Algal bloom situation update
Overview
Parts of South Australia continue to be affected by the ongoing microalgae bloom, Karenia mikimotoi.
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 algal bloom.
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 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.
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.
Latest update
Since the last update on 15 October 2025, moderate to strong MHW conditions have developed in the upper gulf regions and coastal waters west of Elliston where positive sea surface temperature (SST) anomalies between +1ºC to 2ºC are observed.
Neutral MHW conditions are observed across the majority of South Australia’s southern shelf, gulf and coastal waters where SST anomalies up to +1ºC are observed.
Daily satellite measures of chlorophyll-a (chla) levels, an indicator of algae concentrations, show elevated chla concentrations remain around the coastline of Gulf Saint Vincent north of Port Vincent in the west and extending south along the eastern side of the gulf to Seacliff with smaller patches observed nearshore extending southward to Cape Jervis.
Regions of high chla concentrations in Spencer Gulf include along the western coastline from Port Gibbon to Munyaroo, north of Point Lowly, and along the eastern coastline from Hardwicke Bay to Port Pirie.
Since the last update, daily changes in chla concentrations observed on 18 October indicate a general decrease in chla concentrations in Gulf Saint Vincent, particularly north of Edithburgh and along the eastern coastline including from North Haven to the southern tip of the Fleurieu Peninsula.
Small patches of increasing chla concentrations remain along coastline from Ardrossan in the west to Port Gawler.
In Spencer Gulf, decreases in chla concentrations are observed along the western coastline from Arno Bay to Mitchellville and along the eastern coastline from Port Broughton to Port Pirie.
Regions of increasing chla concentrations include near Cowell, Munyaroo, Whyalla and in patches along the eastern coastline form Port Victoria to Tickera.
Oceanographic forecast modelling of particles released from multiple source regions across the state was used to predict the trajectory of water masses over a period of 5 days, starting 21 October and ending 26 October 2025.
Download the full SA 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.
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.
Science forum
A forum was held on 3 June 2025 that was open to the scientific community and brought together leading scientists from State and Federal government agencies, national research institutes and universities, and the private sector. Experts from New Zealand on algal blooms also provided valuable insight.