Page 253 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Accurate GHG flux predictions require reliable, rapid, and integral environmental datasets
Current methods that are used for assessing the microbial diversity and metabolic potential are often tedious, costly, and time consuming. A typical workflow from field sampling to cultivation and sequencing takes at least over a year. To obtain the information needed for more accurate climate predictions, we need faster, easier testing methods to collect more data in a shorter timeframe. We highlighted this need in Chapter 6, in which we reviewed the role of thermokarst lakes in a warming world with a focus on their microbiology. The development of faster and more accessible screening methods, however, requires more insights into system parameters and their interactions, which control microbial activity. For this scientific basis, long-term, in-depth investigations are still essential.
Furthermore, seasonality and diurnal changes play a large role in microbial activity and linked GHG fluxes, especially in cold environments. There is little data on year-round greenhouse gas emissions from thermokarst lakes and permafrost soils, although large differences are expected (Arp et al. 2012; Sepulveda-Jauregui et al. 2015; Mu et al. 2016a). Here, we exposed thermokarst lake sediments and permafrost soils to long-term, constant warming scenarios (Chapter 7 and 9). However, this approach targeted overall fluxes and did not include diurnal variations or seasonal differences. Where diurnal changes do not affect fluxes on the timescale of days, seasonal differences have a pronounced impact on total annual fluxes. Experiments with constant warming exposure, therewith, generate a “maximum potential rate” under highly defined conditions, rather than a seasonal average rate. To reconstruct ecosystem GHG fluxes, such seasonal differences need to be included. One way to include seasonal fluctuations is incubation under real climate scenarios obtained from field measurements. Modern incubation chambers and temperature-controlled bioreactors allow for the incorporation of such scenarios. Most importantly, GHG flux data from these studies are a closer approximation of the field situation.
Current climate models experience a lack in microbial data
Urgent open questions include how we can best incorporate ecosystem greenhouse gas releases into climate models and temperature scenarios, and which datasets should be primarily generated by biogeochemists and (micro)biologists to contribute to the development of climate
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