Physical and Chemical Deterioration of Silicate and Carbonate Rocks by Meristematic Microcolonial Fungi and Endolithic Lichens (Chaetothyriomycetidae)

Abstract

Physicochemical deterioration processes driven by lithobiontic microcolonial fungi (MCF) and endolithic lichens (EL) are still mostly unresolved. Here, the millimetric penetration of MCF strains within silicate and carbonate lithotypes was quantified. The influence of petrographic features in determining hyphal passageways satisfies a model of physical penetration during the early stages of colonization, already described for EL. The MCF and EL secretion of iron-chelating metabolites accounts for iron mobilization in desert-varnish formation, often putatively related to fungal colonization. Increased dissolution of limestone by the model iron chelator desferrioxamine indicates the possible involvement of these MCF and EL secretes in pitting carbonates.

Keywords:

• desferrioxamine
• hyphal penetration
• MCF
• siderophore
• varnish

ACKNOWLEDGMENTS

Part of this research was financially supported by the CRT Bank—Alfieri Project and by MIUR (PRIN funds: project “Dissolution of carbonatic rocks by endolithic lichens: mechanisms, rates and impact on the CO₂ global balance”).

The investigations on chemical and physical deterioration were conducted by the first and the second author, respectively.

Notes

*sensu De Leo and Urzì (2003) and Wiktor et al. (2009).

^aBt, biotite; Cal, calcite; Dol, dolomite; Ep, epidote; Fe-ox, iron-oxyhydroxides; Kfs, K-feldspar; Pl, plagioclase; Qtz, quartz (Kretz 1973).

^bHypidiomorphic: a texture that is a mix of euhedral (bounded by characteristic crystal-face forms), subhedral (partly euhedral), and anhedral (not bounded by any characteristic crystal face) grains.

^cStylolites: non-structural fractures developed along pressure solution surfaces, appearing as jagged disconinuities, often marked with insoluble clays, oxides and/or carbonates.