Peatland Stream Lipid Biogeochemistry Features in an Intermediate Fen Peatland, Ontario Canada

Changes in climate and land use pressures in the boreal region may influence peatland stream sediment organic carbon (C) dynamics. Fifteen to 50% of stream sediment organic C resides in recalcitrant pools, with the lipids accounting for up to 25% of the peatland C pool. Nevertheless, lipid mineralization within peatlands and their draining stream sediments is poorly understood. Potential esterase activity, which is known to be an important enzyme group in recalcitrant C decomposition, is presented as an indicator of lipid hydrolysis in three streams surrounding an intermediate fen peatland. Organic C concentration ranged from 5 to 250 g C kg −1 sediment during the sampling period, with the recalcitrant C pool accounting for 15 to 20%. Fourier Transform Infrared (FT-IR) spectra were typical of humic-like substances, such as aliphatic compounds (including lipids), phenolic and other aromatic structures, carboxyl groups, and polysaccharide structures. Esterase activity was positively correlated with organic C and total nitrogen (N) concentrations, and sediment pH. Esterase was most active in the presence of high organic C fractions and recalcitrant C, supporting the hypothesis that lipid hydrolysis in the peatland stream sediments may be an important and underestimated component of peatland C sequestration dynamics.