Have natural lake expansion and landscape inundationresulted in mercury increases in flooded lakes of the GreatSlave Lowlands (Northwest Territories, Canada)?

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.This research was funded by the Cumulative Impact Monitoring Program (Government of the Northwest Territories), the W. Garfield Weston Foundation (postdoctoral fellowship to JRT), the Brock University Chancellor’s Chair for Research Excellence (MFJP), and the Natural Sciences and Engineering Research Council of Canada (Discovery Grants to MFJP and JMB, Northern Supplement to MFJP and a PDF to JBK)

The jellification of north temperate lakes.

Calcium (Ca) concentrations are decreasing in softwater lakes across eastern North America and western Europe. Using long-term contemporary and palaeo-environmental field data, we show that this is precipitating a dramatic change in Canadian lakes: the replacement of previously dominant pelagic herbivores (Ca-rich Daphnia species) by Holopedium glacialis, a jelly-clad, Ca-poor competitor. In some lakes, this transformation is being facilitated by increases in macro-invertebrate predation, both from native (Chaoborus spp.) and introduced (Bythotrephes longimanus) zooplanktivores, to which Holopedium, with its jelly coat, is relatively invulnerable. Greater representation by Holopedium within cladoceran zooplankton communities will reduce nutrient transfer through food webs, given their lower phosphorus content relative to daphniids, and greater absolute abundances may pose long-term problems to water users. The dominance of jelly-clad zooplankton will likely persist while lakewater Ca levels remain low.This work was primarily supported by grants from the Natural Sciences and Engineering Research Council of Canada and funding from the Ontario Ministry of the Environment.This is the accepted manuscript. The final version is available at http://rspb.royalsocietypublishing.org/content/282/1798/20142449

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

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.Cumulative Impact Monitoring Program (CIMP) of the Government of the Northwest Territories, the W. Garfield Weston Foundation (postdoctoral fellowship to J.R.T.), Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants to M.F.J.P., J.M.B. and M.J.S., an NSERC PDF to J.B.K. and the Northern Scientific Training Program. Logistical support was provided by the Polar Continental Shelf Program

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

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

DATA: PALEO-ECOTOXICOLOGY OF YELLOWKNIFE (NORTHWEST TERRITORIES, CANADA) LAKES IMPACTED BY HISTORIC GOLD MINING ACTIVITIES

Raw data to accompany Persaud (2020), MSc thesis, which explores the ecological impacts of legacy arsenic contamination on Cladocera (Branchiopoda, Crustacea) from historic gold mining in Yellowknife lakes (Northwest Territories, Canada) using a paleo-ecotoxicological approach. Cladocera subfossils preserved in the modern and pre-1850 lake sediments of 23 lakes in the region were examined, as well as the Daphnia resting egg bank of Pocket Lake, a highly contaminated lake in which striking ecological changes were previously recorded

(Paleo)limnological data for small, shallow lakes at or near the Scotty Creek Research Station in the Dehcho region (Northwest Territories, Canada)

Data to accompany Kristen Coleman's PhD dissertation (Geography)

Trends in historical mercury deposition inferred from lake sediment cores across a climate gradient in the Canadian High Arctic

Recent climate change may be enhancing mercury fluxes to Arctic lake sediments, confounding the use of sediment cores to reconstruct histories of atmospheric deposition. Assessing the independent effects of climate warming on mercury sequestration is challenging due to temporal overlap between warming temperatures and increased long-range transport of atmospheric mercury following the Industrial Revolution. We address this challenge by examining mercury trends in short cores (the last several hundred years) from eight lakes centered on Cape Herschel (Canadian High Arctic) that span a gradient in microclimates, including two lakes that have not yet been significantly altered by climate warming due to continued ice cover. Previous research on subfossil diatoms and inferred primary production indicated the timing of limnological responses to climate warming, which, due to prevailing ice cover conditions, varied from ∼1850 to ∼1990 for lakes that have undergone changes. We show that climate warming may have enhanced mercury deposition to lake sediments in one lake (Moraine Pond), while another (West Lake) showed a strong signal of post-industrial mercury enrichment without any corresponding limnological changes associated with warming. Our results provide insights into the role of climate warming and organic carbon cycling as drivers of mercury deposition to Arctic lake sediments

Dataset: Climatic Drivers of Limnological Change in Iqallukvik Lake, Tuktoyaktuk, Northwest Territories, Canada

A dataset of paleolimnological (sediment core) data for Iqallukvik Lake, located near Tuktoyaktuk, Northwest Territories, Canada. The data includes: sediment core dating via Lead-210, organic carbonate and silciclastic content via loss on ignition, particle size analysis, and sedimentary diatom assemblages

DATASET: A paleolimnological approach for interpreting Aquatic Effects Monitoring at the Diavik Diamond Mine (Lac de Gras, Northwest Territories, Canada)

A paleolimnological assessment of Lac de Gras (Northwest Territories, Canada) showed pronounced aquatic ecological and biogeochemical changes occurring since at least ~1950, well before diamond mining operations began in 2000. Three sediment cores were collected from the eastern end of Lac de Gras, near to the Diavik Diamond Mine, dated using 210Pb radioisotopes, and analyzed for metals, organic carbon, nitrogen stable isotopes, and diatoms