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Dissolved organic carbon thresholds affect mercury bioaccumulation in Arctic lakes.

https://arctichealth.org/en/permalink/ahliterature258572
Source
Environ Sci Technol. 2014 Mar 18;48(6):3162-8
Publication Type
Article
Date
Mar-18-2014
Author
Todd D French
Adam J Houben
Jean-Pierre W Desforges
Linda E Kimpe
Steven V Kokelj
Alexandre J Poulain
John P Smol
Xiaowa Wang
Jules M Blais
Source
Environ Sci Technol. 2014 Mar 18;48(6):3162-8
Date
Mar-18-2014
Language
English
Publication Type
Article
Keywords
Animals
Canada
Carbon - analysis - chemistry
Humic Substances
Invertebrates - chemistry - metabolism
Lakes - chemistry
Mercury - analysis - chemistry - metabolism
Methylmercury Compounds - analysis - chemistry - metabolism
Water Pollutants, Chemical - analysis - chemistry - metabolism
Abstract
Dissolved organic carbon (DOC) is known to affect the Hg cycle in aquatic environments due to its overriding influence on complexation, photochemical, and microbial processes, but its role as a mediating factor in the bioaccumulation of Hg in aquatic biota has remained enigmatic. Here, we examined 26 tundra lakes in Canada's western Arctic that span a large gradient of DOC concentrations to show that total Hg (HgT) and methyl mercury (MeHg) accumulation by aquatic invertebrates is defined by a threshold response to Hg-DOC binding. Our results showed that DOC promotes HgT and MeHg bioaccumulation in tundra lakes having low DOC (DOC TC), consistent with bioaccumulation results in a companion paper (this issue) using a microbial bioreporter. Chemical equilibrium modeling showed that Hg bioaccumulation factors were elevated when Hg was associated mainly to fulvic acids, but became dramatically reduced when DOC was >8.5 mg C L(-1), at which point Hg was associated primarily with strong binding sites on larger, less bioaccessible humic acids. This study demonstrates that the biological uptake of Hg in lakes is determined by binding thresholds on DOC, a water quality variable predicted to change markedly with future environmental change.
PubMed ID
24524759 View in PubMed
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Insights Into Arsenite and Arsenate Uptake Pathways Using a Whole Cell Biosensor.

https://arctichealth.org/en/permalink/ahliterature295430
Source
Front Microbiol. 2018; 9:2310
Publication Type
Journal Article
Date
2018
Author
Martin P Pothier
Aaron J Hinz
Alexandre J Poulain
Author Affiliation
Department of Biology, University of Ottawa, Ottawa, ON, Canada.
Source
Front Microbiol. 2018; 9:2310
Date
2018
Language
English
Publication Type
Journal Article
Abstract
Despite its high toxicity and widespread occurrence in many parts of the world, arsenic (As) concentrations in decentralized water supplies such as domestic wells remain often unquantified. One limitation to effective monitoring is the high cost and lack of portability of current arsenic speciation techniques. Here, we present an arsenic biosensor assay capable of quantifying and determining the bioavailable fraction of arsenic species at environmentally relevant concentrations. First, we found that inorganic phosphate, a buffering agent and nutrient commonly found in most bioassay exposure media, was in fact limiting As(V) uptake, possibly explaining the variability in As(V) detection reported so far. Second, we show that the nature of the carbon source used in the bioassay differentially affects the response of the biosensor to As(III). Finally, our data support the existence of non-specific reduction pathways (non-ars encoded) that are responsible for the reduction of As(V) to As(III), allowing its detection by the biosensor. To validate our laboratory approach using field samples, we performed As(III) and As(V) standard additions on natural water samples collected from 17 lakes surrounding Giant Mine in Yellowknife (NWT), Canada. We found that legacy arsenic contamination in these lake water samples was accurately quantified by the biosensor. Interestingly, bioavailability of freshly added standards showed signs of matrix interference, indicative of dynamic interactions between As(III), As(V) and environmental constituents that have yet to be identified. Our results point toward dissolved organic carbon as possibly controlling these interactions, thus altering As bioavailability.
Notes
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PubMed ID
30333804 View in PubMed
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Mercury in freshwater ecosystems of the Canadian Arctic: Recent advances on its cycling and fate.

https://arctichealth.org/en/permalink/ahliterature102698
Source
Sci Total Environ. 2014 Jun 30;
Publication Type
Article
Date
Jun-30-2014
Author
John Chételat
Marc Amyot
Paul Arp
Jules M Blais
David Depew
Craig A Emmerton
Marlene Evans
Mary Gamberg
Nikolaus Gantner
Catherine Girard
Jennifer Graydon
Jane Kirk
David Lean
Igor Lehnherr
Derek Muir
Mina Nasr
Alexandre J Poulain
Michael Power
Pat Roach
Gary Stern
Heidi Swanson
Shannon van der Velden
Source
Sci Total Environ. 2014 Jun 30;
Date
Jun-30-2014
Language
English
Publication Type
Article
Abstract
The Canadian Arctic has vast freshwater resources, and fish are important in the diet of many Northerners. Mercury is a contaminant of concern because of its potential toxicity and elevated bioaccumulation in some fish populations. Over the last decade, significant advances have been made in characterizing the cycling and fate of mercury in these freshwater environments. Large amounts of new data on concentrations, speciation and fluxes of Hg are provided and summarized for water and sediment, which were virtually absent for the Canadian Arctic a decade ago. The biogeochemical processes that control the speciation of mercury remain poorly resolved, including the sites and controls of methylmercury production. Food web studies have examined the roles of Hg uptake, trophic transfer, and diet for Hg bioaccumulation in fish, and, in particular, advances have been made in identifying determinants of mercury levels in lake-dwelling and sea-run forms of Arctic char. In a comparison of common freshwater fish species that were sampled across the Canadian Arctic between 2002 and 2009, no geographic patterns or regional hotspots were evident. Over the last two to four decades, Hg concentrations have increased in some monitored populations of fish in the Mackenzie River Basin while other populations from the Yukon and Nunavut showed no change or a slight decline. The different Hg trends indicate that the drivers of temporal change may be regional or habitat-specific. The Canadian Arctic is undergoing profound environmental change, and preliminary evidence suggests that it may be impacting the cycling and bioaccumulation of mercury. Further research is needed to investigate climate change impacts on the Hg cycle as well as biogeochemical controls of methylmercury production and the processes leading to increasing Hg levels in some fish populations in the Canadian Arctic.
PubMed ID
24993511 View in PubMed
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Mercury in the Canadian Arctic terrestrial environment: an update.

https://arctichealth.org/en/permalink/ahliterature263608
Source
Sci Total Environ. 2015 Mar 15;509-510:28-40
Publication Type
Article
Date
Mar-15-2015
Author
Mary Gamberg
John Chételat
Alexandre J Poulain
Christian Zdanowicz
Jiancheng Zheng
Source
Sci Total Environ. 2015 Mar 15;509-510:28-40
Date
Mar-15-2015
Language
English
Publication Type
Article
Keywords
Air Pollutants - analysis
Arctic Regions
Atmosphere - chemistry
Environmental monitoring
Ice Cover - chemistry
Mercury - analysis
Snow - chemistry
Abstract
Contaminants in the Canadian Arctic have been studied over the last twenty years under the guidance of the Northern Contaminants Program. This paper provides the current state of knowledge on mercury (Hg) in the Canadian Arctic terrestrial environment. Snow, ice, and soils on land are key reservoirs for atmospheric deposition and can become sources of Hg through the melting of terrestrial ice and snow and via soil erosion. In the Canadian Arctic, new data have been collected for snow and ice that provide more information on the net accumulation and storage of Hg in the cryosphere. Concentrations of total Hg (THg) in terrestrial snow are highly variable but on average, relatively low (
PubMed ID
24861531 View in PubMed
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Microbial community structure in lake and wetland sediments from a high Arctic polar desert revealed by targeted transcriptomics.

https://arctichealth.org/en/permalink/ahliterature259499
Source
PLoS One. 2014;9(3):e89531
Publication Type
Article
Date
2014
Author
Magdalena K Stoeva
Stéphane Aris-Brosou
John Chételat
Holger Hintelmann
Philip Pelletier
Alexandre J Poulain
Source
PLoS One. 2014;9(3):e89531
Date
2014
Language
English
Publication Type
Article
Keywords
Arctic Regions
Base Sequence
Biodiversity
DNA Primers
Ecosystem
Geologic Sediments - microbiology
Lakes
Polymerase Chain Reaction
Transcriptome
Water Microbiology
Wetlands
Abstract
While microbial communities play a key role in the geochemical cycling of nutrients and contaminants in anaerobic freshwater sediments, their structure and activity in polar desert ecosystems are still poorly understood, both across heterogeneous freshwater environments such as lakes and wetlands, and across sediment depths. To address this question, we performed targeted environmental transcriptomics analyses and characterized microbial diversity across three depths from sediment cores collected in a lake and a wetland, located on Cornwallis Island, NU, Canada. Microbial communities were characterized based on 16S rRNA and two functional gene transcripts: mcrA, involved in archaeal methane cycling and glnA, a bacterial housekeeping gene implicated in nitrogen metabolism. We show that methane cycling and overall bacterial metabolic activity are the highest at the surface of lake sediments but deeper within wetland sediments. Bacterial communities are highly diverse and structured as a function of both environment and depth, being more diverse in the wetland and near the surface. Archaea are mostly methanogens, structured by environment and more diverse in the wetland. McrA transcript analyses show that active methane cycling in the lake and wetland corresponds to distinct communities with a higher potential for methane cycling in the wetland. Methanosarcina spp., Methanosaeta spp. and a group of uncultured Archaea are the dominant methanogens in the wetland while Methanoregula spp. predominate in the lake.
Notes
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PubMed ID
24594936 View in PubMed
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Physicochemical Drivers of Microbial Community Structure in Sediments of Lake Hazen, Nunavut, Canada.

https://arctichealth.org/en/permalink/ahliterature292428
Source
Front Microbiol. 2018; 9:1138
Publication Type
Journal Article
Date
2018
Author
Matti O Ruuskanen
Kyra A St Pierre
Vincent L St Louis
Stéphane Aris-Brosou
Alexandre J Poulain
Author Affiliation
Department of Biology, University of Ottawa, Ottawa, ON, Canada.
Source
Front Microbiol. 2018; 9:1138
Date
2018
Language
English
Publication Type
Journal Article
Abstract
The Arctic is undergoing rapid environmental change, potentially affecting the physicochemical constraints of microbial communities that play a large role in both carbon and nutrient cycling in lacustrine environments. However, the microbial communities in such Arctic environments have seldom been studied, and the drivers of their composition are poorly characterized. To address these gaps, we surveyed the biologically active surface sediments in Lake Hazen, the largest lake by volume north of the Arctic Circle, and a small lake and shoreline pond in its watershed. High-throughput amplicon sequencing of the 16S rRNA gene uncovered a community dominated by Proteobacteria, Bacteroidetes, and Chloroflexi, similar to those found in other cold and oligotrophic lake sediments. We also show that the microbial community structure in this Arctic polar desert is shaped by pH and redox gradients. This study lays the groundwork for predicting how sediment microbial communities in the Arctic could respond as climate change proceeds to alter their physicochemical constraints.
Notes
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PubMed ID
29922252 View in PubMed
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The ratio of methylmercury to dissolved organic carbon in water explains methylmercury bioaccumulation across a latitudinal gradient from north-temperate to Arctic lakes.

https://arctichealth.org/en/permalink/ahliterature287178
Source
Environ Sci Technol. 2017 Nov 25;
Publication Type
Article
Date
Nov-25-2017
Author
John Chételat
Murray Richardson
Gwyneth A MacMillan
Marc Amyot
Alexandre J Poulain
Source
Environ Sci Technol. 2017 Nov 25;
Date
Nov-25-2017
Language
English
Publication Type
Article
Abstract
We investigated monomethylmercury (MMHg) bioaccumulation in lakes across a 30? latitudinal gradient in eastern Canada to test the hypothesis that climate-related environmental conditions affect the sensitivity of Arctic lakes to atmospheric mercury contamination. Aquatic invertebrates (chironomid larvae, zooplankton) provided indicators of MMHg bioaccumulation near the base of benthic and planktonic food chains. In step with published data showing latitudinal declines in atmospheric mercury deposition in Canada, we observed lower total mercury concentrations in water and sediment of higher latitude lakes. Despite latitudinal declines of inorganic mercury exposure, MMHg bioaccumulation in aquatic invertebrates did not concomitantly decline. Arctic lakes with greater MMHg in aquatic invertebrates either had: (1) higher water MMHg concentrations (reflecting ecosystem MMHg production) or (2) low water concentrations of MMHg, DOC, chlorophyll and total nitrogen (reflecting lake sensitivity). The MMHg:DOC ratio of surface water was a strong predictor of lake sensitivity to mercury contamination. Bioaccumulation factors for biofilms and seston in Arctic lakes showed more efficient uptake of MMHg in low DOC systems. Environmental conditions associated with low biological production in Arctic lakes and their watersheds increased the sensitivity of lakes to MMHg.
PubMed ID
29172471 View in PubMed
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Swift evolutionary response of microbes to a rise in anthropogenic mercury in the Northern Hemisphere.

https://arctichealth.org/en/permalink/ahliterature307728
Source
ISME J. 2020 03; 14(3):788-800
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Date
03-2020
Author
Matti O Ruuskanen
Stéphane Aris-Brosou
Alexandre J Poulain
Author Affiliation
Department of Biology, University of Ottawa, Ottawa, ON, Canada.
Source
ISME J. 2020 03; 14(3):788-800
Date
03-2020
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Keywords
Bacteria - classification - genetics - isolation & purification - metabolism
Bacterial Proteins - genetics - metabolism
Biological Evolution
Canada
Ecosystem
Environmental Pollutants - analysis
Finland
Geologic Sediments - chemistry - microbiology
Mercury - analysis - metabolism
Oxidoreductases - genetics - metabolism
Abstract
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.
PubMed ID
31831837 View in PubMed
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Warming Climate Is Reducing the Diversity of Dominant Microbes in the Largest High Arctic Lake.

https://arctichealth.org/en/permalink/ahliterature304307
Source
Front Microbiol. 2020; 11:561194
Publication Type
Journal Article
Date
2020
Author
Graham A Colby
Matti O Ruuskanen
Kyra A St Pierre
Vincent L St Louis
Alexandre J Poulain
Stéphane Aris-Brosou
Author Affiliation
Department of Biology, University of Ottawa, Ottawa, ON, Canada.
Source
Front Microbiol. 2020; 11:561194
Date
2020
Language
English
Publication Type
Journal Article
Abstract
Temperatures in the Arctic are expected to increase dramatically over the next century, and transform high latitude watersheds. However, little is known about how microbial communities and their underlying metabolic processes will be affected by these environmental changes in freshwater sedimentary systems. To address this knowledge gap, we analyzed sediments from Lake Hazen, NU Canada. Here, we exploit the spatial heterogeneity created by varying runoff regimes across the watershed of this uniquely large high-latitude lake to test how a transition from low to high runoff, used as one proxy for climate change, affects the community structure and functional potential of dominant microbes. Based on metagenomic analyses of lake sediments along these spatial gradients, we show that increasing runoff leads to a decrease in taxonomic and functional diversity of sediment microbes. Our findings are likely to apply to other, smaller, glacierized watersheds typical of polar or high latitude ecosystems; we can predict that such changes will have far reaching consequences on these ecosystems by affecting nutrient biogeochemical cycling, the direction and magnitude of which are yet to be determined.
PubMed ID
33133035 View in PubMed
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