Diversity of Microbial and Metazoan Communities Associated with Salt and Biological Soil Crusts in Saharan Hypersaline Ecosystems

The Sahara Desert, the world’s largest hot desert, is among the most hyper-arid regions on Earth. Its northeastern area contains saline lake ecosystems, known as chotts, composed of two main microbial surface communities: salt crusts and biological soil crusts (biocrusts). These complex associations of soil particles, salts, microorganisms, and extracellular polymeric substances (EPS) host unique extremophile microbes, playing key roles in soil stabilization and fertility. This study investigated cross-domain biodiversity across a saline gradient in the hypersaline ecosystem of Chott Kralla, Algeria. Biocrust and salt crust samples were collected at four sites 3, 13, and 25 km from the chott center. Molecular analyses using 16S rRNA, ITS, and COX1 markers characterized bacterial, fungal, and metazoan communities, respectively. Biodiversity patterns showed significant differences in bacterial communities across sites, while fungal, protozoan, and metazoan biodiversity did not vary significantly. Bacteria were dominated by Bacillota, followed by Pseudomonadota. Ascomycota dominated fungal communities in salt crusts, whereas Basidiomycota were more abundant in biocrusts. Metazoan biodiversity in biocrusts were dominated by Arthropoda, while salt crusts also included Annelida and Nematoda. These findings show that salinity strongly shapes microbial biodiversity and provide valuable insights into extremophiles with potential biotechnological applications.