Abstract:The eutrophication problem caused by various reasons such as excessive nitrogen level in aquaculture wastewater are the most critical obstacle to the sustainability of aquaculture industry in China at present. Denitrification and anaerobic ammonium oxidation (Anammox) are important nitrogen cycling processes in natural water ecosystems, which are the main nitrogen removal pathways in the sediments. Clams could not only purify aquaculture water column by their water-filtering activities and wriggle behaviors, but also change the material transportation which occurs in the sediment/water interface. In the present study, the slurry incubation experiments using the sediment samples collected at the area with or without Manila clam (Ruditapes philippinarum) in a biological wastewater treatment pond in Sept., Oct., Nov. and Dec., 2020 have been performed to investigate the potential denitrification and anammox activity rate, and the relationship between the denitrification or anammox activity rate and the porewater physicochemical parameters have also been analyzed. The results showed that the anammox was found in the sediment of clam culture area in Oct. and Nov., and the denitrification-anammox coupling were also found. The denitrification activity rate of sediments with clam culture in the four months were higher than that of sediments without clam, and the highest rate (0.005 8 μmol/kg·h) was found in the sample of Sept. There was a significant positive correlation (P<0.01) between the denitrification activity rate and porewater temperature in clam culture area, and between the porewater NH4+ level and anammox activity rate. The anammox has been found in the seawater aquaculture pond. The clam promoted denitrification and anammox processes in sediment/water interface which showed a vital role in nitrogen removal in sediment in the present study. The results will not only enrich the nitrogen cycling theory of aquaculture ecosystem, but also provided insights to establishing new biological wastewater treatment measures.
