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The Asian seaweed taking over Andalucía's beaches is back, and scientists say getting rid of it for good is simply not possible
Councils are spending millions removing thousands of tonnes of invasive algae every summer, but the underlying problem is only getting harder to manage
Every morning before dawn, municipal workers are out on Andalucía's beaches clearing seaweed before the sunbathers arrive. It's a scene that plays out all summer along the coast, and the scale of it is striking.In Mijas alone, the Ayuntamiento has removed 1,890 tonnes of Asian seaweed so far this year, 350 of them in July alone, at a cost already exceeding €1.5 million, all funded from the council's own budget without specific support from the Junta de Andalucía or the Spanish government. "The impact on municipal services is total and absolute," the Ayuntamiento stated.
The seaweed in question is Rugulopteryx okamurae, a species native to the northwestern Pacific. It was first detected in massive quantities in the Strait of Gibraltar area in 2015, with beaches from Cádiz to Gibraltar seeing tens of thousands of kilos removed within days during some of the early outbreaks. Researchers believe it most likely arrived in the ballast water of merchant ships, though the exact route has never been confirmed.
What makes this species particularly difficult to deal with is its biology. Unlike many algae, Rugulopteryx okamurae can survive after detaching from the seabed, and every fragment is capable of generating a new individual. That reproductive capacity is precisely why scientists have stopped talking about eradication. "Eradication in the marine environment is a myth, it's impossible," says María García, a researcher at the Blanes Center for Advanced Studies. "What we can do are mitigation measures."
The problem extends well beyond aesthetics. Underwater, the algae forms dense mats that displace native species and interfere with fishing gear. On the beach, once it starts decomposing in the sun, it produces unpleasant smells and attracts insects, making stretches of coastline significantly less appealing.
Researchers are exploring potential uses for the harvested biomass in areas such as fertilisers, bioplastics and pharmaceutical compounds, though EU legislation currently restricts its commercial use while it retains reproductive capacity, to avoid creating economic incentives that might encourage its spread further.
The Junta de Andalucía has developed a management plan covering monitoring, research and removal protocols, but the honest scientific assessment is sobering. "At the moment, it doesn't look good," García says, noting that whether the species eventually stabilises, as some invasives do over time, remains entirely unpredictable.
Councils remove the seaweed, it reappears the next day. That is the reality coastal communities along the Andalucían coast are living with, summer after summer.
Image: Junta de Andalucía
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