Explaining the toxic algae bloom and how it impacts you

There’s been countless theories about what’s caused the toxic algae bloom and how it impacts humans and animals. We’ve answered four of the most frequently asked questions.

It’s the “bushfire of the ocean” that has brought the seafood industry, regional towns and small businesses to its knees.

The toxic algae bloom sweeping across the state has not only killed thousands upon thousands of fish, but has seen sharks, seals, dolphins and even penguins watch up on our beaches.

While it’s the talk of towns, boat ramps and beaches, there is a lot of misinformation about the algae bloom - and it’s having devastating effects on public behaviour across SA.

So, it’s time to dispel a few myths about the algae bloom

Deceased female White Shark that was taken away by Fisheries officers on Friday at Port Broughton. Picture: Danielle Griffin

Is South Australian seafood safe to eat?

As the algae bloom snakes along South Australia’s coastline, demand for locally-caught fish has seen a shocking decline.

Some Yorke Peninsula anglers have been forced to lay off staff as there is simply no fish to catch, while small businesses - such as the Port Vincent Kiosk - are now importing seafood from overseas as buyers fall out of love with local catches.

But despite the horrifying scenes in our waters, fish caught both recreationally and commercially is safe to eat.

That extends to any seafood commercially available in fridges in SA supermarkets, which have undergone strict testing to make sure it meets food safety standards.

Port Vincent Kiosk owner Jo Barrett has started importing fish from overseas. Picture: Brett Hartwig

The state government is even spending $2 million on public information campaigns to help rebuild confidence in not only the seafood industry, but the coastal towns affected by the bloom.

There are some warnings though - don’t eat any dead fish, cockles or shellfish you find washed up on the shores and avoid collecting shellfish from affected beaches.

Premier Peter Malinauskas encouraged all South Aussies to tuck into our state’s seafood.

“We actively encourage people to buy our amazing seafood that is on the shelf,” he said at a press conference on Monday.

“Really simple rule, if it’s on the shelf, you can eat it.

“You can do that with absolute confidence knowing that we have some of the highest quality and rigorous testing regimes anywhere in the world.

“The safety and quality of our produce is second to none, so back it in and eat as much as you possibly can.”

Peter Malinauskas speaking at the Presser on the Ardrossan coastline in the Yorke Peninsula. Pictured on 28th July 2025. Picture Ben Clark

Can I swim at the beach?

While the algae bloom is harmful to marine life, it does not present any long-term issues for humans.

That’s good news for beach lovers who still brave the water in South Australia’s icy winter.

Having said that, it is still essential to avoid swimming or surfing in discoloured or foamy water.

If you do swim in murky water, it’s important to rinse off thoroughly immediately after.

The state government urges anyone who experiences mild symptoms - such as irritated eyes, cough or skin irritation - to see a doctor or call triple-0 if they don’t subside.

Dog owner Patsy Heywood from Semaphore with Mac the Boarder Colley Kelpie Cross and Elvis the Noodle on Henley Beach where Spencer Gulf Algae bloom effected marine life lay dying. Picture: Emma Brasier

Can I still walk my dog at the beach?

For a lot of South Australians, a trip to the beach is not complete without a furry friend by their side.

But with our beaches scattered with dead marine, it’s becoming an unattractive destination for strolls with our beloved pets.

Some South Aussies have raised the alarm since the algae hit popular beaches, with one owner saying her dog suffered bleeding from the gums and sneezing fits while holidaying in Middleton.

Despite these reports, the Department of Environment and Water maintains SA beaches are still safe for our pooches.

It’s just essential for their safety, they don’t eat dead fish or swim in foamy water.

Members of the public rush to help a dolphin on Semaphore Beach. Picture: Supplied

How is the algal bloom killing SA’s marine life?

Since the algal bloom first hit SA’s shores in early March, there have been some heartbreaking scenes across our beaches.

Great white sharks, dolphins, seals and even penguins have washed up, with investigations underway to what role the bloom has played in their deaths.

The algae species - known as Karenia mikimotoi - produces a reactive oxygen species that can damage fish gills, resulting in them effectively drowning.

“We’ve seen fish and sharks wash up with a real pinkish colour to them, that is the haemorrhaging that occurs underneath the surface of the skin,” Deputy Premier Susan Close told The Advertiser earlier this year.

“That is how it is toxic to them, it gets into their gills and poisons them.”

While authorities are performing autopsies on dolphins, seals and sharks, the government said the algae species is not toxic to mammals.

“Overnight the algae sucks up oxygen from the ocean and anything that is underneath it becomes oxygen starved,” Dr Close said.

Originally published as Explaining the toxic algae bloom and how it impacts you