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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Ecological modeling of the lower trophic levels of Lake Erie

Zhang, Hongyan, January 2006 (has links)
Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 211-226).
122

Biodiversidade de caranguejos Braquiúros (Cristacea: Decapoda) associada ao cultivo comercial de mexilhão Pena perna (Linnaeus, 1758) (molusca: Bivalvia) no litoral norte do estado de São Paulo /

Camargo, Flávio de Vasconcelos. January 2011 (has links)
Orientador: Adilson Fransozo / Banca: Valter José Cobo / Banca: Roberto Munehiza Shimizu / Resumo: O objetivo deste estudo é descrever a composição e a estrutura da comunidade de decápodos braquiúros associada ao cultivo de mexilhão Perna perna em Ubatuba, litoral norte paulista (23"27'07 S - 45"02'49 W). Foram realizadas coletas mensais durante o período de março de 2002 a abril de 2003, em sistema "long-line" de cultivo. As amostras das redes de P. perna foram triadas e mensuradas quanto ao volume. Os braquiúros amostrados foram identificados quanto a espécie e sexo, mensurados quanto a largura de carapaça (LC) e analisados quanto a diversidade, equidade e equitabilidade. Foi obtido um total de 849 indivíduos distribuídos em 14 gêneros e 16 espécies, sendo que Panopeus austrobesus e Pachygrapsus transversus apresentaram a maior abundância com 711 e 68 indivíduos respectivamente, correspondendo juntos a 83% do total amostrados, além disso, foram registradas para essas duas espécies os maiores valores de diversidade, constância e abundância. A presença de P. austrobesus e P. tranversus durante todo estudo sugere que essas espécies apresentem maior eficiência competitiva em relação a colonização primária das redes, além disso essas espécies foram consideradas responsáveis pela dinâmica e regulação da comunidade de braquiúros nas redes. A baixa riqueza encontrada nas redes de cultivo quando comparada a ambientes heterogêneos é esperada, devido ao estágio inicial de desenvolvimento da comunidade de caranguejos em relação a um substrato homogêneo e recém-formado e as perturbações por ele sofridas. / Abstract: The main goal of this study is describe the composition and structure of the community of the Decapod Brachyuran associated to the commercial raft of the mussel Perna perna in the southeastern Brazilian coast (23º27"07'S-45º02"49'W). Monthly collections of mussels' net culture were carried out from March, 2002 to April, 2003. The crabs were sexed and identified as juvenile and adult, based on the abdomen morphology, and measured as the largest carapace width (CW). The samples were analyzed for some ecologic index as richness, diversity, constancy, evenness and equitability. A total of 849 individuals was obtained, distributed into 14 genera and 16 species. Panopeus austrobesus and Pachygrapsus transversus were the most abundant species, with 711 and 68 specimens respectively, together corresponding to 68% of the total crab's samples. For these two species were also recorded the largest values for diversity and constancy. The presence of these two species over all sampled period pointing out its high competitive efficiency during the initial phase of the mussel colonization, thereby responsible for the community regulation during this colonization phase. The low values of richness recorded on the mussel rafts are expected for the homogeneous environments, as those created among the mussel shells. So, the crab community established on the mussel raft, in the southeastern Brazilian coast, is dominated for two pioneers' species that are the main pieces for its regulation. / Mestre
123

Růst a přežívání perlorodky říční (Margaritifera margaritifera) pro bioindikační účely / Growth and survival of pearl mussel (Margaritifera margaritifera) for bioindication

NIEDLOVÁ, Eva January 2015 (has links)
Growth and survival of juvenile pearl mussels (Margaritifera margaritifera Linnaeus, 1758) "in-situ" indicates suitable habitats for their rearing and subsequent reintroduction. Six streams in Aš region (Rokytnice, Lužní potok, Pekelský potok, Újezdský potok, Perlový potok, Bockbach) including 15 profiles were evaluated throughout the season (1. 6. 31. 8. 2015). One year old pearl mussels (n = 580) sized from 700 1400 ?m. Mean survival of pearl mussels was 63 % in all streams. Mean absolute growth increment attained 755 ?m throughout the season. Growth of pearl mussels (1+) was positively correlated with the water temperature (R2 = 0,1084). Both the highest survival (70 %) and the highest absolute growth (1027 ?m and 997 ?m) of pearl mussels was determined on localities in Bockbach (Bockbach 11 and 1). In contrast to Bockbach 11 and 1 mean survival (28%) and absolute growth (304 ?m) was the lowest in Lužní potok 2. Survival rate of two years old pearl mussels was higher than that of one year old pearl mussels. Both of these age categories grew similarly.
124

Odhad věku a přírůstků lastur perlorodky říční (Margaritifera margaritifera) / Assessment of age and growth increments of pearl mussel (\kur{Margaritifera margaritifera}) shells

HOLEČKOVÁ, Karolína January 2018 (has links)
The aim of the diploma thesis was to assess the quality of localities and their suitability for possible juvenile reintroduction based on the morphometric parameters and the age of dead freshwater pearl mussels (Margaritifera margaritifera). The age of the dead individuals was determined from the stained cross section of pearl shell layer. Shells were sampled on localities in Aš (Bystřina, Lužní potok, Rokytnice and Újezdský potok) and Šumava (Blanice, Kleine Ohe and Zlatý potok) in the Czech Republic and in the adjacent parts of Germany in 2015 and 2017. A total of 77 shells were used. Shells of larger sizes were found out in the Aš region. The average age of the shells was 46 years and did not differ between the regions. The average annual increments did also not differ between regions. It was 72,5 ?m.year-1. Shells of individuals originated from Rokytnice and Újezdský potok reached the highest age and had the greatest annual increments. Shells of individuals originated from Zlatý potok reached the lowest age and their annual increments were the lowest.
125

The Potential for Quagga Mussel Survival in Canyon Lake

January 2018 (has links)
abstract: Quagga mussels are an aquatic invasive species capable of causing economic and ecological damage. Despite the quagga mussels’ ability to rapidly spread, two watersheds, the Salt River system and the Verde River system of Arizona, both had no quagga mussel detections for 8 years. The main factor thought to deter quagga mussels was the stratification of the two watersheds during the summer, resulting in high temperatures in the epilimnion and low dissolved oxygen in the hypolimnion. In 2015, Canyon Lake, a reservoir of the Salt River watershed, tested positive for quagga mussel veligers. In this study, I used Landsat 7 and Landsat 8 satellite data to determine if changes in the surface temperature have caused a change to the reservoir allowing quagga mussel contamination. I used a location in the center of the lake with a root mean squared error (RMSE) of 0.80 and a correlation coefficient (R^2) of 0.82, but I did not detect any significant variations in surface temperatures from recent years. I also measured 21 locations on Canyon Lake to determine if the locations in Canyon Lake were able to harbor quagga mussels. I found that summer stratification caused hypolimnion dissolved oxygen levels to drop well below the quagga mussel threshold of 2mg/L. Surface temperatures, however were not high enough throughout the lake to prevent quagga mussels from inhabiting the epilimnion. It is likely that a lack of substrate in the epilimnion have forced any quagga mussel inhabitants in Canyon Lake to specific locations that were not necessarily near the point of quagga veliger detection sampling. The research suggests that while Canyon Lake may have been difficult for quagga mussels to infest, once they become established in the proper locations, where they can survive through the summer, quagga mussels are likely to become more prevalent. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2018
126

Nanopartículas de dióxido de titânio e avaliação da sua toxicidade no mexilhão dourado (Limnoperna fortunei)

Girardello, Francine 23 May 2016 (has links)
A nanotecnologia é uma das áreas de maior desenvolvimento da atualidade. Nanopartículas de dióxido de titânio (TiO2-NP) têm sido amplamente utilizadas em diversos produtos e processos nos últimos anos. Como consequência, estas nanopartículas são liberadas em efluentes e águas residuais, atingindo os compartimentos aquáticos. Com isso, a avaliação do impacto biológico das TiO2-NP se torna de grande importância na área de ecotoxicidade. O mexilhão dourado (Limnoperna fortunei) é um molusco bivalve de água doce muito utilizado no biomonitoramento ambiental, considerado organismo alvo para toxicidade de TiO2-NP no ambiente aquático. Neste trabalho, os exemplares do L. fortunei foram expostos às TiO2-NP (1, 5, 10 e 50 μg mL-1), as quais foram previamente caracterizadas físicoquimicamente. A avaliação toxicológica se deu através do ensaio cometa, teste de micronúcleos, avaliação dos danos oxidativo a lipídios e proteínas e avaliação das defesas antioxidantes através da atividade das enzimas superóxido dismutase (Sod) e catalase (Cat) e do conteúdo sulfidril de proteínas. A interação de TiO2-NP com os hemócitos do mexilhão dourado foi avaliada utilizando microscopia eletrônica de transmissão (MET). Os resultados mostraram que as TiO2-NP apresentaram tamanho médio de cerca de 20 nm e são compostas pelas estruturas cristalinas anatase e rutilo, com área superficial de 46,26 m2 g-1. As soluções de 1, 5, 10 e 50 μg mL-1 TiO2-NP utilizadas apresentaram baixa estabilidade com tendência à formação de agregados. A genotoxicidade das TiO2-NP foi evidenciada pelos danos ao DNA do L. fortunei verificados após 2 h de exposição e aumentada após 4 h para todas as concentrações testadas. TiO2-NP não foram capazes de induzir a formação de micronúcleos nos hemócitos do mexilhão dourado. Os mexilhões apresentaram aumento nos níveis de peroxidação lipídica e do conteúdo de proteínas carboniladas após 2 h de exposição às concentrações de TiO2-NP utilizadas. Após 4 h de exposição, esses valores não apresentaram diferença do controle. A atividade da enzima Sod foi diminuída após 2 h de exposição para todas as concentrações testadas de TiO2-NP. A enzima Cat apresentou diminuição na atividade após 2 h de exposição dos mexilhões às concentrações de 10 e 50 μg mL-1 TiO2-NP. As defesas antioxidantes não enzimáticas foram diminuídas após 2 h de exposição dos mexilhões a todas as concentrações de TiO2-NP utilizadas. Após 4 h de exposição, tanto as defesas antioxidantes enzimáticas como as não enzimáticas foram restauradas. Conforme análise das imagens de MET, TiO2-NP foram internalizadas nos hemócitos do mexilhão dourado, ocasionando alterações na estrutura da membrana plasmática. As TiO2-NP causaram efeitos toxicológicos no mexilhão dourado, capazes de causar genotoxicidade e alterações no metabolismo redox nas células dos animais. Estes resultados reforçam os cuidados que devem ser aplicados na liberação das TiO2-NP no ambiente, devido a problemas causados pela exposição às nanopartículas. Além disso, os dados apresentados demonstram o potencial do L. fortunei como organismo biomonitor para a exposição às nanopartículas. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-07-01T17:50:18Z No. of bitstreams: 1 Tese Francine Girardello.pdf: 6715161 bytes, checksum: ebe64da4ad8f569ee542da47e13f60e3 (MD5) / Made available in DSpace on 2016-07-01T17:50:18Z (GMT). No. of bitstreams: 1 Tese Francine Girardello.pdf: 6715161 bytes, checksum: ebe64da4ad8f569ee542da47e13f60e3 (MD5) Previous issue date: 2016-07-01 / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS. / Nanotechnology is one of the fastest-growing areas of the actuality. Nanoparticles of titanium dioxide (TiO2-NP) have been widely used in many products and processes in recent years. As consequence, these nanoparticles are release into effluent and wastewater, reaching water compartments. Thus, the evaluation of the biological impact of TiO2-NP becomes of great importance for ecotoxicity. The golden mussel (Limnoperna fortunei) is a freshwater bivalve mollusk often used in biomonitoring, considered target organism for TiO2-NP toxicity in the aquatic environment. In this work, L. fortunei were exposed to TiO2-NP (1, 5, 10 and 50 μg mL-1), which were previously physic-chemically characterized. The toxicological evaluation was performed using the comet assay, micronucleus test, evaluation of oxidative damage to lipids and proteins, assessment of antioxidant defences through the activity of the enzymes superoxide dismutase (Sod) and catalase (Cat) and the protein sulfhydryl content. The TiO2-NP interaction with the haemocytes of golden mussel was evaluated by transmission electron microscopy (TEM). The results showed that TiO2-NP presented average size about 20nm, composed of the anatase and rutile crystalline structures, with surface area of 46.26 m2 g-1. The TiO2-NP solutions of 1, 5, 10 and 50 μg mL-1 used showed low stability with a tendency to form aggregates. The genotoxicity of TiO2-NP was evidenced by DNA damage of L. fortunei after 2 h of exposure and increased after 4 h for all concentrations tested. TiO2-NP was not able to induce micronucleus in haemocytes of golden mussels. The mussels showed an increase in lipid peroxidation levels and carbonylated proteins content after 2 h of exposure to the concentrations of TiO2-NP used. After 4 h of exposure, these values showed no difference compared to control. Sod enzyme activity was decreased after 2 h of exposure for all tested concentrations of TiO2-NP. Cat enzyme activity decreased after 2 h of exposure of the mussels to concentrations of 10 and 50 μg mL-1 TiO2-NP. The non-enzymatic antioxidant defences decreased after 2 h of mussels exposure of all TiO2-NP concentrations used. The mussels showed increased levels of lipid peroxidation and carbonyl proteins after 2 h of exposure to TiO2-NP, showing no similar effects after 4 h of exposure. The enzymatic and non-enzymatic antioxidants defences were depleted after 2 h of TiO2-NP exposure to the mussels. After 4 h of exposure, both enzymatic antioxidant and non-enzymatic defences were restored. As shown by the TEM image analysis, TiO2-NP was internalized by haemocytes of the golden mussel, causing changes in plasmatic membrane structure. The TiO2-NP cause toxicological effects on the golden mussel, which are able to cause genotoxicity and changes in redox metabolism of cells. These results reinforce the care that must be applied to the release of TiO2-NP in the environment due to problems caused by nanoparticles exposure. Furthermore, the data presented demonstrate the potential L. fortunei as biomonitor organism for exposure to nanoparticles.
127

Rybářský management na lokalitách výskytu perlorodky říční (Margaritifera margaritifera) v České republice / Fish Management in the Locations with Occurence of Freshwater Pearl Mussel (Margaritifera margaritifera) in the Czech Republic

JIRUŠKOVÁ, Lenka January 2011 (has links)
Quality of populations of brown trout (Salmo trutta m. fario) influence of occurence of freshwater pearl mussel (Margaritifera margaritifera) in river in the Czech Republic. Freshwater pearl mussel is a critically endangered species of animals. It does not have a very specific requirements only on environment but mainly on a specific host for holding glochidia (larval stage of pearl mussel). Thus fish management and migratory permeability of flow for support of existing populations is very important. Basic and essential precondition to support populations of freshwater pearl mussels is the presence of viable populations of brown trout, which represents the only suitable host glochidia. There are five locations with the biggest occurrence of pearl mussel in the Czech Republic - river basins the Blanice, the Teplá Vltava, the Malše, the Rokytnice and the Jankovský potok. The management of these flows is under local organizations of Czech Fishing Union, the National Park and Protected Landscape Area of the Šumava, the Secondary School of Fisheries in Vodňany and Faculty of Fisheries and Protection of Waters. The present management was found in the questionnaire for representatives of farming organizations. According to the answers in the questionnaire, the change of plans of restocking was recommended in the river basins of the Teplá Vltava and the Jankovský potok. There is the cooperation with the Germany was recommended in the river basin of the Rokytnice. The restoration of fish nursery is suitable in the river basin of the Malše. There is the first-rate population of brown trout in the river basin of Blanice, thus the continue in the present fish management for next support of this population in sequence on the populations of freshwater pearl mussel was recommended
128

Avaliação de técnicas de controle da incrustação por mexilhão-dourado em hidrogeradores visando minimização da indisponibilidade. / Evaluation of techniques for golden mussel fouling control in hydroelectric power plants aimed at mitigation of unavailability.

Érico Pessoa Felix 24 November 2011 (has links)
O mexilhão-dourado é um organismo invasor que tem causado grandes prejuízos a sistemas de captação de água e usinas hidroelétricas (UHEs). Existem diversos métodos de controle da incrustação destes organismos em tubulações de usinas hidroelétricas, porém o impacto da aplicação desses métodos ainda não é amplamente conhecido. Este trabalho visa desenvolver uma metodologia para avaliar a degradação dos sistemas de resfriamento de UHEs submetidas a tratamentos químicos para o controle da incrustação por mexilhão-dourado. Neste trabalho é usado, como caso exemplo, o sistema de resfriamento do ar do núcleo do gerador e do óleo dos mancais de uma UHE com turbina Kaplan de potência aproximada de 150 MW. A análise proposta baseia-se na aplicação de ensaios acelerados de corrosão, a fim de determinar a taxa de corrosão nas condições normais de operação. Os ensaios executados neste estudo simulam condições operacionais mais severas do que as usualmente enfrentadas pelo sistema, visando reduzir o tempo de execução dos ensaios. Os ensaios acelerados de corrosão baseiam-se no aumento da solicitação térmica e da concentração das substâncias químicas injetadas no fluxo de água que são a adição de gás ozônio e de hipoclorito de sódio. Para realização dos ensaios foi construído um circuito experimental capaz de impor condições de temperatura e concentrações das substâncias químicas. Os resultados dos ensaios acelerados fornecem subsídios para aplicação dos conceitos de confiabilidade estrutural para determinação da probabilidade de falha dos equipamentos em estudo em função do tempo de aplicação do tratamento químico. Verificou-se entre os produtos químicos utilizados neste estudo, que o hipoclorito de sódio é 50% mais agressivo para a liga de cobre níquel e 700% mais agressivo para o aço inoxidável em relação a degradação observada pela ação do ozônio. / The golden mussel (Limnoperna fortunei) is an invader organism that has caused great damage to water catchment systems and hydroelectric power plants. There are various methods of fouling control of these organisms in hydroelectric power plants pipelines, but the impact of the application of these methods is not yet widely known. This work aims at developing a methodology to evaluate the degradation of hydroelectric power plants cooling systems pieces of equipment subjected to chemical treatments for control of golden mussel fouling. This work uses as a case example, the cooling system inside generator and oil bearing of Kaplan hydroelectric turbine with 150MW nominal power output. The analysis is based on the application of accelerated corrosion tests in order to determine the rate of corrosion under normal operation conditions given the rates of corrosion under various accelerated conditions. The tests run on this thesis simulate operating conditions more severe than those usually experienced by the system, to reduce the runtime of the tests. The proposed accelerated corrosion tests are based on increased thermal loading and concentration of chemical substances injected into water flow. The chemical treatments tested in this work are the addition of ozone and sodium hypochlorite. For carrying out the tests an experimental circuit capable of imposing different conditions of temperature and concentration levels was built. The results of accelerated tests provide subsidies for the implementation of structural reliability concepts for determining the failure probability of equipment under consideration. Among the chemical products used in the analysis, the sodium hypochlorite is 50% more aggressive for copper-nickel 90/10 alloy and 700% more aggressive for stainless steel in relation to degradation observed for ozone.
129

Predadores ou dispersores? A relação do mexilhão-dourado Limnoperna fortunei (Dunker, 1857) (Bivalvia, Mytilidae) com quatro espécies de quelônios (Reptilia, Testudines) da planície costeira do Brasil subtropical

Cardoso, Cibele da Costa January 2014 (has links)
Submitted by dayse paz (daysepaz@hotmail.com) on 2016-04-08T01:33:07Z No. of bitstreams: 1 Disserta_o_Mestrado_Cibele_da_Costa_Cardoso_PPGBAC.pdf: 1283718 bytes, checksum: bfbf723b7d30d3f4f0b80e26ea623820 (MD5) / Approved for entry into archive by cleuza maria medina dos santos (cleuzamai@yahoo.com.br) on 2016-04-12T00:18:15Z (GMT) No. of bitstreams: 1 Disserta_o_Mestrado_Cibele_da_Costa_Cardoso_PPGBAC.pdf: 1283718 bytes, checksum: bfbf723b7d30d3f4f0b80e26ea623820 (MD5) / Made available in DSpace on 2016-04-12T00:18:15Z (GMT). No. of bitstreams: 1 Disserta_o_Mestrado_Cibele_da_Costa_Cardoso_PPGBAC.pdf: 1283718 bytes, checksum: bfbf723b7d30d3f4f0b80e26ea623820 (MD5) Previous issue date: 2014 / Nas últimas décadas, a invasão de espécies exóticas recebeu grande atenção da comunidade científica, sendo considerada a segunda causa de extinção de espécies nativas em todo o mundo. O mexilhão-dourado Limnoperna fortunei é um molusco bivalve nativo da China, o qual foi introduzido em diversos locais do mundo, principalmente através da água de lastro de navios, causando impactos econômicos e à biota nos locais de sua introdução. Na América do Sul, seu primeiro registro foi em 1991, no Rio da Prata. No Brasil, essa espécie tem sido registrada em diversas localidades, incluindo o sistema lagunar Patos/Mirim na planície costeira do Rio Grande do Sul. Essa dissertação teve como principal objetivo estudar a relação do mexilhão-dourado com as quatro espécies de quelônios de água doce que ocorrem nessa região. O primeiro capítulo, intitulado “Does the invasive Golden Mussel Limnoperna fortunei (Dunker, 1857) engage in biofouling on native freshwater turltes?”, testa através de experimentos ex situ a capacidade de fixação da espécie invasora L. fortunei nos quelônios da planície costeira do Brasil subtropical, e se esses quelônios poderiam atuar como vetores de dispersão do mexilhão-dourado. O segundo capítulo, intitulado “Avaliando a capacidade de predação do molusco invasor Limnoperna fortunei (Dunker, 1857) (Bivalvia, Mytilidae) por quelônios aquáticos em condições laboratoriais,” trata da capacidade de predação do molusco invasor pelos quelônios nativos. Os resultados encontrados indicam que Acanthochelys spixii, Hydromedusa tectifera e Phrynops hilarii, todas da família Chelidae, possuem alta capacidade de atuarem como vetor de dispersão da espécie invasora enquanto que Phrynops hilarii (Chelidae) e Trachemys dorbigni (Emydidae) são as espécies que apresentaram maiores taxas de predação do mexilhão-dourado. Estas informações ajudam na compreensão dos efeitos causados por esse bioinvasor na planície costeira do Rio Grande do Sul. / In the past decades, the invasion of exotic species has received major attention from the scientific community, and is considered the second cause of extinction of native species worldwide. The golden mussel Limnoperna fortunei is a bivalve mollusk native from China, which was introduced in several localities around the world, primarily through the ballast water of ships, causing impacts both economic such biota. In South America its first record was in 1991 in the La Plata River. In Brazil, this species has been recorded in several localities, including the Patos/Mirim lagoons system in the coastal plain of Rio Grande do Sul. This dissertation, aimed to study the relationship of the Golden Mussel with four species of freshwater turtles that occur in this region. The first chapter entitled "Does the invasive Golden Mussel Limnoperna fortunei (Dunker, 1857) engage in biofouling on native freshwater turtles?" tested through ex situ experiments the ability of fixation of the invasive species L. fortunei on freshwater turtles from coastal plain of the subtropical Brazil and if these turtles could act as vectors of dispersal of Golden Mussel. The second chapter, entitled "Assessing the ability of predation on the invasive Golden Mussel Limnoperna fortunei (Dunker, 1857) (Bivalvia, Mytilidae) by aquatic turtles under laboratory conditions", describes the ability of predation of native freshwater turtles on the Golden Mussel. The results indicate that the Chelids Acanthochelys spixii, Hydromedusa tectifera and Phrynops hilarii, have high capacity to acting as a dispersion vector of the invasive species while Trachemys dorbigni (Emydidae) is the species with higher rates of predation on the Golden Mussel. These findings help in understanding the effects caused by this bioinvasor in the coastal plain of Rio Grande do Sul.
130

Nanopartículas de dióxido de titânio e avaliação da sua toxicidade no mexilhão dourado (Limnoperna fortunei)

Girardello, Francine 23 May 2016 (has links)
A nanotecnologia é uma das áreas de maior desenvolvimento da atualidade. Nanopartículas de dióxido de titânio (TiO2-NP) têm sido amplamente utilizadas em diversos produtos e processos nos últimos anos. Como consequência, estas nanopartículas são liberadas em efluentes e águas residuais, atingindo os compartimentos aquáticos. Com isso, a avaliação do impacto biológico das TiO2-NP se torna de grande importância na área de ecotoxicidade. O mexilhão dourado (Limnoperna fortunei) é um molusco bivalve de água doce muito utilizado no biomonitoramento ambiental, considerado organismo alvo para toxicidade de TiO2-NP no ambiente aquático. Neste trabalho, os exemplares do L. fortunei foram expostos às TiO2-NP (1, 5, 10 e 50 μg mL-1), as quais foram previamente caracterizadas físicoquimicamente. A avaliação toxicológica se deu através do ensaio cometa, teste de micronúcleos, avaliação dos danos oxidativo a lipídios e proteínas e avaliação das defesas antioxidantes através da atividade das enzimas superóxido dismutase (Sod) e catalase (Cat) e do conteúdo sulfidril de proteínas. A interação de TiO2-NP com os hemócitos do mexilhão dourado foi avaliada utilizando microscopia eletrônica de transmissão (MET). Os resultados mostraram que as TiO2-NP apresentaram tamanho médio de cerca de 20 nm e são compostas pelas estruturas cristalinas anatase e rutilo, com área superficial de 46,26 m2 g-1. As soluções de 1, 5, 10 e 50 μg mL-1 TiO2-NP utilizadas apresentaram baixa estabilidade com tendência à formação de agregados. A genotoxicidade das TiO2-NP foi evidenciada pelos danos ao DNA do L. fortunei verificados após 2 h de exposição e aumentada após 4 h para todas as concentrações testadas. TiO2-NP não foram capazes de induzir a formação de micronúcleos nos hemócitos do mexilhão dourado. Os mexilhões apresentaram aumento nos níveis de peroxidação lipídica e do conteúdo de proteínas carboniladas após 2 h de exposição às concentrações de TiO2-NP utilizadas. Após 4 h de exposição, esses valores não apresentaram diferença do controle. A atividade da enzima Sod foi diminuída após 2 h de exposição para todas as concentrações testadas de TiO2-NP. A enzima Cat apresentou diminuição na atividade após 2 h de exposição dos mexilhões às concentrações de 10 e 50 μg mL-1 TiO2-NP. As defesas antioxidantes não enzimáticas foram diminuídas após 2 h de exposição dos mexilhões a todas as concentrações de TiO2-NP utilizadas. Após 4 h de exposição, tanto as defesas antioxidantes enzimáticas como as não enzimáticas foram restauradas. Conforme análise das imagens de MET, TiO2-NP foram internalizadas nos hemócitos do mexilhão dourado, ocasionando alterações na estrutura da membrana plasmática. As TiO2-NP causaram efeitos toxicológicos no mexilhão dourado, capazes de causar genotoxicidade e alterações no metabolismo redox nas células dos animais. Estes resultados reforçam os cuidados que devem ser aplicados na liberação das TiO2-NP no ambiente, devido a problemas causados pela exposição às nanopartículas. Além disso, os dados apresentados demonstram o potencial do L. fortunei como organismo biomonitor para a exposição às nanopartículas. / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS. / Nanotechnology is one of the fastest-growing areas of the actuality. Nanoparticles of titanium dioxide (TiO2-NP) have been widely used in many products and processes in recent years. As consequence, these nanoparticles are release into effluent and wastewater, reaching water compartments. Thus, the evaluation of the biological impact of TiO2-NP becomes of great importance for ecotoxicity. The golden mussel (Limnoperna fortunei) is a freshwater bivalve mollusk often used in biomonitoring, considered target organism for TiO2-NP toxicity in the aquatic environment. In this work, L. fortunei were exposed to TiO2-NP (1, 5, 10 and 50 μg mL-1), which were previously physic-chemically characterized. The toxicological evaluation was performed using the comet assay, micronucleus test, evaluation of oxidative damage to lipids and proteins, assessment of antioxidant defences through the activity of the enzymes superoxide dismutase (Sod) and catalase (Cat) and the protein sulfhydryl content. The TiO2-NP interaction with the haemocytes of golden mussel was evaluated by transmission electron microscopy (TEM). The results showed that TiO2-NP presented average size about 20nm, composed of the anatase and rutile crystalline structures, with surface area of 46.26 m2 g-1. The TiO2-NP solutions of 1, 5, 10 and 50 μg mL-1 used showed low stability with a tendency to form aggregates. The genotoxicity of TiO2-NP was evidenced by DNA damage of L. fortunei after 2 h of exposure and increased after 4 h for all concentrations tested. TiO2-NP was not able to induce micronucleus in haemocytes of golden mussels. The mussels showed an increase in lipid peroxidation levels and carbonylated proteins content after 2 h of exposure to the concentrations of TiO2-NP used. After 4 h of exposure, these values showed no difference compared to control. Sod enzyme activity was decreased after 2 h of exposure for all tested concentrations of TiO2-NP. Cat enzyme activity decreased after 2 h of exposure of the mussels to concentrations of 10 and 50 μg mL-1 TiO2-NP. The non-enzymatic antioxidant defences decreased after 2 h of mussels exposure of all TiO2-NP concentrations used. The mussels showed increased levels of lipid peroxidation and carbonyl proteins after 2 h of exposure to TiO2-NP, showing no similar effects after 4 h of exposure. The enzymatic and non-enzymatic antioxidants defences were depleted after 2 h of TiO2-NP exposure to the mussels. After 4 h of exposure, both enzymatic antioxidant and non-enzymatic defences were restored. As shown by the TEM image analysis, TiO2-NP was internalized by haemocytes of the golden mussel, causing changes in plasmatic membrane structure. The TiO2-NP cause toxicological effects on the golden mussel, which are able to cause genotoxicity and changes in redox metabolism of cells. These results reinforce the care that must be applied to the release of TiO2-NP in the environment due to problems caused by nanoparticles exposure. Furthermore, the data presented demonstrate the potential L. fortunei as biomonitor organism for exposure to nanoparticles.

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