Major implication of the littoral zone for methane release from boreal lakes

Transitions between aquatic and terrestrial environments can be recognized as biogeochemically active ecotones that support high CH 4 release. We studied the links between littoral CH 4 fluxes and aquatic vegetation, hydrologic conditions, and sediment quality, and integrated the CH 4 fluxes into a whole‐lake assessment. Methane fluxes were measured using a closed chamber method in the littoral and pelagic zones of three Finnish mid‐boreal lakes from May to October. The cumulative CH 4 fluxes were spatially integrated over the lake relative to the vegetation coverage in the littoral, and to depth zones in the pelagic regions. During the ice‐free period, 66–77% of the CH 4 was released from the littoral zone, and the mean CH 4 effluxes from these lakes were 0.08–0.42 mol m −2 ice‐free season −1 . Littoral and pelagic productivity was reflected in CH 4 release from the lakes. Our results show that estimates of lake CH 4 release should include an assessment of the vegetated littoral zone.