Understanding energy flow and nutrient pathways is crucial to reveal the dynamics and functions of riverine ecosystems and develop appropriate conservation strategies. In this study, we utilized stable isotopes of δ¹³C and δ¹⁵N to examine the fundamental characteristics of trophic position, trophic niche, and carbon source for the food web in the midstream of the Chishui River, a tributary to the Yangtze River. Our results showed that stable isotope signatures among different sorts of basal resources and consumers were significantly distinguishable and that the food chain consisted of four trophic levels, indicating the multiple trophic pathways and long food chain length here. The trophic guilds of fish were classified into four categories, in which herbivorous and carnivorous fish showed greater trophic diversity and omnivorous fish had higher trophic redundancy, which meant that there was a stable trophic niche structure in the study area. Phytoplankton and periphyton presented the largest contributions to consumers, indicating that autochthonous productivity was the dominant carbon source in the midstream of the Chishui River. Since the Chishui River is still in a natural condition without any dam constructions, the autochthonous productivity, stable trophic niche structure, multiple trophic pathways and long food chain length found here demonstrate its high conservation value. Therefore, the strategy to refrain from damming on this river should persist into the future.

中文翻译：

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长江支流赤水河中游稳定同位素分析揭示的食物网结构和营养相互作用

了解能量流和养分途径对于揭示河流生态系统的动态和功能以及制定适当的保护策略至关重要。在这项研究中，我们利用的δ稳定同位素¹³ C和δ ¹⁵N研究了长江支流赤水河中游食物网的营养位置，营养位和碳源的基本特征。我们的结果表明，在不同种类的基础资源和消费者之间稳定的同位素特征是明显可区分的，并且食物链由四个营养级组成，表明这里有多个营养通道和较长的食物链长度。鱼的营养行会分为四类，其中草食性和食肉性鱼类表现出更大的营养多样性，杂食性鱼类具有更高的营养冗余性，这意味着研究区域内营养种群的生态位结构稳定。浮游植物和水生植物对消费者的贡献最大，这表明赤水河中游的主要生产力是自发生产力。由于赤水河仍处于自然状态，没有任何大坝建设，因此这里的水生生产力，稳定的营养生态位结构，多种营养路径和较长的食物链长度证明了其高保护价值。因此，避免在这条河上筑坝的策略应持续到未来。