EGU24-20301, updated on 11 Mar 2024
https://doi.org/10.5194/egusphere-egu24-20301
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Browning and mining increase the nitrous oxide production in sediments of large boreal lakes during winter

Carlos Palacin-Lizarbe1, Stefan Bertilsson2, Henri J. Siljanen1, Moritz Buck2, Lukas Kolh1, Dhiraj Paul1, Marion Maréchal1, Hannu Nykänen1, Tong Liu2, Mikko Kiljunen3, Sanni L. Aalto4, Antti J. Rissanen5, Christina Biasi1, Anssi Vainikka6, and Jukka Pumpanen1
Carlos Palacin-Lizarbe et al.
  • 1Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio Campus, P.O. Box 1627, FI-79211 Kuopio, Finland
  • 2Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
  • 3Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, 40014 Jyväskylä, Finland
  • 4DTU Aqua, Section for Aquaculture, The North Sea Research Centre, Technical University of Denmark, P.O. Box 101, 9850 Hirtshals, Denmark
  • 5Faculty of Engineering and Natural Sciences, Tampere University, Korkeakoulunkatu 6, 33720 Tampere, Finland
  • 6Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu Campus, P.O. Box 111, 80101 Joensuu, Finland

There is limited knowledge on the N (nitrogen) cycling in winter, on the role of organic matter quality on N cycling, and on the microbes involved.

We studied Lake Viinijärvi and Lake Höytiäinen, large boreal lakes in Finland, each lake with clear-water and brown-water sides. Viinijärvi has an additional side affected by mining activities in the catchment showing higher nitrate and sulphate levels. During winter of 2021 we sampled 5 sites at the beginning and at the end of the ice-covered period. Using the Isotope Pairing Technique we incubated sediment cores with 15NO3- and quantified the products of 1) complete denitrification (N2), 2) truncated denitrification (nitrous oxide, N2O), and 3) dissimilatory nitrate reduction to ammonium (DNRA, NH4+) to infer the process rates. We characterized the DOM using FT-ICR MS. We explore the genetic potential (DNA) of the sediment microbiome by using several sequencing techniques.

During winter the sediment-water interface is an active compartment. The top sediment microbiome has heterotrophic bacteria with flexible metabolism, breaking-down OM during winter despite most of the DOM is recalcitrant. Impacts of browning and mining with major differences between sites. The genetic potential of the sediment microbiome indicates more DNRA and N2O consumption in clear-waters, while in the mining-impacted site and brown-water sites the dominant pathway depends on the sediment layer with truncated denitrification in top layer, and methanogenesis and N-fixation in sub-top layer. The N2O production (d14), that fits the genetic potential, is highest in the mining-impacted site (35-43 µmol N/m2/d), followed by the brown-water sediments (6-11 µmol N/m2/d), with the lowest rates in the clear-water sediments (0-1 µmol N/m2/d).

How to cite: Palacin-Lizarbe, C., Bertilsson, S., Siljanen, H. J., Buck, M., Kolh, L., Paul, D., Maréchal, M., Nykänen, H., Liu, T., Kiljunen, M., Aalto, S. L., Rissanen, A. J., Biasi, C., Vainikka, A., and Pumpanen, J.: Browning and mining increase the nitrous oxide production in sediments of large boreal lakes during winter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20301, https://doi.org/10.5194/egusphere-egu24-20301, 2024.