Evidence of the microbial transformation of nitrate in a freshwater habitat in the presence of methane, nitrate, and ammonia: Linking n-damo with Anammox
Final Report Abstract
Nitrate pollution of freshwaters and methane emissions into the atmosphere are crucial factors in deteriorating the quality of drinking water and in contributing to global climate change. The nitrate dependent anaerobic methane oxidation and the anaerobic oxidation of ammonium (anammox) have the potential to reduce nitrogen loading of aquatic ecosystems and to reduce methane emissions to the atmosphere. In this project we have combined stable isotope compositions of CH4, NO3-, NO2- and NH4+ linked with the microbial community distribution to demonstrate that n-AOM is coupled to anammox in the water column of a stratified lake. A consortium of Crenothrix and NC10 bacteria highly likely controls the n-damo process close to the oxycline, whereas ‘Candidatus Anammoximicrobium’ populations may drive the anammox processes via n-AOM formed nitrite when ammonium is available. Our data set together with the results of the numerical model revealed a redox zone within the water column where both denitrification and anaerobic methane oxidation may be linked, contributing to approximately 70% of methane removal between June and September. Therefore, AOM linked with denitrification represents the dominant methane sink in the water column of lake Fohnsee during summer stratification. However in an extended field-work in 2019 numerical modeling results and the use of specific marker genes (hszB) revealed that the observed shift in δ¹⁵N values of ammonium appears to be mainly the result of mixing between ammonium generated by nitrification in the oxic water column δ¹⁵N values of 25‰, and ammonium that is formed by degradation of organic matter during methanogenesis in the lake sediments with δ¹⁵N values of around 11‰. Our results may indicate that denitrification is the predominant sink of fixed nitrogen in the investigated seasonal stratified and highly dynamic stratified lake, whereas anammox appeared to occur only at very low rates and perhaps sporadically in the absence of H2S.
Publications
- (2019): Investigating the seasonal dynamics of anaerobic methane oxidation coupled to nitrate reduction using stable isotope technique. International Symposium on Isotope Hydrology: Advancing the Understanding of Water Cycle Processes CN-271, 20.-24 May, IAEA Vienna, Austria
Peña, A., Wunderlich, A., Mayer, B., Einsiedl, F.
- (2020): Biogeochemical evidence of anaerobic methane oxidation and anaerobic ammonium oxidation in a stratified lake using stable isotopes. Biogeosciences 17, 20
Einsiedl, F., Wunderlich, A., Sebilo, M., Coskun, Ö. K., Orsi, W. D., Mayer, B.
(See online at https://doi.org/10.5194/bg-17-5149-2020) - (2021): Evidence of anaerobic methane oxidation linked with nitrate reduction in a stratified lake using stable isotopes and numerical modeling, Goldschmidt Conference 4.-9.7.2021
Peña, A., Wunderlich, A., Mayer, B., Einsiedl, F.
- (2021): Supporting the interpretation of δ¹⁵N values of dissolved NH₄⁺ and NO₃⁻ in the water column of a seasonal stratified lake using Numerical modeling and PCR gene amplification. Jahrestagung der Arbeitsgemeinschaft Stabile Isotope e.V 26.-29. September 2021
Peña, A., Duffner, C., Schulz, S., Wunderlich, A., Mayer, B., Einsiedl, F.
- Analysing seasonal variations of methane oxidation processes 1 coupled with denitrification in a stratified lake using stable 2 isotopes and numerical modeling. Geochimica et Cosmochimica Acta
Peña, A., Mayer, B., Wunderlich, A., Rein, A., Einsiedl, F.
(See online at https://doi.org/10.1016/j.gca.2022.01.022)
