-28.845

-28.584

38.653

38.501

Phylum

Rhodophyta

Red algae

Phylum

Chlorophyta

Green algae

Phylum

Ochrophyta

Brown algae

0000-0003-0708-5636

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The island of Faial, located at the western end of the Central Group of the Azores archipelago (38°39′12″N, 28°50′41″W), 8.3 km west of Pico Island, is 21 km long in an east-west direction and 14 km wide, with an area of 173 km². The highest elevation of the island is the Caldeira, whose highest point is 1043 meters above sea level (Dores 2006).

As in the remaining Azorean Islands, the climate is temperate oceanic, with regular and abundant rainfall, high levels of relative humidity and persistent winds, mainly during winter and autumn (Morton et al. 1998). The island lacks a continental shelf, the tidal range is small (<2 m, see Instituto Hidrográfico 1981) and coasts are subjected to swell and surge most of the year. With and extension of approximately 80 km, the island coastline has several bays and small sandy beaches, flanked by rocky cliffs. Intertidal rocky platforms, with variable width and sometimes dissected by channels and gulleys, can be found in several locations (e.g. Feteira, Capelinhos) and are mostly easily accessible by land (Neto pers. observ.).

The rocky-shore communities of Faial, like all over in the archipelago are macroalgae-dominated at both intertidal and shallow subtidal levels (Tittley Neto 1994, Neto Tittley 1995). At the intertidal, a distinct zonation pattern is evident with a higher zone dominated by invertebrates (littorinids and chthamalid barnacles) in which patches of fringes of the algae Fucus spiralis Linnaeus and Gelidium microdon Kützing may occur. This is followed by the mid-shore zone covered by algal turfs composed either by soft algae (e.g. Centroceras, Chondracanthus) and or by articulate calcareous ones (e.g. Corallina and Jania). The lower zone is mainly dominated by calcareous crusts (first strata), covered by corticated macrophytes e.g. Corallina, Pterocladiella (Neto Tittley 1995).

The algae were sampled on occasional collections conducted in a few visits to the island in the years 1990, 1999, 2006 and 2013. Sampling was mainly done at the littoral level in different locations around the island, and sporadically at the subtidal level. Intertidal collections were done at low tide by walking along the shores. Subtidal collections were done by scuba diving. All collected specimens were given an individual registration number and vouchers were deposited at the AZB Herbarium Ruy Telles Palhinha, based at the Faculty of Sciences and Technology of the University of the Azores.

In the laboratory the specimens were accommodated, sorted and studied following standard procedures used in macroalgae identification.

Species identification was based on morphological and anatomical characters and reproductive structures. Identifying small and simple thallus required the observation of the entire thallus with the naked eye and/or using dissecting and compound microscopes. For large and more complex algae, the investigation of the thallus anatomy required histological work to obtain longitudinal and transverse sections needed for the observation of cells, reproductive structures and other diagnosing characteristics.

Various floras and keys from elsewhere were used for species identification, namely Schmidt (1931), Taylor (1967, 1978), Levring (1974), Dixon Irvine (1977), Lawson John (1982), Irvine (1983), Gayral Cosson (1986), Fletcher (1987), Afonso-Carrillo Sansón (1989), Burrows (1991), Boudouresque et al. (1992), Cabioc'h et al. (1992), Maggs Hommersand (1993), Irvine Chamberlain (1994), Brodie et al. (2007), Lloréns et al. (2012) and Rodríguez-Prieto et al. (2013).

For more critical and taxonomically difficult taxa, specimens were taken to the Natural History Museum (London) for comparison with collections there, or sent to appropriate specialists.

A reference collection was made for all specimens collected by giving them an herbarium code number and depositing them at the AZB Herbarium Ruy Telles Palhinha, University of Azores. Depending on the species and on further planned research, different types of collections were made, namely (i) liquid collections using 5% buffered formaldehyde seawater and then replacing it by Kew (Bridsen Forman 1999); (ii) dried collections, either by pressing the algae (most species) following the method described by Gayral and Cosson (1986) or by letting them air dry (calcareous species); and (iii) silica collections.

Nomenclatural and taxonomic status used here follow Algaebase (Guiry Guiry, 2020). The database was organized on FileMaker Pro.

Collections were performed at littoral and sublittoral levels down to approximately 30 m around the island of Faial.

Intertidal collections were made at low tide by walking along the shores. Subtidal collections were made by scuba diving. Sampling encompassed both physical collections and species presence recordings. For the former, in each sampling location, collections were made manually by scraping one or two specimens of all different species found into previously labelled bags. The species recording data was gathered by registering all species present in the sampled locations visited. Complementary data e.g. shore level (high, mid, low), orientation and type of substrate (bedrock, boulders, cobbles, mixed), habitat (tide pool, open rock, gully, crevice, cave) was also recorded.

The methodology adopted to identify each sampled taxon comprised morphological and anatomical observations of the whole specimens or slide preparations with the naked eye and using dissecting and compound microscopes, in order to characterize the diagnosing structures described in the literature and compare them with descriptions from other locations. In more difficult cases, specimens were sent to experts for identification.