A stable carbon and nitrogen isotope study of lake food webs in Canada's Boreal Plain

摘要: 1. Stable carbon and nitrogen isotope fish stomach content analyses were used to investigate food webs in five relatively undisturbed lakes on the Boreal Plain of Canada. Stable analysis was also determine importance external internal sources. 2. Overlap signatures primary producers made it difficult unambiguously feeding habits many invertebrates. However, suggested that inputs detectable aquatic chains one lake with a short water residence time («1 year). In other four lakes, times ≥1 year, autochthonous only source webs. 3. Food these spanned range trophic levels. Both invertebrates appeared eat variety food, often at more than level. 4. With exception (SPH20), top predators northern pike (Esox lucius) fathead minnows (Pimephales promelas), occupied similar positions despite large differences body size morphology. SPH20, where there two additional species, higher position. all each be omnivores generalists. 5. The prevalence omnivory apparent generalist suggest organisms are flexible their will resilient disturbance.