Subaerial Microbial Mats and Their Effects on Soil and Rock

Abstract

Microbial mats (or biofilms) under permanent water cover contain 95-98% biologically stabilised water at ambient temperature , while biofilms in atmospheric environments can be regarded as the maximum biomass maintaining metabolic potential in the presence of the minimum amount of water. Rock or other subaerial biofilms are made up primarily of poikilotroph micro-organisms which thrive on the lowest water activity possible. Biofilms on and in rocks are the main factors in rock decay and the production of patinas, films, varnishes, crusts and stromatolites growing on and in rocks. A poikilotroph microflora is instrumental in maintaining life in truly extreme conditions and over considerable periods of time. The importance of the activity of the rock-dwelling biota and biofilms can be explained in terms of the fractal dimension of the reactive surface of sediment and rock with water and atmosphere , respectively. The weight of the living (mainly microbial) biomass of the planet is recalculated to be 10 2 1 g instead of 10 17 g, by including estimates of deep sedimentary and deep rock microbial biospheres. Poikilotroph biofilms under subaerial conditions are involved in both rock-destroying and rock-forming processes.