%0 Journal Article %A Christian Wurzbacher %A Andrea Fuchs %A Katrin Attermeyer %A Katharina Frindte %A Hans-Peter Grossart %A Michael Hupfer %A Peter Casper %A Michael T. Monaghan %T Vertical organization of freshwater sediment microbial communities: implications for microbial activities and burial processes %D 2016 %R 10.1101/057117 %J bioRxiv %P 057117 %X Microbial activity in lake sediments is responsible for the cycling of organic matter that continuously sinks from the water column. Accumulation and burial of carbon therefore depends on the indigenous sediment organism. This interaction of burial processes and microbial activity in the sediment, that should lead to a vertical succession of organism is largely unexplored in aquatic sediments. Our aim was to provide a basic model for the vertical community structure in sediments. We performed a full biogeochemical and microbial community analysis of 4 replicate sediment cores in a deep, clear lake. Each core was 30 cm, spanning ca. 170 yr of accumulation according to 137Cs dating, and sectioned into layers 1-4 cm thick. DNA-metabarcoding of archaea, bacteria, and eukaryotes delineated three clusters corresponding to distinct communities at <5 cm, 5-14 cm, and 14-30 cm. The two upper clusters (covering ca. 70 years) were dominated by taxonomic replacement, and the replacement component was correlated with parameters indicative of microbial activity (e.g., CO2, CH4, protein production). We term these two clusters the ‘’replacement horizon”. The lower cluster was characterized by the richness component that was correlated with conservative, often historical parameters (e.g., elemental C, N, P). We term the lower horizon the “depauperate horizon”, characterized by taxonomic impoverishment and a dominance of archaea. Our study uncovered a highly structured microbial community in these unexplored freshwater sediments. Based on biogeochemical and microbial characteristics, we here propose a general model of freshwater sediment structure and function. %U https://www.biorxiv.org/content/biorxiv/early/2016/06/06/057117.full.pdf