Abstract
Seafood is the main source of methylmercury (MeHg) exposure for humans and elevated total mercury (Hg) concentrations have been reported in marine fish from Norwegian fjords compared with offshore areas. Hg in tusk fillets (n=201) and liver samples (n=177) were measured in individuals from different habitats including offshore, coastal area, outer and inner Sognefjord. Specifically, the effects of habitat, energy sources and trophic complexity on Hg bioaccumulation pathways in tusk (Brosme brosme) were investigated using stable isotopes of carbon (δ13C) and nitrogen (δ15N). The concentrations of Hg in tusk increased from offshore towards inner Sognefjord. While Hg concentrations in sediment were at background levels, tusk fillet samples from 7 of 8 sites in Sognefjord had higher Hg levels than the maximum level set by European Union. Based on these findings, human consumption advice for tusk from Sognefjord was issued by the Norwegian Food Safety Authority. δ13C values in tusk successfully discriminated individuals from different habitats and were positively correlated to Hg concentrations in tusk across individuals, sites and habitats, outlining the potential importance of terrestrial carbon and most likely the atmospheric deposition of Hg from the catchment to the overall Hg bioaccumulation and exposure regime in tusk. Additionally, we postulate that the effects of terrestrial carbon sources increased towards inner Sognefjord and likely influenced Hg bioavailability throughout the food web. In contrast, δ15N values were patchy throughout the fjord system and although trophic position explained some of the Hg variation between individual fish, it was not correlated with Hg variation across sites and habitats. Our results suggest that tusk can accumulate high levels of Hg in fjord ecosystems and that catchment runoff is likely an important driver of Hg bioaccumulation in this species.
Highlights
Mercury (Hg) is a global pollutant and an important environmental and public health issue (Mason et al, 2012)
In a companion study (Azad et al, 2019a) we reported that in Hardangerfjord, Norway, Hg concentrations in marine biota, seawater and sediment increased towards the point source of Hg pollution in the inner part of fjord
The mean liver Hg levels varied between 0.19 mg kgÀ1 ww in tusk collected at site 9 and 2.6 mg kgÀ1 ww in tusk collected at site 7 (Fig. 2B)
Summary
Mercury (Hg) is a global pollutant and an important environmental and public health issue (Mason et al, 2012). Monomethylmercury (MeHg), the most toxic and bioavailable form, has a very long half-life in fish and biomagnifies with increasing trophic position in marine food webs. In remote regions, such as Norway, atmospheric deposition is the main source of Hg in most areas (Fitzgerald et al, 1998; Berg et al, 2006) some point sources do exist (Azad et al, 2019a). Mercury is highly volatile and has a long atmospheric residence time. Hg can be transported long distances and deposited directly into marine ecosystems or into terrestrial catchments, washed into streams, rivers and lakes and subsequently delivered to estuarine habitats, fjords and coastal areas (Schartup et al, 2015; Obrist et al, 2018)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
