Last year, a 7,500-plus-square-mile area off of South Australia, saw roughly a million marine animals wiped out, one fell swoop. Even some humans have taken curiously ill.
This summer, scientists’ findings are suggesting that a bloom of microalgae called Kernia cristata, which produced several powerful toxins, is the root of it all.
“This can partly explain the scale of the impacts witnessed in this event, which have included the mass mortality of marine invertebrates, fish, mammals and birds, over many months,” University of Technology Sydney Professor of Marine Biology Shauna Murray said in a press statement.
As with most things in the natural world, these algae are critically important within the web of living things. They absorb carbon dioxide, create oxygen and habitats, and feed myriad other creatures.
And as with just about anything, too much of anything can cause problems. Out-of-control algal blooms, called “harmful algal blooms” or HABs, produce dangerous toxins that wreak havoc through water and consumption of contaminated critters.
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Such was deemed to be the case when Murray and colleagues at the University of Technology Sydney conducted lab-based experiments on Karenia cristata, which they found “highly toxic in very low cell concentrations,” adding that they “found that Karenia cristata is an order of magnitude more toxic than the next most toxic microalgae that has been studied to date.” Horrifying stuff, to be sure.
The scientists’ findings, published in the scientific journal Nature Ecology & Evolution point to “substantial amounts” of brevetoxins (BTXs). BTXs produce the types of neurotoxins associated with red tides (Karenia brevis HABs), which often lead to mass whale, dolphin, manatee, sea-lion, and turtle strandings.
“Before now,” Murray said, “the warm water Karenia brevis, which only occurs in the south-eastern United States and also produces brevetoxins, had been considered the most devastating marine HAB species in terms of its environmental, economic and social impacts.”
First detected in March, 2025, the Kernia cristata bloom of South Australia hasn’t dissipated yet. “We now need to fully investigate the factors that cause Karenia to grow and understand its mechanisms of toxicity,” stress Murray et al., who worry that this is “an emerging international threat with unknown consequences,” citing that this species newly in question, found in cold water, “could potentially bloom anywhere with similar coastal water conditions.”
Murray et al. are hoping to find ways to ease the impacts of the bloom, but they’re cautious in their optimism: “A harmful algal bloom is a natural disaster, like a cyclone, and we cannot expect to fully control or reverse it.”
Here’s hoping our coldwater surf-going folk aren’t staring down the barrel of something once unthinkable in colder climes…
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