Дисертації з теми "Microphytobentho"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Microphytobentho".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
Coelho, Helena Isabel Soares Dinis. "Microphytobenthos vs Hydrobia: trophic coupling in estuarine environment." Doctoral thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/3632.
Повний текст джерелаOs estuários são ambientes complexos, biologicamente diversos e muito importantes no que respeita à produtividade primária. As zonas intertidais destes ecossistemas são ocupadas por organismos que possuem uma elevada capacidade de sobrevivência e adaptação face às variadas e rápidas alterações nos factores ambientais (tais como temperatura, salinidade, conteúdo hídrico, etc.). As cadeias tróficas com origem no ecossistema estuarino bentónico são essencialmente herbívoras, regulando o fluxo de energia desde o fundo sedimentar e através do ecossistema. Nas áreas estuarinas intertidais a produção primária é essencialmente suportada pelo microfitobentos (MPB). Estas comunidades de microalgas bênticas constituem uma importante fonte de matéria orgânica e são por si só a principal fonte alimentar para as populações de Hydrobia. Neste contexto, a interacção MPB - Hydrobia é um modelo-chave na investigação da cadeia trófica estuarina de origem bentónica, actuando como um importante canal de transporte de energia para os níveis tróficos superiores, especialmente se considerarmos que Hydrobia é uma importante presa para peixes, aves e caranguejos. O presente estudo tem por objectivos gerais: i) a investigação do controlo ambiental (particularmente da luz e do teor em água do sedimento) e endógeno na migração vertical do MPB e ii) a identificação e potencial utilização de marcadores tróficos (pigmentos e ácidos gordos) úteis à investigação da interacção MPB – Hydrobia em laboratório e em condições naturais, considerando a existência de uma elevada plasticidade trófica por parte da Hydrobia e a elevada densidade populacional que estes organismos podem apresentar. A primeira fase de investigação resultou na comparação do papel dos estímulos ambientais e do controlo endógeno nos padrões de comportamento migratório vertical do microfitobentos, demonstrando a existência de um controlo essencialmente endógeno na formação e desintegração do biofilme superficial. A regulação e manutenção da biomassa à superfície do sedimento são claramente controladas pela variação dos factores ambientais, em especial da luz, cuja presença é essencial à formação total do biofilme microalgal à superfície do sedimento intertidal. Foi proposta uma nova abordagem metodológica com vista à estimativa nãodestrutiva do teor de água de sedimentos intertidais vasosos , possibilitando o estudo da influência da acção do vento no conteúdo hídrico dos sedimentos e o consequente impacto da dessecação na comunidade microfitobêntica. Observou-se que a dessecação provoca efeitos limitantes não só na biomassa superficial mas também na actividade fotossintética dos biofilmes microfitobênticos, conduzindo à diminuição da produtividade primária. No que respeita à dinâmica trófica da interacção MPB - Hydrobia foi estabelecido o uso do pigmento feoforbide a, quantificado nas partículas fecais da fauna, como marcador trófico que permite estimar a quantidade de biomassa de microalgas (clorofila a) incorporada pelos organismos animais.Para tal foi investigada e comprovada a existência de uma relação significativa entre a concentração de feopigmentos excretados e a concentração de clorofila a ingerida. Estes estudos foram desenvolvidos numa primeira fase à escala diária, considerando os efeitos dos ciclos sazonais, dia-noite e maré, e depois com a validação em condições naturais, numa escala mensal. A taxa de ingestão média de indivíduos de H. ulvae varia ao longo do dia, com o máximo em torno dos períodos diurnos de maré baixa, o que pode estar relacionado com a disponibilidade de MPB. As taxas de ingestão (TI) de H. ulvae variam ainda em função da estação do ano (TI verão > TI primavera) e em função da densidade de indivíduos (> densidade, < ingestão). Verificou-se um efeito negativo na concentração de clorofila disponível após herbívoria independentemente da densidade de indivíduos. Finalmente, a comparação dos perfis de ácidos gordos de H. ulvae provenientes de diferentes habitats com os perfis de potenciais fontes alimentares permitiu demonstrar que os ácidos gordos são ferramentas úteis na identificação do habitat ocupado por estes organismos. No entanto, apesar da ocupação de diferentes habitats e da integração de múltiplas fontes de produção primária na sua dieta foram sempre observados significativos níveis de ácidos gordos específicos de microalgas (em particular diatomáceas), reforçando o papel importante das comunidades de microalgas bênticas na dieta das populações de H. ulvae.
Estuaries are biologically diverse and form complex environments, which play an important role on the global primary productivity of aquatic environments. Intertidal areas of estuaries are inhabited by organisms with a strikingly capability to survive and to be adapted to frequent and fast changes in several environmental factors (such as temperature, salinity, water content, etc.). Grazing food chains are common in intertidal mudflats regulating the flow of nutrients and energy from the bottom throughout the estuarine ecosystem. Within intertidal estuarine areas the primary production was predominantly supported by microphytobenthos (MPB). These benthic microalgae assemblages are an important source of organic matter and are a main food source for Hydrobia populations. The MPB - Hydrobia interaction is a key model for the estuarine grazing food chain, acting as a significantly channel of energy to higher trophic levels, since Hydrobia is an important prey item for fish, birds and crabs. The present work addressed: i) the environmental (namely light and sediment water content) and the endogenous control of the vertical migration by microphytobenthos, and ii) the identification and the potential use of trophic markers (pigments and fatty acids) to establish this relationship under laboratory and natural conditions, considering that H. ulvae showed significant trophic plasticity and that mud snails could reach extremely high densities. The role of exogenous cues and endogenous control of the patterns of vertical migratory behavior of intertidal MPB biofilms were compared, showing that the formation and disintegration of the biofilm is endogenously-controlled. The regulation and maintenance of the microalgal biomass at the sediment surface is dependent on the variation of environmental factors, namely light, which is essential for the full formation of the MPB biofilm. A new methodological approach was proposed to estimate the water content of muddy intertidal sediments, enabling the study of the influence of wind on the hydric level of the sediment and the consequent impact of desiccation on the MPB biomass. This investigation showed that desiccation might be responsible to cause important limiting effects on biomass and photosynthetic activity of intertidal MPB biofilms, reducing the primary productivity. Regarding the trophic dynamics of the interaction MPB - Hydrobia, it was established the use of the pigment pheophorbide a, present on Hydrobia ulvae faecal pellets, as a trophic marker to estimate the amount of microalgal biomass incorporated, as chlorophyll a, by benthic macrofauna. A significant relationship between egested pheopigments and ingested chlorophyll a was investigated and validated. These studies were firstly developed on a daily scale, considering the effects of seasonal, tidal and day-night cycles, followed by a validation under natural conditions, on a monthly scale. The mean ingestion rate of H. ulvae individuals varied along the day, with the maximum around the diurnal low tide periods, which may be related with MPB availability. H. ulvae mean ingestion rate (IR) also varies seasonally (IR summer > IR spring) and depending on mud snails density (> density, < ingestion). There was a negative effect on chlorophyll concentration available after grazing, independently of H. ulvae density. Finally, the comparison of fatty acid profiles of mud snails from different habitats with the ones from potential food sources allowed identifying fatty acids as a useful tool to indicate H. ulvae habitat. Although the occupation of different habitats and the integration of multiple primary food sources on mud snails diet, significant inputs of fatty acids specific of microalgae (namely diatoms) were always found, which reinforce the important role of MPB on the diet of H. ulvae populations.
FCT; FSE - SFRH/BD/23720/2005
Consalvey, Mireille. "The structure and function of microphytobenthic biofilms." Thesis, University of St Andrews, 2002. http://hdl.handle.net/10023/2682.
Повний текст джерелаGinnever, Naomi Elizabeth. "The photophysiology of rocky intertidal microphytobenthic biofilms." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/59459/.
Повний текст джерелаLarson, Fredrik R. M. "The role of marine microphytobenthos with emphasis of resilience /." Göteborg : Göteborg University, Department of Marine Ecology, 2005. http://www.gbv.de/dms/goettingen/505476940.pdf.
Повний текст джерелаWeinmann, Birgit Ellen. "Microphytobenthic diversity and function in estuarine soft sediment." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3664.
Повний текст джерелаAllison, Jeffrey Garner. "Dynamics of estuarine microphytobenthos in a shallow water sand bottom habitat." [Pensacola, Fla.] : University of West Florida, 2006. http://purl.fcla.edu/fcla/etd/WFE0000004.
Повний текст джерелаFacca, Chiara. "Phytoplancton et microphytobenthos comme indicateurs de l'état trophique en milieu côtier." Montpellier 2, 2003. http://www.theses.fr/2003MON20148.
Повний текст джерелаBoulcott, Mat. "The dynamics of carbohydrate production, storage and excretion in epipelic diatoms." Thesis, University of Essex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343503.
Повний текст джерелаMorelle, Jerome. "Dynamique spatiale et temporelle de la production primaire de l'estuaire de la Seine." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC252/document.
Повний текст джерелаThe estuaries play an important ecological role and are the site of many human activities because of their strategic position at the interface between continental and marine waters. Seine estuary is characteristic of large anthropized estuaries. Long-term management requires better knowledge of the spatial and temporal dynamics of the estuarine food webs. Phytoplankton and microphytobenthos are the main contributor of primary production (PP) in these ecosystems and are at the basis of trophic food webs. These compartments are often reduced to the chlorophyll concentration and their productivity has never been measured along the Seine estuary. The objective of this study was to estimate the PP of these compartments along the salinity gradient. In order to access to measurements at high spatial resolution, high-frequency measurements of modulated fluorescence (PAM) were coupled to low-frequency carbon (13C) incorporation measurements. The primary production measurements have been put into perspective with the dynamics of the physical and chemical parameters and the structure of phytoplankton communities determined by different techniques (microscopy, cytometry, molecular biology). The dynamics of carbon excreted as TEP (Transparent Exopolymeric Particles) and EPS (Exopolymeric substances) were also studied for each compartment. Beyond the innovative methodologies which demonstrate the interest of high-frequency measurements in these highly dynamic ecosystems, this work provides a new insight into the phytoplankton dynamics and the specific richness of the estuarine microbiome and provides a reliable estimate of primary production
Molesky, Thomas J. "Interactions between oyster reefs and adjacent sandflats : effects on microphytobenthos and sediment characteristics /." Electronic version (Microsoft Word), 2003. http://dl.uncw.edu/etd/2003/moleskyt/tommolesky.doc.
Повний текст джерелаChatterjee, Arnab. "Rôle des micro-algues benthiques dans la zone côtière : biomasse, biodiversité, productivité." Thesis, Brest, 2014. http://www.theses.fr/2014BRES0005/document.
Повний текст джерелаThe most important primary producer groups of the coastal zones are suspended phytoplankton cells (Pannard et al, 2008) and microphytobenthos (MPB) (Woelfel et al., 2010). In these regions, phytoplankton and benthic microalgae are both recognized as being principal components of the diet for economically important suspension-feeding fauna (Gillespie et al., 2000). However, although phytoplankton has been vastly documented, MPB is often understudied.In sufficient light for photosynthesis they can inhabit the top few centimeters of the substrate layers (mud or sand) of marine sediment (Charpy and Charpy-Roubaud 1990, MacIntyre et al. 1996, MacIntyre and Cullen 1996) and play an important role as a food source for higher trophic levels (Revsbech et al. 1981, Sorokin 1991, Charpy and Charpy-Roubaud 1990 ). Benthic microalgal biomass mostly follows a similar distribution to the total organic matter content of surficial sediments indicating that sediment geochemical processes such as nutrient release from the breakdown of organic matter may be important in determining the distribution of MPB (Light, 1998). However, on the other hand, though not proportional with the MPB biomass, benthic production can even surpass the pelagic contribution (Underwood and kromkamp, 1999). With their ability of high primary production benthic microalgal communities can profoundly influence the flux, transformation and turnover of carbon and nutrients in coastal areas. Benthic primary producers contribute to the availability of energy and matter for benthic and pelagic food webs and define benthic and pelagic energy budgets, which affect the chemistry at the sediment-water interface, and regulate sediment stability. The shallow waters, where MPB thrives, allow a more direct interaction between pelagic and benthic processes keeping the benthos much less susceptible to physical and biochemical disturbances such as evaporation, eutrophication, and wind-forcing (Molen, 2011). Because attached microalgae can avoid advective processes and adapt to changes in light availability at short time scales, their importance is particularly enhanced (Phinney, 2004). As a result of the impact that MPB carries in a coastal ecosystem, along with the study of the functional role of MPB, investigations on their diversity have also gained some importance in the last two decades (Sundbaeck & Joensson, 1988; Blanchard, 1990; Montagna et al., 1995). Like phytoplankton, MPB communities can also act as sensitive indicators of water quality as the taxonomic composition of MPB assemblages can vary as per different nutrient levels (Lange-Bertalot, 1979; Kann, 1986). However, although the importance of MPB has been emphasized on intertidal zones (Pinckney & Zingmark, 1993; Colijn & De Jonge, 1984; Herman et al., 2000), the subtidal zones have generally been ignored till yet on this regard and as a result of which not much is known about the MPB dynamics in the subtidal zones. The subtidal zone of Bay of Brest was chosen for this study because there had been comprehensive input of nitrates to the zone in the past century .This zone has being amazingly resistant to eutrophication for quite some time, although silicate and nitrate ratio got down during the past 20 years. Research has been done previously on the spatial distribution of MPB in the zone in terms of primary productivity and biomass, but in order to achieve a more holistic view of these important photoautotrophs, a temporal study is necessary as well. The objectives of this work have been to characterize the temporal distribution of MPB in terms of biomass, productivity and biodiversity in the subtidal zone of Bay of Brest on a monthly scale, assess a comparative reasoning between MPB and the phytoplankton of the overlying water column complying on the same factors and draw an understanding on the significance of seasonal fluctuations of MPB in the overall seasonal distribution of photoautotrophs. […]
Dransfeld, Leonie. "The environmental and photo-physiological control of microphytobenthos primary production on an intertidal mudflat." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/42087/.
Повний текст джерелаBlanchard, Gérard. "Relations trophiques entre la méiofaune et le microphytobenthos d'un marais maritime du littoral charentais." Bordeaux 1, 1989. http://www.theses.fr/1989BOR10605.
Повний текст джерелаMarchais, Violette. "Relations trophiques entre producteurs primaires et quatre consommateurs primaires benthiques dans un écosystème côtier tempéré." Thesis, Brest, 2014. http://www.theses.fr/2014BRES0111/document.
Повний текст джерелаIn coastal euphotic areas, primary producers grow both in the pelagic (water column) and in the benthic zone (in or near the sediment). In these ecosystems, benthic-pelagic coupling is an important process which must be well described. Benthic primary consumers modify this coupling through their diet. Trophic relationships between primary producers and benthic primary consumers are not thoroughly understood. To gain additional information, this thesis was focused on the spatial and temporal dynamic of primary producers in suspended particulate organic matter (SPOM), especially at water-sediment interface. This study highlighted a seasonal variation of microalgal populations at all depths, and a relative dominance of benthic diatoms in SPOM near sediment and in winter. The second objective of the thesis was focused on the trophic relationships between benthic primary consumers (great scallop, black scallop, mussel and ormer) and primary producers in SPOM. Stable isotope analysis in soft tissues of black scallops and mussels showed a predominance of assimilated phytoplankton and the potential contribution of microphytobenthos in their diet (more important for mussel), especially in winter and near the sediment. However, this study highlighted the impact of metabolism on stable isotopic values of soft tissues. An innovative aspect of this thesis was the use of exoskeleton of great scallops and ormers to characterize their diet in natural environment and thus overcome problems related to the utilization of stable isotopes in soft tissues. Experiments in controlled conditions validated food sources integration through metabolic carbon in carbonates of great scallops and shell color for ormer but complementary studies are required on mollusk shell utilization. The last part of this thesis was focused on the ability of great scallops to achieve resuspension of benthic particles by valve movements
Androuin, Thibault. "Ecologie trophique de l'espèce ingénieur Crepidula fornicata et implications pour le fonctionnement de son habitat." Thesis, Brest, 2018. http://www.theses.fr/2018BRES0106.
Повний текст джерелаThe slipper limpet (Crepidula fornicata) is an invasive species of European coasts. Protandric hermaphrodite, this gregarious species forms individuals' stacks which accumulate in high density on bottom. For a long time considered as a detrimental invader, the slipper limpet is also an ecosystem engineer, modifying its habitat both physically and biologically. It is model to study how invasive and engineer species can structure and modify the ecosystem that they colonize. In this Ph.D. thesis, these effects have been examined through the trophic functioning of habitats colonized by the slipper limpet, with a special reference to the primary benthic production. Experimental stimulation of subtidal microphytobenthos (MPB) has been demonstrated by the biological activity of the slipper limpet.The trophic niche of C. fornicata has been redefined following the discovery of the presence of carbonate spherules in its tissues, overestimating the contribution of MPB in its diet. Several trophic markers use (pigments, fatty acids, isotopes)revealed that young motile individuals were likely to graze the MPB associated to shell biofilm. Sessile adults, were likely opportunistic filter-feeders, where detritus but also MPB contribute to their trophic diet. The analysis of several filter-feeders inhabiting Crepidula beds has demonstrated that the slipper limpet was not a trophic competitor for commercially important species (black scallop and flat oyster) due to their trophic sorting mechanisms. At the food web scale, the high density of slipper limpet can lead to a homogenization of the global food web due to organic matter enrichment. Dead Crepidula bed showed trophic complexity similar to maerl bed, which is a high biodiverse ecosystem. This thesis, in addition to characterize the trophic functioning of Crepidula beds, shows that an invasive species, in facilitating different biological compartments (MPB, filter-feeders), can contribute to the ecosystem richness such as the Bay of Brest
Meleder-Tard, Vona. "Étude de la structure des peuplements intertidaux du microphytobenthos : apport de la télédétection visible - infrarouge." Nantes, 2003. http://www.theses.fr/2003NANT2052.
Повний текст джерелаThe aim of this work is to assess the use of multispectral (SPOT ; few large spectral bands) and hyperspectral (DAIS ; many thin spectral bands) visible infrared remote sensing (between 400 and 1000 nm) to study microphytobenthos assemblages in intertidal ecosystems. The study area is a shellfish ecosystem located south of the Loire river, the Bourgneuf bay (47ʿN ; 2ʿW). Microphytobenthos, which is composed of photosynthetic unicellular organisms inhabiting the upper millimetres of intertidal sediments, is dominated by Diatom in Bourgneuf bay. Each pigment of these organisms exhibit absorbance signature allowing the detection of benthic diatom biofilms by field or satellite/airborne swas around 60 mg Chl a. M-2 for a pixel of 5 x 5 m. .
Dyson, Kirstie E. "Biodiversity and ecosystem processes in heterogeneous environments." Thesis, University of St Andrews, 2008. http://hdl.handle.net/10023/698.
Повний текст джерелаBecker, Amani Eve. "Uptake and mobilisation of metals associated with estuarine intertidal sediment by microphytobenthic diatoms." Thesis, University of Stirling, 2017. http://hdl.handle.net/1893/25388.
Повний текст джерелаLiu, Yang. "L'influence de la méiofaune sur le fonctionnement du biofilm lotique en relation avec la qualité de l'eau." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30197/document.
Повний текст джерелаThe role of meiofauna on the functioning of riverine biofilms was examined by studying their potential effect on nitrogen consumption capacity of biofilms in four experiments (Chapters 2 and 3: epilithic phototrophic biofilms; Chapters 4 and 5: heterotrophic biofilms of hyporheic zone). Biofilms are subjected to (1) different levels of densities (meiofauna) and nutrient enrichment or (2) different levels of diversity (biofilm/meiofauna/macrofauna). A part of the microcosms of each level of diversity was exposed to the effect of an herbicide, diuron. Overall, biofilm-associated meiofauna in microcosms was dominated by rotifers. Results in phototrophic biofilms showed that the response of rotifers to short-term nutrient enrichment was significant increases in their density and biomass. In addition, N-NO3 uptake rates appeared significantly higher in microcosms with highest meiofauna densities. This positive effect of meiofauna on biofilm N-NO3 uptake was also found in hyporheic biofilm microcosms, but not under the effect of diuron. Therefore, this thesis highlights that meiofauna can have a significant role in nitrogen consumption processes by lotic biofilms. In addition, the results strongly suggest that invertebrates interact with microorganisms involved in the reduction processes of nitrogen concentrations in the phototrophic biofilm as well as the hyporheic biofilm. Finally, the herbicide exposure resulted in a significant modification of N-NO3 uptake rate in hyporheic microcosms. However, the comparison of the average N- NO3 uptake rate between treatments exposed to herbicide and those unexposed, showed that the presence of invertebrates (meiofauna + macrofauna) significantly reduced the effect of diuron on these processes. This study highlights the potentially important role of microorganism-invertebrate interactions (1) in the nitrogen cycle of biofilms and thus functions related to their contribution to the "self-purification" process in streams, and (2) in resilient capacity of the hyporheic ecosystem to chemical perturbations
Johnson, Vivienne R. "A study of marine benthic algae along a natural carbon dioxide gradient." Thesis, University of Plymouth, 2012. http://hdl.handle.net/10026.1/1230.
Повний текст джерелаNeely, Merrie Beth. "Benthic Microalgae and Nutrient Flux in Florida Bay, USA." Scholar Commons, 2008. https://scholarcommons.usf.edu/etd/426.
Повний текст джерелаSavelli, Raphaël. "Study of microphytobenthos dynamics in temperate intertidal mudflats by using physical-biological coupled modelling and remote sensing data analysis." Thesis, La Rochelle, 2019. http://www.theses.fr/2019LAROS030.
Повний текст джерелаThe high primary production (PP) of intertidal mudflats at temperate latitudes is mostly supported by microphytobenthos (MPB), which support both benthic and pelagic food webs. In the present thesis, we use a physical-biological coupled model to investigate the spatial and temporal variability of MPB dynamics on a large temperate intertidal mudflat of the French Atlantic coast. The model explicitly simulates the MPB biomass and the grazer (Peringia ulvae) biomass and density. The outputs provide key findings on MPB dynamics. In winter-spring, optimal light and mud surface temperature (MST) conditions for MPB growth lead to a MPB spring bloom. Light is the most limiting driver over the year. However, a high MST limits the MPB growth 40% of the time during summer. The photoinhibition of MPB photosynthesis can potentially superimpose on thermoinhibition in spring-summer. Grazing and resuspension of MPB biomass also shape the dynamics of the MPB biomass. Bioturbation by P. ulvae contributes to a chronic export of MPB biomass from the sediment to the water column in spring-summer. Waves contribute to the MPB resuspension through massive resuspension events in winter, spring and fall. 50% of the annual MPB PP is exported to the water column through chronic and massive resuspension events. We also developed a new method that combine remote sensing data with outputs of the physical-biological coupled model into a single algorithm that can predict PP from satellite data. In addition to bring new insights on the MPB dynamics, this work proposes new numerical tools to monitor and predict MPB PP and its fate in coastal waters in a context of climate change
Hanlon, A. R. M. "The effect of simazine on chlorophyll a fluorescence in axenic diatom monocultures and in estuarine microphytobenthic biofilms." Thesis, University of Essex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390991.
Повний текст джерелаChennu, Arjun [Verfasser], Ľuboš Akademischer Betreuer] Polerecký, Antje [Akademischer Betreuer] [Boetius, and Kai-Uwe [Akademischer Betreuer] Hinrichs. "Mapping the microscale variability of microphytobenthos: Development of a hyperspectral imaging method / Arjun Chennu. Gutachter: Antje Boetius ; Kai-Uwe Hinrichs. Betreuer: Lubos Polerecky." Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/1072157284/34.
Повний текст джерелаCARIOU-LE, GALL VALERIE. "Repartition spatio-temporelle du microphytobenthos dans un sediment vaseux intertidal du bassin de marennes-oleron et etude experimentale de sa remise en suspension." Paris 6, 1995. http://www.theses.fr/1995PA066279.
Повний текст джерелаHaubois, Anne-Gaëlle. "Dynamique des transferts trophiques entre le microphytobenthos et le gastéropode déposivore Hydrobia ulvae (Pennant) sur une vasière intertidale de la Baie de Marennes-Oléron." La Rochelle, 2003. http://www.theses.fr/2003LAROS108.
Повний текст джерелаThe goal of my Ph. D. Was to characterize the spatio-temporal variation of the trophic transfer between microphytobenthos and the gastropod Hydrobia ulvae. I therefore investigated structure and dynamics of the two compartments and quantified experimentally the effect of demographic and environmental variables on the individual ingestion rate of H. Ulvae. Microphytobenthic biomass varied between 40 and 150 mg Chl a. M-2 and the diatom assemblage was dominated by small-sized species. The study of H. Ulvae population dynamics showed that the population structure is strongly influenced by large-scale movements of individuals. Individual ingestion rate of H. Ulvae is mainly controlled by the chlorophyll a concentration in the sediment and individual size. The functional response of H. Ulvae, juveniles and adults over a wide range of Chl a concentration is characterized by an increase of the ingestion rate according to a power law. Finally, all results were used to estimate the trophic flux
Guarini, Jean-Marc. "Modelisation de la dynamique du microphytobenthos des vasieres intertidales du bassin de marennes-oleron. Effets des synchroniseurs physiques sur la regulation de la production." Paris 6, 1998. http://www.theses.fr/1998PA066150.
Повний текст джерелаRedzuan, Nurul Shahida. "Microphytobenthos (MPB) biomass variability and sediment-water column exchanges on an intertidal flat : influence of weather-related abiotic factors across neap-spring-neap tidal cycles." Thesis, University of Essex, 2017. http://repository.essex.ac.uk/19959/.
Повний текст джерелаSevilgen, Duygu Sevgi [Verfasser], Thomas [Akademischer Betreuer] Brey, and Kai [Akademischer Betreuer] Bischof. "Microphytobenthos in cold-water sublitoral systems : their ecological role and response to changing environmental conditions / Duygu Sevgi Sevilgen. Gutachter: Thomas Brey ; Kai Bischof. Betreuer: Thomas Brey." Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/1072225670/34.
Повний текст джерелаDuggan, Melissa. "Effect of River Flow on Downstream Productivity in a Tropical Estuary." Thesis, Griffith University, 2012. http://hdl.handle.net/10072/366499.
Повний текст джерелаThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text
Barnett, Alexandre. "Régulation de l'activité photosynthétique du microphytobenthos et conséquence sur la dynamique temporelle de la production primaire dans les vasières intertidales de la côte atlantique de l'Europe de l'Ouest." Thesis, La Rochelle, 2013. http://www.theses.fr/2013LAROS412/document.
Повний текст джерелаMicrophytobentos (MPB) from temperate latitude is mainly composed of diatoms. Those microorganisms can be separated in two groups: the epipelic one from muddy sediments (composed of mobile diatoms) and the epipsammic one from sandy-muddy sediments (composed of diatoms living attached to their substrate). In order to investigate mudflats’ primary production, the MPB compartment was studied through diverse approaches from the physiological level to the ecological one. In the first place, laboratory experiments (in vitro experiments), focusing on light reaction of epipelic and epipsammic diatoms, showed that their life form and their mobility were strongly connected to their physiological photoprotection ability. Thereby, the motionless diatoms were characterized by higher physiological photoprotection abilities than the mobile ones, which could avoid excess of light. In the second place, the fluorescence of collected samples (in vivo experiments) was measured to acquire diatoms’ migration profiles. The results pointed out an internal and light-regulated migration pattern of the MPB and furthermore highlighted the effect of light quality on migration profiles. Besides, the commonly accepted hypothesis of deep cell division phases was tested and confirmed through flow cytometry experiments. Eventually, laboratory measurements were compared to in situ ones realized at the scale of the whole community. These comparisons revealed that diatoms photoprotection in fluctuating light depended on the targeted populations. Epipelic organisms were indeed characterized by an unvarying photoprotection, diatoms migration regulating alone the effect of light fluctuations. On the contrary, motionless epipsammic populations required a light-regulated photoprotection
Nzigou, Aimé Roger. "Production primaire et fonctionnement écologique en milieu estuarien turbide : cas de l’estuaire de la Gironde (France)." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14674/document.
Повний текст джерелаAbstract
Pniewski, Filip Franciszek. "Capacité photosynthétique du microphytobenthos des vasières intertidales de la Baie de l'Aiguillon (Côte atlantique, France) et des lagunes non-tidales de faible profondeur de la Baie de Puck (Mer Baltique, Pologne)." Thesis, La Rochelle, 2010. http://www.theses.fr/2010LAROS300.
Повний текст джерелаThe scope of this thesis includes the characteristics and comparison of photosynthetic activity and photoprotection mechanisms of microphytobenthos assemblages inhabiting the Atlantic intertidal mudflats of Aiguillon Bay (Esnandes, France) and the littoral zone of the Baltic Sea in non-tidal Puck Bay (Władysławowo, Poland). In order to accomplish the main aims of the work the following tasks were carried out: (1) characterization of microphytobenthic assemblages; (2) characterization of their photosynthetic activity and (3) description of photoinhibition and photoprotective mechanisms. The structure of microphytobenthos was described based on observation of the material in light microscope (LM) and through the characteristics of photosynthetic pigments using high performance liquid chromatography (HPLC). Photosynthetic activity was described using various methods including classical (volumetric micro-respirometer) and modern (chlorophyll a fluorescence) ones. In addition, the measurements of variable fluorescence were also used to study photoinhibition and photoprotective mechanisms. Based on the obtained results it was stated that:1.) the Atlantic assemblages were strongly dominated by epipelic diatoms, while the Baltic microphytobenthos was more diverse and cyanobacteria, next to diatoms, were also very important component,2.) it was shown that the Atlantic microphytobenthos was well acclimated to rather low light intensities, while the Baltic assemblages showed good utilization of higher irradiance,3.) the Atlantic diatoms were more susceptible to photoinhibition than the Baltic microalgae,4.) the photosynthetic activity described for the undisturbed microphytobenthos communities revealed circadian and circatidal rhythms, which seemed to be controlled by endogenous factors, supporting diatoms’ behavioural adaptations i.e., vertical migration,5.) in case of the Baltic microphytobenthos, the lack of the ability to move caused their physiological processes the first line of defence against excess irradiances. The analysis revealed extreme flexibility of PSII which was able to follow rapidly the short-term changes in ambient light
Bertolli, Lucielle Merlym. "Estudo da comunidade de diatomáceas (BACILLARIOPHYTA) epifíticas em marismas da costa do sul do Brasil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/158308.
Повний текст джерелаDiatoms are an important component of the epiphyton in coastal environments. The strategies of attachment provide adaptive advantages to these algae; however, they are susceptible to the environmental fluctuations, responding to them with changes in the community composition and structure. Although the relationship between epiphyton and substrate is poorly understood, the architecture of the substrate seems to influence the attached community. The composition, structure and seasonal variations of the epiphytic diatoms were evaluated in Patos Lagoon salt marshes. Three sampling sites were defined, Saco do Silveira, Ilha da Pólvora and São José do Norte, distant 36, 18 and 9 km from the Atlantic Ocean, respectively. The epiphyton attached to Spartina alterniflora Loisel., Spartina densiflora densiflora Brogn., Scirpus maritimus L. e Juncus kraussii Hochst. was scraped with metal blade, oxidized and mounted on permanent slides for the analysis of the diatoms. A total of a hundred and twenty seven taxa were found. The genus Navicula Bory, Nitzschia Hassall e Tryblionella W. Smith showed the highest number of species. The seasonality, spatiality, salinity and substrate influenced the composition and structures of the community. The higher distance of the estuary mouth provided a higher influence of continental waters in the site Saco do Silveira, resulting in a community characterized by freshwater taxa. The winter was characterized by higher values of the community attributes (richness, diversity and evenness). The more complex structure of S. maritimus surface provided the establishment of a richer community. The taxonomic investigation of Nitzschia and Tryblionella was more detailed, including the analysis of the microphytobenthos of the sites. The species Nitzschia papillosa Bertolli et al. was registered for the first time to science in Ilha da Pólvora and São José do Norte. The species has linear-lanceolate outline, cuneate apices and fibulae irregularly distributed, as many other species of the genus. Its main feature is the presence of rounded to squarer silica excrescences, situated on the transapical costae in the internal valve view. The study of the genus Tryblionella showed 11 species, two of them were registered for the first time in Rio Grande do Sul State and one in Southern Brazil. Besides that, two species new to science were proposed, Tryblionella Bertolli et Torgan, which is similar to T. debilis Arnott ex O’Meara in light microscopy, but present asymmetrical transapical ribs in scanning electron microscopy, and T. Bertolli et al. which presents an ornamentation pattern similar to a lace texture in the valve face. The species of Tryblionella and N. papillosa occurred concomitantly in the epiphyton and microphytobenthos, evidencing the interaction between both communities, promoted by the environment dynamics.
Santos, Paulo J. P. dos. "Contribution à l'écologie du méiobenthos et du microphytobenthos dans la zone oligo-mesohaline de l'estuaire de la Gironde et dynamique de population et production secondaire du copepode harpacticoi͏̈de Nannopus palustris Brady, 1880." Bordeaux 1, 1995. http://www.theses.fr/1995BOR11409.
Повний текст джерелаSantos, Paulo J. P. dos. "Contribution à l'écologie du méiobenthos et du microphytobenthos dans la zone oligo-mesohaline de l'estuaire de la Gironde et dynamique de population et production secondaire du copepode harpacticoi͏̈de Nannopus palustris Brady, 1880." Bordeaux 1, 1995. http://www.theses.fr/1995BOR10687.
Повний текст джерелаVanhuysse, Charles. "Impacts de l'ostréiculture à mésoéchelle sur le microphytobenthos et ses performances photosynthétiques, la macrofaune benthique et rôle de l'érosion estuarienne dans les mortalités de naissains d'huitres Crassostrea gigas liées à OsHV-1 μ Var Drivers of epipelic mictophytobenthic photobiology and groth in oyster farm Benthic macrofaunal changes in oyster parks during an OsHV-1 µVar oyster spat mortality outbreak Environmental dynamics of the Ostreid herpes virus (OsHV-1 µVar) in oyster spats and microphytobenthic biofilms during an in situ mortality outbreak In situ resuspension of benthic sediments and biofilm components during an OsHV-1 µVar Crassostrea gigas oyster spat mortality episode". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC262.
Повний текст джерелаSince 2008, the mortality of Pacific oyster spat Crassostrea gigas has mainly been linked to the Ostreid herpesvirus 1 μvariant (OsHV-1 μVar). Environmental parameters favoring the persistence and spread of the virus could affect its propagation dynamics. The objectives of this thesis were to study in situ the interactions between oyster spat and their benthic environment during an episode of mortality. The photobiology of the microphytobenthos beneath the tables seemed to be in a better state compared to that observed in aisles that could promote viral resilience. The oyster tables attenuated light, temperature and desiccation, thus avoiding thermo and photoinhibition of the microphytobenthos. The benthic habitat environmental quality indices based on the macrozoobenthic community showed a degradation of the environment following the influx of organic matter induced by oyster spat mortalities and strandings of the macroalgae. A significant amount of OsHV-1 was found on the surface of the biofilm before the mortalities. Resuspension was preferentially associated with microphytobenthic particles with small currents
Heijden, Luuk van der. "Determination of the food sources and of the role of meiofauna in soft-bottom intertidal habitats of the Marennes-Oléron Bay, France, and the Sylt-Rømø Bight, Germany : importance of the microphytobenthos-meiofauna pathway, highlighted by community structure, trophic markers and linear inverse food web models." Thesis, La Rochelle, 2018. http://www.theses.fr/2018LAROS030/document.
Повний текст джерелаMeiofauna play an important role in ecosystem processes in soft-bottom benthic habitats, e.g. food web dynamics, related to their highproduction, their intermediate trophic position and the energy they transfer towards higher trophic levels. The trophic linkages and flows of organic matter related to the meiofauna remain poorly known or taken into account. To better assess the role of meiofauna, the community structure and trophic relationships between food sources and meiofauna were determined in five intertidal soft-bottom habitats (i.e., mudflat, seagrass bed, sandflat) of the Marennes-Oléron Bay, France, and the Sylt-Rømø Bight, Germany, taking temporal variations into account. Meiofauna communities were dominated by nematodes and benthic copepods. Biomass of microphytobenthos and of sediment organic matter were two of the major drivers of community structure. The combination of trophic markers (i.e., stable isotopes, fatty acids) demonstrated that microphytobenthos and bacteria were the major food sources of meiofauna in the five habitats. Information from community structure assessments and trophic marker analyses were implemented in food web models. In all habitats, these models demonstrated that the main flow of carbon to meiofauna originated from microphytobenthos, highlighting negligible changes in meiofauna feeding behavior besides the large differences in availability and productivity of food sources between these habitats. All trophic groups of nematodes, except for selective deposit feeding nematodes, were highly selective and mainly fed on microphytobenthos, resulting in a high production and a short turn-over time of meiofauna. In conclusion, this thesis demonstrated the important role of meiofauna in soft-bottom habitats as well as the importance of the trophic pathway from microphytobenthos to meiofauna in the functioning of these food webs
Oakes, Joanne. "Microalgae and Mangroves as Carbon Sources for Estuarine Invertebrates: Evidence from Stable Isotope Enrichment Experiments." Thesis, Griffith University, 2007. http://hdl.handle.net/10072/365499.
Повний текст джерелаThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment
Faculty of Environmental Sciences
Full Text
Andersson, Eva. "Benthic-Pelagic Microbial Interactions and Carbon Cycling in Clearwater Lakes." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5798.
Повний текст джерелаAlmeida, Cristiano de Salles. "Distribuição espacial da biomassa microfitobentônica no perfil batimétrico da região de Ubatuba, SP." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/21/21134/tde-10022015-113340/.
Повний текст джерелаMarine microphytobenthos community is composed mainly by diatoms and also phytoflagellates and cyanobacteria, which cover the marine sediments submitted to light. This study aims to survey the spatial distribution of bathymetric profile microphytobenthic biomass in Ubatuba region, SP. The samples were collected in the summer (March, 2013), at three transects: Flamengo, Fortaleza and Mar Virado, with 6 points each, between the isobaths of 5 and 30 meters. The biomass was expressed as chlorophyll a. Chlorophyll a and phaeopigments were extracted with acetone and measured at spectrophotometer. The biomass averages values were: chlorophyll a 18,5 ± 11,4 mg.m-2 and phaeopigments 28,4 ± 16,2 mg.m-2 for Flamengo transect; chlorophyll a 11,9 ± 10,2 mg.m-2 and phaeopigments 18,8 ± 15,2 mg.m-2 for Mar Virado transect; and chlorophyll a 11,8 ± 11,3 mg.m-2 and phaeopigments 13,7 ± 13,6 mg.m-2 for Fortaleza transect. Chlorophyll a and phaeopigments averages values were higher in the shallow regions. The biomass distribution was positively associated to light intensity, silt, clay, total organic carbon and organic matter. Negative correlations were found for depth and coarse grains.
Heijden, Luuk van der [Verfasser]. "Determination of the food sources and of the role of meiofauna in soft-bottom intertidal habitats of the Marennes-Oléron Bay, France, and the Sylt-Rømø Bight, Germany. Importance of the microphytobenthos-meiofauna pathway, highlighted by community structure, trophic markers and linear inverse food web models. / Luuk van der Heijden." Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1191179826/34.
Повний текст джерелаPolsenaere, Pierre. "Echanges de CO2 atmosphérique dans la lagune d’Arcachon et relations avec le métabolisme intertidal." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14253/document.
Повний текст джерелаThe coastal zone is only taken into account since recently in global carbon budgeting efforts. Although covering globally modest surface areas, carbon and nutrient fluxes in the coastal zone appear significant at the global scale. However, little is known about the CO2 behaviour in lagoons and even less in intertidal zones where exchanges with the atmosphere occur alternatively with the water and the sediment. The purposes of this work are, on one hand, to establish the carbon budget between the Arcachon lagoon, the atmosphere and the terrestrial watershed and on the other hand, to link these fluxes with the net ecosystem production (NEP) and better characterize its metabolic status along with the relevant environmental factors. For the first time, CO2 flux measurements by Eddy Correlation have been carried out at different seasons and stations in the tidal flat. In parallel, the total terrestrial carbon export from river waters has been quantified throughout a complete hydrological cycle in nine watercourses flowing into the lagoon. The total carbon export from the watershed through surface river waters is estimated at 116 t C km-2 yr-1 on which 39% is exported to the lagoon as dissolved organic carbon (DOC) owing to the predominance of podzols in the watershed. Intense organic matter mineralization in soils and groundwaters largely over-saturate river waters in CO2 on which export accounts for 21% as dissolved inorganic carbon (DIC). The mathematical “StreamCO2-DEGAS” model formulation based on water pCO2, DIC concentrations and isotopic composition measurements permits to show that 43% of the total carbon export was degassed as CO2 from the riverine surface waters to the atmosphere, lowering then this latter to 66 t C km-2 yr-1. With respect to the CO2 flux measurements in the lagoon, cospectral analysis and the well accordance of results with physical and biological controls at the tidal, diurnal and seasonal time scales permit to validate the Eddy Correlation technique over tidal coastal zone. CO2 fluxes with the atmosphere, during each period, were generally weak and ranged between -13 and 19 µmol m-2 s-1. Low tide and daytime conditions were always characterized by an uptake of atmospheric CO2. In contrast, during the immersion and during low tide at night, CO2 fluxes where either positive or negative, or close to zero, depending on the season and the site. The concomitant analysis of CO2 fluxes with satellite images of the lagoon at low tide during the day clearly discriminate the relative importance of the two distinct metabolic carbon cycling involving the main primary producers, i.e. (1) the Zostera noltii seagrass meadow predominance on the NEP in autumn and summer in the more central station, with an annual cycling and (2) the microphytobenthos community predominance on the gross primary production (GPP) in spring at the same station and in autumn in the inner part of the bay where a rapid carbon cycling during the immersion and the emersion was clearly highlighted. The different results obtained with the Eddy Correlation technique over tidal flats opens interesting perspectives on the knowledge of the carbon budget and the biogeochemical and ecological processes within the coastal zone
Pivato, Mattia. "Water and Sediment Temperature Dynamics in Shallow Tidal Environments." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3427269.
Повний текст джерелаLo scopo della presente ricerca è di studiare la dinamica della temperatura dell'acqua e dei sedimenti in ambienti costieri poco profondi. La temperatura dell'acqua e dei sedimenti è certamente uno dei fattori più importanti per numerosi processi fisici e biologici che determinano l'evoluzione a breve e lungo termine degli ambienti acquatici. In letteratura si trovano pochi dati e pochi lavori che analizzano nello specifico i flussi di calore all’interfaccia sedimenti-acqua (SWI). Abbiamo quindi pianificato e realizzato una campagna di misura ad hoc della durata di un anno in laguna di Venezia al fine di raccogliere dati di temperatura dell’acqua e del fondale. L'analisi dei dati ha mostrato che, nel sito da noi considerato, la temperatura si può assumere distribuita uniformemente nella colonna d'acqua. I dati sono stati quindi utilizzati per stimare il flusso di energia all'interfaccia tra acqua e fondale. Sulla base di questi risultati, abbiamo sviluppato un modello ``puntuale'' per descrivere la dinamica del profilo verticale di temperatura nel continuo acqua-sedimento in ambienti a marea caratterizzati da bassi fondali. Modellando il flusso di energia al fondo come la somma di una componente conduttiva e della radiazione solare residua al fondo, si è osservato che la seconda risulta essere trascurabile. I risultati ottenuti mostrano inoltre che il trasporto orizzontale di calore legato alle correnti di marea, e pertanto l'applicabilità del modello ``puntuale'', è limitata ai periodi caratterizzati da condizioni tali da limitare l'avvezione (i.e. marea di quadratura e/o poca differenza tra la temperatura dell'acqua in mare e all'interno della laguna). I risultati forniti dal modello per periodi caratterizzati da avvezione trascurabile sono soddisfacenti. Sia l’analisi dei dati che i risultati forniti dal modello mostrano che lo scambio di calore tra acqua e fondale è di cruciale importanza per descrivere la temperatura dei sedimenti, mentre risulta trascurabile per la dinamica della temperatura dell’acqua. Questo suggerisce che, in prima approssimazione, la dinamica della temperatura della colonna d’acqua può essere modellata trascurando lo scambio di calore tra acqua e sedimenti. L'applicazione del modello ad una condizione sintetica ha quindi permesso di analizzare l'effetto di diverse condizioni di torbidità della colonna d'acqua sulla dinamica della temperatura della colonna d'acqua stessa e dei sedimenti al fondo, e quindi sulla capacità fotsintetica del microfitobentos, i.e. comunità di micro-alghe tipicamente presenti in ambienti costieri. I risultati mostrano che la dinamica della temperatura dell'acqua risente poco delle diverse condizioni di torbidità, mentre la temperatura dei sedimenti al fondo varia in modo significativo, soprattutto per fondali particolarmente bassi (i.e. ≤ 0.5 m). La capacità fotosintetica del microfitobentos, considerando l'andamento medio a scala annuale, risulta favorita dal condizioni acqua limpida, in quanto la disponibilità di luce al fondo risulta essere il principale fattore limitante per la fotosintesi. I risultati suggeriscono quindi la possibilità di indagare l'esistenza di un possibile feedback positivo tra torbidità della colonna d'acqua e proliferazione del microfitobentos, chiaramente legata alla sua capacità fotosintetica. Il microfitobentos infatti produce un biofilm che, se presente in quantità rilevanti, ha un effetto di bio-stabilizzazione del fondale che limita l'erosione e la risospensione dei sedimenti, e quindi una potenziale riduzione della torbidità dell'acqua.
De, Crignis Margot. "Déterminisme de la production bactérienne dans les vasières intertidales du Bassin de Marennes-Oléron : rôle des exopolysaccharides." Phd thesis, Université de La Rochelle, 2010. http://tel.archives-ouvertes.fr/tel-00605659.
Повний текст джерелаJordan, Leonie Jane. "The survival strategies of microphytobenthos : behaviour and physiology." Thesis, 2009. https://eprints.utas.edu.au/20704/1/whole_JordanLeonieJane2009_thesis.pdf.
Повний текст джерелаRuivo, Michael Philippe Marquês 1986. "Characterization by HPLC of phytoplankton and microphytobenthos photosynthetic pigments." Master's thesis, 2010. http://hdl.handle.net/10451/2415.
Повний текст джерелаAs zonas costeiras são regiões de enorme produtividade, demonstrando elevada diversidade de organismos de fitoplâncton e de microfitobentos. A biomassa e produção destes organismos autotróficos são afectadas, entre outros factores, pela disponibilidade de luz e nutrientes. As clorofilas, carotenóides e ficobilinas são os principais tipos de pigmentos fotossintéticos, sendo essenciais à fotossíntese. A cromatografia líquida de alta precisão (HPLC) é uma técnica que permite a análise qualitativa e quantitativa dos vários pigmentos fotossintéticos, disponibilizando informações acerca de biomassa, composição e estado fisiológico das comunidades de fitoplâncton e de microfitobentos. Capítulo 2 Neste capítulo estudaram-se os efeitos das fases de crescimento, exponencial e estacionária, e da irradiância nas concentrações e razões pigmentares em espécies fitoplanctónicas. No estudo do efeito da fase de crescimento foram utilizadas sete espécies, entre elas dois dinoflagelados, Amphidinium carterae e Gymnodinium catenatum, uma clorofícea, Dunaliella salina, uma prasinofícea, Tetraselmis suecica, duas diatomáceas, Cylindrotheca closterium e Phaeodactylum tricornutum, e uma criptofícea, Rhodomonas sp. Após realização das curvas de crescimento, amostraram-se três réplicas em fase exponencial e três réplicas em fase estacionária. No estudo do efeito da irradiância nas concentrações e razões pigmentares usaram-se 3 espécies, A. carterae, C. closterium e T. suecica, submetidas a três níveis de irradiância (Luz Baixa, LL = 10 μmol fotões m-2 s-1; Luz Média, ML, 100 μmol fotões m-2 s-1; Luz Alta, HL, 400 μmol fotões m-2 s-1). Amostraram-se três réplicas em fase exponencial para cada nível de irradiância. A análise e caracterização pigmentar das várias espécies foi efectuada por HPLC. A comparação entre as fases de crescimento exponencial e estacionária demonstrou a existência de diferenças significativas tanto nas concentrações como nas razões pigmentares. As concentrações de pigmentos fotossintéticos por célula (e.g. clorofila a, clorofila b, fucoxantina e neoxantina) foram superiores durante a fase de crescimento exponencial. Tais resultados podem ser consequência da limitação de nutrientes e/ou da idade celular durante a fase estacionária. Por sua vez, obtiveram-se, consistentemente, maiores concentrações de anteraxantina, diatoxantina e zeaxantina durante a fase estacionária, demonstrando que pigmentos tipicamente com função fotoprotectora tendem a aumentar a sua concentração quando as células entram nesta fase, provavelmente devido ao seu envolvimento na prevenção foto-oxidativa das células. Os ratios pigmento/clorofila a, (exceptuando a violaxantina e o β-Caroteno), violaxantina + anteraxantina + zeaxantina (VAZ)/clorofila a e diadinoxantina + diatoxantina (DD + DT)/clorofila a e os índices de de-epoxidação (DPS) foram sistematicamente superiores durante a fase estacionária. Verificaram-se diferenças inter-específicas para espécies pertencentes ao mesmo grupo taxonómico. Em C. closterium a razão fucoxantina/clorofila a não variou significativamente enquanto em P. tricornutum esta razão foi aproximadamente o dobro na fase estacionária. Nos dinoflagelados, a razão peridinina/clorofila a aumentou menos de 25% entre as fases exponencial e estacionária, todavia essas diferenças só foram significativas em A. carterae. O efeito da irradiância foi significativo nas concentrações dos pigmentos de colheita de luz (LHP) e pigmentos fotoprotectores (PP). As maiores concentrações de LHP ocorreram em LL, intermediárias em ML e finalmente mais baixas em HL. Esta diminuição na concentração de LHP com o aumento da intensidade luminosa é devido à fotoaclimatação das células regulada pelo tamanho das antenas fotossintéticas. Pelo contrário, os PP apresentaram maiores concentrações em HL e menores em LL. A de-epoxidação de violaxantina em anteraxantina e zeaxantina e de diadinoxantina em diatoxantina (ciclo das xantofilas), regula o excesso de energia, consequência do aumento da irradiância, através da dissipação de calor, permitindo a protecção do aparelho fotossintético. Genericamente, as razões de pigmentos com função fotossintética, e embebidos nos complexos de colheita de luz, foram constantes nas diferentes irradiâncias, pois tendem a co-variar com a clorofila a. No entanto, as razões de pigmentos com função protectora foram superiores em HL (e.g. luteína e zeaxantina). No capítulo considerado demonstrou-se o efeito significativo da fase de crescimento e da luz nas razões pigmento/clorofila a. Assim sendo, estas variáveis devem ser consideradas na aplicação dos pigmentos fotossintéticos como indicadores quimiotaxonómicos para o estudo de comunidades fitoplanctónicas. Capítulo 3 Os objectivos deste estudo foram direccionados para a comparação da fotoprotecção fisiológica (utilização dos ciclo das xantofilas como forma de dissipação do excesso de energia no aparelho fotossintético) e comportamental (capacidade de migração vertical que permite às microalgas o controlo do nível de irradiância a que estão expostas) entre comunidades epipélicas e epipsâmicas de substrato vazoso e arenoso no estuário do Tejo. Amostraram-se dois locais: um tipicamente constituído por partículas de dimensões inferiores a 63 μm (denominado vasa), e outro com partículas de calibre entre 125 e 1000 μm (referido como areia). Assim sendo, aspectos como fluorescência, atenuação da luz, curvas rápidas de luz, análise e caracterização pigmentar e avaliação da capacidade migratória foram estudados recorrendo a técnicas de fluorescência de Pulso Modulado (PAM) e HPLC. Na comparação entre as comunidades epipélicas e epipsâmicas verificaram-se diferenças nos diversos parâmetros estudados. Na comunidade de substrato vazoso, denotou-se um efeito da profundidade nos perfis de clorofila a e uma diminuição da concentração de clorofila a ao longo do perfil. O coeficiente de atenuação da luz (k) foi elevado, com um decréscimo na disponibilidade da luz para 33%, 7% e 1% da luz incidente à superfície a profundidades de 200, 400 e 600 μm, respectivamente. Na comunidade de substrato arenoso, não se verificaram diferenças significativas nas concentrações de clorofila a, sendo estas constantes ao longo do perfil. O coeficiente de atenuação de luz foi inferior, comparativamente ao valor obtido no substrato vazoso, com 80%, 50% e 2% de disponibilidade de luz a profundidades, de 200 μm, 400 μm e 3000 μm, respectivamente. As diferenças de k e da concentração de clorofila a ao longo dos perfis de sedimento são devido ao tamanho das partículas, provocando assim, uma diferenciação na distribuição vertical das comunidades bênticas. O calibre das partículas de sedimento e k variam de forma inversamente proporcional. Em substrato vazoso, ocorreu uma diminuição de clorofila a à superfície (0-200 μm) no controlo sob luz alta (Cont HL) quando comparado com luz baixa (LL) e sedimentos tratados com um inibidor de motilidade (Lat A HL). Em simultâneo, observou-se um aumento da percentagem relativa de clorofila a na camada de 200-400 μm. Tal situação, não se verificou em Lat A HL devido à presença do inibidor de motilidade, prevenindo a migração. Estes resultados indicam que as diatomácias epipélicas da vasa submetidas a luz forte migram em profundidade – fotoprotecção comportamental – e corrobora a função de Lat A como um inibidor altamente específico de motilidade em diatomácias. Ambas comunidades estudadas activaram mecanismos fisiológicos de fotoprotecção quando sujeitas a luz forte. No substrato vazoso o índice DPS foi superior em Lat A HL quando comparado com LL (estrato 0-200 μm), mas sem diferenças significativas entre Lat A HL e Cont HL. No substrato arenoso o índice DPS foi inferior para LL, intermédio para Cont HL e superior em Lat A HL. Estes resultados indicam diferenças significativas com Cont HL. A interpretação destes resultados sugere que as comunidades pertencentes aos substratos vazoso e arenoso recorrem ao ciclo das xantofilas como mecanismo de fotoprotecção, independentemente da sua capacidade migratória. Na avaliação da influência dos diferentes tratamentos nos vários parâmetros das curvas rápidas de resposta-luz (taxa máxima relativa de transporte de electrões -rETRmax; declive inicial da taxa fotossintética não saturada - α; parâmetro de saturação de luz - Ek) denota-se um efeito significativo dos vários tratamentos, para ambos substratos em rETRmax, α e Ek. A excepção ocorre no substrato arenoso para Ek, onde não existem diferenças significativas. Porém, no substrato vazoso, os valores de rETRmax, α e Ek foram significativamente mais baixos em Lat A HL que em Cont HL enquanto essas diferenças não foram significativas no substrato arenoso. Estes resultados são consequência das diferentes condições de luz na matriz sedimentar dos substratos estudados, e provavelmente devido a diferenças na composição taxonómica. Este trabalho demonstra as diferentes respostas das células às variações de luz no sedimento: i) através de fotoprotecção fisiológica (ciclo das xantofilas) e/ou ii) movimento vertical descendente ao longo do perfil de sedimento, denominado fotoprotecção comportamental. As comunidades epipélicas, por apresentarem capacidade migratória, utilizam tanto a fotoprotecção fisiológica como comportamental, enquanto as comunidades epipsâmicas, sem capacidade migratória, valem-se apenas de fotoprotecção fisiológica.
Phytoplankton and microphytobenthos communities influence coastal systems productivity and are affected, among other factors, by light and nutrients availability. Growth phase and light variation effect on phytoplankton pigment concentrations and physiological vs. behavioral photo-protection of epipelic and epipsamic microphytobenthos communities were studied using High Performance Liquid Chromatography. Growth phase and light variation showed a significant effect on phytoplankton light harvesting (LHP) and photo-protective (PP) pigments. LHP concentrations were lower during stationary growth phase presumably by nutrient limitation and cellular age whereas photo-protective pigments increased. An increment of pigment ratios from exponential to stationary phase was consequence of the pronounced decrease in chlorophyll a cellular content comparatively with other pigments. Light increase lead to a decrease on photosynthetic pigment concentrations due to cellular photoacclimation, while the photo-protective pigment concentrations increase, allowing the dissipation of excess energy. This study shows that growth phase and light intensity have significant effects on pigment/Chl a ratios, including many marker pigments, and this should be taken into account in the application of chemotaxonomical approaches to phytoplankton natural communities. Microphytobenthos biomass vertical distribution in intertidal mud and sandflats of the Tagus estuary was considerably different depending on the type of sediment. In the mud, a steep decrease in biomass accumulation from the surface down to 1 mm was observed, whereas in the sand Chl a concentrations were relatively stable throughout the profile. Epipelic and epipsamic communities showed different photo-regulaton strategies: both communities photo-regulated using physiological photo-protection while the epipelic community of muddy sediments used physiological and behavioral photoprotection.
Vieira, Sónia Catarina Reis 1978. "Photosynthetic metabolism in microphytobenthos : modulation by temperature and dissolved inorganic carbon." Doctoral thesis, 2016. http://hdl.handle.net/10451/30278.
Повний текст джерелаMain primary producers of estuarine systems include benthic microalgae, predominantly diatoms, and cyanobacteria that colonize subtidal and intertidal zones, commonly referred to as microphytobenthos (MPB). MPB communities account for about 50% of the primary productivity of estuarine systems (e.g. MacIntyre et al., 1996; Barranguet et al., 1998; Underwood and Kromkamp, 1999; Serôdio and Catarino, 2000). This is highly relevant considering that estuarine systems are among the most productive ecosystems in the biosphere (Constanza et al., 1997). Despite the extreme variability of environmental parameters (irradiance, temperature and salinity) that characterizes the estuarine habitat, these communities are able to display high photosynthetic rates. It is common to distinguish two types of MPB communities: epipelic communities (typical of muddy sediments) composed of motile species and epipsammic communities (typical of sandy sediments) composed largely by non-motile species attached to sand grains. Contrary to epipsammic, epipelic diatoms exhibit circadian and circatidal migratory rhythms (Palmer and Round, 1967; Palmer, 1973; Admiraal et al., 1982; Serôdio and Catarino, 2000). Being MPB critical for the function of estuarine and coastal ecosystems, understanding the impact of climate change on its structure and productivity is mandatory. In particular, the increase of temperature and inorganic carbon availability can markedly affect photosynthesis, diversity and productivity of estuarine MPB communities. However, studies of the impact of climate changes on MPB are still scarce, and in particular the effects of the interaction between increased temperature and inorganic carbon availability are, to a large extent, still unknown. Thus, in this project we studied the effects of temperature and dissolved inorganic carbon (DIC) availability in two MPB communities of the Tagus estuary, in central Portugal, applying new methods of remote sensing, namely laser induced fluorescence (LIF) and modulated imaging fluorescence (Imaging-PAM). The LIF methodology (chapter 2) was used to trace migratory rhythms of benthic epipelic microalgae typical of mud sediments. Indeed, it was confirmed that, during the diurnal low tide these microalgae migrate to the surface of sediment to drive photosynthesis and then migrate in depth before the arrival of the tide. Furthermore, epipelic diatoms show photophobic migration when exposed to high light levels, a process known as behavioral photoprotection. This technique proved to be adequate to the study of MPB communities, both for the determination of surface biomass and the study of migratory rhythms. The possibility of using LIF for middle-range remote sensing under natural light conditions opens good perspectives for its use in environmental monitoring of estuarine systems. In the last decades, conventional pulse amplitude modulated fluorescence (PAM) has been increasingly applied to estuarine MPB communities (Serôdio et al., 1997; Kromkamp et al., 1998; Paterson et al., 1998; Serôdio et al., 2001; Honeywill et al., 2002; Perkins et al., 2002; Serôdio, 2003; Stephens et al., 2003; Forster and Kromkamp, 2004; Murphy et al., 2004; Serôdio, 2004; Forster and Jesus, 2005; Murphy et al., 2005). Lower resolution imaging systems allow the mapping of fluorescence parameters over large areas, making it a unique technique to study the spatial heterogeneity of the photosynthetic activity across an autotrophic surface (Scholes and Rolfe, 1996; Hill et al., 2004. This can be particularly relevant in the study of MPB biofilms, characterized by a “patchy,” heterogeneous distribution and can provide useful information about the spatial distribution of biomass and productivity in sediments. Yet, important hardware differences exist between conventional and imaging systems and therefore a comparative study of the results obtained with these technologies in MPB was required (chapter 3). In fact, we observed significant differences between the results obtained with conventional and imaging systems, especially in what refers to the analysis of rapid fluorescence curves as a function of irradiance (RLCs, Rapid Light Curves). Lower values of α (initial slope of the rETR vs. E curve), ETRmax (maximum relative ETR), Ek (light saturation parameter) and Fv/Fm (maximum quantum efficiency of photosystem II of dark-adapted samples) were obtained using the Imaging- PAM system. The discrepancy between instruments was dependent on sample type, being more pronounced in mud than in sandy MPB sediments. The differences may be largely explained by the interplay between the different depth-integration of the fluorescence signal, dependent on the thickness of the photosynthetic layer, and the different attenuation coefficients of the light sources used by the two types of instrument. It is therefore important to take into account the specificity of each fluorescence system when interpreting and comparing chlorophyll fluorescence data of MPB communities, taking full advantage of the application of imaging fluorescence to the MPB communities, in particular in what refers to its unique ability to study the spatial heterogeneity of their photosynthetic activity. The in-depth understanding of the primary production processes of MPB is a prerequisite to assess the impacts of climate change on estuarine systems. Among the global change variables, increased temperature and atmospheric CO2 (and concomitantly dissolved inorganic carbon, DIC) are expected to have the most significant impact over the primary productivity in estuaries. Therefore, we studied their effect, as well as their interaction, on the photosynthesis of MPB biofilms. The short-term effect of increasing temperature in the photosynthetic activity of two communities of MPB (Alcochete and Trancão) was studied (chapter 4). The Trancão MPB community had higher photosynthetic electron transport capacity (higher ETRmax) being photoacclimated at higher irradiance (higher EK) and had lower energy conversion efficiency at limiting irradiance (lower α) .The differences in the species composition and size class may explain the results obtained for the two sites, since smaller cells are generally more metabolically active. However, for the both MPB communities photosynthetic capacity increased with temperature up to 35 °C and decreased with extreme temperature of 42 °C. Photosynthetic efficiencies at low irradiance (α) were not affected by the temperature in the 15-35 °C range, and decreased at 42 °C. These MPB estuarine communities were able to increase the photosynthetic capacity under exposure to short-term high temperatures sediments, similar to happens during the summer midday in the diurnal low tides. We also studied the effect of dissolved inorganic carbon availability (DIC) in photosynthesis, on the two intertidal MPB communities, taking as reference the model diatom species Phaeodactylum tricornutum, using fluorescence imaging (on intact MPB communities) and polarographic oxygen measurement (in cell suspensions) (chapter 5). The parameters of DIC acquisition kinetics (Vmax and Km (DIC)) estimated for MPB communities were higher ((Km (DIC) = 0.31 mM; Vmax = 7.78 nmol min-1 μg (Chl a)-1), than those obtained for Phaeodactylum tricornutum (Km (DIC) = 0.23 mM; Vmax = 4.64 nmol min-1 μg (Chl a)-1), showing that these communities have species with low affinity for DIC and high photosynthetic capacity. The net photosynthesis of MPB suspensions reached saturation at DIC concentrations of 1-1.5 mM, 17 lower than those found in the sediment top 5 mm interstitial water, suggesting that the photosynthesis of these communities is not limited by DIC availability. However, when NaHCO3 was added to intact MPB samples, an increase in the maximum photosynthetic electron transport rate (ETRmax) was observed. These results suggest that the local depletion of DIC in the photic layer of the sediment, where the microalgae accumulate during diurnal low tide, limits the photosynthetic activity of MPB, providing the first experimental evidence of DIC limitation of the productivity of intertidal MPB communities. The interactive effects of temperature and DIC in biomass, species composition and photosynthetic performance of MPB was studied using a microcosm ELSS ('experimental life support system') with tide regime (chapter 6). The longer term effect of increased temperature (24 ° C) had a negative effect on MPB biomass and photosynthetic performance under both simulated DIC conditions (pH = 7.4 and pH = 8.0). Furthermore, at elevated temperatures there was a change in the relative abundance of the major species of diatoms and an increase of cyanobacteria. The long term effect of increasing DIC ( pH = 7.4) under low temperature (18 °C) had a positive effect on biomass MPB, possibly due to decreased local depletion of dissolved inorganic carbon. No significant effects were found on the relative abundance of the major groups of microalgae. Our results suggest that the interactive effects of increased temperature and DIC availability of estuarine MPB communities can have a negative impact on the structure, diversity and productivity of these communities, eventually affecting the entire estuarine ecosystems. Therefore, a deepen understanding of the potential impacts of climate change in these complex ecosystems is required.
Iyer, Kogilam. "The dynamics of microphytobenthos in the Mdloti and Mhlanga estuaries, Kwazulu-Natal." Thesis, 2004. http://hdl.handle.net/10413/2370.
Повний текст джерелаThesis (M.Sc.)-University of KwaZulu- Natal, 2004.
Lee, SH. "The photosynthetic response and extracellular carbohydrate production of tropical and temperate microphytobenthos." Thesis, 2019. https://eprints.utas.edu.au/31419/1/Lee_whole_thesis.pdf.
Повний текст джерела