South Australia’s algal bloom crisis:
a warning we can’t ignore
The devastating algal bloom currently occurring along South Australia’s coastline is a heartbreaking and visible sign of distress in our marine ecosystems.
Stretching across more than 4,400 km² and impacting life to depths of 30 metres, it has transformed once-thriving underwater ecosystems into barren seascapes.
For divers, scientists, the fishing industry and coastal communities, the loss is deeply personal and profoundly troubling.
While algal blooms can occur naturally, this crisis is fuelled by a combination of human-driven pressures: a prolonged marine heatwave caused by climate change, with water temperatures 2.5 °C warmer than usual, altered ocean conditions such as relatively calm marine conditions with little wind and small swells, combined with nutrient-rich runoff flowing from river catchments.
These interacting forces are not random: they are symptoms of a system under stress, and they will only become more common if we continue on our current trajectory.
From algal blooms and fish kills in the south to coral bleaching and ecosystem collapse on the Great Barrier Reef and Ningaloo, we are witnessing the same patterns unfolding in different ways around the continent: warmer waters, weaker protections and a political system still failing to confront the root cause: fossil fuel dependence.
This is why AMCS is pushing for:
- A rapid phase-out of fossil fuels, including a ban on new coal, oil and gas projects that are warming our oceans and fuelling extreme events;
- Strong national nature laws, capable of safeguarding marine life from compounding threats and delivering ecosystem resilience across Australia’s diverse seascapes;
- Sustained federal investment in marine science and conservation, including research and monitoring programs that can detect, understand and respond to crises like this in real time.
We stand with South Australia’s ocean communities – the First Nations people, divers, artists, educators, scientists and fishers who have witnessed this disaster firsthand and are sounding the alarm. Their grief is shared, and their calls for action must be heard.
We don’t yet know how long this bloom will last or how long recovery may take. But we do know what’s driving this disaster – and we know what’s needed to turn the tide. Australia has the tools to build a safer, cleaner and more resilient future.
But only if we act with the scale and urgency this moment demands.
The story of this algal bloom cannot end with silence, inaction or hand-wringing. It must drive political will to confront the climate crisis, reform broken environmental laws, and protect what still remains beneath the surface before it’s too late.
Learn more:
South Australia’s harmful algal bloom: what we know, what we’re learning from the Great Southern Reef Foundation
Before and after: Edithburgh Jetty, South Australia
Image credit: before image by Carl Charter and after image by Paul Macdonald and Elizabeth Solich.
These powerful photographs document the stark transformation of Edithburgh Jetty’s underwater pylons, a once-thriving vertical reef now stripped bare by the devastating bloom.
The “before” images show a vibrant underwater ecosystem cloaked in soft corals, sponges, tunicates, and ascidians, home to sponge crabs, leafy and weedy seadragons, nudibranchs, molluscs, and dozens of fish species.
The “after” images reveal a haunting absence, bare pylons where life once flourished, smothered or starved by the bloom. This loss is more than visual, it represents a collapse in biodiversity, habitat, and ecosystem function.
What took decades to grow was wiped out in weeks. A sobering reminder of how nutrient pollution and climate extremes can unravel even our most iconic marine habitats.
Before and after: Claris Wreck, South Australia
Image credit: before image and after image by Mark Tozer.
“We want people to understand what’s being lost beneath the surface,” Tozer said.
Actions you can take now:
Demand a seismic blasting moratorium
Australia, it’s time to lead on climate action
Add your voice to the Great Southern Reef Foundation formal submission. They’re collecting statements from community members, coastal residents and any concerned Australians to present directly to South Australian and federal decision makers:
SA Algal Bloom Response – Public Concern Submission Form
Dive Deeper
Science of the Algal Bloom – Webinar Recording from Port Environment Centre
Media Assets:
This page provides access to imagery and footage documenting the recent harmful algae bloom impacting South Australia’s coastal waters. These visuals are available for editorial use in coverage relating to the environmental event, its impacts, and the response efforts.
Please credit all images and video as: Stefan Andrews courtesy Great Southern Reef Foundation.
AMCS in the media:
Key statement from Paul Gamblin, CEO of the Australian Marine Conservation Society, regarding the algal bloom in South Australia:
Paul Gamblin said the devastating bloom shows “nowhere is immune from the accelerating impacts of climate change”, and called for “ major coordinated response that matches the scale of this emergency”.
“This unnatural, shocking event needs all hands on deck,” Gamblin said.
The algal bloom is naturally occurring, but the state’s environment department has listed potential contributing factors including a marine heatwave that started in 2024, when sea temperatures were about 2.5C warmer than usual, combined with calm conditions.
Paul Gamblin said “Historically, fishing and aquaculture industries can take years to recover from these algae blooms.”
“It’s an enormous red flashing warning that climate change has arrived off Australia and it is having enormous impacts,” he told AFP.
Media enquiries: [email protected] or 07 3886 5891