Resolution of matrix effects on analysis of total and methyl mercury in aqueous samples from the Florida Everglades

Olson, Mark L.; Cleckner, Lisa B.; Hurley, James P.; Krabbenhoft, D. P.; Heelan, T. W.

doi:10.1007/s002160050435

Cited by 69 publications

(45 citation statements)

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“…In North America, Hg contamination is already the most frequent reason for fish consumption advisories (45). If climate change and prescribed burning increase forest fires in the future in North America (17,(23)(24)(25), and the average annual area of forest burned continues to increase in Asia, Europe, the Caribbean, Oceania, South America, and some parts of Africa as it did from 1990 to 2000 (49), fish Hg contamination could become more widespread.…”

Section: Resultsmentioning

confidence: 99%

Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs

Kelly

Schindler

Louis

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

136

121

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Recent findings indicate that fishes from lakes in partially burned catchments contain greater mercury (Hg) concentrations than fishes from reference catchments. Increased methyl Hg (MeHg) concentrations in fishes can result in serious health problems for consumers. Here we show that a forest fire caused a 5-fold increase in whole-body Hg accumulation by rainbow trout (Oncorhynchus mykiss) and smaller Hg increases in muscle of several fish species in a mountain lake. The enhanced Hg accumulation was caused primarily by increased nutrient concentrations in the lake, which enhanced productivity and restructured the food web through increased piscivory and consumption of Mysis. This restructuring resulted in increases to the trophic positions and Hg concentrations of fishes. Forest fire also caused a large short-term release of total Hg (THg) and MeHg to streams and the lake. This release initiated a small pulse of MeHg in invertebrates that contributed to enhanced Hg accumulation by fishes. Climate change and prescribed burning to compensate for past fire suppression are predicted to increase future forest fire occurrence in North America, and increased Hg accumulation by fishes may be an unexpected consequence.productivity ͉ stable isotopes ͉ methyl mercury ͉ food chain length ͉ climate change

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Section: Resultsmentioning

confidence: 99%

Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs

Kelly

Schindler

Louis

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

136

121

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“…The Hg was reduced to Hg(0) with SnCl 2 in glass bubblers purged with N 2 gas in which the Hg(0) was trapped onto gold-coated beads (31). MeHg samples were distilled, derivatized with tetraethylborate, and purged onto Tenax traps (32,33). When they had been trapped onto gold or Tenax, all Hg compounds were released by thermal desorption, separated by isothermal gas chromatography, pyrolysed to Hg(0), and detected by atomic fluorescence on a Tekran 2500 Hg analyzer (31).…”

Section: Methodsmentioning

confidence: 99%

Active transport, substrate specificity, and methylation of Hg(II) in anaerobic bacteria

Schaefer

Rocks

Zheng

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

263

423

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The formation of methylmercury (MeHg), which is biomagnified in aquatic food chains and poses a risk to human health, is effected by some iron-and sulfate-reducing bacteria (FeRB and SRB) in anaerobic environments. However, very little is known regarding the mechanism of uptake of inorganic Hg by these organisms, in part because of the inherent difficulty in measuring the intracellular Hg concentration. By using the FeRB Geobacter sulfurreducens and the SRB Desulfovibrio desulfuricans ND132 as model organisms, we demonstrate that Hg(II) uptake occurs by active transport. We also establish that Hg(II) uptake by G. sulfurreducens is highly dependent on the characteristics of the thiols that bind Hg(II) in the external medium, with some thiols promoting uptake and methylation and others inhibiting both. The Hg(II) uptake system of D. desulfuricans has a higher affinity than that of G. sulfurreducens and promotes Hg methylation in the presence of stronger complexing thiols. We observed a tight coupling between Hg methylation and MeHg export from the cell, suggesting that these two processes may serve to avoid the build up and toxicity of cellular Hg. Our results bring up the question of whether cellular Hg uptake is specific for Hg(II) or accidental, occurring via some essential metal importer. Our data also point at Hg(II) complexation by thiols as an important factor controlling Hg methylation in anaerobic environments. , methylmercury, MeHg) is a potent neurotoxic compound (1). It is biomagnified in the food webs of aquatic systems, reaching high concentrations in carnivorous fish, thus posing a risk to human health (2). Understanding the mechanism of inorganic Hg methylation and the parameters that control the extent of methylation in the environment is thus essential for relating patterns of Hg pollution to human exposure. The production of MeHg has been linked to obligate anaerobic bacteria in the δ-Proteobacteria, including ironand sulfate-reducing bacteria (FeRB and SRB) that live in soil and sediments (3-6). Although mechanisms of Hg(II) methylation by methylating enzymes have been proposed for some time (7,8), the mechanism of Hg(II) uptake by the bacteria has remained obscure. The dominant view is that cellular uptake occurs by passive diffusion of neutral Hg(II) complexes, particularly sulfide complexes, through external membranes, leading to accidental methylation of some of the intracellular Hg(II) (9). However, this view is based on indirect data and modeling, as the precipitation of metal sulfides in the medium and the extensive Hg binding to the surface of the organisms (10-12) have made it difficult to directly measure Hg(II) uptake in methylating bacteria.In previous work (13), we demonstrated that the cysteine complex of Hg(II) was available to the FeRB Geobacter sulfurreducens PCA and that Hg(II) was likely transported into the cell via an unknown facilitated transport mechanism. Here we examine the energy dependence and specificity of Hg(II) uptake and methylation by both G. sulfurreducens and ...

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“…Three blanks and three standard reference materials (SRMs) were also processed and analyzed along with each batch of samples. Methylmercury analysis followed ethylation, gas chromatograph separation, pyrolysis, and cold vapor atomic fluorescence spectroscopy (CVAFS) detection techniques (Olson et al 1997, Hurley et al 1998). The limit of detection (LOD; MeHg as Hg) was 2 ng/g in tissue.…”

Section: Mercury Analysesmentioning

confidence: 99%

“…Blanks and SRMs each constituted at least 10% of each processing batch. THg analysis used established protocols for dual gold amalgamation and CVAFS techniques (Gill and Fitzgerald 1987, US EPA 1996a, Olson et al 1997, Hurley et al 1998). The LOD was 1 ng/g in tissue.…”

Section: Mercury Analysesmentioning

confidence: 99%

Taking the trophic bypass: aquatic‐terrestrial linkage reduces methylmercury in a terrestrial food web

Bartrons

Gratton

Spiesman

et al. 2015

Ecological Applications

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Abstract. Ecosystems can be linked by the movement of matter and nutrients across habitat boundaries via aquatic insect emergence. Aquatic organisms tend to have higher concentrations of certain toxic contaminants such as methylmercury (MeHg) compared to their terrestrial counterparts. If aquatic organisms come to land, terrestrial organisms that consume them are expected to have elevated MeHg concentrations. But emergent aquatic insects could have other impacts as well, such as altering consumer trophic position or increasing ecosystem productivity as a result of nutrient inputs from insect carcasses. We measure MeHg in terrestrial arthropods at two lakes in northeastern Iceland and use carbon and nitrogen stable isotopes to quantify aquatic reliance and trophic position. Across all terrestrial focal arthropod taxa (Lycosidae, Linyphiidae, Acari, Opiliones), aquatic reliance had significant direct and indirect (via changes in trophic position) effects on terrestrial consumer MeHg. However, contrary to our expectations, terrestrial consumers that consumed aquatic prey had lower MeHg concentrations than consumers that ate mostly terrestrial prey. We hypothesize that this is due to the lower trophic position of consumers feeding directly on midges relative to those that fed mostly on terrestrial prey and that had, on average, higher trophic positions. Thus, direct consumption of aquatic inputs results in a trophic bypass that creates a shorter terrestrial food web and reduced biomagnification of MeHg across the food web. Our finding that MeHg was lower at terrestrial sites with aquatic inputs runs counter to the conventional wisdom that aquatic systems are a source of MeHg contamination to surrounding terrestrial ecosystems.

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Resolution of matrix effects on analysis of total and methyl mercury in aqueous samples from the Florida Everglades

Cited by 69 publications

References 0 publications

Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs

Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs

Active transport, substrate specificity, and methylation of Hg(II) in anaerobic bacteria

Taking the trophic bypass: aquatic‐terrestrial linkage reduces methylmercury in a terrestrial food web

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