알려지지 않은 미생물은 기후 티핑 포인트의 조기 경고 신호일 수 있습니다.

열 수준의 증가는 해양 플랑크톤 및 기타 단세포 유기체를 탄소 임계값으로 밀어내어 지구 온난화를 악화시킬 수 있습니다. 그러나 최근 연구에 따르면 이러한 유기체가 임계점에 도달하기 전에 조기 경고 신호를 식별하는 것이 가능할 수 있습니다.

광범위하지만 종종 간과되는 미생물 종류에 대한 연구를 수행하는 과학자 그룹이 지구 온난화를 증가시킬 수 있는 기후 피드백 루프를 발견했습니다. 그러나 이 발견에는 장점이 있습니다. 조기 경고 신호일 수도 있습니다.

컴퓨터 시뮬레이션을 사용하여 Duke University와 University of California, Santa Barbara의 연구자들은 호수, 이탄 지대 및 기타 생태계에 서식하는 많은 단세포 유기체와 함께 전 세계 해양 플랑크톤의 대다수가 기울어지고 있음을 보여주었습니다. 가리키다. 여기에서 이산화탄소를 흡수하는 대신에 그들은 그 반대의 일을 시작합니다. 이러한 변화는 신진대사가 온난화에 반응하는 방식의 결과입니다.

이산화탄소는 온실 가스이기 때문에 온도를 상승시킬 수 있습니다. 이는 소량의 온난화가 큰 영향을 미치는 급격한 변화로 이어질 수 있는 긍정적인 피드백 루프입니다.

그러나 그들의 풍부함을 주의 깊게 모니터링함으로써 우리는 그것이 여기에 도달하기 전에 티핑 포인트를 예상할 수 있을지도 모른다고 연구원들은 6월 1일 Nature 저널에 발표된 연구에서 보고합니다. 기능 생태학.

새로운 연구에서 연구원들은 두 가지 신진 대사 모드를 혼합하기 때문에 이름이 붙여진 mixotrophs라고 불리는 미생물 그룹에 중점을 두었습니다. 그들은 조건에 따라 식물처럼 광합성을 하거나 동물처럼 먹이를 사냥할 수 있습니다.

“그들은 마치[{” attribute=””>Venus fly traps of the microbial world,” said first author Daniel Wieczynski, a postdoctoral associate at Duke.

During photosynthesis, they soak up carbon dioxide, a heat-trapping greenhouse gas. And when they eat, they release carbon dioxide. These versatile organisms aren’t considered in most models of global warming, yet they play an important role in regulating climate, said senior author Jean P. Gibert of Duke.

Most of the plankton in the ocean — things like diatoms, dinoflagellates — are mixotrophs. They’re also common in lakes, peatlands, in damp soils, and beneath fallen leaves.

“If you were to go to the nearest pond or lake and scoop a cup of water and put it under a microscope, you’d likely find thousands or even millions of mixotrophic microbes swimming around,” Wieczynski said.

“Because mixotrophs can both capture and emit carbon dioxide, they’re like ‘switches’ that could either help reduce climate change or make it worse,” said co-author Holly Moeller, an assistant professor at the University of California, Santa Barbara.

To understand how these impacts might scale up, the researchers developed a mathematical model to predict how mixotrophs might shift between different modes of metabolism as the climate continues to warm.

The researchers ran their models using a 4-degree span of temperatures, from 19 to 23 degrees Celsius (66-73 degrees Fahrenheit). Global temperatures are likely to surge 1.5 degrees Celsius above pre-industrial levels within the next five years, and are on pace to breach 2 to 4 degrees before the end of this century.

The analysis showed that the warmer it gets, the more mixotrophs rely on eating food rather than making their own via photosynthesis. As they do, they shift the balance between carbon in and carbon out.

The models suggest that, eventually, we could see these microbes reach a tipping point — a threshold beyond which they suddenly flip from carbon sink to carbon source, having a net warming effect instead of a cooling one.

This tipping point is hard to undo. Once they cross that threshold, it would take significant cooling — more than one degree Celsius — to restore their cooling effects, the findings suggest.

But it’s not all bad news, the researchers said. Their results also suggest that it may be possible to spot these shifts in advance, if we watch out for changes in mixotroph abundance over time.

“Right before a tipping point, their abundances suddenly start to fluctuate wildly,” Wieczynski said. “If you went out in nature and you saw a sudden change from relatively steady abundances to rapid fluctuations, you would know it’s coming.”

Whether the early warning signal is detectable, however, may depend on another key factor revealed by the study: nutrient pollution.

Discharges from wastewater treatment facilities and runoff from farms and lawns laced with chemical fertilizers and animal waste can send nutrients like nitrate and phosphate into lakes and streams and coastal waters.

When Wieczynski and his colleagues included higher amounts of such nutrients in their models, they found that the range of temperatures over which the telltale fluctuations occur starts to shrink until eventually the signal disappears and the tipping point arrives with no apparent warning.

The predictions of the model still need to be verified with real-world observations, but they “highlight the value of investing in early detection,” Moeller said.

“Tipping points can be short-lived, and thus hard to catch,” Gibert said. “This paper provides us with a search image, something to look out for, and makes those tipping points — as fleeting as they may be — more likely to be found.”

Reference: “Mixotrophic microbes create carbon tipping points under warming” by Daniel J. Wieczynski, Holly V. Moeller and Jean P. Gibert, 31 May 2023, Functional Ecology.
DOI: 10.1111/1365-2435.14350

The study was funded by the Simons Foundation, the National Science Foundation, and the U.S. Department of Energy.