Toxic Algae Turns Australia's Coorong Estuary Into A "Slurry Of Dead Worms" - DeadlyTo At Least 200 Marine Species

When South Australia’s algal bloom arrived in the Coorong, it stained the water like strong tea before turning it into a slurry of dead worms. Many had hoped the storm in late May would break up the bloom of Karenia mikimotoi algae, which has killed more than 200 different marine species. Instead, high tides swept the algae into the Coorong, an internationally significant Ramsar wetland at the mouth of the Murray River.

Once there, the algae began “reproducing madly” in the nutrient rich waters of the North Lagoon, according to estuarine ecologist Faith Coleman. Among the dead were mostly benthic species – estuarine snails, shore crabs, baby flounder and “a thick stew of dead polychaete worms” – a crucial food source for shorebirds and fish.

Levels had declined from their peak but the smell of rotting fish remained, along with algal spores buried in the sediment. “As soon as it warms up again, the likelihood is [the algal bloom will] be back,” Coleman said.

The marine heatwave, a contributing factor to the bloom, persisted off the coast of SA, according to an 11 June update, which showed increases in chlorophyll – an indicator of algae concentrations – along the Coorong coast and western Gulf Saint Vincent.

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https://www.theguardian.com/environment/2025/jun/15/deadly-algal-bloom-in-south-australias-coorong-an-environmental-eye-opener-ecologist-says