Background The macroalgal flora of the Island of São Miguel (eastern group of the Azores archipelago) has attracted the interest of many researchers in the past, the first publications going back to the nineteenth century (see summary in Neto et al. 2014). Initial studies were mainly taxonomic, resulting in the publication of species lists, which were compiled by Neto (1994) in the first checklist of the Azorean benthic marine algae. Later, the establishment of the University of the Azores on the Island permited the logistic conditions to develop both temporal studies and long-term research, and this resulted in a significant increase on research directed at the benthic marine algae and littoral communities of the Island and consequent publications (see revision in Neto et al. 2014 and Haroun et al. 2019). Prior to the present paper, the known macroalgal flora of São Miguel Islandcomprised around 260 species. Despite this richness, a significant amount of the research was never made public, notably Masters and PhD theses encompassing information regarding presence data recorded at littoral and sublittoral levels down to a depth of approximately 40 m around the Island, and the many collections made, which resulted in vouchers deposited in the AZB Herbarium Ruy Telles Palhinha and the LSM- Molecular Systematics Laboratory at the Faculty of Sciences and Technology of the University of the Azores. The present publication lists the macroalgal taxonomic records together with information on their ecology and occurrence around São Miguel Island, improving the knowledge of the Azorean macroalgal flora at local and regional scales. New information A total of 12,781 specimens (including some identified only to genus) belonging to 431 taxa of macroalgae are registered, comprising 284 Rhodophyta, 59 Chlorophyta and 88 Ochrophyta (Phaeophyceae). Of these, 323 were identified to species level (212 Rhodophyta, 48 Chlorophyta and 63 Ochrophyta), of which 61 are new records for the Island (42 Rhodophyta, 9 Chlorophyta and 10 Ochrophyta), 1 an Azorean endemic (Predaea feldmannii subsp. azorica Gabriel), 5 are Macaronesian endemisms (the Rhodophyta Botryocladia macaronesica Afonso-Carrillo, Sobrino, Tittley & Neto, Laurencia viridis Gil-Rodríguez & Haroun, Millerella tinerfensis (Seoane-Camba) S.M.Boo & J.M.Rico, Phyllophora gelidioides P.Crouan & H.Crouan ex Karsakoff and the Chlorophyta Codium elisabethiae O.C.Schmidt), 19 are introduced species (15 Rhodophyta, 2 Chlorophyta and 2 Ochrophyta), and 32 are of uncertain status (21 Rhodophyta, 5 Chlorophyta and 6 Ochrophyta). Introduction Research on the marine algae from the Azores started in the mid nineteenth century (1838) when Guthnick and the two Hochstetters, father and son, visited the archipelago (Neto 1994). Since then, many other researchers and naturalists have visited the archipelago, resulting in several publications on the marine algal flora of this region (see summary in Neto 1994; 1997). Most initial studies were taxonomic focusing on the production of species lists. Almost a century later, the German botanist Otto Christian Schmidt visited several islands, including São Miguel, and initiated a more comprehensive ecological approach describing species associations and their spatial organization (Schmidt, 1931). Ever since the first half of last century, several studies have focused more widely on intertidal and shallow subtidal communities providing information on the vertical distribution of macroalgae and invertebrates and their trophic relations (see Neto 1992, 2000, 2001 for a review on this subject). Taxonomic investigations have continued and the first checklist of the Azorean benthic marine algae published by Neto (1994) brought together the existing published information, provided distributional records within the archipelago and reported 307 species, indicating a moderately rich flora given its isolated mid-Atlantic position. A revision of this first checklist was made by Parente (2010), increasing the number of algae species to 327, but without providing their distributional information on the archipelago. Later, Rosas-Alquicira et al. (2011) published a catalogue of non-fossil geniculate coralline red algae (Corallinales, Rhodophyta) of the Macaronesia in which they made both a critical review of species and infraspecific taxa as ell as an assessment of species diversity in the region. Research by local teams was also dedicated to the Azorean littoral communities and biota conservation (see, for example, Abecasis et al. 2015, Amorim et al. 2015, Chainho et al. 2015). Taxonomic, ecological and biotechnological investigations have continued generating knowledge on the Azorean macroalgae flora, its biotechnological potential and also on the structure and functioning of littoral communities (see revisions on Neto et al. 2014 and Haroun et al. 2019). Recently, several additional studies have been published with important information on the Azorean algae biodiversity, biogeography, conservation, ecology, and taxonomy (see, for example, Bruno de Sousa et al. 2019, Cacabelos et al. 2019, 2020, Freitas et al. 2019, Kellaris et al. 2019, Martins et al. 2019, Parente et al. 2019, 2020, Patarra et al. 2017, 2019, 2020, Sousa et al. 2019, Faria et al. 2020a-b, Vieira et al. 2020). The paper by Freitas et al. (2019) increased the number of macroalgae species occurring in the Azores to 405 and reported that amongst the mid-Atlantic archipelagos, the Azores is second in species richness after the Canary Islands, with 689 species, and followed by Madeira (396), Cabo Verde (333) and Selvagens (295 species). For some species the Azores archipelago forms a boundary in their distribution. Codium effusum (Rafinesque) Delle Chiaje, for example, is as its western distribution limit in the archipelago (León-Cisneros et al. 2012), whereas for Dudresnaya crassa M.Howe, a western Atlantic warm-water species, the Azores extends its known distributional range to the east. Some northern species such as the red alga Schizymenia dubyi (Chauvin ex Duby) J.Agardh and Lomentaria orcadensis (Harvey) Collins come close to their southern limit of distribution in the Azores while some southern warm-water species such as green alga Anadyomene stellata (Wulfen) C.Agardh and the red alga Sebdenia rodrigueziana (Feldmann) Codomier ex Athanasiadis reach their Atlantic northern limit of distribution on the islands (Neto et al. 2005, León-Cisneros et al. 2012). Some species, relatively common in the region a few years ago, have become uncommon or even very rare, e.g. Scytosiphon lomentaria (Lyngbye) Link, Schimmelmannia schousboei (J.Agardh) J.Agardh. In contrast, there has been an increase of unexpected macroalgae in the Azores, with the arrival and establishment of several non-native species (see Cardigos et al. 2006, Micael et al 2014, Vaz-Pinto et al. 2014, Parente et al. 2019, Cacabelos et al. 2019, 2020, Martins et al. 2019). Within the spread of the archipelago there are no marked differences between floras of individual Islands or Island groups, and biogeographically the Azores algal flora reveals to have a mixed nature, with species shared with Macaronesia, North Africa, the Mediterranean Sea, Atlantic Europe and America (Tittley 2003, Tittley & Neto 1995, 2005, 2006, Wallenstein et al. 2009b). This nature of the Azorean marine algal flora was reinforced by the work of Freitas et al. (2019), who using an extensive analysis encompassing data on coastal fishes, brachyurans, polychaetes, gastropods echinoderms and macroalgae, suggested that the Azores should be a biogeographical entity on its own and proposed a redefinition of the Lusitanian biogeographical province, in which they included four ecoregions: the South European Atlantic Shelf, the Saharan Upwelling area, the Azores ecoregion, and a new ecoregion they named Webbnesia, which comprises the archipelagos of Madeira, Selvagens and the Canary Islands. Not all the Azorean Islands have received the same attention regarding the studies on macroalgae. Furthermore, many species may have been overlooked due to their small size, opportunisctic nature or ephemeral life span. To overcome this and gain a better and up to date knowledge of the archipelago’s macroalgae flora, an effort was made by resident teams to undertake a considerable amount of research over the past three decades on several Islands. The present paper is the last one of a series and presents physical, occurrence data, and information gathered from macroalgal surveys undertaken on São Miguel Island between 1989 and 2019 mainly by the Island Aquatic Research Group of the Azorean Biodiversity Centre of the University of the Azores (Link: https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology), the BIOISLE, Biodiversity and Islands Research Group of CIBIO-Açores at the University of the Azores (Link: https://cibio.up.pt/research-groups-1/details/bioisle), and the OKEANOS Centre of the University of the Azores (Link: http://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, and usually very difficult to identify in the field, without the aid of a microscope and specialised literature in the laboratory. This paper aims to provide a valuable marine biological tool to aid research on the systematics, diversity and conservation, biological monitoring, climate change, ecology and more applied studies, such as biotechnological applications, which will be of assistance to a wide range of focal groups including academics, students, governments, private organizations and the general public. Purpose: This paper presents taxonomic records of macroalgae for São Miguel Island and provides general information on their occurrence and distribution. By doing this, it will contribute to address several biodiversity shortfalls (see Cardoso et al. 2011, Hortal et al. 2015), namely the need to catalogue the Azorean macroalgae (Linnean shortfall) to improve current information on their local and regional geographic distribution (Wallacean shortfall), as well as to provide a better understanding of species abundance and dynamics in space (Prestonian shortfall).

Background The algal flora of the Island of Santa Maria (eastern group of the Azores archipelago) has attracted interest of many researchers on numerous past occasions (such as Drouët 1866; Agardh 1870; Trelease 1897; Schmidt 1931; Ardré et al. 1974; Fralick & Hehre 1990; Neto et al. 1991; Morton & Britton 2000; Amen et al. 2005; Wallenstein & Neto 2006; Tittley et al. 2009; Wallenstein et al. 2009a, 2010; Botelho et al. 2010; Torres et al. 2010; León-Cisneros et al. 2011; Martins et al. 2014; Micael et al. 2014; Rebelo et al. 2014; Ávila et al. 2015, 2016; Machín-Sánchez et al. 2016; Uchman et al. 2016; Johnson et al. 2017; Parente et al. 2018). Nevertheless, the Island macroalgal flora is not well-known as published information reflects limited collections obtained in short term visits by scientists. To overcome this, a thorough investigation, encompassing collections and presence data recording, was undertaken at both the littoral and sublittoral levels down to a depth of approximately 40 m, covering an area of approximately 64 km. The resultant taxonomic records are listed in the present paper which also provides information on species ecology and occurrence around the Island, improving, thereby, the knowledge of the Azorean macroalgal flora at both local and regional scales. New information A total of 2329 specimens (including some taxa identified only to genus level) belonging to 261 taxa of macroalgae are registered, comprising 152 Rhodophyta, 43 Chlorophyta and 66 Ochrophyta (Phaeophyceae). Of these, 176 were identified to species level (103 Rhodophyta, 29 Chlorophyta and 44 Ochrophyta), encompassing 52 new records for the Island (30 Rhodophyta, 9 Chlorophyta and 13 Ochrophyta), 2 Macaronesian endemisms (Laurencia viridis Gil-Rodríguez & Haroun; and Millerella tinerfensis (Seoane-Camba) S.M.Boo & J.M.Rico), 11 introduced (the Rhodophyta Acrothamnion preissii (Sonder) E.M.Wollaston, Antithamnion hubbsii E.Y.Dawson, Asparagopsis armata Harvey, Asparagopsis armata Harvey phase Falkenbergia rufolanosa (Harvey) F.Schmitz, Bonnemaisonia hamifera Hariot, Melanothamnus harveyi (Bailey) Díaz-Tapia & Maggs, Scinaia acuta M.J.Wynne and Symphyocladia marchantioides (Harvey) Falkenberg; the Chlorophyta Codium fragile subsp. fragile (Suringar) Hariot; and the Ochrophyta Hydroclathrus tilesii (Endlicher) Santiañez & M.J.Wynne, and Papenfussiella kuromo (Yendo) Inagaki), and 19 species of uncertain status (11 Rhodophyta, 3 Chlorophyta and 5 Ochrophyta). Introduction The marine algal flora of the isolated mid-Atlantic Azores archipelago is considered cosmopolitan, with species shared with Macaronesia, North Africa, the Mediterranean Sea, Atlantic Europe and America (Tittley 2003, Tittley & Neto 2006, Wallenstein et al. 2009b), and relatively rich when compared to that of other remote oceanic Islands (Neto et al. 2005, Tittley & Neto 2005, Wallenstein et al. 2009b). A recent publication by Freitas et al. (2019) list around 400 species of marine macroalgae to the Azores and, in a comparison with other mid-Atlantic archipelagos, reports that the Canary Islands, with 689 species, are by far the most diverse archipelago, followed by the Azores (405), Madeira (396), Cabo Verde (333) and the Selvagens (295 species). Those authors, based on extensive analysis encompassing data on coastal fishes, brachyurans, polychaetes, gastropods echinoderms and macroalgae, suggested that the Azores should be a biogeographical entity of its own and proposed a redefinition of the Lusitanian biogeographical province, in which they consider four ecoregions: the South European Atlantic Shelf, the Saharan Upwelling, the Azores ecoregion, and a new ecoregion they named Webbnesia, which comprises the archipelagos of Madeira, Selvagens and the Canary Islands. It is worth considering that the paper by Freitas et al. (2019) reflects data from only a few of the nine Islands, since not all of them have been thoroughly investigated. São Miguel, with a total number of algal species of 260 at the moment, is the Island with the largest amount of research dedicated to the subject. To overcome this, provide a better understanding of the archipelago’s seaweed flora, research has been conducted over the past three decades on all the Islands. Data on the Islands of Corvo and Flores, Graciosa, Pico, and Terceira is already available on the recently published papers by Neto et al. (2020 a, b, c, d). The present paper presents both physical and occurrence data, and information gathered from macroalgae surveys undertaken on Santa Maria Island mainly by the Island Aquatic Research Group of the Azorean Biodiversity Centre of the University of the Azores (Link: https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology) the BIOISLE, Biodiversity and Islands Research Group of CIBIO-Açores at the University of the Azores (Link: https://cibio.up.pt/research-groups-1/details/bioisle), and the OKEANOS Centre of the University of the Azores (Link: http://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, and usually very difficult to identify in the wild, without the aid of a microscope and specialised literature in the laboratory. The paper aims to provide a valuable marine biological tool for research on systematics, diversity and conservation, biological monitoring, climate change and ecology for academics, students, government, private organizations and the general public. Purpose: In this paper we present taxonomic records of macroalgae for Santa Maria and provide general information on their occurrence and distribution. By doing this, we are contributing to address several biodiversity shortfalls (see Cardoso et al. 2011, 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 abundance and dynamics in space (Prestonian shortfall).

Background The algal flora of the western group of the Azores archipelago (Islands of Flores and Corvo) has attracted the interest of many researchers on numerous past occasions (such as Drouët 1866; Trelease 1897; Gain 1914; Schmidt 1929, 1931; Azevedo et al. 1990; Fralick & Hehre 1990; Neto & Azevedo 1990; Neto & Baldwin 1990; Neto 1996, 1997, 1999; Tittley & Neto, 1996, 2000, 2005, 2006; Azevedo 1998, 1999; Tittley et al. 1998; Dionísio et al. 2008; Neto et al. 2008). Despite this interest, the macroalgal flora of the Islands cannot be described as well-known with the published information reflecting limited collections preformed in short term visits by scientists. To overcome this, a thorough investigation, encompassing collections and presence data recording, has been undertaken for both the littoral and sublittoral regions, down to a depth of approximately 40 m, covering a relatively large area on both Islands (approximately 143 km2 for Flores and 17 km2 for Corvo). This paper lists the resultant taxonomic records and provides information on species ecology and occurrence around both these Islands, thereby improving the knowledge of the Azorean macroalgal flora at both local and regional scales. New information For the Island of Flores, a total of 1687 specimens (including some taxa identified only to genus level) belonging to 196 taxa of macroalgae are registered, comprising 120 Rhodophyta, 35 Chlorophyta and 41 Ochrophyta (Phaeophyceae). Of these taxa, 128 were identified to species level (80 Rhodophyta, 22 Chlorophyta and 26 Ochrophyta), encompassing 37 new records for the Island (20 Rhodophyta, 6 Chlorophyta and 11 Ochrophyta); two Macaronesian endemics (Laurencia viridis Gil-Rodríguez & Haroun and Millerella tinerfensis (Seoane-Camba) S.M.Boo & J.M.Rico); six introduced (the Rhodophyta Asparagopsis armata Harvey, Neoizziella divaricata (C.K.Tseng) S.-M.Lin, S.-Y.Yang & Huisman, and Symphyocladia marchantioides (Harvey) Falkenberg; the Chlorophyta Codium fragile subsp. fragile (Suringar) Hariot; and the Ochrophyta Hydroclathrus tilesii (Endlicher) Santiañez & M.J.Wynne, and Papenfussiella kuromo (Yendo) Inagaki); and 14 species of uncertain status (10 Rhodophyta, 2 Chlorophyta and 2 Ochrophyta). For the Island of Corvo, a total of 390 specimens distributed in 56 taxa of macroalgae are registered, comprising 30 Rhodophyta, 9 Chlorophyta and 17 Ochrophyta (Phaeophyceae). Whilst a number of taxa were identified only to the genus level, 43 were identified to species level (22 Rhodophyta, 8 Chlorophyta and 13 Ochrophyta), comprising 22 new records for the Island (9 Rhodophyta, 4 Chlorophyta and 9 Ochrophyta), two introduced species (the Rhodophyta Asparagopsis armata and the Chlorophyta Codium fragile subsp. fragile, and seven species of uncertain status (5 Rhodophyta and 2 Ochrophyta). 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), is relatively rich when compared to that of other remote oceanic Islands (Neto et al. 2005, Tittley & Neto 2005, Wallenstein et al. 2009). Around 400 species of marine macroalgae have, to date, been recorded for the isolated mid-Atlantic Azores archipelago (Freitas et al. 2019). These authors, based on extensive analysis encompassing data on brachyurans, polychaetes, gastropods, echinoderms, coastal fishes and macroalgae, suggested that the Azores should be a biogeographical entity of its own and proposed a redefinition of the Lusitanian biogeographical province, in which they recognised four ecoregions: the South European Atlantic Shelf, the Saharan Upwelling, the Azores ecoregion, and a new ecoregion herein named Webbnesia, which comprises the archipelagos of Madeira, Selvagens and the Canary Islands. In their paper comparing the Azorean algal flora to that of the new Webbnesia region, they reported that the Canary Islands, with 689 species of marine macroalgae, are by far the most diverse archipelago, followed by the Azores (405), Madeira (396) and Cabo Verde (333). The Selvagens are the least diverse one (295 species). It is worth mentioning that the published information reflects data from only a few of the nine Azorean Islands, since not all of them have been adequately investigated. In the Azores archipelago, São Miguel is by far the Island with the largest amount of research dedicated to the study of its algal flora. The total number of algal species is, at the moment, 260, a number that is likely to increase due to ongoing research by authors of the present paper. Most of the remaining Islands have received less attention. To overcome this, and improve the understanding of the archipelago’s macroalgal flora, research has been conducted over the past three decades on all the Islands. Data on the Islands of Pico, Graciosa and Terceira is already available on the recently published papers by Neto et al. (2020b, c, d). To provide a better understanding of the archipelago’s seaweed flora, a long term research programme of study has been undertaken, mainly by local investigators into the marine macroalgae flora on several of the less studied Azorean Islands. The present paper presents both physical and occurrence data, and information gathered from surveys undertaken on Flores and Corvo Islands mainly by the Island Aquatic Research Group of the Azorean Biodiversity Centre of the University of the Azores (Link: https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology) the BIOISLE, Biodiversity and Islands Research Group of CIBIO-Açores at the University of the Azores (Link: https://cibio.up.pt/research-groups-1/details/bioisle), and the OKEANOS Centre of the University of the Azores (Link: http://www.okeanos.uac.pt). In these surveys particular attention was given to the small filamentous and thin sheet-like species that are often short-lived and fast-growing, and usually very difficult to identify in the wild, without the aid of a microscope and specialised literature in the laboratory. The present paper aims to provide a valuable marine biological tool for research on systematics, diversity and conservation, biological monitoring, climate change and ecology for academics, students, government, private organizations and the general public. Purpose: In this paper we present taxonomic records of macroalgae recorded from the Islands of Flores and Corvo and provide general information on their occurrence and distribution. By doing this, we are contributing to address several biodiversity shortfalls (see Cardoso et al. 2011, 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 abundance and dynamics in space (Prestonian shortfall).