How　microbial　communities　respond　to　wastewater　fluctuations　is　poorly　understood.　Full-scale　surface　flow　constructed　wetlands　(SFCWs)　were　constructed　for　investigating　microbial　communities.　Results　showed　that　influent　wastewater　changed　sediment　bacterial　community　composition　seasonally,　indicating　that　a　single　bacterial　taxonomic　group　had　low　resistance　(especially,　Actinobacteriota　and　Gammaproteobacteria).　However,　copy　numbers　of　16S　rRNA,　ammonia　oxidizing　archaea,　ammonia　oxidizing　bacteria,　nirS　and　nirK　in　the　first　stage　SFCWs　were　2.49　×　1010,　3.48　×　109,　5.76　×　106,　8.77　×　108　and　9.06　×　108　g−1　dry　sediment,　respectively,　which　remained　stable　between　seasons.　Moreover,　decreases　in　the　nitrogen　concentration　in　wastewater,　changed　microbial　system　state　from　heterotrophic　to　autotrophic.　Micro-eukaryotic　communities　were　more　sensitive　to　wastewater　fluctuations　than　bacterial　communities.　Overall,　results　revealed　that　microbial　communities　responded　to　spatio-temporal　fluctuations　in　wastewater　through　state　changes　and　species　asynchrony.　This　highlighted　complex　processes　of　wastewater　treatment　by　microbial　components　in　SFCWs.　©　2024　Elsevier　Ltd