Simultaneous measurements of dark carbon fixation and bacterial production in lake sediment

Abstract

Carbon fixation by chemoautotrophic bacteria represents an autochthonous source of organic matter, and may be of particular importance close to redox boundaries. Despite the known sediment chemoautotrophic potential, the quantitative role and the importance of dark carbon fixation (DCF) in lake sediments are still unknown. We provide here a method to measure DCF and bacterial production simultaneously in stratified sediment cores, using 14C labeled dissolved inorganic carbon (DI14C) and 3H‐leucine incorporation. Beyond the total activity, the method allows measurements of the processes over depth, as a profile into the sediment. DCF increased with depth in our profiles, indicating a predominance of anoxic processes. In addition, the method can yield information about the extent DI14C was allocated into the bacterial proteins (DCFp). Slurry and stratified core incubations were compared and yielded similar results for total DCF activity.