As a result of global warming, the melting of ice-rich permafrost causes the ground to collapse, thereby creating thermokarst lakes, while the greenhouse effect caused by the concurrent release of greenhouse gases results in a positive feedback with climate warming. Microorganisms play important roles in various aspects of the carbon cycle. Understanding the mechanisms of microbial regulation of the carbon cycle in thermally melting lakes is of great significance for coping with future climate change. Therefore, by combining previous studies, this paper first elucidates the formation process of thermokarst lakes and the microorganisms inhabiting these special habitats; subsequently, the main microorganisms involved in organic carbon decomposition, methane production, and methane oxidation, and the regulation mechanisms and influencing factors are analyzed in detail. Based on this analysis, we conclude the following:
The organic matter in thermokarst lakes originates from the land, while some nutrients, such as phosphates, plant biopolymers, and leucine residues, are also transported from the land to the water.
With improvements in temperature and aeration conditions, the availability of most nutrients increases the genetic diversity of microorganisms and promotes their roles in organic carbon decomposition. Changes in temperature, substrate, dissolved oxygen, and microbial community affect the processes of methane production, methane oxidation, and carbon sequestration, thereby affecting the carbon cycle.
Some deficiencies in previous studies are summarized, and a new research perspective is proposed to deepen our understanding of microbial involvement in the carbon cycle in thermokarst lakes. With the help of metagenomic technology and incubation, the regulatory mechanisms of microbes for the carbon cycle can be revealed more clearly, and field observations of carbon emissions from thermokarst lakes under different environmental conditions can be strengthened. Exploring the use of microbes for mitigating the negative effects of climate change should be based on the above fundamental research.