Climate warming and eutrophication are leading drivers of environmental change, and both are likely to alter the role of freshwaters in the global carbon cycle. Recent studies demonstrate that warming of streams can increase freshwater contributions of CO₂ to the atmosphere, yet little is known about how such contributions are modulated by the identity or supply of limiting nutrients. We quantified responses of ecosystem metabolism and metabolic balance to whole-stream enrichments of either nitrogen or phosphorus across a 5°C range of ambient temperature. We show that nutrient enrichment drove large reductions in net ecosystem production, and interactions with temperature amplified these effects in warm N-enriched streams. Partitioning of autotrophic and heterotrophic respiration revealed that these responses were driven by increased respiration of microbial heterotrophs. Our study provides direct experimental evidence that warming-induced increases in CO₂ emissions to the atmosphere are likely intensified in stream ecosystems subject to eutrophication.

中文翻译：

---

营养丰富加剧了变暖对河流生态系统代谢平衡的影响

气候变暖和富营养化是环境变化的主要驱动因素，两者都可能改变淡水在全球碳循环中的作用。最近的研究表明，溪流变暖可以增加 CO _{2的淡水贡献}对大气的影响，但人们对这些贡献如何受到限制性营养素的特性或供应的调节知之甚少。我们量化了生态系统代谢和代谢平衡对 5°C 环境温度范围内氮或磷全流富集的反应。我们表明，养分富集导致生态系统净产量大幅下降，而与温度的相互作用在温暖的富氮溪流中放大了这些影响。自养和异养呼吸的划分表明，这些反应是由微生物异养生物的呼吸增加驱动的。我们的研究提供了直接的实验证据，表明变暖引起的大气 CO ₂排放量增加可能在遭受富营养化的河流生态系统中加剧。