Understanding of harmful algal blooms still murky, disaster survey finds

Public understanding of harmful algal blooms still low, survey finds Thu 25 Jun 2026 at 12:47pm Public understanding about harmful algal blooms remains low despite the devastation wrought across SA this year, a survey has found, amid a drive to better prepare the country for the likelihood of more blooms in coming years. Australian National University medical anthropologist and associate professor Amy McLennan is among a group of trained volunteers, including ocean scientists, epidemiologists and disaster experts, who came together during SA's harmful algal bloom (HAB). Calling themselves The Algal Bloom Shed, their survey found that 57.2 per cent of respondents identified causal factors not scientifically considered to be primary drivers of blooms, while nearly a third nationally said they were unsure of the triggers. "It tells me that even a baseline understanding of ecosystems and algae is pretty limited," said Dr McLennan, a corresponding author of the paper. "And that is surprising, because while we talk about HABs as bad, it's a kind of microalgae, a phytoplankton, and plankton is necessary in the ocean. "It's the lungs of the earth." In fact, phytoplankton absorbs between 30 per cent and 50 per cent of the atmosphere's carbon dioxide and is estimated to absorb as much as all the world's land plants combined. The group's study, Public literacy around systemic disasters: A case study of the South Australian coastal harmful algal bloom, was based on a survey of 1,031 Australian residents. Theories rampant When SA's HAB first emerged earlier this year, killing countless marine animals and affecting human health, social media in particular was awash with theories as to its trigger. They ranged from desalination plants and dumped toxic waste, to chemicals planted by Chinese warships that conducted live-fire drills in the Tasman Sea, or space debris falling into the ocean. "When there is an absence of education and knowledge, it is very easy for misinformation to fill the gaps,"Dr McLennan said. The survey found state and federal government responses, which were broadly consistent with past and current responses to systematic disasters globally, were "reactive rather than anticipatory" and focused on crisis management and the investigation of a specific threat. Its prevailing approach was "evidence-based decision making", which awaited evidence "before implementing protective measures". In the context of systematic disasters, the study found environmental systems could change faster than government departments could respond, "causing data collection, analysis and research infrastructures — and the relationships required — to lag behind". "This not only limits predictive capacity, but also limits the ability to measure effectiveness of future government action, as no baseline evidence is established," the study states. Dr McLennan said state and federal governments had a done a "tremendous job" with evidence-based decision for 50 years, but with "any strength comes a shadow". "These kind of disasters are pretty unique because evidence-based policy making really hobbles you. You have to wait for evidence before you can make safe decisions," she said. "Then you have to make judgement calls, and on whose judgement and with what information, and who is going to hold responsibility if the judgement is the wrong one? "Unfortunately, whoever holds responsibility is mostly crucified in the press if they get it wrong." The Algal Bloom Shed is working to improve processes, stating the study revealed "important insights to inform responses to coastal HABs in future, as well as a baseline of data against which to measure the impact of any interventions". Higher nutrients prime a bloom The state government eventually blamed the HAB on nutrient-rich floodwaters that filled the ocean from the Murray Mouth in 2022-23, a cold-water upwelling in summer 2023-24 that brought more nutrients to the surface, and then a lasting marine heatwave from September 2024 that triggered the bloom. These findings were reflected by survey participants, with higher nutrients in the water identified by 42.7 per cent of participants as a cause, along with seasonal temperature changes (39.1pc) — although a greater proportion of SA respondents identified these factors (52.5pc and 46.3pc, respectively). The study found that a better understanding of cause and effect with regard to HABs could influence public support for policy and funding interventions. It found the role of media and education to be important in this regard, pointing out that the SA HAB did not appear to have generated "sustained media attention or public engagement at a national level to prompt a stronger disaster response beyond the local SA coastal regions". There is also concern among some researchers that pointing to River Murray flooding and climate change shifts responsibility to a national, and even international level, and overlooks localised mitigation measures that could take place. The survey found that Australians remained far more concerned about disasters such as bushfires and flooding than they did HABs, despite 22 million people living with seven kilometres of the coastline and climate change modelling predicting more frequent and severe blooms. Half of national participants did not know HABs could affect human health, and while South Australian respondents demonstrated greater awareness and concern, only a minority reported comprehensive knowledge. "This knowledge gap is concerning, as public understanding plays a critical role in shaping risk perception, behavioural response, policy support, and community resilience and determines the social license for prevention and adaptation measures," the study found. Unprompted, respondents listed bushfires (54.8pc) as among current or recent disasters they were aware of, followed by flooding (40.3pc), cyclones (24.2pc), storms/hail/wind (12.1pc), and drought (8.3pc). Algal blooms and water quality only registered at 2.4pc, although respondents could identify more than one natural disaster. The study also found Australians had a "relatively low prioritisation of disasters — and HABs in particular — when compared with everyday socio-economic concerns". Cost of living and healthcare dominated respondents' concerns in Australia, while environmental and climate change-related risks were perceived as less pressing. Once participants were prompted to consider specific scenarios, however, rather than consider them in abstract terms, their concerns "increased substantially". Of respondents who stated they were quite concerned or very concerned about the SA HAB, what bothered them most was harm to marine life (32.1pc), uncertainty about causes and outcomes (27.3pc) and fears it would spread beyond SA (25.3pc). Health and safety concerns also featured (17.5pc) but economic impacts were lower at 7.3pc. Personal responsibility missing The survey found that most people expected the federal government (77pc) or state government (75pc) to take responsibility for action, followed by environmental protection agencies and regulators (68pc). Some 68.1 per cent of respondents felt more action was needed to address the HAB in SA, and just 35.1pc believed current responses were appropriate. Respondents felt their own personal responsibility was low (28pc). Dr McLennan said that despite there being no community infrastructure in place, such as the CFS in the case of bushfires, or the Red Cross, the HAB in SA prompted people and communities to find "ways to step into that breach". "It's a hallmark of Australian society. It seems we're very good at volunteering in disasters and working as a community," she said. National office launched Meanwhile, the state and federal governments last week announced the opening a $3.2 million National Office for Algal Bloom Research in Adelaide with the SA Research and Development Institute. In a joint announcement, they said it would deliver long-term research programs to better understand the "formation, spread and impacts of algal blooms, with the goal of informing the development of new responses technology that will better protect our ecosystem, industries and communities, both now and into the future". They also said the "collaborative approach to algal bloom research was on full display at the Algal Bloom Research Symposium in Adelaide earlier this month". Members of The Algal Bloom Shed were among those who presented at the symposium.