Non-indigenous seaweeds in the Northeast Atlantic Ocean, the Mediterranean Sea and Macaronesia: a critical synthesis of diversity, spatial and temporal patterns

• Main Authors: Luna M. van der Loos, Quinten Bafort, Samuel Bosch, Enric Ballesteros, Ignacio B??rbara, Estibaliz Bercibar, Aur??lie Blanfun??, Kenny Bogaert, Silke Bouckenooghe, Charles-Fran??ois Boudouresque, Juliet Brodie, Ester Cecere, Pilar D??az-Tapia, Aschwin H. Engelen, Karl Gunnarson, Soha Hamdy Shabaka, Razy Hoffman, Vivian Husa, ??lvaro Israel, Mart Karremans, Jessica Knoop, Line Le Gall, Christine A. Maggs, Fr??d??ric Mineur, Manuela Parente, Frank Perk, Antonella Petrocelli, Conxi Rodr??guez-Prieto, Sandrine Ruitton, Marta Sans??n, Ester A. Serr??o, Adriano Sfriso, Kjersti Sj??tun, Val??rie Stiger-Pouvreau, Gwladys Surget, Thierry Thibaut, Konstantinos Tsiamis, Lotte Van De Weghe, Marc Verlaque, Fr??d??rique Viard, Sofie Vranken, Frederik Leliaert, Olivier De Clerck
• Other Authors: van der Loos, Luna M., Bafort, Quinten, Bosch, Samuel, Ballesteros, Enric, B??rbara, Ignacio, Bercibar, Estibaliz, Blanfun??, Aur??lie, Bogaert, Kenny, Bouckenooghe, Silke, Boudouresque, Charles-Fran??oi, Brodie, Juliet, Cecere, Ester, D??az-Tapia, Pilar, Engelen, Aschwin H., Gunnarson, Karl, Hamdy Shabaka, Soha, Hoffman, Razy, Husa, Vivian, Israel, ??lvaro, Karremans, Mart, Knoop, Jessica, Le Gall, Line, Maggs, Christine A., Mineur, Fr??d??ric, Parente, Manuela, Perk, Frank, Petrocelli, Antonella, Rodr??guez-Prieto, Conxi, Ruitton, Sandrine, Sans??n, Marta, Serr??o, Ester A., Sfriso, Adriano, Sj??tun, Kjersti, Stiger-Pouvreau, Val??rie, Surget, Gwlady, Thibaut, Thierry, Tsiamis, Konstantino, Van De Weghe, Lotte, Verlaque, Marc, Viard, Fr??d??rique, Vranken, Sofie, Leliaert, Frederik, De Clerck, Olivier
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Biodiversity; Chlorophyta; Europe; invasive alien species; non-indigenous species; Phaeophyceae; Rhodophyta; Settore BIO/07 - Ecologia; Pacific; Northeast Atlantic
• Online Access: https://hdl.handle.net/10278/5032641; https://doi.org/10.1101/2023.06.05.543185

Effective monitoring of non-indigenous seaweeds and combatting their effects relies on a solid confirmation of the non-indigenous status of the respective species. We critically analysed the status of presumed non-indigenous seaweed species reported from the Mediterranean Sea, the Northeast Atlantic Ocean and Macaronesia, resulting in a list of 140 species whose non-indigenous nature is undisputed. For an additional 87 species it is unclear if they are native or non-indigenous (cryptogenic species) or their identity requires confirmation (data deficient species). We discuss the factors underlying both taxonomic and biogeographic uncertainties and outline recommendations to reduce uncertainty about the non-indigenous status of seaweeds. Our dataset consisted of over 19,000 distribution records, half of which can be attributed to only five species (Sargassum muticum, Bonnemaisonia hamifera, Asparagopsis armata, Caulerpa cylindracea and Colpomenia peregrina), while 56 species (40%) are recorded no more than once or twice. In addition, our analyses revealed considerable variation in the diversity of non-indigenous species between the geographic regions. The Eastern Mediterranean Sea is home to the largest fraction of non-indigenous seaweed species, the majority of which have a Red Sea or Indo-Pacific origin and have entered the Mediterranean Sea mostly via the Suez Canal. Non-indigenous seaweeds with native ranges situated in the Northwest Pacific make up a large fraction of the total in the Western Mediterranean Sea, Lusitania and Northern Europe, followed by non-indigenous species with a presumed Australasian origin. Uncertainty remains, however, regarding the native range of a substantial fraction of non-indigenous seaweeds in the study area. In so far as analyses of first detections can serve as a proxy for the introduction rate of non-indigenous seaweeds, these do not reveal a decrease in the introduction rate, indicating that the current measures and policies are insufficient to battle the introduction and ...