SA's toxic algal bloom is unlikely to end soon so what are the consequences?

Australia Broadcast Center

2 days ago

It's an unprecedented ecological disaster, and authorities can't say when it will end.
South Australia's toxic algal bloom has been affecting waters off parts of the state's coast since at least March.
There were hopes winter weather conditions would help it dissipate, but so far the bloom hasn't gone away.
So what do we know about the bloom, and — perhaps more importantly — what don't we know?
What caused the bloom?
According to Environment Minister Susan Close, there are three main factors that allowed the algae, Karenia mikimotoi , to bloom.
The first is a lot of nutrients were flushed into South Australian waters as a result of the River Murray floods in 2023, providing a food source for the algae.
There's also been a marine heatwave off the state's coast since October 2024, where sea temperatures have been sitting more than two degrees Celsius above normal.
The third factor was a series of high pressure systems that meant the water was relatively still and didn't wash the algae out to sea.
Susan Close says the algae is not toxic to human beings. ( ABC News: Lincoln Rothall )
Ms Close said all three factors can be attributed to climate change.
"All three of the conditions that lead to this have been exacerbated by climate change," she said.
"We can't hide our head in the sand and pretend that this is somehow a phenomenon that might have somehow happened without climate change."
Marine biologist from the University of Sydney Shauna Murray said it's to early to pinpoint the exact causes.
Small fish have washed up dead on Brighton Beach this week. ( ABC News: Olivia Mason )
"It's certainly true that the marine environment is changing and these changes come with a lack of predictability," she said.
"But I think we don't have the data yet and it's going to take time to look through it all and figure it out."
How does the bloom affect fish?
Foam and dead sea life are the two key hallmarks of the bloom.
Professor Murray said the algae affects fish gills and skin.
" Karenia mikimotoi doesn't actually produce a toxin but it does produce what's called reactive oxygen species so this can damage the gills of fish and it can affect skin cells," she said.
"What this damaging the gills of the fish means is marine animals basically drown if their gills become too damaged."
Professor Shauna Murray is one of only a handful of experts in Australia who research algal blooms. ( Supplied UTS: Toby Burrows )
Professor Murray said low levels of brevetoxin have also been detected in the bloom, which could also be responsible for deaths.
She said Karenia mikimotoi doesn't create brevetoxins, but other species of karenia have also been detected in the bloom
" Karenia mikimotoi is the main species and Karenia mikimotoi doesn't produce brevetoxin so we know that's not the major reason," she said.
The algae produced large amounts of foam at Knights Beach in SA's South Coast in April. ( ABC South East SA: Caroline Horn )
"In this particular bloom we've found several other species of karenia.
"None of them are a smoking gun in terms of we know that they have previously produced brevetoxins but having said that we need to get them into culture and test them."
If it affects gill fish — why are dolphins and seals being found dead?
The official advice is that Karenia mikimotoi isn't toxic to mammals.
The government said it's not uncommon for marine mammal carcasses to wash ashore after winter storms.
But it is testing a dolphin carcass that was found at Tennyson Beach last Monday to see if the bloom contributed to its death.
Professor Murray said the presence of brevetoxin could be a factor.
"It's certainly within the scope that this could be related and I think there would have to be investigation to try and work that out," she said.
Where has the bloom reached?
The bloom was first reported by surfers at Waitpinga Beach in March, after they experienced coughing and respiratory affects from the algae.
Since then, its impacts — foaming seas and fish kills — have been seen along the Fleurieu Peninsula, Kangaroo Island and Yorke Peninsula.
At its largest, the government said it was the size of Kangaroo Island.
The winter storms that many hoped would break up the bloom have dissipated it slightly, but they have also pushed it further into the Gulf St Vincent, where it's now affecting Adelaide's metropolitan beaches.
Low levels of the algae have been found in West Lakes, and testing is being done in the Port River, with fears it could reach there as well.
Why is it persisting, and when will it go away?
The government admits, it didn't anticipate the bloom would be this prolonged, and can't predict how long it will last.
The last time there was a harmful bloom of Karenia mikimotoi was at Coffin Bay in 2014, but while it caused some damage locally, it lasted little more than a week.
Dead sea life can be seen along South Australia's coast. ( ABC News: Che Chorley )
Estuarine ecologist Faith Coleman said most algal blooms pass so quickly, they are rarely noted.
"Then there are this group of blooms that last three to four months and those ones cover a larger area, they're often in the more open marine zone and they attract an awful lot more attention," she said.
"What concerns me is there's this class of blooms that last around the 18 months to two years and there seems to be this gap between three to four months and 18 months to two years.
"So I am deeply concerned that since we have passed that three to four month point with this … that we are looking at a bloom that will now go for 18 months if it doesn't clear this winter."
Ms Coleman said if it persists through winter, it's likely to bloom with more intensity in summer.
Ecologist Faith Coleman started testing water samples from Waitpinga in the days after the initial algal bloom. ( ABC News: Che Chorley )
The other concern is even when the bloom dissipates, Karenia mikimotoi can lie dormant, and bloom again when the conditions are right.
If this bloom continues for a year or more, what are the consequences?
Ms Coleman said eco-systems can quickly bounce back from short algal blooms, but prolonged ones can have major ecological consequences.
A dead dolphin spotted at Grange Beach. ( Supplied: Jock Lawrie )
"One event, fish can swim out, breed somewhere else or miss a breeding for the year and come back in again," Ms Coleman said.
"Also things like fish eggs and spores for the macro algae and the seeds of the seagrasses quite comfortably accommodate one bad season.
"They don't accommodate so well multiple bad seasons. Two is not good, three is quite bad. By the time you get to four or five seasons in a row, you're starting to lose major parts of your ecosystem."
What's being done for the fishing and aquaculture industries?
The bloom has taken its toll on fishing and aquaculture, with some oyster farms on the Yorke Peninsula being closed down, and fishers reporting reduced catch.
Ms Close said the government is working with industry to see how it can help, but this bloom is a "real lesson" to people who rely on the marine environment for their livelihood.
"I think farmers on land have become used to the idea of frequent droughts and they're very well aware that we're in a drying period as a result of climate change," she said.
"I think people who are dependent on the marine environment need to appreciate that they can no longer rely on a stable and predictable marine environment."
Dead pipis along the shoreline at Goolwa Beach. ( ABC News: Che Chorley )
Ms Close said businesses should consider things like business interruption insurance and other measures to make themselves more resilient to climate change.
But she said the good news is that Karenia mikimotoi isn't toxic to humans — and any fish caught in South Australian waters is still safe to eat.
Is there anything we can do?
There's nothing that can be done to dissipate a bloom the size of this one, and addressing climate change takes a global effort.
But Ms Close said there are things that can be done to make the environment more prepared to tackle the impacts of climate change.
"The better we look after the environment, the more resilient it will be when we have these sorts of crises linked to climate change," she said.
"We need to explicitly decouple our economic growth and prosperity from asking nature to always take a bit more of a hit."
A Port Jackson shark has been found dead among other marine life on Adelaide beaches. ( ABC News: Olivia Mason )
Ms Close said examples of where the South Australian government had done that was through establishing marine parks and sanctuaries, and through waterways management.
Professor Murray said one lesson from the bloom is more monitoring of our waters are needed.
"We need to have a bit more regular monitoring of recreational waters and beaches for harmful algal blooms," she said.
"In the past all our monitoring is linked to shellfish aquaculture areas which is obviously very important but just that we need to expand this to other waters."
Faith Coleman says prolonged algal blooms could have major consequences. ( ABC News: Che Chorley )
Faith Coleman said there are ways local communities can respond to the bloom, by establishing more oyster reefs, muscle beds and seagrass beds.
"We're seeing that embayments with lost of seagrasses and lots of macro algae and lots of filter feeders, even though those things are really badly impacted by this algae, those areas that have lots of them are less badly impacted," she said.
"It is a scale that is huge, but if each local community does one, and each local government does one little area then maybe we'll get there at a statewide level."
Ms Close said part of its research into this bloom will be how to best protect marine ecosystems, and what can be done to invest in restoration.
"How are we going to bounce back? Do we need to invest in more reefs? Do we need to invest in an even greater network of marine parks?" she said.
"All of that will be a guide of how we get better to responding to climate change."