Greenhouse gas emissions and organic carbon content in freshwater ponds, lakes, and rivers in the Northeastern Siberian tundra

Abstract

Although permafrost soils are one of the most important carbon reservoir system on earth, permafrost carbon is rarely integrated in analyses of future atmospheric carbon concentrations due to the complexity of different water bodies. Water bodies cover a major part of Arctic permafrost regions and have an important role in the permafrost carbon cycle. The amount and type of carbon concentrations in permafrost water bodies can have a large impact on the release of future atmospheric greenhouse gases. In order to contribute to a better understanding in permafrost freshwater carbon concentrations, over 100 water and gas samples were analysed on POC, DOC, CH4, and CO2 for lakes, ponds, and streams in the Kytalyk nature reserve (Northeastern Siberian tundra). Carbon content of the different water bodies were compared to each other, and to other measured parameters such as salinity, pH, and surface area. Also stable isotope measurements (δ18O and δ2H) were analysed in order to obtain a local evaporation line. Results of this research show not only a higher carbon content, as well as a higher ratio of greenhouse gases (CH4 and CO2) in respect to other carbon forms for ponds compared to lakes and streams. The CH4 concentration in all different water bodies seems equally or even more important as a greenhouse gas compared to CO2 concentrations. The amount of DOC is higher compared to the POC concentrations for all of the measured water bodies. A clear correlation was found between the surface area and pH of the freshwater system and the total carbon content of the pond systems. Stable isotope measurements suggest that ponds are primarily affected by summer precipitation and evapotranspiration, whereas lakes are mainly influenced by thawed ice from ice wedges in the soil.