Carbon and nitrogen (δ13C, δ15N) isotope ratios of zooplankton in Lake Maggiore (Italy): a 13-year dataset

N, C% and N% for 1,084 zooplankton samples (2,168 total isotope analyses). Analyses were performed on zooplankton taxa inhabiting Lake Maggiore, including copepod developmental stages, as well as on pooled organisms from three size-fraction groups (≥80 µm, ≥450 µm and ≥850 µm). We include 1,232 data on Standing Stock Density and Biomass for the ≥450 µm and ≥850 µm size fractions; data for the ≥80 µm fraction were published previously. The ≥450 µm and ≥850 µm size fractions were selected to target organisms preyed upon by fish, whereas the ≥80 µm fraction was included to better understand trophic relationships within the zooplankton community. The dataset resulted from a monitoring program on pelagic zooplankton and persistent organic pollutants, funded by the Commissione Internazionale per la Protezione delle Acque Italo-Svizzere, and conducted between 2010 and 2022. These data enable investigations of trophic relationships within the zooplankton community and fish predation, providing a basis for modelling the transfer of persistent organic pollutants through the pelagic food web.