[en] This thesis improves the knowledge on algal assemblages and their species from sandcovered rocks along the Atlantic Iberian Peninsula, addressing several perspectives: floristic, taxonomic, ecological and conservational. The study was mainly performed through the analysis of 2525 samples of different types of algal assemblages collected in the intertidal and upper subtidal of 138 sites, from 2002 to 2011. A catalogue of 257 species was provided in the first part of this thesis. Morphological descriptions and, in some cases, molecular data of the 35 most common species from sand-covered rocks were included, studying in detail 13 of them which mostly belong to the family Rhodomelaceae. As a result, two new species were described, as well as the sexual structures of four ones, several taxonomic proposals were performed for other taxa, and new chorollogical data were added to the Iberian coast. The second part was focused on the study of the algal assemblages from sand-covered rocks: i) providing a description of the vegetation from a Galician locality, ii) comparing the structure, spatial variability and diversity of the assemblages from sand-covered rocks and rocky shores, iii) monitoring the structure, temporal dynamics and phenology of Erythroglossum lusitanicum through a one-year study, and iv) analzying the turf assemblages from sand-covered rocks, with the description of 29 types of turfs. In the last part of this thesis, the data generated in this study were analyzed from a conservational perspective (distribution, biodiversity, endemisms, nonnative species, threats, etc.) and 20 sites of interest for the conservation of assemblages from sand-covered rocks were proposed.

[gl] Esta tese mellora o coñecemento das especies e comunidades de de algas de hábitats rochoso-areosos do Atlántico Peninsular, abordando diferentes perspectivas: florística, taxonómica, ecolóxica e conservacionista. O estudo foi realizado principalmente analizando 2525 mostras de diferentes tipos de comunidades algais recollidas no intermareal e infralitoral superior de 138 localidades, dende 2002 ata 2011. Na primera parte desta tese preséntase un catálogo de 257 especies. Ademáis inclúense descripcións morfolóxicas e, nalgúns casos, datos moleculares das 35 especies máis características dos hábitats rochoso-areosos, estudando 13 delas en detalle que na sua maioría pertencen á familia Rhodomelacea. Como resultado, se describen duas especies novas e as estructuras sexuais doutras catro, se levan a cabo varias propostas taxonómicas e se proporcionan novos datos corolóxicos para as costas Ibéricas. A segunda parte céntrase no estudo das comunidades de algas de hábitats rochosoareosos: i) se proporciona a descripición da vexetación dunha localidade galega, ii) se estuda comparativamente a estructura, variabilidade espacial e diversidade das comunidades de hábitats rochoso-areosos e hábitats rochosos, iii) se leva a cabo a monitorización da estructura, dinámica temporal e fenoloxía de Erythroglossum lusitanicum ó longo dun ano, iv) se analizan as comunidades cespitosas de hábitats rochoso-areosos, describindo 29 tipos de céspedes algais. Os datos xerados neste estudo foron analizados dende unha perspectiva conservacionista (distribución, biodiversidade, endemismos, especies non nativas, ameazas, etc.) na última parte desta tesis, e se propoñen 20 localidades de interés para a conservación das comunidades de hábitats rochoso-areosos.