Sediments and flow have mainly independent effects on multitrophic stream communities and ecosystem functions

Stream ecosystems are affected by multiple abiotic stressors, and species responses to simultaneous stressors may differ from those predicted based on single-stressor responses. Using 12 semi-natural stream channels, we examined the individual and interactive effects of flow level (low or high flow) and addition of fine sediments (grain size < 2mm) on key ecosystem processes (leaf breakdown, algal biomass accrual) and benthic macroinvertebrate and fungal communities. Both stressors had mostly independent effects on biological responses, with sand addition being the more influential of the two. Sand addition decreased algal biomass and microbe-mediated leaf breakdown significantly, whereas invertebrate shredder-mediated breakdown only responded to flow level. Macroinvertebrate community composition responded significantly to both stressors. Fungal biomass decreased and shredder abundance increased when sand was added; thus, organisms at different trophic levels can exhibit highly vari...

溪流生态系统受到多种非生物胁迫因子（abiotic stressors）的影响，物种对多重胁迫因子共同作用的响应，或与基于单一胁迫因子响应所预测的结果存在差异。本研究依托12个半天然溪流渠道（semi-natural stream channels），探究了水流条件（低流量或高流量）与细颗粒沉积物（fine sediments，粒径<2mm）添加这两个因子的单独效应与交互效应，及其对关键生态系统过程（叶片分解（leaf breakdown）、藻类生物量累积（algal biomass accrual））以及底栖大型无脊椎动物（benthic macroinvertebrate）和真菌群落（fungal communities）的影响。两种胁迫因子对生物响应的影响大多为独立效应，其中细颗粒沉积物添加的影响更为显著。细颗粒沉积物添加会显著降低藻类生物量与微生物介导的叶片分解速率，而无脊椎动物撕食者介导的叶片分解仅对水流条件产生响应。底栖大型无脊椎动物群落组成对两种胁迫因子均存在显著响应。当添加细颗粒沉积物时，真菌生物量下降而撕食者类群丰度上升；由此可见，不同营养级的生物可表现出高度可变...