The hyporheic zone is the area just below a river where constant mixing of groundwater and river water occurs. At this intersection between two sources of water, with different organic carbon and nutrient contents, complimentary pairing of electron donors and acceptors occurs, causing elevated rates of microbial metabolism. Due to these constant changes in electron acceptor and donor availability and because of microbial oxygen consumption dynamics, redox cycling process are constantly occurring and changing within the hyporheic zone. Iron oxides are theorized to play an important role in protecting sediment organic carbon from microbial metabolism through the formation of organo-metal aggregates. This thesis document outlines three related experiments investigating how different sources and forms of organic carbon found in freshwater river and groundwater systems effects hyporheic zone microbial metabolism rates. These studies revealed that deposition of autochthonous and allochthonous organic carbon to the riverbed sediment matrix (i.e. hyporheic zone) was correlated with release of labile dissolved organic carbon. Photosynthetic periphyton biomass (i.e. autochthonous epilithic biomass) was identified as a key source of organic carbon, which lead to highly elevated rates of aerobic respiration, anaerobic respiration, and methanogenesis. The presence of small pockets of anaerobic respiration and methanogenesis was observed within predominantly aerobic metabolizing sediment batch reactors; this shows that hyporheic zone sediment microbial community structure is highly heterogenous with patches of flexible metabolism occurring, depending on electron donor/acceptor availability. Iron bound organic carbon content was correlated with the presence of reactive iron oxide minerals, and these organo-metal aggregates were not biodegraded due to preferential metabolism of more labile pools of carbon such as fresh periphyton POM and DOC. The increase in microbial activity associated with fresh periphyton biomass deposition shows that in freshwater river systems periphyton biomass is a major contributor to ecosystem respiration as well as gross primary productivity. Understanding how natural and anthropogenic inputs of organic carbon, nitrogen, phosphorous and sulfate cause changes in periphyton growth and hence changes in hyporheic zone microbial metabolism is on ongoing challenge to modeling the global carbon cycle.

"Texture" was an important variable at the micro scale that described the community structure. However, texture was correlated with other factors at multiple scales and these correlations are discussed in the context of the gradient of urban influences. The amount of community variance explained by this set of correlated variables was less than 20% indicating that other factors were also important. The effect of sediment carbon composition was explored using multivariate decomposition of spectra recorded using Fourier Transform Infra Red (FT-IR) and Excitation Emission Matrices (EEM). Principal Components Analysis reduced the number of variables from these spectra to a few factors. Using the scores from the reduced factors demonstrated that carbon composition of the sediments also had a significant structuring effect on the denitrifying community. Links between the denitrifying community struture and function were explored in a multiway ANOVA manipulation of sediments collected from streams heavily impacted and lightly impacted by urbanization. Sediments were dosed with carbon substrates thought to mimic either an urban or non urban source, and changes in the response of CO2, CH4 and N2 monitored for one month. Additionally, sediments were treated with the heavy metal zinc, found in higher concentrations in the urban sediments. The result of these manipulations suggested that community function was, depending on the treatment, significantly altered but that stream community structure was not: function was not limited by lack of diversity - the community was functionally adaptable. This research contributes to a growing body of knowledge on the factors affecting the community structure of microorganisms and suggests several variables that should be consistently included in examinations of "wild" bacterial communities. If future studies consistently incorporated an agreed set of basic or core variables, the field of microbial ecology would benefit by making cross comparison and meta-analysis of related studies more practical.

Dissolved organic carbon (DOC) is the dominant form of organic matter in aquatic ecosystems and bacteria play a key role in its mobilization to higher trophic levels. The DOC pool is often divided into broad classes such as labile or recalcitrant, based on its ease of uptake by bacteria; or as autochthonous and allochthonous, based on its production within or outside the ecosystem. In this dissertation, I examined the relationship between the composition of the DOC pool and bacterial community structure and function. The three research chapters address this relationship in different freshwater ecosystems. In the first research chapter, the effect of presence or absence of Microcystis, a dominant primary producer in the western basin of Lake Erie as well as an autochthonous DOC source, on bacterial community structure and heterotrophic productivity was studied. This study revealed that bacterial responses were independent of the presence of the dominant primary producer. In second research chapter, the effect of compositional diversity of DOC within labile and recalcitrant categories, on stream bacterial community structure and denitrification rates was investigated. Use of different compounds within each category, administered individually and in mixtures, contributed to the heterogeneity. Results of this study suggest molecular heterogeneity of DOC can lead to differences in bacterial structure and denitrification potential. In my final research chapter, bacterial responses to differences in proportion of autochthonous and allochthonous DOC between a river and reservoir ecosystem were compared. The findings of this study demonstrated that, rather than the proportion of the two DOC sources, each source, considered individually, played a more important role in determining bacterial response. Regardless of the study, in all cases bacterial community structure was not linked to function, emphasizing the requirement to study both. The results indicate that differences in DOC quality, rather than the quantity, may play a greater role in determining bacterial responses and that structure and function can be decoupled.

Stream Ecosystems in a Changing Environment synthesizes the current understanding of stream ecosystem ecology, emphasizing nutrient cycling and carbon dynamics, and providing a forward-looking perspective regarding the response of stream ecosystems to environmental change. Each chapter includes a section focusing on anticipated and ongoing dynamics in stream ecosystems in a changing environment, along with hypotheses regarding controls on stream ecosystem functioning. The book, with its innovative sections, provides a bridge between papers published in peer-reviewed scientific journals and the findings of researchers in new areas of study. Presents a forward-looking perspective regarding the response of stream ecosystems to environmental change Provides a synthesis of the latest findings on stream ecosystems ecology in one concise volume Includes thought exercises and discussion activities throughout, providing valuable tools for learning Offers conceptual models and hypotheses to stimulate conversation and advance research

The Clean Water Act (CWA) requires that wetlands be protected from degradation because of their important ecological functions including maintenance of high water quality and provision of fish and wildlife habitat. However, this protection generally does not encompass riparian areasâ€"the lands bordering rivers and lakesâ€"even though they often provide the same functions as wetlands. Growing recognition of the similarities in wetland and riparian area functioning and the differences in their legal protection led the NRC in 1999 to undertake a study of riparian areas, which has culminated in Riparian Areas: Functioning and Strategies for Management. The report is intended to heighten awareness of riparian areas commensurate with their ecological and societal values. The primary conclusion is that, because riparian areas perform a disproportionate number of biological and physical functions on a unit area basis, restoration of riparian functions along America's waterbodies should be a national goal.

Praise for the Second Edition “This book should be an essential part of the personal library of every practicing statistician.”—Technometrics Thoroughly revised and updated, the new edition of Nonparametric Statistical Methods includes additional modern topics and procedures, more practical data sets, and new problems from real-life situations. The book continues to emphasize the importance of nonparametric methods as a significant branch of modern statistics and equips readers with the conceptual and technical skills necessary to select and apply the appropriate procedures for any given situation. Written by leading statisticians, Nonparametric Statistical Methods, Third Edition provides readers with crucial nonparametric techniques in a variety of settings, emphasizing the assumptions underlying the methods. The book provides an extensive array of examples that clearly illustrate how to use nonparametric approaches for handling one- or two-sample location and dispersion problems, dichotomous data, and one-way and two-way layout problems. In addition, the Third Edition features: The use of the freely available R software to aid in computation and simulation, including many new R programs written explicitly for this new edition New chapters that address density estimation, wavelets, smoothing, ranked set sampling, and Bayesian nonparametrics Problems that illustrate examples from agricultural science, astronomy, biology, criminology, education, engineering, environmental science, geology, home economics, medicine, oceanography, physics, psychology, sociology, and space science Nonparametric Statistical Methods, Third Edition is an excellent reference for applied statisticians and practitioners who seek a review of nonparametric methods and their relevant applications. The book is also an ideal textbook for upper-undergraduate and first-year graduate courses in applied nonparametric statistics.