‘A dead shark, dead rays, dead fish, dead cuttlefish’: The toxic algal bloom is spreading

The toxic algal bloom that has killed sharks, rays, fish, dolphins and seals along thousands of kilometres of South Australian coastline is now in its fourth month with no sign of abating, as the federal government announced a $14 million funding package but resisted calls to declare a natural disaster.

An outbreak of the microalgae Karenia mikimotoi has sucked all the oxygen from the water, killing fish, marine mammals, invertebrates, seaweed and sea grasses across great swaths of coastal seas from near Victoria to the Spencer Gulf past Adelaide.

Federal Environment Minister Murray Watt told reporters in Adelaide on Monday the algal bloom was “an indication of the type of event that we are likely to face as a nation and as a world in the future due to climate change”.

Watt said the bloom was a “very serious environmental event” but it was wholly within South Australian-controlled waters and therefore did not meet the definition of a natural disaster.

“The Commonwealth natural disaster framework considers events like floods, cyclones and bushfires to be natural disasters, and if they are declared as such, they attract a range of funding,” Watt said.

“What I’ve been focused on doing is not focusing on existing frameworks, but trying to understand what support South Australia needs, and delivering that as quickly as possible.”

Watt said the funding would cover both short-term requirements and longer term needs including beach clean-up, business assistance and scientific research.

South Australian Premier Peter Malinauskas welcomed the funding for the “unprecedented” event.

“It will go a long way to assisting the people that are being affected most harshly through this algal bloom, but also critically, we can turn our minds to how we better prepare for these types of events into the future,” Malinauskas said.

The first reports of a foamy scum covering the ocean and dead marine life washed up on beaches came from the Fleurieu Peninsula in March, and Great Southern Reef Foundation co-founder Stefan Andrews said there were reports it extended as far south as the Victorian border. In the past few weeks it has spread into urban areas around Adelaide and the Spencer Gulf with fears it could disrupt the winter cuttlefish aggregation for winter egg laying near Whyalla.

Andrews said great swaths of the ocean are giant dead zones with neon-green water and floating carcasses, with at least 450 marine species affected in the past month, according to citizen science reports.

“What’s really disturbing when you’re underwater is you see all these fish and everything that have died on the bottom, but there are no decomposers, no crabs and molluscs that usually you would find on dead fish carcasses eating away and recycling those nutrients,” Andrews said.

“There’s just this gross, slimy mould, a sort of slime, that’s forming over those fish and the algae itself will feed on, engulfing the decomposing fish that have already suffered and died from the algae bloom, so it’s further fuelling itself through the dead things, which just really shocking to see.”

Andrews said it needed to be framed as a national issue because it was affecting marine biodiversity on the Great Southern Reef, which stretched all the way from NSW to Western Australia, and was a consequence of national issues such as climate change and Murray River flooding.

Greens environment spokeswoman Sarah Hanson-Young said the bloom should be declared a national disaster.

“Climate change doesn’t care about bureaucracy – it will continue to wreak havoc on our environment and communities until we take it seriously,” Hanson-Young said. “If the rules need fixing, so this catastrophe can be acknowledged as the disaster it is, then let’s get them fixed. The government has the power to act, and they should.”

Dr Christopher Keneally, a microbial ecologist from the University of Adelaide, said the bloom was affecting the internationally significant Coorong wetlands, and even the Port River, where limited flushing meant the impacts could linger for months. He pointed out that prevailing currents could carry it to Western Australia or Victoria.

“Whether we label this a ‘national disaster’ is a legal decision, but scientifically, the scale, potential cross-jurisdictional reach and multi-year legacy effects are on par with the bushfires and floods that routinely trigger federal interventions,” Keneally said. “A national declaration might unlock co-ordinated monitoring, emergency support for fisheries and wildlife rescue, and the rapid mobilisation of Australia’s research capability.”

The South Australian Department of Environment and Water said credible explanations for the bloom included the marine heatwave that started in September 2024, the 2022-23 flood of the Murray River washing extra nutrients into the sea, and an unprecedented cold-water upwelling over summer that brought nutrient-rich water to the surface.

“Similar blooms around the world have lasted from a week to several months, depending on wind, rain and ocean temperatures,” the department said in an update posted late last week. “Nothing can be done naturally to dilute or dissipate the bloom.”

The state environment department said sea surface temperatures had decreased in shallow coastal and gulf waters, but deeper continental shelf waters including around Kangaroo Island and southern Yorke Peninsula were still experiencing moderate to strong marine heatwave conditions of 1 to 2 degrees above average.

Earlier in the outbreak, there was hope the bloom would disperse in winter as the water temperature dropped and cold fronts brought in storms to blow it away.

However, photographer Narelle Autio, who has been documenting the environmental disaster and publishing on the @ChilliOctopus Instagram account, said the storms a few weeks ago blew the bloom up the gulf where it was stuck “moving from side to side”.

The death of marine life has come in waves, Autio said – first thousands and thousands of cuttlefish, then big fiddler rays and Port Jackson sharks, then worms and different types of fish, then dolphins and sharks, and then bivalve shells like razor fish and cockles.

“It just feels like it’s taking out every layer of the ocean,” Auto said. “It just feels devastating.”

Labor MP Mark Butler told ABC Radio on Monday that Australia had never seen a Karenia mikimotoi bloom of this scale and duration.

“My electorate spans a lot of Adelaide’s beaches,” Butler said. “Only the weekend before last I was taking a walk and I saw a dead shark, a number of dead rays, dead fish, dead cuttlefish – scenes I’d never seen in all of my decades walking along Adelaide beaches.”

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