M11 AM Using Stable Isotopes in Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 11:40 AM in 343-344

(FIS-1117-826214) Uses and abuses of stable isotopes in ecotoxicology.

Fisk, A¹, Kidd, K², ¹ University of Georgia, Athens, GA, USA² University of New Brunswick, Saint John, NB, Canada

ABSTRACT- Stable isotopes of carbon (¹³C) and nitrogen (¹⁵N) have become a common tool in ecology for quantifying carbon flow and food web structure. The fate and potential effects of anthropogenic contaminants are largely determined by carbon flow and food web structure, and so, not surprisingly, stable isotopes have become a popular metric for explaining observed patterns of contaminants in food webs. However, there has been a recent wave of publications in the ecological literature questioning some of the assumptions made when using stable isotopes and there is a call for more laboratory experiments. For example, there has been little attention paid to the kinetics of stable isotopes (i.e., how quickly they change after a diet switch) and how they vary across tissue types. Kinetics will determine the length of time it will take an organisms to achieve a stable isotope signature that is in equilibrium with its diet; recent feeding studies suggest this may take 100s of days in fish and other poikilotherms although it is highly dependent on tissue type. Such assumptions or caveats need to be considered when they are applied to contaminant data because the time for a contaminant to achieve equilibrium in an can vary from hours to years and is specific to the chemical. Ignoring these assumptions could lead to erroneous conclusions about the dynamics of contaminants in the environment but consideration of these assumptions could lead to greater insights. This talk will summarize some of the assumptions/caveats involved in stable isotope research and how they affect the application and utility of this tool in ecotoxicology.

Key words: stable isotope, assumptions, methods, food web