DataSheet1_Effects of phytoplankton diversity on resource use efficiency in a eutrophic urban river of Northern China.docx

Freshwater biodiversity has been declining in urban areas, which may threaten ecosystem functions. Although many studies have demonstrated a positive correlation between biodiversity and ecosystem functioning (BEF) in terrestrial and marine ecosystems, little is known about the BEF relationship in freshwater environments, especially in highly urbanized regions where water pollution is a major concern. Eutrophication in urban water bodies may trigger algae blooms, decreasing the evenness or functional divergence (FDiv) of phytoplankton communities, thus negatively affecting ecosystem functioning. Through an annual field investigation, we clarified the relationship between phytoplankton diversity and ecosystem functioning, represented as resource use efficiency (RUE), in an urban river in northern China. Results indicated that evenness in the phytoplankton community contributes most to driving ecosystem functioning compared to environmental factors. The relative abundance of dominant Bacillariophyta was positively correlated with the resource use efficiency of phytoplankton (RUEpp) but negatively correlated with the resource use efficiency of zooplankton (RUEzp). Both phytoplankton evenness and functional divergence were negatively linked to RUEpp but positively to RUEzp. Our findings suggest that the reduction of phytoplankton evenness and functional divergence may seriously threaten resource use efficiency (RUE), and its potential mechanism can provide a crucial reference for water quality protection and sustainable water resource utilization in the basin.

淡水生物多样性在城市地区的下降可能威胁到生态系统的功能。尽管许多研究已在陆地和海洋生态系统中证实了生物多样性（Biodiversity）与生态系统功能（Ecosystem Functioning，简称BEF）之间的正相关关系，但对于淡水环境中的BEF关系，特别是在城市化程度高、水污染成为主要问题的区域，了解甚少。城市水体中的富营养化可能引发藻华，降低浮游植物群落的均匀性或功能分化（Functional Divergence，简称FDiv），从而对生态系统功能产生负面影响。通过年度实地调查，我们阐明了在中国北方一条城市河流中，浮游植物多样性与其生态系统功能（以资源利用效率，Resource Use Efficiency，简称RUE）表示）之间的关系。结果表明，与环境因素相比，浮游植物群落的均匀性对驱动生态系统功能贡献最大。优势硅藻门（Bacillariophyta）的相对丰度与浮游植物的资源利用效率（RUEpp）呈正相关，但与浮游动物的资源利用效率（RUEzp）呈负相关。浮游植物的均匀性和功能分化与RUEpp呈负相关，但与RUEzp呈正相关。我们的研究结果表明，浮游植物均匀性和功能分化的减少可能会严重威胁资源利用效率（RUE），其潜在的机制可为流域水质保护和可持续水资源利用提供重要的参考。