Lisbon, July 24, 2025 (Lusa) - The invasive macroalgae "rugulopteryx okamurae" was first detected in Portugal in 2019, in Sao Miguel in the Azores, and is now present on the mainland coast, especially in the Algarve and Cascais. There is no known way to control it.
On Tuesday, the Government approved the National Strategy for the Management of the Invasive Macroalgae ‘Rugulopteryx okamurae’, which is “spreading at an alarming rate along the Portuguese coast”, according to a statement from the executive.
It is an "exotic species of Asian origin that has been spreading at an alarming rate along the Portuguese coast, particularly in the Algarve and Cascais area," said the joint statement from the Ministry for the Environment and Energy and the Ministry of Agriculture and the Sea.
A document on the algae, to which Lusa had access, indicates that in Cascais the invasive species appeared last year and, in four months, 2,000 tonnes of the species were removed from just two beaches.
The algae barrier has not diminished in the meantime on the affected beaches.
The species is believed to have appeared in 2015 in the Strait of Gibraltar as an invasive species.
It appeared in the Azores four years later, probably arriving in ballast water or on the hulls of ships, and in a few years dominated habitats on rocky surfaces on the south coast of São Miguel. In 2021, it was detected in Faial.
Its rapid reproduction leads to the accumulation of large amounts of biomass, which is carried by the currents and reaches the beaches, according to the document, which recalls that in July 2022 the algae was included in the list of invasive exotic species of concern to the European Union.
Rugulopteryx okamurae is a perennial species of brown algae from the Asian coast whose rapid growth prevents other species from developing, colonising most of the rocky substrate on the seabed and leading to a loss of biodiversity. It causes an unprecedented massive increase in biomass and affects the local fauna, landscape and beaches.
The document, produced by the Cascais city council, indicates that the algae has applications in the pharmaceutical industry, for example, and there are projects for its use as a compound and fertiliser in agriculture or even in bioconstruction.
According to the document, in Andalusia the algae had an impact on fishing, reducing catches of several species and damaging fishing gear, and local authorities spent €1.2 million on cleaning up over a nine-month period (the duration of a study carried out about five years ago).
The local authority document stresses that there is no evidence of risks to human, animal or plant health, but also says that there are no known effective control methods that can be applied at present, nor have any natural regressions of the algae been observed. Early detection is the best solution, it says.
According to a government statement released on Tuesday, a joint order from the ministries for the environment and agriculture outlines an action plan with measures for monitoring, operational response, biomass enhancement, scientific research and institutional coordination, with the aim of mitigating ecological, social and economic impacts.
The measures envisaged include the removal of the algae in critical areas, the study of its use for industrial or agricultural purposes, the mobilisation of regional rapid response teams and the creation of a national database with georeferenced records of the species' evolution.
FP/AYLS // AYLS
Lusa
