Page 178 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Chapter 8. Species-specific responses of enriched thermokarst lake sediments
It is, however, still largely unknown whether and how the prolonged exposure to warming under an increased substrate availability scenario that mimics permafrost thaw affects the species composition and the functional potential of these methanogenic communities. A first attempt to elucidate community-structure changes was made in our previous study by using a 16S rRNA gene-based approach (de Jong et al. 2018). Acetate amendment resulted in an increase in Methanosaetaceae/Methanotrichaceae, TMA amendment led to an enrichment of Methanosarcinaceae and Methanosaetaceae/Methanotrichaceae. This dataset can, however, not provide in-depth insights into changes in both species composition and metabolic potential of the microbial communities exposed to the combined warming and substrate amendment scenario.
To address the above questions, we applied full metagenome sequencing on these communities to unravel species-specific responses to the applied climate change scenario. With the full metagenome datasets, we could study species-level shifts that are difficult to uncover by lower resolution 16S rRNA gene-based sequencing. Understanding species-level responses is important to better comprehend the mechanisms that underlie GHG production from Arctic lakes in a warming world.
Materials and methods
Sampling site
Sediment cores were collected from two thermokarst lakes (Lake Emaiksoun and Unnamed Lake) during a winter field campaign carried out by the Vrije Universiteit Amsterdam in November 2015 to the northernmost US settlement of Utqiaġvik in the North Slope of Alaska, United States. For detailed sampling site description see our previous study (de Jong et al. 2018).
Incubations
Sediment cores were stored at 4°C until further processing. The incubation experiments were started within half a year of sampling. The elemental data from pore water data analysis was used for medium design. For medium description and incubation conditions see de Jong et al. (2018). In short, triplicate incubations were prepared for acetoclastic and methylotrophic
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