Taxonomic, functional and interspecific response of zooplankton to management practices in carp ponds

Ecological management practices in fishponds are evolving rapidly, and zooplankton communities provide a reliable indicator of these effects. Over an eight-month period, in nine experimental ponds in the Czech Republic, we assessed the taxonomic, functional, and interspecific responses of zooplankton communities to three common carp feeding regimes: natural food with grain (NF), with 100% pellets (PP), and with a grain/pellet combination (WP), using redundancy analysis and correlation-based heat maps. The feeding regimes studied did not affect the taxonomic diversity of zooplankton, but significantly altered the abundance and biomass of Copepoda and raptorials. NF feeding resulted in the elimination of copepods, promoted functional variability of zooplankton, and enhanced interspecific interactions driven by large microphagous cladocerans (Bosmina, Daphnia), active rotifers (Asplanchna priodonta, Polyarthra longiremis), and the commensal Brachionus rubens. In contrast, year-round pellet feeding (PP and WP) preserved the importance of copepods but also led to the dominance of small mixophagous rotifers (Keratella quadrata, Brachionus diversicornis, Brachionus calyciflorus) and protozoa, promoting community homogenization and weakening interspecific zooplankton relationships. As the season progressed and trophic status, turbidity, primary production, and fish biomass increased, euryphagous and actively feeding species became increasingly prominent, resulting in a more heterogenous zooplankton network. Our study provides novel evidence that ecological management, particularly feeding regime, directly shapes zooplankton functional structure and interspecific dynamics in carp ponds.