Page 13 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

use oxygen or a range of alternative electron acceptors. Recent discoveries suggest there still is a wide variety of methanotrophic prokaryotes to be discovered.
We studied freshwater peat sediments in a Dutch rural environment in which iron sheet piles were applied for reinforcement (Chapter 3). When the sheet piles were removed after 50 years of service, natural corrosion protective layers (CPLs) were observed on the metal surfaces. These deposit layers have the potential to protect iron sheet piles from corrosion, resulting in a longer life span, with corresponding economic and environmental benefits. Methanogens (Methanobacteriales) were enriched in the deposit layer, indicating a potential link with CPL formation. Upon closer investigation using next-generation sequencing we could reconstruct the microbial food web of the sheet pile environment, providing first insights into the mechanisms leading to CPL formation.
Next, we investigated the potential to convert coal wells into bio-CH4 production sites (Chapter 4). We found that combined nutrient and acetate amendment induces the growth of a methanogenic community, but that methanogenesis from sub-bituminous coal was not stimulated. The amendment strategy is therefore not a sustainable way to transform non- producing coal wells into bioenergy factories. Furthermore, we should consider that, even when biomethanation is successful, CH4 from coal remains a fossil fuel.
We investigated North Sea peat sediments that were remarkably devoid of a methanotrophic community (Chapter 5). We observed CH4 accumulation in the peat deposits, and methanogens could be revived from these 10 thousand-year-old layers upon amendment with methylated substrates, which are substrates commonly produced during marine organic matter degradation. With an estimated carbon storage of 0.74 Gt in the North Sea basin alone, this provides an important global carbon sink with carbon source potential under a changing climate.
The next chapters focus on cold ecosystems that are disproportionally impacted by climate change.
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