| Summary: | Although an extensive professional literature exists on biological soil crusts (BSCs), especially on the species composition of hetero- and autotrophs forming the micro-biological comunity, micromorphological information on BSCs is extremely scarce. In our study, we focused on microstructure of the BSCs from the James Ross Island (Antarctica). We combined the approach of digital microscopy to study surface roughness of the BSCs with taxonomy of BSC-forming autotrophs and chlorophyll fluorescence study focused on the photosynthetic functioning of BSCs when exposed to controlled UV-B stress. Microprofiling of BSCs resulted in the finding that the examined BSCs might be classified as fine-grained surface with roughness characteristics: Ra (37.9 μm) and Rz (136.9 μm). The BSCs were rich in microautotrophs, both algae and cyanobacteria, however, Microcoleus sp. was found dominating species. It formed multifilament ropes on and inside the BSCs. Under UV-B stress, Microcoleus- and Nostoc-dominated BSC parts showed similar sensitivity and acclimatory response so long-term UV-B treatment, however, Microcoleus seemed to be slightly more sensitive to UV-B. Microcoleus-dominated parts of BSCs showed less pronounced acclimation to UV-B treatment than Nostoc-dominated parts. It was reflected in lower values of maximum (FV/FM) and effective (FPSII) quantum yields recorded after 6 d exposition.
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