Algal bloom impacting City of Marion coastline

The City of Marion is acutely aware of the algal bloom crisis affecting South Australian coastlines.

It hits particularly close to home when dead marine life is located along our precious, rocky coast at Marino and Hallett Cove.

We are following the advice of the Department for Environment and Water (DEW), Environment Protection Authority (EPA), Department of Primary Industries and Regions (PIRSA) who we know are working around the clock monitoring this marine crisis.

DEW has provided some answers to some frequently asked questions that we have shared below.

What are the effects of the algal bloom?
The algal bloom has caused discoloured water and foam along parts of South Australia's coastline. Karenia mikimotoi does not cause long-term harmful effects in humans but has affected various marine wildlife, including fish, sharks, rays, and a wide range of invertebrates.

Why has it appeared?
Experts believe there are three potential plausible contributing factors causing the bloom, which started in March:

• A marine heatwave that started in September 2024 – with sea temperatures about 2.5°C warmer than usual – combined with calm conditions, light winds and small swells.
• The 2022-23 River Murray flood washing extra nutrients into the sea.
• An unprecedented cold-water upwelling in summer 2023-24 that has brought nutrient-rich water to the surface.

The last large event of this type of algae recorded in SA was at Coffin Bay in 2014

How long might the bloom last?
Similar blooms around the world have lasted from a week to several months, depending on wind, rain and ocean temperatures.

Is the bloom harmful to people?
Karenia mikimotoi does not cause long-term harmful effects in humans.

However, exposure to discoloured or foamy water can cause short-term skin or eye irritation and respiratory symptoms, including coughing or shortness of breath.

These symptoms usually resolve within several hours of leaving the beach.

What should I do if I experience symptoms?
If you are outdoors and experience irritation, go indoors, close windows and rinse exposed skin.

If symptoms are more severe or do not resolve, seek medical advice from a GP and call 000 if it is a medical emergency.

Can I swim or walk on the beach?
Avoid swimming or surfing in discoloured water, foam or where marine life is dead or in poor health.

If you experience irritation, go indoors, close windows and rinse exposed skin, seek medical advice if symptoms persist or call 000 in an emergency.

Do not touch or eat dead or dying fish, shellfish or marine wildlife. Fish caught alive are safe to eat.

Follow beach signage and directions from NPWS rangers.

What should I do if I'm walking my dog on the beach?
Dog owners should keep their pets under effective control to prevent them eating dead or dying fish, which may cause illness.

Do not let your dog swim in discoloured water and foam, or where marine life is dead or in poor health.

Is it safe to eat seafood from affected areas?
Do not eat dead or dying fish, cockles or other marine life found on the beach. Fish caught live are safe to eat.

Report fish deaths to FISHWATCH on 1800 065 522.

Oyster harvesting areas are temporarily closed at American River, Port Vincent, Coobowie and Stanbury.

Commercial pipi harvesting is temporarily closed from the Murray Mouth to 10km south of the mouth.

A precautionary closure was enacted on July 9 at Boston Bay, Bickers Island, Lower Eyre and Proper Bay harvesting areas after brevetoxins (neurotoxic shellfish poisons) were detected.

Ongoing testing in open harvest areas continues to ensure product safety standards are upheld.

What is being done about the bloom?
Government agencies, including the Department for Environment and Water (DEW), the Environment Protection Authority (EPA), the Department of Primary Industries and Regions (PIRSA) and SA Health are monitoring the situation.

Signs are in place at public entry points to affected beaches and national parks beaches remain open.

Nothing can be done to dilute or dissipate the bloom.

What are the potential effects of the bloom on marine parks?
DEW, SARDI and Fisheries SA are conducting preliminary scoping surveys to assess the effects of the algal bloom on Gulf St Vincent, including marine parks.

This will inform the extent of effect and help determine more detailed assessments.

Is quarry sand contributing to the bloom?
Quarry sand is tested to meet strict environmental standards to ensure it is compatible with existing sand on the beach.

As the algal bloom is naturally occurring, there is no link between it and the delivery of external quarry sand to West Beach and Henley Beach.

Are desalination plants contributing to the bloom?
No health issues are known to be associated with brine discharged from desalination plants and brine is not linked to increased algal growth.

All marine desalination plants operated by SA Water are regulated by the Environment Protection Authority, which ensures appropriate management of brine outflow.

Who should I contact about dead wildlife?
Fish deaths: FISHWATCH 1800 065 522
Marine wildlife: National Parks and Wildlife Service offices

Who should I contact with health questions?
Public health advice: SA Health 13 11 26
SA Health: Water quality alerts
PIRSA: Harmful algal bloom situation update

Visit https://www.environment.sa.gov.au/news-hub/news/articles/2025/07/sa-harmful-algal-bloom-update to read the latest updates and advice from the state government agencies.

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