A naturally occurring harmful algal bloom (species Karenia mikimotoi) has been affecting large areas of South Australia’s coastline since March 2025. Recent environmental events, including a marine heatwave, flooding, and cold-water upwelling, are potential contributing factors.
The algal bloom has been implicated as the cause of significant mortalities of fish, sharks and rays, and the death of a wide range of invertebrates. Other marine wildlife may also be affected, and indirect impacts could include reduced food availability for marine and coastal species.
Water quality is affected in regions where the bloom is occurring, and human exposure to discoloured or foamy water may result in short term health impacts. For public health advice, visit: Water quality alerts | SA Health
Members of the public should avoid touching sick or dead wildlife. The public are encouraged to report observations of sick or dead marine wildlife in South Australia as follows:
For regular updates on this incident, visit Department for Environment and Water - SA harmful algal bloom update.
If you see any other unusual signs of disease or deaths in wildlife anywhere in Australia, you can report it to:
- your local State/Territory WHA Coordinator
- the 24-hour Emergency Animal Disease Hotline on free call 1800 675 888
- your local veterinarian
- the Department of Primary Industries or Agriculture in the State/Territory in which the event is occurring/occurred.