Laboratoire Écologie Fonctionnelle et Environnement, Université de Toulouse, CNRS, INP, UPS, Toulouse, France.
INRAE, Aix Marseille Université, UMR RECOVER, Aix-en-Provence, France.
J Anim Ecol. 2022 Oct;91(10):1975-1987. doi: 10.1111/1365-2656.13710. Epub 2022 May 9.
The balance of energetic losses and gains is of paramount importance for understanding and predicting the persistence of populations and ecosystem processes in a rapidly changing world. Previous studies suggested that metabolic rate often increases faster with warming than resource ingestion rate, leading to an energetic mismatch at high temperature. However, little is known about the ecological consequences of this energetic mismatch for population demography and ecosystem functions. Here, we combined laboratory experiments and modelling to investigate the energetic balance of a stream detritivore Gammarus fossarum along a temperature gradient and the consequences for detritivore populations and organic matter decomposition. We experimentally measured the energetic losses (metabolic rate) and supplies (ingestion rate) of Gammarus and we modelled the impact of rising temperatures and changes in Gammarus body size induced by warming on population dynamics and benthic organic matter dynamics in freshwater systems. Our experimental results indicated an energetic mismatch in a Gammarus population where losses via metabolic rate increase faster than supplies via food ingestion with warming, which translated in a decrease in energetic efficiency with temperature rising from 5 to 20°C. Moreover, our consumer-resource model predicts a decrease in the biomass of Gammarus population with warming, associated with lower maximum abundances and steeper abundance decreases after biomass annual peaks. These changes resulted in a decrease in leaf litter decomposition rate and thus longer persistence of leaf litter standing stock over years in the simulations. In addition, Gammarus body size reductions led to shorter persistence for both leaf litter and Gammarus biomasses at low temperature and the opposite trend at high temperature, revealing that body size reduction was weakening the effect of temperature on resource and consumer persistence. Our model contributes to identifying the mechanisms that explain how thermal effects at the level of individuals may cascade through trophic interactions and influence important ecosystem processes. Considering the balance of physiological processes is crucial to improve our ability to predict the impact of climate change on carbon stocks and ecosystem functions.
能量得失的平衡对于理解和预测在快速变化的世界中种群和生态系统过程的持久性至关重要。先前的研究表明，代谢率通常随着升温而比资源摄取率增加得更快，导致高温下能量不匹配。然而，对于这种能量不匹配对种群动态和生态系统功能的生态后果知之甚少。在这里，我们结合实验室实验和模型来研究沿温度梯度的溪流碎屑食者 Gammarus fossarum 的能量平衡，以及对碎屑食者种群和有机物质分解的影响。我们实验测量了 Gammarus 的能量损失（代谢率）和供应（摄取率），并模拟了升温引起的温度升高和 Gammarus 体型变化对淡水系统中种群动态和底栖有机物质动态的影响。我们的实验结果表明，在一个 Gammarus 种群中存在能量不匹配，其中通过代谢率的损失比通过食物摄取的供应增加得更快，这导致能量效率随着温度从 5°C 升高到 20°C 而降低。此外，我们的消费者-资源模型预测随着升温，Gammarus 种群的生物量减少，与最大丰度降低和丰度峰值后下降更陡峭相关。这些变化导致落叶分解率降低，因此在模拟中多年来落叶存量的持久性增加。此外，Gammarus 体型缩小导致落叶和 Gammarus 生物量在低温下的持久性更短，而在高温下则相反趋势，表明体型缩小削弱了温度对资源和消费者持久性的影响。我们的模型有助于确定解释个体层面的热效应如何通过营养相互作用级联并影响重要生态系统过程的机制。考虑生理过程的平衡对于提高我们预测气候变化对碳储量和生态系统功能的影响的能力至关重要。
