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Dissertations / Theses on the topic 'Marine phytoplankton Phytoplankton populations'
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1
Moore, Timothy S. "Dynamics of phytoplankton community composition in the western Gulf of Maine." Restricted access (UM), 2008. http://libraries.maine.edu/gateway/oroauth.asp?file=orono/etheses/37803141.pdf.
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These (Ph.D.)--University of New Hampshire, 2008.Title from PDF title page. Available through UMI ProQuest Digital Dissertations. Includes bibliographical references (leaves 145-157). Also issued in print.
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Hyde, Kimberly Joy Whitman. "Interannual and seasonal phytoplankton variability in Massachusetts Bay from remote and in situ measurements /." View online ; access limited to URI, 2006. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3248231.
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Longval, Brooke A. "Biomass spectra in Narragansett Bay from phytoplankton to fish /." View online ; access limited to URI, 2009. http://digitalcommons.uri.edu/dissertations/AAI3401124.
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Anning, Tracy. "The expression of photosynthetic genes in natural populations of marine phytoplankton." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307079.
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Al-Haddad, Luan Marie. "Neural network techniques for the identification and classification of marine phytoplankton from flow cytometric data." Thesis, University of South Wales, 2001. https://pure.southwales.ac.uk/en/studentthesis/neural-network-techniques-for-the-identification-and-classification-marine-phytoplankton-from-flow-cytometric-data(808c0828-1803-4e55-8ffd-6788ba36ad34).html.
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This thesis documents the research that has led to advances in the Artificial Neural Network (ANN) approach to analysing flow cytometric data from phytoplankton cells. The superiority of radial basis function networks (RBF) over multi-layer perception networks (MLP), for data of this nature, has been established, and analysis of 62 marine species of phytoplankton represents an advancement in the number of classes investigated. The complexity and abundance of heterogeneous phytoplankton populations, renders an original multi-class network redundant each time a novel species is encountered. To encompass the additional species, the original multiclass network requires complete retraining, involving long optimisation procedures to be carried out by ANN scientists. An alternative multiple network approach presented (and compared to the multi-class network), allows identification of the expanse of real world data sets and the easy addition of new species. The structure comprises a number of pre-trained single species networks as the front end to a combinatorial decision process for determining species identification. The simplicity of the architecture, and of the subsequent data produced by the technique, allows scientists unfamiliar with ANNs to dynamically alter the species of interest as required, without the need for complete re-training. Kohonens Self Organising Map (SOM), capable of discovering its own classification scheme, indicated areas of discrepancy between flow cytometric signatures of some species and their respective morphological groupings. In an attempt to improve identification to taxonomic group or genus level by supervised networks, class labels more reflective of flow cytometric signatures must be introduced. Methods for boundary recognition and cluster distinction in the output space of the SOM have been investigated, directed towards the possibility of an alternative flow cytometric structuring system. Performance of the alternative multiple network approach was comparable to that of the original multi-class network when identifying data from various environmental and laboratory culturing conditions. Improved generalisation can be achieved through employment of optical characteristics more representative of those found in nature.
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Clayton, Sophie A. "Physical influences on phytoplankton ecology : models and observations." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82320.
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Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 143-154).
The physical environment in the oceans dictates not only how phytoplankton cells are dispersed and their populations intermingled, but also mediates the supply of nutrients to the surface mixed layer. In this thesis I explore both of these aspects of the interaction between phytoplankton ecology and ocean physics, and have approached this topic in two distinct but complementary ways, working with a global ocean ecosystem model, and collecting data at sea. In the first half of the thesis, I examine the role of mesoscale physical features in shaping phytoplankton community structure and influencing rates of primary production. I compare the output of a complex marine ecosystem model coupled to coarse resolution and eddy-permitting physical models. Explicitly resolving eddies resulted in marked regional variations in primary production, zooplankton and phytoplankton biomass. The same phytoplankton phenotypes persisted in both cases, and were dominant in the same regions. Global phytoplankton diversity was unchanged. However, levels of local phytoplankton diversity were markedly different, with a large increase in local diversity in the higher resolution model. Increased diversity could be attributed to a combination of enhanced dispersal, environmental variability and nutrient supply in the higher resolution model. Diversity "hotspots" associated with western boundary currents and coastal upwelling zones are sustained through a combination of all of these factors. In the second half of the thesis I describe the results of a fine scale ecological and biogeochemical survey of the Kuroshio Extension Front. I found fine scale patterns in physical, chemical and biological properties that can be linked back to both the large scale horizontal and smaller scale vertical physical dynamics of the study region. A targeted genomic analysis of samples focused on the ecology of the picoeukaryote Ostreococcus clade distributions strongly supports the model derived hypotheses about the mechanisms supporting diversity hotspots. Strikingly, two distinct clades of Ostreococcus co-occur in more than half of the samples. A "hotspot" of Ostreococcus diversity appears to be supported by a confluence of water masses containing either clade, as well as a local nutrient supply at the front and the mesoscale variability of the region.
by Sophie Anne Clayton.
Ph.D.
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Härnström, Karolina. "Bloom dynamics and population genetics of marine phytoplankton : community, species and population aspects /." Göteborg : Department of Marine Ecology, University of Gothenburg, 2009. http://gupea.ub.gu.se/dspace/bitstream/2077/20913/1/gupea_2077_20913_1.pdf.
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Karasiewicz, Stéphane. "The phytoplankton community response(s) to global changes and their effect(s) on ecosystem functioning with a special focus on Phaeocystis spp, a harmful algae." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10191/document.
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Les écosystèmes côtiers, interface entre terre et mer, sont soumis au changement climatique ainsi qu’à de fortes pressions anthropiques. Par conséquent, les eaux côtières sont sujettes à eutrophisation. Le phytoplancton demande une attention particulière dû à son rôle de producteur primaire des écosystèmes marins. Récemment, l’efflorescence des algues nuisibles est devenue mondialement, une inquiétude croissante. Le but de la thèse a été de décrire et de mesurer les réponses temporelles et les causalités de la structure de communauté phytoplanctonique sous impact des changements globaux, en présence d’une algue nuisible. Pour ce faire, le concept de niche écologique et une méthode statistique, ont été adaptés. Les "Within Outlying Mean Indexes" ont été proposés pour affiner l’analyse "Outlying Mean Index" en combinant ses propriétés avec la décomposition de la marginalité de l’analyse "K-select". Les dynamiques des sous-niches de la communauté d’espèce ont été étudiées dans des conditions environnementales d’ abondances basses (L) ou fortes (H) de Phaeocystis spp. Le sous-ensemble H était caractérisé par une large niche de Phaeocystis spp. ainsi qu’une forte diversité de diatomées. Dans le sous-ensemble L, Phaeocystis spp. a subit une forte contrainte biologique probablement induite par la compétition des diatomées pour les ressources. La relation diversité-productivité du phytoplancton s’est avérée plus forte à l’échelle saisonnière que sur le long-terme. Le déséquilibre des ressources n’a pas eu de lien direct avec la productivité à long terme. Le succès à long terme de l’espèce invasive et de son impact sur la productivité, est favorisé par une suite d’années froides avec des ressources élevées et déséquilibrées, augmentant le nombre de petites espèces de diatomées et donc son efflorescence. Enfin, je discute des améliorations méthodologiques, du potentiel d’utilisation de l’approche par traits, et d’éventuelles montages expérimentaux pour supporter les résultats de la thèseCoastal ecosystems, the interfaces between land and sea, are subject to climate change and high anthropogenic pressure. Consequently, most coastal waters are prone to eutrophication. The phytoplankton require a special attention because of its role of primary producer in marine ecosystems. Recently, Harmful Algae Bloom outbreaks has raised concern worldwide. The thesis aim was to describe and to measure the temporal responses and causalities of the phytoplankton community structure, with the occurrence of a harmful algae, under global changes. To do so, the ecological niche concept and a statistical method were adapted. The Within Outlying Mean Indexes was proposed to refine the Outlying Mean Index analysis by combining its properties with the K-select analysis species marginality decomposition. The subniche dynamics of the species composing the community were studied under environmental conditions hosting low (L) and high (H) Phaeocystis spp. abundance. Subset H was characterized by a large Phaeocystis spp. niche and a high diatom diversity. In subset L, Phaeocystis spp. was subject to great biological constrain suspected to be caused by diatom competition for resources. The phytoplankton diversity productivity was stronger at a seasonal scale than on the long-term. The resource imbalance had no direct link with productivity in the long-term. The long-term invasive species success and its impact on productivity is favored by successive cold years with high resource imbalance which rise the number of small species and its bloom. I finally discussed on the methodological improvements, the potential use of the trait-based approach, and possible experimental set-ups to support the thesis results
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Maldonado-Pareja, Maria Teresa. "Iron acquisition by marine phytoplankton." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0022/NQ50215.pdf.
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Browning, Thomas John. "Nutrient limitation of marine phytoplankton." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:e250879e-131e-406a-a3cb-571e00dc0c81.
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Phytoplankton across the majority of the world’s oceans are thought to be limited by the availability of either nitrate or iron (Fe). However, the spatial resolution of experiments confirming this is low. Two thesis chapters present the results of bottle enrichment experiments at high spatial resolution across (i) the South Subtropical Convergence (SSTC) in the South Atlantic, and (ii) the Scotia Sea-Drake Passage sector of the Southern Ocean. These studies have added detail to the boundaries of limiting nutrients in these regions. Patterns of Fast Repetition Rate fluorometry (FRRf) derived parameters, physiological regulation of these parameters including influences of community structure, and the environmental controls driving them are analysed. Given its role as an essential micronutrient, there has been much effort in constraining potential sources of bioavailable Fe to the ocean, with one such source receiving recent interest: erupted ash from volcanoes. Bottle-scale ash-incubation experiments alongside conventional iron additions and laboratory ash-leaching experiments were conducted, the results of which suggest phytoplankton would respond strongly to ash deposition in the High Nitrate, Low Chlorophyll (HNLC) areas of the Southern Ocean. Particularly notable was the evidence these experiments provided for potential (co-)limitation of phytoplankton in these waters by the micronutrient manganese. The first three chapters of this thesis highlight a number of biogeochemical implications of trace metal stress, particularly that of Fe stress. Therefore, the ability to map the oceanographic extent of Fe-stressed regions using remote sensing would represent a particularly useful advance in marine biogeochemistry. Theoretically it could be possible to map Fe stress from space using satellite images of chlorophyll fluorescence, yet there are important uncertainties that need to be addressed before this can be carried out. In particular, a better understanding of the midday non-photochemical quenching driven reductions in chlorophyll fluorescence occurring at the time satellite images are captured is required. Analysis of over 200 non-photochemical quenching experiments collected over three research cruises, has allowed us to explore non-photochemical quenching and its relevance for using sunlight induced chlorophyll fluorescence to assess broad patterns of Fe stress. Our results have confirmed that satellite fluorescence quantum yields have the potential to reveal broad regions of Fe stress, however a dynamic non-photochemical quenching correction derived from our experiments and analysis was necessary to achieve this.
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Mouw, Colleen Beckmann. "Bio-optical and remote sensing investigation of phytoplankton community size structure /." View online ; access limited to URI, 2009. http://digitalcommons.uri.edu/dissertations/AAI3368002.
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Wilson, William Hector. "Characterisation of viruses infecting marine phytoplankton." Thesis, University of Warwick, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283512.
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Kyewalyanga, Margareth Nabuma. "Spectral dependence of photosynthesis in marine phytoplankton." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24750.pdf.
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Wiegman, Saskia. "Photoenhanced toxicity of azaarenes to marine phytoplankton." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/64908.
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Yee, Donald. "Cobalt substitution for zinc in marine phytoplankton." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43289.
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Crawfurd, Katharine. "Marine phytoplankton in a high CO2 world." Thesis, University of Dundee, 2010. https://discovery.dundee.ac.uk/en/studentTheses/82b46f33-e436-4eff-9862-e464f2761dca.
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Marine phytoplankton is responsible for ~50% of global primary productivity, it supports the oceanic food web and affects biogeochemical cycles. I participated in a large mesocosm experiment that observed altered community structure and carbon drawdown in response to increased CO2. There was a 27% reduction in community primary production at the peak of an Emiliania huxleyi-dominated bloom in mesocosms initially at 760 ppm CO2 compared to present day pCO2. There were changes in community structure but not dominance; Synechococcus and large pico-eukaryote abundances were reduced by ~60%, E. huxleyi was reduced by ~50%. A number of E. huxleyi strains persisted throughout the experiment in both treatments and no malformation or significant change in lith size occurred at increased CO2. In a second field experiment in the oligotrophic ocean off the Canary Islands, 760 ppm pCO2 did not change community structure or cell division rates of Synechococcus, Prochlorococcus or pico-eukaryotes.In laboratory experiments, I maintained the diatom, Thalassiosira pseudonana CCMP1335 at 760 ppm and present day pCO2 for ~100 generations in gas equilibrated continuous cultures – one of the longest experiments that has been attempted to investigate the effect of increased CO2 on marine phytoplankton. No clear evidence of adaptation or acclimation to increased CO2 was found, neither were there consistent changes in transcription of RuBisCO or carbonic anhydrase genes. Non-calcified E. huxleyi CCMP1516 and calcified CCMP371 grown in gas equilibrated semi-continuous cultures for several weeks showed no change in cell division rate at 760 ppm CO2. An understanding of the underlying changes in communities is required for modelling responses to increasing CO2, molecular tools may prove useful for this task. The strong community response in the mesocosms shows that rising atmospheric CO2 can greatly affect phytoplankton productivity and biogeochemical cycling.
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See, Jason Holt. "Availability of humic nitrogen to phytoplankton." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539616848.
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The chemical, physical, and biological factors affecting the bioavailability of humic nitrogen (N) to coastal phytoplankton were examined. Historically, humic substances have largely been considered biologically refractory, and humic-N is though to be unavailable biologically without prior oxidation via photochemical cleavage or remineralization by bacteria. This is due in part to the high aromaticity and low N content of humic substances. This dissertation investigates whether these assumptions are valid, and whether humic substances may be a more important source of N to the coastal phytoplankton community than previously believed. The research consisted of four main parts. First, changes in the structure and N content of humic substances were monitored by forming humics in the laboratory and following the changes in structure and chemical composition as they aged. It was found that as humics age, they become more aliphatic and fulvic-like. It was also determined that the commonly used XAD-8 extraction technique may underestimate the N content of aquatic humics by stripping ammonium (NH4+) from the humic structure. Second, whether or not this underestimation of humic-N has an effect on previously reported rates of photochemical N liberation from humic compounds was investigated. It was found that while the potential for the underestimation of photochemical release exists, previously reported rates are close to correct, largely due to physical and chemical interactions of humic substances with the surrounding environment. Third, the bioavailability of humic-N was examined using a suite of coastal phytoplankton strains. In short, all coastal strains exposed to humic substances could take up humic-N in short-term incubations; an open ocean strain tested did not take up humic-N. Furthermore, younger humics appeared to be more labile than those aged for time periods greater than three months. Finally, the significance of the salinity-mediated release was investigated and found to be a potentially important transport mechanism of NH4 + to the mid-saline regions of the estuary. In conclusion, the combination of chemical, physical, and biological processes occurring in the estuarine and coastal ecosystems suggests that humic substances are highly dynamic, biologically active compounds and not the biologically recalcitrant molecules portrayed in current literature.
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Sackmann, Brandon S. "Remote Assessment of 4-D Phytoplankton Distributions off the Washington Coast." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/SackmannBS2007.pdf.
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Fragoso, Glaucia M. "Hydrography and Phytoplankton Distribution in the Amundsen and Ross Seas." W&M ScholarWorks, 2009. http://web.vims.edu/library/Theses/Fragoso09.pdf.
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Lam, Yung-chun Nelson. "Annual distribution of phytoplankton in Tolo Harbour a flow cytometry approach /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22718874.
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Allen, Jason D. "Correlating phytoplankton assemblages with water quality in Illinois lakes and reservoirs : validating models based on historical data /." View online, 2008. http://repository.eiu.edu/theses/docs/32211131464742.pdf.
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Tozzi, Sasha. "Photobiological studies of Ross Sea phytoplankton." W&M ScholarWorks, 2010. https://scholarworks.wm.edu/etd/1539616879.
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The Ross Sea polynya is characterized by high spatial and temporal variability and by an annual cycle of sea ice retreat, water column stratification, large phytoplankton blooms, and months of complete darkness. This region is also highly susceptible to increasingly changing climatic conditions that will significantly affect the hydrography, iron supply, primary production patterns and carbon cycling. This project focused on analyzing how differences in photosynthetic traits between the two major bloom-forming functional groups in the polynya, diatoms and the prymnesiophyte Phaeocystis antarctica, and investigate if these differences can explain their dominance and succession. The study was conducted as part of the Controls on Ross Sea Algal Community Structure (CORSAC) program during two cruises in December 2005-January, 2006, and November-December, 2006. A fast repetition rate fluorometer (FRRF) was used to assess photochemical efficiency on natural phytoplankton assemblages and on monoclonal cultures. Measurements were made on cultures to determinate differences in photorecovery kinetics, as well on a suite of experiments performed to test the effects of temperature, iron, CO2 and micronutrients had on natural assemblages. In addition, FRRF measurements were made on 1,182 discrete samples representative of 98 profiles collected over the two cruises. Phaeocystis antarctica consistently photorecovered faster than the diatoms Pseudo-nitzschia sp., indicating different photosynthetic strategies and ecological niches; in addition, temperature and iron significantly promoted photosynthetic quantum yields, indicating a diffuse iron limitation of the natural assemblages used for the experiments and a high susceptibility to forecasted temperature increases in the region. Experiments also demonstrated that the Ross Sea phytoplankton is capable of maintaining high photosynthetic capacity after extensive periods in the dark. The dominance and successions in the blooms appears to be controlled by a combination of hydrography and in particular by the relative depths of the mixed layer and euphotic zone, as well by the water temperatures and possibly by iron concentrations. Diatom-dominated blooms were found in shallow mixed water layers characterized by higher temperature and fresher waters in the summer in the western part of the polynya, while Phaeocystis antarctica prevailed in colder regions with deeper mixed layer depths in the eastern part of the polynya. The dominance in the bloom significantly affected the relative macronutrient drawdown. Photosynthetic characteristic of natural assemblages were also modeled based on variable fluorescence rapid light curves (RLCs), and photophysiological differences were found between diatoms and Phaeocystis antarctica, with the latter having higher Ek and lower functional absorption cross sections (sigmaPSII) and alpha values, but similar maximum electron transport rates (ETRs). Lastly, correlation between RLC-based modeled photosynthetic rates and 14C based primary production presented some discrepancies due to limitations and differences in methodologies.
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Guo, Jian. "Copper requirements and acquisition mechanisms in marine phytoplankton." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42028.
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Copper nutrition is essential for the growth of marine diatoms, especially under Fe-limiting conditions. I investigated the physiology of Cu in marine phytoplankton by studying how the Fe and Cu availability interact and control Cu uptake and demand. I used short-lived Cu radioisotopes to determine the Cu requirements and steady-state Cu transport rates (ρssCu) of ten species from three classes of marine phytoplankton, isolated from coastal and oceanic environments. I also determined the Cu uptake kinetics of two marine centric diatoms (Thalassiosira oceanica and T. pseudonana) grown under various Fe and Cu conditions (sufficient and limiting). Furthermore, putative genes encoding potential components of Cu transport and homeostasis were identified in T. pseudonana, and their expression was investigated. Copper had significant effects on growth rates and ρssCu of the oceanic phytoplankton, but not the coastal strains. Although Cu quotas (Cu:C) were not significantly higher in oceanic strains, there were five independent lines of evidence supporting a more important role of Cu in the physiology of oceanic phytoplankton. Distinct biphasic Cu transport rates as a function of Cu concentrations were observed in the centric diatoms, Thalassiosira oceanica and T. pseudonana, suggesting the presence of a high- and a low-affinity Cu transport system. The high-affinity Cu transport system followed Michaelis-Menten saturation kinetics, but was controlled differently by Fe and/or Cu availability. A strong interaction between Fe and Cu nutrition in controlling the expression of genes encoding Cu transport and homeostasis was observed. Most genes, including putative Cu transporters (CTR), Cu transporting P-type ATPases, Cu chaperones and putative Zn transporters in T. pseudonana were up-regulated by low Fe, while low Cu either had no effect or the effect was dependent on Fe availability. These results suggest a complex interaction between Cu and Fe response networks. The function of a putative Cu transporter (CTR) in T. pseudonana was examined using functional complementation of Saccharomyces cerevisiae ctr1Δctr3Δmutant. Though the results were inconclusive, various explanations for these findings were discussed. This thesis highlights a complex interaction between Fe and Cu nutrition in marine phytoplankton at the protein and gene expression level.
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Nodwell, Lisa M. "Inorganic colloidal iron use by marine mixotrophic phytoplankton." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30826.
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Three species of photosynthetic flagellates capable of phagotrophy (mixotrophic species) were tested for their abilities to use inorganic iron colloids for growth. Ochromonas sp., Chrysochromulina ericina (a coastal strain) and C. ericina (an oceanic strain) were grown in iron-free seawater supplemented with 1 muM goethite, hematite, magnetite/maghemite or ferrihydrite (90°) in the presence and absence of desferrioxamme B, an iron-binding siderophore. Both strains of Chrysochromulina grew at 35--70% of their maximum rates with goethite, hematite, and magnetite/maghemite, but were unable to use ferrihydrite. Ochromonas, however, grew well with ferrihydrite, but could not use any of the other forms. All the flagellates were able to acquire iron from ingested bacteria. Diatoms that were known only to take up dissolved forms of iron, Thalassiosira oceanica (clone 1003) and T. pseudonana (clone 3H), were unable to use any of the colloids tested. The mechanism of iron acquisition by the flagellates appeared to involve ingestion of the iron colloids as DFB had no effect on colloidal iron availability and bacteria resident in the cultures were unable to use the iron contained in the colloids. Variations in the size of the colloids were hypothesized to account for differences in their availability, independent of colloid chemical stability. The results provide the first strong evidence for direct utilization (i.e. without prior dissolution) of colloidal iron by mixotrophic phytoplankton and document a new pathway of iron acquisition that may be important for their survival in low-iron waters of the sea.
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Miao, Aijun. "Trace metal accumulation and toxicity in marine phytoplankton /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202006%20MIAO.
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Baudoux, Anne-Claire. "The role of viruses in marine phytoplankton mortality." [S.l. : Groningen : s.n. ; University Library Groningen] [Host], 2007. http://irs.ub.rug.nl/ppn/304592706.
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Lee, Jennifer Grant. "Cadmium, a toxin and nutrient for marine phytoplankton." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/37536.
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Butler, Joanne Elizabeth. "Phytoplankton ecology in a high arctic polynya." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25080.
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Primary production was studied in Fram Sound, part of the Hell Gate-Cardigan Strait polynya, from June to August, 1982. Primary production rates, phytoplankton biomass (chlorophyll α), and water transparency were measured and used in conjunction with modelled solar radiation values to numerically model primary production during this time. The major phytoplankton nutrients were also measured.
Early season chlorophyll α concentrations were low, and the increased light availability due to reduced ice cover in this area did not appear to enhance early season production. Chlorophyll concentrations peaked twice; the first peak occured on 20 July and the
second on 14 August. The mean primary production rate and phytoplankton
biomass were 998 mg C.m⁻² .d⁻¹ and 72 mg chl.m⁻² . This production rate
is higher than that measured in other High Arctic areas.
Nitrogen, phosphorus and silica were essentially homogeneously
distributed during the sampling period and these concentrations varied
little from June to August except during 5 days in late August, when
they decreased by half then returned to previous levels.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Thompson, Brian P. "Temporal and Spatial Variability of Phytoplankton Biomass in the Damariscotta River Estuary, Maine, USA." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/ThompsonBP2006.pdf.
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Haskell, Andrew Glenn Edward. "Modeling plankton community structure under environmental forcing on the southeastern U.S. contintental shelf." [Norfolk, VA. : Center for Coastal Physical Oceanography], 1997. http://catalog.hathitrust.org/api/volumes/oclc/39263483.html.
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Mosby, Anna Ford. "Phytoplankton Growth Rates in the Ross Sea, Antarctica." W&M ScholarWorks, 2013. https://scholarworks.wm.edu/etd/1539617935.
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The Ross Sea is a highly productive region of the Southern Ocean characterized by spatially variable distribution of phytoplankton, primarily Phaeocystis antarctica, but phytoplankton growth rates in the region have not been thoroughly investigated. Variability in growth rates was investigated from January to February 2012 on a cruise to the Ross Sea using two methods: 14C-isotopic tracer incubations and dilution experiments. Because all methods of measuring growth rates may not be appropriate in all systems due to errors inherent to each method, I assessed and compared the two methods for possible sources of error by examining the effect of extended incubations on measured growth rates in 14C-incubations, quantifying phytoplankton growth and grazing mortality rates through dilution experiments, and analyzing the effect of irradiance in incubations on carbon:chlorophyll ratios in dilution experiments. I found that dilution experiments yielded variable growth rates based on chlorophyll and cell abundance; the mean growth rate based on chlorophyll was 0.11 d-1 while mean growth rate based on abundance was 0.12 d-1. Chlorophyll-based growth rates may be inaccurate due to carbon:chlorophyll ratios of phytoplankton changing during incubations. This unbalanced growth is likely due to variable mixed layer depth and subsequent variability in light history of phytoplankton. Grazing mortality rates were non-significant in 7 of the 11 dilution experiments conducted and significant mortality rates were low with a mean mortality rate of 0.09 d-1, most likely because of low temperatures rather than the presence of P. antarctica. Growth rates measured in 14C-incubations did not change in extended incubations, indicating that loss of fixed 14C through grazing and respiration was not a major source of error. Growth rates were below those predicted based on temperature alone (p<0.001), and mean growth rate in 14C-incubations was 0.14 d-1. Structural equation modeling indicated that growth rates in 14C-incubations did not strongly vary with mixed layer depth, but were significantly affected by low iron concentrations, most likely due to the seasonal depletion of iron. As grazing is low and physical conditions vary spatially, dilution experiments may not be an appropriate measure of growth rate in the Ross Sea, but 14C-incubations yield relatively low growth rates that are significantly affected by low iron concentrations in the region.#
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McMurray, Helen F., and Helen F. McMurray. "Phytoplankton production in Agulhas bank waters (South Africa)." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/23663.
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Carbon-14 measurements of community and size- fractionated production in continental shelf waters of the Agulhas Bank (South Africa) are presented. Auxiliary measurements included chlorophyll α, nitrate concentrations and thermal profiling of the water column. During the winter and spring surveys, the mixed layer extended deeper than the euphotic zone, with nitrate and phytoplankton biomass being evenly distributed through the euphotic zone. Production maxima occurred at the 40 - 90 % surface irradiance light depths, with some evidence of surface photoinhibition. All surveys during summer months (December - March) showed a thermally stratified euphotic zone (ZeuO.5%/Zm = 1.1 - 2.2), with a well deformed nitracline within the thermocline. A subsurface chlorophyll maximum closely associated with the region of maximum nitrate gradient (3 - 10 % surface irradiance) was typical of summer measurements. Subsurface chlorophyll α concentrations were lower in western Agulhas Bank waters (0.5- 6 μg.l⁻¹) than in eastern Agulhas Bank waters (l- 15 μg.l⁻¹). Highest subsurface chlorophyll α concentrations (15- 40 μg.l⁻¹) were measured during the late summer survey (March 1986) at the Alhard Banks station in a strongly stratified water column. For profiles showing a very well developed subsurface chlorophyll maximum, the production maximum occurred at or slightly shallower than the depth of the chlorophyll maximum. In western Agulhas Bank waters, during surveys when a shallow (<30m) thermocline persisted, production maxima at 90 and 100% surface irradiance intensities were frequently observed. Integrated production values ranged between 70 and 1390 mgC.m⁻².h⁻¹. Minimum areal production rates were observed during winter (July), whilst maximum rates were measured during late summer (March). High euphotic zone production was also measured during the spring survey in western Agulhas Bank waters (347 mgC.m⁻².h⁻¹), associated with the stabilising of the water column after winter mixing. The <15 μm size-fraction was observed to account for much of total production (62-97%) during conditions of deep mixing in winter and a deep upper mixed layer during summer. During the spring survey and those surveys where a shallow (<35m) thermocline persisted, production was predominantly by the netplankton > 15 μm size-fraction (60- 87 %). Periods of enhanced netplankton growth may be crucial for the sustaining of the large biomass of spawning anchovy present in western Agulhas Bank waters. Vertical profiles, the subsurface chlorophyll and production maximum and size-fractionated production measurements are discussed with relevance to the control of phytoplankton production and potential trophic fluxes in Agulhas Bank waters.
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Lau, Winnie W. Y. "Understanding interactions between marine bacteria and phytoplankton : the influence of phytoplankton photorespiration on diversity and succession of glycolate-utilizing bacteria /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/11011.
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Wänstrand, Ingrid. "Pigment and Thiamine Dynamics in Marine Phytoplankton and Copepods." Doctoral thesis, Uppsala universitet, Evolutionsbiologi, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4560.
Full textAbstract:
Based on a field study and several mesocosm experiments, I evaluated the use of pigments as chemotaxonomical biomarkers for phytoplankton community composition in the Baltic Sea and I examined effects of inorganic nutrients on the dynamics of carotenoids and thiamine (vitamin B1) at the phytoplankton–copepod level in marine pelagic food webs. My results show that HPLC pigment analysis combined with CHEMTAX data processing was an accurate alternative to microscopic analysis of Baltic Sea phytoplankton. Experimental supply of N, P and Si affected copepod growth and biochemical status via changes in biomass and composition of their phytoplankton diet. Net population growth rates were generally higher when phytoflagellates dominated (low Si:N ratio) and lower when diatoms dominated (high Si:N ratio). Copepod body concentrations of astaxanthin decreased with fertilization. Correlations with reduced under-water irradiance were consistent with the photo-protective function of this antioxidant. Thiamine concentrations in phytoplankton also decreased with fertilization. In copepods, low Si:N ratios resulted in higher thiamine concentrations than high Si:N ratios. Thiamine concentration and degree of phosphorylation were useful as indicators of thiamine shortage both in phytoplankton and copepods. The concentrations of thiamine and astaxanthin in the copepod communities were positively correlated. As copepods constitute a major link between pelagic primary producers and higher trophic levels, fertilization effects may be responsible for astaxanthin and thiamine deficiencies in salmon suffering from the M74 syndrome, which appeared concurrently with large-scale eutrophication in the Baltic Sea. As both thiamine and astaxanthin are deficient in M74-affected salmon, there is a need for physiological and molecular investigations of possible interactions between the two compounds in living cells.
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Wänstrand, Ingrid. "Pigment and thiamine dynamics in marine phytoplankton and copepods /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4560.
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Weynberg, Karen Dawn. "Isolation and characterisation of novel viruses infecting marine phytoplankton." Thesis, University of Warwick, 2009. http://wrap.warwick.ac.uk/2800/.
Full textAbstract:
Viruses are the most abundant biological agents in the global marine environment. Through cellular lysis viruses influence many biogeochemical and ecological processes, including energy and nutrient cycling, host distribution and abundance, algal bloom control and genetic transfer. Nano- and picophytoplankton are ubiquitous in the world’s oceans and are responsible for a high proportion of the annual global carbon fixation. However, relatively few viruses have been isolated and described that infect these key primary producers and little is known of their diversity, dynamics or propagation strategies. The aims of this study were to detect, isolate and characterise novel marine viruses that infect these important members of the phytoplankton assemblage. Screening of seawater samples for viruses that infect a broad representation of nano and picophytoplankton species was undertaken here. To enable this, a large culture collection of 106 phytoplankton species was established and used to screen seawater samples for viruses on a weekly basis over a two year period. A total of 12 novel viruses infecting the prasinophyte species’ Ostreococcus tauri and Micromonas pusilla were isolated from seawater sampled in coastal waters of the Western English Channel. Viruses were purified by plaque purification or liquid serial dilution techniques. Characterisation of novel virus isolates included growth kinetics, visualisation using transmission electron microscopy, host range analysis and estimates of viral genome sizes using pulsed field gel electrophoresis. Phylogenetic analysis of these viruses was conducted based on the sequence of the conserved DNA polymerase gene. Genome sequencing of two of the viruses infecting O. tauri was completed and revealed many exciting features, including a suite of genes hitherto unreported, or with rare occurrence, in viruses. Evidence is presented for horizontal gene transfer between viruses isolated in this study and their hosts, as well as between other eukaryotic and bacterial sources. Functional characterisation of the viral genomes sequenced and described in this study will provide clearer insights into viral dynamics and evolutionary history.
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Fandino, Laura B. "Molecular ecology of bacteria associated with marine phytoplankton blooms /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3064445.
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Šupraha, Luka. "Phenotypic evolution and adaptive strategies in marine phytoplankton (Coccolithophores)." Doctoral thesis, Uppsala universitet, Paleobiologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302903.
Full textAbstract:
Coccolithophores are biogeochemically important marine algae that interact with the carbon cycle through photosynthesis (CO2 sink), calcification (CO2 source) and burial of carbon into oceanic sediments. The group is considered susceptible to the ongoing climate perturbations, in particular to ocean acidification, temperature increase and nutrient limitation. The aim of this thesis was to investigate the adaptation of coccolithophores to environmental change, with the focus on temperature stress and nutrient limitation. The research was conducted in frame of three approaches: experiments testing the physiological response of coccolithophore species Helicosphaera carteri and Coccolithus pelagicus to phosphorus limitation, field studies on coccolithophore life-cycles with a method comparison and an investigation of the phenotypic evolution of the coccolithophore genus Helicosphaera over the past 15 Ma. Experimental results show that the physiology and morphology of large coccolithophores are sensitive to phosphorus limitation, and that the adaptation to low-nutrient conditions can lead to a decrease in calcification rates. Field studies have contributed to our understanding of coccolithophore life cycles, revealing complex ecological patterns within the Mediterranean community which are seemingly regulated by seasonal, temperature-driven environment changes. In addition, the high-throughput sequencing (HTS) molecular method was shown to provide overall good representation of coccolithophore community composition. Finally, the study on Helicosphaera evolution showed that adaptation to decreasing CO2 in higher latitudes involved cell and coccolith size decrease, whereas the adaptation in tropical ecosystems also included a physiological decrease in calcification rates in response to nutrient limitation. This thesis advanced our understanding of coccolithophore adaptive strategies and will improve our predictions on the fate of the group under ongoing climate change.
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Clark, D. R. "Carbon-nitrogen stress, and the growth of marine phytoplankton." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636260.
Full textAbstract:
A number of phytoplankton species from a range of taxa (including diatoms, dinoflagellates and prymnesiophytes) were grown in batch cultures in closed systems at four dissolved inorganic carbon concentrations. Cultures were supplied with NO3- or NH4+ and growth was limited by C and/or N. Response of the phytoplantkon to C and/or N stress was investigated with measurements including C:N ratios, cell C, N and chl.a quotas, chl.a:C ratios and the internal amino acid pool. Responses to C-limitation included an increase in cell N and chl.a quota, chl.a:C ration and the gln:glu ratio. Responses to increased N-limitation included an increase in the cell C-quota and C:N ratio, together with decreases in cell-N and chl.a quota, chl.a:C ratio, and the gln:glu ratio. Generally indications of N-stress were greater when the N-source was NO3- rather than NH4+ as demonstrated at the level of the cell C, N and chl.a quotas, and at the level of internal amino acid pool, although none of these indicators were found to be consistent for every species. A study of the kinetics of DIC utilisation revealed that to a greater or lesser extent, the utilisation of NO3- relative to NH4+ consistently resulted in a significant decrease in the carbon specific growth rate of all species investigated. The expression of extracellular carbonic anhydrase may endow marine phytoplankton with a competitive advantage, regardless of cell size or motility, while large and chain forming species appeared to be at a relative disadvantage with respect to the kinetics of DIC utilisation. Typically, the species investigated attained a KG for dissolved inorganic carbon of <300 μM. The results of the study suggest that DIC rate limitation of phytoplankton growth may be of minor consequence in the marine environment.
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Lane, Erin Susan. "The interaction between cadmium and iron in marine phytoplankton." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31659.
Full textAbstract:
This study examined the intracellular Cd content (Cd:C) of seven species of
cultured phytoplankton under varying degrees of Fe-limitation. A significant increase in
Cd:C ratios was observed for all species grown under Fe-limitation, with an average 2-
fold increase in Cd quotas. The mechanism behind this increase in Cd quotas was further
investigated in a model diatom, Thalassiosira oceanica. A significant interaction was
found between Cd and inorganic Fe(II). Inorganic Fe(II) uptake rates by Fe-limited T.
oceanica were reduced by 50% when Cd was present, while Cd uptake was inhibited
36% in the presence of Fe(II). Inorganic Fe(II) uptake rates were also 15 times faster in
Fe-limited cultures than in Fe-replete cultures. Cadmium and Fe(II) appear to enter the
cell through common non-specific divalent metal transporters that are up-regulated under
Fe-limitation, thereby leading to enhanced Cd accumulation. In addition to the effect of
Fe-limitation on Cd:C ratios of cultured phytoplankton, a species/phyla effect was
observed. A greater than 65-fold difference in Cd:C ratios was also observed between
species grown under identical Fe concentrations. Oceanic diatoms had the highest Cd
quotas and naked pryrnesiophytes the lowest. The intracellular Cd requirements of
cultured phytoplankton were compared to the Cd content of natural phytoplankton
assemblages from Fe-replete and Fe-limited waters in the subarctic Pacific, as well as to a
global dataset of particulate Cd:P0₄3- ratios in surface waters. The phytoplankton from
the Fe-limited station had the highest Cd:C ratios, which was attributed to a combination
of species composition and Fe limitation. The same trend was found in our global data
with HNLC stations having higher particulate Cd: P0₄
3- ratios than Fe-replete stations.
The combined laboratory, field, and global dataset results suggest that deviations in surface water Cd:PO₄3- ratios can be explained by both changes in species composition
well as Fe-limitation. We propose that the "kink" in the global dissolved Cd:PO₄3-
relationship is a result of the export of Fe-limited diatoms with high intristic Cd:P0₄3-
ratios in HNLC regions.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
41
Elliott, J. A. "Investigating the assembly of phytoplankton communities with PROTECH." Thesis, Edinburgh Napier University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325890.
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Cosgrove, Jeffrey John. "Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence." Cosgrove, Jeffrey John (2007) Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence. PhD thesis, Murdoch University, 2007. http://researchrepository.murdoch.edu.au/503/.
Full textAbstract:
Marine phytoplankton ecophysiological state and primary production measurements have typically been controversial due to potential impacts of measurement techniques. Advances in chl-a fluorescence techniques have provided a means for rapid, non-invasive measurement of electron transport through photosystem 2 (PSII) in dilute phytoplankton suspensions. While studies on higher plants have outlined a close relationship between PSII electron transport and carbon fixation, results from studies on microalgae reveal significant variations in the relationship.
Three species of phytoplankton representing three major taxonomic groups of the marine phytoplankton were used in this study: (1) Chaetoceros muelleri CS176 Lemmermann (Bacillariophyta), (2) Isochrysis galbana CS177 Parke (Haptophyta) and, (3) Nannochloropsis oculata CS179 (Droop) Hibberd (Ochrophyta, eustigmatophyte). Each species was cultured in semicontinuous culture and primary production was estimated using oxygen evolution and carbon fixation techniques and compared against predictions based on chl-a fluorescence measurements. It was found that predicted values of primary production both under-estimated and overestimated actual carbon fixation measured via radioisotope (14C) techniques. This variation was primarily explained by probable errors in the assumed values for PSII density. The relationship between oxygen evolution or carbon fixation with chl-a fluorescence-derived measures was commonly linear below the light saturation parameter, with a departure from linearity occurring at higher irradiances. This departure from linearity was greatest in cultures adapted to low light conditions. At higher light intensities alternative electron pathways such as the Mehler reaction and/or chlororespiration are likely to be more active in low light-adapted cultures, leading to this greater non-linearity.
Chl-a fluorescence measurements were also found to be a useful in characterising ecophysiology using photosynthesis-versus irradiance curves. However, an important caveat on this is the measurement of PSII density ([eta]PSII) rather than use of an assumed value as changes in [eta]PSII can have a profound impact on light curve parameters.
A field study in Fremantle Harbour found a healthy (negligible nutrient starvation), diatom dominated, phytoplankton community. Results suggest that phytoplankton are able to begin boosting photosynthetic capability just prior to morning twilight. Waters in the harbour were well mixed via tidal motion and substantial midday photoinhibition was not observed. Data suggest levels of primary production at the mouth of the harbour are similar to those of coastal waters in the plume of the Ocean Reef wastewater outfall.
43
Salleh, Aishah. "The growth of phytoplankton populations in nature and in culture." Thesis, Royal Holloway, University of London, 1987. http://repository.royalholloway.ac.uk/items/2cb918c8-a73f-4d5d-961c-a0354020224f/1/.
Full textAbstract:
An investigation over a period of more than two years of phytoplankton, and physical and chemical conditions of the River Thames and the Wraysbury Reservoir in Southern England, has indicated seasonal occurrence of phytoplankton populations with diatoms (chiefly Stephanodiscus ref. hantzschii Grun.) forming a large percentage of the populations. During 1984, 1985 and 1986, phytoplankton populations occurred most abundantly during the spring (mainly diatom populations) and during the summer (diatoms and green algae in the River Thames, and blue-green algae in the Wraysbury Reservoir). Selected algal taxa were isolated and grown in culture in the laboratory and experiments carried out in which culture conditions have been manipulated in various ways. Such experiments included those involving suspected nutrient limiting factors (e.g. phosphate) as well as physical factors especially those of temperature and light. Ecological records and experimental cultures indicate that the occurrence and growth of diatoms is encouraged by the increasing water temperatures and light intensity during the spring, and by higher levels of nutrient concentrations (i.e. nitrate-nitrogen, phosphate-phosphorus and silica) at all times. On the other hand, the growth of green algae (Chlorophyceae) and blue-green algae (Cyanophyceae) was influenced by the maximum water temperatures and light intensity of the summer period and despite lower nutrient concentrations. Thus, differences in physical and nutrient requirements by phytoplankton populations help to explain the presence of diatoms during the spring and green algae (in the River Thames) and blue-green algae (in the Wraysbury Reservoir) during the summer. Simple investigation of the growth responses of the River Thames and Wraysbury Reservoir phytoplankton populations to River Thames and Wraysbury Reservoir water as natural culture media were performed. The results indicated that the River Thames and Wraysbury Reservoir are potentially able to support considerable crops of phytoplankton populations, and that the potential is present throughout the year.
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Olivieri, Emilia T. "Phytoplankton growth and zooplankton grazing in the southern Benguela current." Doctoral thesis, University of Cape Town, 1985. http://hdl.handle.net/11427/22590.
Full textAbstract:
Bibliography: pages 135-146.The development and production of several phytoplankton communities and the consumption of these communities plankton were investigated in newly by herbivorous mesozooupwelled waters of the southern Benguela Current by means of an electronic counting and sizing technique (Coulter counter). A feasibility study was initiated to test the accuracy of the Coulter counter (Model TAII) in estimating phytoplankton size and biomass in fresh and preserved samples from the Benguela current. Counting phytoplankton using this method gave a higher degree of reproducibility than the inverted microscope method. Certain recommendations as to the counting procedures were made. The counting of preserved samples was shown to introduce artefacts, resulting in a 77 per cent reduction in particle volume after a year of preservation. Correlations of particle volume with chorophyll a, carbon and nitrogen were calculated, with highest correlations occurring between particle volume and chlorophyll a. Particle volume was shown to represent biomass as accurately as any of the other methods.
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Waite, Tim J. "On the influence of marine micro-organisms upon the iodine system in seawater." Thesis, Oxford Brookes University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251369.
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Chan, Shue-shum. "Phytoplankton size fractions in Tolo Harbour, Hong Kong and their relative contributions to productivity." [Hong Kong] : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12355367.
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Watts, Matthew Charles. "Lagrangian modelling of the marine nitrogen and sulphur cycles." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302076.
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Hare, Clinton Earl. "Consequences of iron limitation and climate change on phytoplankton community composition." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 189 p, 2007. http://proquest.umi.com/pqdweb?did=1264630411&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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au, jcos@iinet net, and Jeffrey John Cosgrove. "Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence." Murdoch University, 2007. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20071129.122222.
Full textAbstract:
Marine phytoplankton ecophysiological state and primary production measurements have typically been controversial due to potential impacts of measurement techniques. Advances in chl-a fluorescence techniques have provided a means for rapid, non-invasive measurement of electron transport through photosystem 2 (PSII) in dilute phytoplankton suspensions. While studies on higher plants have outlined a close relationship between PSII electron transport and carbon fixation, results from studies on microalgae reveal significant variations in the relationship.
Three species of phytoplankton representing three major taxonomic groups of the marine phytoplankton were used in this study: (1) Chaetoceros muelleri CS176 Lemmermann (Bacillariophyta), (2) Isochrysis galbana CS177 Parke (Haptophyta) and, (3) Nannochloropsis oculata CS179 (Droop) Hibberd (Ochrophyta, eustigmatophyte). Each species was cultured in semicontinuous culture and primary
production was estimated using oxygen evolution and carbon fixation techniques and compared against predictions based on chl-a fluorescence measurements. It was found that predicted values of primary production both under-estimated and overestimated actual carbon fixation measured via radioisotope (14C) techniques. This variation was primarily explained by probable errors in the assumed values for PSII density. The relationship between oxygen evolution or carbon fixation with chl-a fluorescence-derived measures was commonly linear below the light saturation parameter, with a departure from linearity occurring at higher irradiances. This departure from linearity was greatest in cultures adapted to low light conditions. At higher light intensities alternative electron pathways such as the Mehler reaction and/or chlororespiration are likely to be more active in low light-adapted cultures, leading to this greater non-linearity.
Chl-a fluorescence measurements were also found to be a useful in characterising ecophysiology using photosynthesis-versus irradiance curves. However, an important caveat on this is the measurement of PSII density (çPSII) rather than use of an assumed value as changes in çPSII can have a profound impact on light curve parameters.
A field study in Fremantle Harbour found a healthy (negligible nutrient starvation), diatom dominated, phytoplankton community. Results suggest that phytoplankton are able to begin boosting photosynthetic capability just prior to morning twilight. Waters in the harbour were well mixed via tidal motion and substantial midday photoinhibition was not observed. Data suggest levels of primary production at the mouth of the harbour are similar to those of coastal waters in the plume of the Ocean Reef wastewater outfall.
50
Godrant, Aur??lie Suzanne Civil & Environmental Engineering Faculty of Engineering UNSW. "The role of superoxide in iron acquisition by marine phytoplankton." Awarded by:University of New South Wales. Civil & Environmental Engineering, 2009. http://handle.unsw.edu.au/1959.4/44509.
Full textAbstract:
It is hypothesised that, under iron limitation, phytoplankton cells develop biochemical mechanisms to increase their iron uptake efficiency with one of these mechanisms involving the production of superoxide in the extracellular environment that increases the bioavailability of iron in seawater by reducing Fe(1II) to the more soluble Fe(II). The main objectives of this work were i) to develop an appropriate method to detect extracellular production of superoxide by marine phytoplankron, and ii) to examine the relationship between extracellular production of superoxide and iron acquisition by Trichodesmium erythraeum. A method to measure O2- production is described using red-CLA and MCLA probes, yielding considerable improvement for analysis compared to other available methods. Extracellular O2" production and iron uptake rates were measured simultaneously on iron replete and iron deplete Tr;chodumium uythraeum IMS 101 laboratory cultures: iron stan'ation l~ds to a 2.9-fold increase in superoxide production rate and 10-fold decrease in the iron uptake rate (except when a reducing compound was added) compared to iron replete cultures. Extracellular superoxide production shows a pronounced circadian rhythm in iron deplete cultures, but less so in iron replete cultures. Overall, no direct impact of extracellular superoxide production by T";chode.smium on iron uptake is obsen'ed, but both processes are shown to be related. Both iron deplete and iron replete cuhures demonstrate greater ability to uptake iron bound to weaker iron-binding ligands such as citrate. Application of the method to field studies in the Great Barrier Reeflagoon showed an accumulation of biologically significant concentrations of reduced trace metals including Fe(JI) when [Od was lower than 1 nM. When [02"] was higher than 1 nM, most of the reduced species were oxidised resulting in high rates of H202 production through catalysed O2" disproportionation. Moreover, two Tr;chode.smium blooms exhibited high O2- production rates, consistent whh laboratory studies. Overall, this thesis permitted the development of a method to detect O2production rates by marine phytoplank[Qn ceUs that could be used routinely in field studies. The observations are in accord with the conclusion that fit the ongoing hypothesis that the established Fe' uptake model for phytoplankton would be strongly influenced by such organisms that are able to modify the redox equilibrium of the solution at their ceU surface.