Terrible invasive Asian moss continues to push through the Mediterranean. Originating from the Far East, it has reached the Iberian Peninsula, with detections previously reported in Ceuta, Granada, and Almería. Recently, growth has been confirmed off the coast of Alicante, suggesting a potential spread to new shoreline points. The concern is high because this algae threatens Posidonia oceanica, a crucial CO2 sink and biodiversity hotspot, along with traditional fisheries and tourism.
Researchers from the University of Alicante (UA) detected Rugulopteryx okamurae along the Alicante coast. There is no exclusion that its range could expand to other parts of the Mediterranean.
Marine biodiversity experts warn that these algae pose a risk to environmental balance, economic activity, and social well‑being in affected areas. Their cytotoxic capacity means they can harm other species in less than 24 hours, potentially disrupting entire coastal ecosystems.
Face and hands are itchy
People working with algal arribazones have reported itchy facial skin and hands. The alga carries a stronger chemical arsenal than native species, contributing to discomfort among those who handle it.
This Rugulopteryx okamurae reached Europe from Asia in 2002 via ballast water from ships. Its presence in the Strait of Gibraltar was documented in 2016, and it is listed in the Invasive Alien Species Catalogue (EEI). Its native region centers around Japan and Korea, among several other nearby countries.
Came to Spain in 2015
In Spain, the alga first appeared in arribazones off the Ceuta coast at the end of 2015 and subsequently spread throughout the Alboran Sea, displaying a high capacity to colonize. This growth has negatively impacted local marine life, traditional fisheries, and tourism, according to UA researchers.
It forms large deposits on beaches that municipal authorities struggle to manage and remove.
Reports indicate the alga has recently been detected in the Canary Islands, as well as in Almería and Granada, with rapid expansion anticipated along the Mediterranean. Given these traits, it has been declared an invasive exotic species, and a national monitoring and control strategy has been established.
Discovery on the Alicante coast
During early March, many samples collected by students and teachers from UA’s Marine Science Degree in Marine Zoology revealed large quantities of the alga along the Alicante coastline.
UA researchers identified Rugulopteryx okamurae through morphological and molecular methods. They also conducted a rapid survey to map distribution and abundance, including beach accumulations or arribazones.
Current expert assessment notes that the alga is abundant in the central Alicante Bay, thriving mainly on dead Posidonia oceanica sea grass, a key ecological feature of the region.
Findings show large populations of Rugulopteryx okamurae settling on the seafloor near beaches such as San Gabriel and Urbanova, and even more distant tourist beaches that are dispersed by wave action and ocean currents.
The danger posed by these algae is extensive. Beyond ecological impact, there are significant socioeconomic effects, especially in the professional fishing sector, with attention to national environmental authorities and coastal communities.
The arrival of this alga in large quantities on beaches also affects tourism and increases the cost of removal for local governments. In 2019, five municipalities in Malaga, Cádiz, and Ceuta were required to clean up as much as 10,000 tons of moss, resulting in costs around 400,000 euros.
National strategy for control and possible eradication of Rugulopteryx okamurae: (National plan documentation and guidance published by the environmental agency) (The government provides ongoing monitoring and response plans.)
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