WIND TRANSPORT OF SAND SURFACES CRUSTED WITH PHOTOAUTOTROPHIC MICROORGANISMS

Wind tunnel experiments show that while surfaces inoculated with photo autotrophic organisms are stable in winds up to 19 m s(-1), only filam entous cyanobacteria, especially Nostoc commune, afford considerable p rotection 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 b e expected for untreated sediment. Surface disintegration encompasses a suite of complex, scale dependent processes which vary with the stru cture, thickness and strength of the crust. independent measurements o f crust strength based on flexure testing are in good agreement with w ind tunnel evaluation of crust stability. The accommodation of a relat ively large amount of deformation without rupture is an important prop erty of fibrous, photoautotrophic mats, perhaps outweighing considerat ion of their peak strength.