Fig. 4.

Depth profiles of prokaryotic cell numbers, prokaryotic activity and geochemical data for Flank site U1316. a. Prokaryotic cell numbers determined by AODC and qPCR of 16S rRNA genes, and bacterial CARD-FISH. The solid line shows Parkes and colleagues (2000) general model for prokaryotic cell distributions in deep marine sediments, and dotted lines represent 95% prediction limits. b. DNA copy numbers of the 16S rRNA genes determined by qPCR of Bacteria, Archaea and Geobacteraceae, and dsrA genes. c and d. Pore water concentrations of sulfate, alkalinity, dissolved Fe and acetate, and in situ methane. e. Potential rates of methanogenesis from H₂ : CO₂ and acetate. f. Rates of thymidine incorporation and acetate oxidation to CO₂. g. Culturable cells from MPN enrichments; heterotrophic, metal-reducing, sulfate-reducing and acetogenic bacteria.