Benthic nutrient fluxes influenced by the common carp Cyprinus carpio in pond polyculture with special reference to nitrification, denitrification and nitrate ammonification

Cyprinus carpio is an important species in pond aquaculture as it can effect bioturbation of sediments which might influence benthic fluxes and biogeochemical processes at the sediment-water interface. In this study, the influence of common carp Cyprinus carpio on nutrient fluxes, specifically nitrification, denitrification and nitrate ammonification rates at the sediment-water interface in pond polyculture was investigated through field experiments and ex situ incubation. C. carpio enhanced the sediment oxygen consumption (SOC) from April to September (except in July). The fish did not influence the NH4+-N flux, but promoted NOx--N (NO2--N and NO3--N) release from the sediment to the water from May to September and it also promoted soluble reactive phosphorus (SRP) release from July to September. Nitrification, denitrification and nitrate ammonification were also significantly promoted by C. carpio. The results suggest that C. carpio can plays a very important role in the migration and transformation of nitrogen and phosphorus at sediment-water interface which could also help nitrogen removal in pond water.