A harmful bloom - marine algae in South AustraliaA harmful bloom - marine algae in South Australia 

Every so often, we are reminded that Mother Nature is really the one in charge.  

One such moment was March 2025, when the first blossoms of what would become the largest harmful algal bloom (HAB) event in our modern history began to unfurl along the South Australian coastline. 

One year later, and the bloom has spread over 20,000 square kilometers, moving and pulsing like a living thing (which it is) as it touches first one community, and then the next. 

Australia is home to many marine organisms that produce toxins, including the world’s oldest fossils of cyanobacteria, found in Archaean rocks in Westen Australia that date to 3.5 billion years ago). In the South Australian case, the main culprit is the dinoflagellate Karenia mikimotoi ,a naturally occurring marine algae.  Karenia is fatal to marine organisms, with Australian wildlife tracking app iNaturalist registering between 400-500 different species affected and thousands of reported deaths. 

It isn’t just taking a toll on marine organisms. People have been told not to go to affected beaches, and if they do, they are met with dead fish, dirty yellow foam and they, or their pets, may have an allergic reaction.  Coastal communities are suffering from a downturn in tourism, fishers have nothing to catch, divers, surfers and snorkellers are stuck on shore. 

We don’t yet fully understand what triggers algae to bloom. However, warm temperatures and nutrient rich waters can trigger the process. Marine biologist and marine biotoxin expert Dr Greta Gaiani has spent decades studying algal blooms.  I asked why we couldn’t predict or prevent this HAB event. 

Dr Gaiani explained that it is difficult to reproduce algal blooms under laboratory conditions, so it isn’t fully possible to replicate the same environment in the lab that the algae experiences in the open ocean. To study blooms, scientists must rely on natural events. Collecting data during an active bloom event is challenging, and costly. 

As we crept closer to the warmer months of summer 25/26, the bloom didn’t budge. So, in October 2025, the South Australian government acted; launching the website Algal Bloom Update to provide public information and the $102.5 million Algal Bloom Summer Plan to support environmental research, industry and tourism grants and community projects. 

Non-Governmental Organisations like Divers for Climate and the Great Southern Reef Foundation have also taken up the call to arms, recording what they see and speaking for their communities to the government. 

The big question remains. What practical steps can we take to make this HAB event go away? I’ve had a few behind closed doors conversations with scientific experts and what most of them have said is that there is very little that science can do to stop it once it’s there. All we can do is wait for it to go away on its own. 

So, what can we do?  Unsurprisingly, and just like the problem of plastic pollution, the answer is to stop it at the source.  

Environmental crises have more than just environmental and economic impacts; they can also affect wellbeing.  Interested to know the impact that the HAB is having on South Australian wellbeing, Dr Brianna Le Busque, of Adelaide University surveyed over 600 participants, asking: 

• What is the level of eco-anxiety experienced by residents during a HAB event?
• What wellbeing impacts do residents report experiencing during a HAB event?

In Le Busque et al (2026), Sixty four percent of respondents reported ‘being directly or personally impacted by the HAB event’, with the key themes being, 

• Disruption of their usual interactions with the ocean (no fishing, no surfing, no swimming)
• Sadness, worry and impacts to mental health,
• Changes to physical health (respiratory issues, etc)

While Dr Le Busque’s research reports on the observable psychological impacts of one particular HAB event, it opens the door on a broader discussion as to if eco-anxiety, or extreme worry about current and future harm to the environment caused by human activity and climate change, can affect general human adaptation and resilience to future events. 

Grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference. 

Attributed to American theologian Reinhold Niebuhr, the original Serenity Poem was adapted and adopted by Alcoholics Anonymous as an introspective reminder to those battling addiction. Its purpose is to reduce emotional turmoil by providing a formula for articulating controllable versus uncontrollable events. 

Taking what we know about the South Australian algal bloom, here are the uncontrollable events: 

• We don’t know when it will be over. 

Okay, so what are the controllable events? As an individual, you can: 

• protect yourself and your animals when near the beach. Do not touch the bloom or any dead species.
• report dead marine life to iNaturalist.
• Stay informed.
• Support local business affected by the downturn in tourism.
• Work to limit release of excess nutrients into the water system in your own home.

As a society, we can support science with the resources needed to both better understand what causes algal blooms as well as the full scale of the environmental and economic impact. And we can educate ourselves about the impacts of eutrophication on our waterways.   This is crucial. While we do not and never will control Mother Nature, we can control human actions, and we can work together to predict and prepare for what may come our way next.