🐟 What Happened? In March 2025 the coast of South Australia began being swamped by an algae toxic to marine life and harmful to humans.
Since then tens of thousands of dead sea creatures have washed up on SA beaches. Now, parts of the Great Southern Reef that had been untouched by the bloom are under siege.
🤢 Toxic Algae: The rare Karenia cristata algae, which had never bloomed in Australia before, was caused by a mix of nutrients flowing from the Murray River, a major ocean upswell and a marine heatwave. This has resulted in an environment for the algae to thrive.
Across the globe ocean temperatures are warming due to the burning of fossil fuels, increasing the planet’s temperature.
🚨 Damage: Marine Ecologist from the University of Tasmania Dr Scott Bennett told the National Account surveys and analysis are ongoing but they’ve already found devastating impacts on species like the iconic Leafy Sea Dragon.
“It is extremely evident from those surveys that the reefs have been severely damaged. A lot of the habitat formers - the seaweeds, understory invertebrates and things like that - have disappeared.”
🏛️ Government response: In November 2025, a Senate inquiry into the bloom provided the Australian government with 14 recommendations including a JobKeeper-style support scheme for affected fishers, large-scale reef restoration funding and a national framework for future bloom events.
The Government responded to the recommendations in March, accepting just one: loans for wild-catch fishing and aquaculture businesses affected by the bloom.
🐠 Port Hughes: Bennett pointed to places like Port Hughes about 135km northwest of Adelaide, that had previously been less affected by the bloom, but which is now suffocated by the algae.
“It avoided the bloom in the peak of it last year, but has subsequently been impacted and there's been a lot of deaths as a result,” he said.
Left: Dec 2025 Right: Feb 2026
🪸 Recovery: Bennett said the algal bloom was not making headline news anymore “but the aftermath and havoc that's breached on our coastal marine systems is there and that's locked in.”
He said the next step is the long process of understanding what’s been lost and rebuilding it.
“It is going to require a huge amount of ongoing funding and support to track these changes and come up with new science to actually help recover these systems at the scale necessary.”
Images: Stefan Andrews courtesy Great Southern Reef Foundation.