Publications by authors named "Catherine Girard"

18 Publications

  • Page 1 of 1

Elevated rates of horizontal gene transfer in the industrialized human microbiome.

Cell 2021 Apr 31;184(8):2053-2067.e18. Epub 2021 Mar 31.

Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA; Center for Microbiome Informatics and Therapeutics, Massachusetts Institute of Technology, Cambridge, MA, USA; The Broad Institute of MIT and Harvard, Cambridge, MA, USA; The Global Microbiome Conservancy, Massachusetts Institute of Technology, Cambridge, MA, USA. Electronic address:

Industrialization has impacted the human gut ecosystem, resulting in altered microbiome composition and diversity. Whether bacterial genomes may also adapt to the industrialization of their host populations remains largely unexplored. Here, we investigate the extent to which the rates and targets of horizontal gene transfer (HGT) vary across thousands of bacterial strains from 15 human populations spanning a range of industrialization. We show that HGTs have accumulated in the microbiome over recent host generations and that HGT occurs at high frequency within individuals. Comparison across human populations reveals that industrialized lifestyles are associated with higher HGT rates and that the functions of HGTs are related to the level of host industrialization. Our results suggest that gut bacteria continuously acquire new functionality based on host lifestyle and that high rates of HGT may be a recent development in human history linked to industrialization.
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http://dx.doi.org/10.1016/j.cell.2021.02.052DOI Listing
April 2021

["Dys" disorders in health care training].

Authors:
Catherine Girard

Soins 2020 Jul - Aug;65(847):34-35

Centre de réadaptation, 7 boulevard des Nations, 68093 Mulhouse, France. Electronic address:

"Dys" disorders must be taken into account by trained teams in order for the people concerned to be able to undertake their training of choice. Learning is not easy, but neither is it impossible. With adapted support and a detailed analysis of the needs and tools required, it is possible to envisage working in the health care sector.
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http://dx.doi.org/10.1016/S0038-0814(20)30145-6DOI Listing
December 2020

Seasonal Regime Shift in the Viral Communities of a Permafrost Thaw Lake.

Viruses 2020 10 22;12(11). Epub 2020 Oct 22.

Département de Biochimie, de Microbiologie et de Bio-Informatique, Université Laval, Québec, QC G1V 0A6, Canada.

Permafrost thaw lakes including thermokarst lakes and ponds are ubiquitous features of Subarctic and Arctic landscapes and are hotspots of microbial activity. Input of terrestrial organic matter into the planktonic microbial loop of these lakes may greatly amplify global greenhouse gas emissions. This microbial loop, dominated in the summer by aerobic microorganisms including phototrophs, is radically different in the winter, when metabolic processes shift to the anaerobic degradation of organic matter. Little is known about the viruses that infect these microbes, despite evidence that viruses can control microbial populations and influence biogeochemical cycling in other systems. Here, we present the results of a metagenomics-based study of viruses in the larger than 0.22 µm fraction across two seasons (summer and winter) in a permafrost thaw lake in Subarctic Canada. We uncovered 351 viral populations (vOTUs) in the surface waters of this lake, with diversity significantly greater during the summer. We also identified and characterized several phage genomes and prophages, which were mostly present in the summer. Finally, we compared the viral community of this waterbody to other habitats and found unexpected similarities with distant bog lakes in North America.
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http://dx.doi.org/10.3390/v12111204DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7690404PMC
October 2020

The outbreak of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): A review of the current global status.

J Infect Public Health 2020 Nov 4;13(11):1601-1610. Epub 2020 Aug 4.

Université du Québec à Chicoutimi (UQAC), Département des sciences fondamentales, Centre intersectoriel en santé durable, Saguenay, Canada. Electronic address:

There is currently an ongoing worldwide pandemic of a novel virus belonging to the family of Coronaviruses (CoVs) which are large, enveloped, plus-stranded RNA viruses. Coronaviruses belong to the order of Nidovirales, family of Coronavirinae and are divided into four genera: alphacoronavirus, betacoronavirus, gammacoronavirus and deltacoronavirus. CoVs cause diseases in a wide variety of birds and mammals and have been found in humans since 1960. To date, seven human CoVs were identified including the alpha-CoVs HCoVs-NL63 and HCoVs-229E and the beta-CoVs HCoVs-OC43, HCoVs-HKU1, the severe acute respiratory syndrome-CoV (SARS-CoV), the Middle East respiratory syndrome-CoV (MERS-CoV) and the novel virus that first appeared in December 2019 in Wuhan, China, and rapidly spread to 213 countries as of the writing this paper. It was officially named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by the international committee on taxonomy of viruses (ICTV) and the disease's name is COVID-19 for coronavirus disease 2019. SARS-CoV-2 is very contagious and is capable of spreading from human to human. Infection routes include droplet and contact, and aerosol transmission is currently under investigation. It is associated with a respiratory illness that may cause severe pneumonia and acute respiratory distress syndrome (ARDS). SARS-CoV-2 became an emergency of international concern. As of July 12, 2020, the virus has been responsible for 12,698,995 confirmed cases and 564,924 deaths worldwide and the number is still increasing. Up until now, no specific treatment has yet been proven effective against SARS-CoV-2. Since the beginning of this outbreak, several interesting papers on SARS-CoV-2 and COVID-19 have been published to report on the phylogenetic evolution, epidemiology, pathogenesis, transmission as well as clinical characteristics of COVID-19 and possible treatments agents. This paper is a systematic review of the available literature on SARS-CoV-2. It was performed in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and aims to help readers access the latest knowledge surrounding this new infectious disease and to provide a reference for future studies.
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http://dx.doi.org/10.1016/j.jiph.2020.07.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7402212PMC
November 2020

Extreme Viral Partitioning in a Marine-Derived High Arctic Lake.

mSphere 2020 05 13;5(3). Epub 2020 May 13.

Département de biochimie, de microbiologie et de bio-informatique, Université Laval, Quebec City, Quebec, Canada

High-latitude, perennially stratified (meromictic) lakes are likely to be especially vulnerable to climate warming because of the importance of ice in maintaining their water column structure and associated distribution of microbial communities. This study aimed to characterize viral abundance, diversity, and distribution in a meromictic lake of marine origin on the far northern coast of Ellesmere Island, in the Canadian High Arctic. We collected triplicate samples for double-stranded DNA (dsDNA) viromics from five depths that encompassed the major features of the lake, as determined by limnological profiling of the water column. Viral abundance and virus-to-prokaryote ratios were highest at greater depths, while bacterial and cyanobacterial counts were greatest in the surface waters. The viral communities from each zone of the lake defined by salinity, temperature, and dissolved oxygen concentrations were markedly distinct, suggesting that there was little exchange of viral types among lake strata. Ten viral assembled genomes were obtained from our libraries, and these also segregated with depth. This well-defined structure of viral communities was consistent with that of potential hosts. Viruses from the monimolimnion, a deep layer of ancient Arctic Ocean seawater, were more diverse and relatively abundant, with few similarities to available viral sequences. The Lake A viral communities also differed from published records from the Arctic Ocean and meromictic Ace Lake in Antarctica. This first characterization of viral diversity from this sentinel environment underscores the microbial richness and complexity of an ecosystem type that is increasingly exposed to major perturbations in the fast-changing Arctic. The Arctic is warming at an accelerating pace, and the rise in temperature has increasing impacts on the Arctic biome. Lakes are integrators of their surroundings and thus excellent sentinels of environmental change. Despite their importance in the regulation of key microbial processes, viruses remain largely uncharacterized in Arctic lacustrine environments. We sampled a highly stratified meromictic lake near the northern limit of the Canadian High Arctic, a region in rapid transition due to climate change. We found that the different layers of the lake harbored viral communities that were strikingly dissimilar and highly divergent from known viruses. Viruses were more abundant in the deepest part of the lake containing ancient Arctic Ocean seawater that was trapped during glacial retreat and were genomically unlike any viruses previously described. This research demonstrates the complexity and novelty of viral communities in an environment that is vulnerable to ongoing perturbation.
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http://dx.doi.org/10.1128/mSphere.00334-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7227771PMC
May 2020

Local fungi, willow and municipal compost effectively remediate petroleum-contaminated soil in the Canadian North.

Chemosphere 2019 Apr 15;220:47-55. Epub 2018 Dec 15.

Center for Northern Studies, Département de Sciences Biologiques, Université de Montréal, Pavillon Marie-Victorin, 90 Vincent d'Indy, Montréal QC, H2V 2S9, Canada. Electronic address:

Low energy-input alternatives based on locally available products are needed for treating petroleum-hydrocarbon spills in northern regions. We tested the efficacy of three local biological components (municipal compost, white-rot fungus: Pleurotus ostreatus and willow: Salix planifolia) to remediate diesel-contaminated soils in a subarctic climate (Whitehorse, YT, Canada), and compared their efficacy to natural attenuation and chemical fertilizers (industry standard). After the first growing season, biologically amended treatments (BAT) that contained >2 biological components, had decreased 69-73% of the diesel's F2 fraction (C-C), which is more than natural attenuation or fertilizer (48 and 51%). By the third growing season, the BAT dropped below the Canadian Council of Ministers of the Environment's (CCME) Agricultural & Residential/Parkland guideline (<150 mg kg) and 86% of willows had survived and developed extensive roots. MiSeq amplicon sequencing of fungal (ITS) and bacterial (16S) rRNA genes showed the BAT's microbial communities were significantly more abundant and diverse. We found 132 bacterial and 35 fungal genera unique to the BAT. Readily-available local biological components such as municipal compost, fungi and willows may provide an effective alternative to applications of imported chemical fertilizers for the bioremediation and revegetation of diesel-contaminated soil in northern environments.
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http://dx.doi.org/10.1016/j.chemosphere.2018.12.108DOI Listing
April 2019

Imidacloprid Decreases Honey Bee Survival Rates but Does Not Affect the Gut Microbiome.

Appl Environ Microbiol 2018 07 18;84(13). Epub 2018 Jun 18.

Department of Integrative Biology, University of Texas at Austin, Austin, Texas, USA.

Accumulating evidence suggests that pesticides have played a role in the increased rate of honey bee colony loss. One of the most commonly used pesticides in the United States is the neonicotinoid imidacloprid. Although the primary mode of action of imidacloprid is on the insect nervous system, it has also been shown to cause changes in insects' digestive physiology and alter the microbiota of larvae. The honey bee gut microbiome plays a major role in bee health. Although many studies have shown that imidacloprid affects honey bee behavior, its impact on the microbiome has not been fully elucidated. Here, we investigated the impact of imidacloprid on the gut microbiome composition, survivorship, and susceptibility to pathogens of honey bees. Consistent with other studies, we show that imidacloprid exposure results in an elevated mortality of honey bees in the hive and increases the susceptibility to infection by pathogens. However, we did not find evidence that imidacloprid affects the gut bacterial community of honey bees. Our experiments demonstrated that honey bee gut bacteria can grow in the presence of imidacloprid, and we found some evidence that imidacloprid can be metabolized in the bee gut environment. However, none of the individual bee gut bacterial species tested could metabolize imidacloprid, suggesting that the observed metabolism of imidacloprid within bee gut cultures is not caused by the gut bacteria. Overall, our results indicate that imidacloprid causes increased mortality in honey bees, but this mortality does not appear to be linked to the microbiome. Growing evidence suggests that the extensive use of pesticides has played a large role in the increased rate of honey bee colony loss. Despite extensive research on the effects of imidacloprid on honey bees, it is still unknown whether it impacts the community structure of the gut microbiome. Here, we investigated the impact of imidacloprid on the gut microbiome composition, survivorship, and susceptibility to pathogens of honey bees. We found that the exposure to imidacloprid resulted in an elevated mortality of honey bees and increased the susceptibility to infection by opportunistic pathogens. However, we did not find evidence that imidacloprid affects the gut microbiome of honey bees. We found some evidence that imidacloprid can be metabolized in the bee gut environment , but because it is quickly eliminated from the bee, it is unlikely that this metabolism occurs in nature. Thus, imidacloprid causes increased mortality in honey bees, but this does not appear to be linked to the microbiome.
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http://dx.doi.org/10.1128/AEM.00545-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6007118PMC
July 2018

The Inuit gut microbiome is dynamic over time and shaped by traditional foods.

Microbiome 2017 11 16;5(1):151. Epub 2017 Nov 16.

Département de sciences biologiques, Université de Montréal, 90 Vincent-d'Indy, Montréal, Qc, H2V2S9, Canada.

Background: The human gut microbiome represents a diverse microbial community that varies across individuals and populations, and is influenced by factors such as host genetics and lifestyle. Diet is a major force shaping the gut microbiome, and the effects of dietary choices on microbiome composition are well documented. However, it remains poorly known how natural temporal variation in diet can affect the microbiome. The traditional Inuit diet is primarily based on animal products, which are thought to vary seasonally according to prey availability. We previously investigated the Inuit gut microbiome sampled at a single time point, and found no detectable differences in overall microbiome community composition attributable to the traditional Inuit diet.

Results: To determine whether seasonal changes in the Inuit diet might induce more pronounced changes in the microbiome, we collected stool and toilet paper samples, and dietary information from Inuit volunteers living in Resolute Bay (Nunavut, Canada), and compared them to individuals of European descent living in Montréal (Québec, Canada) consuming a typical Western diet. We sequenced the V4 region of the 16S rRNA gene to characterize microbiome diversity and composition, and compared samples collected with toilet paper or from stool. Our results show that these sampling methods provide similar, but non-identical portraits of the microbiome. Based on toilet paper samples, we found that much of the variation in microbiome community composition could be explained by individual identity (45-61% of variation explained, depending on the beta diversity metric used), with small but significant variation (3-5%) explained by sex or geography (Nunavut or Montréal). In contrast with our previous study at one time point, sampling over the course of a year revealed that diet explains 11% of variation in community composition across all participants, and 17% of variation specifically among Nunavut participants. However, we observed no clear seasonal shifts in the microbiomes of participants from either Nunavut or Montréal. Within-individual microbial diversity fluctuated more over time in Nunavut than in Montréal, consistent with a more variable and highly individualized diet in Nunavut.

Conclusions: Together, these results shows that the traditional Inuit diet and lifestyle has an impact on the composition, diversity and stability of the Inuit gut microbiome, even if the seasonality of the diet is less pronounced than expected, perhaps due to an increasingly westernized diet.
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http://dx.doi.org/10.1186/s40168-017-0370-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5689144PMC
November 2017

Cooking and co-ingested polyphenols reduce in vitro methylmercury bioaccessibility from fish and may alter exposure in humans.

Sci Total Environ 2018 Mar 31;616-617:863-874. Epub 2017 Oct 31.

Center for Northern Studies (CEN), Département de Sciences Biologiques, Université de Montréal, 90 Vincent-d'Indy, Montreal H2V2S9, Canada; ÉcoLac, Département de Sciences Biologiques, Université de Montréal, 90 Vincent-d'Indy, Montreal H2V2S9, Canada; Groupe de Recherche Interuniversitaire en Limnologie et en Environnement Aquatique (GRIL), Département de Sciences Biologiques, Université de Montréal, 90 Vincent-d'Indy, Montreal H2V2S9, Canada. Electronic address:

Fish consumption is a major pathway for mercury exposure in humans. Current guidelines and risk assessments assume that 100% of methylmercury (MeHg) in fish is absorbed by the human body after ingestion. However, a growing body of literature suggests that this absorption rate may be overestimated. We used an in vitro digestion method to measure MeHg bioaccessibility in commercially-purchased fish, and investigated the effects of dietary practices on MeHg bioaccessibility. Cooking had the greatest effect, decreasing bioaccessibility on average to 12.5±5.6%. Polyphenol-rich beverages also significantly reduced bioaccessibility to 22.7±3.8% and 28.6±13.9%, for green and black tea respectively. We confirmed the suspected role of polyphenols in tea as being a driver of MeHg's reduced bioaccessibility, and found that epicatechin, epigallocatechin gallate, rutin and cafeic acid could individually decrease MeHg bioaccessibility by up to 55%. When both cooking and polyphenol-rich beverage treatments were combined, only 1% of MeHg remained bioaccessible. These results call for in vivo validation, and suggest that dietary practices should be considered when setting consumer guidelines for MeHg. More realistic risk assessments could promote consumption of fish as a source of fatty acids, which can play a protective role against cardiovascular disease.
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http://dx.doi.org/10.1016/j.scitotenv.2017.10.236DOI Listing
March 2018

Gut Microbiome of the Canadian Arctic Inuit.

mSphere 2017 Jan-Feb;2(1). Epub 2017 Jan 4.

Département de sciences biologiques, Université de Montréal, Montreal, Quebec, Canada.

Diet is a major determinant of community composition in the human gut microbiome, and "traditional" diets have been associated with distinct and highly diverse communities, compared to Western diets. However, most traditional diets studied have been those of agrarians and hunter-gatherers consuming fiber-rich diets. In contrast, the Inuit of the Canadian Arctic have been consuming a traditional diet low in carbohydrates and rich in animal fats and protein for thousands of years. We hypothesized that the Inuit diet and lifestyle would be associated with a distinct microbiome. We used deep sequencing of the 16S rRNA gene to compare the gut microbiomes of Montrealers with a Western diet to those of the Inuit consuming a range of traditional and Western diets. At the overall microbial community level, the gut microbiomes of Montrealers and Inuit were indistinguishable and contained similar levels of microbial diversity. However, we observed significant differences in the relative abundances of certain microbial taxa down to the subgenus level using oligotyping. For example, spp., which have been previously associated with high-fiber diets, were enriched in Montrealers and among the Inuit consuming a Western diet. The gut microbiomes of Inuit consuming a traditional diet also had significantly less genetic diversity within the genus, suggesting that a low-fiber diet might not only select against but also reduce its diversity. Other microbes, such as , were associated with geography as well as diet, suggesting limited dispersal to the Arctic. Our report provides a snapshot of the Inuit microbiome as Western-like in overall community structure but distinct in the relative abundances and diversity of certain genera and strains. Non-Western populations have been shown to have distinct gut microbial communities shaped by traditional diets. The hitherto-uncharacterized microbiome of the Inuit may help us to better understand health risks specific to this population such as diabetes and obesity, which increase in prevalence as many Inuit transition to a Western diet. Here we show that even Inuit consuming a mostly traditional diet have a broadly Western-like microbiome. This suggests that similarities between the Inuit diet and the Western diet (low fiber, high fat) may lead to a convergence of community structures and diversity. However, certain species and strains of microbes have significantly different levels of abundance and diversity in the Inuit, possibly driven by differences in diet. Furthermore, the Inuit diet provides an exception to the correlation between traditional diets and high microbial diversity, potentially due to their transitioning diet. Knowledge of the Inuit microbiome may provide future resources for interventions and conservation of Inuit heritage.
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http://dx.doi.org/10.1128/mSphere.00297-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5214747PMC
January 2017

Photodemethylation of Methylmercury in Eastern Canadian Arctic Thaw Pond and Lake Ecosystems.

Environ Sci Technol 2016 Apr 22;50(7):3511-20. Epub 2016 Mar 22.

Centre d'études nordiques (CEN), Département de sciences biologiques, Université de Montréal , 90 Vincent-d'Indy, Montréal, Quebec Canada.

Permafrost thaw ponds of the warming Eastern Canadian Arctic are major landscape constituents and often display high levels of methylmercury (MeHg). We examined photodegradation potentials in high-dissolved organic matter (DOC) thaw ponds on Bylot Island (BYL) and a low-DOC oligotrophic lake on Cornwallis Island (Char Lake). In BYL, the ambient MeHg photodemethylation (PD) rate over 48 h of solar exposure was 6.1 × 10(-3) m(2) E(-1), and the rate in MeHg amended samples was 9.3 × 10(-3) m(2) E(-1). In contrast, in low-DOC Char Lake, PD was only observed in the first 12 h, which suggests that PD may not be an important loss process in polar desert lakes. Thioglycolic acid addition slowed PD, while glutathione and chlorides did not impact northern PD rates. During an ecosystem-wide experiment conducted in a covered BYL pond, there was neither net MeHg increase in the dark nor loss attributable to PD following re-exposure to sunlight. We propose that high-DOC Arctic thaw ponds are more prone to MeHg PD than nearby oligotrophic lakes, likely through photoproduction of reactive species rather than via thiol complexation. However, at the ecosystem level, these ponds, which are widespread through the Arctic, remain likely sources of MeHg for neighboring systems.
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http://dx.doi.org/10.1021/acs.est.5b04921DOI Listing
April 2016

Spatio-Temporal Multiscale Denoising of Fluoroscopic Sequence.

IEEE Trans Med Imaging 2016 06 21;35(6):1565-74. Epub 2016 Jan 21.

In the past 20 years, a wide range of complex fluoroscopically guided procedures have shown considerable growth. Biologic effects of the exposure (radiation induced burn, cancer) lead to reduce the dose during the intervention, for the safety of patients and medical staff. However, when the dose is reduced, image quality decreases, with a high level of noise and a very low contrast. Efficient restoration and denoising algorithms should overcome this drawback. We propose a spatio-temporal filter operating in a multi-scales space. This filter relies on a first order, motion compensated, recursive temporal denoising. Temporal high frequency content is first detected and then matched over time to allow for a strong denoising in the temporal axis. We study this filter in the curvelet domain and in the dual-tree complex wavelet domain, and compare those results to state of the art methods. Quantitative and qualitative analysis on both synthetic and real fluoroscopic sequences demonstrate that the proposed filter allows a great dose reduction.
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http://dx.doi.org/10.1109/TMI.2016.2520092DOI Listing
June 2016

High Methylmercury in Arctic and Subarctic Ponds is Related to Nutrient Levels in the Warming Eastern Canadian Arctic.

Environ Sci Technol 2015 Jul 12;49(13):7743-53. Epub 2015 Jun 12.

†Centre d'études nordiques, Département de sciences biologiques, Université de Montréal, Montreal, Quebec Canada, H2V 2S9.

Permafrost thaw ponds are ubiquitous in the eastern Canadian Arctic, yet little information exists on their potential as sources of methylmercury (MeHg) to freshwaters. They are microbially active and conducive to methylation of inorganic mercury, and are also affected by Arctic warming. This multiyear study investigated thaw ponds in a discontinuous permafrost region in the Subarctic taiga (Kuujjuarapik-Whapmagoostui, QC) and a continuous permafrost region in the Arctic tundra (Bylot Island, NU). MeHg concentrations in thaw ponds were well above levels measured in most freshwater ecosystems in the Canadian Arctic (>0.1 ng L(-1)). On Bylot, ice-wedge trough ponds showed significantly higher MeHg (0.3-2.2 ng L(-1)) than polygonal ponds (0.1-0.3 ng L(-1)) or lakes (<0.1 ng L(-1)). High MeHg was measured in the bottom waters of Subarctic thaw ponds near Kuujjuarapik (0.1-3.1 ng L(-1)). High water MeHg concentrations in thaw ponds were strongly correlated with variables associated with high inputs of organic matter (DOC, a320, Fe), nutrients (TP, TN), and microbial activity (dissolved CO2 and CH4). Thawing permafrost due to Arctic warming will continue to release nutrients and organic carbon into these systems and increase ponding in some regions, likely stimulating higher water concentrations of MeHg. Greater hydrological connectivity from permafrost thawing may potentially increase transport of MeHg from thaw ponds to neighboring aquatic ecosystems.
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http://dx.doi.org/10.1021/acs.est.5b00763DOI Listing
July 2015

Unsuspected functional disparity in Devonian fishes revealed by tooth morphometrics?

Naturwissenschaften 2014 Sep 31;101(9):735-43. Epub 2014 Jul 31.

Institut des Sciences de l'Evolution, Université Montpellier, UMR 5554, CNRS, IRD, 34095, Montpellier, France.

The shape of features involved in key biological functions, such as teeth in nutrition, can provide insights into ecological processes even in ancient time, by linking the occupation of the morphological space (disparity) to the occupation of the ecological space. Investigating disparity in radiating groups may provide insights into the ecological diversification underlying evolution of morphological diversity. Actinopterygian fishes initiated their radiation in the Devonian, a period characterized by the diversification of marine ecosystem. Although a former morpho-functional analysis of jaw shape concluded to conservative and poorly diversified morphologies in this early part of their history, fish tooth disparity evidenced here an unsuspected diversity of possible functional significance in the pivotal period of the Late Devonian (Famennian). All teeth being caniniforms, some were stocky and robust, in agreement with expectations for active generalist predators. More surprisingly, elongated teeth also occurred at the beginning of Famennian. Their needle-like shape challenges morpho-functional interpretations by making them fragile in response to bending or torsion. The occurrence of both types of fish teeth during the beginning of the Famennian points to a discrete but real increase in disparity, thus testifying a first burst of feeding specialization despite overall conservative jaw morphology. The disappearance of these needle-like teeth in the Late Famennian might have been related to a relay in dental diversity with abundant co-occurring groups, namely conodonts and chondrichthyans (sharks).
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http://dx.doi.org/10.1007/s00114-014-1211-1DOI Listing
September 2014

Mercury in freshwater ecosystems of the Canadian Arctic: recent advances on its cycling and fate.

Sci Total Environ 2015 Mar 30;509-510:41-66. Epub 2014 Jun 30.

Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.

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.
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http://dx.doi.org/10.1016/j.scitotenv.2014.05.151DOI Listing
March 2015

Mercury in the marine environment of the Canadian Arctic: review of recent findings.

Sci Total Environ 2015 Mar 19;509-510:67-90. Epub 2014 Jun 19.

Centre for Earth Observation Science, 497 Wallace Bldg., University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2; Fisheries and Oceans Canada, Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba, Canada R3T 2N6.

This review summarizes data and information which have been generated on mercury (Hg) in the marine environment of the Canadian Arctic since the previous Canadian Arctic Contaminants Assessment Report (CACAR) was released in 2003. Much new information has been collected on Hg concentrations in marine water, snow and ice in the Canadian Arctic. The first measurements of methylation rates in Arctic seawater indicate that the water column is an important site for Hg methylation. Arctic marine waters were also found to be a substantial source of gaseous Hg to the atmosphere during the ice-free season. High Hg concentrations have been found in marine snow as a result of deposition following atmospheric mercury depletion events, although much of this Hg is photoreduced and re-emitted back to the atmosphere. The most extensive sampling of marine sediments in the Canadian Arctic was carried out in Hudson Bay where sediment total Hg (THg) concentrations were low compared with other marine regions in the circumpolar Arctic. Mass balance models have been developed to provide quantitative estimates of THg fluxes into and out of the Arctic Ocean and Hudson Bay. Several recent studies on Hg biomagnification have improved our understanding of trophic transfer of Hg through marine food webs. Over the past several decades, Hg concentrations have increased in some marine biota, while other populations showed no temporal change. Marine biota also exhibited considerable geographic variation in Hg concentrations with ringed seals, beluga and polar bears from the Beaufort Sea region having higher Hg concentrations compared with other parts of the Canadian Arctic. The drivers of these variable patterns of Hg bioaccumulation, both regionally and temporally, within the Canadian Arctic remain unclear. Further research is needed to identify the underlying processes including the interplay between biogeochemical and food web processes and climate change.
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http://dx.doi.org/10.1016/j.scitotenv.2014.05.133DOI Listing
March 2015

Disparity changes in 370 Ma Devonian fossils: the signature of ecological dynamics?

PLoS One 2012 27;7(4):e36230. Epub 2012 Apr 27.

Institut des Sciences de l'Evolution, Université Montpellier 2, CNRS, Montpellier, France.

Early periods in Earth's history have seen a progressive increase in complexity of the ecosystems, but also dramatic crises decimating the biosphere. Such patterns are usually considered as large-scale changes among supra-specific groups, including morphological novelties, radiation, and extinctions. Nevertheless, in the same time, each species evolved by the way of micro-evolutionary processes, extended over millions of years into the evolution of lineages. How these two evolutionary scales interacted is a challenging issue because this requires bridging a gap between scales of observation and processes. The present study aims at transferring a typical macro-evolutionary approach, namely disparity analysis, to the study of fine-scale evolutionary variations in order to decipher what processes actually drove the dynamics of diversity at a micro-evolutionary level. The Late Frasnian to Late Famennian period was selected because it is punctuated by two major macro-evolutionary crises, as well as a progressive diversification of marine ecosystem. Disparity was estimated through this period on conodonts, tooth-like fossil remains of small eel-like predators that were part of the nektonic fauna. The study was focused on the emblematic genus of the period, Palmatolepis. Strikingly, both crises affected an already impoverished Palmatolepis disparity, increasing risks of random extinction. The major disparity signal rather emerged as a cycle of increase and decrease in disparity during the inter-crises period. The diversification shortly followed the first crisis and might correspond to an opportunistic occupation of empty ecological niche. The subsequent oriented shrinking in the morphospace occupation suggests that the ecological space available to Palmatolepis decreased through time, due to a combination of factors: deteriorating climate, expansion of competitors and predators. Disparity changes of Palmatolepis thus reflect changes in the structure of the ecological space itself, which was prone to evolve during this ancient period where modern ecosystems were progressively shaped.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0036230PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3338699PMC
September 2012

Use of X-ray computed microtomography for non-invasive determination of wood anatomical characteristics.

J Struct Biol 2004 Oct;148(1):11-21

Laboratory of Plant Ecology, Ghent University, Belgium.

Quantitative analysis of wood anatomical characteristics is usually performed using classical microtomy yielding optical micrographs of stained thin sections. It is time-consuming to obtain high quality cross-sections from microtomy, and sections can be damaged. This approach, therefore, is often impractical for those who need quick acquisition of quantitative data on vessel characteristics in wood. This paper reports results of a novel approach using X-ray computed microtomography (microCT) for non-invasive determination of wood anatomy. As a case study, stem wood samples of a 2-year-old beech (Fagus sylvatica L.) and a 3-year-old oak (Quercus robur L.) tree were investigated with this technique, beech being a diffuse-porous and oak a ring-porous tree species. MicroCT allowed non-invasive mapping of 2-D transverse cross-sections of both wood samples with micrometer resolution. Self-developed software 'microCTanalysis' was used for image processing of the 2-D cross-sections in order to automatically determine the inner vessel diameters, the transverse cross-sectional surface area of the vessels, the vessel density and the porosity with computer assistance. Performance of this new software was compared with manual analysis of the same micrographs. The automatically obtained results showed no significant statistical differences compared to the manual measurements. Visual inspection of the microCT slices revealed very good correspondence with the optical micrographs. Statistical analysis confirmed this observation in a more quantitative way, and it was, therefore, argued that anatomical analysis of optical micrographs can be readily substituted by automated use of microCT, and this without loss of accuracy. Furthermore, as an additional application of microCT, the 3-D renderings of the internal microstructure of the xylem vessels for both the beech and the oak sample could be reconstructed, clearly showing the complex nature of vessel networks. It can be concluded that the use of microCT in wood science offers an interesting potential for all those who need quantitative data of wood anatomical characteristics in either the 2-D or the 3-D space.
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http://dx.doi.org/10.1016/j.jsb.2004.05.001DOI Listing
October 2004