In shallow lakes, methane (CH₄) is mainly produced in the anoxic sediment by methanogenic archea and eutrophication and rising temperature generally increase CH₄ emissions, while higher rooted plant abundance generally reduce them.  The mechanisms behind the latter are not clear, with the action of methane-oxidizing bacteria (MOB) associated with plants and oxidized rootzone a possible cause. Little is also known about the combined effect of temperature and nutrients on CH₄ production/oxidation and how their balance shapes emissions. We then tried to define a CH₄ total budget in shallow lakes, by determining CH₄ production/oxidation patterns across habitats at different temperature, nutrient levels and macrophyte abundance. The experiment took place at the world’s longest running shallow lake mesocosm system at AU, Denmark, where there are 24 mesocosms with 2 nutrients and 3 temperature treatments. Using bottle incubations, potential CH₄ production and oxidation activity associated with sediment and plants were estimated for each mesocosm. Microbial analysis were run to quantify abundance of methanogenic archea and MOB through mcrA and pmoA gene amplification with quantitative polymerase chain reaction. Diffusive and ebullitive CH₄ emissions were estimated from dissolved gas concentrations and bubble traps in each mesocosm. Results show that plants play an important direct and indirect role in shaping CH₄ fluxes, but with different rates among species and treatments. Further results about how different activity of CH₄ production/oxidation can shape emissions will be discussed

Primary Presenter: Chiara Esposito, Aarhus University (che@ecos.au.dk)

Authors:

Joachim Audet, Aarhus University  (joau@ecos.au.dk)

Eti Levi, Aarhus University  (eel@ecos.au.dk)

Wantong Zhang, Chinese Academy of Agricultural Sciences  (zhangwantongt@163.com)

Ian Marshall, Aarhus University  (ianpgm@bio.au.dk)

Thomas Davidson, Aarhus university  (thd@ecos.au.dk)