Biological Soil Crusts (BSC) constitutes a pivotal ecological element among different ecosystems of the world. The effects of these BSC at the micro-site scale have been related to the further development of diverse plant species that, otherwise, might be strongly limited by the harsh abiotic conditions of such ecosystems. We describe for the first time, the composition of the BSC of the Maritime Antarctica and we also evaluated their effect on the fitness of Colobanthus quitensis, one of the two native Antarctic vascular plants. In this context, we characterize by amplicon fingerprinting the microbial composition of the soil crust community and the effect of these BSC on various soil properties and performance of C. quitensis. For this, we compared the photochemical performance, foliar nutrient, biomass, and reproductive investment between individuals growing with and without the influence of BSC. Our results revealed a high diversity of prokaryotes present in these soil communities. Furthermore, in soils where BSC were present, a significant increase in their water retention, nutrient levels and enzymatic activities was observed compared to control soils. Regarding the effect of BSC on C. quitensis, we found that the ecophysiological performance was significantly higher on plants that grow influenced by BSC. We conclude that the presence of BSC in Antarctic soils is a key element for various biochemical processes that may speed soil development and could exert a direct impact on the development of the accompanying flora, acting this way, as ecosystem engineers for the terrestrial Antarctic ecosystem.