Vinh et al Methanogenic Diversity Two Vegetation Types

Vinh et al Methanogenic Diversity Two Vegetation Types

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  RESEARCH POSTER PRESENTATIONDESIGN © 2012 www.PosterPresentations.com • Microbial activity within freshwater wetland sediments is the largest natural source of atmospheric methane (CH4), an important greenhouse gas (GHG)1. • Wetland methane production is controlled by watershed and wetland hydrology and vegetation morphology and physiology. • Urbanized wetlands can receive increased water, nutrient, and organic matter loading rates. • How does the diversity of methanogenic prokaryotes differ between sediments underlying two vegetation types? Rationale Sediment gas fluxes: - measured in situ with triplicate closed chambers2. - Methane, carbon dioxide, and nitrous oxide determined with a Bruker 450-GC GHG analyzer. Methods Study Site Findings GHG fluxes • Methane contributed only 0.04% of total gaseous C loss from sediments suggesting high rates of methane oxidation (Fig. 2). • Methane production was highest at the Typha site (B) (Fig. 2), which also had higher aboveground biomass, sediment C/N, and porewater PO4 3- (Table 1). • Methane fluxes as both sites were linearly correlated with sediment temperature (not shown). Methanogenic diversity • 159 mcrA sequences were classified into 19 species-level OTUs (cutoff value: 86% sequence similarity; Figs. 3 & 4). • Methanolobus and Methanosarcina genera of the family Methanosarcinaceae made up of 65% of the sequences (Fig. 3). • Significant inter-site differences in vegetation, sediment biogeochemistry and methane flux dynamics were not associated with differences in methanogen community composition (Table 2). Methanogenic Diversity and Methane Efflux Across Two Vegetation Zones of an Urban Freshwater Wetland References 1Bridgham SD, Cadillo-Quiroz H, Keller JK, Zhuang Q. 2013. Methane emissions from wetlands: biogeochemical, microbial, and modeling perspectives from local to global scales. Global Change Biology. 19 (5): 1325-1346. 2Howes BL, Dacey JW, Teal JM. 1985.Annual carbon mineralization and belowground production of Spartina alterniflora in a New England salt marsh. Ecology. 66 (2): 595-605. 3Steinberg LM, Regan JM. 2008. Phylogenetic comparison of the methanogenic communities from an acidic, oligotrophic fen and an anaerobic digester treating municipal wastewater sludge.Applied and environmental microbiology. 74 (21): 6663-6671. Tran QV1, Takeuchi M2, Mouginot C1, and Hamersley MR1 1Soka University of America, Aliso Viejo, CA 2School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA Table 1. Vegetation and sediment properties of study sites. Results Acknowledgements Funding was provided by Soka University ofAmerica. We thank the J.H. Martiny Lab (UC, Irvine) for technical assistance and The City of Newport Beach and M. Yurko (CA Coastal Commission)for access to the site. Date Oct Jan Apr Jul Oct SedimentCO2flux(mgm -2 h-1 ) 0 100 200 300 400 500 Sediment Temperature (°C) 5 10 15 20 SedimentCO2flux(mgm -2 h-1 ) 0 100 200 300 400 500 2012 2013 Date Oct Jan Apr Jul Oct SedimentCH4flux(µgm -2 h-1 ) 0 50 100 150 200 400 600 800 Sediment Temperature (°C) 5 10 15 20 SedimentCH4flux(µgm -2 h-1 ) 0 50 100 150 200 400 600 800 2012 2013 Figure 2. Sediment metabolic fluxes.A: CO2, B: CH4 Figure 4. Rarefaction curves. Additional sequences would have to be recovered to sample all of the mcrA diversity (MOTHUR v.1.37.0). Figure 3. Phylogenetic tree of mcrA (species OTUs) (Geneious version 7.1). 0 5 10 15 20 0 40 80 120 160 NumberofOTUs Number of mcrA sequences recovered Species Genus Family Table 2. Inter-site and inter-season PERMANOVA comparisons of methanogen community structure by mcrA sequence (E-PRIMER 7). DNA samples: - extracted from triplicate 5-cm deep sediment plugs collected in triplicate during 3 seasons (Jan, Jun, Sept). - Methyl coenzyme M reductase (mcrA) sequences amplified with mlas and mcra-rev primers3. - Sanger sequenced (Beckman Genomics). Figure 1. Sampling sites within the 1.7-ha freshwater Newport Valley Wetland, Newport Beach, CA Site Site A Site B Vegetation Scirpus sp. Typha sp. Peak biomass (g m-2)a 465 ± 15 2320 ± 180 Sediment (top 5 cm)b Density (g cm-3) 0.39 ± 0.03 0.24 ± 0.01 C/N (molar) 23.7 29.9 Porewater (top 5 cm)c Nitrate (µmol L-1) 2.63 ± 0.48 2.20 ± 0.82 Phosphate (µmol L-1) 2.79 ± 1.37 14.2 ± 3.1 an = 3, bn = 15 (Site A) and n- 18 (Site B), cn =6 Scirpus site Typha site A B A B Newport Valley wetland: Scirpus sp. Typha sp. Eriogonum fasciculatum Upland Urbanized Riparian Estuary N 50 m 100 ft A B Newport Valley wetland: Scirpus sp. Typha sp. Eriogonum fasciculatum Upland Urbanized Riparian Estuary N 50 m 100 ft Comparison Pseudo-F P-value Pseudo-F P-value Species OTUs Site (Typha vs. Scirpus ) 0.35 0.78 1.04 0.39 Season (Jan, Jun, Sept) 0.91 0.48 0.9 0.52 Family OTUs Site (Typha vs. Scirpus ) 0.8 0.54 1.39 0.28 Season (Jan, Jun, Sept) 1.16 0.42 1 0.61 α diversity (OTU richness & evenness) β diversity (OTU richness) Methanobacteriales Methanosarcinales Methanocellales Methanocmassiliicoccales Methanomicrobiales