Spatial and taxonomic variation of mercury concentration in low trophic level fauna from the Mediterranean Sea

Abstract

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.

Mediterranean Mercury Assessment 2022: An Updated Budget, Health Consequences, and Research Perspectives

“…Regional comparisons of Hg concentrations in marine organisms are thus complicated by the combination of the high number of factors involved in contaminant bioaccumulation and may differ according to the organisms studied . Mediterranean organisms, from sponges to fish, marine mammals, and seabirds, are known for their higher Hg concentrations than their Atlantic counterparts. ,,,,− Within the MED, some geographic regions such as the North Adriatic Sea, the Tyrrhenian Sea, and the Sea of Marmara ,, are known hot spots for Hg bioaccumulation, while the Aegean Sea, Ionian Sea, the Black Sea, and the Tunisian coast appear to be less contaminated. Locally, the Hg concentration in one species may vary by an order of magnitude, as observed for mussels on French MED coasts .…”

“…178 Mediterranean organisms, from sponges to fish, marine mammals, and seabirds, are known for their higher Hg c o n c e n t r a t i o n s t h a n t h e i r A t l a n t i c c o u n t e rparts. 21,48,164,165,179−182 Within the MED, some geographic regions such as the North Adriatic Sea, the Tyrrhenian Sea, and the Sea of Marmara 174,180,181 are known hot spots for Hg bioaccumulation, while the Aegean Sea, 183 Ionian Sea, 174 the Black Sea, 156 and the Tunisian coast 162 appear to be less contaminated. Locally, the Hg concentration in one species may vary by an order of magnitude, as observed for mussels on French MED coasts.…”

Mercury concentrations in biota in the Mediterranean Sea, a compilation of 40 years of surveys

“…Mercury pollution is globally distributed but elevated biological concentrations of methylmercury are mainly found in seafood consumers and wildlife such as fish 4,5 , birds 6 , and marine mammals 7 . Methylmercury exposure is associated with neurotoxicity in humans and impacts the behaviour, physiology and reproductive success of wildlife 7 .…”

Mercury Biogeochemistry and Biomagnification in the Mediterranean Sea: Current Knowledge and Future Prospects in the Context of Climate Change

“…By contrast, MeHg content increased by about one order of magnitude from phytoplankton to larger macrozooplankton organisms that feed on micro-and mesozooplankton (Figure 2). To better highlight MeHg biomagnification at the lower levels of trophic food webs, Figure 2 also reports the concentrations measured by Buckman et al [80] in unfiltered water samples and the most abundant macrozooplankton taxa from different regions of the western and eastern Mediterranean basins, including some sites with anthropogenic and natural sources of Hg. In agreement with the data reported above on the spatial distribution of MMHg in Mediterranean waters, the highest concentrations were found in samples from the western Mediterranean and, in particular, from the Tyrrhenian and Balearic Seas.…”