CW archaeal communities were composed of Euryarchaeota(66–99%) and Thaumarchaeota (1–34%) (Fig. 4). The three studied CW systems showed different depth-related change pattern of Euryarchaeota proportion. In wetland WG, the proportion of archaeal phylum Euryarchaeota decreased with increasing wetland depth.However, in either wetland WS or wetland WZ, Euryarchaeota proportion showed a slight increase followed by a considerable decrease.For the three CW systems, their Euryarchaeota proportion differed considerably in lower part, but slightly in upper and middle parts.