Dissertations / Theses on the topic 'Marine foods'

Three New Zealand marine species, hoki (Macruronus novaezealandiae), kahawai (Arripis trutta) and trevally (Pseudocaranx dentex) were used to develop model fermented fish sausage. The formulation comprised fish mince, carbohydrate, minced garlic and salt in a mass ratio of 1 (fish): 0.15: 0.05: 0.03, respectively. The carbohydrate source was cooked rice or glucose. (Endogenous lactic acid bacteria (LAB) failed to ferment rice). Folate was also added to the mixture as a factor. The mixtures were extruded into 50 mL plastic syringes, where the needle end of the barrel had been excised by lathe. The lubricated barrel was overfilled to 60 mL, capped with a layer of ParafilmTM and aluminium foil, sealed tightly by rubber band and incubated at 30°C. Over time the piston was progressively advanced to yield samples for microbiological, physical, and chemical analysis. Over 96 hours an increase in the LAB count was observed with a concomitant decrease in pH. After fermentation was complete, the samples contained around 8.77 log cfu LAB g-1 with the pH range from 4.38 to 5.08. The microbiological and pH behaviour of each species varied between preparations. Hardness, adhesiveness, springiness and cohesiveness of the treatments increased with fermentation, except for hoki. The treatments showed different colour characteristics with fermentation. The light reflectance (L* values) of the trevally and kahawai treatments increased, while the a* (redness) and b* (yellowness) values decreased. Hoki exhibited smaller colour changes except for yellowness, which increased markedly. Proteolysis, measured colorimetrically by soluble peptide bonds, was greatest for trevally. Lipid oxidation, measured by the thiobarbituric acid method, was least for hoki, notably the species with the lowest fat content. Biogenic amines, which are a general quality indicator of fermented products, increased during fermentation. The trevally treatment generated the highest concentration of amines, but these values were lower than those reported for fermented fish sausage in Southeast Asia. Notably there were no important difference between folate treatments and those without folate. The results point to commercial opportunities and further research with New Zealand marine species, especially trevally. To improve the product quality and to show geographical exclusivity, further research could be done by using starter culture, and a New Zealand staple carbohydrate source such as kumara and potato, and spices and herbs which are commonly used in New Zealand, such as rosemary, thyme and sage or specific to New Zealand, such as horopito. In addition, sensory studies should also be performed before the products could be tested in the market.

Thesis (M.S.)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains xi, 87 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Marine brown algae (seaweeds) are a rich source of fucoxanthin, a xanthophyll carotenoid that is naturally, an accessory pigment in the process of photosynthesis of sea vegetation such as Sargassum incisifolium. Fucoxanthin has been exploited by nutraceutical companies for its anti-obesity effects that has resulted in an increase of seaweed slimming preparations such as FucoThin™. The field is getting widespread consumer attention as interest in fucoxanthin has also transcended to its widespread biological potential which include cytotoxicity, anti-diabetic, anti-oxidant, anti-inflammatory and anti-plasmodium effects. We therefore wanted to identify a reliable source(s) of fucoxanthin from diverse samples of South African marine brown algae in order to explore our medicinal chemistry interests around the cytotoxicity and anti-malarial potential of fucoxanthin. A known source, Sargassum incisifolium, was used to isolate (maceration in CH₂Cl₂/MeOH at 35 °C followed by a hexane/EtOAc step gradient silica column of the crude extract and reversed phase semi-prep HPLC) and characterize (1D and 2D NMR) fucoxanthin (reference standard) in order to develop an analytical method for its determination in selected diverse brown algae commonly found in South Africa. The HPLC [Column: Phenomenex® Synergi™ (250 x 3.0 mm i.d); Mobile phase: ACN/H2O (95:5)] method developed for this analysis was validated according the guidelines set by the International Conference on Harmonization (ICH). Fifteen species were then assessed for fucoxanthin content (μg/g of dried weight) using the developed method. Stability studies on fucoxanthin were also carried out to assess photo- and pH degradation of fucoxanthin. Zonaria subarticulata (KOS130226-18) from Kenton-On-Sea beach and Sargassum incisifolium (PA130427-1) from Port Alfred beach were found to be the highest producers of fucoxanthin with 0.50 mg/g and 0.45 mg/g dried weight respectively. Fucoxanthin was found to be both photo-labile and sensitive to both acidic and basic pH environments. However, the pigment was more photostable in pure as opposed to extract form and also showed to be more stable at pH 10.0. Our findings show that Z. subarticulata and S. incisifolium could be reliable sources of fucoxanthin and can be considered as the algae to use in optimized extraction procedures in further studies. Also, when working with fucoxanthin, it is important to protect it from light. Any consideration of taking fucoxanthin preparation orally (as a nutraceutical) should consider protecting the active from the harsh conditions of the gastrointestinal tract. Any upscale production of fucoxanthin from seaweed should consider variations such as geographical, seasonal, lifecycle stage, etc. of identified algae as these may be important factors in obtaining effective concentrations of fucoxanthin.

Les relations entre les conditions de propagation acoustique et les caracteristiques geotechniques des sediments marins sont bien determinees par des experiences effectuees en laboratoire. Par contre, en mer, les conditions ambiantes (pression, contrainte, temperature) influencent le comportement des ondes acoustiques. L'objectif des recherches est d'etablir un modele de propagation des ondes sonores en fonction des caracteristiques du milieu considere et des proprietes des sediments marins, pondere par l'influence des facteurs ambiants, principalement les differentes pressions exercees sur les sediments. Les donnees experimentales acquises permettant de proposer un modele ont ete obtenues dans une enceinte de mesure haute pression creee pour quantifier l'effet de la pression interstitielle, representant la pression hydraulique des grands fonds, ainsi que la contrainte effective, symbolisant le poids des sediments sus-jacents

En acoustique sous-marine moyenne et haute frequence (de 30 khz a plusieurs centaines de khz), l'hypothese d'un corps parfaitement rigide pour les cibles recherchees est couramment admise et le rapport longueur d'onde sur taille de l'objet conduit a utiliser les principes dits de l'acoustique physique pour decrire l'interaction onde-cible. Par ailleurs, il est experimentalement bien connu que les echos d'objets situes au voisinage du fond sont differents en amplitude et forme des echos des memes objets situes en pleine eau. Malgre la presence d'interfaces (telles que le fond ou la surface) nous montrons que les principes de l'acoustique physique sont encore utilisables dans ce cas. Dans un premier temps nous developpons une methode generale pour evaluer les index et structures des echos d'objets simples situes pres du fond et observes aux incidences rasantes et nous exposons les resultats d'une simulation informatique mettant en uvre cette methode. Dans un deuxieme temps, nous presentons la validation experimentale de la modelisation proposee au moyen de deux types d'experimentations: - une premiere serie d'experimentations a echelle reduite effectuee a 200 khz. - deux series d'experimentations en vraie grandeur effectuees a 50-60 khz. L'ensemble des resultats obtenus durant ces experimentations se revelent en bon accord avec les predictions de la modelisation envisagee

Cette thèse est une contribution à la caractérisation des fonds sous-marins par des techniques acoustiques. On s'intéresse aux fonds sédimentaires, principalement sédiments sableux. Les fonds de sables sont en effet fréquemment rencontrés par petits fonds sous nos latitudes. Les procédés existants de caractérisation acoustique des fonds visent le plus souvent à qualifier la géométrie du sol ou du sous-sol: morphologie du fond, typologie des faciès sédimentaires, identification du toit rocheux ... Toutefois, les détails du sous-sol marin (stratification et composition des sables) nous échappent le plus souvent et on a alors recours à des sondages in-situ ponctuels, coûteux et souvent difficiles à réaliser. Afin de résoudre ce problème, nous avons développé SCAMPI (Système de Caractérisation Acoustique Marine Propagation Interface). C'est un dispositif de caractérisation géoacoustique breveté qui vise justement à réduire notre myopie chronique dans les premiers mètres des sous-sols sableux immergés en calculant des profils verticaux des vitesses du son. Le système développé est typique d'un processus d'inversion basé sur des mesures distantes et indirectes (on ne touche pas le sol). Disposer de profils de vitesses pour caractériser le sous-sol est une étape nécessaire, mais insuffisante pour les applications visées. Pour ces dernières, il s’agit notamment de déterminer si le sable est fin ou grossier, s'il est homogène ou hétérogène, s'il contient des coquilles, s'il est compacté ou pas.Pour répondre à de telles questions, il est nécessaire d'utiliser des relations entre les vitesses du son et les propriétés des matériaux granulaires. Ces relations géoacoustiques sont quasi-inexistantes pour les sables marins, surtout pour les sables grossiers. Pour constituer de nouvelles relations géoacoustiques, il est proposé d’établir des bases de données à partir de mesures in-situ des vitesses acoustiques et des analyses des échantillons de sédiments prélevés au même endroit. Pour cela, un prototype de célérimètre a été développé, INSEA (INvestigation of SEdiment by means of Acoustic), qui permet de mesurer les vitesses et l'atténuation du son dans des sédiments, y compris dans des sables grossiers
This thesis is a contribution to the seabed exploration by means of acoustical methods. We focus on sediment seabeds, especially on sand sediments because there are often encountered off European coasts. Existing acoustic methods for seabed characterization generally aim to qualify the sub-seafloor: sediment thickness or bedrock cap detection.Nevertheless, accurate sediment stratification or details of the involved sediment are generally out of reach. This is why SCAMPI (Sub-seafloor Characterization by Acoustic Measurements & Parameters Inversion) have been have designed. This patented device is a geoacoustical inversion method based on an underwater acoustic instrumentation towed in water column. It aims to identify and characterize sediment layers over a thickness of 5-10 meters below the seabed, quantifying major physical parameters as compressional speed. But vertical sound speed profiles of the sub-seabed is a necessary step but is insufficient to predict refined information about the sediment: is it coarse, homogeneous, does it contain inclusions ..?To give answers to these questions, geoacoustical relations linking acoustic parameters to sedimentological parameters are required. But these relations are sparse, particular for coarse sands.A velocimeter prototype INSEA (INvestigation of SEdiment by means of Acoustic) have been designed, to measure in situ acoustical parameters of the first centimeters of the seafloor, even in coarse sands. This work is the preliminary work leading to a new project which consist in building specific data bases to elaborate these geoacoustical relations and theoretical modeling in granular wet media suited to marine geophysics applications

L'imagerie acoustique des fonds marins par sonar latéral présente certaines difficultés que pourrait résoudre la technique de l'ouverture synthétique. Les systèmes sonar permettant d'obtenir une résolution fine dans le sens du déplacement du porteur d'antenne (azimut) sont généralement composés d'antennes très longues ou utilisent des hautes fréquences peu propices à se propager à grande distance. De plus, la résolution se dégrade généralement avec la distance antenne-fond. La synthèse d'ouverture permet d'intégrer le mouvement du porteur pour calculer une antenne plus longue que l'antenne physique utilisée. Cette méthode permet ainsi d'obtenir une résolution azimutale fine et, grâce à la focalisation dynamique, de la maintenir constante. Le but de ce travail est d'analyser les problèmes liés à l'implantation d'une telle méthode en milieu marin. Une approche nouvelle est développée, montrant les avantages de l'émission de signaux large bande: simplification du calcul, amélioration des résolutions temporelle et azimutale, possibilité de lutter contre l'effet Doppler différentiel ou d'augmenter la vitesse de couverture. Différents schémas de calcul sont proposés et leurs performances comparées. On étudie, à l'aide de simulations, les conséquences des perturbations de la trajectoire du porteur d'antenne en utilisant un critère quantifiant une focalisation correcte. Des essais en cuve sont effectués dans des conditions bien contrôlées pour valider les concepts en obtenant des images acoustiques de cibles canoniques ou plus complexes. Des essais en mer ont permis de montrer l'intérêt des traitements développés et de vérifier le bon fonctionnement de l'ouverture synthétique dans des conditions expérimentales plus sévères. Grâce à ces essais, on est en mesure de montrer le gain d'une méthode d’auto-focalisation permettant de pallier le problème de la trajectoire erratique de la plate-forme remorquée
Sea bed acoustical imaging is classically achieved by means of side looking sonars which are operated with very long arrays or high frequencies. These heavy or short range systems give generally images with azimuthal resolution decreasing with range. Synthetic aperture techniques could solve these difficulties in taking profit of both the array translation and the dynamic focussing. The aim of this work is to analyse the possibility of such techniques, in the ocean medium. A new approach is developed, showing the interest of wideband signals transmission: both range and azimuthal resolutions and coverage rate increase, processing simplicity, differential Doppler effect decrease. Several processing schemes are proposed and their performance are compared in the case of a perfect trajectory. Thanks to a simulation software, the consequences of trajectory perturbations are studied. This approach is completed by two experimental validations. Tank experiments are conducted in well controlled conditions in order to validate the concepts with simple or more complex targets. Sea trials have been achieved with an experimental prototype and the first images show the validation of the developed processing. The interest of synthetic aperture is clearly shown in a more severe experimental environment. Thanks to these trials, we can point out interesting results of an auto focussing method which allows to solve some problems linked to the erratic trajectory of the towed body

L'onde emise par les sondeurs 3,5 khz penetre les couches de sediment. La succession des tirs acoustiques permet ainsi de reconstituer une coupe verticale du sous-sol marin. Les traitements classiques proposent un suivi de l'interface eau-fond mais ne fournissent pas d'information sur les strates sedimentaires successives. Nous decrivons une methode originale de detection des reflecteurs, fondee sur l'analyse en paquets d'ondelettes et qui utilise la correlation entre les tirs voisins. Une approche image est cependant plus appropriee pour tracer les reflecteurs et nous presentons un algorithme de suivi de contour multiresolution, mene, soit a partir de la transformee en ondelettes, soit a partir d'une pyramide de chehikian. Considerer l'image a differentes echelles permet d'obtenir des reflecteurs continus, avec une localisation precise et peu de structures erronees. Par ailleurs, un algorithme de recherche automatique des seuils a partir de la distribution des donnees est mis au point. Nous etudions ensuite la possibilite d'estimer le coefficient d'attenuation des ondes de compression : les methodes de filtrage adapte, rapport des spectres et decalage de la frequence centrale doivent etre adaptees aux signaux recueillis pour compenser la longueur du signal source et l'absence de modulation d'amplitude. Une etude theorique et des simulations menees a partir d'un modele de fond stratifie permettent de proposer des solutions et demontrent l'interet des distributions temps-frequence pour analyser ces signaux. Les resultats sur des profils reels sont egalement presentes. Nous envisageons egalement l'identification de la nature de la premiere couche de sediment a partir du signal compose de l'echo de fond et du premier reflecteur. Cette demarche s'appuie sur les etapes d'extraction de parametres et de selection des caracteristiques a l'aide d'une analyse factorielle discriminante. Une classification est effectuee par un reseau a fonction a base radiale.

Le travail présenté aborde le problème de la caractérisation acoustique du fond marin à partir de l'étude de la dispersion de célérité des ondes d'interface de type Stoneley-Scholte. De telles ondes, dont les propriétés sont fortement liées à la nature du fond sédimentaire, se propagent à l'interface eau-sédiment. Le premier chapitre est consacré à la définition et à la description de l'onde de Stoneley-Scholte à partir d'une combinaison d'ondes planes évanescentes acoustiques. La seconde partie étudie, pour différentes configurations marines, la dispersion des célérités de phase et de groupe de l'onde d'interface lors de sa propagation. Le troisième chapitre concerne l'étude expérimentale de la propagation de l'onde d'interface ainsi que la simulation de traces sismiques par le code SISMOS. Les expérimentations sont réalisées sur des maquettes de fonds marins où des dispositifs spécifiques d'excitation et de détection de l'onde de Stoneley-Scholte ont été mis au point. L'étude de la dispersion de célérité de groupe est alors effectuée à partir d'une analyse temps-fréquence basée sur la distribution de Wigner-Ville. Quelques couples (fréquence,célérité) de ces courbes de dispersion servent de données d'entrée aux algorithmes du problème inverse, objet de la quatrième partie. Deux méthodes d'optimisation ont été utilisées pour la résolution du problème inverse. La première, la méthode du gradient conjugué, nécessite la connaissance d'informations a priori sur la solution du problème. Sensible aux perturbations des données d'entrée, elle ne converge pas toujours vers la solution désirée. La seconde, plus robuste, basée sur un réseau neuronal, ne nécessite aucune information a priori et fournit une très bonne estimation des paramètres acoustiques du fond sédimentaire
This work tackles the problem of the acoustical characterization of the sea bottom from the analysis of the velocity dispersion of interface waves of the Stoneley-Scholte type. Such waves, which properties are close! y linked to the properties of the sea bottom, propagate along the water-sediment interface. The first chapter is devoted to the definition and the description of the Stoneley-Scholte wave from a combination of acoustical evanescent plane waves. The second part studies, for different marine configurations, the phase and the group velocities dispersion of the interface wave during the propagation. The third chapter is devoted to the experimental study of the propagation of the interface wave and the simulation of seismic signals thanks to the SISMOS code. The experiments are carried out using sea bottom mock-ups and specific devices have been developed to generate and detect the Stoneley-Scholte wave. The study of the group velocity dispersion is performed from a time-frequency analysis based on the Wigner-Ville distribution. A few (frequency,velocity) couples picked-up on the velocity dispersion curves are used as input data of the inverse problem algorithms, aim of the fourth part of the work. Two optimization methods have been developed to solve the inverse problem. The first one, called the conjugate gradient method, needs a priori information about the solution to find. This method is sensitive to noisy data and does not always converge to the desired solution. The second method is based on a neural network. It is more robust and does not require a priori guess and leads to very good estimations of the acoustical parameters of the sea bottom

Les sondeurs multifaisceaux grands fonds basse frequence (13 khz) permettent d'obtenir simultanement la bathymetrie et la reflectivite acoustique de larges zones. Dans un tel contexte de caracterisation des fonds, la grandeur pertinente utilisable est l'indice de retrodiffusion angulaire. L'interpretation des donnees experimentales a l'aide des modeles classiques est parfois sujette a des ambiguites, principalement dues a la penetration du signal dans le volume sedimentaire. L'objectif de cette these est de proposer differentes approches permettant de mieux comprendre les liens existant entre l'acoustique et la geologie. La stratification des premiers metres de sediment est modelisee via l'indice de retrodiffusion ramene, base sur des modeles classiques de retrodiffusion et la propagation d'ondes planes dans un milieu multicouche. Les effets de l'enfouissement, de la refraction et de l'attenuation affectant les diverses contributions sont pris en compte ainsi que la presence eventuelle de variations continues des parametres acoustiques. L'utilisation de ce modele conjointement a une analyse geotechnique detaillee permet de lever certaines ambiguites d'interpretation. La presence d'inclusions de dimensions non negligeables vis-a-vis de la longueur d'onde est modelisee a l'aide de la diffusion par des cibles spheriques. La comparaison avec des donnees experimentales, provenant tant de mesures en laboratoire que d'enregistrements du sondeur, montre la capacite de cette approche a decrire correctement l'evolution angulaire et l'ordre de grandeur des indices de retrodiffusion. L'interet d'utiliser la theorie de biot pour decrire le comportement acoustique des sables sedimentaires a ete etudie. Certains des parametres mis en jeu ont ete mesures en utilisant des dispositifs experimentaux developpes en acoustique aerienne. Les mesures de vitesses du son dans les sables satures d'eau ont mis en evidence la dispersion des ondes due a la diffusion par les grains. L'onde lente n'a pas pu etre visualisee. L'utilisation de cette theorie pour decrire la propagation des ondes dans les sediments marins non consolides est sans doute moins necessaire que la prise en compte des effets d'inhomogeneites de volume.

Une large part des deformations observees dans les marges actives est liee a la subduction des reliefs du plancher oceanique (volcans sous-marins, rides et plateaux volcaniques). Afin d'etudier les mecanismes et la cinematique de ces deformations, nous avons analyse des donnees geophysiques provenant de campagnes oceanographiques et des donnees experimentales issues de modelisations analogiques. L'etude des deformations en trois dimensions de la structure interne de la marge a permis de mettre en evidence le role majeur que joue la subduction des reliefs oceaniques dans l'evolution structurale de la plaque chevauchante et dans les transferts de matiere au sein de la marge. La subduction de ces asperites engendre un champ de contraintes caracteristique qui se traduit par un soulevement et un poinconnement de la marge en avant du relief qui subduit, suivie par une phase de subsidence tres rapide en arriere. La propagation du niveau de decollement basal est fortement perturbee par la subduction du relief et se traduit par la formation d'une zone abritee dans son sillage. Une partie du front de la marge est alors entrainee en subduction en arriere du relief puis finalement sous-plaquee a la base de la marge. L'intense fracturation de la marge favorise aussi l'expulsion des fluides et a probablement pour consequence une diminution de la pression de fluide au niveau du decollement basal et donc une augmentation locale du couplage mecanique inter-plaque.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第21804号
農博第2317号
新制||農||1065(附属図書館)
学位論文||H31||N5176(農学部図書室)
京都大学大学院農学研究科応用生物科学専攻
(主査)教授 菅原 達也, 教授 佐藤 健司, 教授 松井 徹
学位規則第4条第1項該当

Cette étude concerne la modélisation de la réverbération par petits fonds, réalisée en couplant un modèle de propagation et un modèle de diffusion. Ce couplage est basé sur la décomposition en ondes planes du champ acoustique et sur la description des interfaces au moyen d'index de diffusion. La complexité de cette décomposition dépend du modèle utilisé pour les calculs de propagation. La théorie des modes normaux fournit un accès quasi-direct au spectre du champ incident, mais trouve ses limitations pour un environnement variable en distance. L'utilisation de modèles basés sur la théorie de l'équation parabolique est courante pour l'analyse des milieux variables mais ne peut fournir directement le spectre des ondes planes. Le modèle développé, REVPA, est basé sur une approximation "grand-angle" de l'équation parabolique (Padé à l'ordre 4). Il permet de résoudre les problèmes de propagation dans des configurations variées (fond rigide/sédimentaire, profil de célérité constant/variable). La prise en compte des index de diffusion nécessite de réaliser une décomposition en ondes planes. La transformée de Fourier spatiale, couramment utilisée, se heurte à une limitation importante en présence de fonds sédimentaires. Une méthode de décomposition modale basée sur l'approximation WKB a donc été développée. Les avantages et les limitations de ces techniques ont été analysés au travers de nombreuses simulations dont les résultats ont été comparés à ceux obtenus avec un modèle de référence. Ces comparaisons ont permis notamment de montrer les fortes limitations liées à la transformée de Fourier. Même si elle possède également ses limitations, la décomposition modale permet de pallier celles de la décomposition de Fourier. De nombreux tests ont permis de valider le modèle REVPA associé à cette décomposition (erreur< 0,2 dB). Sa validation finale ainsi que sa comparaison avec des modèles basés sur des approches modales nécessitent la comparaison à des données expérimentales
This study deals with shallow-water reverberation modeling. The coupling of a propagation model and a scattering one made the modeling possible. This coupling is based on a plane-wave decomposition of the acoustic field and the description of the interfaces by scattering indexes. The difficulty of the decomposition depends on the model used for propagation modeling. The normal mode theory gives a straight access to the spectrum of the incident field but is limited in the case of a variable environment. Models based on the parabolic equation are usually used for the analysis of range dependent environments but they cannot provide directly the plane-wave spectrum. The developed model, REVPA, is based on a wide-angle approximation of the parabolic equation (4th order Padé). It can solve propagation problems for several Environmental configurations (rigid or sedimentary bottom, constant or variable sound-speed profile). In order to introduce scattering indexes in the mode!, the amplitudes and phases of the plane waves must be determined by means of plane-wave decomposition. The spatial Fourier transform, usually used, is strongly limited for sedimentary bottom. A modal decomposition based on the WKB approximation has therefore been developed. The advantages and limitations of each technique have been analysed through different simulations, the results of which have been compared to those obtained with a reference model. These simulations have pointed out the major limitations of the Fourier transform especially when the reverberation phenomena are localised on a sedimentary bottom. Although it possesses its own limitations, the modal decomposition allows overcoming those of the Fourier transform. The REVPA model associated with this decomposition has been validated through numerous tests (discrepancy less than 0,2 dB). The final validation and the comparison of the REVPA model with those based on normal mode method require several comparisons with experimental data

Dans le cadre du programme européen MAST III, le Laboratoire de Mécanique Physique a développé un nouveau sonar frontal (COSMOS). La géométrie frontale permet d'observer le fond selon une succession d'angles différents. La réponse angulaire de rétrodiffusion locale est ainsi accessible et des données acoustiques a été enregistrée au cours d'une campagne. Le choix des zones était fondé sur la grande variété de la nature des fonds. Nous présentons dans cette thèse les résultats concernant à la segmentation et la classification du fond en exploitant la réponse angulaire de rétrodiffusion. Après une brève exposition sur les différents systèmes d'exploration acoustique des fonds marins, les caractéristiques du système COSMOS sont détaillées. L’état de l’art sur la caractérisation du fond marin moyennant sonars est présenté. La modélisation de l’interface eau/sédiment est décrite. Le processus de segmentation et le classement des sédiments est développé. Les réponses angulaires de rétrodiffusion sont projetées dans une base de composantes principales, plus classées. Ce processus a permis de délimiter correctement les zones homogènes du fond. La plupart du temps, on peut identifier directement ces zones sur les mosaïques d'images de rétrodiffusion, mais la segmentation a fait aussi apparaitre d'autres zones que ces images seules ne permettent pas de discriminer. Un classement est réalisé en ajustant les paramètres du modèle physique aux réponses observées. Les paramètres de chaque classe résultant de ce processus sont ensuite associés à un type de sédiment. La comparaison avec l'analyse des échantillons prélevés in situ pendant la campagne est satisfaisante

Le but de ce travail est de contribuer a la connaissance des lois qui regissent la stabilite des carbonates dans la nature, en particulier dans les solutions hydrothermales et dans les eaux interstitielles des sediments marins. Apres analyse des donnees de la litterature, l'auteur est amenee, entre autres, a mesurer jusqu'a cent degres les constantes apparentes de dissociation de l'acide carbonique et le produit de solubilite de la calcite dans l'eau de mer. De meme, les premieres determinations experimentales du produit de solubilite de la dolomite a haute temperature sont realisees dans des solutions de chlorure de sodium. Pour tous les parametres etudies, des interpolations en fonction de la temperature sont proposees en tenant compte des mesures effectuees et des donnees de la litterature. A l'issue de cette etude il est etabli que le produit de solubilite de la calcite dans l'eau de mer diminue lorsque la temperature augmente, effet difficile a deceler uniquement a partir des donnees en dessous de vingt-cinq degres. Des essais de dissolution de longue duree montrent que l'eau de mer est sursaturee par rapport a l'anhydrite des quatre-vint-dix degres et suggerent que la calcite joue un role dans la cristallisation de phyllosilicates magnesiens. Par ailleurs, des essais a deux cents degres conduisant a la dolomitisation de la calcite en milieu marin permettent de calculer le produit de solubilite de l'anhydrite et mettent en evidence les presences simultanees de calcite magnesienne, dolomite calcique et magnesite calcique. Pour tous les parametres etudies, a l'exception de la constante de dissolution du gaz carbonique, les courbes en fonction de la temperature dans l'eau de mer s'ecartent sensiblement des courbes dans les solutions de chlorure de sodium dans la gamme de concentration consideree

Jellyfish populations in the Irish Sea have been increasing. This has caused a variety of economic problems, such as the destruction of aquaculture installations, and new opportunities, such as the establishment of a jellyfish fishery. However, interactions between jellyfish and other biota in the ecosystem is poorly characterised and ecological consequences of an increasing jellyfish population remains unknown. Molecular gut content analysis methodologies were developed to address this data gap. Cnidarian specific primers were developed and showed using more than 2500 stomachs that, during February and March, moon and mauve-stinger jellyfish were consumed by common fish species including herring, whiting, and lesser-spotted dogfish. Revisiting the ecosystem in October with 375 additional samples, the primers indicated jellyfish predation varied temporally: small jellyfish were still targeted by mackerel, however moon jellyfish adults were not preyed upon. To understand the context in which jellyfish consumption occurred a high throughput sequencing (HTS) approach using two universal primers was developed. A meta-analysis of HTS studies suggested results contained a quantitative signal, and the methodology could be used to move beyond a presence/absence approach. Using 188 samples from nine fish species, it was shown that jellyfish were consumed as part of a generalised diet during summer months. Finally, the approaches used to model jellyfish in the ecosystem model Ecopath with Ecosim (EwE) were reviewed. Jellyfish were included more frequently over time, however approaches remained relatively crude in the absence of high quality data in many ecosystems. Together, these approaches have gone some way towards addressing the data gap: jellyfish interactions with other biota have been recorded, and new approaches for studying these interactions have been developed. This has established a baseline for novel research opportunities such as mechanistic modelling of jellyfish, exploration of quantitative HTS approaches, and the generation of dietary time-series data to be conducted.

La sécurité alimentaire, qui est la garantie de l’approvisionnement et de la qualité des aliments tout en gérant les ressources de manière durable, est intrinsèquement liée à la connaissance de la biologie et l’écologie des espèces consommées. Dans un contexte de dérèglement climatique menaçant la salubrité des produits de la mer, il est donc nécessaire d’établir un référentiel sur le fonctionnement des systèmes marins, ainsi que sur l’occurrence des nutriments et des contaminants dans les produits de la mer. C’est d’autant plus important pour les Petits Etats Insulaires en Développement (PEID), qui dépendent des ressources marines pour leur subsistance, et où les produits de la pêche sont la première source de protéines et micronutriments (éléments traces essentiels) pour les populations locales. Malgré l’importance des systèmes tropicaux pour la sécurité alimentaire, ces systèmes sont peu étudiés comparés aux systèmes polaires et tempérés. Cette thèse vise à mieux comprendre le fonctionnement des systèmes marins tropicaux, et à établir un référentiel sur l’occurrence des micronutriments et des contaminants métalliques dans les produits de la pêche aux Seychelles (Océan Indien), un PEID tropical. En étudiant les concentrations en éléments traces aux niveaux inter- et intraspécifique, nous avons identifié différents facteurs intrinsèques et extrinsèques influençant la bioaccumulation de ces éléments dans les ressources marines tropicales. Nous avons aussi montré l’importance de considérer différentes échelles (individu, espèce et écosystème) pour mieux comprendre l’occurrence des éléments traces essentiels et non-essentiels dans les produits de la mer
Food security, that is guarantying food supply and quality while sustainably managing resources, is closely linked to knowing the biology and ecology of consumed species. In a context of global changes that are threatening seafood safety, it is thus necessary to establish baselines on marine ecosystem functioning, as well as nutrient availability and contamination occurrence in seafood. This is all the more important in Small Island Developing States (SIDS), where populations rely on marine resources for their subsistence, and where capture fisheries resources are the main sources of proteins and micronutrients (i.e. essential trace elements) in local populations’ diet. In spite of the importance of tropical systems in ensuring food security, they remain largely understudied compared to polar and temperate systems. This thesis thus aims to better understand the functioning of tropical marine systems, and to establish a baseline on micronutrient availability and metal(loid) contamination in a wide diversity of capture fisheries resources from the Seychelles (Western Indian Ocean), a tropical SIDS. By investigating trace element concentration patterns at the inter- and intraspecific levels, it was possible to identify intrinsic and extrinsic factors influencing trace element bioaccumulation in tropical capture fisheries resources. We thus highlighted the importance of considering different scales (individual, species, and ecosystem) to better understand essential trace element availability and non-essential trace element occurrence in seafood

Aquatic microbial food webs are in general size structured. Phytoplankton, which constitute the base of the food web, are grazed by protozoa and mesozooplankton, which in turn are consumed by planktivorous fish. Food web efficiency (FWE) is a measure of how efficiently energy is transported up the food web. FWE is low if the phytoplankton is inedible by the grazers, while FWE is higher if the phytoplankton community is dominated by edible phytoplankton. Recently, the presence of microfungi in aquatic food webs have been suggested to facilitate energy transfer up the food web, via the “mycoloop”. The aim of the study was to set-up a model system of phytoplankton – zooplankton food chains, relevant to the Baltic Sea, and to test FWE in diatom and flagellate-based food webs. Further, I wanted to introduce microfungi in the system and observe their impact on FWE. After many phytoplankton and zooplankton species tests, I decided to perform grazing experiments using one grazer, the ciliate Tetrahymena pyriformis, and two phytoplankton species: a diatom (Skeletonema marinoi) and a flagellate (Rhodomonas baltica). I hypothesized that T. pyriformis would more efficiently feed on flagellates than on diatoms. I performed a grazing experiment where the increase in ciliate abundance was measured, the consumption of the phytoplankton monitored and the FWE estimated. The diatom-based food web led to 14 times higher FWE than the flagellate-based food web. The variation in FWE may be explained by a difference in initial abundances introduced in the experimental treatment, which created unequal grazer:prey ratio between treatments. Further, the swimming behaviour of the flagellate might have reduced the capture efficiency by the ciliate. Microfungi were introduce in an experiment, from a natural seawater sample, but fungal infection was not observed for any of the tested phytoplankton species. Further development is needed to test the effects of microfungi on marine FWE.

La présente étude est une analyse du régime juridique défini par la convention des Nations-Unies sur le droit de la mer du 10 décembre 1982 pour l'exploitation des ressources minérales des grands fonds marins. La convention du 10 décembre 1982 consacre définitivement les principes de la RE commun de l'humanité. Elle opte par conséquent pour un régime d'internationalisation, c'est à dire une mise en valeur collective des ressources par la communauté internationale. Ainsi, pour l'exploitation des nodules polymétalliques des grands fonds marins, la convention institue un système d'exploitation parallèle aux conséquences très lourdes pour les opérateurs des pays industrialisés. En effet, pour permettre à l'entreprise internationale de l'autorité de devenir opérationnelle au même titre que les autres contractants, la convention oblige ces derniers à mettre à la disposition de l'entreprise les ressources financières et technologiques nécessaires a son fonctionnement effectif. Hormis la lourdeur des mécanismes prévus, le système conventionnel se trouve sérieusement compromis du fait aussi des législations adoptées par quelques États industrialises qui organisent les activités de leurs entreprises dans un cadre purement national. Consciente de ces difficultés, la troisième conférence a prévu un régime transitoire applicable avant l'entrée en vigueur de la convention. La commission préparatoire créée par la résolution no 1 a été chargée a cet effet de prendre toutes les mesures susceptibles de favoriser l'installation effective de l'autorité dès l'entrée en vigueur de la convention. En vertu de la résolution no 2, elle a pour mission aussi de procéder à l'enregistrement des investisseurs pionniers remplissant les conditions requises. La commission préparatoire qui a commencé ses travaux depuis mars 1983 pourra, malgré des résultats encore maigres, enregistrer dès la session de mars 1987, les investisseurs pionniers de la première catégorie (Inde, France, URSS et Japon)
This study is an analysis of the judicial regime which was defined by the united nations convention about the sea rights, on the 10th of December 1982, concerning the deep sea bed hard mineral resources exploitation. The convention of the 10th of December 1982 definitely sanctions the principles of the resolution 2749 (xxv) voted on the 17th of December 1970, which declares that the deep sea bed zone is a common heritage of humanity. Consequently, it decides in favor of an internationalization regime, that is to say, of a collective pointing out of the resources by the international community. Thus, in order to exploit the deep sea bed polymetallic nodules, the convention sets up a parallel exploiting method which brings about very heavy consequences for the industrialized countries operators. As a matter of fact, to permit to the authority international enterprise to become operational on the same level as the other contracting parties, the convention compels the latter to place the necessary technological and financial resources for its effective working at the enterprise's disposal. Save the heaviness of the rated mechanisms, the conventional system finds itself seriously endangered too by the adoption, by some industrialized countries, of legislations which organize their enterprises activities inside a strictly national framework, fully aware of these difficulties, the third conference provided for a temporary regime that can be applied before the convention comes into operation. To this end, the preparatory commission, created by the resolution no 1, was charged with adopting all the measures likely to favor the authority effective setting up, as soon as the convention comes into operation. By virtue of the resolution no 2, its mission also is to register the pioneer investors who are in the required position. In spite of still poor results, the preparatory Commission, which has started working since March 1983, will be able to register the first category of pioneer investors (India, France, U. S. S. R and Japan) as early as the session of March 1987 begins

Au cours des dernières décennies, les avancées en termes de technologies robotiques sous-marines ont permis de réaliser des levés sur les fonds marins à l'aide de véhicules sous-marins autonomes (AUV). Ainsi, équiper un AUV avec un sonar latéral permet de scanner une vaste zone de manière rapide. Naturellement, les forces armées se sont intéressées à de tels dispositifs pour effectuer des missions de chasses aux mines rapides et sécurisées pour le facteur humain. Néanmoins, analyser des images sonar par un ordinateur plutôt que par un opérateur reste très complexe. En effet, les chaînes de reconnaissance automatique de cibles (ATR) doivent faire face à la variabilité de l'environnement marin et il a été démontré qu'une forte relation existe entre la texture d'une image et la difficulté d'y détecter des mines. Effectivement, sur des fonds fortement texturés, voire encombrés, les performances d'une chaîne ATR peuvent être très dégradées. Ainsi, intégrer des informations environnementales dans le processus apparaît comme une piste crédible pour améliorer ses performances. Ces travaux de thèse proposent d'étudier la manière de décrire cet environnement marin et comment l'intégrer dans un processus ATR. Pour répondre à ces défis, nous proposons tout d'abord une nouvelle représentation des images sonar basée sur l'utilisation du signal monogène. Ce dernier permet d'extraire des informations énergétiques, géométriques et structurelles sur la texture locale d'une image. La nature multi-échelle de cet outil permet de tenir compte de la variabilité en taille des structures sous-marines. Ensuite, le concept de dimension intrinsèque est introduit pour décrire une image sonar en termes d'homogénéité, d'anisotropie et de complexité. Ces trois descripteurs sont directement reliés à la difficulté de détection des mines sous-marines dans un fond texturé et permettent de réaliser une classification très précise des images sonar en fonds homogènes, anisotropes et complexes. De notre point de vue, la chasse aux mines sous-marines ne peut pas être réalisée de la même manière sur ces trois types de fond. En effet, leurs natures et caractéristiques propres mènent à des challenges variés pour le processus ATR. Pour le démontrer, nous proposons de réaliser un premier algorithme de détection spécifique, appliqué aux zones anisotropes, qui prend en considération les caractéristiques environnementales de ces régions
In the last decades, advances in marine robot technology allowed to perform accurate seafloor surveys by means of autonomous underwater vehicles (AUVs). Thanks to a sidescan sonar carried by an AUV, a wide area can be scanned quickly. Navies are really interested in using such vehicles for underwater mine countermeasures (MCM) purposes, in order to perform mine hunting missions rapidly and safely for human operators. Nevertheless, on-board intelligence, which intends to replace human operator for sonar image analysis, remains challenging. Current automatic target recognition (ATR) processes have to cope with the variability of the seafloor. Indeed, there is a strong relationship between the seafloor appearance on sidescan sonar images and the underwater target detection rates. Thus, embed some environmental information in the ATR process seems to be a way for achieving more effective automatic target recognition. In this thesis, we address the problem of improving the ATR process by taking into account the local environment. To this end, a new representation of sonar images is considered by use of the theory of monogenic signal. It provides a pixelwise energetic, geometric and structural information into a multi-scale framework. Then a seafloor characterization is carried out by estimating the intrinsic dimensionality of the underwater structures so as to describe sonar images in terms of homogeneity, anisotropy and complexity. These three features are directly linked to the difficulty of detecting underwater mines and enable an accurate classification of sonar images into benign, rippled or complex areas. From our point of view, underwater mine hunting cannot be performed in the same way on these three seafloor types with various challenges from an ATR point of view. To proceed with this idea, we propose to design a first specific detection algorithm for sand rippled areas. This algorithm takes into consideration an environmental description of ripples which allow to outperform classic approaches in this type of seafloor

The purpose of this study was to identify if terrestrial arthropod predators on Baltic Sea shores vary in their use of marine versus terrestrial food items, and to construct a bottom-up food web for Baltic Sea shores. The inflow of marine nutrients in the area consists mainly of marine algal detritus and emerging aquatic insects (e.g. phantom midges, Chironomidae). Diets of coastal arthropods were examined using carbon and nitrogen stable isotope analysis, and a two source mixing model was used to examine proportions of marine carbon to diets. The results suggest that spiders are the terrestrial predators mainly utilizing nutrients and energy of marine origin on Baltic Sea shores, while insect predators such as beetles and hemipterans mainly utilize nutrients and energy derived from terrestrial sources, possibly due to differences in hunting behaviour. That spiders are the predators that benefit the most from the marine inflow suggest that eventual effects of marine subsidies for the coastal ecosystem as a whole are likely mediated by spiders.

Ecological models have problems showing the positive relationship between diversity and stability found in nature. Theory states that complex food webs have high extinction risks and low stability. However, persistent food webs found in nature are large and complex containing many interconnections between species. There are many possible mechanisms enabling persistent food webs such as; complex interaction patterns, asynchronous fluctuations of species densities, environmental fluctuations and spatial distribution. These factors have not been used in classical models. In this study, coloured environmental 1/f noise and dispersal between subpopulations were incorporated into a diamond shaped food web based on a model by Vasseur and Fox 2007. Contradictions between theoretical and empirical results regarding food webs can be resolved by detailed analyses of models, withholding stabilizing mechanisms. Weak environmental 1/f noise generated an increased coefficient of stability but the stabilizing effect of noise can be questioned because of a decreased mean food web biomass and reduced stabilizing effect when reddened. However, detailed studies of the food web revealed that noise can redistribute density proportions between species, evading lowest species density and thereby increase food web resistance to demographic stochasticity and catastrophes. Noise induced density proportion shifts imply that large population sizes are no insurance towards future increase in environmental variance. Synchrony of species environmental responses and dispersal between subpopulations can both have major influences on stability and extinction risk of smaller food webs indicating that spatial structure could be one of the dominating factors stabilizing complex food webs found in nature.

L'apport de la convention de 1982 sur le droit de la mer est considerable mais ce sont ses dispositions relatives a l'exploration et a l'exploitation des ressources minerales des grands fonds marins qui sont les plus novatrices. Ces dispositions qui font l'objet de la partie xi de la convention et de ses annexes iii et iv, ont d'ailleurs suscite les plus vives controverses lors des negociations et empechent encore actuellement l'entree en vigueur de la convention en effet, le systeme a vocation universelle mis en place par la convention n'est pas accepte par les pays industrialises qui seuls possedent la technologie et le financement necessaires a l'exploitation des fonds oceaniques. Ces etats ont d'ailleurs adopte des legislations nationales en attendant l'entree en vigueur de la convention. Au dela de l'apparente contradiction entre ces deux modeles de gestion des grands fonds marins, une conciliation s'avere possible. Conciliation qui est tentee au sein de la commission preparatoire, le forum international ou se joue actuellement l'avenir du droit des grands fonds marins
The contribution of the 1982 u. N. Convention on the law of the sea is significant but its provisions concerning deep seabed mining are not accepted by the industrialized states. They have adopted domestic legislation pending the entry into force of the convention. In consequence there is an opposition between the convention regime and the alternative regime based on a network of national laws but beyond this apparent contradiction, a conciliation is possible, the majority of the interested countries are tyring within the preparatory commission to render the convention regime acceptable to all. The future of the deep seabed mining international law depends on the work of this forum

Certains fonds marins présentent des zones d'instabilités aux conséquences économiques et humaines graves sur les ouvrages offshores. Il serait donc impératif d'estimer, pour un champ donné, la probabilité d'avoir un glissement en un point donne. Dans une première partie bibliographique sur la morphologie et les causes de glissements des fonds marins, nous justifions l'importance de l'objet de l'étude à savoir les glissements translationnels rétroprogressifs déclenchés par une action sismique ou un apport rapide et massif de sédiments. La progression pouvant se traiter par des probabilités de transition, nous présentons les outils de cette modélisation de fiabilité des talus avec une représentation de la variabilité spatiale des propriétés des sols par des champs stochastiques (Vanmarcke 77 et 83). Dans la deuxième partie nous présentons d'abord un modèle de glissement élémentaire probabiliste 3D développé sur la base des observations décrites dans la bibliographie. On définit alors, pour une profondeur donnée, les dimensions horizontales d'un glissement optimum, avec sa probabilité de ruine et les probabilités des glissements adjacents. Nous définissons ensuite un modèle analytique probabiliste qui permet de décrire l'évolution des glissements translationnels successifs. Ainsi, nous définissons la probabilité de rupture en un point donné. Nous utilisons en général la simulation numérique pour calculer la probabilité des chemins qui conduisent à la rupture en ce point. Nous analysons enfin l'évolution des glissements à partir d'un point de départ donné. Cette évolution est décrite par simulation numérique pour laquelle nous définissons un critère d'arrêt pour obtenir les formes les plus probables d'un champ de glissements successifs

Un programme d'inversion des formes d'ondes sismiques a ete developpe pour estimer les proprietes d'un milieu stratifie elastique dans le domaine temps-distance. Ce programme est capable de prendre en compte des donnees hautes frequences (0-50 hz) et des milieux finement stratifies, ce qui en fait une methode particulierement adaptee a l'inversion de profils de sismique marine, y compris ceux enregistres par des sismographes fond de mer. Le probleme inverse est resolu par une technique de moindres carres generalisee. Cette technique necessite de pouvoir resoudre rapidement le probleme direct et calculer efficacement la matrice des derivees de frechet qui represente la sensibilite au premier ordre des champs d'ondes par rapport a de faibles modifications des parametres elastiques du modele. Le probleme direct est resolu en utilisant une technique classique de matrices de reflexion-transmission generalisee combinee avec une integration en nombres d'ondes discrets. Les derivees de frechet sont obtenues sous forme analytique a l'aide des fonctions de green du milieu non perturbe. Nous proposons deux approches pour calculer ces derivees. La premiere consiste a les calculer directement dans le domaine temps-distance en representant les interfaces par des arrangements reguliers de points diffractants. La deuxieme approche est une nouvelle methode de calcul basee sur une formulation analytique qui permet d'evaluer avec rapidite et precision les derivees de frechet pour une perturbation des parametres elastiques d'une couche plane d'extension infinie. La methode d'inversion proprement dite utilise une technique de gradients conjugues dans le domaine temps-distance, en integrant toutes les techniques developpees precedemment. La methode est illustree par des exemples d'inversion de donnees synthetiques realistes, mais aussi par des enregistrements reels de type obs de la campagne malis en mer ligure. La robustesse de la methode a ete etudiee en imposant aux donnees ou au milieu de propagation certaines erreurs violant les hypotheses de base de l'algorithme. La methode permet par ailleurs de considerer un grand nombre de geometries source-recepteur et peut s'appliquer en particulier a des enregistrements de profils sismiques verticaux, ainsi qu'a des modeles presentant une forte variabilite des proprietes elastiques suivant la profondeur.

Thesis (Ph.D.) - Simon Fraser University, 2006.
Theses (School of Resource and Environmental Management) / Simon Fraser University. Senior supervisor : Dr. Frank A. P. C. Gobas. Included bibliographical references : leaves 226-248.

2011/2012
SUMMARY Biotoxins produced by harmful algae during their proliferation can be accumulated by filter feeding organisms, such as bivalve shellfish, within their flesh. Furthermore, these toxins gradually are transferred to the higher trophic levels in the food chain, posing a threat to human health, after consumption of contaminated seafood. Filter-feeding invertebrates are organisms in which the toxin accumulation is a well-known phenomenon, especially during harmful algal blooms. Mussels, cockles, oysters, and scallops feed on toxic dinoflagellates, transferring them from the gills to digestive organs where the toxins accumulate. Different algal toxins can simultaneously contaminate edible shellfish, representing a world-wide sanitary and economic problem. Among them, Palytoxin (PLTX) is a highly toxic polyhydroxylated compound associated to human seafood intoxications in tropical and subtropical areas, but recently it has been detected also in microalgae and shellfish from temperate areas, as Mediterranean Sea. In the last years, also Yessotoxin (YTX) was frequently detected in mussels from Mediterranean Sea and a possible co-exposure to both PLTX and YTX can occur through contaminated seafood consumption. Therefore, the research was initially focused on the detection and quantification of PLTX and YTX in mussels collected in the Gulf of Trieste in order to verify the simultaneous shellfish contamination by these toxins and, subsequently, to study their toxic effects after simultaneous oral exposure. Analyses by liquid chromatography coupled mass spectrometry (LC-MS) did not reveal the presence of PLTX in mussels but identified the presence of YTX together with the diarrheic toxins okadaic acid (OA) and its acyl esters. Consequently, the final goal of this part of the research was the determination of these toxins in mussels from the Gulf of Trieste by LC-MS as well as that of OA and its esters by a functional assay, the protein phosphatase 2A (PP2A) inhibition assay (comparing the results obtained from two different protocols for the PP2A assay). These assays were used to analyse both cooked and uncooked mussel samples, to verify the influence of the heating procedure on the toxin content of mussels. Globally, no significant difference in toxins concentration between uncooked and cooked mussels was observed. However, comparing the data of single samples, a slight increase (not statistically significant) of toxin concentrations was detected in the cooked mussels with respect to the uncooked ones. The mussel analysis by LC-MS/MS detected also the presence of significant amounts of yessotoxin. Contrary to OA group toxins, yessotoxin was slightly less concentrated in the cooked mussels, probably because of its higher polarity that allows a dissolution in the water lost during the cooking procedure. In the other hand and as it was mentioned before, the palytoxin produced by Ostreopsis sps. microalgae have become a problem in more occasions for the attendance of the coastal environment, both for recreation and for business, representing a loss, as well as to public health, even for the tourism and the aquaculture industry. World market globalization, climatic changes and increasing overseas traffic are considered the main responsible for the appearance of these toxins. The expand of these toxins to temperate regions may be due in part to ballast water of ships and also to general changes in climate conditions, enough to induce bloom formation. Despite the extent of the contaminated area, few methods are currently available for palytoxins detection and quantitation in seafood. Moreover, among palytoxins, only palytoxin is commercially available, though expensive, and no certified standard material is currently sold. For monitoring purposes, a combination of screening methods followed by a chemical confirmatory analysis, such as LC-MS, is commonly used to detect palytoxins. Other methods for PLTX analysis include mouse bioassay, cytotoxicity assays, haemolysis assays, receptor binding assays, and immunoassays. Even if there were no food poisoning from palytoxin in the Mediterranean countries, the toxin was detected in shellfish, which gave positivity to the official test for the lipophilic toxins of algal origin (okadaic acid and derivatives, azaspiracids, yessotoxins and pectenotoxins). Some different experiments were applied in the evaluation of palytoxin toxicity in this study (Haemolytic assay, sandwich ELISA, LC-MS/MS and cytotoxicity studies were carried out). Haemolytic assay, carried out incubating mouse erythrocytes with palytoxin for 4 h (standard assay) or for 1 h in diluted PBS (abbreviated assay) is able to detect palytoxin at picomolar concentrations. Nevertheless, with the aim to detect the toxin in mussels, a significant matrix effect impairing the toxin quantification was observed already at the mussel extract concentration of 0.048 mg edible tissues equivalents/mL, which was more evident by the abbreviated assay. However, most of the experiments lack specificity or have other limitations. Thus, an indirect sandwich ELISA has been set up. The ELISA assay (indirect sandwich) was developed using the monoclonal antibody 73D3, and a rabbit polyclonal antibody produced at the University of Trieste. The assay detects the PLTX in a range of concentrations ranging from 1.25 to 40 ng/ml and is able to quantify with very similar sensitivity also biotinilated PLTX as well as 42-OH-PLTX, this latter isolated and characterized from the chemical point of view during the latter years from the group of prof. E. Fattorusso (University of Naples Federico II), in a sample of palytoxin kindly provided by Dr. M. Poly (Maryland, USA). The incapacity to detect okadaic acid (OA), domoic acid (DA), brevetoxin-3 (PbTx-3), saxitoxin (STX) and yessotoxin (YTX)(toxins that may be present along with PLTX in fish contaminated) indicates the specificity of the assay. The structure of Palytoxins is very complex. In addition to this structural complexity, there is still a lack of knowledge about the different congeners involved in this contamination and therefore there is still a very limited availability of standards and reference materials. These issues made difficult the advances in the development and optimization of analytical methods, particularly in the case of LC-MS/MS. Despite of this, a significant progress has been made over the last few years in the development of analytical techniques, particularly on LC-MS/MS approaches. In this part of the study, a LC-MS/MS method was optimized for the analysis of PLTXs in order to be able to detect, quantify and confirm the presence of this toxins in natural samples. During the PhD period, there was the possibility to get some natural contaminated samples to be evaluated by ELISA developed assay and then compare the results with the analysis by the developed LC-MS/MS method. The study was carried out with samples from 3 distinct sites characterized by having different coastal morphologies and continental hydrodynamic conditions: i) Madeira Islands’ archipelago in the NE Atlantic Ocean, Selvagens island in particular (Long, Lat) during the upwelling of August 2008; ii) Cascais, on the west coast of Portugal mainland, located at the northern side of Lisbon bay during the upwelling occurred during the favourable northerly wind periods (from April to September 2011); and iii) Algarve, Lagos, on the South Portuguese coast, also in 2011.
RIASSUNTO Biotossine prodotte da alghe nocive durante la loro proliferazione possono essere accumulati da organismi di alimentazione per filtrazione, come molluschi bivalvi, nell'ambito della loro carne. Inoltre, queste tossine vengono trasferite gradualmente ai livelli trofici superiori della catena alimentare, che rappresenta una minaccia per la salute umana, dopo il consumo di frutti di mare contaminati. Invertebrati con filtro-alimentazione sono organismi in cui l'accumulo di tossine, è un fenomeno ben noto, soprattutto durante fioriture algali nocive. Cozze, vongole, ostriche e capesante si nutrono di dinoflagellati tossici, trasferendoli dalle branchie agli organi digestivi, dove le tossine si accumulano. Diverse tossine algali possono contemporaneamente contaminare molluschi commestibili, che rappresenta un problema mondiale sanitario ed economico. Tra questi, Palitossina (PLTX) è un composto altamente tossico poliossidrilato associato ad intossicazioni ittici dell'uomo nelle zone tropicali e subtropicali, ma recentemente è stato rilevato anche in microalghe e molluschi dalle zone temperate, come il Mare Mediterraneo. Negli ultimi anni, anche yessotossina (YTX) è stato spesso rilevato nei mitili dal Mare Mediterraneo e una possibile co-esposizione sia PLTX e YTX può avvenire attraverso il consumo di frutti di mare contaminati. Pertanto, la ricerca è stata inizialmente concentrata sul rilevamento e la quantificazione di PLTX e YTX nei mitili raccolti nel Golfo di Trieste, al fine di verificare la contaminazione simultanea nei frutti di mare da queste tossine e, in seguito, per studiare i loro effetti tossici dopo esposizione orale simultanea. Analisi mediante cromatografia liquida accoppiata alla spettrometria di massa (LC-MS) non ha rivelato la presenza di PLTX in mitili ma è stata identificata la presenza di YTX insieme alle tossine diarroiche acido okadaico (AO) e suoi esteri. Di conseguenza, l'obiettivo finale di questa parte della ricerca è stata la determinazione di queste tossine nei mitili del Golfo di Trieste mediante LC-MS così come quella di AO e suoi esteri da un saggio funzionale, il Saggio d’inibizione Proteina Fosfatasi 2A (PP2A)(confrontando i risultati ottenuti da due diversi protocolli per il saggio PP2A). Questi test sono stati utilizzati per l'analisi di campioni di mitili sia crude e cotte, per verificare l'influenza della procedura di riscaldamento sul contenuto di tossina nei mitili. A livello globale, nessuna differenza significativa nella concentrazione di tossine tra cozze crude e cotte è stata osservata. Tuttavia, confrontando i dati dei singoli campioni, un lieve aumento (non statisticamente significativo) delle concentrazioni di tossine è stato rilevato nelle cozze cotte rispetto a quelli crude. L'analisi dei mitili per LC-MS/MS rilevò anche la presenza di quantità significativa di yessotossina. Contrariamente alle tossine gruppo OA, yessotossina era leggermente meno concentrata nelle cozze cotte, probabilmente a causa della sua polarità superiore che permette una dissoluzione in acqua persa durante la cottura. Altrimenti e come è stato detto prima, la palitossina prodotta da Ostreopsis sps. microalghe sono diventate un problema in più occasioni per la partecipazione dell'ambiente costiero, sia per la ricreazione e per le imprese, con una perdita, così come per la salute pubblica, anche per il turismo e l'industria dell'acquacoltura. Globalizzazione del mercato mondiale, i cambiamenti climatici e l'aumento del traffico all'estero sono considerati il principale responsabile della comparsa di queste tossine. L'espansione di queste tossine per le regioni temperate può essere dovuto in parte alla acque di zavorra delle navi e anche a cambiamenti delle condizioni climatiche generali, tanto da indurre la formazione di fioritura. Nonostante e dovuto alla estensione dell'area contaminata, alcuni metodi sono disponibili per il rilevamento e la quantificazione di palitossina in frutti di mare. Inoltre, tra palitossine, solo palitossina è disponibile in commercio, anche se costoso, e nessun materiale standard certificato è attualmente venduto. A scopo di monitoraggio, una combinazione di metodi di screening seguita da una analisi chimica di conferma, ad esempio LC-MS, è comunemente utilizzato per rilevare palitossine. Altri metodi di analisi includono PLTX biotest sui topi, saggi di citotossicità, saggi emolici, saggi di legame al recettore e saggi immunologici. Anche se non ci sono stati identificate intossicazione alimentare da palitossina nei paesi del Mediterraneo, la tossina è stata rilevata nei molluschi, che ha dato positività al test ufficiale per le tossine lipofile di origine algale (acido okadaico e derivati, azaspiracidi, yessotossine e pectenotossine). Alcuni esperimenti diversi sono stati applicati nella valutazione della tossicità della palitossina in questo studio (saggio emolitico, ELISA, LC-MS/MS e studi di citotossicità sono state effettuate). Saggio emolitico, effettuato incubando eritrociti di topo con palitossina per 4 h (saggio standard) o per 1 h in PBS diluito (saggio abbreviato) è in grado di rilevare la palitossina a concentrazioni picomolari. Tuttavia, con lo scopo di rilevare la tossina nelle cozze, un significativo effetto matrice ledere la quantificazione di tossina è stata osservata già alla concentrazione di estratto di cozze 0,048 mg equivalenti tessuti commestibili/mL, che è stato più evidente con il saggio abbreviato. Tuttavia, per la maggior parte degli esperimenti mancano specificità o hanno altre limitazioni. Così, un indiretto sandwich ELISA è stato istituito. Il saggio ELISA (sandwich indiretto) è stato sviluppato utilizzando gli 73D3 anticorpi monoclonali, e un anticorpo policlonale di coniglio prodotto nella Università di Trieste. Il saggio rileva la PLTX in un intervallo di concentrazioni variabili 1,25-40 ng / ml ed è in grado di quantificare con sensibilità molto simile anche PLTX biotinilata così come 42-OH-PLTX, quest'ultimo isolata e caratterizzata dal punto di vista chimico durante gli ultimi anni dal gruppo del prof. E. Fattorusso (Università degli Studi di Napoli Federico II), in un campione di palitossina gentilmente fornito dal Dr. M. Poli (Maryland, USA). L'incapacità di individuare acido okadaico (AO), acido domoico (AD), brevetossina-3 (PbTx-3), saxitossina (STX) e yessotossina (YTX) (tossine che possono essere presenti insieme a PLTX nel pesce contaminato) indica la specificità del dosaggio. La struttura della palitossina è molto complessa. In aggiunta a questa complessità strutturale, vi è ancora una mancanza di conoscenza sui diversi congeneri coinvolti in questa contaminazione e quindi c'è ancora molto limitata disponibilità di standard e materiali di riferimento. Questi problemi reso difficili gli progressi nello sviluppo e ottimizzazione di metodi analitici, in particolare nel caso di LC-MS/MS. Nonostante, un progresso significativo è stato compiuto negli ultimi anni allo sviluppo di tecniche analitiche, in particolare su approcci LC-MS/MS. In questa parte dello studio, un metodo LC-MS/MS stato ottimizzato per l'analisi di PLTXs per essere in grado di rilevare, quantificare e confermare la presenza di queste tossine in campioni naturali. Durante il periodo di dottorato di ricerca, c’è stata la possibilità di ottenere alcuni campioni naturali contaminati da valutare tramite il saggio ELISA sviluppato e poi confrontare i risultati con l'analisi con il metodo sviluppato di LC-MS/MS. Lo studio è stato effettuato con campioni da 3 posti diversi caratterizzati d’avere diverse morfologie e condizioni idrodinamiche costiere continentali: i) arcipelago Isole Madeira nel nord-orientale dell'Oceano, Selvagens isola in particolare durante il mese di agosto 2008; ii) Cascais, sulla costa occidentale del Portogallo continentale, che si trova sul lato settentrionale della baia di Lisbona durante i periodi favorevoli di vento dal nord (da aprile a settembre 2011), e iii) Algarve, Lagos, sulla costa sud-portoghesa, anche nel 2011.
XXV Ciclo
1983

Ce travail de thèse propose d’analyser les signaux issus des sondeurs de sédiment et renvoyés par le sol marin en vue de caractériser quantitativement les sédiments marins aux moyennes fréquences (entre 1 kHz et 10 kHz) et en incidence normale. L’étude se décline donc en deux volets l’analyse du problème direct puis l’inversion. La première partie du travail est focalisée sur la détermination d’un modèle direct de rétrodiffusion en considérant : la configuration de mesure (monostatique, incidence normale, antennes d’émission/réception très ouvertes), les caractéristiques des signaux (chirps à modulation de fréquence linéaire travaillant entre 1 kHz et 10 kHz), les propriétés du fond (stratification, atténuation, rugosité, couches aléatoires et inhomogènes), et en prenant en compte la problématique inverse. Après avoir montré la prédominance des retours d’énergie cohérente sur la diffusion, cette analyse mène sur la formulation d’un modèle multicouche modifié pour l’approche directe afin d’offrir le meilleur compromis entre les possibilités d’inversion et les paramètres pris en compte (coefficient de réflexion pour la stratification, coefficient d’atténuation, écart-type des hauteurs de rugosité et épaisseur de couche inhomogène). La précision du modèle multicouche modifié est calculée puis il est validé expérimentalement grâce à des mesures en laboratoire sur des plaques multicouches absorbantes, puis avec des données in situ acquises avec le sondeur Echoes 3 500 de la société IXSEA pour un fond stratifié comportant des gradients continus d’impédance. Enfin, l’inversion du modèle est effectuée de manière itérative sur chaque pic de réflexion : les paramètres dépendant de la fréquence (atténuation, rugosité, gradient d’impédance) sont d’abord évalués par filtrage adapté en minimisant l’erreur absolue afin de rendre le problème direct linéaire puis, le coefficient de réflexion est évalué au sens du maximum de vraisemblance équivalent au critère de moindres carrés. Finalement, la procédure d’inversion est testée sur deux exemples synthétiques afin d’apprécier dans quelle mesure l’opération inverse est performante
This work deals with sub-bottom profiling signals backscattered by the seafloor and aims at remotely characterize marine sediments at middle frequencies (1 kHz - 10 kHz) and at normal incidence. For that, the study is divided into two parts: the direct modelling analysis and the inverse problem. The work firstly focuses on determining a direct backscattering model which may take into account: measurement geometry (monostatic, normal incidence, and low directive antennas), signal’s properties (linear chirp defined between 1 kHz and 10 kHz), seafloor’s features (layering, attenuation, rough interfaces, inhomogeneous and random layers) and the inverse problem. After justifying predominance of specular energy returns on scattering, the analysis leads to a direct modified layered model which may offer the best compromise between inversion possibility and seafloor parameters accounted for (reflection loss for layering, attenuation coefficient, standard deviation of roughness heights and thickness of an inhomogeneous layer). Accuracy of modified layered model is also calculated and it is experimentally validated with laboratory measurements on absorbent layered plates, and then, with in situ data recorded with sub-bottom profiler Echoes 3 500 from the firm IXSEA on a layered seabed with continuous impedance variations. Then, model inversion is applied with an iterative process on each echo. Frequency dependent parameters (attenuation, roughness, and continuous impedance variations) are firstly evaluated with a wavelet modelling approach while minimising absolute error in order to get a direct linear problem. Next, reflection coefficient is estimated thanks to the method of maximum likelihood equivalent to least square minimisation criteria. Finally, inversion algorithm is implemented on two synthetic examples in order to evaluate efficiency of the inverse operation

Le sonar haute resolution constitue un moyen efficace pour observer la couche superficielle du fond de la mer. Ces dernieres annees, de nombreuses ameliorations ont rendu ces sonars de plus en plus performants. En contrepartie, la quantite d'information a sensiblement augmente et rend aujourd'hui necessaire l'automatisation de la classification de ces fonds marins. La cartographie des fonds marins en imagerie sonar est l'application privilegiee de l'etude. Nous proposons une approche qui combine une methode de caracterisation texturale des images et un classifieur neuronal. L'invariance en rotation des attributs est recherchee pour faciliter et ameliorer l'apprentissage du classifieur. Nous montrons que la modelisation autoregressive bidimensionnelle possede des atouts pour notre application, bien qu'elle ne soit pas robuste vis-a-vis des rotations d'images. Nous proposons alors trois methodes de caracterisation de la texture basees sur une modelisation autoregressive de l'image a laquelle nous associons une propriete d'invariance en rotation. La premiere methode est basee sur une modelisation autoregressive circulaire qui fournit directement un nombre restreint de parametres caracteristiques significatifs et robustes vis-a-vis des rotations d'images. Parallelement, nous developpons deux autres methodes qui conservent la modelisation autoregressive 2d non-causale et rendent invariants en rotation les parametres extraits. Celles-ci font appel respectivement aux moments de zernike et a la transformation log-polaire. Un perceptron multicouche est utilise comme classifieur. De nombreux resultats experimentaux comparatifs, obtenus sur images reelles et images tournees artificiellement (pour obtenir une grande variete dans les orientations des textures), sont fournis pour illustrer les performances des methodes de caracterisation proposees. Enfin, une chaine complete de reconnaissance d'images sonar est proposee et validee sur des images sonar reelles.

L'objet de ce travail est la detection de cible en eau peu profonde. On cherche a etablir l'expression du champ de pression dans un guide d'onde acoustique contenant une coque spherique elastique. Pour cela, une formulation originale permettant de prendre en compte le caractere elastique de la coque est mise en uvre. Les simulations numeriques indiquent que l'influence d'une cible dans une colonne d'eau est tres peu significative. Il est donc difficile de detecter un obstacle dans un tel environnement. En outre, l'etude met en evidence qu'une cible immergee dans une colonne d'eau se comporte comme une source secondaire pour chacun des modes incidents du guide d'onde. Parallelement, afin de valider la theorie on developpe une experience en cuve simulant des conditions de propagation par petits fonds marins. On travaille sur cette cuve avec une lame d'eau de quelques centimetres et des frequences d'une centaine de kilohertz. Les resultats obtenus confirment la theorie et fournissent une bonne comprehension des phenomenes de propagation guidee en presence d'une cible.

The relative strength of bottom-up and top-down processes operating within food webs is a fundamental determinant of community structure and function. In marine systems, inconspicuous but often highly abundant invertebrate herbivores (mesograzers) are implicated as strong consumers of primary production and important prey for higher-order consumers. Because of their small size, however, mesograzer abundance is not easily manipulated in the field, which limits our ability to adequately assess their grazing impacts. Seagrass systems present a pressing need for the study of food web dynamics because anthropogenic nutrient and sediment inputs decrease the amount of light reaching seagrass leaves, which limits the depth distribution of seagrasses via reduced photosynthesis to respiration ratios. Mesograzers benefit seagrass through their consumption of epiphytic algae and thus may mitigate the loss of seagrass beds due to nutrient enrichment. I test the relative impacts of nutrient enrichment and crustacean mesograzer abundance on epiphytes in a natural seagrass bed without using cages. My work presents the first cage-free tests of crustacean mesograzing impacts in natural seagrass communities. I successfully decreased crustacean abundance for extended periods of time in multiple experiments using a degradable chemical deterrent. Crustacean mesograzer reduction led to concomitant increases in epiphytic algal biomass, while nutrients increased epiphytes only in the absence of mesograzers. My results validate early work from mesocosm and field cage studies designed to test grazing impacts of mesograzers and support the hypothesis that mesograzers indirectly benefit seagrass through a positive indirect interaction.

Some of the major problems we face today are human induced changes to the nitrogen (N), phosphorus (P) and carbon (C) cycles. Predicted increases in rainfall and temperature due to climate change, may also increase dissolved organic matter (DOM) inflows to freshwater ecosystems in the boreal zone. N, P, C and light, are essential resources that most often limit phytoplankton (PPr) and bacterial production (BP) in the pelagic zone of lakes. PPr and BP not only constitute the total basal C resource for the pelagic aquatic food web, but also influence ecosystem function and biogeochemical cycles. In this thesis I studied how N, P, C and light affect the relative and absolute rates of PPr and BP, along a wide latitudinal and trophic gradient using published data, and in two in situ mesocosm experiments in a clear water oligotrophic lake. In the experiments I manipulated bottom-up drivers of production and top-down predation to examine how these factors interact to affect pelagic food web structure and function. The most important predictors of PPr globally (Paper I) were latitude, TN, and lake shape. Latitude alone explained the most variation in areal (50%) and volumetric (40%) PPr. In terms of nutrients PPr was primarily N-limited and BP was P-limited. Therefore bacteria and phytoplankton were not directly competing for nutrients. BP:PPr was mostly driven by PPr, therefore light, N, temperature and other factors affecting PPr controlled this ratio. PPr was positively correlated with temperature, but not BP, consequently, higher temperatures may reduce BP:PPr and hence the amount of energy mobilised through the microbial food web on a global scale. In papers II and III interaction effects were found between C-additions and top-down predation by young-of-the-year (YOY) perch. Selective predation by fish on copepods influenced the fate of labile C-addition, as rotifer biomass increased with C-addition, but only when fish were absent. Interaction effects between these top-down and bottom-up drivers were evident in middle of the food web, which is seldom examined in this type of study. Although the energy pathway from bacteria to higher consumers is generally longer than from phytoplankton to higher trophic levels, increased BP still stimulated the biomass of rotifers, calanoid copepods and YOY fish. However, this appeared to be mediated by intermediate bacterial grazers such as flagellates and ciliates. Light was an important driver of crustacean zooplankton biomass (paper IV), but the light:nutrient hypothesis was inadequate to predict the mechanisms behind the decrease in zooplankton biomass at low light. Instead, it appeared that reduced edibility of the phytoplankton community under low light conditions and reduced BP most strongly affected zooplankton biomass. Thus, the LNH may not apply in oligotrophic lakes where PPr is primarily N-limited, Daphnia is rare or absent and mixotrophic phytoplankton are abundant. N, P, C and light manipulations have very different effects on different parts of the pelagic food web. They influence the relative rates of PPr and BP, affect phytoplankton community composition, alter the biomass of higher trophic levels and change pathways of energy transfer through the pelagic food web. This thesis adds valuable information as to how major changes in these resources will affect food web structure and function under different environmental conditions and future climate scenarios.
Lake ecosystem response to environmental change

This thesis is a summary of enclosure and microcosm experiments that aimed to study the impact of allochtonous subsidies on food web dynamics in a heterogeneous food web. In the enclosure studies, a three trophic level littoral food web was used. The food web consisted of two growth forms of primary producers: phytoplankton and periphyton and their associated herbivores: scraping and filtering herbivores. The predator used, YOY perch, affects both pathways in the food web. Manipulation of the openness for the different trophic levels showed that the inflow of phytoplankton and cross-habitat foraging by the herbivore level reinforced the compensatory response between the two growth forms of primary producers

In the microcosm experiment, the response of an herbivore food web and a microbial community to inflow of resources and food web configuration was studied, using a model food web. The model food web consisted of two forms of primary producers, i.e. phytoplankton and periphyton, and two herbivores, i.e. Daphnia pulex feeding on phytoplankton, and Chydorus sphaericus feeding on both periphyton and phytoplankton. Three different food web configurations, all having the phytoplankton and periphyton, but either one of the herbivores, or both, were set up. The flow regimes consisted of an open treatment receiving a constant supply of phytoplankton, and a closed treatment with an initial resource pool. The effect of the inflow of phytoplankton was affected by the food web configuration. In the presence of D. pulex, the inflow of phytoplankton was made accessible to periphyton, and indirectly to C. sphaericus, which increased to such high densities that D. pulex was negatively affected. The inflow of phytoplankton had an indirect negative effect on the microbial community, since the biomass of herbivores increased, which imposed a higher grazing pressure on all parts of the microbial community.

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.