Main drivers of mercury levels in Southern Ocean lantern fish Myctophidae
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Myctophids are the most abundant fish group in the Southern Ocean pelagic ecosystem and are an important link in the Antarctic marine food web. Due to their major ecological role, evaluating the level of mercury (Hg) contamination in myctophids is important as a step towards understanding the trophic pathway of this contaminant. The concentrations of total Hg were determined in muscle, gill, heart and liver tissue of 9 myctophid species to quantify tissue partitioning variability between species. Organic Hg concentration and proportion in muscle was also determined. Hg concentrations were higher in the liver and heart than in muscle and gills, but the proportion of organic Hg was almost 100% in muscle, indicating that the main uptake route for Hg is through the diet. Most of the species analysed have similar vertical and horizontal distributions, and similar feeding modes and prey. Geographical and temporal variability of Hg concentrations was examined using samples from 3 different years (2007/08, 2015/16 and 2016/17) and 2 locations (South Georgia and South Orkneys Islands). Our results appear to indicate a decreasing trend in Hg contamination over the last decade, particularly gill tissue, which is in agreement with a previous study on squid from the same region. There was no significant variability in Hg concentration between the different sampling locations. Hg levels were consistent with values reported previously for myctophids around the world, indicating low global-scale geographic variability. A positive relationship between fish size and Hg concentration was found for most species, with the exception of Electrona antarctica females, which may be explained through Hg elimination by egg laying. We estimate that myctophids collectively comprise a Southern Ocean mercury ‘reserve’ of ≈1.82 metric tonnes.
Seco , J , Xavier , J C , Bustamante , P , Coelho , J P , Saunders , R A , Ferreira , N , Fielding , S , Pardal , M A , Stowasser , G , Viana , T , Tarling , G A , Pereira , E & Brierley , A S 2020 , ' Main drivers of mercury levels in Southern Ocean lantern fish Myctophidae ' , Environmental Pollution , vol. 264 , 114711 . https://doi.org/10.1016/j.envpol.2020.114711
Copyright © 2020 Elsevier Ltd. All rights reserved. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1016/j.envpol.2020.114711
DescriptionAuthors acknowledge the Portuguese Foundation for the Science and Technology (FCT) for the PhD grant to JS (SRFH/PD/BD/113487). JPC is funded by CESAM (UID/AMB/50017/2019) and the Integrated Program of SR&TD ‘Smart Valorization of Endogenous Marine Biological Resources Under a Changing Climate’ (Centro-01-0145-FEDER-000018), co-funded by Centro 2020 program, Portugal 2020 and the European Regional Development Fund. The Institut Universitaire de France (IUF) is acknowledged for its support to PB as a Senior Member. We also thank MARE (MARE - UID/MAR/04292/2019) for the support to JX. Ecosystems Programme at the British Antarctic Survey supported GAT, GS, RAS and SF.
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