Arrival and proliferation of the invasive seaweed Rugulopteryx okamurae in NE Atlantic islands

The present study reports the recent occurrence and expansion of Rugulopteryx okamurae in the Azores archipelago (NE Atlantic). Morphological and molecular characters confirmed the species identification. Quick surveys around the island of São Miguel showed that it has successfully colonized the island and is quickly expanding. In some locations, R. okamurae is currently the dominant organism smothering all other benthic biota and posing a serious threat to the benthic ecosystems across the region. The species first record dates from 2019 near the main harbour of the island, suggesting that its introduction was driven by human-assisted transport, via boat ballast waters or adhered to ship hulls and likely originating from the Mediterranean populations that have been proliferating in recent years across the Strait of Gibraltar. ### Competing Interest Statement The authors have declared no competing interest.