First confirmed occurrence of Codium fragile (Suringar) Hariot in the Iberian Peninsula coast of Portugal

Invasive macroalgae represent a major threat to marine ecosystems worldwide. Codium fragile ssp. fragile is one of the most invasive species in the world. The species has deleterious impacts on marine ecosystems, but can also coexist with other Codium congeners, with neutral impact. Several invasive macroalgae have been described to occur along the west coast of the Iberian Peninsula, including C. fragile. However, despite its presence being noted in citizen science surveys, the occurrence of C. fragile on the coast of Portugal was not confirmed (except in the Azores Islands). The cryptic nature of this invasive macroalga has led to several misidentifications, and strict taxonomic approaches must therefore be used to confirm sightings. Previous intensive field sampling (2017–2018) aimed at recording the presence of different macroalgae did not find C. fragile along the Portuguese coast, northwards from Praia do Matadouro. Here, we report the first confirmed record of C. fragile on the coast of Portugal, in the Avencas Marine Park. Identification of the alga was confirmed by microscopic examination of the utricles. Early detection of invasive species is essential, and further research should be carried out in the surrounding areas in order to better understand the invasion pathways to enable correct application of management plans.