Anthropogenic increases in temperature and nutrient loads will likely impact food web structure and stability. Although their independent effects have been reasonably well studied, their joint effects—particularly on coupled ecological and phenotypic dynamics—remain poorly understood. Here we experimentally manipulated temperature and nutrient levels in microbial food webs and used time-series analysis to quantify the strength of reciprocal effects between ecological and phenotypic dynamics across trophic levels. We found that (1) joint—often interactive—effects of temperature and nutrients on ecological dynamics are more common at higher trophic levels, (2) temperature and nutrients interact to shift the relative strength of top-down versus bottom-up control, and (3) rapid phenotypic change mediates observed ecological responses to changes in temperature and nutrients. Our results uncover how feedback between ecological and phenotypic dynamics mediate food web responses to environmental change. This suggests important but previously unknown ways that temperature and nutrients might jointly control the rapid eco-phenotypic feedback that determine food web dynamics in a changing world.

温度和营养负荷的人为增加可能会影响食物网结构和稳定性。尽管它们的独立效应已得到相当深入的研究，但它们的联合效应——尤其是耦合生态和表型动力学方面的效应——仍然知之甚少。在这里，我们通过实验控制微生物食物网中的温度和营养水平，并使用时间序列分析来量化跨营养级生态和表型动力学之间相互影响的强度。我们发现 (1) 温度和养分对生态动态的联合——通常是相互作用——影响在较高的营养水平上更为常见，(2) 温度和养分相互作用以改变自上而下与自下而上控制的相对强度，(3) 快速的表型变化介导了观察到的对温度和养分变化的生态反应。我们的结果揭示了生态和表型动力学之间的反馈如何调节食物网对环境变化的反应。这表明温度和营养物质可能以重要但以前未知的方式共同控制决定变化世界中食物网动态的快速生态表型反馈。