Dissertations / Theses on the topic 'Marine light'
To see the other types of publications on this topic, follow the link: Marine light.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Marine light.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Niclasen, Niclas Oddur. "Light weight marine vessels operating in brash Ice." Thesis, KTH, Lättkonstruktioner, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-180043.
Full textAbstract:
This is a master thesis, done as a part of the ongoing research projects ”Vattenvägen 365” and ”LightIce - Light weight marine vessels operating in brash Ice”. This work is a study of the design of a high speed craft, intended for use in the public transportation network in the Stockholm area. Emphasis is put on investigating the consequences of the ice conditions in the area during winter. The work is primarily done as a case study, based on the design of a high speed passenger vessel, intended to navigate in ice. The ice conditions considered are light ice conditions, like brash ice and thin ice sheets. In connection with the high speed craft design, work is done on the effect of the choice of material concept. The scope of the work is as follows. To look into the existing literature on the topics of ice loads on high speed crafts and the use of lightweight materials in the construction of ice-going vessels. Create an initial design of a high speed craft suitable for passenger transportation in the Stockholm area. Gain insight into the ice loading on a high speed craft, and looking into the use of composite and lightweight materials.A literature review on literature related to ice loading of high speed crafts is done. A vessel is brought into the initial design stage, basing the design on a operational profile developed for a suggested route for commuter transportation in the Stockholm area. This high speed craft is used as a basis for comparison of different methods for estimation of ice loading. Testing is planned to investigate the ice loading of high speed crafts, based on the operational profile and vessel design. In connection with testing, a loading scenario is created by estimating the expected maximum ice thickness during a winter in the intended area of operation, an impact scenario is defined and work is done with regards to estimation of ice floe size and modelling of the impact between the vessel under normal operational conditions and an ice floe. For the testing, full scale hull panels are designed in four different materials, both metal and composite. Testing is planned using the defined loading and the designed hull panels.The thesis serves as a basis for conducting further research into the topic of ice loading of high speed crafts.
2
Burrow, Andrew D. "Marine Corps light armored vehicle automated data collection analysis." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5037.
Full textAbstract:
Approved for public release; distribution is unlimitedThis thesis describes the analysis of a Sense and Respond Logistics program as applied to the United States Marine Corps' Light Armored Vehicle. This program was initialized in 2003 by the Program Manger, Light Armored Vehicle in an effort to provide both users and commanders with real-time logistics information. This real-time information is collected from the Light Armored Vehicle via sensors that are placed in critical areas. The analysis carried out for this thesis centers upon the data collected from the aforementioned sensors during Phase II and Phase III of the overall program. The sensor data is compared to normal operating parameters for the respective component. The data collected in Phase II is also compared with Phase III. Most of the data from both phases falls within normal limits, 77% and 63% respectively. However, there is evidence to suggest a statistical difference between Phase II and Phase III. Due to the lack of baseline data, it is impossible to determine which phase is more accurate. Only nonparametric methods are used in this analysis.
3
Birkett, Daryl Anne. "Effects of light on phosphate uptake by marine macroalgae." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359021.
Full text
4
Mangogna, Manuela. "Studies of light perceptionin marine diatoms and discovery of a novel blue light cryptochrome photoreceptor." Thesis, Open University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446292.
Full text
5
Chuck, Adele Louise. "Biogenic halocarbons and light alkyl nitrates in the marine environment." Thesis, University of East Anglia, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251499.
Full text
6
Brown, Conrad Nelson. "Cost analysis of recapitalizing Marine light attack helicopter assets : a case study /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA306101.
Full textAbstract:
Thesis (M.S. in Management) Naval Postgraduate School, December 1995.Thesis advisor(s): Shu S. Liao, David F. Matthews. "December 1995." Includes bibliographical references. Also available online.
7
Gilfoyle, Christopher. "Interactions of light with nitrogen limitation in marine microalgae in chemostat culture." Thesis, Queen Mary, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410145.
Full text
8
Duchêne, Carole. "Light sensing in the Ocean : studying diatom phytochrome photoreceptors." Electronic Thesis or Diss., Sorbonne université, 2022. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2022SORUS164.pdf.
Full textAbstract:
Les algues marines telles que les diatomées possèdent un large éventail de photorécepteurs de lumière bleue et verte, mais aussi des phytochromes (DPH), capable de réguler l'expression des gènes en réponse à la lumière RL chez la diatomée modèle Phaeodactylum tricornutum (Pt). Cependant, la fonction biologique de ce photorécepteur est encore inconnue. Grâce à un système rapporteur permettant de suivre l'activité de PtDPH in vivo, j’ai pu caractériser ses propriétés photochimiques, modéliser son activité dans différents champs lumineux marins, et montrer que les DPH en détectent les variations liées à la profondeur et la concentration de phytoplancton. J'ai également recherché les DPH dans les génomes et transcriptomes de diverses diatomées et analysé leur distribution dans l'environnement en utilisant les données méta-omiques générées au cours de l'expédition Tara Oceans. Cela a révélé que les diatomées planctoniques du groupe des centriques possédant des DPH sont présentes dans les zones polaires et tempérées, tandis que les diatomées pennées, vivant dans les sédiments peuvent présenter une duplication du gène DPH. Nous avons montré que ces gènes dupliqués ont des propriétés spectrales différentes, et que certaines diatomées benthiques montrent une adaptation spécifique à la lumière R qui pourrait être régulée par DPH. Ce travail apporte de nouvelles connaissances sur les mécanismes de perception de la lumière chez les diatomées, et leurs importances pour coloniser différentes niches environnementalesLight is an essential source of energy and information for photosynthetic organisms. In the marine environment, red and far-red lights are quickly attenuated in the water column compared to blue and green light. Accordingly, predominant marine algae such as diatoms possess a wide array of blue and green light photoreceptors, but also red (R)/far-red (FR) light sensing phytochrome photoreceptors (DPH), capable of regulating gene expression in response to FR light in the model diatom Phaeodactylum tricornutum (Pt). However, the biological function of this photoreceptor is still unknown. By setting up a reporter system to monitor PtDPH activity in vivo, I was able to characterize its photochemical properties, model its activity in different marine light fields, and show that DPHs can detect variations related to depth and phytoplankton concentration. Using bioinformatics approaches, I looked for DPH in the available genomes and transcriptomes of diverse diatoms and analyzed their distribution in the environment using the meta-omics data from the Tara Oceans expedition. This revealed that planktonic diatoms of the centric group possessing DPH are present in temperate and polar regions. In these species DPH may work as sensor of depth and phytoplankton concentration. Pennate diatoms living in sediments can present duplications of the DPH gene. We showed that these duplicated genes can have different spectral properties, and that some benthic diatoms show a specific adaptation to R light that could be regulated by DPH. This work brings new insights into DPH-mediated light perception mechanisms in diatoms, and their significance for colonizing various environmental niches
9
Maxey, Johnathan Daniel. "Shedding Light on the Estuarine Coastal Filter: The Relative Importance of Benthic Macroalgae in Shallow Photic Systems." W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539617924.
Full text
10
Squire, Louise R. "Natural variations in the zooxanthellae of temperate symbiotic Anthozoa." Thesis, Bangor University, 2000. https://research.bangor.ac.uk/portal/en/theses/natural-variations-in-the-zooxanthellae-of-temperate-symbiotic-anthozoa(a6342fd8-ff91-441e-85db-8b5b1c59167e).html.
Full textAbstract:
Few previous studies of zooxanthellae have considered temperate Anthozoan symbioses. The present study investigates how the characteristics of zooxanthellae symbiotic with temperate Anthozoa vary in response to natural variations in environmental parameters. Variations in the number (density), division rate, size and ultrastructure of zooxanthellae from the temperate anemones Anemonia viridis (Forskal) and Anthopleura ballii (Cocks) were examined in response to season, water depth and artificial irradiance (A. viridis in aquaria). In addition, variations in chlorophyll concentrations were considered in intertidal and laboratorymaintained A. viridis. Zooxanthellae from both intertidal and shallow subtidal A. viridis showed variations which correlated with seasonal variations in environmental parameters. Zooxanthella density in intertidal A. viridis showed an inverse relationship with temperature, daylength and sunshine. Higher zooxanthella density was observed in A. viridis from a shallow, subtidal habitat during February 1998 (2.06 ± 0.11 x 108 cells g"' wet weight) than during July 1998 (1.01 ± 0.09 x 108 cells g'' wet weight; T= 7.67, p< 0.001). Stereological analysis of transmission electron micrographs showed that zooxanthellae in intertidal A. viridis had significantly higher chloroplast volume fraction during February (32.1 ± 1.5 %) than July (21.8 ± 2.1 %; T= 4.07, p<0.05). The proportion of chlorophyll a per zooxanthella was significantly higher in December than all other months except January (ANOVA, F= 5.62 p<0.05). The zooxanthellae of A. viridis may thus photoadapt to low winter irradiances by increasing zooxanthellae density, chloroplast volume and the proportion of chlorophyll a per cell. By contrast, zooxanthellae from A. viridis maintained in artificial irradiances in the laboratory of 4 µmol m=2 s' and 20 pmol m2 s' showed no variation in density or ultrastructure, due either to the low irradiances used or a lack of variation in other physical parameters compared to the field. A. ballii zooxanthella density responded to both depth and season and was lower at 6m during summer than at 6m during winter and at 18 m during both summer and winter. Chloroplast volume fractions in A. ballii was not affected by depth during winter, nor by season at 18 in. Starch and lipid stores in zooxanthellae from both A. viridis and A. ballii responded to seasonal fluctuations. Lipid was present in zooxanthellae during summer (intertidal A. viridis, volume fraction 19.8 ± 3.4 %) and absent during winter, and starch volume was significantly higher from zooxanthellae in A. ballii at 6 in in winter (14.3 ± 4.2 %) than 18 min winter (4.7 ± 1.6 %) or summer (4.7 ± 1.1 %; ANOVA, F= 6.04 p< 0.05). It is concluded that the zooxanthellae of the temperate anemones A. viridis and A. ballfi show variations in zooxanthellae characteristics which correspond to variations in dayto-day weather, season and water depth.
11
Van, Horsten Natasha. "Photosynthetic response of Southern Ocean phytoplankton under iron and light limitations : bioassay experiments." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97861.
Full textAbstract:
Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The Southern Ocean (SO) is of significant interest in the understanding of the global carbon cycle and therefore many studies have been conducted to determine the limiting factors controlling the biological pump within the region. During photosynthesis phytoplankton require various nutrients such as NO3, PO4, inorganic carbon and the micronutrient Fe. The SO is a High-Nutrient Low-Chlorophyll region, therefore no macronutrient limitation is experienced by resident phytoplankton but instead the micronutrient Fe is a significant limiting factor within these waters due to limited inputs. Due to deep mixed layer depths, ice cover, low sun angles and cloud cover throughout parts of the year, light is also considered a limiting factor in the SO. Fe and light limitation cause a decrease in photosynthetic efficiency and therefore a decrease in carbon fixation capabilities. During this study we conducted five bioassay shipboard incubation experiments during two cruises along the Greenwich meridian between South Africa and the ice edge, SOSCEx during March and SAFePool during January to February, in which we varied Fe concentrations and light levels to determine the effects of Fe and light limitation or co-limitation within resident phytoplankton. Spatial and temporal variations in phytoplankton response were studied to determine varying effects of limitation across water masses and different stages of bloom decline within the study area. The combined addition of Fe and light gave the largest increase in biomass, photosynthetic capacity and nutrient uptake. In support of the hypotheses tested changes in the photosynthetic apparatus led to changes in the photosynthetic efficiency and growth of the SO phytoplankton, as a result of variations in Fe and light availability. Variability was also observed in the response of phytoplankton to Fe and light amendments due to spatial and temporal variation in resident phytoplankton communities. It was therefore concluded that both Fe and light are significant controls in the resident phytoplankton photosynthetic apparatus, photosynthetic capabilities, organic carbon fixation and therefore the biogeochemical cycles within the Atlantic sector of the SO.
AFRIKAANSE OPSOMMING: Die Suidelike Oseaan (SO) is van beduidende belang in die begrip van die globale koolstofsiklus en dus is baie studies gedoen om die beperkende faktore te bepaal wat die biologiese pomp in die streek beheer. Tydens fotosintese benodig fitoplankton verskillende voedingstowwe soos NO3, PO4, anorganiese koolstof en die mikrovoedingstof Fe. Die SO is 'n High-Nutrient Lae-Chlorofil streek, dus word geen makrovoedingstof beperking ervaar deur inwoner fitoplankton maar in plaas daarvan is die mikrovoedingstof Fe 'n beduidende beperkende faktor binne hierdie waters weens beperkte insette. As gevolg van diep gemengde laag dieptes, ysbedekking, lae son hoeke en wolkbedekking deur dele van die jaar, word lig ook beskou as 'n beperkende faktor in die SO. Fe en lig beperking veroorsaak 'n afname in die fotosintetiese doeltreffendheid en dus 'n afname in koolstof binding vermoëns. Tydens hierdie studie het ons vyf biotoets inkubasie eksperimente aan boord die skeep gedoen tydens twee vaarte langs die Greenwich meridiaan tussen Suid-Afrika en die ys rand, SOSCEx gedurende Maart en SAFePool gedurende Januarie tot Februarie, waarin ons Fe konsentrasies en lig vlakke gewissel het om die gevolge van Fe en lig beperking, of medebeperking, binne inwoner fitoplankton te bepaal. Ruimtelike en temporale variasies in fitoplankton reaksie was bestudeer om wisselende gevolge van die beperking oor watermassas en verskillende stadiums van bloei afname in die studie area te bepaal. Die gekombineerde byvoeging van Fe en lig het die grootste toename in biomassa, fotosintetiese kapasiteit en voedingsopname gegee. Ter ondersteuning van die getoetste hipoteses, veranderinge in die fotosintetiese apparaat het gelei tot veranderinge in die fotosintetiese doeltreffendheid en groei van die SO fitoplankton, as 'n gevolg van variasies in Fe en lig beskikbaarheid. Veranderlikheid is ook waargeneem in die reaksie van fitoplankton om Fe en lig wysigings weens die ruimtelike en tydelike variasie in inwoner fitoplankton gemeenskappe. Dus was dit by die gevolgtrekking gekom dat beide Fe en lig beduidende kontrole in die inwoner fitoplankton fotosintetiese apparaat, fotosintetiese vermoëns, organiese koolstof binding en daarom die biogeochemiese siklusse binne die Atlantiese sektor van die SO.
12
Bunse, Carina. "Bacterioplankton in the light of seasonality and environmental drivers." Doctoral thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-69130.
Full textAbstract:
Bacterioplankton are keystone organisms in marine ecosystems. They are important for element cycles, by transforming dissolved organic carbon and other nutrients. Bacterioplankton community composition and productivity rates change in surface waters over spatial and temporal scales. Yet, many underlying biological processes determining when, why and how bacterioplankton react to changes in environmental conditions are poorly understood. Here, I used experiments with model bacteria and natural assemblages as well as field studies to determine molecular, physiological and ecological responses allowing marine bacteria to adapt to their environment. Experiments with the flavobacterium Dokdonia sp. MED134 aimed to determine how the metabolism of bacteria is influenced by light and different organic matter. Under light exposure, Dokdonia sp. MED134 expressed proteorhodopsin and adjusted its metabolism to use resources more efficiently when growing with lower-quality organic matter. Similar expression patterns were found in oceanic datasets, implying a global importance of photoheterotrophic metabolisms for the ecology of bacterioplankton. Further, I investigated how the composition and physiology of bacterial assemblages are affected by elevated CO2 concentrations and inorganic nutrients. In a large-scale experiment, bacterioplankton could keep productivity and community structure unaltered by adapting the gene expression under CO2 stress. To maintain pH homeostasis, bacteria induced higher expression of genes related to respiration, membrane transport and light acquisition under low-nutrient conditions. Under high-nutrient conditions with phytoplankton blooms, such regulatory mechanisms were not necessary. These findings indicate that open ocean systems are more vulnerable to ocean acidification than coastal waters. Lastly, I used field studies to resolve how bacterioplankton is influenced by environmental changes, and how this leads to seasonal succession of marine bacteria. Using high frequency sampling over three years, we uncovered notable variability both between and within years in several biological features that rapidly changed over short time scales. These included potential phytoplankton-bacteria linkages, substrate uptake rates, and shifts in bacterial community structure. Thus, high resolution time series can provide important insights into the mechanisms controlling microbial communities. Overall, this thesis highlights the advantages of combining molecular and traditional oceanographic methodological approaches to study ecosystems at high resolution for improving our understanding of the physiology and ecology of microbial communities and, ultimately, how they influence biogeochemical processes.
13
Heijde, Marc. "Molecular study of light responses in the marine microalgae Phaeodactylum triconortum and Ostreococcus tauri." Paris 6, 2008. http://www.theses.fr/2008PA066164.
Full textAbstract:
Le phytoplancton inclue les diatomées et les prasinophycées qui sont deux groupes d’importance écologique majeure ayant maintenant intégré l’ère de la génomique grâce au séquençage de génomes et à la disponibilité d’outils moléculaires. Dans cette thèse, j’ai travaillé avec deux espèces, Ostreococcus tauri qui est une algue verte, et Phaeodactylum tricornutum qui est une diatomée pennée. Le génome d’O. Tauri a révélé la présence de cinq gènes de la famille des cryptochromes / photolyases et j’ai poursuivi la caractérisation fonctionnelle de deux d’entre eux (expression, activité photolyase, liaison à l’ADN, chromphores et activité de répresseur transcriptionnel). En plus de l’identification de ces mêmes récepteurs dans le génome de P. Tricornutum j’ai tenté de comprendre l’effet de la qualité et du cycle de la lumière sur l’ expression de ces gènes. En parallèle j’ai construit une banque d’ESTs et développé une puce à ADN qui m’a permis de faire une étude du transcriptome en lumière bleue.
14
Strydom, Simone. "Investigating the effects of changes in light quality on different life history stages of seagrasses." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2017. https://ro.ecu.edu.au/theses/1995.
Full textAbstract:
Seagrass meadows provide crucial ecosystem services to the coastal zone but globally are threatened. Seagrass loss to date has mainly been attributed to anthropogenic activities that reduce light quantity, such as dredging, declining water quality from urban and agricultural run-off and eutrophication. However, light quality (wavelengths of light) is also altered by these anthropogenic stressors as well as natural events. This study consisted of three main components: (1) characterising light quality to which seagrasses are exposed across a local natural estuarine-ocean gradient and with a human impact pressure; (2) the influence of monochromatic light quality (blue λ=451 nm; green λ=522 nm; yellow λ=596 nm and red λ=673 nm wavelengths and full-spectrum light λ=400 – 700 nm, at 200 μmol photons m-2 s-1) on Halophila ovalis and Posidonia australis at different life-history stages; and (3) the effects of light quality and quantity representative of a commercial dredging operation (15 mg L-1 TSS, 50 and 200 μmol photons m-2 s-1) on H. ovalis adult plants. The field work demonstrated that the quality of light to which seagrasses are exposed varies along a natural gradient but the nature of the shift is also dependent on time of year. Additionally, human impact such as dredging can expose seagrasses to spectra outside of the natural range detected in this study, and the magnitude of this shift is dependent on depth and TSS concentrations. Results from the monochromatic light quality experiments demonstrated, for the first time, the seagrass responses to light quality across several plant scales as well as different life-history stages. Halophila ovalis and P. australis showed different responses, likely due to their respective growth strategies. Adult H. ovalis (a colonising species) plants were negatively impacted by monochromatic blue, green and yellow light treatments, while seeds and seedlings performed better under red and full-spectrum light. Conversely, P. australis (a persistent species) adults showed no significant responses to any of the monochromatic light quality treatments, while seedlings demonstrated a physiological acclimation to blue light. The simulated dredging spectrum experiment demonstrated a significant impact of reduced light quantity on H. ovalis photo-physiology and growth, but the only significant effect of light quality was on the concentration of the pigment antheraxanthin. The lack of effect of light quality on growth indicates that: a) while seagrass are sensitive to changes in light quality, not all shifts induce negative biomass responses; b) the effects of altered light quality are less severe when a mixture of wavelengths are present; and c) in this species, reduced light quantity was more important than changes in light quality. Therefore, when considering the practical management of seagrasses in relation to short-term dredging activities, using light quantity thresholds is sufficient for management triggers. Overall, while there were some (positive and negative) responses to blue, green, yellow and red light, lethal effects were not detected for either the colonising or persistent species, suggesting that seagrasses have the VI capacity to acclimate to and/or tolerate extreme changes in light quality and maintain short-term growth at sufficiently high irradiances. However, sub-lethal responses were determined which may affect the ability of seagrasses to maintain resilience against other stressors. Therefore, environmental conditions that alter light quality have the potential to indirectly influence the overall resilience seagrasses.
15
Nickless, Stewart R. "Analysis of the operating costs for Light Armored Vehicles in the United States Marine Corps." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA363387.
Full textAbstract:
Thesis (M.S. in Management) Naval Postgraduate School, December 1998."December 1998." Thesis advisor(s): Joseph San Miguel, Brad R. Naegle. Includes bibliographical references (p. 63-66). Also available online.
16
Flori, Serena. "Light utilization in microalgae : the marine diatom Phaeodactylum tricornutum and the green algae Chlamydomonas reinhardtii." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV080/document.
Full textAbstract:
Les microalgues ont développé des approches distinctes pour moduler l'absorption de la lumière et son utilisation par leurs photosystèmes en réponse à des stimuli environnementaux. Dans ce rapport de Thèse je présente les différentes stratégies employées par une algue d'eau douce (Chlamydomonas reinhardtii) et une algue marine (Phaeodactylum tricornutum) pour optimiser leur acclimatation à l'environnement.Dans la première partie de ce rapport, je propose un modèle de cellules entières de la diatomée marine Phaeodactylum tricornutum obtenue par analyses spectroscopiques et biochimiques ainsi que par l’obtention d’images par microscopie électronique et reconstitution 3-D. Ce modèle a été utilisé pour répondre aux questions suivantes i. comment est structuré un chloroplaste secondaire pour faciliter les échanges avec le cytosol à travers les quatre membranes qui le délimitent ii. comment sont structurées les membranes photosynthétiques afin d’optimiser l'absorption de lumière et le flux d'électrons et iii. comment les chloroplastes et les mitochondries sont organisés pour optimiser l'assimilation du CO2 par échange ATP / NADPH.La deuxième partie de ce rapport porte sur la régulation de la collection de la lumière et de sa dissipation chez Chlamydomonas grâce à l'étude d'une part du rôle de la perception de la couleur de la lumière et d'autre part du métabolisme sur la dissipation de l'excès de lumière par quenching non photochimique (NPQ). En utilisant des approches biochimiques et spectroscopiques, j'ai mis en évidence un lien moléculaire entre la photoréception, la photosynthèse et la photoprotection chez Chlamydomonas via le rôle du photorécepteur phototropine, démontrant ainsi que le métabolisme, en plus de la lumière, peut aussi affecter ce processus d'acclimatation.En conclusion, ce travail de thèse révèle l'existence et l'intégration des différentes voies de signalisation dans la régulation des réponses photoprotectrices mises en place chez les microalgues marines et d'eau douceMicroalgae have developed distinct approaches to modulate light absorption and utilization by their photosystems in response to environmental stimuli. In this Ph.D Thesis, I characterised different strategies employed by freshwater (Chlamydomonas reinhardtii) and marine algae (Phaeodactylum tricornutum) to optimise their acclimation to the environment.In the first part of this work, I used spectroscopic, biochemical, electron microscopy analysis and 3-dimentional reconstitution to generate a model of the entire cell of the marine diatom Phaeodactylum tricornutum. This model has been used to address the following questions: i. how is a secondary chloroplast structured to facilitate exchanges with the cytosol via its four membranes envelope barrier ii. how have diatoms shaped their photosynthetic membranes to optimise light absorption and downstream electron flow and iii. how the cellular organelles interact to optimise CO2 assimilation via ATP/NADPH exchanges.In the second part, I have focused on the regulation of light harvesting and dissipation in Chlamydomonas by studying the role of perception of light colour and metabolism on excess light dissipation via the Non-Photochemical Quenching of energy (NPQ). Using biochemical and spectroscopic approaches, I found a molecular link between photoreception, photosynthesis and photoprotection in Chlamydomonas via the role of the photoreceptor phototropin on excess absorbed energy dissipation (NPQ) and also demonstrated that besides light, downstream metabolism can also affect this acclimation process.Overall this Ph.D work reveals the existence and integration of different signal pathways in the regulation of photoprotective responses by microalgae living in the ocean and in the land
17
Collier, Catherine J. "Characterising responses of the seagrass Posidonia Sinuosa to changes in light availability." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2006. https://ro.ecu.edu.au/theses/344.
Full textAbstract:
The unrelenting threat of seagrass loss resulting from reduced light availability has motivated this characterisation of responses of Posidonia sinuosa Cambridge et Kuo to light availability and their application as monitoring tools. The study comprised of three major components: an assessment of P. sinuosa characteristics across a depthrelated gradient in long-term light availability; an in situ experiment to test for responses to short-term light reduction; and experimental investigations into the role of translocation to cope with reduced light availability. Across depth-related gradients of light, in two locations, near Perth in Western Australia, the minimum light requirement (MLR) of P. sinuosa at the depth limit was 8.5% of sub-surface irradiance. Shoot density and biomass consistently differed across the gradient while other morphological and growth differences between depths were inconsistent between location and season or did not follow the gradient of light reduction. Physiological characteristics including RLC-derived characteristics, light harvesting and photoprotective pigments and nutrient and carbohydrate concentration demonstrated few depth-related differences but showed limited adjustment between seasons. The light dependency of these observations was validated experimentally by in situ shading at a shallow (3- 4 m) and deep (7- 8 m) site with light (LS; 87% of ambient light), moderate (MS; 27%) and heavy shading (HS; 9% at shallow only). After 106 d, significant shoot loss had occurred but complete loss did not occur after 206 d. Shoot loss substantially reduced the light attenuation coefficient of the canopy (and self-shading) from 2.8 (control) to 0.5 m-1 (HS). Carbohydrate reduction occurred in most shade treatments probably supporting respiration and growth (which was not affected by shading except in MS at the deep site). Few other responses were observed in treatments near or above MLR, but in those below MLR (HS at the shallow and MS at the deep site) photosynthetic and morphological responses were detected including photosynthetic characteristics, length/weight ratio of leaf growth and δ13Cvalues. Following removal of shading, recovery of shoot density was slow, remaining significantly lower than the control after 384 d, and depended on shoot density; rate of shoot production was faster when higher shoot densities remained following shading. Nutrient translocation of 15N and 13C within and between shoots was investigated in the early phase of imposed shading. Following incubation of a mature leaf (ML), the 13C and 15N accumulated in the young growing leaf(YL) and rhizome, with up 32% and 44% of the 15N and 13C, respectively, appearing in the YL after 29 d. Resorption of structural nitrogen (N) from the ML may also contribute to YL N requirements but not for carbon (C). For 13C and 15N exported from the shoot, there was a trend for greater 13C accumulation away from, rather than towards, the rhizome apex but not for 15N. Most of the C and N was recovered in the rhizome, and not shoots, after 8 and 15 d. There was no evidence that the translocation of C or N within or between shoots is altered as an early response to shading. For P. sinuosa, shoot density reductions dominate the response to reduced light availability at light intensities above MLR and can be considered a meadow-scale response with benefits for reduced self-shading. Growth rate of shoots is usually unaffected by depth (during summer) or shading. Below MLR, other morphological and physiological responses can also occur. Clonal integration via the rhizome is important for carbohydrate storage and remobilisation during periods of low light, but changes to translocation between or within shoots are not important shade responses. These findings should also be relevant to other meadow-forming and persistent seagrass species. Shoot density was recommended as an appropriate monitoring indicator because it is consistently responsive and crucial in P. sinuosa's response mechanisms, while other physiological responses including carbohydrates in the rhizome have potential as monitoring tools.
18
Hague, Mark. "Ice - ocean - atmosphere interactions in the Southern Ocean and implications for phytoplankton phenology." Doctoral thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33708.
Full textAbstract:
The annual advance and retreat of sea ice in the Southern Ocean is recognised as one of the largest seasonal events on Earth. Such considerable physical changes have profound effects on the vertical structure of the water column, and hence controls the availability of both light and nutrients to phytoplankton. This means that in the region seasonally covered by sea ice (the SSIZ), the timing of the growth and decline (phenology) of phytoplankton is determined to a large degree by the dynamic interactions between ice, ocean and atmosphere. However, this region is simultaneously one of the most poorly observed in the global ocean, and one of the most complex. This has led to significant gaps in our understanding of how sea ice modulates the exchanges of heat and momentum between atmosphere and ocean, as well as the implications this has for phytoplankton phenology in the SSIZ. This study seeks to address these gaps by combining both model and observationallybased methods. The lack of observational data are directly tackled through an analysis of BGC-Argo float data sampling under ice. Such data reveal high growth rates in the presence of near full ice cover and deep mixed layers, conditions previously thought to prevent growth. These results suggest a revision of our current understanding of the drivers of under ice phytoplankton phenology, which should take into account the unique character of Antarctic sea ice and its effect on the under ice light environment. In addition, results obtained from several numerical process studies indicates that phytoplankton may have a higher affinity for low light conditions than previously thought. From a modelling perspective, an analysis and intercomparison of 11 Earth System Models (ESMs) and their representation of vertical mixing and phenology is presented. This revealed that misrepresentations in phenology where driven by model biases in sea ice cover and vertical mixing. That is, only models with either too much or too little ice cover were able to simulate phenology close to observations. Furthermore, a strong correlation between the location of the ice edge and the extent of vertical mixing suggested that ESMs overly dampen ocean-atmosphere fluxes as mediated by sea ice. This led to the development of a regional ocean-sea ice model of the Atlantic sector of the Southern Ocean, from which experiments enhancing both heat and momentum fluxes could be conducted. It was found that the model responded more uniformly to enhanced heat flux, generally deepening the mixed layer closer to observations in winter. On the other hand, the effects of enhanced momentum flux (implemented by increased air-ice drag) where more complex and spatially heterogeneous, with contrasting responses depending on the initial vertical density structure of the water column. Overall, the argument is made that the unique features of Antarctic sea ice should be included in models if we are to improve the representation of the SSIZ mixed layer, and hence phenology
19
Hancke, Kasper. "Photosynthetic responses as a function of light and temperature: Field and laboratory studies on marine microalgae." Doctoral thesis, Norwegian University of Science and Technology, Department of Biology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1586.
Full textAbstract:
The aim of my thesis is to elucidate the different pathways of light in the marine environment, from underwater irradiance to the absorption of photons in microalgae. The pathway is followed through light harvesting and the subsequent electron transfer, to the fuelling of the photosynthetic process (Fig. 1.1, Papers 1, 2 & 3). In addition, the effect of temperature on photosynthesis and respiration in pelagic and benthic microalgae has been investigated (Papers 3 & 4). A novel approach to estimate the light absorption in Photosystem II (PSII) is evaluated in combination with Pulse Amplitude Modulated (PAM) fluorescence measurements, to calculate the rate of photosynthetic oxygen production (Paper 2). The approach was evaluated against measured rates of oxygen production and 14C-assimilation, as a function of temperature (Papers 2 & 3).
20
Matallana, Surget Sabine-Astrid Biotechnology & Biomolecular Sciences Faculty of Science UNSW. "Physiological and molecular responses of the marine oligotrophic ultramicrobacterium Sphingopyxis Alaskensis rb2256 to visible light and ultraviolet radiation." Awarded By:University of New South Wales. Biotechnology & Biomolecular Sciences, 2009. http://handle.unsw.edu.au/1959.4/43251.
Full textAbstract:
Ultraviolet radiation reaching the Earths surface (UVR, 280-400 nm) may penetrate deep into the clear oligotrophic waters influencing a large part of the euphotic layer. Marine heterotrophic bacteria at the surface of the oceans are especially sensitive to the damaging solar radiation due to their haploid genome with little or no functional redundancy and lack of protective pigmentation. In a context of climate change and ozone depletion, it is clearly important to understand the physiology and underlying molecular UVR responses of abundant marine bacteria species. We chose the marine ultramicrobacterium Sphingopyxis alaskensis as a reference species to study the impact of solar radiation due to its numerical abundance in oligotrophic waters and its photoresistance, previously reported. For this purpose, we focused on the formation of the two major UVB-induced DNA photoproducts (CPDs and 6-4PPs) as well as the differential protein expression under solar radiation. We first demonstrated that the GC content of prokaryotic genome had a major effect on the formation of UVB-induced photoproducts, quantified by HPLC-MS/MS. Due to its high GC content, S. alaskensis presented a favoured formation of highly mutagenic cytosine-containing photoproducts and therefore would be more susceptible to UVinduced mutagenesis. By comparing S. alaskensis to another marine bacterium Photobacterium angustum, we observed for the latter strain a remarkable resistance to high UVB doses associated with a decrease in the rate of formation of CPDs explained by a non-conventional activity of photolyase. We also demonstrated that DNA damage in S. alaskensis was markedly modulated by growth temperature and time spent in stationary phase. In order to assess the effects that environmental UV-R had on regulatory networks and pathways of S. alaskensis, and determine how the cells physiology was affected, a quantitative proteomics investigation was performed. Changes in proteome were analyzed, with the recent and powerful mass spectrometry based approach using iTRAQ methodology. Approximately, one third of the proteome of S. alaskensis was identified, with 119 statistically and significantly differentially abundant proteins. Cellular processes, pathways and interaction networks were determined and gave us unique insight into the biology of UV response and adaptation of S. alaskensis.
21
Faithfull, Carolyn. "Productivity and carbon transfer in pelagic food webs in response to carbon, nutrients and light." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43467.
Full textAbstract:
Some of the major problems we face today are human induced changes to the nitrogen (N), phosphorus (P) and carbon (C) cycles. Predicted increases in rainfall and temperature due to climate change, may also increase dissolved organic matter (DOM) inflows to freshwater ecosystems in the boreal zone. N, P, C and light, are essential resources that most often limit phytoplankton (PPr) and bacterial production (BP) in the pelagic zone of lakes. PPr and BP not only constitute the total basal C resource for the pelagic aquatic food web, but also influence ecosystem function and biogeochemical cycles. In this thesis I studied how N, P, C and light affect the relative and absolute rates of PPr and BP, along a wide latitudinal and trophic gradient using published data, and in two in situ mesocosm experiments in a clear water oligotrophic lake. In the experiments I manipulated bottom-up drivers of production and top-down predation to examine how these factors interact to affect pelagic food web structure and function. The most important predictors of PPr globally (Paper I) were latitude, TN, and lake shape. Latitude alone explained the most variation in areal (50%) and volumetric (40%) PPr. In terms of nutrients PPr was primarily N-limited and BP was P-limited. Therefore bacteria and phytoplankton were not directly competing for nutrients. BP:PPr was mostly driven by PPr, therefore light, N, temperature and other factors affecting PPr controlled this ratio. PPr was positively correlated with temperature, but not BP, consequently, higher temperatures may reduce BP:PPr and hence the amount of energy mobilised through the microbial food web on a global scale. In papers II and III interaction effects were found between C-additions and top-down predation by young-of-the-year (YOY) perch. Selective predation by fish on copepods influenced the fate of labile C-addition, as rotifer biomass increased with C-addition, but only when fish were absent. Interaction effects between these top-down and bottom-up drivers were evident in middle of the food web, which is seldom examined in this type of study. Although the energy pathway from bacteria to higher consumers is generally longer than from phytoplankton to higher trophic levels, increased BP still stimulated the biomass of rotifers, calanoid copepods and YOY fish. However, this appeared to be mediated by intermediate bacterial grazers such as flagellates and ciliates. Light was an important driver of crustacean zooplankton biomass (paper IV), but the light:nutrient hypothesis was inadequate to predict the mechanisms behind the decrease in zooplankton biomass at low light. Instead, it appeared that reduced edibility of the phytoplankton community under low light conditions and reduced BP most strongly affected zooplankton biomass. Thus, the LNH may not apply in oligotrophic lakes where PPr is primarily N-limited, Daphnia is rare or absent and mixotrophic phytoplankton are abundant. N, P, C and light manipulations have very different effects on different parts of the pelagic food web. They influence the relative rates of PPr and BP, affect phytoplankton community composition, alter the biomass of higher trophic levels and change pathways of energy transfer through the pelagic food web. This thesis adds valuable information as to how major changes in these resources will affect food web structure and function under different environmental conditions and future climate scenarios.Lake ecosystem response to environmental change
22
Barcelos, e. Ramos Joana [Verfasser]. "Responses of selected species of marine phytoplankton to increasing carbon dioxide and light / Joana Barcelos e Ramos." Kiel : Universitätsbibliothek Kiel, 2009. http://d-nb.info/1019869658/34.
Full text
23
Matallana, Surget Sabine. "Physiological and molecular responses of the marine oligotrophic ultramicrobacterium Sphingopyxis alaskensis RB2256 to visible light and ultraviolet radiation." Paris 6, 2009. http://www.theses.fr/2009PA066080.
Full textAbstract:
Les rayonnements ultraviolets (UVR) pénétrent en profondeur dans les eaux claires oligotrophes affectant une large part de la couche euphotique. Les bactérie hétérotrophes marines jouent un rôle fondamental dans la reminéralisation de la matière organique dissoute et sont spécialement sensibles aux UVR à la surface des océans. Dans un contexte de changement climatique et réduction de la couche d'ozone, il est fondamental de mieux comprendre la physiologie et la réponse de bactéries marines abondantes, exposées aux UVR. Nous avons choisi comme modèle d'étude, la bactérie Sphingopyxis alaskensis, numériquement abondante dans les eaux oligotrophes et précédemment décrite comme photorésistante. Nous avons démontré que les dommages ADN sont fortement modulés par le GC%, la température de croissance et temps passé en phase stationnaire. Les modifications du protéome ont été également analysées par technique iTRAQ et des processus cellulaires originaux ont été caractérisés en réponse aux UVR.
24
Watters, Jessica A. "The Effects of Ecological Light Pollution and Silhouette Height on the Nesting Densities of Caretta caretta in Broward County, Florida." NSUWorks, 2007. http://nsuworks.nova.edu/occ_stuetd/101.
Full textAbstract:
Many environmental parameters, both physical and anthropogenic, can influence nest site selection. One of the most basic requirements for a suitable nesting habitat is a dark beach. With the increases in coastal development, the beaches of Broward County, Florida are becoming more polluted by artificial light, making dark beaches a rarity. On urban beaches in Boca Raton, Florida, it was found that turtles nested directly in front of tall structures, such as high-rise condominiums and clusters of Australian pine trees (Casuarina equisetifolia), that blocked the sky glow from the city providing darker sections of the beach more suitable to nesting females (Salmon et al., 1995). The goal of this project was to compare the previous four years (2002-2005) of nesting with the heights of the buildings and the sky brightness, in historically high nesting zones of Broward County (Mattison, 2004). Nesting distributions were plotted using GIS (Global Information Systems), and the beach was subdivided into smaller sections according to the buildings in each section. The number of nests in front of a building, in front of a gap between the buildings, and in residential zones were compared. The average nesting density (nests/10m) over all four years, as well as the individual yearly densities were analyzed. Ecological light pollution (sky brightness) was measured in nine different directions and angles. The brightest direction for all three locations was when the meter was pointed directly at the structures and the gaps between them at an elevation of 40° (Building and Gap 40°). There was no evidence of higher light intensities from sky glow above the buildings at an angle of 65o (Building and Gap 65°). There was a difference in sky brightness among the three zones, with the tall buildings and gaps being consistently brighter than the residential zones. Contrary to expectations, the gaps were not brighter than the buildings, and there was no significant relationship between sky brightness and nesting densities (Spearman rank correlation). There was also no relationship between the nesting densities and the heights of the buildings (Spearman rank correlation). There was also no association among nesting density, sky brightness, and height (Kendall’s coefficient concordance). These results are contradictory to the theory that suggests females nest more in front of buildings where the sky brightness is blocked (Salmon et al., 1995). This may be due to the fact the buildings and residences were not incompliance with lighting ordinances, causing very high light levels, or it could be caused by the close spacing of the buildings, which resulted in similar light intensities in front of buildings and gaps. These results could provide valuable insight into appropriate management of light pollution and conservation efforts for sea turtles nesting in Broward County.
25
Jeong, Gill-Ran. "Investigation of Mineral Dust Aerosols - Chemistry Intractions in the Marine Environments." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19805.
Full textAbstract:
Mineral dust aerosols play an important role in atmospheric chemistry through photolysis and heterogeneous uptake. Both mechanisms strongly depend on the size and composition of mineral dust. Because of the complex nature of dust, chemistry modeling commonly relies on simplified assumptions about the properties of dust particles relevant to physiochemical processes. The goal of this thesis is to investigate the impact of size-resolved composition of dust aerosols on atmospheric photochemistry. The relative importance of dust characteristics in photolysis and heterogeneous loss and the relative roles of the two mechanisms on atmospheric photochemistry are investigated.
A new block of spectral aerosol optical properties was developed and incorporated into the tropospheric ultraviolet and visible radiation transfer code in order to calculate spectral actinic fluxes and photolysis rates, J-values. The Fuchs-Sutugin approximation was employed to compute mass transfer from gas to dust mineral species and heterogeneous loss rate, kloss,j. The J-values and kloss,j were incorporated into a one-dimensional photochemistry model to simulate the diurnal cycle of a vertical profile of photochemical species. Several cases of dust loading were considered in the clean and polluted marine environments. A size-resolved mineralogical composition was constructed by selecting a range of the mass fraction of the three main mineral species such as iron oxide-containing clay minerals, carbonate-containing species, and quartz.
This work demonstrates that differences in microphysical and chemical properties of mineral dust lead to the important changes in spectral optical properties, J-values, and kloss,j. It also shows that non-linear relationships of photochemical species with two mechanisms result in various changes in the photochemical oxidant fields and that the most important factor controlling the photochemistry field is the dust size distribution, followed by the amount of mineral species with high uptake coefficients and the amount of iron oxide-clay aggregates.
This work demonstrates that accounting for regional differences in microphysical and chemical properties of mineral dust will improve the assessment of the impact of mineral dust on tropospheric photochemistry. In addition, it suggests that the size and composition of mineral dust will lead to a deeper understanding of the impact of mineral dust on the global climate system.
26
Hagemann, Andreas. "Cold storage of eggs of Acartia tonsa Dana: effects of light, salinity and short-term temperature elevation on 48-h egg hatching success." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13002.
Full textAbstract:
Copepods play a key role in the marine ecosystem where they form a vital trophodynamic link between primary and tertiary producers, and are the dominant prey of many marine fishes during their larval stage. Because of their naturally high nutritional quality, copepods are excellent alternatives to traditional live feed organisms for intensive marine fish production. For aquaculturists, it is important to have continuous access to live feed organisms when rearing altricial fish larvae. Cold stored subitaneous copepod eggs are highly relevant as inoculum for culturing live food.In the present study, the effects of light, salinity and short-term elevations in temperature on the 48-h hatching success (HS, %) of cold stored (2 °C) A. tonsa eggs were evaluated. A light experiment exposed the eggs to three different environments with respect to light for a period of up to 7.5 months; one treatment exposed the eggs to an artificial light source, the second treatment had eggs stored in complete darkness, and the third treatment had eggs stored under the storage conditions applied at NTNU Sealab (SSC-treatment). A salinity experiment stored eggs in seawater of four different salinities (34, 50, 75 and 100 ) for a period of up to 7.5 months to evaluate if this was beneficial for long-term cold storage of A. tonsa eggs. A short-term temperature elevation experiment was conducted in order to simulate shipping conditions with insufficient cooling for consignments of A. tonsa eggs. Cold stored eggs were exposed to temperatures elevated to 9 and 17 °C for 12 and 24 hours, with and without oxygen present in the storage media, whereupon they were put back in cold storage for a period of one week before determining the HS.The results for the light experiment showed that light had a profound negative effect on the HS of the cold stored A. tonsa eggs. No hatching was observed for eggs that were stored under constant light after 3 months of cold storage. Eggs stored in darkness showed a significantly higher HS at the final sampling of month 7.5 compared to the SSC treatment, and less dispersion in HS between the replicates throughout the experiment. The salinity experiment showed that the eggs could be stored in seawater with a salinity of 50 for up to 3 months with a high HS, whereas storage in seawater of 75 and 100 showed a low HS for most samplings and thus proved as a poor cold storage media. The short-term elevation in temperature experiment showed that the HS was significantly affected by the oxygen concentration in the seawater upon a cold storage period of 3 weeks, and that short-term elevations in temperature, up to 17 °C for a duration of 24 hours, did not significantly affect the HS when hatched one week after the onset of incubation. The viability of the hatched nauplii post temperature exposures was assessed in a feeding incidence experiment. It showed that neither of the conducted temperature elevations utterly inhibited the nauplii from feeding.
27
Foster, Kristi A. "Effects of Reduced Light and Elevated Temperature on the Zooxanthellae Concentrations and Diameters, Pigment Concentrations, and Colony Color of Montastrea cavernosa." NSUWorks, 2005. http://nsuworks.nova.edu/occ_stuetd/275.
Full textAbstract:
This study measured certain biological characteristics (zooxanthellae concentrations and diameters, pigment concentrations, and colony color) of Montastrea cavernosa from the outer reef (16.8 - 26.5 m) in Broward County, FL in response to reduced light and elevated temperature stresses. The low light treatment simulated a lowering of light in the summertime (possibly associated with a turbidity increase from an event such as a hurricane, ship grounding, or dredging). The high temperature treatment was set at the maximum expected anomaly (3°C above the average summer maximum) to simulate the effect of warmer than normal seawater. The combination treatment tested for synergistic effects. Zooxanthellae concentrations and cell sizes were measured microscopically. Photosynthetic pigment (chlorophyll a, chlorophyll c, peridinin, diadinoxanthin, and β-carotene) concentrations were measured by high performance liquid chromatography. Significant decreases were found in zooxanthellae and pigment concentrations due to the elevated temperature treatments. No significant changes in zooxanthellae and pigment concentrations were observed due to the low light conditions or due to interactions from the combined stresses. Zooxanthellae cell sizes-did not change significantly, regardless of treatment.
Coral color change, "bleaching", was measured by a novel RGB color analysis method. Significant decreases were found in coral color due to the elevated temperature treatments. No significant changes were observed due to the low light conditions or due to interactions from the combined stresses. These results agreed with those for zooxanthellae and pigment concentrations, indicating that RGB color analysis was an acceptable, non-destructive method to quantify coral bleaching. RGB color analysis has benefits over qualitative visual observations that include (i) the reproducibility of color values despite differences in color perception and changes in ambient lighting and (ii) comparisons of color change within variable-colored coral species (e.g. Montastrea cavernosa) and between two or more species of different colors (e.g. Acropora cervicornis and Siderastrea radians).
28
Riley, Scott. "Measuring Viability of the Red-Tide Dinoflagellate Lingulodinium polyedra Following Treatment with Ultraviolet (UV) Light." NSUWorks, 2014. http://nsuworks.nova.edu/occ_stuetd/4.
Full textAbstract:
Harmful algae blooms (HABs) have caused millions dollars in annual losses to the aquaculture industry, inhibited beach recreation, and have threatened marine and human health. HABs and red tides can develop suddenly and their frequency, geographic range, and intensity have increased over the past decade. A possible source for spreading and seeding new areas expanding the geographic range of HABs is ballast water. The process of ballast water discharge has been identified as a primary vector for the translocation of non-indigenous species (NIS) and invasive species. National and international efforts are currently underway to address the impact of NIS and invasive species. Policy is being developed detailing stringent rules to kill, remove, or otherwise inactive organisms in ballast water prior to or upon discharge. Currently, vendors are developing technologies to treat ballast water and U.S. and international facilities are testing these technologies to verify their efficacy. Ultraviolet (UV) radiation is commonly employed in ballast water treatment technologies. Previous studies have shown that UV light is effective for disinfecting drinking water, but the response of non-pathogenic and marine organisms is largely unknown.
The purpose of this research was to measure the viability of the durable red-tide forming dinoflagellate, Lingulodinium polyedra following UV treatment. Two methods were used to measure the viability signal; manual epifluorescence microscopy with correlated viability stains and Pulse Amplitude Modulated (PAM) fluorometry to measure the physiological state of the organism following UV treatment. The number of cysts was also enumerated. The results showed that there was a significant decrease in the number of living L. polyedra cells following a UV treatment of more than 100 mWs cm-2. The results also have showed a significant increase in the number of L. polyedra cysts following UV treatment as low as 50 mWs cm-2.
29
Kolowrat, Christian. "Effect of high light and ultraviolet radiations on the cell cycle and amino acid uptake of the marine picocyanobacterium Prochlorococcus Marinus PCC9511." Paris 6, 2010. http://www.theses.fr/2010PA066130.
Full textAbstract:
La cyanobactérie unicellulaire Prochlorococcus domine la communauté phytoplanctonique dans les gyres océaniques. Le but principal de cette thèse a été d'étudier comment elle s'adapte aux cycles jour/nuit de lumière. Une adaptation clé de Prochlorococcus est sa capacité de photohétérotrophie. Pour savoir si l'incorporation d'acides aminés est un processus continu au cours de la journée, la souche axénique P. Marinus PCC9511 a été synchronisée par un cycle J/N modulé et les variations au cours du temps de sa capacité d'incorporation de méthionine et leucine radioactives ont été mesurées. Un rythme nycthéméral pronounce d'incorporation de ces composés a été observé, avec des taux faibles à l'aube et forts au crépuscule, juste avant la division cellulaire. Le coeur de ce travail de thèse a concerné l'effet d'une irradiation par les UV sur la dynamique du cycle cellulaire de PCC9511. L'effet le plus visible des UV était un décalage de la phase de réplication de l'ADN vers la période obscure. Les gènes dont l'expression était la plus perturbée étaient ceux impliquées dans la replication de l'ADN et la division cellulaire. La forte décroissance du niveau d'expression génique de dnaA, qui code pour la protéine d'initiation de la replication serait suffisante en elle-même pour explique le délai observé. Cependant, il est plus probable que ce délai résulte de la combinaison complexe de l'ensemble des processus biologiques altérés par la présence d'UV. Ces résultats apportent une nouvelle lumière sur la vie quotidienne de Prochlorococcus, l'un des organismes clés de la communauté phytoplanctonique de l'océan oligotrophe, et sur sa capacité de survivre dans cet environnement extrême.
30
Wilson, Megan. "An Analysis of Policies and Conservation Techniques to Reduce the Accidental Deaths of Sea Turtle Hatchlings due to Light Pollution in Broward County, FL." NSUWorks, 2009. http://nsuworks.nova.edu/occ_stuetd/224.
Full textAbstract:
Light pollution is any excessive or obtrusive man made light source which disrupts the natural environment. Hatchling marine turtles are adversely affected by light pollution and therefore unlit nesting beaches are essential habitats for all marine turtle species. In Broward County, the most significant conservation issue facing nesting and hatchling marine turtles is the amount of light pollution present on urban sea turtle nesting beaches. The reduction of hatchling mortality from light pollution is an ongoing conservation goal of the State of Florida, Broward County, and the Broward County Sea Turtle Conservation Project (BCSTCP). Conservation techniques and policies intended to reduce hatchling mortality due to light pollution in Broward County have included: mass nest relocation using restraining and self release hatcheries, limited individual relocation of nests, and lighting ordnances in coastal municipalities. Until the 2006 sea turtle nesting season the BCSTCP utilized a mass relocation scheme which removed nests from unsafe and well lighted beach areas to other hatching areas which were not as severely impacted by light pollution. In 2006 the use of hatcheries was phased out and only limited relocation continued. Along with limited relocation, municipalities were strongly encouraged to reduce light pollution.
Comparisons will be made based on the 2003-2008 nesting seasons determine which policies and conservation tools were the most effective at reducing hatchling mortality due to light pollution. This study tested the following hypotheses: (1) there has been no significant decrease in light pollution in Broward County, (2) there has been no significant decrease in disoriented hatchlings on Broward County beaches, (3) recent changes to relocation techniques have not improved hatchling production with in Broward County. Results showed that the despite efforts by municipalities no overall reduction in light pollution has occurred. Initially hatchling disorientation events and the number of disoriented hatchlings increased after the policy change but have decreased during the most recent nesting season. Limited relocation yields a higher hatchling success rate then mass relocation. Although some improvements have been made light pollution control and reduction is still needed in order to reduce the accidental deaths of hatchlings due to disorientation.
31
Schuback, Nina. "On the light and iron dependent coupling of carbon fixation and photosynthetic electron transport in Arctic and Subarctic marine phytoplankton." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59198.
Full textAbstract:
Marine phytoplankton primary productivity, the photosynthetic conversion of CO₂ into organic carbon by microscopic photosynthetic algae in the surface ocean, plays a fundamental role in ecosystem dynamics and global biogeochemical cycles. Consequently, the ability to accurately measure, monitor and predict environmental influences on this process over a range of spatial and temporal scales is crucial. The work presented in this thesis evaluates the application of fast repetition rate fluorometry (FRRF) for instantaneous, high resolution estimates of phytoplankton primary productivity. Results from both laboratory experiments and field work in Arctic and Subarctic marine waters show that the conversion factor required to derive carbon-based primary productivity estimates from FRRF-derived rates of electron transport in photosystem II (ETR) varies significantly in response to the interacting effects of iron and light availability (Chapter 2), over diurnal cycles (Chapter 3), and in response to nitrogen and light availability under low temperatures (Chapter 4). At a photo-physiological level, a high conversion factor is observed under conditions of excess excitation energy, where the amount of light energy absorbed in the pigment antenna exceeds the capacity for downstream metabolic processes, i.e. carbon fixation. Phytoplankton employ numerous mechanisms to alleviate excess excitation energy after charge separation, and these processes are postulated to be responsible for the increased de-coupling of ETR and carbon fixation. Consistent with this hypothesis, a strong correlation was observed between the derived conversion factor and the dissipation of excess excitation energy before charge separation, which can be estimated as non-photochemical quenching (NPQ). Because NPQ can be estimated from FRRF measurements, it can be used as a proxy for the magnitude and variability of the conversion factor between carbon fixation and ETR, and this approach holds potential to significantly improve carbon-based primary productivity estimates from FRRF measurements. The work presented in this thesis advances our understanding of the coupling between light absorption, photo-chemistry, and carbon fixation in response to various environmental gradients. The experimental approach taken demonstrates how an appreciation of photo-physiological processes of photosynthesis is critical for improved estimates of phytoplankton primary productivity at regional scales.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
32
Yin, Kedong. "Short-term interaction between nitrate and ammonium uptake for cells of a marine diatom grown under different degrees of light limitation." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28361.
Full textAbstract:
The short-term interaction between nitrate and ammonium uptake was examined for a marine diatom, Thalassiosira pseudonana, grown in the continuous turbidostat cultures under different degrees of light limitation. Nitrate uptake in the absence and in the presence of ammonium and ammonium uptake in the absence and in the presence of nitrate were measured during a 6 min time course after a solution of both nitrate and ammonium was passed across the cells trapped on the filter.
It was found that the interaction between nitrate and ammonium uptake occurred immediately and continued for the remainder of the time course. The effect of light on the interaction was apparent. In the less light-limited cultures, nitrate uptake was depressed by ammonium. In contrast, in the most light-limited culture, the depression of nitrate uptake by ammonium disappeared. Ammonium uptake was dependent on the degree of light limitation of the cultures. For all the cultures, ammonium uptake was initially enhanced and then declined with time. However, only the initial (1 min) enhanced uptake of ammonium was suppressed by the presence of nitrate, and the subsequent ammonium uptake rate was unaffected. Possible explanations and the ecological significance of the interaction are discussed.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
33
Jiang, Yuelu. "Cell death, growth and physiological responses of a marine diatom to silicon and nitrogen starvation and resupply in the light and dark /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?AMCE%202009%20JIANG.
Full text
34
Manzotti, Alessandro. "Response to light stimuli in the marine diatom Phaeodactylum tricornutum : Involvement of bHLH-PAS proteins in the circadian clock and plastid physiology." Electronic Thesis or Diss., Sorbonne université, 2022. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2022SORUS232.pdf.
Full textAbstract:
Les diatomées sont des microalgues eucaryotes qui représentent l'un des groupes de phytoplancton plus répandus. Cependant, peu d'informations sont disponibles sur la régulation de l'expression génique chez ces algues. En utilisant la diatomée modèle Phaeodactylum tricornutum, les travaux présentés ont mis en évidence le rôle des facteurs de transcription bHLH-PAS dans la régulation de deux processus lumière-dépendants. Il a été montré que la protéine bHLH1a, renommée RITMO1, est impliquée dans la modulation de la rythmicité endogène régulée par les cycles lumière-obscurité. La surexpression et la mutation KO de RITMO1 conduisent à une perturbation des oscillations journalières de la fluorescence cellulaire, de la photosynthétique et de l'expression génique en lumière continue, l'identifiant comme le premier composant de l'horloge circadienne des diatomées. Il a été montré que RITMO1 dimérise avec son paralogue bHLH1b et que la mutation de cet facteur de transcription mène à des perturbations de la rythmicité de la fluorescence cellulaire, indiquant sa co-implication dans l'horloge. Différemment, la protéine bHLH-PAS bHLH2, est impliqué dans la modulation de la photosynthèse dans un mécanisme dépendant de l'intensité lumineuse et non contrôlé par l'horloge. Souches transformées avec des ARN-interférents contre bHLH2 montrent un flux d'électrons réduit au niveau du thylakoïde et un déficit de croissance subséquent. L'expression de cette protéine dépend d'un système de signalisation rétrograde, mettant ainsi en évidence une communication croisée noyau-plaste. Cette étude représente la première caractérisation des protéines bHLH-PAS dans un organisme photosynthétiqueDiatoms are eukaryotic microalgae representing one of the most successful groups of phytoplankton. However, little information is available on the regulatory mechanisms controlling gene expression in diatoms. Through the use of the model diatom Phaeodactylum tricornutum, the work presented highlighted the role of bHLH-PAS family transcription factors in the regulation of two important light-dependent processes. On the one hand, it was shown that bHLH1a protein, renamed RITMO1, is involved in the modulation of endogenous rhythmicity regulated by light-dark cycles. Overexpression and knock-out mutation of this gene led to a disruption of daily cellular fluorescence oscillations, photosynthetic activity and gene expression under constant light condition, identifying RITMO1 as the first component of diatom circadian clock. It was shown that a paralogous transcription factor, bHLH1b, dimerizes with RITMO1 and a mutation of this protein led to disruptions of cellular fluorescence rhythmicity, indicating its co-implication in the timekeeper. Differently, bHLH-PAS protein bHLH2 has been shown to be involved in the modulation of photosynthetic activity in a light intensity-dependent mechanism not controlled by the endogenous clock. Cell lines presenting a construct for RNA-interference against bHLH2 showed reduced electron flow at the thylakoid level and a subsequent growth deficit. It has been shown that the expression of this protein is controlled by retrograde signalling, thus highlighting a crosstalk between nucleus and plastid. This study represented the first characterization of bHLH-PAS proteins in a photosynthetic organism
35
Kreh, Paul D. "Optimizing lighting regimes for rearing Orbicella faveolata and Acropora cervicornis recruits." Thesis, NSUWorks, 2019. https://nsuworks.nova.edu/occ_stuetd/518.
Full textAbstract:
Coral reef decline worldwide has led to the need for coral reef restoration. The use of sexual reproduction in restoration efforts is required to increase genetic diversity; however, the procedures for rearing newly-settled coral recruits ex situ still need to be optimized. Recruits initially require low light irradiance, but it is unclear when higher irradiances are required to enhance growth and survival. Here we determined the optimal light regime for Orbicella faveolata and Acropora cervicornis recruits. Newly settled recruits were reared under treatments with varied rates of increasing irradiance (after reaching 5 weeks of age), and their survival, growth, and coloration was assessed weekly until they were 16 weeks old. Orbicella faveolata and Acropora cervicornis growth and survival were significantly affected by light irradiance regimes. Coloration also varied between treatments with a general trend of darkening pigmentation over the sixteen weeks. We found that low irradiances (< 40 mmol photons m-2s-1) were optimal for new recruits up to 8-10 weeks of age, which is possibly related to the full establishment of symbiosis and/or the ability to feed and digest food. Aposymbiotic recruits were able to survive for a longer period under low irradiances but experienced high mortality when exposed to higher irradiance, regardless of their age, possibly due to low levels or the lack of mycosporine like amino acids and other antioxidants produced by the Symbiodiniaceae that protect against high irradiances and reactive oxygen species. After Weeks 8-10, high irradiance levels similar to the ones that are optimal for adults (> 120 mmol photons m-2s-1) were required by zooxanthellate coral to survive and to boost their growth. This further suggests that the acquisition of symbionts from the family Symbiodiniaceae is at least one key component in the shift toward tolerating higher irradiances.
36
Sierra, Flores Rogelio. "Environmental management of Atlantic cod (Gadus morhua) and turbot (Scophthalamus maximus) : implications of noise, light and substrate." Thesis, University of Stirling, 2014. http://hdl.handle.net/1893/20047.
Full textAbstract:
During the last decades marine aquaculture has steadily expanded and diversified to include a wider range of commercial species. Despite the intense effort towards understanding the biological requirements of farmed species, several issues remain to be addressed. Mariculture success is restricted by a number of production bottlenecks including limited seed supply, caused mainly through a combination of compromised productivity in broodstock paired with high mortalities during the early life stages. Productivity and survival success is often dependent on the successful recreation of natural environmental conditions. While in a commercial setting a concerted effort is generally made to simulate key environmental stimuli there remains a lack of understanding of the significance of many potential signals. The overarching aim of this thesis was to investigate the effects of some of the overlooked environmental stimuli on fish performance in enclosed facilities and where possible relate this to the natural setting from which the species have been removed. The studies contained in this text are focused on the effects of anthropogenic noise, light spectral composition and substrate on the performance of broodstock and juvenile development of two valuable commercial marine species Atlantic cod (Gadus morhua) and turbot (Scophthalmus maximus). The aim of Chapter 3 was to test if artificial sound can act as a stressor in Atlantic cod and thereafter to examine if chronic sound disturbances can compromise broodstock spawning performance in land-based facilities. Results showed that anthropogenic noises in a land-based marine farm are within the auditory thresholds of cod and other fish species. Juvenile cod exposed to 10 min of artificial noise (100-1,000 Hz) from 10 to 20 dB 1 re µPa above background sound levels presented a typical acute stress response with a 4 fold elevation of plasma cortisol levels within 20 min, with a return to basal levels after 40 min, while the intensity of the stress response (in terms of amplitude and return to normal levels) appeared to be correlated to the noise level applied. When a similar artificial noise of 35 dB 1 re µPa above background sound level was applied to a broodstock population daily on a random schedule during the spawning season, it significantly impacted on reproductive performances in comparison to a control undisturbed population with notably a reduction in fertilisation rate that correlated with increased egg cortisol contents. Overall, these studies confirmed, for the first time, that artificial noise mimicking anthropogenic sounds generated in marine land-based facilities trigger a typical acute stress response if a similar sound exposure is then applied in a chronic manner it resulted in reduced broodstock spawning performances. Overall this work provides novel evidence on the potential of anthropogenic noise to act as stressor in fish. The possible implications for both captive and wild stock are discussed. In chapter 4 the effects of light spectrum and tank background colour on Atlantic cod and turbot larval performance from hatch until the end of metamorphosis were investigated. In both species larvae exposed to shorter wavelengths (blue and green spectrums) showed significantly enhanced growth in terms of standard length, myotome height, eye diameter and condition factor in comparison to larvae exposed to longer wavelengths (red). Larvae performances in the colour background experiment differed between species. Atlantic cod larvae reared in a red tank background displayed the best growth and survival, while larvae in blue tank background had a significant positive effect on final survival rate. In contrast, turbot larvae survival rates were the highest in the red tank background colour with the lowest growth parameters, while larvae in the blue tank background displayed the best growth. In both species, white tank background colour resulted in the lowest final survival rate. These results highlight the biological relevance of light spectrum and background colour in marine larvae performance and survival, demonstrating the importance of considering the light composition of the light units used in the hatcheries for larval rearing. Subsequently in chapter 5 the effects of light spectrum in juvenile turbot growth, appetite, stress response and skin pigmentation were investigated. Two sets of experiments were performed with post-metamorphosed (1 g) and on-growing (100 g) turbot. Results demonstrated that short wavelength treatments had a significant positive effect on growth parameters (total length and wet weight), food intake and feeding response. Light treatments caused a positive correlation between plasma glucose and cortisol levels with significant differences between the short and long wavelength treatments. Skin pigmentation was affected by the light treatments, showing a relationship between wavelength and brightness (negative) and darkness (positive). Blue light treatment resulted in brighter and lighter skin colouration, while red light had the opposite effect: darkening of the skin. Overall these results confirm that turbot juveniles performance is enhanced by exposing them to a similar photic environment than the one from the natural ecological niche. Light spectrum intervenes in skin pigmentation and the possible mechanisms behind the variations are discussed. In general chapter 5 provides background knowledge of the possible implications of light spectrum in fish juveniles performance and possible commercial applications. The final two experimental chapters turned focus back on the optimisation of broodstock environmental management and subsequent effects on their productivity. In Chapter 6 the importance of crepuscular light simulation was investigated in Atlantic cod broodstock spawning performance. No significant impact could be observed in terms of egg production and quality in association with dawn/dusk simulation compared to abrupt lights on/off. This suggests, at least for Atlantic cod, that crepuscular light simulation is not a key factor affecting spawning performance during the spawning window. The possible implications of twilight on gamete quality prior ovulation are discussed. In Chapter 7 the effect of a “breeding nest” containing a substrate (i.e. sand) in turbot broodstock spawning performance was investigated. Behavioural observation recorded active occupancy of the nests with the suggestion of social structuring as specific individuals (females) occupied the nest preferentially. However no fertilised, naturally released eggs were collected from the overflow during the spawning seasons. This would suggest that the presence of a nest is not enough to induce natural spawning behaviour in turbot in itself however the elective occupancy suggests that nests and/or their substrate was a physical enrichment that was valued by the fish which should be explored further. Overall the studies contained in this thesis highlight further the importance of considering noise and light as crucial environmental factors in marine aquaculture. Results from the different chapters offer a possible application within the enclosed facilities that might contribute to the success of the industry. Present findings contribute towards the understanding of the effects of environmental signals in fish and provide further insight to guide further lines of research on the involvement of light spectrum on fish physiology.
37
McMahon, Nicholas J. "Optimization of Light Irradiance During the Early Life of Sexually-Produced Porites astreoides and Agaricia agaricites Recruits." Thesis, NSUWorks, 2018. https://nsuworks.nova.edu/occ_stuetd/493.
Full textAbstract:
Current solutions of coral restoration rely mainly on fragmentation. Though a reliable technique, this asexual form of reproduction does not benefit the genetic diversity of the coral reef. With many global and local stressors threatening corals’ existence, the resiliency of corals to future ocean conditions depends highly on sexual reproduction to produce new genotypes. New technology allows coral spawning/larval release, larval settlement and rearing to be carried out in an aquarium system. Many of the techniques necessary to maintain coral recruits are well-established, however the effects of light intensity remain to be studied for these early life stages. Newly settled corals have been found on vertical surfaces and the undersides of ledges and crevices, suggesting full solar irradiance is detrimental to their health. Newly settled Porites astreoides and Agaricia agaricites recruits were placed under varying irradiance levels to test their survivorship, growth and pigmentation. In the first four weeks post-settlement, growth was significantly different between recruits under a PAR of 10 µmol quanta m-2 s-1 and 240 µmol quanta m-2 s-1. In a separate experiment, growth curves were significantly different between six different irradiance increase regimens in the first 14 weeks post-settlement. This study shows, for the first time, a definitive preference by newly settled coral recruits to lower intensity irradiance, devoid of ultraviolet radiation, in the first four weeks post-settlement, and that Porites astreoides recruits can acclimatize to higher intensities at a rate of ~ 11 µmol quanta m-2 s-1 per week for up to 15 weeks.
38
Bricaud-Wehrlin, Annick. "Propriétés optiques du phytoplancton : étude théorique et expérimentale : application à l'interprétation de la couleur de la mer." Paris 6, 1989. http://www.theses.fr/1989PA066074.
Full textAbstract:
Une étude théorique des propriétés optiques des particules selon leurs caractéristiques physiques a permis de proposer une modélisation de l'absorption (effet de discrétisation), ainsi que de l'atténuation et de la diffusion de la lumière par le phytoplancton. De plus la variabilité de la relation concentration en pigments-production primaire a été examinée à partir des données in situ de diverses zones.
39
Perez, Denise. "Light-Use Efficiency of Coral-Reef Communities: A Sensitivity Analysis Using an Optically Based Model of Reef Productivity and Calcification." NSUWorks, 2013. http://nsuworks.nova.edu/occ_stuetd/99.
Full textAbstract:
Biogeochemical processes of reefs have been studied for over fifty years, however, information is still lacking on several fundamental reef processes. This lack of information has been limited essentially by techniques that cannot repeatedly sample large spatial areas. These limitations can be reduced with the use of an optical model to estimate biogeochemical processes. This project applied Monteith's light-use efficiency model to coral reef communities for determining photosynthetic and calcification efficiency of light. Gross primary production and net calcification were pooled from the peer-reviewed literature to calculate efficiency. Process efficiency was then compared across functional types of reef communities (i.e., coral, algae/seagrasses, mixed, and sand), and by year, location, season, and depth. Photosynthetic efficiency was calculated from 19 studies, showing an average of 0.039 mol O2 mol-1 photons. Photosynthetic efficiency differed significantly for mixed communities between studies, and for algae/seagrass communities among depths. Calcification efficiency averaged at 0.007 mol CaCO3 mol-1 photons. Significant differences were found in calcification efficiency of algae/seagrasses and mixed reef communities among studies and localities. Additionally, calcification efficiency of algae/seagrasses varied significantly in accordance with depth. Future use of the light-use efficiency model will require determining the efficiency of each functional type to estimate gross production and calcification. Additionally, further investigation of the light-use efficiency model will require long-term measurements of APAR, which is the fraction of incident light absorbed, and the incorporation of environmental parameters that reduce efficiency.
40
van, Dijk Jeroen. "Size and Abundance of Late Pleistocene Reticulofenestrid Coccoliths from the Eastern Indian Ocean in Relation to Temperature and Aridity." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325273.
Full textAbstract:
Measurements on coccolith abundance and mass can be used as a signal of primary productivity and pelagic calcification in response to environmental change. The Leeuwin Current (LC) is known to transport warm and low-salinity waters from the Indo-Pacific Warm Pool (IPWP) southwards along the coast of West Australia. Along with the onset of continental aridity during late Neogene, increased strength of the LC may have played a role in reef expansion on the Northwest Shelf. In this study the morphological variation in size and mass of reticulofenestrid coccoliths was assessed in material from IODP Site U1461 in the eastern Indian Ocean spanning the past 500 ka. Both the absolute abundance of all reticulofenstrid coccoliths (Emiliania huxleyi, Reticulofenestra spp., Gephyrocapsa spp. and Pseudoemiliania spp.) was determined, as well as the relative abundance of large versus small coccoliths. Coccolith size and mass were measured quantitatively under circularly polarized light. The data was compared to variations in sea surface temperatures (SST) of the LC, and to continental aridity of Australia. SST fluctuations could influence coccolithophore productivity by affecting their metabolic rate, whereas continental aridity may influence the influx of terrestrial matter by wind. The investigated interval is dominated by small species of Gephyrocapsa. Peak values of absolute abundance and mass were observed during Marine Isotope Stage (MIS) 11, an interglacial period of extended warmth and humidity. These results coupled with high densities of aragonite needles in the same samples indicate the sediments were diluted by material overflowing from the adjacent shallow- water carbonate platform, analogous to the whiting events observed in the modern-day Bahamas. A decrease in abundance of Gephyrocapsa caribbeanica at 240 ka can be linked to the timing of their last common occurrence (LCO), within MIS 7. The subsequent shift to Gephyrocapsa oceanica as the dominant large species may indicate an ecological replacement of G. caribbeanica, or signify warm and low-salinity waters.Mätningar av abundans och massa hos coccoliter kan användas som en signal för primärproduktion och pelagisk förkalkning som resultat av miljöförändringar. Leeuwin Current (LC) är känd för att transportera varmt vatten och vatten med låg salthalt från Indo-Pacific Warm Pool (IPWP) söderut längs kusten i västra Australien. Tillsammans med början av kontinental torka under sen Neogen kan ökad styrka hos LC ha spelat en roll i expansionen av rev på nordvästsockeln. I denna studie bedömdes den morfologiska variationen i storlek och massa hos coccoliter i material från IODP plats U1461 i östra Indiska oceanen från de senaste 500 000 åren. Både den absoluta abundansen av alla reticulofenstridcoccoliter (Emiliania huxleyi, Reticulofenestra spp., Gephyrocapsa spp. och Pseudoemiliania spp.) bestämdes, liksom den relativa abundansen av stora jämfört med små coccoliter. Storlek och massa av coccoliter mättes kvantitativt under cirkulärt polariserat ljus. Uppgifterna jämfördes med variationer i havsytans temperatur (SST) hos LC, och med kontinental torrhet i Australien. SST-fluktuationer kan påverka produktiviteten hos coccolitoforider genom att påverka deras metabolism, medan kontinental torrhet kan påverka inflödet av markmaterial med vind. Det undersökta intervallet domineras av små arter av Gephyrocapsa. Toppvärden av absolut abundans och massa observerades under marinisotopsteget (MIS) 11, en interglacial period med förlängd värme och fuktighet. Dessa resultat kombinerat med hög densitet av aragonitnålar i samma prover indikerar att sedimenten späddes ut med material som svämmade över från den intilliggande grunda karbonatplattformen, vilket är jämförligt med de vitningshändelser som har observerats i dagens Bahamas. En minskning i abundans av Gephyrocapsa caribbeanica vid 240 ka kan kopplas till tidpunkten för deras senaste gemensamma förekomst (LCO) inom MIS 7. Den efterföljande övergången till Gephyrocapsa oceanica som den dominerande stora arten kan indikera en ekologisk ersättning av G. caribbeanica, eller indikera varmt vatten med låg salthalt.
41
Levavasseur, Guy. "Plasticité de l'appareil pigmentaire des algues marines : Macrophytes : regulation en fonction de l'environnement." Paris 6, 1986. http://www.theses.fr/1986PA066121.
Full textAbstract:
Méthode d'étude et matériel: Chlorophycées, Pheophycees et Rhodophycées de la région de Roscoff. Méthodes d'extraction des diloroplastes et de leur membranes et de complexes protéine-chl. Caractéristiques pigmentaires des algues et activités photosynthétiques, et relation avec la localisation des algues dans les zones médio- et infra-littorale. Effet des saisons et de la durée d' éclairement
42
McMillian, Christina A. "Light interaction." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/52581.
Full textAbstract:
In the heart of a park, a path spirals up a hill. Follow it and the trees part to reveal a building halfway up. Its thick, rough walls are pulled apart at moments, allowing light and movement into the space. The path leads between the walls. The narrow passage continues in a counter-clockwise motion up a staircase, leading you towards the light; moving from opacity to transparency, darkness to light, thick to thin, and exploring the mo- ments between. The space marks the passage of time. You see sunrise, marked by three narrow slits oriented to capture the light on the Winter and Summer solstices, and Spring and Fall equinoxes. The curved walls leading from the white art glass windows cradle the light like a cupped hand. The midday sun illuminates the central core, translated through the medium of semi-circular, veneer screens. The light and wood interact, revealing what is hidden, allowing the glowing screens to illuminate the outer circle. On the opposite side of the space are similarly-oriented windows to capture the Summer, Spring, Fall, and Winter sunsets, completing the day. It is a space apart from the world into which only the light and the self may enter. The only view of the outside world is the changing sky at the center. It is a space looks at light and how it moves through, is captured by, or is reflected by material. Light changes the materials in the space, is changed by them and marks the passage of time -- days and the seasons.Master of Architecture
43
Schramm, Kenneth Edward. "The medium tactical vehicle replacement program-an analysis of a multi-service office." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FSchramm.pdf.
Full text
44
Stock, Ute Birgit Cosima. "The ethics of the poet : Marina Tsvetaeva's art in the light of conscience." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620023.
Full text
45
Stone, Elizabeth J. "The Effect of Charcot-Marie-Tooth Disease Mutations in Neurofilament Light on Neurofilaments." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1585652615669143.
Full text
46
Kleybolte, Lisa Marie [Verfasser], and Roman [Akademischer Betreuer] Schnabel. "Sensitivity Enhancement of Optomechanical Measurements using Squeezed Light / Lisa Marie Kleybolte ; Betreuer: Roman Schnabel." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2019. http://d-nb.info/1197801464/34.
Full text
47
Gylle, A. Maria. "Physiological adaptations in two ecotypes of Fucus vesiculosus and in Fucus radicans with focus on salinity." Doctoral thesis, Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-13308.
Full textAbstract:
The in origin intertidal marine brown alga Fucus vesiculosus L. grow permanently sublittoral in the brackish Bothnian Sea, side by side with the recently discovered F. radicans L. Bergström et L. Kautsky. Environmental conditions like salinity, light and temperature are clearly different between F. vesiculosus growth sites in the Bothnian Sea (4-5 practical salinity units, psu; part of the Baltic Sea) and the tidal Norwegian Sea (34-35 psu; part of the Atlantic Ocean). The general aims of this thesis were to compare physiological aspects between the marine ecotype and the brackish ecotype of F. vesiculosus as well as between the two Bothnian Sea species F. vesiculosus and F. radicans. The result in the study indicates a higher number of water soluble organic compounds in the marine ecotype of F. vesiculosus compared to the brackish ecotype. These compounds are suggested to be compatible solutes and be due to an intertidal and sublittoral adaptation, respectively; where the intertidal ecotype needs the compounds as a protection from oxygen radicals produced during high irradiation at low tide. The sublittoral ecotype might have lost the ability to synthesize these compound/compounds due to its habitat adaptation. The mannitol content is also higher in the marine ecotype compared to the brackish ecotype of F. vesiculosus and this is suggested to be due to both higher level of irradiance and higher salinity at the growth site. 77 K fluorescence emission spectra and immunoblotting of D1 and PsaA proteins indicate that both ecotypes of F. vesiculosus as well as F. radicans have an uneven ratio of photosystem II/photosystem I (PSII/PSI) with an overweight of PSI. The fluorescence emission spectrum of the Bothnian Sea ecotype of F. vesiculosus however, indicates a larger light-harvesting antenna of PSII compared to the marine ecotype of F. vesiculosus and F. radicans. Distinct differences in 77 K fluorescence emission spectra between the Bothnian Sea ecotype of F. vesiculosus and F. radicans confirm that this is a reliable method to use to separate these species. The marine ecotype of F. vesiculosus has a higher photosynthetic maximum (Pmax) compared to the brackish ecotype of F. vesiculosus and F. radicans whereas both the brackish species have similar Pmax. A reason for higher Pmax in the marine ecotype of F. vesiculosus compared to F. radicans is the greater relative amount of ribulose-1.5-bisphosphate carboxylase/oxygenase (Rubisco). The reason for higher Pmax in marine ecotype of F. vesiculosus compare to the brackish ecotype however is not due to the relative amount of Rubisco and further studies of the rate of CO2 fixation by Rubisco is recommended. Treatments of the brackish ecotype of F. vesiculosus in higher salinity than the Bothnian Sea natural water indicate that the most favourable salinity for high Pmax is 10 psu, followed by 20 psu. One part of the explanation to a high Pmax in 10 psu is a greater relative amount of PsaA protein in algae treated in 10 psu. The reason for greater amount of PsaA might be that the algae need to produce more ATP, and are able to have a higher flow of cyclic electron transport around PSI to serve a higher rate of CO2 fixation by Rubisco. However, studies of the rate of CO2 fixation by Rubisco in algae treated in similar salinities as in present study are recommended to confirm this theory.Fucus vesiculosus L. (Blåstång) är en brunalg som i huvudsak växer i tidvattenzonen i marint vatten men arten klarar också att växa konstant under ytan i det bräckta Bottenhavet. Norska havet och den del av Bottenhavet, där algerna är insamlade i denna studie, har salthalterna 34-35 psu (praktisk salthaltsenhet) respektive 4-5 psu. F. radicans L. Bergström et L. Kautsky (Smaltång) är en nyligen upptäckt art (2005) som har utvecklats i Bottenhavet. F. radicans och Bottenhavets ekotyp av F. vesiculosus växer sida vid sida och har tidigare ansetts vara samma art. Sett till hela Östersjön, så ändras ytans salthalt från 25 till 1-2 psu mellan Östersjöns gräns mot Kattegatt och norra Bottenviken. Den låga salthalten i Östersjön beror på det höga flödet av sötvatten från älvarna och på ett litet inflödet av saltvatten i inloppet vid Kattegatt. Salthaltsgradienten är korrelerad med antalet arter som minskar med minskad salthalt. Östersjön är ett artfattigt hav och de arter som finns är till stor del en blandning av söt- och saltvattenarter. Det finns bara ett fåtal arter som är helt anpassade till bräckt vatten och F. radicans är en av dem. Exempel på miljöskillnader för F. vesiculosus i Norska havet och i Bottenhavet är salthalten, tidvattnet, ljuset och temperaturen. Tidvattnet i Norska havet gör att algerna växlar mellan att vara i vattnet och på land, vilket utsätter algerna för stora ljusskillnader, snabba och stora temperaturväxlingar samt även torka. De alger som växer i Bottenhavet har däremot en jämnare och lägre temperatur, istäcke på vintern och mindre tillgång på ljus eftersom de alltid lever under vattenytan. Skillnaderna i miljön mellan växtplatserna leder till skillnader i fysiologiska anpassningar. Anledningen till att F. vesiculosus och F. radicans valdes som studieobjekt i denna avhandling är att de är viktiga nyckelarter i Bottenhavet. F. vesiculosus och F. radicans är de enda större bältesbildande alger som finns i det artfattiga ekosystemet och de används därför flitigt som mat, gömställe, parningsplats och barnkammare för t.ex. fisk. Att de är nyckelarter gör det angeläget att försöka förstå hur algerna är anpassade och hur de reagerar på miljöförändringar för att få veta hur de kan skyddas och bevaras. F. radicans inkluderades även för att se hur en naturlig art i Bottenhavet är anpassad i jämförelse med den invandrade F. vesiculosus. Marin F. vesiculosus inkluderades för att vara en artreferens från artens naturliga växtplats. Studien visar att det finns fler vattenlösliga organiska substanser (finns vissa organiska substanser som har en proteinskyddande funktion) i den marina ekotypen av of F. vesiculosus än i Bottenhavets ekotyp. Anledningen till detta föreslås vara en anpassning till att växa i tidvattenzonen. Vid lågvatten utsätts F. vesiculosus från Norska havet för starkt ljus, uttorkning, och snabba temperatur- växlingar vilket gör att den kan behöva dessa organiska substanser som skydd mot fria syreradikaler som bildas under lågvattenexponeringarna. F. vesiculosus från Bottenhavet har troligen mist förmågan att syntetisera dessa substanser på grund av anpassning till att hela tiden växa under ytan. Mängden mannitol (socker) är högre i den marina ekotypen av of F. vesiculosus än i Bottenhavets ekotyp. Detta föreslås bero på högre fotosyntetiskt maximum i F. vesiculosus från Norska havet jämfört med ekotypen från Bottenhavet. Skillnaden i fotssyntetiskt maximum är bland annat kopplat till ljus- och salthaltskillnaden på algernas växtplatser. Denna teori styrks av att både fotosyntesen och halten av mannitol ökar i Bottenhavets ekotyp när den behandlas i högre salthalt. Studien visar även att båda ekotyperna av F. vesiculosus samt F. radicans har ett ojämnt förhållande mellan fotosystem II och I (PSII och PSI) med en dominans av PSI. Denna slutsats är baserad på fluorescens emissions mätningar vid 77 K (-196 °C) och mätning av den relativa mängden D1 protein (motsvarar PSII) och PsaA protein (motsvarar PSI). F. vesiculosus från Bottenhavet visar ett emission spektrum som pekar mot en jämnare fördelning av PSII och PSI jämfört med den marina ekotypen och F. radicans. Detta stämmer dock inte med förhållandet mellan D1/PsaA som indikerar att alla tre har mer PSI än PSII. Förklaringen till avvikelsen mellan metoderna antas vara att F. vesiculosus från Bottenhavet har större ljus-infångande antennpigment än marin F. vesiculosus och F. radicans. De tydliga skillnaderna i 77 K fluorescens emission spektra mellan Bottenhavets F. vesiculosus och F. radicans visar att denna metod kan användas som säker artidentifiering. Den marina ekotypen av F. vesiculosus har högre fotosyntetiskt maximum än de båda arterna från Bottenhavet. Mätningar av den relativa mängden av enzymet Rubisco, viktigt för upptaget av koldioxid hos växter och alger, visar att mängden enzym är en sannolik förklaring till skillnaden i fotosyntetiskt maximum mellan den marina ekotypen av F. vesiculosus och F. radicans och detta är troligen en normal artskillnad. Mängden Rubisco kan dock inte förklara skillnaden i fotosyntetiskt maximum mellan de båda ekotyperna av F. vesiculosus. För att undersöka vad skillnaden mellan dessa två beror på så föreslås istället mätningar av Rubisco’s koldioxidfixeringshastighet. Det är en ökning av fotosyntetiskt maximum i Bottenhavets ekotyp av F. vesiculosus när den behandlas i högre salthalt (10, 20 och 35 psu) och det högsta fotosyntetiska maximumet uppmättes i alger som behandlats i 10 psu. Denna ökning beror inte på ökning i den relativa mängden av Rubisco. Ökningen i fotosyntesen speglas dock av en ökning av den relativa mängden PsaA. Detta antas bero på att det behövs mer energi i form av ATP och att en ökning av detta kan ske på grund av att mer PsaA kan driva den cykliska elektrontransporten i fotosyntesreaktionen. Ökat behov av ATP antas bero på en ökning av Rubisco aktiviteten men mätning av aktiviteten krävs för att bekräfta detta.
48
Borisova, Marina E. [Verfasser]. "p38-MK2 signaling axis regulates RNA metabolism after UV-light-induced DNA damage / Marina E. Borisova." Mainz : Universitätsbibliothek Mainz, 2019. http://d-nb.info/1178732967/34.
Full text
49
Gropp, Claire-Marie [Verfasser]. "Regulation of Melanopsin and PACAP mRNA by Light, Circadian and Sleep Homeostatic Processes / Claire-Marie Gropp." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2014. http://d-nb.info/1052530117/34.
Full text
50
Romanelli, Elisa. "Growth response of Thalassiosira pseudonana under combined light and temperature changes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textAbstract:
The rise of atmospheric CO2 concentrations due to human activities is warming the upper levels of the ocean leading to changes in mixing and thus affecting the upward nutrient supply and the level of light available for phytoplankton. Researchers have focused on investigating how these fast-approaching changes are affecting phytoplankton; however, it is still difficult to obtain a consistent understanding of the expected response because of interactive effects to simultaneous changes in multiple stressors. This study aims to present an alternative way to determine the growth rate of phytoplankton through the measure of their optical properties (1). In addition, this study investigates the interactive effects of light and temperature changes on the growth rate (µ) of diatom Thalassiosira pseudonana CCMP 1335 (2). We monitored the growth rate of T. pseudonana at four temperatures (13.4, 18.5, 22.5 and 24.4°C) and eight light regimes (35, 50, 65, 80, 95, 110, 125 and 140µmol photons m-2s-1) by measuring the cultures chlorophyll fluorescence F0, optical density (OD680 and OD720) and cells number. Our results show an overall statistically highly significant correlation between µF0 and µOD and µ based on cell counts (n: 25 p < 0.001). We assume this relationship to be light and temperature dependent and F0 and OD to be valuable proxies for cell counts under our experimental conditions. We highlight the importance of testing the correlations for each species individually. Our multi-drivers experiments show light limitation for all our cultures at 35 and 50µmol photons m-2s-1 and temperature limitation at 13.4 and 18.5°C. Furthermore, we found the optimal growth conditions of our T. pseudonana cultures at 22.5°C and 110µmol photons m-2s-1. Interesting interactive effects between light and temperature were found at 18.5°C and 24°C and at 110µmol photons m-2s-1. These results show that simultaneous changes in temperature and light exposure lead to interactive effects.