Algal Bloom Expansion in South Australia
Modelling predicts that the algal bloom, which has affected South Australia’s coastlines since March 2025, will spread further through the Spencer Gulf in the coming months. The gulf, located between the Yorke and Eyre peninsulas, was initially believed to be relatively unaffected. However, this changed in early 2025 when the bloom appeared at the south-western tip of the Yorke Peninsula. Since then, the harmful algae Karenia cristata has been increasingly observed along the eastern coastline of the Spencer Gulf, raising concerns among local communities and businesses.
Despite these concerns, some regional residents emphasize the importance of staying alert without panicking. New modelling from oceanographer Jochen Kaempf suggests that the bloom may continue to grow in the gulf, with harmful brevetoxin moving northward and lingering for a longer period.
Dr Kaempf’s findings follow an announcement by the Department of Primary Industries SA (PIRSA) last week confirming the presence of Karenia in Boston Bay and other areas of the lower Eyre Peninsula. According to PIRSA’s website, elevated levels of Karenia have been detected at seven of the 32 onshore testing sites on the Eyre Peninsula, with Boston Bay recording the highest concentration at 372,480 cells per litre.
New Model Predicts Movement
In 2025, Dr Kaempf developed a model predicting the movement of the algal bloom, suggesting it would extend into Gulf St Vincent based on currents, nutrients, and water temperature. Using recent data from the South Australian Research and Development Institute (SARDI) and scientific information on current movements, Dr Kaempf has released an updated model predicting the potential for growth into the Spencer Gulf.
“In this model, it starts in May and uses the temperature and salinity and currents that exist as a starting point, and only adds algae at a concentration of 100 cells per millilitre,” Dr Kaempf explained. “In this simulation, this patch now spreads slowly along the west coast northward in the Spencer Gulf and reaches by about August, September, October the upper Spencer Gulf.”
Dr Kaempf noted that the conditions are similar to those seen last year. He predicted that the algal bloom would “hang around much longer” than previously thought. “Now we have the same situation; the algal bloom was actually declared over, but we are in a similar season. Last year, the algae bloom started in late March … now we have another hotspot around Boston Bay. With my expertise, I can see that this is potentially the second wave, I call it.”
Citizen Science Helps Get Results
At North Shields beach, about 11 kilometres north of Port Lincoln, resident Wendy Lambert walks down the jetty every day to collect water samples. She uses a homemade filter to gather samples and check for toxins. Ms Lambert is one of many citizen scientists across the state who collaborate with trained scientists in the Phytoplankton of South Australia group, working together to track the harmful algal bloom.
Earlier this week, Ms Lambert received a call from friends who found nearly 1,000 fish, some still gasping for air, when the tide receded. “There were all these tiny bait fish, sardines or something small scattered around,” she said. “They looked very healthy; they were shiny and bendy. That was a bit concerning, and before that I’d found Karenia in my water samples off the North Shields jetty and Louth Bay jetty.”
Ms Lambert has observed fish washing up as early as April. “Lots of pufferfish … there was a fairy penguin [and] a New Zealand octopus, which I’d never seen before,” she said. She described the collaboration between government and citizen scientists as a “hunter-gather” style effort. “They’re the ones that need to know, and that’s where the citizen science comes in … we can work hand in hand. We can hunt it and if we find it, if they’re interested, they can have another look.”
Keeping Perspective
Sacheen Hopewell, acting chief executive of the District Council of the Lower Eyre Peninsula, urged people to “be alert but not alarmed.” She emphasized that speculation and innuendo could be as harmful to the industry and economy as the bloom itself. “We encourage everyone to get their data from the government experts, from PIRSA and SARDI. It’s being actively managed, and I think as a council we’re comfortable that those agencies are doing their job and keeping us informed.”
Ms Hopewell pointed out that while elevated levels of Karenia have been detected, it is important to maintain perspective. Outbreaks in metro areas often reach counts into the millions, compared to the hundreds of thousands in the local region.
Multiple Lines of Evidence Needed
A PIRSA spokesperson stated that ongoing monitoring continues to rule out the presence of Karenia in most South Australian waters. However, the government acknowledges that there is no guarantee the bloom will not return. “The government is aware of, and acknowledges, the modelling produced by Jochen Kaempf and others,” they said. “However, the bloom has evolved differently to some modelled scenarios at various stages of the event, reinforcing the need to rely on multiple lines of evidence, including field sampling, satellite observations, and oceanographic monitoring to develop improved early detection and predictive capability.”
Water testing occurs twice weekly in areas with elevated Karenia activity, such as near the lower Eyre Peninsula. In addition to regular testing, the state government has invested in six early detection and environmental monitoring buoys, including one in Boston Bay, which can provide early detection of harmful algal blooms.
