Thousands of tons of a tenacious invasive seaweed originating from Southeast Asia have amassed on the beaches of the Strait of Gibraltar and Spain’s southern coastline, posing a significant threat to the region’s biodiversity. Since May, the local authorities in Cádiz have removed 1,200 tons of the algae known as Rugulopteryx Okamurae from La Caleta, the city’s most popular beach, including a record-breaking 78 tons in a single day. José Carlos Teruel, responsible for Cádiz city council’s beaches, expressed deep concern, stating, “We’re completely overwhelmed. This is an environmental catastrophe.” The algae is believed to have arrived in the ballast tanks of ships passing through the Suez Canal and then discharged in the Mediterranean Sea.
Over the past decade, the species has rapidly colonized the Strait of Gibraltar, Spain’s southern coast, the Canary Islands, the Azores, and as far north as the Cantabrian Sea and the Basque Country. Juan José Vergara, a professor of biology at the University of Cádiz, first identified it in Ceuta, Spain’s North African enclave, ten years ago. Vergara emphasized the importance of early intervention to combat invasions, likening it to catching cancer before it spreads. Additionally, he highlighted that what washes up on the shore represents only a fraction of what lies underwater.
The abundance of seaweed has severely affected the local economy, impairing tourism in Cádiz and nearby Tarifa, which is popular among windsurfers. Fishing activities have also been impacted as the seaweed traps fishing nets and lines while depleting oxygen from the water. Moreover, taxpayers bear the cost of disposing of the algae. The seaweed’s impact on biodiversity is most worrying as it displaces native plants and lacks predators in the region. It reproduces both sexually and asexually, making it difficult to eradicate.
Currently, the seaweed is discarded in landfills, but a local business is seeking permission to recycle it into energy, containers for beverages, and as fuel or fertilizers. Spain’s law on invasive species, however, prohibits their commercial exploitation unless they pose a health and safety risk or contribute to their eradication, which seems applicable to Rugulopteryx Okamurae. The regional government in Andalucía has recently launched a four-part plan addressing the crisis, focusing on research, monitoring, education, and options for recycling the seaweed
Source: https://www.theguardian.com/environment/2025/jul/27/thousands-of-tons-of-invasive-seaweed-overwhelming-spanish-beaches
