Absence of fractionation of mercury isotopes during trophic transfer of methylmercury to freshwater fish in captivity.
We performed two controlled experiments to determine the amount of mass-dependent and mass-independent fractionation (MDF and MIF) of methylmercury (MeHg) during trophic transfer into fish. In experiment 1, juvenile yellow perch (Perca flavescens) were raised in captivity on commercial food pellets and then their diet was either maintained on unamended food pellets (0.1 μg/g MeHg) or was switched to food pellets with 1.0 μg/g or 4.0 μg/g of added MeHg, for a period of 2 months. The difference in δ(202)Hg (MDF) and Δ(199)Hg (MIF) between fish tissues and food pellets with added MeHg was within the analytical uncertainty (δ(202)Hg, 0.07 ‰; Δ(199)Hg, 0.06 ‰), indicating no isotope fractionation. In experiment 2, lake trout (Salvelinus namaycush) were raised in captivity on food pellets and then shifted to a diet of bloater (Coregonus hoyi) for 6 months. The δ(202)Hg and Δ(199)Hg of the lake trout equaled the isotopic composition of the bloater after 6 months, reflecting reequilibration of the Hg isotopic composition of the fish to new food sources and a lack of isotope fractionation during trophic transfer. We suggest that the stable Hg isotope ratios in fish can be used to trace environmental sources of Hg in aquatic ecosystems.
Department of Earth and Environmental Sciences, University of Michigan, 1100 N. University Avenue, Ann Arbor, Michigan 48109, United States. saeyunk@umich.edu
Sae Yun
SY
Kwon
Joel D
JD
Blum
Michael J
MJ
Carvan
Niladri
N
Basu
Jessica A
JA
Head
Charles P
CP
Madenjian
Solomon R
SR
David
D000818:Animals; D005591:Chemical Fractionation; D017753:Ecosystem; D004784:Environmental Monitoring; D005398:Fisheries; D005502:Food; D005618:Fresh Water; D060106:Lakes; D008629:Mercury Isotopes; D008767:Methylmercury Compounds / Q000378:metabolism*; D010471:Perches / Q000378:metabolism*; D014337:Trout / Q000378:metabolism*; D014922:Wisconsin
D008629:Mercury Isotopes; D008767:Methylmercury Compounds