Natural and restoration peatland pools contain mainly contemporary carbon

Peatlands accumulate soil carbon (C) over millennia and are a globally important long-term terrestrial C store. This C store is at risk of destabilisation by climate and human disturbance. Many peatlands have pools or ponds at the surface which often contain very high C concentrations in organic (dissolved and particulate organic C) and gaseous (CO2 and CH4) forms. The radiocarbon composition (14C) of this C can tell is where these high C concentrations are primarily generated; i.e., from contemporary primary production or C released from deeper, old peat layers due to destabilisation. We present novel 14C and stable C (δ13C) isotope data from six peatland pool locations in the United Kingdom. Our data are from two distinct pool types: natural peatland pools and those formed by ditch blocking efforts to rewet peatlands (restoration pools). We focus on dissolved and particulate organic C and dissolved CO2, with additional sediment, CH4 and ebullition (bubble) observations (total n = 97). The majority of pools contained mainly contemporary C, with the most C (~50-75%) in all forms being younger than 300 years old. Both natural and restoration pools were found to transform and decompose organic C in the water column and emit CO2 to the atmosphere. Mixing with ambient atmosphere and subsequent greenhouse gas emissions were more evident in the generally larger natural pools. Little evidence of deep, old C was found either in natural or restoration pools, even though there is substantial old C in the surrounding peat matrix. We did observe some potential evidence for old C emission via CH4 ebullition, however. Our results suggest that some millennial-aged C can be emitted by peatland pools. But the overwhelming age of C in our sampled pools was contemporary. Our results suggest that restoration pools formed by management interventions such as ditch blocking can be effective at preventing the release of old C via the aquatic pathway.