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

Abstract

Feeding experiments were performed to investigate mercury (Hg) isotope fractionation during trophic transfer and internal distribution of total Hg (THg) in marine fish on exposure to natural seafood. Young-of-the-year amberjack (Seriola dumerili) were fed with either blackfin tuna (Thunnus atlanticus; 2647ng/g THg) or brown shrimp (Farfantepenaeus aztecus; 25.1ng/g THg) for 80 d or 50 d, respectively, and dissected for muscle, liver, kidney, brain, and blood. After 30 d of tuna consumption, Hg isotopes (Hg-202 and Hg-199) of the amberjack organs shifted to the tuna value (Hg-202=0.55 parts per thousand, Hg-199=1.54 parts per thousand,), demonstrating the absence of Hg isotope fractionation. When amberjack were fed a shrimp diet, there was an initial mixing of the amberjack organs toward the shrimp value (Hg-202=-0.48 parts per thousand, Hg-199=0.32 parts per thousand), followed by a cessation of further shifts in Hg-199 and a small shift in Hg-202. The failure of Hg-199 to reach the shrimp value can be attributed to a reduction in Hg bioaccumulation from shrimp resulting from feeding inhibition and the Hg-202 shift can be attributed 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 must be considered in biosentinel fish studies. Environ Toxicol Chem 2013;32:2322-2330. (c) 2013 SETAC