Changes in the ecological stoichiometry of primary producers may have considerable implications for energy and matter transfer in food webs. We hypothesized that nutrient enrichment alters the trophic position of omnivores, as the nutritional quality of primary producers increases. This hypothesis was tested by analysing the ecological stoichiometry and stable isotope signature of primary producers and a wide range of aquatic macroinvertebrates, including primary consumers and secondary consumers (both potential omnivores and strict carnivores), along a eutrophication gradient in an agricultural landscape. Our results showed (1) that carbon:nutrient ratios of primary producers decreased along the eutrophication gradient, while the elemental composition of consumers remained homeostatic, and (2) that the trophic position of several omnivores and the generalist predator Notonecta decreased, while the trophic position of most other consumers remained constant. These findings suggest that shifts in the diets of aquatic invertebrates induced by increasing eutrophication may affect species interactions and food web structure in aquatic ecosystems.

中文翻译：

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富营养化导致水生食物网中无脊椎动物的营养位置发生变化

初级生产者生态化学计量的变化可能对食物网中的能量和物质转移产生相当大的影响。我们假设，随着初级生产者营养质量的提高，营养丰富会改变杂食动物的营养位置。通过分析初级生产者和各种水生大型无脊椎动物，包括初级消费者和次级消费者（潜在的杂食动物和严格的食肉动物）的生态化学计量学和稳定同位素特征，沿着农业景观中的富营养化梯度对这一假设进行了测试。我们的结果表明（1）初级生产者的碳：养分比沿着富营养化梯度下降，而消费者的元素组成保持稳态，(2) 几种杂食动物和全能捕食者 Notonecta 的营养位置下降，而大多数其他消费者的营养位置保持不变。这些发现表明，由富营养化程度增加引起的水生无脊椎动物饮食的变化可能会影响水生生态系统中的物种相互作用和食物网结构。