Les éléments transposables (ET) sont des séquences d‟ADN capables de se déplacer dans les génomes qui les hébergent. Les ET de type mariner (mariner-like element : MLE) ont été caractérisés chez les animaux et chez les plantes à fleurs terrestres mais pas chez les microalgues marines. Dans le présent travail, les MLE ont été recherchés chez les diatomées marines (Bacillariophycées) qui sont des microalgues possédant une enveloppe externe siliceuse. Elles ont colonisé tous les milieux aquatiques et constituent une part majeure du phytoplancton; de ce fait, elles jouent un rôle écologique clé dans le milieu marin.La caractérisation des MLE des diatomées a été réalisée au moyen d‟approches moléculaire et bio-informatique. La présence de MLE dans le génome de 10 espèces de diatomées a été mise en évidence grâce à l‟amplification de fragments d‟environ 380 pb. Ces fragments correspondent à une partie de la séquence conservée codant l‟enzyme responsable de la transposition des MLE : la transposase. L‟analyse des séquences obtenues, par des méthodes phylogénétiques, ainsi que la classification des MLE de diatomées mettent en évidence leur appartenance au groupe des MLE végétaux de la superfamille Tc1-mariner. Néanmoins, les séquences MLE de diatomées divergent considérablement par rapport aux MLE des plantes terrestres. Afin de déterminer si les diatomées ont la capacité de produire la transposase, l‟expression des MLE a été recherchée chez des diatomées soumises à des stress thermiques de courte durée (5 h). Nos travaux montrent que les MLE sont exprimés chez les trois espèces testées incluant la diatomée modèle Phaeodactylum tricornutum dont le génome a été séquencé récemment. L‟expression des MLE des diatomées est variable selon les conditions thermiques et selon les espèces.L‟ensemble de nos résultats suggère que les MLE sont ubiquistes dans les génomes de diatomées et qu‟ils sont présents de manière ancestrale dans la lignée végétale. Les MLE des diatomées forment trois nouvelles sousfamilles de la superfamille Tc1-mariner, la plus répandue des superfamilles d‟ET. De plus, leur expression suggère qu‟il existe des MLE capables de se déplacer dans le génome des diatomées. Si la transposition était vérifiée, ils pourraient alors être développés comme outils de mutagenèse.

Fighting Power: Interpretive Issues The 1st Provisional Marine Brigade, 1950 Hammes, Thomas Xavier Lincoln College Submitted for Doctor of Philosophy in History Trinity Term 2008 When the Korean War broke out on 25 June 1950, the Marine Corps was ordered to deploy an air-ground brigade from California in less than ten days. Due to five years of massive budget and manpower cuts, the Marine Corps did not have even a brigade immediately available. The only way to meet the sailing timeline was to organize, man and equip the force while actually embarking it. As it embarked, the brigade had to incorporate marines flown in from posts all over the western United States; draw equipment from war reserves held hundreds of miles away; reorganize many of the existing units under new tables of organization; and add an experimental helicopter detachment from the east coast of the United States. Despite these enormous handicaps and numerically superior enemy forces, the brigade won every engagement. This performance was in stark contrast to the performance of all other US forces at this stage of the war. The brigade’s brief existence (7 July to 6 Sept 1950), combined with its exceptional combat record under adverse conditions, provides the opportunity to study the impact of institutional culture, education, doctrine, organization, training and leadership on performance in combat. Research showed that a key element of the brigade’s success was the Marine Corps’ institutional culture. In particular, the culture of remembering ensured marines understood the unchanging aspects of war and provided its men with the education, training, doctrine and organization to cope with its enduring friction, fog and chance. At the same time, the culture of learning ensured the marines understood what was changing in the character and tools of war so the brigade was well adapted to the realities of modern war from its first day in combat.

Les éléments transposables (ET) sont des séquences d‟ADN capables de se déplacer dans les génomes qui les hébergent. Les ET de type mariner (mariner-like element : MLE) ont été caractérisés chez les animaux et chez les plantes à fleurs terrestres mais pas chez les microalgues marines. Dans le présent travail, les MLE ont été recherchés chez les diatomées marines (Bacillariophycées) qui sont des microalgues possédant une enveloppe externe siliceuse. Elles ont colonisé tous les milieux aquatiques et constituent une part majeure du phytoplancton; de ce fait, elles jouent un rôle écologique clé dans le milieu marin.La caractérisation des MLE des diatomées a été réalisée au moyen d‟approches moléculaire et bio-informatique. La présence de MLE dans le génome de 10 espèces de diatomées a été mise en évidence grâce à l‟amplification de fragments d‟environ 380 pb. Ces fragments correspondent à une partie de la séquence conservée codant l‟enzyme responsable de la transposition des MLE : la transposase. L‟analyse des séquences obtenues, par des méthodes phylogénétiques, ainsi que la classification des MLE de diatomées mettent en évidence leur appartenance au groupe des MLE végétaux de la superfamille Tc1-mariner. Néanmoins, les séquences MLE de diatomées divergent considérablement par rapport aux MLE des plantes terrestres. Afin de déterminer si les diatomées ont la capacité de produire la transposase, l‟expression des MLE a été recherchée chez des diatomées soumises à des stress thermiques de courte durée (5 h). Nos travaux montrent que les MLE sont exprimés chez les trois espèces testées incluant la diatomée modèle Phaeodactylum tricornutum dont le génome a été séquencé récemment. L‟expression des MLE des diatomées est variable selon les conditions thermiques et selon les espèces.L‟ensemble de nos résultats suggère que les MLE sont ubiquistes dans les génomes de diatomées et qu‟ils sont présents de manière ancestrale dans la lignée végétale. Les MLE des diatomées forment trois nouvelles sousfamilles de la superfamille Tc1-mariner, la plus répandue des superfamilles d‟ET. De plus, leur expression suggère qu‟il existe des MLE capables de se déplacer dans le génome des diatomées. Si la transposition était vérifiée, ils pourraient alors être développés comme outils de mutagenèse. / Transposable elements (TE) are sequences able to move between two loci in the host genomes. Mariner-like element (MLE) are well characterized in animal and land plant genomes but not in marine microalgae. In this work, we have looked for MLE in marine diatoms (Bacillariophyceae) that are microalgae having a siliceous wall. They have colonized all aquatic environments and are a major component of the phytoplankton, so they play a major role in the ecology of marine environments.To characterize the diatom MLE, molecular and bio-informatics approaches were used. The presence of MLE was detected in ten diatom species which exhibited sequence fragments of about 380 pb. These fragments were identified as a section of the conserved sequence which encodes the enzyme responsible for MLE transposition, the transposase. Phylogeny and classification analysis of these fragments revealed that diatom MLE belong to the Tc1-mariner superfamily, and more precisely to the vegetal MLE group. Nevertheless, diatom MLE sequences diverged from the flowering plant MLE. In order to determine if MLE transposase is produced in diatoms, MLE expression was looked for in diatoms under thermal stresses. Our results showed that diatom MLE were expressed in the three species tested, including the model diatom Phaeodactylum tricornutum which was completely sequenced recently. Diatom MLE expression was dependent on the thermal conditions and on the species.Our results suggest that MLE are widespread in diatom genomes and that they have an ancestral presence in the green lineage. Diatom MLE cluster in three subfamilies in the huge ET Tc1-mariner superfamilly. Finally, the diatom MLE expression detected could reflect the existence of active MLE in diatom genomes. If this hypothesis were verified, it could lead to the development of mutagenesis tools.

Les bactéries magnétotactiques (MTB) représentent un groupe de bactéries diverses sur le plan phylogénétique, morphologique et physiologique et elles ont la capacité de s'orienter grâce au champ géomagnétique terrestre afin de trouver leurs conditions optimales de développement. Ce comportement remarquable est appelé le magnétotactisme. Les connaissances actuelles de la formation des magnétosomes et du magnétotactisme sont basées principalement sur l'étude des souches magnetospirilla d'eau douce. Au cours de cette thèse, j'ai participé à l'annotation et réalisé des analyses génomiques, physiologiques et génétiques des deux MTB marines. Mes résultats ont révélé un mécanisme d'adaptation de la souche magnetospirillum QH-2 à l'habitat intertidal et des voies métaboliques (autotrophie,- fixation de l'azote, transport du fer) ainsi que des mécanismes de détection environnementaux distincts des magnétospirilla d'eau douce. La souche marine ovoïde MO-1 possède un génome composé de fortes proportions de gènes avec des origines possibles de gamma-(23,6 %), delta-(16,8 %), alpha-(13,2 %) et bêta- (9,1 %) protéobactéries. Cette constatation suggère que MO-1 est un ancêtre fossile ou une nouvelle sous-classe des Proteobacteria. J'ai caractérisé le comportement magnétoctatique de la souche MO-1 et montré que le magnétotactisme est bénéfique et même essentiel pour la croissance des MTB. Par ailleurs, j'ai caractérisé des glycoprotéines essentielles pour la structure et la fonction de l'appareil flagellaire de MO-1. L'ensemble de ces résultats contribue à notre compréhension de la diversité et l'évolution des MTB, ainsi que l'importance environnementale du magnétotactisme. / Magnetotactic bacteria (MTB) consist of a phylogenetically, morphologically and physiologically diverse group of gram-negative bacteria. They have the unique capacity of synthesizing magnetic crystal enveloped with membrane, referred to as magnetosomes, which allow the bacteria swimming along magnetic fields lines (magnetotaxis) to seek optimal oxygen concentration with maximal efficiency. Current knowledge of magnetosome formation and magnetotaxis mainly steams from the study of freshwater magnetospirillum strains. In this thesis, I participated to the expert annotation and performed genomic, physiological and genetic analyses of two marine MTB. I revealed the adaptation of marine magnetospirillum strain QH-2 to the intertidal habitat and metabolic pathways (autotrophy, N2-fixation, iron-transport) and environmental sensing mechanism distinct from those of the freshwater magnetospirilla. In addition, the genome of the marine ovoid strain MO-1 is composed of high proportions of genes with possible origins of gamma- (23.6%), delta- (16.8%), alpha- (13.2%) and beta- (9.1%) proteobacteria. This finding suggests that MO-1 is either a fossil ancestor or a new subclass of the Proteobacteria. I characterized the magnetotactic behavior of the strain MO-1 and showed that magnetotaxis is beneficial and even essential for the growth of MTB. In addition, I carried out proteomic and biochemical studies of glycol-proteins being components of the MO-1 flagellar apparatus or possibly serving as lubricants for the flagellar motor. Together these results contribute to our understanding of the diversity and evolution of MTB as well as the environmental significance of magnetotaxis.

La ville du Havre et son agglomération sont implantées entre l'estuaire de la Seine et le plateau crayeux du Pays de Caux. Ce territoire côtier est soumis à des risques naturels typiques des zones littorales que sont les submersions marines et l'érosion des falaises. L'étude a été réalisée à partir de photographies aériennes et de relevés topographiques aériens LiDAR (laser altimétrique). Elle a visé à cartographier les zones de débordement et d'inondations historiques (1981, 1983 et 1984) et potentielles de la ville basse du Havre en superposant divers scenarii de niveaux d'eaux statiques et la topographie haute précision de la zone urbaine. Les falaises littorales de la pointe de Caux, situées entre le Cap de La Hève et le Cap d'Antifer subissent une dynamique gravitaire à mouvements de terrain récurrents. L'étude de la zone entre 1985 et 2008 (23 ans) montre un taux d'érosion moyen du haut de falaise de 18 cm/an. L'accumulation de dépôts d'éboulis a formé un talus continu en pied de falaise qui atteint un volume de 36,7 millions de m3. Les dépôts d'éboulis sont localement très variables en taille, volume et composition, du nord au sud du secteur d'étude et n’est atteint que sur 10 % du linéaire étudié lors des hautes mers de vive-eau. L'impact d'une augmentation du niveau marin au Havre (1,6 à 2,4 mm/an) est susceptible d'amplifier à long terme l'intensité de ces deux aléas côtiers, mais il apparaît cependant comme faible par rapport à l'influence des facteurs météorologiques. / Le Havre suburb is located between the Seine estuary and the chalk plateau of the Paris basin NW boundary. This coastal territory is submitted to typical natural hazards observed on coastal areas that are coastal floods and cliffs erosion. The study use data from aerial photographs and LiDAR surveys. The lower part of Le Havre town, built around historical tidal docks, is sensitive to coastal floods hazard. Three urban coastal floods occurred in 1981, 1983 and 1984 resulting to a combination between high water level of spring tides and surges produced by low air pressure and/or strong winds. The aim is to map, in the lower part of Le Havre town, the areas of potential overflow and flood. Different scenarii of static water levels have been applied on the accurate urban topography from LiDAR. Coastal cliffs, located between La Hève and Antifer Capes, showed recurrent gravitational movements. On the period 1985-2008 (23 years), the cliff top shows an average erosion rate of 18 cm/yr. The accumulation of sedimentary instabilities had formed a continuous wedge of 36.7 million m3. The wedge deposits are very variable in size, volume and nature, from north to south. At Le Havre, the impact of the sea-level rise may amplify, in long-term scale, the intensity of these two coastal hazards. However, the SLR impact appears to be low compared to the influence of meteorological factors.

Após a construção do Emissário Submarino de Esgoto de Santos, todo efluente da cidade de Santos e parte de São Vicente passou a ser descartado na Baía de Santos após Pré-condicionamento. Diante desse aspecto a CETESB iniciou monitoramento de controle sobre os materiais que estão sendo lançados pelo emissário. Nessa dissertação foram estudadas amostras de sedimentos no entorno dessa malha de monitoramento. A partir de duas coletas em períodos distintos - Abril de 2004 e Outubro de 2004 - obtiveram-se 20 amostras de sedimentos. Nessas amostras foram realizadas análises granulométricas e químicas (elementos maiores e traços determinados por DRX e ICPOES para 16 elementos com predomínio de metais). Os resultados granulométricos obtidos nas amostras de sedimentos mostraram serem esses constituídos predominantemente por areias e sedimentos em suspensão. A dispersão dessas frações sofre influência direta do fluxo dos materiais descartados pelo emissário. Dos diversos elementos analisados detectou-se que o Cobalto (Co) e Enxofre (S) ultrapassaram os limites de referência utilizados. O elemento Bário exibiu sempre concentrações elevadas nas análises realizadas. Foi notado, por outro lado, que a distribuição dos elementos Cu, Zn, Cr, Mn e Ni, sempre exibiu maiores concentrações no período de maior pluviosidade. Esses resultados corroboram para a indicação que alguns desses elementos químicos (Cu, Zn, Cr, Mn e Ni) devem provir de materiais intemperizados de rochas do entorno e que outros elementos (Co e S) possuem uma contribuição antropogênica sobre os sedimentos depositados pelo emissário. A determinação das razões C/N e C/S não permitiu determinar se a carga de efluentes do emissário contribui para o aumento do teor de matéria orgânica. Os resultados obtidos e interpretações realizadas conduzem a confirmar a influência do emissário sobre os sedimentos de fundo do seu entorno. Esses diversos resultados apontam para uma indicação de que o tratamento dos efluentes na Estação de Pré-Condicionamento de Esgoto de Santos não é o ideal, visto que alguns elementos considerados poluentes encontram-se depositados nos sedimentos analisados. / After the construction of the Ocean Outfall of Santos\'s sewage, all of Santos\'s and part of São Vicente\'s effluents started to be discarded in the Santos Bay after Preconditioning. In light of that aspect, CETESB began a monitoring control of the materials dumped through the emissary. In this dissertation sediments samples in the environment of that monitoring mesh. From two collections in different periods - April 2004 and October 2004 - 20 samples of sediments were obtained. Granulometric and chemical analyses (larger and trace elements for DRX and ICP-OES for 16 elements with prevalence of metals) were developed. The granulometric results obtained in the sediment samples showed that those were predominantly constituted by sands and sediments in suspension. The dispersion of the prior fractions suffers direct influence of the flow of discarded materials by the emissary. Of the several analyzed elements, it was detected that the Cobalt (Co) and Sulfur (S) concentrations surplused the reference limits. The element Barium (Ba) was always highly concentrated in analysis. It was noticed, on the other hand, that the distribution of the elements Copper (Cu), Zinc (Zn), Chromium (Cr), Manganese (Mn) and Nickel (Ni), always exhibited larger concentrations in the period of greater rainfall. Those results corroborate the indicators that some of those chemical elements (Cu, Zn, Cr, Mn and Ni) comes from materials of naturally eroded rocks and that other elements (Co and S) were deposited by the emissary, constituting anthropogenic actions. The determination of the Carbon/Nitrogen (C/N) and Carbon/Sulfur (C/S) reasons didn\'t determine if the deposit of the emissary\'s effluents contributes in the increase of the concentration of organic matter. The results and interpretations obtained in the experiments confirm the emissary\'s influence on the environment\'s bottom sediments. Those results point that the effluent treatment in the Sewer\'s Pre-conditioning Station in Santos is not ideal, because some elements, considered pollutants, are found in deposits in the analyzed sediments.

L’onde acoustique est utilisée par de nombreux systèmes et organismes marins pour communiquer, naviguer ou inférer de l’information sur l’environnement. Le développement des activités humaines liées au monde de la mer induit une augmentation du nombre de sources acoustiques en activité simultanée dans l’océan. L’environnement acoustique sous-marin (ASM) est donc partagé par de nombreuses sources hétérogènes (sonars, modems, mammifères marins, ...) entrant involontairement en compétition pour l’utilisation d’une ressource offerte par le canal de transmission. L’objectif de ce travail de thèse est de proposer des solutions permettant aux systèmes de communications ASM d’adapter leurs paramètres de transmission de manière intelligente, autonome et décentralisée selon l’environnement acoustique dans lequel ils évoluent. A plusieurs égards, les problématiques de ce sujet de thèse sont proches de celles ayant motivé le développement des recherches sur la radio cognitive. Cependant, les spécificités du milieu acoustique, les sources d’interférencesde diverses natures, et l’absence de standards de communications posent de nouvelles difficultés. / Underwater acoustic waves are used by many systems and biologic organisms to communicate, navigate or infer information about the environment. Future developments of human maritime activities imply an increase of the number of active acoustic sources in the oceans. The underwater environment is therefore shared by many heterogeneous sources (sonars, modems, marine mammals, ...) competing involuntarily for using the physical resources offered by the communication channel.The goal of this thesis is to provide solutions allowing autonomous and decentralized adaptation of the transmission strategies of underwater acoustic communication systems, according to the environment. To some extent, this work deals with topics that are closely related to what has motivated the first researches on cognitive radio systems. However, the specific properties of the underwater environment, the heterogeneity of interfering acoustic sources, and the absence of communication standards rise new difficulties.

The title of The Edifice Complex presents two metaphors which combine to form the focus of this study's research. The first of these refers to the Oedipus Complex of Freudian psychology: metaphorically, Marine recruits fall in love with the folklore of the Marine Corps they wish to join, yet unwittingly change that Corps over time, thus figuratively killing the older generations of Marines--their forefathers in uniform. In the second metaphor, the edifice is the structure of informal folklore and recorded history; the complex is the rites of passage or maze traversed in time by Marines. As Marines are indoctrinated in the Marine Corps' culture, they internalize the meanings of the edifice's building blocks: its symbols, rituals and myths. Bit by bit, generations of Marines individually and collectively alter the shape of the metaphorical maze and change the meanings of some elements of folklore. The purpose of the study was to analyze the causes and effects of cultural change affecting Marines and the Marine Corps from the mid-1950s to the mid1980s. Using ethnographic field methods and content analysis, the researcher investigated internal and external planned and unplanned changes in the Marine Corps. Cultural data was collected during 1984 and 1985 from print, motion picture and other media, and through interviews with Marine infantrymen, recruiters, journalists, drill instructors, historians, musicians and others, in several cultural settings. The study focused on the cultural reality of primarily male, enlisted Marines. Findings support the working hypothesis that folklore is a behavior-shaping tool which the Marine Corps effectively uses to control the behavior of Marines. Findings reveal that cultural changes have allowed or caused some Marines to value the Marine Corps materially as a source of valuable competencies and material rewards rather than professionally or patriotically as the calling of the profession of arms. Conclusions of The Edifice Complex parallel conclusions in organizational change theory, in that changes in the symbolic realm of the organization's culture are most difficult to change but have significant impact upon members of the organization. Findings and conclusions are also mutually supported in the educational, social and behavioral psychologies.

The discipline of ecology is habitually divided up into a whole range of different specialities, and this thesis forms part of what is commonly known as "community ecology" (Diamond and Case 1986). To be more precise, my work has centred on the degree to which the trophic relationships that exist between the organisms constituting a food web govern the structure and dynamics of the communities they form. I approached the subject from an experimental point of view and all the work was carried out in the field by means of what are referred to as "natural experiments", with all the advantages and disadvantages that this supposes. The chosen ecosystem was the coastal marine benthos or, to be more specific, rocky infralittoral communities, a propitious place in which to work since this setting has seen the production of some highly important contributions to community ecology, above all in the development of experimental techniques (review by Castilla 2000).Owing to the existence of previous investigations, my work, strictly speaking, does not break any new ground, since the subject matter has already been well studied in other oceans (see Castilla 2000 for a revision). Paradoxically, the Mediterranean, them cradle of the natural sciences (Aristotle, 350 BC) and home to the invention of scuba diving by Gagnan and Cousteau in 1944, has generally not been witness to any of the most important advances in experimental benthic science. Whilst not wanting to question the universality of discoveries regarding benthic communities made in other waters, it can surely not be an excessive precaution to attempt to understand the way regional peculiarities - the Mediterranean is a very singular sea in many ways (Margalef 1985) - affect general principals.One highly significant way in which benthic experiments in the Mediterranean are playing a part in current debate is the role that marine reserves or protected marine areas (PMAs) can be expected to play as management tools in ecosystems adversely affected by human action. In this sense, my work shares a characteristic with many others: the use of marine reserves as experimental sites that can be compared with nearby unprotected zones in order to try and judge their worth.As a final reflection on the main object of study in my thesis it is worth remarking that the system under study relates on a trophic level macroscopic algae - the main primary producers in the phyto-benthos - to their herbivores, which in the coastal Mediterranean benthos are essentially a sea urchin (Paracentrotus lividus), a fish, the salema (Sarpa salpa), and a guild of omnivorous fish that include optional grazers of algae and predators on sea urchins. My study investigated the interactions taking place between all the actors in this complex community and not just the interactions occurring between a certain group of species, although inevitably, given its central position, the sea urchin Paracentrotus lividus has been the focal point of our efforts. As a means of simplifying, throughout this paper I often refer to the "triangle" 'algae-sea urchins-fish', which is described in more detail in Annex 1.I feel that my work has two main applications. Aside from any knowledge gained from the experimental study of the interactions within a complex community under natural conditions, our results have, firstly, a clear role to play in the management of coastal areas and biological conservation in general. It is known that high densities of sea urchins can cause a regression and a loss of diversity in algal communities (that can be compared to the effects of desertification on the biodiversity of forest ecosystems).Studying experimentally the mechanisms that regulate these interactions is a way of searching for valid management criteria. Secondly, we looked at the relevance of the role played by changes of anthropic origin such as eutrophication or overfishing in the proliferation of sea urchins and the regression of algal communities. / Dins el ventall d'especialitats en que s'acostuma a dividir l'ecologia, aquesta tesi s'enquadra en l'anomenada "ecologia de comunitats" (Diamond i Case 1986). Amb més precisió, el meu treball ha estat dedicat a investigar el grau en que les relacions tròfiques entre els organismes que formen una xarxa tròfica arriben a governar l'estructura i dinàmica de la comunitat que formen. L'aproximació es experimental i tot el treball s'ha realitzat al camp, basat en el que hom anomena "experiments naturals" amb les seves virtuts i inconvenients. L'ecosistema triat ha estat el bentos marí litoral, i en concret les comunitats de l'infralitoral rocós. Es tracta d'un marc de treball favorable, ja que aquest escenari ha produït algunes de les contribucions més importants a l'ecologia de comunitats, sobretot en el que fa al desenvolupament de la seva vessant experimental (revisat per Castilla 2000).A causa d'aquests treballs precedents, una part dels objectius del meu treball no és estrictament novedosa, ja que han estat molt estudiats en altres mars (veure Castilla 2000 per a una revisió). Paradoxalment tractant-se del mar que ha estat el bressol de les ciències naturals (Aristòtil, cap el 350 a.C.) i de la invenció de l'escafandre autònom per Gagnan i Cousteau el 1944, la Mediterrània ha quedat en gran mesura fora de l'àrea on han tingut lloc els avenços de l'ecologia bentònica experimental. Tot i que confíem en l'universalitat de les descobertes més sòlides de l'ecologia de comunitats bentòniques, mai serà una precaució excessiva per als ecòlegs copsar la forma en que les particularitats regionals (la Mediterrània es un mar en molts sentits singular; Margalef 1985) modelen aquests principis generals.A més, almenys en una part sí que les experiències d'ecologia bentònica mediterrànies participen de la més disputada actualitat, i és en el paper que hom pot esperar que realitzin les Reserves Marines o Àrees Marines Protegides (MPA's) com eines de gestió racional d'uns ecosistemes massa castigats per l'acció humana. En aquest sentit el meu treball comparteix amb molts altres que es realitzen actualment el tret d'utilitzar les Reserves Marines com un dels tractaments experimentals estudiats i, per comparació amb el que succeeix a les zones properes no protegides, tracta d'esbrinar els seus efectes.Per acabar de focalitzar el tema objecte de la meva tesi només cal afegir que el sistema estudiat és el que relaciona tròficament les algues macroscòpiques, com principals productors primaris del fito-bentos, amb els seus herbívors, que al bentos litoral mediterràni es poden simbolitzar en una espècie de garota de mar ("Paracentrotus lividus") i un peix ("Sarpa salpa"), i amb el gremi de peixos omnívors entre els que es compten opcionals pasturadors d'algues i depredadors de les garotes herbívores. L'estudi aborda les interaccions entre tots els elements d'una comunitat complexa, i no només d'algunes espècies selectes, encara que, pel seu paper central, la garota "Paracentrotus lividus" ha concentrat més esforços que la resta. Al llarg de la memòria i per simplificar, parlarem sovint d'aquest "triangle" algues-garotes-peixos, que es descriu amb més detalls en l'Annex 1.Crec que l'interès d'aquest treball pot ser doble. Més enllà del coneixement que pot aportar a l'Ecologia de comunitats l'estudi experimental de les interaccions d'una comunitat complexa en condicions naturals, els resultats tenen un clar interès aplicat per a la gestió dels litorals i per a la biologia de la conservació. És sabut que altes densitats de garotes poden provocar la regressió de les comunitats algals i una forta pèrdua de diversitat (que pot ser comparada als efectes de la desertització sobre la biodiversitat dels ecosistemes forestals). Estudiant experimentalment els mecanismes que regulen aquestes interaccions busquem aportar criteris vàlids per a la gestió. Un tema d'especial interès ha estat esbrinar quin paper han pogut jugar canvis d'origen antròpic, com els derivats de l'eutrofització o de la sobre-pesca, en la proliferació de les garotes i la regressió de les comunitats algals.

Reproduction de : Thèse de doctorat : Sciences : Traitement du Signal et de l'Image : Toulon : 2005. / Titre provenant du cadre-titre. Bibliographie p.167-173.