Page 105 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

of IJmuiden (52°), the Netherlands, to the latitude of Kiel (56°), Germany (Fig. 1B). This region includes the Doggerbank, the Frisian Front, and the Brown Bank and ocean depths ranging from 19 m to 60 m.
A total of 34 cores were collected across 20 sites (see Table S1 for the location and analysis details of all cores and sites). The sites were named according to nearby shipwrecks using Emodnet (EMODnet 2018), with the exception of Darci’s site.
Methane measurements were performed at all sites. Four sites in the Vlieland (Vittorio, Max Gundelach, Senator Westphal SW, Westland) and Doggerbank (Dorthea Shallow SW, Dorthea SSW, Dorthea NW, Fredricksborg NE) regions were chosen for microbial sequencing analysis and microbial activity studies, respectively. Loss On Ignition (LOI) was performed on these eight sites. Two sites were chosen for plant macrofossil analysis (Vittorio and Fredricksborg NE) and radiocarbon dating. Cores were photographed and texturally described at the facilities of TNO-GDN according to protocol (Bosch 2000) and will be available at www.dinoloket.nl.
Sediment sampling
Shallow vibrocores (3-4.5m) were collected during two separate cruises in June 2017 and July 2018 on board the NIOZ research vessel Pelagia. Before the cruise, digital maps of peat occurrences in the southern North Sea were prepared using the DINO digital database of TNO- Geological Survey of The Netherlands (Van Der Meulen et al. 2013). Based on these maps, areas were selected for geophysical research using sub-bottom profiler and sparker systems. The seismic profiles were directly interpreted on board to identify the presence and depth of basal-peat beds. The seismic data were used to select sampling sites from a range of water depths and latitudes and within the capability of the vibrocorer (within 4 m of the seabed).
At each site, two or three cores were collected. From one core, samples for CH4 were taken as soon as the core was on deck. Before sampling or after (in the case of CH4 sampling only), the cores were cut into 1-m sections. One of the three recovered cores was cut lengthways following recovery. Sediment for molecular analysis was sampled immediately after opening the core sections and frozen at -80°C until further analysis. Subsequently, pore water samples were collected, and sedimentary samples were taken to determine porosity. All sections were stoppered and sealed at the base and top and stored in a refrigerated container (4°C).
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