Sensitivity and reliability of diatom metrics and guilds in detecting the impact of urbanization on streams

Abstract

• The impact of urbanization on diatoms yet to be elucidated in China. • Diatom composition constrained by %Urban, TN, COD and WD. • Simpson’s index, Shannon-Wiener index, %Stalked individuals, %Prostrate individuals and TDI significantly responded to urbanization. • TDI variation explained by urbanization and nutrients. The impact of land use changes on stream biota is the major concern of aquatic biodiversity conservation in the context of the rapid global population growth. Benthic diatoms are good indicators to detect land use impact and provide insights into environmental management. However, the impact of urbanization on benthic diatoms has not been well understood in China. In the hope of promoting the understanding of this issue, a research program is designed to examine the responses of selected diatom metrics to urbanization in the Qiantang River Basin. The study identifies a total of 143 taxa belonging to 34 genera and 20 families, with an average of 32 taxa per site. It shows that urbanization greatly has degraded stream chemical and physical quality in terms of high nutrients concentration and fine sediments. Meanwhile, the redundancy analysis reveals that urban stream diatom compositions are mainly associated with %Urban, TN, COD and WD. A total of three metrics (Simpson’s index, Shannon-Wiener index and TDI) and two guilds (%Stalked individuals and %Prostrate individuals) respond to urbanization significantly, and their variations are explained more by land uses at watershed scale than by those at local scale. Watershed land use (% Urban and % Forest) and nutrients (TN) explain 55% of the variation in TDI. The results of the study highlight the sensitive responses of diatom metrics and guilds to urbanization, which may provide effective tools in the assessment of urbanization impact on streams in China.