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Benthic and pelagic pathways of methylmercury bioaccumulation in estuarine food webs of the northeast United States.

Chen CY, Borsuk ME, Bugge DM, Hollweg T, Balcom PH, Ward DM, Williams J, Mason RP - PLoS ONE (2014)

Bottom Line: MeHg concentrations in water column particulate material, but not in sediments, were predictive of MeHg concentrations in fish (killifish and Atlantic silversides).In contrast, bulk sediment MeHg concentrations were only predictive of concentrations of MeHg in the infaunal worms.Our results across a broad gradient of sites demonstrate that the pathways of MeHg to lower trophic level estuarine organisms are distinctly different between benthic deposit feeders and forage fish.

View Article: PubMed Central - PubMed

Affiliation: Dartmouth College, Department of Biological Sciences, Hanover, New Hampshire, United States of America.

ABSTRACT
Methylmercury (MeHg) is a contaminant of global concern that bioaccumulates and bioamagnifies in marine food webs. Lower trophic level fauna are important conduits of MeHg from sediment and water to estuarine and coastal fish harvested for human consumption. However, the sources and pathways of MeHg to these coastal fisheries are poorly known particularly the potential for transfer of MeHg from the sediment to biotic compartments. Across a broad gradient of human land impacts, we analyzed MeHg concentrations in food webs at ten estuarine sites in the Northeast US (from the Hackensack Meadowlands, NJ to the Gulf of Maine). MeHg concentrations in water column particulate material, but not in sediments, were predictive of MeHg concentrations in fish (killifish and Atlantic silversides). Moreover, MeHg concentrations were higher in pelagic fauna than in benthic-feeding fauna suggesting that MeHg delivery to the water column from methylation sites from within or outside of the estuary may be an important driver of MeHg bioaccumulation in estuarine pelagic food webs. In contrast, bulk sediment MeHg concentrations were only predictive of concentrations of MeHg in the infaunal worms. Our results across a broad gradient of sites demonstrate that the pathways of MeHg to lower trophic level estuarine organisms are distinctly different between benthic deposit feeders and forage fish. Thus, even in systems with contaminated sediments, transfer of MeHg into estuarine food webs maybe driven more by the efficiency of processes that determine MeHg input and bioavailability in the water column.

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Related in: MedlinePlus

Relational diagram for total Hg and MeHg in sediment and water column and biotic compartments.The magnitude and sign of the coefficients represent the relative contribution of the independent variable in the prediction of the dependent variable located at the head of each arrow. These were calculated by multiplying the linear regression coefficients by the ratio of standard deviations of the independent and dependent variables, respectively.
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pone-0089305-g007: Relational diagram for total Hg and MeHg in sediment and water column and biotic compartments.The magnitude and sign of the coefficients represent the relative contribution of the independent variable in the prediction of the dependent variable located at the head of each arrow. These were calculated by multiplying the linear regression coefficients by the ratio of standard deviations of the independent and dependent variables, respectively.

Mentions: Past studies on MeHg in estuarine sediments have examined the role of organic carbon quantity and quality in controlling MeHg production [23], [37]–[40], [76]. While these studies have suggested that sediment organic matter may limit Hg methylation in human impacted sites, a more recent study suggests that Hg methylation is greatest in sites with the highest Hg content (relative to carbon) and that organic matter is not the only factor influencing methylation. The level of sediment sulfur is also an important consideration. In the water column, studies on the relationship between DOC and Hg in freshwater also show a positive relationship indicative of the binding of Hg by DOC [82]–[85]. In our study, MeHg in sediment is not strongly related to TOC and DOC is only marginally related to MeHg in water column particulates, indicating that the relationships between carbon and MeHg in sediment and water column compartments are complex (Figure 7). Other factors, such as the rate of production of MeHg in sediments and the sediment binding capacity for MeHg influence the potential for sediments to be a source of MeHg to the overlying waters. As noted, DOC impacts the bioavailability of MeHg in the water column to plankton, and DOC could influence the rate of degradation of MeHg by photochemical processes within the water column. However, it is not just the amount but also the type and nature of the organic matter (e.g. fraction of reduced S present) that influences the fate, transport and bioaccumulation of MeHg in estuarine systems.


Benthic and pelagic pathways of methylmercury bioaccumulation in estuarine food webs of the northeast United States.

Chen CY, Borsuk ME, Bugge DM, Hollweg T, Balcom PH, Ward DM, Williams J, Mason RP - PLoS ONE (2014)

Relational diagram for total Hg and MeHg in sediment and water column and biotic compartments.The magnitude and sign of the coefficients represent the relative contribution of the independent variable in the prediction of the dependent variable located at the head of each arrow. These were calculated by multiplying the linear regression coefficients by the ratio of standard deviations of the independent and dependent variables, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3928433&req=5

pone-0089305-g007: Relational diagram for total Hg and MeHg in sediment and water column and biotic compartments.The magnitude and sign of the coefficients represent the relative contribution of the independent variable in the prediction of the dependent variable located at the head of each arrow. These were calculated by multiplying the linear regression coefficients by the ratio of standard deviations of the independent and dependent variables, respectively.
Mentions: Past studies on MeHg in estuarine sediments have examined the role of organic carbon quantity and quality in controlling MeHg production [23], [37]–[40], [76]. While these studies have suggested that sediment organic matter may limit Hg methylation in human impacted sites, a more recent study suggests that Hg methylation is greatest in sites with the highest Hg content (relative to carbon) and that organic matter is not the only factor influencing methylation. The level of sediment sulfur is also an important consideration. In the water column, studies on the relationship between DOC and Hg in freshwater also show a positive relationship indicative of the binding of Hg by DOC [82]–[85]. In our study, MeHg in sediment is not strongly related to TOC and DOC is only marginally related to MeHg in water column particulates, indicating that the relationships between carbon and MeHg in sediment and water column compartments are complex (Figure 7). Other factors, such as the rate of production of MeHg in sediments and the sediment binding capacity for MeHg influence the potential for sediments to be a source of MeHg to the overlying waters. As noted, DOC impacts the bioavailability of MeHg in the water column to plankton, and DOC could influence the rate of degradation of MeHg by photochemical processes within the water column. However, it is not just the amount but also the type and nature of the organic matter (e.g. fraction of reduced S present) that influences the fate, transport and bioaccumulation of MeHg in estuarine systems.

Bottom Line: MeHg concentrations in water column particulate material, but not in sediments, were predictive of MeHg concentrations in fish (killifish and Atlantic silversides).In contrast, bulk sediment MeHg concentrations were only predictive of concentrations of MeHg in the infaunal worms.Our results across a broad gradient of sites demonstrate that the pathways of MeHg to lower trophic level estuarine organisms are distinctly different between benthic deposit feeders and forage fish.

View Article: PubMed Central - PubMed

Affiliation: Dartmouth College, Department of Biological Sciences, Hanover, New Hampshire, United States of America.

ABSTRACT
Methylmercury (MeHg) is a contaminant of global concern that bioaccumulates and bioamagnifies in marine food webs. Lower trophic level fauna are important conduits of MeHg from sediment and water to estuarine and coastal fish harvested for human consumption. However, the sources and pathways of MeHg to these coastal fisheries are poorly known particularly the potential for transfer of MeHg from the sediment to biotic compartments. Across a broad gradient of human land impacts, we analyzed MeHg concentrations in food webs at ten estuarine sites in the Northeast US (from the Hackensack Meadowlands, NJ to the Gulf of Maine). MeHg concentrations in water column particulate material, but not in sediments, were predictive of MeHg concentrations in fish (killifish and Atlantic silversides). Moreover, MeHg concentrations were higher in pelagic fauna than in benthic-feeding fauna suggesting that MeHg delivery to the water column from methylation sites from within or outside of the estuary may be an important driver of MeHg bioaccumulation in estuarine pelagic food webs. In contrast, bulk sediment MeHg concentrations were only predictive of concentrations of MeHg in the infaunal worms. Our results across a broad gradient of sites demonstrate that the pathways of MeHg to lower trophic level estuarine organisms are distinctly different between benthic deposit feeders and forage fish. Thus, even in systems with contaminated sediments, transfer of MeHg into estuarine food webs maybe driven more by the efficiency of processes that determine MeHg input and bioavailability in the water column.

Show MeSH
Related in: MedlinePlus