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Copious amounts of rain over the last few months means that the Mar Menor is facing a growing algae problem, and one local council has decided to do something about it. Los Alcázares has become the first local authority in Spain to receive official permission to remove concentrations of Caulerpa prolifera, an invasive algae that has been spreading through the lagoon for years and is now posing a new threat to the fragile ecosystem.

 

The scale of the issue has already given scientists cause for concern. In January 2026 alone, 1,158 tonnes of algae biomass were removed from the Mar Menor, up as much as 60% on previous years. A further 535 tonnes had already been collected by early February.

 

Caulerpa prolifera has colonised the lagoon since changes in salinity following the opening of the Estacio canal, and the problem has accelerated since the ecological collapse of 2016. As well as generating unpleasant sludge that puts swimmers off, it's blocking the recovery of Cymodocea nodosa, the native protected plant the lagoon depends on.

 

In a pioneering move for Los Alcázares, specialist dive teams will carry out the work by hand using rakes at three beaches, Los Narejos, Carrión and La Concha, with the first three extractions due to be completed before March 15.

 

Mayor Mario Pérez Cervera explained that the teams will be supervised by experts and that floating barriers will be installed first to stop sediment from spreading during the work. Heavy machinery is banned entirely from the process.

 

Once removed, the algae will be drained on floating platforms before being brought ashore, and there are plans to explore using it for composting or as an agricultural substrate, meaning nothing need go to waste.

 

Image: COMU-IEO / CSIC