Species identity matters when interpreting trophic markers in nearshore aquatic food webs

Session: 57. - Advances in Understanding Nearshore Ecosystems in Great Lakes and Connecting Channels

Carolyn Foley, Illinois-Indiana Sea Grant, cfoley@purdue.edu
Zachary Feiner, Purdue Univ., Dept. Forestry & Natural Resources, zsfeiner@gmail.com
Harvey Bootsma, University of Wisconsin-Milwaukee, hbootsma@uwm.edu
Sergiusz Czesny, University of Illinois, Illinois Natural History Survey, czesny@Illinois.edu
John Janssen, University of Wisconsin-Milwaukee, jjanssen@uwm.edu
Jacques Rinchard, The College at Brockport, State University of New York, jrinchar@brockport.edu
Tomas Hook, Purdue University, Dept. Forestry and Natural Resources, thook@purdue.edu

Abstract

In aquatic systems, food web linkages are assessed using diet contents, stable isotope ratios, and, increasingly, fatty acid composition of organisms.  These vary in their temporal resolution and power to elucidate trophic behavior of organisms.  Understanding whether assumed linkages between different trophic metrics and the trophic behavior of individuals are coherent and consistent across species is an important step toward their effective use in food web studies.  To assess links among trophic markers, we compared relationships between important diet components, fatty acids, and stable isotope ratios in yellow perch (Perca flavescens), round goby (Neogobius melanostomus), and spottail shiner (Notropis hudsonius) collected from nearshore Lake Michigan.  We found some evidence for agreement between metrics, especially between diet components, n-3:n-6 fatty acid ratios, and ?¹³C and ?¹⁵N stable isotope ratios.  However, we also observed significant variation in relationships among markers and species, potentially due to taxonomic variation in the specific diet items consumed (e.g., chydorids and Dreissena) and species-specific biochemical processes.  Understanding the effects of taxonomic variation on prey and predator signatures could significantly improve the usefulness of fatty acids in food web studies, whereas diet contents and stable isotopes appear to be reliable indicators of trophic niche in aquatic food webs.

1. Keyword
food chains

2. Keyword
stable isotopes

3. Keyword
fish diets

4. Additional Keyword
fatty acid