Oz & NZ Marine Heatwaves Provide A Preview Of Our Future: Kelp Wiped Out, Shellfish Die-Offs
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Marine heatwaves are generally out of sight and out of mind until one gets so bad it becomes impossible to ignore, says CSIRO research scientist Alistair Hobday. A marine heatwave happens when the ocean temperature is much warmer than usual for the time of year from sunlight heating the surface water or warm water being brought via ocean currents – or both.
Climate change is causing marine heatwaves to happen more frequently and with more intensity. There may not be scorched earth or destroyed homes left in its wake, but a marine heatwave impacts our future in different ways – and serves as a warning. “Marine heatwaves provide a window into what our oceans will look like in the future, which is why it’s important to keep track of them,” Hobday says.
In 2015, New Zealand experienced its longest and most intense marine heatwave on record. For some it was good news – “It brought down valuable tropical species like kingfish and snapper,” Hobday says. For the aquaculture industry, however, it brought disease outbreaks in oyster farms, disruptions to salmon farming and abalone deaths along the coast. When an extreme marine heatwave lingered over the Shark Bay world heritage area in 2011, seagrass and kelp forests died en masse. Some kelp species became regionally extinct over hundreds of kilometres, says marine ecologist Cayne Layton from the University of Tasmania. “That [kelp loss] was a direct effect of the heat, but also due to herbivorous fish following the warm water and moving in to munch on the kelp.”
Like coral, kelp provides habitat structure, shelter and food for an entire ecosystem – without it the ecosystem would cease to exist. But, also like coral, the planet is losing kelp forests to climate change at an alarming rate. Forests of giant kelp, known as Macrocystis pyrifera, used to dominate Tasmania’s coastline. But in recent years, 95% have been lost and largely replaced by common kelp, says Layton.
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https://www.theguardian.com/environment/2019/mar/05/australias-marine-heatwaves-provide-a-glimpse-of-the-new-ecological-order
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