Global drivers of variation in blood mercury of seabirds

Overview

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Key numbers

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• seabird blood. Based on our own fieldwork and a literature review, we compiled 478 mean THg values from 108
• mated to have increased by 330 % between 1960 and 2021 (Qiu et al., 2023). Comparative studies, often limited to specific taxonomic groups
• 2019). Approximately 90 % of Hg released from natural and anthropo­ level and reliance on mesopelagic prey (Carravieri et al., 2014; Pollet
• processes (Fitzgerald et al., 2007). MeHg bioaccumulates in organisms concentrations across a wide range of seabird species inhabiting
• signal of Hg contamination across specific spatial and temporal scales specific ocean regions (Table 1). Extending such methodology to a
• wide range of seabird species that forage across diverse marine envi­ et al., 2016). While blood of chicks can reflect Hg exposure around the
• pics to the poles (Table 2). These species also represent a broad spectrum in adults (Ackerman et al., 2016). The half-life of THg in whole blood is
• isms (Table 2). Based on THg concentrations in the blood of these Furthermore, collecting samples during the breeding period, when
• magnification (Pollet et al., 2022; Padilha et al., 2023), and in those Table 1). However, challenges remain in using feathers, due to inter- and
• senting 10 seabird species breeding in Japan, Alaska, and Aotearoa New (Table S1). For Leach’s storm-petrel, we collected 0.3 mL of clotted blood
• podensis, n = 20; D. a. gibsoni, n = 20), black-legged kittiwake Rissa tri­ in 2021. All blood samples were stored at − 20 ◦ C or below until analysis.
• dactyla (n = 29), Leach’s storm-petrel Hydrobates leucorhous (n = 1), Some samples were preserved as is, while others were preserved in 70 %
• pelagic cormorant Urile pelagicus (n = 30), rhinoceros auklet Cerorhinca ethanol (Table S1). We measured THg in these samples using atomic
• monocerata (n = 306), streaked shearwater Calonectris leucomelas (n = absorption spectrometry with a Hg analyzer (MA-3000, Nippon In­
• 20), tufted puffin Fratercula cirrhata (n = 66), common diving petrel struments Corporation, Kyoto, Japan or Altec AMA 254, LECO, Michi­
• Pelecanoides urinatrix (n = 70), South Georgia diving petrel (subspecies: gan, USA) after drying and homogenizing them. Detailed information on
• Pelecanoides georgicus whenuahouensis, n = 77), and Westland petrel the THg measurement process for our own samples is provided in Sup­
• Procellaria westlandica (n = 20) (Table S1). For all species except Leach’s plementary Materials 1A.
• mean was not available). In addition, we compiled the sampling year, Burger (2002) and Birds of the World. When body mass differed between
• ony, wintering area), sampling period (i.e., breeding or non-breeding), we used median values (Supplementary Materials 3).
• weight using water content values in blood (79.13 % for whole blood, approach. First, we examined the general diet of each species to deter­
• Eagles-Smith et al., 2008; 67.84 % for red blood cells, Lavoie et al., mine whether they consume mesopelagic prey. We reviewed the depth
• blood cells (wet weight basis) corresponds to 55.6 % of that in whole at least one mesopelagic prey species, recording the presence or absence
• risk thresholds originally proposed by Ackerman et al. (2016), which sponding to the recorded home range in the wintering areas) based on
• of whole blood (79.13 %, Eagles-Smith et al., 2008). Based on a litera­ etry, and geolocators (methods: Supplementary Materials 1A, data:
• moderate impacts on health and reproduction; high risk (14.4–19.2 μg 2.8. Phytoplankton biomass within the seabird foraging range
• linked to reproductive failure or mortality. range, we downloaded long-term average (2002− 2023) images of sea
• divided the world’s oceans into the following seven regions: North Pa­ the OCL algorithm. The spatial mean of chl-a was extracted within a 300
• Fox and Weisberg, 2019). We used the emmeans function and contrast only epipelagic prey feeder species, we estimated the spatial variation in
• function from the emmeans package (Lenth, 2024) to evaluate the sig­ Hg contamination inferred from the blood THg of seabirds, hereafter
• from explanatory variable because 93.7 % of the data originated from lished data). We used mean values of ocean-model THg for the year 2010
• ized linear model assuming a beta distribution (betareg function in the seabirds from 141 studies (Table S2). After excluding studies with
• the mgcv package (version 1.9.1; Wood, 2011). We used log₁₀-trans­ and 2025, with over 80 % published after 2010. We also added the blood
• in blood THg while minimizing the influence of biological and envi­ our own sampling (Table S1). Combined, our total dataset consisted of
• models in the GLM analyses as explanatory variables (i.e., body mass, species from 6 orders and 13 families (Table S4). The most frequently
• trophic level index, the interaction term between the presence or represented families were Laridae (25.5 % of the 478 values), Alcidae
• concentration), along with species (treated as a categorical variable), (9.0 %), with other families contributing between 1.0 % and 5.4 % to the
• assuming linear effects. To estimate spatial variation in blood THg, we dataset (Table S4). For the GLM and GAM analyses, we included only
• we used a tensor product smoother combining a thin plate spline for THg values by ocean region and decade in Table S3. Most data origi­
• latitude and a cyclic cubic spline for longitude to allow for two- nated from the Arctic (28.9 %), North Atlantic (29.7 %), and North
• dimensional spatial smoothing. When interpreting the results of such Pacific (15.5 %) regions, while data from the Indian Ocean and the three
• oceanic Hg contamination the predicted patterns represent. While sea­ % of the total. The sampling years ranged from the 1970s to the 2020s,

Methods (brief)

• 1. Introduction blood and feathers can often be collected in a non-lethal manner
• during the breeding period, which allows researchers to collect samples ination and to validate ocean biogeochemical model estimates.
• advantage over other marine top predators. Tissue samples such as biogeochemical models could serve as a valuable validation step,
• ation of its effectiveness (Evers et al., 2016, 2024). majority of samples obtained at seabird breeding colonies and additional
• We conducted a meta-analysis by compiling total Hg (THg) con­ samples collected from non-breeding area. Blood of adults is particularly
• centrations in the blood of adult seabirds worldwide, including our own valuable for monitoring recent Hg exposure because it can be collected
• isms (Table 2). Based on THg concentrations in the blood of these Furthermore, collecting samples during the breeding period, when
• with elevated THg concentrations. We hypothesized that THg levels individuals. Feathers, like blood, can be collected non-lethally and have
• forage in marine environments following the list of seabird species in We collected data on THg in the red blood cells or whole blood of
• For our own field sampling, we collected blood samples during the from a wing or leg vein using a heparinized syringe. In some cases, blood
• breeding period between 2017 and 2024 from 659 individuals, repre­ samples were centrifuged to separate red blood cells and plasma
• senting 10 seabird species breeding in Japan, Alaska, and Aotearoa New (Table S1). For Leach’s storm-petrel, we collected 0.3 mL of clotted blood
• Zealand: Antipodean albatross (subspecies Diomedea antipodensis anti­ from the heart of a dead adult bird collected during chick-rearing period
• podensis, n = 20; D. a. gibsoni, n = 20), black-legged kittiwake Rissa tri­ in 2021. All blood samples were stored at − 20 ◦ C or below until analysis.
• dactyla (n = 29), Leach’s storm-petrel Hydrobates leucorhous (n = 1), Some samples were preserved as is, while others were preserved in 70 %
• pelagic cormorant Urile pelagicus (n = 30), rhinoceros auklet Cerorhinca ethanol (Table S1). We measured THg in these samples using atomic
• Pelecanoides georgicus whenuahouensis, n = 77), and Westland petrel the THg measurement process for our own samples is provided in Sup­
• storm-petrel, we caught adult birds and collected 0.3 to 1 mL of blood From our literature review, we collated data on THg in seabird blood

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)
• Mercury
• Mercury
• Tin

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