Scientists studying a group of often neglected microorganisms have made a significant discovery regarding a climate feedback loop that could amplify global warming. However, this finding also presents a silver lining as it could serve as an early warning signal.
Using computer simulations, researchers from Duke University and the University of California, Santa Barbara, have demonstrated that a majority of global oceanic plankton and various unicellular organisms found in lakes, peatlands, and other ecosystems may reach a tipping point. Rather than absorbing carbon dioxide, these organisms begin to release it due to changes in their metabolic response to warming.
This change can potentially lead to a positive feedback loop, where increased carbon dioxide further raises temperatures, resulting in an amplified impact. However, the researchers propose that by closely monitoring the abundance of these organisms, it might be possible to anticipate the tipping point before it occurs, according to a study published in the journal Functional Ecology on June 1.
The focus of the study was on a group of tiny organisms known as mixotrophs, which possess the ability to carry out both photosynthesis like plants and consume food like animals, depending on environmental conditions. Mixotrophs, often referred to as the “Venus fly traps of the microbial world,” play a vital role in climate regulation despite being overlooked in most global warming models, explains Daniel Wieczynski, the study’s first author and a postdoctoral associate at Duke University.
During photosynthesis, mixotrophs absorb carbon dioxide, a greenhouse gas. Conversely, when they consume food, they release carbon dioxide. These versatile organisms are abundant in the ocean, including diatoms and dinoflagellates, as well as in lakes, peatlands, damp soils, and beneath fallen leaves.
Wieczynski points out that if a cup of water from a nearby pond or lake were placed under a microscope, it would likely reveal thousands or even millions of these mixotrophic microbes.
Due to their ability to both capture and emit carbon dioxide, mixotrophs act as “switches” that can either mitigate or worsen climate change, according to Holly Moeller, a co-author and assistant professor at the University of California, Santa Barbara.
To understand the potential impact of these organisms on a larger scale, the researchers developed a mathematical model that predicts how mixotrophs may shift between different metabolic modes as the climate continues to warm.
Using temperature ranges from 19 to 23 degrees Celsius (66-73 degrees Fahrenheit), which are expected to be surpassed within the next five years, the analysis revealed that as temperatures rise, mixotrophs rely increasingly on consuming food rather than photosynthesis. This shift alters the balance between carbon intake and release.
The models suggest that these microbes could eventually reach a tipping point, after which they switch from being a carbon sink to a carbon source. In other words, they contribute to warming instead of cooling the environment. Once this tipping point is crossed, significant cooling, surpassing one degree Celsius, would be necessary to restore their cooling effects.
However, the researchers offer a glimmer of hope by suggesting that these shifts might be detectable if changes in mixotroph abundance are closely observed over time. A sudden transition from relatively stable abundances to rapid fluctuations could serve as a warning sign indicating the approaching tipping point.
The study also highlights the influence of nutrient pollution as a crucial factor that affects the detectability of early warning signals. High nutrient levels stemming from wastewater treatment facilities, agricultural runoff containing chemical fertilizers and animal waste, and their subsequent entry into lakes, streams, and coastal waters can diminish the range of temperatures within which these fluctuations occur. In some cases, the warning signal may vanish entirely, leading to an abrupt arrival of the tipping point without any apparent advance notice.
While real-world observations are still needed to verify the model’s predictions, the researchers stress the importance of investing in early detection to capture fleeting tipping points. These findings provide researchers with a search image to enhance the chances of identifying such tipping points, even if they are brief.
The study received funding from the Simons Foundation, the National Science Foundation, and the U.S. Department of Energy.
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Frequently Asked Questions (FAQs) about climate tipping point
What are mixotrophs and why are they important in climate change?
Mixotrophs are tiny organisms that can carry out both photosynthesis like plants and consume food like animals. They play a crucial role in climate change because they have the ability to either absorb or release carbon dioxide, a greenhouse gas. This dual behavior makes them “switches” that can either mitigate or exacerbate global warming.
How do mixotrophs contribute to the amplification of global warming?
As temperatures rise, mixotrophs tend to rely more on consuming food rather than photosynthesis. This shift in their metabolic response alters the balance between carbon intake and release. Eventually, these organisms can reach a tipping point where they switch from being a carbon sink to a carbon source. This transition contributes to the amplification of global warming by releasing more carbon dioxide into the atmosphere.
Can the abundance of mixotrophs serve as an early warning signal for climate tipping points?
Yes, monitoring the abundances of mixotrophs can potentially serve as an early warning signal for climate tipping points. According to the research, a sudden change from relatively stable abundances to rapid fluctuations could indicate an approaching tipping point. By closely observing these fluctuations over time, it may be possible to anticipate the tipping point before it occurs.
How does nutrient pollution affect the detectability of early warning signals?
Nutrient pollution, caused by factors such as wastewater discharges and agricultural runoff, can affect the detectability of early warning signals. High nutrient levels in water bodies can alter the range of temperatures within which the fluctuations in mixotroph abundances occur. In some cases, nutrient pollution can diminish or even eliminate the warning signal, making it harder to detect the approaching tipping point.
What further research is needed to validate the findings of this study?
While the computer simulations provided valuable insights, further research is needed to validate the findings of this study. Real-world observations are necessary to confirm the model’s predictions. Additionally, more studies are required to understand the specific mechanisms and behaviors of mixotrophs in different ecosystems and their overall impact on climate change.
More about climate tipping point
- Functional Ecology – The research study published in the journal Functional Ecology.
- Duke University – Website of Duke University, one of the institutions involved in the research.
- University of California, Santa Barbara – Website of the University of California, Santa Barbara, another institution involved in the research.
- Simons Foundation – The organization that provided funding for the study.
- National Science Foundation – The National Science Foundation, which also provided funding for the research.
- U.S. Department of Energy – The U.S. Department of Energy, another funding source for the study.
