13: Impacts to the Atmosphere
- Page ID
- 131992
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“… the impact of climate change will depend heavily on responses of microorganisms”
—Cavicchioli et al. (2019)
Earth’s atmosphere consists of layers of gases which we call ‘air’ that surround the planet. By volume, dry air contains 78.09% dinitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, varying amounts of water vapor, and trace amounts of several other gases. Levels of these gases reflect the rates at which they are added and removed from the atmosphere, which depend on numerous physical, chemical, and biological processes.
In this chapter, we focus our attention on examples of ways that microorganisms impact atmospheric concentrations of oxygen \(\left(\text{O}_{2}\right)\) and three greenhouse gases: carbon dioxide \(\left(\text{CO}_{2}\right)\), methane \(\left(\text{CH}_{4}\right)\), and nitrous oxide \(\left(\text{N}_{2} \text{O}\right)\). Atmospheric oxygen levels affect surficial redox processes and have been a major influence on the evolution of Earth’s organisms (Reinhard et al., 2016) and minerals (Hazen et al., 2008). Greenhouse gas levels are a major control on Earth’s climate. Some can also impact ozone levels. Methane helps form hazardous tropospheric ozone (i.e., smog), whereas nitrous oxide is destructive to beneficial stratospheric ozone. Thus, microbial impacts to levels of these gases in the atmosphere help determine the habitability of our planet for humans and other organisms.
One important detail to note as you read this chapter is that microorganisms help determine greenhouse gas levels, but there are many controls. For a comprehensive quantitative analysis of atmospheric gas budgets, the reader is referred to Friedlingstein et al. (2022) for carbon dioxide, Saunois et al. (2020) for methane, and Tian et al. (2020) for nitrous oxide. Moreover, additional details about all three greenhouse gases and climate change research in general are available from the United Nations Intergovernmental Panel on Climate Change (IPCC) reports (e.g., IPCC, 2021).
- 13.1: Oxygen
- Changes in the oxygen level of Earth's atmosphere over geologic timescales. Roles played by oxygenic phototrophic microorganisms in the rise in atmospheric oxygen.
- 13.2: Trends in greenhouse gases
- Trends in the three most influential greenhouse gases (carbon dioxide, methane, and nitrous oxide) in Earth's atmosphere over human timescales. How human activities that affect greenhouse gases impact microbes involved in global biogeochemical cycles.
- 13.3: Carbon dioxide
- Microbial influence on the carbon dioxide content of their environments, including water, soils, and the atmosphere. Discussion of and practice problems for Henry's Law.
- 13.4: Methane
- Microbial impacts on methane content of their environments, with focus on wetlands and lake sediments.
- 13.5: Nitrous oxide
- Pathways of microbial nitrous oxide production. Environmental contexts of microbial nitrous oxide production in soils and thermally stratified reservoirs.
- 13.6: Responses of microorganisms to climate change
- Examples of climate change impacts on environmental controls for microbial activity. Possible effects of microbial impact to greenhouse gases on climate change.
- 13.7: Managing greenhouse gas emissions
- Developing strategies to alter microbial activity in particular environments, for the reduction of greenhouse gas emissions. Includes discussion of previous research examples in this area.