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Spatial Variability of Methane Production and Methanogen Communities in a Reservoir: Importance of Organic Matter Source and Quantity

Berberich, Megan E.
http://orcid.org/0000-0001-5363-892X
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1511861542523088

Abstract Details

2017, MS, University of Cincinnati, Arts and Sciences: Biological Sciences.
Freshwater reservoirs are an important source of the greenhouse gas methane (CH4) to the atmosphere, but global emission estimates are poorly constrained (13.3 – 52.5 Tg C yr-1) due, in part, to extreme spatial variability in emission rates within and among reservoirs. While morphological characteristics, including water depth, contribute to the variation in emission rates, spatial heterogeneity of biological methane production rates by sediment dwelling methanogenic archaea may be another important source of variation. An important constraint on CH4 production rates is the availability of organic matter (OM). Laboratory experiments have shown that both the quantity and quality of OM influences production rates. For example, CH4 production rates have been shown to respond strongly to algal-derived OM, a highly labile OM source. It is unclear, however, whether this pattern persists at the field scale where other sources of organic matter, such as sediment loads from the watershed, may play an important role in CH4 generation. We measured methane production rates, sediment OM source, OM quantity, and methanogen community composition at fifteen sites in a temperate, eutrophic reservoir to assess OM drivers of spatial variability in CH4 production rates. Areal CH4 production rates (g CH4 m-2) were highest in the riverine portion of the reservoir below the main inlet where OM quantity (g OM cm-2) was greatest, presumably due to high sedimentation rates. The pattern of high CH4 production rates in the riverine portion of the reservoir persisted even when rates were normalized to OM quantity (g CH4 g-1 OM), suggesting that not only was OM more abundant in the riverine zone, it was more readily utilized by methanogens. Sediment stable isotopes and elemental ratios indicated a greater proportion of allochthonous OM in the riverine zone than other areas of the reservoir, suggesting that watershed derived OM is an important driver of CH4 production in the system. Methanogens were abundant at all sampling sites but the functional diversity of methanogens was highest in the riverine zone. Variation in functional diversity of methanogens likely reflects differences in decomposition processes or OM quality across the reservoir. In contrast to previous reports of water column primary productivity as a key predictor of CH4 emission rates in reservoirs, we found that measures of OM quantity best explained variation in CH4 production rates within the reservoir and that the highest production rates occurred at sites with a strong contribution of terrestrial OM. This indicates that while OM source is important, the total OM quantity, regardless of source, is the primary driver of CH4 production rates.
Ishi Buffam, Ph.D. (Committee Chair)
Jake Beaulieu, Ph.D. (Committee Member)
Trinity Hamilton (Committee Member)
86 p.
Biogeochemistry
methanogenesis; reservoir; organic matter; methanogen; methane

Recommended Citations

Citations

  • Berberich, M. E. (2017). Spatial Variability of Methane Production and Methanogen Communities in a Reservoir: Importance of Organic Matter Source and Quantity [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1511861542523088

    APA Style (7th edition)

  • Berberich, Megan. Spatial Variability of Methane Production and Methanogen Communities in a Reservoir: Importance of Organic Matter Source and Quantity. 2017. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1511861542523088.

    MLA Style (8th edition)

  • Berberich, Megan. "Spatial Variability of Methane Production and Methanogen Communities in a Reservoir: Importance of Organic Matter Source and Quantity." Master's thesis, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1511861542523088

    Chicago Manual of Style (17th edition)

ucin1511861542523088
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This open access ETD is published by University of Cincinnati and OhioLINK.