Higher late summer methane emission from central than northern European lakes

Abstract

Quantifying methane (CH 4

Influence of water column stratification and mixing patterns on the fate of methane produced in deep sediments of a small eutrophic lake

“…Sediment‐produced CH 4 is transported in the water column by turbulent diffusion (Adams ), bubble‐mediated transport (McGinnis et al ), plant‐mediated transport (Juutinen ; Carmichael et al ), or migrating zooplankton (McGinnis et al ; Carey et al ). Although considerable efforts have been invested in quantifying the surface aquatic CH 4 fluxes and the relative contribution of the different emissions pathways (Bastviken et al ; Rinta et al ), the in‐lake mechanisms regulating rates of CH 4 production, transport, and oxidation in stratified systems are still poorly understood. Here, we investigate the role of water column hydrodynamics in promoting or restricting the different pathways.…”

“…Turbulent vertical diffusivity partly regulates the magnitude of vertical fluxes across the thermocline (Kreling et al ). Strong water column stratification therefore limits vertical gas exchange between the hypolimnion and epilimnion resulting in increasing bottom water CH 4 storage (Juutinen et al ; Kankaala et al ; Rinta et al ). High oxidation rates are often observed near the thermocline of stratified lakes, where both CH 4 and O 2 concentrations overlap (Sundh et al ; Oswald et al ), although microaerobic CH 4 oxidation can also occur just below the chemocline in anoxic waters (Blees et al ).…”

“…Turbulent vertical diffusivity partly regulates the magnitude of vertical fluxes across the thermocline (Kreling et al 2014). Strong water column stratification therefore limits vertical gas exchange between the hypolimnion and epilimnion resulting in increasing bottom water CH 4 storage (Juutinen et al 2009;Kankaala et al 2013;Rinta et al 2017). High oxidation rates are often observed near the thermocline of stratified lakes, where both CH 4 and O 2 concentrations overlap (Sundh et al 2005;*Correspondence: domvachon@gmail.com;daniel.mcginnis@unige.ch This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.…”

Flotsam samples can help explain the δ13C and δ15N values of invertebrate resting stages in lake sediment

“…In addition, we measured surface water TP and TN concentrations in the lake 172 centre, [CH 4 ] 10 cm above the sediment in the deepest part and in the near-shore 173 zone, difference between dissolved oxygen concentrations in surface and bottom 174 water (DO 2 ), the stratification stability, and the d 13 C and d 15 N values of SOM from the 175 deepest part of the lake and the near-shore zone. Most physio-chemical measurements 176 are described in Rinta et al (2015Rinta et al ( , 2017 and therefore just briefly summarized here. 177…”

“…[CH 4 ] are found in deeper, more strongly stratified lakes. A more detailed discussion 306 of the methane cycling and limnological profiles in the study lakes is provided 307 elsewhere (Rinta et al 2015(Rinta et al , 2017. 308…”