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Accueil du site → Doctorat → États-Unis → 1979 → Endolithic algae of semi-desert sandstones : systematic, biogeographic and ecophysiologic investigations

Arizona State University (1979)

Endolithic algae of semi-desert sandstones : systematic, biogeographic and ecophysiologic investigations

Bell, R.A.

Titre : Endolithic algae of semi-desert sandstones : systematic, biogeographic and ecophysiologic investigations

Auteur : Bell, R.A.

Université de soutenance : Arizona State University

Grade : Doctor of Philosophy (PhD) 1979

Résumé
Investigations were conducted into the ecology of an unusual algal community in northern Arizona. These microorganisms are called endolithic algae because they occur beneath the surface of rocks. Eighteen taxa, including representatives of both eukaryotic and prokaryotic genera, were isolated from below the surface of eight sandstones in four semi-desert and cold temperate biomes of the Colorado Plateau. As the macroclimate of the area changes from cold temperature desert scrub to cold temperate forest the taxonomic composition of the endolithic algal communities shifts from domination by coccoid blue-green algae to domination by coccoid and sarcinoid green algae. The algal communities varied in generic composition, chlorophyll a content, and in their location within the different sandstones. Investigations into the microclimate of the endolithic algal zone in two adjacent but differently-colored sections (white and brown) of Coconino sandstone have demonstrated differences between the environment above the rock surface and that just beneath the surface. In seasonal samples of the Coconino sandstone, chlorophyll a content ranged from 50 to 100 mg x m/sup -2/ in the white rock and 8 to 45 mg x m/sup -2/ in the brown rock. Primary production (as measured by /sup 14/CO/sub 2/ incorporation) displayed marked seasonal patterns that appear to be correlated to the environmental conditions within the rocks as opposed to those outside the rocks. The widespread distribution of certain algae in the endolithic habitats of the Colorado Plateau and their presence in rocks at quite distant locations suggests that the endolithic habitat may be utilized by algae whenever it provides more favorable conditions than the surrounding surfaces

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