Tracking the impacts of recent warming and thaw of permafrost peatlands on aquatic ecosystems: A multi-proxy approach using remote sensing and lake sediments

Regions within the discontinuous permafrost zone of the southern Northwest Territories (Canada) are experiencing accelerated thaw of permafrost as a result of recent warming. We used remotely-sensed imagery (1947–2012) to track changes in the extent of peat plateau collapse around two study lakes: KAK-1 and TAH-7. Subfossil diatoms were analyzed from sediment cores to reconstruct limnological changes over the past ~300 years and assess whether peatland subsidence affected lake ecology. Extensive peat plateau collapse was evident in catchments between 1970 and present day. In TAH-7, diatom assemblages indicated a substantial increase in coloured dissolved organic carbon coincident with the time of peat collapse, suggesting that permafrost thaw has resulted in increased transport of terrestrial organic matter to the lake. At KAK-1, while also tracking changes linked to climate warming, no changes in diatom assemblages could be linked to peat plateau collapse. Using our combined approaches, we conclude that collapsing peat plateaus may significantly alter aquatic ecosystems, but the impacts of permafrost thaw on aquatic ecosystems in the sporadic discontinuous permafrost zone are complex.