SREL Reprint #2776

 

 

 

Dietary mercury exposure and bioaccumulation in larvae of the southern leopard frog, Rana sphenocephala

Jason Unrine and Charles Jagoe

Savannah River Ecology Laboratory, University of Georgia, P.O. Drawer E, Aiken, SC 29803, USA

Abstract: We investigated dietary mercury exposure and bioaccumulation in larvae of the southern leopard frog, Rana sphenocephala. Aufwuchs, an important dietary source for many larval amphibians was collected from three reservoirs, a constructed wetland used for groundwater treatment and from mercury-enriched mesocosms in South Carolina, USA to determine the relationship between inorganic mercury and methylmercury in aufwuchs. Four experimental diets were formulated with mercury enriched aufwuchs, trout pellets, rabbit pellets, agar, and gelatin to concentrations that bracketed those observed in aufwuchs from the field and reported in the literature from sites contaminated primarily by atmospheric deposition. The diets were fed to southern leopard frog larvae in the laboratory for the entire larval period (60-254 d) and metamorphs and tadpoles that died before metamorphosis were analyzed for inorganic and methylmercury content by GC-CVAFS. We found that methylmercury concentration increased with total mercury concentration in aufwuchs, but the proportion of methylmercury to total mercury decreased with increasing total mercury concentration. In the feeding experiment, bioaccumulation factors were low and were inversely related to exposure concentration for both methylmercury and inorganic mercury. Methylmercury was transferred from diets to larvae 4.7 times more efficiently than inorganic mercury suggesting that subcellular fractionation of Hg in algal cells that constituted the aufwuchs used to formulate experimental diets governed relative assimilation efficiencies of the two mercury species.

Keywords: amphibian, diet, exposure, bioaccumulation factor, aufwuchs

SREL Reprint #2776

Unrine, J. M. and C. H. Jagoe. 2004. Dietary mercury exposure and bioaccumulation in larvae of the southern leopard frog, Rana sphenocephala. Paper 83 In: M. Horvat, N. Ogrinc, and J. Kotnik (Eds.). 7th International Conference on Mercury as a Global Pollutant. Jožef Stefan Institute, Ljubljana, Slovenia.

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