Stable Isotope Food Web Analysis of a Large Subtropical Lake: Alternative Explanations for 15N Enrichment of Pelagic vs. Littoral Fisheries
The complex nature of lake food webs has been well established from several decades of research. Simple models of food chains with distinct trophic levels[1,2] have been replaced by complex models with indistinct trophic positions[3,4]. Tight coupling between pelagic, benthic, and littoral components of the lake ecosystem is a generally acknowledged principle[5,6,7], but one requiring further study. Most of the recent insights into food web structure in lakes have been based on stable isotope analysis. This approach uses naturally occurring isotopes of elements such as carbon (13C:12C) and nitrogen (15N:14N) in order to evaluate food web structure. The carbon isotope composition (δ13C) varies widely among different producers, but the isotopic composition of a consumer resembles that of its prey, and the carbon isotope composition of a top predator can, under appropriate circumstances, be used to infer the basal carbon sources that support its growth.