The diatom Encyonema nevadense S.Blanco & al. sp. nov. is described as a new species, from epilithic samples collected from a high mountain pond in Sierra Nevada National Park. This taxon is characterized by the presence of narrow lanceolate valves with a moderate dorsiventrality, and the presence of areolae with irregular external openings. The type population is compared with Encyonema perpusillum (A.Cleve) D.G.Mann and its varieties, the morphologically closest species within the genus. The ecological and biogeographic implications of the discovery are briefly discussed.

Se describe la diatomea Hantzschia gadorensis como especie nueva a partir de muestras recogidas en una balsa ganadera en la Sierra de Gádor en Almería, España. Sus principales características son un bajo grado de dorsiventralidad, la ausencia de nódulo central y la presencia de conopeo que se registra por primera vez en el género, lo que permite distinguirla de especies similares. Los humedales de este sistema montañoso se confirman así como interesantes focos de biodiversidad aún por explorar.

We investigated the diatom communities and physicochemical water variables in the Abrud River catchment area (the Roșia Montană mining area, Romania) at 16 sampling sites, some of them impacted by acid mine drainage (AMD) and heavy metals. Diatoms serve as effective indicators of water characteristics owing to their ubiquity and sensitivity to environmental variables. This study aimed to enhance the understanding of the key environmental factors influencing the diatom flora of polluted rivers across various spatial and temporal scales, thereby informing the optimization of ecosystem management strategies. This work contributes to the knowledge of Romanian diatom flora through the identification of 274 taxa belonging to 63 genera, including 35 taxa recorded for the first time in the country. The spatial and temporal variations in the species richness patterns highlighted the effects of water pollution resulting from past mining activities, revealing distinctions between the main Abrud River stream and its tributaries, some of which exhibited extremely low species richness with few or no identified taxa. This contrasted sharply with the cleaner upstream waters of the Roșia Valley, where a notably rich diatom community (85 taxa) persisted, highlighting the severe localized impact of mining discharges on biodiversity.

The diatom Berkeleya transfretana is described as a new species from samples collected at Playa Punta Sauciño, an intertidal coastal area in Ceuta, North Africa. Its main features are the comparatively small size in relation to other Berkeleya species and the very fine and dense striae pattern (more than 40 striae per 10 µm). The new species is here described under light and scanning electron microscopy and compared to related taxa. The benthos of these rocky beaches are interesting spots of biodiversity still to be explored.