Abstract
Methylmercury (MeHg) is a potent neurotoxin that bioaccumulates in seafood. Co-occurrence of selenium (Se) may affect the bioavailability and toxicity of MeHg in organisms. Here we report the concentrations of total mercury (Hg) and Se in 17 teleost fish species (n = 8459) sampled during 2006–2015 from the North East Atlantic Ocean (NEAO) and evaluate species variation and effects of geography. Mean Hg concentration ranged from 0.04 mg kg−1 ww in Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou) to 0.72 mg kg−1 ww in blue ling (Molva dypterygia). Se concentrations were less variable and ranged from 0.27 mg kg−1 ww in Atlantic cod (Gadus morhua) to 0.56 mg kg−1 ww in redfish (Sebastes spp.). The mean Se:Hg molar ratio ranged from 1.9 in blue ling to 43.3 in mackerel. Pelagic species had the lowest Hg concentrations and the highest Se:Hg ratios, whereas demersal species had the highest Hg concentrations and the lowest Se:Hg ratios. Se and Hg concentrations were positively correlated in 13 of the 17 species. Hg concentrations increased from the North to South in contrast to the Se:Hg molar ratio which exhibited the opposite trend. Fish from fjord and coastal areas had higher concentrations of Hg and lower Se:Hg molar ratios compared to fish sampled offshore. All species had average Se:Hg molar ratios >1 and Hg concentrations were largely below the EU maximum level of 0.5 mg kg−1 ww with few exceptions including the deep water species tusk (Brosme brosme) and blue ling sampled from fjord and coastal habitats. Our results show that two fillet servings of tusk, blue ling or Atlantic halibut (Hippoglossus hippoglossus) exceeded the tolerable weekly intake of MeHg although the surplus Se may possibly ameliorate the toxic effects of MeHg. However, some individuals with selenium deficiencies may exhibit greater sensitivity to MeHg.
Highlights
Seafood is the main dietary source of methylmercury (MeHg) exposure for humans (Berry and Ralston, 2008; Hrenchuk et al, 2011; Rice et al, 2000) and MeHg is a primary contaminant of concern for seafood consumption advisories
We studied different marine fish species between 50.2°N and 75.6°N whereas they analyzed a low trophic level fish from more southern latitudinal range from 38.4°N to 45.2°N in estuarine habitats, which are dramatically different compared to offshore ecosystems and fjord and coastal areas
A gradual increasing trend of Hg concentrations from north to south was observed, where fish from southern areas had higher concentrations of Hg and lower Se:Hg molar ratios compared to fish from northern sectors of the study area
Summary
Seafood is the main dietary source of methylmercury (MeHg) exposure for humans (Berry and Ralston, 2008; Hrenchuk et al, 2011; Rice et al, 2000) and MeHg is a primary contaminant of concern for seafood consumption advisories. During the past 150 years, human activities, mostly gold mining and coal combustion, have dramatically increased the concentrations of anthropogenic mercury (Hg) in the environment, some recent studies have shown a decreasing trend in atmospheric Hg concentration (Zhang et al, 2016) and in Hg concentrations in fish from the North Atlantic Ocean (Cross et al, 2015; Lee et al, 2016). Fish are mainly exposed to MeHg through their diet (Lindqvist et al, 1991), and factors such as trophic level, age and foraging depth may affect the MeHg concentrations in marine fish (Choy et al, 2009). When species from extensive geographical areas are compared environmental factors that vary across broad spatial areas may influence the overall bioaccumulation regime of marine fish. Temperature is one of the most important environmental parameters that can directly affect MeHg bioaccumulation by increasing the rate of Hg elimination (Trudel and Rasmussen, 2006)
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