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 a dead or sick marine mammal 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. Since the last update on 13 May, there has been a stabilization of sea surface temperature decreases due to seasonal cooling across the state’s coastal waters. Current temperatures remain up to 2 to 3°C above average for this time of the year. These elevated temperatures are considered to be a contributing factor to the Harmful Algal Bloom (HAB).
Daily satellite measures of chlorophyll-a (chla) levels, an indicator of algae concentrations, with connectivity to the HAB bloom identified off the Fleurieu Peninsula in mid-March, indicate elevated sea surface chla concentrations are currently persisting in Investigator Strait between Kangaroo Island, the foot of Yorke Peninsula and the southern tip of the Fleurieu Peninsula, and along the western coast of Gulf Saint Vincent. However, since the last update, chla concentrations have decreased in Investigator Strait, along the northern and eastern coastlines of Kangaroo Island, along the south-eastern foot of Yorke Peninsula, around parts the Fleurieu Peninsula and in waters offshore from Port Lincoln, Arno Bay, Tumby Bay, Point Turton and Port Victoria in Spencer Gulf. Areas of increasing sea surface chla are observed along the western coastline of Gulf Saint Vincent between Edithburgh and Ardrossan, Newland Head on the Fleurieu Peninsula, Boston and Louth Bays near Port Lincoln, and between Robe and Beachport in the southeast.
Ocean circulation forecasts covering a 5-day period ending 21 May 2025, provide an indication of where water masses, and any microalgae contained within them, may move from multiple source locations based on prevailing ocean currents. These forecasts help anticipate potential shifts in bloom distribution where the presence of HAB species has been confirmed by water sampling.
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.
