Forest Detected as One of the Key Factors for Maintaining Phytoplankton Species Richness in a Lowland Rural Catchment

Environmental change accelerates biodiversity loss, especially in vulnerable freshwater ecosystems. Aquatic ecosystems are exposed to multiple stressors. Hereby, it is valuable to understand how impacts of multiple stressors are translated into changes of aquatic biodiversity. Phytoplankton as a key biological element in the aquatic ecosystem, its species richness is an important pointer to interpret the ecological respond under environmental alterations. In this study, we evaluate the responses of riverine phytoplankton species richness to multiple stressors by an interdisciplinary modelling approach. Firstly, a random forest model was developed for ranking the stressors’ importance, and then generalized addictive mixed models were established for quantifying and simulating the potential response of phytoplankton biodiversity evoked by the main stressors. The share of forest and pasture areas had an outstanding explanation to the variation of riverine phytoplankton species richness. Hereby, forest share had a positive effect while pasture affected species richness in a negative way. Our result also enlightened the important influence of the flow regime. Specifically, in deriving indicators of hydrological alteration of short time scale, their close linkage with the phytoplankton biodiversity pattern was shown. Further, our findings highlighted the spatial variability of independent effects of land cover and hydrological alteration impacts on the phytoplankton community structures among different subbasins. Our integrated models’ framework was shown to be beneficial to deal with complex environmental condition analysis and could be applied in river basin management. As a recommendation we would emphasize the significance of preservation of forest area in protecting the aquatic algal biodiversity as key point in maintaining the functioning of river ecosystems