1 research outputs found
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 (<i>Perca flavescens</i>) 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<sup>202</sup>Hg (MDF) and Δ<sup>199</sup>Hg (MIF) between fish
tissues and food pellets with added MeHg was within the analytical
uncertainty (δ<sup>202</sup>Hg, 0.07 ‰; Δ<sup>199</sup>Hg, 0.06 ‰), indicating no isotope fractionation. In experiment
2, lake trout (<i>Salvelinus namaycush</i>) were raised
in captivity on food pellets and then shifted to a diet of bloater
(<i>Coregonus hoyi</i>) for 6 months. The δ<sup>202</sup>Hg and Δ<sup>199</sup>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