Endolithic lichens

Experimental studies of mineral weathering rates in the presence of oxalic acid demonstrate the importance of LPD. For example, in the presence of 1 mM oxalic acid, rates of silica elution from feldspar can increase up to 15-fold at circumneutral pH, while A1 elution rates can increase by two orders of magnitude (Barker et al, 1997). Similar results are reported for quartz and olivine (Grandstaff, 1986 Bennett et al, 1988), and indicate that oxalate leaching of aluminium, calcium, magnesium and other cations from primary silicate minerals can yield a silica-rich residue similar to that found in association with endolithic lichens (Johnston Vestal, 1993 Lee Parsons, 1999). 

Wessels, D. C. J. Schoeman, P. (1988). Mechanism and rate of weathering of Clarens sandstone by an endolithic lichen. South African Journal of Science, 84, 274-7. 

The lichen prefer rock surfaces that face north because they are warmed by solar radiation, as demonstrated by Miotke (1979a) in Taylor Valley. His results indicated that the temperature at a depth of 10 cm in marble and dolerite fluctuated daily and approached +10°C in the afternoon, provided that the sun was shining. Liquid water that forms by melting of snow can infiltrate the underlying rock where it supports the metabolic activity of the endolithic organisms (Friedmann 1978) and promotes chemical weathering (Miotke 1980). When the weathering rind flakes off, the endolithic lichen are exposed at the surface where they cannot survive. 

The endolithic lichen and algae of Antarctica are a remarkable adaptation of these plants to the harsh climatic conditions, especially in the winter when the sun does not shine and the temperature can drop to about -60°C (Heinrich 1976). 

These considerations warrant further study to determine exposure ages of rock surfaces in the ice-free valleys of southern Victoria Land by means of cosmogenic nuclides (Schafer et al. 1999 Summerfield et al. 1999) and to measure the abrasion rate of rocks in the ice-ffee valleys by natural processes (Miotke 1979a, b Malin 1984). The endolithic lichen and algae have continued to attract the attention of microbiologists of North America and Europe (Friedmann and Ocampo 1976 Friedmann 1977 Hirsch et al. 1988 Meyer et al. 1988 Palmer and Friedmann 1988 Ocampo-Friedmann et al. 1988 Bonani et al. 1988). 

Kushnir, E., a. Tietz, and M. Galun Oil Hyphae of Endolithic Lichens and their Fatty Acid Composition. Protoplasma 97, 47 (1978). 

S, 161°05 E,). The Linnaeus Terrace was protected because of the presence of endolithic algae and lichens in the Beacon Sandstone at that site (Friedmann etal. 1988). 

In spite of the harsh climate that characterizes the Transantarctic Mountains, bacteria, algae, lichens, and moss grow in sheltered places in the soil and some plants have adapted by becoming endolithic. Even mites and nematodes have been discovered in the ice-free valleys and algal mats thrive in the warm brines that occur at the bottom of the largest and deepest lakes. 

Arino X, Hernandez-Marine M, Saiz-Jimenez C (1997) Colonization of Roman tombs by calcifying cyanobacteria. Phycologia 36 366—373 Ascaso C, Wierzchos J, CasteUo R (1998) Study of the biogenic weathering of calcareous litharenite stones caused by lichen and endolithic microorganisms. Int Biodeter Biodegr 42 29-38... 

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