Stable isotopes of nitrogen and carbon in an aquatic food web recently invaded by Dreissena polymorpha (Pallas)

The carbon and nitrogen concentrations and the stable isotopic compositions (delta(13)C and delta(15)N) Of major abiotic and biotic constituents were determined in Oneida Lake, New York. This lake was invaded by the zebra mussel (Dreissena polymorpha) in 1990 and there have been concomitant changes in various biotic and abiotic lake properties. The C (46-49%) and N (12%) concentrations and C:N ratios (3.9-4) of zebra mussel flesh were similar to those reported for other lakes. Trophic positions were reflected in the delta(15)N values for which walleye > gizzard shad and yellow perch > Daphnia spp. and zebra mussel flesh > seston and sediment. There was an average increase of 3.6 parts per thousand N-15 per trophic transfer. Results from the delta(13)C analysis suggest that Daphnia spp. were using a distinct source of organic carbon whereas zebra mussel were using the entire seston resource. Only yellow perch showed a significant shift in delta(13)C values (1.1 parts per thousand), possibly reflecting a shift in food source and diet from 1992 to 1993.