Biological indicators of ecological quality in typical urban river-lake ecosystems: The planktonic rotifer community and its response to environmental factors

Abstract

River-lake system is the framework of the “sponge city”, tackling urban water problems of flooding. Rotifers, an essential zooplankton component of water ecosystems, are sensitive to environmental changes. However, the utility of rotifers as indicators of water quality in urban river-lake ecosystems is still unclear. We investigated the response of rotifer community to environmental factors and evaluated the availability of traditional taxonomic indicators and individual rotifer indicators in the river-lake ecosystem of Changde, south central China. A total of 95 rotifer species were identified in 15 sampling sites during a year survey. Rotifer abundance ranged from 1 (the Yuan River) to 2628 ind.·L−1 (Lake Liuye). Temperature, water depth and trophic state were the key factors for spatial-temporal variation of rotifer community in the urban river-lake ecosystems. Individual rotifer indicators, biodiversity indices, the Brachionus: Trichocerca ratio and the Keratella-index were less useful in evaluating the trophic status in this study. However, we founded that the rotifer trophic state index (TSIROT) values and total rotifer abundance were most consistent with values of the comprehensive trophic level index (TLIc). Furthermore, TSIROT values showed stability and resistance to changes when the time horizon increased. This study suggests that the TSIROT index is a reliable indicator of water quality in river-lake ecosystems with high water depth variation. This is a pilot study for evaluating of reliable bioindicators for sponge city design. Long-term studies in more sponge cities should be taken to validate our findings.