Nitrous oxide emissions to the atmosphere from an artificially oxygenated lake

Nitrous oxide (N 2 O) production at the sediment surface of eutrophic Lake Baldegg was quantified with three independent methods: pore‐water samplers, benthic chambers, and mass balances of the aerated‐oxygenated hypolimnion. N 2 O production at the sediment surface was the most important source in this lake and led to an accumulation in the hypolimnion during summer stratification. Highest rates of N 2 O emission to the atmosphere (24 µ mol m −2 d −1 ) were observed after the onset of winter overturn, when hypolimnetic water enriched in N 2 O came in contact with the atmosphere. During summer stratification N 2 O emissions to the atmosphere decreased to ∼4 µ mol m −2 d −1 . The winter fluxes are close to the highest reported N 2 O emissions from marine systems.