Overall, these studies also show the complexity and mosaic-like characteristics of Hg pollution at the regional to the global scales, underling the need for further local research and tools to understand the global picture better. Simultaneously monitoring MeHg pollution and its potential toxicity to biota also remains a significant challenge. Evaluating the stress of local biota related to MeHg requires a complex analysis of bioavailability, bioaccumulation, biomagnification, and physiological characteristics of organisms. Even doing this makes it difficult to establish a clear relation between MeHg concentrations and any negative effect on biota. Furthermore, it is challenging to assess MeHg toxicity in the frequent presence of other co-occurring stressors with the potential for synergic or antagonist effects. Ecotoxicological studies offer feasible alternatives to address this complex issue. A good example is how the toxicity of methylmercury to loggerhead turtles was evaluated by [PERSON] et al. [4] using the activity of the enzymes superoxide dismutase (SOD), glutathione S-transferase (GST), and lipid peroxidation by malondialdehydedehyde (MDA) as biomarkers of environmental pollution and oxidative stress. Another major issue in the anthropogenic perturbation of the Hg biogeochemical cycle is assessing the impact of historical and current gold mining activities. Historical mining activities are still sources of Hg for downstream ecosystems. [PERSON] et al. [5] show evidence of the persistent contamination of abandoned and inactive mines in the Philippines, even 50 to 70 years later, releasing high amounts of Hg into riverine and marine environments. In current alluvial gold mines of the Amazon region, [PERSON] et al. [6] highlight the impact of soil degradation on the Hg release into downstream hydrosystems. [PERSON] et al. [7] demonstrate that particulate Hg and MeHg transport rises downstream from gold mine sites, with the highest emissions during high water regimes (rainy season). In contrast, the highest releases of dissolved MeHg (up to 30% of THg) occur mainly during low water regimes. In downstream receptacle aquatic ecosystems, the methylation of accumulated Hg is generally enhanced. [PERSON] et al. [8] show that, in mine-impacted high-altitude aquatic ecosystems of the Andes, the production and release of MeHg is driven by sediment effluxes to the water column and diel redox oscillations. Finally, they highlight that, although MMHg loading from the PW to the SW is large, MMHg photodegradation and demethylation by microorganisms control net MMHg accumulation in the water column. These studies converge toward the idea that, even though Hg is banned, current gold-mining practices still release natural Hg that, added to the Hg inherited from older and modern mining practices, impact downstream ecosystems. The improvement of mining practices is thus key to regulating and mitigating these Hg emissions. Indeed, [PERSON] et al. [9] demonstrate that recent rehabilitation efforts in French Guyana's mining sites show promising results that depend on the type of ecological rehabilitation protocols. They demonstrate that specific plant species (e.g., fabaceous species) positively affect soil quality that can significantly reduce mercury mobility and toxicity.