Mercury Exposure and Risk in Mediterranean Marine Wildlife: A Modelling Approach

Marine ecosystems play a critical role in the transformation of inorganic mercury (Hg) species into methylmercury (MeHg), which then bioaccumulates and biomagnifies through food webs. As a result of biomagnification, marine ecosystems represent a major exposure pathway also for terrestrial organisms that rely on marine resources, including humans. The well-documented toxicity of MeHg, tragically demonstrated by historical events such as the outbreak of the Minamata disease, underscores the need for a deeper understanding of its environmental dynamics and for sustained monitoring of Hg levels in both biotic and abiotic compartments. This need has become increasingly urgent in light of the profound and ongoing ecosystem alterations driven by climate change.

High-resolution numerical simulations of Hg fate and transport in the Mediterranean Sea were run to provide insights into the spatial and temporal variability of Hg species concentrations in seawater and within the plankton food web. This information was used to extrapolate Hg concentration in fish of different trophic levels and estimate ecological risk. The risk is estimated by combining modeled MeHg concentrations across different functional groups with established ecotoxicological thresholds for dietary exposure and information on fish habitat, allowing an assessment of potential ecological risks. Although uncertainties in model predictions remain - primarily due to relatively sparse observational data and limited mechanistic understanding of key processes such as methylation - coupled models have been shown to reproduce large-scale spatial gradients observed in the field reliably. This approach provides a novel framework for linking environmental dynamics with Hg distribution and trophic transfer, identifying areas of elevated exposure risk and supporting more informed monitoring and management strategies.