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Analysis of a Lake Superior coastal food web with stable isotope techniques

June 7, 1996

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

Publication Year 1996
Title Analysis of a Lake Superior coastal food web with stable isotope techniques
DOI 10.4319/lo.1996.41.1.0136
Authors Janet R. Keough, Michael E. Sierszen, Cynthia Hagley
Publication Type Article
Publication Subtype Journal Article
Series Title Limnology and Oceanography
Index ID 70203753
Record Source USGS Publications Warehouse
USGS Organization National Wetlands Research Center; Wetland and Aquatic Research Center