Wang et al. 2023 — Climate-driven changes in global marine mercury cycles to 2100
This PNAS study models how projected climate change will alter global marine mercury biogeochemical cycles and methylmercury (MeHg) concentrations in marine food webs through 2100. Under high-emissions scenarios (RCP8.5), ocean warming, acidification, and changes to primary productivity are projected to increase MeHg bioaccumulation in upper-trophic-level fish by 5–20 percent relative to baseline, with the largest increases in polar and sub-polar regions. Ocean deoxygenation expands anoxic zones that favor mercury methylation, amplifying MeHg in pelagic food webs. The findings suggest that climate mitigation is necessary alongside anthropogenic mercury emission controls to prevent increasing dietary MeHg exposure from seafood consumption.
Key numbers
- Projected MeHg increase in upper-trophic fish under RCP8.5: 5–20% by 2100 relative to 2000 baseline
- MeHg methylation rate enhancement in expanded oxygen minimum zones: up to 2× in high-latitudes
- Current global mean MeHg concentration in pelagic marine fish: approximately 100–400 µg/kg (wet weight) depending on trophic level (from reviewed baseline literature)
- Climate scenarios modeled: RCP4.5 (low emission) and RCP8.5 (high emission)
Methods (brief)
Coupled Earth system and marine biogeochemical model integrating Hg cycling with ocean circulation, temperature, productivity, and oxygen dynamics. MeHg trophic transfer modeled using bioaccumulation factors from empirical literature. No speciation analysis of individual fish samples; this is a forward-projections modeling study.
Implications
Certification: Establishes climate change as an emerging driver of increasing MeHg in seafood over the certification program’s operational time horizon; relevant to trend language on seafood product pages. Courses: Context for long-term seafood MeHg risk trajectories. App: Supports geographic flagging of high-latitude seafood sources as higher-MeHg risk under future climate scenarios. Microbiome: Not directly applicable.