Добірка наукової літератури з теми "Anoxie – Thau, Étang de (France)"
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Дисертації з теми "Anoxie – Thau, Étang de (France)":
Regis, Julie. "Impact des hypoxies sur la mobilité des nutriments et ETMM présents dans les sédiments des lagunes méditerranéennes." Electronic Thesis or Diss., Nîmes, 2024. http://www.theses.fr/2024NIME0002.
Studies carried out in recent years have shown that oxygen concentration in the water column is the main factor controlling all biogeochemical reactions in surface sediment, as well as controlling transfers of nutrients, trace elements (TE) at the sediment water interface (SWI). Three lagoons on France’s Mediterranean coast (Berre, Thau and Prévost) are among the world’s most eutrophied coastal zones impacted by hypoxia episodes, with high accumulations of nutrients, metals and metalloids in their sediment. They are also characterized by different benthic habitats, some of which include macrophytes, which have been shown to regulate nutrient flux at IES. This thesis project aims to better understand the impact of deoxygenation phenomena on the mobility of nutrients and TE present in Mediterranean lagoon sediment, in the presence of different benthic habitats representing their eutrophication gradient. The results show that the Berre lagoon is the site most impacted by long-lasting (1 week) and seasonal episodes of deoxygenation; the Prévost lagoon exhibits wide nycthemeral variations, going from hypoxia to hyperoxia in less than 12 h during the summer season; the Thau lagoon site seems the most resilient about deoxygenation. Under summer conditions, sediment and porewater concentrationprofiles show enrichments in nutrients and sulfides in the substrates of benthic habitats in lagoons with the most advanced eutrophication status (Berre and Prévost), and also in the presence of macroalgae (Prévost and Thau). These enrichments are the result of strong organic matter mineralization, and the more reducing conditions in these habitats binding the TE (As, Sb, Cd, Pb, Zn, Ni, Cu, Co, Hgtot) to the solid phase of the sediment. Comparison with available environmental thresholds enables us to identify habitats in the Berre lagoon that are highly at risk in terms of eutrophication support, remobilization of TE at SWI and ecotoxicological risk. The acquisition of dissolved oxygen concentration gradients within the benthic boundary layer (BBL) at high temporal resolution has enabled us to identify the high oxygen demand of sediment in the Berre lagoon and the nighttime deoxygenations resulting from the presence of opportunistic macroalgae in the Prévost lagoon. The punctual acquisition of concentration gradients illustrates nutrient exports from the sediment to the water column that are more intense under anoxic and euxinic conditions, and exports ofMn, Fe, As, Co under hypoxic conditions. However, concentration gradients under euxinic conditions indicate the trapping of TE (Mn, Fe, Cu,Mo) with the sulfide phases of the sediment. In addition, in situ and ex situ incubation experiments under "forced" deoxygenation conditions for the various benthic habitats present at these three sites yielded SWI fluxes that also followed this trend. Nutrient fluxes were shown to intensify following deoxygenation in eutrophied bare sediment habitats affected by deoxygenation (Berre) and specifically in habitats containing opportunistic (Prévost) and perennial (Thau) macroalgae. For these same habitats, the most intense exports of TE (Mn, Fe, As, Co, V , Mo) were measured under hypoxic and anoxic conditions, while fluxes decreased or reversed under euxinic conditions. This comparative and experimental field approach brings an integrative biogeochemical perspective on the chemical quality of sediment in lagoon environments undergoing re-oligotrophication. It provides a context for their great temporal variability, as well as their vulnerability to climate change
Ben, Maïz Naceur. "Flore algale (Rhodophyta, Phaeophyceae, Chlorophyceae, Bryopsidophyceae) de l'Etang de Thau (Hérault)." Aix-Marseille 2, 1986. http://www.theses.fr/1986AIX22057.
Gangnery, Aline. "Etude et modélisation de la dynamique des populations de bivalves en élevage ("Crassostrea gigas" et "Mytilus galloprovincialis") dans le bassin de Thau (Méditerranée, France) et des ascidies solitaires associées." Montpellier 2, 2003. http://www.theses.fr/2003MON20022.
Sécolier, Pierre. "Une communauté lagunaire en mutation : l'étang de Thau et ses petits métiers." Perpignan, 2008. http://www.theses.fr/2008PERP0812.
There has been quite an intense development of traditional industries around the « étang de Thau », the largest lagoon in the Gulf of Lions. Of these, fishing and shellfish farming make up what is nowadays known as the “small enterprises” of the lagoon. In an undefined category that is not quite a micro society, this community has managed, thanks to its great vitality, to adapt to changes in the socioeconomic context. Since settling on the shores of the lagoon they have had to overcome a lot of problems – linked to the climatic environment, fishing, fish-farming techniques and the usual disputes. Difficulties arise from the new redefined role of women in production, from the sharing of space and resources and from the various phytosanitary crises. These constraints do not prevent shellfish lovers from paying their homage by organising religious ceremonies, games and festivities all around the lagoon. When the party is over, no one can forget the ever-present tensions between a constantly expanding human activity. In order to preserve the quality of the environment while satisfying the requirements of all users, some professionals have joined forces to get round a certain number of intermediary social organisations that do not have their total confidence. Their knowledge of issues relating to the use of the area has allowed them to take a stand in managing disturbances - particularly those brought about by continually increasing numbers of people using the lagoon. In this way, they have managed, insofar as is possible, to preserve the resources of the lagoon, and ensure the survival of the “little jobs”
Genovesi-Giunti, Benjamin. "Initiation, maintien et récurrence des efflorescences toxiques d’Alexandrium catenella (dinophyceae) dans une lagune méditerranéenne (Thau, France) : rôle du kyste dormant." Montpellier 2, 2006. http://www.theses.fr/2006MON20202.
The toxic blooms of Alexandrium catenella in Thau lagoon (France) are related to paralytic shellfish poisoning syndrome. Understanding and predicting their developments depend on the identification of the seeding pattern and potential "hot spots" for bloom initiation. Mapping reveals three preferential zones for resting cysts accumulation which are linked to hydrodynamism. Low resting cyst density in sediments is related probably to a new invasion process. However, higher densities linked to a patchy distribution mode are recorded in the creek of l’Angle which is considered as a significant hot spot for bloom initiation. Bloom recurrence results from cyst survival in sediments, whose renewal depends on the encystment phase. The germination of A. Catenella resting cyst does not depend on light and nutrients in the culture medium. High rates of excystment and synchrony occur in a large "environmental window" (temperature and salinity). However, the low realized seeding ratio limits significantly the initiation phase. The confrontation with numerical simulations suggests that a short duration of water column stability/confining period associated with a frontal structure reduces dispersion, supports the cohesion of bottom cell clusters and allows the seeding population to reach a critical density as a condition for successful bloom initiation
Rudloff, Marie-Anne. "La construction d'un marché contingent : une application à la qualité de l'eau." Montpellier 1, 1998. http://www.theses.fr/1998MON10024.
Derolez, Valérie. "Approche dynamique et intégrée de l'évaluation d'un socio-écosystème côtier : application à la lagune de Thau, son état écologique et ses bouquets de services écosystémiques sur la période 1970-2018." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTG021.
The Thau lagoon is one of the largest Mediterranean coastal lagoons and it supports many uses such as shellfish farming and fishing, priority activities of the territory, and more recently recreational activities. Since the 1960s, the increase in anthropogenic inputs, linked to the sudden growth of the population, led to microbiological contaminations of shellfish and to the eutrophication of the lagoon, with negative impacts at sanitary, ecological and socio-economic levels. Since the 1970s, the considerable work carried out on the waste water system on the watershed has made it possible to restore the lagoon, which then began an oligotrophication trajectory, a process that has still few been studied in coastal environments.Subject to a variety of pressures and disturbances, Thau can be studied as a complex system, within which the ecosystem interacts with society, constituting a socio-ecosystem (SES). The general objective of the thesis is to propose benchmarks able to assess the state and to analyze the trajectory of the Thau SES from 1970 to 2018, in a dynamic and integrated way, based on the approaches and tools proposed by: i) restoration ecology and ii) ecosystem services (ES) approach. From the point of view of the state and functioning of the ecosystem, statistical analyzes of long-term data series on autotrophic compartments have highlighted shifts in the composition of communities, as well as phenomena of resilience or inertia during oligotrophication. By applying the interdisciplinary tool of timelines, we distinguished three contrasting periods in the trajectory of the SES: P1) 1970-1989: degraded state, predominant traditional uses and sectoral management; P2) 1990-2004, transition period: start of improvement in water quality, development of recreational uses and structuring of management; P3) 2005-2018: oligotrophication, diversification of uses and integrated management. Through the dynamic analysis of: i) bundles of ecosystem services (matches or gaps between ES’ potential and consumption); ii) and of forms of ES demands potentially driving change (impacting, unsatisfied, conservation), we identified the main interactions between ecological and social processes and the main determinants of the phases of stability or change in the SES
Jarry, Vincent. "Etude pluridisciplinaire en écologie lagunaire (étang de Thau, France) : stratégie d'échantillonnage et organisation spatiale du phytoplancton." Montpellier 2, 1990. http://www.theses.fr/1990MON20204.
Borsa, Philippe. "Génétique des populations bivalves en milieu lagunaire : la palourde dans l'étang de Thau (Méditerranée)." Paris 6, 1990. http://www.theses.fr/1990PA066416.
The genetic structuration of populations of the palourde, Ruditapes decussatus, a bivalve species of the Mediterranean coastal lagoons, was studied at the enzymatic gene level, in relation to their ecology and their demography. A genetic comparison of local populations of the Languedocian lagoons suggested that they constitute a metapopulation. In the Thau lagoon, genetic heterogeneity could be related to demographic features. Genetic differences between cohorts appeared to account for significant heterozygote deficiencies, although not fully explaining them. For this, a Wahlund effect could be rejected. The hypothesis of selection affecting pre-recruits appeared most likely and it was confirmed by preliminary results of experiments conducted on larvae. It was shown that mean heterozygosity increases in a cohort monitored over one generation. This also occurs during sudden environmental stress (malaigue). Selective intercations between loci also could be detected. Thus, consistent observations account for the existence of a selective control of the distribution of multilocus, as well as monolocus genotypes, at both the larval and post-settled stages, between individuals within a cohort, and between cohorts within the population
Gerbal, Maryse. "Analyse spatio-temporelle des peuplements phytobenthiques de substrat meuble de l'étang de Thau (Hérault, France)." Aix-Marseille 2, 1994. http://www.theses.fr/1994AIX22007.