Transfer of marine mercury to mountain lakes

• Published in: Scientific reports 2017-10, Vol.7 (1), p.12719-12, Article 12719
• Main Authors: Hansson, Sophia V., Sonke, Jeroen, Galop, Didier, Bareille, Gilles, Jean, Séverine, Le Roux, Gaël
• Format: Article
• Language: English
• Subjects: 140/125; 704/158/2178; 704/172/4081; 704/47/4112; Aquaculture; Aquatic ecosystems; Biological magnification; Biota; Ecology, environment; Ecosystem assessment; Environmental Sciences; Fish; Fish farms; Fish feeds; Freshwater ecosystems; Freshwater environments; Freshwater lakes; Geochemistry; High-altitude environments; Humanities and Social Sciences; Isotopes; Lakes; Life Sciences; Marine ecosystems; Mercury; Mountain lakes; multidisciplinary; Pollution sources; Salmo trutta; Scales; Science; Science (multidisciplinary); Stable isotopes; Stocking; Trophic levels; Trout
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-13001-2

Stocking is a worldwide activity on geographical and historical scales. The rate of non-native fish introductions have more than doubled over the last decades yet the effect on natural ecosystems, in the scope of biologically mediated transport and biomagnification of Hg and Hg-isotopes, is unknown. Using geochemistry (THg) and stable isotopes (N, Sr and Hg), we evaluate natal origin and trophic position of brown trout ( Salmo trutta fario ), as well as mercury biomagnification trends and potential pollution sources to three high-altitude lakes. Farmed trout show Hg-isotope signatures similar to marine biota whereas wild trout shows Hg-isotope signatures typical of fresh water lakes. Stocked trout initially show Hg-isotope signatures similar to marine biota. As the stocked trout age and shifts diet to a higher trophic level, THg concentrations increase and the marine Hg isotope signatures, induced via farm fish feed, shift to locally produced MeHg with lower δ 202 Hg and higher Δ 199 Hg. We conclude that stocking acts a humanly induced biovector that transfers marine Hg to freshwater ecosystems, which is seen in the Hg-isotopic signature up to five years after stocking events occurred. This points to the need of further investigations of the role of stocking in MeHg exposure to freshwater ecosystems.