Ecotoxicology of methylmercury: a transdisciplinary challenge

Mercury in the environment: Biogeochemical transformation, ecological impacts, human risks, and remediation strategies

Mercury (Hg), a pervasive environmental pollutant, poses a significant threat to ecosystems and human health due to its complex biogeochemical transformations. Emitted from both natural sources and anthropogenic activities, Hg undergoes atmospheric transport, deposition, and intricate chemical conversions, including microbial methylation, which produces the highly toxic methylmercury (MeHg). This bioavailable form of Hg accumulates in aquatic food webs, leading to biomagnification and severe ecological consequences. The environmental fate of Hg is governed by dynamic interactions between abiotic and biotic factors, including redox conditions, microbial activity, and organic matter composition. Aquatic ecosystems, particularly wetlands and estuaries, serve as hotspots for Hg methylation, exacerbating the risk of bioaccumulation in fish and, consequently, human exposure through seafood consumption. Chronic Hg toxicity in humans is linked to neurodevelopmental disorders, cardiovascular diseases, and immunotoxicity, posing serious public health challenges. Addressing Hg contamination requires an integrated approach, combining advanced remediation strategies such as phytoremediation, bioremediation, sorbent-based technologies, and nano-engineered materials. Regulatory frameworks like the Minamata Convention play a crucial role in mitigating Hg emissions, but novel interdisciplinary solutions are imperative to reduce Hg persistence in the environment. This review explores the intricate pathways of Hg transformation, its cascading effects on biodiversity and human health, and cutting-edge remediation strategies. Understanding these complex dynamics is essential for developing sustainable mitigation measures, ensuring ecological balance, and safeguarding public health in the face of increasing environmental Hg burdens.

Long term trends of Hg uptake in resident fish from a polluted estuary

Mercury contamination of fish is dependent upon a system's ability to transform inorganic Hg into biologically available forms; however, fish biometrics also play an important role. To assess long term trends in Hg concentrations in sand flathead (Platycephalus bassensis) a polynomial model, corrected for fish length, was used to evaluate temporal trends and spatial variability, while growth rates were estimated using the Von Bertalanffy length-at-age model. Hg concentrations showed no decrease over time, and generally remained near recommended consumption levels (0.5 mg kg(-1)). Previously reported spatial differences in Hg concentrations were not supported by the data once the models were corrected for fish length. Growth rate variation accounted for a large part of the previously published spatial differences. These results suggest that inclusion of fish biometrics is necessary to facilitate an accurate interpretation of spatial and temporal trends of contaminant concentrations in long term estuarine and marine monitoring programs.