Contaminants and Nutrients in Traditional Food Fishes in Kluane Lake, YT

This report, produced for Kluane First Nation, details in plain-language the major findings of their joint research project, investigating levels of environmental contaminants and nutrients and fatty acids in fish from their traditional territory.The outcomes of a collaborative project led by the Kluane First Nation (KFN), in partnership with the Arctic Institute of Community-Based Research (AICBR), the University of Waterloo, and Western University, are presented here. This research project was initiated by KFN to answer questions about contaminants in fish in Kluane Lake, to determine the health benefits of eating fish from Kluane Lake, and to develop a youth exchange between KFN and university partners. The funded program has accomplished all of the program objectives. The key scientific findings are: - Average concentrations of mercury in Lake Trout and Lake Whitefish are beneath the Health Canada subsistence consumption guideline for mercury. - No Lake Trout or Lake Whitefish of any size exceed the Health Canada commercial sale guideline. - Lake Trout and Lake Whitefish from Kluane Lake have extremely low concentrations of mercury compared to other northern Canadian lakes. - Concentrations of organochlorines in Lake Trout < 750 mm long and average concentrations in Lake Whitefish are beneath US EPA consumption guidelines. - Lake Trout and Lake Whitefish from Kluane Lake have similar or lower concentrations of organochlorines compared to other northern Canadian lakes. - Lake Trout and Lake Whitefish in Kluane Lake are rich sources of omega-3 fatty acids and beneficial micronutrients, such as selenium, zinc, and copper. - Ratios of selenium (nutrient) to mercury (contaminant) in both Lake Trout and Lake Whitefish from Kluane Lake are better than in any other lake in Canada’s north. KFN, AICBR, the University of Waterloo and Western University had a very successful exchange of youth and community members in Spring 2016. KFN youth were involved in many aspects of the research, including fish collection and processing, and mercury analysis. This exchange will hopefully be the first of many that will empower and educate youth as well as contribute to both scientific and traditional knowledge (AICBR related project on traditional knowledge)Northern Contaminants Program || the Dän Keyi Renewable Resource Council, Surplus Fund || Yukon Fish and Wildlife Enhancement Trust || Northern Scientific Training Program || Wildlife Conservation Society-Weston Foundation Fellowship || Engineering Research Council, Discovery and Northern Research Supplement || Canada Research Chair Progra

A Synthesis of Rates and Controls on Elemental Mercury Evasion in the Great Lakes Basin

Rates of surface-air elemental mercury (Hgo) fluxes in the literature were synthesized for the Great Lakes Basin (GLB). For the majority of surfaces, fluxes were net positive (evasion). Digital land-cover data were combined with representative evasion rates and used to estimate annual Hgo evasion for the GLB (7.7 Mg/yr). This value is less than our estimate of total Hg deposition to the area (15.9 Mg/yr), suggesting the GLB is a net sink for atmospheric Hg. The greatest contributors to annual evasion for the basin are agricultural (~55%) and forest (~25%) land cover types, and the open water of the Great Lakes (~15%). Areal evasion rates were similar across most land cover types (range: 7.0 to 21.0 μg/m2-yr), with higher rates associated with urban (12.6 μg/m2-yr) and agricultural (21.0 μg/m2-yr) lands. Uncertainty in these estimates could be partially remedied through a unified methodological approach to estimating Hgo fluxes

Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

Climate change scenarios predict increases in temperature and organic matter supply from land to water, which affect trophic transfer of nutrients and contaminants in aquatic food webs. How essential nutrients, such as polyunsaturated fatty acids (PUFA), and potentially toxic contaminants, such as methylmercury (MeHg), at the base of aquatic food webs will be affected under climate change scenarios, remains unclear. The objective of this outdoor mesocosm study was to examine how increased water temperature and terrestrially-derived dissolved organic matter supply (tDOM; i.e., lake browning), and the interaction of both, will influence MeHg and PUFA in organisms at the base of food webs (i.e. seston; the most edible plankton size for zooplankton) in subalpine lake ecosystems. The interaction of higher temperature and tDOM increased the burden of MeHg in seston (\u3c 40 μm) and larger sized plankton (microplankton; 40–200 μm), while the MeHg content per unit biomass remained stable. However, PUFA decreased in seston, but increased in microplankton, consisting mainly of filamentous algae, which are less readily bioavailable to zooplankton. We revealed elevated dietary exposure to MeHg, yet decreased supply of dietary PUFA to aquatic consumers with increasing temperature and tDOM supply. This experimental study provides evidence that the overall food quality at the base of aquatic food webs deteriorates during ongoing climate change scenarios by increasing the supply of toxic MeHg and lowering the dietary access to essential nutrients of consumers at higher trophic levels

Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

Climate change scenarios predict increases in temperature and organic matter supply from land to water, which affect trophic transfer of nutrients and contaminants in aquatic food webs. How essential nutrients, such as polyunsaturated fatty acids (PUFA), and potentially toxic contaminants, such as methylmercury (MeHg), at the base of aquatic food webs will be affected under climate change scenarios, remains unclear. The objective of this outdoor mesocosm study was to examine how increased water temperature and terrestrially-derived dissolved organic matter supply (tDOM; i.e., lake browning), and the interaction of both, will influence MeHg and PUFA in organisms at the base of food webs (i.e. seston; the most edible plankton size for zooplankton) in subalpine lake ecosystems. The interaction of higher temperature and tDOM increased the burden of MeHg in seston (< 40 mu m) and larger sized plankton (microplankton; 40-200 mu m), while the MeHg content per unit biomass remained stable. However, PUFA decreased in seston, but increased in microplankton, consisting mainly of filamentous algae, which are less readily bioavailable to zooplankton. We revealed elevated dietary exposure to MeHg, yet decreased supply of dietary PUFA to aquatic consumers with increasing temperature and tDOM supply. This experimental study provides evidence that the overall food quality at the base of aquatic food webs deteriorates during ongoing climate change scenarios by increasing the supply of toxic MeHg and lowering the dietary access to essential nutrients of consumers at higher trophic levels

Mercury Biogeochemical Cycling: A Synthesis of Recent Scientific Advances

The focus of this paper is to briefly discuss the major advances in scientific thinking regarding: a) processes governing the fate and transport of mercury in the environment; b) advances in measurement methods; and c) how these advances in knowledge fit in within the context of the Minamata Convention on Mercury. Details regarding the information summarized here can be found in the papers associated with this Virtual Special Issue of STOTEN

Moisture contents regulate peat water-leachable concentrations of methylmercury, inorganic mercury, and dissolved organic matter from boreal peat soils

Boreal peatlands are “hotspots” of net methylmercury (MeHg) production and may become drier in the future due to climate change. This study investigates a critical gap by analyzing the nuanced relationship between soil moisture content and the release of MeHg, inorganic mercury (IHg), sulfate (SO42-), and dissolved organic matter (DOM) in a laboratory incubation of boreal peat soils. Dried peat soils exhibited heightened releases of IHg, MeHg, and SO42- during re-wetting events. Both dried and saturated peat soils released more DOM than moist peat soils during re-wetting events, and DOM released from dried soils had higher bioaccessibility than that from the saturated soils (p<0.05). There was an equilibrium of IHg concentrations between peat soils and pore waters, but long-term severe drought may disrupt this equilibrium and then release more IHg to pore waters during re-wetting events. Contrary to expectations, positive relationships between IHg concentrations and SUVA254 did not exist in all treatments. MeHg and SO42- were depleted quickly because there was no external input of Hg and SO42- to this static system. More bioaccessible DOM than aromatic DOM was released from peat soils with different soil moisture contents after 32 weeks during the re-wetting event (p<0.05). These results imply that re-wetting of peat soils after droughts can increase the release of MeHg from peat soils and may also increase net MeHg production due to the release of SO42- and bioaccessible DOM from peat soils, reshaping our understanding of soil moisture's role in mercury dynamics. This novel insight into soil moisture and MeHg dynamics carries significant implications for mitigating mercury contamination in aquatic ecosystems

Chemical Oxidation and Reduction Pathways of Mercury Relevant to Natural Waters: A Review

Mercury (Hg) pollution in the environment is a global issue and the toxicity of mercury depends on its speciation. Chemical redox reactions of mercury in an aquatic environment greatly impact on Hg evasion to the atmosphere and the methylation of mercury in natural waters. Identifying the abiotic redox pathways of mercury relevant to natural waters is important for predicting the transport and fate of Hg in the environment. The objective of this review is to summarize the current state of knowledge on specific redox reactions of mercury relevant to natural waters at a molecular level. The rate constants and factors affecting them, as well as the mechanistic information of these redox pathways, are discussed in detail. Increasing experimental evidence also implied that the structure of natural organic matter (NOM) play an important role in dark Hg(II) reduction, dark Hg(0) oxidation and Hg(II) photoreduction in the aquatic environment. Significant photooxidation pathways of Hg(0) identified are Hg(0) photooxidation by hydroxyl radical (OH&bull;) and by carbonate radical (CO3&minus;&bull;). Future research needs on improving the understanding of Hg redox cycling in natural waters are also proposed

The hydrology and methylmercury dynamics of a Precambrian Shield headwater peatland

Hydrobiogeochemical investigation of a small headwater peatland located in the Experimental Lakes Area, northwestern Ontario, Canada, examined the surface and subsurface hydrologic pathways and their relation to the movement and spatial variability of methylmercury (CH 3Hg+).T he hydrology of the peatland controls the mass flux of CH3Hg+ to a downstream pond from the terrestrial ecosystems and influences the production and/or accumulation of CH3Hg+ in the peatland

Mercury cycling in freshwater systems - An updated conceptual model

12 pages, 4 figuresThe widely accepted conceptual model of mercury (Hg) cycling in freshwater lakes (atmospheric deposition and runoff of inorganic Hg, methylation in bottom sediments and subsequent bioaccumulation and biomagnification in biota) is practically accepted as common knowledge. There is mounting evidence that the dominant processes that regulate inputs, transformations, and bioavailability of Hg in many lakes may be missing from this picture, and the fixation on the temperate stratified lake archetype is impeding our exploration of understudied, but potentially important sources of methylmercury to freshwater lakes. In this review, the importance of understudied biogeochemical processes and sites of methylmercury production are highlighted, including the complexity of redox transformations of Hg within the lake system itself, the complex assemblage of microbes found in biofilms and periphyton (two vastly understudied important sources of methylmercury in many freshwater ecosystems), and the critical role of autochthonous and allochthonous dissolved organic matter which mediates the net supply of methylmercury from the cellular to catchment scale. A conceptual model of lake Hg in contrasting lakes and catchments is presented, highlighting the importance of the autochthonous and allochthonous supply of dissolved organic matter, bioavailable inorganic mercury and methylmercury and providing a framework for future convergent research at the lab and field scales to establish more mechanistic process-based relationships within and among critical compartments that regulate methylmercury concentrations in freshwater ecosystemsWith the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI