Marine heatwaves are having severe impacts on ecosystems around the world, with species in Australian waters particularly vulnerable, scientists say.

The number of marine heatwave days a year jumped 54 per cent in the 1987-2016 period compared with three decades earlier, according to research published in scientific journal Nature Climate Change on Tuesday. The Pacific, Atlantic and Indian Oceans are particularly at risk of large-scale biodiversity losses.

The kelp forest off Western Australia was badly affected by a marine heatwave in 2011, as these before and after images show. Credit:Thomas Wernberg

While temperatures have gradually risen because of climate change, it is the advent of heatwaves that can cause the worst damage, said Thomas Wernberg, an associate professor at the University of Western Australia's Oceans Institute and School of Biological Sciences and an author of the paper.

“They reset ecosystems,” he said. "They kill off a lot of animals and plants, and that can have long-lasting implications."