The vertical microdistribution of cyanobacteria and green algae within desert crusts and the development of the algal crusts

Abstract

Substantial amounts of algal crusts were collected from five different desert experimental sites aged 42, 34, 17, 8 and 4 years, respectively, at Shapotou (China) and analyzed at a 0.1 mm microscale of depth. It was found that the vertical distribution of cyanobacteria and microalgae in the crusts was distinctly laminated into an inorganic-layer (ca.0.00-0.02 mm, with few algae), an algae-dense-layer (ca.0.02-1.0 mm) and an algae-sparselayer (ca.1.0-5.0 mm). It was interesting to note that in all crusts Scytonema javanicum Born et Flah (or Nostoc sp., cyanobacterium), Desmococcus olivaceus (Pers ex Ach., green alga) Laundon and Microcoleus vaginatus Gom. (cyanobacterium) dominated at the depth of 0.02-0.05, 0.05-0.1 and 0.1-1.0 mm, respectively, from the surface. Phormidium tenue Gom. (or Lyngbya cryptovaginatus Schk., cyanobacterium) and Navicula cryptocephala Kutz.(or Hantzschia amphioxys (Ehr.) Grun. and N. cryptocephala together, diatom) dominated at the depth of 1.0-3.0 and 3.5-4.0 mm, respectively, of the crusts from the 42 and 34 year old sites. It was apparent that in more developed crusts there were more green algae and the niches of Nostoc sp., Chlorella vulgaris Beij., M. vaginatus, N. cryptocephala and fungi were nearer to the surface. If lichens and mosses accounted for less than 41.5% of the crust surface, algal biovolume was bigger when the crust was older, but the opposite was true when the cryptogams other than algae covered more than 70%. In addition to detailed species composition and biovolume, analyses of soil physicochemical properties, micromorphologies and mineral components were also performed. It was found that the concentration of organic matter and nutrients, electric conductivity, silt, clay, secondary minerals were higher and there were more micro-beddings in the older crusts than the less developed ones. Possible mechanisms for the algal vertical microdistribtion at different stages and the impact of soil topography on crust development are discussed. It is concluded that biomethods (such as fine species distribution and biovolume) were more precise than mineralogical approaches in judging algal crust development and thus could be a better means to measure the potentiality of algal crusts in desert amelioration.Abbreviations: I.V. -Important Value; PLM -Polarizing Light Microscope; SEM -Scanning Electron Microscopy

Small-Scale Vertical Distribution of Algae and Structure of Lichen Soil Crusts

“…This indicates that GLSCs have a more obvious increase in the green algae biomass. An explanation for this result might be related to the physiochemical characteristics of different microenvironments [21]. The increase in photosynthetic organism biomass, especially the increase in green algae with high photosynthetic efficiency and large photosynthetic advantage during low water status [32,33], strongly improves primary productivity, thereby facilitating the development of the entire crust ecosystem.…”

“…Few studies have been performed on their inner structures, algae distribution. All BSCs [19][20][21], underwater microbial mats [22], rice field soils [23], and stromatolites [22] have similar vertical stratified properties caused by the effects of resources, such as light and water. Although the organisms can transfer up and down under some certain conditions [24,25], they have a relatively fixed distribution most of the time, which is an important strategy in their adaptations to the living environment.…”

“…Hu et al [21] classified the ASCs into three layers from up to bottom: an inorganic layer, an algae-dense layer, and an algae-sparse layer. They showed that the inorganic layer was formed by the extracellular polymers, which were secreted by the algae, adsorbing and intercepting sand grains and dusts [6].…”

Growth of soil algae and cyanobacteria on gold mine tailings material

“…Biological soil crusts (BSCs) consisting of bryophytes, lichens, algae and associated microorganisms are known to establish in extreme environments [9][10][11] such as mine tailings 12,13 and can contribute significantly to the stabilisation of soils through soil aggregate formation [14][15][16][17] . BSCs could therefore potentially provide protection against the erosive forces of wind and water on tailings material.…”

Diversity of Cyanobacteria in Biological Crusts on Arid Soils in the Eastern Region of India and their Molecular Phylogeny

“…Many cyanobacterial species have been reported from the arid regions of the world, e.g. Dead Sea valley and Negev desert, Israel 8,9 ; Colorado Plateau, USA 10,11 ; Tengger and Ningxia dry land, China 12 , and Chadormalu desert, Iran 13 . However, the occurrence of these organisms in the arid soils of India has not yet been analysed.…”