Since March 2025, South Australia's coastline has been grappling with a harmful algal bloom (HAB) that has severely impacted marine life, the fishing industry, and tourism.
The bloom, attributed to the proliferation of the microalgae Karenia mikimotoi, has led to the deaths of thousands of marine creatures and has caused health issues among beachgoers, including respiratory problems and eye irritation.
The crisis has been exacerbated by a series of environmental factors. Floodwaters from the River Murray in 2022-23 introduced additional nutrients into the sea, while a cold-water upwelling in the summer of 2023-24 brought more nutrients to the surface. Since September 2024, a marine heatwave has raised water temperatures by approximately 2.5°C, creating ideal conditions for the algae to thrive. Scientists have linked these changes to the broader impacts of climate change.
The extent of the bloom is unprecedented in Australia, affecting approximately 30% of South Australia's coastline. The densest occurrences have been reported along the coast from the top of Gulf St Vincent down to Brighton Beach. The bloom has also spread to Kangaroo Island and into the Coorong, posing a significant threat to local ecosystems.
The economic repercussions are profound. The fishing and aquaculture industries have suffered substantial losses, with local fishers reporting dead marine life and declining catches. Tourism has also been affected, as popular beaches and coastal attractions experience reduced visitor numbers due to health concerns and unsightly conditions.
In response, the state and federal governments have allocated AU$28 million for research, clean-up efforts, community support, and public information campaigns. Measures include the installation of a bubble curtain to protect the breeding grounds of the unique giant cuttlefish population in the Upper Spencer Gulf and a AU$1.4 million program to safeguard the endangered Australian sea lions.
Environmental organizations emphasize the need for long-term strategies to address the root causes of such blooms. They advocate for reducing nutrient pollution, restoring marine habitats like kelp forests and seagrass beds, and implementing policies to mitigate climate change impacts.
As the algal bloom persists, it serves as a stark reminder of the interconnectedness of environmental health and human activities. Coastal communities, industries, and policymakers are urged to collaborate on sustainable solutions to prevent future occurrences and protect Australia's rich marine biodiversity.
