The Role of Lichens and Associated Fungi in the Chemical Weathering of Rock

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Abstract
Using iron chelation as a measure of biochemical weathering, and employing a spectrometric technique to measure the chelation, the authors studied rock lichens and fungi isolated from the same rock surfaces. The isolated symbionts (mycobionts and phycobionts) of four species of lichens showed no chelation ability after growth on synthetic media. Squamatic acid extracted from the lichen Cladonia squamosa chelated iron in solution. Many of the fungi isolated from the same sandstone, particularly species of Penicillium and Cephalosporium, were able to chelate iron in solution from twice to as much as six times that of the squamatic acid, as was true for citrate. Lichens that produce lichen acids and rock-surface fungi may be significant biochemical weathering agents in nature.