Dissertations / Theses on the topic 'Variation with salinity'

Behavioural responses of the colour forms of Carcinus maenas to salinity variation were investigated, and related to their physiology and distribution in an estuary. Red males, characterised by a thicker carapace were unable to survive in as low salinities as green males; this was reflected in their poorer osmoregulatory capabilities. Haemolymph osmolality and ion concentrations of red crabs decreased at a faster rate and reached lower levels than in green crabs. Haemolymph osmolality and choice behaviour did not vary with size. In the tidally mixed estuary male and female crabs occurred in roughly similar proportions. Most were green and generally smaller than their open shore counterparts. Migration out of the estuary in winter was reversed in late spring. Differences in salinity tolerance of red and green crabs were reflected in salinity preference behaviour. Green crabs persisted longer in the lowest range of salinities tested, especially if a shelter was available. Prior acclimation affected the timing of choice behaviour; the lower the salinity of acclimation the faster the time of exit from the lowest range of salinities tested, and vice versa. Estuarine green crabs exhibited endogenous locomotor activity of circatidal periodicity and were less responsive to episodes of low salinity than open shore red and green crabs. Constant low salinity initiated a rhythm of circatidal periodicity in arhythmic red and green crabs; red crabs reacted faster and were more active upon salinity change than green crabs. The amount of locomotor activity induced after prior acclimation was similar within each acclimation salinity tested. Carcinus detected salinity variation by responding to the concentrations of Na and Cl in seawater, and was able to differentiate between salinities separated by as little as 0.5ppt., - General physiological changes appear to occur before behavioural responses are mediated; they probably act as cues for the behavioural responses, which appear not to be triggered by specific receptors. Behavioural and physiological responses combing to enhance, the survivability of crabs in changing salinities.

The contribution of phytoplankton productivity to higher trophic levels in salt marshes is not well understood. My study furthers our understanding of possible mechanisms controlling phytoplankton productivity, abundance, and community composition in salt marshes. Across three consecutive springs (2001 to 2003), I sampled the upper Nueces Delta in south Texas, a shallow, turbid, salt marsh system stressed by low freshwater inflow and wide ranging salinity (<15 to >300 ppt). Water column productivity and respiration were estimated using a light-dark bottle technique, and phytoplankton biovolume and community composition were determined using inverted light microscopy. To determine their effect on the phytoplankton community, zooplankton and bacterioplankton abundance and several physical parameters were also assessed. Meaningful relationships among the numerous variables evaluated in this study were identified using principal component analysis (PCA). Despite high turbidity, phytoplankton productivity and biovolume were substantial. Resuspension appeared to play a major role in phytoplankton dynamics, as indicated by a positive relationship between ash weight and biovolume that explained up to 46% of the variation in the PCA. Negative relationships between zooplankton grazers and pennate diatoms of optimal sizes for these grazers suggested a functional grazing food chain in this system. Salinity also may have been important in phytoplankton dynamics, whereas nutrients appeared to play a minor role. Salinity increases may have been responsible for a decoupling observed between phytoplankton and grazers during late spring. Findings suggest hypotheses for future studies focused on the role of phytoplankton in salt marshes, particularly those stressed by reduced freshwater inflow and high salinities.

Thesis (MSc)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: This investigation was undertaken to determine whether elevated concentrations of dissolved inorganic carbon (DIC) supplied to plant roots could improve plant growth and alleviate the effects of salinity stress on tomato plants infected with arbuscular mycorrhizae. Lycopersicon esculentum cv. FI44 seedlings were grown in hydroponic culture (pH 5.8) with 0 and 75 mM NaCI and with or without infection with the fungus Glomus mosseae. The root solution was aerated with ambient CO2 (360 ppm) or elevated CO2 ( 5 000 ppm) concentrations. The arbuscular and hypha I components of mycorrhizal infection as well as the percentages total infection were decreased or increased according to the variation in seasons. The plant dry weight of mycorrhizal plants was increased by 30% compared to non-mycorrhizal plants at elevated concentrations of CO2, while the dry weight was decreased by 68% at ambient CO2 concentrations. Elevated CO2 also stimulated the growth of the mycorrhizal fungus. Elevated CO2 increased the plant dry weight and stimulated fungal growth of mycorrhizal plants possibly by the provision of carbon due to the incorporation of HCO)- by PEPc. Plant roots supplied with elevated concentrations of CO2 had a decreased CO2 release rate compared to roots at ambient CO2. This decrease in CO2 release rate at elevated CO2 was due to the increased incorporation of HC03- by PEPc activity. Under conditions of salinity stress plants had a higher ratio of N03-: reduced N in the xylem sap compared to plants supplied with 0 mM NaCI. Under salinity stress conditions, more N03- was transported in the xylem stream possibly because of the production of more organic acids instead of amino acids due to low P conditions under which the plants were grown. The N03· uptake rate of plants increased at elevated concentrations of CO2 in the absence of salinity because the HCO)- could be used for the production of amino acids. In the presence of salinity, carbon was possibly used for the production of organic acids that diverted carbon away from the synthesis of amino acids. It was concluded that mycorrhizas were beneficial for plant growth under conditions of salinity stress provided that there was an additional source of carbon. Arbuscular mycorrhizal infection did not improve the nutrient uptake of hydroponically grown plants.
AFRIKAANSE OPSOMMING: In hierdie studie was die effek van verhoogde konsentrasies opgeloste anorganiese koolstof wat aan plant wortels verskaf is, getoets om te bepaal of dit die groei van plante kan verbeter asook of sout stres verlig kon word in tamatie plante wat met arbuskulêre mikorrhizas geïnfekteer was. Lycorpersicon esculentum cv. FJ44 saailinge was in water kultuur gegroei (pH 5.8) met 0 en 75 mM NaCI asook met of sonder infeksie met die fungus Glomus mosseae. Die plant wortels was bespuit met normale CO2 (360 dele per miljoen (dpm)) sowel as verhoogde CO2 (5 000 dpm) konsentrasies. Die arbuskulere en hife komponente, sowel as die persentasie infeksie was vermeerder of verminder na gelang van die verandering in seisoen. Die plant droë massa van mikorrhiza geïnfekteerde plante by verhoogde CO2 konsentrasies was verhoog met 30% in vergelyking met plante wat nie geïnfekteer was nie, terwyl die droë massa met 68% afgeneem het by gewone CO2 konsentrasies. Verhoogde CO2 konsentrasies het moontlik die plant droë massa en die groei van die fungus verbeter deur koolstof te verskaf as gevolg van die vaslegging van HCO)- deur die werking van PEP karboksilase. Plant wortels wat met verhoogde CO2 konsentrasies bespuit was, het 'n verlaagde CO2 vrystelling getoon in vergelyking met die wortels by normale CO2 vlakke. Die vermindering in CO2 vrystelling van wortels by verhoogde CO2 was die gevolg van die vaslegging van HC03- deur PEPk aktiwiteit. Onder toestande van sout stres, het plante 'n groter hoeveelheid N03- gereduseerde N in die xileemsap bevat in vergelyking met plante wat onder geen sout stres was nie, asook meer NO)- was in die xileemsap vervoer moontlik omdat meer organiese sure geproduseer was ten koste van amino sure. Dit was die moontlike gevolg omdat die plante onder lae P toestande gegroei het. Die tempo van NO.; opname was verhoog onder verhoogde CO2 konsentrasies en in die afwesigheid van sout stres omdat die HCO)- vir die produksie van amino sure gebruik was. In die teenwoordigheid van sout was koolstof moontlik gebruik om organiese sure te vervaardig wat koolstof weggeneem het van die vervaardiging van amino sure. Daar is tot die slotsom gekom dat mikorrhizas voordelig is vir die groei van plante onder toestande van sout stres mits daar 'n addisionele bron van koolstof teenwoordig is. Arbuskulere mikorrhiza infeksie het 'n geringe invloed gehad op die opname van voedingstowwe van plante wat in waterkultuur gegroei was.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Acidificação oceânica, processo resultante das emissões de gás carbônico (CO2) na atmosfera pelas atividades de natureza antrópica, vem causando nas últimas décadas uma modificação no equilíbrio químico do sistema bicarbonato/carbonato e consequentemente uma diminuição do pH dos oceanos. Estimativas apontam que esta diminuição pode ser de 0,7 unidades até ano de 2300, o que pode afetar o crescimento, reprodução e até mesmo a sobrevivência das espécies. Nesse sentido, são necessários estudos que avaliem o impacto da acidificação oceânica ao nível fisiológico e molecular nas diferentes espécies marinhas. O siri Callinectes danae é um importante recurso ecológico e econômico da Região da Baixada Santista e habitante de diferentes faixas de salinidade. O presente estudo avaliou os efeitos da acidificação oceânica no siri C. danae sobre um conjunto de parâmetros fisiológicos (consumo de oxigênio, excreção de amônia, razão O:N, índice hepatossomático e capacidade osmo-e ionorregulatória da hemolinfa), e a expressão gênica da Na+/K+- ATPase, enzima importante no processo de osmorregulação e equilíbrio ácido base. Os animais foram mantidos em diferentes salinidades (20, 25, 30, 35 e 40) e nos pHs 8,0 (controle) e 7,3 (acidificado) por um período de três e trinta dias. Foi observado aumento no consumo de oxigênio nas salinidades 25 (3 dias), 20 e 40 (30 dias) provavelmente devido a uma maior necessidade energética para a manutenção de sistemas relacionado a regulação ácido-base. Também foi observada depressão metabólica na salinidade de 30 (30dias). A excreção de amônia sofreu redução nas salinidades 30 (3 dias), 25, 30 e 35 (30 dias) possivelmente devido a competição entre os transportadores Na+/H+ e Na+/NH+4. O índice hepatossomático teve aumento nas salinidades de 30 (3 dias) e 40 (30 dias) devido a uma possível necessidade acumulo de reservas em situações estressantes. O substrato energético e o padrão osmorregulatório permaneceram inalterados em todos os tratamentos. Já a concentração de Cl- e Na+ foram reduzidas nas salinidades de 25 e 35 (30dias), provavelmente devido a alguma alteração nos seus transportadores. Molecularmente, foi observada uma regulação da expressão da Na+/K+ ATPase, com diminuição nas salinidades de 35 e 40 (3 dias), e posterior aumento no período de 30 dias. O trabalho foi o primeiro a avaliar os parâmetros fisiológicos e moleculares de C.danae em diferentes salinidades. Os animais que permaneceram por mais tempo sobre a exposição de alta pCO2 são mais afetados negativamente do que os animais que foram expostos em 3 dias. As alterações observadas podem indicar que apesar de C. danae ser um animal eurialino e habitar diferentes ambientes, a acidificação oceânica pode alterar seus padrões fisiológicos e moleculares, tirando os organismos de sua homeostase, tendo consequências no crescimento, no desenvolvimento e na distribuição da espécie.
Oceanic acidification, a process resulting from the emission of carbon dioxide (CO2) in the atmosphere by activities of anthropic nature, has been causing in recent decades a change in the chemical balance of the bicarbonate / carbonate system and consequently a decrease in the pH of the oceans. Estimates indicate that this decrease can be 0.7 units per year of 2300, which can affect the growth, reproduction and even survival of the species. In this sense, studies are needed to evaluate the impact of oceanic acidification on physiological and molecular levels in different marine species. The Callinectes danae crab is an important ecological and economic resource of the Region of the Baixada Santista and inhabitant of different ranges of salinity. The present study evaluated the effects of ocean acidification on C. danae crab on a set of physiological parameters (oxygen consumption, ammonia excretion, O: N ratio, hepatosomatic index and osmo-and ionoregulatory capacity of hemolymph), and gene expression of Na + / K + - ATPase, an important enzyme in the process of osmoregulation and acid base balance. The animals were kept at different salinities (20, 25, 30, 35 and 40) and at pHs 8.0 (control) and 7.3 (acidified) for a period of three and thirty days. It was observed an increase in the oxygen consumption in salinities 25 (3 days), 20 and 40 (30 days) probably due to a greater energy requirement for the maintenance of systems related to acid-base regulation. Metabolic depression was also observed at the salinity of 30 (30 days). Ammonia excretion decreased in salinities 30 (3 days), 25, 30 and 35 (30 days) possibly due to competition between Na + / H + and Na + / NH + 4 transporters. The hepatosomatic index had an increase in salinities of 30 (3 days) and 40 (30 days) due to a possible accumulation of reserves in stressful situations. The energy substrate and the osmoregulatory pattern remained unchanged in all treatments. However, the Cl- and Na + concentrations were reduced at the salinity of 25 and 35 (30 days), probably due to some changes in their transporters. Molecularly, a regulation of Na + / K + ATPase expression was observed, with a decrease in salinities of 35 and 40 (3 days), and a subsequent increase in the period of 30 days. The work was the first to evaluate the physiological and molecular parameters of C.danae in different salinities. Animals that remained longer on exposure to high pCO2 are more negatively affected than animals that were exposed in 3 days. The observed changes may indicate that although C. danae is an eurialan animal and inhabits different environments, ocean acidification can alter its physiological and molecular patterns, taking organisms out of their homeostasis, having consequences on the growth, development and distribution of the species .

The reproductive success for pelagic spawning Baltic flounders is strongly linked to the hydrodynamics in the spawning areas. Egg survival is dependent upon the ability to achieve neutral buoyancy at a depth interval where temperature and oxygen concentrations are favourable for egg development. The main focus of this thesis was to compare egg survival probabilities of pelagic eggs from Baltic flounder in the Bornholm, Gdansk and Gotland basins, prior to and after the saline water inflow in December 2014. The results showed greatly enhanced survival probabilities in Bornholm basin 2015 (p<0.01), as egg survival increased from 47% in 2014 to 100% the following year. In Gdansk basin the situation was similar, and survival probability increased from 13% to 100% (p<0.01). In Gotland basin no difference in survival probability was identified, although the dominant cause of mortality shifted from sedimentation, i.e. due to low salinity conditions in 2014, to oxygen deficiency in 2015 (p<0,01).
BONUS INSPIRE-project, the joint Baltic Sea research and development programme (Art 185), funded jointly by the European Union’s Seventh Programme for research, technological development and demonstration and the Swedish Research Council Formas

[Truncated abstract] In southern Australian farming systems the replacement of deep-rooted perennial native vegetation with shallow-rooted annual crops and pastures has resulted in rising groundwater tables and an increased incidence of dryland salinity. It has been suggested that to address this issue by restoring hydrological balance, large areas of agricultural land need to be vegetated with perennial plants. One of the most agriculturally productive ways to do this is to introduce perennial pastures, both into upslope groundwater

Many geologic processes occur in association with hydrothermal fluids and some of these fluids are eventually trapped as fluid inclusions in minerals formed during the process. Fluid inclusions provide valuable information on the pressure, temperature and fluid composition (PTX) of the environment of formation, hence understanding PTX properties of the fluid inclusions is required. The most important step of a fluid inclusion study is the identification of Fluid Inclusion Assemblages (FIA) that represent the finest (shortest time duration) geologic event that can be constrained using fluid inclusions. Homogenization temperature data obtained from fluid inclusions is often used to reconstruct temperature history of a geologic event. The precision with which fluid inclusions constrain the temperatures of geologic events depends on the precision with which the temperature of a fluid inclusion assemblage can be determined. Synthetic fluid inclusions trapped in the one-fluid-phase field are formed at a known and relatively constant temperature. However, microthermometry of synthetic fluid inclusions often reveals Th variations of about ± 1- 4 degrees Centigrade, or one order of magnitude larger than the precision of the measurement for an individual inclusion. The same range in Th was observed in well-constrained natural FIAs where the inclusions are assumed to have been trapped at the same time. The observed small variations are the result of the effect of the fluid inclusion size on the bubble collapsing temperature. As inclusions are heated the vapor bubble is getting smaller until the pressure difference between the pressure of the vapor and the confining pressure reaches a critical value and the bubble collapses. It was observed that smaller inclusions reach critical bubble radius and critical pressure differences at lower temperatures than larger inclusions within the same FIA. Homogenization temperature (Th) variations depend on many factors that vary within different geological environments. In order to determine minimum and acceptable Th ranges fro FIAs formed in different environments we investigated several geologic environments including sedimentary, metamorphic, and magmatic hydrothermal environments. The observed minimum Th ranges range from 1-4 degrees Centigrade and acceptable Th range from 5-25 degrees Centigrade. The variations are mostly caused by the fluid inclusion size, natural temperature and pressure fluctuations during the formation of an FIA and reequilibration after trapping. Fluid inclusions containing H₂O-CO₂-NaCl are common in many geologic environments and knowing the salinity of these inclusions is important to interpret PVTX properties of the fluids. A technique that combines Raman spectroscopy and microthermometry of individual inclusions was developed to determine the salinity of these inclusions. In order to determine the salinity, the pressure and temperature within the inclusion must be known. The pressure within the inclusions is determined using the splitting in the Fermi diad of the Raman spectra of the CO₂ at the clathrate melting temperature. Applying the technique with to synthetic fluid inclusions with known salinity suggests that the technique is valid and useable to determine salinity of H₂O-CO₂-NaCl fluid inclusions with unknown salinity.
Ph. D.

Les argiles sont répandues dans la proche surface de la Terre, et ont un fort impact sur la perméabilité des formations géologiques. Leur très faible perméabilité fait des formations argileuses des "pièges géologiques" d’intérêt dans divers domaines d’étude des géosciences (notamment pour le pétrole et le gaz, la géothermie, le stockage des déchets nucléaires, entre autres). Les minéraux argileux présentent une charge de surface et une surface spécifique très importantes, ce qui génère le développement d’une double couche électrique particulièrement importante. La polarisation provoquée spectrale (PPS) est une méthode géoélectrique active qui permet d’obtenir de manière non-invasive la conductivité électrique complexe en fonction de la fréquence d’un géo-matériau du mHz au kHz. La conductivité complexe informe sur la capacité du matériau sondé à conduire un courant électrique et sur sa capacité à se polariser (à mobiliser de manière réversible des charges électriques). Cette thèse présente un protocole de laboratoire détaillé pour obtenir des mesures de PPS sur différents types d’argiles à des salinités variables, ainsi que des mélanges hétérogènes artificiels d’illite et demontmorillonite. Les résultats de la première étude montrent que la partie réelle de la conductivité électrique augmente avec la salinité, mais la partie imaginaire augmente jusqu’à un maximum et puis diminue. Cette diminution est due à la coagulation des argiles à hautes salinités. Cette coagulation potentielle des argiles altérerait l’espace poral puis modifierait les mécanismes de polarisation en jeu. Par ailleurs, en comparant le rapport de la conductivité de surface (imaginaire versus réelle) et d’autres données de la littérature, on remarque que ce rapport diminue avec la teneur en argile. Pour la deuxième étude, on observe que la montmorillonite domine la polarisation par rapport à l’illite. Cependant, les deux argiles ont un effet sur la conduction des mélanges. Les lois de mélanges sont une approche efficace pour modéliser ce type de mélange hétérogène d’argiles. Les modèles de réseaux de conductance complexes sont également utiles pour prédire la forme des spectres de polarisation. Les résultats de ce travail de thèse ouvrent de nouvelles perspectives pour la caractérisation des matériaux argileux avec la PPS
Clays are ubiquitously present in the Earth’s near surface and they have a high impact on the permeability of a system. Due to this property, clay formations are used in a variety of geology related applications (oil and gas, geothermal, nuclear waste storage, critical zone research, among others). Clays have a high surface charge and a high specific surface area, this property gives clays a particularly strong electrical double layer (EDL). Spectral induced polarization (SIP) is an active geo-electrical method thatmeasures in a non-invasive manner the frequency-dependent complex conductivity of a geo-material from themHz to the kHz. The complex conductivity informs about the ability the probed material has to conduct an electrical current and the ability to polarize (to reversibly store electrical charges). This thesis presents a detailed laboratory protocol to obtain SIP measurements of different types of clay at varying salinities, as well as an artificial heterogeneous mixture of illite and red montmorillonite with a salinity of around 10¡2 mol L¡1. The results of the first study show that the real part of the electrical conductivity increases with salinity, but the imaginary part increases until a maxima and then decreases. An interpretation of the decrease can come fromthe fact that clays coagulate at high salinities. The potential coagulation of clays would alter the pore space and then alter the polarization mechanisms in play. Furthermore, when comparing the ratio of the surface conductivity (imaginary versus real) of these resultswith other data in the literature, we notice that this ratio decreaseswith clay content. For the second study, we observe that red montmorillonite dominates the polarization with respect to illite. However, both clays effect the conduction of the mixtures. Mixing laws are an effective approach to model the complex conductivity of these heterogeneous mixtures. Complex conductance network models are better at predicting the shape of the polarization spectra. The results of this thesis work open new opportunities for clay characterization using SIP

Salinity is one of the fundamental ocean state variables. Variations of ocean salinity can be used to infer changes in the global water cycle and air-sea freshwater exchange. Many institutions have developed gridded Argo products of global coverage. However, the existing gridded salinity products have not yet been dedicatedly intercompare and assessed. In this study, the mean state, annual and interannual variabilities, and decadal changes of ocean salinity from five Argo-based gridded salinity products, available from UK Met Office, JAMSTEC, Scripps Institution of Oceanography, China Second Institute of Oceanography, and International Pacific Research Center, are examined and compared for their overlapping period of 2005-2015 within two depth intervals (0-700 m and 700-2000 m), as well as the sea surface. Though some global and regional features are relatively reproducible, obvious discrepancies are found particularly for the deeper layer. These discrepancies are not apparent on the 11-year climatological mean or the trend patterns, but are readily evident on temporal variations. For instance, the potentially undersampled current systems in the North Atlantic and Southern Ocean are one of the main reasons for the observed discrepancies. The gridded products from Scripps, JAMSTEC and Met Office show large deviation from the ensemble mean, particularly in regions like the Atlantic Ocean and the tropical Pacific. Large disagreements are found in the first and final years, which can lead to different estimates on decadal trends. This study can serve as a useful reference on how to utilize and improve the existing gridded salinity products.

Doutoramento em Biologia
Rapid climatic changes are taking place in Arctic, subarctic and cold temperate regions, where predictions point to an increase in freeze-thaw events, changes in precipitation, evaporation and salinity patterns. Climate change may therefore result in large impacts in ecosystem functioning and dynamics, especially in the presence of contaminants due to intense anthropogenic activities. Even though multiple stress approaches have received increasing interest in the last decades, the number of such studies is limited. In particular, knowledge on the effect of freezethaw events and salinity fluctuations on ecotoxicology of soil invertebrates is lacking, especially important when considering supralittoral species. Therefore, the aim of this thesis was to investigate the effects of low temperature and salinity fluctuations, singly and in combination with contaminants, in the freeze-tolerant and euryhaline enchytraeid Enchytraeus albidus. The assessment of population level endpoints (survival and reproduction), along with physiological and biochemical parameters such as levels of cryoprotectants, ice/water content, oxidative stress biomarkers, cellular energy allocation, and tissue concentration of chemicals (when applied), provided new and valuable knowledge on the effects of selected physical and chemical stressors in E. albidus, and allowed the understanding of adjustments in the primary response mechanisms that enable worms to maintain homeostasis and survival in harsh environments such as polar and temperate-cold regions. The presence of moderate levels of salinity significantly increased freeze-tolerance (mainly evaluated as survival, cryoprotection and ice fraction) and reproduction of E. albidus. Moreover, it contributed to the readjustments of cryoprotectant levels, restoration of antioxidant levels and changed singnificantly the effect and uptake of chemicals (copper cadmium, carbendazim and 4-nonylphenol). Temperature fluctuations (simulated as daily freeze-thaw cycles, between -2ºC and -4ºC) caused substancial negative effect on survival of worms previsouly exposed to non-lethal concentrations of 4-nonylphenol, as compared with constant freezing (-4ºC) and control temperature (2ºC). The decrease in cryoprotectants, increase in energy consumption and the highest concentration of 4-nonylphenol in the tissues have highlighted the high energy requirements and level of toxicity experienced by worms exposed to the combined effect of contaminants and freezing-thawing events. The findings reported on this thesis demonstrate that natural (physical) and chemical stressors, singly or in combination, may alter the dynamics of E. albidus, affecting not only their survival and reproduction (and consequent presence/distribution) but also their physiological and biochemical adaptations. These alterations may lead to severe consequences for the functioning of the ecosystems along the Arctic, subarctic and cold temperate regions, where they play an important role for decomposition of dead organic matter. This thesis provides a scientific basis for improving the setting of safety factors for natural soil ecosystems, and to underline the integration of similar investigations in ecotoxicology, and eventually in risk assessment of contaminants.
As alterações climáticas estão a atingir rapidamente as regiões do Ártico, SubÁrtico e as regiões temperadas, apontando as previsões para um aumento de eventos de congelamento-descongelamento, bem como mudanças nos padrões de precipitação, evaporação e de salinidade. Estas alterações climáticas poderão resultar em impactos francamente negativos no funcionamento e dinâmica de ecossistemas, especialmente quando associados à presença de contaminantes resultantes da intensa atividade antropogénica. Embora a incorporação de stressores múltiplos em estudos de ecotoxicidade tenha recebido um crescente interesse pela comunidade científica, o seu número é ainda reduzido. Particularizando, o conhecimento dos efeitos de eventos de congelamento-descongelamento e de flutuações de salinidade permanecem desconhecidos, especialmente quando se consideram espécies supra-litorais. Neste contexto, o objetivo geral da presente tese consistiu em investigar os efeitos das flutuações de temperaturas e salinidade, individualmente ou em combinação com contaminantes, no enquitraídeo tolerante ao frio e eurialino - o Enchytraeus albidus. A avaliação de parâmetros populacionais (sobrevivência, reprodução e bioacumulação), fisiológicos (níveis de crioprotetores, conteúdo em gelo / água, temperatura de fusão e sobrecongelamento) e bioquímicos (biomarcadores de stress oxidativo, alocação de energia celular) permitiu compilar novas e valiosas informações sobre os efeitos dos stressores físicos e químicos selecionados no enquitraídeo e compreender quais os reajustes nos mecanismos de resposta primários que lhes permitem manter a homeostasia e sobrevivência em ambientes inóspitos como as regiões Polares e temperadas-frias. A presença de níveis moderados de salinidade aumentou significativamente a tolerância a temperaturas congelantes (essencialmente avaliada como sobrevivência, crioprotecção e fracção de gelo extracelular) e a reprodução do E. albidus. Além disso, contribuiu para a regulação de crioprotectores, restauração dos níveis de antioxidantes nestes organismos e alterou significativamente o efeito e a incorporação/absorção de substâncias químicas (cádmio, cobre carbendazim e 4-nonilfenol). As flutuações de temperatura (simuladas como ciclos diários de congelamento-descongelamento, com temperaturas entre 2ºC e -4ºC) causaram um efeito substancialmente negativo na sobrevivência de organismos previamente expostos a concentrações não letais de 4-nonilfenol, quando comparados com organismos expostos a uma temperatura congelante constante (-4ºC) ou à temperatura controlo (2ºC). A diminuição na crioproteção, o aumento no consumo de energia e a maior concentração de 4-nonilfenol nos tecidos vieram sublinhar o elevado gasto energético e o nível de toxicidade sofrido pelos organismos expostos à combinação de contaminantes e eventos de congelamento e descongelamento. Os resultados apresentados nesta tese demonstram, assim, que a presença de stressores naturais (físicos) e químicos, isoladamente ou em combinação, podem alterar a dinâmica do E. albidus, afetando não só a sua sobrevivência e reprodução (e consequente presença / distribuição), mas também as suas adaptações fisiológicas e bioquímicas. Essas alterações podem levar a consequências graves para o funcionamento dos ecossistemas do Ártico, subÁrtico e regiões temperadas-frias, uma vez que estes organismos desempenham um papel importante para a decomposição de matéria orgânica morta. Esta tese fornece ainda uma base científica para melhorar a atribuição de coeficientes de segurança para os ecossistemas naturais do solo, alertando para a integração de investigações semelhantes em ecotoxicologia, e, eventualmente, para a avaliação de risco ecológico de contaminantes.

Les efflorescences de Microcystis aeruginosa se développent sur l’ensemble des continents et leurs intensités et fréquences devraient s’accroître avec le changement climatique. Ces proliférations sont associées à la production de toxines appartenant à la famille des microcystines. Dans ce contexte, l’aire de répartition de M. aeruginosa tend à s’étendre aux zones estuariennes. Sa présence ainsi que celles des microcystines en zone côtière est principalement due au transfert des efflorescences d’eau douce par le continuum eau douce – estuaire. Ce transfert peut aboutir à la lyse des cellules libérant les microcystines dans l’environnement. Le risque sanitaire lié au transfert de M. aeruginosa et les conséquences d’une augmentation de la salinité sur sa croissance, sa production de microcystines et plus généralement sur sa physiologie ont été peu étudiés. L’objectif principal de cette thèse a été d’étudier les réponses physiologiques et métaboliques de M. aeruginosa à une augmentation de salinité. Cette étude a tout d’abord permis le développement d’une méthode d’extraction et d’analyse des microcystines par chromatographie liquide couplée à la spectrométrie de masse pour l’analyse d’échantillons de cellules et d’eau, prélevés en milieu salin. La réponse physiologique de M. aeruginosa confrontée à une augmentation de la salinité a été étudiée chez deux souches (PCC 7820 et PCC 7806) par stress et après acclimatation à la salinité. Ces travaux ont mis en évidence que M. aeruginosa peut tolérer des variations de salinité par l’accumulation de solutés compatibles tels que le tréhalose (PCC 7820) et le saccharose (PCC 7806). Les analyses conduites en métabolomique ont révélé l’existence d’une diversité de métabolites spécifiques d’une réponse à une augmentation de salinité. Chez les souches acclimatées, l’accumulation de lipides membranaires (monogalactosylglycerol) a été mise en évidence. Également, la production de microcystines est apparue corrélée au taux de croissance de M. aeruginosa en réponse à une augmentation de la salinité. Ces travaux suggèrent que les variations de salinité chez M. aeruginosa n’affectent pas directement la nature et la quantité des microcystines produites. Ces analyses menées sur des échantillons naturels et en laboratoire suggèrent que les cellules peuvent survivre et croître en condition mésohaline
M. aeruginosa is one of the most pervasive toxic freshwater cyanobacterial species worldwide. The frequency and intensity of M. aeruginosa blooms are expected to increase in response to climate change. The influence of M. aeruginosa is extending to estuaries and coastal environment due to the transfer of freshwater bloom across the freshwater-estuary continuum. This transfer can ultimately result in cell lysis and the subsequent release of dissolved microcystins. Little is known about this phenomenon and the effect of salt increase on growth, microcystin production and M. aeruginosa physiology. This PhD project therefore aimed to better describe the physiological and metabolic response of M. aeruginosa to salt increase. First, a method using liquid chromatography coupled to mass spectrometry was developed and characterized in order to conduct the quantification of microcystins in cells and water samples taken from estuaries. The physiological responses of M. aeruginosa, subjected to a salinity increase was monitored on two acclimated and non-acclimated strains (PCC 7820 and PCC 7806). This work provided insights into the accumulation of compatible solutes like trehalose (PCC 7820) and sucrose (PCC 7806) in response to salt increase. Metabolomic analyses revealed the existence of specific metabolites involved in salt stress and acclimation responses. In acclimated strains, the synthesis of monogalactosyldiacylglycerol in response to salt increase was found. Overall, the different experiments conducted on M. aeruginosa revealed that the microcystin production rate was correlated to the growth rate. Taken together, the results obtained from laboratory and field samples suggest that cell lysis is not an immediate phenomenon and that M. aeruginosa cells could survive and proliferate in mesohaline conditions

L’objectif de ce travail de thèse est de clarifier le débat de la littérature d’écologie des communautés sur les variations d’interactions plante-plante le long de gradients de stress hydrique. Nous nous sommes focalisés sur l’importance du type de stress (ressources vs. non-ressources) et la méthode utilisée (observationnelle vs. expérimentale) pour quantifier les interactions biotiques. Les dépressions salines continentales (Sebkhas) de Tunisie se caractérisant par l’existence d’un gradient marqué de salinité dans des contextes climatiques contrastés est un excellent système modèle pour clarifier ce débat notamment en séparant les effets de la salinité de ceux du stress hydrique.Dans une première étape, nous avons effectué une étude observationnelle à l’échelle de la zone aride tunisienne afin d’identifier les conséquences des interactions possibles existant entre la topographie et le climat et déterminant les variations de stress salin et hydrique et donc la structure, la composition des communautés végétales et le fonctionnement des écosystèmes. Nous avons mis en place un dispositif de terrain croisant un traitement de position topographique (avec quatre habitats) et un traitement de stress hydrique (avec deux situations climatiques, le climat faiblement aride et le climat fortement aride) avec quatre répétitions à l’échelle régionale. Nous avons également effectué deux expérimentations, une première sur les l’effet des voisins par la méthode observationnelle avec transplantation de trois espèces dominantes dans l’ensemble des traitements et une sur l’effet de la méthode (observationnelle vs. expérimentale) avec transplantation de trois Poaceae dans les deux habitats les moins salés.L’étude observationnelle a clairement montré que la salinité est le facteur direct majeur déterminant la composition, la diversité et la structure des communautés, ainsi que la productivité des écosystèmes et leur fertilité. L’aridité a des effets moindres plus subtiles et son effet ne peut être comparé spatialement que dans l’habitat le moins salé entre les zones très et faiblement arides.La première étude expérimentale a montré que le stress salin (facteur direct non de ressource) entrainait un collapse de la facilitation et que ce collapse s’accentuait avec l’aridité croissante, aussi bien temporellement que spatialement. Nous n’avons pas trouvé de retour de la compétition en situation d’aridité extrême comme le prédit la littérature. Ceci est sans doute due à la stratégie faiblement compétitrice des Chaméphytes dominants les habitats les plus salés. La seconde étude expérimentale a montré qu’avant la saison sèche estivale les interactions de court-terme mesurées par la méthode expérimentale (removal method) sont négatives alors que les interactions de long-terme, mesurées par combinaison des méthodes observationnelle et expérimentale sont positives, confirmant nos hypothèses et la littérature. Cependant, après la saison sèche estivale les interactions de court-terme deviennent positives, alors que les interactions de long-terme collapsent par disparition de l’effet tampon du sol végétalisé sur l’humidité.Ces résultats sont cruciaux car ils montrent que dans ce système aride et à important stress salin le collapse de la facilitation est le processus majeur expliquant la structure, la diversité et le fonctionnement des écosystèmes et ce aussi bien le long des gradients de salinité que lorsque que le stress hydrique augmente. D’autre part la combinaison des méthodes observationnelle et expérimentale nous a permis de démontrer que l’augmentation de la facilitation prédite par le SGH lors d’une augmentation modérée de stress hydrique n’est qu’une réponse des plantes à l’effet négatif croissant de l’environnement abiotique, contrairement à l’augmentation de la compétition dans les environnements non stressés et celui de la facilitation des environnements très à moyennement stressés, qui sont des processus d’origine biotique
We aim to clarify the debate of the community ecology literature on changes in plant-plant interaction along water stress gradients. We focused on the importance of the type of stress (resources vs. non-resources) and the method used (observational vs. experimental) to quantify biotic interactions. The continental saline depressions (Sebkhas) of Tunisia, characterized by the existence of a strong gradient of salinity in contrasting climatic conditions, is an excellent model system to clarify this debate, in particular by separating the effects of salinity from water stress.In a first step, we carried out an observational study on the scale of the Tunisian arid zone in order to identify the consequences of the possible interactions existing between topography and climate and determining variations in salinity and water stress and ultimately the structure, composition of plant communities and ecosystem functioning. We set up a field design combining a topographic position treatment (with four habitats) and a water stress treatment (with two climate conditions: the wet arid climate and the dry arid climate) with four replicates at the regional scale. We also carried out two experiments, one on the effect of neighbors using the observational method with transplants of three dominant species in all treatments and a second on the effect of the method (observational vs. experimental) with transplantation of three Poaceae in the two least saline habitats.The observational study clearly showed that salinity was the major direct factor determining the composition, diversity and structure of communities, as well as the productivity of ecosystems and their fertility. Aridity has less, more subtle effects, which can only be spatially compared in the least saline habitat between the low and high arid climates.The first experimental study showed that salinity stress (a direct, non-resource factor) induced a facilitation collapse that increased with increasing aridity, both temporally and spatially. The switch to competition in extreme conditions of aridity predicted in the literature was not found. This is very likely due to the weakly competitive strategy of Chamaephytes dominating the most saline habitats. The second experimental study showed that, before the dry summer season, the short-term interactions measured by the experimental method (removal method) were negative whereas the long-term interactions, measured by the combination of the observational and experimental methods were positive, thus, supporting our hypotheses and the literature. However, after the dry summer season, the short-term interactions turned to positive, whereas the long-term interactions collapsed due to vanishing the buffering effect of the vegetated soil on humidity.These results are crucial because they showed that in this arid and saline system, the collapse of facilitation is the major process explaining the structure, diversity and functioning of ecosystems, both along salinity gradients and when water stress increases. On the other hand, the combination of the observational and experimental methods was crucial to show that the increase in facilitation predicted by SGH with increasing water stress is only a response of plants to the increasing negative effect of abiotic environment (environmental-severity effect). This contrasts with the increased competition in unstressed environments and increased facilitation from highly stressed to intermediate environments, both being neighbor-trait effects

The flux of CO2 between the ocean and the atmosphere is an important measure in determining local, global, and regional, as well as short term and long term carbon budgets. In this study, air-sea CO2 fluxes measured using a floating chamber were used to examine the spatial and temporal variability of CO2 fluxes in Florida Bay. Measurements of dissolved inorganic carbon and total alkalinity obtained concurrently with chamber measurements of CO2 flux allowed calculation of ΔpCO2 from flux measurements obtained at zero wind velocity. Floating chamber measurements of ΔpCO2 were subsequently coupled with wind speed data to provide a simple yet reliable means of predicting absolute flux values. Florida Bay is a marine-dominated, sub-tropical estuary located at the southern tip of the Florida peninsula. Spatial variability within the bay reveals four distinct regions that appear to be affected by a variety of physical, chemical and biological processes. In the eastern part of the bay, the waters tend to be oversaturated with respect to CO2, likely due to the input of freshwater from Taylor Slough. The central portion of the bay is characterized by a number of extremely shallow semi-isolated basins with limited exchange with the rest of the bay. This area is typically undersaturated with respect to CO2 and provides a sink for atmospheric CO2. Both the northern and southern regions were highly variable both spatially and temporally.

Le Loup ou Bar Dicentrarchus labrax est une espèce euryhaline dont les femelles pondent généralement en eau de mer. Pendant son cycle de vie, des migrations vers les estuaires et les lagunes, peuvent exposer très tôt les jeunes stades à des variations de salinité. Les mécanismes de l'osmorégulation sont bien connus chez les prélarves, les larves et les adultes de D. labrax en eau de mer (EM, 38) et en eau de mer diluée (EMD, 5), cependant les possibilités d'osmorégulation et leurs mécanismes sont inconnus chez les embryons. Le but de cette étude a été d'évaluer la mise en place de la fonction osmorégulatrice chez les embryons de D. labrax.Tout d'abord le développement embryonnaire des différents sites osmorégulateurs a été décrit, en se focalisant sur le tube digestif, en incluant le pharynx et les premières fentes branchiales. La formation de ces structures débute au stade 12 somites (S) et a été décrite jusqu'à l'ouverture de la bouche, 5 jours après l'éclosion.En second lieu, le lieu et la cinétique d'apparition des premières cellules osmorégulatrices, les « ionocytes » ont été recherchés. Ces cellules ont été identifiées au stade 12S sur la membrane de la vésicule vitelline et au niveau des premières fentes branchiales et du tube digestif primitif au stade 14S. La fonctionnalité de ces cellules a été étudiée grâce à des immunomarquages des principales protéines transmembranaires impliqués dans l'osmorégulation [l'ATPase Na+/K+ (NKA), le cotransporteur Na+/K+/2Cl- (NKCC) et le canal à chlore (CFTR)], et avec une étude ultrastructurale. Des ionocytes potentiellement fonctionnels sont présents à partir du stade 25S au niveau de la membrane de la vésicule vitelline et du tube digestif primitif, mais les ionocytes des premières fentes branchiales ne sont pas totalement fonctionnels à l'éclosion. L'existence d'un phénomène de boisson passive qui permettrait la régulation hydrique chez D. labrax est envisagé.Finalement, l'osmorégulation embryonnaire existant en EM et en EMD a été étudiée. Des mesures nanoosmométriques des fluides embryonnaires indiquent une capacité à hyper- et hypo-osmoréguler. Cependant, en EMD, des analyses en qRT-PCR et des immunomarquages de NKA, NKCC et CFTR révèlent que les mécanismes de l'hyper-osmorégulation peuvent limiter les pertes ioniques mais ne sont pas suffisamment efficaces pour permettre une acclimatation totale à l'EMD à ce stade très précoce
The European sea bass Dicentrarchus labrax is a euryhaline species which usually spawns in seawater. Due to its life cycle that includes migrations to lagoon and estuaries, young stages can be exposed early to salinity variations. Osmoregulatory patterns are well known in prelarvae, larvae and adults D. labrax in seawater (SW, 38) and in dilute seawater (DSW, 5), but the possibility and mechanisms of embryonic osmoregulation are still unknown. The goal of this study was to investigate the occurence of the omoregulatory function in the embryos of D. Labrax.First, the embryonic development of the different osmoregulatory sites was described, focusing on the digestive system including the pharynx and the first gill slits. The formation of these structures is initialized at stage 12 somites (S) and was described throughout the opening of the mouth five days after hatching.Secondarily, the time and the location of the occurrence of the first osmoregulatory cells, the ionocytes were followed. These cells were identified at stage 12S on the yolk sac membrane and at stage 14S in the first gill slits and in the posterior primitive gut. The functionality of these cells was studied, using immunostaining of the main ionic transporters involved in osmoregulation [the Na+/K+ ATPase (NKA), the Na+/K+/2Cl- cotransporter (NKCC) and the chloride channel (CFTR)], and through ultrastructural investigations. Potentially functional ionocytes are present from stage 25S in the yolk sac membrane and in the gut, but gill slits ionocytes are not fully functional at hatching. Passive drinking is suspected to regulate water balance in D. labrax.Finally, the embryonic osmoregulation in SW and DSW was investigated. Nanoosmometry measurements of the embryonic fluids demonstrated some capabilities of hyper- and hypo-osmoregulation. However, in DSW, qRT-PCR and imunostaining of NKA, NKCC and CFTR, reveal that hyper-osmoregulatory mechanisms can only limit ion loss but are not efficient enough to allow a full acclimation at this early life stage

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 thèse est d'analyser la variabilité océanique en température et salinité sur la période 1993-2008. Pour cela, nous utilisons des données in situ de température et de salinité, et des données satellites de température de surface de l'eau et de hauteur de mer. Plusieurs étapes sont indispensables : créer une base de données solide et cohérente, comparer les jeux de données, puis développer des méthodes de combinaison afin d'assembler les jeux de données. L'intercomparaison des jeux de données Altimétrique et Argo permet dans un premier temps de vérifier la qualité du jeu de données Argo. Le jeu de données Argo permet d'améliorer les comparaisons effectuée par Guinehut et al, (2006) sur la comparaison entre les hauteurs de mer altimétriques et hydrologiques. Nous expliquons pourquoi et détaillons les améliorations. Nous étudions également l'impact du retrait du cycle saisonnier et l'influence de la structure verticale de l'océan dans la répartition barotrope/barocline de la circulation. Nous terminons sur l'analyse de la circulation saisonnière et inter-annuelle à 1000 mètres de profondeur. Les champs Armor3d, combinaison de champs satellites et de profils in situ existent depuis plusieurs années. Le récent jeu de données fourni par les flotteurs Argo permet de considérablement améliorer les paramètres de la combinaison, de couvrir une meilleure zone géographique et d'avoir des champs plus profonds. Nous montrons que les deux types de mesures sont indispensables, même pour étudier la variabilité grande échelle de l'océan. Enfin, nous utilisons nos champs Armor3d pour étudier la variabilité océanique des 16 dernières années
The objective of this thesis is to analyze the oceanic variability in temperature and salinity over the period 1993-2008. For that purpose, it is necessary to use the maximum of observations available, namely in situ data of temperature and salinity, but also satellite data of sea surface temperature and sea height. To reach our objective, several steps are necessary: create a solid and coherent database, compare datasets to have a better physical understanding of the contents of every type of data then develop methods of combination to assemble the datasets. The cross-comparison of the altimetric and Argo datasets allows at first to verify the quality of the Argo dataset. In 2006, Guinehut and al published a paper on the comparison of SLA (Sea Level Anomaly) and DHA (Dynamic Height Anomaly). Today, the Argo dataset allows improving the comparisons. We explain why and we detail the differences between both studies. We also study the impact of the removal of the seasonal cycle and the influence of the vertical structure of the ocean in the barotrope / barocline distribution of the oceanic circulation. We end on the analysis of the SLA-DHA signal in term of seasonal and inter-annual circulation at 1000 meters deep. Armor3d Field, combination of satellite fields and in situ profiles exist for several years. The recent dataset supplied by Argo profilers allows improving considerably the parameters of the combination, to cover a better geographical zone and to have deeper fields. We show that both types of measures are needed, even to study the large scale variability of the ocean. Finally, we use our Armor3d fields to study the oceanic variability of the last 16 years

Cette etude a pour objectif de mettre en evidence le role de la circulation oceanique dans les liens climatiques interhemispheriques a partir des archives que sont les sediments marins des oceans austral et indien. Pour cela, j'ai tout d'abord reconstruit les paleoenvironnements marins des 300 derniers ka : les changements de la salinite en surface ont ete estimes a partir de la composition isotopique de l'oxygene des foraminiferes planctoniques n. Pachyderma s. Et g. Bulloides, les variations de la circulation thermohaline a partir de la composition isotopique du carbone du foraminifere benthique c. Wuellerstorfi, enfin, l'existence d'une debacle de la calotte antarctique a ete mis en evidence grace aux comptages des elements d'origine detritique. De plus, une etude micropaleonthologique realisee a l'universite de bordeaux 1 a permis de reconstruire les temperatures de surface. Puis, j'ai etabli une echelle de temps precise de ces enregistrements a partir de dates 1 4c et a partir de la correlation graphique de la composition isotopique de l'oxygene des foraminiferes benthiques avec une courbe de reference. Les resultats montrent l'existence d'au moins deux modes de circulation oceanique : un premier, lors des optima climatiques, est equivalent a celui de la periode actuelle tandis qu'un second, caracterise par un arret de la propagation d'eau profonde originaire de l'atlantique nord au niveau de l'ocean austral, prend place lors des periodes plus froides. Dans le premier mode, la circulation thermohaline peut jouer le role de lien climatique interhemispherique en diminuant les temperatures de l'ocean austral en surface lors d'une baisse de l'intensite de celle-ci. Pour les periodes froides la circulation profonde ne peut etre un lien climatique interhemispherique en particulier car il y a tres peu d'echange entre l'ocean austral et l'eau originaire de l'atlantique nord.

Un bilan minéralogique et géochimique des sédiments du Site ODP 659 a permis d’établir un nouveau modèle de dépôt des sédiments au niveau du plateau du Cap Vert qui constitue une zone clé dans la restitution des apports éoliens à l’Atlantique depuis le continent africain. Nous avons apporté des contraintes supplémentaires sur les zones d’alimentation et les voies de transport du matériel sédimentaire au plateau du Cap Vert et montré un lien étroit entre la sédimentation de cette zone et les changements de la mousson Nord africaine. Nous avons ainsi établi de nouveaux traceurs minéralogiques et géochimiques des changements passés de la mousson africaine. Outre un contrôle très étroit de la mousson africaine par l’insolation reçue par la Terre aux basses latitudes, nous avons mis en évidence l’existence de changements du régime de la mousson qui échappe à tout contrôle orbital. Ceux-ci semblent liés aux changements paléogéographiques du domaine méditerranéen en liaison avec l’assèchement progressif et la remise en eau du bassin de la Méditerranée lors des évènements majeurs de la crise de salinité messinienne. Les isotopes stables de l’oxygène et du carbone des foraminifères benthiques Cibicides wuellerstorfi ont également permis de restituer, sur une échelle d’âge orbitale, les variations de l’hydrologie profonde en Atlantique ainsi que les variations du niveau marin. Plus particulièrement, nous avons confirmé que la fermeture des ponts océaniques entre la Méditerranéen et l’Atlantique au cours de la crise de salinité messinienne n’est pas contrôlée par les variations du niveau marin mais bien par la tectonique
Mineralogical and geochimical results on sediments of Site ODP 659 permitted to establish a new model of sediment deposit in Cap Verde rise which constitute a key area on restitution of eolian input from Africa to Atlantic Ocean. We brought additional constraints on feeding zones and detritals inputs of the sedimentary material to the Cap Verde rise and shown a close link between the sedimentation of this zone and the variations of African Northern monsoon. We thus established new mineralogical and geochemical tracers of the last changes of African monsoon. In addition to a very narrow control of African monsoon by the insolation received by the Earth at the low latitudes, we highlighted the existence of changes in the monsoon which escapes of orbital control. Those seem related to the palaeogeographic changes of the Mediterranean field in connection with the progressive draining and drought of the Mediterranean Sea at the time of the major events of the messinian salinity crisis. On an orbital timescale, study of oxygen and carbon stable isotopes obtained on benthic Foraminifera Cibicides wuellerstorfi permit to reconstruct the variations of major hydrology in the Atlantic as well as the variations of world sea level. More particularly, we confirmed that the closing of the oceanic bridges between the Mediterranean Sea and the Atlantic Ocean during the messinian salinity crisis are not controlled by the variations of the sea level but well by tectonic movements

Le metabolisme energetique a ete etudie chez les juveniles de saumon atlantique (parrs et smolts), simultanement en conditions de metabolisme standard et de routine. Les modifications qui surviennent au cours de la smoltification ont ete interpretees en fonction des variations du facteur thermique (isoenzymes) et des facteurs endocriniens qui sous-tendent ce processus. L'action stimulante majeure du metabolisme energetique apparait resulter d'une potentialisation de l'effet de l'hormone de croissance par la triiodothyronine. Il a pu etre etabli que les modifications du metabolisme standard, consecutives a des transferts d'eau douce en eau de mer, etaient differentes selon le niveau d'adaptation au milieu marin acquis par les smolts: diminution chez les presmolts, amplification au terme de la smoltification. Ces effets resultent essentiellement des modifications du metabolisme intermediaire induites par l'augmentation de salinite ambiante. De plus, le surcout energetique de l'osmoregulation serait plus faible que ce qui etait admis jusqu'alors. Parallelement, a ete mise en evidence une diminution du metabolisme de routine, interpretable comme une adaptation comportementale a une limitation des possibilites d'approvisionnement tissulaire en oxygene. Chez le saumon adulte, le transfert inverse d'eau de mer en eau douce induit une diminution du metabolisme energetique, une augmentation de la capacite de diffusion gazeuse des branchies, ainsi que des modifications des concentrations ioniques plasmatiques entrainant une alcalose du compartiment extracellulaire et une augmentation de l'affinite de l'hemoglobine pour l'oxygene. Ces effets pourraient constituer des processus adaptatifs pour la migration anadrome

L'action de modifications experimentales progressives ou brutales, separees ou conjointes de la salinite et de la temperature du milieu aquatique sur le metabolisme hydro-mineral du milieu interieur et erythrocytaire est effectue par des mesures de la pression osmotique de l'hematocrite et de principaux ions inorganiques (na**(+),k**(+),cl)

碩士
國立中興大學
植物學系
88
Zoysia spp., a perennial C4 grass with longer stolon shorter culm, is a very good stuff. It distribute in littoral regions of Taiwan, and can adapt to saline environment. Ramets colonizing distribution rely upon physiological integration with connected parent ramets to overcome salt stress associated with hypersaline environments. Under saline environment, Zoysia spp. not only challenge to the ionic toxicities, but also adapted to the osmotic stress which was caused by the high concentration of salt ions. The salt stress can lead to the reduce of the water potential, ralative water contents and chlorophyll of leaves. Under salt stress, the cell membrance was damaged by the accumulation of ions and increased the eletrolyte laekage. Physiological integration of connected ramets facilitates water movement in the stolon, which may moderate the effects of salt stress on ramet water potential, related water contents, eletrolyte leakage and carotenoid. These connections provide the potential for water sharing among ramets, which in turn can promote survuval in hypersaline environments. For Zoysia spp., the effect of osmotic stress is more earnest than ionic stress. The genetic relationship among Zoysia spp. cultivars were estimated using RAPD ( Random amplified polymorphic DNA ) analysis. All of the analyzed samples were classified to the populations based on similarity, geography and morphological characters (spike length). Base on the similarity, AMOVA analysis on RAPD data revealed that, of the total variation of the taxon, 29.49% was attributable to population differences and 62.27% to individual differences within population. The among population variance component was shown to be highly significant (p< 0.001) . It indicated that Zoysia spp. had genetic divergence among populations. The distribution of Zoysia spp is related with the normal annual total precipitation. It indicated that the distribution of populations is correlated with environmental osmotic stress.

Salinity is a major concern in agriculture since it adversely affects plant growth, development, and yield. Domestication of crops exerted strong selective pressure and reduced their genetic diversity. Meanwhile, wild species continued to adapt to their environment becoming valuable sources of genetic variation, with the potential for enhancing modern crops performance in today’s changing climate. Some wild species are found in highly saline environments; remarkable examples are the endemic wild tomatoes from the Galapagos Islands, forming the Solanum cheesmaniae and Solanum galapagense species (hereafter termed Galapagos tomatoes). These wild tomatoes adapted to thrive in the coastal regions of the Galapagos Islands. The present work includes a thorough characterization of a collection of 67 accessions of Galapagos tomatoes obtained from the Tomato Genetics Resource Center (TGRC). Genotyping-by-sequencing (GBS) was performed to establish the population structure and genetic distance within the germplasm collection. Both species were genetically differentiated, and a substructure was found in S. cheesmaniae dividing the accessions in two groups based on their origin: eastern and western islands. Phenotypic studies were performed at the seedling stage, subjecting seedlings to 200 mM NaCl for 10 days. Various traits were recorded and analysed for their contribution to salinity tolerance, compared to control conditions. Large natural variation was found across the collection in terms of salt stress responses and different possible salt tolerant mechanisms were identified. Six accessions were selected for further work, based on their good performance under salinity. This experiment included scoring several plant growth and yield-related traits, as well as RNA sequencing (RNAseq) at the fruit-ripening stage, under three different NaCl concentrations. Accession LA0421 showed an increased yield of almost 50% in mild salinity (150 mM NaCl) compared to control conditions. The transcriptome data obtained could reveal the genes involved in the salt stress-related yield increase. The knowledge obtained so far will be useful for scientists and breeders to select accessions of interest based on recorded traits. It will allow the use of Galapagos tomatoes as genetic sources for salinity tolerance traits in commercial tomatoes, thereby contributing to feed and nourish the growing human population in the years to come.

It was observed over several years of monitoring Landcare plantings that a number of locally-occurring native species showed variation in seedling establishment, particularly on degraded soils in the Upper Shoalhaven Catchment, a region of extreme frost. The variation appeared to be linked to different seed source locations. The question arose of whether habitat adaptation was occurring and, if it was leading to biodiversity within local species. This was key information needed for seed source selection in rehabilitation projects, for degraded soils on the Southern Tablelands of NSW. The primary aim of this research project was to investigate whether or not habitat differences in parent trees could be linked to measurable differences in the waterlogging and salinity tolerances of their progeny. The germination experiment was proposed as a method for investigating variation within local species, measuring germination rates under six different treatments of salinity and waterlogging. Populations of ten native tree and shrub species were selected for trial and seed was sourced from seven different habitat types in the Upper Shoalhaven Catchment and neighbouring areas, within a 100km radius of Braidwood, NSW. Glasshouse experiments were conducted over a six week period, from November to December. Experiments included a saline treatment with addition of a biofertiliser called 'PuraCast', a microbiologically active liquid, derived from worm castings. Species investigated were: Eucalyptus ovata, E.pauciflora, E.dives, E.blakelyi, E.aggregata, Acacia melanoxylon, A.decurrens, Casuarina littoralis, C.stricta, Leptospermum flavescens. There was a highly significant difference found between parent tree habitat and the germination response of progeny, particularly to treatments of medium salinity, waterlogging and waterlogging with salinity (P<0.001 in most cases). There was a moderately significant interaction between treatment and parent habitat type, with highly saline habitats, waterlogged and acidic soils producing seedlings tolerant of high salinity and combination treatments (P<0.05). Response to the biofertiliser was varied and further research is warranted for all of the above.

碩士
國立澎湖科技大學
水產養殖系水產資源與養殖碩士班
106
The coverage of seagrass Halophilaovalis in Citou Bay is the highest of all the seagrass meadows in Penghu. It has high ecological importance because there are abundant species of creatures. However, the distribution of the seagrass meadow is shrinking because of the influence of human disturbance and environmental changing. In this study, it revealed that the coverage dropped twice in a year, during July to August and December to February. The third pair of leaves was obviously smaller during the high-water temperature period of July to August. There were two peaks of biomass, rhizome length, and leaf amount during April to July and November to January; moreover, blooming and fruiting periods appeared as well. The ratio of shoot system to root system were 0.49±0.11. There were four undulations of the curve showed that it has a short life cycle and rapid growing speed. The length of rhizome grew longer during October to January for anchoring in the monsoon season. There was the best growth rate under the salinity of 25 and 35ppt and the temperature of 30℃. After germinating, the cotyledon extended and radicle stretched, and then the first to the fifth leaf and the first pair of buds grew consecutively. Low salinity would not only promote the germination rate but also shorten the time frame of germination. There was no statistical significant difference of germinate rate between the group with and without artificial light. However, the average germination days of the group without artificial light was obviously shorter than the other. Providing light to the young seedlings would be helpful on growing more leaves. Considering the growth of young seedlings, the best germination condition would be under the salinity of 10ppt with light, although the best germination index was the condition under the salinity of 5ppt without light. Therefore, the best preservation condition for seagrass seeds was 10℃ and 35ppt. Keywords: Halophila ovalis, biomass, germination

This study has several objectives. Firstly, to investigate the sexual reproductive ecology and germination requirements of Bolboschoenus caldwellii and Bolboschoenus medianus. Secondly, to examine the asexual growth mechanisms and responses of Bolboschoenus caldwellii and Bolboschoenus medianus to interesting salinity. Thirdly, to assess the genetic diversity of Bolboschoenus caldwellii and Bolboschoenus medianus stands from three wetlands with contrasting environmental conditions in the Gippsland Lakes region.

博士
大同大學
資訊工程學系(所)
96
Global ocean salinity and temperature variations are attracting increasing attention, due to its influence on global climate change. This research presents an efficient technique for analyzing Argo ocean data comprising time series of salinity and temperature measurements where informative salinity and temperature patterns are extracted. Most traditional mining techniques focus on finding associations among items within one transaction and are therefore unable to discover rich contextual patterns related to location and time. In order to show the associated salinity and temperature variations among different locations and time intervals, for example, “if the salinity rose from 0.15psu to 0.25psu in the area that is in the east-northeast direction and is near Taiwan, then the temperature will rise from 0℃ to 1.2℃ in the area that is in the east-northeast direction and is far away from Taiwan next month”, the research designs a transformation method to convert Argo spatial-temporal data to market-basket type data and then a quantitative inter-transaction association rules mining algorithm is proposed to apply to the transformed data set to get salinity and temperature variation patterns. The FITI and the PrefixSpan algorithms are adopted to maximize the mining efficiency. Next, a fuzzy inference model that employs the discovered salinity and temperature patterns as its rule base is designed to predict salinity and temperature variations. The strategy is applied to ocean salinity and temperature measurements obtained from the waters surrounding Taiwan. These experimental evaluations show that the proposed algorithm achieves better performance than other inter-transaction association rule mining algorithms.

碩士
大同大學
資訊工程學系(所)
96
The domain experts find that ocean salinity and temperature play an important role in global climate changes. Global ocean salinity and temperature abnormal variations attract researchers to find interesting patterns. Data mining strategy is used to discover association rules from Argo ocean salinity and temperature variations. In the past, the association rules are only described in rule forms. A visualization system is constructed to help users observe the association rules and their variations. In our research, the ocean salinity and temperature variation data along the Taiwan coast were analyzed. Traditional mining techniques focus on finding associations among items within one transaction. They are unable to discover rich contextual patterns related to location and time. FITI algorithm is used to find the association rules. The quantitative inter-transaction association rules mining algorithm is proposed to find the salinity and temperature abnormal variation patterns from the transformed data set. Example from the discovered association rules looks like, “If the salinity near the northern Taiwan rose 0.1psu to 0.2psu, then the temperature near the northeast Taiwan will rise from 0℃ to 0.8℃ in the next month.” This study focuses on ocean salinity and temperature variations obtained from the waters surrounding Taiwan. A visualization system is constructed for users to easily understand inter-transaction association rules from ocean salinity and temperature variations.

Tese de doutoramento em Biociências, na especialidade de Ecologia Marinha, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
The human species is responsible for changes in the environment since its appearance. The rate of those changes increased as civilizational advances required progressively more resources, which led to the globalization of pressures and impacts on biosphere and the planet. Among those global trends, we may find global warming and the increase in the number of extreme climatic events. These are responsible for a decline in biodiversity. Global changes are threatening biodiversity-based stability, with highly unpredictable outcomes. Current changes have a global manifestation, but its effects should be studied locally, where they may be more notorious. Anthropogenic pressures are felt across all ecosystems, and estuarine systems are no exception. Estuaries are under large cyclic environmental parameters oscillations, beside strong gradients from freshwater to marine conditions, shaping communities within estuaries. Nevertheless, estuaries are responsible for a large amount of biological processes and functions that are fundamental for human populations. Due to the cyclic environmental conditions of estuaries, the effects of global changes may be concealed. However, some of the global changes’ effects are already noticeable, such as declines in biodiversity. The biodiversity reduction due to anthropogenic pressures is impairing ecosystem stability and functioning. As such, the Biodiversity-Ecosystem Functioning is one of the most important debates in Ecology and more recently in Marine Ecology. Ecosystem processes and functions are influenced by biodiversity modifications induced by global changes, affecting ecosystem stability. The analysis of natural processes such as bioturbation allows us a better knowledge on the relationships between biodiversity and ecosystem functioning. One of the most recognized sources of biodiversity reduction is the transport and introduction of non-native species, with invasive potential, and which effects are enhanced by the interactions with other global changes pressures. Estuaries are often close to large human settlements and are areas where several activities linked with biological invasion are carried out, thus becoming highly susceptible areas to the introduction of non-native invasive species. The bivalve Corbicula fluminea is one of the most invasive freshwater organisms and is able to invade the oligohaline sections of estuaries. The species, with its origin in Southeast Asia, has currently an almost global distribution. In order to understand how global changes interact with biodiversity shifts and how these impair estuarine ecosystems’ functioning, we tried to assess which ecosystem functions are affected by the introduction of non-native species and by global climatic changes. The chapter I describes the paths of the invasion and worldwide dispersion of C. fluminea, as well as the chronology of the invasion, based in scientific literature and public reports. Some biogeographic tendencies were observed. The species is limited by altitude and low winter temperature. Nevertheless, global warming and local changes events may be responsible for an increase in the current range of the species. Chapter II describes a field experience where the survival ability of C. fluminea along the gradient of the Mondego river estuary was tested. The current limits of the species in this system were defined, as well as its population structure along the estuarine gradient. Simultaneously the estuarine resistance to the invasion by C. fluminea was evaluated. In the winter there were almost no mortality among C. fluminea, while in summer we found a LT50 (median lethal time) of 9 days in the most downstream site. 100% mortality was never achieved during the testing period, adding concern to the species invasion potential in estuarine systems. Chapter III complements the information of the former chapter, as it allowed the assessment of C. fluminea’s contribution to the ecosystem processes (bioturbation) and functions (nutrients release). The interaction of temperature increase and salinity variation, as consequence of climate change, with the C. fluminea individuals’ size/age, was tested. Bioturbation was mostly influenced by size, and less by temperature and salinity, while the nutrients in the water column were influenced by different interactions among the studied variables. This chapter showed that invasion consequences are context dependent. Also, the potential for the invasive species to simultaneously occupy multiple components of a system was highlighted. The chapter IV describes the results of a field experiment where the effects of a mild temperature rise on the estuarine benthic communities in a seagrass bed and a sandflat were tested. This temperature increase was within the values declared as acceptable by recent international agreements. Different habitats responded differentially with the warmness, as the seagrass bed showed some temperature buffering ability. The seagrass bed offered thermal protection, ensuring higher stability when facing external disturbances. However, the effect of the habitat itself on the benthic communities was greater than the effect of the temperature increase. Once again we verified that context defines local ecological responses to global changes. The Mondego estuary has been a proficient data source on anthropogenic disturbances for nearly three decades, supported by a substantial scientific literature. This database allow us to clarify the ecological mechanisms underlying the effects of anthropogenic induced changes in Biodiversity-Ecosystem Functioning relationships in estuaries.
A espécie humana tem sido responsável, desde o seu surgimento, por alterações ambientais. À medida que os avanços civilizacionais exigiram uma maior utilização de recursos, globalizaram-se um conjunto considerável de pressões sobre a biosfera e o planeta, entre as quais encontramos o aquecimento global e o aumento do número de eventos climáticos extremos, contribuindo para uma redução na biodiversidade. A estabilidade garantida pela biodiversidade encontra-se ameaçada sob o efeito das alterações globais, cujas consequências apresentam um elevada imprevisibilidade. Além de estas alterações se manifestarem globalmente, é a nível local que os seus efeitos são detetados de forma mais óbvia. As pressões antropogénicas fazem-se sentir em todos os ecossistemas, e os sistemas estuarinos não são exceção. Os estuários encontram-se sujeitos a grandes variações cíclicas nos seus parâmetros físico-químicos e fortes gradientes entre água doce e marinha, condicionando as suas comunidades biológicas. No entanto, os estuários são responsáveis por um grande número de processos e funções biológicas, importantes para as populações humanas. A natureza cíclica dos estuários pode mascarar os efeitos das alterações globais, apesar de serem já discerníveis algumas das suas consequências. Um dos efeitos mais prementes das pressões antropogénicas prende-se com a redução da biodiversidade, pondo em causa a estabilidade e funcionamento dos ecossistemas. Assim a Biodiversidade e Funcionamento do Ecossistema destaca-se como um dos mais importantes debates em Ecologia, e mais recentemente na área da Ecologia Marinha. As alterações na biodiversidade como consequência das alterações globais influenciam processos e funções do ecossistema e põem em causa a sua estabilidade. A avaliação de processos naturais como a bioturbação permite-nos perceber melhor as relações entre a biodiversidade e o funcionamento do ecossistema. Uma das principais causas reconhecidas para a redução global da biodiversidade é a introdução de espécies não-nativas, potencialmente invasoras, cujos efeitos são magnificados pelas interações com outras alterações globais. Os estuários são particularmente suscetíveis, pela sua proximidade às populações humanas, sendo áreas onde são realizadas inúmeras atividades responsáveis pela introdução de espécies invasoras. O bivalve Corbicula fluminea é um dos principais invasores em água doce, podendo invadir as áreas oligohalinas dos estuários. Originária do Sudeste Asiático, a espécie tem atualmente uma distribuição quase global. Na presente dissertação, procurou-se responder às questões sobre que funções do ecossistema são mais afetadas pela introdução de espécies invasoras e como as funções são alteradas num cenário de alterações climáticas. No capítulo I traçaram-se as vias pelo qual a C. fluminea se dispersou globalmente, bem como a cronologia dessa invasão, baseando-se em literatura científica e relatórios técnicos. Observaram-se algumas tendências biogeográficas. A espécie encontra-se limitada entre pela altitude e baixas temperaturas invernais. No entanto, o aquecimento global e modificações a nível local poderão ser responsáveis pelo alargamento da área invadida. O capítulo II descreve uma experiência de campo onde se determinou a capacidade de sobrevivência da espécie C. fluminea ao longo do gradiente do estuário do rio Mondego. Definiram-se os limites atuais da espécie e a sua estrutura populacional neste sistema. Além disso, avaliou-se de que forma o gradiente estuarino limita a invasão da C. fluminea. Durante o inverno praticamente não houve mortalidade, enquanto no verão se verificaram valores de LT50 (tempo letal mediano) de 9 dias para o local mais a jusante. Em nenhuma das condições experimentais se verificou 100% mortalidade, aumentando a preocupação em relação à espécie, enquanto invasora de sistemas estuarinos. O capítulo III permitiu quantificar a contribuição da espécie para os processos (bioturbação) e funções (libertação de nutrientes) do ecossistema, com base numa experiência laboratorial. Testou-se a interação de variáveis que refletem alterações climáticas (temperatura e salinidade) com o tamanho/idade de indivíduos de C. fluminea. Os valores de bioturbação foram influenciados pelo tamanho dos indivíduos, sendo que a temperatura e salinidade tiveram uma influência menor. A concentração de nutrientes na coluna de água foi influenciada por diferentes interações entre as variáveis em estudo. Demonstrou-se que as consequências das invasões dependem do contexto em que ocorrem. Foi ainda destacado o potencial da espécie para ocupar simultaneamente diferentes componentes de um sistema. No capítulo IV testaram-se os efeitos de uma ligeira elevação de temperatura sobre as comunidades bentónicas estuarinas dos bancos de macrófitas e de zona arenosa. O ligeiro aumento da temperatura corresponde ao, preconizado como objetivo global segundo recentes acordos internacionais. Os dois habitats responderam diferencialmente a este incremento de temperatura, pois os bancos de macrófitas apresentaram uma proteção térmica garantindo assim uma maior estabilidade contra perturbações externas. O efeito do tipo de habitat foi mais significativo sobre as comunidades estudadas do que o aumento de temperatura. Mais uma vez se verificou que o contexto condiciona as repostas ecológicas locais às alterações globais. O estuário do Mondego tem sido uma profícua fonte de dados sobre perturbações antropogénicas, suportada numa substancial literatura científica. Esta base de dados permitiu-nos clarificar alguns dos mecanismos subjacentes aos efeitos das alterações antropogénicas nas relações entre a Biodiversidade e Funcionamento do Ecossistema em estuários.
POPH - Human Potential Operational Programme
QREN (National Strategic Reference Framework)
COMPETE (Programa Operacional Factores de Competitividade)

According to recent reports, increases in water acidification and changes in seawater salinity are predicted to occur in the next 100 years. The increase of atmospheric CO2 already caused a pH reduction in surface waters by more than 0.1 units below the pre-industrial average of 8.1, and it is expected to decrease between -0.13 and -0.43 units by the end of this century. Climate change can also occur through alterations in seawater salinity. Warmer temperatures and reduced rainfall increase seawater salinity, while extreme rainy events decrease seawater salinity. Both situations will promote species responses. Therefore, identifying the effects of predicted climate change in aquatic ecosystems must be a priority in order to maintain their biodiversity. Aside from climate change, there is an increasing concern about the large number of emerging pollutants that have been released into the environment without yet being regulated. Among these emerging pollutants are Engineered nanoparticles (ENPs). One of the types of ENPs that are most commonly used in recent years are Carbon Nanotubes (CNTs). Due to their unique chemical and nanotoxicological properties, it is expected that CNTs enter aquatic environments and accumulate in aquatic biota. As a matter of fact, CNTs toxicology in aquatic systems is complex. In the first instance particle size, shape, chemistry and capping agents will all play a role regarding the stability, and thus bioavailability. However, nanomaterial toxicity not only has been attributed to core structure and surface modification/functionalization, but also by the physico-chemical parameters of the media where the CNTs are presented, altering their dispersion and consequently their detection: aggregation/disaggregation, adsorption/desorption, sedimentation/resuspension and dissolution. Several works have described their impacts in the aquatic environment; however, no information is known on how predicted Climate Change could alter the CNT’s toxicity and their effects on marine organisms. Benthic species are a good model to evaluate the impacts of Climate Change and ENPs as they are sensitive to several environmental constrains. Essentially due to their life-history characteristics, as well as their relatively rapid response to pollution, several studies have been using benthic species as bioindicators for anthropogenic and natural stresses. Thus, the evaluation of the impacts of CNTs, under salinity changes and pH reduction on aquatic organisms is an urgent issue needing attention. Particularly, Ruditapes philippinarum (bivalve), Hediste diversicolor and Diopatra neapolitana (polychaetes) have been identified by several authors as a group of marine invertebrates that respond quickly to environmental disturbances, with a wide spatial distribution and economic relevance, namely in Portugal. Thus, the present proposal evaluated the toxic effects in terms of biochemical (energy reserves and metabolic activity, oxidative and neuro status) and physiological responses (regenerative capacity) in the cited species of salinity shifts and pH variation and the presence of CNTs acting along and in combinations. The two CNT materials selected in the present study were the pristine multi walled carbon nanotubes (Nf-MWCNTs) and the chemically functionalized MWCNTs, by introducing polar groups such as carboxyl groups (-COOH) increasing their stability and dispersibility in the water media. As a starting point we evaluated the possible effects of the carboxylation/functionalization of the surface of MWCNTs in organisms for each exposure concentration. In all invertebrate species it was possible to observe a dose-dependent increased of the toxicity, especially in terms of oxidative status, which is in line with the information provided by the literature. Moreover, comparing the toxic effects of both CNTs, in all invertebrate species major cellular damage was induced by carboxylated forms of MWCNTs in comparison to the pristine one. Subsequently we selected the two most deleterious concentrations of Nf-MWCNTs and f-MWCNTs, and we exposed the three invertebrate species to the combination of CNT materials with salinity shifts and pH variations assessing if both climate change factors altered the toxicity of both MWCNT materials as well as the sensitivity of all these species exposed to these contaminates. The present findings underlined that Nf-MWCNTs and f-MWCNTs under control salinity and low pH generated major toxic impacts in the organisms compared to individuals maintained under low salinity and control pH, confirming that salinity shifts and pH variations may alter the chemical behaviour of both MWCNTs and consequent fate in exposed individuals. Moreover, we observed species-dependent sensitivity to contaminants confirming that the higher susceptibility observed in some species would however be expected not only to depend on the characteristics of the compounds, but also on the physiology of that particular species. For a better environment protection, the Ecological Risk Assessment of the mentioned stressors must include ecologically relevant endpoints and exposure scenarios to drive accurate safety levels towards biodiversity conservation.
De acordo com publicações recentes, nos próximos 100 anos prevê-se um aumento na acidificação da água do mar e alterações na sua salinidade. Nas águas superficiais, o aumento do CO2 atmosférico já causou uma diminuição do pH em mais de 0,1 unidades comparando com 8,1, a média referente à época pré-industrial. Está previsto que até ao final deste século, esta redução do pH possa atingir valores na ordem das 0,13 e 0,43 unidades. As alterações climáticas podem também resultar em alterações na salinidade da água do mar. A salinidade é mais alta quando as temperaturas são mais altas e os períodos de chuva são reduzidos enquanto que, eventos de chuva intensa diminuem a salinidade da água do mar. Em qualquer dos cenários, estas alterações irão promover respostas por parte das espécies. Portanto, é imperativo identificar os efeitos das alterações climáticas nos ecossistemas aquáticos de modo a conservar a sua biodiversidade. Para além das alterações climáticas, há uma preocupação crescente com o grande número de poluentes emergentes que têm sido descartados no meio ambiente sem serem devidamente regulamentados. Entre estes poluentes emergentes estão as nanopartículas artificiais (Engineered nanoparticles - ENPs). Um dos tipos de ENPs mais usados nos últimos anos são os Nanotubos de Carbono (Carbon nanotubes - CNTs). Devido às suas propriedades químicas e nano-toxicológicas únicas, é expectável que os CNTs entrem nos ambientes aquáticos e se acumulem na fauna que lá vive. De facto, a toxicologia dos CNTs em sistemas aquáticos é complexa. Numa primeira análise, o tamanho, a forma, a estrutura química e os agentes de revestimento desempenharão um papel no que diz respeito à estabilidade e, portanto, à biodisponibilidade da partícula. No entanto, a toxicidade dos nano-materiais tem sido atribuída não só à sua estrutura central e modificação/funcionalização da sua superfície, mas também aos parâmetros físico-químicos do meio em que os nanotubos se apresentam e que podem alterar a sua dispersão e consequentemente a sua deteção: agregação/desagregação, adsorção/dessorção, sedimentação/ressuspensão e dissolução. O impacto dos nanotubos no meio aquático já foi descrito por vários autores; no entanto, ainda não se sabe de que forma as alterações climáticas podem alterar a toxicidade dos CNTs e subsequentemente os efeitos sobre os organismos marinhos. As espécies bentónicas são um bom modelo para avaliar os impactos das Alterações Climáticas e ENPs, uma vez que são sensíveis às mudanças ambientais. Principalmente devido às características do seu ciclo de vida, bem como à sua resposta relativamente rápida à poluição, há vários estudos que usam espécies bentónicas como bioindicadores para fatores de stress antropogénicos e naturais. Sendo assim, é urgente avaliar os impactos dos CNTs, sob alterações de salinidade e redução do pH em organismos aquáticos. Ruditapes philippinarum (bivalve), Hediste diversicolor e Diopatra neapolitana (poliquetas) são invertebrados marinhos que respondem rapidamente a perturbações ambientais e são caracterizados por uma ampla distribuição espacial e relevância económica, nomeadamente em Portugal. Pelo que, esta tese pretendeu avaliar os efeitos tóxicos de desvios de salinidade, variação de pH e presença de CNTs (atuando isolados ou em combinação) ao nível da resposta bioquímica (reservas de energia e atividade metabólica, estado oxidativo e neurotoxicidade) e da resposta fisiológica (capacidade regenerativa) das espécies acima citadas. Neste estudo, os dois materiais de CNT selecionados foram os nanotubos de carbono de parede múltipla, não funcionalizados (pristine multi walled carbon nanotubes - Nf-MWCNTs) e os MWCNTs quimicamente funcionalizados através da introdução de grupos polares como grupos carboxilo (-COOH), que aumentam sua estabilidade e capacidade de dispersão no meio aquoso. Como ponto de partida, para cada concentração de exposição, avaliamos os possíveis efeitos da carboxilação/funcionalização da superfície dos MWCNTs nos organismos. Em todas as espécies de invertebrados foi possível observar uma relação positiva entre o aumento da dose e a toxicidade, principalmente no que diz respeito ao estado oxidativo, o que está de acordo com a informação disponível na literatura. Além disso, comparando os efeitos tóxicos de ambos os CNTs, em todas as espécies de invertebrados, verificaram-se maior dano celular induzido pela forma carboxilada da MWCNT em comparação com a forma não funcionalizada. Posteriormente, selecionamos as duas concentrações de Nf-MWCNTs e f-MWCNTs mais perniciosas, e expusemos as três espécies de invertebrados à combinação destes materiais CNT com variações de salinidade e variações de pH, avaliando desta forma se estes fatores relacionados com as alterações climáticas modificavam a toxicidade de ambos os materiais MWCNT bem como a sensibilidade das espécies expostas a esses contaminantes. Os resultados obtidos salientam que Nf-MWCNTs e f-MWCNTs sob salinidade controlo e pH baixo, geraram grandes impactos tóxicos nos organismos em comparação com indivíduos mantidos em condições de salinidade baixa e pH controlo. Confirmou-se desta forma que, alterações de salinidade e variações de pH podem alterar o comportamento químico de ambos os MWCNTs e consequentemente o efeito em indivíduos expostos. Além disso, observamos que a sensibilidade ao contaminante é dependente da espécie o que confirma que a maior suscetibilidade observada em algumas espécies não é apenas um resultado das diferentes características dos compostos usados, mas também da fisiologia dessas espécies em particular. Para uma melhor proteção do meio ambiente, a Avaliação de Risco Ecológico dos fatores de stress mencionados, deve incluir objetivos e cenários de exposição ecologicamente relevantes para impulsionar medidas de segurança corretas e adaptadas com respeito à conservação da biodiversidade.
Programa Doutoral em Biologia e Ecologia das Alterações Globais