Дисертації з теми "Planktic"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Planktic.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Planktic".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Caromel, Aude Genevieve Marcelle. "Form and function in planktic foraminifera." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.628998.
Повний текст джерелаАнотація:
Planktic foraminiferal tests and their morphology have been the subject of extensive study for biostratigraphy and palaeoenvironmental reconstructions. Iterative evolution of morphological designs and correlations between morphology and environmental parameters suggest either fundamental intrinsic constraints on form , or a functional control, or both. Yet the adaptive significance of the test morphologies in terms of these constraints has never been rigorously explored, and is the focus of this thesis. The developmental and growth constraints delimiting the scope of action for evolution were determined through ontogenetic reconstructions based on SRXTM scans. Differences in growth patterns between the globigerinid and globorotalid groups imply a different potential for diversification. Different metabolic processes dominate growth at different stages of ontogeny due to changes in surface area-to-volume ratios, so mechanisms of evolution responding to environmental factors may change depending on when they occur in ontogeny. Imposed on these are constructional considerations, which were gauged through estimation of coiling patterns through ontogeny from the reconstructions. Coiling in early ontogeny is constrained across all species to maximise lateral growth. From the neanic stage, changes in coiling occur to accommodate new chamber shapes, and are modulated by the migration of the aperture. Developmental processes of evolution must therefore operate within this framework. Computational fluid dynamic simulations were used to assess the functional role of the test in adjusting settling velocity, by varying morphological and water parameters independently. The range of evolutionary options open to foraminifera is a result of trade-offs between changes in size, shape and density, and environmentally required fluctuations can easily be accommodated by the natural within-population variability. The findings of this thesis imply that, in the compromise between function and constraints acting with the environment to define adult morphology and diversification, intrinsic factors are likely to play a more important role than function in plank tic foraminifera.
2
Beer, Christopher James. "Planktic foraminifera, ocean sediments and the palaeo-marine carbonate system." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/208361/.
Повний текст джерела
3
Schmuker, Barbara. "Recent planktic foraminifera in the Caribbean sea : distribution, ecology and taphonomy /." [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13559.
Повний текст джерела
4
Pados, Theodora [Verfasser]. "Recent planktic foraminifera in the Fram Strait : ecology and biogeochemistry / Theodora Pados." Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/1059109166/34.
Повний текст джерела
5
Rückheim, Sylvia. "The onset of planktic foraminifera in the mid-Cretaceous of the Boreal Realm." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975763350.
Повний текст джерела
6
Steel, Blair Andrew. "Molecular and palaeontological approaches to the reconstruction of neogene spinose planktic foraminiferal phylogeny." Thesis, Royal Holloway, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429407.
Повний текст джерела
7
Stewart, Iain A. "The molecular evolution of planktic foraminifera and its implications for the fossil record." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/13020.
Повний текст джерелаАнотація:
The marine microfossils of planktic foraminifers are widely used for investigating palaeoceanographic and palaeoclimatic conditions. The objective of this project was to investigate genotypic variation within planktic foraminiferal morphospecies and the spatial distribution of genotypes in the subpolar, transitional and subtropical North Atlantic. Foraminiferal genomic DNA was extracted and the ~1000 base pair 3' terminal region of the small subunit ribosomal RNA gene was amplified using the polymerase chain reaction. Using distance-based molecular phylogenetic analysis, a neighbour-joining phylogeny was reconstructed based on 31 planktic and15 benthic previously sequenced foraminifera and extended to include 15 genotype sequences obtained from the North Atlantic during this study. Bulk plankton samples were collected for preliminary examination of genotype/morphotype relationships. The molecular phylogeny is largely consistent with the foraminiferal fossil record. It supports the suggestion that the origins of planktic foraminifers are polyphyletic, as the spinose planktic foraminifers cluster separately from the non-spinose planktic foraminifers within the phylogeny. Brachn length variation within the planktic cluster reflects large differences in evolution rate between morphospecies. Within the North Atlantic, genotypic variation has been identified within the morphospecies, Globigerina bulloides, Turborotalita quinqueloba, Globigerinella siphonifera, Globigerinella calida, Globigerinoides ruber and Neogloboquadrina pachyderma. The distribution of genotypes is complex, and it has been found that genotypes, representing a single morphospecies, often co-exist within the water column. This could be indicative of cryptic speciation, suggesting that North Atlantic planktic foraminiferal diversity is much higher than fossil record interpretations have indicated. The genotypes within G. bulloides, G. siphonifera, G. calida and T. quinqueloba have different geographic distributions within the North Atlantic. It is apparent that G. bulloides Types IIa and IIb and G. siphonifera Types IIa and IIb have extensive distributions suggesting that they are more generalist in adaptation, and tolerant to a wide range of oceanic conditions.
8
Palmer, Denise D. "Late Holocene planktic foraminiferal assemblages from Orca Basin : effects of dissolution on faunal assemblages." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001693.
Повний текст джерела
9
D'ONOFRIO, Roberta. "Planktic foraminiferal response to the early Eocene climatic perturbations: the post-PETM hyperthermals and the EECO event." Doctoral thesis, Università degli studi di Ferrara, 2017. http://hdl.handle.net/11392/2488050.
Повний текст джерелаАнотація:
Obiettivo di questa ricerca è l’indagine di alcuni episodi di riscaldamento estremo a breve e lunga durata dell’Eocene inferiore associati a profonde variazioni del ciclo del Carbonio e condizioni paleooceanografiche: ipertermali e Early Eocene Climatic Optimum (EECO).
A tal fine sono state selezionate tre successioni eoceniche di mare profondo da diversi contesti paleoceanografici: dalle basse latitudini, la sezione della Tetide centro occidentale del Terche (Italia nord orientale) e il Site Atlantico occidentale ODP 1051 (Blake Nose) dalle medie latitudini il Site Atlantico sud orientale ODP 1263 (Walvis Ridge). Questi casi-studio sono stati affrontati integrando analisi micropaleontologica e geochimica. La prima è principalmente basata sui foraminiferi planctonici, ampiamente utilizzati per studi paleoambientali poiché registrano effetti delle perturbazioni delle acque superficiali nella chimica dei gusci e nelle variazioni delle associazioni.
Le indagini degli ipertermali H1 o ETM2, H2 e I1 nella sezione di Terche mostrano rilevanti cambiamenti nelle associazioni del plancton calcareo che indicano aumento di eutrofia associato a un indebolimento della stratificazione termica delle acque superficiali, sebbene le variazioni siano transitorie e più intense durante l’ETM2. Ciascun evento coincide con anomalie marnose riconducibili all’aumento della diluizione terrigena poiché gli indicatori di dissoluzione non mostrano variazioni significative. Le condizioni di perturbazione persistono anche durante la fase di recupero del ciclo del carbonio implicando tassi di ripresa più lenti per ambiente e biota.
L'analisi dell’EECO nei Site atlantici rivela significativi cambiamenti nelle associazioni a foraminiferi planctonici. Il più evidente è la drastica riduzione in abbondanza e numero di specie di Morozovella e un parallelo incremento nelle abbondanze e diversificazione di Acarinina. Le possibili cause di questo turnover globale e permanente, già documentato in altre località delle basse latitudini, possono essere molteplici ed includono: temperature elevate, prolungati alti livelli di pCO2, acidificazione delle acque superficiali, perdita dei simbionti (bleaching) o competizione ecologica.
Il test sui morozovellidi del Site 1051, per verificare l'ipotesi del bleaching attraverso l'analisi del segnale del δ13C, mostra evidenze di bleaching e riduzione nella dimensione dei gusci in alcune specie di Morozovella poco sopra l'evento J. Questo segnale è tuttavia transitorio ed interessa anche gli acarininidi invalidando così questa ipotesi per spiegare il calo permanente di Morozovella. Varie specie di Morozovella non recuperano la massima dimensione del guscio; ciò implica il superamento della loro soglia di optimum ecologico durante l’EECO.
L’analisi della direzione di avvolgimento nei morozovellidi dei Site 1051 e 1263 evidenzia una preferenza nell’avvolgimento destrorso durante l'intervallo che precede l’EECO. Tuttavia, si osserva una prima marcata inversione verso un avvolgimento sinistrorso poco sopra il J che diviene permanente poco sopra il K/X. Incrementi temporanei delle forme sinistrorse si verificano anche durante alcuni ipertermali pre-EECO. Precedenti interpretazioni prediligono una spiegazione genetica per le inversioni dell’avvolgimento piuttosto che una risposta ecologica. Questi nuovi dati non possono convalidare o negare la prima ipotesi, ma stimolano una rinnovata considerazione della seconda.
Alla base dell’EECO nel Site 1263 si registra inoltre la virtuale scomparsa dei chiloguembelinidi e la riduzione nell’abbondanza dei subbotinidi riconducibili ad una contrazione delle nicchie ecologiche dovuta all'indebolimento della stratificazione termica delle acque.
Il segnale a foraminiferi planctonici sottolinea il sorprendente effetto della perturbazione di lunga durata indotta dall’EECO che si è sovrapposto ed ha prevalso sui cambiamenti effimeri legati agli ipertermali.The main goal of this research was to investigate some extreme warming episodes characterizing the early Eocene climate and related to profound variations on the global carbon cycle and paleoceanographic conditions, the short-lived hyperthermals and the long-lasted Early Eocene Climatic Optimum (EECO). To pursue this aim three early Eocene deep-sea successions were selected from different paleoceanographic settings: the low-latitude central western Tethyan Terche section (northeastern Italy) and the western Atlantic ODP Site 1051 (Blake Nose), and the mid-latitudes southeastern Atlantic ODP Site 1263 (Walvis Ridge). These case studies were approached with integrated micropaleontological and geochemical analysis. The former is mainly based on planktic foraminifera, widely employed in the study of past environments as they record the effects of surface waters perturbations both in test chemistry and changes within the assemblages. Investigation of the three hyperthermals, H1 or ETM2, H2 and I1 at the Tethyan Terche section highlights significant changes in calcareous plankton assemblages across these events, suggesting increase in surface-water eutrophication coupled with a weakening of the upper water-column thermal stratification, although these changes were transient and more intense during the ETM2. Each event coincides with lithological anomalies interpreted as essentially linked to increased terrigenous dilution, as dissolution proxies do not display significant variations. The perturbed conditions persisted during the early CIE recovery, implying slower recovery rates for the environment and biota than for the carbon cycle. The analysis of the Atlantic sites encompassing the EECO reveals major changes in planktic foraminiferal assemblages across this perturbation mainly consisting in a permanent reduction in abundance and number of species of Morozovella paralleled by increase in abundance and diversification of Acarinina. Possible causes to explain this global and permanent overturn, previously documented in other low-latitude locations, are manifold and may include the sustained elevated temperature, prolonged high level of pCO2, surface-waters acidification, loss of photo-symbionts (bleaching) or even ecological competition. A test on Morozovella species from Site 1051 was performed to verify the bleaching hypothesis through analysis of the δ13C signal. Evidences of bleaching and test-size reduction were documented in a number of Morozovella species just above the J event. Nonetheless, the bleaching signal was transient and also involved acarininids, thus invalidating this hypothesis to explain the Morozovella permanent drop. Some Morozovella species never recover their maximum test-size implying that their ecological optimum threshold was crossed during the EECO. Analysis of the Morozovella coiling direction at Sites 1051 and 1263 highlight a dominant dextral preference for this genus during the interval preceding the EECO. However, all species show a first prominent flip to sinistral coiling starting slightly above the J event that became permanent slightly above the K/X event. Temporary switches towards sinistral coiling mode also occurred during several pre-EECO hyperthermals. Previous interpretations favour genetic explanations for coiling flips rather than ecological responses. These new data cannot validate or disprove the former idea, but should stimulate renewed thought on the latter idea. Planktic foraminiferal response to the EECO at Site 1263 also includes the virtual disappearance of the chiloguembelinids and abundance reduction of the thermocline-dweller subbotinids, interpreted as a result of ecological niches contraction probably related to weakening of the upper water-column thermal stratification. The whole planktic foraminiferal signal emphasizes the striking effect of the long-lasted EECO perturbation that superimposed and prevailed on the ephemeral changes linked to the hyperthermals.
10
Soldan, D. M. "REVISION OF PALEOCENE-EOCENE PLANKTIC FORAMINIFERAL BIOSTRATIGRAPHY AND EVOLUTIONARY HISTORY OF THE GENUS IGORINA THROUGH PARSIMONY ANALYSIS." Doctoral thesis, Università degli Studi di Milano, 2011. http://hdl.handle.net/2434/152906.
Повний текст джерелаАнотація:
The evolution of planktonic foraminifera in the Paleocene-Eocene time interval is characterized by a high rate of diversification after the major extinction event observed at the Cretaceous/Paleogene boundary. The accelerated speciation rate resulted in the appearance of several new genera (i.e., Praemurica, Igorina, Morozovella, Acarinina among others) each of them identified on the basis of distinctive wall texture of the shell. Phylogenetic relationships within many genera are still poor understood including the origin and phylogeny of the genus Igorina. This group, characterized by a thick, nonspinose and incrusted wall, appears in Subzone P3a (early late Paleocene, Selandian) and disappears in Zone E9 (middle Eocene, Lutetian). To date, eight species have been assigned to the genus Igorina (I. pusilla, I. trichotrocha, I. tadjikistanensis, I. albeari, I. laevigata, I. lodoensis, I. broedermanni and I. anapetes) based on both wall texture and morphologic similarities. However, the taxonomic identification at species level is affected by several problems, mainly related to poor descriptions and illustrations of the type-material of several species. Consequently, for many years the morphological features proper of each species have been frequently misinterpreted.
This study is aimed to reconstruct the phylogeny and evolution of the igorinid species throught cladistic analysis by applying the method of parsimony. To perform the study, two hundred
samples have been analysed from Ocean Drilling Program (ODP) Leg 198 Hole 1209B (Shatsky Rise, Central Pacific Ocean), Leg 143 Hole 865B (Allison Guyot, Central Pacific Ocean), Leg 15 Sites 151 and 152 (Caribbean Sea) and Leg 113 Hole 690B. The biostratigraphic analysis of sub-tropical localites revealed some problems in applying the previous biostratigraphic scheme (Berggren and Pearson, 2005) mainly because some marker species 1) have been misinterpreted and/or misidentified several times in previous studies, 2) show a delayed appearance with respect to what reported from other localities, and 3) are very rare or absent in the studied samples. Species identification was mainly performed through comparison with the original descriptions and illustrations and partially follows Subbotina (1953), Blow (1979), Olsson and others (1999), Pearson and others (2006). Phylogenetic relationships of the species assigned to Igorina are determined through stratocladistic analysis by using a data matrix of 23 taxa (including key species of Acarinina), 31 morphological characters (unordered), and a stratigraphic character (ordered) mapping the first occurrence of the taxa under investigation. The morphological characters included in this analysis are based on morphometric measurements such as the angle of chambers, maximum diameter of the shell, maximum diameter of the inner whorls, angle of peripheral margin among others. The same characters were also measured on the SEM illustrations of the type species of each holotype and, hence, included in the data matrix.
Some morphotypes of uncertain taxonomic identification but showing consistent morphological and wall texture features have been coded and analysed separately as morphotypes A, B, C, D, E and F to determine their ancestor-descendant relationships and evaluate their validity as discrete species. The software PAUP* (Swofford 2002) has been used to process the data and to obtain a numerical matrix with codified the selected characters, then the matrix has been processed using the heuristic search option to discover the most parsimonious trees.
Results suggest that Igorina pusilla is the first representatives of the Igorina lineage and is subsequently followed by I. laevigata. I. albeari, and I. tadjikistanensis in agreement with their stratigraphic distribution. Morphotypes (C, E, F) have been included in Igorina paraspiralis (Soldan and others, in press) while Igorina morphotype A represents a single species (Igorina praecarinata Soldan and others, in press). Morphotypes B and E fall in the variability of well-know species. Moreover, the analysis provides evidence that I. trichotrocha, I. lodoensis, I. broedermanni and I. anapetes are more closely related to genus Acarinina than Igorina and clearly belong to a different lineage. A preliminary analysis of the wall texture architectures the broedermanni group has been performed to assess their ancestor-descendant relationships and to evaluate the possibility to place them in a discrete new genus.
11
Abahazi, Matthew A. "Tropical North Atlantic Sea Surface Temperature Reconstruction for the Last 800 Years Using Mg/Ca Ratios in Planktic Foraminifera." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1239392022.
Повний текст джерела
12
Reichelt, Kerstin. "Late Aptian-Albian of the Vocontian Basin (SE-France) and Albian of NE-Texas biostratigraphic and paleoceanographic implications by planktic foraminifera faunas /." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974321591.
Повний текст джерела
13
Reynolds, Caitlin Elizabeth. "Environmental controls on the geochemistry of Globorotalia truncatulinoides in the Gulf of Mexico: Implications for paleoceanographic reconstructions." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7355.
Повний текст джерелаАнотація:
Modern observations of planktic foraminifera from sediment trap studies help to constrain the regional ecology of paleoceanographically valuable species. Results from a weekly-resolved sediment trap time series (2008–2014) in the northern Gulf of Mexico demonstrate that 92% of Globorotalia truncatulinoides flux occurs in winter (January, February, and March), and that encrusted and non-encrusted individuals represent calcification in distinct depth habitats. We use individual foraminiferal analysis (IFA) of G. truncatulinoides tests to investigate differences in the elemental (Mg/Ca) and isotopic composition (18O and 13C) of the encrusted and non-encrusted ontogenetic forms of G. truncatulinoides, and to estimate their calcification depth in the northern Gulf of Mexico. We estimate that non-encrusted and encrusted G. truncatulinoides have mean calcification depths of 66 ± 9 meters and 379 ± 76 meters, respectively. We validate the Mg/Ca-calcification temperature relationship for G. truncatulinoides and demonstrate that the 18O and Mg/Ca of the non-encrusted form is a suitable proxy for winter surface mixed layer conditions in the Gulf of Mexico. Care should be taken not to combine encrusted and non-encrusted individuals of G. truncatulinoides for down core paleoceanographic studies.
14
Came, Rosemarie Evangeline. "Abrupt climate change in the Atlantic Ocean during the last 20,000 years : insights from multi-element analysis of benthic and planktic foraminifera and coupled OA-GCM." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33945.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2005.Includes bibliographical references.
Minor and trace element records of planktic and benthic foraminifera from Atlantic sediment cores, as well as output from a coupled OAGCM, were used to investigate the magnitude and distribution of the oceanic response to abrupt climate events of the past 20 kyr. The study addressed three major questions: 1) What is the magnitude of high-latitude sea surface temperature and salinity variability during abrupt climate events? 2) Does intermediate depth ventilation change in conjunction with high-latitude climate variability? 3) Are the paleoclimate data consistent with the response of a coupled OAGCM to a freshwater perturbation? To address these questions, analytical methods were implemented for the simultaneous measurement of Mg/Ca, Zn/Ca, Cd/Ca, Mn/Ca and Al/Ca in foraminiferal samples using inductively-coupled plasma mass spectrometry. Paired records of planktic foraminiferal [delta]¹⁸O and Mg/Ca from the subpolar North Atlantic reveal trends of increasing temperatures ([approx.] 3⁰C) and salinities over the course of the Holocene, which were punctuated by abrupt events. The variability does not appear to be periodic, but tends to recur within a broad millennial band. The records provide the first evidence of open-ocean cooling (nearly 2⁰C) and freshening during the 8.2 kyr event, and suggest similar conditions at 9.3 ka.
(cont.) However, the two largest temperature oscillations ([approx.] 2⁰C) occurred during the last 4,000 years, suggesting a recent increase in temperature variability relative to the mid-Holocene. Benthic foraminiferal Cd/Ca from an intermediate depth, western South Atlantic core provides insights into changes in the southward penetration of North Atlantic Intermediate Water (NAIW). Cd seawater estimates (Cdw) for the last glacial are consistent with the production of NAIW and its export into the South Atlantic. At [approx.] 14.5 ka, the NAIW contribution to the South Atlantic began to decrease, marking a transition from a glacial subsurface geometry to a Younger Dryas geometry, which occurred concurrently with the onset of the Bolling-Allerod to Younger Dryas cooling. High Cdw in both the deep North Atlantic and the intermediate South Atlantic imply reduced export of deep and intermediate water during the Younger Dryas, and a major decrease in northward heat transport. Modern subsurface geometry was established at [approx.] 9 ka, concurrently with the establishment of Holocene warmth in the North Atlantic region, further supporting a close linkage between subsurface circulation and North Atlantic climate.
(cont.) Paired benthic foraminiferal Mg/Ca and [delta]¹⁸O data from two intermediate depth low latitude western Atlantic sites - one from the Florida Current and one from the Little Bahama Bank- provide insights into the spatial distribution of intermediate depth temperature and salinity variability during the Younger Dryas. The Florida site lies within the deeper portion of the Florida Current; the Little Bahama Bank site lies within the deeper, unventilated portion of the North Atlantic subtropical gyre. During the Younger Dryas, temperatures increased at the Florida Current site and temperatures decreased at the Little Bahama Bank site. The temperature increase within the Florida Current is consistent with the reduced northward heat transport associated with a reduction in the Atlantic meridional overturning circulation (MOC); the temperature decrease at Little Bahama Bank is consistent with a cooling of high latitude surface waters. To test the possibility that a freshening of the surface North Atlantic caused the terrestrial and oceanographic changes during the Younger Dryas, the GFDL R30 coupled ocean-atmosphere general circulation model was forced using a North Atlantic freshwater perturbation of 0.1 Sv for a period of 100 years. The freshwater flux causes an overall reduction in the Atlantic overturning from 25 Sv to 13 Sv.
(cont.) However, at [approx.] 1,100 meters water depth, ventilation increases, causing decreases in both temperature and salinity throughout much of the intermediate depth North Atlantic. In the open North Atlantic, intermediate depth temperatures decrease by approximately 1⁰C; at the eastern side, intermediate depth temperatures decrease by less than 0.4⁰C. Intermediate depth temperatures at the western boundary, however, increase due to a reduction in northward heat transport, and also due to a shift in the location of the Intertropical Convergence Zone, which causes a reduction in surface salinity and a decrease in the upwelling of colder, deeper waters. Benthic foraminiferal Cd/Ca from an intermediate depth Florida Current core documents the history of the northward penetration of southern source waters within the return flow of the Atlantic meridional overturning circulation (MOC). Cd seawater estimates (Cdw) for the last glacial are consistent with the reduced influence of southern source waters at this location relative to the present.
(cont.) At [approx.] 18.5 ka, the southern source contribution to the Florida Current began to increase significantly, marking the onset of a transition from a glacial circulation pattern to a deglacial pattern, which lasted from [approx.] 17 ka to [approx.] 14 ka. At [approx.] 12.5 ka, following the onset of the Younger Dryas cooling in the North Atlantic and the reduction in North Atlantic Deep Water (NADW) production, the influence of southern source waters within the Florida Current decreased abruptly. A renewed influence of southern source waters occurred at [approx.] 9 ka, concurrent with the establishment of Holocene warmth in the North Atlantic region.
by Rosemarie Evangeline Came.
Ph.D.
15
Žarić, Snježana [Verfasser], Gerhard [Akademischer Betreuer] Fischer, Gerold [Akademischer Betreuer] Wefer, and Michael [Akademischer Betreuer] Schulz. "Seasonal variability of planktic foraminiferal downward fluxes induced by environmental sensitivity of foraminiferal species from observation to prediction / Snježana Žarić. Gutachter: Gerold Wefer ; Michael Schulz. Betreuer: Gerhard Fischer." Bremen : Staats- und Universitätsbibliothek Bremen, 2005. http://d-nb.info/1072302578/34.
Повний текст джерела
16
Munz, Philipp Moritz [Verfasser], and Hartmut [Akademischer Betreuer] Schulz. "Studying the Indian monsoon variability over the Early Holocene and Common Era in high resolution with numerical reconstructions based on planktic foraminifera / Philipp Moritz Munz ; Betreuer: Hartmut Schulz." Tübingen : Universitätsbibliothek Tübingen, 2016. http://d-nb.info/116416984X/34.
Повний текст джерела
17
Munz, Philipp [Verfasser], and Hartmut [Akademischer Betreuer] Schulz. "Studying the Indian monsoon variability over the Early Holocene and Common Era in high resolution with numerical reconstructions based on planktic foraminifera / Philipp Moritz Munz ; Betreuer: Hartmut Schulz." Tübingen : Universitätsbibliothek Tübingen, 2016. http://d-nb.info/116416984X/34.
Повний текст джерела
18
Wall-Palmer, Deborah. "Response of pteropod and related faunas to climate change and ocean acidification." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1398.
Повний текст джерелаАнотація:
Recent concern over the effects of ocean acidification upon calcifying organisms in the modern ocean has highlighted the aragonitic shelled thecosomatous pteropods as being at a high risk. Laboratory studies have shown that increased pCO2, leading to decreased pH and low carbonate concentrations, has a negative impact on the ability of pteropods to calcify and maintain their shells. This study presents the micropalaeontological analysis of marine cores from the Caribbean Sea, Mediterranean Sea and Indian Ocean. Pteropods, heteropods and planktic foraminifera were picked from samples to provide palaeoenvironmental data for each core. Determination of pteropod calcification was made using the Limacina Dissolution Index (LDX) and the average shell size of Limacina inflata specimens. Pteropod calcification indices were compared to global ice volume and Vostok atmospheric CO2 concentrations to determine any associations between climate and calcification. Results show that changes in surface ocean carbonate concentrations throughout the Late Pleistocene did affect the calcification of thecosomatous pteropods. These effects can be detected in shells from marine sediments that are located well above the aragonite lysocline and have not undergone post-depositional dissolution. The results of this study confirm the findings of laboratory studies, showing a decrease in calcification during interglacial periods, when surface ocean carbonate concentrations were lower. During glacial periods, calcification was enhanced due to the increased availability of carbonate. This trend was found in all sediments studied, indicating that the response of pteropods to past climate change is of global significance. These results demonstrate that pteropods have been negatively affected by oceanic pH levels relatively higher and changing at a lesser rate than those predicted for the 21st Century. Results also establish the use of pteropods and heteropods in reconstructing surface ocean conditions. The LDX is a fast and appropriate way of determining variations in surface water carbonate saturation. Abundances of key species were also found to constrain palaeotemperatures better than planktic foraminifera, a use which could be further developed.
19
Volkmann, Renate. "Planktic foraminifer ecology and stable isotope geochemistry in the Arctic Ocean : implications from water column and sediment surface studies for quantitative reconstructions of oceanic parameters = Ökologie planktischer Foraminiferen und stabile Isotope im Arktischen Ozean /." Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung, 2000. http://www.gbv.de/dms/bs/toc/315939354.pdf.
Повний текст джерела
20
Meilland, Julie. "Rôle des foraminifères planctoniques dans le cycle du carbone marin des hautes latitudes (Océan Indien Austral)." Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0059/document.
Повний текст джерелаАнотація:
Les foraminifères planctoniques vivants (LPF) contribuent à la pompe biologique du carbone océanique en générant des flux de Corg (cytoplasme) et de Cinorg (test calcaire). Dans cette étude, la morphométrie des tests, les abondances et les compositions spécifiques des assemblages de LPF dans l'océan Indien Sud (30°S-60°S, 50°E-80°E), ont été caractérisées à partir de la collecte par filet à plancton stratifié (Multinet) sur 19 stations échantillonnées pendant trois étés consécutifs (2012- 2014). En démontrant l'efficacité d'échantillonnage du Continuous Plankton Recorder pour spatialiser les données observées en 19 stations, l’étude de la dynamique de population des LPF montre l'effet de la position des fronts sur la production des LPF. Pour mieux contraindre l'impact des LPF dans la pompe biologique du carbone des hautes latitudes, la biomasse protéique et la masse calcique de plus de 2000 foraminifères ont été mesurées. Les différences de biomasse protéique et de poids normalisé par la taille entre années, espèces et masses d'eau suggèrent que les paramètres environnementaux affectent la production de Corg et de Cinorg des LPF. Le rôle des LPF sur la pompe biologique de carbone marin dépend des conditions hydrologiques et trophiques du milieu. Le rapport Corg/Cinorg est très différent selon les espèces considérées. L'applicabilité des tests de foraminifères planctoniques comme proxy de paléopompe du carbone dans les hautes latitudes dépendrait donc de l'effet exercé par les variations des conditions écologiques, et de la composition de l’assemblage. Cette étude propose une première estimation des budgets Corg et Cinorg produits par les LPF dans l’Océan Indien AustralPlanktonic foraminifera contribute to the marine biological carbon pump by generating organic (cytoplasm) and inorganic (shell) carbon fluxes. In this study, we characterized LPF total abundances, assemblages and test morphometry (minimum diameter) along 19 stations sampled by stratified plankton net (Multinet), during three consecutive austral summers (2012-2014) in the Southern Indian Ocean (30°S-60°S, 50°E-80°E). By demonstrating the efficiency of CPR for LPF sampling, we analysed population dynamic between 19 multinet sampling stations, showing the effect of frontal position on LPF production. To better constrain the impact of those organisms in the biological carbon pump at high latitudes, we have quantified the individual protein-biomass and test calcite mass of more than 2000 LPF. Differences in size-normalized protein-biomass and in size-normalized weight between years, species, and water bodies suggest that environmental parameters affect the production of planktonic foraminifera organic and inorganic carbon to varying degrees. Consequently, planktonic foraminifera are assumed to affect the biological carbon pump, depending on ecological conditions and biological prerequisites. The applicability of planktonic foraminifera tests as proxy of the past biological carbon pump in high latitudes would hence critically depend on the effect exerted by changing in ecological conditions, and the presence of different species. This study proposes a first estimation of planktonic foraminifera Corg and Cinorg standing stock and fluxes in the Southern Indian Ocean
21
Cárdenas, Andrés L. "Paleobiological assessment of controls underlying long-term diversity dynamics." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4021.
Повний текст джерелаАнотація:
Deciphering the factors underlying both long-term patterns of diversity and taxonomic turnover rates (i.e., extinction, and origination) has been one of Paleobiology's major foci for the past three decades. The importance of documenting these components is that they will expand our ability to interpret and model the evolutionary processes underlying those trends, highlight the evolutionary impact of historical events, and contribute to the formulation of robust predictions about the future of global diversity in response to the current anthropologically driven environmental changes. Accordingly, the first part of this study examines the possible occurrence of global marine evolutionary environmental controls into a `deep-time' perspective, using a statistical time-series approach between the most recent Phanerozoic global marine generic origination rates with coeval mean global marine geochemical and geological signatures of environmental proxies. After this examination, significant positive correlations were found between changes in origination rates and global mean signatures of 87Sr/86Sr and δ34S, as well as a significant negative correlation between variability in both origination rates and eustatic sea level. They suggest that over secular timescales, nutrient availability, as controlled by continental weathering, phosphorus recycling, and the relative extent of shelf exposure, is an important regulator of genus-level origination in the marine realm, with periods of increased nutrient availability associated with higher origination rates.
22
Striebel, Maren. "PLANKTON DYNAMICS." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-92597.
Повний текст джерела
23
Del, Giorgio Paul A. "Heterotrophy in lake plankton." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41362.
Повний текст джерелаАнотація:
The overall aim of this thesis was to determine the relative importance of heterotrophy and autotrophy in lake plankton. Empirical analyses using extensive surveys of literature data revealed three specific patterns in metabolism and biomass structure in freshwater plankton. First, the ratio of phytoplankton production to plankton respiration (P/R ratio) tends to be low in unproductive lakes ($<$1), and increases along gradients of enrichment. Second, the contribution of planktonic heterotrophs (bacteria and zooplankton) to community respiration is highest in oligotrophic lakes. Third, planktonic heterotrophs dominate community biomass in oligotrophic lakes, whereas phytoplankton increasingly dominate plankton biomass along gradients of enrichment. These three distinct patterns were then tested simultaneously in a set of lakes that span a wide trophic gradient. Results indicated that the plankton of oligotrophic and mesotrophic lakes were characterized by P/R ratios well below unity, and a high contribution of heterotrophs to both community respiration and biomass. These trends are completely the opposite in the most productive lakes. The plankton communities of oligotrophic temperate lakes are predominantly heterotrophic and extensively utilize external inputs of carbon, and therefore only the plankton of eutrophic lakes conformed to the classical phytoplankton-based food web. In most lakes, excess heterotrophic activity could be supported by inputs of organic matter from the drainage basin. Excess plankton respiration, fueled by allochthonous organic carbon, could represent an important source of CO$ sb2$ to lakes.
24
Birch, Daniel A. "Plankton modeling at multiple scales." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3274810.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed October 9, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 132-138).
25
Kotrc, Benjamin. "Evolution of Silica Biomineralizing Plankton." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10969.
Повний текст джерелаАнотація:
The post-Paleozoic history of the silica cycle involves just two groups of marine plankton, radiolarians and diatoms. I apply paleobiological methods to better understand the Cenozoic evolution of both groups. The Cenozoic rise in diatom diversity has long been related to a concurrent decline in radiolarian test silicification. I address evolutionary questions on both sides of this coevolutionary coin: Was the taxonomic diversification of diatoms accompanied by morphological diversification? Is our view of morphological diatom diversification affected by sampling biases? What evolutionary mechanisms underlie the macroevolutionary decline in radiolarian silicification? Conventionally, diatom diversification describes a steep, monotonic rise, a view recently questioned due to sampling bias. For a different perspective, I constructed a diatom morphospace based on discrete characters, populated through time using an occurrence-level database. Distances between taxa in morphospace and on a molecular phylogeny are not strongly correlated, suggesting that morphospace was explored early in their evolutionary history, followed by relative stasis. I quantified morphospace occupancy through time using several disparity metrics. Metrics describing average separation of taxa show stasis, while metrics describing occupied volume show an increase with time. Disparity metrics are also subject to sampling biases. Under subsampling, I find that disparity metrics show varied responses: metrics describing separation of taxa into morphospace are unaffected, while those describing occupied volume lose their clear increases. Disparity can have geographic components, analogous to \(\alpha\) and \(\beta\) taxonomic diversity; I find more evidence of stasis in an analysis of \(\bar{\alpha}\) disparity. Overall, these results suggest stasis in Cenozoic diatom disparity. The radiolarian decline in silicification could result from either macroevolutionary processes operating above the species level (punctuated queilibria) or anagenetic changes within lineages. I measured silicification in three phyletic lineages, Stichocorys, Didymocyrtis, and Centrobotrys, from four tropical Pacific DSDP sites. Likelihood-based model fitting finds no strong support for directional evolution, pointing toward selection among species, rather than within species. Each lineage shows a different trajectory, perhaps due to differences in the ecological role played by the test. Because Stichocorys shows close correspondence to the assemblage-level trend, abundance may be an important factor through which within-lineage changes can influence the macroevolutionary pattern.Earth and Planetary Sciences
26
Mantilla, Jose G. (Jose Gabriel) 1972. "Models of plankton biomass spectra." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80212.
Повний текст джерела
27
Martin, Mark A. "The influence of seasonal and climatic environmental changes on plankton in the marine mixed layer /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/6788.
Повний текст джерела
28
Kramer, Kurt A. "Identifying plankton from grayscale silhouette images." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001402.
Повний текст джерела
29
Pitchford, Jonathan William. "Dynamics of multi-species plankton populations." Thesis, University of Leeds, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397772.
Повний текст джерела
30
Pascual-Dunlap, Maria Mercedes. "Some nonlinear problems in plankton ecology." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38049.
Повний текст джерела
31
Matuszewski, Damian Janusz. "Computer vision for continuous plankton monitoring." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-24042014-150825/.
Повний текст джерелаАнотація:
Plankton microorganisms constitute the base of the marine food web and play a great role in global atmospheric carbon dioxide drawdown. Moreover, being very sensitive to any environmental changes they allow noticing (and potentially counteracting) them faster than with any other means. As such they not only influence the fishery industry but are also frequently used to analyze changes in exploited coastal areas and the influence of these interferences on local environment and climate. As a consequence, there is a strong need for highly efficient systems allowing long time and large volume observation of plankton communities. This would provide us with better understanding of plankton role on global climate as well as help maintain the fragile environmental equilibrium. The adopted sensors typically provide huge amounts of data that must be processed efficiently without the need for intensive manual work of specialists. A new system for general purpose particle analysis in large volumes is presented. It has been designed and optimized for the continuous plankton monitoring problem; however, it can be easily applied as a versatile moving fluids analysis tool or in any other application in which targets to be detected and identified move in a unidirectional flux. The proposed system is composed of three stages: data acquisition, targets detection and their identification. Dedicated optical hardware is used to record images of small particles immersed in the water flux. Targets detection is performed using a Visual Rhythm-based method which greatly accelerates the processing time and allows higher volume throughput. The proposed method detects, counts and measures organisms present in water flux passing in front of the camera. Moreover, the developed software allows saving cropped plankton images which not only greatly reduces required storage space but also constitutes the input for their automatic identification. In order to assure maximal performance (up to 720 MB/s) the algorithm was implemented using CUDA for GPGPU. The method was tested on a large dataset and compared with alternative frame-by-frame approach. The obtained plankton images were used to build a classifier that is applied to automatically identify organisms in plankton analysis experiments. For this purpose a dedicated feature extracting software was developed. Various subsets of the 55 shape characteristics were tested with different off-the-shelf learning models. The best accuracy of approximately 92% was obtained with Support Vector Machines. This result is comparable to the average expert manual identification performance. This work was developed under joint supervision with Professor Rubens Lopes (IO-USP).Microorganismos planctônicos constituem a base da cadeia alimentar marinha e desempenham um grande papel na redução do dióxido de carbono na atmosfera. Além disso, são muito sensíveis a alterações ambientais e permitem perceber (e potencialmente neutralizar) as mesmas mais rapidamente do que em qualquer outro meio. Como tal, não só influenciam a indústria da pesca, mas também são frequentemente utilizados para analisar as mudanças nas zonas costeiras exploradas e a influência destas interferências no ambiente e clima locais. Como consequência, existe uma forte necessidade de desenvolver sistemas altamente eficientes, que permitam observar comunidades planctônicas em grandes escalas de tempo e volume. Isso nos fornece uma melhor compreensão do papel do plâncton no clima global, bem como ajuda a manter o equilíbrio do frágil meio ambiente. Os sensores utilizados normalmente fornecem grandes quantidades de dados que devem ser processados de forma eficiente sem a necessidade do trabalho manual intensivo de especialistas. Um novo sistema de monitoramento de plâncton em grandes volumes é apresentado. Foi desenvolvido e otimizado para o monitoramento contínuo de plâncton; no entanto, pode ser aplicado como uma ferramenta versátil para a análise de fluídos em movimento ou em qualquer aplicação que visa detectar e identificar movimento em fluxo unidirecional. O sistema proposto é composto de três estágios: aquisição de dados, detecção de alvos e suas identificações. O equipamento óptico é utilizado para gravar imagens de pequenas particulas imersas no fluxo de água. A detecção de alvos é realizada pelo método baseado no Ritmo Visual, que acelera significativamente o tempo de processamento e permite um maior fluxo de volume. O método proposto detecta, conta e mede organismos presentes na passagem do fluxo de água em frente ao sensor da câmera. Além disso, o software desenvolvido permite salvar imagens segmentadas de plâncton, que não só reduz consideravelmente o espaço de armazenamento necessário, mas também constitui a entrada para a sua identificação automática. Para garantir o desempenho máximo de até 720 MB/s, o algoritmo foi implementado utilizando CUDA para GPGPU. O método foi testado em um grande conjunto de dados e comparado com a abordagem alternativa de quadro-a-quadro. As imagens obtidas foram utilizadas para construir um classificador que é aplicado na identificação automática de organismos em experimentos de análise de plâncton. Por este motivo desenvolveu-se um software para extração de características. Diversos subconjuntos das 55 características foram testados através de modelos de aprendizagem disponíveis. A melhor exatidão de aproximadamente 92% foi obtida através da máquina de vetores de suporte. Este resultado é comparável à identificação manual média realizada por especialistas. Este trabalho foi desenvolvido sob a co-orientacao do Professor Rubens Lopes (IO-USP).
32
Prince, Emily Katherine. "Chemically-mediated interactions in the plankton:." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22701.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Biology, Georgia Institute of Technology, 2008.Committee Chair: Kubanek, Julia; Committee Member: Hay, Mark; Committee Member: Jiang, Lin; Committee Member: Pavia, Henrik; Committee Member: Snell, Terry.
33
Johnson, Kevin Brett. "Predation on planktonic marine invertebrate larvae." Thesis, Thesis (Ph. D.)--University of Oregon, 1998, 1998. http://hdl.handle.net/1794/10086.
Повний текст джерела
34
Menezes, Sunshine. "Nanoplankton biodiversity in the Pettaquamscutt River estuary, Rhode Island, U.S.A. /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3186914.
Повний текст джерела
35
Beck, Kristin. "Experimentelle Überprüfung der "Intermediate Disturbance Hypothesis" (Connell 1978) an Modell-Lebensgemeinschaften planktischer Bakterienisolate." [S.l. : s.n.], 2000. http://e-diss.uni-kiel.de/diss.
Повний текст джерела
36
Gjersdal, Jan. "Instrumentering og styring av produksjonsprosess for plankton." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14084.
Повний текст джерелаАнотація:
I denne oppgaven er det presentert instrumentering og reguleringssystem av produksjonsprosess for plankton. Systemet er utviklet og implementering med to tanker for produksjon av planktonet rotatorier. PC brukes som styresystem og grensesnitt mot bruker. Regulering av rotatorietetthet med en ny strategi for tilførsel av fôr og vann er implementert og testet. Systemet fungerte tilfredsstillende foruten den nye strategien som trenger mer testing for å fungere optimalt.
37
Basu, Ben Kumar. "Plankton development and trophic interactions in rivers." Thesis, University of Ottawa (Canada), 1997. http://hdl.handle.net/10393/10146.
Повний текст джерелаАнотація:
The factors regulating the development and trophic interactions of planktonic communities were determined in 31 medium to large size temperate rivers. In addition, the Rideau River, Ontario, was studied in detail over three field seasons. Variables measured included: phytoplankton biomass as measured by chlorophyll $\alpha$ concentration; zooplankton biomass (rotifers and crustaceans); heterotrophic bacterial abundance; heterotrophic flagellate abundance; nutrient concentrations (phosphorus and nitrogen); dissolved organic carbon concentration; river discharge; water residence time; depth; temperature; and light attenuation. Phytoplankton was abundant in eutrophic rivers ($>$15 $\mu$g L$\sp{-1}$ of chlorophyll a) and was most strongly related to nutrient concentrations, primarily total phosphorus, which explained up to 76% of the variation in chlorophyll a. Phytoplankton biomass in the rivers was not related to the hydrological parameters of water residence time or discharge, possibly due to the short generation time of phytoplankton (hours to days). Light did not appear to limit phytoplankton biomass due to shallow depths and extensive vertical mixing. In the Rideau River phytoplankton biomass exhibited longitudinal heterogeneity, but in general increased in a downstream direction, concomitant with increases in nutrient concentrations. Phytoplankton biomass did not appear to be affected by zooplankton grazing in the rivers. However, phytoplankton biomass may have been negatively impacted by benthic filter feeders, in particular the invasive zebra mussel (Dreissena polymorpha), in the downstream reaches of the Rideau River. Zooplankton biomass in the rivers was low (usually 20 $\mu$g L$\sp{-1}$ dry mass) and small taxa dominated the zooplankton communities (e.g. rotifers, bosminids). Large zooplankton taxa, such as Daphnia sp., were much less abundant. Due to longer generation times (days to weeks), zooplankton biomass was primarily related to water residence time which explained 33% of the variation. Zooplankton appeared susceptible to advective loss in the rivers. A positive resource effect of either nutrients or phytoplankton on zooplankton biomass, typically observed in lakes, was weaker in the rivers. In comparison to lakes, zooplankton appeared less tightly coupled to phytoplankton. As with phytoplankton, zooplankton biomass in the Rideau River increased with downstream travel and appeared to be negatively affected by benthic filter feeders. Heterotrophic bacteria were abundant in the rivers (4.5 $\times$ 10$\sp6$ cells ml$\sp{-1})$ and, as in lakes, bacteria were most strongly related to nutrient concentrations (total phosphorus) and phytoplankton biomass (chlorophyll a). In contrast to lakes, no relationship between bacterial abundance and dissolved organic carbon was observed, possibly due to the more allochthonous, refractory nature of river dissolved organic carbon. Heterotrophic flagellates were also abundant in the rivers $(4.0\times10\sp{3}$ cells ml$\sp{-1})$ and were most strongly related to bacterial abundance and nutrient concentrations (total phosphorus). Neither bacterial nor flagellate abundance was related to water residence time. A negative relationship between zooplankton biomass and bacterial or flagellate abundance was not observed, possibly because of the low biomass (hence low grazing pressure) of zooplankton in the rivers. Due to the scarcity of zooplankton in rivers, there may be little transfer of energy from the planktonic microbial food web to planktonic metazoans.
38
Currie, Warren J. S. "Scale-invariance and patchiness in the plankton." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ61972.pdf.
Повний текст джерела
39
Pearson, Paul Nicholas. "Evolution and phylogeny of Palaeogene planktonic foraminifera." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386154.
Повний текст джерела
40
Seears, Heidi. "Biogeography and phylogenetics of the planktonic foraminifera." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/11879/.
Повний текст джерелаАнотація:
The planktonic foraminifera are a highly abundant and diverse group of marine pelagic protists that are ubiquitously distributed throughout the worlds’ oceans. These unicellular eukaryotes are encased in a calcareous (CaCO3) shell or ‘test’, the morphology of which is used to identify individual ‘morphospecies’. The foraminifera have an exceptional fossil record, spanning over 180 million years, and as microfossils provide a highly successful paleoproxy for dating sedimentary rocks and archiving past climate. Molecular studies, using the small subunit (SSU) ribosomal (r) RNA gene are used here to investigate the biogeographical distributions and phylogenetic relationships of the planktonic foraminifera. Biogeographical surveys of two markedly different areas of the global ocean, the tropical Arabian Sea, and the transitional/sub-polar North Atlantic Ocean, revealed significant genotypic variation within the planktonic foraminifera, with some genetic types being sequenced here for the first time. The foraminiferal genotypes displayed non-random geographical distributions, suggestive of distinct ecologies, giving insight into the possible mechanisms of diversification in these marine organisms. The ecological segregation of genetically divergent but morphologically cryptic genetic types could, however, have serious repercussions on their use as paleoproxies of past climate change. Phylogenetic analyses of the foraminifera based firstly on a partial ~1,000 bp terminal 3´ fragment of the SSU rRNA gene, and secondly on the ~3,000 bp almost complete gene supported the hypothesis of the polyphyletic origins of the planktonic foraminifera, which appear to be derived from up to 5 separate benthic ancestral lineages. The almost complete gene is sequenced here in the planktonic taxa for the first time, though amplification was problematic. In a first step to addressing a pressing need for new genetic markers to support data gained from the SSU rRNA gene, a culture system was established for the benthic foraminifera, in order to provide a reliable source of DNA for EST library construction or full genome sequencing. Finally, to overcome difficulties associated with the PCR amplification of the foraminifera, a new lysis buffer and DNA extraction procedure was developed. A highly successful buffer was created, allowing high quality DNA to be extracted from foraminiferal specimens, whilst leaving the delicate calcitic shell intact for morphological reference.
41
Barker, S. "Planktonic foraminiferal proxies for temperature and pCO2." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596364.
Повний текст джерелаАнотація:
The thesis aims to describe developments in the uses of planktonic foraminiferal calcite for oceanographic applications, specifically Mg/Ca ratios and foraminiferal shell weights as proxies for calcification temperature and paleo-pCO2 respectively. Sample preparation for the analysis of Mg/Ca and Sr/Ca ratios in foraminiferal calcite is investigated with the aim of defining a method that will give reproducible results and minimise signal contaminations. Each step of the cleaning procedure is scrutinised in order to gauge which are most important and which may be omitted as unnecessary and potentially detrimental to the elemental measurements being made. Success in the application of Mg/Ca-thermometry depends on the ability to quantify and compensate for any alteration of the primary signal after deposition. Compositional variations in foraminiferal calcite may be associated with partial dissolution at the seaflow. Investigation is made into the excessive scatter observed within a latitudinal transect of core-top Mg/Ca and Sr/Ca ratios and attributed to partial dissolution. Possible means of correcting or minimising the effects of such alteration are investigated and assessed. Recent interest in planktonic foraminiferal shell weight loss as a proxy for dissolution, and as such a potential means of quantifying compositional variability, demands investigation into the possibility that initial shell weight may not be constant. It is demonstrated that considerable variability does occur in the shell weights of several species of planktonic foraminifera in the modern surface ocean. It is proposed that initial shell weight is a function of calcification rate and controlled ultimately by the carbonate ion concentration, [CO3=], of ambient seawater during calcification. A first attempt is made to calibrate the effects of [CO3=] on shell weight in the modern ocean. The potential effects of anthropogenic atmospheric CO2 increases on marine calcification are then synthesised using the mineral relations between [CO3=] and calcification rate.
42
Guirey, Emma Jane. "Application of synchronisation theory to plankton patchiness." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/63137/.
Повний текст джерелаАнотація:
This study applies a metapopulation dynamics approach to modelling a distribution of plankton by representing a region of ocean as an ensemble of plankton populations interacting through the stirring and mixing eects of the ow. The methods of synchronisation theory are applied within this framework to gain insight into emergent spatial structure in biophysical simulations. The manifestation of synchronisation, including statistically stable local clustering of populations, frequency-locking or phase-locking of the entire ensemble and fully synchronised dynamics, is found to depend upon: the biological model used; the strength of mixing between populations; the number of populations or, equivalently, spatial resolution of the modelled region; the level of mismatch between and spatial arrangement of population natural frequencies; the strength of stirring of the ensemble at spatial scales larger than the grid-cell. The study therefore highlights a number of biophysical modelling parameters determining the properties of emergent spatial structure in simulations of surface ocean biological dynamics. This study shows that persistent spatial heterogeneity (patchiness) can result from what intuitively should be a homogenising in uence: mixing can increase the level of disorder between the plankton populations. Furthermore, the work shows that synchronisation eects occur generically under a range of simulation scenarios, giving condence that synchronisation theory can explain some of the spatial structure, or `patchiness', observed in plankton distributions, and providing one possible answer as to how populations of planktonic organisms maintain coherent spatial structures under the mixing and stirring action of the oceanic flow.
43
Coxall, Helen Katherine. "Hantkeninid planktonic foraminifera and Eocene palaeoceanographic change." Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/8efa1d22-0ff8-45a3-9a5c-bd5ea90e266f.
Повний текст джерелаАнотація:
The morphological and ecologicalevolution of middle-upper Eocene planktonic foraminiferal family Hantkeninidae is investigated in the context of the dramatic palaeoceanographic and climatic changes that marked the transition from Paleogene "greenhouse" to Neogene "icehouse" climatic conditions. Morphometric analysis proves that evolution in family Hantkeninidae was gradual but complex in detail with periods of relative stasis. Multiple lines of evidence demonstrate that Hantkenina evolved from planispiral clavate genus Clavigerinella and not, as was previously believed, from Pseudohastigerina micra. The ancestor of Clavigerinella was probably a low trochospiral form Paragloborotalia sp., which has been recognized for the first time in this study at a number of sites. Trends in chamber inflation, tubulospine angle and the position of the tubulospine on each chamber show the most dramatic evolutionary changes, indicating that these are the most useful characters for taxonomy. These morphological changes correlate well with known palaeoceanographic changes as well as the shift in hantkeninid ecology from a deep to a surface water habitat. Hantkeninids underwent pronounced adaptive evolution in depth habitats during the initial phase of the climatic transition. Lower middle Eocene forms lived in a cool deep-water environment within or below the oceanic thermocline and shifted to warmer surface waters in the late middle Eocene. They evolved in the low latitudes and were primarily. a tropical-subtropical group. The occurrence of Hantkenma australis at relatively high northerly and southerly latitudes during the middle Eocene may record a temporary expansion of warmer water conditions into these regions, possibly representing a hitherto unknown "hyperthermal" event. Clavigerinella is rare in middle Eocene open-ocean sequences but occasionally occurs in relative abundance in other localities (such as on continental margins and oceanic seamounts), suggesting that it was specialized for living in upwelling regions. A revised taxonomy of family Hantkeninidae is presented that reflects new understanding ofhantkeninid evolution. The reconstructed phylogeny demonstrates that the tubulospine-bearing genera Hantkenina and Cribrohantkenina represent a monophyletic clade. Multivariate analysis suggests that more than one morphological population existed at several times and that these may represent biological species. The results demonstrate that the hantkeninids are not merely passive recorders of ocean conditions but have instead evolved morphology and changed habitat in response to climate change.
44
Guo, Weihua. "Computational Modeling of Planktonic and Biofilm Metabolism." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/79669.
Повний текст джерелаАнотація:
Most of microorganisms are ubiquitously able to live in both planktonic and biofilm states, which can be applied to dissolve the energy and environmental issues (e.g., producing biofuels and purifying waste water), but can also lead to serious public health problems. To better harness microorganisms, plenty of studies have been implemented to investigate the metabolism of planktonic and/or biofilm cells via multi-omics approaches (e.g., transcriptomics and proteomics analysis). However, these approaches are limited to provide the direct description of intracellular metabolism (e.g., metabolic fluxes) of microorganisms.
Therefore, in this study, I have applied computational modeling approaches (i.e., 13C assisted pathway and flux analysis, flux balance analysis, and machine learning) to both planktonic and biofilm cells for better understanding intracellular metabolisms and providing valuable biological insights. First, I have summarized recent advances in synergizing 13C assisted pathway and flux analysis and metabolic engineering. Second, I have applied 13C assisted pathway and flux analysis to investigate the intracellular metabolisms of planktonic and biofilm cells. Various biological insights have been elucidated, including the metabolic responses under mixed stresses in the planktonic states, the metabolic rewiring in homogenous and heterologous chemical biosynthesis, key pathways of biofilm cells for electricity generation, and mechanisms behind the electricity generation. Third, I have developed a novel platform (i.e., omFBA) to integrate multi-omics data with flux balance analysis for accurate prediction of biological insights (e.g., key flux ratios) of both planktonic and biofilm cells. Fourth, I have designed a computational tool (i.e., CRISTINES) for the advanced genome editing tool (i.e., CRISPR-dCas9 system) to facilitate the sequence designs of guide RNA for programmable control of metabolic fluxes. Lastly, I have also accomplished several outreaches in metabolic engineering.
In summary, during my Ph.D. training, I have systematically applied computational modeling approaches to investigate the microbial metabolisms in both planktonic and biofilm states. The biological findings and computational tools can be utilized to guide the scientists and engineers to derive more productive microorganisms via metabolic engineering and synthetic biology. In the future, I will apply 13C assisted pathway analysis to investigate the metabolism of pathogenic biofilm cells for reducing their antibiotic resistance.Ph. D.
45
Engström-Öst, Jonna. "Effects of cyanobacteria on plankton and planktivores." Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/mat/ekolo/vk/engstrom-ost/.
Повний текст джерела
46
Veloza, Adriana J. "Transfer of Essential Fatty Acids by Marine Plankton." W&M ScholarWorks, 2005. http://www.vims.edu/library/Theses/Veloza05.pdf.
Повний текст джерела
47
Svee, Astrid. "Development and Testing of an Acoustic Plankton Recorder." Doctoral thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1477.
Повний текст джерелаАнотація:
Recent years have brought cross-disciplinary focus on possibilities, constraints and consequences of large scale zooplankton harvesting. Development of acoustic measurement technology is an important part of that work. Because of the small size of the plankton, the measurement frequencies have to be high compared to fishery acoustics. Based on a model of the size and shape of the plankton and its physical properties, the use of multiple frequency measurements will allow inverse modeling of the size and concentration of plankton. This thesis presents the development and test results of an Acoustical Plankton Recorder (APR). The system uses three frequencies, 200 kHz, 710 kHz, and 1 MHz. The system parameters are designed with a focus on measuring the zooplankton Calanus finmarchicus, which plays an important role in the Norwegian Sea ecosystem. The APR is a prototype instrument built to gain experience for future generations of instruments for plankton measurements. Different aspects of multi-frequency acoustical measurements are discussed with a focus on uncertainties and critical factors. The results from various experiments and measurements are presented. The estimated concentration of scatterers from data recovered by the Acoustical Plankton Recorder shows good agreement with biological samples.
48
Haupt, Florian. "Plankton vertical migrations - Implications for the pelagic ecosystem." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-135130.
Повний текст джерела
49
Sanderson, Rory J. "Ecology of freshwater plankton in contrasting hydraulic environments." Thesis, University of Leicester, 1998. http://hdl.handle.net/2381/29785.
Повний текст джерелаАнотація:
The effects of contrasting water residence time on the planktonic community of three water bodies was studied. The sites were Rutland Water, Covenham reservoir and the River Nene, in order of decreasing retention time. The river was the only site where the residence time was sufficiently short to directly impact upon planktonic populations. The importance of physical mechanisms of control in the river was indicated by the dominance of r-selected phytoplankton, namely diatoms and green algae, and zooplankton, namely rotifers. This pattern was in contrast to that of the reservoirs in which slower-growing cyanobacteria and cladocerans dominated. Riverine rotifers were found to have rapid population turnover, due to a combination of short pre-adult duration and high maximum growth rates. Some species also showed a shift in reproductive behaviour to the constant production of resting eggs. This was assumed to convey benefits in a system where resting stages may be less susceptible than adults to downstream displacements. The total chlorophyll 'a' concentration achieved per unit phosphorus was significantly lower in the river than either of the reservoirs. Algal density was negatively associated with discharge in the Nene, suggesting the importance of physical control. The relationship was not a simple one, however, as periods of increased retention time during the summer were associated with low algal density. The absolute density of rotifers was found to be constrained by discharge. Animals were rare above a threshold flow velocity of 0.08ms-1. Simple models of water flow in open channels were insufficient to account for the continued persistence of a plankton in the Nene given the level of advection. It was assumed that the overall retention time of the system was increased by the presence of dead zones within the channel which 'held' planktonic organisms for sufficient time for populations to develop. This behaviour was important during the spring when population density increased in the main channel.
50
Bradburn, Mark James. "Light and planktonic nitrogen fixation in Colorado reservoirs." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442959.
Повний текст джерела