Environmental Sectoral Conference approved a management strategy concerning Rugulopteryx okamurae, a species of invasive algae that originated in Asia and now spreads along rocky seabeds, displacing native organisms and gradually eroding marine biodiversity off the Andalusian coast.
The threat from these algae is substantial, with implications not only for biology and ecology but also for social and economic life. The Ministry of Ecological Transition and Demographic Challenge highlighted the impact, especially on professional fisheries, where livelihoods are tightly linked to the coastal marine environment.
The appearance of large quantities of this algae on beaches is affecting tourism and increasing the cost of removal for responsible authorities. In 2019, five municipalities across Malaga, Cadiz and Ceuta reported cleanups reaching up to 10,000 tons, with costs around 400,000 euros.
The strategy provides an overview of the species in Spain, including an updated analysis of its current and projected distribution and its ecological and economic consequences.
It calls for intensified action, public awareness campaigns, and more effective communication channels to address this environmental challenge and to improve intergovernmental coordination. The aim is to minimize the conditions that favor the species and to safeguard coastal ecosystems.
Rugulopteryx okamurae, commonly known as “roña” among fishermen, has spread along the Andalusian coast in recent years and poses a risk of further expansion into the Mediterranean. Its only notable benefit is occasional use as a spicy condiment, which is not widespread.
“Destroy everything in your way”
Marine biodiversity experts warn that these algae threaten environmental, economic, and social sustainability in affected areas. Their presence can endanger the stability of local ecosystems; in fact, their cytotoxic capacity means they can kill other species in less than 24 hours.
Rugulopteryx okamurae arrived in Europe from Asia in 2002 via ballast water from ships and was observed in the Strait of Gibraltar by 2016. It is listed in the Invasive Alien Species Catalogue. A scientific committee’s opinion, approved in 2020, notes a rapid, explosive rise of the species through the Bosphorus and its dominance in some areas, with adverse effects on fisheries and tourism and notable changes in marine communities.
Those who study the algae point to a robust chemical arsenal that it relies on, which can outperform native species in certain conditions.
Asian moss on a beach in the Strait of Gibraltar area.
Rugulopteryx okamurae is described as a perennial alga that persists through a network of rhizomes. Its leaves grow quickly, break off, and regrow, a cycle that can occur several times annually, according to scientific assessments.
This leads to a continuous accumulation of algal leaves on the seabed, which later drift ashore and form accumulations along the coast.
Damage to the fishing industry
In the Strait of Gibraltar region, the algae settle on rocky bottoms at depths of roughly 20 to 30 meters from shore, sometimes achieving nearly complete coverage and reaching depths beyond 40 meters. They also attach to various objects, including ropes and nets, causing damage to fishing activities. Because the algae tend to monopolize the substrate, native species struggle to settle, resulting in habitat homogenization and altered coastal communities.
Additionally, the massive biomass that accumulates and decomposes introduces another wave of impacts on coastal ecosystems that have yet to be fully evaluated but are undoubtedly significant both on the seabed and along the coast.
The scientific committee outlined seven reasons for classifying these algae as an invasive alien species:
– They change and threaten natural biodiversity by displacing native species and homogenizing benthic communities.
– They exhibit very rapid growth, continuously producing new leaves throughout the year.
– They have high asexual reproductive potential through spores and vegetative propagules and can settle on many substrates, including ropes and nets.
– They contribute to large accumulations and decomposition of biomass on the seafloor and in the tidal zone.
– They damage local fishermen, especially those using longlines, trammel nets, and purse seines.
– Management incurs high costs and hurts the tourism industry.
Notes on the Rugulopteryx okamurae issue can be found in discussions and forums such as the Rugulopteryx okamurae forum.