SREL Reprint #3438

Investigating biomagnification of Hg and 137Cs in Nerodia floridana using stable isotopes

Melissa E. Lech1, Tracey D. Tuberville2, and Melissa A. Pilgrim1

1Division of Natural Sciences and Engineering, University of South Carolina Upstate,
Spartanburg, SC 29303
2Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29802

Abstract: Determining the fate of contaminants in ecosystems is important for conservation efforts and human health. Previous studies have shown that some contaminants bioaccumulate in organisms and can biomagnify through food webs. Stable isotope techniques provide a non-lethal approach for evaluating trophic transfer of contaminants. In this study, we used the nitrogen isotopic composition (δ15N) of Nerodia floridana (Florida Green Watersnake) collected from former nuclear cooling reservoirs to examine the potential biomagnification of two contaminants - mercury (Hg) and radiocesium (137Cs). We used scale samples taken from N. floridana (N=74) captured at three locations on the Savannah River Site (i.e., Par Pond, Pond B, and Pond 2) to quantify snake δ15N. We dried scale samples and weighed 0.3 mg of scale into tin capsules. The δ15N of packaged samples was determined using an isotope ratio mass spectrometer. We found a positive relationship between δ15N and Hg concentrations (r2=0.29, df=73, p<0.001). We found a significant positive relationship between δ15N and 137Cs for individuals collected at Par Pond (r2=0.85, df=9, p<0.001) and a non-statistically significant relationship between δ15N and 137Cs concentrations for individuals collected at Pond B and Pond 2. In addition, δ15N values ranged from 5.6 to 9.3, which is typically interpreted as a span of two trophic levels. Our results support that biomagnification of contaminants is occurring in our study systems. Future directions include establishing a δ15N system baseline for each study site by quantifying contaminant concentrations and δ15N of prey organisms occurring at each site.

SREL Reprint #3438

Lech, M. E., T. D. Tuberville, and M. A. Pilgrim. 2017. Investigating biomagnification of Hg and 137Cs in Nerodia floridana using stable isotopes. USC Upstate Student Research Journal X(Fall): 17-25.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).