Mercury flow through an Asian rice-based food web

Area of Science:

• Environmental Science
• Ecotoxicology
• Wildlife Biology

Background:

• Mercury (Hg) is a global pollutant toxic to wildlife.
• Asian Hg exposure pathways, including rice consumption, differ from other regions.
• Impacts of Hg on wildlife in Asian rice-based ecosystems remain unclear.

Purpose of the Study:

• Investigate Hg flow through rice-based food webs in Guizhou, China.
• Assess Hg exposure risks for wildlife in mining and non-mining areas.
• Identify key species and pathways for Hg transfer in these ecosystems.

Main Methods:

• Measured total Hg (THg) and methylmercury (MeHg) in soil, rice, and 38 animal species.
• Analyzed Hg concentrations across multiple trophic levels.
• Examined relationships between stable isotopes and Hg concentrations.

Main Results:

• Confirmed biomagnification of THg/MeHg with a high trophic magnification slope.
• Invertivorous songbirds exhibited feather THg concentrations significantly above reproductive impairment thresholds.
• High Hg levels in rice consumers and granivorous birds suggest rice as a primary exposure source.
• Spiders showed the highest invertebrate THg concentrations, potentially acting as a Hg vector.

Conclusions:

• Significant population-level health effects and biodiversity loss are possible in Asian agricultural wetlands.
• Invertivorous songbirds are potential indicators of Hg contamination impacts.
• Rice-based ecosystems require further investigation regarding Hg risks to wildlife.