Marine algal (seaweed) flora of Terceira Island, Azores

Background As for many other Azorean islands, the macroalgal flora of Terceira (central group of the archipelago) is poorly known, the published information reflecting occasional collections of sporadic visitors to the island. In order to overcome this, and contribute to improve the knowledge of Azorean macroalgal flora at both local and regional scales, a thorough investigation was conducted and both collections and presence data recordings were undertaken at the littoral and sublittoral levels down to approximately 40 m around the island (total area of approximately 49 km2). This paper lists the taxonomic records and provides information on each species’ ecology and occurrence on the island’s littoral. New information A total of 418 specimens (including taxa identified only to genus level) belonging to 147 taxa of macroalgae, comprising 95 Rhodophyta, 33 Chlorophyta and 19 Ochrophyta (Phaeophyceae) are registered. Of these, 113 were identified to species level (73 Rhodophyta, 24 Chlorophyta and 16 Ochrophyta), encompassing 35 new records for the island (27 Rhodophyta, 6 Chlorophyta and 2 Ochrophyta). Most species are native including the Macaronesian endemisms (Codium elisabethiae O.C.Schmidt, Millerella tinerfensis (Seoane-Camba) S.M.Boo & J.M.Rico and Phyllophora gelidioides P.Crouan & H.Crouan ex Karsakoff), eight are introduced and 15 have uncertain origin. Introduction The macroalgal flora of the isolated mid-Atlantic Azores archipelago, as a whole, may be considered relatively rich when compared to that of other remote oceanic islands such as the Shetlands and Faroes in the colder North Atlantic, and Ascension and Tristan da Cunha in the Southern Atlantic (Neto et al. 2005; Tittley & Neto 2005; Wallenstein et al. 2009). With approximately 400 species (Freitas et al. 2019), the Azorean algal flora has been considered cosmopolitan, as it shares species with Macaronesia, North Africa, the Mediterranean Sea, Atlantic Europe and America (Tittley 2003; Tittley & Neto 2006; Wallenstein et al. 2009). The published information, however, reflects data from only a few of the nine islands. Terceira, the second largest island of the central group and the third largest of the archipelago, is among the lesser studied ones. To overcome this and contribute to a better understanding of the seaweed flora of the Azores archipelago, a thorough investigation was conducted in the period between 2000 and 2014, mainly by the Island Aquatic Research Group of the Azorean Bio