Toxic Algal Bloom Off South Australia Declared Natural Disaster

• 23 Jul 2025

On 22nd July 2025, South Australia’s Premier declared the ongoing toxic algal bloom a “natural disaster,” citing its severe impact on marine biodiversity, fishing, and tourism.

Key Points:

• Scale of Outbreak: The algal bloom, detected in March 2025, covers 4,500 square km and has killed or harmed over 400 marine species.
• Species Involved: The outbreak is caused by Karenia mikimotoi, a toxic algae species that clogs fish gills and depletes oxygen in water as it decays.
• Rising Temperatures: A marine heatwave that began in 2024—raising ocean temperatures by 2.5°C—has intensified the bloom.
• Ecological Damage: Over 13,850 marine animals, including sharks, rays, and invertebrates, have been found dead, as reported on the iNaturalist app.
• Impact on Industry: Oyster and mussel farms were forced to shut down; tourism and local fisheries also suffered significant losses.
• Government Response: South Australia announced a A$14 million support package, matched by the federal government, totaling A$28 million for cleanup, research, and economic relief.
• Public Health Alert: Authorities continue to monitor water safety, and seafood harvesting remains restricted in affected zones.