Playing scales in the methane cycle: From microbial ecology to the globe
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106
Two of the great challenges in understanding the planet's climate system are that (i) biogeochemical cycles (e.g., carbon, water, energy, etc.) are tightly coupled, and (ii) important drivers of those cycles occur at all scales of biogeochemical organization. At the largest scale of space and time are phenomena such as the “Great Ocean Conveyor” (1), which circulates water (plus chemicals and heat) through the oceans of the planet, or the Hadley convection cells (2), which produce the latitudinal climate belts. At the smallest scales of organization, however, there are equally critical processes. For example, in atmospheric chemistry, the kinetics of hydroxyl radical formation and consumption regulate the redox chemistry of the atmosphere (3), whereas the adsorption of nitrogen oxides to ice crystals in stratospheric clouds regulates ozone destruction (4). In biology, global models increasingly find that they must capture the physiology of plant photosynthesis to get the overall C cycle “right” (5).
Microbes and Global Cycles
At the smallest scale of life are microorganisms: bacteria, fungi, and unicellular algae. Microbial processes dominate global biogeochemistry, accounting for roughly half of global photosynthesis and almost all organic matter decomposition, nitrification, denitrification, methane production, etc. (6). Microbial processes, however, are regularly treated as a simplistic black box, although the details of microbial physiology can have large impacts on global biogeochemical cycles and the planet's climate system, as illustrated in the article by Gauci et al. (7) in this issue of PNAS. The article evaluates the importance of industrial S emissions on the global methane cycle, an interaction that …
