Ocean productivity and trophic structure drive patterns of mercury

Overview

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Key numbers

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• assemblages exhibit a broader δ15N range, consistent with elongated, vertically structured food chains or mul­
• (Mason and Fitzgerald, 1990; Lin et al., 2021; Luo et al., 2023), although region are limited and primarily derived from long-range atmospheric
• Current evidence indicates that MeHg levels in marine organisms are hosting nearly 80% of South America’s natural Hg reserves. This con­
• numerous commercially valuable and ecologically vulnerable species stable carbon and nitrogen isotopes (δ13C and δ15N, respectively) as
• considered a proxy for MeHg, which typically represents >71% of total
• alyses, and stable isotope data (Table 1).
• specimens utilized in total mercury analyses (n), body size (fish–standard length; crustaceans and cephalopods–total length), stable isotopes values (δ15N and δ13C, ‰), and total mercury concentrations (Hg, μg⋅g− 1 dw).
• Table 1 (continued )
• transformed Hg values, accounting for unequal variances and unbal­ similarity in the δ13C range, the FNR species occupied a broader isotopic
• (Length)), δ15N values, and region (AMZ vs. FNR), with two-way in­ Baseline differences were also evident. Zooplankton δ15N mean values in
• teractions between region and the covariates (log(Hg) ~ log(Length) × FNR ranged between 3.2 and 3.3‰, while in AMZ they ranged between
• packages ggplot2 (Wickham, 2016), rstatix (Kassambara, 2023), and to 0.81 μg⋅g− 1 in Gigantura indica (Table 1).
• In FNR, δ15N values ranged from 2.0‰ in ZOO-B (100–200 μm) to δ15N and Hg values than vertically migrating taxa in both regions.
• 12.8‰ in Notostomus gibbosus, and δ13C ranged from − 20.0‰ in ZOO-A Similarly, micronekton feeders showed higher δ15N values and Hg
• ranged from 5.9‰ (ZOO-B) to 11.5‰ (N. gibbosus), and δ13C values alopods and fishes exhibited significantly higher δ15N ratios and Hg
• ostris; Table 1). found between total Hg concentrations and body length for all species,
• Fernando de Noronha Ridge (FNR, orange box-plots). Asterisks (*) denote significant differences (p < 0.05; Welch’s two-sample t-tests) between regions. NA indicates
• (Smith and DeMaster, 1996; M’hamdi et al., 2025), δ13C ranges were
• δ15N ranges (Biddanda et al., 2001; Ward and McCann, 2017; Gloeckler downstream transport (Freitas et al., 2017). This retention is amplified
• effects models confirmed that these regional differences persisted and Marine total Hg levels are estimated to have increased by up to 300%
• stable isotope ratios (δ13C and δ15N) in pelagic nekton assemblages of the south-
• Farias, G.B., Molinero, J.C., Carré, C., Bertrand, A., Bec, B., Melo, P.A.M. de C., 2022. Mercury stable isotopes reveal the vertical distribution and trophic ecology of deep-
• C., 2018. Stable isotope analysis of micronekton around Hawaii reveals suspended Environ. Sci. 4 (3), 386–402. American Institute of Mathematical Sciences. https://

Methods (brief)

• Deep-pelagic animals are typically small-sized organisms (<30 cm) organisms collected in the two contrasting regions. Beyond this
• carbon flux to the deep ocean (Klevjer et al., 2016). Additionally, by Deep-pelagic organisms were collected from two oceanographically
• Dried and homogenized tissue samples were analyzed using an
• samples, was better than 0.15‰ for both δ13C and δ15N. Since differing
• only a few samples indicated high lipid content, they were excluded
• acidifying the samples to remove carbonates.
• mg of dried and powdered sample by thermal decomposition, gold
• amalgamation, and atomic absorption spectrophotometry (DMA-80,
• To support isotopic interpretations, zooplankton were also sampled
• multinet (300 μm mesh size). After collection, samples were pooled,
• cations, then measured, weighed, and sampled for tissue analyses.
• Zooplankton samples were acidified to remove carbonates, and all size
• fractions were included in the analysis. Samples were either oven-dried
• both regions (n = 19), Welch’s two-sample t-tests were applied to log-
• anced sample sizes. niche space along the δ15N axis, with a spread of approximately 5‰
• Fig. 2. Isotopic biplot (δ13C vs δ15N values, ‰) of species collected off the Amazon River mouth (AMZ) and the Fernando de Noronha Ridge (FNR). The lines
• values in specimens from FNR than in those from AMZ. Linear mixed- alongside key ecological traits of deep-pelagic organisms collected in the
• ship likely reflects early-life ontogenetic habitat shifts, as all sampled

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

Wiki pages this source may touch

• Fish — marine, predatory (tuna, swordfish, shark, king mackerel)
• Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
• Shellfish (shrimp, crab, lobster, clams, oysters, mussels)
• Mercury
• Mercury

Verification notes

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.