Toxic Algal Bloom Off South Australia Declared Natural Disaster

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.

What’s happening?

  • A toxic bloom caused by Karenia mikimotoi, a planktonic alga, has spread across 4,500 sq km of South Australia’s waters.
  • The algae damage fish and shellfish gills, block sunlight, and rob ecosystems of oxygen, turning biodiverse reefs into lifeless zones.
  • About 450 marine species—including leafy seadragons, bottlenose dolphins, and surf crabs—have perished.

Cause of the Bloom

  • A marine heatwave in September 2024 raised ocean temperatures by 2.5°C.
  • Prior flooding in 2022 flushed nutrient-rich runoff into ....
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Ecology & Environment