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Greens senator Sarah-Hanson Young is calling on the federal government to declare a national disaster.
"It's just like a dead zone. It's like a bomb has gone off. Everything is dead. Everything is decimated."
A toxic algal bloom is devastating marine life in her home state.
"What we're seeing unfolding on the South Australian coastline, and now right along Adelaide's metro beaches, is this algae bloom that is killing our sea life and our wildlife, killing the vegetation within the sea beds, and it's a disaster, it's an environmental catastrophe."
Susan Close is the Deputy Premier of South Australia, and Minister for Climate Change, Energy and Water.
"We've counted almost 400 different species that have washed up, and probably tens of thousands, if not more, of individual animals."
Professor Shauna Murray is a marine biologist with the University of Technology Sydney.
She's been studying toxic algal blooms for 20 years, and the South Australian government sent her some samples back in mid-March.
"And that was when I was able to identify the cells that was most abundant in the sample as Karenia mikimotoi."
The algal bloom grew to 4,400 square kilometres - close to the size of Kangaroo Island - and 20 metres deep.
There was a dramatic increase in number of marine creatures washing up dead.
Professor Murray explains why.
"It doesn't produce an actual toxin, but it can damage the gill cells of fish by producing things called reactive oxygen species, which can damage fish gills. So it seems like then the fish might die through drowning, essentially."
Susan Close says the bloom is spreading - including into the Port Adelaide River - but the harmful algae is less highly concentrated than it was before.
"Now that it's so thinly distributed, it's harder to describe how big it is. It's certainly widely spread - it is in some concentration along much of our coastline, certainly metropolitan, the other side of this gulf and into the next gulf, into Saint Vincents and Spencer Gulf - but mapping its size is difficult because we don't know always how deep it is. When it was the size of Kangaroo Island and 20 metres deep, that was easy to imagine. This is getting more thinly distributed."
One person who will be watching anxiously as the bloom spreads is Ben Barnes, the Chair of the South Australian Professional Fishers Association.
"Where the algae has grown and bloomed, the fishermen have just stopped catching fish. Everything's gone. I would say there'd be, just in the marine scale fishery, there'd be a hundred fishers in that area that will eventually be affected. But the effect goes on to all sorts of charter boat operators, crab fishermen, and it goes all to the restaurants, to caravan parks, the fish processors, the freight companies. It's going to have a flow on effect that's going to be a massive effect."
The South Australian government announced a relief package valued at up to $500,000 on Tuesday.
Businesses in affected industries will see licence fee relief backdated to April, and Primary Industries Minister Clare Scriven says more help may flow, depending on what happens next.
"We're really waiting to see what happens with the algal bloom. We know that a lot of fishers are doing it very, very tough at the moment, and that's why it was important to work with them to come up with this initial set of assistance. Now, if the bloom dissipates tomorrow, that would be wonderful. It doesn't necessarily mean that everything will bounce back. There are a lot of unknowns about this algal bloom, and about the long term impacts."
One of those unknowns is why the bloom has grown to such a massive size.
Susan Close says a range of factors are thought to have been at play.
"The preconditions that have created this problem for us is essentially that we had a lukewarm bath full of nutrients off the southern coast of Adelaide, South Australia, and created the perfect conditions to have a very large and very problematic bloom."
Since September 2024, South Australia has been experiencing a marine heatwave, with temperatures up to 2.5 degrees warmer than average.
In the two years before that, floods in the Murray River washed sediment out to sea, and an unprecedented cold water current carried nutrients to the surface.
Ben Barnes says he's worried these conditions won't be short-lived.
"I believe the marine heatwave is going to be an issue for a while. I think it'll have a major effect on the fishery and within 20 years we'll be looking back on a fishery that's completely different. So, I said to forecast the exact changes to the fishery is near impossible, but my belief is that we're going to be stuck with algal blooms for quite some time."
He says this is prompting tough questions.
"I mean fishermen are very, very, very proud people. They're not likely to come out and say it, but I know from personal friends and stuff that there's some fairly stressed out people out there and they're all very, very sceptical on how their future looks in this industry."
The psychological impacts are being felt more broadly too.
Dr Brianna Le Busque is a psychologist researching human connections to nature.
he's collecting data on the public response.
"We don't have it all yet and we haven't analysed it yet, but even just already coming through, people definitely are talking about experiencing grief from this and feeling, like, one of the quotes that's come through as feeling like a loved one has died, because they spend so much time by the ocean and are so connected to the ocean. So seeing it and seeing these animals wash up really is having that grief impact. We're also hearing people talking about anxiety and feeling quite overwhelmed."
The algae has also caused allergic reactions in many people - forcing beachgoers to avoid the water.
But there are more hopeful responses, too, as people pitch in to help.
"So there is a little bit of that shift and people are definitely getting involved in things like we've got lots of citizen science projects happening where people are giving data to scientists about the species that are washing up. So it feels like there's a little bit of hope there."
Those citizens scientists are supporting an intensive monitoring program put in place by the state government.
And Professor Murray says that although the evidence shows once a species has established itself, harmful blooms are more likely to recur, another disaster on this scale is not guaranteed.
“There was a bloom of a similar Karenia species in Wellington Harbour in New Zealand back in the 1990s, and its effects lasted, so I'd say three to five years. That one was more a smaller region, but a similar sort of intense effect on that smaller region. So I'd say we could be looking at a similar kind of recovery period of several years."
And she also says the link to climate change is not as clear as it may seem.
"My understanding of harmful algal blooms, and particularly of Karenia mikimotoi, is as I said that it's more of a temperate, a cool temperate species that's common in the Atlantic and the north of China."
She doesn't rule out rising temperatures have played a role.
"But I do think it's probably premature to be speculating about that right now, because to me, what's needed for that kind of thing is the sort of high quality data of the exact environments of the Karenia mikimotoi in terms of the water conditions at that time and place, and also the growth experiments."
Professor Murray is currently culturing species of algae to learn more about the South Australian bloom.
"There does seem to be other Karenia species also probably present in this bloom. And some of them, or one of them seems to be producing a toxin called brevetoxin. So that can also be having a harmful effect."
She says it's not clear how much harm the brevetoxins are causing, and Karenia mikimotoi does seem to be the main problem.
As research continues, senator Sarah Hanson-Young says the Greens will also move to establish an inquiry when parliament returns.
"Originally, the state government in South Australia was telling people that we just needed a bit of rain and a bit of wind, and this would break up this algae and, you know, and we'd move on. We're now being told, actually, it has really taken hold. Some scientists are telling us we need to be prepared for this to be killing our marine life for the next 18 months. So, you know, Adelaide is going to be hosting, hopefully, the world's largest climate conference in 18 months time. I hope that we have some of our beautiful beaches and marine life left by the time the world comes to visit."
