Biogeochemical Cycling and Global Climate Change Study Notes

Presented by UCLA Prof. Berthet.
Focus on the interplay between biogeochemical cycling and global climate change, particularly in relation to microbial activities and their implications.

Impacts of Temperature on Disease:
- Warmer temperatures lead to longer mating seasons for mosquitoes, which increases the risk of spreading disease-causing microbes.
- Climate change may facilitate the introduction of diseases such as malaria and COVID-19 to the United States.
Biogeochemical Cycling:
- Defined as the sum of microbial, physical, and chemical processes that drive the flow of elements in the ecosystem.

Types of Processes:
- Abiotic Processes: Nonliving processes, including erosion.
- Biotic Processes: Also referred to as nutrient cycling; related to living organisms' contributions.
Role of Microbes:
- Surface-level microbes contribute to rapid nutrient cycling.
- Deep-surface microbes influence elemental cycling over geological timescales, spanning millions of years.

Definition of Redox Potential:
- A measure of the tendency of molecules in a system to accept or donate electrons.
- The redox potential of an environment is determined by the electrical potential difference between the environment and a standard hydrogen electrode.
High Redox Potentials:
- Environments with high redox potentials are more likely to accept electrons when new compounds are introduced.
- The redox state is crucial for determining the microbial community composition present in any environment.
Terminal Electron Acceptors:
- Relevant for anaerobic respiration processes where available molecules accept electrons.
Reduced Molecules:
- Serve as electron donors essential for microbial respiration processes.

Mineralization:
- The process of decomposing organic matter into simpler, inorganic compounds. May or may not recycle nutrients.
Immobilization:
- Nutrients converted into biomass become temporarily unavailable for nutrient cycling.
Role of Saprophytes:
- Important for mineralizing immobilized organic compounds; they derive nutrition from decomposing organic matter rather than living hosts. Example: Rhizopus stolonifer is a commonly referenced saprophyte.

Continuous Transformation of Carbon:
- Carbon is continuously cycled through various forms; initially, plants and microbes fix carbon dioxide (CO2).
Reduction to Methane (CH4):
- CO2 can be anaerobically reduced to methane ( ext{CH}_4).
- Methane can be further oxidized either aerobically by bacteria or anaerobically by archaea.
Methane Environments:
- Typical sites include rice paddies, ruminant animals, coal mines, sewage treatment plants, landfills, and marshes.

Influencing Factors:
- Oxidation-Reduction Potential
- Availability of Competing Nutrients
- Abiotic Conditions: such as pH, temperature, O2 levels, and osmotic conditions.
- Microbial Community Composition.

Lignin:
- Microbes secrete hydrolytic enzymes to degrade lignin, which contains only carbon, hydrogen, and oxygen.
- Microbes have to acquire additional nutrients essential for growth.
- Commonly limiting nutrients include nitrogen, phosphorus, and iron.
- Liebig's Law of the Minimum: states that the growth of an organism is limited by the most scarce resource.

Role of Microbial Activity:
- Critical in maintaining the dynamic equilibrium that defines the biosphere.
Definition of Global Climate Change:
- Reflects changes in patterns of wind, precipitation, and temperatures in oceans and the atmosphere.

Function of Greenhouse Gases:
- Gases trap heat reflected from Earth's surface in the atmosphere, preventing it from radiating into space.
- Accumulation occurs when the rate of gases entering the atmosphere exceeds the natural carbon and nitrogen cycles' ability to remove them.
Consequences of Accumulation:
- Leads to global warming, with various environmental implications.

Global Warming Potential of Methane:
- Methane ( ext{CH}4) has approximately 30 times the global warming potential compared to carbon dioxide ( ext{CO}2).
- One molecule of ext{CH}4 has the same thermal retention capability as 30 molecules of ext{CO}2.
- Methane levels increased 2.5 times over the past 150 years.
- Methanogens convert hydrogen and carbon dioxide produced by other microbes into methane, which is released by animals during digestion.

Metrics of Global Climate Change:
- Climate change is measured over decades, using parameters such as:
- Surface temperatures on land and sea, and in the atmosphere.
- Rates of precipitation.
- Frequency and severity of extreme weather events.

Diversity in the Stratosphere:
- The stratosphere hosts diverse microbial communities that may aid in mitigating climate change.
- Study emphasizes methanotrophs, microorganisms that oxidize methane.
Research Aims:
- Nationwide sampling using 3D-printed bioaerosol samplers.
- Build a comprehensive database of airborne microbes to advance climate science and STEM education.

Develop a standardized, cost-effective bioaerosol sampling kit and involve STEM students in data collection.
Identify stratospheric microbial communities via 16S rRNA sequencing.
Determine ecological niches that promote methanotrophs.

Testing: Ground testing of the bioaerosol sampler.
Methods: High Altitude Balloons will be used for sampling.
Collaboration: Nationwide engagement of STEM students for samples and data gathering.
Database Development: Creation of a comprehensive database to encompass microbial findings.

Engagement with STEM programs at the College of the Canyons.
Completion of bioaerosol sampler design.
Prototype is currently in development including sample collection filters and fans.

Understanding microbial roles in cycling elements through Earth’s ecosystems is becoming essential.
Human activities are disrupting normal cycling levels; hence, knowledge of normal cycles and disturbances is vital.
Begin by learning the standard cycle and then assess deviations from that norm.

Differentiate between "global warming" and "global climate change"; identify greenhouse gases.
Explain the relationship between greenhouse gas accumulation and the microbial cycling of carbon and nitrogen.
Discuss the origins of greenhouse gases including CO2, methane, and nitrogen oxides.