Warming alters food web-driven changes in the CO2 flux of experimental pond ecosystems

Evidence shows the important role biota play in the carbon cycle, and strategic management of plant and animal populations could enhance CO2 uptake in aquatic ecosystems. However, it is currently unknown how management-driven changes to community structure may interact with climate warming and other anthropogenic perturbations to alter CO2 fluxes. Here we showed that under ambient water temperatures, predators (three-spined stickleback) and nutrient enrichment synergistically increased primary producer biomass, resulting in increased CO2 uptake by mesocosms in early dawn. However, a 3°C increase in water temperatures counteracted positive effects of predators and nutrients, leading to reduced primary producer biomass and a switch from CO2 influx to efflux. This confounding effect of temperature demonstrates that climate scenarios must be accounted for when undertaking ecosystem management actions to increase biosequestration.

已有研究证实，生物群（biota）在碳循环中发挥着关键作用，对动植物种群实施战略性管理，可增强水生生态系统对二氧化碳（CO₂）的吸收能力。然而目前尚不清楚，管理措施驱动的群落结构变化，会如何与气候变暖及其他人为扰动相互作用，进而改变二氧化碳通量。本研究发现，在环境水温条件下，捕食者（三刺鱼（three-spined stickleback））与养分富集会协同提升初级生产者生物量，使得黎明早期的中型实验生态系统（mesocosms）的二氧化碳吸收量显著增加。但当水温升高3摄氏度后，捕食者与养分的正向效应会被抵消，导致初级生产者生物量下降，且系统的二氧化碳通量从流入转为流出。这种温度带来的混杂效应表明，在开展旨在提升生物固碳能力的生态系统管理工作时，必须将气候情景纳入考量范畴。