A study published in the journal Functional Ecology by researchers at Duke University and the University of California Santa Barbara reveals that a warming climate has the potential to transform globally abundant microbial communities from carbon sinks to carbon emitters, potentially pushing climate change towards tipping points. The research highlights the crucial role of mixotrophic microbes, single-celled organisms including ocean plankton, in this process.
These mixotrophic microbes, which are prevalent in freshwater and marine environments and make up a significant portion of marine plankton, have the ability to switch between photosynthesizing like plants (absorbing carbon dioxide) and consuming like animals (releasing carbon dioxide). Through a computer simulation, the researchers demonstrated that under warming conditions, these microbes transition from being carbon sinks to carbon emitters.
The implications are profound: as temperatures rise, these abundant microbial communities could shift from having a cooling effect on the planet to a warming one. The study emphasizes that mixotrophic microbes play a more critical role in ecosystem responses to climate change than previously recognized.
Dr. Daniel Wieczynski, lead author of the study from Duke University, emphasizes the significance of these findings: “Our findings reveal mixotrophic microbes are much more important players in ecosystem responses to climate change than previously thought. By converting microbial communities to net carbon dioxide sources in response to warming, mixotrophs could further accelerate warming by creating a positive feedback loop between the biosphere and the atmosphere.”
Dr. Holly Moeller, co-author from the University of California Santa Barbara, emphasizes the potential impact of these tiny organisms: “Because mixotrophs can both capture and emit carbon dioxide, they are like ‘switches’ that could either help reduce climate change or make it worse. These bugs are tiny, but their impacts can really scale up. We need models like this to understand how.”
The study also identifies a potential early warning system for climate change tipping points. The researchers discovered that just before mixotrophic microbe communities shift to emitting carbon dioxide, their abundance begins to fluctuate significantly. Monitoring these changes in the abundance of mixotrophic microbes could offer crucial early warning signals for climate change tipping points.
However, the researchers also found that these warning signals can be dampened by increased nutrient levels, such as nitrogen from agricultural runoff. The introduction of higher nutrient amounts diminishes the range of temperatures over which the fluctuations occur, ultimately eliminating the warning signal and leading to tipping points without apparent prior indication.
Dr. Moeller warns of the challenges in detecting these warning signs, particularly as nutrient pollution makes them increasingly subtle. Missing these signals could have significant consequences, potentially leading to ecosystems contributing greenhouse gases to the atmosphere instead of removing them.
While the study’s mathematical modeling draws on limited empirical evidence, the researchers emphasize the need for further experimental and observational testing to validate the results. They stress that theoretical findings must ultimately be supported by empirical data.