Biological soil crusts consisting of algae, cyanobacteria, lichens, fungi, bacteria, and mosses are common in habitats where water and nutrients are limited and vascular plant cover is discontinuous. Crusts alter soil factors including water availability, nutrient content, and erosion susceptibility, and thus are likely to both directly and indirectly affect plants. To establish this link, we must first understand the crust landscape. We described the composition, abundance, and distribution of microalgae in crusts from a periodically burned, xeric Florida shrubland, with the goal of understanding the underlying variability they create for vascular plants, as well as the scale of that variability. This is the first comprehensive study of crusts in the southeastern United States, where the climate is mesic but sandy soils create xeric conditions. We found that crusts were both temporally and spatially heterogeneous in depth and species composition. For example, cyanobacteria and algae increased in abundance 10-15 years after fire and away from dominant shrubs. Chlorophyll a levels recovered rapidly from small-scale disturbance relative to intact crusts, but these disturbances added to crust patchiness. Plants less than 1 m apart can experience different crust environments that may alter plant fitness, plant interactions, and plant community composition.
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"A potentially significant nutrient source is nitrogen-fixing cyanobacteria found in soil crusts in rosemary scrubs. Density of cyanobacteria increases from zero immediately post-fire to a peak 8-15 years post-fire and declines thereafter (Hawkes and Flechtner 2002). "
". However, our understanding of the community structure remains very limited, not least because the majority of studies investigating phototroph diversity in BSCs have used culture dependent methods which are prone to bias , , , , , or molecular methods that target 16S rRNA of bacteria, which ignore the diversity of eukaryotic phototrophs , , , , , . Molecular microbial community analysis of bacterial diversity at the soil surface has shown a dominance by cyanobacteria , , , , for example, Abed et al.  found that 77–81% of clones from BSCs of Oman had close homology to cyanobacteria. "
[Show abstract][Hide abstract] ABSTRACT: The upper few millimeters of soil harbour photosynthetic microbial communities that are structurally distinct from those of underlying bulk soil due to the presence of light. Previous studies in arid zones have demonstrated functional importance of these communities in reducing soil erosion, and enhancing carbon and nitrogen fixation. Despite being widely distributed, comparative understanding of the biodiversity of the soil surface and underlying soil is lacking, particularly in temperate zones. We investigated the establishment of soil surface communities on pasture soil in microcosms exposed to light or dark conditions, focusing on changes in phototroph, bacterial and fungal communities at the soil surface (0-3 mm) and bulk soil (3-12 mm) using ribosomal marker gene analyses. Microbial community structure changed with time and structurally similar phototrophic communities were found at the soil surface and in bulk soil in the light exposed microcosms suggesting that light can influence phototroph community structure even in the underlying bulk soil. 454 pyrosequencing showed a significant selection for diazotrophic cyanobacteria such as Nostoc punctiforme and Anabaena spp., in addition to the green alga Scenedesmus obliquus. The soil surface also harboured distinct heterotrophic bacterial and fungal communities in the presence of light, in particular, the selection for the phylum Firmicutes. However, these light driven changes in bacterial community structure did not extend to the underlying soil suggesting a discrete zone of influence, analogous to the rhizosphere.
"However, aggregate stabilization is known to be primarily due to adsorption and binding of particulates by polysaccharides or microbial origin together with environment by living microbial filaments (Burns and Davies, 1986). When inoculated on to irrigated sandy soils through center pivot sprinklers, mass-cultured Chlamydomonas and Asterococcus species (Chlorophyceae) have been shown to significantly improve the integrity of soil aggregates in the face of disruption by wind and slaking in water (Hawkes and Flechlner, 2002). "
[Show abstract][Hide abstract] ABSTRACT: Algae are a large and diverse group of microorganisms that can carry out photosynthesis since they capture energy from sunlight. Algae play an important role in agriculture where they are used as biofertilizer and soil stabilizers. Algae, particularly the seaweeds, are used as fertilizers, resulting in less nitrogen and phosphorous runoff than the one from the use of livestock manure. This in turn, increases the quality of water flowing into rivers and oceans. These organisms are cultivated around the world and used as human food supplements. They can produce a clean and carbon-neutral food also and can be grown on abandoned lands and arid desert lands with minimal demands for fresh water. Seaweeds are an important source of iodine. Iodine levels in milk depend on what the cow producing the milk has been fed with. Feeding milk cattle with seaweeds can increase the quantity of iodine in milk, according to Fuzhou Wonderful Biological Technology. Egg-laying rate in hen is also increased by algae feed additives. In this article, we discussed the most important aspects of algae and its agricultural uses to those who work in this area.