Ecological improvement by restoration on the Jialu River: water quality, species richness and distribution

Abstract

The Jialu River has experienced serious water quality deterioration and biodiversity decline. An ecological restoration project was undertaken. We investigated water quality, species richness and distribution before and after restoration to describe ecological improvements on the Jialu River. After the project, total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD) and ammonium nitrogen (NH4+-N) decreased by 38.69, 40.52, 39.06 and 45.07% respectively. Concentrations of these indices were maintained at steady levels after restoration, indicating stable purification capacity had been established. However, TN, TP and NH4+-N concentrations were still higher than Level V of the Chinese surface water standards. In all, 155 species, belonging to 94 families, were found, with shore plants accounting for the largest proportion (26.53%). The biota showed different distribution patterns over space and time, except for species of zooplankton and phytoplankton, which were evenly distributed over space and time. Most species (71.71%) occurred in only one or two sites. Compared with July 2013, by July 2015 species richness had increased, on average, 65.61%. Furthermore, 31 novel native species were found in July 2015, covering the main functional groups (hydrophytes, zoobenthos and fishes). The recovery of an intact food chain as a result of the project facilitated water purification in the short term and the return of birds to the Jialu River in the long term. This study evaluated the recovery of the Jialu River and the results will inform future ecosystem restoration projects.