title: Three-dimensional structure and cyanobacterial activity within a desert biological soil crust.
abstract: Desert biological soil crusts (BSCs) are formed by adhesion of soil particles to polysaccharides excreted by filamentous cyanobacteria, the pioneers and main producers in this habitat. Biological soil crust destruction is a central factor leading to land degradation and desertification. We study the effect of BSC structure on cyanobacterial activity. Micro-scale structural analysis using X-ray microtomography revealed a vesiculated layer 1.5-2.5 mm beneath the surface in close proximity to the cyanobacterial location. Light profiles showed attenuation with depth of 1%-5% of surface light within 1 mm but also revealed the presence of 'light pockets', coinciding with the vesiculated layer, where the irradiance was 10-fold higher than adjacent crust parts at the same depth. Maximal photosynthetic activity, examined by O2 concentration profiles, was observed 1 mm beneath the surface and another peak in association with the 'light pockets'. Thus, photosynthetic activity may not be visible to currently used remote sensing techniques, suggesting that BSCs' contribution to terrestrial productivity is underestimated. Exposure to irradiance higher than 10% full sunlight diminished chlorophyll fluorescence, whereas O2 evolution and CO2 uptake rose, indicating that fluorescence did not reflect cyanobacterial photosynthetic activity. Our data also indicate that although resistant to high illumination, the BSC-inhabiting cyanobacteria function as 'low-light adapted' organisms.
authors: Department of Plant and Environmental Sciences, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
authors: Hagai
authors: H
authors: Raanan
authors: Institute of Soil Science and Soil Conservation, Justus Liebig University Giessen, 35392, Giessen, Germany.
authors: Vincent J M N L
authors: VJ
authors: Felde
authors: Deparment of Soil Science, Faculty of Ecological Agriculture, University of Kassel, 37213, Witzenhausen, Germany.
authors: Stephan
authors: S
authors: Peth
authors: Institute of Soil Science and Soil Conservation, Justus Liebig University Giessen, 35392, Giessen, Germany.
authors: Sylvie
authors: S
authors: Drahorad
authors: The Max Planck Institute for Marine Microbiology, Celsius Str. 1, 28359, Bremen, Germany.
authors: Danny
authors: D
authors: Ionescu
authors: Department of Plant and Environmental Sciences, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
authors: Gil
authors: G
authors: Eshkol
authors: Department of Plant and Environmental Sciences, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
authors: Haim
authors: H
authors: Treves
authors: Institute of Soil Science and Soil Conservation, Justus Liebig University Giessen, 35392, Giessen, Germany.
authors: Peter
authors: P
authors: Felix-Henningsen
authors: Department of Plant and Environmental Sciences, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.|Arid Ecosystems Research Center, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
authors: Simon M
authors: SM
authors: Berkowicz
authors: Department of Plant and Environmental Sciences, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
authors: Nir
authors: N
authors: Keren
authors: Institute of Plant Nutrition and Soil Science, Christian Albrechts University of Kiel, 24118, Kiel, Germany.
authors: Rainer
authors: R
authors: Horn
authors: Institut für Biowissenschaften, Universität Rostock, D-18059, Rostock, Germany.
authors: Martin
authors: M
authors: Hagemann
authors: Department of Plant and Environmental Sciences, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.|Arid Ecosystems Research Center, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
authors: Aaron
authors: A
authors: Kaplan
mesh_terms: D000458:Cyanobacteria / Q000378:metabolism*; D003889:Desert Climate; D017753:Ecosystem; D008027:Light; D010788:Photosynthesis / Q000502:physiology*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013472:Sunlight
chemical_list: D012987:Soil