Silicified Microbes in a Geyser Mound: The Enigma of Low-Temperature Cyanobacteria in a High-Temperature Setting

摘要

A geyser mound, which has formed around the vent of an abandoned well-bore in the Tokaanu geothermal area (North Island, New Zealand) over the last 50 years, is formed primarily of white opal-A along with lesser amounts of black opal-A, reticulate, amorphous or poorly crystalline clay, halite, and scattered detrital quartz grains. Despite the boiling water ejected from the vent, at least 19 taxa of silicified microbes are present in the geyserite. Calothrix, Phormidium, and Synechococcus dominate. Other microbes, including local concentrations of diatoms, are widely scattered. The dominance of cyanobacteria is enigmatic given that these microbes typically are found in cooler water environments (< 60°C) on the medial to distal parts of geyser and hot-spring discharge aprons.