Besides the known source of GHGs emissions like energy, industry, and agriculture, intrinsic emissions from natural inland water bodies like wetland, rivers, reservoirs, estuaries, etc. The persistent rise in concentrations of greenhouse gases (GHGs) in the earth’s atmosphere is responsible for global warming and climate change. The physical and chemical effects of stormwater may have significant implications for nutrient and pollutant transport through and biogeochemical reactions in reservoirs, as well as habitat for organisms and processing of organic matter and greenhouse gases in these dynamic ecosystems. Because the relative volume of inflowing water relative to stored water in a reservoir embayment determines the distance stormwater propagates, management of both the urban landscape (which affects runoff volumes) and of reservoir water levels affects the spatial footprint of urban stormwater. Stormflow can also break down the thermal stratification that exists during non-storm periods. Here, we show that signals of stormwater from a small urban stream can propagate more than 800 m from the stream mouth. Determining the spatial distribution of urban stormwater in reservoirs is an important step in understanding the effects of the heat and contaminant loads in these systems, which provide multiple services for adjacent cities. The physical and chemical interactions between inflowing stormwater of urban streams and their termination in large impoundments, however, is poorly understood. Overall, this work contributes to understanding how animal behavior may impact variation in greenhouse gas emissions and provides insight into how frequency of disturbance may impact emissions.įlashy hydrology and high solute loads in stormflow are well-studied effects of the built environment on urban streams. Low frequency mechanical disruption results in lower methane ebullition compared to higher frequency treatments, which in turn resulted in reduced overall methane release, likely through enhanced methanotrophic activities, though this could not be identified in this work. However, total methane emissions were not simply a function of methanogen populations and were likely impacted by the residence time of methane in the lower frequency disturbance treatments. This was further supported by a linear decrease in quantitative abundance of methanogens (assessed by qPCR of the mcrA gene), with increased disturbance frequency in bioturbated sediments (1 cm) as opposed to those below the zone of bioturbation (3 cm). Methanothrix paradoxum demonstrated no change in abundance, suggesting disturbance negatively and preferentially impacted other methanogen populations, likely through oxygen exposure.
Methanothrix paradoxum) was observed for the highest frequency treatments and at depths impacted by disturbance (1 cm). Looking specifically at methanogenic Archaea however, a shift toward greater relative abundance of a putatively oxygen-tolerant methanogenic phylotype ( ca. In terms of total microbial community structure, no statistical difference was observed in the total community structure of any disturbance treatment (0, 3, 7, and 14 days) or sediment depth (1 and 3 cm) measured. This work investigated the corresponding impacts of disturbance treatments on the microbial communities associated with producing methane. The lowest emissions were for the highest frequency treatment (3 days). Greenhouse gas emissions were largely driven by methane ebullition and were highest for the intermediate disturbance frequency (disturbance every 7 days). To explore how the frequency of disturbance impacts the levels of methane emissions in our previous work we quantified greenhouse gas emissions in sediment microcosms treated with various frequencies of mechanical disturbance, analogous to different levels of activity in benthic feeding fish. However, it is likely that variation in experimental fish density, and consequently the frequency of bioturbation by fish, impacts this outcome. For example, the impacts of fish bioturbation on methane emissions in the literature have been shown to result in a gradient of reduced to enhanced emissions from sediments.
This is in part due to the challenge of modeling biologic parameters that affect methane emissions from a wide range of sediments.
Methane emissions from aquatic ecosystems are increasingly recognized as substantial, yet variable, contributions to global greenhouse gas emissions.
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