Carbon, Nitrogen, and Mercury Isotope Evidence for the Biogeochemical History of Mercury in Hawaiian Marine Bottomfish

Sackett, Dana K.; Drazen, Jeffrey C.; Popp, Brian N.; Choy, C. Anela; Blum, Joel D.; Johnson, Marcus W.

doi:10.1021/acs.est.7b04893

Cited by 34 publications

(45 citation statements)

References 56 publications

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“…The overall ∆ 199 Hg/∆ 201 Hg slope for penguin blood samples (1.16 ± 0.05) (Supplementary Fig. S2 ) is consistent with those previously reported in marine fish muscle 41 , 42 , 55 and seabird eggs 43 . Due to the predominance of MeHg in penguin blood, and assuming a potential diminution in MIF slope due to low DOC concentrations in subantarctic waters, the obtained ratio indicates an accumulation of residual MeHg that has principally undergone photochemical demethylation.…”

Section: Discussionsupporting

confidence: 90%

“…Theoretical slopes have been experimentally designed in aquatic systems 34 , corresponding to 1.36 ± 0.02 for MeHg photodemethylation and 1.00 ± 0.02 for inorganic Hg photoreduction in freshwater with natural DOC. Although studies in freshwater fish also reported Δ 199 Hg/Δ 201 Hg slopes close to 1.3 48 , 49 , 51 , slightly lower Δ 199 Hg/Δ 201 Hg slopes have been observed in marine organisms 41 – 43 , 52 – 55 . This effect may be the result of different ligands associated with Hg in aqueous solutions, such as dissolved organic matter 34 , 56 , 57 , or dissolved cations or halogens in seawater 40 .…”

Section: Discussionmentioning

confidence: 87%

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Identification of sources and bioaccumulation pathways of MeHg in subantarctic penguins: a stable isotopic investigation

Renedo¹,

Amouroux²,

Pedrero³

et al. 2018

Sci Rep

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Seabirds are widely used as bioindicators of mercury (Hg) contamination in marine ecosystems and the investigation of their foraging strategies is of key importance to better understand methylmercury (MeHg) exposure pathways and environmental sources within the different ecosystems. Here we report stable isotopic composition for both Hg mass-dependent (e.g. δ202Hg) and mass-independent (e.g. Δ199Hg) fractionation (proxies of Hg sources and transformations), carbon (δ13C, proxy of foraging habitat) and nitrogen (δ15N, proxy of trophic position) in blood of four species of sympatric penguins breeding at the subantarctic Crozet Islands (Southern Indian Ocean). Penguins have species-specific foraging strategies, from coastal to oceanic waters and from benthic to pelagic dives, and feed on different prey. A progressive increase to heavier Hg isotopic composition (δ202Hg and Δ199Hg, respectively) was observed from benthic (1.45 ± 0.12 and 1.41 ± 0.06‰) to epipelagic (1.93 ± 0.18 and 1.77 ± 0.13‰) penguins, indicating a benthic-pelagic gradient of MeHg sources close to Crozet Islands. The relative variations of MeHg concentration, δ202Hg and Δ199Hg with pelagic penguins feeding in Polar Front circumpolar waters (1.66 ± 0.11 and 1.54 ± 0.06‰) support that different MeHg sources occur at large scales in Southern Ocean deep waters.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 87%

Identification of sources and bioaccumulation pathways of MeHg in subantarctic penguins: a stable isotopic investigation

Renedo¹,

Amouroux²,

Pedrero³

et al. 2018

Sci Rep

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“…For Station ALOHA the Δ 199 Hg/Δ 201 Hg ratio (Figure 4a) for all samples measured, with the exception of precipitation, was 1.21 ± 0.003 (York Regression,1 SD). This slope from the NPSG samples is similar to other marine and estuary fish studies (1.23 ± 0.01, 1 SD; Gehrke et al, 2011;Kwon et al, 2015;Li et al, 2016;Sackett et al, 2017;Senn et al, 2010) suggesting that the MIF values were produced by similar MMHg photochemical degradation mechanisms. This is supported by the good correlation between Δ 199 Hg and δ 202 Hg with a slope of 2.68 ± 0.12 (Figure 4b, 1 SD), which agrees with the experimentally derived photochemical degradation slope for MMHg of 2.43 ± 0.10 .…”

Section: Photochemical Demethylation Within the Mixed Layersupporting

confidence: 87%

Mercury Cycling in the North Pacific Subtropical Gyre as Revealed by Mercury Stable Isotope Ratios

Motta

Blum

Johnson

et al. 2019

Global Biogeochemical Cycles

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The oceans are an important global reservoir for mercury (Hg), and marine fish consumption is the dominant human exposure pathway for its toxic methylated form. A more thorough understanding of the global biogeochemical cycle of Hg requires additional information on the mechanisms that control Hg cycling in pelagic marine waters. In this study, Hg isotope ratios and total Hg concentrations are used to explore Hg biogeochemistry in oligotrophic marine environments north of Hawaii. We present the first measurements of the vertical water column distribution of Hg concentrations and the Hg isotopic composition in precipitation, marine particles, and zooplankton near Station ALOHA (22°45′N, 158°W). Our results reveal production and demethylation of methylmercury in both the euphotic (0–175 m) and mesopelagic zones (200–1,000 m). We document a strong relationship between Hg isotopic composition and depth in particles, zooplankton, and fish in the water column and diurnal variations in Δ199Hg values in zooplankton sampled near the surface (25 m). Based on these observations and stable Hg isotope relationships in the marine food web, we suggest that the Hg found in large pelagic fish at Station ALOHA was originally deposited largely by precipitation, transformed into methyl‐Hg, and bioaccumulated in situ in the water column. Our results highlight how Hg isotopic compositions reflect abiotic and biotic production and degradation of methyl‐Hg throughout the water column and the importance of particles and zooplankton in the vertical transport of Hg.

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“…Recently, Hg isotopic signatures have been used to characterize the complex biogeochemical cycle of this contaminant. Hg isotopes allowed to identify primary food sources of the accumulated-Hg in marine fish (Sackett et al, 2017(Sackett et al, , 2015 and to determine the habitats leading to Hg exposure, by discriminating between estuarine and oceanic affinities (Li et al, 2016, Senn et al, 2010 or benthic versus pelagic habits (Gehrke et al, 2011). These innovative analytical techniques, as well as the carbon stable isotope analysis of methylmercury (Masbou et al, 2015), are thus promising tools to get better insights in the origin, fate and ecodynamics of mercury in the marine food webs of this region with high fishing potential.…”

Section: E P T E D M a N U S C R I P T Conclusionmentioning

confidence: 99%

Stable isotope analyses revealed the influence of foraging habitat on mercury accumulation in tropical coastal marine fish

Croizier

Schaal

Point

et al. 2019

Science of The Total Environment

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Bioaccumulation of toxic metal elements including mercury (Hg) can be highly variable in marine fish species. Metal concentration is influenced by various species-specific physiological and ecological traits, including individual diet composition and foraging habitat. The impact of trophic ecology and habitat preference on Hg accumulation was analyzed through total Hg concentration and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) analyses in the muscle of 132 fish belonging to 23 different species from the Senegalese coast (West Africa), where the marine ecosystem is submitted to nutrients inputs from various sources such as upwelling or rivers. Species-specific ecological traits were first investigated and results showed that vertical (i.e. water column distribution) and horizontal habitat (i.e. distance from the coast) led to differential Hg accumulation among species. Coastal and demersal fish were more contaminated than offshore and pelagic species. Individual characteristics therefore revealed an increase of Hg concentration in muscle that paralleled trophic level for some locations. Considering all individuals, the main carbon source was significantly correlated with Hg concentration, again revealing a higher accumulation for fish foraging in nearshore and benthic habitats. The large intraspecific variability observed in stable isotope signatures highlights the need to conduct ecotoxicological studies at the individual level to ensure a thorough understanding of mechanisms driving metal accumulation in marine fish. For individuals from a same species and site, Hg variation was mainly explained by fish length, in accordance with the bioaccumulation of Hg over time. Finally, Hg concentrations in fish muscle are discussed regarding their human health impact. No individual exceeded the current maximum acceptable limit for seafood consumption set by both the European Union and the Food and Agriculture Organization of the United Nations. However, overconsumption of Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. some coastal demersal species analyzed here could be of concern regarding human exposure to mercury.

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Carbon, Nitrogen, and Mercury Isotope Evidence for the Biogeochemical History of Mercury in Hawaiian Marine Bottomfish

Cited by 34 publications

References 56 publications

Identification of sources and bioaccumulation pathways of MeHg in subantarctic penguins: a stable isotopic investigation

Identification of sources and bioaccumulation pathways of MeHg in subantarctic penguins: a stable isotopic investigation

Mercury Cycling in the North Pacific Subtropical Gyre as Revealed by Mercury Stable Isotope Ratios

Stable isotope analyses revealed the influence of foraging habitat on mercury accumulation in tropical coastal marine fish

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