231 non-indigenous marine species now recorded in Portuguese waters
A recent study led by researchers from MARE|ARNET, published in the journal Marine Pollution Bulletin, reveals that 231 non-indigenous marine species have now been confirmed in mainland Portugal, the Azores and Madeira, five of which had never before been recorded in the country.
This is the most comprehensive update to the national inventory of non-indigenous marine species since 2015, involving the collaboration of 31 researchers from 11 Portuguese universities. Of the 231 confirmed species, 159 are found in mainland Portugal, 81 in the Azores and 62 in Madeira. The five newly recorded species were detected on the southwest coast of the mainland, in the area of the Port of Sines, a region monitored since 1997 by a long-term environmental monitoring programme.
Regarding geographic origin, the study points to two distinct patterns depending on the region. On the mainland, species originating from the North Pacific predominate (39%), followed by the North Atlantic (24%). In the archipelagos, the pattern is reversed, with the North Atlantic leading, both in Madeira (27%, ahead of the Tropical Atlantic at 24%) and in the Azores (37%, followed by the North Pacific at 19%), a profile closer to that observed on the mainland. The main pathway for these species entering Portugal is maritime transport, namely through ballast water and hull biofouling, with aquaculture an additional significant vector on the mainland. Given its position at the crossroads of routes connecting Asia, the Mediterranean, the United States and Africa, the Port of Sines, the largest deep-water port in mainland Europe, is identified in the study as a strategic gateway for these species.
Beyond traditional morphological identification, the team compiled an unprecedented watch list of 22 species detected solely through environmental DNA. This approach functions as an early warning system, making it possible to flag potential invasive species before they are visually identified in the field.
The researchers also found that, although 71% of the catalogued species are already listed in international genetic databases, only 12.5% have sequences from specimens collected in Portuguese waters. In practice, this means that most of the genetic references used to identify these species in Portugal come from populations in other parts of the world, which can compromise the reliability of rapid detection tools such as environmental DNA and make it harder to distinguish between genetically similar species in the country. According to the authors, stepping up sample collection within national territory should be a priority for making genetic surveillance faster and more accurate.
"Marine invasions are a dynamic, cross-border phenomenon, and understanding them requires science capable of working at the same scale. This study allowed us to go well beyond a simple update of species numbers, revealing introduction patterns, gaps in genetic knowledge and priorities for future monitoring," says Romeu Ribeiro, MARE researcher at the Faculty of Sciences of the University of Lisbon and first author of the study.
The research was coordinated by researcher Paula Chainho, of MARE, at the Faculty of Sciences of the University of Lisbon, and involved the participation of the Directorate General for Natural Resources, Safety and Maritime Services (DGRM), the Portuguese Institute for the Sea and Atmosphere (IPMA), the Institute for Nature Conservation and Forests (ICNF), and researchers from 11 Portuguese universities. The work was funded, among other sources, by the Recovery and Resilience Plan (PRR), through the NEXUS Agenda, and the Foundation for Science and Technology (FCT).
Text by: Vera Sequeira e Patrícia Chaves
Photos: Paula Chainho, Bruno Pinto e Ana Cristina Costa