Des épisodes à Dinophysis affectent périodiquement l'exploitation des fruits de mer dans le Bassin d'Arcachon. Le réseau de surveillance interne au Bassin d'Arcachon montre que Dinophysis est advecté de l'océan ouvert. Le but de cette étude est de déterminer l'origine de Dinophysis. Des campagnes en mer sur le plateau continental Aquitain ont permis d'identifier une zone propice au développement de Dinophysis au large de Capbreton. Les épisodes à Dinophysis dans le bassin d'Arcachon se produisent suite à des vents d'Ouest qui induisent des courants vers le Sud d'après la littérature. L'étude des données hydrodynamiques acquises pendant les campagnes met en évidence un processus complexe et nouveau suite aux vents d'Ouest: de forts courants le long de la côte vers le Nord capables de transporter Dinophysis de Capbreton jusqu'au Bassin d'Arcachon. Un travail de modélisation a permis de reproduire ce courant et d'étudier son mécanisme particulier lié coin Sud-Est du Golfe de Gascogne. / Abstract

Made available in DSpace on 2016-04-28T20:17:25Z (GMT). No. of bitstreams: 1 2007-Geisi Ferreira Marine.pdf: 800208 bytes, checksum: b24185c0919f8244f06ce7f08948693e (MD5) Previous issue date: 2007-06-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The okadaic acid phycotoxin AO is produced by a group of micro seaweed known as Dinoflagellated. The mussels when feeding themselves from this micro seaweed accumulate in their hepatopancreas, this toxin, trigging in the human being the Syndrome or Diarrhetic Shellfish Poisoning (DSP). The symptoms appear at around 30 minutes after the consumption of the contaminated clam; the symptoms vary among abdominal nauseas, pains, vomits and diarrhea. When the toxin ingestion happens in amounts lower than 48 μg.g-1, the above described symptoms do not develop, however, its continued consumption favors the appearing of tumors in the gastrointestinal tract due to the high carcinogenic power of AO. This study intended to detect and quantify the diarrheic toxin AO in Perna perna mussels collected between the months of May and December of the 2006 and verification of the potentially toxic micro seaweed presence, in the seasons Spring/Summer (from September until December of 2006). Since May until december of 2006, mussels (Perna perna) were collected and analyzed regarding to the presence of the Phycotoxin Ao .In order to collect the micro seaweed were used a plankton net (20μm of mesh) and Bomb Rule 2000. The identification of the dinoflagellates ones was carried through in inverted biological microscope. The detection of AO in the mussels was carried through by High Efficiency of Liquid Chromatography with Fluorimetric Detection (HPLC-FC). The chromatographic results had indicated the presence of AO toxin in all the gotten mussel samples from May until October of 2006 in low concentrations. In the analyses of phytoplankton, the diatoms were the most representative group compared with the Dinoflagellated. The species Prorocentrum micans and P. gracile examined were not pointed as toxin producers until the moment. Among the Dino-flagellated potentially toxic were found the species : Dinophysis acuminata, D. tripos, D. rotundata and D. fortii. The results indicate the necessity of elaboration and effective application of a hygienic-sanitary controlling program of the clams as well as monitoring the environment, aiming above everything the public health Safety. / A ficotoxina ?cido ocadaico (AO) ? produzida por um grupo de microalgas conhecidas como dinoflagelados. Os mexilh?es ao se alimentarem destas microalgas acumulam em seu hepatop?ncreas, esta toxina, desencadeando no ser humano a S?ndrome ou Envenenamento Diarr?ico por Moluscos - EDM. Os sintomas se apresentam em torno de 30 minutos ap?s o consumo do molusco contaminado; variando entre n?useas, dores abdominais, v?mitos e diarr?ia. Quando a ingest?o da toxina acontece em quantidades inferiores a 48 μg.g-1, os sintomas acima descritos n?o se desenvolvem, por?m, seu consumo continuado favorece o surgimento de tumores no trato gastrointestinal devido ao poder carcinog?nico do AO. Este estudo pretendeu detectar e quantificar a toxina diarr?ica AO em mexilh?es Perna perna coletados entre os meses de maio e dezembro de 2006, e a verifica??o da presen?a de microalgas potencialmente t?xicas, nas esta??es primavera/ver?o (setembro a dezembro de 2006). De maio a dezembro de 2006, mexilh?es (Perna perna) foram coletados e analisados quanto ? presen?a da ficotoxina AO. As microalgas foram coletadas entre setembro e dezembro de 2006, com aux?lio de uma rede de pl?ncton (de 20μm de malha) e Bomba Rule 2000. A identifica??o dos dinoflagelados foi realizada em microsc?pio biol?gico invertido. A detec??o do AO nos mexilh?es foi realizada por Cromatografia L?quida de Alta Efici?ncia com Detec??o Fluorim?trica (CLAE-DF). Os resultados cromatogr?ficos indicaram a presen?a da toxina AO em todas as amostras obtidas de mexilh?es, de maio a outubro de 2006, em baixas concentra??es. Nas an?lises do fitopl?ncton, as diatom?ceas foram o grupo mais representativo comparado aos dinoflagelados. As esp?cies Prorocentrum micans e P. gracile observadas n?o foram apontadas como produtoras de toxinas at? o momento. Dentre os dinoflagelados potencialmente t?xicos foram encontradas as esp?cies: Dinophysis acuminata, D. tripos, D. rotundata e D. fortii. Os resultados indicam a necessidade da elabora??o e aplica??o efetiva de um programa de controle higi?nico-sanit?rio dos moluscos assim como monitoramento do ambiente, objetivando acima de tudo a seguran?a ? sa?de p?blica.

Mixoplankton are protist plankton that are capable of phototrophy and phagotrophy. These organismsare increasingly recognised not just as freaks of nature, but as a substantial part of marineplankton. Most existing plankton models still assume a strict dichotomy between phototrophsand heterotrophs. Few models consider mixoplanktonic activity as a synergism of the two trophicmodes. Many different mixoplankton functional types exist on a gradient between heterotrophy andphototrophy. The cryptophyte (Teleaulax)-Mesodinium-Dinophysis (TMD) complex is a specificpredator-prey interaction of different types of mixoplankton and a good example of the complexityof mixoplankton interaction and trophodynamics. The specialist non-constitutive mixoplankton(SNCM) Mesodinium acquires its chloroplasts strictly from a specific constitutive mixoplankton(CM) cryptophyte, while the harmful algal bloom (HAB) species Dinophysis acquires its third-handchloroplasts exclusively from Mesodinium.The generic NPZ-style protist model developed here shows that mixoplankton displays dynamicsthat are distinctly different from strict heterotrophs and autotrophs in terms of growth and theway they shape their environment. In addition, there is a clear niche separation between differentmixoplankton types (general non-constitutive mixoplankton (GNCM), SNCM and CM) according tonutrient, prey and light resource availabilities indicating a niche separation of each type. Thus,considering the different mixoplankton functional types in specialised multi-organism relationshipsas they are found in the TMD-complex may be important for their understanding and accurateprediction of growth and biomass development. Currently, none of the many models of Dinophysiscapture the biological dependencies. Results from a nitrogen-based TMD model suggest thatthe timing and quantity of prey availability is crucial for the bloom dynamics of Mesodinium andDinophysis. Some CMs may only feed when phosphate is the limiting nutrient. The results ofthe variable stoichiometric “Perfect Beast” model that was configured as Teleaulax amphioxeia incombination with experimental data strongly suggest that the cryptophyte feeds on bacteria tocompensate for phosphate limitation.This work shows the importance of considering mixoplankton in ecosystem models alongsidestrict heterotrophs and autotrophs and that distinction between different mixoplankton functionaltypes matters. Mixoplankton distinctly differ in their nutrient utilisation and growth dynamics.Predator-prey interactions have different implications for mixoplankton than for heterotrophs andtheir inclusion in models could improve our understanding of the formation of harmful mixoplanktonblooms. The unique physiology of mixoplankton and their nutrient utilisation and trophic levelsneed consideration in species specific models. / Le mixoplancton inclut les protistes planctoniques capables de phototrophie et de phagotrophie.Ces organismes sont de plus en plus reconnus comme une partie importante du plancton marin.Toutefois, la plupart des modèles mathématiques planctoniques existants supposent encoreune stricte dichotomie entre les organismes phototrophes et hétérotrophes et peu de modèlesconsidèrent l’activité mixoplanctonique comme une synergie entre les deux modes trophiques.De nombreux types fonctionnels mixoplanctoniques différents existent dans un gradient entrel’hétérotrophie et la phototrophie. Le complexe cryptophyte (Teleaulax)-Mesodinium-Dinophysis(TMD) est une interaction prédateur-proie spécifique entre différents types de mixoplancton et unbon exemple de la complexité des interactions et des relations trophodynamiques du mixoplancton.Mesodinium, mixoplancton spécialiste non constitutif (SNCM), ne peut acquérir ses chloroplastesque de cryptophytes (mixoplancton constitutif (CM)) spécifiques (tel que Teleaulax), tandis quel’espèce Dinophysis, responsable d’efflorescences algales nuisibles, acquiert ses chloroplastesexclusivement de Mesodinium. Le modèle générique de protistes, de type NPZ, développé dansce travail montre que le mixoplancton présente une dynamique nettement différente de celle deshétérotrophes et autotrophes strictes en termes de croissance et de la façon dont ils façonnentleur environnement. En outre, il existe une séparation de niches claire entre les différents typesde mixoplancton (mixoplancton généraliste non-constitutif (GNCM), SNCM et CM) en fonction dela disponibilité en lumière, en nutriments et en proies. En conséquence, la prise en compte desdifférents types fonctionnels du mixoplancton dans des relations multi-organismes spécialisées,telles qu’on les trouve dans le complexe TMD, peut être importante pour leur compréhension et laprédiction précise de leur croissance et biomasse. Actuellement, aucun des modèles existants deDinophysis ne rend compte de ces dépendances biologiques. Les résultats d’un modèle TMD basésur l’azote suggèrent que le moment et la quantité de proies disponibles sont des facteurs cruciauxpour la dynamique de Mesodinium et de Dinophysis. Certains CM peuvent se nourrir uniquementlorsque le phosphate est le nutriment limitant. Les résultats du modèle à stoechiométrie variable"Perfect Beast", qui a été configuré pour représenter Teleaulax amphioxeia sur base de donnéesexpérimentales, suggèrent fortement que le cryptophyte se nourrit de bactéries pour compenserla limitation en phosphate. Ce travail montre l’importance de prendre en compte le mixoplanctondans les modèles d’écosystème en plus des hétérotrophes et des autotrophes stricts et que ladistinction entre les différents types fonctionnels de mixoplancton est importante. Le mixoplanctonse distingue par son utilisation des nutriments et sa dynamique de croissance. Les interactionsprédateur-proie n’ont pas les mêmes implications pour le mixoplancton que pour les hétérotropheset leur prise en compte dans les modèles pourrait améliorer notre compréhension de la formationdes efflorescences nuisibles de mixoplancton. La physiologie unique du mixoplancton, sonutilisation des nutriments et ses niveaux trophiques doivent être pris en compte dans les modèlesspécifiques aux espèces. / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

This thesis deals with the question of whether planktonic protits of the genus Dinophysis have permanent plastids (=chloroplasts) or practice kleptoplasty, i.e. acquire plastids via predation on other microorganisms. Sequencing the plastid 16S rDNA of Dinophysis spp. collected from 4 different geographical regions unveiled two different plastid genotypes within this genera: one that was found at all locations investigated, identical to that of the free-living cryptophyte Teleaulax amphioxeia, and another found only in the Greenland Sea, closely related to that of the cryptophyte Geminigera cryophila. Both types were found within the species D. acuminata. These findings imply that the plastids in Dinophysis spp. were not inherited from a common ancestor, but acquired from feeding. By using flow cytometry in combination with an acidotrophic probe, it was shown that 71 % of the cells in a D. norvegica population in the aphotic zone of the Baltic Sea had food-vacuoles. Dinophysis used to be regarded as a primarily phototrophic organism, and this was a higher proportion of cells with food-vacuoles than reported earlier. To further study if Dinophysis needs constant refill of new plastids from the environment, a new method combining flow-cytometry and quantitative real-time PCR was developed to compare the levels of nuclear and plastid DNA in different phases of the cell-cycle. Results showed that plastid acquisition in Dinophysis was uncoupled with the cell-cycle, which is different than the pattern seen in microalgal species with permanent plastids. Furthermore, when quantitative real-time PCR combined with flow-cytometry was used to follow D. caudata cultures during a 65 days starvation/feeding experiment, the cells first went through a steady decrease in plastid DNA during starvation. In contrast, after feeding on the ciliate Myrionecta rubra, plastid DNA in starved cells increased 7-fold, thereby directly revealing the kleptoplastic behavior. The main conclusion from this thesis is that Dinophysis cells are actively taking up kleptoplastids from the ciliates on which they feed, and that kleptoplasty is an important key to understand Dinophysis ecology. Part of this thesis work has also been dedicated to the application and optimization of new methods, and it shows how quantitative real-time PCR, flow cytometry and molecular methods in different combinations can be used as powerful tools for the study of plankton ecology.