Dissertations / Theses on the topic 'Marine light'
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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 textBurrow, 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 textThis 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.
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 textMangogna, 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 textChuck, 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 textBrown, 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 textThesis advisor(s): Shu S. Liao, David F. Matthews. "December 1995." Includes bibliographical references. Also available online.
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 textDuchêne, 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 textLight 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
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 textSquire, 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 textVan, 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 textENGLISH 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.
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 textHeijde, Marc. "Molecular study of light responses in the marine microalgae Phaeodactylum triconortum and Ostreococcus tauri." Paris 6, 2008. http://www.theses.fr/2008PA066164.
Full textStrydom, 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 textNickless, 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 text"December 1998." Thesis advisor(s): Joseph San Miguel, Brad R. Naegle. Includes bibliographical references (p. 63-66). Also available online.
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 textMicroalgae 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
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 textHague, 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 textHancke, 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 textThe 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).
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 textFaithfull, 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 textLake ecosystem response to environmental change
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 textMatallana, 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 textWatters, 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 textJeong, 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 textHagemann, 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 textFoster, 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 textRiley, 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 textKolowrat, 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 textWilson, 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 textSchuback, 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 textScience, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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 textScience, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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 textManzotti, 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 textDiatoms 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
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 textSierra, 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 textMcMahon, 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 textBricaud-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 textPerez, 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 textvan, 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 textMätningar 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.
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 textMcMillian, Christina A. "Light interaction." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/52581.
Full textMaster of Architecture
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 textStock, 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 textStone, 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 textKleybolte, 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 textGylle, 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 textFucus 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.
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