Unveiling the Cause of South Australia's Harmful Algal Bloom

The bloom has affected approximately 20,000 square kilometres, accounting for about 30% of South Australia's coastline. It has led to the deaths of thousands of marine creatures and has caused health issues among beachgoers, including respiratory problems and eye irritation.

Collaborative efforts involving the South Australian Research and Development Institute (SARDI), Flinders University, the University of Technology Sydney, and the University of Tasmania have been instrumental in studying the bloom. DNA sequencing has confirmed the presence of Karenia cristata, a species previously unknown in Australian waters, as the primary culprit.

Brevetoxins produced by Karenia cristata have been detected in commercial shellfish farms, leading to temporary closures, and in foam washed up on beaches, with health authorities issuing advice for asthmatics. The presence of these toxins has raised concerns about seafood safety and public health.

In response to the crisis, the state government has imposed temporary fishing restrictions on several species from 1 November 2025 to allow their numbers to recover. These restrictions include a 50% reduction in bag and boat limits for charter boat fishing in the Gulf St Vincent/Kangaroo Island Fishing Zone and a 50% reduction in bag and boat limits for squid, garfish, blue crab, and King George whiting in the Spencer Gulf Fishing Zone.

Efforts to mitigate the bloom's impact are ongoing. The state and federal governments have announced a $1.4 million program to protect Australian sea lions, an endangered species heavily affected by the bloom. Additionally, $850,000 has been pledged to fund the restoration of 15 oyster reefs around Yorke Peninsula, Eyre Peninsula, and Kangaroo Island over three years.

Researchers continue to monitor the situation closely, with 94 coastal sites being regularly assessed by SARDI. While some areas have shown signs of improvement, the bloom remains a significant concern for South Australia's marine ecosystem and related industries.