The invasive algae Rugulopteryx okamurae is occupying extensive areas of the seabeds on the Alentejo Coast, in a strip that extends between Melides, in the municipality of Grândola, and Azenha do Mar, in Odemira. In some areas, the species is already disseminated up to 12 meters deep, with São Torpes and Pessegueiro Island, in the municipality of Sines, among the most affected areas.
Joaquim Parrinha, researcher at the University of Coimbra and the Marine and Environmental Sciences Centre (MARE), warned of the strong expansion of the species in the last two to three years. The algae was detected about a decade ago at Sines Port Marina, but the most significant change occurred recently. "With the increase in water temperature, an exponential 'boom' was noted in all areas up to 12 meters deep," the researcher told the Lus news agency, adding that, in the shallower areas, "everything is occupied" by the invasive species.
Rugulopteryx okamurae forms dense concentrations on the seabed, occupying space used by local marine communities and limiting the development of native species. The high density of the algae can reduce the passage of light and the availability of oxygen near the seabed, affecting coralline algae, wracks, kelp and caulerpa. "The forest that this algae creates, while not lacking beauty, is not natural for native species and considerably harms their development," explained Joaquim Parrinha.
Portugal has had, since July 2025, a National Strategy for the Management of the Invasive Macroalgae Rugulopteryx okamurae, approved by Order no. 270-A/2025/1. The strategy provides for monitoring of expansion, mechanical removal in critical areas and study of ways to valorize the collected biomass. The researcher advocates for the removal of biomass accumulated on beaches and possible agricultural uses, after salt treatment, as well as interventions in the marine environment to free the rocky surfaces needed by local algae.
