title: Biomagnification of mercury and selenium in two lakes in southern Norway.
abstract: We have investigated bioaccumulation and trophic transfer of both mercury (Hg) and selenium (Se) in two lakes in southern Norway to reveal a suggested mitigating effect of Se on Hg biota accumulation. The study included analysis of total Se (Se), total Hg (Hg), and methyl-mercury (MeHg) in water, littoral and pelagic invertebrates and perch (Perca fluviatilis), together with stable isotope analysis (δ(15)N and δ(13)C) in biota. Mean dissolved Se ranged from 22 to 59ngL(-1), while Hg and MeHg in lake water ranged from 1 to 3ngL(-1) and 0.01 to 0.06ngL(-1). Biota Se and Hg concentrations (dry weight) ranged from 0.41mgSekg(-1) and 0.06mgHgkg(-1) in primary littoral invertebrates and up to 2.9mg Sekg(-1) and 3.6mgHgkg(-1) in perch. Both Hg and Se biomagnified in the food web, with a trophic magnification factor (TMF) of 4.64 for Hg and 1.29 for Se. The reported positive transfer of Se in the food web, despite the low measured dissolved Se, suggest that a major proportion of the Se in these lakes are both highly bioavailable and bioaccumulative. However, we did not find support for a Se-facilitated inhibition in the accumulation of Hg in perch, as Se and Hg concentrations in perch muscle correlated positively and Se did not explain any variations in Hg after we controlled for the effects of other important covariates. We postulate that this may be a result of insufficient concentrations of dissolved Se and subsequently in biota in our studied lakes for an efficient Hg sequestration up the food web.
authors.affiliation: Department of Environmental and Health Studies, University College of Southeast Norway, Hallvard Eikas Plass 1, 3800 Bø, Norway. Electronic address: asle.okelsrud@hit.no.
authors.forename: Asle
authors.initials: A
authors.lastname: Økelsrud
authors.affiliation: Department of Environmental and Health Studies, University College of Southeast Norway, Hallvard Eikas Plass 1, 3800 Bø, Norway.
authors.forename: Espen
authors.initials: E
authors.lastname: Lydersen
authors.affiliation: Norwegian Institute for Water Research, Gaustadalléen 21, 0349 Oslo, Norway.
authors.forename: Eirik
authors.initials: E
authors.lastname: Fjeld
mesh_terms: D000818:Animals; D004784:Environmental Monitoring; D020387:Food Chain; D007448:Invertebrates / Q000378:metabolism*; D060106:Lakes / Q000032:analysis*; D008628:Mercury / Q000032:analysis / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000032:analysis / Q000378:metabolism; D009664:Norway; D010471:Perches / Q000378:metabolism*; D012643:Selenium / Q000032:analysis / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury; D012643:Selenium
keywords: Bioaccumulation; European perch; Mercury; Norwegian lakes; Selenium; Stable isotopes