14 Feb 2022
14 Feb 2022
Status: this preprint is currently under review for the journal BG.

Assessing the spatial and temporal variability of MeHg biogeochemistry and bioaccumulation in the Mediterranean Sea with a coupled 3D model

Ginevra Rosati, Donata Canu, Paolo Lazzari, and Cosimo Solidoro Ginevra Rosati et al.
  • National Institute of Oceanography and Applied Geophysics - OGS

Abstract. Human exposure to mercury (Hg) is a cause of concern, due to the biomagnification of the neurotoxic species monomethylmercury (MMHg) in marine ecosystems. Previous research revealed that commercial fish species in the Mediterranean Sea ecosystems are particularly enriched in Hg, due to a combination of physical and ecological factors. Since the fate of Hg depends on the interactions among several biogeochemical and physical drivers, biogeochemical modelling is crucial to support the integration and interpretation of field data. Here, we develop and apply a coupled transport-biogeochemical-metal bioaccumulation numerical model (OGSTM-BFM-Hg), to simulate the biogeochemical cycling of the main Hg species (HgII, Hg0, MMHg, and DMHg) in seawater, organic detritus, and through the planktonic food web. The model is applied to a 3D domain of the Mediterranean Sea to investigate the spatial and temporal variability of MeHg distribution and bioaccumulation. Model results reproduce the strong vertical and zonal gradients of MeHg concentrations related to primary production consistently with the observations, and highlight the role of winter deep convection and summer water stratification in shaping the MeHg vertical distribution, including sub-surface MeHg maximum. The modelled bioaccumulation dynamics in plankton food webs are characterized by a high spatial and temporal variability that is driven by plankton phenology, and are in agreement with available field data of concentrations in plankton and with other indicators, such as bioconcentration factors (BCFs) and trophic magnification factors (TMFs). Model results pointed out that the increment in water temperature linked to a decline of deep convection can cause an increase in water MeHg concentrations with cascading effects on plankton exposure and bioaccumulation.

Ginevra Rosati et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-14', Yanxu Zhang, 28 Feb 2022 reply

Ginevra Rosati et al.

Model code and software

OGSTM-BFM-Hg model code Rosati Ginevra, Canu Donata, Lazzari Paolo, Solidoro, Cosimo

Ginevra Rosati et al.


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Short summary
Methylmercury (MeHg) is accumulated in marine food webs, posing concerns for human exposure through seafood consumption. We develop a numerical model to integrate the main physical, chemical, and biological processes affecting the Hg cycle. We explore the spatial-temporal changes of MeHg distribution and bioaccumulation in the Mediterranean Sea highlighting important biological processes, as well as physical processes such as winter mixing, which is declining in some areas due to climate change.