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Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2018-08-14T17:26:05Z No. of bitstreams: 1 Dissertação - Catalogada Igor.pdf: 1880759 bytes, checksum: 622a5c7c24e54df511092cf0eed620d5 (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2018-08-17T12:20:33Z (GMT) No. of bitstreams: 1 Dissertação - Catalogada Igor.pdf: 1880759 bytes, checksum: 622a5c7c24e54df511092cf0eed620d5 (MD5) / Made available in DSpace on 2018-08-17T12:20:33Z (GMT). No. of bitstreams: 1 Dissertação - Catalogada Igor.pdf: 1880759 bytes, checksum: 622a5c7c24e54df511092cf0eed620d5 (MD5) Previous issue date: 2017-12-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / O feijão caupi (Vigna unguiculata) é produzido principalmente em pequenas propriedades da região nordeste do país. Com o déficit na oferta de feijão e os preços atrativos observados na entressafra, grandes produtores da região Centro-Oeste passaram a cultivar feijão caupi, especialmente da variedade Bico de Ouro. Por se tratar de uma dicotiledônea com hábito de crescimento indeterminado, as plantas apresentam vagens secas, vagens no ponto ideal e vagens verdes no momento da colheita. A colheita manual em grandes propriedades é inviável, sendo necessária a aplicação de herbicidas para uniformizar a senescência das plantas e o grau de maturação dos grãos para, então, viabilizar a colheita mecanizada. Desta forma objetivou-se com o presente estudo: (1) Avaliar as consequências da utilização de herbicidas dessecantes em pré-colheita sobre propriedades químicas e tecnológicas do feijão caupi da variedade Bico de Ouro, e (2) Avaliar efeitos da temperatura e da atmosfera de armazenamento sobre propriedades tecnológicas do feijão caupi da variedade Bico de Ouro. Os herbicidas glifosato (GLI), glifosato mais carfentrazona (GLI/CAR) e paraquate (PAR) foram testados em pré-colheita, no primeiro estudo. Grãos colhidos manualmente foram utilizados como controle (SEM). Os grãos foram, também, armazenados a 25ºC, por 8 meses, para avaliar a suscetibilidade ao envelhecimento. Para o segundo estudo, grãos de feijão caupi da variedade Bico de Ouro foram armazenados por 8 meses com nitrogênio ou em atmosfera hermética, a 15, 20 ou 25°C. A aplicação de herbicidas dessecantes na pré-colheita proporcionou alterações nos parâmetros de qualidade. Grãos obtidos de plantas tratadas com PAR e GLI apresentaram coloração mais escura logo após a colheita. No entanto, no armazenamento, a cor do tegumento dos grãos obtidos de plantas tratadas com PAR se manteve mais estável. A aplicação de GLI proporcionou acúmulo em níveis mais elevados de compostos fenólicos, principalmente compostos complexos como as proantocianidinas. Foi possível identificar moléculas de discriminação do feijão caupi em função do herbicida utilizado, sendo elas: catequina-3-glicosídeo e epicatequina (para grãos obtidos de plantas tratadas com GLI), ácido cítrico (para grãos de plantas tratadas com GLI/CAR), e quercetina e ácido glucônico (para grãos obtidos de plantas não submetidas ao tratamento com herbicidas). Os teores residuais de glifosato e paraquate foram superiores aos limites máximos tolerados pelo Codex Alimentarius e pela União Européia. Em relação ao segundo objetivo apresentado, o feijão caupi armazenado em atmosfera com nitrogênio a 20°C manteve atributos de cor, cocção e dureza muito próximos aos grãos armazenados pelo mesmo período a 15°C. / Cowpea (Vigna unguiculata) is produced mainly in small properties in the northeastern region of the country. With the deficit in the supply of beans and the attractive prices observed in the off season, large producers of the central-west region began to grow cowpea beans, especially the Bico de Ouro variety. Because it is a dicotyledon with an indeterminate growth habit, the plants present dry pods, pods at the ideal point and green pods at the time of harvest. The manual harvesting on large properties is impracticable, being necessary the application of desiccants to standardize the senescence of the plants and the degree of maturation of the grains in order to allow the mechanized harvesting. Thus, this study aimed to: 1) To evaluate the consequences of using pre-harvest desiccants, end 2) Evaluate effects of storage temperature and atmosphere on the technological properties of cowpea, variety Bico de ouro. The herbicides glyphosate (GLI), glyphosate with carfentrazone (GLI/CAR), end paraquat (PAR) were tested in pre-harvest, in the first study. Cowpeas collected manually were used as control (SEM). The grains were also stored at 25°C for 8 months to evaluate the susceptibility to aging. In the second study, cowpea of the Bico de ouro variety were stored for 8 months under nitrogen or in a hermetic atmosphere at 15, 20 or 25°C. The application of herbicides in the pre-harvest changed the quality parameters of the cowpea. Cowpeas obtained from PAR and GLI treated plants showed darker coloration soon after harvest. However, in storage, the color of the cowpea coat treated with PAR remained more stable. The application of GLI provided accumulation at higher levels of phenolic compounds, especially complex compounds such as proanthocyanidins. It was possible to identify molecules of cowpea discrimination as a function of the herbicide used, being them: catechin-3- glycoside and epicatechin (for grains obtained from plants treated with GLI), Citric acid (for grains obtained from plants treated with GLI/CAR), end quercetin end gluconic acid (for grains obtained from plants not submitted to treatment with herbicides). Residual levels of glyphosate and paraquat were higher than the maximum levels tolerated by the Codex Alimentarius and the European Union. With regard to the second objective, the cowpea stored in nitrogen atmosphere at 20°C maintained color, firing and hardness attributes very close to the grains stored for the same period at 15°C.

Made available in DSpace on 2016-04-26T19:39:29Z (GMT). No. of bitstreams: 1 2006-Luciano Lopes Reis.pdf: 1765828 bytes, checksum: e031c34734485e7d84bd20e5fcc0d59b (MD5) Previous issue date: 2006-02-24 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This study had as objective to monitor the process of environmental reclamation of tanks filled with residues from bauxite washings, vegetated by hydro-sowing legume trees species inoculated with rhizobia, and asbuscular mycorrhizal fungi. Nutrient fertilizers, without nitrogen, were added at the mixture at sowing. Later it was planted a mixture of native tree species seedlings, with a high proportion of N2-fixing legumes, in an experiment with additional increasing levels of fertilizers and liming, except for nitrogen. The deposits of sterile bauxite subsoil, vegetated with the mix of native species, with high proportion of legumes capable of N2 fixation and mineral fertilization, were evaluated at different periods of time, for the chemical and biological attributes of soil and plants. Samples of soil, leaves, litter, and soil invertebrates fauna were taken in 2002, 2003 and 2004, to measure nutrient availability in soil; foliar nutrient level of indicator plants; soil microbial biomass and activity; soil fauna activity, diversity and ecological indexes; and evaluation of vegetal coverage of the SP1 residue tank. The results of foliar analyses indicated that even at the highest level of fertilizer and lime additions in the SP1 residue tank were not sufficient to meet the adequate plant nutrition requirements, indicating the need of higher input of nutrients. By using multivariate statistical analyses of the data, it was possible to distribute the studied systems along Cartesian axis, where the native forest area, used as testimony, and old vegetated mining sites (planted in 1984, 1992 and 1994) were clustered together; while the most recent vegetated mining sites and the tanks filled with residues formed a distant cluster. Among the index attributes studied Al+3, total C, total N, K, soil pH, microbial carbon and respiration; and Ca and Mg from litter were the principal factors determining the ordering and distinction between reclamation sites. The reclamation methodology used in the residue tank SP1, which combined the hydro-sowing with application of low solubility fertilizers, using a mix of seeds from medium cycle legume trees inoculated and with mycorrhizae, with later planting of native seedlings and manual dispersion of seeds, showed to be an important technique to stimulate natural vegetation growth. Also, the technique resulted in a high capacity of addition of decidual material, and the legume tree Acacia holosericea showed the best capacity for soil coverage and input of nutrients. / Com o objetivo de monitorar o processo de recupera??o ambiental de tanques de dep?sito de rejeito da lavagem da bauxita, revegetados atrav?s da hidrossemeadura de leguminosas fixadoras de N2 e com adi??o de fungos micorrizicos, mais aporte de nutrientes. Posteriormente, foi feito o plantio de mudas nativas em experimento de n?veis de aduba??o e calagem, sem aplica??o de nitrog?nio. Os dep?sitos de subsolo est?ril em bauxita revegetados com mistura de esp?cies nativas, com grande propor??o de leguminosas fixadoras de N2 e aduba??o mineral na cova, avaliados em diferentes idades, foram utilizados atributos qu?micos e biol?gicos do solo e planta. Foram realizadas coletas de solo, de folhas, de serapilheira e da fauna de invertebrados do solo, nos anos de 2002, 2003 e 2004, para determina??o da disponibilidade de nutrientes no solo; dos teores foliares de nutrientes das plantas indicadoras; da biomassa e atividade microbiana; da atividade, diversidade de grupos e ?ndices ecol?gicos da comunidade da fauna do solo; e avalia??o da cobertura vegetal do tanque de rejeito SP1. Os resultados da an?lise foliar das esp?cies indicadoras e de disponibilidade de nutrientes no solo indicaram que nem os maiores n?veis de aduba??o e calagem utilizados no experimento do tanque de rejeito SP1 foram suficientes para permitir uma adequada nutri??o ?s plantas, indicando a necessidade de novos aportes de nutrientes. Atrav?s da aplica??o de ferramentas de estat?stica multivariada aos dados, foi poss?vel ordenar os sistemas estudados ao longo de eixos cartesianos, onde a ?rea de mata nativa, usada como testemunha, e reflorestamentos sobre res?duos de minera??o com maior idade (realizados nos anos de 1984, 1992 e 1994) se ordenam pr?ximos uns dos outros, enquanto que os reflorestamentos sobre est?ril mais recentes e ?reas dos tanques de rejeito se ordenam distantes destes, formando grupamentos entre si. Dentre os atributos indicadores utilizados, o Al+3, C total, N total, K e pH do solo; a respira??o e carbono microbiano; e o Ca e Mg da serapilheira foram os mais determinantes para o ordenamento e distin??o entre os sistemas em recupera??o. A metodologia de recupera??o utilizada no tanque de rejeito SP1 que combinou a pr?tica da hidrossemeadura com aplica??o de formas de adubos pouco sol?veis, utiliza??o de coquetel de sementes de leguminosas arb?reas de ciclo m?dio inoculadas e micorrizadas, posterior plantio de mudas nativas e lan?amento manual de sementes, mostrou-se como importante t?cnica propulsora da regenera??o natural. A t?cnica tamb?m resultou em elevada capacidade de aporte de material decidual, sendo a leguminosa arb?rea Acacia holosericea, a esp?cie que apresentou melhor capacidade de cobertura do solo e aporte de nutrientes.

La synthèse d'acide polyamique (APA) comportant des blocs élastomères de type oligo-oxyéthylène et -oxypropylène et des polyimides correspondants (PEI) a été étudiée et leurs propriétés de perméation gazeuse déterminées pour He, N2, O2, H2, CH4 et CO2. Il a été montré que la présence de la phase élastomère augmentait de façon très importante les coefficients de perméabilité au gaz comparativement aux polyimides aromatiques conventionnels. La perméabilité du CO2, augmentée de façon préférentielle par rapport celles de tous les autres gaz, conduit à des sélectivités idéales tout à fait remarquables, en particulier vis-à-vis de N2 (≈40). L’incorporation de nanoparticules de silice dans les PEI (de 1 à 15% en masse) a été effectuée lors de l’étape de cyclo-déshydratation de l'APA, soit par ajout de silice hydrophobes (16 nm) ou hydrophiles (12 nm), soit par méthode Sol-Gel à partir de précurseurs alcoxysilanes (TMOS et TEOS). L'influence des charges SiO2 sur les propriétés de perméation gazeuse a été étudiée par la méthode du temps de retard (time-lag) essentiellement sur la série préparée avec des particules préformées. On a observé que les nano-charges de silice ne semblent pas interférer dans le processus de cyclisation et que les propriétés mécaniques sont renforcées ; la perméabilité aux gaz varie surtout selon la quantité de charges incorporées mais aucune augmentation spectaculaire de perméabilité n’a pu être observée. On peut en déduire que, vraisemblablement, c’est la phase élastomère qui est le lieu d’incorporation des particules de SiO2. Ces résultats montrent l’intérêt des membranes PEI et PEI/SiO2 dans des applications industrielles de séparation de gaz, notamment pour la séparation de mélanges CO2/N2 / The synthesis of polyamic acids (PAA) with oligo-oxyethylene and -oxypropylene rubbery blocks and the related polyimides (PEI) has been studied and their gas permeation properties determined for He, N2, O2, H2, CH4 and CO2. It was shown that the rubbery phase dramatically increased the gas permeability coefficients compared to conventional aromatic polyimides. The permeability of CO2 is preferentially increased in comparison to all other gases, leading to remarkable ideal selectivities, especially for the N2 mixture (≈40). The incorporation of silica nanoparticles in PEI (from 1 to 15 wt%) was carried out during the cyclo-dehydration of the PAA by adding fumed hydrophobic (16 nm) or hydrophilic (12 nm) silica, or by Sol-Gel approach using alkoxysilane precursors (TMOS and TEOS). The effect of SiO2-fillers on the properties of gas permeation has been studied by the time-lag method mainly on the series prepared with fumed silica. It was observed that nano-particles of silica do not seem to disturb the PAA cyclization process and that the mechanical properties are improved; the gas permeability varies essentially depending on the amount of fillers incorporated but no spectacular increase in permeability could be shown due to the nano-particles amounts. Apparently, it can be deduced that it is the rubbery phase which accommodates the SiO2 particles. These results showed the value of PEI and PEI/SiO2 membranes in industrial applications of gas separation, especially for the separation of CO2/N2 mixtures

Background. Feelings of doubt and perseverative behaviours are key symptoms of obsessive–compulsive disorder (OCD) and have been linked to hyperactive error and conflict signals in the brain. While enhanced neural correlates of error monitoring have been robustly shown, far less is known about conflict processing and adaptation in OCD. Method. We examined event-related potentials during conflict processing in 70 patients with OCD and 70 matched healthy comparison participants, focusing on the stimulus-locked N2 elicited in a flanker task. Conflict adaptation was evaluated by analysing sequential adjustments in N2 and behaviour, i.e. current conflict effects as a function of preceding conflict. Results. Patients with OCD showed enhanced N2 amplitudes compared with healthy controls. Further, patients showed stronger conflict adaptation effects on reaction times and N2 amplitude. Thus, the effect of previous compatibility was larger in patients than in healthy participants as indicated by greater N2 adjustments in change trials (i.e. iC, cI). As a result of stronger conflict adaptation in patients, N2 amplitudes were comparable between groups in incompatible trials following incompatible trials. Conclusions. Larger N2 amplitudes and greater conflict adaptation in OCD point to enhanced conflict monitoring leading to increased recruitment of cognitive control in patients. This was most pronounced in change trials and was associated with stronger conflict adjustment in N2 and behaviour. Thus, hyperactive conflict monitoring in OCD may be beneficial in situations that require a high amount of control to resolve conflict, but may also reflect an effortful process that is linked to distress and symptoms of OCD.

Dans le cadre de la réduction des émissions de gaz à effet de serre, une des approches possibles consiste en l’utilisation de membranes pour séparer le CO2 de mélanges gazeux. Durant ce travail de thèse, la séparation CO2 / N2 dans des conditions de post-combustion a été étudiée pour des membranes à matrice mixte composées de matériaux organométalliques poreux, les MOF, insérés dans des polymères. Plus spécifiquement, la thèse porte sur la caractérisation de ces membranes à l’aide des spectroscopies vibrationnelles (IR et Raman). Différentes membranes polymériques et membranes à matrice mixte basées sur des polymères commerciaux comme le Matrimid ou le PEBAX ou des nouveaux polymères comme le PIM-1 ou 6FDA-DAM plus performants ont ainsi été étudiées. La spectroscopie Raman a d’abord été utilisée pour contrôler l’homogénéité des membranes et la bonne dispersion du MOF au sein du polymère à l’aide du Raman. Les interactions entre le polymère et le MOF ont également été étudiées à l’aide des spectroscopies IR in situ et Raman, notamment pour des composites modèles permettant de maximiser les interactions entre les deux composés. La deuxième partie du travail a été axée sur la caractérisation spectroscopique (IR operando) de ces membranes dans les conditions de post-combustion, simultanément à la mesure de leurs performances en séparation. Un système de mesures dédié a donc été spécialement développé. Cette méthodologie permet de comparer directement les données d’adsorption et de séparation des membranes. En développant une nouvelle approche couplant les aspects cinétiques et thermodynamiques de l’adsorption et de la perméation, les données expérimentales ont été modélisées afin de déterminer les paramètres d’adsorption et de diffusion des différentes membranes. / In the frame of the abatement of greenhouse gases, one of the possible approaches concern the use of membranes to separate CO2 from gas mixtures. During this PhD work, CO2 / N2 separation in post-combustion conditions has been studied for Mixed Matrix Membranes constituted by porous organometallic materials, MOFs, inserted into polymers. More specifically, this work aims at the characterization of these membranes using vibrational spectroscopies (IR and Raman). Different membranes, purely polymeric or Mixed Matrix Membranes, based on commercial polymers such as Matrimid or PEBAX as well as new polymers such as PIM-1 or 6FDA-DAM have been studied. Raman spectroscopy was first used to control the homogeneity of the membranes and the good dispersion of the MOF within the polymer. The interactions between the polymer and the MOF were also studied using IR in situ and Raman spectroscopies, notably for composites allowing maximizing the interactions between the two components. The second part of the work focused on the characterization of these membranes under operating post-combustion conditions, simultaneously with the measurement of their separation performance. For this purpose, a specifically designed measurement system has been developed in order to be able to test the membranes using IR operando. This methodology allows the direct comparison of adsorption and separation data. By the development of a new approach coupling kinetic and thermodynamic aspects of adsorption and permeation, experimental data were modelled to determine adsorption and diffusion parameters of the various membranes.

The thermosphere-ionosphere regions are mainly controlled by the solar, but also by geomagnetic activity. In this case study, the Earth’s ionospheric response to the 25-26 August 2018 intense geomagnetic storm is investigated using the International GNSS System (IGS) Total Electron Content (TEC) observations. During this major storm, the minimum disturbance storm time (Dst) index reached -174 nT. We use observations and model simulations to analyse the ionospheric response during the initial phase and the main phase of the magnetic storm. A significant difference between storm day and quiet day TEC is observed. The O/N2 ratio observed from the GUVI instrument onboard the TIMED satellite is used to analyse the storm effect. The result shows a clear depletion of the O/N2 ratio in the high latitude region, and an enhancement in the low latitude region during the main phase of the storm. Furthermore, the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model simulations were used. The results suggest that the CTIPe model can capture the ionospheric variations during storms. / Die Regionen der Ionosphären und Thermosphäre werden hauptsächlich von der Sonne sowie auch von geomagnetische Aktivität beeinflusst. In dieser Fallstudie wurde die ionosphärische Reaktion der Erde auf den starken geomagnetischen Sturm vom 25./26. August 2018 unter Verwendung der Gesamtelektronengehaltsdaten (Total Electron Content, TEC) vom Internationalen GNSS Service untersucht. Während dieses großen Sturms wurde ein ”Disturbance Storm Time Index” Dst von -174 nT erreicht. Beobachtungen und Modellsimulationen wurden verwendet, um die ionosphärische Reaktion während der Anfangsphase und der Hauptphase des magnetischen Sturms zu untersuchen. Ein signifikanter Unterschied zwischen TEC während eines Sturmtages und eines ruhigen Tages wurde beobachtet. Das vom GUVI-Instrument an Bord des TIMED-Satelliten beobachtete O/N2 -Verhältnis wurde verwendet, um den Sturmeffekt weiter zu untersuchen. Das Ergebnis zeigt eine deutliche Abnahme/Zunahme des O/N2 Verhältnis in hohen/niedrigen Breiten während der Hauptphase des Sturms. Darüber hinaus wurde das Coupled Thermosphere Ionosphere Plasmasphere ectrodynamics (CTIPe) Modell verwendet. Die Ergebnisse legen nahe, dass das CTIPe-Modell die ionosphärischen Schwankungen während eines Sturms erfassen kann.

The interactions of electrons with ions and ions with neutrals are among the most important processes in the chemical evolution of molecules, allowing us to gain a deeper understanding of chemical processes in low-temperature environments in space such as interstellar gas clouds and to obtain feedback for quantum-mechanical calculations. Vari- ous plasma parameters such as kinetic and rotational temperature of ions, their concen- tration, etc. can vary by several orders of magnitude and different diagnostic techniques are used to determine them. Diagnostics such as SA-CRDS and Cryo-CRDS were used in this work. The subject of the study were two molecular ions: N2H+ and N+ 2 from the temperature range of 80-350 K, where we examined their recombination and absorption rate coefficients utilizing the absorption line involving the most populated states. 1

The most widely used classification system describing enzyme-catalysed reactions is the Enzyme Commission (EC) number. Understanding enzyme function is important for both fundamental scientific and pharmaceutical reasons. The EC classification is essentially unrelated to the reaction mechanism. In this work we address two important questions related to enzyme function diversity. First, to investigate the relationship between the reaction mechanisms as described in the MACiE (Mechanism, Annotation, and Classification in Enzymes) database and the main top-level class of the EC classification. Second, how well these enzymes biocatalysis are adapted in nature. In this thesis, we have retrieved 335 enzyme reactions from the MACiE database. We consider two ways of encoding the reaction mechanism in descriptors, and three approaches that encode only the overall chemical reaction. To proceed through my work, we first develop a basic model to cluster the enzymatic reactions. Global study of enzyme reaction mechanism may provide important insights for better understanding of the diversity of chemical reactions of enzymes. Clustering analysis in such research is very common practice. Clustering algorithms suffer from various issues, such as requiring determination of the input parameters and stopping criteria, and very often a need to specify the number of clusters in advance. Using several well known metrics, we tried to optimize the clustering outputs for each of the algorithms, with equivocal results that suggested the existence of between two and over a hundred clusters. This motivated us to design and implement our algorithm, PFClust (Parameter-Free Clustering), where no prior information is required to determine the number of cluster. The analysis highlights the structure of the enzyme overall and mechanistic reaction. This suggests that mechanistic similarity can influence approaches for function prediction and automatic annotation of newly discovered protein and gene sequences. We then develop and evaluate the method for enzyme function prediction using machine learning methods. Our results suggest that pairs of similar enzyme reactions tend to proceed by different mechanisms. The machine learning method needs only chemoinformatics descriptors as an input and is applicable for regression analysis. The last phase of this work is to test the evolution of chemical mechanisms mapped onto ancestral enzymes. This domain occurrence and abundance in modern proteins has showed that the / architecture is probably the oldest fold design. These observations have important implications for the origins of biochemistry and for exploring structure-function relationships. Over half of the known mechanisms are introduced before architectural diversification over the evolutionary time. The other halves of the mechanisms are invented gradually over the evolutionary timeline just after organismal diversification. Moreover, many common mechanisms includes fundamental building blocks of enzyme chemistry were found to be associated with the ancestral fold.

Native oysters have been promoted as a means to improve water quality in Chesapeake Bay. This project added important insights into the potential of oyster aquaculture to process and remove nutrients from Bay waters. Results clarified that nutrient removal of nitrogen (N), phosphorous (P), and carbon (C) through harvest of cultivated oyster biomass can be quantified and modeled with high levels of statistical confidence. A simple, yet accurate, method is now available for estimating the amount of nutrients removed via harvesting aquacultured oysters. Based on model estimates, 106 harvest sized oysters (76 mm TL) remove 132 kg TN, 19 kg TP, and 3,823 kg TC. Previous work suggested that potentially substantial quantities of N may be removed through enhancement of the coupled nitrification-denitrification pathway in sediments as a result of oyster biodeposition. Using 15N and N2/Ar methods to measure N2 production in sediments, encompassing direct denitrification (DNF), coupled nitrification- denitrification, and anaerobic ammonium oxidation (anammox) pathways, at two oyster aquaculture sites and two reference sites (no aquaculture), we found that oyster biodeposition did not accelerate sediment N removal. We estimate sediment N removal rates via N2 production at an oyster cultivation site producing 5 x 105 oysters (1750 m2) to range from 0.49-12.60 kg N yr-1, compared to 2.27-16.72 kg N yr-1 at a reference site of the same area; making the contribution of oyster cultivation to N removal via sediment N2 production inconsequential as a policy initiative for Chesapeake Bay eutrophication mitigation. Molecular approaches and direct abundance measures have improved our understanding of the sediment microbial community response to oyster biodeposition. Overall, sediments impacted by oyster biodeposition had a significantly different denitrifying community composition than sediments a few meters away or at the non-aquaculture reference sites. Bacterial abundance in sediments was determined by site rather than by oyster biodeposition. No apparent effects of oyster biodeposition were evident in nitrifying bacterial abundance patterns at either site, indicating that oyster biodeposition does not enhance coupled nitrification-denitrification by increasing the abundance of nitrifiers in sediments.