Wind transport of sand surfaces crusted with photoautotrophic microorganisms

Wind tunnel experiments show that while surfaces inoculated with photoautotrophic organisms are stable in winds up to 19 m s−1, only filamentous cyanobacteria, especially Nostoc commune, afford considerable protection against abrasion from windborne particles. Crusts formed by the polysaccharide secreting alga Chlamydomonas acidophila break down easily under impact, the entrainment of large, low density aggregates possibly contributing to higher transport rates than would otherwise be expected for untreated sediment. Surface disintegration encompasses a suite of complex, scale dependent processes which vary with the structure, thickness and strength of the crust. Independent measurements of crust strength based on flexure testing are in good agreement with wind tunnel evaluation of crust stability. The accommodation of a relatively large amount of deformation without rupture is an important property of fibrous, photoautotrophic mats, perhaps outweighing consideration of their peak strength.