Millions of fish and other marine life have been died along the coast of South Australia since at least March this year, with no end in sight and no solutions on the table.
The government is blaming algal bloom, while others are suggesting it could be pollution from a desalination plant.
There seems to be a push that it could only be one or the other, with the government ruling out pollution from the desalination plant, and the problem possibly being a combination of both algal bloom and pollution isn’t something the government seems keen on investigating.
Below: “All these photos are from today’s, 28/8/2025, 600m walk along the high tide line at Tennyson Beach in Adelaide.” (From Instagram account – crab.e.cam) (Click on the arrow, in the middle on the right-hand side, of the below picture to see more pictures)
Algal bloom
On the 24th of March 2025 The Conversation published an article titled, “Mystery solved: our tests reveal the tiny algae killing fish and harming surfers on SA beaches” which start off:
Confronting images of dead seadragons, fish and octopuses washed up on South Australian beaches – and disturbing reports of “more than 100” surfers and beachgoers suffering flu-like symptoms after swimming or merely breathing in sea spray – attracted international concern last week.
Speculation about the likely cause ranged from pollution and algae to unusual bacterial infections or viruses. Today we can reveal the culprit was a tiny – but harmful – type of planktonic algae called Karenia mikimotoi.
The SA government sent us water samples from Waitpinga Beach, Petrel Cove Beach, Encounter Bay Boat Ramp and Parsons Headland on Tuesday. We studied the water under the microscope and extracted DNA for genetic analysis.
Our results revealed high numbers of the tiny harmful algal species – each just 20 microns in diameter (where one micron is one thousandth of a millimetre). While relatively common in Australian coastal waters, blooms of K. mikimotoi occur only sporadically. But similar harmful algal blooms and fish kills due to K. mikimotoi have happened in the past, such as the 2014 bloom in Coffin Bay, SA. And this latest one won’t be the last.
and:
Unanswered questions remain
A question for many people is whether increasing water temperatures make blooms of K. mikimotoi more likely.
Another concern is whether nutrient runoff from farms, cities and aquaculture could cause more harmful algal blooms.
Unfortunately, for Australia at least, the answer to these questions is we don’t know yet. While we know some harmful algal blooms do increase when nutrient runoff is higher, others actually prefer fewer nutrients or colder temperatures. (Click here to read more)
The ABC reported (29/8/25):
“Part of the problem is that researchers are still struggling to tell exactly what it is they’re fighting.”
“We actually do not know yet, with certainty, the identities of the bloom-forming species,” she says.
This makes it hard to say what has caused and exacerbated the bloom — for instance, while researchers generally think warmer waters could be a driver, there may be species in the water that prefer the cold. (Click here to read more)
The Guardian reported (29/8/25):
SA’s algal bloom probably started in January and, over months, has grown to more than 4,500 sq km. By March, surfers complained of a mysterious sea foam, along with irritated eyes and hacking coughs. The algae species responsible was identified as Karenia mikimotoi.
By July it had hit metropolitan beaches: suddenly many more people were witnessing the foam, the piles of seaweed as kelp died off and the animal deaths.
Karenia mikimotoi is not toxic to humans, although it can cause eye, nose and throat irritation. But it has proved catastrophic for fish and marine animals. The iNaturalist site has logged about 34,000 dead animals from about 480 different species.
“We don’t see it stopping anytime soon,” Bennetts says. Satellite imagery has shown the bloom continuing to “pulsate”, dashing hopes that winter would see it off.
and:
The science says the bloom was caused by an ongoing marine heatwave, a phenomenon likely to become more common with global heating, as well as nutrients in the water from the 2022-23 Murray-Darling Basin floods and an “upwelling” of colder water towards the surface. But there are still many unknowns. (Click here to read more)
If “nutrients in the water from the 2022-23 Murray-Darling Basin floods” are part of the problem that opens up a whole new can of worms the government doesn’t seem keen on exploring. For example, what “nutrients in the water” and where did they come from? Farms?
Pollution from the desalination plant at Lonsdale
In the below video environmentalist Simon Mulvany from Save the Bees Australia calls out South Australian Premier for “lies” about the dying fish:
In the above video Simon Mulvany says a desalination plant killed fish in Saudi Arabia which is true.
The BBC reported in January 2019:
Desalination plants around the world are pumping out far more salt laden brine than previously believed, according to a new study.
The salty effluent is a by-product of efforts to extract fresh water from the sea.
Researchers found that plants are now producing 50% more of this chemical laden cocktail than expected.
The brine raises the level of salinity and poses a major risk to ocean life and marine ecosystems.
The problem with all this hyper salty water is that it often contains other contaminants and can pose a significant threat to marine life.
“The salt level in the sea water is further increased because of this disposal of the concentrate brine,” said Dr Manzoor Qadir from the UN University Institute for Water, Environment and Health, one of the study’s authors.
“There is an increase in the temperature of this zone of the sea, together they decrease the dissolved oxygen level, which is called hypoxia and that impacts the aquatic life in that zone.”
Hypoxia often leads to what are called dead zones in the oceans – Scientists say these zones have quadrupled since 1950, mainly as a result of climate change. Now the salt is adding to these problems.
“High salinity and reduced dissolved oxygen levels can have profound impacts on benthic organisms, which can translate into ecological effects observable throughout the food chain,” said lead author Edward Jones, at Wageningen University, in the Netherlands. (Click here to read more)
SA’s current and proposed desalination plants
“South Australia has a desalination plant at Lonsdale that is owned and operated by SA Water” and “The SA government has committed $100 million to investigate a $5 billion proposal to deliver” a desalination plant in partnership with BHP via the Northern Water Supply Project (NWSP). (Click here to read more)
The South Australian government and BHP have invested a lot of money in the proposed desalination plant and have even more riding on it being approved. So, they have a huge incentive to make sure that the cause of the fish kill is not the current desalination plant.
In the above video SA Premier Peter Malinauskas is certain the desalination plant has nothing to do with the fish kill but how would he know given the above BBC report which says, “There is an increase in the temperature of this zone of the sea, together they decrease the dissolved oxygen level, which is called hypoxia and that impacts the aquatic life in that zone.”.
If the current desalination plant is linked to the fish kill then the government and BHP would have trouble moving forward with the proposed $5billion Northern Water Supply Project and the government would be liable for $millions, and possibly $billions, in compensation for all the businesses that have lost income because of the fish kill.
The Federal and State governments have already pledged money: “The $28 million package spans science and research, clean-ups, industry and community support and communications.” and every day it continues, more money will be needed.
There are a lot of questions to be answered and every possibility needs to be investigated in full. SA Premier Peter Malinauskas doesn’t seem the right person to be in charge if we want to get to the truth.
I’ll keep following up on this story and if you know more please make a comment below.
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Categories: Peter Malinauskas
I’m no marine scientist, but why haven’t they been able to see what toxins are in the sea water and in the dead fish? Surely it would show up in the dead fishes organs? We have concerned people that get their own tests done, in the local shire water catchments when we have acid soil run offs?
Follow the money – BHP, desalilnation plants, SA Govt
Good work KCA this is the first I’ve heard about this possible link
https://www.algalbloom.sa.gov.au/home/where-the-algal-bloom-is
1. ” no marine scientist, but why haven’t they” reminds me of my father’s basic argument against climate change which starts off with some variant of ‘I dont understand how they got this result so therefore it’s not true’.
To analyse for a toxin of unknown origin is potentially a needle in a haystack approach but given “they” have access to a HPLC MS or GCMS I would posit that it is probably a part of the analysis.
2. DNA analysis is a very sensitive method and appears to have already identified the organism.
3. Satellite data shows the algal bloom that occurred as flood water left the Murray River and can be tracked as it entered the gulfs.
4. The same data does not show the bloom being initiated off the coast of the desal plant. Desal plants do have an environmental impact but the question not asked above is ‘was it switched on’ and ‘what volumes of salt were being discharged’.
5. Blooms of biomass require large amounts of initiating nutrients (principally N and P, but sometimes others). If you want to “follow the money” then the most likely target will be farming and agricultural runoff after the heavy rainfall.
The desalination planets would be contributing. Here is some more info I picked up awhile ago. Sorry reference is lost.
Kathryn
The Adelaide Desalination Plant in Lonsdale was fully commissioned in late 2012 and began operations, with a significant event occurring in March/April 2013 when an algal bloom, identified as Chaetoceros diatoms, led to the deaths of sixteen dolphins, thousands of dead fish, two penguins, and an unusual amount of sea grass. This was observed at Port Noarlunga reef, O’Sullivan’s Beach, and Aldinga Beach.
• In 2025, following the plant’s ramp-up to full capacity in February, a larger die-off of sea life was reported, aligning with the timing mentioned in the comment.
• The plant discharges brine and trace amounts of process chemicals into Gulf St Vincent at the same outfall site used since 2013, an enclosed body of water that may be more sensitive to changes in salinity and oxygen levels.
• A strong correlation has been noted between the 2013 and 2025 bloom events, with the 2025 bloom potentially exacerbated by nutrient spikes from misuse of the Murray River. @cleanoceanfoundationaus offers solutions to ocean outfalls.
Interesting times. I think Saudi is having same issues.
A novel theory: shipping effluent as a contributing factor
https://x.com/ctindale/status/1954651975884403004?s=46
I immediately suspected that this latest environmental disaster was manmade when I saw the initial news reports. Thank you for taking the time to investigate. I will reshare your article everywhere. The Australian people deserve so much better than the current batch of selected incompetent doormats in key positions of authority in this country.
Interesting theory but the extent of the SA coastal bloom stretches a long distance from the site of the desalination plant so it doesn’t seem to automatically follow that there is a connection. Climate change causing higher than normal sea water temperatures is being suggested as the main cause.