6: Basic Environmental Controls
- Page ID
- 131836
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“... as we continue to explore biogeochemical cycling we become increasingly aware of the subtle influences shaping these processes.”
- Kappler and Bryce (2017)
As discussed in Chapter 5, microorganisms play many roles in driving the global biogeochemical cycles. You may be wondering what connects all of these contributions together and causes microbial communities to transition between different roles or functions. Why might microbial communities catalyze denitrification at one location but nitrification in another, for example? You may also be wondering what controls the identity of the microbial species that are catalyzing the reactions. Numerous species can catalyze denitrification, for example. Why might those responsible differ between environments?
Generally, there are no simple answers to these questions. To understand patterns of microbial activity in the environment, we need to consider the wide variety of ways that environments influence microbial communities. The chemical composition of an environment impacts physiological constraints on microorganisms and the thermodynamic and kinetic controls on their reactions. Biological interactions between species affect their ability to grow. Transport of mass in and out of microbial habitats impacts resource supply and waste accumulation. Among other potential controls, the stability of an environment, the extent to which conditions change over time, is also influential.
Part 2 of this book (Chapters 6-10) will help you start to make sense of these relationships and connect the various contributions of microorganisms within the global biogeochemical cycles. We begin with an overview of controls and then, in the next few chapters, turn our attention to nutrient and energy resources, thermodynamics, kinetics, and biological controls. Factors that influence the distribution of microbial activity are superimposed on one another and can be challenging to pull apart and yet, by doing so, we can better understand and potentially alter patterns of microbial activity in the environment.
- 6.1: Categories of controls
- The classification of processes that control microbial community assembly, into deterministic and stochastic controls.
- 6.2: Basic properties of the environment
- Overview of how basic environmental properties (temperature, pressure, oxygen and water availability, and pH) affect the species and activity level of microbial life in the environment.
- 6.3: Transport processes
- How transport processes can form an environmental control on the distribution and activities of microbial populations, as illustrated by various examples.
- 6.4: Environment stability
- How disturbances in environmental stability can serve as an environmental control on microbial populations.
- 6.5: Dispersal mechanisms and barriers
- The environmental effects of dispersal limitations on microbial population distributions.
- 6.6: Interactions between controls
- Overview of interaction effects between environmental controls and how they can affect microbial populations.