Abstract Nitrate removal rates and dissolved oxygen (DO) levels were evaluated in small batch-mode wetland mesocosms with two different plant species, cattail (Typha spp.) and bulrush (Scirpus spp.), and associated mineral-dominated sediment collected from a mature treatment wetland. Nitrate loss in both cattail and bulrush mesocosms was first-order in nature. First-order volumetric rate constants (kV) were 0.30 d−1 for cattail and 0.21 d−1 for bulrush and rates of nitrate loss were significantly different between plant treatments (p 15 mg N/L). Areal removal rates were on average 25% higher in cattail versus bulrush mesocosms. DO in mesocosm water was significantly higher in bulrush versus cattail (p