used coralline algae, the pink-coloured marine life in the centre, to test the ability of reef species to adapt.
The research used coralline algae, the pink-coloured marine life in the centre, to test the ability of reef species to adapt. CHRISTOPHER CORNWALL/SUPPLIED

In this project, the generations were exposed to acidic waters. At first, their growth slowed. But by the sixth generation, their offspring were thriving and growing normally.

They handled the comparatively acidic waters much better than freshly exposed algae, Cornwall said. The findings suggest some algal species might be able to survive in the changing oceans.

“This offers a glimmer of hope that at least certain species can gain traits that would allow them to resist some forms of climate change, if they’re given enough time,” he said. “But things like marine heatwaves, there’s no time to acclimatise to that, it could knock a whole population out.”

Cornwall has worked at reefs around the world and seen the devastating effects of hotter and more acidic oceans in person, such as the bleaching of coral. He worries that by the time his children – now aged 5 and 7 – are grown, many of these beautiful habitats may be lost.

“We can’t ever restore the ecosystem to the state it used to be before we came along, but we have an obligation to keep it how it is now, at least.”

Cornwall is careful not to say he’s breeding tolerant algae. Instead, the experiments offer a window into the future.

A coral reef during a bleaching event. The white-coloured coral has ejected its algae. The black-coloured coral is dead.
A coral reef during a bleaching event. The white-coloured coral has ejected its algae. The black-coloured coral is dead. CHRISTOPHER CORNWALL/SUPPLIED

“In the future, you could grow organisms in the lab and put them back out on the reef, but the problem is these reefs are so big, it would require trillions of dollars to do it,” he added.

“While assisted evolution could help with fast-growing temperate kelp forests, it’s less likely to save the tropical coral reefs. The only thing that will really save those reefs is stopping our carbon dioxide emissions.”

Cornwall felt a rush of emotions after hearing that he’d been named as 2020’s emerging scientist for the Prime Minister’s Science Prizes, announced today. “It was a moment of pure elation,” he said. “It’s recognition of all those 16-hour days, you’re out in the field in the Kimberley, and it’s like 40 degrees Celsius and the water’s 40C and you’re baking yourself for weeks on end.”

Following the tank experiments, Cornwall and fellow biologist Steve Comeau​, of Sorbonne University, are modelling the survival chances of the world’s reefs, based on all the relevant research.

Olivia Wannan, Stuff, 13 April 2021. Full article.

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