Dissertations / Theses on the topic 'Bivalves – Habitat'

A better understanding of the fundamental role large woody debris (LWD) plays within mangrove ecosystems may provide further insights into important ecological processes, such as wood degradation and biodiversity maintenance within mangrove forests.Though the volume of fallen wood in mangrove forests can be huge, little is known of the breakdown pathways and biodiversity maintenance of LWD in mangrove ecosystems. The degree of mangrove fauna dependent upon LWD and the need for such substratum in mangrove ecosystems may provide further insights in to the important role of woody biomass in these otherwise globally shrinking habitats due to forest harvesting. The breakdown, recycling and flux of nutrients from LWD within mangrove forests is maintained by biodegrading organisms in areas from terrestrial to marine habitats. The tidal inundation sets limits on the wood degrading communities within the mangrove forests of Sulawesi. This study presents details of the environmental and biological association of biodegrading organisms within the forests in the Wakatobi Marine Park (WMP), Sulawesi. Wood boring animals belonging to the family Teredinidae are the dominant biodegraders of LWD in the mid- to low intertidal areas of the mangrove forests. Teredinid attack greatly reduces the volume of LWD in the mid- to low intertidal areas of the forests. Within the forests, emersion time was the greatest influence of the distribution of the biodegrading organisms spanning from the supra-tidal down to the low intertidal. The response of Rhizophora stylosa prop-roots to physical damage and the activity of teredinids upon damaged prop-roots were investigated. With severe levels of root damage, the level of teredinid activity increases, resulting in root death and detrital input. However, when the roots were exposed to a superficial and moderate level of damage, an over-compensation of tissue re-growth was observed. LWD in the intertidal zone is often tunnelled by teredinids. The tunnels are blind-ending cylinders that taper to a small opening at the wood surface. However, larger openings appear when wood is heavily tunnelled and the surface is broken open. Teredinid death then leaves niches for cryptofauna. The greater the number of teredinid tunnels within LWD, the more diversity was found. Animals of particular interest were the dartfish, Parioglossus interruptus and the intertidal spider, Desis martensi found in the vacant teredinid tunnels. Desid spiders were abundant within the LWD and dartfish collected from within teredinid-attacked LWD were smaller than dartfish populations not within LWD. Desids and dartfish residing within the wood may benefit from the significantly lower temperatures within teredinid-attacked detritus compared to external air temperatures. Desis martensi has a life-history strategy centred on strong parental care, with lots of energy invested in to its young. Vulnerable stages of dartfish exploit the vacant teredinid tunnels. If it were not for the tunnels created by the teredinids the unusual behaviour adopted by dartfish and spiders would not be possible. Thus, many animals in mangrove forests of the WMP rely on LWD as a predation refuge enhanced by the teredinid tunnels within the LWD. A variety of different species were found inside teredinid attacked LWD, and the cryptic behaviour of the fauna ranged from breeding to predator avoidance. These findings indicate that in forests where wood is harvested, reduced availability of LWD will result in reduced biodiversity.

L'objectif de cette thèse est d'analyser le déterminisme du recrutement des bivalves de milieux côtiers tempérés à travers la fonction de nurserie des habitats benthiques, les contraintes liées à la mytiliculture et à la pêche à pied récréative et les variations qualitatives et quantitatives des ressources trophiques disponibles. Les bivalves juvéniles des habitats benthiques structurés par des espèces ingénieurs ont une meilleure condition physiologique, bien qu'ils s'alimentent sur la même ressource trophique. Alors que la mytiliculture sur bouchots augmente localement l'hétérogénéité des assemblages de recrues de bivalves, la pratique du ratissage impacte négativement la fixation primaire de ces organismes. Mes travaux révèlent notamment l'importance des processus de post-fixation. Enfin, le déclenchement de la phase de fixation/métamorphose des bivalves est marqué dans l'environnement par une modification de la composition en acides gras de la matière organique particulaire indiquant l'apparition de picoeucaryotes planctoniques
The objective of this thesis is to analyze the determinism of the bivalve recruitment in a temperate coastal environment through the nursery function of benthic habitats, anthropogenic constraints of mussel farming and recreational hand-raking fishing, and the qualitative and quantitative variations of the available trophic resources. Juveniles of bivalve from benthic habitats structured by engineer species have better physiological condition, although they feed on the same trophic resource. While the mussel farming locally increases the heterogeneity of bivalve recruits assemblage, the practice of raking negatively impacts the primary fixation of these organisms. My work reveals the particular importance of post-fixation process. Finally, the triggering of the settlement phase is marked in the environment by changing the fatty acid composition of the particulate organic matter indicating the occurence of planktonic picoeukaryotes

Com a assinatura do Brasil, em 1982, da Convenção das Nações Unidas sobre o Direito do Mar (CNUDM), que trata do uso de mares e oceanos, surge a necessidade de se conhecer melhor, através de pesquisa, a Zona Econômica Exclusiva Brasileira (ZEE). Iniciase, desse modo, o REVIZEE - Programa de Avaliação do Potencial Sustentável de Recursos Vivos da Zona Econômica Exclusiva - visando um levantamento dos recursos vivos marinhos e coordenado pelo Ministério de Meio Ambiente, dos Recursos Hídricos e da Amazônia Legal. O presente trabalho tem o objetivo de contribuir com informações que subsidiem o Programa em questão e expandir o conhecimento sobre a diversidade malacológica da Plataforma Continental Externa e do Talude Continental do Rio Grande do Sul. O litoral compreendido entre o Cabo de São Tomé (RJ) e Chuí (RS) está inserido na Costa Sul do REVIZEE. O material de estudo é proveniente da pernada sul da campanha de Bentos, radial 45, estações hidrográficas: 6839 (32º55’S e 50º34’W - 99 m), 6840 (33º01’S e 50º12’W - 600 m), 6841 (33º00’S e 50º22’W - 500 m) e 6842 (32º57’S e 50º29’W - 187 m), realizada no dia 4 de abril de 1998 pelo Navio Oceanográfico “Prof. W. Besnard”. Estão localizadas na Plataforma Continental Externa e Talude Continental, ao largo de Rio Grande, Rio Grande do Sul, Brasil. Utilizaram-se os amostradores de fundo do tipo “van Veen”, “Box Corer” e draga de arrasto. Os moluscos bivalves foram separados dos demais grupos taxonômicos e posteriormente triados sob estereomicroscópio. Foram, então, identificados, sempre que possível, até o nível de espécie; quantificados; ilustrados (fotos e/ou desenhos); e caracterizados - dados da coleta, aspectos morfológicos e medida(s) da(s) valvas(s), habitat, distribuição geográfica e outros aspectos peculiares a cada espécie. A identificação foi feita com base em bibliografia especializada, por comparação com exemplares depositados nas coleções do Museu Oceanográfico Eliézer de C. Rios (MORG), Museu de Zoologia da USP (MZSP), Museu de Paleontologia da UFRGS (MPUFRGS) e com auxílio dos especialistas Dra. Deusinete Tenório (UFPE), Dr. Ricardo Absalão (UFRJ), Msc. Maria Júlia Chelini (USP), Carlo Magenta (MZSP) e Iara Swoboda (MORG). Contabilizou-se um material bastante volumoso, totalizando 37.422 valvas dissociadas e 993 conchas com as valvas unidas. Foram identificados 77 táxons, dos quais 60 até espécie, 13 até gênero e quatro até família, incluídos em 37 famílias de Bivalvia. As famílias com maior número de táxons foram Veneridae (oito), Tellinidae (seis) e Pectinidae (cinco). A espécie Limopsis janeiroensis foi a espécie que apresentou o maior número de exemplares, com 8.810 valvas dissociadas e 8 conchas com as valvas ainda unidas. Cita-se, pela primeira vez para o estado do Rio Grande do Sul, oito espécies de bivalves (Limatula hendersoni, Thyasira trisinuata, Cyamium copiosum, Abra brasiliana, Vesicomya albida, Transenella stimpsoni, Corbula operculata e Poromya granulata), aos quais somamse 5 gêneros citados pela primeira vez para o Brasil (Yoldiella, Cyamium, Mysella, Neaeromya e ?Glans). São feitos novos registros de maior profundidade para nove táxons (Crassinella aff. marplatensis, Macoma uruguayensis, Mactra isabelleana, Transenella stimpsoni e Vesicomya albida a 99 m; Myrtea lens a 187 m; Tellina trinitatis e Yoldia riograndensis a 500 m; e Nuculana larranagai a 600 m) e menor profundidade para dois (Abra aff. brasiliana e Cyclocardia moniliata), todas essas consideradas de origem provavelmente autóctone. Discute-se o grande volume de valvas/conchas de bivalves coletados e discute-se a provável autoctonia e aloctonia do material coletado, bem como possíveis origens de transporte das conchas a partir da Laguna dos Patos e Rio da Prata.

Les etudes theoriques et experimentales de structure genetique en milieu marin ont generalement souligne l'importance de parametres tels que le potentiel de dispersion, la distance et la fragmentation de l'habitat dans la differentiation des populations. Les nacres perlieres pinctada mazatlanica et p. Margaritifera cumingii possedent le meme potentiel de dispersion larvaire et sont respectivement reparties le long des cotes pacifiques americaines et dans les iles du pacifique central, dans des habitats cotiers a priori continu et fragmente. La distribution de la variabilite genetique dans les populations naturelles a ete etudiee simultanement a l'aide des marqueurs mitochondriaux et nucleaires anonymes, et, dans le cas de p. Margaritifera, comparee aux donnees allozymiques preexistantes. Un modele d'isolement par la distance est observe avec les marqueurs mitochondriaux entre les localites d'echantillonnage de p. Mazatlanica, du golfe de californie a panama, tandis que les marqueurs nucleaires ne mettent en evidence quasiment aucune differenciation. Cette analyse a en outre montre que l'espece avait subi les consequences genetiques d'une reduction d'effectif, et propose l'importance des courants en tant que barriere au flux genique, elements importants pour la conservation de cette espece. L'analyse de l'heterogeneite des frequences alleliques entre les echantillons de p margaritifera de polynesie (i) montre une faible variabilite mitochondriale en accord avec l'hypothese d'une recolonisation post-glaciaire de cette zone, (ii) suggere l'existence de selection sur certains locus allozymiques, (iii) met en evidence l'existence d'au moins quatre stocks differencies sur la base des locus nucleaires anonymes (iv) laisse supposer l'importance des courants dans l'organisation spatiale du flux genique.

Organisms that are part of complex ecosystems interact not only with other organisms but also with their environment, affecting ecosystem functions. In aquatic ecosystems filter feeders affect ecosystem functioning by transferring energy and nutrients from the water to the benthos. The filter-feeding unionoid mussels can have strong effects on nutrient release and biodeposition in streams, affecting primary and secondary production. In a 90-day field cage experiment during winter 2019-2020, effects of the critically endangered freshwater pearl mussel (Margaritifera margaritifera) and leaf litter on benthic macroinvertebrate communities were tested using a factorial study design. Benthic macroinvertebrates were collected from the cages and examined in the lab. No significant effects of mussels, leaf litter or their interaction on the abundance and diversity of invertebrates were found for most groups. The abundance of Simulidae was however lower in cages with mussels compared to cages without mussels. The presence of mussels in streams may therefore affect ecosystem function, here shown as a possible effect on the interspecific competition for food sources between filter feeders.
Organismer i komplexa ekosystem interagerar inte bara med andra organismer utan också med sin miljö, samt påverkar ekosystemfunktioner. I akvatiska ekosystem påverkar filtrerare ekosystemfunktioner genom att överföra energi och näringsämnen från vattnet till det bentiska samhället. De filtrerande unionoida musslorna kan ha stora effekter på närsalter och biodeposition i vattendrag, vilket påverkar primär- och sekundärproduktionen. I ett 90-dagars fältbursförsök under vintern 2019-2020 testades effekterna av den starkt hotade sötvattenspärlemusslan (Margaritifera margaritifera) och löv på bentiska samhällen. Makroevertebrater provtogs i burarna och undersöktes på lab. Det fanns inga signifikanta effekter av musslor, löv eller deras interaktion på makroevertebraters tätheter och diversitet för de flesta grupper. Tätheter av Simulidae var dock lägre i burar med musslor jämfört med burar utan musslor. Förekomsten av musslor i vattendrag kan därför påverka ekosystemets funktion, här visat som en möjlig effekt på mellanartskonkurrens mellan filtrerare.

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Mussel culture is an important activity in the state of Santa Catarina, where is developed in almost all the bays and roadsteads. This activity places the state in evidence in Latin America s production. However, this development has been spread in a disorganized way, generating environmental impacts, mainly those arisen from bio deposition of organic material at cultivation areas. The main purpose of this research was to evaluate a roadstead under cultivating influences, determining changes in sediment and benthic macro invertebrate s communities. Three sampling points were chosen according to activity time and intensity. Therefore, the level of organic material in the sediment, the structure and composition of the benthic community were accessed. Results showed that sand was the main material in sediment and rough particles are predominant near the shore side. The carbonate, silt and gravel levels were high at intense cultivating areas. However, differences concerning organic materials were not observed between cultivated and non-cultivated areas. The fauna collected was represented by 65 species belonging to 7 phyla, being the ophiurans more frequently found in the samples. Even though there were no meaningful differences between time and place for picking up samples, higher density and abundance occurred during winter and fall within non-cultivated areas, where debris eater s mollusks are highlighted. Higher richness and diversity were detected during winter and summer time in intensively cultivated areas, with great participation of polychaeta species. Results showed that mussel cultures are not causing direct impacts once the wind action promotes a situation of high hydrodynamics in the region and is a determinative factor in sediment constitution and benthic fauna.
O cultivo de mexilhões é uma atividade econômica importante no Estado de Santa Catarina, onde é desenvolvido em praticamente todas as baías e enseadas, e cuja produção é destaque para América Latina. O crescimento constante dos cultivos se fez de forma desordenada, sem considerar a geração de impactos ambientais, essencialmente aqueles decorrentes da biodeposição de matéria orgânica nas áreas de cultivo. Este trabalho teve como objetivo avaliar uma enseada sob influência da mitilicultura, determinar as alterações no sedimento e na comunidade de macro-invertebrados bentônicos. Foram selecionados três pontos de amostragem considerando o tempo e a intensidade da atividade de cultivo. Durante o período de um ano foram analisados os teores de materiais minerais e biogênicos no sedimento, bem como a composição e a estrutura da comunidade bentônica. Os resultados indicaram a fração areia como material de maior concentração no sedimento, com predominância de partículas grosseiras nas áreas mais próximas da orla. Os teores de carbonatos, silte e cascalho, foram mais elevados na área de cultivo mais intenso, contudo não se observou diferença quanto à matéria orgânica nas diferentes áreas de estudo. Quanto à fauna bentônica, foram coletadas 65 espécies pertencentes a sete filos sendo que os ofiuros foram os mais freqüentes nas amostras. Apesar das diferenças entre os períodos e os locais de coleta não serem significativas, os resultados apontaram uma maior abundância e densidade de indivíduos no inverno e no outono, nas áreas sem cultivos, com destaque aos moluscos detritívoros, e a maior riqueza e diversidade foram detectadas no inverno e verão na área com cultivo mais intenso, com participação maior de espécies de poliquetos. Concluise que os cultivos de mexilhões não estão causando impacto direto no ambiente bentônico da Enseada da Armação do Itapocoroy, sendo a ação indireta dos ventos, ao promover um maior hidrodinamismo na região, o fator determinante na caracterização na constituição do sedimento e na estrutura e composição da fauna bentônica.

The freshwater mussel fauna of the Clinch River in Southwest Virginia has declined in recent decades, principally due to habitat degradation from poor land-use patterns and pollutants. A study was undertaken to determine the feasibility of using river water in a flow-through culture system to rear juvenile freshwater mussels. The culture method placed juvenile mussels, confined in small dishes, into oval troughs supplied with untreated river water. Two of three years produced acceptable survival rates of 27% and 19% to an age of 90 days or greater. The third year yielded very low survival rates of less than 3%, demonstrating that failures in culture production can occur. Growth rates of juveniles in the culture system using river water were almost double those in laboratory culture systems, provided that juveniles were placed in the oval troughs during June. Otherwise, growth was comparable to that attained in laboratory culture systems.
Ph. D.

Freshwater mussel propagation techniques were tested at the Virginia Department of Game and Inland Fisheries Aquatic Wildlife Conservation Center through a series of three experiments. Experiment 1 tested the suitability of a pond and raceway for rearing juvenile oystermussels (Epioblasma capsaeformis) and wavyrayed lampmussel (Lampsilis fasciola). This experiment was prematurely terminated due to predation on mussels by fathead minnows (Pimephales promelas). Experiment 2 evaluated growth and survival of juvenile rainbow mussels in outdoor troughs and indoor aquaria. There was no significant difference in survival or growth between the two systems. Experiment 3 used troughs similar to those in Experiment 2 to rear E. capsaeformis and L. fasciola under two silt regimes. Survival for Experiment 3 was significantly greater for L. fasciola. The comparison between silt regimes indicated that individuals in the high-silt treatment had better survival than those in the low-silt treatment. The difference between these 2 treatments may be a reflection of increased escapement in the low-silt treatment, which may have resulted from more frequent disturbance during sampling. Growth of L. fasciola was significantly greater than E. capsaeformis, and was greater in the low-silt treatment. A habitat survey of the Clinch River, Virginia was conducted from Blackford, Clinch River Kilometer (CRK) 478 to the Tennessee border, CRK 325. Physical characteristics identified in the survey were combined with water quality and impact source data to develop a habitat suitability index for freshwater mussels within this study reach. Model parameters were indexed and weighted to give a final suitability ranking. Habitat units having the highest overall ranking included: Nash Ford (CRK 449), Artrip (CRK 442), several riffles and runs below Carterton (CRK 417), upstream of Mill Island (CRK 389.5), and Pendleton Island (CRK 365), and Speers Ferry (CRK 333-325). Potential locations for habitat restoration projects and additional monitoring were also identified.
Master of Science

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The objective of this study was to model the habitat suitability for the bivalve Corbicula fluminea, and the fishes Pimelodus pintado, Parapimelodus nigribarbis and Loricariichthys anus in relation to environmental variables in Guaíba Lake, Rio Grande do Sul, Brazil. Guaíba Lake, a large water body beside Porto Alegre city with approximately 50 km long and 19 km wide at the widest point. It has north to south pollution gradient, different sediment characteristics and habitat configurations in its margins. Samples (n = 54) of C. fluminea were collected with Ekman dredge (10 subsamples, sampled area=2225 cm2) and the fish sampled with gill nets with different mesh sizes exposed during 20 hours at the same sampling points. We used Generalized Additive Models (GAM) to fit a model for C. fluminea abundances. The variables evaluated for the model fitting comprise the distance from streams and channels, the distance in meters from north to south, depth, water velocity, amount of thermotolerant coliform (TC) and sediment characteristics. The model selected for C. fluminea (r2 = 0. 55) used depth (p = 2-16) and the diversity sand grain sizes (p = 2. 52-15) as predictors. For fish modeling, three approaches were evaluated (GAM), Boosted Regression Trees (BRT) and Generalized Linear Modeling (GLM).GLM was the method more accurately among the three methodologies for the three species: P. pintado, r2 = 0. 60, Root Mean Squared Error (RMSE) = 4. 71; P. nigribarbis, r2 = 0. 84, RMSE = 6. 77; and L. anus, r2 = 0. 72, RMSE = 2. 40. The most important predictors in the model for P. pintado were related to the sediment and current speed. The model selected for P. nigribarbis had the most important variables: depth, distance from margins and CT. The adjusted model for L. anus had the most important predictors CT and distance from margins. The results suggest that the distribution of C. fluminea, P. pintado, P. nigribarbis and L. anus is not random, though structural and environmental predictors influence the habitat occupation of these organisms. Furthermore, the results show the spatial distribution of species assessed on a small-scale, concerning the majority of spatial distribution studies. Thus, the findings contribute to a better understanding of the autoecology for those species, allowing the prediction to future scenarios in Lake Guaíba, constituting as a tool for environmental management and conservation actions.
O objetivo deste estudo foi modelar a adequabilidade de hábitat para o bivalve Corbicula fluminea e os peixes Pimelodus pintado (pintado), Parapimelodus nigribarbis (mandi) e Loricariichthys anus (viola) em relação a variáveis ambientais no Lago Guaíba, Rio Grande do Sul,, Brasil. O Lago Guaíba é um grande corpo hídrico que banha a cidade de Porto Alegre com aproximadamente 50 km de comprimento e 19 km de largura no ponto mais largo, apresenta um gradiente de poluição de norte ao sul e diferentes características de sedimento e configurações de hábitat nas margens. As amostras (n=54) de C. fluminea foram coletadas com draga Ekman (10 sub-amostras, área total amostrada = 2,225 cm2) e os peixes amostrados com redes com diferentes tamanhos de malha por 20 horas nos mesmos pontos de amostragem. As variáveis avaliadas para o ajuste do modelo compreenderam medidas de distância da margem, distância de arroios e canais, distância em metros de norte a sul, profundidade, velocidade da água, quantidade de coliformes termo-tolerantes (CT) e características do sedimento. O modelo de distribuição usado para C. fluminea foi um Generalized Additive Models (GAM). O modelo selecionado para C. fluminea (r2 = 0. 55) usou profundidade (p = 2e-16) e a diversidade dos tamanhos dos grãos de areia (p = 2. 52- 15) como preditores. Para a modelagem dos peixes, três metodologias foram avaliadas (GAM), Boosted Regression Trees (BRT) e Generalized Linear Modeling (GLM). GLM foi o método com maior acurácia dentre as três metodologias para as três espécies: P. pintado, r2 = 0. 60, Root Mean Squared Error (RMSE) = 4,71; P. nigribarbis, r2 = 0,84, RMSE = 6. 77; e L. anus, r2 = 0,72, RMSE = 2,40. Os preditores mais importantes no modelo para P. pintado foram relacionados a profundidade, características do sedimento e velocidade de corrente. O modelo selecionado para P. nigribarbis teve como variáveis mais importantes: profundidade, distância dos tributários e CT. O modelo ajustado para L. anus teve como preditores mais importantes CT e distância das margens. Os resultados apresentados sugerem que a distribuição de C. fluminea, P. pintado, P. nigribarbis e L. anus não é aleatória e preditores estruturais e ambientais influenciam a ocupação de hábitat destes organismos. Além disso, os resultados apresentam a distribuição espacial para as espécies avaliadas em pequena escala, considerando a maioria dos estudos de distribuição espacial. Desta maneira, os achados contribuem para um melhor entendimento da autoecologia das espécies, permitindo a previsão de cenários futuros no Lago Guaíba, além de constituir uma ferramenta para gestores ambientais e ações conservacionistas.

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Conselho Nacional de Pesquisa e Desenvolvimento Cient?fico e Tecnol?gico - CNPq
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
The objective of this study was to model the habitat suitability for the bivalve Corbicula fluminea, and the fishes Pimelodus pintado, Parapimelodus nigribarbis and Loricariichthys anus in relation to environmental variables in Gua?ba Lake, Rio Grande do Sul, Brazil. Gua?ba Lake, a large water body beside Porto Alegre city with approximately 50 km long and 19 km wide at the widest point. It has north to south pollution gradient, different sediment characteristics and habitat configurations in its margins. Samples (n = 54) of C. fluminea were collected with Ekman dredge (10 subsamples, sampled area=2225 cm2) and the fish sampled with gill nets with different mesh sizes exposed during 20 hours at the same sampling points. We used Generalized Additive Models (GAM) to fit a model for C. fluminea abundances. The variables evaluated for the model fitting comprise the distance from streams and channels, the distance in meters from north to south, depth, water velocity, amount of thermotolerant coliform (TC) and sediment characteristics. The model selected for C. fluminea (r2 = 0.55) used depth (p = 2-16) and the diversity sand grain sizes (p = 2.52-15) as predictors. For fish modeling, three approaches were evaluated (GAM), Boosted Regression Trees (BRT) and Generalized Linear Modeling (GLM). GLM was the method more accurately among the three methodologies for the three species: P. pintado, r2 = 0.60, Root Mean Squared Error (RMSE) = 4.71; P. nigribarbis, r2 = 0.84, RMSE = 6.77; and L. anus, r2 = 0.72, RMSE = 2.40. The most important predictors in the model for P. pintado were related to the sediment and current speed. The model selected for P. nigribarbis had the most important variables: depth, distance from margins and CT. The adjusted model for L. anus had the most important predictors CT and distance from margins. The results suggest that the distribution of C. fluminea, P. pintado, P. nigribarbis and L. anus is not random, though structural and environmental predictors influence the habitat occupation of these organisms. Furthermore, the results show the spatial distribution of species assessed on a small-scale, concerning the majority of spatial distribution studies. Thus, the findings contribute to a better understanding of the autoecology for those species, allowing the prediction to future scenarios in Lake Gua?ba, constituting as a tool for environmental management and conservation actions.
O objetivo deste estudo foi modelar a adequabilidade de h?bitat para o bivalve Corbicula fluminea e os peixes Pimelodus pintado (pintado), Parapimelodus nigribarbis (mandi) e Loricariichthys anus (viola) em rela??o a vari?veis ambientais no Lago Gua?ba, Rio Grande do Sul,, Brasil. O Lago Gua?ba ? um grande corpo h?drico que banha a cidade de Porto Alegre com aproximadamente 50 km de comprimento e 19 km de largura no ponto mais largo, apresenta um gradiente de polui??o de norte ao sul e diferentes caracter?sticas de sedimento e configura??es de h?bitat nas margens. As amostras (n=54) de C. fluminea foram coletadas com draga Ekman (10 sub-amostras, ?rea total amostrada = 2,225 cm2) e os peixes amostrados com redes com diferentes tamanhos de malha por 20 horas nos mesmos pontos de amostragem. As vari?veis avaliadas para o ajuste do modelo compreenderam medidas de dist?ncia da margem, dist?ncia de arroios e canais, dist?ncia em metros de norte a sul, profundidade, velocidade da ?gua, quantidade de coliformes termo-tolerantes (CT) e caracter?sticas do sedimento. O modelo de distribui??o usado para C. fluminea foi um Generalized Additive Models (GAM). O modelo selecionado para C. fluminea (r2 = 0.55) usou profundidade (p = 2e-16) e a diversidade dos tamanhos dos gr?os de areia (p = 2.52- 15) como preditores. Para a modelagem dos peixes, tr?s metodologias foram avaliadas (GAM), Boosted Regression Trees (BRT) e Generalized Linear Modeling (GLM). GLM foi o m?todo com maior acur?cia dentre as tr?s metodologias para as tr?s esp?cies: P. pintado, r2 = 0.60, Root Mean Squared Error (RMSE) = 4,71; P. nigribarbis, r2 = 0,84, RMSE = 6.77; e L. anus, r2 = 0,72, RMSE = 2,40. Os preditores mais importantes no modelo para P. pintado foram relacionados a profundidade, caracter?sticas do sedimento e velocidade de corrente.. O modelo selecionado para P. nigribarbis teve como vari?veis mais importantes: profundidade, dist?ncia dos tribut?rios e CT. O modelo ajustado para L. anus teve como preditores mais importantes CT e dist?ncia das margens. Os resultados apresentados sugerem que a distribui??o de C. fluminea, P. pintado, P. nigribarbis e L. anus n?o ? aleat?ria e preditores estruturais e ambientais influenciam a ocupa??o de h?bitat destes organismos. Al?m disso, os resultados apresentam a distribui??o espacial para as esp?cies avaliadas em pequena escala, considerando a maioria dos estudos de distribui??o espacial. Desta maneira, os achados contribuem para um melhor entendimento da autoecologia das esp?cies, permitindo a previs?o de cen?rios futuros no Lago Gua?ba, al?m de constituir uma ferramenta para gestores ambientais e a??es conservacionistas.

Research Doctorate - Doctor of Philosophy (PhD)
Seagrasses are generally known for their significant role in marine and estuarine ecosystems. The growth in human population along the coastal regions, where the seagrass live, makes them very vulnerable to the human-induced disturbances. Large-scale seagrass decline has been reported worldwide due to this problem. There is an evident need to monitor seagrass population to predict future changes and to protect coastal ecosystems from further degradation. The decline of seagrass beds results in their fragmentation and appearance of smaller patches of seagrass isolated from each other, The first goal of this thesis is to study how fragmentation of seagrass beds influence their role in the ecosystem. This study focused on how fragment size and its distance from the main bed influence abundance of mobile epifauna associated with seagrass. Artificial seagrass units were constructed to mimic the seagrass fragmentation at a small scale. The result from this experiment suggested neither fragment size nor on-patch location (edge vs middle) adequately account for variation in the abundance of seagrass-associated epifauna. The distance from large beds of seagrass was important, however. Fragments placed far away from the natural seagrass were colonized to a grater degree than the fragments placed near seagrass beds. Large fragments were also colonized more than the small ones at the furthest distance from natural beds. Thus, fragmentation does not necessary lead to decease in epifaunal abundances. The small isolated patches may serve as refuge sites of the marine organisms. The second part of the thesis specifically deals with the effect of heavy metal contamination on seagrass and associated fauna. Despite the well-publicised issue of metal contamination of highly urbanised estuaries and its effect on seagrasses, this is the first study that assessed the contamination effect on the seagrass community using a range of bioindicators and biomarkers in order to obtain an integral picture of the contamination effect. It was found the seagrass, Zostera capricorni accumulated high concentration of heavy metals and provide a good correlation between the concentration in their tissues and in the sediment. Moreover, there was no evidence of impact on the seagrass biomass, shoot and leaf density. Thus, this seagrass can be used as a good bioindicator because of the above reasons, and also they are sedentary and abundant in the polluted site, which makes them easily available for sampling. The abundance of epifaunal organisms associated with the seagrass was used as a bioindicator at the community level. Only gastropods decreased in abundance in the contaminated site in spring (when the number of seagrass fauna generally higher), and this might potentially be a good bioindicator in this system. Shell dimension and fluctuating asymmetry were used as biomarkers for this purpose. It was found that a bivalve associated with seedgrass, the ark cockle Anadara trapezia, in the polluted location (Cockle Baby) showed distinct morphological characters compared to the ones in unpolluted locations. The cockles were bigger, heavier and had bigger shell-height/shell-length ratios, but appeared much less abundant, which is contradicted with historically high abundance of this species in this location (Cockle Bay). Moreover, the cockles exhibited higher shell asymmetry compared to the ones in unpolluted locations. Leaf dimensions and leaf asymetry of seagrasses, and Halophila ovalis, were also employed as biomarkers. The results revealed that there was no significant difference in leaf asymmetry of seagrass from polluted and unpolluted locations. The effect of heavy metal might have been surpassed by other factors such as nutrients, which were also high in the polluted area. Interestingly, the leaves of seagrass in the polluted location compared to unpolluted ones were longer and wider indicating that there was a possibility that the detrimental effect of heavy metals on seagrass was compensated by favourable effects of elevated nutrients. Laboratory studies were conducted to determine whether heavy metals themselves affected seagrasses. The results revealed that heavy metals exposure affected the growth of seagrass, and lead to increase in fluctuating asymmetry. Thus, leaf dimensions, shell dimensions and fluctuating asymmetry of seagrass and seagrass associated fauna were sensitive to metal pollution and they might be suitable to indicated contamination in seagrass system.

Dissertação de Mestrado em Biologia Clínica e Laboratorial
A leptospirose é uma doença zoonótica reemergente com distribuição mundial provocada por espiroquetas patogénicas do género Leptospira. As leptospiras patogénicas são mantidas na natureza por numerosos reservatórios selvagens e domésticos, que constituem uma potencial fonte de infeção para humanos e outros hospedeiros suscetíveis. O habitat natural destas espiroquetas é o rim dos hospedeiros infetados, sendo eliminadas para o ambiente via urina, onde se mantém viáveis em condições de humidade e temperatura adequadas, nomeadamente em águas doces superficiais Os estudos que têm vindo a ser efetuados na região de Trás-os-Montes demonstram elevadas prevalências de anticorpos em animais domésticos e selvagens, corroboradas pelo isolamento de estirpes locais, nomeadamente pelo isolamento do serovar Altodouro – um novo serovar de Leptospira kirschneri, isolado a partir de Mus musculus. O presente estudo tem por objetivo detetar a presença de leptospiras em amostras de águas e de bivalves de água doce, em vários pontos do rio Sabor. Foram analisadas 40 amostras de bivalves e amostras de águas que foram recolhidas nos locais onde forma capturados os bivalves (n=5). Estas amostras foram pré-preparadas (as águas foram filtradas e os bivalves macerados) para posterior extração de DNA, realizou-se a técnica de Nested-PCR e em seguida a eletroforese em gel de agarose. Das 45 amostras, detetou-se a presença de DNA leptospírico em dois bivalves e em duas amostras de águas. Dos três pontos (troços) do rio Sabor amostrados, três revelaram a presença de leptospiras. O presente estudo tem um carater inovador e permitiu revelar a presença de bactérias do Leptospiras patogénicas, ao longo do rio Sabor, sendo necessário tomar medidas de prevenção no âmbito da Saúde Pública, nas áreas afetadas. A obtenção de resultados positivos neste tipo de amostras é difícil pelas baixas concentrações de DNA leptospírico, indicando uma boa seleção das técnicas aplicadas neste estudo.
Leptospirosis is a re-emerging zoonotic disease with worldwide distribution, caused by pathogenic spirochetes of the genus Leptospira. Pathogenic leptospires are maintained in the ecosystems by numerous wild and domestic reservoirs, which constitute a potential source of infection for humans and othersusceptible hosts. The natural habitat of these spirochetes is the kidney of the infected hosts, being eliminated to the environment via urine, where they remain viable under adequate humidity and temperature conditions, namely in superficial fresh water. The studies that have been carried out in the region of Trás-os-Montes demonstrate high prevalence of antibodies among domestic and wild animals, corroborated by the isolation of local strains, namely by the isolation of the serovar Altodouro – a new serovar of Leptospira kirschneri, isolated from a Mus musculus. The present study aims to detect the presence of leptospires in water samples and freshwater bivalves at various points in the Sabor river. Forty samples of bivalves and also water samples that were collected from the places where the bivalves were captured were analyzed (n=5). These samples were pre-prepared (the water samples were filtered and the bivalves macerated) for further DNA extraction, the Nested-PCRtechnique was performed, followed by agarose gel electrophoresis. Of the 45 samples, the presence of Leptospiral DNA was detected in three of the bivalve samples and in two water samples. The present study has an innovative character and reveals the presence of pathogenic leptospires along the Sabor river, therefore, making it necessary to take preventive measures in the context of Public Health in the affected areas. Obtaining positive results in this type of samples is difficult, due to the low concentrations of leptospiral DNA, indicating a good selection of the techniques applied in this study.

I examined the suspension feeding of four freshwater unionid mussels, Elliptio complanata, Elliptio dilatata, Fusconaia flava and Strophitus undulatus to help explain how more than 30 species can coexist in a single river, as well as to contribute new insights into their basic biology. I examined whether the flux of algae affected the suspension feeding (clearance rate, CR) of unionids in a flow chamber. CR varied with seston flux (J = UC, where U is the velocity and C is the algal concentration) for the 4 species examined. The lotic species (E. dilatata) cleared up to four times more water than lentic species (E. complanata). Differences in CRs were found among E. dilatata, F. flava, and S. undulatus from the same hydrodynamic habitat at the highest flux tested; the CR of E. dilatata varied with the hydrodynamics of its native river. These results provide new insight into how seston flux influences unionid suspension feeding, which may help to explain niche breadth in this group.