Harmful algal bloom (HAB) situation update
Parts of South Australia continue to be affected by the ongoing microalgae bloom, Karenia mikimotoi.
The naturally occurring bloom continues to affect beaches on the Fleurieu Peninsula and Kangaroo Island and is increasingly prevalent along the southern coast of the Yorke Peninsula.
This is a dynamic situation as the bloom travels depending on weather and water conditions and the impact on people in these areas can therefore be unpredictable.
The event is likely being driven by an ongoing marine heatwave impacting southern Australian waters, with water temperatures currently 2.5°C warmer than usual, as well as relatively calm marine conditions with little wind and small swells.
The last time a large event of this type of algae was recorded in SA was in 2014 in Coffin Bay.
Nothing can be done to dilute or dissipate the bloom.
Government agencies are working together to monitor the situation, conduct sample tests at various locations, and to ensure the community has access to the environmental, primary production and health information they need to safely enjoy the coast.
Similar outbreaks around the world have generally lasted between a week to several months depending on wind, rain and ocean temperature fluctuations.
The bloom is expected to remain present until the state receives strong westerly winds, which historically start around the end of April. However, persistent high pressure systems affecting southern Australia have delayed these winds.
All beaches in National Parks are open and accessible to the community. Visitors should follow health advice, provided via signs that have been installed at public entry points to the beaches, and avoid contact with discoloured or foamy water.
Impacted wildlife
Karenia mikimotoi can cause marine species mortalities at varying concentrations and is known to impact the gills of fish.
Report any marine mortalities to Fishwatch on 1800 065 522 so they can be added to the testing regime being carried out by PIRSA.
We encourage anyone who discovers dead or sick marine wildlife to contact their local National Parks and Wildlife Service office.
Health advice
The algae does not produce a toxin that is harmful to humans or one that could cause long-term effects. However, exposure can cause:
- skin irritation
- eye irritation
- respiratory symptoms such as coughing and shortness of breath.
These symptoms resolve within several hours after leaving the beach and adjacent area.
People are advised to avoid swimming at beaches where there is discoloured water and foam, and to avoid walking on beaches if experiencing symptoms.
If people are experiencing symptoms outside their homes, SA Health recommends they remain indoors with windows closed until the symptoms pass. If symptoms are more severe or do not resolve, then seek medical advice from a GP and call 000 in a medical emergency.
No health issues are known to be associated with brine discharged from desalination plants, and brine is not associated with greater algal growth. All marine desalination plants operated by SA Water are licensed by the Environment Protection Authority (EPA) and must comply with strict environmental standards, including the management of brine outflow from the desalination process.
See water quality alerts on the SA Health website for further health advice.
Food safety
PIRSA conducts regular ongoing monitoring of shellfish harvesting areas by the South Australian Quality Assurance Program (SASQAP), which conducts a rigorous ongoing testing regime aimed at assuring consumers of commercially harvested oysters, mussels, cockles and scallops that they are safe to eat. As part of this program, harvesting areas are often temporarily closed as a precaution to ensure food safety standards are upheld.
Currently this testing regime has led to precautionary closures at the American River, Port Vincent and Stanbury oyster harvesting areas and the commercial harvesting of pipis between the Murray Mouth to 10 km south of the mouth.
Remaining oyster and commercial pipi harvesting areas remain open with produce from those areas safe to eat. Regular ongoing testing in these open harvest areas continues to ensure the harvested produce food safety standards are upheld. This means there is no public health concern.
SA Health advises that fish caught live are safe to eat. However, SA Health does not recommend people eat fish or cockles found dead because of likely spoilage and decomposition.
Latest update
A marine heatwave (MHW) has been affecting southern Australia since September 2024. Like heatwaves on land, MHWs are periods of exceptionally warm ocean temperatures. These elevated temperatures are considered to be a contributing factor to the harmful algal bloom (HAB).
Since the last update on 1 July 2025, MHW conditions have continued to remain neutral across most of the states coastal and gulf waters. Persistent moderate to strong MHW conditions remain in deeper waters along the state’s continental shelf margin and adjacent oceanic waters, with moderate MHW conditions persistent in the waters surrounding Kangaroo Island.
Daily satellite measures of chlorophyll-a (chla) levels, an indicator of algae concentrations, show elevated chla concentrations persist across most of upper Gulf Saint Vincent as far south as Troubridge Point in the west and West Lakes in the east.
Other regions of high chla concentrations include large areas along the western and eastern coastlines of Spencer Gulf, including from Port Lincoln to Franklin Harbor.
Since the last update, daily changes in chla concentrations observed on the 2 July 2025 show broad areas of increasing chla in upper Gulf Saint Vincent, particularly along the western coastline of Gulf Saint Vincent from Troubridge Point to Port Wakefield, and along the northern and northwestern coasts of Kangaroo Island.
Widescale increases in chla are observed across multiple regions of Spencer Gulf, including the southern gulf region, along the western coastline from Port Lincoln to Franklin Harbor, and large areas along the east coast of Spencer Gulf.
Chla concentrations have continued to decrease across coastal waters along the eastern side of Gulf Saint Vincent from Outer Harbour to Aldinga, along the Coorong and around Chinaman Wells on the Yorke Peninsula.
Download the full SA harmful algal bloom situation update ().
Modelling
Latest oceanographic forecast modelling of particle trajectories representing microalgae for different source locations using the PIRSA eSA-Marine system. Blue arrows indicate the model wind speed and direction. Red lines highlight the convex envelope, or polygon, with the shortest perimeter that encloses the particles tracked from each source location across the simulation period.