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got it! The protist Paramecium bursaria is one of the many moss-inhabiting microorganisms commonly found in peatlands.Credit: Daniel Wiczynski
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The protist Paramecium bursaria is one of the many moss-inhabiting microorganisms commonly found in peatlands.Credit: Daniel Wiczynski
The plain peat swamp gives an image of a sticky brown expanse. But it has turned out to be a superpower in the fight against climate change.
For thousands of years, the world's peatlands have absorbed and stored vast amounts of carbon dioxide, keeping this greenhouse gas underground rather than in the air. Although peatlands make up only 3% of the earth's land, they play a huge role in carbon storage, holding twice as much as all the world's forests.
In the face of climate change, the fate of all that carbon is uncertain. Now, new research suggests the future of this important carbon sink may be influenced, at least in part, by tiny, often overlooked organisms.
Most of the carbon in peatlands is trapped in the spongy layer of living and dead moss that covers the ground. There, the cold, soggy, and oxygen-deficient conditions make it difficult for plants to decompose. This allows the carbon absorbed during photosynthesis to be trapped in the soil rather than leaking into the atmosphere.
But rising global temperatures are drying out peatlands, turning them from carbon sinks to potential carbon sources.
In a study published March 3 in the journal Global Change Biology, a research team led by Duke University biology professor Jean-Philippe Gibert and doctoral student Christopher Kilner found that peatland moss They tested the effects of climate change on the tiny creatures called protists that live inside.
Not only are protists abundant and together weigh twice as much as all the animals on Earth, they also play a role in the overall transfer of carbon between peatlands and the atmosphere.
This is because when protists carry out life activities such as eating and reproducing, they also suck in carbon and produce large quantities of it.
Some protists take in CO2 from the air to fuel their growth. Other protists are predators and devour the nitrogen-fixing bacteria that peatland moss relies on to stay healthy.
In a swamp in northern Minnesota, researchers led by Oak Ridge National Laboratory have constructed 10 open-top enclosures 40 feet in diameter designed to mimic various global warming scenarios.
The enclosures are controlled at temperatures ranging from no heating at all to 9 degrees Celsius higher than the surrounding peatland.
Half of the enclosures were grown in normal air. The other half is exposed to more than twice the current concentration of carbon dioxide, which could be reached by the end of the century if fossil fuel combustion is left unchecked.
Five years after the simulation experiment began, the Duke University team was already seeing surprising changes.
“Protists started doing things we didn't expect,” Kilner said.
At current CO2 levels, most of the more than 200,000 protists they measured have increased in abundance due to warming. But as CO2 rose, that trend reversed.
Furthermore, the combined effects of global warming and increased carbon dioxide are changing the feeding habits of protists, the amount of carbon dioxide they emit during respiration, and, in other words, how much protists themselves contribute to climate change. Reorganization of other traits known to influence growth occurred.
It is unclear exactly what such changes will mean for the future ability of peatlands to mitigate climate change, but they are likely to be important.
Overall, the results show that neglected parts of peatland microbial food webs are also susceptible to climate change, something that is “currently not taken into account in models predicting future warming.” No,” Gibert said.
Further information: Christopher L. Kilner et al. Temperature and CO2 mutually drive changes in the compositional and functional structure of peatland protist communities, Global Change Biology (2024). DOI: 10.1111/gcb.17203
Magazine information: Global Change Biology
