Bacteria-Induced Carbonate Degradation: A Taphonomic Case Study of Cibicides lobatulus from a High-Boreal Carbonate Setting

The process of bacterial degradation of skeletal-binding organic matter forces selective carbonate dissolution in aerobic and turbulent coarse-grained environments. This is demonstrated in a Scanning Electron Microscope study on the benthic foraminifer Cibicides lobatulus from a coastal platform in northern Norway. High CO (sub 2) partial pressures are created by rod-shaped bacteria colonies under the protective extracellular polymer surface (EPS) film. The impact of degradative bacteria on biogenic carbonates is strongly controlled by a) the microstructural composition of the infested particles, and b) the distribution and supply of organic compounds on and within the skeletal construction. Both factors have strong influences on variations in rates of decay, biasing fossil preservation. In aerobic systems, carbonate dissolution may be regarded as a metabolic by-product through bacterial-induced decomposition of skeletal-binding organic matter. This study supports the increasing amount of evidence pointing to carbonate dissolution and maceration phenomena from shelf environments, especially from cold sea environments, and stresses microbial input in early diagenesis.