Uncovering biological soil crusts: Carbon content and structure of intact Arctic, Antarctic and alpine biological soil crusts

Abstract

Abstract. Arctic, Antarctic and alpine biological soil crusts (BSCs) are formed by adhesion of soil particles to exopolysaccharides (EPS), excreted by cyanobacterial and green algal communities, the pioneers and main producers in these habitats. These BSCs provide and influence many ecosystem services such as soil erodibility, soil formation and Nitrogen-(N) as well as carbon-(C) cycles. In cold environments degradation rates are low and BSCs increase continuously soil organic C, whereby these soils are considered as CO2 sinks. This work provides a novel, non-destructive and highly comparable method 15 to investigate intact BSCs with a focus on cyanobacteria and green algae and their contribution to soil organic C. A new terminology arose, based on confocal laser scanning microscopy (CLSM) 2D biomaps, dividing BSCs into a photosynthetic active layer (PAL), made of active photoautotrophic organisms and a photosynthetic inactive layer (PIL), harbouring remnants of cyanobacteria and green algae glued together by their remaining EPS. By the application of CLSM image analysis (CLSM-IA) to 3D biomaps, C coming from photosynthetic active organisms could be visualized as depth profiles with C peaks at 0.5 20 to 2 mm depth. Additionally, the CO2 sink character of these cold soil habitats dominated by BSCs could be highlighted, demonstrating that the first cm³ of soil is made of between 7 and 17 % total organic carbon, identified by loss on ignition.

Strong in combination: Polyphasic approach enhances arguments for cold‐assigned cyanobacterial endemism

“…On the other hand, soil properties such as pH, organic carbon, nitrogen, and phosphorous contents are very similar at Antarctica and the Arctic sites (Mann, Sletten, & Ugolini, ; Otero, Fernández, de Pablo Hernandez, Nizoli, & Quesada, ). Confocal laser scanning microscopy (CLSM) images of the BSCs from Geopol showed that these factors lead to a thin photosynthetic active layer (PAL; Jung et al., ). Differences between BSC functional group compositions of Geopol and Ny‐Ålesund were shown by Williams, Borchhardt, et al.…”

“…Hochtor harboring the most diverse cyanobacteria dominated BSC supports previous ideas. An extremely thick PAL structure was visualized by CLSM connected to high diversity for Hochtor and the opposite for Livingston Island (Jung et al., ). Besides water availability the light regime could also be a responsible factor, because all four sites share similar daylight times with photosynthetic active radiation (PAR) exceeding 1200 μmol m −2 s −1 (Barták, Váczi, & Hájek, ; Colesie, Green, Raggio, & Büdel, ; Xiong & Day, ), but with the strongest fluctuations at Hochtor (Büdel et al., ).…”

“…A brief description of the sampling sites is summarized in Table , and more information is given in Jung et al. ().…”

“…Ten samples per site were randomly selected from areas where BSC dominated (including bryophytes, lichens, cyanobacteria, and green algae) as described in Jung et al. ().…”

“…Currently, terrestrial aspects of cold ecosystems with high BSC coverage found at Hochtor (European Alps), Geopol, Ny‐Ålesund (both Arctic, Svalbard), and Livingston Island (Antarctica) have been addressed (Jung, Briegel‐Williams, Simon, Thyssen, & Büdel, ; Rippin et al., ; Williams, Borchhardt, et al., ), but the cyanobacterial community composition received little attention. In Svalbard high bacterial abundance was found in vegetated soils, this was strongly related to the availability of organic matter, inorganic nutrients, and moisture supply (Kaštovská, Elster, Stibal, & Šantrůčková, ; Pessi, Lara, et al.…”