Depuis plusieurs années il est devenu essentiel de comprendre le déterminisme sexuel des espèces à fort intérêt économique afin d’optimiser leur production au sein d’écloseries émergentes.L’objectif principal de cette thèse était de mettre en évidence les mécanismes impliqués dans la détermination et la différenciation sexuelle, et notamment du sexe femelle, chez l’huître perlière P. margaritifera, espèce hermaphrodite protandre et espèce clé de la perliculture, la seconde ressource économique pour la Polynésie française. Pour atteindre cet objectif, deux approches ont été menées : une approche transcriptomique visant à étudier les mécanismes moléculaires du déterminisme et de la différenciation sexuelle, et une approche expérimentale visant à comprendre le phénomène de la sexualisation par des forçages environnementaux et hormonaux en s’intéressant plus particulièrement au déterminisme et à la différenciation sexuelle femelle.Dans l’approche transcriptomique, le transcriptome de la gonade de P. margaritifera a été séquencé à partir de plusieurs échantillons gonadiques d’huîtres de sexe mâle et femelle à différents stades de développement. Après le séquençage Illumina et l'assemblage du transcriptome, 70 147 contigs ont été obtenus. L’analyse fonctionnelle de ces 70 147contigs, a permis d’identifier des gènes d’intérêt et ainsi de constituer un catalogue de 87 ARNm codant pour 67 protéines impliquées dans la détermination, la différenciation sexuelle et/ou la gamétogenèse. Ensuite une analyse stricte des données de quantification RNAseq a révélé 1 937 contigs exprimés de manière différentielle entre les catégories histologiques des gonades. À partir de l’analyse de leurs profils d’expression au sein de chaque échantillon, un nouveau modèle de la reproduction de P. margaritifera, basé sur une double approche analytique, eg. histo-moléculaire, a été proposé. Ce modèle révèle notamment que le déterminisme sexuel de P. margaritifera chez l’adulte se produirait durant une phase de régression de la gonade. Considérant ainsi les nouveaux stades définis par ce modèle, 9 gènes biomarqueurs de la voie sexuelle femelle ont pu être identifiés révélant un modèle prédictif de la voie sexuelle basé sur 3 rapports d’expressions de gènes impliquant 2 gènes inconnus pmarg-c43476 et pmarg-c54338 et 2 gènes connus pmarg-foxl2 et pmarg-fem1-like. Ce deuxième modèle suggère fortement l'implication de pmarg-foxl2 et pmarg-fem1-like dans le déterminisme du sexe de P. margaritifera. Dans l’approche expérimentale, deux expérimentations séparées ont été réalisées pour mettre en évidence l’effet i) de plusieurs combinaisons de température et de niveau trophique, et ii) de l’œstradiol-17β administré par injection directe dans la gonade ; sur le sexe, la gamétogenèse et l’expression des neuf gènes biomarqueurs de la voie sexuelle femelle identifiés précédemment. Les résultats ont montré que la condition combinant la température de 28°C et la concentration en algues de 40 000 cellules mL-1 était la plus favorable non seulement à la maturation des gonades mâles et femelles mais aussi au maintien du sexe femelle. Ce serait dans cette condition environnementale qu’il serait possible d’induire un changement de sexe de mâle vers femelle. Dans la seconde expérimentation, il a été clairement démontré que la reproduction de P. margaritifera pouvait être régulée par les hormones œstrogènes. Les résultats montrent un effet négatif de l’œstradiol sur le développement et la différenciation mâle. Enfin les résultats du modèle prédictif de la voie sexuelle de P. margaritifera, suggèrent une programmation génétique du sexe femelle qui toutefois resterait soumise aux conditions environnementales validant ainsi l’hypothèse d’un mode de détermination mixte du sexe chez P. margaritifera. / For several years it has become essential to understand sex determination of species with high economic interest to maximize their production in emerging hatcheries.The main objective of this thesis was to identify the mechanisms involved in sex determination and sex differentiation, and particularly in female sex, in the pearl oyster P. margaritifera, a protandrous hermaphrodite species and the key species of the pearl farming, the second economic resource for French Polynesia. To achieve this goal, two approaches were undertaken: a transcriptomic approach to investigate the molecular mechanisms of sex determinism and sex differentiation, and an experimental approach to understand the phenomenon of sexualization by environmental and hormonal forcing focusing especially on female sex determinism and female sex differentiation.In the transcriptomic approach, the gonad transcriptome of P. margaritifera was sequenced from several samples of male and female oyster gonads at different stages of development. After Illumina sequencing and assembly of the transcriptome, 70,147 contigs were obtained. Functional analysis of these 70,147 contigs identified genes of interest and allowed the constitution of a catalog of 87 mRNAs encoding 67 proteins involved in sex determination, sex differentiation and/or gametogenesis. Then a strict analysis of RNAseq quantification data revealed 1,937 contigs differentially expressed between the histological categories of gonad. From the analysis of their expression profiles in each sample, a new model of reproduction of P. margaritifera, based on dual analytical approach, i.e. histo-molecular, has been proposed. This model shows that sex determination of adult P. margaritifera pearl oysters occur during a regression phase of the gonad. And considering the new stages defined on this model, 9 biomarkers genes of the female sexual pathway have been identified revealing a 3-gene-pair expression ratio based model, which makes it possible to predict the sexual pathway in this hermaphrodite species. This predictive model involves two unknown genes pmarg-c43476 and pmarg-c54338 and 2 known genes pmarg-foxl2 and pmarg-fem1-like, and strongly suggests the involvement of pmarg-foxl2 and pmarg-fem1-like in sex determinism in P. margaritifera.In the experimental approach, two separated experiments were conducted to demonstrate the effect of i) various combinations of temperature and trophic level, and ii) 17β-estradiol administered by direct injection into the gonad; on sex, gametogenesis and expression of the nine biomarkers genes of the female sexual pathway previously identified. The results showed that the condition combining a temperature of 28 °C and a concentration of 40 000 cells of algae mL-1 was the most favorable not only for the maturation of the male and female gonads but also for the maintenance of the female sex. It would be in this environmental condition that it would be possible to induce a sex change from male to female. In the second experiment, it was clearly demonstrated that the reproduction of P. margaritifera could be regulated by estrogen hormones. The results show a negative effect of estradiol on male development and differentiation. Finally the results of the predictive model of the sexual pathway of P. margaritifera, suggest a genetic programming of the female sex, which however remain subject to environmental conditions, thus validating the hypothesis of a mixed sex determinism mode in P. margaritifera.

Mollusc shells are unique adaptations that serve to protect the organisms that make them, and are a defining feature of the phylum. However the molecular underpinnings of shell forming processes are still largely unexplored. To further understand mollusc shell formation, I studied three bivalve species in this project: the blue mussel Mytilus edulis, the Pacific oyster Crassostrea gigas, and the king scallop Pecten maximus. While previous analyses of the shell proteomes showed species specificity, transcriptomes of the mantle tissues revealed more commonalities. To reconcile these differences, I studied differential gene expression in shell damage-repair experiments and during the formation of the first larval shell, to produce a comprehensive overview of shell formation processes. Expression data showed large biological variability between individuals, requiring matched-pair experimental designs to detect differential gene expression during shell repair. Loci differentially expressed during shell repair and in the larvae encoded shell matrix proteins, transmembrane transporters, and novel transcripts. A large number of shell matrix proteins, encoded in differentially expressed loci, were common in all three species during shell formation, indicating that shell forming proteins between different species may be more common than previously thought. Differential expression of transmembrane transporters during shell repair indicated that the animals may be regulating bicarbonate ions during shell formation. Finally, the experiments revealed novel transcripts, with unknown annotations to public datasets, that may putatively be involved in shell formation.

Submitted by Alberto Vieira (martins_vieira@ibest.com.br) on 2018-05-24T18:20:50Z No. of bitstreams: 1 278148.pdf: 9125580 bytes, checksum: 862e99d463533276f40617d6a6808f1f (MD5) / Made available in DSpace on 2018-05-24T18:20:50Z (GMT). No. of bitstreams: 1 278148.pdf: 9125580 bytes, checksum: 862e99d463533276f40617d6a6808f1f (MD5) Previous issue date: 1998-12-14 / CAPES / A laguna de Araruama, localizada no estado do Rio de Janeiro, com 220 Km2, tem uma grande importância ecológica e sócio econômica. É a maior laguna hipersalina do mundo em regime permanente. Sua estreita comunicação com o mar, sua fraca profundidade e as condições climáticas explicam a sua hipersalinidade constante (>50). A interferência antrópica crescente é um dos seus principais problemas. A fim de analisar a composição zooplanctônica e sua variação espaço-temporal ao longo de um ano, foram coletadas amostras a cada 16 dias, em dez estações na laguna. Temperatura, salinidade e transparência da água foram medidas simultaneamente. A variação diária do zooplâncton foi avaliada através de coletas em diferentes horários durante dois períodos, em uma estação fixa (07-09/09/93 e 07-10/04/95). Os resultados revelam a predominância de um zooplâncton de baixa diversidade e de pequeno porte, composto principalmente pela espécie eurihalina de copépode Oithona oswaldocruzi e larvas de bivalve. Os demais organismos holoplanctônicos, raramente encontrados, não devem reproduzir-se dentro da laguna. O.oswaldocruzi completa seu ciclo vital, estando adaptada às condições estressantes do meio. Copépodes e larvas de bivalve apresentam um máximo de abundância entre setembro e novembro, além de picos menores. A porcentagem de femeas... / The Araruama Lagoon, located in the state of Rio de Janeiro, measuring 220 Km2, has a great ecological and socio-economic importance. It is the largest permanent hypersaline lagoon in the world. Its constant hypersalinity can be explained by its narrow communication with the ocean, its shallowness, and the climate conditions. The increasing anthropic influence is one of its main problems. ln order to analyze the zooplankton composition and its spatial and temporal variations during one annual cycle, the samples were taken every 16 days, during 1994, in 10 stations in the lagoon. Simultaneously, temperature, salinity and transparency of water were measured. The daily variation of the zooplankton was analyzed by drags in different hours of the day in two periods, from November 7th to 9th 1993, and April 7th to 10th 1995. The results revealed the predominance of a zooplankton of small size and low diversity, composed basically of the eurihaline specie of copepod called Oithona oswaldocruzi and bivalve larvae. The other holoplanktonics organisms rarely found, may not reproduce in the lagoon. The O.oswaldocruzi is able to complete its life cycle, suggesting that it is adapted to the stressing conditions of the environment. The greatest abundance of copepods and bivalve larvae happens from September to November. The percentage of females...

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química. / Made available in DSpace on 2012-10-20T02:38:57Z (GMT). No. of bitstreams: 1 198314.pdf: 1042707 bytes, checksum: ee32f871929e9280cd1472be22c9d471 (MD5) / Moluscos bivalves são freqüentemente utilizados como indicadores para análises de contaminação aquática representando a base de inúmeros programas de monitorização ambiental. Com a perspectiva de se avaliar riscos potenciais à saúde humana, este trabalho investigou a qualidade de mexilhões Perna perna e ostras Crassosstrea gigas cultivadas em zonas costeiras da Ilha de Santa Catarina ao longo dos anos de 1999 e 2000, quanto ao teor de elementos traço. Três pontos de coleta foram selecionados: Enseada da Pinheira, Praia do Ribeirão da Ilha e Praia de Sambaqui. Parâmetros físico-químicos da água do mar considerados relevantes na medida do grau de eutrofização mostraram valores compatíveis com a dinâmica do meio ambiente estudado. Concentrações de elementos metálicos e semi-metálicos foram determinadas na água do mar, nas fases dissolvida e particulada, nos tecidos dos bivalves e no sedimento. As concentrações foram similares ou menores do que aquelas encontradas em outros países. Também foram determinadas as concentrações dos elementos traço nos sedimentos coletados nas regiões de cultivo, na sua forma total e nas frações obtidas pela aplicação do método modificado de extração seqüencial proposto pela European Community Bureau of Reference, hoje Standards, Measurements and Testing Programme. Foram utilizadas a técnica de espectrometria de massa com fonte de plasma indutivamente acoplado, na determinação de Ag, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se, Sn, V, Zn em amostras ambientais (sedimentos, mexilhões, ostras e água do mar). Para a determinação de elementos traço na fase dissolvida da água do mar foi usado um sistema de injeção em fluxo para a separação e pré-concentração do analito, acoplados ao espectrômetro e introdução do eluato orgânico através de um nebulizador pneumático, também foi usado um vaporizador eletrotérmico para introdução da amostra. A validação da metodologia aplicada para cada amostra foi realizada pela análise de materiais de referência certificados de composição similar às amostras. Valendo-se do programa Statisticaâ 5.0 aplicou-se a correlação de Pearson, tendo sido encontrados indícios que relacionam os níveis de alguns elementos traço como Hg, Mn, Ni, Pb e Zn na fase dissolvida e particulada da água do mar com parâmetros físico-químicos, como oxigênio dissolvido, pH, matéria orgânica e inorgânica particulada. Também entre as concentrações dos elementos traço no tecido de mexilhões e ostras e as concentrações obtidas nas frações do sedimento. Estes indícios foram importantes para se entender as relações dos elementos traço no ambiente marinho e recomendar o uso de moluscos bivalves em programas de monitorização da poluição marinha. Não foram encontradas indicações de poluição por metais e semi-metais nos compartimentos estudados. No entanto, os dados obtidos certamente serão muito úteis em futuras avaliações de poluição, servindo como um importante banco de dados da situação no biênio. Os moluscos criados nas áreas estudadas são adequados para o consumo humano em relação aos teores de elementos traço.

Marine aquaculture is already vital to global food security and will continue to become more important in the coming years. Crassostrea gigas (Pacific oysters) is the primary oyster species cultivated worldwide. The FAO and IPCC predict that climate change will create uncertainty and challenges for marine aquaculture. Baynes Sound, British Columbia, is a productive region for aquaculture, producing >50% of British Columbia’s total annual bivalve production by live weight and value. Major summer mortality events have been documented in farmed Crassostrea gigas globally since the 1950’s. These events are believed to be caused by a multiplicity of factors including changes induced by anthropogenic climate change. One of the major contributors to summer mortality is the proliferation of Vibrio bacteria, specifically Vibrio aestuarianus, which has been shown to increase in abundance and virulence when seawater temperatures rise. Despite this connection and the economic importance of oyster farming in the region, little is known about the presence of V. aestuarianus in Baynes Sound. Our 17-month study sampled 7 sites in Baynes Sound on 33 occasions from May 2019 to September 2020. We found a positive correlation between seawater temperature and total Vibrio detected in water samples in Baynes Sound, an association that was stronger when the overall temperature regime was warmer. We found no significant correlation between any of the bacterial assays tested and salinity, pH, or Ωarag saturation. We also did not identify a geographic pattern to bacterial abundance or virulence amongst test C. gigas in the field. Understanding that flagellates are the predominant type of microalgae present in Baynes Sound when summer mortality events occur, in lab trials, we found that incorporating V. aestuarianus into marine aggregates with flagellate microalgae caused higher mortality than aggregates with diatoms or planktonic V. aestuarianus. These results were not statistically significant but led us to look at how exposure to husbandry stress pre and post inoculation with V. aestuarianus incorporated into marine aggregates affects mortality. We found that stress was a significant driver of mortality, particularly when administered 24h post inoculation, suggesting that farmers should avoid sorting or tumbling their oysters in the summer, and particularly immediately after a marine heatwave. Oysters lack adaptive immune systems and are grown in an open ocean environment where it is not possible to eliminate their exposure to pathogens. These factors make it impossible to use vaccines or antibacterial disinfectants to combat diseases. Therefore, breeding genetic resistance to V. aestuarianus may be the most effective way to fight summer mortality. Creating a repeatable and accurate protocol for inoculating oysters with marine bacteria is key to accurate heritability measurements and the estimation of breeding values of different families. Key factors include controlling for dose per animal, laboratory efficiency, and inoculation via a mechanism that mimics real-world infection and does not bypass the animal’s immune defenses. We designed a protocol which controls for these factors, separating each animal into individual containers and adding a controlled dose of planktonic bacteria to each. Previously used methods of injection or using an infected “donor” animal in a group tank do not control for dose or bypass parts of the oysters’ natural immune system, potentially creating inaccuracies in survival data generated with these methods. After designing this protocol, we tested 32 full-sib families and estimated the heritability of survival to V. aestuarianus on the observed and underlying liability scales to be 0.095 (SE = 0.043), and 0.15 (SE = 0.068) respectively. We also found a strong negative correlation between oyster size and survival, with a gram of additional weight creating a 73% increase in the risk of death. Fast growth and large size are two traits which have been explicitly bred into C. gigas stock. Our work suggests that breeding a slower-growing, smaller animal may reduce summer mortality. / Graduate / 2022-09-15

Canadian bitumen is mainly transported in a diluted form via pipeline and train, all posing a risk as they can lead to the release of diluted bitumen (dilbit) in the environment. In the summer of 2018, a collaborative large-scale field experiment was conducted at the International Institute for Sustainable Development - Experimental Lakes Area (IISD-ELA), a world-renowned aquatic research facility. The research objectives of the Boreal lake Oil Release Experiment by Additions to Limnocorrals (BOREAL) project were to understand the fate, behaviour, and potential toxic effects of dilbit in a freshwater Boreal lake to inform evidence-based management strategies for the transport of dilbit. A range of controlled dilbit spills was performed in seven 10 m diameter limnocorrals (~100,000 L of water) resulting in environmentally realistic dilbit:water dilutions ranging from 1:69,200 to 1:504, representing the upper half of the distribution of oil spill sizes in North America in the last decade. Additionally, two limnocorrals not treated with dilbit were studied as controls. This thesis identifies the bioaccumulating compounds derived from naturally weathered dilbit in adult giant floater mussels (Pyganodon grandis), to determine the rates at which they were accumulated and excreted. More specifically, the bioaccumulation potential and toxicokinetic parameters of polycyclic aromatic compounds (PACs) and various metals were assessed in mussels exposed ex situ for 41 days (25 days of exposure and 16 days of depuration) to water from the limnocorrals. These compounds have shown to be toxic, carcinogenic, and mutagenic to aquatic organisms. Mussels exposed to dilbit-contaminated water experienced significantly greater TPACs concentrations (0.40 – 0.90 µg L-1, n=12) compared to mussels from the Control (0.017 µg L-1, n=4). Furthermore, dilbit-contaminated water had a higher proportion of alkylated PACs compared to their parent counterpart, demonstrating petrogenic PAC profiles. We detected significantly greater TPACs concentrations in mussels exposed to dilbit-contaminated water (25.92 – 27.79 µg g-1, ww Lipid, n=9, at day 25 of the uptake phase) compared to mussels from the Control (average of 2.62 ± 1.95 µg g-1, ww Lipid; ±SD, n=17). Alkylated PACs represented 96.4 ± 1.8%, ±SD, n=12 of TPACs in mussels from dilbit-contaminated treatments at day 25 of the uptake phase, indicating the importance of conducting a more inclusive assessment of petrochemical mixtures as most studies only focus on parent PACs. From first-order one-compartment models derived from nonlinear curve fitting of the accumulation phase or sequential modelling method, uptake (0.66 – 24.65 L g-1 day-1, n=87) and depuration (0.012 – 0.37 day-1, n=87) kinetic rate constants, as well as bioconcentration factors (log values from 3.85 – 6.12 L kg-1, n=87) for the 29 PACs that bioaccumulated in mussels suggested that alkylated PACs have greater bioaccumulation potential compared to their parent PAC counterpart. Results from this study also demonstrated that giant floater mussels could be used to biomonitor PAC contamination following oil spills as PACs accumulated in mussel tissue and were still present following the 16 day depuration phase. The results of this study are the largest, most comprehensive set of toxicokinetic and bioaccumulation information of PACs (44 analytes) in freshwater mussels obtained to date. Metal contamination following the controlled dilbit spill was minimal, but mussels exposed to water contaminated with naturally weathered dilbit experienced elevated concentrations of dissolved zinc (30.26 – 38.26 µg L-1, n=12) compared to the mussels in the uncontaminated water (6.75 ± 3.31 µg L-1, n=4), surpassing the Canadian water quality guidelines for the protection of aquatic life. However, it is not clear if dilbit contamination caused elevated zinc concentrations in the water as other factors, such as limnocorral building materials and/or galvanized minnow traps used in the limnocorrals, could have contributed to zinc contamination. Nonetheless, giant floater mussels did not accumulate zinc in their tissues.

yes / The Mg/Ca ratios of biogenic calcite is commonly seen as a valuable palaeo-proxy for reconstructing past ocean temperatures. The temperature dependence of Mg/Ca ratios in bivalve calcite has been the subject of contradictory observations. The palaeoceanographic use of a geochemical proxy is dependent on initial, rigorous calibration and validation of relationships between the proxy and the ambient environmental variable to be reconstructed. Shell Mg/Ca ratio data are reported for the calcite of two bivalve species, Mytilus edulis (common mussel) and Pecten maximus (king scallop), which were grown in laboratory culturing experiments at controlled and constant aquarium seawater temperatures over a range from 10 to 20 C. Furthermore, Mg/Ca ratio data of laboratory- and fieldgrown M. edulis specimens were compared. Only a weak, albeit significant, shell Mg/Ca ratio¿temperature relationship was observed in the two bivalve species: M. edulis (r2=0.37, p<0.001 for laboratory-cultured specimens and r2=0.50, p<0.001 for field-cultured specimens) and P. maximus (r2=0.21, p<0.001 for laboratory-cultured specimens only). In the two species, shell Mg/Ca ratios were not found to be controlled by shell growth rate or salinity. The Mg/Ca ratios in the shells exhibited a large degree of variability among and within species and individuals. The results suggest that the use of bivalve calcite Mg/Ca ratios as a temperature proxy is limited, at least in the species studied to date. Such limitations are most likely due to the presence of physiological effects on Mg incorporation in bivalve calcite. The utilization is further limited by the great variability both within and among shells of the same species that were precipitated under the same ambient conditions

no / The potential of Mg in Arctica islandica as a climate proxy is explored through analysis of live-collected shells from Irvine Bay, NW Scotland. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis of the right hand valve from two specimens indicates that seasonal Mg/Ca variations do not correlate with seawater temperature. The highest Mg/Ca typically occurs at the annual growth checks in ~ November¿February. Mg/Ca variations between growth checks are significant in one specimen but usually not significant in the other. Mg/Ca measurements taken laterally across the band (i.e. perpendicular to direction of the growth) to determine heterogeneity of the aragonite deposited at the same time indicates that Mg/Ca concentration decreases with increasing distance from the periostracum in both shells. X-ray Absorption Near Edge Spectroscopy (XANES) indicates that Mg is not substituted into aragonite but is hosted by a disordered phase e.g. organic components or nanoparticles of an inorganic phase. Shell Mg/Ca variations may reflect changes in the concentration or composition of the disorded phase, as well as changes in the composition of the extrapallial fluid used for calcification. Such changes could reflect the relative transportation rates of Mg and Ca to the calcification site.

Thesis (MA)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This study addresses the sustainable development and employment creation potential of bivalve mariculture with reference to the case of Saldanha. The first section of the study looks at various theoretical perspectives relating to sustainable development. The development of modernist theory is presented, as are its shortcomings. The People-Centred Development theory is presented as an alternative theoretical perspective. This theory is relevant to the present study because it prioritises the participation of local individuals in the development process, rather than prioritising the increase of capital gain. One of the development approaches within people-centred development is the Learning Process Approach. The learning process approach provides a development model through which people-centred development can take place. The study then focuses on empirical cases. The development of four mariculture case studies from different countries and farming different organisms is then considered. The development process of these case studies is used to draw lessons on what factors affect the sustainable development of a mariculture sector. It is shown that five key factors play a role in the sustainable development of each of the four cases. The five factors are the state, the market, funding, the environment and the local community. These five factors provide a typology with which to measure the potential for the sustainable development of the bivalve mariculture sector in Saldanha. Literature on Saldanha is then reviewed, giving a background to rising unemployment in Saldanha and the need to consider the expansion of alternative sectors. This is followed by presenting the methods and results of empirical research involving the collection of primary data in Saldanha. The research methods used in conducting empirical research in Saldanha are presented. This research elicited data on bivalve mariculture employees and bivalve mariculture directors in Saldanha as well as state representatives. The key findings of this study are that the restrictive state policies on mariculture and a lack of funding are the primary limitations to the sector‟s expansion. The sector has the potential to expand by a factor of four, providing employment for over 200 households in Saldanha. / AFRIKAANSE OPSOMMING: Hierdie ondersoek fokus op die volhoubare ontwikkeling en werkskeppingspotensiaal van tweekleppige marikultuur met verwysing na die geval van Saldanha. Die eerste gedeelte van die ondersoek handel oor verskillende teoretiese perspektiewe met betrekking tot volhoubare ontwikkeling. Die ontwikkeling van modernistiese teorie word aangebied, tesame met sy tekortkominge. Die Mens-Gesentreerde Ontwikkelingsraamwerk word as 'n alternatiewe teoretiese perspektief aangebied. Die mens-gesentreerde ontwikkelingsraamwerk is relevant tot die huidige ondersoek omdat dit die deelname van plaaslike individue in die ontwikkelingproses, eerder as die verhoging van kapitaalwins, vooropstel. Een van die ontwikkelingsbenaderings binne mens-gesentreerde ontwikkeling is die Leerproses Benadering. Die leerproses benadering bied 'n ontwikkelingsmodel waardeur mens-gesentreerde ontwikkeling kan plaasvind. Die leerproses benadering word dan gebruik om die ontwikkeling van ander marikultuur gevalleondersoeke te bespreek. Die tweede deel van die huidige ondersoek beskou die ontwikkeling van vier marikultuur gevalleondersoeke uit verskillende lande wat met verskillende organismes boer. Die ontwikkeling van hierdie gevalleondersoeke is gebruik om lesse op te stel oor watter faktore 'n invloed op die ontwikkeling en volhoubaarheid van 'n marikultuursektor het. Dit is getoon dat die vyf belangrikste faktore wat 'n rol in die volhoubaarheid en uitbreidingspotensiaal van elk van die gevalle gespeel het die staat, die mark, finansiering, die omgewing en die plaaslike gemeenskap behels. Hierdie vyf faktore is gebruik as 'n tipologie om die volhoubaarheid en uitbreidingspotensiaal van die tweekleppige marikultuursektor in Saldanha te meet. Die geval van Saldanha word eerstens in die literatuur aangebied vir 'n agtergrond oor stygende werkloosheid in Saldanha en die noodsaaklikheid om die uitbreiding van alternatiewe sektore te oorweeg. Derdens is primêre navorsing oor Saldanha se tweekleppige marikultuursektor onderneem. Data is versamel vanaf werknemers, direkteure en staatsverteenwoordigers. Die belangrikste bevindings van hierdie ondersoek is dat die beperkende staatsbeleid oor marikultuur en 'n gebrek aan fondse die primêre beperkings op die uitbreiding van die sektor is. Die sektor het die potensiaal om met 'n faktor van vier uit te brei. Teen hierdie grootte sal meer as 200 huishoudings in Saldanha 'n inkomste hê.

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&reg;. 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&reg; e QGIS 2.12.2- Lyon&reg;, foram desenvolvidos mapas de calor com os dois clusters espaciais encontrados para as detecções de DSP em moluscos e os quatro para Dinophysis acuminata (&ge;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&reg;. 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&reg; and QGIS 2.12.2-Lyon&reg; softwares, we developed heatmaps with two clusters found for DSP detection in shellfish and the four found for Dinophysis acuminate (&ge;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.