Bacteria will worsen climate change, scientists say

16 November 2019

Invisible to the naked eye, bacteria are often overlooked by people. Yet we ignore them at our own peril. Not only can they make us sick, they can also make the planet sicker.

To wit: warming temperatures brought on by climate change will speed up the respiration rate of bacteria, which will cause them to release more carbon. That could worsen climate change.

This finding comes from a new study, “Community-level respiration of prokaryotic microbes may rise with global warming, published in the journal Nature Communications.

Bacteria and archaea, which are collectively known as prokaryotes, account for half of Earth’s biomass and so while these organisms may seem negligible individually, they can pack a mighty punch collectively. Most prokaryotes release carbon dioxide during perspiration, the rate of which can change in response to variations in temperature.

The study’s authors, from Imperial College London in the United Kingdom, set out to examine how rises in temperature will affect these tiny organisms’ respiration rate and carbon output. To do that, they looked at 482 types of prokaryote living in a wide variety of environmental conditions across the planet from Antarctic lakes with temperatures below 0°C to thermal pools where heat is above 120°C.

The researchers wanted to see how these various organisms respond to changes in temperature. What they have found was that most prokaryotes increase their carbon output at a greater rate than previously thought in response to higher temperatures.

Prokaryotes that usually operate in a medium temperature range, below 45°C, especially respond markedly to changing temperatures, increasing their rate of respiration both over the short and long terms. Prokaryotes that operate in higher temperature ranges, above 45°C, don’t show this response because they already operate at high temperatures.

“In the short term, on a scale of days to hours, individual prokaryotes will increase their metabolism and produce more carbon dioxide. However, there is still a maximum temperature at which their metabolism becomes inefficient,” explains Samraat Pawar, a scientist at the Department of Life Sciences at Imperial College London who was the lead researcher.

“In the longer term, over years, these prokaryote communities will evolve to be more efficient at higher temperatures, allowing them to further increase their metabolism and their carbon output,” Pawar elucidates. “Rising temperatures therefore cause a ‘double whammy’ effect on many prokaryote communities, allowing them to function more efficiently in both the short and long term, and creating an even larger contribution to global carbon and resulting temperatures.”

This is bad news because the carbon output of prokaryotes could well be higher than generally assumed and this has not been taken into account in most climate models. “Most climate models assume that all organisms’ respiration rates respond to temperature in the same way, but our study shows that bacteria and archaea are likely to depart from the ‘global average’,” says Thomas Smith, from the university’s Department of Life Sciences who was the study’s lead author.

“Given that these micro-organisms are likely to be significant contributors to total respiration and carbon output in many ecosystems, it’s important for climate models to take into account their higher sensitivity to temperature change at both short and long timescales,” Smith adds. “Importantly for future climate predictions, we would also like to know how the numbers of prokaryotes, and their abundance within local ecosystems, might change with increasing temperatures.”

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