A soja é a principal cultura do agronegócio brasileiro, setor responsável por cerca de 30% do PIB e por aproximadamente 40% das exportações totais do país. Do ponto de vista dos agroquímicos a soja é a cultura de maior mercado para os defensivos agrícolas, tendo sido, em 2007, responsável por 42,6% das receitas totais do segmento. O glifosato é o ativo herbicida mais utilizado nas plantações de soja e leva em sua formulação grande quantidade de tensoativos, os quais servem para aumentar a molhabilidade sobre as folhas e facilitar a aplicação. Realizada sob a forma de pulverização, a aplicação normalmente é feita antes do plantio da cultura e quando as plantas atingem o estágio V2 de crescimento, pois é quando ocorre competição da cultura com a daninha. A pulverização torna inevitável o contato da formulação com a soja, bem como com o aplicador. Medidas de ângulo de contato foram feitas sobre folha de soja e de uma gramínea que tipicamente acomete esta cultura. Foram testadas soluções de tensoativos comuns (aniônico, catiônico e neutro), de um tensoativo utilizado em formulações de herbicida e de uma formulação, a qual consiste numa mistura de tensoativos. Gotas dessas soluções foram mantidas em contato com a folha de soja e de gramínea até total evaporação e foi avaliada a mudança na morfologia das mesmas após esse contato através de microscopia eletrônica de varredura, comparando com as folhas analisadas logo após colheita. A cera da soja foi extraída com clorofórmio e analisada por cromatografia gasosa acoplada a espectrômetro de massas. A cera extraída foi testada contra bactérias Gram-positiva e Gram-negativa a fim de avaliar sua atividade antimicrobiana. Carbonato de cálcio foi utilizado como adsorvente para o glifosato como proposta de uma formulação de herbicida sólida a qual libere o ativo no solo ao longo do tempo, minimizando o contato com o aplicador e contaminação de solos e águas. O método colorimétrico para quantificação de fosfato foi utilizado para avaliar a eficiência de adsorção e dessorção do glifosato sobre carbonato. A caracterização do sólido formado após adsorção foi feita através de microscopia eletrônica de varredura e difração de raios-X. Os tensoativos mostraram afinidade pela cera epicuticular da folha de soja, solubilizando-a e causando perda de sua estrutura. Tensoativos com maior cmc, tipicamente os carregados e de cadeia mais curta, mostraram maior potencial de solubilização. A cera, composta por hidrocarbonetos, éster e amida de cadeia longa, não mostrou atividade biocida frente às bactérias, evidenciando que a morfologia é a responsável pela má adesão física de patógenos sobre a superfície da folha e consequente proteção da mesma. O glifosato mostrou ter grande afinidade pelo carbonato de cálcio, promovendo mudança na sua estrutura cristalina e tornando inviável sua utilização como formulação de herbicida. Entretanto, a forte interação entre os dois coloca o carbonato como um possível pré-concentrador de glifosato no tratamento de águas contaminadas. / Soybean is the main culture of Brazilian agribusiness, sector responsible for about 30% of the Gross Domestic Product and 40% of the countrys exportation. In relation to agrochemicals, soybean has the biggest market for agricultural defensives. In 2007 it was responsible for 42.6% of the incomes in the segment. Glyphosate is the most widely used herbicide active on soy crops; its formulation contains surfactants, which serve to increase the wettability on the leaves and to make its application easier. The application, in the form of spraying, is usually done before planting the crop and when the plants reach the growth stage V2, when there is competition between the culture and the weed. Spraying makes inevitable the contact of the formulation with soybeans, as well as with the applicator. Contact angle measurements were made on soybean leaf and a grass that typically afflicts this culture. Solutions of common surfactants (anionic, cationic and neutral), a surfactant used in herbicide formulations and a formulation, which is a mixture of surfactants, were tested. Drops of these solutions were kept in contact with soy and grass leaves until total evaporation and their change in morphology was evaluated after this contact through scanning electronic microscopy, comparing with the leaves analyzed right after harvest. Soy wax was extracted with chloroform and analyzed by gas chromatography coupled to mass spectrometer. The wax extracted was tested against Gram-positive and Gram-negative bacteria in order to evaluate its antimicrobial activity. Calcium carbonate was used as adsorbent for glyphosate as a proposition of a solid herbicide formulation which releases the active in the soil over time, minimizing the contact with the applicator and contamination of soils and waters. The colorimetric method for quantification of phosphate was used to evaluate the efficiency of absorption and desorption of glyphosate on carbonate. The characterization of the solid formed after adsorption was made using scanning electron microscopy and X-ray diffraction. Surfactants showed affinity for epicuticular wax of soybean leaves, solubilizing it and causing loss of its structure. Surfactants with greater cmc, typically those with charged head and shorter chain, showed the greatest potential of solubilization. Wax, composed of hydrocarbons, ester and long-chain amide, showed no biocidal activity against bacteria, showing that the morphology is responsible for weak adhesion of pathogens on the leaf surface and subsequent protection of the same. Glyphosate showed great affinity for calcium carbonate, promoting change in its crystalline structure and making it impossible to be used as an herbicide formulation. However, the strong interaction between them enables the pre-concentration of glyphosate in the treatment of contaminated water.

Cianobactérias, conhecidas por sua habilidade de sintetizar metabólitos com ação tóxica, podem se tornar dominantes em águas com altas concentrações de nitrogênio e fósforo. Embora a toxicidade do glifosato, o herbicida mais usado no mundo, em alguns organismos aquáticos seja conhecida, poucos estudos abordam o efeito desse composto sobre a produção de metabólitos secundários por cianobactérias. O objetivo deste trabalho foi avaliar a influência de diferentes concentrações de glifosato (produto técnico) sobre o crescimento e produção de cianotoxinas e microgininas pelas cepas brasileiras Microcystis aeruginosa LTPNA 08 e Cylindrospermopsis raciborskii CENA 302. Na presença de 15 mg/L de glifosato, o crescimento e a produção de toxinas pela M. aeruginosa foram reduzidos e de microgininas significativamente aumentada. Já a C. raciborskii, quando exposta à 20 mg/L de glifosato teve seu crescimento e síntese de clorofila-a, carotenoides e saxitoxinas aumentados. Concentrações superiores a 20 e 30 mg/L impediram o crescimento celular das cepas LTPNA 08 e CENA 302, respectivamente. A análise de ácidos graxos mostrou perfis bastante distintos entre as cepas. Na cepa LTPNA 08, enquanto que na presença de 10 mg/L de glifosato ocorreu diminuição do teor do ácido linoleico, o ácido estearidônico foi aumentado. Nenhuma das concentrações testadas promoveu alteração sobre o perfil de ácidos graxos da cepa CENA 302. A toxicidade de 5 produtos formulados a base de glifosato foi comparada ao produto técnico em ambas as linhagens-teste. Observou-se uma resistência distinta entre as cepas e toxicidade também variável entre as formulações comerciais. Sendo assim, diante da elevada resistência das cianobactérias M. aeruginosa e C. raciborskii ao glifosato, e considerando-se a elevada interferência antrópica através das práticas agrícolas, pode-se inferir que o uso excessivo e frequente desse herbicida é capaz de estimular o crescimento e dominância desses organismos, podendo modificar a estrutura e funcionalidade de ecossistemas aquáticos / Cyanobacteria, known for their ability to synthesize toxic metabolites, can become dominant in water bodies with high concentrations of nitrogen and phosphorus. Although the toxicity of glyphosate, the most widely used herbicide in the world, in some aquatic organisms is well known, few studies address the effect of this compound on the production of secondary metabolites by cyanobacteria. The aim of this study was to evaluate the influence of different concentrations the herbicide glyphosate (technical grade) on growth and production of cyanotoxins and microginins by Brazilian strains of Microcystis aeruginosa LTPNA 08 and Cylindrospermopsis raciborskii CENA 302. In the presence of 15 mg/L of glyphosate, growth and toxin production by M. aeruginosa were reduced and microginins cell quota significantly increased. The C. raciborskii strain, when exposed to 20 mg/L of glyphosate, had the growth, and chlorophyll-a, carotenoids and saxitoxins production increased. Concentrations above 20 and 30 mg/L prevented cell growth of LTPNA 08 and CENA 302 strains, respectively. Fatty acid analysis showed distinct profiles among the strains. When exposed to 10 mg/L of glyphosate, a decrease in the linoleic acid and increase in stearidonic acid content were observed in M. aeruginosa LTPNA 08 strain. None of the tested concentrations of glyphosate promoted change on the fatty acid profile of CENA 302 strain. The toxicity of 5 glyphosate formulated products was compared to technical product to both strains. There was a distinct resistance among strains and also a variable toxicity among formulated products. Thus, given the high glyphosate resistance of M. aeruginosa and C. raciborskii cyanobacteria, and considering the high anthropogenic interference through agri cultural practices, it can be inferred that excessive and frequent use of this herbicide is able to stimulate growth and dominance of these organisms, which may modify the structure and function of aquatic ecosystems

Apesar de todas as inovações, a sociedade visa produzir alimentos saudáveis sem degradar ou poluir o meio ambiente. Diante disso, todos os alimentos destinados ao consumo humano ou animal ficam sujeitos a um limite máximo de resíduo (LMR) legalmente permitido ou reconhecido como aceitável. Sendo assim, a alta eficiência no controle das plantas daninhas, aliada às características positivas quanto a aspectos toxicológicos, ecotoxicológicos, aumento de produtividade, dentre outras, tornaram o Glifosato o principal herbicida para uso em vários ambientes agrícolas e não agrícolas ao redor do mundo ao longo de mais de 30 anos, e a cultura agrícola brasileira da soja é a que mais cresceu nas últimas três décadas e corresponde a 49% da área plantada em grãos do país. Diante disso, neste estudo avaliou-se o risco da presença de resíduos de Glifosato e do seu metabólito ácido aminometilfosfônico (AMPA) em grãos de soja e em amostras de solo, verificando o comportamento do produto em determinadas áreas de aplicação e se há diferença no comportamento ambiental quando comparada a aplicação em culturas convencionais e as geneticamente modificadas. Foram escolhidas cinco das áreas definidas por regiões representativas do plantio da soja no Brasil, levando em consideração as diversas características de cada região. O procedimento analítico baseou-se na extração dos dois compostos com solução aquosa básica e purificação dos extratos em resina de troca catiônica. As amostras de grãos de soja e de solo foram quantificadas por um cromatógrafo líquido equipado com um sistema de reação pós-coluna com o-ftaldeído e detector de fluorescência. Os resultados mostraram que as áreas com temperaturas mais elevadas resultaram em concentrações de Glifosato e AMPA maiores que as demais áreas, contudo, as amostras de solo e grãos de soja apresentam baixos níveis de glifosato e AMPA, não ocasionando riscos ao meio ambiente e à saúde dos indivíduos, mesmo nos casos das concentrações de AMPA encontradas serem mais altas que as concentrações de Glifosato. / Despite of all innovations, our society aims to produce healthy food without degrading or polluting the environment. Therefore, all foods intended for human or animal consumption are subject to a maximum residue limit (MRL) legally permitted or recognized as acceptable. Thus, the high efficiency in controlling the weeds, combined with the positive characteristics related to toxicological and ecotoxicological aspects, increased productivity, among others, made glyphosate the main herbicide for use in various agricultural and non-agricultural environments all over the world for the last 30 years, and the Brazilian soybean crop is the fastest growing in the last three decades and corresponds to 49% of the cultivated grain area in the country. Therefore, this study evaluated the risk of the presence of glyphosate residue and its metabolite aminomethylphosphonic acid (AMPA) in soybean grains and soil samples, checking the performance of the product in certain application areas and if it presented any environmental changes when compared to the application in conventional and genetically modified crops. It was chosen five specific areas defined by representative regions of soybean crop in Brazil. It also took in consideration the many characteristics of each region. The analytical procedure was based in the extraction of the two components as basic aqueous solution and purification of extracts with cation exchange resin. The samples of soybean grains and soil were analyzed by liquid chromatography equipped with a system of post-column reaction with o- phthaldehyde and fluorescence detection. The results showed that areas with higher temperatures resulted in higher concentrations of glyphosate and AMPA than other areas, however, soil samples and soybeans grains presented low levels of glyphosate and AMPA, causing no risks to the environment or to consumers health, even with the concentrations of AMPA found to be higher than the concentrations of glyphosate.

O presente trabalho descreve o preparo, a caracterização e o uso de eletrodo modificado com polímero de azul de metileno (PMB) imobilizado sobre a superfície de eletrodo de carbono vítreo (GCE-PMB) na análise do herbicida glifosato. O método utilizado para a preparação dos filmes do PMB foi a eletropolimerização. Os filmes preparados por este método apresentam características diferenciadas tais como robustez, estabilidade e propriedade redox satisfatória. As condições experimentais otimizadas foram a velocidade de varredura (50 mV s-1), o intervalo de potencial (-0,4 a +1,2 V), o número de ciclos (30) e o pH da solução do eletrólito suporte (pH 8). A solução de eletrólito suporte foi preparada a partir das soluções de tampão fosfato (0,05 mol L-1) e NaNO3 (0,1 mol L-1), pH 8. A mesma foi utilizada no preparo da solução de azul de metileno (MB) (0,25 x 10-3 mol L-1), no pré-tratamento do eletrodo de carbono vítreo (GC) por voltametria cíclica (CV) e no preparo de soluções para os estudos iniciais com o GCE-PMB. O pré-tratamento da superfície do eletrodo de GC foi realizado aplicando + 0,9 V por 240 s seguido de várias varreduras cíclicas de -0,4 a +1,0 V com velocidade de varredura de 50 mV s-1 até obter um perfil estável do voltamograma do eletrodo. Após o preparo do GCE-PMB, a atividade eletrocatalítica do eletrodo foi investigada para o Ácido Ascórbico (AA) e a L-Cisteína (L-Cys) por CV de -0,4 a +0,6. Foi observado aumento da corrente de pico e diminuição do sobrepotencial em relação ao eletrodo de GC. Nos estudos na presença do glifosato, o GCE-PMB apresentou resposta eletroquímica direta, por voltametria cíclica, para o glifosato (1,0 x 10-3 mol L-1) em solução de KCl 0,1 mol L-1 (pH 5,3) de -0,4 a +0,6 V e velocidade de varredura 50 mV s-1. A resposta voltamétrica apresentou picos anódico e catódico em 0,2 e 0, respectivamente. Para os estudos realizados por meio da técnica de voltametria de onda quadrada (SWV), os parâmetros freqüência, amplitude e incremento de varredura foram otimizados. A partir desses estudos foi possível obter informações relevantes sobre a interação do GCE-PMB com o glifosato. Os resultados mostraram que é possível observar a eletroatividade do herbicida glifosato sobre uma superfície eletródica sem a presença de metais como agentes complexantes. / This work describes the preparation, characterization and the use of the modified electrode with methylene blue polymer (PMB) immobilized onto the surface of glassy carbon electrode (GCE-PMB) in the analysis of the herbicide glyphosate. Concerning the methodology aspects, the method used for the preparation of the films PMB was the electropolymerization. The films prepared by this method present a differentiated characteristic such as robustness, stability and good redox properties. The optimized experimental conditions are the scan rate (50 mV s-1), the potential range (-0.4 to +1.2 V), the number of cycles (30) and the pH of the supporting electrolyte (pH 8). The supporting electrolyte solution was prepared from phosphate buffer solutions (0.05 mol L-1) and NaNO3 (0.1 mol L-1), pH 8. The same solution was used to prepare the solution of methylene blue (MB) (0.25 x 10-3 mol L-1), the pretreatment of the GC electrode by cyclic voltammetry (CV). It was also utilized in preparing solutions for the initial studies with GCE-PMB. The pre-treatment of the electrode surface of GC was performed, considering 0.9 V during 240 s, followed by several cyclic scans from -0.4 to 1.0 V (with scan rate of 50 mV s-1) until a stable profile of the voltammogram. After preparing the GCE-PMB, electrocatalytic activity it was investigated for Ascorbic Acid (AA) and L-Cysteine (L-Cys) by CV from -0.4 to +0.6 V. It was observed increase in peak current and decrease the overpotential comparing to glassy carbon electrodes. The GCE-PMB presented direct electrochemical response, for glyphosate (1 x 10-3 mol L-1) in KCl 0.1 mol L-1 (pH 5.3) from -0.4 to +0.6 V and scan rate 50 mV s-1. The voltammetric response showed anodic and cathodic peaks in 0.2 and 0, respectively. Using the square wave voltammetry (SWV), the parameters frequency, amplitude and scan increment were optimized. It was possible to find relevant information about the interaction between GCE-PMB and glyphosate. These results showed that is possible observe the electroactivity of glyphosate on a modified electrodic surface in absence of metals or complexing agents.

Phragmites australis (hereafter Phragmites) often forms dense monocultures, which displace native plant communities and alter ecosystem functions and services. Managers tasked with controlling this plant need science-backed guidance on how to control Phragmites and restore native plant communities. This study took a large-scale approach - to better match the scale of actual restoration efforts - to compare two herbicides (glyphosate vs. imazapyr) and application timings (summer vs. fall). Five treatments were applied to 1.2 ha plots for three consecutive years: 1) summer glyphosate; 2) summer imazapyr; 3) fall glyphosate; 4) fall imazapyr; and 5) untreated control. Dead Phragmites following herbicide treatments was mowed in the first two years. Efficacy of treatments and the response of native plant communities were monitored for three years. We report that fall herbicide applications were superior to summer applications. No difference was found between the two herbicides in their ability to reduce Phragmites cover. Plant communities switched from emergent to open water communities and were limited by Phragmites litter and water depth. Although, some plant communities showed a slow trajectory towards one of the reference sites, cover of important native emergent plants did not increase until year three and remained below 10%. These results suggest that fall is the best time to apply herbicides for effective large-scale control of Phragmites. Active restoration (e.g. seeding) may be needed to gain back important native plant communities. Methods to reduce Phragmites litter after herbicide applications should be considered.

L'objectif de ce travail est d'évaluer et de comparer le comportement environnemental du glyphosate, utilisé dans un contexte d'introduction de plantes génétiquement modifiées (GM), par rapport aux comportements d'autres herbicides classiquement utilisés pour le désherbage des mêmes cultures non résistantes au glyphosate: trifluraline et métazachlore pour le colza, métamitrone pour la betterave, sulcotrione pour le maïs. En effet, les conséquences sur l'environnement de ces modifications des pratiques de désherbage ont été jusqu'à présent peu étudiées. Trois sites représentatifs des principales situations où sont cultivées ces plantes, aux points de vue climatique et pédologique, ont été choisis pour cette étude (localisés près de Châlons-en-Champagne, Dijon et Toulouse). Dans la première partie de ce travail, les comportements des herbicides dans les trois sols ont été comparés au laboratoire dans les mêmes conditions (sol, température, humidité, dose). Leur rétention, dégradation dans les sols après application directe ou après absorption dans les tissus végétaux dans les cas particuliers du glyphosate et de la sulcotrione (herbicides foliaires) ont été déterminées. Dans la seconde partie, les résultats obtenus au laboratoire ont été utilisés pour estimer les impacts environnementaux des herbicides à partir de trois méthodes de précision croissante: indice de lixiviation GUS (risque de contamination des eaux souterraines), indicateur I-Phy (risque de contamination de l'air, de l'eau de surface et de l'eau souterraine), et modèle numérique de devenir des pesticides, PRZM. Les stocks et flux des herbicides et de leurs métabolites obtenus par modélisation ont ensuite été agrégés avec le modèle USES (analyse de cycle de vie et d'impacts) pour estimer les impacts finaux des différents systèmes de culture existants sur les trois sites (rotations avec colza et betterave GM ou non-GM, monoculture de maïs GM ou non-GM) sur plusieurs cibles de l'environnement (eau, sédiments, écosystèmes, population humaine). Le glyphosate est généralement l'herbicide pour lequel les risques de dispersion dans l'environnement sont les plus faibles (rétention élevée, dégradation rapide), mais ils dépendent cependant du type de sol. Les vitesses et taux de minéralisation des herbicides diminuent fortement avec la température, de même que la formation de résidus non extractibles, avec une préservation des molécules sous forme extractible donc potentiellement disponible. La formation d'un métabolite majeur plus persistant a été observée dans les cas du glyphosate (acide aminométhylphosphonique, AMPA), du métazachlore (non identifié) et de la sulcotrione (acide 2-chloro-4-méthylsulfonylbenzoïque, CMBA). En conséquence, ces métabolites présentent des risques pour l'environnement plus importants que les molécules herbicides. Enfin, l'absorption du glyphosate dans les tissus végétaux diminue sa dégradation. L'accumulation de glyphosate non dégradé dans les tissus végétaux pourrait augmenter les quantités de glyphosate dans le sol après restitution des résidus de récolte ou lors de la chute des feuilles traitées. Ce résultat a été pris en compte dans la modélisation. Le calcul de l'indice GUS a montré que les herbicides présentent peu de risque de contamination des eaux souterraines, le calcul de l'indicateur I-Phy a conduit à des résultats similaires pour les eaux souterraines, ainsi que pour les eaux de surface et l'air. Le modèle PRZM a été préalablement testé à partir d'une expérimentation en conditions de plein champ: il permet des simulations correctes du devenir des herbicides à partir des données obtenues au laboratoire, mais a néanmoins été calé dans les cas du glyphosate et de la trifluraline. Les résultats des simulations des différentes pratiques de désherbage ont montré que plus la fréquence de retour des cultures GM est élevée et plus l'impact sur l'environnement du glyphosate pourrait être important comparé aux herbicides sélectifs. En particulier, les stocks d'AMPA dans le sol après douze ans d'application annuelle de glyphosate dans une monoculture de maïs pourraient être particulièrement élevés. Du point de vue de la contamination de l'environnement par les herbicides, les bénéfices des cultures GM dépendent donc des types de sol, des cultures et des herbicides remplacés. La persistance de l'AMPA dans les sols soulève néanmoins un problème général de durabilité de cette innovation, et impose d'étudier plus en détail le comportement de cette molécule à long terme.

Cette étude vise à développer un système de dépollution d'eau et de sédiments viticoles. Le glyphosate, diuron et 3,4-dichloroaniline (3,4-DCA) sont considérés, en tenant compte de la charge en cuivre. L'augmentation du temps de séjour des polluants dans le système et le choix de la bioaugmentation couplée à la phytoremédiation est la stratégie retenue. Chaque composante d'un triplet « sorbant-inoculum bactérien-plante » a été sélectionnée en laboratoire et le triplet mis en œuvre en microcosmes en conditions partiellement contrôlées. La sélection de matériaux sorbants dans différentes matrices liquides en présence des polluants seuls ou en mélange montre que les capacités de sorption des différents matériaux testés varient selon le polluant, sa formulation (seul ou en mélange) et la matrice liquide. Le sédiment se révèle être le meilleur sorbant pour le glyphosate ; le sable pour le diuron et le 3,4-DCA. Les performances de dissipation des colonies tolérantes isolées varient fortement selon le polluant. Le consortium sélectionné pour le procédé dissipe le glyphosate, le diuron et le 3,4-DCA en milieu liquide et complexe par ailleurs le cuivre. L'expérience en microcosmes montre que le temps de rétention hydraulique influe sur l'efficacité du système et que les matériaux sorbants sont efficaces. De plus les performances de dissipation atteintes sont bonnes. L'effet de la bioaugmentation sur les performances de dissipation n'est pas significatif pour le glyphosate et le 3,4-DCA, mais améliore en moyenne la dissipation du diuron. Un temps d'action prolongé dans la matrice solide s'avère nécessaire pour obtenir une bonne efficacité du procédé.

The Laurentian Great Lake, Lake Erie is an invaluable global resource and its watershed is home to over 11 million people. The pressures placed on the lake because of this high population caused Lake Erie to experience numerous environmental problems, including seasonal hypoxia and harmful algal blooms. While these topics have been widely studied in Lake Erie for over 40 years a more nuanced understanding of the interaction between phytoplankton and nutrient is needed to properly address the problems continuing to face the lake. In this study we combine classical limnological and cell growth experiments with modern molecular biological techniques and microscopy to more completely describe the aquatic microbial ecology of the lake. We used an oxalate rinse technique to examine the surface absorbed P pool of the toxic cyanobacterium Microcystis aeruginosa grown under a range of P conditions, as well as the general Lake Erie plankton assemblage. Our results suggest that while Microcystis is plastic in its cellular P needs, the ratio of intracellular to extracellular P remains stable across growth conditions. We describe the effect of the phosphonate herbicide glyphosate on the Lake Erie phytoplankton community using laboratory cell growth studies, field microcosm experiments and PCR amplification of a gene implicated in the breakdown of this compound from the environment. Results from these experiments suggest that the presence of glyphosate can affect community structure in multiple ways and may explain areas of unexplained phytoplankton diversity in coastal areas of Lake Erie. We also show heterotrophic bacteria are likely critical to the breakdown of glyphosate and further illustrate that understanding the context of the larger microbial community is critical to understanding the ecology of the constituent members of the community. Finally, we investigate the activity of the phytoplankton community in winter months with a focus on diatoms abundant in Lake Erie under the ice. We show these diatoms are active and that the winter bloom is a likely source of carbon important to seasonal hypoxia formation. Together, these studies significantly enrich our understanding of how phytoplankton influence important ecological processes in Lake Erie.

Studies were conducted in 2004, 2005, and 2006 in south Texas to evaluate fall, winter, and spring weed control for commercial rice production, study tillage intensity and herbicide rate interactions for rice production, and determine the tolerance of red rice ecotypes from Texas rice fields using selected herbicides at varying rates. A single application of any herbicide or combination of herbicides was not adequate for weed control throughout the fall, winter, and spring. Fall applications of clomazone plus flumioxazin provided consistent weed control. Addition of flumioxazin to glyphosate provided excellent winter annual grass control with winter application. A residual herbicide, coupled with the proper contact herbicide is the key to extending control. In 2006, all tillage by herbicide treatments in all studies provided ≥ 90% control of all weed species. The conventional tillage treatment with low herbicide input provided the highest rice grain yield in 2005 and 2006, though they were not significantly different from the spring stale seedbed program with medium or high herbicide input in 2006. In 2006, fall stale seedbed treatments were among the lowest in yield. A stale seedbed program may be useful, but with substantial weed pressure, increasing the intensity of herbicide applications is necessary to overcome the absence of tillage. All rice ecotypes were adequately controlled by glyphosate and only one ecotype was found to be tolerant to 2x rates of both imazethapyr and imazamox. All ecotypes were adequately controlled by 2x rates of more than two of the four herbicides which included imazethapy, imazamox, glufosinate, and glyphosate. Ecotypes from the 3.2 group, genetically similar to the ecotype TX4, appear to be the most likely to exhibit tolerance to a given herbicide. Tolerance to glufosinate was found in 70% of the group 3.2 ecotypes. Sixty percent of ecotypes from group 3.1, genetically similar to Oryza rufipogon were not adequately controlled by glufosinate.

Glyphosate-based herbicides are the dominant pesticide on the market and are utilized worldwide in both the agricultural and forestry industries. Their prevalence comes at a time when concern over the potential effects of pesticide application in amphibian spawning grounds is growing. The primary goal of this thesis was to determine if the glyphosate-based herbicide WeatherMax® has the potential to disrupt sexual differentiation and growth in the wood frog (Lithobates sylvaticus) in a pulse exposure at the predicted maximal environmental concentration (PMEC) of 2.88 mg acid equivalent per liter. This was carried out in laboratory, mesocosm and in-situ field exposures, in an attempt to determine how a potential disruption might vary between experimental environments. In this study, tadpoles from three split-wetlands targeted at the PMEC for WeatherMax were found to display no significant change in survival or growth, however gene expression of several genes involved in steroidogenesis during sexual differentiation (cyp19, cyp17, star, foxl2) were found to be affected. The effects on these genes appeared to be dependant on the exposure concentration of WeatherMax in each wetland, which varied even though all three wetlands were meant to target the PMEC. The wetland that was measured as having the highest herbicide concentration (PMEC 13) was found to have a female biased sex ratio. The results found in the field varied from those found in the more artificial exposures. In the laboratory the PMEC of WeatherMax experienced complete mortality, whereas in the mesocosms survival was not significantly affected. Sex ratios were unaffected in the laboratory, however at the PMEC there was a significant male bias in the mesocosms. The discrepancies in the results obtained from the different exposure types highlights the importance of real world exposures. That the same concentration that caused complete mortality in the laboratory caused sublethal effects in the field is of importance as it denotes that these endpoints may not be easily investigated in these synthetic exposures. This project is a part of the Long Term Experimental Wetlands Area (LEWA) and contributes to the body of information amassed therein on the impact of a glyphosate-based herbicide on amphibians in a wetland ecosystem.