Despite the devastating damage caused across SA this year, public understanding of harmful algal blooms remains low, a survey has found. It comes amid a push to better prepare the country for the possibility of further outbreaks in the coming years.
Australian National University medical anthropologist and associate professor Amy McLennan is among a group of trained volunteers, including marine scientists, epidemiologists and disaster experts, who came together during SA’s harmful algal bloom (HAB).
Their survey, called “Algal Bloom Shed,” found that 57.2% of respondents identified a cause that is not scientifically thought to be the main factor in bloom outbreaks, and nationally, nearly one-third said they did not know the cause.
Amy McLennan (right) presented at a symposium in June with Shed member and public health researcher Jacqueline Stevens. (Provided by: Algae Bloom Hut)
“It shows that even the basic understanding of ecosystems and algae is quite limited,” said Dr McLennan, corresponding author of the paper.
“And this is surprising, because even though we talk about HABs as being bad, HABs are a type of microalgae, phytoplankton, and plankton is what the ocean needs.
“It’s the lungs of the earth.”
In fact, it is estimated that phytoplankton absorb 30 percent to 50 percent of the carbon dioxide from the atmosphere, as much as all the world’s land plants combined.
The group’s study, ‘Public literacy on systemic disasters: a case study of harmful algal blooms off the South Australian coast’, is based on a survey of 1,031 Australian residents.
widespread theory
When SA’s HAB first emerged earlier this year, killing countless marine animals and impacting human health, social media in particular was awash with theories about its trigger.
Shovelnose ray found at Christie’s Beach during the June 2025 HAB. (891 ABC Adelaide: Malcolm Sutton)
These range from desalination plants and dumped toxic waste to chemicals implanted by Chinese warships conducting live-fire exercises in the Tasman Sea and space junk that has fallen into the ocean.
“When there is a lack of education and knowledge, it is very easy for misinformation to fill that gap.” Dr. McLennan said.
The study found that state and federal responses have been largely consistent with past and current responses to organized disasters around the world, but have been “reactive rather than proactive” and focused on crisis management and investigating specific threats.
Adelaide’s rainwater problem
Its general approach was “evidence-based decision-making,” waiting for evidence “before taking protective measures.”
In situations of organized disasters, environmental systems can change faster than government sector responses, and “data collection, analysis, research infrastructure, and necessary relationships can cause delays,” the study found.
“This not only limits predictive ability, but also the ability to measure the effectiveness of future government actions, as the underlying evidence has not been established,” the study states.
Sea foam at Christie’s Beach, July 2025. At the time, dead marine life was washing up on the beach. (891 ABC Adelaide: Malcolm Sutton)
Dr. McLennan said the state and federal governments have done a “great job” of making evidence-based decisions for 50 years, but “with every power comes a shadow.”
“This type of disaster is very special because it really hampers evidence-based policy making. You have to wait for evidence before you can make safe decisions,” she says.
“Then, whose judgment should be based on, what information should be used to make the judgment, and if the judgment is wrong, who is responsible?
“Unfortunately, those responsible, if they make a mistake, are almost always crucified in the press.”
Algal Bloom Shed is working to improve its processes and said the study revealed “important insights to inform future coastal HAB responses and a baseline of data against which to measure the impact of any interventions.”
Higher nutrients promote flowering
The state government ultimately blamed HAB for the bloom, which was caused by nutrient-rich floods that filled the ocean from the Murray Estuary in 2022-23, cold water upwelling in the summer of 2023-24 that brought more nutrients to the surface, and a subsequent marine heat wave that began in September 2024.
What the public wasn’t told about SA toxic algae blooms
These findings were mirrored by survey participants, with 42.7% of participants identifying increased nutrients in the water as contributing factors, along with seasonal temperature changes (39.1%), while a larger proportion of SA respondents identified these factors (52.5% and 46.3%, respectively).
This study found that a deeper understanding of the causes and consequences associated with HABs can influence public support for policy and financial interventions.
The report determined that the role of media and education was important in this regard, noting that the SA HAB did not appear to generate “sustained media attention or public engagement at a national level to encourage stronger disaster response beyond the local SA coastal region”.
There are also concerns among some researchers that pointing to Murray River flooding and climate change will shift responsibility to the national or even international level and overlook possible local mitigation measures.
During last year’s algal bloom outbreak, rainwater flowed from Adelaide’s Brighton drainage ditch into Gulf St Vincent. (Provided by: Warwick Noble, Aquatic Assessments)
The study found that with 22 million people living within seven kilometers of coastline, Australians are far more concerned about disasters such as bushfires and floods than HABs, despite climate change models predicting more frequent and severe blooms.
Half of the national participants did not know that HABs could affect human health, and although South Australian respondents showed greater awareness and concern, only a minority reported comprehensive knowledge.
Information on blue-green algae outbreaks is “inconsistent”
“This knowledge gap is concerning because public understanding plays a critical role in shaping risk perceptions, behavioral responses, policy support, and community resilience, and determines social license for prevention and adaptation measures,” the study found.
Respondents were silent and cited forest fires (54.8%) as current or recent known disasters, followed by floods (40.3%), cyclones (24.2%), storms/hail/wind (12.1%), and drought (8.3%).
Although respondents were able to identify multiple natural hazards, algae blooms and water quality were only registered 2.4% of the time.
Algal Bloom Shed members gathered for a Launch Sprint event in February. (Provided by: Algae Bloom Hut)
The survey also found that Australians “rank disasters, and HABs in particular, as a relatively low priority when compared to everyday socio-economic concerns”.
In Australia, the cost of living and health care dominated respondents’ concerns, while environmental and climate change-related risks were perceived as less pressing.
However, when participants were encouraged to consider concrete scenarios rather than thinking in abstract terms, their concerns “significantly increased.”
Among respondents who said they were very concerned or extremely concerned about SA HABs, their top concerns were damage to marine life (32.1 people), uncertainty about cause and effect (27.3 people), and fear of it spreading beyond SA (25.3 people).
Health and safety concerns were also raised (17.5%), while economic impact was lower at 7.3%.
lack of personal responsibility
The survey found that most people expect the federal government (77%) or state governments (75%) to be responsible for actions, followed by environmental protection agencies and regulators (68%).
Approximately 68.1 per cent of respondents felt that more action was needed to address SA’s HABs, and only 35.1 per cent believed that the current response was adequate.
Respondents perceived themselves as having low personal responsibility (28%).
A fiddler ray was found surrounded by stones by local residents during the flowering season at Christie’s Beach. (891 ABC Adelaide: Malcolm Sutton)
Dr McLennan said SA’s HABs had inspired people and communities to find “a way to step into that breakthrough”, despite the lack of community infrastructure like CFS or the Red Cross in case of bushfires.
“This is a characteristic of Australian society. We seem to be very good at volunteering and working as a community during disasters,” she says.
National office established
Meanwhile, the state and federal governments last week announced the opening of the SA Research and Development Institute and a $3.2 million national office for algal bloom research in Adelaide.
In a joint announcement, the companies said they will deliver a long-term research program to “better understand the formation, spread, and impacts of algae, with the goal of informing the development of new response technologies that will better protect our ecosystems, industries, and communities now and in the future.”
They also said that “the collaborative approach to algal bloom research was on full display at the Blue Algae Research Symposium held in Adelaide earlier this month.”
Among those presenting at the symposium were members of the Algar Bloom Shed.
