Spatial and taxonomic variation of mercury concentration in low trophic level fauna from the Mediterranean Sea
Studies of mercury (Hg) in the Mediterranean Sea have focused on pollution sources, air-sea mercury exchange, abiotic mercury cycling, and seafood. Much less is known about methylmercury (MeHg) concentrations in the lower food web. Zooplankton and small fish were sampled from the neuston layer at both coastal and open sea stations in the Mediterranean Sea during three cruise campaigns undertaken in the fall of 2011 and the summers of 2012 and 2013. Zooplankton and small fish were sorted by morphospecies, and the most abundant taxa (e.g. euphausiids, isopods, hyperiid amphipods) analyzed for methylmercury (MeHg) concentration. Unfiltered water samples were taken during the 2011 and 2012 cruises and analyzed for MeHg concentration. Multiple taxa suggested elevated MeHg concentrations in the Tyrrhenian and Balearic Seas in comparison with more eastern and western stations in the Mediterranean Sea. Spatial variation in zooplankton MeHg concentration is positively correlated with single time point whole water MeHg concentration for euphausiids and mysids and negatively correlated with maximum chlorophyll a concentration for euphausiids, mysids, and “smelt” fish. Taxonomic variation in MeHg concentration appears driven by taxonomic grouping and feeding mode. Euphausiids, due to their abundance, relative larger size, importance as a food source for other fauna, and observed relationship with surface water MeHg are a good candidate biotic group to evaluate for use in monitoring the bioavailability of MeHg for trophic transfer in the Mediterranean and potentially globally.
KeywordsMethylmercury Zooplankton Mediterranean Sea Euphausiid Myctophid
We gratefully acknowledge the assistance of the captain and crew of the RV Urania in accomplishing successful sampling campaigns, as well as the collaborative spirit and congeniality of the science parties. V. Taylor and B. Jackson of the Dartmouth Trace Element Analysis Core were instrumental in achieving low biomass sample detection. Technical assistance of E. Begu and K. Obu Vazner to carry out some of the MeHg analysis of sea water is also acknowledged, as is support from L.Tier for assistance with 2013 sample collections. The cruise campaigns performed in the framework of the ongoing Med-Oceanor measurements program were funded by the Italian National Research Council and were also supported by the FP7 (2010–2015) Global Mercury Observation System (GMOS) project. The financial support of the EC funded project GMOS (Grant agreement no: 265113) and the Slovenian ARRS funded program P1-0143 are acknowledged. In addition, funding for the research presented in this publication was provided by the National Institute of Environmental Health Sciences of the National Institutes of Health (Stanton P42 ES007373). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
The research was funded in part the European Commission 7th Framework Program Global Mercury Observation System (265113, coordinated by Pirrone), the Slovenian Research Agency (P1-0143, Horvat), and the National Institute of Environmental Health Sciences of the National Institutes of Health (P42 ES007373, Stanton). Ship time was provided by the Italian Research Council as part of the Med-Oceanor program.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants performed by any of the authors. All applicable guidelines were followed for collection and use of invertebrate and fish samples in this study
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