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Seasonal Variations of the Planktonic Foraminiferal Assemblages and Stable Isotopic Compositions: Sediment Trap Results from the Kao-ping Submarine Canyon and Northern South China SeaWang, Wei-chiao 26 June 2003 (has links)
Abstract
The carbon and oxygen isotopes of planktonic foraminifera, faunal assemblage, and coarse fraction of trap materials were analyzed in this study. The sediment traps were deployed in two lacations. One was in the Kao-ping submarine canyon and the other was in the northern South China Sea.
Variations of the individual concentrations from Kao-ping submarine canyon are small throughout the deployment interval except for the period when the Typhoon Chi-Te invaded southern Taiwan in July 2000. The results that benthic foraminifer abundances (#/g) are higher than that of planktonic foraminifera after typhoon invasion reflect the influence of particle settling by lateral transport. In addition, the major planktonic foraminifera found in canyon are Globigerinoides aequilateralis, Globigerinoides ruber, Globigerinoides sacculifer, and Neogloboquadrina dutertrei. At the same time, we also found Globigerina bulloides that usually lives in the high latitudes and cold temperature. It reveals the effect of nutrient supply along coastal region.
The coarse fraction contents and foraminiferal abundances collected by the traps in the northern South China Sea are both increasing in January and March. It could be associated with the enhanced surface productivity. The planktonic foraminifera divided into two groups based on their preferrence. The G. bulloides and N. dutertrei live in cold environment while G. aequilateralis, G. ruber, G. sacculifer, and Pulleniatina obliquiloculata preferr warm areas. In this study, G. bulloides and N. dutertrei were found in January whereas G. aequilateralis, G. rubber, G. sacculifer, and P. obliquiloculata were mostly in March.
The difference of carbon isotopes of planktonic foraminifera between species are distinct. Orbulina universa is the heaviest and G. ruber was the lightest. Foraminiferal d18O are depleted in October and enriched in January and March. It is suggested that sea surface temperature might be responsible for the variations of planktonic foraminiferal oxygen isotopes. Comparisons of foraminiferal d18O with the hydrographic data provide some informations. The results show that G. ruber lives in shallow water (~10m), G. sacculifer lives in 25m on average, and O. universa lives in deeper water layer (~70m) in northern South China Sea. Moreover, both the carbon isotopes and foraminiferal abundance of G. ruber show a negative correlation with the particles fluxes.
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Descrição morfológica da ontogenia de Hippocampus reidi Ginsburg, 1933 (Teleostei, Syngnathidae): período embrionário à fase reprodutivaPontes, Júlia Roberta Sá 27 August 2010 (has links)
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Previous issue date: 2010-08-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Ontogenetic studies constitute an important step to increase the knowledgebase
about shifts in food preference and micro-habitats, as well as for
improving taxonomy, production for aquaculture, and fisheries management;
they may also shed new light on the implications of the extraction of a high
volume of animals for trade. This study aimed to estimate the initial growth of
the seahorse Hippocampus reidi, and to morphologically describe its ontogeny,
from the embryonic period to the reproductive phase. Both aspects are relevant
in face of (1) the morphological and biological singularities of the genus,
including the ability to bend the body and the body covering formed by bony
rings, a prehensile tail and the development of a pouch in males and (2) the
need to increase our understanding of the biology and ecology of seahorses, a
group globally threatened by overfishing and habitat loss. Growth was
estimated using ex-situ data obtained from two different broods of H. reidi,
while description of the ontogeny was done using data collected both in-situ
and ex situ. Data were grouped into two distinct phases: planktonic and postplanktonic
(when juveniles are able to use holdfasts). The main results obtained
in the study are: H. reidi exhibited an initial daily growth rate of 0.017 cm;
juveniles showed a decrease in the percentage of the head, and in the depth of
the snout and trunk in relation to standard length with age. During the
planktonic phase, juveniles exhibited a a positive growth in the tail region, weak
pigmentation and had the pectoral fins positioned near the base of the head.
After that period, the body acquired a more solid structure, and various base
became evident (at 2.59 cm); the snout became more elongated, and the
pectoral fins were positioned near the level of the orbits. / Estudos acerca da ontogenia constituem uma etapa importante para ampliar o
entendimento sobre mudanças na preferência alimentar e por micro-habitats,
bem como para o aprimoramento da taxonomia, otimização da produção em
s e l e ; a r i e u q s e p o ã t s e g a a r a p e a r u t l u c i u q a a m u r a i c i p o r p m e d o p m é b m a t
maior compreensão acerca das implicações da extração de um alto volume de
animais para o comércio. O presente trabalho buscou estimar o crescimento
inicial da espécie de cavalo-marinho Hippocampus reidi e descrever
morfologicamente sua ontogenia, do período embrionário à fase reprodutiva.
Ambos aspectos são relevantes face às (1) singularidades morfológicas e
biológicas do gênero, que incluem a capacidade de dobrar o corpo dorsoventralmente
e a presença de placas ósseas dispostas em forma de anel ao
longo do corpo, a cauda preênsil e o desenvolvimento de uma bolsa incubadora
nos machos e (2) à necessidade de ampliar o conhecimento acerca da biologia
e ecologia dos cavalos-marinhos, um grupo globalmente ameaçado pela
sobrepesca e pela perda de habitat. Para a análise de crescimento, foram
obtidos dados ex-situ de duas diferentes proles de H. reidi. A descrição
ontogenética foi realizada utilizando-se dados obtidos in-situ e ex-situ .
Foram consideradas duas fases distintas: planctônica e pós-planctônica (quando
os jovens são capazes de se prender a estruturas de apoio). Principais
resultados obtidos no estudo: H. reidi apresentou uma taxa de crescimento
inicial de 0,017 cm ao dia; indivíduos jovens apresentaram decréscimo no
percentual da cabeça, da altura do focinho e do tronco em relação ao
comprimento padrão, com a idade. Durante a fase planctônica, os jovens
exibiram cauda em processo de crescimento, pigmentação discreta e
nadadeiras peitorais implantadas próximas à base da cabeça. Após este
período, a estrutura corporal tornou-se mais sólida e cores de base variadas
tornaram-se evidenciadas (aos 2,59 cm); o focinho tornou-se mais alongado e
as nadadeiras peitorais passaram a se posicionar próximo à linha das órbitas.
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Avaliação da metanogênese e sulfetogênese em reatores anaeróbios em batelada e de leito fixo, sob condições termofílicas / Evaluation of methanogenesis and sulfidogenesis of batch and differential anaerobic reactors under thermophilic conditionsMercia Regina Domingues 30 November 2001 (has links)
Neste trabalho, investigou-se o crescimento e as interações de microorganismos, anaeróbios, em batelada com células planctônicas e em reatores diferenciais com biofilme, sob condições termofílicas (55ºC). Foram utilizadas técnicas clássicas para caracterizar os microorganismos anaeróbios estritos e biologia molecular (FISH), com sondas fluorescentes específicas, para caraterizar e quantificar os microrganismos pertencentes ao domínios Archea e Bacteria. Foram realizadas experimentos com meios de cultivo contendo acetato de sódio e propionato de sódio, na presença de sulfato de sódio. Os resultados do FISH mostraram, para os ensaios em batelada com acetato e sulfato, o predomínio de organismos pertencentes ao Domínio Archea (ARC915+MB1174) representados pelo gênero Methanosarcina sp. e bacilos fluorescentes. No biofilme, para a mesma condição, houve predomínio de células do Domínio Bacteria (EUB338) e relacionadas com a oxidação do acetato. Para a condição de cultivo com lactato e sulfato, as células bacterianas semelhantes a Desulfotomaculum sp. predominaram nos reatores em batelada e diferenciais, justificando a elevada porcentagem de células do Domínio Bacteria. Os resultados do NMP mostraram uma maior concentração de anaeróbios totais na condição lactato e sulfato (\'10 POT.11\' - \'10 POT.12\'). Para as arqueas metanogênicas essa concentração foi eveidenciada para a condição de cultivo com acetato e sulfato (\'10 POT.4\'). Os resultados desse trabalho sugeriram que em reatores em batelada, na condição de cultivo com acetato e sulfato, ocorreu equilíbrio entre metanogênese, oxidação de acetato e sulfatogênese, enquanto no biofilme, foram favorecidos os dois primeiros tipos de metabolismo. A condição lactato mais sulfato favoreceu a sulfetogênese em ambos os reatores. No reator diferencial, alimentado com proprionato e sulfato ocorreu fermentação com crescimento sintrófico entre oxidadoras de proprionato, metanogênicas e redutoras de sulfato hidrogenotróficas. / In this work, were investigated the growth and interactions of anaerobic microorganisms, in batch and differential reactors with planktonic cells and biofilm, respectively, in thermophilic conditions (55°C). Classic and molecular biology methods (FISH) were utilized to characterize strict anaerobes, with specific fluorescence probes, to characterize the Archaea and Bacteria Domain cells. Experiments with sodium acetate, s01ium lactate and sodium propionate plus sodium sulfate were realized. To the acetate and sulfate batch assays the results of FISH showed the predominance of Archaea Domain cells (ARC915+MB1174), represented by genera Methanosarcina sp. and fluorescents rods. Under the same conditions the biofilm results showed predominance of Bacteria Domain cells (EUB338) and those related to the acetate oxidation. In lactate plus sulfate condition the bacteria cells, as Desulfotomaculum sp., predominated in batch and differential reactors, justifying the high percentage of Bacteria Domain cells. The MPN results showed a high concentration of total anaerobes under lactate plus sulfate condition (\'10 POT.11\' - \'10 POT.12\'). For methanogenic arquea this concentration was obtained in the acetate plus sulfate condition (\'10 POT.4\'). These results suggest a process equilibrium may have occurred among methanogenesis, acetate oxidation and sulfidogenesis in batch reactors under acetate plus sulfate conditions. However, methanogenesis and acetate oxidation metabolisms predominated in the biofilm. Sulfidogenesis was easier in both reactors, under lactate plus sulfate conditions. In the differential reactors with propionate plus sulfate, the fermentation was in syntrophic co-culture among propionate oxidizing bacteria, methanogenic and hydrogenotrophic sulfate reducing bacteria.
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Life histories predict genetic diversity and population structure within three species of octopus targeted by small-scale fisheries in Northwest MexicoDomínguez-Contreras, José F., Munguia-Vega, Adrian, Ceballos-Vázquez, Bertha P., Arellano-Martínez, Marcial, García-Rodríguez, Francisco J., Culver, Melanie, Reyes-Bonilla, Hector 15 February 2018 (has links)
The fishery for octopus in Northwest Mexico has increased to over 2,000 tons annually, but to date the specific composition of the catch has been ignored. With at least three main species targeted by artisanal fisheries in the region with distinct life histories, the lack of basic biological information about the distribution, metapopulation size and structure of each species could impede effective fisheries management to avoid overexploitation. We tested if different life histories of three species of octopus could help predict observed patterns of genetic diversity, population dynamics, structure and connectivity and how this information could be relevant to the sustainable management of the fishery. We sequenced two mitochondrial genes and genotyped seven nuclear microsatellite loci to identify the distribution of each species in 20 locations from the Gulf of California and the west coast of the Baja California peninsula. We tested five hypotheses derived from population genetic theory based on differences in the fecundity and dispersal potential for each species. We discovered that Octopus bimaculoides with low fecundity and direct development (without a planktonic phase) had lower average effective population size and genetic diversity, but higher levels of kinship, population structure, and richness of private alleles, than the other two species. These features indicated limited dispersal and high local recruitment. In contrast, O. bimaculatus and O. hubbsorum with higher fecundity and planktonic phase as paralarvae had higher effective population size and genetic diversity, and overall lower kinship and population structure than O. bimaculoides. These observations supported higher levels of gene flow over a larger geographical scale. O. bimaculatus with the longest planktonic paralarval duration and therefore larger dispersal potential had differences in the calculated parameters possibly associated with increased connectivity. We propose O. bimaculoides is more susceptible to over exploitation of small, isolated populations and could have longer recovery times than the other two species. This species may benefit from distinct fishery management within each local population. O. bimaculatus and O. hubbsorum may benefit from fishery management that takes into account metapopulation structure over larger geographic scales and the directionality and magnitude of larval dispersal driven by ocean currents and population connectivity among individuals of each locality. The distribution of each species and variations in their reproductive phenology is also important to consider when establishing marine reserves or seasonal fishing closures.
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The effects of clofazimine on mycobacterium smegmatis biofilm formationMothiba, Maborwa Tebogo 05 July 2013 (has links)
Chemotherapy of tuberculosis (TB), a disease caused by Mycobacterium tuberculosis (M. tuberculosis), is successful against actively-growing bacilli but ineffective against dormant/persistent organisms, found mainly in a protective lipid-laden granuloma, possibly necessitating the use of lipophilic antibiotics. In vitro, these bacilli are encased in lipid-rich biofilms. In this study, the antimycobacterial activity of one such agent, clofazimine, and its nanoparticle formulation, have been investigated against Mycobacterium smegmatis (M. smegmatis), as a surrogate for M. tuberculosis, by determining the bacteriostatic and bactericidal activities of the native (NC) and spray-dried (SDC) preparations of this agent on planktonic and biofilm populations, as well as their effects on biofilm formation and its lipid compositions, specifically free mycolic acid (FM) content. Both preparations were comparable, being bacteriostatic for rapidly-proliferating bacilli, bactericidal for slow-growing, biofilm-producing sessile bacteria, but ineffective against non-replicating, biofilm-encased M. smegmatis organisms. However, similar studies in M. tuberculosis are required. / Dissertation (MSc)--University of Pretoria, 2013. / Immunology / Unrestricted
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Foraminiferal biostratigraphic studies from Mesozoic succession of selected wells from the Orange Basin, western offshore, South AfricaBeukes, Genevieve January 2020 (has links)
Masters of Science / Located on the western offshore on the Atlantic Ocean margin of Southern Africa, the Orange Basin is the youngest and largest of the South Africa’s seven sedimentary basins. This passive margin basin in known for its hydrocarbon potential and therefore is the focus of attraction of several oil exploration companies.
The study area lies near the continental margin in which four exploratory wells were drilled. An attempt has been made in this work to understand the depositional settings of these reservoirs and their biostratigraphy.
Distribution of important planktonic index foraminifera helps in dating the reservoir sections. Paleoecological studies of benthic foraminifera were used for understanding the prevailing environment during the Cretaceous period. The study indicates that most of the reservoirs are distributed in the Albian (Early Cretaceous) and a few in the Cenomanian age sediments. Relatively shallow shelf sedimentation prevailed in the Late Aptian to middle part of Albian with deposition of arenaceous units. There were periodic localised deepening as well as very shallow depositional condition leading to exposure (diastem) as indicated by lithology and faunal composition. Gradual rise in sea level started in Late Albian and the entire area was under bathyal environment till the end of Cenomanian stage. This is indicated by deposition of claystone rich units and the associated fossil benthics indicates deposition in slope area. The few relatively minor argillaceous sandstone and siltstone units are with poor reservoir quality.
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Comparative proteomic and genomic analysis of Flavobacterium johnsoniae-like biofilm, planktonic and agar surface-associated cellsFlemming, Leonard 03 1900 (has links)
Thesis (PhD(Microbiology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Pathogenic Flavobacterium spp. cause serious disease outbreaks in a variety
of farmed fish, which lead to large economic losses in the aquaculture industry
on an annual basis. The ability of Flavobacterium johnsoniae-like isolates to
grow as surface-associated communities (biofilms) in aquaculture systems
poses a threat to fish health over extended periods of time. The biofilmforming
ability of 28 F. johnsoniae-like isolates obtained from diseased fish
were correlated with their chitin-degrading abilities and extracellular
carbohydrate complexes (ECC) and their pulsed-field gel electrophoresis
(PFGE) genotypes. Physiological changes in the proteome of 5 day
planktonic, biofilm and agar surface-associated cultures of F. johnsoniae-like
isolates YO12 and YO64 were analyzed by two-dimensional (2-D) gel
electrophoresis and 17 differentially expressed and 14 uniquely expressed
proteins were identified using matrix-assisted laser desorption ionization-time
of flight mass spectrometry (MALDI-TOF MS). Thirty-two differentially
expressed genes in 5 day biofilm and agar surface-associated cultures of F.
johnsoniae-like isolates YO12 and YO64 were identified using suppression
subtractive hybridization (SSH). Significant negative correlations were
observed between the chitin-degrading abilities and ECC and the biofilmforming
capacity of 24 h biofilm cultures of F. johnsoniae-like isolates.
Genetic heterogeneity was displayed by the F. johnsoniae-like isolates
following PFGE. A significant positive correlation was observed between
PFGE types and fish host species. Differentially and uniquely expressed
proteins identified in planktonic, biofilm and agar surface-associated phases
by 2-D/MS as well as differentially expressed genes identified in the biofilm
and agar surface-associated phases by SSH were categorized as being
involved in adaptation/protection, metabolic processes, membrane/transport/
motility and transcription/ translation. As far as we know, this is the first report
on the characterization of differentially expressed genes and gene products of
F. johnsoniae-like isolates obtained from diseased fish in South Africa. / AFRIKAANSE OPSOMMING: Patogene Flavobacterium spp. veroorsaak ernstige infeksie uitbrake in ’n
verskeidenheid gekweekte vissoorte, wat jaarliks tot groot ekonomiese
verliese in die akwakultuur bedryf lei. Die vermoë van Flavobacterium
johnsoniae-tipe isolate om as oppervlak-gehegde gemeenskappe (biofilms) in
akwakultuur sisteme te groei bedreig visgesondheid oor verlengde periodes.
Die vermoë van 28 F. johnsoniae-tipe isolate om biofilms te vorm is vergelyk
met hul vermoë om chitien te degradeer, die profiel van hul ekstrasellulêre
koolhidraat komplekse (EKK) en bandpatrone verkry met puls-veld jel
elektroforese (PVJE). Fisiologiese veranderinge in die proteoom van 5-dagoue
planktoniese-, biofilm- en agar oppervlak-geassosieerde kulture van F.
johnsoniae-tipe isolate YO12 en YO64 is met twee-dimensionele (2-D) jel
elektroforese geanaliseer. Sewentien differensieël uitgedrukte en 14 uniek
uitgedrukte proteïene is deur middel van matriks-geassisteerde laser
desorpsie ioniserings-tyd van vlug-massa spektrometrie (MGLDI-TVV MS)
geïdentifiseer. Twee-en-dertig differensieël uitgedrukte gene in 5-dag-oue
biofilm- en agar oppervlak-geassosieerde kulture van F. johnsoniae-tipe
isolate YO12 en YO64 was deur middel van suppressie afgetrokke
hibridisasie (SAH) geïdentifiseer. Beduidende negatiewe korrelasies is tussen
die chitin-degraderings vermoë en EKK en die biofilm-vormings kapasiteit van
24-uur-oue biofilm kulture van F. johnsoniae-tipe isolate waargeneem.
Resultate verkry met PVJE het die heterogene samestelling van F.
johnsoniae-tipe isolate uitgewys. ‘n Beduidende positiewe korrelasie is tussen
PVJE groeperings en vis gasheer spesie waargeneem. Differensieël en uniek
uitgedrukte gene geidentifiseer in die planktoniese-, biofilm- en agar
oppervlak-geassosieerde fases is deur middel van 2-D/MS asook differensieël
uitgedrukte gene geïdentifiseer in die biofilm en agar oppervlakgeassosieerde
fases deur middel van SAH was as betrokke by
aanpassing/beskerming, metaboliese prosesse, membraan/vervoer/
beweeglikheid en transkripsie/translasie gekategoriseer. Sover bekend is
hierdie die eerste beskrywing van differensieël uitgedrukte gene en
geenprodukte van F. johnsoniae-tipe isolate afkomstig van geinfekteerde vis
in Suid Afrika.
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Évolution paléoclimatique et paléohydrologique de la Méditerranée occidentale au cours des derniers 30 000 ans : contribution des dinokystes et des foraminifères planctoniquesRouis-Zargouni, Imène 13 February 2010 (has links)
Cinq carottes de la Méditerranée occidentale ont fait l’objet des approches multidisciplinaires basées essentiellement sur l'analyse des dinokystes, des foraminifères planctoniques et des isotopes afin d'identifier et préciser l'évolution climatique de ce bassin. L'ensemble de l'Holocène correspond au maximum de développement des dinokystes S. mirabilis et I. aculeatum et des foraminifères planctoniques G. inflata et G. ruber tandis que les épisodes froids sont caractérisés par la présence de Nematosphaeropsis labyrinthus et a un degré moindre de Spiniferites elongatus. Si dans la proximité du détroit de Gibraltar il est possible de distinguer les évènements de Heinrich du Maximum Glaciaire (LGM) cette distinction est moins évidente en se dirigeant vers l’Est. Au contraire le Younger Dryas s’exprime de façon identique sur l'ensemble du bassin occidental et se caractérise par le développement optimal de N. labyrinthus s’accompagnant d’après les fonctions de transfert dinos d’une baisse importante de la salinité. Cet épisode est marqué aussi par des concentrations maximales de dinokystes remarquablement corrélées à une augmentation du ?13C de G. bulloides. Cette augmentation de la productivité primaire au Dryas Récent est à relier à l’intensification des échanges Méditerranée-Atlantique. Par opposition, l'Holocène inférieur montre une baisse de la productivité primaire en Méditerranée occidentale contemporaine de la mise en place du sapropéle S1 dans le bassin oriental. Comme dans l'océan Atlantique, le refroidissement du "8.2 event" est clairement observée en Méditerranée occidentale ainsi que trois autres épisodes correspondant à ~9,3 ka; ~7 ka et ~2,7 ka cal. BP. / A multidisciplinary approach is occurred on five western Mediterranean cores based on dinocysts, planktonic foraminifera and isotopes to identify the climatic evolution of this region. The Holocene correspond to the maximal development of dinocysts S. mirabis and I. aculeatum and planktonic foraminifera G. inflata and G. ruber but the cold periods are characterised by the presence of N. labyrinthus and Spiniferites elongatus. The microfaunistic assemblages show that it's less easier to distinguish the LGM to Heinrich events (HE) when the study sites are far to strait of Gibraltar. The Younger Dryas is marked by the optimal development of N. labyrinthus on the entire basin in association to an important decrease of Sea Surface Salinity reconstructed on the basis of dinocyst transfer function. During this period, an intensification of Mediterranean-Atlantic water masses exchange is recorded by the increase of the ?13C of G. bulloides associated to the maximal dinocysts concentration. By contrast, the lower Holocene shows a decrease of primary productivity in western Mediterranean contemporaneous to the deposition of S1 sapropel in eastern basin. As in Atlantic Ocean, the 8.2 event is clearly observed in western Med with three other cold events at 9.3 ka, 7 ka and 2.7 ka cal. BP.
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Caracterização paleoceanográfica de um testemunho da Baía de Santos com base em foraminíferos planctônicos durante o Holoceno / Paleoceanographic characterization of one piston core from Santos Basin based on planktonic foraminifera during the HoloceneSantarosa, Ana Claudia Aoki 15 October 2010 (has links)
Para o desenvolvimento deste estudo, foi utilizado um testemunho de alta resolução coletado no talude da Bacia de Santos, em que foram realizadas análises de foraminíferos planctônicos e isótopos de oxigênio. Os resultados foram complementados por dados de razões de Fe/Ca e Ti/Ca e permitiram a compreensão do cenário paleoceanográfico no setor oeste do Atlântico Sul nos últimos 15 mil anos. Condições mais frias foram encontradas no início do registro até aproximadamente 8 mil anos A.P., com predomínio da fauna fria (G. truncatulinoides, N. dutertrei, e G. inflata) e valores mais altos de ? 18O. Maior produtividade também é sugerida pela componente principal 2 (CP2), relacionada à camada de mistura e caracterizada pela assembléia G. ruber (white) e G. sacculifer. As razões de Fe/Ca e Ti/Ca indicam maior aporte de terrígenos pela pluma do Rio da Prata para o ambiente oceânico, provavelmente contribuindo para fertilização das águas superficiais. A partir de 8 mil anos A.P. observa-se aumento dos valores da curva paleoclimática e diminuição progressiva dos valores de ? 18O. A CP2 apresenta valores máximos entre 10 e 5 mil anos A.P., indicando uma coluna de água mais quente e altamente estratificada. Neste período, apresentam-se os mínimos de razões de Fe/Ca e Ti/Ca, indicando um período mais seco, relacionado ao mínimo de insolação de verão no hemisfério sul e posicionamento da ZCIT mais ao norte. A partir de 5 mil anos A.P. até o final do registro, observa-se novamente menores valores da CP2 e razões crescentes Fe/Ca e Ti/Ca, indicando condições mais úmidas e de maior produtividade no Holoceno superior. / For this study, faunal changes in foraminifer\'s assemblages and oxygen stable isotopes were carried out on a high- resolution core retrieved from the slope of Santos Basin. The results, complemented with Fe/Ca and Ti/Ca ratios enabled the understanding of paleoceanografic changes occurred in the last 15 Kyr. Cold conditions were recognized in the late deglaciation until 8 mil Kyr B.P., characterized by the cold assemblage (G. truncatulinoides, N. dutertrei, and G. inflata) and higher values of ? 18O. The low values of principal component 2 (PC 2), related to the mixed layer and dominated by the species G. ruber (white) and G. sacculifer suggest enhanced surface productivity. The Fe/Ca and Ti/Ca ratios on the sedimentary record indicate a high terrigenous input from the Plata Plume outflow in the oceanic environment, which probably contributed to the fertilization of superficial waters. From 8 Kyr B.P., an increase in the paleoclimatic curve values and gradual reduction in the ? 18O were observed in the data. The PC 2 yields maximum values between 10 and 5 Kyr B.P., indicating warm and highly stratified water-column conditions. In this period, low Fe/Ca and Ti/Ca ratios point out dryer conditions, related to the low peak austral summer insolation and the ITCZ located farther north. From 5 mil Kyr B.P. decreasing PC 2 values and increasing Fe/Ca and Ti/Ca ratios may be a sign of more productivity and humid conditions in the late Holocene.
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Assembléias de foraminíferos planctônicos: Implicações paleoceanográficas nos últimos 450.000 anos em testemunhos do sudoeste do Atlântico Sul / Planktonic foraminifera assemblages: Paleoceanographic implications in the last 450.000 years on southwest margin cores from South AtlanticIwai, Fabiane Sayuri 17 December 2010 (has links)
O conhecimento das preferências ecológicas de espécies de foraminíferos planctônicos tem sido muito utilizada em investigações paleoceanográficas obtendo bons resultados. O presente estudo realizou inferências sobre as condições oceanográficas das águas superficiais da porção sudoeste do Atlântico Sul nos últimos 450.000 anos através da variação da abundância de foraminíferos planctônicos em dois testemunhos da Bacia de Campos. A partir da Análise de Correspondência foram identificados os três principais fatores responsáveis pela variação dos foraminíferos planctônicos encontrados em cada um dos testemunhos. No testemunho KF-13 os três fatores principais foram interpretados como temperatura, espessura da camada de mistura e sazonalidade; enquanto para o testemunho KF-14 os fatores foram definidos como espessura da camada de mistura, produtividade e sazonalidade. Com esses fatores foram identificados os intervalos de maior intensidade de ventos e produtividade na região. As principais mudanças climáticas do Atlântico Sul encontram-se relacionadas às mudanças de intensidade de ventos e dos sistemas dependentes deles como o Giro Subtropical do Atlântico e a Zona de Convergência Subtropical. / Paleoceanographic investigations based on planktonic foraminifera ecologic preferences are widely and succesfully applied. The present study infered surface waters oceanographic conditions from the South Atlantic southwest margin in the past 450.000 years through the planktonic foramifera abundance variation in two cores from Campos Basin. Correspondence Analysis defined three principal factors responsible for the planktonic foraminifera abundance variation in each core. The three KF-13 main factors were interpreted as temperature, mixed layer thickness and sazonality; KF-14 principal factors were defined as mixed layer thickness, productivity and sazonality. These factors made it possible to identify higher wind stress and higher productivity intervals in this region. The main climatic variations in South Atlantic are due to changes in wind stress and the systems which depend on it such as the Atlantic Subtropical Gyre and the Subtropical Convergence Zone.
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