Algae. Algae everywhere. The kind that touches your foot while you’re swimming and… ugh!!!! Disgusting! Well, one of these, very toxic by the way, is devastating the biodiversity in southern Australia and creating what scientists are already describing as underwater deserts.
What is this algae?
It’s Karenia mikimotoi, an invasive alga that has turned more than 4,500 square kilometers of marine ecosystems into areas completely void of life. Apparently, it emerged due to a marine heatwave (so now we believe in climate change, right?). It has made more than 15,000 animals disappear almost like magic and has hit the fishing sector hard.
But the consequences aren’t just ecological. Humans are affected too, and so is the economy. Remember, we’re all in the same wheel. Here’s everything we know so far about this horrible invasion.
An ecological disaster on the shore
It all started in March, when some surfers came out of the water with dry coughs, blurry vision, and a strange yellow foam in the waves. It seemed like an isolated phenomenon, but it quickly became an environmental emergency when the first dead animals started washing up on shore.
Studies confirmed that it was a toxic bloom of Karenia mikimotoi, a dangerous microalga that blocks sunlight, generates hypoxia, and destroys the gills of fish and mollusks, suffocating marine life.
Entire ecosystems wiped out
Scott Bennett, one of the first to study this, described a bleak picture: “100% of the razor clams were dead and rotting on the seafloor”. This area of the Great Southern Reef is home to unique biodiversity, with more than 70% of endemic species, which means their disappearance is permanent and there’s no turning back.
Catastrophic economic consequences
Of course, it’s not just the seafloor. Fishing is at a minimum. Nathan Eatts, a local fisherman, said he hasn’t been able to catch a single squid since April. His business has come to a halt, and so have many others who depend on what the sea provides.
According to the Marine Fishers Association, a third of the state’s waters are empty of life. This affects not only fishermen, but also distributors, seafood markets, and restaurants. The economic damage is estimated at more than 480 million Australian dollars…
What caused this deadly bloom?
Everything points to climate change being one of the main factors. The 2022 floods dragged nutrients into the sea, the upwelling of colder water with more nutrients disrupted the balance, and a marine heatwave in September 2024 raised ocean temperatures by 2.5 ºC above normal, creating the perfect environment for these microalgae to spread without control.
How can it be stopped?
It can’t. It’s not a fire or a flood. A toxic alga can’t be extinguished or contained with physical barriers, and that’s where the main problem lies.
The Premier of South Australia, Peter Malinauskas, admitted that this is an unprecedented disaster and they don’t know how to proceed, even though the government has allocated 28 million Australian dollars for cleanup and aid. But it still hasn’t been officially declared a “natural disaster”, which limits the funds and emergency measures available.
A warning from the future (or the present)
Experts agree that this event is not an isolated case, but a reflection of the real effects of climate change on the oceans. Bennett insists that we must act wisely and quickly to protect key habitats like kelp forests, seagrass meadows, and oyster reefs if we don’t want the area to become completely dead.
Painful testimonies
“You see it and your heart breaks”, said Nathan Eatts after seeing a dead dolphin on his beach. “You take the beauty of your surroundings for granted… until something like this comes and wipes it all out”.