Biology Theses and Dissertations
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Item Methane Biogeochemistry and Microbial Communities in Natural and Restored Freshwater Depressional Wetlands(2024) Hamovit, Nora David; Yarwood, Stephanie A; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Wetlands are the largest natural source of methane (CH4), a potent greenhouse gas. Wetland CH4 emissions are dependent on rates of microbial CH4 production (methanogenesis) and consumption (methanotrophy). These processes vary spatially and temporally with environmental conditions, edaphic characteristics, and microbial community structure, making it difficult to predict wetland CH4 emissions. This high variability can be further pronounced in restored wetlands that have undergone environmental and edaphic disturbances. The following work aims to understand this variability by assessing patterns of methanogenesis and methanotrophy, and their associated microbial communities, across natural and restored freshwater depressional wetlands on the Delmarva Peninsula (USA). Sites addressed in this work were restored from agricultural land between 1986 and 2004 through multiple programs funded by the United States Department of Agriculture (USDA). In the first set of experiments, we identified a high abundance of active acetoclastic methanogens in intact core incubations from a restored wetland suggesting a higher potential for methanogenesis in situ compared to the natural wetland assessed. The co-occurrence of active methanogens and Fe-reducing bacteria in these restored wetland cores contradicted the hypothesis that loss of competition may allow methanogens to be the primary users of acetate. Following assessments across vegetative-hydrologic zones in a series of restored wetlands of varying ages, and their natural counterparts, highlighted vegetation type and extent as a driver of methanogen community abundance, composition, and activity. In turn, restored wetlands showed elevated potentials rates of methanogenesis compared to natural sites. Potential rates of methanotrophy (aerobic and anaerobic), however, were also elevated in restored wetlands, which could constrain CH4 emissions in situ. Variability of environmental conditions (ie. hydrology and vegetation) and edaphic measures (ie. soil organic matter (SOM)) across all sites sampled are reflected in distinct microbial community composition and CH4 biogeochemistry. Clear patterns of SOC accumulation and CH4 biogeochemistry with restoration age were not observed for these wetlands, and variability in environmental conditions and edaphic measures across the sites (restored and natural), emphasize the need for continued monitoring and maintenance of the wetlands. Our results suggest efforts to manage herbaceous vegetation extent and maintain regular seasonal hydrology in future restorations may help prevent high potentials for CH4 production, and thus emissions.Item QUANTIFYING NITROUS OXIDE AND METHANE FLUXES USING THE TOWER-BASED GRADIENT METHOD ON A DRAINAGE WATER MANAGED FARM ON THE EASTERN SHORE OF MARYLAND(2022) Zhu, Qiurui; Davidson, Eric A.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Excess nitrogen resulting from agricultural fertilizer and manure applications on the Eastern Shore degrades the Chesapeake Bay's water quality and causes environmental issues such as algal blooms and "dead zones". Drainage water management (DWM) is an effective best management practice (BMP) to reduce hydrological nitrate export from croplands to surface and ground water by controlling the timing and the amount of ditch discharge and retaining water within ditches and adjacent fields using drainage control structures (DCS). While promoted denitrification in the subsurface and reduction in nitrate leaching are intended consequences of maintaining higher water table level, an unintended environmental consequence is possible production of nitrous oxide (N2O) from denitrification and methane (CH4) from methanogenesis, which are both potent greenhouse gases (GHGs). Whether the application of DWM leads to a "pollution swapping" concern (i.e., trading reduction of nitrate concentrations in ditch water for increases in emissions of N2O and CH4 to the atmosphere) is a question that must be addressed before more widespread implementation of DWM can be endorsed. In this dissertation, I employed a micrometeorological method called the flux gradient (FG) method to a corn-soybean rotation agricultural system with DCS in eastern Maryland on the Delmarva Peninsula to answer this question. This method was chosen because it allows near-continuous measurements of soil trace gas exchanges at multiple locations with a single laser spectrometer at a fine temporal resolution without disturbing the microclimate between soils and the atmosphere. Soil N2O and CH4 fluxes were quantified using the FG method on this drainage water managed farm for three consecutive years when no fertilizer, synthetic fertilizer, and biosolids were applied in 2018 (soybean), 2019 (corn), and 2020 (corn), respectively. Statistical tests indicated that there were no consistent treatment effects of DWM on soil GHG emissions between DWM and non-DWM conditions, suggesting that DWM did not trade the intended consequence of reduced nitrate leaching for the unintended consequence of increased soil GHG emissions. The biosolid addition in 2020 led to the largest N2O emissions among the three years, while the lowest N2O emissions in the growing season were found in the unfertilized soybean year of 2018. In contrast, different fertilization regimes did not yield distinct differences between the three years for CH4 fluxes. In addition, some potential methodological concerns associated with this tower-based micrometeorological approach were addressed and resolved, conferring confidence that the FG method can be applied simultaneously to multiple plots for N2O and CH4 measurements. This research adds to the existing understanding of the impacts of DWM on soil GHG emissions and suggests that this BMP could be applicable in other regions of the Chesapeake Bay as well as other watersheds. This work also contributes to the efforts of studying the impacts of soil organic amendments on soil GHG emissions and deriving improved estimates of emission factors (EFs) for organic amendments.Item Insights into benthic macroinvertebrate ecology in the northern Bering and southern Chukchi Seas from stable isotope analysis(2022) Green, Emma Mackenzie; Cooper, Lee W; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the Pacific Arctic Region, the northern Bering Sea and southern Chukchi Sea support large and diverse communities of benthic macroinvertebrates that provide an important link to the pelagic communities and marine mammals that rely on the benthic populations for food. While the abundance and biomass of these benthic macroinvertebrates are well documented, little is known about how benthic macroinvertebrates interact with each other and how these interactions are affected by climate change. I measured the stable isotope composition (bulk δ15N and δ13C values) of similar species collected in 2014, 2016, 2017, and 2021 in the northern Bering and southern Chukchi Seas. Although there was little change over time in either δ15N or δ13C values, both stable isotope ratios were significantly different between stations with differing production phenologies. The southern Chukchi Sea (a productive set of sites with high chlorophyll concentrations throughout the summer) had lower δ15N values and higher δ13C values, while the northern Bering Sea site with production mostly associated with the period of sea ice breakup had higher δ15N values and lower δ13C values. This pattern was observed across similar species and feeding types. The higher δ15N values in the northern Bering Sea could be due to an extra step in the food chain from bacterial reworking. The contrast between these two regions in δ13C might indicate higher primary production in the southern Chukchi Sea compared to the northern Bering Sea. The differing food web dynamics between these two sites highlight the benthic diversity across small scales and similar organisms in Pacific Arctic food webs.Item EVALUATING CARBON SEQUESTRATION POTENTIAL OF NATURAL AND RESTORED TIDAL MARSHES IN CHESAPEAKE BAY THROUGH QUANTIFICATION OF METHANE FLUXES AND IDENTIFICATION OF DRIVERS(2022) Hanacek, Daniella; Staver, Lorie; Cornwell, Jeffrey; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The production of methane in brackish marshes may offset the carbon sequestered by these wetlands. Brackish tidal marshes are widespread in Chesapeake Bay and there exists a need for understanding the carbon balance of these ecosystems. This thesis presents the results of measurements of methane flux, through static flux chamber experiments, and analysis of marsh porewater to examine biogeochemical and plant-mediated drivers of methane flux in marshes of Chesapeake Bay. In addition, there is growing interest from the scientific and resource management community in how natural marshes cycle carbon and whether restored marshes show biogeochemical similarities. Therefore, I tested my hypotheses in the natural marshes of Monie Bay, part of the Chesapeake Bay National Estuarine Research Reserve – Maryland, and in restored tidal marshes created with dredged sediments at Poplar Island. Methane emissions offset annual carbon storage at Monie Bay and Poplar Island by 0.7 and 2.1 percent, respectively, based on average values of annual fluxes. However, there remains uncertainty in the accuracy of this estimate given the spatial and temporal variability in my observed fluxes, and the limited sampling frequency and spatial extent of my study. Within such uncertainty lays a justification for continued long-term monitoring of methane emissions in restored and natural marshes of Chesapeake Bay to resolve this important marsh management question.Item EXAMINATION OF SOIL GREENHOUSE GAS FLUXES AND DENITRIFICATION TO ASSESS POLLUTION SWAPPING IN AGRICULTURAL DRAINAGE WATER MANAGEMENT(2022) Hagedorn, Jacob; Davidson, Eric A; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increases in agricultural nitrogen (N) inputs driven by synthetic N fertilizer application over the past century have led to higher crop yields but have also intensified riverine nitrate (NO3-) loading, contributing to environmental degradation. Drainage water management (DWM) is a best management practice (BMP) implemented on agricultural ditches to reduce downstream NO3- loading by slowing ditch discharge with drainage control structures that raise the in-field water table, creating anaerobic conditions. More anaerobic conditions stimulate denitrification and possibly methanogenesis. Denitrification consumes NO3-, thereby reducing the downstream N loading, but also increases production of N gases nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2). This research examined the potential consequence of greenhouse gas (GHG) emissions, specifically methane (CH4) and N2O, as a result of DWM-induced low oxygen conditions in a replicated experimental design. Using multiple methods such as soil gas flux measurements, N isotope analyses, gases dissolved in groundwater, and N budgets, this project examined the potential pollution trade-offs between dissolved NO3- and soil GHG fluxes. In chapter 2, I quantified soil N2O and CH4 fluxes using static chambers over three years in a corn/soybean rotation system. I also measured soil environmental variables to assess controls on gas production. Results indicated that the DWM treatment raised the groundwater level near the ditch edge but did not increase the surface soil moisture, which likely led to the observation that DWM did not significantly increase soil N2O and CH4 emissions. Variation in N2O fluxes were heavily influenced by N fertilizer application events. A N budget indicated that this farm site had a lower than average N use efficiency in the U.S. and higher than average soil N2O emissions. In chapter 3, I qualitatively and quantitatively examined the role of denitrification in this DWM system by using natural abundance NO3- isotopes measured across a leaching continuum (topsoil to deep soil to groundwater to ditch water). Results demonstrated that isotopic values of δ15N and δ18O increased in residual NO3- along the leaching continuum, providing evidence of denitrification. However, the net effects of nitrification and denitrification resulted in NO3- less enriched in 15N than expected by denitrification alone. These isotopic values were then applied to a mass balance of total N and δ15N to quantitively calculate the magnitude of total gaseous N export and to constrain that estimate using a net N isotopic discrimination factor. The calculated gaseous N export and denitrification rates fell within but toward the high end of previously reported literature ranges. The N budget indicated lower hydrologic N export in the DWM treatment, suggesting increased denitrification, but uncertainty of the corresponding estimates of increased gaseous N export was greater than the difference between treatments, rendering inconclusive the hypothesis that DWM treatment causes more total gaseous N production and denitrification. Inclusion of isotopes in the N mass balance established a lower bound of total gaseous N export, which was still large relative to other budget terms. In chapter 4, I synthesized results from the previous two chapters to explore the components of total gaseous N export. I also estimated annual export via dissolved N2O and N2 in groundwater entering the drainage ditches. Soil N2 emissions were estimated by subtracting annual estimates of soil N2O and groundwater dissolved N2 and N2O from the total gaseous N export. Results showed that soil N2 emissions dominated the gaseous N export. The N2O/(N2 + N2O) ratios of soil emissions were within but on the lower side of the literature range. This study demonstrated that, at least for this farm, the decrease in hydrologic N loading due to implementation of DWM outweighed the small and statistically non-significant observed increase in GHG production. This result lends support for policies to further incentivize adoption of DWM in ditched agricultural settings. This study also provides a novel, multi-methodological approach for quantitatively assessing and constraining denitrification rates and N2 emissions. It also is the first study to incorporate measurement of multiple fractions of total gaseous N export on the farm scale as part of annualized agricultural N budget.Item INSIGHTS INTO DINOFLAGELLATE NATURAL PRODUCT SYNTHESIS VIA CATALYTIC DOMAIN INTERACTIONS(2022) Williams, Ernest Patrick; Place, Allen R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Dinoflagellates are protists that can be split into two evolutionary groups, the parasitic syndinians and the largely photosynthetic “core” dinoflagellates. They represent a major portion of aquatic biomass which means that they are responsible for large portions of carbon that are both fixed and released. Other than biomass, the fixed carbon can be made into natural products such as polyunsaturated fatty acids that support the biota of many ecosystems or toxins that are harmful to aquatic life and humans. DNA and RNA analyses have been used to discover the putative genes that may make these compounds, but their non-colinear arrangement in the genome is very different from model organisms and their gene copy number is very high, making it nearly impossible to determine the exact biosynthetic pathways. The goal of my studies was to develop methods to differentiate biosynthetic pathways such as lipid and toxin synthesis by comparing the ability of domains to interact with each other with the assumption that domains that preferentially interact are more likely to participate in the same pathway. Initially, a survey was performed on available dinoflagellate transcriptomes to enumerate domains potentially involved in natural product synthesis and bin them based on sequence similarity to identify genes that could be used in biochemical assays. An interesting integration of analogous genes involved in lipid synthesis with those involved in natural product synthesis was observed as well as trends in domain expansion and contraction during core dinoflagellate evolution. Ultimately, the domain that scaffolds natural product synthesis, the thiolation domain, was chosen for further study because it exhibited two clear functional bins and is acted on directly by another enzyme, a phosphopantetheinyl transferase (PPTase). The PPTase activates the thiolation domain by transferring the phosphopantetheinate group from Coenzyme A to the thiolation domain, creating a free thiol group upon which the natural products are synthesized. These PPTases were then enumerated in dinoflagellates and characterized by looking for sequence motifs and observing expression patterns over a diel cycle as well as during growth in the model species Amphidinium carterae, a basal toxic dinoflagellate. Amphidinium carterae appears to have three PPTases, two of which (PPTase 1 and 2) are very similar, except that PPTase 2 does not appear to have a stop codon and has never been observed as a full-size protein. The remaining two PPTases (PPTase 1 and 3) had alternating expression patterns that did not appear to directly correlate to the acyl carrier protein, the thiolation domain required specifically for lipid biosynthesis. This carrier protein, like other enzymes for natural product synthesis in dinoflagellates, had a chloroplast targeting sequence while the three PPTases did not. To investigate the ability of these three PPTases to activate various thiolation domains, a total of 8 domains from A. carterae were substituted into the blue pigment synthesizing gene BpsA from Streptomyces lavendulae. These recombinant constructs were used for coexpression in E. coli as well as in vitro to reduce as many artifacts as possible and assess the interactions of each PPTase with the thiolation domains. Some of the recombinant BpsA genes were able to make blue dye with all three PPTases, while others never made blue dye both in E. coli as well as in vitro. In vitro quantification of free thiol added by the PPTase showed that all the thiolation domains, as well as the acyl carrier protein could be phosphopantetheinated by all the PPTases. This generalist substrate recognition, along with the alternating expression patterns and lack of chloroplast signaling peptide, indicate that the two active PPTases are performing the same function on all available thiolation domains, probably before export to the chloroplast. This lack of pathway segregation by PPTases is a completely novel way of synthesizing natural products compared to bacteria and fungi, likely due to the acquisition of both photosynthesis and natural product/lipid biosynthesis during dinoflagellate evolution that was not present in the common ancestor. Additionally, the techniques to identify genes of interest and perform biochemical characterization developed here are useful for future experiments annotating the function of dinoflagellate genes.Item ECOLOGICAL SIGNIFICANCE OF DISSOLVED ORGANIC MATTER COMPOSITION AND REACTIVITY IN DEPRESSIONAL FRESHWATER WETLANDS(2022) Armstrong, Alec William; Palmer, Margaret; Gonsior, Michael; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Dissolved organic matter (DOM) plays a central role in the biogeochemistry of aquatic ecosystems and is an important flux of carbon (C) from terrestrial to aquatic systems. Wetlands are rich sources of DOM to downstream waters, but the origins of wetland DOM and its role in biogeochemical processes in wetlands and downstream are not fully understood. To better understand the role of wetlands in mediating the movement and transformation of organic matter between terrestrial and aquatic ecosystems, I characterized the chemical composition and the microbial and photochemical reactivity of wetland DOM in a depressional wetland setting in the interior Delmarva Peninsula. I used laboratory experiments to understand DOM reactivity. I characterized sensitivity to photodegradation, concluding most wetland DOM was somewhat sensitive though site differences affected sensitivity. In another experiment, wetland DOM showed little biodegradability, but C losses to microbes were enhanced after photodegradation. This suggested photochemical and biological degradation may have interacted to influence wetland DOM composition within wetlands and in downstream waters. I also found terrestrial sources of DOM (plant and soil leachates) were more biodegradable than wetland surface water. I concluded wetland DOM was largely comprised of leftover material from previous microbial metabolism in soils or wetland water. To characterize wetland DOM and explore its environmental influences, I undertook a field sampling campaign of 22 wetlands over 18 months. Samples were characterized using a suite of DOM measurements, and variability in these data was modeled using water level, regional air temperature, a proxy for site canopy cover, estimated photosynthetically active radiation, and others. DOM varied considerably seasonally and among sites, and modeling suggested that complex seasonal and site-related interactions influenced DOM, not including water level. This research indicates that depressional freshwater wetlands accumulate and process DOM, some of it likely originating from soils and some within wetlands, but spatial and seasonal variability lead to DOM variability. Wetland DOM exported to downstream waters has intrinsically low biodegradability, though this may be enhanced by photodegradation downstream. This research may be useful for efforts to improve representation of depressional freshwater wetlands in mineral soils in C cycle models and inform policy concerned with wetland biogeochemical functions and connections with downstream waters.Item INVESTIGATING WATERSHED-SCALE CONTROLS ON STREAMWATER NITRATE EXPORT USING STABLE ISOTOPES(2022) Bostic, Joel; Nelson, David M; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Dramatic increases in anthropogenic nitrogen inputs to watersheds over the past century have elevated riverine nitrate (NO3¯) loads, impairing downstream ecosystems. Impacts to receiving waters are largely determined by the amount and timing of streamwater NO3¯ export, and knowledge of the watershed-scale controls on spatiotemporal patterns of NO3¯ export is thus critical for effective mitigation. Land-use activities produce generalizable patterns of streamwater NO3¯ in specific watersheds but it remains unclear how land use might modulate more widespread nitrogen inputs, such as atmospheric deposition, and regulate temporal dynamics of streamwater NO3¯ export. To address these questions, I quantified nitrogen sources and inferred watershed-scale nitrogen cycling processes using stable nitrogen and oxygen isotopes and concentrations of NO3¯ in Chesapeake Bay watersheds. In my first chapter, I quantified streamwater export of atmospheric NO3¯ using triple oxygen isotopes (Δ17O) of NO3¯ in 832 streamwater samples collected from 14 sub-watersheds of diverse land use, nitrogen input rates, size, and lithology across two years during a range of hydrologic conditions. Results indicate that watersheds with either greater impervious surface areas or higher terrestrial nitrogen input rates associated with agricultural practices retain less unprocessed atmospheric NO3¯. I use these results to extend the kinetic nitrogen saturation conceptual model to atmospheric NO3¯ streamwater export and from forested to non-forested systems. In my second chapter, I used seasonal patterns of, and relationships between, NO3¯ concentrations, δ15N of NO3¯, and discharge in the same 832 samples to assess the relative importance of watershed-scale controls on spatiotemporal patterns of streamwater NO3¯ export. Surprisingly, similar seasonal patterns of δ15N-NO3¯ were measured across all watersheds. Similar seasonality of δ15N-NO3¯ suggests consistent temporal variation in biological processes, such as denitrification and/or assimilation, across diverse watersheds. In my third chapter, I used δ15N and Δ17O of NO3¯, as well as isotopes of water, to investigate NO3¯ source export in storm events relative to baseflow in two Baltimore County, Maryland, watersheds with contrasting land use. In the more developed watershed I found that storms had a disproportionate impact on atmospheric NO3¯ export, and the amount of NO3¯ deposited on impervious surfaces was approximately equivalent to the amount of atmospheric NO3¯ streamwater export during storms, while atmospheric NO3¯ exhibited approximately chemostatic behavior in the less developed watershed. These results highlight the importance of reducing hydrologic effects of impervious surfaces to limit atmospheric NO3¯ export, especially given predictions that increasing precipitation intensity will be associated with future climate change. In conclusion, my results demonstrate that land use modulates the retention of atmospheric NO3¯, but biological processes impart a consistent seasonal signal on streamwater NO3¯ irrespective of land use.Item USING A HIGH RESOLUTION, MECHANISTIC MODEL OF FILTRATION, BIODEPOSITION, HYDRODYNAMICS, AND SEDIMENT BIODGEOCHEMISTRY IN ORDER TO UNDERSTAND THE DRIVING FORCES BEHIND NITROGEN DYNAMICS ON OYSTER REEFS(2022) Kahover, Kevin James; Harris, Lora; Testa, Jeremy; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The overarching goal of this work was to develop a modeling tool that can provide quantitative predictions of ecosystem services related to N removal and biomass production using oyster restoration metrics such as reef size and oyster planting densities. I expanded the predictive capability of an existing advection-diffusion model of particle capture on an oyster reef to incorporate oyster biodeposit production, transport, and relationship to nutrient cycling. The resulting oyster reef filtration, biodeposition, and ecosystem services model (ReeFBioDES) utilizes modeled or measured current velocities, temperature, salinity, and chlorophyll-a in a given reef environment (reef length, oyster size and density) to predict spatial patterns of biodeposition production, transport, and denitrification. I applied the model at Little Neck Reef in Harris Creek (Choptank River) over an annual cycle for a range of oyster densities and found the model reproduced both the spatial dynamics of along-reef water-column concentrations of TSS, as well as generating rates of on-reef denitrification that are comparable to recently measured rates in experimental incubations of intact oyster clumps from Harris Creek. The model is now available for scenarios simulations to quantify ecosystem services associated with ongoing and future oyster restoration sites in Chesapeake Bay and other temperate coastal ecosystems that C. virginica occupies.Item QUANTIFYING EFFECTS OF SEASONAL INUNDATION ON METHANE FLUXES FROM FORESTED FRESHWATER WETLANDS(2021) Hondula, Kelly Lynn; Palmer, Margaret A; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Developing effective strategies for reducing methane and other greenhouse gas emissions requires a quantitative understanding of their global sources and sinks. Decomposition of organic matter in wet soils is one of the largest sources of methane to the atmosphere, but it is a highly variable process that remains difficult to quantify because we lack a predictive understanding of how environmental factors control methane emissions in wetlands. Hydrology is one of the most important factors controlling methane production wetlands along with temperature and vegetation, however it is unclear how to relate aspects of a wetland’s hydrologic regime to the timing, magnitude, and spatial extent of its methane emissions. Furthermore, discrepancies between the magnitude of global methane emissions calculated using different techniques indicate that current methods for measuring the extent and dynamics of wetland areas in global models may not adequately represent processes controlling methane cycling in wetlands and other small water bodies. I studied the role of seasonal hydrologic variability on methane emissions from forested mineral soil wetlands to inform modeling techniques at different scales. In Chapter 1, I show the importance of inundation extent and duration as major drivers of wetland methane emissions, that methane fluxes have a non-linear relationship with water level, and that methane fluxes are higher when water levels are falling rather than rising. In Chapter 2, I demonstrate a new technique for calculating methane emissions using high resolution satellite data to quantify wetland inundation time series, and some limits of current technology for modeling surface water dynamics in forested wetlands. Chapter 3 presents and applies a modeling framework for quantifying hydrologic fluxes of methane in the context of common forms of wetland restoration In combination, these studies establish how and why quantifying the hydrologic regime of seasonally inundated forested wetlands enables a more accurate estimation of methane emissions at multiple scales, that water level drawdown associated with the natural hydrologic regime of forested wetlands considerably reduces methane producing areas, and that improved methods for detecting and modeling surface water dynamics in low relief landscapes will improve our ability to quantify methane emissions.