Michael E. Sierszen Cynthia Hagley Janet R. Keough 1996 <p>Food-web components of a Lake Superior coastal wetland and adjacent offshore waters were examined&nbsp;with stable isotope ratio techniques for carbon and nitrogen. We found distinct carbon isotope ratio signatures&nbsp;for organisms collected in the wetland and from offshore. Both food-web groups seemed to be based on&nbsp;carbon fixed by phytoplankton. Compared to offshore organisms, the wetland food web was depleted in ¹³C.&nbsp;We found the nitrogen isotope ratio signatures to be enriched in&nbsp;¹⁵N by ~3% at each succeeding trophic&nbsp;level in both wetland and lake samples. No evidence of a direct energy link between the abundant macrophyte&nbsp;biomass in the wetland and the fisheries food web was found. The carbon ratio of rainbow smelt (<i>Osmerus&nbsp;mordux</i>) and walleye (<i>Stizostedion vitreum</i>) exhibited a shift from a wetland signature in young-of-the-year&nbsp;to an offshore signature in juveniles and adults. Yellow perch (<i>Perca flavescens</i>) young-of-the-year exhibited&nbsp;a planktivorous δ¹⁵N signature, while adults were enriched in ¹⁵N. Both examples illustrate the utility of&nbsp;stable isotope ratio techniques in confirming feeding shifts associated with growth and habitat change. </p> application/pdf 10.4319/lo.1996.41.1.0136 en Analysis of a Lake Superior coastal food web with stable isotope techniques article