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The fraction of MeHg in Beaufort beluga whales from feeding in the Beaufort Sea calculated based on different ratios (R) between the MeHg concentration of beluga diet in the Beaufort Sea and in the Bering Sea. The horizontal dashed line and the yellow shade indicate the observed beluga MeHg concentrations (mean AE standard error; wet weight based) across 2005-2012 from subsistence harvests in the BSS. The arrows point to the calculated fractions of MeHg in Beaufort beluga whales from foraging in the Beaufort Sea.
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High levels of methylmercury (MeHg) have been reported in Arctic marine biota, posing health risks to wildlife and human beings. Although MeHg concentrations of some Arctic species have been monitored for decades, the key environmental and ecological factors driving temporal trends of MeHg are largely unclear. We develop an ecosystem-based MeHg bio...
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Context 1
... we explore how Beaufort beluga MeHg concentrations vary depending on the extent of feeding in the Bering Sea vs. Beaufort Sea, under two scenarios of the concentration ratio (R ¼ 2 or 4) between the two Arctic regions (Fig. 5). The observed MeHg concentration of beluga came from subsistence harvests in the Mackenzie Delta, 39 where about 90% of the landed catch of Beaufort beluga in the past occurred in July, shortly aer their spring migration from Bering Sea. 96,100 Given belugas' foraging behavior in the Chukchi and Bering Seas prior to summering in the ...
Context 2
... in human populations 101,102 ), the MeHg uptake in the Chukchi and Bering seas should account for a signicant fraction of the MeHg burden in these beluga whales, even aer they forage in Beaufort for 1-2 months prior to the harvest. We estimate that only 16 to 44% of MeHg in Beaufort beluga whales comes from their food uptake in the Beaufort Sea (Fig. 5), revealing the necessity of monitoring Hg contamination in other feeding grounds (i.e., Chukchi and Bering Seas) for further understanding the levels and trends of the Hg burden in Beaufort ...
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The Ria de Aveiro is an important coastal lagoon for wildlife in Portugal, where the production of bivalves reaches approximately 2700 tonnes annually. However, the illegal overfishing of bivalves is frequent in this lagoon, which causes critical changes in the ecosystem. In this study, using a developed food-web model (Ecopath model), the ecologic...
Citations
... Not only is MeHg directly introduced into these systems, but also microbial Hg methylation in anaerobic sediments can be stimulated by wildfire runoff inputs [56]. However, fire has also resulted in lower soil, litterfall, throughfall, and stream water Hg due to volatilization and loss of organic soil horizon [57]. Changes to water chemistry, like DOC and pH, from wildfire runoff can mediate or enhance microbial methylation rates [53,58,59]. ...
Mercury (Hg) is a naturally occurring element, but atmospheric Hg has increased due to human activities since the industrial revolution. When deposited in aquatic environments, atmospheric Hg can be converted to methyl mercury (MeHg), which bioaccumulates in ecosystems and can cause neurologic and endocrine disruption in high quantities. While higher atmospheric Hg levels do not always translate to higher contamination in wildlife, museum specimens over the past 2 centuries have documented an increase in species that feed at higher trophic levels. Increased exposure to pollutants presents an additional threat to fish and wildlife populations already facing habitat loss or degradation due to global change. Additionally, Hg cycling and bioaccumulation are primarily driven by geophysical, ecological, and biogeochemical processes in the environment, all of which may be modulated by climate change. In this review, we begin by describing where, when, and how the Hg cycle may be altered by climate change and how this may impact wildlife exposure to MeHg. Next, we summarize the already observed physiological effects of increased MeHg exposure to wildlife and identify future climate change vulnerabilities. We illustrate the implications for wildlife managers through a case study and conclude by suggesting key areas for management action to mitigate harmful effects and conserve wildlife and habitats amid global change.
... While phytoplankton efficiently accumulate MeHg from the water column (Lee and Fisher 2016;Mason et al. 1995), suspension-feeding bivalves accumulate MeHg primarily from consumed phytoplankton (Metian et al. 2020;Pan and Wang 2011;Wang et al. 2004). Thus, they act as conduits of MeHg from the base of the food web to higher trophic levels (Blackmore and Wang 2004;Dang and Wang 2010;Li et al. 2022). Various species of suspension-feeding bivalves, including mussels (Mytilus edulis and Mytilus galloprovincialis), oysters (Crassostrea gigas and Isognomon alatus), and clams (Ruditapes philippinarum) are used globally as biomonitors as they are sessile and exposed to local pollutants (Briant et al. 2017;da Silveira Fiori et al. 2018;Giani et al. 2012;Goldberg 1975). ...
... For mammals, the liver is considered a primary organ for MeHg demethylation to inorganic mercury, although demethylation can also occur in kidneys, the gastro-intestinal tract and the brain (Chételat et al. 2020). Low percent MeHg is considered an indicator of active demethylation in the organ (Vahter et al. 1995;Eagles-Smith et al. 2009), and other lines of evidence for active demethylation include the presence of mercury-selenide nanoparticles (Gajdosechova et al. 2016) and mercury stable isotope tracing (Li et al. 2022;Evans et al. 2016). In a dosing experiment, mink fed a diet containing isotopespecific MeHg showed conversion of MeHg to inorganic mercury in both liver and kidney (Evans et al. 2016). ...
Wolverines are facultative scavengers that feed near the top of terrestrial food chains. We characterized concentrations of mercury and other trace elements in tissues of wolverine from a broad geographic area, representing much of their contemporary distribution in northwestern North America. We obtained tissues from 504 wolverines, from which mercury was measured on muscle (n = 448), kidney (n = 222), liver (n = 148), hair (n = 130), and brain (n = 52). In addition, methylmercury, seven trace elements (arsenic, cadmium, chromium, cobalt, lead, nickel, selenium), and arsenic compounds were measured on a subset of samples. Concentrations of mercury and other trace elements varied between tissues and were generally highest in kidney compared to brain, liver and muscle. Mercury was predominately as methylmercury in brain and muscle, but largely as inorganic mercury in liver and kidney. Mercury concentrations of hair were moderately correlated with those of internal tissues (Pearson r = 0.51–0.75, p ≤ 0.004), making hair a good non-lethal indicator of broad spatial or temporal differences in mercury exposure to wolverine. Arsenobetaine was the dominant arsenic compound identified in tissues, and arsenite, arsenocholine and dimethylarsinic acid were also detected. A preliminary risk assessment suggested the cadmium, lead, mercury, and selenium concentrations in our sample of wolverines were not likely to pose a risk of overt toxicological effects. This study generated a comprehensive dataset on mercury and other trace elements in wolverine, which will support future contaminants study of this northern terrestrial carnivore.
... 36 These past applications of EwE for the Beaufort Sea suggest that changes to the ecosystem were driven more by reductions in sea ice and increases in sea surface temperature (SST) compared to the harvest mortality impact 35 and that ecosystem stability (indicated by the trophic structure) has remained relatively stable over time. 36 Li et al. 34 developed an Ecotracer model to simulate MeHg bioaccumulation in the Canadian Beaufort Sea Shelf, which was able to capture real-world MeHg biomagnification patterns in the food web. ...
... 28 Other modules can also be used on top of the base Ecopath food web representation to add specific layers of capabilities. Here, we use Ecotracer for modeling contaminant bioaccumulation, using the Ecotracer module for the BSS developed by Li et al., 34 which itself built on the EwE model previously developed for the BSS. 37 In Ecotracer, the amount of MeHg in each functional group is based on predator−prey interactions, direct uptake of MeHg from seawater, internal metabolism, internal decay, and harvest (mortality). ...
... We use this time period to compare modeled MeHg concentrations to observed data presented by Loseto et al., 5 in which beluga MeHg concentrations were measured until 2012. Ecotracer parameters for the BSS model (uptake rate, elimination rate, and assimilation efficiency) are described by Li et al. 34 We adjusted the initial MeHg concentration conditions in Ecotracer to reflect 1970 conditions, the starting point of the simulation. We set the initial concentrations for each group according to the concentration output from a parametrized model run at a steady state with the estimated 1970 environmental (i.e., water) concentration. ...
While mercury occurs naturally in the environment, human activity has significantly disturbed its biogeochemical cycle. Inorganic mercury entering aquatic systems can be transformed into methylmercury, a strong neurotoxicant that builds up in organisms and affects ecosystem and public health. In the Arctic, top predators such as beluga whales, an ecologically and culturally significant species for many Inuit communities, can contain high concentrations of methylmercury. Historical mercury concentrations in beluga in the western Canadian Arctic’s Beaufort Sea cannot be explained by mercury emission trends alone; in addition, they could potentially be driven by climate change impacts, such as rising temperatures and sea ice melt. These changes can affect mercury bioaccumulation through different pathways, including ecological and mercury transport processes. In this study, we explore key drivers of mercury bioaccumulation in the Beaufort Sea beluga population using Ecopath with Ecosim, an ecosystem modeling approach, and scenarios of environmental change informed by Western Science and Inuvialuit Knowledge. Comparing the effect of historical sea ice cover, sea surface temperature, and freshwater discharge time series, modeling suggests that the timing of historical increases and decreases in beluga methylmercury concentrations can be better explained by the resulting changes to ecosystem productivity rather than by those to mercury inputs and that all three environmental drivers could partially explain the decrease in mercury concentrations in beluga after the mid-1990s. This work highlights the value of multiple knowledge systems and exploratory modeling methods in understanding environmental change and contaminant cycling. Future work building on this research could inform climate change adaptation efforts and inform management decisions in the region.
... 36 These past applications of EwE for the Beaufort Sea suggest that changes to the ecosystem were driven more by reductions in sea ice and increases in sea surface temperature (SST) compared to the harvest mortality impact 35 and that ecosystem stability (indicated by the trophic structure) has remained relatively stable over time. 36 Li et al. 34 developed an Ecotracer model to simulate MeHg bioaccumulation in the Canadian Beaufort Sea Shelf, which was able to capture real-world MeHg biomagnification patterns in the food web. ...
... 28 Other modules can also be used on top of the base Ecopath food web representation to add specific layers of capabilities. Here, we use Ecotracer for modeling contaminant bioaccumulation, using the Ecotracer module for the BSS developed by Li et al., 34 which itself built on the EwE model previously developed for the BSS. 37 In Ecotracer, the amount of MeHg in each functional group is based on predator−prey interactions, direct uptake of MeHg from seawater, internal metabolism, internal decay, and harvest (mortality). ...
... We use this time period to compare modeled MeHg concentrations to observed data presented by Loseto et al., 5 in which beluga MeHg concentrations were measured until 2012. Ecotracer parameters for the BSS model (uptake rate, elimination rate, and assimilation efficiency) are described by Li et al. 34 We adjusted the initial MeHg concentration conditions in Ecotracer to reflect 1970 conditions, the starting point of the simulation. We set the initial concentrations for each group according to the concentration output from a parametrized model run at a steady state with the estimated 1970 environmental (i.e., water) concentration. ...
Climate change impacts have been particularly acute and rapid in the Arctic, raising concerns about the conservation of key ecologically and culturally significant species (e.g. beluga whales, Arctic cod), with consequences for the Indigenous community groups in the region. Here, we build on an Ecopath with Ecosim model for the Canadian Beaufort Sea Shelf and Slope to examine historical (1970–2021) changes in the ecological dynamics of the food web and key species under climate change. We compare the individual and cumulative effects of (i) increased sea surface temperature; (ii) reduced sea ice extent; (iii) ocean deoxygenation; and (iv) changing ocean salinity in the ecosystem models. We found that including salinity time series in our ecosystem models reduced the diversity found within the ecosystem, and altered the trophic levels, biomass, and consumption rates of some marine mammal and fish functional groups, including the key species: beluga whales, as well as Arctic and polar cods. Inclusion of the dissolved oxygen time series showed no difference to ecosystem indicators. The model findings reveal valuable insights into the attribution of temperature and salinity on Arctic ecosystems and highlight important factors to be considered to ensure that existing conservation measures can support climate adaptation.
... While phytoplankton efficiently accumulate MeHg from the water column (Lee and Fisher 2016;Mason et al. 1995), suspension-feeding bivalves accumulate MeHg primarily from consumed phytoplankton (Metian et al. 2020;Pan and Wang 2011;Wang et al. 2004). Thus, they act as conduits of MeHg from the base of the food web to higher trophic levels (Blackmore and Wang 2004;Dang and Wang 2010;Li et al. 2022). Various species of suspension-feeding bivalves, including mussels (Mytilus edulis and Mytilus galloprovincialis), oysters (Crassostrea gigas and Isognomon alatus), and clams (Ruditapes philippinarum) are used globally as biomonitors as they are sessile and exposed to local pollutants (Briant et al. 2017;da Silveira Fiori et al. 2018;Giani et al. 2012;Goldberg 1975). ...
In estuarine food webs, bivalve molluscs transfer nutrients and pollutants to higher trophic levels. Mercury (Hg) pollution is ubiquitous, but it is especially elevated in estuaries historically impacted by industrial activities, such as those in the U.S. Northeast. Monomethylmercury (MeHg), the organic form of Hg, is highly bioaccumulative and transferable in the food web resulting in the highest concentrations in the largest and oldest marine predators. Patterns of Hg concentrations in marine bivalve molluscs, however, are poorly understood. In this study, inorganic Hg (iHg), MeHg, and the total Hg (THg) in soft tissues of the northern quahogs (Mercenaria mercenaria), eastern oysters (Crassostrea virginica), and ribbed mussels (Geukensia demissa) from eastern Long Island sound, a temperate estuary of the western North Atlantic Ocean was investigated. In all three species, concentrations of THg remained similar between the four sampling months (May, June, July, and September), and were mostly independent of animal size. In quahogs, MeHg and iHg displayed significant (p < 0.05) positive (iHg in May and June) and negative (MeHg in July and September) changes with shell height. Variability in concentrations of THg, MeHg, and iHg, both inter- and intra-specifically was high and greater in quahogs and oysters (THg: 37, 39%, MeHg: 28, 39%, respectively) than in mussels (THg: 13%, MeHg: 20%). The percentage of THg that was MeHg (%MeHg) was also highly variable in the three species (range: 10–80%), highlighting the importance of measuring MeHg and not only THg in molluscs.
... Only publications were considered where the species' trophic level was discernible, muscle samples were analysed, it was evident whether the concentration was provided as wet or dry weight fraction, only fresh samples with an uninterrupted freezing were assessed and the work was published in English. To validate the modelled values, the model/observed (M/O) ratio was derived as follows [68]: ...
... The closer to 1 the derived value is, the more closely the modelled value represents the observed value. The normalized mean bias (NMB), where n is the number of empirical studies generating the observed mean mercury concentration value [68]: ...
Mercury is a naturally occurring heavy metal that has also been associated with anthropogenic sources such as cement production or hydrocarbon extraction. Mercury is a contaminant of concern as it can have a significant negative impact on organismal health when ingested. In aquatic environments, it bioaccumulates up the foodweb, where it then has the potential to impact human health. With the offshore hydrocarbon platforms in the North Sea nearing decommissioning, they must be assessed as a potential source for the environmental release of mercury. International treaties govern the handling of materials placed in the ocean. Studies have assessed the ecologic and economic benefits of (partial) in situ abandonment of the infrastructure as artificial reefs. This can be applied to pipelines after substantial cleaning to remove mercury accumulation from the inner surface. This work outlines the application of an approach to modelling marine mercury bioaccumulation for decommissioning scenarios in the North Sea. Here, in situ decommissioning of cleaned pipelines was unlikely to have a negative impact on the North Sea food web or human health. However, significant knowledge gaps have been determined, which must be addressed before all negative impacts on ecosystems and organismal health can be excluded.
... Benthic and epibenthic invertebrates are preyed upon by marine fishes (Giraldo et al. 2016), sharks (McMeans et al. 2015, seals , diving sea birds, walruses, gray whales (Lovvorn et al. 2018), and beluga whales (Loseto et al. 2008). Thus, benthic animals are a conduit for MeHg transfer from the sediment and benthic boundary layer to the pelagic food web in the Arctic Ocean (Chen et al. 2008;Griffiths et al. 2017;Amiraux et al. 2023b;Li et al. 2022). MeHg is efficiently assimilated from diet, and it bioaccumulates and biomagnifies through food webs, leading to toxicological risk for some apex predators (Dietz et al. 2022). ...
... Complex multi-decadal temporal trends in MeHg accumulation have also been documented for beluga (Loseto et al. 2015). By comparison, benthic invertebrates have received minimal research focus for the Beaufort Sea (though see Loseto et al. 2008), despite their relevance for evaluating environmental and ecological drivers of spatial and temporal trends of MeHg in marine mammals (Loria et al. 2020;Li et al. 2022). ...
... MeHg concentrations in the benthic invertebrates of this study varied by two orders of magnitude over three trophic levels. Differential prey selection could have important consequences for MeHg trophic transfer to marine vertebrate predators (Li et al. 2022). The highest MeHg concentrations in this study, found in the carnivorous sunstar C. papposus (367 ± 93 ng/g dw), are higher than most MeHg and total mercury concentrations in Arctic marine invertebrates reported in other studies, where concentrations are generally below 210 ng/g dw (Barst et al. 2022). ...
This study investigated methylmercury (MeHg) concentrations in Arctic benthic invertebrates from two shelf sites in the Canadian Beaufort Sea. Carbon, nitrogen, and sulfur stable isotopes and fatty acids were measured to examine diet influences on MeHg concentrations in 476 individuals from 53 taxa of benthic invertebrates representing three different feeding guilds. Taxonomic identifications were based on DNA-barcoding and traditional taxonomy. MeHg concentrations ranged from 3 to 421 ng/g dry weight and increased over three trophic levels (δ¹⁵N range = 4.4–14.2‰). Organic matter sources had small but significant influences on MeHg bioaccumulation in the benthic food web. Carbon stable isotope ratios (δ¹³C, range = −25.5 to −19.8‰) were positively correlated with MeHg concentrations, suggesting greater reliance on benthic carbon contributed to higher concentrations. Sulfur stable isotopes were unrelated to MeHg concentrations. Fatty acids suggested feeding on diatoms versus dinoflagellates, and reliance on benthic resources influenced MeHg concentrations. Higher MeHg concentrations were observed at the site closer to the Mackenzie River mouth than the Cape Bathurst site. This study generated the most taxonomically rich dataset of MeHg concentrations in invertebrates from the Arctic marine benthos to date and provides a basis for future research on food web MeHg dynamics in the Canadian Beaufort Sea.
... Zooplankton and benthic production fuel initially the MMHg transfer to the upper TLs through diet (Figures 4a and S4). 9,13 Globally, large zooplankton and benthic production supply 4633 and 589 kmol yr −1 of MMHg to pelagic fish and demersal fish, respectively. Whether zooplankton or benthic taxa contribute more varies geographically depending on their MMHg concentrations. ...
... Whether zooplankton or benthic taxa contribute more varies geographically depending on their MMHg concentrations. 9,43 After entering the fish food webs, the medium-sized fish (e.g., the largest epipelagic and mesopelagic fish) are the most critical intermediaries in transferring MMHg to higher TLs (Figure 4a). They digest 5586 kmol yr −1 of MMHg from their prey, accounting for 71% of the total MMHg intake by fish from food (Figure 4b), and transfer 2397 kmol yr −1 of MMHg to the higher TLs, representing 84% of the total MMHg transferred by fish to their predators (Figure 4a), higher than their biomass in proportion to the total one (∼50%). ...
Marine fish is an excellent source of nutrition but also contributes the most to human exposure to methylmercury (MMHg), a neurotoxicant that poses significant risks to human health on a global scale and is regulated by the Minamata Convention. To better predict human exposure to MMHg, it is important to understand the trophic transfer of MMHg in the global marine food webs, which remains largely unknown, especially in the upper trophic level (TL) biota that is more directly relevant to human exposure. In this study, we couple a fish ecological model and an ocean methylmercury model to explore the influencing factors and mechanisms of MMHg transfer in marine fish food webs. Our results show that available MMHg in the zooplankton strongly determines the MMHg in fish. Medium-sized fish are critical intermediaries that transfer more than 70% of the MMHg circulating in food webs. Grazing is the main factor to control MMHg concentrations in different size categories of fish. Feeding interactions affected by ecosystem structures determine the degree of MMHg biomagnification. We estimate a total of 6.1 metric tons of MMHg potentially digested by the global population per year through marine fish consumption. The model provides a useful tool to quantify human exposure to MMHg through marine fish consumption and thus fills a critical gap in the effectiveness evaluation of the convention.
... Where dry weight mercury concentrations were used, the values were divided by the wet-to-dry conversion factors published by Cinnirella et al. [70] and necessary unit conversion were conducted. In addition, the modelled (M) versus mean observed (O) mercury concentration ratio was calculated for each trophic level, following the example of Li et al. [71] where: ...
... The M/O value was used to determine when the modelled value output is predictive of actual environments and where the model over-or under-estimated the biota concentration. Additionally, the normalised mean bias of the M/O ratio, as outlined by Li et al. [71] was determined: ...
Subsea pipelines carrying well fluids from hydrocarbon fields accumulate mercury. If the pipelines (after cleaning and flushing) are abandoned in situ, their degradation may release residual mercury into the environment. To justify pipeline abandonment, decommissioning plans include environmental risk assessments to determine the potential risk of environmental mercury. These risks are informed by environmental quality guideline values (EQGVs) governing concentrations in sediment or water above which mercury toxicity may occur. However, these guidelines may not consider e.g., the bioaccumulation potential of methylated mercury. Therefore, EQGVs may not protect humans from exposure if applied as the sole basis for risk assessments. This paper outlines a process to assess the EQGVs' protectiveness from mercury bioaccumulation, providing preliminary insights to questions including how to (1) determine pipeline threshold concentrations, (2) model marine mercury bioaccumulation, and (3) determine exceedance of the methylmercury tolerable weekly intake (TWI) for humans. The approach is demonstrated with a generic example using simplifications to describe mercury behaviour and a model food web. In this example, release scenarios equivalent to the EQGVs resulted in increased marine organism mercury tissue concentrations by 0-33 %, with human dietary methylmercury intake increasing 0-21 %. This suggests that existing guidelines may not be protective of biomagnification in all circumstances. The outlined approach could inform environmental risk assessments for asset-specific release scenarios but must be parameterised to reflect local environmental conditions when tailored to local factors.
