Marine algal flora of Santa Maria Island, Azores

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).