Diversity of primary vegetation species of lake shore impacts largely carbon emissions in thermokarst lakes on the Qinghai-Tibet plateau.

Terrestrial organic matter from surrounding primary vegetation is critical for carbon cycling in thermokarst lakes. However, the characteristics and contribution of this vegetation in shaping microbial community and affecting carbon emissions in thermokarst lakes remain poorly understood. This study quantifies the influence of lakeshore primary vegetation characteristics on microbial community and carbon emissions across lakes with different vegetation types on the Qinghai-Tibet Plateau (QTP).

Dissolved organic matter quality in thermokarst lake water and sediments across a permafrost gradient, Western Siberia.

Thermokarst (thaw) lakes of permafrost peatlands are among the most important sentinels of climate change and sizable contributors of greenhouse gas emissions (GHG) in high latitudes. These lakes are humic, often acidic and exhibit fast growing/drainage depending on the local environmental and permafrost thaw. In contrast to good knowledge of the thermokarst lake water hydrochemistry and GHG fluxes, the sediments pore waters remain virtually unknown, despite the fact that these are hot spots of biogeochemical processes including GHG generation.

Size matters: Aerobic methane oxidation in sediments of shallow thermokarst lakes.

Shallow thermokarst lakes are important sources of greenhouse gases (GHGs) such as methane (CH ) and carbon dioxide (CO ) resulting from continuous permafrost thawing due to global warming. Concentrations of GHGs dissolved in water typically increase with decreasing lake size due to coastal abrasion and organic matter delivery. We hypothesized that (i) CH oxidation depends on the natural oxygenation gradient in the lake water and sediments and increases with lake size because of stronger wind-induced water mixing; (ii) CO production increases with decreasing lake size, following the dissolved organic matter gradient; and (iii) both processes are more intensive in the upper than deeper sediments due to the in situ gradients of oxygen (O ) and bioavailable carbon.

Fractionation of organic C, nutrients, metals and bacteria in peat porewater and ice after freezing and thawing.

To better understand freezing - thawing cycles operating in peat soils of permafrost landscapes, we experimentally modelled bi-directional freezing and thawing of peat collected from a discontinuous permafrost zone in western Siberia. We measured translocation of microorganisms and changes in porewater chemistry (pH, UV absorbance, dissolved organic carbon (DOC), and major and trace element concentrations) after thawing and two-way freezing of the three sections of 90-cm-long peat core. We demonstrate that bi-directional freezing and thawing of a peat core is capable of strongly modifying the vertical pattern of bacteria, DOC, nutrients, and trace element concentrations.