‘Super’ heat tolerant kelp restores hope for underwater forests battling climate change

Heat tolerant giant kelp is flourishing at trial sites along the east coast of Tasmania, indicating all is not lost for the world’s largest algae.

Underwater forests of giant kelp (Macrocystis pyrifera) were once shipping hazards marked on maritime charts, and during the 1960s supported a booming alginate industry.

But climate change, which is strengthening the East Australian Current, or EAC, has put these forests at risk.

The EAC transports warm, nutrient-poor water to southern Tasmania which displaces the colder, nutrient-rich water characteristic of the Tassie coastline.

As the amount of warm water has increased, giant kelp communities have decreased by up to 95 per cent.

Dr Cayne Layton, a researcher with the Institute of Marine and Antarctic Studies at the University of Tasmania, has been helping the kelp adapt to the changing conditions.

“We’re looking at that remaining (population) to identify whether there’s individuals … that are more tolerant of warm water,” he said.

“They’re the individuals we can replant back in the ocean, hopefully to give our habitat restoration efforts a fighting chance.”

Three trial patches were planted out last spring. Dr Layton said while one site wasn’t successful, the remaining two had taken off and the kelp was flourishing.

“Across the two patches we now have … almost 200 ‘teenage’ giant kelp growing quite happily,” he said.

“(They are) an average size of around 50 to 60 centimetres, but some of the biggest ones are over four metres.

The “super” kelp is living up to its name. During the past summer they were happier and healthier than their wild counterparts, which bleach when heat stressed, much like a pot plant at home, Dr Layton said.

“That was a nice encouraging sign that our lab results … might actually translate into the field,” he said.

“Now that the juvenile kelp plants have passed the warm temperature ‘danger zone’ of summer, we’re optimistic that the majority will continue to survive and thrive.”

‘They will never see what I saw’

Mick Baron co-owns the Eaglehawk Neck Dive Centre on the Tasman Peninsula and has dived in coastal waters of Tasmania since the 1970s.

He remembers when giant kelp forests were so prolific and dense he didn’t need an anchor.

“Because the kelp was so thick it had a major buffering effect on the energy of the ocean waves,” Mr Baron said.

“You could grab (the kelp) and just hold your boat still while it would be blowing 20 knots on the outside.”

Giant kelp forests were once a significant drawcard for the region, but the loss of tourism isn’t top of mind for Mr Baron. It’s thoughts of the future and his grandchildren he finds most distressing.

“I’ve been lucky enough to actually witness this … and now I’ve got two little grandkids, they’re five and three.

“They will never see what I saw.”

Helping giant kelp survive in a warming world isn’t just about restoring a bygone era.

Jennifer Hemer, water and marine program manager at the government-funded Natural Resource Management organisation, said giant kelp forests did not just look good — they were also an economic powerhouse.

“They play important roles in (the) cycling of blue carbon and coastal nutrients, and provide habitat for commercially and recreationally important species,” she said.

“They are ecosystems which provide services to people and the planet.”

The Great Southern Reef

Dr Layton said kelp was as important for southern Australia as corals were in the north.

“Instead of the Great Barrier Reef, where corals are the foundation species, we have the Great Southern Reef which stretches across 8000 kilometres … and instead of corals, kelp are the foundation,” he said.

Despite promising results, binging back entire forests of giant kelp won’t be easy.

The current planting technique involves bolting plastic plates to the ocean floor — a time-consuming and expensive process.

Dr Layton, however, believes nature is up to the task and just needs a helping hand.

“It’s about kickstarting a natural process,” he said. “It’s never going to work for us to go out and plant every single generation.

“That will be the next exciting step for us, when these patches become self-sustaining (and) potentially also self-expanding.”