Page 123 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

low, with averages of 1.6% and 0.8%, respectively. The JS1 lineage is a subgroup of the candidate phylum Atribacteria (Nobu et al. 2016a). Metabolic reconstructions have indicated the potential of JS1 bacteria for fermentative metabolism and syntrophic acetate oxidation (Lee et al. 2018). Aerophobetes and GIF9 phylum bacteria were more characteristic of the Senator Westphal S (6.7%) and Westland (8.1%) sites and were present only at low abundance at the Vittorio (1.6%) and Max Gundelach (0.8%) sites. Candidate GIF9 bacteria were only detected at the Senator Westphal S (3.4%) and Westland (7.2%) sites. In addition, MSB.5B2, TA06, SBR1031, Pla_1 lineage (Senator Westphal S site only), Pirellulales (Senator Westphal S site only) and Phycisphaerales (Westland site only) were unique to specific cores.
Archaeal species diversity was greater at the Senator Westphal S (Simpson: 0.24; Shannon: 2.13) and Westland (Simpson: 0.19; Shannon: 2.85) sites than at the Vittorio (Simpson: 0.21; Shannon: 2.28) and Max Gundelach (Simpson: 0.23; Shannon: 1.96) sites (Fig. S4A). The archaeal community structure was similar among the cores, as supported by non-metric multidimensional scaling (Fig. S5).
The high microbial diversity of these peat sediments was reflected in the alpha diversity indices. Compared to inundated mangrove peat soils, the bacterial alpha diversity in the North Sea peat sediments sampled in the present study was higher (Shannon diversity of up to 5 vs 2.81, Fig. S4B.) (Chambers et al. 2016). The indicators of diversity observed here are comparable to or higher than those observed in tropical peat swamp forests in Thailand (Shannon diversity of 5.07) and Indonesia (2.0-2.5), but the largest estimated Chao1 index was much higher (1,054 for Thailand peat vs 1,500-4,500 observed in our study) (Chambers et al. 2016; Kwon et al. 2016).
Discussion
A newly measured CH4 store
This study presents geochemical conditions, vegetation composition, microbial diversity and metabolic potential in the context of the CH4 cycle. The geographic expanse of this study is large compared to previous studies that have measured CH4 concentrations in marine sediments, (Niemann et al. 2005; Egger et al. 2016, 2017; Steinle et al. 2016). The broad distribution of the sample locations (study area in Fig. 1A; 43,158 km2) indicates that this dataset is
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