Evidence for microbial activity at the glass-alteration interface in oceanic basalts

• Published in: Earth and planetary science letters 1998-10, Vol.162 (1), p.165-176
• Main Authors: Torsvik, Terje, Furnes, Harald, Muehlenbachs, Karlis, Thorseth, Ingunn H, Tumyr, Ole
• Format: Article
• Language: English
• Subjects: alteration; basalts; Costa Rica Rift; geochemistry; Marine; microorganisms; volcanic glass
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/S0012-821X(98)00164-2

A detailed microbiological and geochemical study related to the alteration of basaltic glass of pillow lavas from the oceanic crust recovered from Hole 896A on the Costa Rica Rift (penetrating 290 m into the volcanic basement) has been carried out. A number of independent observations, pointing to the influence of microbes, may be summarized as follows: (1) Alteration textures are reminiscent of microbes in terms of form and shape. (2) Altered material contains appreciable amounts of C, N and K, and the N/C ratios are comparable to those of nitrogen-starved bacteria. (3) Samples stained with a dye (DAPI) that binds specifically to nucleic acids show the presence of DNA in the altered glass. Further, staining with fluorescent labeled oligonucleotide probes that hybridize specifically to 16S-ribosomal RNA of bacteria and archaea demonstrate their presence in the altered part of the glass. (4) Disseminated carbonate in the glassy margin of the majority of pillows shows δ 13C values, significantly lower than that of fresh basalt, also suggests biological activity. The majority of the samples have δ 18O values indicating temperatures of 20–100°C, which is in the range of mesophilic and thermophilic micro-organisms.