The　emerging　antibiotics　in　mariculture　wastewater　has　challenged　conventional　biological　treatment　processes,　but　the　impact　of　sulfamethoxazole　(SMX)　on　saline　microalgal-bacterial　symbiotic　systems　and　the　underlying　microbial　response　mechanisms　remain　unclear.　This　study　investigated　the　resilience　of　a　microalgal-bacterial　symbiotic　moving　bed　biofilm　reactor　(MBS-MBBR)　treating　saline　wastewater　under　SMX　stress,　focusing　on　nitrogen　removal　performance,　microbial　physiological　activities,　and　ecological　interactions.　The　ammonia　removal　efficiency　remained　stable　(＞99.0%)　at　0.1–1　mg/L　SMX　but　decreased　to　62.3%　at　5　mg/L　SMX.　Elevated　SMX　inhibited　microbial　respiration,　but　enhanced　extracellular　polymer　substances　synthesis　and　intracellular　antioxidant　activities.　Microbial　community　analysis　revealed　that　0.1–1　mg/L　SMX　promoted　the　enrichment　of　denitrifer　(Denitromonas),　while　5　mg/L　SMX　suppressed　nitrifiers　(Nitrosomonas,　Nitrospira).　SMX　exhibited　differential　impacts　to　distinct　nitrogen　metabolic　functions.　Furthermore,　microalgal-bacterial　consortia　exhibited　enhanced　cooperative　interactions　under　SMX　stress.　This　study　provides　theoretical　support　to　stabilize　engineering　mariculture　wastewater　treatment　processes.　©　2025　Elsevier　Ltd