21 Jan 2020

Seaweed may be key to protecting coral from climate change - NZ study

7:22 am on 21 January 2020

A common seaweed could throw a lifeline to precious coral reefs, according to a new study from Victoria University of Wellington.

Landscape of the Great Barrier Reef in the Coral Sea off the coast of Queensland, Australia, 2018.

Coral locations like Great Barrier Reef in the Coral Sea off the coast of Queensland, Australia, are in danger of dying due to climate change. Photo: AFP / Stringer / Imaginechina

This seaweed - called coralline algae - glues reefs together and helps protect them from erosion. Marine biologist Dr Christopher Cornwall said without it, reefs as we know it wouldn't exist.

In a new study, published today in Nature Climate Change, Dr Cornwall has found some species of this seaweed have built tolerance to acidification - an effect of climate change.

"Coralline algae go through a natural process of calcification, where they build a calcium carbonate skeleton," he said.

"Skeletons like this provide structure, allow them to grow, and protect these organisms. Our research has shown that growth of these skeletons is susceptible to climate change, at least initially."

Dr Cornwall said coralline algae was common around the world, and in New Zealand. After the uplift that resulted around the Kaikōura coast following the 2016 quakes, rocks that were previously covered in this seaweed began to erode, Dr Cornwall said.

"Once that coralline algae was dead, they sort of eroded, so they form like a cap over the rocks and limit erosion from the sea, wave action and marine critters that like to burrow into the rocks.

"These species also act as a nursery for many marine species, including native New Zealand pāua and kina, and are the main player in temperate reef formation in New Zealand oceans."

Coralline algae are a useful way to study how reefs adapt over time as they grow to maturity in six weeks as opposed to over years like some coral species

"This research could also provide a starting point for growing coral species under "assisted evolution" that could be more resistant to climate change, although there are complex logistical and ethical considerations to map out before we go down that road."

Through studying the seaweed in the lab, he found that it evolved to gain resistance to ocean acidification.

This happened over several generations, and while it was no silver bullet, it could help the fight against coral reef resistance to warmer and more acidic oceans.

Dr Cornwall said the next step was to test more species of coralline algae.

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