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MERCURY AND STABLE ISOTPOES OF CARBON AND NITROGEN IN MINK
Citation:
LAKE, J. L., S. A. RYBA, J. R. SERBST, C. F. BROWN, AND L. GIBSON. MERCURY AND STABLE ISOTPOES OF CARBON AND NITROGEN IN MINK. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 26(12):2611-2619, (2007).
Impact/Purpose:
This manuscript presents the results of a study to determin Hg concentrations and stable isotope levels in the mink and their stomach contents in Rhode Island. The study was undertaken to determine whether analysis of stomach contents could provide useful insight to the dietary composition and to advance understanding of bioaccumulation of Hg by these aquatic dependent predators. Significant relationships between stomanch contents and mink muscle tissues for Hg concentrations and stable isotope values. These results suggest that, although stomach contents represent a partially digested, point-in-time estimate of diet, their analysis may yeild useful information about dietary composition, trophic positioning and contaminant accumulation. The results of this study will be used to facilitate estimations of dietary uptake of Hg at numberous small stream sites that comprise the habitat for mink, and thereby allow development of exposure fields from collection and analysis of easily collected field prey.
Description:
The total mercury concentrations, δ15N and δ13C in tissues of mink (Mustela vison) captured in Rhode Island during winters of the years 1999-2004 showed samples to be statistically distinct based on location. Mink captured in salt marsh environments (salt marsh group mink, SMGM) showed significantly lower mean Hg concentrations in liver and muscle tissue and significantly higher values of δ15N and δ13C in muscle, than corresponding samples of mink from upland freshwater locations (upland group mink, UPGM). Further separation of UPGM on the basis of watershed showed no significant differences in mean mercury concentration in liver or muscle samples among watersheds. However, small, but significant, differences in mean δ15N and δ13C in mink muscle were found among these watersheds. Stomach content samples obtained from the mink carcasses showed fish, frogs and crayfish were the dominant food items in UPGM, but in SMGM, fish predominated. Significant correlations were found for total Hg concentrations and stable isotope values between stomach contents and tissues. Comparisons of increases in Hg concentrations and δ15N values from stomach contents to muscle tissue showed nonsignificant differences between UPGM and SMGM for Hg concentrations (SMGM, factor of 4.2; UPGM, factor of 3.9) and δ15N (SMGM, difference of 3.9 ‰; UPGM, difference of 3.1 ‰). These results suggest that the length of the trophic step and the extent of accumulation of Hg was about equal in both mink groups in spite of the differences in dietary composition and possible differences in accumulation of organic and inorganic mercury. The correspondence of stable isotope values and Hg concentrations between mink tissues and their stomach contents represents a positive first step in the development of an approach to estimate Hg exposure for mink from analysis of prey.