Thousands of tonnes of an aggressive invasive seaweed from East Asia are accumulating on the beaches of the Strait of Gibraltar and Spain's southern coast, prompting warnings from environmentalists of a major threat to biodiversity. The alga, Rugulopteryx okamurae, has overwhelmed local authorities in the region, who describe the situation as an environmental catastrophe.
Since May, the local authority in Cádiz has removed 1,200 tonnes of the seaweed from La Caleta, the city's most popular beach, including 78 tonnes in a single day. José Carlos Teruel, responsible for Cádiz city council's beaches, said: “We're completely overwhelmed. This is an environmental catastrophe. Whenever the wind is westerly, we know we're in for another wave of seaweed.”
The alga is thought to have arrived in the ballast tanks of ships passing through the Suez Canal before discharging in the Mediterranean. In little more than a decade, it has colonised the Strait of Gibraltar, much of Spain's southern coast, the Canary Islands, the Azores, and, farther north, the Cantabrian Sea and the Basque Country. Juan José Vergara, a professor of biology at the University of Cádiz, noted that it was first spotted ten years ago in Ceuta, Spain's north African enclave, by a researcher from Málaga university, but that authorities were slow to react.
The seaweed is having a significant impact on the local economy, affecting tourism in Cádiz and nearby Tarifa, a town popular with windsurfers, and fishing, as it traps nets and lines and removes oxygen from the water. Perhaps most worrying is its effect on biodiversity: at La Caleta, it has driven out many indigenous plants, and it is unclear whether the damage is temporary or irreversible. The alga attaches to rocks and surfaces, wipes out native species, has no natural predators in the region, and can reproduce both sexually and asexually, making it virtually impossible to eradicate.
Currently, the seaweed is sent to landfill sites. Vergara said a local business has sought permission to recycle it into drinks containers or use it as fuel and fertiliser, converting it into biomass for energy. However, Spain's law on invasive species prohibits commercial exploitation unless it poses a threat to health or safety or aids eradication, which would appear to apply in this case. This week, the Andalusian government launched a four-part plan to confront the crisis, based on research, monitoring, education, and recycling options.
Vergara expressed doubt that such measures would be sufficient, saying: “It's an interesting idea but I doubt it will be able to eradicate or even significantly diminish the intensity of the invasion when hundreds of thousands of tonnes can wash up on a single beach.” The scale of the invasion, he added, has made control impossible, unlike earlier phases where intervention could have been effective.
