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

[摘要] Human exposure to mercury (Hg) is a cause of concern, dueto the biomagnification of the neurotoxic species monomethylmercury (MMHg)in marine ecosystems. Previous research revealed that commercial fishspecies in the Mediterranean Sea ecosystems are particularly enriched in Hg,due to a combination of physical and ecological factors. Since the fate ofHg depends on the interactions among several biogeochemical and physicaldrivers, biogeochemical modeling is crucial to support the integration andinterpretation of field data. Here, we develop and apply a coupledtransport–biogeochemical–metal bioaccumulation numerical model(OGSTM–BFM–Hg) to simulate the biogeochemical cycling of the main Hgspecies (Hg II , Hg 0 , MMHg, and DMHg) in seawater, organic detritus,and through the planktonic food web. The model is applied to a 3D domain ofthe Mediterranean Sea to investigate the spatial and temporal variability ofmethylmercury (MeHg) distribution and bioaccumulation and major uncertainties in Hg cycling.Model results reproduce the strong vertical and zonal gradients of MeHgconcentrations related to primary production consistently with theobservations and highlight the role of winter deep convection and summerwater stratification in shaping the MeHg vertical distribution, includingsubsurface MeHg maximum. The modeled bioaccumulation dynamics in planktonfood webs are characterized by a high spatial and temporal variability thatis driven by plankton phenology and is consistent with available field dataof Hg concentrations in plankton, as well as with other indicators, such asbioconcentration factors (BCFs) and trophic magnification factors (TMFs).Model results pointed out that the increment in water temperature linked toa decline of deep convection can cause an increase in water MeHgconcentrations with cascading effects on plankton exposure andbioaccumulation.

[学科分类] 大气科学