Enhancing nitrogen removal in antibiotic-contaminated sediments: The remediation potential of Tubifex tubifex

Sediment nitrogen (N) removal is critical in eutrophic aquatic ecosystems but is often impaired by antibiotic stress. While Tubifex tubifex has shown potential to enhance N removal, its effectiveness and underlying mechanisms under antibiotic exposure remain unclear. A lab-scale trial investigated sediment N removal under antibiotic stress by the addition of T. tubifex . The results showed that the addition of T. tubifex accelerated sediment organic matter (OM) and N loss under antibiotic stress, with averages of 25.5% and 20.5% increased loss (IL) in both antibiotics and T. tubifex addition treatment compared to treatment only-antibiotics addition in the 120-day experiment, respectively. The percentages of the increased in water to the IL in sediment were only 1.4%, 0.3%, 2.5% and 0.5% for NH 4 + -N, NO x - -N, TN and COD, respectively, at the end of the experiment. In general, the absolute abundances of nitrifying genes (AOA, AOB, and nxrA ) and denitrifying genes ( napA , narG , nirS , nirK , qnorB , and nosZ ) decreased by 3.3- to 196.7-fold following the only-addition of antibiotics, but increased by 1.7- to 194.1-fold with the co-addition of T. tubifex . Therefore, adding T. tubifex is an effective strategy for sediment N removal under antibiotic stress without substantially increasing the water N concentration, which provides support for sediment remediation in eutrophic aquatic ecosystems affected by antibiotic pollution. • Sediment N removal under antibiotic stress was accelerated by T. tubifex addition. • T. tubifex aided OM decay under antibiotics without raising sediment available N . • T. tubifex boosted sediment N loss but slightly raised water N under antibiotic stress. • T. tubifex raised nitrification-denitrification and anammox genes under antibiotics. • T. tubifex addition is a potential strategy for antibiotic-sediment N removal.