No description available.

No description available.

Activités de recherche L'ensemble de mes recherches à l'Université de Corse porte sur l'utilisation des organismes comme descripteurs de la qualité du milieu. En effet, certains organismes sont très sensibles aux variations des conditions environnementales, qu'elles soient d'origine biotique ou abiotique et y répondent proportionnellement par des changements mesurables à différents niveaux d'intégration (spatial, morphologique, physiologique ou bien encore cellulaire). Tous ces changements, peuvent, s'ils sont bien utilisés, constituer des bioindicateurs, outils précoces et fiables pour fournir une aide à la gestion des milieux. Dans un premier temps, et ce, jusqu'en juillet 2005, mes travaux se sont portés, au sein de l'Equipe Ecosystèmes Littoraux, sur l'étude des peuplements de macrophytes marines et lagunaires, afin d'appréhender leur réactions face à des stress de diverses origines, tels que les pollutions chimiques, les activités aquacoles, l'eutrophisation du milieu, ou encore la compétition interspécifique, et d'identifier des indicateurs de vitalité chez ces espèces. En Septembre 2005, mon intégration à l'Equipe Feux de l'UMR CNRS 6134, m'a permis d'appliquer l'ensemble de mes connaissances aux peuplements forestiers. Les recherches cette fois ci sont menées principalement sur les réponses de Pinus laricio soumis, d'une part aux brûlages dirigés, et d'autre part aux changements climatiques.

In this thesis, the distribution and state of Posidonia oceanica meadows along the Turkish coast of the north eastern Mediterranean was investigated. The study area was a unique site due to the presence of eastern geographical limit of Posidonia oceanica meadows in Mediterranean Sea. It was aimed to assess the possible reasons of the absence and/or regression in relation to environmental changes. The study was conducted from September 2004 to January 2007 in 5 main regions between Anamur/Mersin and Samandag/Hatay. The regions were determined according to the presence/absence of Posidonia oceanica meadows / 1 region including the boundary meadow at the geographical distribution limit, 1 region western and 3 regions eastern to that boundary meadow. To describe the hydrological characteristics of the study area temperature, salinity and light were measured as abiotic descriptors. Additionally sedimentological analysis was carried out to check the suitability of the substrate type for Posidonia oceanica colonization. The main differences between the regions were found in temperature and light conditions. Both, the recordings of temperature loggers at 10 and 15 meter depths and the sea surface temperature retrieved from satellite (NOAA-AVHRR) showed that the eastern stations with no Posidonia oceanica meadows were warmer than the western stations. Consequently in this study the maximum tolerable temperature limit for Posidonia oceanica growth was determined as 28.4&deg / C from the data collected by the temperature loggers placed to natural meadows near to the boundary meadow. Generally, the whole study area had a limiting light condition for seagrass growth due to low penetration depths of the 10% of surface irradiation. This was a generalized minimum light requirement for growth of seagrasses. Especially in Mersin and Iskenderun bays the minimum required light level did not reached deeper than 10 meter depths in coastal stations. The biological parameters of the Posidonia oceanica meadows were investigated under 3 complementary methods in the first two regions. The structural descriptors were measured in-situ. The lowest shoot density and leaf lengths were found to be in boundary meadow. This meadow had also the lowest depth limit among other stations. The functional descriptors were examined by the lepidochronological and phenological analysis in laboratory. Most of the measurements varied either with respect to depth or among stations according to the abiotic factors of the stations. The lepidochronological cycles obtained from sheath thicknesses were further correlated with abiotic descriptors via a mathematical model. Finally, the first transplantation experiment of Posidonia oceanica along Turkish coasts has been conducted in 2 regions where presently no meadows exist. The survival of cuttings in one station indicated the success of the methodology, while the failure in other stations provided information on the possible reasons of absence/degradation of natural meadows in the area. These included the destructive impact of bottom trawling, the high pressure of grazing (the potential causes of Lessepsian migration) and the long term changes in climate resulting in alterations of environmental conditions such as increasing temperature and reduced light penetration.

Includes bibliographical references (leaves 290-333). / xxiv, 333 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Describes research into the nutritional value of aquatic plants as novel or non-conventional feedstuffs for ruminants in general and for sheep in particular, with especial reference to those which are available in high amount in southern Australia, such as the seagrass, Posidonia australis. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Science, 1996?

Introducción. En el mar Mediterráneo la mayor cantidad de restos vegetales acumulados en la arena pertenecen a Posidonia oceánica (P.oceanica), estos se depositan en los arribazones. Existen diferentes usos de estos arribazones: sellado de vertederos, construcción, farmacia, industria y medio ambiente, aunque hasta la fecha, no hay evidencias de que se estén empleando en el sector de la agricultura, es por ello que el objetivo general de esta tesis fue estudiar la viabilidad del uso de los arribazones de P.oceanica en la agricultura. Experiencia I: empleo de arribazones de Posidonia oceanica como enmienda orgánica. Para dicha experiencia se realizaron 3 ensayos: (1) Evaluación de las características físico-químicas de P.oceanica como enmienda orgánica; (2) Evaluación de la composición de lixiviados procedentes de suelos agrícolas enmendados con P.oceanica y (3) Evaluación del efecto de los lixiviados obtenidos de suelos enmendados con P.oceanica en la germinación de Lycopersicum esculentum Mill. Según la caracterización físico-química de la P. oceanica, esta puede ser empleada como enmienda orgánica de acuerdo con la legislación. La capacidad de retención de agua de los suelos enmendados con P. oceanica aumentó entre un 200 y un 300%, en función del suelo empleado. El suelo ácido, mostró mayores ventajas tras ser enmendado con P.oceanica, ya que elevó el pH del medio hasta los valores de máxima disponibilidad de los nutrientes del suelo y enriqueció la disolución del suelo en Ca, Mg, y K. Para los lixiviados procedentes de los distintos suelos enmendados con P. oceanica tuvo un efecto bioestimulante en la germinación y el crecimiento. Experiencia II: empleo de arribazones de Posidonia oceanica como sustrato de cultivo. Para llevar a cabo esta experiencia se realizaron 2 ensayos: (1) Evaluación de las características físico-químicas de P.oceanica como sustrato de cultivo; (2) Desarrollo de plantas de tomate empleando P. oceanica como sustrato de cultivo. La caracterización físico-química de la P. oceanica, resultó cumplir con la actual legislación como sustrato de cultivo no inerte. Las plantas de tomate cultivadas con P. oceanica cribada (PSL) y cribada y lavada (PL) mostraron síntomas de estrés. En las PSL, pudo ser generado por la elevada salinidad del medio, mientras que para las PL, fue consecuencia de una elevada liberación de metabolitos secundarios. Las plantas PSL mostraron una menor productividad que las desarrolladas en fibra de coco, mientras que en las PL fue similar que para el sustrato control. Como las plantas cultivadas en P.oceanica estaban sometidas a estrés, los frutos presentaron mayores contenidos en compuestos fenólicos y licopeno, aumentando el valor nutricional respecto a los cultivados en fibra de coco. Experiencia III: efecto de la aplicación de extractos acuosos de Posidonia oceanica sobre el desarrollo vegetal. Para dicha experiencia se realizaron 3 ensayos: (1) Obtención y caracterización de extractos vegetales de P. oceanica; (2) Efecto de la aplicación de extractos acuosos de P. oceanica sobre la germinación de semillas de tomate Seny 1 y (3) Efecto de la aplicación foliar de extractos acuosos de P. oceanica a plantas de tomate sometidas a estrés salino. De los dos extractos de P. oceanica, el diluido, estimuló la germinación de las semillas. La aplicación de dicho extracto redujo el estrés oxidativo producido por salinidad, mejorando la integridad de las membranas plasmáticas de las células radiculares, y reduciendo el contenido en prolina, MDA y H2O2 foliar. Estos efectos beneficiosos frente al estrés salino confirmarian la actividad elicitora de los extractos de P.oceanica, debido a la presencia de Si en su composición y compuestos fenólicos.

No description available.

Las zonas costeras han sido históricamente caracterizadas por ser una fuente de riqueza, adquiriendo gran relevancia como lugar de descanso y ocio. Esto ha generado muchas actuaciones antrópicas que han provocado desequilibrios, más importantes cuanto mayor ha sido esa presión. Para conocer la evolución futura de esos cambios es necesario comprender su origen. Los Sistemas de Información Geográfica (GIS) proporcionan la herramienta para realizar este análisis. En esta investigación se emplean para conocer los cambios en la línea de costa, clima marítimo, batimetría, la morfología del fondo marino y las especies vegetales presentes, prestando especial atención a la Posidonia oceanica. También se han estudiado las propiedades de los sedimentos y su distribución espacial. Así mismo, se han identificado los impactos que han tenido las acciones antrópicas sobre el medio costero, como el encauzamiento de ríos, la construcción de puertos y obras de defensa costera o la urbanización de los entornos litorales. Para ello se han analizado 20 playas representativas del litoral de las provincias de Alicante, Valencia y Murcia.

[Truncated abstract] There is a well-documented global decline of seagrass meadows in response to anthropogenic pressures. Transplantation of rhizome fragments into denuded areas has been used to enhance natural recovery but nutrient limitation and poor root growth may contribute to low success rates. Addition of nutrients to sediments has been proposed as a means of enhancing growth and survival of seagrass transplants by alleviating nutrient limitation but there is limited information of the effects of nutrient additions to seagrass transplants, particularly root development and morphology. In addition to nutrient limitation, sulphide accumulation in sediments with high organic matter has been shown to reduce seagrass growth and experimental iron additions have been shown to enhance seagrass growth by buffering the development of reduced conditions in organic rich sediments. This thesis examines responses (growth, morphology and nutrient status) of Posidonia australis and Posidonia sinuosa transplants to nitrogen (N), phosphorus (P) and chelated iron (Fe EDTA) additions, and includes a detailed investigation of root growth and morphology in response to these additions. Experiments were carried out in underwater plots in Oyster Harbour, a sheltered estuarine inlet with seasonal river flow, located on the southern coast of Western Australia. In the first experiment, nutrients (N, P and N+P) and Fe EDTA were added to sediment underlying transplants at the end of summer (March 2005). ... Nitrogen (both N and N+P) addition also reduced overall biomass allocation to roots. Nitrogen concentrations increased with N addition in P. sinuosa only but both species had more negative d15N values with N and N+P addition indicating that added N had been taken up. In contrast, P addition had little effect on root growth, and P concentrations only increased in P. australis. However, tissue concentrations of Zn, Co, and Mo in both species increased with P addition. Roots showed limited morphological variation (total root length, mean root diameter, root fineness, specific root length, surface area) in response to nutrient addition. Combined N and P addition increased lateral root density (branches m-1) but had no effect on other morphological parameters of the root compartment. Iron addition had no effect on P. sinuosa but P. australis transplants significantly reduced root growth and productivity, particularly in spring/summer growth period, due to lower primary and lateral growth rates. Overall, N or P additions did not enhance growth although these nutrients were taken up. Iron additions also had little effect on transplant growth. Seagrass transplants had significant root growth although they appeared not to respond to nutrient or iron addition. Both species produced extensive root systems capable of taking up sediment nutrients, which suggests that root development was not a limiting factor in establishment and growth of transplants in the temperate estuary, Oyster Harbour.

Le Golfe de Gabès, situé dans le bassin méditerranéen oriental, réunit plusieurs traits distinctifs lui conférant une forte sensibilité vis à vis des contaminations d'origine anthropique. D'une part, l'influence des courants Atlantiques y très limitée, d'autre part, son orientation et sa morphologie caractérisée par une faible profondeur sur une grande étendue ne permettent qu'un faible taux de renouvellement des eaux. Dans cet environnement vulnérable, plus de 200 millions de tonnes de phosphogypse (sous- produit résultant de la production d'acide phosphorique) ont été rejetés dans l'environnement marin depuis près d'un demi-siècle en ayant comme conséquence une dégradation conséquente de l'écosystème benthique en particulier des herbiers de posidonies. La caractérisation du phosphogypse conduit à identifier les différentes modalités des transferts au sein des milieux marins des métaux contenus initialement dans le phosphate. Sa charge en métaux toxiques est essentiellement associée à la matière organique qui s'agrège lors de son transfert dans l'émissaire industriel pour former une mousse se déplaçant à la surface de la mer. Cette mousse présente une structure complexe constituée de matière organique amphiphile jouant le rôle de tensioactif au contact de l'eau de mer et de gypse synthétique qui en constitue le squelette auxquels s'ajoutent halite, sphalérite et francolite. Elle se dégrade en fonction de l'état d'agitation du milieu marin via la dissolution du gypse relarguant ainsi sa charge polluante selon l'amplitude de la houle. Une fraction limitée des métaux passe directement en solution transportés par l'action des courants côtiers. Enfin, des grains de phosphate brut sont transportés soit par roulement-saltation soit en suspension. Ils s'accumulent surtout au niveau de la plage de Chatt Essalam du fait des impacts hydrodynamiques des structures portuaires du site. Les métaux toxiques affectent également les sédiments de surface et les organismes benthiques. En particulier, les mattes posidonies jouent le rôle d'archivage de la contamination permettant ainsi de retracer l'évolution de la contamination métallique des eaux marines depuis le début du développement industriel de la côte en 1972. Enfin, une première évaluation des pertes financières associées aux services écosystémiques fournis par les herbiers de Posidonies à l'activité économique de la pêche côtière, conduit à mettre en perspective le coût d'une partie des externalités négatives associées à la contamination chronique à l'échelle de la partie centrale du Golfe de Gabès. / The Gulf of Gabes, located in the oriental Mediterranean basin, has many particular properties making it very sensitive to anthropogenic contaminations. One of the distinguishing features of Gabes Gulf is low water flush-activity related mainly to its orientation and morphology marked by its largely-extended shallow plateau as well as to the limited influence of Atlantic water currents. For more than 50 years, than 200 million tons of phosphogypsum (by-product of phosphoric acid production) have been continuously dumped in this vulnerable environment leading to an accentuated degradation of the local benthic habitat represented mainly by the seagrass meadows of Posidonia oceanica. Within this context, knowing the characterization of phosphogypsum will certainly help to identify the different transfer modalities of the metals (composing the initial phosphate ore) within the marine environment. The pollutants load of phosphogypsum is mainly associated to the organic matter which aggregates during the transfer process via the evacuation channel leading to the formation of floating foam. These latter foams are passively transported by winds and local currents to distant areas and are found to be rich in organic matter with an amphipathic character that makes them act as a surfactant in contact with seawater. The skeleton of phosphogypsum foam was also found to be composed of synthetic gypsum as well as halite, sphalerite and francolite. The degradation of the phosphogypsum foam is accentuated by the degree of agitation/hydrodynamics of the marine environment through the dissolution of gypsum, leading to the release of its polluting components following the swell amplitude. It is worth noting that a limited metal fraction passes directly into solution. These latter metals are hence transported by the coastal currents. As for the phosphate grains, they are trained towards the south either by rolling-saltation or in suspension, and end by accumulating mainly in Chat Essalam beach due to the hydrodynamics effects exerted by the ports structures leading to modify the coastline. In addition, the toxic metals affect also the surface sediments as well as the benthic organisms and hence these latter can inform about the health status and the contamination history of the local marine environment. Within this context, the mats of Posidonia oceanica meadows can be used as an archiving tool of the contamination history in the Gulf of Gabes and allow hence retracing the evolution of metallic contamination of sea waters since the set-up of the coastal industrial complex in Gabes city (i.e. 1972). Finally, a first assessment of the financial losses linked to the ecosystemic services provided by Posidonia oceanica seagrass beds to coastal fisheries activity was conducted allowing to evaluate the cost of a part of the negative consequences linked to the industrial chronic pollution at the central part of Gabes Gulf.