Influence of the outflow from constructed wetlands on selected streams draining the agricultural landscape at the end of summer

Abstract

We investigated the impact of the effluent from four constructed wetlands on the structure of the macroinvertebrate and macrophyte communities in the receiving watercourses including the river Pesnica and the Sejanci Stream and Pavlovci Stream in NE Slovenia. Macroinvertebrates and macrophytes were sampled on the sites upstream and downstream of the inflows. Selected environmental parameters were also analyzed on each site. Among the measured chemical and physical parameters, the concentration of NH4–N in the water was the only one that was changed significantly by the inflow from constructed wetlands (CWs). The metrics obtained on the base of the macroinvertebrate community, including the values of diversity indices, the proportion of sensitive taxa and the saprobic index, revealed no significant statistical differences between the upstream and downstream values. Inflows of effluent also have no detectable impact on macrophytes. The removal of degradable organic matter, nitrogen, phosphorus, and suspended solids from the wastewater in studied CWs was sufficient to support this situation, and this has been encouraging to construct new CWs.