Abstract
Fish consumption is a major route of human exposure to mercury (Hg), yet limited understanding of how anthropogenic activities drive geographic variations in fish Hg worldwide hinders effective Hg pollution management. Here we characterized global geographic variations in total Hg (THg) and methylmercury (MeHg), compared THg and MeHg levels between the United States and China, and used a structural equation model to link the geographic variability of MeHg in fish to human activities. Despite previously reported higher Hg emissions in China, Chinese fish have lower THg and MeHg levels than fish in the United States owing to a lower trophic magnification slope, shortened food chains and shorter fish lifespans. The structural equation model revealed strong impacts of human activities on MeHg levels in fish. In the future, China may face elevated MeHg levels in fish with the ongoing recovery of food web ecology, highlighting the importance of local policies.
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Data availability
The authors declare that all data supporting the findings of this study are available within the article and Supplementary Information. Source data are provided with this paper.
Code availability
The LMM code is available from the corresponding author Yongguang Yin (ygyin@rcees.ac.cn) upon request.
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Acknowledgements
This work is partially supported by the National Natural Science Foundation of China (22193051, 42394091, 22425606, 22006151, 21527901), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0750200) and NSF program (ECS1905239). This is publication #1765 from the Institute of Environment at Florida International University. Y.Y. acknowledges the support from the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Y202011). We extend our gratitude for the support from the Fundamental Research Funds for the Central Universities (SWU-XDJH202320) from Southwest University to the Climate Change and its Environmental Implications (CCEI) Thrust. We thank Y. Zhang and Z. Song of Nanjing University for their help in calculating the annual Hg deposition and atmospheric Hg concentration.
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Conceptualization: G.L., Y.Y. and Y.C. Investigation: Y.X. and Y.Y. Funding acquisition: Y.X., Y.Y., Y.C. and G.J. Writing—original draft: Y.X. Writing—review and editing: G.L., Y.Y., Y.L., D.W., Y.C. and G.J.
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Extended data
Extended Data Fig. 1 Map of the site locations of peer-reviewed studies.
a, Worldwide, b, the US and c, China. Administrative boundary data of worldwide and China are supported by the Data Center for Resources and Environmental Sciences, Chinese Academy of Sciences (http://www.resdc.cn). Administrative boundary data of the US are supported by Natural Earth (https://www.naturalearthdata.com). The list of papers reviewed and the detailed sample points are present in the Source Data.
Extended Data Fig. 2 THg and MeHg concentrations (μg kg-1 ww), as well as MeHg% in fish of China with different dietary behaviors.
a–c, Freshwater fish, d–f, marine fish. The detailed sample sizes are provided in the Source Data, and “n” represents the number of data points per graph. Green: herbivores, yellow: planktivores, blue: ominivores, and orange: carnivores.
Extended Data Fig. 3 Hg concentrations of different fish species in China.
a, THg (µg kg-1 ww), b, MeHg (µg kg-1 ww), c, MeHg%. The difference analysis of THg, MeHg and MeHg% among fish species was conducted by Rank transformed one-way ANOVA, owing to the non-normal distribution (Kolmogorov-Smirnov test, K-S test) and non-homogeneity of the variances (Levene test). Categories that share common letter do not differ significantly (two-sided tests): lower case letters are for comparison of Hg among freshwater species and capital letters are for comparison of Hg among marine fish species. The detailed sample sizes are provided in the Source Data, and “n” represents the number of data points per graph.
Extended Data Fig. 4 Hg concentrations in wild and farmed fish across China.
a, THg (µg kg-1 ww), b, MeHg (µg kg-1 ww), c, MeHg%. Data are the comprehensive presentation of Fig. 2. FW and FF are short for freshwater wild and farmed fish, and MW and MF are short for marine wild and farmed fish, respectively. The detailed sample sizes are provided in the Source Data, and “n” represents the number of data points per graph. A Mann-Whitney U test was performed to compared fish Hg levels between groups. Based on Monte Carlo analysis (two-sided), a p-value less than 0.05 indicates statistically significance.
Extended Data Fig. 5 Trophic levels of fish observed in China and the US.
FW and MW are short for freshwater and marine wild fish, respectively. The detailed sample sizes are provided in the Source Data, and “n” represents the number of data points per graph. A Mann-Whitney U test was performed to compared fish TL between groups. Based on Monte Carlo analysis (two-sided), a p-value less than 0.05 indicates statistically significance.
Extended Data Fig. 6 The growth traits of wild fish across China and the US collected.
a, Fish age, b, growth rate (cm/year). FW and MW are short for freshwater and marine wild fish, respectively. The detailed sample sizes are provided in the Source Data, and “n” represents the number of data points per graph. A Mann-Whitney U test was performed to compared fish age and growth rate between groups. Based on Monte Carlo analysis (two-sided), a p-value less than 0.05 indicates statistically significance.
Extended Data Fig. 7 The hypothesized fish mercury accumulation model summarizing pathways that directly and/or indirectly mediated mercury levels in fish.
Solid arrows pointing straight to fish mercury without any intermediate factors are the predicted direct pathways, while others are the predicted indirect pathways. Dotted arrows represent the modulating effect.
Supplementary information
Supplementary Information
Supplementary Tables 1–3 and 5, Notes 1–9 and References.
Supplementary Table 4
Detailed calculation process of UDF 1 for each sampling site in China (a) and the United States (b).
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Xiang, Y., Liu, G., Yin, Y. et al. Human activities shape important geographic differences in fish mercury concentration levels. Nat Food 5, 836–845 (2024). https://doi.org/10.1038/s43016-024-01049-z
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DOI: https://doi.org/10.1038/s43016-024-01049-z
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