Stable Isotope Analysis of Carbon Flow in a Tundra River System

Stable isotope analysis was used to identify the major sources of carbon utilized by fish and aquatic invertebrates in the Koroc River, a tundra river system in northern Quebec. Juvenile arctic char (Salvelinus alpinus), together with adults and juveniles of other species of fish in freshwater, obtained their carbon from either allochthonous or autochthonous sources within the river system, via the invertebrate fauna. However, adult anadromous char caught in the river clearly derived their biomass carbon from feeding at sea. Despite the limited development of riparian vegetation throughout much of the lower river catchment, terrestrial organic matter was the most likely source of energy fueling the animal communities of small tributary streams and rapids of the mainstem Koroc. In contrast, epilithic algae made a significant contribution to food chains within Alik Lake, a deep basin along the main river channel. Aquatic mosses appeared to be of, at most, tertiary importance as a source of energy to the animal communities of the lake, despite their considerable biomass.