Marc Amyot | Université de Montréal (original) (raw)

Papers by Marc Amyot

Geochimica et Cosmochimica Acta

Journal of Hazardous Materials

Estuarine, Coastal and Shelf Science

Water Resources Research

Co‐loading of mercury (Hg) with dissolved organic carbon (DOC) is a key driver of the observed sp... more Co‐loading of mercury (Hg) with dissolved organic carbon (DOC) is a key driver of the observed spatial and temporal Hg patterns among aquatic ecosystems. Their strong biogeochemical coupling has spurred the use of DOC as a predictor of Hg concentrations and exports in boreal regions where sampling logistics for Hg are costly and complex. Yet relationships between Hg and methylmercury (MeHg) with DOC have recently been shown to be highly variable in terms of slope and strength, suggesting that mechanisms other than co‐transport along the land‐water continuum may drive the relationship between Hg and DOC across landscapes. In this study, we explore the relationship between Hg and MeHg with DOC across 18 boreal rivers collectively draining over 350,000 km2 of the eastern James Bay territory (Québec), comprising watersheds with a wide range of vegetation, water residence time and riverine DOC concentrations and optical properties. Our results show that although a large portion of the va...

Journal of Geophysical Research: Biogeosciences

Large rivers are major contributors of mercury (Hg) fluxes to the ocean, as they integrate proces... more Large rivers are major contributors of mercury (Hg) fluxes to the ocean, as they integrate processes of loading and loss occurring at the watershed level. Stream‐scale studies have revealed that specific landscape properties, such as wetlands or lakes, are hotspots for Hg and methylmercury (MeHg) loading, sinks and transformation, but we still do not know how they operate at the whole network scale and over large geographic gradients. In this study, we evaluate how landscape metrics are related to riverine concentrations and yields of total Hg and MeHg in 18 large boreal rivers draining watersheds ranging from 44 to 209,453 km2, distributed along a 650 km latitudinal transect in the James Bay region of Québec. Our analyses of landscape metrics using elastic net models and mixed models reinforce the role of wetlands as sources of MeHg, but further show that surface coverage of water in the watershed is the major driver of both Hg and MeHg concentrations and fluxes at the whole networ...

Chemosphere

Current guidelines tend to limit fish consumption based on mercury (Hg) or monomethylmercury (MeH... more Current guidelines tend to limit fish consumption based on mercury (Hg) or monomethylmercury (MeHg) content in fish flesh, without considering the presence of antagonist chemical elements that could modulate Hg toxicity. However, it is difficult to assess the potential for antagonistic interactions of these elements since their covariation within muscle tissues is poorly known. Here we present the first study simultaneously mapping multiple metal(oid)s (Hg, As and Se), lipids and proteins in fish fillets in order to assess the magnitude of intra-organ variability of metals and the potential for antagonistic interactions. We mapped two fish species (Striped Bass and Northern Pike) with contrasting muscular structure with respect to the presence of white, intermediate and red muscles. In individual Striped Bass muscle tissues, metals varied on average by 2.2-fold. Methylmercury and selenium covaried strongly and were related to protein content as assessed by % N; arsenic was inversely related to these elements and was associated with the lipid fraction of the muscle. In Pike, no such relationship was found because the contents in proteins and lipids were less variable. Arsenic speciation revealed that arsenobetaine and arsenolipids were the only As species in those fish species, whereas the toxic inorganic As species (As 3þ) was under the detection limit. Arsenobetaine was related to % N, whereas arsenolipids covaried with % lipids. Elemental associations found with muscle lipids and proteins could help explain changes in bioaccumulation patterns within and between individuals with potential implications on fish toxicology, biomonitoring and human consumption guidelines.

Journal of Hazardous Materials Advances, 2021

Abstract The redox transformations of arsenic (As) in lakes are thought to be mainly controlled b... more Abstract The redox transformations of arsenic (As) in lakes are thought to be mainly controlled by algal/microbial processes. We tested if photochemical oxidation could also be a significant redox process in northern freshwater systems. We exposed filtered natural water samples from four northern mine-impacted lakes (Northwest Territories, Canada) and three unimpacted ponds (Nunavik, Canada) to simulated solar radiation, and followed As(III) oxidation. During short-term incubation experiments (less than 8 h), all samples amended with As(III) displayed a rapid photooxidation (ca. 0.06-0.27 h−1) whereas no significant oxidation was observed in the dark. This photooxidation process was controlled by UV radiation, was influenced by short-lived oxidants and was partly driven by the concentrations of organic matter. Natural As complexes in unamended water samples were more rapidly photooxidized than in samples with As(III) amendments. Addition of goethite or simulation of snowmelt did not alter photooxidation rates significantly. Overall, these results imply that photooxidation of As should be considered as a potentially significant mechanism controlling inorganic As speciation in aquatic systems. This is particularly true for northern systems affected by mining activities and by changes of inputs of organic matter related to climate change.

Water Resources Research, 2020

Reservoirs are known to accelerate the mobilization and cycling of mercury and carbon as a result... more Reservoirs are known to accelerate the mobilization and cycling of mercury and carbon as a result of flooding of terrestrial organic matter, which can lead to environmental concerns at local and broader spatial scales. We explored the covariation of mercury (Hg) and carbon (C) functional pools in natural and recently dammed portions of the aquatic network of the Romaine River watershed in Northern Quebec, Canada, to understand how the fate of these elements varies across systems with contrasting hydrology and environmental conditions. We found that total Hg (THg) concentrations in surface waters were relatively constant along the network, whereas both the concentrations and proportions of MeHg tended to increase in reservoirs compared to surrounding nonflooded systems, and along the cascade of reservoirs. Whereas THg was related to total and terrestrial pools of dissolved organic carbon (DOC), MeHg was weakly related to DOC but strongly linked to surface concentrations of CO2, as we...

Environmental Science & Technology, 2021

Unlike large dams which favor methylation of Hg in flooded soils over long periods, run-of-river ... more Unlike large dams which favor methylation of Hg in flooded soils over long periods, run-of-river dams are designed to flood a limited area of soils and are therefore not expected to significantly affect mercury (Hg) cycling or carbon processing. We studied the Hg and carbon cycles within food webs from several sectors along the Saint-Maurice River, Quebec, Canada, that differ in how they are influenced by two run-of-river dams and other watershed disturbances. We observed peak Hg concentrations in fish five-year post-impoundment, but these levels were reduced three years after this peak. Methylmercury concentrations in low trophic level fish and invertebrates were related to their carbon source (δ 13 C) rather than their trophic positions (δ 15 N). Biomagnification, measured by trophic magnification slopes, was driven mainly by methylmercury concentrations in low trophic level organisms and environmental factors related to organic matter degradation and Hg methylation. River sectors, δ 13 C, and δ 15 N predicted up to 80% of the variability in food web methylmercury concentrations. The installation of run-of-river dams and the related pondages, in association with other watershed disturbances, altered carbon processing, promoted Hg methylation and its accumulation at the base of the food web, and led to a temporary increase in Hg levels in fish.

Environmental Pollution, 2019

Our knowledge of the processes leading to the bioaccumulation of rare earth elements (REE) in aqu... more Our knowledge of the processes leading to the bioaccumulation of rare earth elements (REE) in aquatic biota is limited. As the contamination of freshwater ecosystems by anthropogenic REE have recently been reported, it becomes increasingly urgent to understand how these metals are transferred to freshwater organisms in order to develop appropriate guidelines. We exposed rainbow trout (Oncorhynchus mykiss) to an REE, yttrium (Y), to either a range of Y-contaminated prey (Daphnia magna) or a range of Ycontaminated water. For the feeding experiment, the relationship between the Y assimilation by O. mykiss and the Y subcellular fractionation in D. magna was evaluated. Assimilation efficiency of Y by O. mykiss was low, ranging from 0.8 to 3%. These values were close to the proportion of Y accumulated in D. magna cytosol, 0.6-2%, a theoretical trophically available fraction. Moreover, under our laboratory conditions, water appeared as a poor source of Y transfer to O. mykiss. Regardless of the source of contamination, a similar pattern of Y bioaccumulation among O. mykiss tissues was revealed: muscles < liver < gills < intestine. We conclude that the trophic transfer potential of Y is low and the evaluation of Y burden in prey cytosol appears to be a relevant predictor of Y assimilation by their consumers.

PLOS ONE, 2019

A subarctic fish community in mine-impacted Yellowknife Bay (Great Slave Lake, Northwest Territor... more A subarctic fish community in mine-impacted Yellowknife Bay (Great Slave Lake, Northwest Territories, Canada) was investigated for biological and ecological processes controlling arsenic bioaccumulation. Total concentrations of arsenic, antimony, and metals were measured in over 400 fishes representing 13 species, and primary producers and consumers were included to characterize food web transfer. Yellowknife Bay had slightly more arsenic in surface waters (~3 μg/L) relative to the main body of Great Slave Lake (<1 μg/L), resulting in twofold higher total arsenic concentrations in muscle of burbot (Lota lota), lake whitefish (Coregonus clupeaformis), and northern pike (Esox lucius). Other mining-associated contaminants, specifically antimony, lead, and silver, were typically below analytical detection in those fish species. No evidence was found for enhanced bioaccumulation of arsenic in longlived, slow-growing subarctic fishes. Food web biodilution of total arsenic occurred between primary producers, aquatic invertebrates, and fish, although trophic position did not explain arsenic concentrations among fishes. Pelagic-feeding species had higher total arsenic concentrations compared to littoral fishes. Arsenic accumulated in subarctic fishes to comparable levels as fishes from lakes around the world with similar water arsenic concentrations. This first comprehensive study for a subarctic freshwater food web identified the importance of water exposure, biodilution, and habitat-specific feeding on arsenic bioaccumulation.

Environmental Science & Technology, 2018

Scientific reports, Jan 30, 2018

Human activities have increased the global circulation of mercury, a potent neurotoxin. Mercury c... more Human activities have increased the global circulation of mercury, a potent neurotoxin. Mercury can be converted into methylmercury, which biomagnifies along aquatic food chains and leads to high exposure in fish-eating populations. Here we quantify temporal trends in the ocean-to-land transport of total mercury and methylmercury from fisheries and we estimate potential human mercury intake through fish consumption in 175 countries. Mercury export from the ocean increased over time as a function of fishing pressure, especially on upper-trophic-level organisms. In 2014, over 13 metric tonnes of mercury were exported from the ocean. Asian countries were important contributors of mercury export in the last decades and the western Pacific Ocean was identified as the main source. Estimates of per capita mercury exposure through fish consumption showed that populations in 38% of the 175 countries assessed, mainly insular and developing nations, were exposed to doses of methylmercury above...

Limnology and Oceanography: Methods, 2017

Low molecular mass (LMM) thiols are ubiquitous organosulfur peptides that play key roles in bioge... more Low molecular mass (LMM) thiols are ubiquitous organosulfur peptides that play key roles in biogeochemical element cycling. These LMM thiols, found at low concentrations in the water column, are highly sensitive to oxidation and degradation processes which may lead to problems with detection and analysis. Natural water samples should be stored and handled appropriately to reduce thiol loss in the time period from sampling to analysis. Storage temperatures were investigated for optimal preservation of four thiols species. Thiol degradation varied between species and was generally slower in samples stored at −80°C and 4°C compared to −20°C and 21°C. Two natural freshwater matrices were tested, one from a fluvial lake subject to agricultural inputs and one from an oligotrophic pristine lake. After 6 d of storage at −20°C, the most affected thiol species was glutathione with a degradation rate (kD) of (3.0 ± 0.5) × 10−3 h−1 in the fluvial lake water and l‐cysteine‐l‐glycine (CYS‐GLY) wi...

Environmental Chemistry, 2011

Environmental context Recent research has been directed towards the exchange of microorganisms an... more Environmental context Recent research has been directed towards the exchange of microorganisms and chemical compounds between snow and air. We investigate how microorganisms and chemical species in snow from the Arctic and temperate regions are transferred to the atmosphere and altered by the sun's energy. Results suggest that snow photo-biochemical reactions, in addition to physical‐chemical reactions, should be considered in describing organic matter in air–snow exchanges, and in investigations of climate change. Field and laboratory studies of organic compounds in snow (12 species; concentrations ≤17 µg L–1) were conducted and microorganisms in snow and aerosols at urban and Arctic sites were investigated (snow: total bacteria count ≤40000 colony forming units per millilitre (CFU mL–1), fungi ≤400 CFU mL–1; air: bacteria ≤2.2 × 107 CFU m–3, fungi ≤84 CFU m–3). Bio-organic material is transferred between snow and air and influence on snow-air exchange processes is demonstrated...

Environmental Pollution, 2021

Diet, age, and growth rate influences on fish mercury concentrations were investigated for Arctic... more Diet, age, and growth rate influences on fish mercury concentrations were investigated for Arctic char (Salvelinus alpinus) and brook trout (Salvelinus fontinalis) in lakes of the eastern Canadian Arctic. We hypothesized that faster-growing fish have lower mercury concentrations because of growth dilution, a process whereby more efficient growth dilutes a fish's mercury burden. Using datasets of 55 brook trout and 133 Arctic char, linear regression modelling showed fish age and diet indices were the dominant explanatory variables of muscle mercury concentrations for both species. Faster-growing fish (based on length-at-age) fed at a higher trophic position, and as a result, their mercury concentrations were not lower than slower-growing fish. Muscle RNA/DNA ratios were used as a physiological indicator of short-term growth rates (days to weeks). Slower growth of Arctic char, inferred from RNA/DNA ratios, was found in winter versus summer and in polar desert versus tundra lakes, but RNA/DNA ratio was (at best) a weak predictor of fish mercury concentration. Net effects of diet and age on mercury concentration were greater than any potential offset by biomass dilution in faster-growing fish. In these resource-poor Arctic lakes, faster growth was associated with feeding at a higher trophic position, likely due to greater caloric (and mercury) intake, rather than growth efficiency.

Goldschmidt Abstracts, 2020

Environmental Research, 2016

Highlights-93 lightening soaps and 98 creams were purchased in West Africa and Canada.-Mercury, h... more Highlights-93 lightening soaps and 98 creams were purchased in West Africa and Canada.-Mercury, hydroquinone and clobetasol propionate were measured.-68 to 84% of all creams exceeded regulatory guidelines.-Levels reported on labels were often inaccurate.