Assessment of the Rugulopteryx okamurae invasion in Northeastern Atlantic and Mediterranean bioregions: Colonisation status, propagation hypotheses and temperature tolerance thresholds

The recent proliferation of the invasive macroalga Rugulopteryx okamurae in the Mediterranean and Northeastern Atlantic regions poses significant ecological and socioeconomic threats. This study analyses the current state of knowledge on the invasion, assesses the primary dispersal vectors, and evaluates its invasive potential through temperature tolerance. Using Web of Science and Google Scholar databases, publications from 2004 to 2024 were reviewed and categorized into five key areas: physiology, distribution and spread, ecological impacts, socioeconomic consequences, and management strategies. The bibliographic search evidenced a significant increase in studies concerning R. okamurae over the last years (from 1 in 2020 to 38 in 2024). The results also indicated a certain agreement regarding the vector of introduction of this alga into the Strait of Gibraltar in 2015–2016 (ballast waters of merchant ships) but the rapid spread towards Mediterranean and Atlantic areas remains unclear. Nonetheless, aquaculture activities and currents were pointed out as significant dispersal vectors. The temperature analyses highlighted the broad thermal tolerance range of R. okamurae, from 10 °C to 30 °C, which contribute to its extensive colonisation. Therefore, this study underscores the need for urgent management actions to limit the expansion of R. okamurae and mitigate the negative effects observed on coastal ecosystems and economies of colonised areas.