Background The oldest reference to marine life in Formigas Islets (oriental group of the Azores archipelago) goes back to the XVI century. Nevertheless, their macroalgal flora is poorly known, the published information mainly resulting from occasional collections of sporadic visitors. To overcome this and contribute to the knowledge of Azorean macroalgal flora at both local and regional scales, a thorough investigation was conducted in 1990 and 1991 under two expeditions promoted by the Marine Biology Research Group of the Department of Biology, University of the Azores. Collections and presence data recordings were done at the littoral and sublittoral levels down to approximately 40 m, in an area of approximately 0.04 Km2. This paper lists the taxonomic records and provides information regarding each species’ ecology and occurrence on the islets’ littoral. New information A total of 320 specimens are registered (including taxa identified only at generic level) belonging to 90 taxa of macroalgae, from which 70 were diagnosed at species level. The confirmed species comprise 39 Rhodophyta, 12 Chlorophyta and 19 Ochrophyta (Phaeophyceae), distributed by 22 orders (13 Rhodophyta, 3 Chlorophyta and 6 Ochrophyta) and 37 families (24 Rhodophyta, 6 Chlorophyta and 7 Ochrophyta). Sixty-one species represent new records for the islets, from which Botryocladia macaronesica Afonso-Carrillo, Sobrino, Tittley & Neto and Laurencia viridis Gil-Rodriguez & Haroun are Macaronesian endemisms. Most species are native to the Azores, but six have an uncertain origin and four are introduced (the Rhodophyta Asparagopsis armata Harvey; Laurencia dendroidea J.Agardh; Neoizziella divaricata (C.K.Tseng) S.-M.Lin, S.-Y.Yang & Huisman; and the Ochrophyta Hydroclathrus tilesii (Endlicher) Santiañez & M.J.Wynne). Introduction The Formigas Islets are located about 20 miles NE of Santa Maria Island and 34 miles SE of São Miguel Island (oriental group of Azorean archipelago, approximately 37°16′35″N, 24°46′54″W). They are arranged in a N-S direction, over a total length of about 165 m and a width of 80 m. Together with the submersed bank of Dollabarat, they form the Nature Reserve of Formigas Bank (DLR n° 11/88/ A). The oldest reference to life in Formigas Islets consists of descriptions of its marine fauna in the XVI century manuscript "Saudades da terra" written by the naturalist clergyman Gaspar Frutuoso. Subsequently, these islets were occasionally studied in sporadic visits by researchers, the first reference to the marine macroalgae being that of Piccone (1889). After that, several expeditions were made in order to study of the fauna and flora of the islets, which resulted in a few publications (see revision in Azevedo et al. 1991). An important finding was the first Azorean record of the brown alga Laminaria ochroleuca Bachelot de la Pylaie made by Ardré et al. (1973). Despite these efforts, the algal flora of these islets remained poorly known until the nineties, when a thorough investigation conducted by the Marine Biology Research Group of the Department of Biology, University of the Azores took place. This research group went to the islets in 1990 and 1991 and undertook collections and presence data recordings at the littoral and sublittoral levels down to approximately 40 m, in an area of approximately 0.04 Km2. Purpose This paper, aimed at contributing to a better understanding of the seaweed flora of the Azores archipelago, lists the macroalgae recorded on surveys undertaken at Formigas Islets (Azores, eastern group) and presents a general information for each taxon’s occurrence on the islets’ littoral, thus contributing to address several biodiversity shortfalls (see Hortal et al. 2015), namely the need to catalogue the Azorean macroalgae (Linnean shortfall) and improve the current information on their local and regional geographic distribution (Wallacean shortfall), as well as on species abundances and dynamics in space (Prestonian shortfall). It is intended as a resource for academics, students, government, private organizations, and the general public, and also as a practical basis for biological studies such as systematics, diversity and conservation, biological monitoring, climate change and ecology.

Background The seaweed flora of Pico Island (central group of the Azores archipelago) has attracted interest of researchers on past occasions. Despite this, the macroalgal flora of the island cannot be considered well-known as published information reflects only occasional collections. To overcome this, a thorough investigation, encompassing collections and presence data recording, was undertaken. Research under the Campaigns “AÇORES/89”, “PICO/91”, “PICOBEL/2007” and “LAUMACAT/2011” covered a relatively large area (approximately 39 km2) around the island encompassing the littoral and sublittoral levels down to about 40 m. This paper improves the knowledge of the Azorean macroalgal flora at local and regional scales by listing taxonomic records and providing information on the ecology and occurrence of each species present on the island’s littoral. New information A total of 4043 specimens (including taxa identified only to genus level) belonging to 303 taxa of macroalgae are registered, comprising 197 Rhodophyta, 53 Chlorophyta and 53 Ochrophyta (Phaeophyceae). From these, 225 were identified to species level (142 Rhodophyta, 41 Chlorophyta and 42 Ochrophyta), encompassing 110 new records for the island (69 Rhodophyta, 20 Chlorophyta and 21 Ochrophyta), three Macaronesian endemisms (Botryocladia macaronesica Afonso-Carillo, Sobrino, Tittley & Neto; Laurencia viridis Gil-Rodríguez & Haroun; and Codium elisabethiae O. C. Schmidt), 14 introduced, and 25 species with an uncertain status. Introduction The Azorean algal flora, considered cosmopolitan with species shared with Macaronesia, North Africa, the Mediterranean Sea, Atlantic Europe and America (Tittley 2003, Tittley & Neto 2006, Wallenstein et al. 2009), has been considered relatively rich when compared to that of other remote oceanic islands (Neto et al. 2005; Tittley & Neto 2005; Wallenstein et al. 2009). Even so, it is worth mentioning that the published information (approximately 400 species, Freitas et al. 2019) reflects data from only a few of the nine islands, since not all of them have been thoroughly investigated. To overcome this, and improve the understanding of the archipelago’s seaweed flora, an effort has been made by local investigators over the past three decades and research on the marine macroalgae flora has been conducted on several of the less studied Azorean islands. This paper comprises both physical and occurrence data and compiles the gathered information from macroalgae surveys developed in Pico Island mainly by the Island Aquatic Research Group of the University of the Azores (https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology). It aims to constitute a practical resource for biological studies such as systematics, diversity and conservation, biological monitoring, climate change and ecology, and also for academics, students, government, private organizations, and the general public. Purpose By listing taxonomic records for Pico and presenting general information for each taxon occurrence on the island’s littoral, this paper addresses several biodiversity shortfalls (see Hortal et al. 2015), namely the need to catalogue the Azorean macroalgae (Linnean shortfall) and improve the current information on their local and regional geographic distribution (Wallacean shortfall), as well as on species abundances and dynamics in space (Prestonian shortfall).

Background The macroalgal flora of Graciosa (central group of Azores archipelago) is poorly known, the published information reflecting occasional collections from sporadic field visits to the island. To overcome this, a thorough investigation under the Expedition “GRACIOSA/2004”, the Campaigns “PADEL/2006”, “MACROBIOLMOL/2014” and “PIMA-BALA/2017” involving sample collecting and presence data recording, was undertaken over an area of 19 km2 encompassing littoral and sublittoral levels down to about 40 m. This paper lists the taxonomic records and provides information on species ecology and occurrence around the island improving the knowledge of the Azorean macroalgal flora at both local and regional scales. New information A total of 1692 specimens belonging to 250 taxa of macroalgae (and including 55 taxa identified only at the genus level) are registered, comprising 166 Rhodophyta, 36 Chlorophyta and 48 Ochrophyta (Phaeophyceae). From these, 195 are identified to the species level (126 Rhodophyta, 31 Chlorophyta and 38 Ochrophyta) and comprise 156 native, 20 of uncertain origin and 14 introductions to the island. Predaea feldmannii subsp. azorica Gabriel is an Azorean endemic, whereas Codium elisabethiae O.C. Schmidt, Botryocladia macaronesica Afonso-Carrillo, Sobrino, Tittley & Neto, Phyllophora gelidioides P.Crouan & H.Crouan ex Karsakoff and Laurencia viridis Gil-Rodríguez & Haroun represent Macaronesian endemics. Seventy-nine species are newly recorded to the island. Introduction Around 400 species have been recorded in the isolated mid-Atlantic Azores archipelago so far (Freitas et al. 2019). When compared to that of other remote oceanic islands (e.g. the Shetlands and Faroes in the colder North Atlantic, and Ascension and Tristan da Cunha in the Southern Atlantic), the algal flora of the Azores can be considered relatively rich (Tittley 2003, Neto et al. 2005; Tittley & Neto 2005; Tittley & Neto 2006, Wallenstein et al. 2009). It is a cosmopolitan flora with species shared with Macaronesia, North Africa, the Mediterranean Sea, Atlantic Europe and America. Overall, it shares more species with the east Atlantic flora than with the west (Tittley & Neto 2006, Wallenstein et al. 2009). Although São Miguel has been thoroughly investigated, most of the Azorean islands have received little attention, there algal flora being scarcely studied. To overcome this, and improve the understanding of the archipelago’s seaweed flora, research has been conducted over the past three decades. This paper presents both physical and occurrence data, and information gathered from macroalgae surveys undertaken on Graciosa (central group of the archipelago) by the Island Aquatic Research Group of the Azorean Biodiversity Centre of the University of the Azores (https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology) the MARBE, Marine Biodiversity and Environment Research Group of CIBIO-Açores at the University of the Azores (http://cibio.uac.pt/en/research-groups/marbe-marine-biodiversity-and-environment), and the OKEANOS Centre of the University of the Azores (www.okeanos.uac.pt). In these surveys particular attention was given to the small filamentous and thin sheet like forms that are often short-lived and fast-growing species, very difficult to identify in the wild, requiring the aid of a microscope. The paper aims to provide a practical resource for biological studies, such as systematics, diversity and conservation, biological monitoring, climate change and ecology, and also for academics, students, government, private organizations, and the general public. Purpose In this contribution we list taxonomic records for Graciosa and present general information for the occurrence of each taxon around the island. By doing this, we are contributing to address several biodiversity shortfalls (see Hortal et al. 2015), namely the need to catalogue the Azorean macroalgae (Linnean shortfall) and improve the current information on their local and regional geographic distribution (Wallacean shortfall), as well as on species abundances and dynamics in space (Prestonian shortfall).

This occurrence dataset lists the macroalgal taxonomic records compiled under occasional collections done at São Jorge Island (central group of the Azores archipelago) and provides information on each species’ ecology and occurrence on the island’s littoral. Collections were undertaken mainly by Island Aquatic Research Group of the Azorean Biodiversity Centre of the University of the Azores (https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology) at the littoral and shallow sublittoral levels. A total of 84 specimens are registered (including taxa identified only at generic level) belonging to 49 taxa of macroalgae, comprising 34 Rhodophyta, 9 Chlorophyta and 6 Ochrophyta (Phaeophyceae). From these, 21 are new records for the island, three are introduced, and five have an uncertain status. Most species were only sporadically observed on the island’s littoral, but four were commonly found, namely: the Rhodophyta Carradoriella denudata (Dillwyn) A. M. Savoie & G. W. Saunders, Ellisolandia elongata (J. Ellis & Solander) K. R. Hind & G. W. Saunders, and Gelidium spinosum (S. G. Gmelin) P. C. Silva; and the Chlorophyta Ulva intestinalis Linnaeus. Although representing an incomplete list of the seaweeds occurring in the island of São Jorge, this occurrence dataset is a contribution to the knowledge of the marine alga flora of that island. For each taxon presented, it provides general information on its occurrence on the island’s littoral, and thus contributes to address several biodiversity shortfalls (see Hortal et al. 2015), namely the need to catalogue the Azorean macroalgae (Linnean shortfall) and improve the current information on their local and regional geographic distribution (Wallacean shortfall), as well as on species abundances and dynamics in space (Prestonian shortfall). It aims to provide information for biological studies such as systematics, diversity and conservation, biological monitoring, climate change and ecology, and for academics, students, government, private organizations, and the general public.

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 Biodiversity Centre of the University of the Azores (https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology). In these surveys, special attention was dedicated to the sheet-like and filamentous forms that are difficult to identify in the wild, the seasonal and fast growing annuals, and particularly to the small forms that are often short-lived and fast growing species, very difficult to identify without the aid of a microscope. This paper compiles physical, occurrence and survey data and is intended as a practical resource for biological studies (such as systematics, diversity and conservation, biological monitoring, climate change and ecology), and for academics, students, government, private organizations, and the general public. Purpose By listing the taxonomic records for Terceira and presenting general information for each taxon’s occurrence on the island’s littoral, this paper addresses several biodiversity shortfalls (see Hortal et al. 2015), namely the need to catalogue the Azorean macroalgae (Linnean shortfall) and improve the current information on their local and regional geographic distribution (Wallacean shortfall), as well as on species’ abundances and dynamics in space (Prestonian shortfall).

This occurrence dataset lists the macroalgal taxonomic records compiled from occasional collections done at Faial Island (central group of the Azores archipelago) and provides information on each species’ ecology and occurrence on the island’s littoral. Collections were undertaken mainly by Island Aquatic Research Group of the Azorean Biodiversity Centre of the University of the Azores (https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology) at the littoral and shallow sublittoral levels. A total of 95 specimens are registered (including taxa identified only at generic level) belonging to 59 taxa of macroalgae comprising 33 Rhodophyta, 15 Chlorophyta and 11 Ochrophyta (Phaeophyceae). From these, 12 are new records for the island, three are introduced, and eight have an uncertain status. Most species were only sporadically observed on the island’s littoral, but five Rhodophyta were commonly found, namely: Chondracanthus acicularis (Roth) Fredericq, Corallina officinalis Linnaeus, Halarachnion ligulatum (Woodward) Kützing, Hypnea musciformis (Wulfen) J.V.Lamouroux and Osmundea hybrida (A. P. de Candolle) K. W. Nam. Although representing an incomplete list of the seaweeds occurring in Faial, this occurrence dataset is a contribution to the knowledge of the marine alga flora of that island. For each taxon presented, it provides general information on its occurrence on the island’s littoral, and thus contributes to address several biodiversity shortfalls (see Hortal et al. 2015), namely the need to catalogue the Azorean macroalgae (Linnean shortfall) and improve the current information on their local and regional geographic distribution (Wallacean shortfall), as well as on species abundances and dynamics in space (Prestonian shortfall). It aims to provide information for biological studies such as systematics, diversity and conservation, biological monitoring, climate change and ecology, and for academics, students, government, private organizations, and the general public.