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

(KID-1117-850549) Advantages and Limitations of Using Stable Isotope Ratios to Understand the Accumulation of Persistent Organic Pollutants in Aquatic Food Webs.

Kidd, K.¹, Fisk, A.², Borgå, K.³, Muir, D. ⁴, ¹ University of New Brunswick, Saint John, NB, Canada² University of Georgia, Athens, GA, USA³ Norwegian Polar Institute, Tromsø, Norway⁴ Environment Canada, Burlington, ON, Canada

ABSTRACT- An increasing number of studies are using ratios of stable nitrogen isotope ratios (¹⁵N) to characterize the trophic positioning of organisms, and quantify the length of the food web and biomagnification of persistent organic pollutants (POPs) in freshwater and marine systems. These studies have shown that concentrations of DDT, PCBs and other chlorinated organics in biota are significantly related to their trophic position. The slope of regression of the (log) pollutant versus trophic level based on ¹⁵N has been termed a bioaccumulation rate and its antilog the trophic magnification factor (TMF). The TMF can be positive or negative depending on the extent of magnification or metabolism of a contaminant by upper-trophic-level biota. Studies have now been completed in several Great Lakes (both Laurentian and African), in productive and unproductive systems, in marine and freshwaters, and at arctic through tropical latitudes; these results can be contrasted on a broader scale to improve our understanding of food web magnification of POPs. As an example, the TMFs of log p,p'-DDE versus ¹⁵N are consistently positive and vary by a factor of 2 from tropical to arctic latitudes in freshwater food webs. In contrast, negative TMFs have been observed for compounds such as phthalate esters, indicating that food web metabolism of some pollutants can be quantified with this technique. Data from tropical, temperate and arctic lakes and oceans are compiled herein to determine whether patterns in the slopes of the relationships of specific POPs versus trophic level/¹⁵N exist across systems, and whether these differences can be explained by system-specific factors such as productivity or by broader influences such as climate. In addition, we discuss the advantages to and limitations of using this technique in studies of pollutants in aquatic food webs.

Key words: stable isotopes, biomagnification, food webs