Date of Award


Publication Type

Master Thesis

Degree Name



Great Lakes Institute for Environmental Research

First Advisor

Pitcher, Trevor (Biological Sciences), Fryer, Brian (Earth & Environmental Sciences), Fisk, Aaron (Earth & Environmental Sciences)


Biology, Oceanography.




Stable isotope studies often rely on only two tracers (usually [delta] 13C and [delta]15N) to study marine ecosystems, which are inherently complex. The ability of elements to act as additional tracers of ecological processes in marine organisms and in a marine food web was investigated. The element analysis of two sleeper shark species, Pacific ('Somniosus pacificus') and Greenland ('Somniosus microcephalus'), collected from different ecosystems demonstrated that elements are useful indicators of physiological and exposure differences between closely related species. The Greenland shark's food web about Iceland was more clearly resolved concerning trophic links and carbon sources by combining mercury data with stable isotope and stomach content data. Mercury also indicated that 'Lycodes' potentially belonged to a different food web than the other fishes. Results from this research demonstrated the value of elemental tracers in food web studies and generated new questions about the application and interpretation of trophic position designations.