Thousands of tons of aggressive algae have flooded the beaches of seaside resorts

Thousands of tons of invasive seaweed have "infested" Spanish beaches. The algae, which originated in Southeast Asia, pose a serious threat to biodiversity, experts say, warning of an environmental disaster.

Huge quantities of aggressive invasive seaweed from Southeast Asia are accumulating on beaches in the Strait of Gibraltar and on the southern coast of Spain, posing a serious threat to the region's biodiversity, according to local environmentalists.

Since May, local authorities in Cadiz have removed 1,200 tonnes of the seaweed Rugulopteryx okamurae from the city's most popular beach, La Caleta, including 78 tonnes in one day, The Guardian reports.

"We are absolutely stunned. It is an ecological disaster," laments José Carlos Teruel, responsible for beaches at the Cadiz city council. "Every time the west wind blows, we know that another wave of algae is coming."

Like many other invasive marine species, the algae is believed to be carried into the ballast tanks of ships passing through the Suez Canal and then discharged into the Mediterranean Sea.

In little more than a decade, the species has colonised the Strait of Gibraltar, much of the southern coast of Spain, the Canary Islands, the Azores and, further north, the Cantabrian Sea and the Basque Country, The Guardian notes.

“This type of algae was first noticed 10 years ago in Ceuta, the Spanish North African enclave, by a researcher from the University of Malaga, but the authorities have always been too slow to react,” says Juan José Vergara, a professor of biology at the University of Cadiz.

"In the first stage of an infestation like this, it can be controlled. It's like catching cancer early, before it spreads," Vergara said, adding that what washes ashore is only a small fraction of what's underwater.

"But now the scale of this makes it impossible to control. In other seaweed outbreaks, we have seen the situation return to normal after 10-15 years, but many scientists say they have never seen an outbreak of this scale," the researcher states.

The seaweed has a major impact on the local economy, especially on tourism in Cadiz and nearby Tarifa, a town popular with windsurfers, and on fishing, as it gets tangled in fishermen's nets and lines and sucks oxygen out of the water. The taxpayer also has to pay for its disposal, The Guardian adds.

Perhaps most alarming is the impact of invasive algae on biodiversity. At La Caleta Beach, the algae have displaced many native plants. It is unclear whether the damage is temporary or permanent.

The algae attaches to rocks and other surfaces and also floats freely, devastating native algae species. There are no predators in the region, and its ability to reproduce both sexually and asexually and absorb toxins makes it virtually impossible to eradicate, experts say.

Currently, the algae are dumped in landfills. Vergara said a local business that processes the algae into beverage containers or for use as fuel and fertilizer has requested permission to use Rulopteryx okamuraea as biomass for energy production.

However, Spain's invasive species law prohibits their commercial exploitation unless they pose a threat to health and safety or contribute to their destruction, which appears to be the case for Rulopteryx okamuraeas.

The Andalusian government has recently launched a four-part plan to combat the crisis, based on research, monitoring and education, and including options for recycling seaweed.

To use the seaweed as biomass, the regional government would have to negotiate with Spain's Environment Ministry, but Vergara believes that even if an agreement is reached, it could only be part of the solution: "It's an interesting idea, but I doubt it could eradicate or even significantly reduce the intensity of an infestation where hundreds of thousands of tons of seaweed could be washed up on a single beach."