Diet shifts drive mercury bioaccumulation and distribution in

Overview

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Key numbers

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lancetfish (Alepisaurus ferox, n = 69 individuals), and measure total mercury (THg) and MeHg
However, over 80% of global tuna landings by mass consist of species that primarily forage
1997). Over 90 % of the Hg burden in muscle tissues of high trophic level fishes is present
Whole lancetfish (n = 69) were collected by fisheries observers of the National Oceanic
nearest mm (FL), and weighed whole to the nearest 0.1 g. The ranges of FLs and masses of
to subsequent samples. The average variation of replicate measurements was 4.1 %, and
analyses of DORM-4 (average measured THg = 417 ± 26 ng Hg/g dry weight, n = 161)
and TORT-3 (296 ± 15 ng Hg/g dry weight, n = 40) were within 1.2 % and 1.5 % of mean
from 10 lancetfish representing a range of masses (116.0–3920.8 g) for MeHg analysis
(n = 40 samples total). We also analyzed brains from 33 whole lancetfish for MeHg.
201HgII (96.3 % purity) (Gilmour and Riedel, 1995; Hintelmann et al., 2000; Hintelmann
with standards prepared from a certified 1000 ppm MeHg(II) chloride standard (Alfa Aesar).
to 4.8 using 2 M acetate/glacial acetic acid buffer before ascorbic acid (2.5 % w/v) was
added. Samples were ethylated with sodium tetraethylborate (1 % NaTEB in 2 % potassium
was 6.7 %, and analyses of DORM-4 (average measured MeHg = 363 ± 24 ng Hg/g dry
weight, n = 9) and TORT-3 (128 ± 8 ng Hg/g dry weight, n = 9) were within 2.3 % and 6.9
into “small” (<1.8 kg, n = 46) and “large” size classes (≥1.8 kg, n = 23), reflecting a
THg measurements (Table S1). Percent MeHg was calculated as the MeHg concentration
of t-values: 5.64–12.72, all p-values <1.78e −6; Fig. 1A; Table S2a). THg concentrations in
(range of t-values: 2.38–3.73, all p-values <0.02), while concentrations in liver, intestine,
stomach lining, and gallbladder did not (range of t-values: 0.15–0.92, all p-values >0.37;
Fig. 1B, Table S2b). In large lancetfish, THg concentrations did not change in any tissues
with lancetfish mass (range of t-values: 0.34–1.70, all p-values >0.11; Fig. 1C, Table S2c)
lancetfish (Fig. 2; Table 1). Besides accumulation with size, higher Hg concentrations
lancetfish (Table 1B). Because intestines were analyzed whole, their THg concentrations
filament, and stomach lining, and finally by gonad and gallbladder (Fig. 2A; Table 1A).
size classes, followed by intestine, dorsal muscle, stomach lining, and brain (Fig. 2B; Table
Across all lancetfish, 89 % of the Hg in the liver, on average, was MeHg (Table 1B). MeHg
concentrations, it had low proportions of MeHg (on average, 46 % across lancetfish size
classes; Table 1B). MeHg is rapidly absorbed through the intestinal wall into the blood and
concentrations (Fig. 2A; Table 1A). Lancetfish muscle tissue is mostly white skeletal
it is sampled from (Bosch et al., 2016; Harley et al., 2015). Meanwhile, stomach lining
both lancetfish size classes (Fig. 2A; Table 1A). Previous studies on fishes also found
stores bile, which not only has high water content (on average, 92 % across size classes;
Table 1A) but also accumulates Hg at a slow rate (Ballatori and Boyer, 1986). While the
intestine, stomach lining, and dorsal muscle (Fig. 2B; Table 1B). If Hg simply accumulated
(Table S5), they may not capture species-specific variability in Hg bioaccumulation. Many
Hintelmann H, Ogrinc N, 2002. Determination of stable mercury isotopes by ICP/MS and their
Wood SN, 2011. Fast stable restricted maximum likelihood and marginal likelihood estimation of
comparisons of (THg) and (MeHg) between tissues are provided in Tables S3 and S4,

Methods (brief)

collection of biological samples at appropriate spatiotemporal scales. This is especially true in
Moteki et al., 2001; Olson et al., 2014). Large pelagic fishes like tunas are already collected
high sample coverage of Hg over large ocean regions, both geographically and vertically
2.1. Sample collection
Whole lancetfish (n = 69) were collected by fisheries observers of the National Oceanic
and eastern North Pacific Ocean (Fig. S1). Observers sampled lancetfish from the Hawaii-
lancetfish collected were 325–1400 mm and 51.3–3920.8 g, respectively.
intestine, liver, and stomach lining. Only white muscle tissue was sampled; dorsal muscle
was sampled posterior to the operculum at the base of the dorsal fin insertion and anterior
to the vent, and caudal muscle was sampled posterior to the adipose fin and anterior to
before analysis. Gonads were sampled whole and were not distinguished as testes or ovaries
samples, placed in pre-weighed Whirl-Paks, and weighed before and after drying to measure
vessels and tools were cleaned with 95 % ethanol between samples.
MA-3000 Direct Mercury Analyzer (DMA), which uses direct thermal decomposition, gold
amalgamation, and cold vapor atomic absorption spectroscopy. For quality assurance and
were weighed out for THg analysis, and replicate samples and DORM-4 were analyzed
every seven samples. A blank boat was combusted after samples expected to have high
to subsequent samples. The average variation of replicate measurements was 4.1 %, and

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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.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised