Cryogenic lakes are strong seasonal emitters of methane.

Gas isotopes reveal origin of methane.

Greenland ice retreat exposes nascent soil.

Iron oxidizing bacteria dominate bioreactor surface.

Nitrogen cycling is controlled by sediment microbiome

Root biomass is high above permafrost.

Sampling roots of thermokarst plants is challenging.

Soil methane is sampled at depth of permafrost.