• Broad-scale lake expansion and flooding inundates essential wood bison habitat

      Korosi, Jennifer; Thienpont, Joshua; Pisaric, Michael; deMontigny, Peter; Perreault, Joelle; McDonald, Jamylynn; Simpson, Myrna; Armstrong, Terry; Kokelj, Steven; Smol, John; et al. (Nature, 2017-02-23)
      Understanding the interaction between the response of a complex ecosystem to climate change and the protection of vulnerable wildlife species is essential for conservation efforts. In the Northwest Territories (Canada), the recent movement of the Mackenzie wood bison herd (Bison bison athabascae) out of their designated territory has been postulated as a response to the loss of essential habitat following regional lake expansion. We show that the proportion of this landscape occupied by water doubled since 1986 and the timing of lake expansion corresponds to bison movements out of the Mackenzie Bison Sanctuary. Historical reconstructions using proxy data in dated sediment cores show that the scale of recent lake expansion is unmatched over at least the last several hundred years. We conclude that recent lake expansion represents a fundamental alteration of the structure and function of this ecosystem and its use by Mackenzie wood bison, in response to climate change.
    • Have natural lake expansion and landscape inundationresulted in mercury increases in flooded lakes of the GreatSlave Lowlands (Northwest Territories, Canada)?

      Thienpont, Joshua; Perreault, Joelle; Korosi, Jennifer; Pisaric, Michael; Blais, Jules (Springer Netherlands, 2018-11-30)
      The inundation of terrestrial vegetation following landscape flooding is an important potential source of mercury to aquatic ecosystems, and may modify mercury cycling, such as through increased methylation. In the Great Slave Lowlands of Canada’s Northwest Territories, remarkable landscape flooding has occurred over the recent past, which is the most notable in at least the last several centuries. The potential for this flooding to increase inorganic mercury flux to the lakes of the region has not yet been explored. In this study we used sediment cores from five lakes experiencing a range of recently documented lake expansion to test whether inundation of terrestrial areas has increased the total mercury concentrations in sediments, and resulted in increased total mercury flux. Increases in sedimentary mercury concentrations and fluxes in sediment cores from the expanding lakes were relatively small and within the range of non-expanded systems, suggesting that, to date, flooding has not resulted in major total mercury enrichment, unlike in experimental and natural reservoir impoundments. The potential for increased methylation of existing inorganic mercury following expansion was not explored in this paper because methylmercury is dynamic in sediments and does not preserve well, but is an important consideration for future work.