Contrasting the ecology of planktonic crustaceans from freshwaters: Insights from stable isotopes (δ13C, δ15N)

• 3 lakes across latitudinal gradient in Europe (Croatia, Poland, Lithuania) were sampled. • Stable isotopes of carbon and nitrogen were measured in tissues of planktonic crustaceans. • Strong partitioning of isotopic niches among planktonic crustaceans was found. • C:N ratio (proxy for lipid content) declined with trophic level. We examined the feeding ecology of planktonic crustaceans at three waterbodies situated across a latitudinal gradient in Europe (Croatia, Poland, Lithuania) using stable isotope measurements (δ 13 C, δ 15 N) in animal tissues. Relative, lake-specific values of δ 15 N showed that in all lakes, calanoid copepods occupied the highest trophic position, while Daphnia sp. and Diaphanosoma sp. were located closer to primary producers with Cyclopoid copepods located between these groups. We found a negative correlation between C:N ratio (proxy for lipid content) and δ 15 N, which indicates lipid content declined with the trophic level of the animals. Employment of stable isotope-based approach allows better recognition of trophic linkages than could be inferred from classical methods, and therefore our results contribute improvement of management strategies developed for aquatic ecosystems.