John Wiley & Sons, Ltd.

Application of mercury isotopes for tracing trophic transfer and internal distribution of mercury in marine fish feeding experiments

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We performed feeding experiments to investigate mercury (Hg) isotope fractionation during trophic transfer and internal distribution of total Hg (THg) in marine fish upon exposure to natural seafood. Young‐of‐the‐year amberjack (Seriola dumerili) were fed with either blackfin tuna (Thunnus atlanticus) (2647 ng/g THg) or brown shrimp (Farfantepenaeus aztecus) (25.1 ng/g THg) for 80 and 50‐days, respectively, and dissected for muscle, liver, kidney, brain, and blood. After 30 days of consuming tuna, Hg isotopes (δ202Hg and Δ199Hg) of the amberjack organs shifted to the tuna value (≏202Hg= 0.55 ‰, Δ199Hg= 1.54 ‰,), demonstrating the absence of Hg isotope fractionation. When amberjack were fed a shrimp diet, there was initial mixing of the amberjack organs toward the shrimp value (≏202Hg= −0.48 ‰, Δ199Hg= 0.32 ‰), followed by a cessation in further shifts in Δ199Hg and a small shift in ≏202Hg. We attribute the failure of Δ199Hg to reach the value of the shrimp diet to a reduction in Hg bioaccumulation from shrimp due to feeding inhibition, and the ≏202Hg shift to a small internal fractionation during excretion. Given that the feeding rate and Hg concentration of the diet can influence internal Hg isotope distribution, these parameters need to be considered in biosentinel fish studies. Environ Toxicol Chem © 2013 SETAC

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