The influence of benthic faunal diversity on the stability of nitrogen removal and greenhouse gas emissions in constructed wetlands under antibiotic disturbance

Benthic fauna play a crucial role in ecosystem processes in constructed wetlands (CWs), yet their influences on the stability of nitrogen removal and greenhouse gas (GHG) emissions under antibiotic stress remain unclear. In this study, we investigated the effects of benthic fauna species richness (zero, one, and three species) and species compositions on the stability of nitrogen removal and GHG emissions in CWs under antibiotic stress. Results showed that: (1) At a species richness of three, reduced stability of the nitrifying bacterium Nitrospira abundance led to decreased stability of effluent nitrate concentrations. In contrast, systems containing Bellamya aeruginosa and Chironomus riparius enhanced the stability of effluent ammonium and total inorganic nitrogen concentrations. This improvement was mainly attributed to more stable plant nitrogen uptake, stabilized activities of key nitrogen-cycling enzymes (nitrate reductase and nitric oxide reductase: NOR), and stabilized denitrifying and organic matter-degrading bacterial communities. (2) At a species richness of one, increased stability of key denitrification enzymes, including NOR and nitrous oxide reductase, enhanced the stability of N₂O emissions. Moreover, benthic fauna compositions regulated the stability of plant antioxidant enzymes, key nitrogen transformation enzymes, methylotrophic bacteria, and carbon mineralization–associated bacteria, thereby influencing the stability of GHG emissions. (3) Multifunctionality stability analysis further indicated that the Corbicula fluminea systems exhibited relatively poor performance and should be avoided in practical applications. Overall, our findings demonstrate that benthic fauna diversity is a key determinant of CW stability under antibiotic stress, with important implications for the optimization of CW design and management.