Ancient lake microbes triggered 304-million-year-old warming

A recent study uncovers ancient warming secrets of a Paleozoic ice age.
Sade Agard
Concept image of microbes in a lake environment.
Concept image of microbes in a lake environment.


Our planet has a long history of global warming, spanning millions of years, as evidenced by a recent study published in Geology, which delves into a pivotal era 304 million years ago during the Late Paleozoic Ice Age

The findings reveal evidence of increased sea surface temperature, continental ice decline, and oceanic environments flooding the land.

Ancient lake emissions

Dr. Liuwen Xia and a team of researchers from Nanjing University, China, embarked on a quest to uncover the secrets of an ancient warming episode. 

To unravel the mystery, the team investigated the impact of methane emissions from alkaline lakes with pH levels ranging from 9 to 12.

Methane, a potent greenhouse gas, can trap heat in the atmosphere 28 times more effectively than carbon dioxide over a century. 

The microorganisms responsible for methane production contribute to a substantial portion of global methane emissions, – accounting for 74 percent. 

Understanding the conditions that enable these microorganisms to thrive is crucial for comprehending climate change dynamics.

The researchers focused on the Junggar Basin in northwest China, where they meticulously examined methane levels derived from microbial activity. 

Ancient lake microbes triggered 304-million-year-old warming
Model of methane production from microbial activity in an alkaline lake.

Core samples from the lake bed were subjected to rigorous chemical analyses, providing insights into carbon sources, including aquatic green algae, photosynthesizing cyanobacteria, and extremophilic halophilic archaea that inhabit high salt environments.

A crucial revelation emerged from their investigations: a specific type of microorganism, alkalophilic methanogenic archaea, thrived in the lake's low sulfate anoxic conditions.

This microorganism harnesses energy from methane production, releasing it into the atmosphere. The findings suggest that microbial methane emissions during this era may have reached a staggering 2.1 gigatons.

Potential solutions

The researchers connected this surge in methane emissions to the Late Paleozoic Ice Age, marked by a peak in atmospheric methane 304 million years ago. They propose that the collective impact of alkaline lakes globally could have significantly influenced greenhouse gas levels. 

In the context of northwest China alone, methane emissions could have surpassed 109 gigatonnes, equivalent to the potential greenhouse impact of up to 7521 gigatonnes of carbon dioxide.

The implications of these findings are profound, underscoring the influential role of methane in shaping our climate. Potential solutions include altering lake pH, introducing specific clays, or even modifying lakebeds. 

However, each solution introduces its own set of environmental repercussions. Additionally, identifying alkaline lakes worldwide will present its own challenges. 

The complete study was published in Geology.

Study abstract:

Methane (CH4) is an important greenhouse gas, but its behavior and influencing factors over geological time scales are not sufficiently clear. This study investigated the Late Paleozoic Ice Age (LPIA), which is thought to have experienced an interval of rapid warming at ca. 304 Ma, that may have been analogous to modern warming. To explore possible causes of this warming event, we investigated ancient alkaline lakes in the Junggar Basin, northwestern China. Results show that microbial CH4 cycling here was strong, as evidenced by carbonate δ13C (δ13Ccarb) values of >5‰, ∼+0.6‰ offsets between pristane δ13C (δ13CPr) and phytane δ13C (δ13CPh) values, a 3β-methylhopane index of 9.5% ± 3.0%, and highly negative δ13C values of hopanes (−44‰ to −61‰). Low sulfate concentrations in the alkaline lakes made methanogenic archaea more competitive than sulfate-reducing bacteria, and the elevated levels of dissolved inorganic carbon promoted methanogenesis. Biogenic CH4 emissions from alkaline lakes, in addition to CO2, may have contributed to rapid climate warming.

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