Multi-scale temporal dynamics of epilithic algal assemblages: evidence from a Chinese subtropical mountain river network

Abstract

Research on multi-scale temporal dynamics of lotic algal assemblages remains scarce. In this study, we analyzed epilithic algae sampled monthly from a Chinese subtropical mountain river network from 2004 to 2007, by using a multivariate time series modeling approach. We hypothesized that (1) multi-scale temporal dynamics exist within algal communities; (2) physical and chemical conditions drive algal temporal dynamics; and (3) tributary sites differ in algal temporal changes. This study revealed 2–4 site-specific algal temporal dynamics, contributed by 23–45% component taxa. Among the time-related taxa, percentages of high profile guild taxa were higher than both the low profile and the motile guild taxa. Several algal temporal dynamics were found to be driven by water temperature, conductivity, or current velocity, within which influences of conductivity at two sites resulted in directional changes in algal communities. Furthermore, tributary sites differed in algal temporal changes when compared to the two mainstream sites. Our findings imply that natural fluctuations and agricultural disturbance together shaped algal temporal dynamics in the studied river network. In conclusion, for accurately tracking algal temporal dynamics, we recommend that long-term and high-frequency biomonitoring protocols are developed. Moreover, both the mainstream and tributary sites should be monitored simultaneously.