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Le document présente une méthode originale d'étude de la répartition de la crépidule dans la baie de Saint-Brieuc (Manche occidentale), au moyen du sonar latéral et de l'imagerie sous-marine. Une évaluation quantitative du stock complète cette distribution et permet d'estimer la biomasse de crépidules dans la baie à environ 250 000 tonnes (poids frais). The aim of this report is to provide an original method of mapping slipper limpet beds in the bay of Saint-Brieuc (Western Channel) by means of side scan sonar and submarine video. An evaluation of the biomass completes the distribution of limpets. The total fresh weight is about 250 000 tons

Comprendre la variabilité du recrutement est une problématique majeure en halieutique. Dans ce travail, nous explorons une nouvelle approche pour étudier les facteurs qui déterminent le recrutement, dans le cadre de la modélisation biophysique. Le schéma de ponte des adultes peut influencer la survie des larves car il détermine les conditions environnementales qu'elles rencontrent pendant cette période critique. Notre cas d'étude est l'anchois du golfe de Gascogne Engraulis encrasicolus, qui est une espèce à pontes multiples. L'objectif de la thèse est de comprendre l'effet de l'environnement vécu par un individu i) sur l'énergie disponible pour la reproduction et ii) sur l'étalement des pontes et ses conséquences sur la croissance, le développement et la survie des larves. Pour appréhender les processus métaboliques en jeu, la théorie Dynamic Energy Budget est un outil particulièrement adapté. Cette théorie permet d'identifier les processus communs et les spécificités de chaque stade. Nous apportons tout d'abord une révision de la courbe de croissance de l'anchois du golfe de Gascogne. Nous reproduisons la croissance des juvéniles en tenant compte du fait qu'ils expérimentent en moyenne une température plus élevée durant cette phase que celle vécue ensuite par les adultes. La croissance larvaire diffère de la croissance des juvéniles et des adultes. Nous proposons de considérer la relation entre prise de nourriture et longueur de l'individu pour expliquer cette croissance. Ce travail nous permet ensuite de mieux comprendre et de quantifier l'effet des conditions environnementales vécues par un individu sur la durée de sa saison de reproduction. Ces conditions déterminent d'une part la taille de l'individu donc son potentiel reproducteur et d'autre part la quantité d'énergie qu'il peut effectivement mettre en réserve pour la reproduction. En conditions limitantes de nourriture, cette énergie peut en effet être mobilisée pour sa survie. Ainsi la structure en taille de la population et les conditions limitantes rencontrées par les individus sont des facteurs déterminants des fenêtres de ponte. La thèse permet enfin d'identifier les conditions de nourriture nécessaires à la survie jusqu'au stade juvénile, pour des larves issues de fenêtres de pontes différentes. Nous obtenons ce résultat à partir de la sélection des scénarios environnementaux qui reproduisent l'âge et la taille de l'otolithe à la métamorphose en fonction de la date d'ouverture de la bouche. Le lien entre métabolisme du poisson et formation de l'otolithe (une pièce calcifiée de l'oreille interne) est explicitement modélisé. Nous démontrons le potentiel du modèle pour la reconstruction de la quantité d'énergie assimilée par un individu au cours de sa vie à partir des variations observées de l'opacité dans l'otolithe. L'approche développée dans ce travail est une approche déterministe du lien environnement – individu, au travers des processus bioénergétiques. Cette approche nous permet de proposer des mécanismes originaux sous-jacents à certaines observations classiques en halieutique telles que le découplage entre la croissance de l'otolithe et la croissance en longueur du poisson et la phase exponentielle de la croissance pendant le stade larvaire. Une meilleure compréhension des cycles de vie requiert également la prise en compte du comportement et des stratégies individuelles. Ce travail peut constituer la base sur laquelle de telles études pourront à l'avenir s'appuyer. Understanding the recruitment variability of fish populations is a major challenge in fishery sciences. In the present work, we explore a new approach to study the potential factors that determine this recruitment in the context of biophysical modelling. The adult spawning pattern might influence the survival of the larvae as it determines the environmental conditions they experience during this critical period. We apply our study to the Bay of Biscay anchovy Engraulis encrasicolus, which is a multiple-batch spawner. The objective of the study is to understand the effect of the environmental conditions experienced by an individual i) on the energy available for reproduction and ii) on the temporal distribution of the spawning events and its consequences on larval growth, development and survival. To study these processes, the Dynamic Energy Budget (DEB) theory is particularly suitable. This theory allows us to identify the common processes and the specificities of each life stage. First, we actualise the growth curve of Bay of Biscay anchovy. Juvenile growth is reproduced by taking into account they experience in average a higher temperature during this stage than the adults thereafter. Larval growth in fish typically deviates from later juvenile and adult growth. We suggest to consider how food intake depends on body length to explain the observed growth patterns. Second, the present work allows us to better understand and quantify the effect of environmental conditions experienced by an individual on the length of its spawning season. These conditions determine on one hand the length of the individual and thus its reproduction potential, and on the other hand the amount of energy that it can actually store for reproduction. In limiting conditions, this energy can be mobilised for survival. Hence, the length structure of the population and the limiting conditions encountered by the individuals are determinant factors of the spawning windows. Third, we are able to identify the food conditions that allow survival until the juvenile stage for larvae issued from different spawning windows. We obtain this result from the selection of environmental scenarios that reproduce the observed age and otolith radius at metamorphosis according to first feeding date. The link between fish metabolism and otolith formation (a complex crystal in the inner ear of the fish) is explicitly modelled. We show the potential of the model to reconstruct individual life history from the observed variations of opacity in the otolith. The approach we used is a deterministic approach of the link between the environment and the individual, through bioenergetic processes. It allows us to formulate original mechanisms underlying classical observations in fishery sciences. As a better understanding of fish life cycles requires the study of individual behavior and strategies in response to environmental variations, we suggest the present work can be used as a basis for such studies.

On the bathyal slope for continental margins, steep and rocky substrates punctuated with cliffs and collapsing zones are frequently found. As survey and sampling with the classical technics from the sea surface is practically impossible in such an environment, in situ exploration with a submersible allows significant advances in ecology, with implications in paleoenvironment reconstruction. Mixing of material from shallow-water and deep-sea origins into bathyal sedimentation suggests that the so-called "fossil assemblages of outer platform" were frequently misinterpreted. Dense populations of animals closely related to fossil groups which were only considered as relict of the Past ("living fossils") and previously interpreted as shallow-water inhabitants during geological times can be discovered living in such bathyal communities. The role of bathyal ecological niches during global bioevents brings a new vision of the history of life in the Ocean through geological time and has to be further investigated. Examples from cruises monitoring the diving saucer Cyana (SP 3000) in the Bay of Biscay and off New Caledonia are given.

The primary production (phytoplankton and microphytobenthos) of a coastaL shallow water ecosystem (0.5 m) was investigated in two sandy areas, differing by their wave exposure. The physical and chemical parameters, the functional chlorophyll and pheopigments as well as the primary production were measured monthly, throughout a two-year study. The bivalve Ruditapes decussatus was the dominant species in the sheltered station (RD), whereas Donax trlmcu/us inhabited the other station (DT) which was exposed to the open-sea waves. Microphytic biomasses were determined after extracting chlorophyll a and pheopigments in 90% acetone. by spectrophotometric measurements before and after acidification. Gross hourly primary production was estimated by measuring the oxygen balance in light and dark enclosures. The mlcrophytobenthos was considered in the upper centimetre. The main characteristics of the water. temperature. salinity and dissolved oxygen were more variable in the sheltered area; the redox potential was generally lower in this sediment and the vertical profile revealed a "redox potential discontinuity"• which usually did not appear in the open site. In the water column (phytoplankton seasonal fluctuations were similar in both stations. The annual average values of Chla and primary production were equivalent (1.40±0.56 and 1.94±078 mg Chla.m2: 19.60±11.09 and 20.29±8.45mgCm- 2.h- 1 in RD and DT respectively). On the other hand. for the microphytobenthos. the autumn blooms were more pronounced in the sheltered station (RD) than in the wave-exposed one (DT). The annual average value of the biomass (ChIa in upper cm of sediment) was Il times higher at the RD than the DT station (42.89 ± 6.86 and 3.87 ± 1.84 mg Chla.m• 2) and the annual average of primary production 4 limes higher (19.94±6.13 and 4.77 ± 3.12 mgC m-2 .h-1). The benthic biomass was 30 times higher at the sheltered station (RD) than the planktonic one. whereas the primary production values were similar. In the wave-exposed station (DT), the benthic biomass was only twice that of the planktonic one and the planktonic primary production 4 times higher than the benthic one. The P/E ratios (assimilation numbers) indicated a better efficiency at the planktonic level [14 mgC(mg ChIa) -1.h-1 for the sheltered site and 10.46 for the open station]. They were only of 0.46 and 1.23 mgC(mg Chla) -1 - h-1 for the benthos. Such results revealed that the primary production did not exhibit the same difference between the two stations as the chlorophylI A correlation analysis gave evidence of strong relationships between both stations for the pelagic parameters, but no correlations were found between the two sites at the benthic level. When considering the primary producers (plankton + benthos) as a whole. the sheltered station was richer and more productive than the wave-exposed one. The waters were similar in both sites. indicating a common origin, but the productivity was more important in the sheltered area. due to the richness of the benthic microflora On a comparé durant deux années la biomasse (Chla fonctionnelle) et la production primaire (bilans d'oxygène) des microphytes benthiques et planctoniques de deux plages de sables fins (0,5 m de profondeur), soumises à des conditions hydrodynamiques différentes. La station de mode calme (RD) abrite notamment un peuplement de Ruditapes decussatus (pélécypode) tandis que la station de mode agité (DT) soumise à l'influence du large, est habitée par des peuplements d'un autre pélécypode, Donax trunculus. Dans le compartiment pélagique (phytoplancton) les variations saisonnières sont à peu près identiques dans les deux stations. Les moyennes annuelles de la biomasse et de la production primaire sont sensiblement équivalentes (1.40 ± 0,56 et 1,94 ± 0,78 mg Chla.m - 2: 19,60 ± 11.09 et 20,29 ± 8.45 mgc.m - 2.h -1 respectivement en RD et DT). En revanche, dans le compartiment benthique (microphytobenthos), des floraisons d'automne sont plus accentuées à la station de mode calme (RD) qu'à la station de mode agité (DT). La moyenne annuelle de biomasse (1er cm d'épaisseur du sédiment) est Il fois plus élevée à la station RD qu'à la station DT (42,89 ± 6,86 et 3,87 ± 1,84 mg Chla.m- 2) et la moyenne de la production primaire 4 fois supérieure (19,94 ± 6,13 contre 4,77 ± 3,12 mgC.m- 2.h- 1). Dans la station RD (calme), la biomasse benthique (1er centimètre) est 30 fois supérieure à la biomasse planctonique, alors que les productions primaires sont équivalentes. Dans la station de mode agité (DT) la biomasse benthique est seulement double de la biomasse planctonique et la production primaire planctonique est 4 fois supérieure à la production benthique. L'étude des corrélations montre que des liaisons étroites existent entre les deux stations pour les paramètres du domaine pélagique, alors que dans le domaine benthique, les moyennes et les évolutions sont différentes dans les deux sites. La station de sables fins de mode calme est, au total. à l'échelon primaire (plancton + benthos), plus riche et plus productive que la station de mode agité.

A better understanding of energy efficiency in the Swiss building stock, currently insufficient at the local level, is fundamental to achieve the goals of the Swiss energy strategy 2050. This study focuses on energy retrofitting of multi-family residential buildings in Geneva, integrating technical, economical, financial and environmental aspects, as well as preservation of cultural heritage.The first part provides a detailed overview of the current physical, structural and energy-using characteristics of existing building stock and analyzes the renovation market dynamics as well as the actors involved and their practices. The assessment of the energy performance of several retrofit operations revealed in the second part that the real space heating demand of the retrofitted buildings were consistently higher than those provided by calculation. It also shows that the higher the predicted space heating saving potential is, the higher share of this potential will be reached in reality. The last part evaluates the theoretical energy saving potential for space heating in the multi-family building stock and provides concrete recommendations to mobilize efficiently this potential.In conclusion, the achievement of the ambitious goals set by the Swiss federal government, particularly those which aim to reduce by half the space heating demand by 2050, is hardly possible without an improvement of the current practices regarding the actors involved in building retrofit process (process that starts with the energy audit and ends with the use of the buildings by the occupants and energy managers). Dans le cadre de la Stratégie énergétique suisse 2050, cette étude fournit d'abord un état des lieux des caractéristiques physiques, énergétiques et structurelles du secteur résidentiel collectif genevois et analyse la dynamique du marché de la rénovation et les pratiques des acteurs impliqués. Les retours d'expérience effectués ont ensuite révélé que les besoins réels en chauffage des bâtiments rénovés étaient systématiquement supérieurs à ceux prévus par calcul. Il ressort aussi que plus le potentiel prévu d'économie de chauffage est important, plus la part effectivement réalisée de ce potentiel est importante. L'étude évalue enfin le potentiel théorique d'économie de chauffage du secteur et propose une série de recommandations pour mobiliser plus efficacement ce potentiel. En conclusion, l'atteinte des objectifs de réduction fixés par la Confédération s'avère très difficile sans une amélioration des pratiques des acteurs de la filière de la rénovation, depuis l'audit jusqu'à l'usage des bâtiments par les occupants et les gestionnaires de l'énergie.

Cinq pièges à particules ont été déployés à des profondeurs comprises entre 4400 et 4 900 rn sur deux stations dans la plaine abyssale de Demerara et une station dans la plaine abyssale du Cap Vert (Atlantique tropical). Dans le même temps, un échantillonnage intensif du sédiment superficiel a été réalisé à l'aide d'un carottier de 0,25 m2 d'ouverture. Le flux particulaire total mesuré varie de 372 mg de matière sèche/m2/jour à 87,7 mg/m2/g de matériel récolté. Dans les sédiments superficiels, elle n'est plus que d'environ 4 mg/g. Il existe une relation directe entre l'intensité du flux organique et la richesse en composés organiques du sédiment. D'après nos estimations, plus de 90% du matériel organique arrivant sur le fond sont consommés par les organismes benthiques abyssaux et seulement 1% est perdu dans la sédimentation permanente. Pour 100 calories consommées par le benthos, 99 le sont par la petite faune et la flore vivant dans le sédiment, 0, 7 calories sont utilisées par les holothuries (mégafaune) et 0,3 calories par les poissons. La composition biochimique des particules se caractérise, à toutes les stations, par la prédominance des composés organiques transformées néobiogéniques ( « humus ») dans la matière organique totale (plus de 55%). La part des molécules de la matière vivante varie d'une station à l'autre: à la station la plus océanique, les protéines dominent et composent 200/o de l'énergie totale des apports. Dans la station plus soumise aux influences continentales, la concentration en lipides augmente et peut égaler celle des protéines. Dans ce cas, le taux de glucides des particules est très faible (7% des apports organiques). Enfin, les préférences nutritionnelles des animaux qui s'alimentent sur ces particules se portent principalement sur les molécules les plus énergétiques (lipides) et les plus facilement hydrolysables (protéines labiles) : les autres molécules, comme les composés néobiogéniques sont moins recherchés bien qu'ils contribuent pour moitié à l'énergie consommée par les animaux benthiques abyssaux Five particle traps were deployed at depths of 4 400 to 4 900 rn at two stations on the Demerara abyssal plain and one station on the Cape Verde abyssal plain (tropical Atlantic). At the same time, an intensive sampling of superficial sediments was carried out using a 0,25 m2 box corer. The total particle flux varied from 372 to 87,7 mg dry weightfm2/day. The average concentration of organic carbon was 40 mg/g of material collected. ln the surface sediment this was only 4 mg/g. A direct relationship existed between the intensity of the flux of organic matter and the richness of the organic matter of the deposited sediment. According to our calculations, more than 90% of the organic matter arriving at the bottom is consumed by the abyssal benthos and only 1% is lost to permanent sediment deposits. For 100 calories consumed by the benthos, 99 are utilized by the infauna and flora, 0, 7 by the holothurian egafauna and 0,3 by near-bottom fisches. The biochemical composition of the particles is characterized at ali stations by a predominance of "humic" material in the total organic matter (more than 55%). The part of the molecules unaltered form living material varied from on station to another: for the most oceanic station the protein dominated, composing 20% of the total energy. At the station onder the influence of the continent the lipid fraction grew and was almost equal to that of the protein. ln this case, the carbohydrate fraction was very weak (7% of the organic matter). Finally the preference of the animais which feed on the particles is principally for the most energetic (lipid) and the most easily hydrolysable (labile protein) molecules: the other molecules, such as the humic matter, are less preferred, although they still contribute to about half of the energy consumed by the abyssal benthic animais.

Because of strong tidal currents, the bottom of the Dover Strait consists of coarse sediment which is colonized by a pebble community. A quantitative study, based on 0.1 m(2) quadrat samples taken by divers, was conducted on this community to establish the richness of benthic macrofauna (in terms of biomass and diversity) and to provide conclusive data on global community structure (spatial and temporal heterogeneity, trophic structure). Eight samples were taken between June 1992 and June 1993, eight replicates being taken on each sampling visit. One hundred and one species were identified, in 10 zoological groups, and a mean biomass of 281 g.m(-2) (ash free dry weight) was calculated. The Shannon diversity index was low (H' = 1.24) because of the strong dominance of three species. The echinoderm Ophiothrix fragilis and the two cnidarians Urticina felina and Alcyonium digitatum accounted for at least 97 % of the total biomass at all sampling periods. Spatial heterogeneity, studied at the settle of 0.1 m(2) by hierarchical cluster analysis based on Sorensen's qualitative similarity index and by Factor Correspondence Analysis on biomasses,seemed low and was due to the strong dispersion of rare species. Hierarchical cluster analysis and FCA, performed at the scale of 0.8 m(2) on periods of sampling, showed temporal homogeneity. The seasonal influence on biomass did not affect its distribution in species or trophic groups. Suspension-feeders accounted for 99.8% of total biomass.

On utilise depuis plusieurs années les dispositifs de contrôle de l'admission de la lumière du jour afin d'éviter le réchauffement excessif des intérieurs résidentiels. Cependant, il n'existe que peu d'études qui quantifient de façon significative les avantages réels de ces dispositifs. Also available in English: Solar shading devices save energy in houses

Renewable and available in abundance, incident solar radiation is an ideal candidate for energy production. The development of nanostructured coatings for the improve- ment of technologies that convert solar energy into heat and electricity opens interesting new perspectives for the future. This PhD thesis presents an approach based on iterative cycles for the development and optimisation of such materials with a view to industrial scale production. Two ap- plications are investigated : chromium-free black selective coatings for durable thermal solar absorbers and orange coloured interferential filters for photovoltaic collectors with a view to their architectural integration. The first part of this work describes in detail the different production stages of the black selective coating from the preparation of the solutions to the manufacturing of a prototype. According to our study, the optimal coating for stainless steel tubes with a length of two meters is composed of a superposition of thin layers of Cu-Co-Mn-O//Cu- Co-Mn-Si-O//Si-O applied through sol-gel technology and annealed by an innovative induction heating process for which a patent request has been filed. The nanocomposite coating has the advantage of combining the optical properties αsol = 0.93 and εth = 0.12 with durability properties that make it eligible for possible industrialisation. The second part of the thesis describes the production of orange coloured interferen- tial filters applied on photovoltaic collectors through magnetron sputtering, a process for which another patent application has been filed. The obtained samples meet the expectations of the market with regard to such a product with a relative performance reduction of 10 to 15% in comparison with an identical collector without a filter. An in- dustrial prototype of 1190 mm x 412 mm has been produced and is being characterised at the moment these lines are written.