Investigating the impact of watershed and local environmental variables on the spatial distribution, composition and functional diversity of benthic algal communities in the upper Red River Basin, China

Understanding the complex relationships between benthic algal communities and environmental factors is crucial for ecosystem management and conservation. In this study, we investigated benthic algal communities in the upper Red River Basin in China. We collected data on land use, topography and other factors at the watershed scales to gain a comprehensive understanding in the upper Red River Basin in China. Partial canonical correspondence analysis, partial redundancy analysis and variance partitioning analysis methods were used to assess the effects of watershed and local environmental factors on benthic algal communities and their variation. The percentage of landscape that was forest (F-PL), the percentage of landscape that was cropland (C-PL), the percentage of landscape that was water (W-PL), elevation, slope, pH and water level fluctuation (WF) were identified as significant factors affecting the distribution of benthic algal communities. The diversity of benthic algal communities were greatly affected by environmental factors as F-PL, W-PL, precipitation (Prcp), slope, permanganate index (CODMn) and index of substrate (IOS). Slope, F-PL and Prcp showed a positive correlation with species evenness and a negative correlation with community density. The characteristics of functional groups of benthic algae were also shown to be strongly influenced by C-PL and IOS. According to the variance decomposition (VPA) results, it can be seen that, although the explanatory power of individual local and watershed environmental factors was roughly similar, their joint explanatory power was relatively low. Therefore, the influence of watershed environmental factors on benthic algal communities should not be overlooked.