Mort-making marine heatwaves to happen more often: study

William Stoichevski

Ocean heat waves that threaten marine life and aquaculture are more long-lasting and frequent than they were a century ago, new research suggests.

Dr. Eric Oliver, Dalhousie University, Halifax, Canada

Sudden ocean heat, rather than sudden cold as in Canada, was recently spotlighted when the fish mortality records of Scottish salmon farms were made public. Heatwave-related deaths were many. The response from industry has been to vaccinate, while in Canada research on salmon genetically altered to tolerate heat has begun.

The findings of Dalhousie University scientist, Eric Oliver, and his colleagues worldwide suggest we’ll see more mortality in the short-term. Dr. Oliver’s work suggests that between 1925 and 2016 annual marine heatwave days are up 54 percent “with an accelerating trend since 1982”.

Worsening trend
“This means a marine ecosystem that used to experience 30 days of extreme heat per year in the early 20th century is now experiencing 45 marine heatwave days per year,” Dr. Oliver was quoted by University chroniclers as saying.

“That extra exposure time to extreme heat can have detrimental effects on ecosystem health, with impacts on biodiversity as well as economic activities including fisheries and aquaculture.”

Unlike heatwaves on land, marine heatwaves don’t usually make headlines. Some should have, however.

Deadly: satellite imagery of a marine heatwave in the Pacific Ocean

In 2011, a marine heatwave in Western Australia caused an ecosystem shift: kelp was replaced by seaweed after a period of heat, even after temperatures returned to normal. It means areas can sea long-standing change.

In 2012, a marine heatwave off Maine produced an early landing of lobster, and prices dropped.

Read Scottish morts cross-section shows higher cost of disease

Damaging heat waves at sea will continue, Dr. Oliver said, adding that they’re “mostly explained by” ocean temperatures worldwide.

“We will continue to see impacts on our marine ecosystems, making them less stable and predictable,” Dr. Oliver explained. “These are systems that many around the world rely on for food, livelihoods and recreation.”

He said he and researchers in the UK and Australia will now try better know what’s coming.

“Our next step is to quantify what the future changes will be,” he said.


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