Abstract:ABSTRACT. Arctic lakes can provide a long-term perspective on environmental change, including trends in long-range atmospheric transport and deposition of contaminants, inferred from studies of sediment cores. In this study, we conducted the first detailed bathymetric survey of Lake Hazen (Quttinirpaaq National Park, Ellesmere Island, Nunavut), the world's largest lake north of 74˚ latitude. With these data we were able to determine optimal locations for sediment coring and to collect and analyze profundal sed… Show more
“…Annual runoff in excess of 1 × 10 9 m 3 occurred in three of the five years between 2007 and 2012, but only twice in the previous 58 years. The large input of glacier meltwaters into Lake Hazen has reduced the residence time of water in the lake from its historical average of ~89 years 10 to only 25 years. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…5 Sediment record of diatom abundance, geochemical parameters, contaminants and sedimentation rates. Diatom, geochemical and contaminant analyses were completed on three separate sediment cores collected in close proximity in May 2013 from the deepest location in Lake Hazen 10 . One of these cores was used for 210 Pb radiometric dating (also see Supplementary Fig.…”
Section: Resultsmentioning
confidence: 99%
“…Three intact sediment cores with clearly defined sediment–water interfaces were collected in close proximity to one another in May 2013 from the location of maximum depth (260 m) in Lake Hazen 10 using a UWITEC gravity corer with an 8.6 cm inner diameter PVC tube. Cores were carefully returned to the Lake Hazen field laboratory where they were extruded and sectioned into 0.5 cm intervals on the same day.…”
Section: Methodsmentioning
confidence: 99%
“…The first people of European descent to explore the region were members of the ill-fated “Lady Franklin Bay Expedition” led by Lieutenant Adolphus Greely, as part of the USA contribution to scientific discovery during the first International Polar Year (1882–1883) 8 . Lake Hazen has a maximum depth of 267 m 10 , a surface area of 540 km 2 and a catchment area of 6860 km 2 11 . The NW half of its catchment is extensively glaciated, while the Hazen Plateau characterized by polar desert tundra lies to the SE.…”
Using a whole-watershed approach and a combination of historical, contemporary, modeled and paleolimnological datasets, we show that the High Arctic’s largest lake by volume (Lake Hazen) has succumbed to climate warming with only a ~1 °C relative increase in summer air temperatures. This warming deepened the soil active layer and triggered large mass losses from the watershed’s glaciers, resulting in a ~10 times increase in delivery of glacial meltwaters, sediment, organic carbon and legacy contaminants to Lake Hazen, a >70% decrease in lake water residence time, and near certainty of summer ice-free conditions. Concomitantly, the community assemblage of diatom primary producers in the lake shifted dramatically with declining ice cover, from shoreline benthic to open-water planktonic species, and the physiological condition of the only fish species in the lake, Arctic Char, declined significantly. Collectively, these changes place Lake Hazen in a biogeochemical, limnological and ecological regime unprecedented within the past ~300 years.
“…Annual runoff in excess of 1 × 10 9 m 3 occurred in three of the five years between 2007 and 2012, but only twice in the previous 58 years. The large input of glacier meltwaters into Lake Hazen has reduced the residence time of water in the lake from its historical average of ~89 years 10 to only 25 years. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…5 Sediment record of diatom abundance, geochemical parameters, contaminants and sedimentation rates. Diatom, geochemical and contaminant analyses were completed on three separate sediment cores collected in close proximity in May 2013 from the deepest location in Lake Hazen 10 . One of these cores was used for 210 Pb radiometric dating (also see Supplementary Fig.…”
Section: Resultsmentioning
confidence: 99%
“…Three intact sediment cores with clearly defined sediment–water interfaces were collected in close proximity to one another in May 2013 from the location of maximum depth (260 m) in Lake Hazen 10 using a UWITEC gravity corer with an 8.6 cm inner diameter PVC tube. Cores were carefully returned to the Lake Hazen field laboratory where they were extruded and sectioned into 0.5 cm intervals on the same day.…”
Section: Methodsmentioning
confidence: 99%
“…The first people of European descent to explore the region were members of the ill-fated “Lady Franklin Bay Expedition” led by Lieutenant Adolphus Greely, as part of the USA contribution to scientific discovery during the first International Polar Year (1882–1883) 8 . Lake Hazen has a maximum depth of 267 m 10 , a surface area of 540 km 2 and a catchment area of 6860 km 2 11 . The NW half of its catchment is extensively glaciated, while the Hazen Plateau characterized by polar desert tundra lies to the SE.…”
Using a whole-watershed approach and a combination of historical, contemporary, modeled and paleolimnological datasets, we show that the High Arctic’s largest lake by volume (Lake Hazen) has succumbed to climate warming with only a ~1 °C relative increase in summer air temperatures. This warming deepened the soil active layer and triggered large mass losses from the watershed’s glaciers, resulting in a ~10 times increase in delivery of glacial meltwaters, sediment, organic carbon and legacy contaminants to Lake Hazen, a >70% decrease in lake water residence time, and near certainty of summer ice-free conditions. Concomitantly, the community assemblage of diatom primary producers in the lake shifted dramatically with declining ice cover, from shoreline benthic to open-water planktonic species, and the physiological condition of the only fish species in the lake, Arctic Char, declined significantly. Collectively, these changes place Lake Hazen in a biogeochemical, limnological and ecological regime unprecedented within the past ~300 years.
“…1). Low Hg contamination (max [THg] <100 ng g −1 dw) sites included Lake Hazen (LAH) in NU sampled in May 2015 in the Canadian High Arctic [17], and Lake Kevojärvi (KEV), Lake Vuolimus Cieskuljavri (VUO), and Lake Pulmankijärvi (PUL) subarctic sites sampled in April 2016 in Finland [18]. To sample moderate Hg contamination (max [THg] from 100 to 1000 ng g −1 dw) through long-range transport, we obtained sediment-extracted DNA from a previous study of Aquatuk Lake (AQT), ON, Canada [16], sampled in August 2010; this site also allowed us to validate our original findings using different approaches for quantification and sequencing.…”
Anthropogenic mercury remobilization has considerably increased since the Industrial Revolution in the late 1700s. The Minamata Convention on Mercury is a United Nations treaty (2017) aiming at curbing mercury emissions. Unfortunately, evaluating the effectiveness of such a global treaty is hampered by our inability to determine the lag in aquatic ecosystem responses to a change in atmospheric mercury deposition. Whereas past metal concentrations are obtained from core samples, there are currently no means of tracking historical metal bioavailability or toxicity. Here, we recovered DNA from nine dated sediment cores collected in Canada and Finland, and reconstructed the past demographics of microbes carrying genes coding for the mercuric reductase (MerA)-an enzyme involved in Hg detoxification-using Bayesian relaxed molecular clocks. We found that the evolutionary dynamics of merA exhibited a dramatic increase in effective population size starting from 1783.8 ± 3.9 CE, which coincides with both the Industrial Revolution, and with independent measurements of atmospheric Hg concentrations. We show that even low levels of anthropogenic mercury affected the evolutionary trajectory of microbes in the Northern Hemisphere, and that microbial DNA encoding for detoxification determinants stored in environmental archives can be used to track historical pollutant toxicity.
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