Page 111 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

calculated based on a liquid volume of 50 ml and assuming that all of the substrate dissolved over time.
For substrate consumption rates, the per cm3 substrate conversions were calculated by dividing the total substrate conversion numbers by 16.67 cm3, which corresponds to the quantity of compacted peat sediment inoculated per batch incubation.
Gas samples (50 μl) were withdrawn with a gas-tight glass syringe (Hamilton, Reno, NE) and injected into an HP 5890 gas chromatograph (Hewlett Packard, Palo Alto, CA) equipped with a Porapaq Q 100/120 mesh (Sigma Aldrich, Saint Louis, MI) and a flame ionization detector (FID) for CH4 detection and a thermal conductivity detector (TCD) for measuring H2, CH4 and CO2 simultaneously using N2 as the carrier gas. An Agilent 6890 series gas chromatograph coupled to a mass spectrometer (Agilent, Santa Clara, CA) equipped with a Porapak Q column heated at 80°C with He as the carrier gas was used for measurements of 13CO2, 13CH4 and O2.
Plant macrofossil analysis
Two sites, the Max Gundelach site and the Fredricksborg NE site, were selected for plant macrofossil analysis. The Max Gundelach site is in the southern North Sea near the coast of the Netherlands (4°51.07’E, 53°20.09’N), and the Fredricksborg NE site is in the Doggerland region (3°26.42’E, 55°49.48’N).
The Max Gundelach site was analysed with low sample resolution but high taxonomic resolution, showing the main peat components as well as an overview of the less abundant taxa. The Fredericksborg NE site was analysed with high sample resolution but low taxonomic resolution, showing only the main peat components.
From the Max Gundelach core, 8 samples (slices with a thickness of 1 cm or, in two cases, 2 cm, and a volume ranging from 8 to 11 cm3) for plant macrofossils were taken every 10 cm. From the Fredricksborg NE core, 15 subsamples were taken with a resolution ranging from 1 to 4 cm and volumes ranging from 3 to 8 ml. The samples were heated near the boiling point in 5% NaOH solution and then gently washed through a 150-μm mesh sieve with tap water. After sieving, the plant macrofossils were stored in a known volume of water. The sample material was systematically examined at 15 to 40X magnification using a stereomicroscope.
Substrate and product analysis
109
5