Variation In Hg Concentrations Research Articles

Regional differences in Hg contents in the liver and muscle of the green turtle (Chelonia mydas) from three foraging grounds in Northeast Brazil.

Mercury (Hg) is a highly toxic pollutant that endangers several marine animals, including green sea turtles (Chelonia mydas), particularly in their foraging grounds along Brazilian coastal waters. Environmental Hg levels differ along this extensive littoral, rendering mandatory Hg long-term assessments of the different Hg fate in different sectors of the Brazilian coast. This study quantifies total Hg concentrations in the liver and muscle of green sea turtle populations from three foraging coastal regions in northeastern Brazil and analyzes Hg concentration differences given the locality and size of 61 juvenile individuals sampled. The results showed wide variations in Hg concentrations in the liver (81-3135 ng g-1) and muscle (10.1-8569 ng g-1). There was no significant correlation between animal size and Hg concentrations. Also, no difference was found among areas, reflecting the opportunistic feeding habit of juveniles of this species. This suggests that, in the case of green turtles, the ontogenetic change of diet plays an important role in influencing Hg concentrations found in this species.

Climate and industrial pollution determine the seasonal and spatial mercury variations in the China's Weihe River

Natural processes and human activities impact mercury (Hg) pollution in rivers. Investigating the individual contributions and interactions of factors affecting variations in Hg concentrations, particularly under climate change, is crucial for safeguarding watershed ecosystems and human health. We collected 381 water samples from China's Weihe River Basin (WRB) during dry and wet seasons to assess the total Hg (THg) concentration. Results revealed high Hg concentrations in the WRB (0.1–2200.9 ng/L, mean 126.2 ± 335.5 ng/L), with higher levels during the wet season (wet season: 249.1 ± 453.5 ng/L, dry season: 12.7 ± 14.0 ng/L), particularly in the mainstream and southern tributaries of the Weihe River. Industrial pollution (contributing 26.2 %) and precipitation (contributing 33.5 %) drove spatial heterogeneity in THg concentrations during the dry and wet seasons, respectively. Notably, combined explanatory power increased to 47.9 % when interaction was considered, highlighting the amplifying effect of climate change, particularly precipitation, on the impact of industrial pollution. The middle and downstream of the Weihe River, especially the Guanzhong urban agglomeration, were identified as high-risk regions for Hg pollution. With ongoing climate change the risk of Hg exposure in the WRB is expected to escalate. This study lays a robust scientific foundation for the effective management of Hg pollution in analogous river systems worldwide.

Understanding drivers of mercury in lake trout (Salvelinus namaycush), a top-predator fish in southwest Alaska's parklands

Mercury (Hg) is a widespread element and persistent pollutant, harmful to fish, wildlife, and humans in its organic, methylated form. The risk of Hg contamination is driven by factors that regulate Hg loading, methylation, bioaccumulation, and biomagnification. In remote locations, with infrequent access and limited data, understanding the relative importance of these factors can pose a challenge. Here, we assessed Hg concentrations in an apex predator fish species, lake trout (Salvelinus namaycush), collected from 14 lakes spanning two National Parks in southwest Alaska, U.S.A. We then examined factors associated with the variation in fish Hg concentrations using a Bayesian hierarchical model. We found that total Hg concentrations in water were consistently low among lakes (0.11–0.50 ng L−1). Conversely, total Hg concentrations in lake trout spanned a thirty-fold range (101–3046 ng g−1 dry weight), with median values at 7 lakes exceeding Alaska's human consumption threshold. Model results showed that fish age and, to a lesser extent, body condition best explained variation in Hg concentration among fish within a lake, with Hg elevated in older, thinner lake trout. Other factors, including plankton methyl Hg content, fish species richness, volcano proximity, and glacier loss, best explained variation in lake trout Hg concentration among lakes. Collectively, these results provide evidence that multiple, hierarchically nested factors control fish Hg levels in these lakes.

Mercury Sources, Emissions, Distribution and Bioavailability along an Estuarine Gradient under Semiarid Conditions in Northeast Brazil

In the semiarid coast of northeast Brazil, climate change and changes in land use in drainage basins affect river hydrodynamics and hydrochemistry, modifying the estuarine environment and its biogeochemistry and increasing the mobilization of mercury (Hg). This is particularly relevant to the largest semiarid-encroached basin of the region, the Jaguaribe River. Major Hg sources to the Jaguaribe estuary are solid waste disposal, sewage and shrimp farming, the latter emitting effluents directly into the estuary. Total annual emission reaches 300 kg. In that estuary, the distribution of Hg in sediment and suspended particulate matter decreases seaward, whereas dissolved Hg concentrations increase sharply seaward, suggesting higher mobilization at the marine-influenced, mangrove-dominated portion of the estuary, mostly in the dry season. Concentrations of Hg in rooted macrophytes respond to Hg concentrations in sediment, being higher in the fluvial endmember of the estuary, whereas in floating aquatic macrophytes, Hg concentrations followed dissolved Hg concentrations in water and were also higher in the dry season. Animals (fish and crustaceans) also showed higher concentrations and bioaccumulation in the marine-influenced portion of the estuary. The variability of Hg concentrations in plants and sediments agrees with continental sources of Hg. However, Hg fractionation in water and contents in the animals respond to higher Hg availability in the marine-dominated end of the estuary. The results suggest that the impact of anthropogenic sources on Hg bioavailability is modulated by regional and global environmental changes and results from a conjunction of biological, ecological and hydrological characteristics. Finally, increasing aridity due to global warming, observed in northeast Brazil, as well as in other semiarid littorals worldwide, in addition to increased water overuse, augment Hg bioavailability and environmental risk and exposure of the local biota and the tradition of human populations exploiting the estuary's biological resources.

Mercury and stable isotopes portray colony-specific foraging grounds in southern rockhopper penguins over the Patagonian Shelf.

Mercury pollution is a serious global environmental issue and the characterization of its distribution and its driving forces should be urgently included in research agendas. We report unusually high mercury (Hg) concentrations (>5μg/g) along with stable isotopes values in feathers of southern rockhopper penguins (Eudyptes chrysocome) from colonies in the Southwest Atlantic Ocean. We found a highly heterogenous prevalence of Hg throughout the study area and over a three-fold higher mean Hg concentration in southernmost colonies. Variation in Hg concentrations among colonies is primarily explained by site, rather than by trophic position. We provide further support to the existence of a Hg hotspot in the food web of the Patagonian Shelf and spatially restrict it to the southern tip of South America. Our findings highlight the need for regional and colony-based seabird conservation management when high local variability and plasticity in foraging habits is evident.

Mercury biomagnification in benthic, pelagic, and benthopelagic food webs in an Arctic marine ecosystem

Mercury (Hg) is a ubiquitous toxic metal that biomagnifies in food webs, and can reach high concentrations in top predators. Evaluating Hg biomagnification in Arctic marine food webs is critical for understanding Hg dynamics and estimating exposure to understudied fish and wildlife consumed by humans. The majority of studies conducted on Hg biomagnification in the Arctic have focused on pelagic food webs. Benthic and benthopelagic food webs in Arctic marine ecosystems also support many species of subsistence and commercial importance, and data are lacking for these systems. In this study, we investigated food web structure and Hg biomagnification for the benthic, pelagic, and benthopelagic marine food webs of inner Frobisher Bay in Nunavut. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N), as well as total (THg) and methyl (MeHg) mercury concentrations were measured in fish, invertebrates, and zooplankton. Biomagnification in each food web was quantified with Trophic Magnification Slopes (TMS) and Trophic Magnification Factors (TMF). The highest TMS and TMF values were exhibited by the benthopelagic food web (TMS = 0.201; TMF = 1.59), followed by the pelagic food web (TMS = 0.183; TMF = 1.52), and lastly the benthic food web (TMS = 0.079; TMF = 1.20), with δ15N explaining 88%, 79%, and 9% of variation in Hg concentrations, respectively. TMS and TMF values were generally low compared to other Arctic marine food webs. Results from food web structure analyses indicated that the benthic food web had the greatest trophic diversity, trophic redundancy, and largest isotopic niche area of all food webs studied. Greater food web complexity may thus result in reduced MeHg biomagnification, but further study is required. Acquiring Hg and food web structure data is critical for predicting the effects of climate-induced environmental change on Hg dynamics, especially in the context of Arctic marine ecosystems.

Mercury hazard of earthquakes in the Baikal seismic zone

Abstract. On the west coast of Lake Baikal, we defined long-term and short-term variations in Hg concentrations of groundwater in 2017 to 2019 and from 2019 to the present, respectively; the latter variations were associated with the 2020 2021 Baikal-Khubsugul seismic reactivation of active faults. We inferred that increasing Hg concentration in groundwater was due to crustal extension with the highest Hg enrichment related to aftershocks. We argue that a Hg flux depends on the nature of fault activities and elevated Hg concentrations in sedimentary layers may designate the release of Hggas and Hggw from seismically active faults in the past 14.4 Ka.

Trophic position, altitudinal distribution, and water dependence as determining factors for mercury concentrations in tropical montane anurans

Mercury (Hg) is a widespread and toxic contaminant with potential for long-range atmospheric transport. Previous work has shown that temperate and subtropical montane ecosystems have great potential for deposition of this element. However, little information exists regarding Hg dynamics in tropical mountains. In present study, we evaluated the influence of altitudinal distribution, size, trophic position, and degree of water dependence on Hg concentration in amphibians. For this purpose, we determined the mercury concentration in topsoil and amphibian samples collected at 32 points distributed between 327 and 2181 m above sea level in Serra dos Órgãos, a mountainous complex located in southeastern Brazil. We analyzed the concentration of mercury in whole body samples of 200 individuals of 30 amphibian species. Trophic position of the specimens was estimated by nitrogen stable isotope (δ15N) composition in muscle tissues. We observed a positive relationship between elevation and Hg concentration in topsoil samples from rainforest sites. However, in samples from nebular forest and campos de altitude (highland grasslands) sites, the concentration of Hg was considered lower than expected by the trend in rainforest points, indicating that the vegetation structure plays an important role in the deposition of atmospheric mercury. Mercury concentration in amphibians varies according to the functional characteristics of the species and the environment in which the individual is inserted. Elevation, trophic level and water dependence explained at least some degree of variation in Hg concentration in amphibian tissues. Thus, this community-level analysis suggests that mountainous areas in the tropical region, as recorded for temperate and subtropical mountains, act as regional convergence and deposition sites for atmospheric mercury.

Mercury accumulation in reef fishes: a comparison among red grouper, scamp, and gag of the Atlantic southeastern US and evaluation of "grouper" consumption guidelines.

In fish consumption advisories pertaining to Hg, grouper species in the family Serranidae are often lumped together and labeled generically as Grouper. However, grouper species vary considerably in growth rate, maximum age, and maximum size. This study examined the variability of Hg concentrations and bioaccumulation rates (increase of Hg concentrations in relation to age) for populations of three long-lived, slow-growing, protogynous hermaphrodite grouper species, gag Mycteroperca microlepis, scamp M. phenax, and red grouper Epinephelus morio, which are commercially and recreationally important in the offshore waters of the US southeastern region. A total of 268 samples from the three grouper species were processed for Hg analysis from 2013-2015. Concentrations of Hg ranged from 0.03 to 0.87ppm wet weight, with a mean of 0.30ppm. Gag accumulated Hg at a faster rate (as measured by the increase of Hg with fish age) than the other two species. Size, age, and δ15N were significant predictors for Hg in the two Mycteroperca species, while size and age were significant predictors for Hg in red grouper. Two of the three species had mean Hg concentrations within the one meal per week "Good Choices" consumption category (red grouper and scamp), and one species (gag) had a mean Hg level within the two meals per week "Good Choices" consumption category as advised by the US EPA and US FDA. These results support the separation of grouper species in advisories.

Influence of Species-Specific Feeding Ecology on Mercury Concentrations in Seabirds Breeding on the Chatham Islands, New Zealand.

Mercury (Hg) is a toxic metal that accumulates in organisms and biomagnifies along food webs; hence, long-lived predators such as seabirds are at risk as a result of high Hg bioaccumulation. Seabirds have been widely used to monitor the contamination of marine ecosystems. In the present study, we investigated Hg concentrations in blood, muscle, and feathers of 7 procellariform seabirds breeding on the Chatham Islands, New Zealand. Using bulk and compound-specific stable isotope ratios of carbon and nitrogen as a proxy of trophic position and distribution, we also tested whether Hg contamination is related to the species-specific feeding ecology. Mercury exposure varied widely within the seabird community. The highest contaminated species, the Magenta petrel, had approximately 29 times more Hg in its blood than the broad-billed prion, and approximately 35 times more Hg in its feathers than the grey-backed storm petrel. Variations of Hg concentrations in blood and feathers were significantly and positively linked to feeding habitats and trophic position, highlighting the occurrence of efficient Hg biomagnification processes along the food web. Species and feeding habitats were the 2 main drivers of Hg exposure within the seabird community. The Pterodroma species had high blood and feather Hg concentrations, which can be caused by their specific physiology and/or because of their foraging behavior during the interbreeding period (i.e., from the Tasman Sea to the Humboldt Current system). These 2 threatened species are at risk of suffering detrimental effects from Hg contamination and further studies are required to investigate potential negative impacts, especially on their reproduction capability. Environ Toxicol Chem 2021;40:454-472. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Atmospheric mercury in the Southern Hemisphere – Part 2: Source apportionment analysis at Cape Point station, South Africa

Abstract. Mercury (Hg) contamination is ubiquitous. In order to assess its emissions, transport, atmospheric reactivity, and deposition pathways, worldwide Hg monitoring has been implemented over the past 10–20 years, albeit with only a few stations in the Southern Hemisphere. Consequently, little is known about the relative contribution of marine and terrestrial Hg sources, which is important in the context of growing interest in effectiveness evaluation of Hg mitigation policies. This paper constitutes Part 2 of the study describing a decade of atmospheric Hg concentrations at Cape Point, South Africa, i.e. the first long-term (> 10 years) observations in the Southern Hemisphere. Building on the trend analysis reported in Part 1, here we combine atmospheric Hg data with a trajectory model to investigate sources and sinks of Hg at Cape Point. We find that the continent is the major sink, and the ocean, especially its warm regions (i.e. the Agulhas Current), is the major source for Hg. Further, we find that mercury concentrations and trends from long-range transport are independent of the source region (e.g. South America, Antarctica) and thus indistinguishable. Therefore, by filtering out air masses from source and sink regions we are able to create a dataset representing a southern hemispheric background Hg concentrations. Based on this dataset, we were able to show that the interannual variability in Hg concentrations at Cape Point is not driven by changes in atmospheric circulation but rather due to changes in global emissions (gold mining and biomass burning).

A National-Scale Assessment of Mercury Bioaccumulation in United States National Parks Using Dragonfly Larvae As Biosentinels through a Citizen-Science Framework.

We conducted a national-scale assessment of mercury (Hg) bioaccumulation in aquatic ecosystems, using dragonfly larvae as biosentinels, by developing a citizen-science network to facilitate biological sampling. Implementing a carefully designed sampling methodology for citizen scientists, we developed an effective framework for a landscape-level inquiry that might otherwise be resource limited. We assessed the variation in dragonfly Hg concentrations across >450 sites spanning 100 United States National Park Service units and examined intrinsic and extrinsic factors associated with the variation in Hg concentrations. Mercury concentrations ranged between 10.4 and 1411 ng/g dry weight across sites and varied among habitat types. Dragonfly total Hg (THg) concentrations were up to 1.8-fold higher in lotic habitats than in lentic habitats and 37% higher in waterbodies with abundant wetlands along their margins than those without wetlands. Mercury concentrations in dragonflies differed among families but were correlated (r2 > 0.80) with each other, enabling adjustment to a consistent family to facilitate spatial comparisons among sampling units. Dragonfly THg concentrations were positively correlated with THg concentrations in both fish and amphibians from the same locations, indicating that dragonfly larvae are effective indicators of Hg bioavailability in aquatic food webs. We used these relationships to develop an integrated impairment index of Hg risk to aquatic ecosytems and found that 12% of site-years exceeded high or severe benchmarks of fish, wildlife, or human health risk. Collectively, this continental-scale study demonstrates the utility of dragonfly larvae for estimating the potential mercury risk to fish and wildlife in aquatic ecosystems and provides a framework for engaging citizen science as a component of landscape Hg monitoring programs.

Spatial Variation in Mercury Bioaccumulation and Magnification in a Temperate Estuarine Food Web

Estuaries are renown sinks or repositories of contaminants and reflect historical pollution of persistent compounds. In particular, mercury (Hg) contamination is widespread in coastal environments and occurs in both inorganic (THg) and highly toxic organic forms (OHg) with high bioaccumulation potential. Trophic magnification factors have been increasingly used to quantify biomagnification and represent the average rate of change in contaminant concentration throughout a food web. Here, we assessed small-scale spatial variation in THg and OHg concentrations, as well as variations in local trophic magnification factors in three segregated areas of the Tejo estuary. Selected sites covered a gradient of contamination from industrial Hg hotspots to a natural reserve area, and are key nursery areas for multiple fishes. We analyzed concentrations in sediment and biota, representing the entire local food webs. Samples included sediments, primary producers (salt marsh plants), primary consumers (macrobenthic invertebrates) and top consumers (fish muscle and liver), and the trophic web structure was characterized via SIAR mixed-modeling of nitrogen and carbon isotopic ratios. Spatial variation in Hg concentrations was observed in sediment and biota (but not for all species), with highest concentrations in the area near historical mercury input. Hg concentrations increased with trophic level, and so did the OHg fraction (% of OHg relative to THg), with mean maximum values up to 48.7% and 94.9% in invertebrates and fish, respectively. Trophic magnification factors were positive for all sites (p<0.05 for all regressions), ranging between 1.56 to 1.76 and 1.78 to 2.47 for THg and OHg, respectively. Overall, rates of mercury bioaccumulation were similar across sites with variations in biota´s Hg concentrations reflecting baseline differences in site environmental levels. Understanding mercury bioaccumulation and magnification in estuarine biota is critical to safeguard the multiple ecologic functions and economic benefits estuaries provide.

Organ-specific differences in mercury speciation and accumulation across ringed seal (Phoca hispida) life stages

Methylmercury (MeHg) is a central nervous system toxicant and exposures can adversely affect the health of marine mammals. Mercuric selenide (HgSe) in marine mammal tissues is hypothesized to result from a protective detoxification mechanism, but toxicokinetic processes contributing to its formation are poorly understood. Here, new data is reported on speciated Hg concentrations in multiple organs of n = 56 ringed seals (Phoca hispida) from Labrador, Canada, and compare concentrations to previously published data from Greenland seals. A higher proportion of Hg is found to accumulate in the kidney of young-of-the-year (YOY) ringed seals compared to adults. A toxicokinetic model for Hg species is developed and evaluated to better understand factors affecting variability in Hg concentrations among organs and across life stages. Prior work postulated that HgSe formation only occurs in the liver of mature seals, but model results suggest HgSe formation occurs across all life stages. Higher proportions of HgSe in mature seal livers compared to YOY seals likely results from the slow accumulation and elimination of HgSe (total body half-life = 500 days) compared to other Hg species. HgSe formation in the liver reduces modeled blood concentrations of MeHg by only 6%. Thus, HgSe formation may not substantially reduce MeHg transport across the blood-brain barrier of ringed seals, leaving them susceptible to the neurotoxic effects of MeHg exposure.

Wet deposition of mercury in Qingdao, a coastal urban city in China: Concentrations, fluxes, and influencing factors

Mercury (Hg) is a global pollutant of public concern because of its high toxicity and capability for worldwide distribution via long-range atmospheric transportation. Wet atmospheric deposition is an important source of Hg in both terrestrial and aquatic environments. Concentrations of various Hg species in precipitation were monitored from March 2016 to February 2017 in a coastal urban area of Qingdao, and their wet deposition fluxes were estimated. The results showed that the volume-weighted mean (VWM) concentrations of total mercury (THg), reactive mercury (RHg), dissolved THg (DTHg), particulate THg (PTHg), total methylmercury (TMeHg), and dissolved and particulate MeHg (DMeHg and PMeHg) in Qingdao's precipitation were 13.6, 1.5, 5.4, 8.2, 0.38, 0.15, and 0.22 ng L−1, respectively, and their annual deposition fluxes were estimated to be 5703.0 (THg), 666.6 (RHg), 2304.0 (DTHg), 3470.4 (PTHg), 161.6 (TMeHg), 64.0 (DMeHg), and 95.7 (PMeHg) ng m−2 y−1, respectively. A relatively high proportion of MeHg in THg was observed in precipitation (3.0 ± 2.6%) possibly due to higher methylation and contributions from an oceanic source to MeHg in the precipitation. Obvious seasonal variations in Hg concentrations and deposition fluxes were observed in the precipitation in Qingdao. Correlation analyses and multiple regression analyses showed that SO2, pH, and NO3− were the controlling factors for THg in precipitation, whereas the MeHg concentration was primarily controlled by the SO2, WS, Cl−, and THg concentrations. PM2.5 and Cl− were the major controlling factors for PMeHg/TMeHg, whereas the TMeHg/THg ratio was mainly influenced by Cl−. The THg and MeHg fluxes were primarily controlled by precipitation, whereas Cl− was also an important factor for the MeHg wet deposition flux. The results of a 72-h backward trajectory analysis in the study region with the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model indicated that Hg deposition in Qingdao mainly originated from four major sources, i.e., the local area, northwestern China, southeastern China and an oceanic source. This oceanic source is an important source of Hg (especially MeHg) in the precipitation in Qingdao.

Levels of Mercury in Feathers of Clapper Rails (Rallus crepitans) over 45 Years in Coastal Salt Marshes of New Hanover County, North Carolina.

We sampled clapper rail (Rallus crepitans) feathers from museum specimens collected between 1965 and 2010 to investigate changes in mercury (Hg) availability in coastal marshes of New Hanover County, North Carolina. Stable isotope analysis (δ(13)C and δ(15)N) was conducted to control for dietary shifts that may have influenced Hg exposure. Hg concentrations ranged from 0.96 to 9.22μg/g (ppm), but showed no significant trend over time; diet (δ(15)N) or foraging habitat (δ(13)C) also provided little to no explanatory power to the variation in Hg concentrations among clapper rails. Our findings suggest the bioavailability of Hg to clapper rails in coastal North Carolina salt marshes has remained consistent over time, despite the global trend of increasing mercury in many other bird species, providing an excellent baseline for any future assessment of Hg availability to salt marsh birds in coastal North Carolina.

Mercury bioaccumulation in an estuarine predator: Biotic factors, abiotic factors, and assessments of fish health

Estuarine wetlands are major contributors to mercury (Hg) transformation into its more toxic form, methylmercury (MeHg). Although these complex habitats are important, estuarine Hg bioaccumulation is not well understood. The longnose gar Lepisosteus osseus (L. 1758), an estuarine predator in the eastern United States, was selected to examine Hg processes due to its abundance, estuarine residence, and top predator status. This study examined variability in Hg concentrations within longnose gar muscle tissue spatially and temporally, the influence of biological factors, potential maternal transfer, and potential negative health effects on these fish. Smaller, immature fish had the highest Hg concentrations and were predominantly located in low salinity waters. Sex and diet were also important factors and Hg levels peaked in the spring. Although maternal transfer occurred in small amounts, the potential negative health effects to young gar remain unknown. Fish health as measured by fecundity and growth rate appeared to be relatively unaffected by Hg at concentrations in the present study (less than 1.3 ppm wet weight). The analysis of biotic and abiotic factors relative to tissue Hg concentrations in a single estuarine fish species provided valuable insight in Hg bioaccumulation, biomagnification, and elimination. Insights such as these can improve public health policy and environmental management decisions related to Hg pollution.

Pan-Arctic concentrations of mercury and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in marine zooplankton

Zooplankton play a central role in marine food webs, dictating the quantity and quality of energy available to upper trophic levels. They act as “keystone” species in transfer of mercury (Hg) up through the marine food chain. Here, we present the first Pan-Arctic overview of total and monomethylmercury concentrations (THg and MMHg) and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in selected zooplankton species by assembling data collected between 1998 and 2012 from six arctic regions (Laptev Sea, Chukchi Sea, southeastern Beaufort Sea, Canadian Arctic Archipelago, Hudson Bay and northern Baffin Bay). MMHg concentrations in Calanus spp., Themisto spp. and Paraeuchaeta spp. were found to increase with higher δ15N and lower δ13C. The southern Beaufort Sea exhibited both the highest THg and MMHg concentrations. Biomagnification of MMHg between Calanus spp. and two of its known predators, Themisto spp. and Paraeuchaeta spp., was greatest in the southern Beaufort Sea. Our results show large geographical variations in Hg concentrations and isotopic signatures for individual species related to regional ecosystem features, such as varying water masses and freshwater inputs, and highlight the increased exposure to Hg in the marine food chain of the southern Beaufort Sea.

Species-specific mercury bioaccumulation in a diverse fish community.

Mercury bioaccumulation models developed for fish provide insight into the sources and transfer of Hg within ecosystems. Mercury concentrations were assessed for 16 fish species of the western reach of Lake Diefenbaker, Saskatchewan, Canada. For top predators (northern pike, Esox Lucius; walleye, Sander vitreum), Hg concentrations were positively correlated to δ(15)N, and δ(15)N to fish age, suggesting that throughout life these fish fed on organisms with increasingly higher trophic values and Hg concentrations. However, fish mass and/or age were the principal parameters related to Hg concentrations for most species. For 9 common species combined, individual variation in Hg concentration was explained in declining order of importance by fish mass, trophic position (δ(15)N), and fish age. Delta (15)N value was not the leading variable related to Hg concentration for the assemblage, probably because of the longevity of lower--trophic-level species (3 species ≥ 20 yr), substantial overlap in Hg concentration and δ(15)N values for large-bodied fish up to 3000 g, and complex relationships between Hg concentration and δ(15)N among species. These results suggest that the quantity of food (and Hg) consumed each year and converted to fish mass, the quantity of Hg bioaccumulated over years and decades, and trophic position were significant determinants of Hg concentration in Lake Diefenbaker fish.

Phytoscreening-based assessment of mercury in soil.

This study was conducted to determine whether phytoscreening techniques could be used to characterize the distribution of Hg in soil at the South River, VA. An estimated 500 to 1000 kg of Hg was released to the South River in the 1930s and 1940s from a synthetic fiber manufacturing plant located in Waynesboro, contaminating the floodplain downstream. Under background conditions (soil Hg <0.03 μg/g), phytoscreening sample Hg concentrations ranged from 1.9 to 3.9 ng/g. With soil Hg concentrations ranging from 0.1 to 94 μg/g in the top 30.5 cm of nearby soil, phytoscreening sample Hg concentrations ranged from 5.0 to 145 ng/g. The variability of Hg concentrations in soil solution over the scale of the entire rhizosphere of the large trees sampled was likely high. Furthermore, the mean depth of water uptake and the exact proximity of the soil profile samples for each tree could not be determined. Nevertheless, the phytoscreening results of this study could be used to reliably provide a qualitative delineation of Hg-contaminated soil.