TY - JOUR A1 - Jung, Patrick A1 - Lakatos, Michael A1 - Brand, Rebekah A1 - Briegel-Williams, Laura A1 - Werner, Lina A1 - Jost, Emily A1 - Lentendu, Guillaume A1 - Singer, David A1 - Athavale, Rujuta A1 - Nürnberg, Dennis J. A1 - Alfaro, Fernando D. A1 - Büdel, Burkhard T1 - The symbiotic alga Trebouxia fuels a coherent soil ecosystem on the landscape scale in the Atacama Desert N2 - Biocrusts represent associations of lichens, green algae, cyanobacteria, fungi and other microorganisms, colonizing soils in varying proportions of principally arid biomes. The so‑called grit crust represents a recently discovered type of biocrust situated in the Coastal Range of the Atacama Desert (Chile) made of microorganisms growing on and in granitoid pebbles, resulting in a checkerboard pattern visible to the naked eye on the landscape scale. This specific microbiome fulfills a broad range of ecosystem services, all probably driven by fog and dew‑induced photosyn‑ thetic activity of mainly micro‑lichens. To understand its biodiversity and impact, we applied a polyphasic approach on the phototrophic microbiome of this biocrust, combining isolation and characterization of the lichen photobionts, multi‑gene phylogeny of the photobionts and mycobionts based on a direct sequencing and microphotography approach, metabarcoding and determination of chlorophylla+b contents. Metabarcoding showed that yet unde‑ scribed lichens within the Caliciaceae dominated the biocrust together with Trebouxia as the most abundant eukary‑ ote in all plots. Together with high mean chlorophylla+b contents exceeding 410 mg m−2 , this distinguished the sym‑ biotic algae Trebouxia as the main driver of the grit crust ecosystem. The trebouxioid photobionts could be assigned to the I (T. impressa/gelatinosa) and A (T. arboricola) clades and represented several lineages containing five potential species candidates, which were identified based on the unique phylogenetic position, morphological features, and developmental cycles of the corresponding isolates. These results designate the grit crust as the only known coherent soil layer with significant landscape covering impact of at least 440 km 2 , predominantly ruled by a single symbiotic algal genus. KW - Lichens KW - Mycobionts KW - Photobionts KW - Caliciaceae KW - Green algae Y1 - 2024 U6 - https://doi.org/10.1186/s40793-024-00601-5 VL - 2024 PB - BioMed Central CY - London ER -