Australian Institute of Marine Science, Indian Ocean Marine Research Centre, Crawley, Western Australia, Australia.
Oceans Institute, The University of Western Australia, Crawley, Western Australia, Australia.
Nature. 2021 Apr;592(7852):76-79. doi: 10.1038/s41586-021-03352-2. Epub 2021 Mar 1.
In ecosystems, the efficiency of energy transfer from resources to consumers determines the biomass structure of food webs. As a general rule, about 10% of the energy produced in one trophic level makes it up to the next. Recent theory suggests that this energy transfer could be further constrained if rising temperatures increase metabolic growth costs, although experimental confirmation in whole ecosystems is lacking. Here we quantify nitrogen transfer efficiency-a proxy for overall energy transfer-in freshwater plankton in artificial ponds that have been exposed to seven years of experimental warming. We provide direct experimental evidence that, relative to ambient conditions, 4 °C of warming can decrease trophic transfer efficiency by up to 56%. In addition, the biomass of both phytoplankton and zooplankton was lower in the warmed ponds, which indicates major shifts in energy uptake, transformation and transfer. These findings reconcile observed warming-driven changes in individual-level growth costs and in carbon-use efficiency across diverse taxa with increases in the ratio of total respiration to gross primary production at the ecosystem level. Our results imply that an increasing proportion of the carbon fixed by photosynthesis will be lost to the atmosphere as the planet warms, impairing energy flux through food chains, which will have negative implications for larger consumers and for the functioning of entire ecosystems.
在生态系统中，能量从资源向消费者的传递效率决定了食物网的生物量结构。一般来说，在一个营养级中产生的能量大约有 10%可以传递到下一个营养级。最近的理论表明，如果温度升高增加了新陈代谢的成本，这种能量传递可能会受到进一步的限制，尽管在整个生态系统中缺乏实验验证。在这里，我们量化了人工池塘中淡水浮游生物的氮传递效率——一种整体能量传递的替代指标，这些池塘已经经历了七年的实验加热。我们提供了直接的实验证据表明，与环境条件相比，4°C 的升温最多可使营养级转移效率降低 56%。此外，升温池塘中的浮游植物和浮游动物生物量都较低，这表明能量吸收、转化和传递发生了重大变化。这些发现将在不同类群中观察到的与变暖相关的个体生长成本和碳利用效率的变化与生态系统水平上总呼吸与总初级生产力的比值增加联系起来。我们的研究结果表明，随着地球变暖，光合作用固定的碳有越来越大的比例将损失到大气中，从而削弱食物链中的能量流动，这将对大型消费者和整个生态系统的功能产生负面影响。
