The NSS Bulletin - ISSN 1090-6924
Volume 48 Number 1: 26-30 - June 1986

A publication of the National Speleological Society

Bacterial Deposition of Iron and Manganese Oxides in North American Caves
Stewart B. Peck


Deposits of hydrated iron and manganese oxides are common as stalactites, wall crusts, and as thick layers in sediment in caves at Dubuque, Iowa, and are known to occur elsewhere. Some of the deposits are composed of abundant, microscopic, curved, rod-like structures produced by the iron and manganese precipitatiing sheath bacteria Leptothrix and Crenothrix. Bacteriological enrichment techniques cultured the iron precipitating bacteria Leptothrix sp. and Gallionella sp. in abundance from active iron oxides stalacties, mud and water from caves near Dubuque. The metal oxide deposits are concluded to be at least partly the result of organic (bacterial) rather than inorganic precipitation reactions. Observations from many caves in the eastern United States with concentrations of iron-precipitatiing bacteria at seeps, but without associated animals, suggest that these bacteria do not form an important base of a food chain for cave-inhabiting invertebrates.

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