Main drivers of mercury levels in Southern Ocean Lantern fish Myctophidae

• Published in: Environmental Pollution
• Main Authors: Seco, José, Xavier, José, Bustamante, Paco, Coelho, Joao, Saunders, Ryan, Ferreira, Nicole, Fielding, Sophie, Pardal, Miguel, Stowasser, Gabriele, Viana, Thainara, Tarling, Geraint, Pereira, Eduarda, Brierley, Andrew
• Other Authors: Marine and environmental research centre - IMAR-CMA (Coimbra, Portugal), University of Coimbra Portugal (UC), Pelagic Ecology Research Group, Scottish Oceans Institut, British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Marine and Environmental Sciences Centre (MARE UC), Universidade de Coimbra Coimbra, LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), CESAM and Department of Biology, Universidade de Aveiro, Government of South Georgia and the South Sandwich Islands, CESAM & Department of Chemistry, Centre for Functional Ecology, Department of Life Sciences (CFE), University of Coimbra, Calçada Martim de Freitas, Scottish Oceans Institute, University of St Andrews Scotland
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: bioaccumulation; metal; Trace element; Antarctic; mesopelagic fish; envir; geo; Southern Ocean; The Antarctic; Antarc*; Antarctica
• Online Access: https://doi.org/10.1016/j.envpol.2020.114711; https://hal.archives-ouvertes.fr/hal-02570100/file/Seco%20et%20al%202020%20ENPO.pdf; https://hal.archives-ouvertes.fr/hal-02570100

International audience 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.