Molecular Evidence for Bacterial Mediation of Calcite Formation in Cold High-Altitude Caves

Abstract

Three samples of moonmilk from high-altitude caves in northeast Italy were analysed for their lipid biomarker content, providing the first organic geochemical investigation into the relationship between cave bacterial communities and calcitic speleothems. The results demonstrate a positive association between the moonmilk deposits analysed and bacterial input, which we propose relates to bio-mediation of calcite nucleation processes. Comparison of the analysed moonmilk and a stalagmite from a geographically and climatically related cave suggest that this association is at least partially driven by the characteristics of the soil and overlying vegetation, thus demonstrating the potential use of moonmilk in palaeoenvironmental research.

Keywords:

• moonmilk
• bacteria
• speleothems
• fatty acids
• n-alkanols
• calcite morphology
• crystal nucleation

This work was supported by NERC studentship NER/S/A/2003/ 11297 awarded to AJB. GC-MS support was provided by Paul Donohoe of Newcastle University. S. Frisia was supported by the project OLOAMBIENT funded by the Provincia Autonoma di Trento, Fondo Unico per la Ricerca.