Microbial Biomass in Eutrophic Peatlands: Stock, Structure, and Activity

Oligotrophic peatlands traditionally have a high profile in microbiological research. Eutrophic peatlands are studied by residual principle and their research is generally focused on the active layer, acrotelm. The purpose of our study was to assess microbial biomass, its structure and activity in the full profiles of peatlands of various geneses. We investigated eutrophic peatlands of lacustrine, forest, and floodplain origins in Tver and Tomsk regions. Luminescent microscopy was used to analyze the microbial biomass. Microbial respiration was examined by gas chromatography. Microbial biomass stocks calculated for a three-meter layer of the studied peatlands varied from 7 to 13 t/ha. Eukaryotic biomass stocks reached 3-9 t/ha, and prokaryotic biomass stocks were about 3-4 t/ha. Eukaryotes predominated in the microbial biomass of the acrotelm, while prokaryotes predominated in the microbial biomass of the catotelm. Bacteria dominated in the structure of prokaryotic biomass all over the profiles of the studied peatlands. The fraction of actinomycetic mycelium did not exceed 15%. It was found that prokaryotic biomass depends on the botanical composition of peat in the eutrophic peatlands. This dependence becomes stronger from the woody peat to the herbaceous peat. The comparison of eutrophic peatlands of different geneses demonstrated their microbial specificity. Thus, the peatland of forest bogging had the maximum microbial pool among all peatlands. The peatland of lacustrine origin was characterized by the saturation of the acrotelm with microbial biomass. The peatland of floodplain origin was maximally enriched in bacterial biomass. In many layers of studied peatlands, the potential respiration level was 2-5 times higher than the actual one. Microbial respiration reached its maximum intensity in the peatland of floodplain origin.