Ecophysiological groups of bacteria from cave sediments as potential indicators of paleoclimate

Abstract

Six bacterial ecophysiological groups from Pleistocene sediment samples collected from two Romanian caves were identified and evaluated for their potential contribution to the interpretation of paleoclimate. Denitrifiers and nitrite oxidizers were present in the culture plates of all samples, the ammonia oxidizers were absent, and the iron-reducers were confirmed solely in the deepest sample of one of the caves. The aerobic mesophilic heterotrophs were much less abundant in sediments with high clay content, while the ammonifiers were positively correlated to the organic matter content measured in the sediments. In both caves optically stimulated luminescence (OSL) dating, geochemical, sedimentological and grain size analyses were performed and results were correlated to the different groups of bacteria. Results point to the importance of surface conditions during the time of sediment inflow inside the caves, although the bacterial communities have continuously been shaped since deposition. The present study aims to connect features of the paleoclimate with preliminary data on bacteria from old cave sediments.