Les lagunes côtières sont des écosystèmes semi-fermés à l'interface de la terre et des océans et sous l'influence de ces deux compartiments. De par ces caractéristiques, elles sont soumises à de fortes variations spatiales et saisonnières de leurs ressources trophiques. De par leur nature fermée et peu profonde, elles vont amplifier la force des processus qui conditionnent la disponibilité des ressources alimentaires et par conséquent l'écophysiologie des organismes benthiques qui composent les assemblages associés. Ce travail de thèse se propose de caractériser l'écophysiologie trophique de deux espèces de bivalves filtreurs (Nodipecten subnodosus et Spondylus crassisquama) au sein d'une lagune du Pacifique Nord-est (Basse Californie, Mexique). Une approche mufti-tissus et multi-traceurs (isotopes stables, acides gras, stérols et analyse isotopique sur acides gras) a été adoptée afin de pouvoir caractériser l'écologie trophique des espèces, mais aussi leurs régulations physiologiques face aux variations environnementales. Deux facteurs clés se sont révélés largement explicatifs de la variabilité spatio-temporelle observée dans le régime alimentaire : la période (hiver vs été) et la localisation dans la lagune par rapport à l'embouchure. L'importance des apports de phytoplancton océanique a été démontrée dans l'ensemble de la lagune, avec une contribution plus importante de diatomées océaniques notamment en période estivale pour les individus à proximité de l'embouchure. Par ailleurs, les bivalves en fond de lagune semblaient davantage dépendre de la matière organique locale, en particulier issue du recyclage bactérien, voire de la production des herbiers de phanérogames. Ces contrastes spatiaux se reflétaient également dans la composition des membranes cellulaires, mettant en évidence les interactions entre apports trophiques et régulations métaboliques des compositions en acides gras chez ces deux bivalves. Cette thèse présente une approche intégrée dédiée à la compréhension des variations spatiales et saisonnières des ressources trophiques d'un écosystème lagunaire, ainsi que leurs répercutions trophiques et physiologiques sur les assemblages benthiques. / Coastal lagoons are semi-enclosed ecosystems at the interface between land and ocean and under the influence of these two compartments. Owing to these characteristics these ecosystems are submitted to spatial and seasonal variations in their trophic resources. Because of their enclosed and shallow nature, lagoons amplify the intensity of processes conditioning the availability of food resources and consequently the ecophysiology of the benthic organisms which compose associated assemblages. This thesis aims to characterize the trophic ecophysiology of two species of suspension feeding bivalves (Nodipecten subnodosus and Spondylus crussisquomo) within a lagoon of Northeast Pacific (Baja California, Mexico). A mufti-tissue and multi-tracer approach (stable isotopes, fatty acids, sterols, and isotope analysis on fatty acids) was used in order to characterise the trophic ecology of both species, as well as their physiological regulations against environmental variations. Two key factors have been found to explain the observed spatio-temporal variability: the period (winter vs summer), and the location in the lagoon with respect to the distance from the mouth. The importance of oceanic phytoplankton inputs has been highlighted throughout the lagoon, with a greater contribution of oceanic diatoms particularly during the summer period for individuals near the mouth. Bivalves from the inner lagoon seemed more dependent of local organic matter, in particular resulting from bacterial recycling, or even from the production of eelgrass. These spatial contrasts were also reflected in the composition of cell membranes, highlighting the interactions between trophic contributions and metabolic regulation of fatty acid composition in both bivalves. This thesis presents an integrated approach to understand spatial and seasonal variations of the trophic resources of a lagoon ecosystem, as well as their trophic and physiological repercussions on benthic assemblages.

No description available.

The Enemy Release Hypothesis proposes that introduced species often achieve larger individual sizes and greater population abundance in their introduced range because they have escaped their natural enemies - predators and parasites - that regulate populations in their native range. The main objective of this study is to test the Enemy Release Hypothesis (ERH) by investigating the identity, prevalence and intensity of parasites in two marine species introduced to New Zealand - the recently introduced but spatially restricted Asian portunid crab, Charybdis japonica, and the longer-established Asian nesting mussel, Musculista senhousia. Host choice of a native generalist parasite presented with the non-native and native mussels, and prey selection by a native predator presented with these bivalves will be examined. This is the first study of its kind in New Zealand. The parasite fauna of the only established New Zealand population of C. japonica (Waitemata Harbour, Auckland), was compared to that from (a) a population of C. japonica from its native region (Japan) and (b) to multiple populations of the native New Zealand crab Ovalipes catharus, a native New Zealand portunid. Results showed the introduced crab harboured only one species of endoparasite (a nematode), and two types of melanised lesions. Neither the parasite nor the lesions were present in the native crab populations. The native crab was host to only one parasite species, which occurred at very low prevalence, and was present in only one of the six populations examined from throughout New Zealand. Carapace width in the introduced crab was no larger than that reported in literature from its native are, but was larger than carapace widths of the Japanese sample. M. senhousia was examined from five sites within New Zealand. Parasites in M. senhousia were compared with a sympatric native bivalve, Austrovenus stutchburyi, two native mytilids, (Perna canaliculus and Xenostrobus pulex) and with samples of M. senhousia from Italy and the USA where it is introduced, and Japan where it is native. Two native generalist parasites, the pea crab Pinnotheres novaezelandiae, and a copepod, were found within M. senhousia in New Zealand, but only at low prevalence. A greater array of organisms was associated with the native bivalves. No parasites were recovered from any of the overseas samples of M. senhousia, including the Japanese samples. This may be caused by the preservation medium used, but could be a true reflection of the parasite fauna in these populations. The site where the two native parasites were exploiting M. senhousia was the only site sampled where two native mussels, P. canaliculus and X. pulex, also occurred. Consequently, effects of these two generalist parasites on the three mussel species were examined. In P. canaliculus, presence of native pea crabs was associated with lower tissue dry weight and greater shell depth. Shell width and depth were both greater in the presence of copepods. However, the prevalence of pea crabs and copepods was much lower in M. senhousia compared to the two native mussels, indicating some release from the effects of these parasites for the non-native species. Experimental choice tests showed that the pea crab, P. novaezelandiae, does not actively select M. senhousia as a host, preferring the larger native mussel, P. canaliculus. Rates of infection of M. senhousia are, therefore, likely to remain low in natural habitats where there are large numbers of native hosts. In addition, a generalist predator, the crab O. catharus, showed no preference when foraging on the three mussel species under experimental conditions. Thus, some predation pressure may be exerted on M. senhousia by this native crab in the natural environment. Investigation of multiple populations of both native and non-native species has shown large variation in parasite prevalence and intensity among populations of each species. After examining C. japonica and the comparable native O. catharus, evidence to support the ERH was found to be weak. As the native crab was relatively free of parasites, it seems unlikely that parasite infection is important within native populations and therefore, the success of C. japonica is unlikely to be caused by comparatively greater freedom from parasites (a central tenet of the ERH). There was also no evidence for host-switching by native parasites into the introduced C. japonica population. In contrast, native parasites were present at very low prevalence in the non-native mussel M. senhousia. Length of time since introduction can be an important factor in host switching between native and introduced hosts, but unless prevalence of these parasites is high, the introduced species still escapes from enemies that could control a population. Therefore every non-native species needs to be examined using multiple populations to investigate variation in parasite fauna, prevalence and intensity, as the same species, if introduced numerous times, could potentially show contrasting results for the ERH unless multiple populations are examined.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Rhipidodontini (Rhipidodonta Mörch, 1853 + Diplodon Spix in Wagner, 1827) é grupo de bivalves de água doce tem taxonomia complicada, devido às descrições originais sucintas e muitas vezes pouco ou não ilustradas, somado a isto, estes bivalves carecem de uma revisão detalhada. Estas lacunas de informação têm gerando uma grande flutuação nas espécies consideradas válidas pelos diferentes autores, dificultando a identificação das mesmas, assim como da biologia e distribuição. Assim, se propôs neste estudo a revisão taxonômica das espécies de Rhipidodontini nas bacias do alto rio Paraná, rio São Francisco e rios costeiros do Atlântico Leste, Norte e Nordeste. Para alcançar este objetivo vistoriamos material em coleções no Brasil e exterior. Coletas foram realizadas em diversas localidades para obtenção de exemplares para descrição das partes moles e gloquídios. As informações obtidas, somado ao descrito na literatura, foram utilizadas para traçar um panorama de distribuição e conservação das espécies. As principais características das conchas foram utilizadas para elaboração de uma chave dicotômica para auxílio na identificação. Uma análise morfométrica foi empregada com o intuito de distinguir as espécies através da forma da concha. Reconhecemos Diplodon e Rhipidodonta incluídos na tribo Rhipidodontini. Em Diplodon foram identificadas seis espécies nas bacias estudadas: Diplodon ellipticus Spix in Wagner, 1827; Diplodon fontainianus (dOrbigny, 1835); Diplodon jacksoni Marshall, 1928; Diplodon multistriatus (Lea, 1831); Diplodon paulista (Ihering, 1893) e Diplodon rhombeus Spix in Wagner, 1827. Apesar de Diplodon granosus (Bruguière, 1792) possuir extensos registros na região estuada, a espécie foi limitada a região amazônica na nossa avaliação. Em Rhipidodonta, foi reconhecida uma única espécie, Rhipidodonta garbei (Ihering, 1910). Entre estas espécies, temos algumas tradicionalmente reconhecidas como válidas (e.g. D. ellipticus e D. granosus), contudo, outras foram revalidadas (e.g. D. jacksoni e R. garbei) e redefinidas perante a análise do material tipo, partes moles e gloquídio. Não foi possível a eleição de uma única característica morfológica para a separação das espécies, porém detalhes das brânquias, estômago, contorno da concha e escultura umbonal figuraram entre as mais utilizadas. Para a separação dos gêneros de Rhipidodontini foram empregados atributos dos gloquídios (e.g. gancho gloquidial, protuberância e forma do gloquídio) e das brânquias (e.g. forma da brânquia e conexão entre as lamelas). A chave dicotômica com base em características das conchas auxiliou a separar as espécies de Rhipidodontini. A análise morfométrica constituiu uma ferramenta útil na separação das espécies, corroborando as identificações prévias. Salientamos que o estudo aqui apresentado deve ser expandido para outras bacias hidrográficas sul-americanas com o intuito de se conhecer a real diversidade destes bivalves de água doce / Rhipidodontini (Rhipidodonta Mörch, 1853 + Diplodon Spix in Wagner, 1827) is a tribe of freshwater bivalves with a complicated taxonomy, mainly due to the poor original descriptions, sometimes without illustrations, thereby a group needing a careful revision. The lack of information created a great variation in species considered valid by deferent authors, complicating the study of other aspects like distribution and biology. Therefore, were proposed in this study the taxonomic revision of Rhipidodontini in watersheds of Paraná River, São Francisco River and Coastal Atlantic rivers of East, North and Northeast. In order to achieve this goal museum collections were visited in Brazil and in other countries. Fields surveys were done in several localities to obtain fresh specimens to describe soft parts and glochidium. The information obtained added to information available in the literature were used to present and overview about distribution and conservation of the species. The main shell characteristics were employed to prepare an identification key to aid species differentiation. A morphometric analysis was used to distinguish species based on shell measurements. Diplodon and Rhipidodonta were recognized as valid genus included in tribe Rhipidodontini. Inside Diplodon were identified six species in the surveyed watersheds: Diplodon ellipticus Spix in Wagner, 1827; Diplodon fontainianus (dOrbigny, 1835); Diplodon jacksoni Marshall, 1928; Diplodon multistriatus (Lea, 1831); Diplodon paulista (Ihering, 1893) and Diplodon rhombeus Spix in Wagner, 1827. Despite Diplodon granosus (Bruguière, 1792) has extensive records in the studied region, this species was restricted to Amazonian region in our evaluation. In the genus Rhipidodonta were recognized only one species Rhipidodonta garbei (Ihering, 1910). Among these species, there are some traditionally accepted as valid (e.g. D. ellipticus e D. granosus), however other were revalidated and redefined based on analysis of type material, soft parts and glochidium (e.g. D. jacksoni e R. garbei). It was impossible to choose only one morphologic characteristic to discriminate the species, but details of gills, stomach, shell outline and umbonal sculpture were among the most important. The genera of Rhipidodontini were separate using attributes of glochidium (e.g. gloquidial hook, protuberance and shape of glochidium) and gills (e.g. gills shape and lamellar connections). The identification key based on shell characteristics helped to distinguish the species of Rhipidodontini. The morphometric analysis was considered a useful tool to separate the species, supporting the previous identification. The evaluation presented here should be expanded to other South American hydrographic catchments for determining the real diversity of these freshwater mussels

The Late Rhaetian (Late Triassic) extinction event is characterised by shelled species showing a reduction in size, and thickness, which together with changed mineralogy is thought to be as a result of increased atmospheric pCO2 levels. Similar morphological changes have been demonstrated for extant species exposed experimentally to high CO2 leading to the hypothesis that Late Triassic extinctions were linked with global ocean acidification and increased oceanic palaeotemperatures. Consequently, the aim of this present work was to test this ocean acidification hypothesis by investigating morphological changes in selected shelled fossil species across this extinction event, and attempt to correlate them with changes in environmental temperature and pCO2. The abundance, size, shell thickness and mineralogy was determined for three common species, the bivalves Liostrea hisingeri and Plagiostoma gigantea and the ostracod Ogmoconchella aspinata collected from Triassic and Jurassic rocks from two locations in southwest England. Palaeotemperature was reconstructed from examination of these fossils and from the literature and atmospheric pCO2 estimated from published accounts. The shell size of bivalves increased during periods of high pCO2 and high palaeotemperature at both locations. Ostracod carapace sizes increased at St Audrie’s Bay but decreased at Lyme Regis during periods of high pCO2, while ostracod carapace size decreased during periods of high palaeotemperature at St Audrie’s Bay. However, ostracod shell thickness increased and decreased as pCO2 increased but shows no relationship with palaeotemperature at either location. Laboratory experiments on the effect of elevated pCO2 and elevated temperature on three modern species of ostracod was carried out. Modern species Leptocythere sp. and L. castanea subjected to either elevated pCO2 or elevated temperature showed increased dissolution, however size and thickness did not significantly change. In the same experimental conditions L. lacertosa showed increased dissolution however size continued to increase, while thickness was maintained. Comparison of fossil bivalve and ostracod data to modern high pCO2 and high temperature experiments illustrates some correlations to the modern experiments results indicating high pCO2 and high palaeotemperature conditions could have been occurring during the Triassic-Jurassic boundary interval. From the evidence presented, combined with an appropriate trigger (CAMP volcanism), it can be concluded that both ocean acidification and palaeotemperature were contributing to the species adaptations identified across the Triassic-Jurassic boundary interval.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Rhipidodontini (Rhipidodonta Mörch, 1853 + Diplodon Spix in Wagner, 1827) é grupo de bivalves de água doce tem taxonomia complicada, devido às descrições originais sucintas e muitas vezes pouco ou não ilustradas, somado a isto, estes bivalves carecem de uma revisão detalhada. Estas lacunas de informação têm gerando uma grande flutuação nas espécies consideradas válidas pelos diferentes autores, dificultando a identificação das mesmas, assim como da biologia e distribuição. Assim, se propôs neste estudo a revisão taxonômica das espécies de Rhipidodontini nas bacias do alto rio Paraná, rio São Francisco e rios costeiros do Atlântico Leste, Norte e Nordeste. Para alcançar este objetivo vistoriamos material em coleções no Brasil e exterior. Coletas foram realizadas em diversas localidades para obtenção de exemplares para descrição das partes moles e gloquídios. As informações obtidas, somado ao descrito na literatura, foram utilizadas para traçar um panorama de distribuição e conservação das espécies. As principais características das conchas foram utilizadas para elaboração de uma chave dicotômica para auxílio na identificação. Uma análise morfométrica foi empregada com o intuito de distinguir as espécies através da forma da concha. Reconhecemos Diplodon e Rhipidodonta incluídos na tribo Rhipidodontini. Em Diplodon foram identificadas seis espécies nas bacias estudadas: Diplodon ellipticus Spix in Wagner, 1827; Diplodon fontainianus (dOrbigny, 1835); Diplodon jacksoni Marshall, 1928; Diplodon multistriatus (Lea, 1831); Diplodon paulista (Ihering, 1893) e Diplodon rhombeus Spix in Wagner, 1827. Apesar de Diplodon granosus (Bruguière, 1792) possuir extensos registros na região estuada, a espécie foi limitada a região amazônica na nossa avaliação. Em Rhipidodonta, foi reconhecida uma única espécie, Rhipidodonta garbei (Ihering, 1910). Entre estas espécies, temos algumas tradicionalmente reconhecidas como válidas (e.g. D. ellipticus e D. granosus), contudo, outras foram revalidadas (e.g. D. jacksoni e R. garbei) e redefinidas perante a análise do material tipo, partes moles e gloquídio. Não foi possível a eleição de uma única característica morfológica para a separação das espécies, porém detalhes das brânquias, estômago, contorno da concha e escultura umbonal figuraram entre as mais utilizadas. Para a separação dos gêneros de Rhipidodontini foram empregados atributos dos gloquídios (e.g. gancho gloquidial, protuberância e forma do gloquídio) e das brânquias (e.g. forma da brânquia e conexão entre as lamelas). A chave dicotômica com base em características das conchas auxiliou a separar as espécies de Rhipidodontini. A análise morfométrica constituiu uma ferramenta útil na separação das espécies, corroborando as identificações prévias. Salientamos que o estudo aqui apresentado deve ser expandido para outras bacias hidrográficas sul-americanas com o intuito de se conhecer a real diversidade destes bivalves de água doce / Rhipidodontini (Rhipidodonta Mörch, 1853 + Diplodon Spix in Wagner, 1827) is a tribe of freshwater bivalves with a complicated taxonomy, mainly due to the poor original descriptions, sometimes without illustrations, thereby a group needing a careful revision. The lack of information created a great variation in species considered valid by deferent authors, complicating the study of other aspects like distribution and biology. Therefore, were proposed in this study the taxonomic revision of Rhipidodontini in watersheds of Paraná River, São Francisco River and Coastal Atlantic rivers of East, North and Northeast. In order to achieve this goal museum collections were visited in Brazil and in other countries. Fields surveys were done in several localities to obtain fresh specimens to describe soft parts and glochidium. The information obtained added to information available in the literature were used to present and overview about distribution and conservation of the species. The main shell characteristics were employed to prepare an identification key to aid species differentiation. A morphometric analysis was used to distinguish species based on shell measurements. Diplodon and Rhipidodonta were recognized as valid genus included in tribe Rhipidodontini. Inside Diplodon were identified six species in the surveyed watersheds: Diplodon ellipticus Spix in Wagner, 1827; Diplodon fontainianus (dOrbigny, 1835); Diplodon jacksoni Marshall, 1928; Diplodon multistriatus (Lea, 1831); Diplodon paulista (Ihering, 1893) and Diplodon rhombeus Spix in Wagner, 1827. Despite Diplodon granosus (Bruguière, 1792) has extensive records in the studied region, this species was restricted to Amazonian region in our evaluation. In the genus Rhipidodonta were recognized only one species Rhipidodonta garbei (Ihering, 1910). Among these species, there are some traditionally accepted as valid (e.g. D. ellipticus e D. granosus), however other were revalidated and redefined based on analysis of type material, soft parts and glochidium (e.g. D. jacksoni e R. garbei). It was impossible to choose only one morphologic characteristic to discriminate the species, but details of gills, stomach, shell outline and umbonal sculpture were among the most important. The genera of Rhipidodontini were separate using attributes of glochidium (e.g. gloquidial hook, protuberance and shape of glochidium) and gills (e.g. gills shape and lamellar connections). The identification key based on shell characteristics helped to distinguish the species of Rhipidodontini. The morphometric analysis was considered a useful tool to separate the species, supporting the previous identification. The evaluation presented here should be expanded to other South American hydrographic catchments for determining the real diversity of these freshwater mussels

Submitted by Jordan (jordanbiblio@gmail.com) on 2017-03-13T15:32:07Z No. of bitstreams: 1 DISS_2015_Anderson Wakinaguni Michiura.pdf: 703669 bytes, checksum: 60597a6b6125e23795b4c0739d397627 (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2017-03-14T15:58:39Z (GMT) No. of bitstreams: 1 DISS_2015_Anderson Wakinaguni Michiura.pdf: 703669 bytes, checksum: 60597a6b6125e23795b4c0739d397627 (MD5) / Made available in DSpace on 2017-03-14T15:58:39Z (GMT). No. of bitstreams: 1 DISS_2015_Anderson Wakinaguni Michiura.pdf: 703669 bytes, checksum: 60597a6b6125e23795b4c0739d397627 (MD5) Previous issue date: 2015-02-27 / CAPES / Os bivalves de água doce são um grupo com alto risco de extinção devido às mudanças climáticas, expansão urbana, construção de reservatórios hidrelétricos, crescimento populacional, eutrofização, degradação dos habitats, poluição pontual e difusa dos ecossistemas aquáticos. O objetivo deste trabalho foi identificar quais fatores físicos e químicos da água e sedimento que determinam a estrutura da comunidade de bivalves em 18 lagoas adjacentes ao rio Cuiabá, nos ambientes urbanos e não urbanos. A amostragem dos bivalves foi realizada pelo tateio no fundo das lagoas e por coleta de sedimentos ao longo do transecto com auxílio de uma peneira. Variáveis físicas e químicas da água e % de matéria orgânica do sedimento foram mensuradas e usadas como preditoras da abundância e estrutura da comunidade de bivalves pela ordenação da análise de componentes principais, regressão multivariada e análise de redundância (RDA). A RDA demonstrou uma relação das concentrações de nitrato e % de matéria orgânica com a estrutura da comunidade de bivalves. As espécies encontradas foram A. trapesialis (50,66%), Pisidium sp. (26,98%), C. fluminea (7,48%), C. inflata (6,82%) e A. elongatus (6,16%). As populações de A. trapesialis e A. elongatus estiveram relacionadas positiva e significativa com o nitrato. O aumento da % de matéria orgânica no sedimento esteve relacionado com menor abundância de A. elongatus, entretanto pouca relação com a classe de comprimento das valves. A espécie A. trapesialis teve efeito positivo e significativo com a variável oxigênio dissolvido em relação à classe de comprimento das valves. Os fatores ambientais que refletem os nutrientes podem influenciar na distribuição da comunidade de bivalves de água doce, no entanto, não determinam a estrutura da comunidade em lagoas urbanas e não urbanas. / Freshwater mussels are a group at high risk of extinction due to climate change, urban expansion, construction of hydroelectric reservoirs, population growth, eutrophication, habitat degradation, pollution and diffuse spot of aquatic ecosystems. This works was to identify which physical and chemical factors of the water and sediment that determine the structure of mussels community in 18 of ponds the Cuiaba river, in urban and non-urban environments. Sampling of mussels was conducted by groping the bottom of ponds and collecting sediment along transect with the aid of a sieve. The physical and chemical water variables and % organic matter in the sediment were measured and used as predictors of abundance and structure of the mussel community by ordering the principal component analysis, multivariate regression and redundancy analysis (RDA). The RDA showed a ratio of nitrate concentrations and % organic matter having the structure of mussels community. The species were A. trapesialis (50,66%), Pisidium sp. (26.98%) C. fluminea (7,48%), C. inflata (6,82%) and A. elongatus (6,16%). Populations of A. trapesialis and A. elongatus were positively and significantly related to nitrate. Increased % of organic matter in the sediment was associated with a lower abundance of A. elongatus, however little to do with the length class of valves. The species A. trapesialis had a positive and significant effect on the variable dissolved oxygen relative to the valves length class. Environmental factors that reflect the nutrients may influence the distribution of freshwater mussels community, however, not determine the community structure in urban and non-urban environments.

Les dernières décennies ont été marquées par l’intensification et l’expansion des efflorescences de micro-algues toxiques (HAB). Connues pour perturber les écosystèmes côtiers et pour leur toxicité sur les organismes marins, les HAB sont suspectées d’être à l’origine de défauts de recrutement de bivalves. Cette thèse avait pour objectif d’étudier les conséquences des efflorescences du dinoflagellé toxique Alexandrium minutum, producteur de toxines paralysantes (PST) et des composés bioactifs extracellulaires (BEC), sur la reproduction, le développement et le recrutement de l’huître Crassostrea gigas, une espèce à l’importance économique majeure. Les gamètes libres et les jeunes stades de développement se révèlent être les plus sensibles, en particulier aux BEC produits par A. minutum qui inhibent la fécondation et l’embryogenèse. A. minutum modifie le comportement des larves véligères, provoque une diminution de leur filtration, de leur croissance et du taux de fixation. Une exposition des adultes, pendant la gamétogenèse, affecte le développement des descendants, traduisant des altérations du contenu gamétique et/ou un transfert vertical des PST. Les modalités d’action des PST et des BEC devront être précisées. Nos expérimentations, réalisées à des concentrations de micro-algues rencontrées dans l’environnement, suggèrent que des efflorescences récurrentes d’A. minutum lors des périodes de reproduction et de développement larvaire pourraient, sur le long terme, affecter la structure des populations naturelles et cultivées de C. gigas. / Recent decades have witnessed the intensification and spread of harmful algal blooms (HAB). HAB are known to disrupt coastal ecosystems and to be toxic for marine organisms. These phenomena are also suspected to be responsible for recruitment failures of bivalves. The aim of this PhD was to study the consequences of blooms of toxic dinoflagellate Alexandrium minutum on the reproduction, development and recruitment of the oyster Crassostrea gigas, a species of major economic importance. A. minutum is known to produce paralytic shellfish toxins (PST) and bioactive extracellular compounds (BEC). Gametes and early life stages were the most sensitive, particularly to the bioactive extracellular compounds (BEC) produced by A. minutum, which inhibited fertilization and embryogenesis. A. minutum modified the behaviour of veliger larvae, decreased their filtration, growth and settlement. Exposure of adult oysters during gametogenesis affected the development of offspring, reflecting alterations in gamete content and/or vertical transfer of PST. Mode of action of PST and BEC are to further investigate. These oyster exposures, conducted at environmentally relevant concentrations of microalgae, suggest that recurrent blooms of A. minutum during oyster spawning and larval development could have long-term consequences on the structure of wild and cultured populations of C. gigas.

Moluscos bivalves são organismos filtradores capazes de concentrar susbtâncias produzidas por microalgas tóxicas. No estado de Santa Catarina, líder na produção nacional, os cultivos têm sido oficialmente monitorados para a detecção de ficotoxinas causadoras dos Envenenamentos Diarreico (DSP), Amnésico (ASP) e Paralisante (PSP) por Consumo de Moluscos nas partes comestíveis. Amostras de água também são coletadas para a quantificação de algas nocivas. O objetivo deste trabalho foi sugerir o uso de áreas amostrais para coletas semanais, bem como calcular o tamanho das amostras agrupadas e analisar os dados de ocorrência. Diferentes cenários foram desenvolvidos para simular a variação dos tamanhos amostrais, utilizando-se o EpiTools®. Considerando-se uma alta prevalência e altas sensibilidades dos testes, é possível sugerir dois pools amostrais para a detecção de Toxinas Lipofíficas (2x30), duas para detectar PSP (2x15) e uma para detectar ASP (1x20) em cada uma das 24 áreas amostrais sugeridas. Se o teste de Cromatografia Líquida com Espectrometria de Massa (LC-MS/MS) for validado para todas as biotoxinas, apenas um pool amostral seria suficiente (1x15). Informações espaçotemporais de ocorrência também foram analisadas e apenas ficotoxinas causadoras de DSP foram encontradas. Utilizando-se os softwares SaTScan® e QGIS 2.12.2- Lyon®, foram desenvolvidos mapas de calor com os dois clusters espaciais encontrados para as detecções de DSP em moluscos e os quatro para Dinophysis acuminata (≥100cels/L) em amostras de água. Os resultados com maiores riscos relativos corresponderam ao cluster temporal do segundo semestre de 2014, os clusters espaciais das áreas 7 a 11 para DSP e áreas de 7 a 9 para D. acuminata. Esses resultados poderão contribuir para o planejamento de estratégias a serem incorporadas num futuro sistema de vigilância de moluscos bivalves do estado. / Bivalve molluscs are filtering organisms capable to concentrate substances produced by toxic microalgae. In Santa Catarina state, main Brazilian producer, the crops have been officially monitored for the detection of phycotoxins that cause Diarrheic (DSP), Amnesic (ASP), and Paralyzing (PSP) Shellfish Poisonings in edible parts. Water samples are also collected for harmful algae quantification. The goal of this study was to suggest the use of areas to be weekly sampled, as well as to calculate pooled sample sizes and to analyze the occurrence data. Different scenarios were developed to simulate the variation of sample sizes in EpiTools®. Considering a high prevalence and high tests sensitivities, we can suggest two pools to detect Lipophilic Toxins (2x30), two to detect PSP (2x15), and one to detect ASP (1x20) in each of the 24 suggested sampling areas. If the test of Liquid Chromatography with Mass Spectrometry (LC-MS/MS) becomes validated for all biotoxins, only one pool would be enough (1x15). Space-time occurence information was also analyzed and only phycotoxins causing DSP were found. Using SaTScan® and QGIS 2.12.2-Lyon® softwares, we developed heatmaps with two clusters found for DSP detection in shellfish and the four found for Dinophysis acuminate (≥100cels/L) in water samples. The results with higher relative risk values corresponded to the time cluster of the second semester of 2014, spatial cluster of the areas 7 to 11 for DSP, and areas 7 to 9 for D. acuminate. These results can contribute for the strategic plans to be incorporated in a future bivalve molluscs surveillance system of the state.

Microplastic pollution (particles < 5mm) is one of the most widespread impacts from modern society. Here, microplastic impacts were investigated through experimental assessments considering different exposure scenarios using mussels and micro-PVC as models. These aimed to investigate mussels\' physiological signs of stress under acute and chronic exposures and microplastics transference, assimilation and retention along food chains. In acute exposures, PVC intake affected mussels\' physiology over time, also influenced by plastics additives and particle concentration. Interactions among exposure factors (time, presence of additives and concentration) were more relevant than their individual effect, indicating the singularity of each contamination scenario. Long-term contact did not affect mussels, indicating the influence of time to acclimation. Microplastics were not assimilated and retained along food chains, but only biotransferred from prey tissues to predators\' tract, showing the influence of prey contamination on the effectiveness of microplastics biotransference. To evaluate risks in nature, microplastic ingestion was investigated in mussels from the Santos Estuary. Santos Estuary contained microplastics in 75% of sampled mussels, an issue of environmental and human concern. This study illustrated that microplastics impacts on mussels vary with microplastics characteristics, exposure scenario and species vulnerability, highlighting the need for more toxicological and risk evaluation studies. / Os microplásticos (< 5mm) são um dos impactos mais difundidos da sociedade moderna. Aqui, eles foram estudados em ensaios experimentais, considerando diferentes composições de exposição de mexilhões à micro-PVCs. O objetivo foi investigar: sinais fisiológicos de estresse sob exposições aguda e crônica; e transferência, assimilação e retenção de microplásticos em cadeias tróficas. Para avaliar seus potenciais riscos na natureza, a ingestão por mexilhões também foi investigada no Estuário de Santos. As exposições agudas afetaram a fisiologia dos mexilhões, sendo influenciadas pelo tempo e concentração de exposição, e pela presença de aditivos plásticos. Interações entre esses fatores (tempo, concentração e aditivos) foram mais relevantes do que eles individualmente, sugerindo a singularidade dos cenários de poluição. A exposição de longo prazo não afetou os mexilhões, indicando a influência do tempo na aclimatação ao microplástico. O PVC não foi assimilado e retido nas cadeias tróficas, mas biotransferido do tecido das presas para o trato dos predadores, mostrando a influência do estado da presa na efetividade da biotransferência dos microplásticos. Dentre os mexilhões coletados, 75% estavam contaminados, revelando uma importante questão socioambiental. Esse trabalho ilustrou a complexidade dos impactos dos microplásticos para a biota marinha, ressaltando a necessidade de mais estudos sobre seus riscos.