We present an annotated checklist of the benthic marine and brackish algae of the Galician coasts (Spain) based on literature records and new collections. This checklist includes 618 species: 118 Cyanophyta, 296 Rhodophyta, 127 Ochrophyta, and 77 Chlorophyta. The number of specific, infraspecific taxa, and stages is 643: 121 Cyanophyta, 309 Rhodophyta, 135 Ochrophyta, and 79 Chlorophyta. Hyella caespitosa var. nitida, Calothrix fasciculata, Gracilariopsis longissima, Compsonema minutum, and Sphacelaria tribuloides are new records for Galicia, and there are also some new provincial records. We state the presence of each species for Lugo (Lu), A Coruña (Co), and Pontevedra (Po) provinces. The number of species found in Galicia is high, since 85% of the species recorded for the warm-temperate NE Atlantic Ocean grow in Galicia. Biogeographical comments comparing the Galician data with the neighboring areas of Britain and Ireland, Basque coast, Portugal, southern Iberian Peninsula, Canary Islands and Atlantic coast of Morocco are given. Finally, we present lists of cold-temperate, warm-temperate, Lusitanic Province endemics, and alien species growing in Galicia.

Microbial communities of natural subaerial biofilms developed on granitic historic buildings of a World Heritage Site (Santiago de Compostela, NW Spain) were characterized and cultured in liquid BG11 medium. Environmental barcoding through next-generation sequencing (Pacific Biosciences) revealed that the biofilms were mainly composed of species of Chlorophyta (green algae) and Ascomycota (fungi) commonly associated with rock substrata. Richness and diversity were higher for the fungal than for the algal assemblages and fungi showed higher heterogeneity among samples. Cultures derived from natural biofilms showed the establishment of stable microbial communities mainly composed of Chlorophyta and Cyanobacteria. Although most taxa found in these cultures were not common in the original biofilms, they are likely common pioneer colonizers of building stone surfaces, including granite. Stable phototrophic multi-species cultures of known microbial diversity were thus obtained and their reliability to emulate natural colonization on granite should be confirmed in further experiments.

Diatoms and water quality of the rivers of the Galician Central Massif (Ourense, N.O. Spain) through the use of diatom indicesMountain rivers diatoms from a complex of sierras that form the Galician Central Massif (Ourense province), place of communitarian importance, have been studied. For that study, eight rivers and one spring have been sampled, over one and a half years (from 2001 to 2003) and water samples were also taken to obtain some physico-chemical parameters (pH, conductivity, temperature, and dissolved oxygen). The most abundant species are Achnanthidium minutissimum, Diatoma mesodon, Fragilaria capucina, Gomphonema parvulum, G. rhombicum, and Hannaea arcus. With the diatoms' abundances, the IPS, IBD, and CEE indices were calculated to study the water quality, using the OMNIDIA program. The results of the indices classify the waters of these mountain rivers as of good or very good quality.

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The species composition of cyanobacteria assemblages was studied in six thermo-mineral springs of spas in Atlantic environments of Galicia (NW Spain). Two are considered hot (T a ≥ 40 °C), two intermediate (T a 20-40 °C) and two cold (T a ≤ 20 °C), and four contain hydrogen sulphide. A total of 21 taxa (14 genera) have been recorded. Two diversity indices, Shannon index and Evenness were determined. The Shannon-Wiener index ranged between 0.31 and 0.73 and the Evenness index between 0.44 and 0.88. nMDS ordination showed that cyanobacteria assemblage composition was influenced mostly by temperature. Of the species identified, the most diverse genus is Leptolyngbya with four species, followed by Chroococcus with three species and Aphanocapsa, Phormidium and Lyngbya with two species. The most abundant species was Jaaginema angustissimum, followed by Leptolyngbya laminosa and Symploca thermalis. In the two cold springs, seven different species were found, and only Aphanocapsa conferta was common to both springs. Cyanobacterial species were more numerous in the four hot springs, with 15 different species and only Calothrix thermalis common to these hot springs. It is difficult to establish characteristic cyanobacterial flora for the thermo-mineral waters of the Galician springs since there are significant differences in the communities from the six sites studied.