Spatial and temporal variabilities of delta super(13)C and delta super(15)N within lower trophic levels of a large lake: implications for estimating trophic relationships of consumers

• Published in: Hydrobiologia Vol. 675; no. 1; pp. 41 - 53
• Main Authors: Guzzo, Matthew M, Haffner, GDouglas, Sorge, Stuart, Rush, Scott A, Fisk, Aaron T
• Format: Journal Article
• Language: English
• Published: 01.10.2011
• Subjects: Dreissena polymorpha; Freshwater; Morone americana; Perca flavescens; North America, Erie L
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/s10750-011-0794-1

Stable isotopes of carbon ( delta super(13)C) and nitrogen ( delta super(15)N) often have unique values among lake habitats (e.g. benthic, littoral, pelagic), providing a widely used tool for measuring the structure and energy flow in aquatic food webs. However, there has been little recognition of the spatial and temporal variabilities of these isotopes within habitats of aquatic ecosystems. To address this, delta super(13)C and delta super(15)N were measured in seston, zebra mussels (Dreissena polymorpha) and young-of-year (YOY) yellow (Perca flavescens), and white perch (Morone americana) collected from four sites across the offshore habitat of the western basin of Lake Erie during June-September 2009. Values of delta super(13)C and delta super(15)N showed significant spatial and temporal variations, with month accounting for >50% of the variation, for both stable isotopes and all the species except seston. Such variation in isotope values has the potential to significantly influence or confound interpretation of stable isotopes in measures, such as trophic position (TP) which use lower trophic level organisms as their baseline. For example, TP was found to vary up to 0.7 for yellow and white perch (TP = delta super(15)N sub(fish) - delta super(15)N sub(zebra mussel)/diet-tissue fractionation factor) depending on the zebra mussel data used (e.g., from a different location or a different collection month). As the use of stable isotopes continues to move from qualitative to more quantitative measures of trophic structure, food web research must recognize the importance of stable isotopes' variability in lower trophic level organisms, especially in large lake systems.