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Author: Kurt Yakimovich
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Freshwater lake sediments play key roles in the cycling of carbon. This includes hosting microbial communities responsible for mineralizing large amounts of carbon into greenhouse gases-namely CO2 and CH4. Yet despite the important roles of sediment communities, their ecology and community structure linkages to biogeochemical cycling are not well known, and little data exists exploring how sediment microbial communities respond to different organic matter inputs. Here I start by reviewing previous literature on lake sediment microbial communities and the physicochemical factors affecting their composition and diversity. Next I report on data from two experiments, first an in-vitro lab study and then an in-situ field study, in which lake sediments were amended with different plant litters that could result from land use change and or succession in catchments. Microbial communities were examined with next generation amplicon sequencing. These data were linked to rates of CO2 and CH4 flux and dissolved organic matter (DOM) components present in pore water were examined as potential controls on community structure and function. I observed in-vitro that methanogen community composition and activity were affected by OM type, with macrophyte derived C enhancing microbial activity, whereas high concentrations of polyphenolic compounds from terrestrial tree litters inhibited methanogen activity. The polyphenols had an environmental filtering effect, selecting for different bacteria, fungi and methanogen communities. The in-situ experiments involved installing mesocosms with artificial sediments with variable amounts of deciduous and coniferous tree leaf litter. In these mesocosms we observed a link between methanogen community composition and decomposition rates, as measured with bulk CO2 and CH4 production and DOM humification. Decomposition rates were influenced by lake physicochemical factors, particularly the degree of photoexposure. With increased decomposition, specialist taxa of methanogens could thrive that conferred higher rates of methanogenesis. The work presented here demonstrates the adaptability of methanogen lake sediment communities as terminal decomposers under changing terrestrial OM subsidies.
Author: Kurt Yakimovich
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Freshwater lake sediments play key roles in the cycling of carbon. This includes hosting microbial communities responsible for mineralizing large amounts of carbon into greenhouse gases-namely CO2 and CH4. Yet despite the important roles of sediment communities, their ecology and community structure linkages to biogeochemical cycling are not well known, and little data exists exploring how sediment microbial communities respond to different organic matter inputs. Here I start by reviewing previous literature on lake sediment microbial communities and the physicochemical factors affecting their composition and diversity. Next I report on data from two experiments, first an in-vitro lab study and then an in-situ field study, in which lake sediments were amended with different plant litters that could result from land use change and or succession in catchments. Microbial communities were examined with next generation amplicon sequencing. These data were linked to rates of CO2 and CH4 flux and dissolved organic matter (DOM) components present in pore water were examined as potential controls on community structure and function. I observed in-vitro that methanogen community composition and activity were affected by OM type, with macrophyte derived C enhancing microbial activity, whereas high concentrations of polyphenolic compounds from terrestrial tree litters inhibited methanogen activity. The polyphenols had an environmental filtering effect, selecting for different bacteria, fungi and methanogen communities. The in-situ experiments involved installing mesocosms with artificial sediments with variable amounts of deciduous and coniferous tree leaf litter. In these mesocosms we observed a link between methanogen community composition and decomposition rates, as measured with bulk CO2 and CH4 production and DOM humification. Decomposition rates were influenced by lake physicochemical factors, particularly the degree of photoexposure. With increased decomposition, specialist taxa of methanogens could thrive that conferred higher rates of methanogenesis. The work presented here demonstrates the adaptability of methanogen lake sediment communities as terminal decomposers under changing terrestrial OM subsidies.
Author: Philips Olugbemiga Akinwole
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 168
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Sedimentary microbial communities play a critical ecological role in lotic ecosystems and are responsible for numerous biogeochemical transformations, including dissolved organic matter (DOM) uptake, degradation, and mineralization. The goals of this study were to elucidate the benthic microbes responsible for utilization of humic DOM in streams and to assess overall variability in microbial biomass and community structure over time and across multiple spatial scales in stream networks, as DOM quality and quantity will likely change with stream order. In Chapter 2, multiple spatial patterns of microbial biomass and community structure were examined in stream sediments from two watersheds; the Neversink River watershed (NY; 1st, 3rd and 5th order streams sampled) and the White Clay Creek watershed (PA; 1st through 3rd order streams sampled). Microbial biomass and community structure were estimated by phospholipid phosphate and phospholipid fatty acids (PLFA) analyses. Multivariate analysis showed that sedimentary C:N ratios, percent carbon, sediment surface area and percent water content explained 68% of the variations in total microbial biomass. Overall, the magnitude of within stream variation in microbial biomass was small compared to the variability noted among streams and between watersheds. Principal component analysis (PCA) of PLFA profiles showed that microbial community structure displayed a distinct watershed-level biogeography, as well as variation along a stream order gradient. Chapter 3 demonstrated that benthic microbial biomass was seasonally dynamic and significantly correlated to a combination of high and low flood pulse counts, variability in daily flow and DOC concentration in the White Clay Creek. Additionally, the seasonal pattern of variation observed in microbial community structure was as a result of shift between the ratios of prokaryotic to eukaryotic component of the community. This shift was significantly correlated with seasonal changes in median daily flow, high and low flood pulse counts, DOC concentrations and water temperature. Compound-specific 13C analysis of PLFA showed that both bacterial and microeukaryotic stable carbon isotope ratios were heaviest in the spring and lightest in autumn or winter. Bacterial lipids were isotopically depleted on average by 2 - 5 / relative to δ13C of total organic carbon suggesting bacterial consumption of allochthonous organic matter, and enriched relative to δ13C algae-derived carbon source. In Chapter 4, heterotrophic microbes that metabolize humic DOM in a third-order stream were identified through trace-additions of 13C-labeled tree tissue leachate (13C-DOC) into stream sediment mesocosms. Microbial community structure was assessed using PLFA biomarkers, and metabolically active members were identified through 13C-PLFA analysis (PLFA-SIP). Comparison by PCA of the microbial communities in stream sediments and stream sediments incubated in both the presence and absence of 13C-DOC showed our mesocosm-based experimental design as sufficiently robust to investigate the utilization of 13C-DOC by sediment microbial communities. After 48 hours of incubation, PLFA-SIP identified heterotrophic α, β, and γ- proteobacteria and facultative anaerobic bacteria as the organisms primarily responsible for humic DOC consumption in streams and heterotrophic microeucaryotes as their predators. The evidence presented in this study shows a complex relationship between microbial community structure, environmental heterogeneity and utilization of humic DOC, indicating that humic DOC quality and quantity along with other hydro-ecological variables should be considered among the important factors that structure benthic microbial communities in lotic ecosystems.
Author: Chloé Shoshana Jessica Orland
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Matti Olavi Ruuskanen
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Since the Industrial Revolution at the end of the 18th century, anthropogenic changes in the environment have shifted from the local to the global scale. Even remote environments such as the high Arctic are vulnerable to the effects of climate change. Similarly, anthropogenic mercury (Hg) has had a global reach because of atmospheric transport and deposition far from emission point sources. Whereas some effects of climate change are visible through melting permafrost, or toxic effects of Hg at higher trophic levels, the often-invisible changes in microbial community structures and functions have received much less attention. With recent and drastic warming-related changes in Arctic watersheds, previously uncharacterized phylogenetic and functional diversity in the sediment communities might be lost forever. The main objectives of my thesis were to uncover how microbial community structure, functional potential and the evolution of mercury specific functions in lake sediments in northern latitudes (>54{486}N) are affected by increasing temperatures and Hg deposition. To address these questions, I examined environmental DNA from sediment core samples and high-throughput sequencing to reconstruct the community composition, functional potential, and evolutionary responses to historical Hg loading. In my thesis I show that the microbial community in Lake Hazen (NU, Canada) sediments is structured by redox gradients and pH. Furthermore, the microbes in this phylogenetically diverse community contain genomic features which might represent adaptations to the cold and oligotrophic conditions. Finally, historical Hg pollution from anthropogenic sources has likely affected the evolution of microbial Hg resistance and this deposition can be tracked using sediment DNA on the Northern Hemisphere. My thesis underscores the importance of using culture-independent methods to reconstruct the structure, functional potential and evolution of environmental microbial communities.
Author: Matthew John Hoostal
Publisher:
ISBN:
Category : Erie, Lake
Languages : en
Pages : 189
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Book Description
Lake Erie demonstrates the greatest productivity of the Laurentian Great Lakes, yet has been critically impacted by anthropogenic activities throughout the Lake Erie watershed. Lake Erie is comprised of three major basins, with east-to-west gradients of increasing drainage areas, increasing riverine inputs of nutrients and xenobiotics, as well as decreasing depth. These large-scale geochemical gradients may be expected to result in spatial patterns of microbial community composition, nutrient cycling, and xenobiotic transformation. As such, Lake Erie provides an excellent system to examine the local adaptation of microbial communities throughout a large freshwater ecosystem. Spatial patterns of microbial community composition, as well as functional diversity, across the three basins of Lake Erie were assessed to examine the potential adaptation of microbial communities to local selective pressures. Community composition was investigated through the generation of 16S rDNA libraries, while functional diversity was evaluated with substrate-induced respiration (SIR) and extracellular enzyme activities (EEA) profiles. EEA profiles were subsequently measured to examine microbial community resilience to metal inoculations in sediments contaminated with heavy metals compared to relatively pristine sediments. Bioinformatic studies of bacterial genes involved in the efflux of heavy metals from the cell were performed to provide a conceptual framework of how horizontal gene transfer may expedite the adaptation of bacterial communities to heavy metal stress. Finally, the local adaptation of bacterial communities to PCBs and PAHs was assessed by comparing the diversity of bphA, a gene that initiates PCB metabolism, in polluted and relatively unpolluted sediments within the Lake Erie watershed. Collectively, results suggested large-scale spatial patterns of microbial community composition, functional diversity, and metabolic resilience consistent with the local adaptation of sediment bacterial communities to allochthonous inputs of organic matter and heavy metal pollutants into Lake Erie. Furthermore, estimates of diversity from bphA environmental gene libraries suggest that PCB and PAH contamination represents a driving force in the adaptation of microbial communities in polluted sediments. Results from this study suggest that microbial communities are highly integrated assemblages of multiple taxa locally adapted to differential inputs of nutrients and xenobiotics across geochemical gradients within freshwater ecosystems.
Author: K. Ramesh Reddy
Publisher: CRC Press
ISBN: 0429531931
Category : Science
Languages : en
Pages : 926
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Book Description
The globally important nature of wetland ecosystems has led to their increased protection and restoration as well as their use in engineered systems. Underpinning the beneficial functions of wetlands are a unique suite of physical, chemical, and biological processes that regulate elemental cycling in soils and the water column. This book provides an in-depth coverage of these wetland biogeochemical processes related to the cycling of macroelements including carbon, nitrogen, phosphorus, and sulfur, secondary and trace elements, and toxic organic compounds. In this synthesis, the authors combine more than 100 years of experience studying wetlands and biogeochemistry to look inside the black box of elemental transformations in wetland ecosystems. This new edition is updated throughout to include more topics and provide an integrated view of the coupled nature of biogeochemical cycles in wetland systems. The influence of the elemental cycles is discussed at a range of scales in the context of environmental change including climate, sea level rise, and water quality. Frequent examples of key methods and major case studies are also included to help the reader extend the basic theories for application in their own system. Some of the major topics discussed are: Flooded soil and sediment characteristics Aerobic-anaerobic interfaces Redox chemistry in flooded soil and sediment systems Anaerobic microbial metabolism Plant adaptations to reducing conditions Regulators of organic matter decomposition and accretion Major nutrient sources and sinks Greenhouse gas production and emission Elemental flux processes Remediation of contaminated soils and sediments Coupled C-N-P-S processes Consequences of environmental change in wetlands# The book provides the foundation for a basic understanding of key biogeochemical processes and its applications to solve real world problems. It is detailed, but also assists the reader with box inserts, artfully designed diagrams, and summary tables all supported by numerous current references. This book is an excellent resource for senior undergraduates and graduate students studying ecosystem biogeochemistry with a focus in wetlands and aquatic systems.
Author: Lunhui Lu
Publisher: Frontiers Media SA
ISBN: 2832539874
Category : Science
Languages : en
Pages : 188
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Book Description
Dams or barriers are among the most significant anthropogenic threats to global freshwater ecosystems, although they provide invaluable services for shipping, hydropower generation, flood protection, and storage of drinking and irrigation water. River fragmentations due to dams and barriers lead the aquatic landscape into isolated river sections, resulting in hydromorphological discontinuities along longitudinal or lateral gradients. Fragmented river habitats are unstable. They experience uncertain disturbances in both time and space with random and complex hydrological and environmental processes, such as water flow, particulate matter sedimentation, reservoir regulation, and terrestrial input. The diversity, composition, functionality, and activity of microbial communities are important indicators of river ecosystem functions and services. Yet, river fragmentations are likely to disrupt and reconstruct microbial communities, redirecting the patterns of biogeochemical cycles of biogenic elements. Methodology, such as mathematical models, is still limited to describing and elucidating microbial processes under changing hydrological environments in the fragmented rivers. Thus, how do the riverine microbial communities and ecosystem functions respond to the fragmentation in rivers? This Research Topic represents a collective focus on microbial ecology, functional diversity, and new microbial modeling in fragmented rivers. We wish to present new findings in community assembly mechanisms, biotic interactions, functional diversity, and ecosystem functioning responses to the river fragmentations. New perspectives will also provide us with deep insights into the ecological effects of river fragmentation. This Research Topic aims to present the original research articles and reviews to provide new findings on microbial diversity and ecosystem functioning in fragmented rivers worldwide. We welcome original research, reviews, mini-reviews, opinions, methods, hypotheses and theories, and perspectives. The directions include but are not limited to the following aspects: - The continuum of the microbial community in responses to dams or barriers. - Novel microbial community assembly mechanisms, functional traits, and biotic interactions in fragmented rivers at local, regional, and global scales. - Functional genes, functional groups, and functional diversity in driving biogenic element cycles. - Mathematical modeling in aquatic microbial ecology.
Author: Horst D. Schulz
Publisher: Springer Science & Business Media
ISBN: 9783540664536
Category : Science
Languages : en
Pages : 498
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Book Description
A summary of the latest research in this field. The topics comprise the sedimentological examination and physical properties of the sedimentary solid phase, pore water and pore water constituents, organic matter as the driving force of most microbiological processes, biotic and abiotic redox reactions, carbonates and stable isotopes as proxies for paleoclimate reconstruction, metal enrichments in ferromanganese nodules and crusts as well as in hot vents and cold seeps on the seafloor. The current model conceptions lead to the development of different types of computer models, allowing the global mass exchanges between oceans and sediments to be balanced.
Author: Stephen D. Killops
Publisher: John Wiley & Sons
ISBN: 1118697200
Category : Science
Languages : en
Pages : 673
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Book Description
An Introduction to Organic Geochemistry explores the fate of organic matter of all types, biogenic and man-made, in the Earth System. investigates the variety of pathways and biogeochemical transformations that carbon compounds can experience over a range of time scales and in different environments scope widened to provide a broad and up-to-date background - structured to accommodate readers with varied scientific backgrounds essential terminology is defined fully and boxes are used to explain concepts introduced from other disciplines further study aided by the incorporation of carefully selected literature references It investigates the variety of pathways and biogeochemical transformations that carbon compounds can experience over a range of time scales and in different environments.
Author: G. P. Robertson
Publisher: Oxford University Press, USA
ISBN: 0195120833
Category : Nature
Languages : en
Pages : 481
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Book Description
The goal of the volume is to facilitate cross-site synthesis and evaluation of ecosystem processes. The book is the first broadly based compendium of standardized soil measurement methods and will be an invaluable resource for ecologists, agronomists, and soil scientists."--BOOK JACKET.
