Australia's Largest Toxic Algae Bloom Ever Persists After A Year; More Than 780 Species Hit By Deadly Impacts

The largest and most destructive algal bloom in Australia’s history is persisting along parts of the South Australian coastline, a year on from when it was first detected. From a distance, it can be hard to grasp just how unusual and devastating the crisis has been.

Most harmful blooms only last a few weeks. This one has been unrelenting. Since March last year it has affected 20,000 sq km of coast – an area twice the size of greater Sydney – and ranks among the worst for marine mass mortality globally, killing millions of sea creatures – from tiny shellfish to top predators like white sharks.

It is Australia’s first bloom of Karenia cristata, a rare and toxic type of algae deadly to marine life and harmful to human health, according to Prof Shauna Murray, from the University of Technology Sydney. Murray, who was the first to identify the species in water samples from SA, says the species has only been recorded in two other places worldwide – South Africa and an island off the coast of Newfoundland, Canada.

Prof David Booth, a marine ecologist who specialises in sea dragons at the University of Technology Sydney, describes the impact on marine life as “the most awful, tragic thing I’ve personally seen in the ocean in my 40-year career”. More than 780 species have been affected, including “devastating losses” of the state’s marine emblem, the leafy sea dragon, reported by divers and citizen scientists.

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https://www.theguardian.com/environment/ng-interactive/2026/mar/14/algal-bloom-south-australia-update-one-year-on