Tesis sobre el tema "Massive corals"

Cette étude a pour but d'identifier les principales maladies coralliennes, de quantifier leurs prévalences sur les récifs de la Réunion, d'Afrique du Sud et de Mayotte et de déterminer leurs variations spatiales et saisonnières. Les résultats ont révélé la présence de six grands types de maladies coralliennes. Les prévalences totales moyennes des maladies ont été plus élevées à la Réunion (7.5 ± 2.2%) qu'en Afrique du Sud (3.9 ± 0.8%) et qu'à Mayotte (2.7 ± 0.3%). Les genres coralliens Acropora et Porites ont été les plus vulnérables aux maladies dans les trois régions étudiées. Des variations spatiales et saisonnières ont été détectées pour la maladie de la bande noire (BBD) et les syndromes blancs (WS) à la fois à la Réunion et en Afrique du Sud avec des prévalences plus élevées sur les récifs peu profonds et pendant la saison chaude. Ce travail a également pour but de caractériser deux maladies non décrites à ce jour : le syndrome des patches blancs (PWPS) et le syndrome du patch noir (PBPS) chez Porites. PWPS, observé à fois à la Réunion, en Afrique du Sud et à Mayotte est caractérisé par d'importantes fragmentations tissulaires généralement associées à des corps ovoïdes basophiles ressemblant à des agrégats bactériens. L'analyse bactérienne a révélé une grande variabilité entre les tissus infectés et sains. L'identification des pathogènes responsables de PWPS a également été réalisée en laboratoire. Sur les 14 souches bactériennes sélectionnées et testées, seule la P180R, génétiquement proche de Vibrio tubiashii a généré des signes de PWPS. Pour finir, PBPS, une forme atypique de BBD a été observée sur les récifs de la Réunion. Les suivis réalisés ont montré des variations spatiales et saisonnières avec des prévalences plus élevées sur le platier et pendant l'été. L'histologie a mis en évidence la présence de cyanobactéries et de corps basophiles dans les tissus infectés du corail. L'analyse génétique a révélé la présence d'une plus grande diversité de taxons dans les tissus infectés par PBPS que dans les tissus sains représentés par le genre Vibrio
During the past two decades, the emergence and spread of infectious diseases have caused substantial declines in the biodiversity and abundance of reef-building corals. Despite their increased global prevalence and virulence, little is known about coral diseases on Indian Ocean coral reefs. This study aims to fill this gap in knowledge by identifying the main coral diseases and quantify their prevalence at three localities Reunion, South Africa and Mayotte, determining their spatial distribution and seasonal variation. Principal findings of this study demonstrated the presence of six main coral diseases including black band disease (BBD), white syndromes (WS), pink line syndrome (PLS), growth anomalies (GA), skeleton eroding band (SEB) and Porites white patch syndrome (PWPS). The overall disease prevalence was higher in Reunion (7.5 ± 2.2%; mean ± SE) compared to South Africa (3.9 ± 0.8%; mean ± SE) and Mayotte (2.7 ± 0.3%; mean ± SE). Acropora and Porites were the genera most vulnerable to disease. Spatial variability was detected in both Reunion and South Africa with BBD and WS more prevalent on shallow than deep reefs. There was also evidence of seasonality in two diseases: BBD and WS, their prevalence being higher in summer than winter. Corals exhibiting signs of PWPS revealed extensive tissue fragmentation, generally associated with ovoid basophilic bodies resembling bacterial aggregates within the mesoglea of the body wall. Other organisms, including Cyanobacteria, Nematoda, Ciliata and endophytic algae, were also observed on diseased tissues and were generally associated with the dead epidermis and cell debris. Results of 16S rRNA sequence analysis revealed a high variability between bacterial communities associated with PWPS-infected and healthy tissues in Porites lutea. Several bacterial ribotypes affiliated to potential putative pathogens notably Shimia marina and Vibrio hepatarius were consistently found among the 16S rRNA sequences derived from the PWPS lesions, and absent and/or poorly represented in HT. Primary pathogens involved in the PWPS were also investigated in this study using traditional culturing techniques and laboratory infection trials. Of the 14 isolates selected for the inoculation trials, only the bacterial strain P180R mostly phylogenetically closely related8 to Vibrio tubiashii with its closest known sister taxon, V. hepatarius, was shown to cause signs resembling those of PWPS and satisfied the four Henle-Koch’s postulates. P180R displayed focalised and progressive tissue paling 12 h after inoculation and visible lesions of PWPS were observed 12 h thereafter. Signs of PWPS appeared on 90% of the exposed coral fragments (27 of 30) under controlled environmental conditions. Moreover, the virulence of this marine pathogen was tested and seemed to be strongly dependent on seawater temperature, resulting in significantly higher tissue loss at 30°C than 28°C and 26°C. Finally, a multidisciplinary approach involving field surveys, gross lesion monitoring, histopathology and 454-pyrosequencing was investigated to characterize an atypical form of BBD named PBPS. Histology revealed cyanobacterial penetration of the compromised tissue as well as the presence of basophilic bodies resembling bacterial aggregates in the living tissue, adjacent to the bacterial mat. Bacterial 16S rRNA sequences yielded a broader diversity of bacterial taxa in PBPS-infected tissues than in healthy tissue, represented by the genus Vibrio (24.9%), followed by sulfate-reducers or sulfide-oxidizers such as Desulfovibrio (20%), Clostridium (12.9%) and Arcobacter (9.9%). PBPS appears to be a multi-stage disease triggered by cyanobacterial invasion and resulting in secondary infections by environmental bacteria that grow in mucus-like decomposing tissue

Bright bands in massive corals of the species Porites lutea have been associated with periods of increased rainfall. However, stain experiments involving Porites lutea from Mo Phuket have shown that bright bands are deposited during the dry season. Thus, one of the main objectives of this thesis was to understand more fully the processes that are involved in the production of fluorescent bands. The second major objective was to build a device that could reliably record fluorescent emissions directly from solid coral. It was hoped that the fluorescent emissions recorded in this way could then be compared with environmental factors, and in particular rainfall. In order to achieve the first objective, solid state coral fluorescence was examined to determine (1) what effects porosity (macro and micro) have on coral fluorescence, and (2) the distribution of fluorophores in the skeleton. By studying the fluorescence of solutions in which the CaCO₃ has been removed by acid dissolution, it was possible to determine the effects of both fluorophore concentration and the metal ions, iron and manganese, on coral fluorescence. Environmental samples (soil, sediment, seawater and polyp tissue) were also examined in an attempt to identify the source(s) of coral fluorophores. Although Boto and Isdale (1985) have suggested that terrestrial humic acid is responsible for bright band fluorescence in Porites lutea, the same, or very similar, fluorophores were found in both bright and dull bands. Two main types of fluorophore were identified, a 330-340 nm excitation peak group and a 390 nm excitation peak group. Work has shown that changes in the absolute concentration of these fluorophores (i.e. their relative concentrations remain constant) appears to be the main control on fluorescent banding. Increases in fluorophores concentration can result in both a change in the colour of coral fluorescence as well as a change in intensity. When solid coral was viewed using a fluorescence microscope, two main types of fluorescence were seen, yellow/orange fluorescent patches and a blue background fluorescence. The yellow/orange fluorescent patches were randomly distributed, ranged in size from 8-35 μm and appeared to be due to black, possibly organic, inclusions (sub-micron to 3 μm). Although the distribution of these patches was not mapped, observations suggested that they were more numerous in bright bands. This thesis suggests that differences in the ratio of yellow/orange fluorescent patches to background fluorescence controls the colour of coral fluorescence. As fluorescent emissions in the solid state are dominated by short wavelength emissions, the background region of the coral (which is also dominated by short wavelength emissions) is thought to exert the main control on fluorescent intensity. Although terrestrial surface soil contained the most concentrated source of coral-like fluorophores, it was not possible to confirm the origin of coral fluorescence as coral-like fluorophores were found in all the environmental samples.

Les récifs coralliens sont de plus en plus menacés par les changements globaux qui affectent à la fois les processus d’accrétion et d’érosion. Parmi ces processus, la bioérosion récifale est un processus de dégradation naturelle majeur résultant de l’action de divers organismes sur et dans les substrats carbonatés. Depuis peu, une attention particulière est portée sur la meilleure compréhension des rôles joués par les microflores bioérodantes (ou perforantes) comprenant des cyanobactéries, microalgues et fungi, dans le fonctionnement des récifs coralliens, et notamment le bilan carbonaté du fait de leur rôle important dans la dissolution récifale des carbonates morts à court terme (jour, mois, année). La présente thèse avait donc pour objectif principal d’étudier les effets de certains facteurs environnementaux, dont le réchauffement et l’acidification des océans à long terme (décennie) sur à la fois la composition, la distribution et l’abondance de communautés microperforantes récifales. Etant donné que des expériences à long terme avec des coraux morts sont peu envisageables, plusieurs carottes coralliennes issues de deux genres coralliens massifs (Diploastrea sp. et Porites sp.) à croissance lente, ont été collectés le long du Canal du Mozambique et en particulier à Mayotte, permettant de couvrir les dernières décennies (30 à 50 ans). Ces coraux massifs sont connus pour être de véritables bioarchives géologiques largement colonisées par les microflores perforantes qui, en dissolvant le CaCO3, créent des galeries. Pour étudier la dynamique des microflores perforantes dans les deux genres coralliens ciblés, deux méthodes innovantes ont été développées: le machine learning pour analyser rapidement et précisément des milliers d’images de galeries microperforantes prises au Microscope Électronique à Balayage (MEB) le long de trois transects verticaux parallèle à l’axe principal de croissance du corail, et l’étude de biomarqueurs lipidiques le long d’une carotte corallienne (Diploastrea sp.). La méthode du machine learning basée sur un model CNN a d’abord été développée sur le corail Diploastrea sp. avec une précision de 93%, puis adaptée au Porites sp. en modifiant notamment un hyperparamètre (précision de 95%). L’approche géochimique a consisté à tenter d’identifier des marqueurs lipidiques spécifiques de la microalgue Ostreobium sp. et du corail Diploastrea sp. au cours des dernières décennies. Les résultats ont montré que l’abondance des galeries microperforantes est 3 à 4 fois plus importante dans le corail Diploastrea sp. que dans le Porites sp. et qu’elle a diminué quelque soit le genre corallien, au cours des dernières décennies. Chez Diploastrea sp., la diminutation est de 90% en 54 ans et est couplée à un changement très important dans la composition des communautés entre 1985-1986. La densité (bulk) du Diploastrea sp. a également chuté de manière significative les 5 dernières décennies. Des régressions logistiques ont montré que la température, la vitesse des vents, le pH interne du corail, plus ou moins couplés, sont correlés à l’abondance des traces microperforantes. L’approche géochimique a également mis en évidence la diminution importante d’un biomarqueur lipidique, les amides, au cours des dernières décennies. Bien qu’il soit difficile d’attribuer les amides à un taxon ou une espèce en particulier présente dans le squelette corallien, j’émets l’hypothèse que potentiellement ces dernières pourrait refléter la présence de communautés microperforantes. Pour confirmer ou infirmer les tendances observées, il est nécessaire d’étudier un plus large nombre de carottes coralliennes sur un temps plus long. En outre, d’autres facteurs pourraient être étudiés pour mieux comprendre la diminution de l’abondance des communautés microperforantes et son implication dans la santé et la résilience des coraux, tels que les métaux traces ou d’autres variables du système des carbonates
Coral reefs are increasingly threatened by global changes as they affect both accretion and erosion processes. Among these processes, reef bioerosion is a major natural process of degradation resulting from the action of various organisms on and in carbonate substrates. Recently, a particular attention has been given to the roles played by bioeroding (or perforating) microflora, which include cyanobacteria, microalgae, and fungi, in the functioning of coral reefs, especially in the carbonate budget, because of their important role in the dissolution of dead carbonates over short term (day, month, year). The thesis's main objective was thus to study the effects of global change factors such as ocean warming and acidification, on the composition, distribution, and abundance of reef microbioeroding communities over long term. Since long-term experiments with dead corals are difficult to carry out, several coral cores from two slow-growing massive coral genera (Diploastrea sp. and Porites sp.) were collected along the Mozambique Channel, particularly in Mayotte. Those cores covered the last decades (30 to 50 years). Such massive corals are known to be natural geological archives largely colonized by microbioeroding communities which leave traces while dissolving CaCO3. To study the dynamics of microbioeroding communities in the two targeted coral genera, two innovative methods were developed: a machine learning approach to quickly and accurately analyze thousands of Scanning Electron Microscope pictures of microbioeroding traces along three vertical transects parallel to the main coral growth axis, and a lipid biomarkers approach along a coral core of Diploastrea sp.. The machine learning method based on a CNN model was first developed on the coral Diploastrea sp. with an accuracy of 93%. It was then adapted to Porites sp. by modifying a hyperparameter (95% accuracy). The geochemical approach tried identifying specific lipid markers of the boring microalga Ostreobium sp. and the coral Diploastrea sp. during the last decades. The results showed that the abundance of microbioeroding traces is 3 to 4 times higher in the coral Diploastrea sp. than in Porites sp and has decreased in both coral genera over the last decades. In Diploastrea sp., the decrease was 90% over the last 54 years and was coupled with a very important change in community composition between 1985-1986. The density (bulk) of Diploastrea sp. has also dropped significantly over the last 5 decades. Logistic regressions showed that temperature, wind speed, and internal pH of the coral, more or less coupled, are correlated to the abundance of microbioeroding traces. The geochemical approach also highlighted a significant decrease of a lipid biomarker group, the amides, over the last decades. Although it is difficult to attribute amides to a specific taxon or species in the coral skeleton, I hypothesize that they could potentially reflect the presence of microbioeroding communities. To confirm or refute the observed trends, there is a need to study more coral cores, from different areas, and over a longer period. In addition, other factors should be studied to understand better the decrease in the abundance of microbioeroding communities and its implication in coral health and resilience, such as trace metals and other variables of the carbonate system

Les coraux tropicaux sont des archives naturelles qui permettent d’une part, de reconstruire la variabilité océanique et, d’autre part, d’évaluer les impacts du réchauffement climatique et de l’acidification des océans sur ces organismes calcifiants.À partir d'un jeu de données unique issu de 40 colonies de corail massif couvrant l’ensemble de l'Océan Pacifique, de nouvelles calibrations de température ont été développées via l’analyse géochimique élémentaire de leur squelette pour la période 2010-2016. Ainsi, l’utilisation de l’approche « multi-traceurs » couplant Sr/Ca-Li/Mg permet de réduire les incertitudes de reconstruction des températures à ± 0,87 °C. Grâce à cela, deux séries temporelles de température dérivées de colonies de Porites et de Diploastrea de Palaos (Micronésie) ont été comparées. Celles-ci révèlent une discordance marquée des variations temporelles selon le traceur utilisé ou le genre étudié et donc, la nécessité de mieux comprendre les processus de bio-minéralisation. Pour cela, l'analyse géochimique (B/Ca et δ11B) de squelettes coralliens a été réalisée afin de reconstruire les propriétés chimiques des carbonates au sein du fluide de calcification (cf).Ce travail doctoral met en évidence la capacité des coraux massifs à réguler la chimie des carbonates de leur cf avec, pour Porites une hausse du pHcf (~ 8,41) à la fois sur un site témoin (pHsw ~ 8,03) et sur un site naturellement acide de Palaos (pHsw ~ 7,85), favorisant ainsi le processus de calcification.À l’échelle du bassin Pacifique, il en résulte que la température conjointement à la chimie des carbonates de l’eau de mer (pHsw, DICsw et Ωsw) pilotent cette régulation interne ainsi que les paramètres de croissance. Parmi eux, la densité du squelette des Porites diminue de 14 % en condition acide, ce qui pourrait à terme, les rendre plus vulnérables.En revanche, la régulation interne du genre Diploastrea semble plus sensible au réchauffement de l'océan et mérite donc une attention particulière dans les études futures afin d’évaluer leur capacité à supporter ce réchauffement conjugué à l'acidification des océans
Tropical corals provide natural archives to reconstruct oceanic variability and evaluate the impacts of global warming and ocean acidification on these calcifying organisms.From a unique dataset of 40 massive coral colonies across the Pacific Ocean, I developed temperature calibrations via elemental geochemical analysis of their skeletons for the period 2010-2016. The use of a "multi-proxy" approach coupling Sr/Ca-Li/Mg reduces the reconstructed temperature uncertainties to ± 0.87 °C. Thereby, two temperature time series derived from Porites and Diploastrea colonies from Palau (Micronesia) were reconstructed and compared. These reveal a substantial discrepancy in temporal variations by proxy or genus of interest and hence, the need to better understand bio-mineralization processes. With this aim, I analysed the B/Ca and δ11B of the coral skeletons in order to determine the carbonate system properties of the calcifying fluid (cf).My results highlight the ability of massive corals to regulate the carbonate chemistry of their cf with, for Porites, an increase in pHcf (~ 8.41) both at a control site (pHsw ~ 8.03) and at a naturally acidic site in Palau (pHsw ~ 7.85), promoting the calcification process.At the Pacific Ocean level, it emerges that temperature together with seawater carbonate chemistry (pHsw, DICsw and Ωsw) influence this internal regulation as well as the growth parameters. In particular, the skeletal density of Porites decreases by 14% under acidic conditions, which might ultimately lead to a greater vulnerability to further damages.In contrast, internal regulation of the genus Diploastrea is more likely to be sensitive to ocean warming and therefore, deserve forefront attention in the future studies to assess their ability to endure increasing global ocean warming and acidification

Includes bibliographical references.
Coral δ¹⁸O and Sr/Ca records from massive corals in the western Indian Ocean (WIO) are used to establish the heterogeneous distribution of warming rates across the tropical and subtropical regions and to investigate if it corresponds with that from instrumental sea surface temperatures (SSTs). The coral records correlate with instrumental data better on monthly time scales compared to annual time scales. Coral thermal stress was assessed by the Degree Heating Months (DHM) technique and even though the coral DHM aligns quite well with instrumental DHM, the values from coral data are generally 2-3 times greater in magnitude than the DHM values from instrumental data. It was found that the accumulated thermal stress, calculated from coral and instrumental data, for the majority of the tropical and subtropical WIO sites has been increasing since the 1970’s. From 1870 to 1995, both the tropics and the subtropics have been warming in general, although with different and varying rates as recorded by the coral and the instrumental SSTs. It was further revealed that both the tropical and the subtropical WIO warmed during the summer and winter periods during 1870-1995. On longer time scales, the relationship between the coral records in the WIO and climate indices showed a significant interannual variability approximately centered at periods 3-6 years, indicating a probable link with ENSO and IOD. The extent to which coral reefs from different sites in the WIO are prepared to survive climate change based on historical SST variability and intensity of warming rates are described. It could therefore be suggested that some corals may be more favoured to survive warming climate compared to others because corals in the WIO are located in different oceanographic conditions and experience different climatic variations.

Porites lobata is an important reef building coral in the tropical eastern Pacific and the dominant Porites species in the Galápagos archipelago. Following the 1982-83 El Niño-Southern Oscillation the Galápagos Islands experienced 97-99% coral mortality, leaving many areas throughout the archipelago denuded of corals. Because very few long term assessments have been conducted on the growth and resilience of P. lobata to natural disturbances in the Galápagos Islands (Glynn et al., 2001; Glynn et al., 2009), benthic surveys were performed on a uniquely dense aggregation of P. lobata colonies at Devil’s Crown, Floreana Island between 1993 and 2011. Annual changes in live tissue area were calculated for the majority of the population (n=17) using Coral Point Count with Excel extensions (CPCe 3.6) software to determine growth and recovery trends for this aggregation. Total live tissue area (n=10) increased from 1993 to 2011, however due to high interannual variability this increase was not significant. Within this overall pattern, a general trend of decline was observed in live tissue cover from 1993 to 2000, with increases in tissue area observed from 2000 to 2011. Severe bleaching (85-100%) was observed during the 1998 survey, followed by 42% tissue loss (n=10), coinciding with sea water warming associated with the very strong 1997-1998 El Niño-Southern Oscillation event. Subsequent regrowth of coral tissue was observed during the 2001 survey with continued recovery through 2009. Multiple comparison testing revealed a significant difference between the impacted state (1999) and the recovered state (2009), (p = 0.002, Dunn’s method, n=17), suggesting this aggregation required a period of ten years to recover from this disturbance. During this recovery period the moderately strong 2007-2008 La Niña, with accompanying stressful low temperatures, occurred but did not interrupt tissue regrowth. Warmer than average sea surface temperatures occurred during the warm months from 2008 to 2011, during which time a cool period occurred from 2010 to 2011. While the magnitude and duration of temperature anomalies during warming were not as great as those observed during the 1997-98 ENSO, low temperatures observed during the cool period were similar to those experienced throughout the 2007-08 La Niña. During this time total live tissue cover was reduced by 19% (n=10); however it is unknown whether this was due to warming or the following cool period. Based on results from the 1997-98 El Niño and 2007-08 La Niña, this reduction in live tissue was most likely caused by elevated sea surface temperatures. Data on the growth and resilience of P. lobata populations at Devil’s Crown will be used for conservation and management of this important resource.

The ability of corals to build reefs can be attributed to their relationship with single-celled algae of the familySymbiodiniaceae.Through the process of photosynthesis, these algae can provide their coral hosts with over 90% of their daily energy requirements. Most coral species acquire multiple species of symbionts from the surrounding water during their larval stage or immediately after settling. However, over time, the coral will select a dominant symbiont speciesthat can depend on the local environment. Until this study, the size or age of the coral at which this transition from multiple Symbiodiniaceaespecies to one dominant species occurs has remained uncertain. Likewise, it was unclear whether the selection of Symbiodiniaceaespeciesis influenced by the environment. The environmental conditions and symbiont composition of one hundred and eighteen juvenile Siderastrea siderea were assessed across four sites in Broward County, Florida. Presuming newly settled corals acquire multiple symbionts and then select just one dominant species, it was determined that the transition from multiple symbiont speciesto one dominant species in Siderastrea sidereaoccurs in the single polyp stage, between the time of settlement and approximately 4 to 6 months of age. The results also suggest that the selection of these dominant symbiont speciesis influenced by the environment, and that juveniles commonly select the same species as adults inhabiting similar environmental conditions. The selection of symbionts homologous to adult corals combined with environmental influences may be an early indicator of acclimatization in Siderastrea siderea.

2012/2013
The subject of modelling flow near wall is still open in turbulent wall bounded flows, since there is no wall layer model which works perfectly. Most of the present models work well in attached flows, specially for very simple geometries like plane channel flows. Weakness of the models appears in complex geometries, and many of them do not capture flow separation accurately in detached flows, specially when the slope of wall changes gradually. In many engineering applications, we deal with complex geometries. A possible way to simulate flows influenced by complex geometry using a structured grid, is to consider the geometry as immersed boundary for the simulation. Current wall layer models for the immersed boundaries are more complex and less accurate than the body-fitted cases (cases without immersed boundaries). In this project the accuracy of wall layer model in high Reynolds number flows is targeted, using LES for attached flows as well as detached flows (flows with separation). In addition to the body fitted cases, wall layer model in the presence of immersed boundaries which is treated totally different also regarded. A single solver LES-COAST (IE-Fluids, University of Trieste) is used for the flow simulations, and the aim is to improve wall layer model in the cases with uniform coarse grid. This is in fact novelty of the thesis to introduce a wall layer model applied on the first off-wall computational node of a uniform coarse grid, and merely use LES on the whole domain. This work for the immersed boundaries is in continuation of the methodology proposed by Roman et al. (2009) in which velocities at the cells next to immersed boundaries are reconstructed analytically from law of the wall. In body-fitted cases, since smaller Smagorinsky constant is required close to the walls than the other points, wall layer model in dynamic Smagorinsky sub-grid scale model using dynamic k (instead of Von Karman constant) is applied to optimize wall function in separated flows. In the presence of immersed boundaries, the present wall layer model is calibrated, and then improved in attached and also detached flows with two different approaches. The results are also compared to experiment and resolved LES. Consequently the optimized wall layer models show an acceptable accuracy, and are more reliable. In the last part of this thesis, LES is applied to model the wave and wind driven sea water circulation in Kaneohe bay, which is a bay with a massive coral reef. This is the first time that LES-COAST is applied on a reef-lagoon system which is very challenging since the bathymetry changes very steeply. For example the water depth differs from less than 1 meter over the reef to more than 10 meters in vicinity of the reef, in lagoon. Since a static grid is implemented, the effect of wave is imposed as the velocity of current over the reef, which is used on the boundary of our computational domain. Two eddies Smagorinsky SGS model is used for this simulation.
XXVI Ciclo
1983

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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A construção de campos com localização em cordas foi realizada rigorosamente há pouco mais de uma década. Nesta abordagem, os campos são operadores em algum espaço de Hilbert, e portanto não há graus de liberdade não-físicos tais como "ghosts". Além de permitir a construção de campos carregados inteiramente num espaço espaço de Hilbert, os campos com localização em cordas exibem um bom comportamento no regime ultravioleta e, entre outras características, são possíveis candidatos para descreverem consistentemente a matéria escura. No intuito de obter uma prova da renormalizabilidade em modelos perturbativos no esquema de Epstein-Glaser com campos quânticos localizados em cordas, é necessário evidenciar a liberdade que se tem ao definir produtos temporalmente ordenados do Lagrangeano de interação. Este trabalho proporciona um primeiro passo significativo nesta direção. O problema básico é a presença de um conjunto aberto de n-uplas de cordas que não podem ser cronologicamente ordenadas. Nós resolvemos este problema ao mostrar que quase todas (i.e. exceto num subconjunto de medida nula) tais configurações de cordas podem ser dissecadas num número finito de pedaços, os quais por sua vez podem ser cronologicamente ordenados. Com isso, tem-se que o produto temporalmente ordenado de fatores lineares de campos está fixo fora de um conjunto de medida nula de configurações de cordas. A construção do ordenamento temporal geométrico de cordas é feita de modo a servir para o estudo da renormalizabilidade de quaisquer teorias quânticas de campos com localização em cordas.
The construction of string-localized fields was rigorously accomplished a little over a decade ago. In this approach, the fields are operators in some Hilbert space, and therefore there are no unphysical degrees of freedom such as ghosts. In addition to allowing the construction of charged fields entirely in a Hilbert space, the string-localized fields exhibit, in general, a good behavior in the ultraviolet regime and, among other features, the class (representation) of string-localized fields with m = 0 and s = oo are possible candidates to consistently describe dark matter. In order to obtain a proof of renormalizability of perturbative models in the Epstein—Glaser scheme with string-localized quantum fields, one needs to know what freedom one has to define time-ordered products of the interaction Lagrangian. This work provides a first significant step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all (i.e. outside a null set) such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. The construction of the geometric time ordering of strings is realized in such a way that it will serve to study the renormalizability of any quantum field theories with string-localized fields

Image analysis was used to measure basal areas of selected colonies of Montastraea annularis and Porites astreoides, following the colonies over a three-year period from 2002 to 2004. Existing digital images of permanently-marked quadrats in the Caye Caulker Marine Reserve, Belize, were selected based on image quality and availability of images of selected quadrats for all three years. Annual growth rates were calculated from the basal-area measurements. Mean growth rates (radial skeletal extension) for M. annularis and P. astreoides were 0.02 cm yr-1 and -0.20 cm yr-1, respectively. Basal area measurements demonstrated a large degree of variability. Increases were approximately balanced by declines giving the impression of stasis. By removing negative values and correcting by 25% to allow for comparison with vertical growth rates, mean values increased to ~0.5 cm yr-1 for M. annularis and ~0.8 cm yr-1 for P. astreoides. Basal area as a growth measure was compared to methods used in earlier studies. A new growth index based on basal area and perimeter was proposed and modeled. This growth index can be useful for reporting growth measured from basal areas and comparable other methods. The index also measures negative growth, or mortality, which conventional methods cannot do.

L’océan Pacifique est le siège de variabilités climatiques interannuel et multi-décennale, El Niño Southern Oscillation (ENSO) et la Pacific Decadal Oscillation (PDO), dont les répercussions (via des téléconnections) peuvent être mondiales. Des impacts importants sur les populations, les activités socio-économiques et sur l’environnement ont été attribuées à ENSO. Il est alors primordial d’améliorer notre compréhension de la dynamique Pacifique et notamment du phénomène ENSO ainsique son évolution sous l’effet du changement climatique.Les mesures géochimiques (Sr/Ca et 818O) réalisées sur les coraux constituent des enregistrements paléoclimatiques de choix pour l’étude de l’évolution d’ENSO et sont essentielles pour mettre en perspective la dynamique actuelle du climat par rapport à sa dynamique passée. Après avoir évaluer la robustesse du paléothermomètre géochimique corallien (Sr/Ca), cette thèse a permis la reconstruction de température de surface océanique (SST) à partir de coraux de l’atoll de Clipperton (Pacifique tropical Est) et de l’archipel des Marquises (Pacifique tropical centre) couvrantplusieurs parties du dernier millénaire. Nos résultats suggèrent que la structure spatiale d’ENSO étaitplutôt stable au cours des deux derniers siècles, montrant majoritairement une structure de type ENSOcanonique (Est Pacifique) par opposition à l’ENSO Modoki (centre Pacifique). Bien qu’encore débattue, cette structure spatiale pourrait avoir évoluée très récemment, en liaison avec le changement climatique global (et cela pourrait continuer dans le futur). A l’échelle décennale, nos deux zones d’étude (centre et Est Pacifique) sont influencées par la PDO.Les résultats de cette thèse tendent également à suggérer que l’activité d’ENSO actuelle (sous l’effet du forçage anthropique) n’est pas atypique à l’échelle du dernier millénaire. En effet, son intensité et sa fréquence étaient plus fortes au début du petit âge glaciaire (LIA, 16ème siècle). La comparaison deces résultats avec un ensemble de simulations climatiques (PMIP3) montre que la variabilité ENSO estbien reproduite par ces modèles climatiques mais qu’ils échouent à reproduire correctement l’état moyen des températures du Pacifique
The Pacific Ocean is the place of interannual and multi-decadal climate variabilities, namely the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). There can have globals impacts via teleconnections. Major impacts on populations, economic and environmental activitieshave been attributed to ENSO. It is therefore essential to improve our understanding of the Pacificdynamic, particularly ENSO activity and its evolution under recent climate change.Geochemical measurements (Sr/Ca and 818O) performed on corals are relevant paleoclimatic records for studying the evolution of ENSO and are essential to put into perspective the current climatedynamic in comparison to past climate.After an evaluation of the robustness of the coral geochemical paleothermometer (Sr/Ca), we present the reconstruction of sea surface temperature (SST) from Eastern tropical Pacific coral (Clippertonatoll) and central tropical Pacific coral (Marquesas archipelago) covering several parts of the last millennium. Our results suggest that ENSO spatial pattern was relatively stable over the past two centuries, mainly indicating an eastern Pacific ENSO pattern (canonical) in comparison to the centralPacific ENSO (Modoki). Although still debated, this spatial pattern could have recently changed dueto global climate change (and this could continue in the future). At the decadal timescale, both studiedareas (central and eastern Pacific) are influenced by the PDO.The results of this Phd thesis also suggest that the present day ENSO activity (under the influence ofanthropogenic forcing) is not atypical throughout the last millennium. The intensity and frequency of ENSO were stronger in the early Little Ice Age (LIA, 16th century). These results are compared withan ensemble of climate simulations (PMIP3) and indicate that ENSO variability is correctly reproduced by numerical climate models but that these models fail to correctly reproduce the mean temperature state of the Pacific

L'étude des paléoclimats tropicaux est importante pour cerner les variabilités climatiques liées au changement global et, à terme, l'augmentation de la capacité de prédiction climatique. A ce titre, les coraux massifs apparaissent comme d'excellents enregistreurs des climats marins tropicaux. Ainsi les variations du contenu géochimique des squelettes des coraux massifs varient corollairement à l'évolution des paramètres environnementaux. Ce travail met en évidence l'intérêt d'analyses couplées (isotopes stables δ18O et δ13C et éléments trace, Sr/Ca, U/Ca, Ba/Ca, Mg/Ca et Ba/Ca) pour comprendre entre autre la variabilité des températures et des salinités de surface de l'océan. Les méthodes existantes ainsi que celles développées dans le cadre de cette étude lors de la phase de calibration sont appliquées à deux sites d'étude situés dans le pacifique tropical Sud Ouest. Ainsi, plus de 500 ans d'enregistrement des températures et des salinités sont reconstruites en continu, montrant des variations de type interdécennales marquées, qui s'expliquent essentiellement par la courantologie des masses d'eaux au Sud de l'île de la Nouvelle Calédonie. De forts événements ENSO (El Niño Southern Oscillation) ont également été mis en évidence aux alentours de 1600. L'autre site d'étude, Wallis, d'interprétation plus complexe, semble présenter des variations liées aux modulations basse fréquence de la SPCZ (South Pacific Convergence Zone). Finalement, ces résultats sont remis en perspective dans un cadre plus général et une synthèse des différents outils offerts aux paléoclimatologues est produite, incorporant les résultats issus des présents travaux.

L'objectif de cette étude est de retracer les voies de distributions atmosphériques et océaniques du plomb au cours du 20ème siècle, en relation avec la variabilité climatique de l'Atlantique Subtropical Nord, à l'aide des archives coralliennes et des émissions anthropiques de plomb. Dans une première phase, l'impact des émissions atmosphériques américaines et européennes a été quantifié sur deux colonies coralliennes de la Mer des Carai͏̈bes (Ile de Mona et Ile de la Martinique) à partir des analyses du plomb et de ses isotopes stables par Spectrométrie de Masse à Thermo-Ionisation (TIMS). Les mesures réalisées indiquent que les archives coralliennes sont de bons enregistreurs des émissions anthropiques de plomb. La résolution annuelle obtenue, notamment sur la colonie de l'île de Mona, permet de retracer l'impact des émissions de plomb dans l'Atlantique Nord au cours du 20ème siècle. Cette résolution autorise l'accès aux cinétiques de transferts des aérosols à l'échelle du bassin. Par comparaison avec les profils réalisés sur différents sites (Bermudes, Floride, Barbade, Péninsule du Yucatan, Basin de Cariaco et Ile de Ste. Croix), il ressort que la distribution des aérosols dans l'Atlantique Subtropical est contrôlée par les paramètres météorologiques et réagit aux oscillations climatiques de l'Atlantique Nord (ONA). Du fait du temps de résidence très court du plomb dans l'atmosphère (moins de 10 jours), le décalage dans le temps d'événements marqués comme l'interdiction des essences plombées aux Etats Unis puis en Europe a conduit, à travailler également sur le compartiment océanique. Les anomalies océaniques déduites des enregistrements 18O sur les colonies coralliennes de Porto-Rico, de la Martinique et de la Guadeloupe peuvent en partie expliquer les déphasages observés. Les fluctuations océaniques saisonnières ont été établies et les variations interannuelles répondent à la fois aux ONA et aux perturbations climatiques de l'océan Pacifique (ENSO-PDO)
The main purpose for this study is to reconstruct atmospheric and oceanic transport of pollutant lead in relation to climate variability in the subtropical North Atlantic during the XXth. Century. This shall be performed using geochemical coral records and anthropogenic lead emission archives. We did first quantify the relative impact of the main anthropogenic sources to Caribbean corals (Mona Island and Martinique) with lead and its stable isotope (low level analysis by thermal ionisation mass spectrometry). Data show the capacity of corals to faithfully record input from industrialized continental sources (Northern and Central America, Western Europe) as well as meteorological events such as hurricanes. This high resolution study evidence the role of climate oscillations such as the NAO on the distribution of continental pollutants into oceanic surface waters. Discrepancies between the transient pollutant lead emission and its record inot corals from different locations in the Western North Atlantic did strongly suggest a significant control of oceanic circulation on lead distribution. Surface Seawater Temperature anomalies as recorded by 18O do evidence the seasonal impact of the Pacific meteorological indices (ENSO-PDO) on the North Atlantic circulation

Ce travail s'inscrit dans une démarche visant à quantifier l'impact de la diagenèse sur les ratios élémentaires Sr/Ca, Mg/Ca et U/Ca caractéristiques de l'exosquelette (aragonite biogénique) de coraux Porites sp. Ces ratios élémentaires sont très utilisés comme paléo thermomètres en paléo climatologie tropicale pour reconstruire les paléo variables environnementales comme la température de surface de l'océan. On considère dans un premier temps un corail moderne prélevé in vivo et un corail fossile daté au 14C de l'Holocène Moyen (5445 ans BP). Les deux coraux ne présentent aucune trace d'altération diagénétique. On mesure Sr/Ca, Mg/Ca, U/Ca dans l'exosquelette par spectrométrie de masse couplée à un plasma inductif et à la microsonde de Castaing pour Sr/Ca. Les températures de l'océan du temps du vivant des coraux sont alors reconstruites à partir de la géochimie des échantillons et validées. L'approche est ensuite étendue à des coraux pléistocènes (~125000 ans BP) altérés par la diagénèse e.g., apparition de calcite au détriment de l'aragonite initiale sous l'action de l'eau douce percolant dans les récifs. Cette calcitisation affecte les ratios Sr/Ca et Mg/Ca originels et est susceptible d'entacher les reconstructions d'un biais qu'il est important de bien connaître. En s'appuyant sur la spectrométrie Raman et la microanalyse X, on confirme les tendances qualitatives rapportées dans la littérature sur l'impact de la calcite sur les proxies du climat : la présence de calcite diminue (resp. rehausse) le ratio Sr/Ca (resp. Mg/Ca) créant donc des artéfacts chauds dans les températures reconstruites.

Dans le cadre de la dualité holographique entre une vaste famille de vides 1/2-maximalement supersymétriques Anti-de Sitter à quatre dimensions (AdS₄) et des théories des champs superconformes N=4 supersymétriques à trois dimensions (sCFT₃), nous étudions des questions théoriques majeures de gravité quantique et de théories de jauge. Ce travail a deux directions principales : La premiere partie est consacrée aux mécanismes par lesquels le graviton AdS₄ peut acquérir une petite masse, tandis que la seconde partie concerne la cartographie de la variété superconforme des sCFT₃ considérées. En ce qui concerne la question du mecanisme de Higgs pour le graviton d’AdS₄, nous proposons un nouveau mécanisme qui repose sur le couplage ”faible” de deux sCFT₃s, initialement découplées, en jaugent une symmétrie globale commune. Les deux tenseurs de stress initialement conservés se mélangent et le résultat est une combinaison conservée et une combinaison orthogonale, dont la dimension acquiert une petite dimension anormale. Holographiquement, cette configuration correspond à la connexion de deux univers AdS₄ initialement découplés via un AdS₅ × S⁵ fin, autrement appelé une “gorge” de Janus. Le résultat est une théorie AdS₄-bimétrique, avec un graviton sans masse et un graviton massif, dont la petite masse correspond à la dimension anormale de la combinaison duale de tenseurs de stress. Nous calculons la masse du graviton, qui est exprimée en termes de données géométriques de la ”gorge” de Janus et de l’univers AdS₄ vers zéro, résulte en une théorie de gravité massive dans AdS₄. En ce qui concerne la deuxième direction de ce travail, les déformations superconformes des sCFT₃s considérées qui génèrent la variété superconformale sont des déformations préservant N = 2 supersymétrie, générées par des opérateurs exactement marginaux. Nous présentons comment tous ces opérateurs peuvent être systématiquement extraits de l’index superconforme. Les opérateurs de branche de Coulomb et de Higgs sont pris en compte, tandis qu’une attention particuli ère est accordée aux opérateurs mixtes. On montre que les modules de branches mixtes de ces théories sont des opérateurs à double-corde qui se transforment dans la représentation (Adj, Adj) des groupes de saveursélectriques et magnétiques, modulo un surcomptage pour les quivers avec des noeuds de jauge abéliens. Enfin, nous commentons sur l’interprétation holographique des résultats, en affirmant que les supergravités mesurées peuvent capturer l’espace des modules tout entier si, outre les paramètres de la solution d’arri ère-plan, les modules de quantification des conditions aux limites sontégalement pris en compte
Based on the holographic duality between a large class of half-maximally supersymmetric four-dimensional Anti-de Sitter (AdS₄) vacua and three-dimensional N = 4 superconformal field theories (sCFT₃), we study quantum gravitational and gauge theoretic questions. This work has two main directions: The first part is devoted to the mechanisms through which the low-lying AdS₄-graviton can acquire a small mass whereas the second part regards the mapping of the superconformal manifold of the considered sCFT₃s. Regarding the question of the graviton Higgsing in AdS₄, we propose a new mechanism which relies on ”weakly” coupling two initially decoupled sCFT₃s, by gauging a common global symmetry. The two initially conserved stress tensors mix and the result of this mixing is a conserved combination and an orthogonal combination, the scaling dimension of which acquires a small anomalous dimension. Holographically, this setup is dual to connecting two initially decoupled AdS₄ universes via a thin AdS₅ × S⁵ or Janus ”throat”. The result is an AdS₄- bimetric theory, with one massless and one massive graviton, the small mass of which corresponds to the anomalous dimension of the dual stress tensor combination. We compute the mass of the graviton, which is expressed in terms of the geometric data of the Janus ”throat” and of the considered AdS₄ universe. A special decoupling limit of this theory, where the effective four-dimensional gravitational coupling of one of the two universes vanishes, results to an AdS₄-Massive gravity theory. Regarding the second direction of this work, superconformal deformations of the considered sCFT3s which generate the superconformal manifold, are N = 2 supersymmetry preserving deformations, generated by exactly marginal operators. We present how all these operators can be consistently extracted from the superconformal index. Coulomb and Higgs branch operators are considered, while particular attention is payed to mixedbranch operators. It is shown that the mixed-branch moduli of these theories are double-string operators transforming in the (Adj,Adj) representation of the electric and magnetic flavour groups, up to overcounting for quivers with abelian gauge nodes. Finally, we comment on the holographic interpretation of the results, arguing that gauged supergravities can capture the entire moduli space if, in addition to the parameters of the background solution, quantization moduli of boundary conditions are also taken into account

Les eaux du gyre subtropical du Pacifique sud sont majoritairement transportées vers l'ouest par le Courant Equatorial Sud (SEC) situé entre 2°S et 30°S. Se dirigeant vers l'équateur via les courants de bord ouest, les eaux de thermocline (∼300 m de profondeur) ont notamment été identifiées comme contribuant à la modulation basse fréquence du phénomène climatique El Niño-Oscillation Australe (ENSO). Initialement large et zonal, le SEC se divise en plusieurs jets et courants de bord ouest à la rencontre des archipels de Fidji (18◦ S-180◦ E), du Vanuatu (16◦ S-168◦ E), de la Nouvelle Calédonie (22◦ S-165◦ E) et des côtes australiennes. Entre 10◦ S et 20◦ S, ces eaux entrent en mer de Corail sous la forme de deux jets zonaux: le Jet Nord Calédonien (18◦ S-16◦ S) et le Jet Nord Vanuatu (14◦ S-11◦ S). Dans cette thèse, nous nous sommes consacrés à documenter la circulation océanique à l'aide de données hydrologiques issues de campagnes océanographiques (1993-2010) en adoptant deux méthodes d'inversion: le " modèle inverse en boite " et l'" analyse multi-paramétrique optimale ". Nous avons ensuite abordé la variabilité interannuelle pour replacer ces analyses et déterminer les impacts sur la circulation. Dans la première partie, nous avons étudié des situations synoptiques afin de mettre en évidence le Courant Est Calédonien alimentant le Jet Nord Calédonien. Ces deux courants similaires sont fins (100 km) et profonds (0-1000 m) et transportent environ 15 Sv (1 Sverdrup = 106 m3.s-1). Plus au nord, le Jet Nord Vanuatu est plus large (∼300 km) et moins profond (0-500 m); il transporte environ 20 Sv. Ces eaux se dirigent vers l'Australie où elles alimentent la mer des Salomon par l'intermédiaire du Sous-courant Côtier de Nouvelle Guinée estimé à 30 Sv. Ces analyses, au cours desquelles nous avons appliqué la méthode du modèle inverse en boite, montrent que ces structures de courants sont caractérisées par les propriétés des masses d'eau. Dans une deuxième partie, à l'aide d'une analyse multi-paramétrique optimale avec les paramètres (T, S, et O2), nous nous sommes focalisés sur les masses d'eau en établissant un lien avec la circulation dynamique. Nous avons mis en évidence le tra jet et le mélange des eaux intermédiaires et des eaux de thermocline. Dans la thermocline, l'alimentation du Sous-courant Côtier de Nouvelle Guinée est essentiellement assurée par les masses d'eau transportées par le Jet Nord Vanuatu, tandis que les eaux intermédiaires sont issues du Jet Nord Calédonien. Cette vision complémentaire de la circulation océanique alimentant la bande équatoriale montrent que les eaux intermédiaires sont principalement transportées par les courants profonds tandis que les eaux de thermocline sont issues majoritairement du Jet Nord Vanuatu. Dans une troisième partie, la variabilité de la circulation océanique est analysée sur la période 1993-2010 à l'aide d'une simulation numérique au 1/10◦ et d'une méthode de reconstruction de profils hydrologiques utilisant les données satellitaires. Nous montrons que la variabilité interannuelle du SEC suit de trois mois le phénomène ENSO, et qu'elle est dominée par la variabilité du Jet Nord Vanuatu. Contrôlée par les vents, la variabilité du SEC est associée à une modulation de la pente de la thermocline, qui induit une intensification de 6 ± 4 Sv suite à un évènement El Niño et un ralentissement de 4 ± 4 Sv après un évènement La Niña. Nous montrons également que la modulation de la thermocline entraîne l'apparition d'anomalies de température et de salinité, susceptibles d'être transmises vers la bande équatoriale. Ce travail de thèse a ainsi permis d'augmenter la compréhension de la circulation régionale et fournit de nouvelles pistes d'investigations pour l'étude de la dynamique de la mer de Corail.

Les eaux du gyre subtropical du Pacifique sud sont majoritairement transportées vers l'ouest par le Courant Equatorial Sud (SEC) situé entre 2°S et 30°S. Se dirigeant vers l'équateur via les courants de bord ouest, les eaux de thermocline (~300 m de profondeur) ont notamment été identifiées comme contribuant à la modulation basse fréquence du phénomène climatique El Niño-Oscillation Australe (ENSO). Initialement large et zonal, le SEC se divise en plusieurs jets et courants de bord ouest à la rencontre des archipels de Fidji (18° S-180° E), du Vanuatu (16°S-168° E), de la Nouvelle Calédonie (22° S-165° E) et des côtes australiennes. Entre 10° S et 20° S, ces eaux entrent en mer de Corail sous la forme de deux jets zonaux: le Jet Nord Calédonien (18° S-16° S) et le Jet Nord Vanuatu (14° S-11° S). Dans cette thèse, nous nous sommes consacrés à documenter la circulation océanique à l'aide de données hydrologiques issues de campagnes océanographiques (1993-2010) en adoptant deux méthodes d'inversion: le " modèle inverse en boite " et l'" analyse multi-paramétrique optimale ". Nous avons ensuite abordé la variabilité interannuelle pour replacer ces analyses et déterminer les impacts sur la circulation. Dans la première partie, nous avons étudié des situations synoptiques afin de mettre en évidence le Courant Est Calédonien alimentant le Jet Nord Calédonien. Ces deux courants similaires sont fins (100 km) et profonds (0-1000 m) et transportent environ 15 Sv (1 Sverdrup = 106 m3. S-1). Plus au nord, le Jet Nord Vanuatu est plus large (~300 km) et moins profond (0-500 m); il transporte environ 20 Sv. Ces eaux se dirigent vers l'Australie où elles alimentent la mer des Salomon par l'intermédiaire du Sous-courant Côtier de Nouvelle Guinée estimé à 30 Sv. Ces analyses, au cours desquelles nous avons appliqué la méthode du modèle inverse en boite, montrent que ces structures de courants sont caractérisées par les propriétés des masses d'eau. Dans une deuxième partie, à l'aide d'une analyse multi-paramétrique optimale avec les paramètres (T, S, et O2), nous nous sommes focalisés sur les masses d'eau en établissant un lien avec la circulation dynamique. Nous avons mis en évidence le tra jet et le mélange des eaux intermédiaires et des eaux de thermocline. Dans la thermocline, l'alimentation du Sous-courant Côtier de Nouvelle Guinée est essentiellement assurée par les masses d'eau transportées par le Jet Nord Vanuatu, tandis que les eaux intermédiaires sont issues du Jet Nord Calédonien. Cette vision complémentaire de la circulation océanique alimentant la bande équatoriale montrent que les eaux intermédiaires sont principalement transportées par les courants profonds tandis que les eaux de thermocline sont issues majoritairement du Jet Nord Vanuatu. Dans une troisième partie, la variabilité de la circulation océanique est analysée sur la période 1993-2010 à l'aide d'une simulation numérique au 1/10 et d'une méthode de reconstruction de profils hydrologiques utilisant les données satellitaires. Nous montrons que la variabilité interannuelle du SEC suit de trois mois le phénomène ENSO, et qu'elle est dominée par la variabilité du Jet Nord Vanuatu. Contrôlée par les vents, la variabilité du SEC est associée à une modulation de la pente de la thermocline, qui induit une intensification de 6 ± 4 Sv suite à un évènement El Niño et un ralentissement de 4 ± 4 Sv après un évènement La Niña. Nous montrons également que la modulation de la thermocline entraîne l'apparition d'anomalies de température et de salinité, susceptibles d'être transmises vers la bande équatoriale. Ce travail de thèse a ainsi permis d'augmenter la compréhension de la circulation régionale et fournit de nouvelles pistes d'investigations pour l'étude de la dynamique de la mer de Corail
Waters from the South Equatorial Current, the northern branch of the South Pacific subtropical gyre, have been identified as having an important contribution to climate variability and El Niño-Southern Oscillation. Initially a broad westward current extending from 2°S to 30°S, the South Equatorial Current splits upon the major archipelagos of Fiji (18°S, 180°E), Vanuatu (16°S, 168°E), New Caledonia (22°S, 165°E) and Australian coasts resulting in two main zonal jets entering the Coral Sea: the North Caledonian Jet (18°S, 180°E) and the North Vanuatu Jet (16°S, 168°E). In this work, we focus on the oceanic circulation using hydrographic data from sea cruises and we apply two inverse methods: the "inverse box model" and the "optimal multi-parametric analysis". Then, we report interannunal variability and its impacts on the Coral Sea circulation. We first study the East Caledonian Current which runs along the east coast of New Caledonia and feeds the North Caledonian Jet. Both currents extend about 100 km horizontally, to at least 1000 m depth vertically and transport 15 Sv (1 Sv = 106 m3. S-1). In the northern part, the North Vanuatu Jet is larger (~300 km) and shallower (0-500 m) and transports around 20 Sv. A part of these waters reaches Australia and supplies the Solomon Sea via its western boundary current, the New Guinea Coastal Undercurrent estimated at 30 Sv. These structures are characterized by water mass properties. Secondly, we emphasize the thermocline and intermediate waters to depict water mass pathways and mixing. In the thermocline, the New Guinea Coastal Undercurrent is mainly supplied by North Vanuatu Jet waters at the thermocline level while in the intermediate level, waters come from the North Caledonian Jet. This complementary approach shows that intermediate waters are mainly carried by deep currents and subsurface waters by the North Vanuatu Jet. In the last part, interannual variability is analyzed on the 1993-2010 period with a 1/10° numerical simulation and a proxy method based on altimetric data. Interannual variability of the South Equatorial Current mass transport follows the El Niño-Southern Oscillation with a 3-months lag. The North Vanuatu Jet leads this variability. Controlled by winds, the South Equatorial Current variability is associated with thermocline depth modulation, which involves intensification after an El Niño event (6 ±4 Sv) and a decrease after La Niña (4 ±4 Sv). We also show that temperature and salinity anomalies are the result of thermocline depth modulation

Monitoring the responses of corals to environmental change and linking responses to past environmental changes are difficult and rely on correlative proxy techniques. To date, there has been no means to directly measure biologically meaningful effects of environmental changes on corals that could both explain the consequences of sublethal stress and enhance the interpretation of proxy environmental records. Massive Porites are extremely widespread in the Indo-Pacific. While not exceptionally fecund, fast-growing or competitively dominant, they appear to possess a peculiar robustness, often becoming the dominant corals on reefs that have been heavily impacted. The longevity of Porites colonies and the existence of annual density bands in their skeletons, makes them organism of choice for Indo-Pacific researchers interested in the construction of proxy climate records. This project aimed to address the lack of knowledge about the biological responses of Porites to various types of stress and to relate these responses to proxy environmental records derived from the corals' skeletons. In addition, the project sought to develop a measure of sublethal stress which could be adapted into a general reactive monitoring protocol. The thickness of the tissue layer (TTL) of a colony of Porites is a product of linear skeletal extension at its upper surface and periodic (up to monthly) uplift of its lower margin. A survey of 20 reefs on the GBR, as well as several reefs in PNG and the Gulf of Thailand indicated that tissue thickness of massive Porites conils varies in space and time. Spatial variation in TTL is mostly a manifestation of local (habitat-level) environmental conditions rather than an indication of broad geographic trends in conditions. Seasonal trends in TTL variation of Porites on the central GBR manifest as summer maxima and winter minima, as reported for calcification and linear extension. SST and insolation are the factors most likely to be responsible for seasonal cycles in TTL. TTL variation is a sensitive indicator of incipient or sublethal stress in massive Porites. Lack of stress-specific responses precludes distinguishing between chronic and acute stress solely from the thickness of the tissue layer. Continual mobilization of the lower portion of the tissue layer provides a unique mechanism by which massive Porites can control its response to stressful conditions. Moreover, tissue thickness and lipid levels appear to be interchangeable indications of the energy level of the polyp under stress, although extreme responses such as bleaching are more closely linked to tissue thickness than lipid levels. The response of corals to environmental impacts is dictated largely by their available energy reserve. Diminishment of a coral's ability to acquire energy leads to a reduction in linear extension as the coral adapts. Reduction of the coral's somatic reserve past a critical point leads to a bleaching response concomitant with shutdown of other functions. Mass spectroscopic analysis of skeletal cores taken from colonies used in the long term stress experiment revealed that proxy environmental reconstruction techniques based on isotope ratios within the coral skeleton are able to capture stress events in the life of a coral identified by TTL changes. Changes to the amplitude and range of /)180 and /)13C cycles during experimental shading suggest that chronic stress changes the way that corals record environmental variation. The sensitivity of isotopic techniques is diminished, however, by previous stress events. Likewise, interpretation of the nature of the stress event from the proxy record is problematic: proximal environmental variation is not recorded, and nonrelated stress events can leave identical signatures in the isotope record. Skeletal proxy techniques will therefore underestimate the frequency of environmental impacts. These findings shed light on why it has so far been difficult to reconcile proxy records from different studies. The use of TTL variation as a simple reactive monitoring technique is not readily achievable. Between-colony, habitat and seasonal variation, as well as the need to contextualize measurements to previous history, all place severe constraints on its utility as a simple technique. However, localized spatial gradients in TTL can identify environmental gradients and map their severity. As such, changes in TTL can be used as a broad-scale tool to identify habitats with sub-optimal or impacted environments.

Samples of Porites coral were removed from seven different reefs (No Name, Hastings, Upolu, Thetford, Batt, Green Island and Brook Islands Reefs), including two from the same reef (Green Island Reef), within Australia's Great Barrier Reef Marine Park. Chemical and morphological data retrieved from these samples were used to investigate historical change in water quality surrounding the growing corals, particularly as this related to the increased use of phosphatic fertiliser on the nearby mainland. The study focused on a narrow section of the continental shelf adjacent to the mouth of the Barron River. In this area coral reefs are close to a mainland significantly altered for anthropogenic purposes. No Name Reef (approximately 300 km north of the study area and reasonably distant from known anthropogenic input) was included as a control. The Brook Islands Reef (approximately 300 km south of the study area) was added for geographic variability. Support data was gained by a two year nutrient monitoring programme of the Barron and Mossman River catchments, and marine waters adjacent to these two river systems. Additional information was acquired by the experimental supplementation of Acropora formosa corals with 2.0 μM, 4.0 μM and 8.0 μM PO₄. Stream phosphate levels responded rapidly to rainfall. During the April 1989 flood period between 710 and 2,850 tonnes of Superphosphate were delivered into the ocean. Estimates vary according to the presumed ratio of soluble to particulate phosphate in the flood plume (e.g. see Cosser 1987 and Brodie & Mitchell 1992). The lower figure is nearly half the total industry estimated fertiliser usage (1810 tonnes) for the Far Northern Statistical Division during 1988. The greater figure is more than a third higher than Australian Bureau of Statistics figures for the same period (Pulsford 1990). The marine monitoring program suggested that nutrient monitoring was an insufficient method of estimating water quality. The phosphate supplementation experiment showed that elevated levels of phosphate hindered calcium carbonate production with considerable alteration to the internal and external morphology of the coral skeleton. Chemical analysis of the Porites samples suggested that intra-reefal variation in the coral skeleton was minor, but with sufficient inconsistencies in the annual record to suggest that localised, micro-environmental conditions exist and should be recognised when attempting to reconstruct environmental records from the coral skeleton. Statistically, the inner- and inner/mid-shelf sample sets were significantly different from each other and from all other sample sets. No significant statistical difference could be distinguished in the mid- to outer-shelf sample sets, but the relative contribution of each element differed for each of these sample sets. The difference between the samples from nearer to shore and those from the outershelf was also apparent in the reconstructed coral inferred environmental record. Strontium-based sea-surface temperature estimates provided an adequate record of historical sea surface temperatures from the mid- to outer-shelf samples (No Name, Hastings, Upolu and Thetford Reefs), but were unreliable for the closer to shore samples (Batt, Green Island and Brook Island Reefs). Similar inconsistencies were noted in associations with climatic variables. Data from the outer-shelf No Name Reef sample correlated with climatic data associated with the Southern Oscillation Index (SOI) while data from the Green Island Reef sample correlated with Mean Sea Level Pressure read at Darwin. These inconsistencies were inherent in the coral-inferred record and were not associated with anthropogenic influence. However, ambiguities in the chemical composition and morphological structure of the Green Island sample were noted post-1950. These inconsistencies were statistically correlated to the use of fertiliser on the nearby mainland. Changes to the internal porosity of the coral skeleton were similar to those noted in the experimental phosphate supplementation programme. The study concludes that chemical and morphological variations in the skeleton of the massive Porites coral are suitable for hindcasting paleoenvironmental conditions laid down in the skeleton at the time of precipitation. The study further concludes that there is significant evidence of anthropogenic influence in the Green Island sample, and that this influence is related to the use of fertilisers on the nearby mainland.

Choi Mei Mei.
Thesis submitted in: December 2002.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.
Includes bibliographical references (leaves 214-236).
Abstracts in English and Chinese.
Abstract --- p.i
Acknowledgements --- p.vi
Table of Contents --- p.viii
List of Tables --- p.xi
List of Figures --- p.xii
Chapter Chapter One: --- General Introduction --- p.1
Chapter 1.1 --- Introduction --- p.1
Chapter 1.1.1 --- Coral bleaching --- p.2
Chapter 1.1.2 --- Predation of corals by corallivorous gastropods --- p.20
Chapter 1.2 --- Introduction of Study Sites- Tung Ping Chau --- p.33
Chapter 1.3 --- Objectives of the Study --- p.35
Chapter 1.4 --- Structure of this Thesis --- p.36
Chapter Chapter Two: --- "Coral Bleaching and Predation by Corallivorous Gastropods in the Coral Communities of A Ye Wan and A Ma Wan, Tung Ping Chau" --- p.40
Chapter 2.1 --- Introduction --- p.40
Chapter 2.2 --- Materials and Methods --- p.45
Chapter 2.2.1 --- Quantitative surveys --- p.45
Chapter 2.2.2 --- "Quantifying the colour of corals, Porites lobata, in Tung Ping Chau" --- p.47
Chapter 2.2.3 --- Physical parameters --- p.49
Chapter 2.2.4 --- Data and statistical analysis --- p.49
Chapter 2.3 --- Results --- p.50
Chapter 2.3.1 --- Live coral coverage in A Ye Wan and A Ma Wan --- p.50
Chapter 2.3.2 --- Proportion of Porites lobata paled --- p.52
Chapter 2.3.3 --- Changes in colour intensity of Porites lobata between seasons --- p.54
Chapter 2.3.4 --- Density of corallivorous gastropods --- p.55
Chapter 2.3.5 --- Percentage coverage of live and dead Acropora tumida --- p.55
Chapter 2.3.6 --- Physical parameters --- p.57
Chapter 2.4 --- Discussion --- p.59
Chapter 2.4.1 --- Live coral cover in A Ye Wan and A Ma Wan --- p.59
Chapter 2.4.2 --- Bleaching of Porites lobata in summer and winter --- p.61
Chapter 2.4.3 --- Colour intensity of Porites lobata in different seasons --- p.67
Chapter 2.4.4 --- Predation on corals by corallivorous gastropods --- p.69
Chapter Chapter Three: --- "Study on Coral Bleaching, Pontes bbata, in Tung Ping Chau by using Permanent Quadrats" --- p.103
Chapter 3.1 --- Introduction --- p.103
Chapter 3.2 --- Materials and Methods --- p.104
Chapter 3.2.1 --- Study sites --- p.104
Chapter 3.2.2 --- Permanent quadrat monitoring --- p.105
Chapter 3.2.3 --- Corals sampling for zooxanthellae density and chlorophyll a concentration analysis --- p.106
Chapter 3.2.3.1 --- Tissus collection --- p.106
Chapter 3.2.3.2 --- Zooxanthellae counting --- p.107
Chapter 3.2.3.3 --- Chlorophyll a determination --- p.107
Chapter 3.2.3.4 --- Determination of coral surface area --- p.108
Chapter 3.2.4 --- Data analysis --- p.108
Chapter 3.3 --- Results --- p.109
Chapter 3.3.1 --- Monitoring of bleaching of porties lobata in permanent quadrat --- p.109
Chapter 3.3.2 --- Density of Zooxanthellae in Porites lobata --- p.111
Chapter 3.3.3 --- Concentration of Chlorophyll a in Porites lobata --- p.112
Chapter 3.3.4 --- Chlorophyll a per zooxanthellae --- p.113
Chapter 3.4 --- Discussion --- p.114
Chapter Chapter Four --- Study of Predation on coral Acropora tumida by Corallivorous Gastropods in Tung Ping Chau --- p.138
Chapter 4.1 --- General Introduction --- p.138
Chapter 4.2 --- Materials and Methods --- p.140
Chapter 4.2.1 --- Study sites --- p.140
Chapter 4.2.2 --- Preliminary evaluation of corallivorous gastropods as the coal predator --- p.141
Chapter 4.2.3 --- Monthly monitoring of permanent quadrat --- p.142
Chapter 4.2.4 --- Data and statistical analysis --- p.144
Chapter 4.3 --- Results --- p.145
Chapter 4.3.1 --- Species of corallivorous gastropods in Tung Ping Chau --- p.145
Chapter 4.3.2 --- Feeding behavior of corallivorous gastropods in Tung Ping Chau --- p.146
Chapter 4.3.3 --- Density of corallivorous gastropods --- p.147
Chapter 4.3.3.1 --- Monthly change in density of corallivorous gastropods --- p.147
Chapter 4.3.3.2 --- Correlation between gastropod density and temperature --- p.149
Chapter 4.3.4 --- Cumulative percentage of area of feeding scar over time --- p.149
Chapter 4.3.5 --- Monthly percentage change in the areas of feeding scar --- p.152
Chapter 4.3.5.1 --- Monthly percentage change in the areas of feedling scar due to predation by Cronia margariticola and Drupella rugosa --- p.152
Chapter 4.3.5.2 --- Correlation between gastropod density and monthly percentage change in area of scar --- p.153
Chapter 4.3.5.3 --- Correlation between temperature and monthly percentage in area of the feeding scar --- p.154
Chapter 4.3.6 --- Rate of predation --- p.154
Chapter 4.3.6.1 --- Rate of predation by the corallivorous gastropods --- p.154
Chapter 4.3.6.2 --- "Correlation between rate of predation, gastropod density and seawater temperature" --- p.155
Chapter 4.3.7 --- Population size structure of the corallivorous gastropods --- p.156
Chapter 4.3.7.1 --- Population size structure of Cronia margariticola --- p.156
Chapter 4.3.7.2 --- Population size structure of Drupella rugosa --- p.158
Chapter 4.4 --- Discussion --- p.159
Chapter 4.4.1 --- Feeding behaviours of corallivorous gastropods --- p.159
Chapter 4.4.2 --- Density of corallivorous gastropods --- p.162
Chapter 4.4.3 --- Cumulative percentage of area of feeding scar --- p.170
Chapter 4.4.4 --- Monthly percentage change of area of feeding scar --- p.173
Chapter 4.4.5 --- Rate of predation --- p.175
Chapter 4.4.6 --- Size structure of population size --- p.178
Chapter 4.4.7 --- Predatory pressure from corallivorous gastropods in Tung Ping Chau --- p.185
Chapter Chapter Five --- Summary and Perspectives --- p.207
References --- p.214

In massive Porites colonies, living tissue invests only a thin layer on the outer perimeter of the skeleton, normally around 25-50% of an annual growth increment in healthy colonies. The depth to which skeleton is occupied by tissue is referred to as ‘tissue thickness’. Tissue thickness has been argued to be a sensitive bioindicator that may be potentially used to monitor changes in coral health prior to collapse and mortality. The primary goal of this study was to assess the response of tissue thickness in massive Porites colonies at Lihir Island (3005’S 152038’E) to an anthropogenically increased turbidity regime associated with mining activities. In order to achieve this goal it was also necessary to identify possible sources of natural variability in tissue thickness, both spatial and temporal, and to quantify their influence. Possible sources of tissue thickness variability identified through both literature review and observation included: i) changes in thickness through the lunar month as a function of skeletal growth patterns; ii) change in thickness due to differences in local environmental conditions; iii) change in tissue thickness with differences in colony size and shape. Where possible, the influence of all of these factors was examined in both shallow (<11 m) and deep (>14 m) habitats, across sites around Lihir Island and between years (sampling took place in 2001, 2002, and 2003). Tissue thickness in massive Porites changes over a lunar month as part of skeletal growth processes. This study looked for ways in which allowance could be made and procedures devised for sampling at different times of the lunar month. Tissue thickness decreased, on average, by 20% on the day after the full moon. Tissue thickness increased, on average, by 0.3 m per day during the lunar month. These patterns of variation were consistently observed between study sites, at different depths, and in different sampling years. The only exception appeared to be when tissue thickness became critically thin (below 2.2 mm), which was only found at a site heavily affected by turbidity. Hence, growth processes in massive Porites were reduced or halted when limited energy reserves were available under stressful conditions. Monthly tissue uplift in the same colonies was resumed when an increase in tissue thickness above the minimum threshold of 2.2 mm was achieved. The consistency of tissue variations throughout the lunar month in all but these very few extremely stressed individuals allowed measurements taken from individuals at different times of the lunar month to be easily adjusted for comparison. In the second study, changes in tissue thickness in response to increased turbidity were examined by measuring tissue thickness in massive Porites colonies along an anthropogenic turbidity gradient in 2001, 2002 and 2003. Tissue thickness was significantly less where turbidity levels reached 15- 30mg l-1. This was the maximum turbidity encountered near coral reefs in this study. Tissue thickness was not significantly reduced by lower turbidity levels, but it was always less in colonies in deeper water than in colonies in shallow water. Some variability of tissue thickness was also observed between study sites and years. However, neither spatial nor temporal variability masked the general pattern of decreasing tissue thickness with increasing turbidity. The final study examined differences in tissue thickness with colony size and shape and looked at environmentally-induced changes in tissue thickness in colonies with different morphologies. Massive Porites corals on Lihir Island were found to occur in six distinct growth forms, namely rounded, round-encrusting, pyramidical, pyramid-encrusting, encrusting and vertical encrusting. Some of these shapes could be described quantitatively by height/circumference ratios. However, the angle of substrata slope was found to be a better indicator for changes in shapes with study sites and water depth. Allowing for changes in tissue thickness with depth, colony morphology did not affect tissue thickness. Hence, colony morphology was not a significant factor in sampling for tissue thickness. Similar-sized colonies were selected for sampling. The effects of colony size on tissue thickness were tested and colony size could also be excluded as a factor which significantly affected tissue thickness. Patterns of change in tissue thickness in Porites colonies at Lihir Island indicated that mining activities had affected, and were affecting, corals and coral communities over a much more restricted area than predicted by the mine’s environmental impact statement. Tissue thickness patterns corresponded closely with indices of live coral cover and turbidity measurements. Tissue thickness was found to be a simple and reliable bioindicator for turbidity stress on corals on Lihir Island. Changes in tissue thickness indicate when corals are being adversely affected by anthropogenic activities. This gives tissue thickness a huge advantage over other monitoring techniques, because these mostly detect change after it has occurred - and not while it is occurring.

A monthly resolved, 133 year record of coral Sr/Ca variations has been developed from a massive Porites coral that was drilled in the shallow waters of a submerged carbonate platform (Sabine Bank, 15.9°S, 166.14°E) located ~50 km west of Espiritu Santo, Vanuatu. This truly open-ocean site, at which daily measurements of temperature and salinity are available for ~ 6 years, permits the reconstruction of local environmental variability using variations in coral skeletal geochemistry. Coral Sr/Ca-SST variations are well matched to variations in local SST, but bear little relation to changes in local SSS indicating little or no influence of salinity on coral Sr/Ca. The complete coral Sr/Ca-SST time series is characterized by abundant inter-annual variability, a strong trend towards warming (i.e., lower Sr/Ca values) from ~1980-2006. Interannual SSTA variations at Sabine Bank correspond reasonably well to SSTA variations from the central Pacific cool tongue (Niño 3.4 region), indicating that coral Sr/Ca variations record ENSO variability in the region.
text

Massive Porites colonies develop a bumpy growth surface as they increase in size. Development of a bumpy growth surface occurs when skeletal growth no longer provides the necessary increase in surface area to accommodate tissue growth. A massive Porites colony becomes bumpy when it reaches a critical size determined by the ratio of its tissue growth to its skeletal growth. This ratio also determines the degree of bumpiness which develops at the growth surface. X-radiographs of skeletal slices cut from the vertical growth axis of massive Porites colonies display annual density banding and skeletal architecture associated with corallites, that is, skeleton deposited by individual polyps. Density bands outline former positions of the growth surface. Examination of X-radiographs of Porites shows that new corallites are initiated on, or towards, the summit of bumps, whilst older corallites are compressed and ultimately occluded at the bottom of valleys formed between bumps. X-radiographs show that it takes 4 to 7 years from the formation of a corallite to its occlusion. Polyps on the growth surface of a bumpy Porites colony must, therefore, be continually lost. All polyps are lost and replaced during a 4 to 7 year period. Consequently, tissue covering the growth surface of a massive Porites colony can be no older than 7 years, even though the colony may have been growing for several centuries. Computer models designed to simulate growth of a massive Porites colony indicated that the growth form displayed by a Porites colony is determined by the ratio of tissue growth to skeletal growth. Models having a relatively faster tissue growth compared with skeletal growth developed a bumpy surface sooner, and the amount of bumpiness developed was greater, than for models having a relatively slower tissue growth compared with skeletal growth. Predictions from computer models accorded with observations and measurements made on actual colonies and on X-radiographs of skeletal slices cut from colonies. Thus, the ratio of tissue growth to skeletal growth determines important aspects of the growth form displayed by massive Porites colonies. The ratio of tissue growth to skeletal growth was shown to significantly affect the rate of polyp loss and replacement in Porites colonies. The longevity of polyps is less in Porites colonies displaying a well developed bumpy growth surface than in colonies displaying a smoother growth surface. Hence, the age of polyps, and therefore the tissue, covering a bumpy growth surface is less than polyps and tissue covering a smooth growth surface. Skeletal surface area in massive Porites colonies was shown to be a useful indicator of tissue biomass. Measurements of change in surface area of Porites colonies with increasing size show that the rate of tissue growth must decrease as the colony grows. Development of a bumpy growth surface alleviates this geometric restriction for only months to a couple of years. Development of a bumpy growth surface is an indication that tissue growth is becoming constrained by skeletal growth. Once a colony becomes bumpy, the tissue growth is almost totally constrained by the rate by skeletal extension. Significant differences in growth and growth form characterised massive Porites colonies collected from different reef environments. Measurements made on the colonies suggested that differences in environmental conditions probably altered the ratio of tissue growth to skeletal growth and caused the colonies to grow in different ways. Differences in growth were reflected in the resulting growth form. Information about relative rates of tissue and skeletal growth within a massive Porites colony gained from observations and measurements of the growth form can be used to provide further information about coral growth and details of environmental conditions obtaining during growth.

L'objectif de cette étude est de retracer les voies de distributions atmosphériques et océaniques du plomb au cours du 20ème siècle, en relation avec la variabilité climatique de l'Atlantique Subtropical Nord, à l'aide des archives coralliennes et des émissions anthropiques de plomb. Dans une première phase, l'impact des émissions atmosphériques américaines et européennes a été quantifié sur deux colonies coralliennes de la Mer des Caraïbes (Ile de Mona et Ile de la Martinique) à partir des analyses du plomb et de ses isotopes stables par Spectrométrie de Masse à Thermo-Ionisation (TIMS). Les mesures réalisées indiquent que les archives coralliennes sont de bons enregistreurs des émissions anthropiques de plomb. La résolution annuelle obtenue, notamment sur la colonie de l'île de Mona, permet de retracer l'impact des émissions de plomb dans l'Atlantique Nord au cours du 20ème siècle. Cette résolution autorise l'accès aux cinétiques de transferts des aérosols à l'échelle du bassin. Par comparaison avec les profils réalisés sur différents sites (Bermudes, Floride, Barbade, Péninsule du Yucatan, Basin de Cariaco et Ile de Ste. Croix), il ressort que la distribution des aérosols dans l'Atlantique Subtropical est contrôlée par les paramètres météorologiques et réagit aux oscillations climatiques de l'Atlantique Nord (ONA). Du fait du temps de résidence très court du plomb dans l'atmosphère (moins de 10 jours), le décalage dans le temps d'événements marqués comme l'interdiction des essences plombées aux Etats Unis puis en Europe a conduit, à travailler également sur le compartiment océanique. Les anomalies océaniques déduites des enregistrements Δ18O sur les colonies coralliennes de Porto-Rico, de la Martinique et de la Guadeloupe peuvent en partie expliquer les déphasages observés. Les fluctuations océaniques saisonnières ont été établies et les variations interannuelles répondent à la fois aux ONA et aux perturbations climatiques de l'océan Pacifique (ENSO-PDO).