The annual global loss of organic carbon from terrestrial ecosystems into rivers is similar to the organic carbon stored in soils each year. Dissolved organic matter (DOM) flows through the food web to macroinvertebrates, but little is known about the effect of DOM increase on stream food webs and how much macroinvertebrates may contribute to the regulation of carbon fluxes in rivers. Using a before and after control impact (BACI) experimental design, we increased by 12% (+ 0.52 mg C L⁻¹) the concentration of DOM in a stream for three weeks by adding sucrose, with a distinctive δ¹³C signature, to simulate a pulse of natural DOM supply from soils. We partitioned the diet of macroinvertebrates from carbon sources according to the green pathway (autotrophs) and detrital pathways (bacteria and terrestrial organic matter). Our flow food web approach based on C fluxes, with bacteria as a key node, showed the dominant contribution of the detrital pathways for macroinvertebrates in the reference stream. DOM addition induced changes in the diets of individual taxa, but did not have any strong effects on the relative overall contribution of the detrital pathways versus the green pathway. Autotrophic uptake of CO₂ respired by bacteria was much larger than bacterial C flux to invertebrates (that is, the classic microbial loop) and allowed a significant fraction of natural allochthonous organic carbon to make its way to macroinvertebrates via autotrophs fixing CO₂ respired by bacteria. Overall macroinvertebrates did not regulate directly to any great extent the flux of stream DOM towards downstream ecosystems.

从陆地生态系统到河流的全球年度有机碳损失与每年存储在土壤中的有机碳相似。溶解的有机物（DOM）穿过食物网流向大型无脊椎动物，但关于DOM增加对河流食物网的影响以及多少大型无脊椎动物可能有助于调节河流中的碳通量，人们所知甚少。之前和之后控制冲击（BACI）实验设计使用，我们提高了12％（+ 0.52毫克C L ^-1）DOM的在三个星期流的浓度通过加入蔗糖，具有鲜明的δ ¹³C签名，模拟土壤中天然DOM供应的脉冲。我们根据绿色途径（自养生物）和碎屑途径（细菌和陆生有机质）从碳源划分了大型无脊椎动物的饮食。我们基于C通量的流动食物网方法（以细菌为关键节点）显示了参考流中碎屑途径对大型无脊椎动物的主要贡献。DOM的添加会导致单个类群的饮食发生变化，但对碎屑途径相对于绿色途径的相对总体贡献没有任何强烈影响。自养性吸收CO ₂被细菌呼吸的细菌比进入无脊椎动物的细菌C通量要大得多（即经典的微生物环），并允许很大一部分天然异源有机碳通过自养生物固定细菌呼吸的CO ₂进入大型无脊椎动物。总体而言，大型无脊椎动物在很大程度上没有直接调节河流DOM向下游生态系统的通量。