‘We’re trying to call on everybody that we can’: South Australia scrambles to fight its pulsating algal bloom
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Version 0 of 2. State considers its options to control Karenia mikimotoi, which has left beaches littered with dead seaweed and sealife Get our breaking news email, free app or daily news podcast New satellite imagery of South Australia’s devastating algal bloom shows it shifting and surging around the coast, where it has killed tens of thousands of marine animals. On the video, a light green smudge explodes into an angry, purplish red mass, indicating a high concentration of chlorophyll. It expands and contracts as the weather changes from January to August. “The bloom pulsates,” says Prof Mike Steer. Steer is the head of the South Australian Research and Development Institute (Sardi), which has been monitoring the Karenia mikimotoi bloom as it litters South Australian beaches with mounds of dead seaweed and carcasses of fish, sea dragons, sharks and other marine life. The chlorophyll concentration in the satellite imagery gives a “strong indication” of how severe the bloom is. Citizen scientists have recorded more than 32,000 dead animals from 480 species, a number likely to be a fraction of the actual dead, and the bloom isn’t expected to disappear anytime soon. Sign up: AU Breaking News email “It declines or disappears and we have a level of optimism … but then later on we see that oceanographic and weather conditions re-promote the bloom,” Steer says. “[In April] we had a couple of weather systems that came through. [We thought] ‘Oh, this is going to blow away, oh, it’s disappearing. Fantastic.’ And then the sun comes out and the weather clears up and it’s back again.” Blooms can last months or years, and disappear for a while as balance is restored, then break out again. While there are some potential weapons against the bloom – such as modified clay, algicides, physical disruptions, and even an algae called a “sea sparkle” that is a naturally occurring enemy – there is little hope for now. The state government is preparing a plan for summer when waters warm and the bloom is expected to take off again just as people start returning to the beach. The government has asked for help from a man premier Peter Malinauskas has described as “the foremost expert globally” on harmful algal blooms: Dr Donald Anderson, the director of the United States’ National Office for Harmful Algal Blooms at the Woods Hole Oceanographic Institution. “We’re trying to call on everybody and anybody,” Malinauskas says. What is it Algal blooms are complex, but the prevailing theory is that the 2022-23 floods washed nutrients down the Murray-Darling Basin system and out to sea. A marine heatwave and an “upwelling” of nutrients from the bottom of the ocean combined to create the perfect conditions for Karenia mikimotoi to flourish. Deadly for various marine species, in humans it can cause mild symptoms such as coughing and skin and eye irritation. But people are still worried about its effect on them, their pets and on sea life without gills, including dolphins and whales. There are species other than mikimotoi in the bloom, and the brevetoxins (heat-stable neurotoxins) they emit have led to the closure of shellfish farms. Bi-valves – a class of aquatic molluscs – accumulate the toxins, and if people eat them they can suffer neurological and gastrointestinal problems. Anderson says Karenia mikimotoi tolerates a wide range of temperatures and salinity levels; it kills species and then thrives on the nutrients their carcasses release. It also engages in “chemical warfare” by releasing chemicals that damage its competitors. Anderson understands Australians’ concern about the bloom, but he says it is not an “exceptional” phenomenon. China’s “green tide” of Ulva prolifera was visible from space, and in Russia, a bloom killed up to 95% of sea life on the Kamchatka peninsula. Florida has been battling “red tides” on its beaches for years, from blooms that leave patches of dead fish floating offshore. “This is a big one,” Anderson says of the South Australian bloom, “[but] it’s not the biggest.” What can be done Governments have scrambled to provide support to affected industries, pouring money into better monitoring and data collection, funding a national testing facility, combating misinformation and keeping people informed, and exploring mitigation. Sign up to Breaking News Australia Get the most important news as it breaks after newsletter promotion A form of modified clay is the most applicable and scalable treatment, Anderson says. It can be sprayed into the water, where it sticks to the algal cells and produces clumps called “floc”. “It looks like snow. And they will fall, they will settle,” he says. The technology has been used in China and Korea for decades, but it’s not approved in the US or Australia. It would need to be tested on a small scale to see how it works in this specific scenario, what the outcomes are and whether there are any unintended consequences. Academics have investigated if they can physically block or disturb the algae, pump air into the water to make “bubble curtains” to stop it from moving, use algicides, restore seagrass that contain algicidal bacteria, or restore shellfish reefs that act as filters. They say the bloom is far too big for these to work, but some methods could be used at high-risk sites, such as the breeding grounds for the giant Australian cuttlefish. The US National Office for Harmful Algal Blooms lists biological controls, or the “release of one organism to control another”, a phrase likely to bring cane toads to mind for Australians. Then there’s Amoebophrya, a parasite that can infect algae – but that has had “negative long-term consequences”. Chemical controls have been proposed but are “primarily conceptual in nature”. One experiment used crop dusters with copper sulfate, but “the broad lethality of copper resulted in considerable collateral mortality of other marine organisms”. Climate change Anderson stresses that South Australia’s experience is not unique, but he also warns that the climate crisis is already having a “huge effect” on the likelihood of more blooms. He says there is a dangerous bloom on Alaska’s coast, which is a pristine, cold environment. “I have a member of my staff on a vessel up in the Alaskan Arctic,” he says. “The reason we’re up there is because the waters up there have warmed so much that toxic [algae] is moving into those waters. “Throughout the world we’re seeing that kind of … range shift. There are areas that are getting warmer and more receptive [to blooms] but then there’s some areas that are getting too warm and the species can’t survive any more.” The CSIRO has long-term forecasts to predict marine heatwaves, which cause coral bleaching and fish kills as well as algal blooms and other disruptions to ecosystems. “Marine heatwave forecasting tells you how you might be loading the dice for a range of ecological impacts,” CSIRO chief research scientist, Dr Alistair Hobday, told the latest briefing. “Marine heatwaves are a stress test for the future as well because what we see today in a heatwave is what we’ll experience every day in 20 years’ time.” Anderson wants Australians to know that many places have experienced harmful algal blooms, and come out the other side. “It’s new and it’s scary to you,” he says. “But part of my role here is to say: ‘You’re not alone.’” |