Sighting of Saccorhiza polyschides (Lightfoot) Batters (Phaeophyceae, Stramenopiles) in Algeria (Mediterranean Sea): an insight into range expansion routes

In the Mediterranean Sea, the north-east Atlantic seaweed Saccorhiza polyschides (Lightfoot) Batters is uncommon. The only permanent populations are located in the Alboran Sea near the Strait of Gibraltar and the Strait of Messina (Italy). In contrast, since the early 19^th century, several sightings, on ship’s hulls or in harbours, reflect the dispersal of propagules which failed to establish in the Mediterranean. Here we report a new sighting of Saccorhiza polyschides, near the port of Jijel, Algeria. This first new record in the Mediterranean for more than a century indicates that the dispersal of propagules continues today. In addition, because of its spectacular size and ease of its observation, it sheds light on the expansion routes of a species at the limit of their current range area.