Marine algal (seaweed) flora of Faial Island, Azores

Collections and data recording were done by David Milla-Figueras, Ana Isabel Neto, Fernando Tempera, Ignacio Moreu, Afonso C. L. Prestes, Roberto Resendes, Raul M. A. Neto, Ian Tittley, Pedro Afonso, Célia Albuquerque, Norberto Serpa, Gustavo Martins, Maria Vale, Steve Hawkins, Isabel Lima, João Brum, Sara Vanessa Santos, João Gonçalves, Andrea Zita Botelho and Rodrigues Marcos between 1990 and 2018.

Preliminary in situ identifications were carried out by: David Milla-Figueras, Ana Isabel Neto, Fernando Tempera, Sara Vanessa Santos, Afonso C. L. Prestes, Ian Tittley, Gustavo Martins and Andrea Zita Botelho.

David Milla-Figueras, Ana Isabel Neto, Ian Tittley and Fernando Tempera were responsible for the final species identification.

Voucher specimen management was mainly undertaken by David Milla-Figueras, Ana Isabel Neto, Fernando Tempera, Afonso C. L. Prestes, Roberto Resendes, Ian Tittley and Andrea Zita Botelho.

Faial Island is located at the western end of the Azores’ central island group (38°39′12″N, 28°50′41″W, Fig. 1). The Island is 21 km long along an east-west direction and 14 km wide in a north-south direction, with an area of 173 km². 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 is fringed by a narrow (avg. 2.5 km) shelf that attains its broadest point on the ca. 8 km passage that separates it from the neighbouring Pico Island (Tempera 2008). The tidal range is small (maximum 1.5 m, Instituto Hidrográfico 1981) and coasts are subjected to strong oceanic swells throughout the year. With an extension of approximately 80 km, the island coastline has several bays and small sandy beaches, flanked by rocky cliffs. Intertidal rocky platforms, with variable widths and sometimes dissected by channels and gullies, can be found in a few locations (e.g. Feteira, Capelinhos, Porto da Eira) and are mostly easily accessible from land (authors, pers. observ.).

The rocky-shore communities of Faial Island, like all others in the Archipelago, are macroalgae-dominated at both intertidal and shallow subtidal levels (Tittley and Neto 1994, Neto and Tittley 1995). A distinct intertidal zonation pattern is evident with a higher zone dominated by littorinids, followed by the upper zone of the mid-littoral where chthamalid barnacles in which patches of fringes of the algae Fucus spiralis Linnaeus and Gelidium microdon Kützing may occur (Fig. 2). This is followed by the lower zone of the mid-littoral, covered by algal turfs composed either by soft algae (e.g. Centroceras sp., Chondracanthus sp.) and/or by articulate calcareous ones (e.g. Corallina sp. and Jania sp., Fig. 3). The lower intertidal zone is mainly dominated by calcareous and non-calcareous encrusting species (notably crustose Corallinaceae and Codium adhaerens C.Agardh) often interspersed with articulated coralline species, such as Ellisolandia elongata (J. Ellis & Solander) K.R.Hind & G.W.Saunders and corticated macrophytes, such as Pterocladiella capillacea (S.G.Gmelin) Santelices & Hommersand (Neto et al. 2005).

In the subtidal zone, rocky bottoms are mainly covered by algal turfs where calcareous and/or non-calcareous macroalgae fronds form short, dense multispecific mats (Tempera et al. 2013). The first 10 m are commonly colonised by Pterocladiella capillacea, Dictyota spp. and Halopteris filicina (Grateloup) Kützing. Dense stands of Codium elisabethiae are found in sheltered areas between 10 and 25 m depth in the southeast of the Island (Tempera 2008). Zonaria tournefortii (J.V.Lamouroux) Montagne (Fig. 4) dominates between 15 and 30 m, although facies of Padina pavonica (Linnaeus) Thivy can be found in well-lit areas, such as Baixa do Sul. Deeper infra-littoral areas (around 40 m) are often characterised by Halopteris filicina and the rarer Dictyopteris polypodioides (De Candolle) J.V.Lamouroux, Carpomitra costata (Stackhouse) Batters or Sporochnus pedunculatus (Hudson) C.Agardh (Milla-Figueras, pers.observ.).

Caulerpa webbiana and C. prolifera are examples of recent introductions detected over the last two decades (Cardigos et al. 2006, Amat 2008, Cacabelos et al. 2019). Caulerpa webbiana, in particular, have been steadily expanding around Faial and neighbouring coasts since it was first recorded (Fig. 5), although, since 2021, it has been replaced by the invasive species Rugulopteryx okamurae (E.Y.Dawson) I.K.Hwang, W.J.Lee & H.S.Kim (Milla-Figueras, pers.observ.).

The algae were sampled during surveys conducted under various IMAR-DOP/Okeanos projects (1999, 2000, 2002, 2003, 2004, 2005, 2006, 2013, 2015, 2016 and 2018), as well as during a few visits to the Island made by the IBBC-GBA/cE3c group in the years 1990, 1999, 2006 and 2013. Sampling was mainly done by SCUBA divers at subtidal level in various locations spread around the Island and sporadically at the intertidal level (Fig. 6) targeting intertidal platforms at low tide. All specimens collected by the IBBCGBA/cE3c group 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. Specimens collected by IMAR-DOP/Okeanos were also stored in vouchers with an individual registration number at the DOP Herbarium, University of the Azores.

This study was mainly financed by the following projects/scientific expeditions:

• Portuguese National Funds, through FCT – Fundação para a Ciência e a Tecnologia, within the projects UID/BIA/00329/2019 and UID/BIA/00329/2020-2023;
• Portuguese Regional Funds, through DRCT – Direção Regional da Ciência e Tecnologia, within several projects, since 2013;
• CIRN/DB/UAc (Research Centre for Natural Resources, Universidade dos Açores, Departamento de Biologia);
• CIIMAR (Interdisciplinary Centre of Marine and Environmental Research, Porto, Portugal);
• MARÉ (Life-Nature B4-3200/98/509);
• OGAMP (INTERREG IIIb— MAC/4.2/A2 2001);
• MARMAC (INTERREG IIIb—03/MAC/4.2/A2 2004);
• BALA – “Elaboration of the implementation program of the marine strategy framework directive - biodiversity of the coastal environments of the Azores” (2 /DRAM /2015), funded by the Government of the Azores - Regional Secretariat for the Sea, Science and Technology, Regional Directorate for Sea Affairs, GRA /SRMCT-DRAM;
• MoniZEC-ARP - Monitorização de Áreas Marinhas Protegidas dos Açores com Regulamentação de Restrição à Pesca (30/DRAM/2018), funded by the Government of the Azores - Regional Secretariat for the Sea, Science and Technology, Regional Directorate for Sea Affairs, GRA /SRMCT-DRAM;
• Seaforest Portugal Project (FA_06_2017_067), supported by the Portuguese Government grant Fundo Azul;
• RESTORESEAS – Marine Forests of animals, plants and algae: nature-based tools to protect and restore biodiversity (Ref M2.2/RESTORESEAS/002/2022) funded through the joint 2019-2020 Biodiversa & Water JPI joint call for research proposals, under the BiodivRestore ERA-net COFUND programme and with Regional Science and Technology Fund of the Azores (FRCT);
• MoniCO Programme – “Azores Coastal Resources and Environmental Monitoring Program”, SRMCT/DRP. IMAR.

Sampling and collections were performed at intertidal and subtidal levels down to approximately 40 m around the Faial Island (Table 2, Fig. 6).

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 records. For the former, collections were made manually in each sampling location by scraping off one or two specimens of all different species found into previously labelled bags. The species presence records were gathered by registering all species present in the sampling locations visited (Fig. 7). Complementary data, for example, shore level (high, mid, low), orientation, type of substrate (bedrock, boulders, cobbles, mixed) and habitat (tide pool, open rock, gully, crevice, cave) were also recorded.

To identify each sampled taxon we used: 1) morphological observations of the whole specimens with the naked eye and 2) slide preparations examined using dissecting and compound microscopes. This allowed characterisation of diagnosing structures as described in literature and comparison with descriptions from other locations. In more difficult cases, specimens were sent to experts for identification.

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 the 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 neighbouring territories and biogeographic regions were used for species identification, namely Schmidt 1931, Taylor 1967, Levring 1974, Dixon and Irvine 1977, Taylor 1978, Lawson and John 1982, Anonymous 1983, Gayral and Cosson 1986, Fletcher 1987, Afonso-Carrillo and Sansón 1989, Burrows 1991, Boudouresque et al. 1992, Cabioc'h et al. 1992, Maggs and Hommersand 1993, Irvine and Chamberlain 1994, Brodie et al. 2007, Lloréns et al. 2012, 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 a herbarium code number and depositing them at the AZB Herbarium Ruy Telles Palhinha, University of Azores. Depending on the species and further planned research, different types of collections were made, namely: (i) liquid collections using 5% buffered formaldehyde seawater and then replacing it with Kew (Bridsen and 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 and Guiry 2021). The database was organised on FileMaker Pro.

Faial Island, Azores, Macaronesia, Portugal (approximately 38°39′12″N 28°50′41″W).

38.489 and 38.653 Latitude; -28.845 and -28.5589 Longitude.

All macroalgae were identified to genus or species level. In total, 118 taxa were identified belonging to 24 orders and 50 families, distributed by the phyla Rhodophyta (12 orders and 31 families), Chlorophyta (4 orders and 8 families), Ochrophyta (7 orders and 10 families) and Cyanobacteria (1 order and 1 family).

AZB|Marine macroalgae collection of Faial Island-Occasional sampling; DOP|Marine macroalgae occurrence of Faial Island (Azores)-Project BALA; DOP|Marine macroalgae occurrence of Faial Island (Azores)-Project MARÉ; DOP|Marine macroalgae occurrence of Faial Island (Azores)-Project MARMAC; DOP|Marine macroalgae occurrence of Faial Island (Azores)-Project MONIZEC-ARP; DOP|Marine macroalgae occurrence of Faial Island (Azores)-Project OGAMP; DOP|Marine macroalgae collection of Faial Island-Occasional sampling.

9fdfcab6-69d9-45bc-8210-b9b91eef474f; 1b1bd2dc-3c74-4467-b620-b663789826b5; 2aad17d8-428d-42ca-b22d-ab51c5dbcd2b; e0e7c8f9-56c4-4302-8db3-45e52af9f822; 0ac2d400-8e09-4d70-9f4c-a7d1ee50b478; ce6485b1-82ed-44ea-80e4-276fa4aee65b; a791eabf-5003-492d-be2e-69d921f9840f

AZB Herbarium Ruy Telles Palhinha, Faculty of Sciences and Technology of the University of the Azores; n/a; n/a; n/a; n/a; n/a; DOP Herbarium, Faculty of Sciences and Technology of the University of the Azores.

Specimens were preserved as follows: air-dry, dried and pressed; liquid (Formalin; Alcohol), silica.

AZB Herbarium Ruy Telles Palhinha, Faculty of Sciences and Technology of the University of the Azores and DOP Herbarium, Faculty of Sciences and Technology of the University of the Azores.

Marine algal (seaweed) flora of Faial Island, Azores

https://doi.org/10.15468/dsajcw

https://www.gbif.org/dataset/a5650ad0-caa5-4d2d-ad71-cd24356df369; http://ipt.gbif.pt/ipt/resource?r=faial_seaweed

2