South Australia's algal bloom - all your questions answered

What’s going on with SA’s algal bloom? And should you still swim, surf or eat seafood? We’ve got the facts.

First things first: what actually is an algal bloom?

This particular algal bloom is caused by a naturally occurring marine algae called Karenia.

It’s part of a group called harmful algal blooms (HABs), which form when ocean conditions – like warmer water and nutrient levels – let algae grow quickly and spread.

This bloom first appeared off the Fleurieu Peninsula in March and has since spread along the coast – now affecting metro beaches, the Port River, West Lakes, Kangaroo Island, southern Yorke Peninsula and the Coorong.

While Karenia isn’t toxic to humans, it has been deadly for marine life – affecting more than 400 species of fish, sharks, rays, shellfish, seahorses and other creatures.

Why is this happening now?

Scientists believe a mix of three factors created the perfect storm:

• A marine heatwave, with ocean temperatures around 2.5°C above average since September 2024
• Nutrient-rich water from the 2022–23 River Murray flood entering the sea
• A rare cold-water upwelling last summer, which brought even more nutrients to the surface.

These kinds of blooms have happened before in SA – including at Coffin Bay in 2014 – but the scale of this one is bigger and more widespread.

Can I still swim or surf?

Yes – but avoid swimming or surfing in water that looks discoloured, foamy, or where there’s dead marine life. If in doubt, stay out.

What if you've already been in the water?

Don’t panic. For most people, any symptoms like eye or skin irritation, coughing or a tight chest will go away within a few hours.

If you feel unwell:

• Rinse off in clean water
• Head indoors and close windows
• See a GP if symptoms don’t go away – or call 000 in an emergency.
• People with asthma should follow their usual management plan just in case.

What if I'm just going for a walk?

It’s safe to visit the beach — but steer clear of the water if it looks off.

And if you’re walking through a national park, follow signs and listen to National Parks and Wildlife Service rangers.

If you feel unwell after being outdoors – things like irritation, coughing or shortness of breath – head inside, rinse off, and close the windows.

If symptoms stick around or get worse, see a GP or call 000.

What should I do if I'm walking my dog on the beach?

Keep your pooch away from dead fish – eating them can make dogs sick.

Also avoid letting them swim in discoloured or foamy water, or anywhere you see dead or struggling marine life.

Can I still eat seafood?

All commercially available seafood from South Australian water is safe to eat.

Shellfish available for sale is frequently tested to make sure it meets strict safety standards.

If you catch fish, crabs, prawns, lobsters, or squid yourself, they are safe to eat if cleaned thoroughly and gutted before cooking.

Visit algalboom.sa.gov.au for more information on eating seafood safely.

Is it safe for dolphins, too?

The algae has been detected in the Port River, home to the Adelaide Dolphin Sanctuary.

Right now, the dolphins are not believed to be at immediate risk, but their water quality is being closely monitored by rangers and researchers.

Is this going to go away?

It will – but no one can predict exactly when. Blooms like this usually fade after a few weeks or months, depending on wind, rain and sea temperatures.

It’s expected to ease when strong westerly winter winds return, but SA’s run of calm weather has delayed that.

There’s no quick fix – we can’t chemically treat or flush the ocean, so nature has to do the work.

So… should we be worried?

This bloom has had a serious impact on marine life and the industries that rely on it – especially fishing, aquaculture and tourism.

But for the average beachgoer, you’re not in danger if you follow public health advice.

This is a natural phenomenon, made worse by unusually warm water and nutrient build-up – and it’s being taken seriously.

What’s being done?

A statewide taskforce has been set up, bringing together scientists, health and environment agencies, industry reps, and First Nations voices.

Here’s what’s happening behind the scenes:

• 42 sites across Adelaide and SA are tested every week for algae levels
• Underwater drones are helping track the impact on ecosystems
• Scientists from SA, interstate and New Zealand are working together to improve monitoring and prep for future blooms
• Harvest areas are closed or reopened based on real-time testing.
  

What support is available for affected communities and industries?

In late July, the SA and Australian Governments announced a $28 million support package to help communities, industries and ecosystems recover.

The package includes funding to analyse citizen science data and develop a response plan for future bloom events.

What help is there for small businesses?

South Australian small businesses impacted by the algal bloom are eligible for grants of up to $10,000, while hardest hit commercial fisheries and aquaculture licence holders can apply for up to $100,000 in support.

Visit the South Australian government hub to find out more.