Ecotoxicology (2024) 33:325–396

Overview

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Key numbers

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reliable and repeatable measures both temporally and spa- methylation potential (Gorski et al. 2008; Wyn et al. 2009;
a wide range of microbial communities (Fleming et al. hammer et al. 2011; Ackerman et al. 2016; Evers 2018;
dataset, and therefore using geometric means are preferable or MTI (Pauly and Watson 2005). As a result, a threshold of
to using arithmetic means. However, the published data trophic level 3.5 was used for visualization for some graphs.
long-term trends in Hg concentrations in ﬁsh and wildlife. and associated aquatic ecosystems (Table 1). Where
erman et al. 2019; Chételat et al. 2020). Thus, for effec- (range of years covered was 1972 to 2023) emphasized Hg
Table 1 Potential choices of bioindicator species for ecological and human health as grouped by major terrestrial biomes and their associated aquatic ecosystems (as described and adapted from
et al. (2008), 96DesGranges et al. (1998), 97Peterson et al. (2016b), 98Reif et al. (2015), 99Krey et al. (2015), 100Perkins et al. (2016), 101Eagles-Smith and Ackerman (2009), 102Eagles-Smith and
in three risk categories based on mean data derived from a survey of >0.46 = high. Letters indicate additional available ﬁsh Hg samples that
than 75%) are not as high as those in higher trophic level iation. The raw data underlying the averaged statistics used
ﬁsh (>95%; Driscoll et al. 2007). herein were not always available and therefore, individual
Table 2 Fish Hg concentrations and meal frequency ingestion for people, based on U.S. guidelinesa
communities (AMAP 2015), and by the World Health ized previously (Depew et al. 2012a, b; Table 3a) and
(e.g., shellﬁsh such as mussels) at trophic level 2 generally 0.50 µg/g, ww or higher (Depew et al. 2012a) (Table 3a). A
such as tuna, swordﬁsh and shark can have elevated MeHg risk categories for diet (Table 3a) and various tissue types
0.46 µg/g, ww; Table 2)). While the European Union (EU) both laboratory and wildlife populations has improved
Table 3 a. Screening benchmarks of MeHg in the diet of piscivorous ﬁsh and birds for reproductive endpoints. b. Estimated effect Hg concentrations in two broad feeding groups of birds – ﬁsh
Assuming dietary Hg is adjusted for >95% MeHg
monitoring purposes (Table 4). There are many available maternal transfer of MeHg to offspring during reproduction
from tissue types for targeted biotic groups (Table 4). inﬂuence the interpretation of MeHg concentrations in
purposes is in the MeHg form (i.e., generally >95%), ana- marine ﬁsh (Ward et al. 2010; Baumann et al. 2017). In
Table 4 Major biota groupings and tissues identiﬁed for MeHg monitoring using non-lethal methods
Fish Muscle ﬁllet 75–95% ww or dw THg or MeHg Bloom (1992); Lescord Recent evidence indicates that
(but varies on average et al. (2018) %MeHg may be lower for some ﬁsh species (Manceau et al. 2021a) and for
as low as 65%) some cooking approaches (Wang et al. 2013) so to conﬁrm the expected
amounts. 10% of ﬁsh should be analyzed for MeHg content.
Muscle biopsy 75–95% dw THg Peterson et al. (2004) dw is best because of moisture loss concerns. Muscle biopsy to muscle ﬁllet has
Blood >95% ww or dw THg Assumed to be >95% MeHg based on other vertebrates.
Sea turtles Scutes, carapace ~10% fw (or dw if scutes need THg Rodriguez et al. (2019); While scutes are keratinized material the %MeHg may be relatively low and
Blood >95% ww or dw THg Assumed to be >95% MeHg based on other vertebrates.
Muscle >95%? ww or dw THg Assumed to be >95% MeHg based on other vertebrates.
Birds Blood >95% ww or dw THg Rimmer et al. (2005); Elimination of MeHg in adult blood comprises an initial fast phase, with half-
Dried Blood on >95% dw THg Perkins and Basu Sayers et al. (2023) supports this approach with new caveats.
Feather ~100% dw or fw whole feathers THg Burger (1993), Renedo Use feathers with care for interpretation; see Peterson et al. (2019) for a tool and
Rhamphotheca >95% fw THg Outer surface of the beak that consists of a thin sheath of keratin and were 2-fold
Nails or claws or talons >95% fw THg Hopkins et al. (2007) Total Hg gull ‘claws’ better reﬂect Hg concentrations in internal organs vs.
Eggs >96% dw or ww THg Ackerman et al. (2013) Wet weight can be problematic if eggs are not collected immediately after laying
(96% for 22 species) because of potential moisture loss (Stickel et al. 1973; Dolgova et al. 2018).
Eggshells and >95% dw THg Peterson et al. (2017) Membranes are assumed to be primarily MeHg, but shells are entirely inorganic
Muscle >95% ww or dw THg Renedo et al. (2021) MeHg comprised over 99% of total Hg in breast muscle of waterfowl (Sullivan
Marine Skin >90% dw THg Wagemann et al. (1998) Muktuk (in marine mammals) includes layers of skin and blubber.
Fur or hair >90% dw (or fw if fur is not THg Evans et al. (2000) Use fur with caution; fur/hair may not relate to blood and muscle depending on

Methods (brief)

sources of information that should be collected in a stan- Fish trophic levels were assigned by species using
collected from the published literature include individual reason why, in 2004, the Convention on Biological Diver-
samples that do not meet strict criteria) or during statistical movement, and physiology in addition to changes in the
analysis (if sample sizes are sufﬁcient, by including these availability of MeHg in the environment (Chételat et al.
All biotic samples were assigned a Taxonomic Serial ﬁred power plants and artisanal small-scale gold mining
Zamani-Ahmadmahmoodi et al. (2009), 215White and Cristol (2014), 216Hill et al. (2008), 217Goutner and Furness (1997), 218Alves et al. (2023), 219Bustamante et al. (2023), 220Quillfeldt et al.
in three risk categories based on mean data derived from a survey of >0.46 = high. Letters indicate additional available ﬁsh Hg samples that
invertebrates are not considered. Therefore, organisms such The data collected and incorporated into GBMS repre-
as phyto and zooplankton are not included for biomoni- sent the arithmetic mean, or individual sample concentra-
the organism sampled (i.e., species, date, location, size/age, major taxonomic group (i.e., cartilaginous and bony ﬁsh,
and tissue analyzed); (2) an appropriate method of sample sea turtles, birds and marine mammals) and tissue type and
vicianus) and piscivorous waterbirds (common loons, and atomic absorption detection has simpliﬁed Hg deter-
Gavia immer) and is well supported by data collected in mination and made analysis more accessible to those
can be non-lethally collected in the ﬁeld. Samples that can transferred from females to their offspring differs among
Composite samples are sometimes used to estimate popu- animals. For instance, rapid growth of juvenile birds can
Biota group Tissue type % MeHg Sample preparation Analysis type Source reference Comments about use of tissue type
Eggs >96% dw or ww THg Ackerman et al. (2013) Wet weight can be problematic if eggs are not collected immediately after laying
Sample preparation type that is underlined is the preferred type, but the alternative is acceptable if properly performed; Reported as wet weight (ww), dry weight (dw), and/or fresh weight (fw).

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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