A naturally occurring, harmful algal bloom, Karenia, is affecting parts of South Australia's coastline, including metropolitan beaches and estuarine sites, Port River, West Lakes, Fleurieu Peninsula, Kangaroo Island, southern Yorke Peninsula and the Coorong.
This page brings together the latest information from the South Australian Government to help you stay informed, stay safe, and understand how the situation is being managed.
What are the effects of the algal bloom?
The algal bloom has caused discoloured water and foam along parts of South Australia's coastline. It does not cause long-term harmful effects in humans.
The algal bloom has affected about 400 species of fish, invertebrates and associated marine and coastal biodiversity.
Why has it appeared?
Experts believe there are three potential plausible contributing factors causing the bloom, which started in March 2025:
- 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 algal bloom last?
Similar blooms around the world have lasted from a week to several months, depending on wind, rain and ocean temperatures.
The bloom occurs naturally and no human intervention can dilute or dissipate it.
Is the algal bloom harmful to people?
The algal bloom 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.
Follow beach signage and if in a national park, follow directions from National Parks and Wildlife Service 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?
Seafood such as fish, crabs, prawns, and lobsters caught live are safe to eat provided they are properly cleaned, and the viscera/digestive tracts are removed prior to cooking and eating. Seafood from retail outlets is safe to eat too as rigorous testing is undertaken.
Shellfish from recreational areas should not be consumed.
Do not eat dead or dying fish, cockles or other marine life found on the beach.
Report fish deaths to FISHWATCH on 1800 065 522.
Oyster harvesting areas are temporarily closed at American River, Port Vincent, Coobowie and Stansbury.
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.
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?
- SA Health public health advice: 13 11 26
- SA Health: Water quality alerts
What support is available for commercial fishers?
The state government is offering an initial relief package to affected licence holders to waive fees from April to June 2025.
Eligible fees for relief consideration include:
- PIRSA Fisheries and Aquaculture annual licence fees
- Biosecurity SA Food Safety Scheme and audit fees
- Aquaculture lease and licence fees
For more information visit the PIRSA website.
What is being done about the algal bloom?
The state government has established an algal bloom taskforce and reference group to help industries and stakeholders respond to and recover from the algal bloom affecting South Australia’s environment and coastline.
The Harmful Algal Bloom Reference Group, which comprises representatives from Seafood Industry South Australia, RecFish SA, Conservation Council, Tourism Industry Council and First Nations groups will:
- Represent sectors to identify key issues for government to consider in managing and recovering from the algal bloom
- Identify opportunities to further engage with and provide more information to industry sectors, stakeholders and the community
- Provide ideas for government consideration to support an expanded scientific monitoring program.
Agencies, including the Department for Environment and Water (DEW), Department of Primary Industries and Regions (PIRSA), Environment Protection Authority (EPA), South Australian Tourism Commission (SATC) and SA Health, met with commercial fishers, tourism operators and local councils at a forum on July 4.
The meeting was held to provide an update, including ongoing public health information and environmental effects, and address future research priorities associated with the algal bloom to better understand how to mitigate future outbreaks.
How is the algal bloom being monitored?
South Australia’s flagship fisheries patrol vessel Southern Ranger is conducting underwater observations of the harmful algal bloom in the Gulf St Vincent to understand the effect on the ecosystem.
Numerous locations are being visually surveyed with remote operated vehicles and this information will help authorities to better understand the rate of potential recovery once the bloom dissipates.
Marine sanctuaries, where an extensive data set already exists, will be surveyed to provide a comparison with the observations from the trip.
State government agencies are also taking weekly water samples at 18 metropolitan sites, including West Lakes, the Port River, the Patawalonga River and the end of four jetties at Largs Bay, Grange, Glenelg and Port Noarlunga.
Test results are made available on the South Australian Harmful Algal Bloom Water Sampling Dashboard.
Related information
SA Health public health advice: 13 11 26
Report fish deaths: FISHWATCH 1800 065 522
Report marine wildlife: National Parks and Wildlife Service South Australia
Relief for commercial fishers - PIRSA
Fact sheet for health professionals – SA Health
Water quality alerts – SA Health
South Australian Harmful Algal Bloom Water Sampling Dashboard - Department for Environment and Water
Harmful algal blooms (HABs) and marine heat waves - Environment Protection Authority
Harmful algal bloom situation update, including algal bloom mapping - PIRSA
Tourism sector information - SATC
