Supplementary Figures and Tables

Supplementary Figure S1: Riverwaterlevels at time of sampling.

Water levels of the river Rhine at the sampling station Lobith (the Netherlands). The left panel depicts the water levels relevant for the 2006-2007 sampling events while the right panel shows the relevant water levels preceding the July 2009 sampling of the intact core.The arrows indicate sampling events. The dashed line indicates the water level (10.40m) at which water enters the oxbow lake and starts flooding the lowest part of the sampling plot. Data are obtained from the Dutch “waterbase”website (http://www.rijkswaterstaat.nl/water/scheepvaartberichten_waterdata/historische_waterdata/waterbase/index.aspx).

Supplementary Figure S2: Methane flux from experimental plot.

Methane flux measurements as recorded in May-July and October 2007 as function of elevation within the experimental-site located in a riparian floodplain of the river Rhine.Black circles indicate samples taken in May,red in July and blue in October 2007.

Supplementary Figure S3: pmoA based cloning of experimental plot.

pmoA DNA neighbour tree showing the phylogenetic positions of the clones obtained from the wetland study site. The number of clones belonging to either of the three major clades of methanotrophs is indicated. The scale bar indicates the estimated number of base changes per nucleotide sequence position.

Supplementary Figure S4: Methane oxidation and kinetics as function of soil water content.

Methane oxidation activity (panel A) and specific affinity of soil methane consumption (panel B) as function of soil water content of soil samples (0-2cm) collected in September (2006), May,July and October (2007) in a floodplain of the river Rhine (the Netherlands). The shaded boxes indicate the range of moisture contents with concurrent high methane consumption or specific affinity, respectively.

Supplementary Figure S5: Micro array probe signals as function of methane oxidation.

Relative probe signals of as a function of the initial methane consumption activity of the 0-2cm layer of soil cores sampled in a riparian floodplain in September 2006, May, July and October 2007. Probes coverage: MB292 = Methylobacter sp. (Ia); Mb-LW12-211 = Methylobacter tudripaludum (Ia); Mb271 = Methylobacter sp. (Ia); Mm275 = Methylomonas (Ia); Ia193 = Generic type Ia probe; Ib453 = Generic type Ib probe; 501-286 = uncultured 1b cluster; II509+II630 = Generic type II probes. R2 indicates the adjusted R2 of a linear regression analyses. The p value indicates the significance of the linear regression fit as determined by ANOVA analyses.

Supplementary Figure S6: PCA analyses of measured variables.

Principal component analyses of variables as analysed in the 0-2cm layer of soil cores sampled in September 2006, May,July and October 2007. The arrows above the figure indicate that all methanotrophic activity components (left of the graph) are correlated to type Ia and 1b methanotrophs and are mainly positively influenced by moisture and are all negatively related to elevation (right part of the graph, while type II parameters are negatively related to all type I components and relate to elevation and methane production and emission.Abbreviations: Nwater = Water extractable nitrogen (i.e. NH4+, NO2-, NO3-); WFPS = water filled pore space; Org. matter = Organic matter content; Spec. aff = specific affinity (i.e. Vmax/Km); PMOini = initial methane oxidizing activity; PMOind = Induced methane oxidizing activity; Ia193+Ia509 = generic probes covering all type Ia MOB; Ib453+Ib559 = generic probes covering all type Ib MOB; II509+II630 = generic probes covering all type II MOB; Ia:Mb292 = probe targeting a subset of Methylobacter species;Ia:Mb271 = probe targeting a subset of Methylobacter species; Ia:Mm275 = probe targeting Methylomonas species; Ia:Mm531 = probe targeting a subset of Methylomonas species; Ib:501-286+IB:501-375 = probes targeting a subset of Ib MOB related sequences without cultured representative;Ib:Mc396 = probe targeting Methylococcus species; II:Mcy264 = Probe targeting Methylocystis species

Supplementary Figure S7: pmoA transcript numbers as function of methane uptake in intact cores.

Number of pmoA transcripts as function of whole core methane consumption in soil cores collected in July 2009 in a riparian floodplain. Lower number of samples indicate to low copy numbers in the respective samples. R2 indicates the adjusted R2 of a linear regression analyses. The p value indicates the significance of the linear regression fit as determined by ANOVA analyses.

Supplementary Figure S8: Methane consumption in intact soil cores.

Methane consumption by intact soil cores, retrieved from a riparian floodplain in July 2009. Bars represent the average of 3 replicate cores with error bars showing standard deviation.

Supplementary Figure S9: Changes of peptide ion mass distributions after incubation with 13C methane. Representative MS spectra showing the peptide ion mass distribution of (A) peptide sequence LGEFNTAGVR and (B) peptide TVQVTASDAAWEVYR both of methane monooxygenase/ammonia monooxygenase, subunit B from sample core 3 (Elevation +0,267m). Intensity values are given as relative intensity of highest peak in the depicted section. These peptides match with pmoB subunit of Methylobacter tundripaludum, which is a type Ia MOB.

Supplementary Tables

Supplementary Table S1: Correlations of measured variables.

Supplementary Table S2: Protein identification data with respect to 3 replicate soil cores taken at elevation level -0,12m (Core 1).

Supplementary Table S3: Protein identification data with respect to 3 replicate soil cores taken at elevation level 0,07m (Core 2).

Supplementary Table S4: Protein identification data with respect to 3 replicate soil cores taken at elevation level 0,27m (Core 3).

Supplementary Table S5: Protein identification data with respect to 3 replicate soil cores taken at elevation level 0,64m Core 4).

Supplementary Table S6: Protein identification data with respect to 3 replicate soil cores taken at elevation level 1,04m Core 5).