7am The giant cuttlefish and the deadly algal bloom
Aug 12, 2025
In this gripping discussion, marine ecologist Dr. Scott Bennett, who studies algal blooms at the University of Tasmania, shares his alarming findings from South Australia. He details the unprecedented algal bloom affecting the region, leading to the death of over 12,000 marine animals, including rare species like leafy sea dragons and giant cuttlefish. Scott emphasizes the threats posed by rising ocean temperatures and marine heatwaves, urging urgent conservation measures to protect delicate ecosystems from further decline.
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Ghostly Reefs And Dead Invertebrates
- Scott said he'd never seen so many dead animals on the seabed, with invertebrates like sea stars and crabs lined up dead.
- He noted reefs were ghostly quiet with many expected fish absent despite some seaweeds remaining healthy.
Unprecedented Multi-Species Toxic Bloom
- The bloom comprises multiple harmful microalgae, notably reported as Karenia mikimotoi, and contains unfamiliar toxins like brevotoxins.
- This event's scale is unprecedented in Australia despite HABs being common annually.
Heatwave Plus Nutrients Triggered Bloom
- Warm temperatures, long daylight and nutrients combined with an intense marine heatwave appear to have triggered the bloom.
- The exact nutrient source remains unknown, but nutrients plus heat were key drivers.