I first went to South Australia in mid June, at which point, Yeah, the bloom was in full swing. The large number of fish and marine life have been washing up dead along the shore, including two penguins in the past week.
It's been one year since dead fish began washing up on South Australian beaches as the largest algal bloom in Australia's history spread along the coast. Marina College Ast doctor Scott Bennett was part of the team that first surveyed the bloom.
Nobody was looking under the water, nobody had seen impacts on the reef, and in discussion with colleagues in South Australia, they had really limited capacity to get out there and have a look.
Seven Am spoke with doctor Bennett in August twenty twenty five after he had just come face to face with the devastating impact of the largest algal bloom Australia has ever seen. Twelve months on, the bloom is still there, the damage are spread and many of the warning scientists made in those early days have proved well founded, especially the damage to marine life. I'm Daniel James and you're listening to seven AM today.
We're bringing you.
An episode from August twenty twenty five where host Ruby Jones speaks to marine ecologist doctor Scott Bennett about what caused bloom. What we saw beneath the surface are what it means for the fate of the ocean. It's Sunday, March twenty two.
Calls are growing for the Commonwealth to declare an enormous algal bloom off the coast of South Australia a natural disaster. It's been described as an underwater bushfire because of the devastating effect on marine life.
Scott, You've conducted the only underwater survey of the impacts of the algal bloom in South Australia, So can you tell me about what you saw.
It was one of the most devastating dive trips I've ever been on, to be honest. So you know, we do these trips around the country monitoring biodiversity of our reefs, and when we do them, they typically really enjoyable trips. Obviously, we have just these amazing help forest ecosystems throughout Southern Australia.
Visibility is often really nice.
You can see a lot of life and diversity on these dives, so they're really exciting trips to go on. This trip, the whole spectra of it was unlike anything we normally do.
Beach goers first sounded the alarm about the micro algal bloom back in March, after dead marine life washed up along the Flurio Peninsula and surfers reported feeling unwell.
You know.
On the first dive, To be honest, kind of fulfilled our expectations. We actually couldn't see anything. It was just so turbid and stirred up. But we continued on and conditions over the day and that week got better, but the realization of the impacts on the marine life were really reinforced.
The algal bloom has spread into the Gulf of Saint Vincent, with smaller mini blooms likely present in the Spencer Golf too.
I've never seen so many dead animals on the bottom of the ocean. Normally, if things die, they get consumed or washed away or taken away pretty quickly.
This wasn't the case. Right now.
There's a lot of dead, particularly invertebrate animals, the things like sea stars, crabs, dead and lying around on the bottom.
More than twelve thousand animals are estimated to have died so far, including fish, sting, rays, dolphins, and sharks. Commercial fishes have been forced to pause their operations indefinitely.
A lot of fish that you would expect to see just weren't there.
A lot of the reefs would ghostly quiet.
But at the same time, a lot of the seaweeds and a lot of the reefs were okay, like reasonably healthy, and so it wasn't a complete apocalypse.
Okay, Well, tell me more about the algal bloom itself. What is it exactly and how did it start?
Yeah, So, in this case, the hat the harmful algal bloom is a bloom of microalgae, harmful micro algae in this context. The reported species a lot is Krenia mikimoti, but it's actually a multiple species that are forming this bloom. But what's concerning is there's a number of there's types of toxins, so things brevity toxins which are being found in these blooms haven't been recorded in Australia before. So while harmful algal blooms are actually really common around Australia,
we see them in all states. We see them in some form each year, We've never seen anything of this magnitude before this scale.
And so what are the conditions that lead to a bloom like this? What do you need to have in the ocean.
So typically we need warm temperatures, long days, plenty of light and nutrients. And for this bloom, what we saw was we had a really intense marine heatwave. It's one of the most intense marine heat waves recorded in South Australia, which seems to have been a real trigger. It obviously occurred in summertime where we still have long days, and
it was on this base of high nutrient conditions. So the nutrient trigger or the nutrients sauce is still unknown, but yeah, certainly nutrients are an important factor as well as temperature.
What is it like for you as someone who has spent their working life in reefs gone on? I'm sure many dives seen incredible things underwater. What is it like to do a dive like this and witness the state of the reef right now?
It's really devastating to see the state of the reef the moment. And for me as a scientist as well, South Australia is a really unique place for the bider diversity, least reef biodiversity. Around seventy percent of the species that live on the reefs in this area are unique to the region, unique to Southern Australia. They're unique because they've been isolated literally for tens of millions of years here at the bottom of the earth, basically not found anywhere
else on Earth. And until now, South Australia has been a bit of a refuge for a lot of these unique temperate species. We've had huge impacts on our east and west coast of the country due to marine heat waves and the like, and for whatever reason, South Australia hadn't suffered those heat waves and those impacts until now, and so the population levels of some of our most rare and bizarre organisms were stable or high in South
Australia where they collapsed everywhere else. And now that refuge is under attack.
Can you tell me more about those species? What sorts of creatures are we talking about?
I mean, there's a whole host of really weird, wonderful things. I think some of the most iconic, like our leafy sea dragons, particularly around the Adelaide coastline, and the fluri of Peninsula places like Rapid Bay and Victor Harbor. These are real tourist attractions to come and see these leafy sea dragons, which you only find in South Australia and
in parts of southwestern Australia across the Brema Bay. But in the early days of the bloom people were finding dozens of these washed up and you know, they're not huge populations, so they're obviously a massive concern. Another massive concern, which is a really live issue at the moment, are the giant cuttlefish. And each year there's this remarkable event where just thousands on thousands of cuttlefish come and aggregate
in this small area to mate and lay eggs. At the moment, the bloom is tracking up the Spencer Gulf towards these aggregations. Currently the adults have laid their eggs and they're now going through their natural senescence phase.
There's a lot of concern for.
What will become of this new cohort that's about to hatch, and if the bloom continues to move up, it could.
Reach there in the next weeks. If nothing changes.
Coming up, what will happen if the cuttlefish and the bloom collide. Scott the algal bloom in South Australia is still spreading and it's getting closer and closer to the gathering of these giant cuttlefish that's happening right now. So if the bloom does spread to where they are, what impact will that have.
Well, there's a real risk that we lose this entire cohort, which means this entire population is under genuine and serious threat from the hab There's been a number of emergency meetings trying discussing possible interventions and things like this. But the scale of these aggregations and these breeding events, and the time frame that we're working with, which is literally you know now, things have to happen immediately, it is significant.
Interventions aren't really on the table. Things like removing eggs and relocating them, you know, just the feasibility of those things are deemed not possible right now, and so there is a real risk these populations are lost or they're going to be severely impacted we would expect.
And one of the scariest things about this algal bloom is the scale of it. And it's still spreading, I believe. So as you watch that happen, what is that telling you about the fate of our oceans?
More broadly, Yes, I think One of the scary things about this is the scale of the impact. Is the largest harmful algal bloom that we've seen in Australia, most devastating. It's spanning across tens of thousands of squadkilometers of reef, of marine habitat, and we don't expect this to be an isolated or unique event to South Australia. This is quite symptomatic of the impacts of climate change that we're
seeing throughout our coastlines around Australia. I mean, it was only this summer that northwestern Australia, up off Ningaloo, the roly Shoal, some of our most iconic coral reefs, suffered some of the most devastating bleaching events that they've ever experienced as well. So this is happening in parallel with the hab down here. We know in southeastern Australia these synergistic or compounding impacts of really rapid rates of warming
down the coast of Tasmania eastern Victoria. That's bringing new species further and further south. And so in the case of Tasmania, it's bringing this long spine sea urch and further south, and these long spine search is overgrazing that they're voracious herbivores. They feed on kelp and seaweeds and they create these large baron areas that are devoid of vegetation.
And those barren areas are spreading really rapidly through Tasmania, Eastern Victoria, in the far south of New South Wales now and it's another one of these synergistic effects of climate change that we're seeing on our coasts. That's affecting thousands of kilometers and the future of hundreds of thousands of reef species.
So with all of that already happening, what could be done now to protect this marine life.
Yes, so the have was really triggered by the intense marine heat wave we had in South Australia. We know heat waves are becoming more frequent and more intense with climate change, and so we really need to act on climate change as an Australian community, as a global community, reduce our carbon emissions immediately. We can't avoid or get around that. That has to be a number one priority.
It's also obviously a long game. There's so much inertia in the system, and so at a more regional local context, there are things we can also do so. Looking after our coastal waterways and minimizing nutrient pollution is really important and there are several ways we can do that.
So we know.
Our marine habitats play a really crucial role in filtering the water. So kelp forests, seagrasses and oyster reefs amazing filters of the water. They uptake nutrients and keep our coastal water waste clear. So maintaining healthy habitats is one of the best things we can do to bolster the resilience of our coastal systems.
And if those changes don't happen, what's at stake here?
This have has really shown what's at stake. You know, the algor bloom in South Australia is just crippled local fishing industry, it's crippled the tourism industry, and it's had an enormous emotional psychological effect on South Australian people and the Australian society more. And these impacts are very real at a human level, they're very real and they.
Affect us personally.
At an ecological environmental scale, we could be losing thousands upon thousands of species that are unique, that have been swimming these waters for literally tens of millions of years, and they could be gone on our watch.
Well, Scott, thank you so much for speaking with me today.
Thanks very much.
For tomorrow, we're bringing you an episode with journalist Tamus McDonald and where to draw the line between facts and fiction in a world where deep fakes and disinformation are increasingly weaponized online?
What happens to democratic society, What happens to community? What happens to our ability to solve problems If we can't agree on a set of facts to begin with, the think it is a really profound challenge for us.
I'm Daniel James. This is seven am. Thanks for listening.