Dortmund, Universiẗat, Diss., 2001.

Techn. Hochsch. Diss., 2003--Aachen.

Hamburg, Universiẗat, Diss., 2001.

Techn. Hochsch., Diss., 2003--Aachen.

[pt] A reconstrução da temperatura da superfície do mar (TSM) através de proxies geoquímicos orgânicos tem sido um tema central das pesquisas paleoclimáticas nos últimos anos. Determinações da variabilidade da paleotemperatura no Atlântico Sul são de grande interesse dado o papel da TSM no transporte de calor global, mas este tema ainda requer estudos mais aprofundados. O sistema de ressurgência de Cabo Frio (SRCF) representa uma área de estudo particularmente interessante por ser um sistema de ressurgência de contorno oeste sujeito a vários processos oceanográficos peculiares. Este projeto tem como objetivo a utilização de proxies geoquímicos orgânicos como indicadores de paleotemperatura, tais como: o índice de insaturação das alquenonas (U37K), o índice dos tetraéteres (TEX86H) e o índice dos diois de cadeira longa (LDI) registrados em sedimentos da margem continental sudeste brasileira. Também foram testados os índices de metilação e de ciclização dos tetraéteres ramificados (MBT e CBT) como indicadores da temperatura média anual do ar (TMAA) e do pH do solo. O presente trabalho possui dois focos: (i) investigar a aplicabilidade dos índices U37K, TEX86H e MBT/CBT considerando as condições ambientais locais e regionais observadas na região da Bacia de Campos utilizando 53 amostras de sedimento superficiais; (ii) aplicar uma abordagem multiproxy (U37K, TEX86H e LDI) para reconstruir a paleotemperatura durante o período do Holoceno a partir de dois testemunhos sedimentares localizados nas plataformas adjacentes a Cabo Frio e Rio de Janeiro. Os resultados revelam que U37K e TEX86H são proxies de temperatura adequados para estudos paleoclimáticos em escala regional na margem continental do sudeste brasileiro. Exceções na forma de desvios negativos entre a TSM média anual reconstruída e observada (World Ocean Atlas 2013) foram observados na porção sul da região estudada e ressaltam que, em escala local, os efeitos da ressurgência devem ser levados em consideração ao aplicar esses proxies na mesma região. Em relação aos índices MBT/CBT, os resultados se encaixam na faixa superior do pH do solo e na faixa inferior da TMAA encontrados na bacia de drenagem adjacente para a maioria das amostras. No entanto, a distribuição dos GDGTs ramificados apontam para a existência de diferentes fontes e efeitos pós deposicionais, e.g. degradação seletiva e produção in situ, que comprometem a aplicabilidade desses proxies nos sedimentos marinhos na Bacia de Campos. Ao aplicar os proxies U37K, TEX86H e LDI na reconstrução da temperatura para os últimos 14,5 kyr no testemunho do Rio de Janeiro e 7,1 kyr no testemunho de Cabo Frio, as variações observadas estão em acordo com diversos dados paleoclimáticos pré-existentes para a mesma região e período. Na plataforma do Rio de Janeiro, uma fase distinta antes de 7,5 cal kyr BP coincide com o período em que o nível do mar se encontrava baixo e passou a aumentar gradualmente. Na plataforma de Cabo Frio, a transição entre o Holoceno médio e o tardio é bem marcada pelo aumento na TSM-U37K e da TSMLDI provavelmente relacionados a uma atividade mais intensa da Corrente do Brasil (BC) sobre a plataforma, enquanto a temp-TEX86H apresentou uma tendência oposta de resfriamento que pode ser um resultado da ressurgência das Águas Centrais do Atlântico Sul em subsuperfície. Uma diminuição na temperatura reconstruída após cerca de 2,0 cal kyr BP pode ser explicada pelo estabelecimento do SRCF às condições modernas. Diferenças entre o Rio de Janeiro e Cabo Frio provavelmente estão relacionadas às instabilidades locais da CB próximo à região do SRCF. De forma geral, para o período investigado em ambos os testemunhos, a TSM-LDI mostrou-se mais quente, a TSM-TEX86H obteve uma clara tendência a temperaturas mais frias de subsuperfície e a TSM-U37K foi a mais afetada pela variação no nível do mar e pelo fluxo da CB. As diferenças entre os proxies forneceram informações valiosas sobre as mudanças paleoceanográficas locais durante o Holoceno, contribuindo para os estudos paleoclimáticos na margem sudeste do Brasil. / [en] The reconstruction of past sea surface temperature (SST) using organic geochemical proxies has been a central theme of paleoclimatic research in recent years. Paleotemperature variability determinations in the South Atlantic are of great interest given the SST role in the global heat transport, but still requires further studies. The Cabo Frio Upwelling System (CFUS) is a particularly interesting study area for being a western boundary upwelling system subject to several peculiar oceanographic processes. This thesis aims at using organic geochemical proxies as indicators of paleotemperature, namely: the alkenoneunsaturation index (U37K), the tetraether index (TEX86 H ) and the long-chain diols index (LDI) as registered in sediments in the south-eastern Brazilian continental margin. The methylation of branched tetraether index (MBT’) and the cyclization of branched tetraether index (CBT) were also tested as potential indicators of continental mean annual air temperature (MAAT) and soil pH. There are two focuses: (i) to investigate the applicability of U37K, TEX86H and MBT’/CBT proxies under local and regional environmental conditions in the Campos Basin region using 53 surface sediments; (ii) to use a multiproxy approach (U37K, TEX86H and LDI) to reconstruct the paleotemperature during the Holocene period from two sediment cores located in the shelves adjacent to Cabo Frio and Rio de Janeiro. The results reveal that U37K and TEX86H are suitable temperature proxies for paleoclimate studies in regional scale in the SE Brazilian continental margin. Exceptions in the form of strong negative biases between reconstructed and observed mean annual SST (World Ocean Atlas 2013) were observed in the southern portion of the Campos Basin and highlight that, on a local scale, the effects of upwelling must be taken in consideration when applying these proxies to the same region. Regarding the MBT/CBT proxies, the results for most of the marine sediments agree with the upper range of soil pH and lower range of MAAT found in the adjacent drainage basin. However, the spatial distribution of the branched GDGTs points to the existence of different sources and post-depositional effects, e.g. selective degradation and in situ production, that compromise the applicability of these proxies to the marine sediments in the Campos Basin, especially more offshore. When applying the U37K, TEX86H and LDI proxies to reconstruct the SST for the past 14.5 kyr in the Rio de Janeiro core and 7.1 kyr in the Cabo Frio core, the variations observed agreed with several pre-existing paleoclimatic data for the same region and period. In the Rio de Janeiro shelf, a distinct phase before 7.5 cal kyr BP coincides with the period when the sea level was low and gradually increased. In the Cabo Frio shelf, the transition between mid- and late Holocene is well marked by a warming in SST-U37K and SST-LDI, probably related to a more intense Brazil Current (BC) activity over the shelf, whereas temp-TEX86H showed an opposite cooling trend that may be a result of the subsurface upwelling of the cold South Atlantic Central Waters. A decrease in reconstructed temperatures after ca 2.5 kyr BP may be related to the establishment of the CFUS to modern conditions. Differences between Rio de Janeiro and Cabo Frio can be explained by the local instabilities of the BC near de CFUS region. Overall, for the entire covered period in both sediment cores, SST-LDI was warmer, SST-TEX86H was clearly biase towards colder subsurface temperatures and SST-U37K was the most affected by the sea level variation and BC flow. The differences between the proxies signal provided valuable information about the local paleoceanographic changes during the Holocene period, contributing to the paleoclimatology studies in the southeastern Brazilian margin. / [de] Die Rekonstruktion Oberflächenwassertemperaturen in der Vergangenheit mit organisch geochemischen Proxies ist in den vergangenen Jahren ein wichtiges Thema der Palaoklimaforschung gewesen. Die Rekonstruktion von Palaotemperaturvariabilitat im Südatlantik ist hierbei in Anbetracht der wichtigen Rolle der Ozeane im globalen Wärmetransport von zentraler Bedeutung, erfordert jedoch noch weiterführende Untersuchungen. Das Auftriebssystem von Cabo Frio ist in diesem Zusammenhang wegen seiner speziellen Lage auf der westlichen Seite eines Ozeanbeckens und der damit zusammenhangenden besonderen ozeanographischen Prozesse ein interessantes Arbeitsgebiet. Diese Arbeit hat zum Ziel, die organisch-geochemischen Proxies U37K (Alkenon-UntersattigungsIndex), TEX86H (Tetraether-Index an sogenannten GDGTs, Glycerol Dialkyl Glycerol Teteraether) und LDI (Langkettige-Diole-Index) aufgezeichnet in Sedimenten des sudostlichen brasilianischen Kontinentalrands zu verwenden. Zudem wurden die Indices MBT und CBT, die die Methylierung bzw. Zyklisierung verzweigter GDGTs quantifizieren, als Proxies fur die Jahresmitteltemperatur an Land und fur den pHWert der Boden getestet. Der Fokus der Arbeit liegt hierbei einerseits darauf i) die Anwendbarkeit der Proxies U37K, TEX86H , MBT/CBT im unter den lokalen und regionalen Umwelteinflussen des Campos Bessens auf Grundlage von 53 Oberflachensedimentproben zu uberprufen und ii) eine sogenannte multi-proxy Rekonstruktion der Palaoumweltbedingungen anhand der U37K, TEX86H und LDI Proxies an zwei Sedimentkernen vom Schelf vor Cabo Frio und Rio de Janeiro zu erstellen. Es zeigt sich, dass sich sowohl U37K als auch TEX86H fur regionale Palaoumweltstudien am sudostlichen brasilianischen Kontinentalrand eignen. Ausnahmen in Form von starken negativen Abweichungen zwischen rekonstruierter und instrumentell beobachteter (World Ocean Atlas 2013) Oberflachenwassertemperatur treten im sudlichen Teil des Campos Beckens auf und zeigen, dass sehr lokal die Auswirkungen von Auftrieb bei der einer regionalen Anwendung dieser Proxies berucksichtigt werden mussen. Die Ergebnisse der MBT/CBT Proxies an marinen Sedimenten stimmen mit den Gegebenheiten an Land weitgehend uberein, wobei die pH-Rekonstruktionen im oberen Bereich der Beobachtungen im angrenzenden Einzugsgebiet liegen, wahrend die Rekonstruktion der Jahresmitteltemperatur an Land zu den niedrigeren Werten der Beobachtungen neigen. Die raumliche Verteilung der verzweigten GDGTs in deutet zudem auf unterschiedliche Quellen sowie diagenetische Effekte wie selektiven Abbau und in-situ Produktion von verzweigten GDGTs hin, die die Anwendbarkeit der MBT/CBT Proxies an marinen Sedimenten des Campos Beckens, insbesondere in den kustenfernen Regionen, einschranken. Die Rekonstruktion der Palao-Oberflachenwassertemperaturen mithilfe von U37K, TEX86H und LDI fur die letzten 14.5 kyr vor Rio de Janeiro und fur die letzten 7.1 kyr vor Cabo Frio ergab eine Variabilitat, die mit Ergebnissen aus mehreren vorherigen palaoklimatischen Studien fur die Region ubereinstimmt. Auf dem Schelf vor Rio de Janeiro kann eine Phase vor 7.5 kyr deutlich vom Rest der Zeitreihe unterschieden werden, wahrend derer der Meeresspiegel niedriger war und allmahlich anstieg. Auf dem Schelf vor Cabo Frio ist der ubergang vom mittleren ins spate Holozan von deutlichen Anstiegen der U37K - und LDI-basierten Temperaturrekonstruktionen gepragt, die wahrscheinlich mit der Intensivierung des Brasilstroms auf dem Schelf in Verbindung stehen. Im Gegensatz dazu verzeichnet die TEX86H -basierte Temperaturrekonstruktion eine deutliche Abkuhlung, die das Ergebnis von verstarktem Auftrieb von kaltem sudatlantischem Zentralwasser sein kann. Eine Abnahme der rekonstruierten Temperaturen nach 2.5 kyr vor heute deutet auf die Etablierung moderner Bedingungen im Cabo Frio Auftriebssystem hin. Unterschiede zwischen den Temperaturrekonstruktionen fur die Regionen Cabo Frio und Rio de Janeiro konnen mit lokaler Instabilitat des Brasil-Stroms im Bereich des Cabo Frio Auftriebssystems zusammenhangen. Insgesamt sind über die gesamte Untersuchungsperiode die Temperaturrekonstruktionen auf Grundlage von LDI am warmsten, die auf TEX86H basierenden von kalteren Temperaturen in etwas groberen Wassertiefen beeinflusst und diejenigen auf Grundlage von U37K am starksten von Meeresspiegelanderungen und Variabilitat im Brasil-Strom betroffen. Diese Unterschiede zwischen den einzelnen Proxies liefern wertvolle Informationen uber die lokalen palaozeanographischen Veranderungen wahrend des Holozans und somit einen Beitrag zum Verstandnis des Palaoklimas am sudostlichen brasilianischen Kontinentalrand.

In cultured medaka testis fragments, cells remained viable for the entire culture period (17h), and spermatids that developed from spermatocytes were viable and motile. Primary cultures were characterized over a period of two days with respect to cell viability and the distribution of adherent and suspended cells. These two cell populations were maintained in dynamic equilibrium in vitro for several days. Proliferating cells were predominant among clusters of suspended cells, as determined by BrdU labeling, and CFSE and propidium iodide PI labeling. Based on cytological criteria, the proliferating cells were mostly spermatogonia and possibly also preleptotene spermatocytes. Differentiation of spermatocytes into spermatids or spermatozoa was also observed, mainly among the suspended cells. These results suggest that the organ and primary culture systems are suitable systems for studying the effects of substances that interfere with spermatogenesis in the medaka, a model vertebrate. The organ and primary culture systems were used to analyze the effects of a synthetic estrogen, EE2, on cell proliferation in medaka testis. Both organ and primary culture were suitable for this purpose consistently small concentrations (0.01 and 1 nM) of EE2 stimulated cell proliferation slightly, while higher concentrations (100 nM) had an inhibitory effect. To investigate the effect of phytoestrogens on cell proliferation in spermatogenesis, selected flavonoids [genistein (1, 10, 100 µg/ml), quercetin (0.01, 1, 100 µM), and 8-prenylnarigenin (0.001, 0.1, 1, 10 µM)] were added to medaka testis primary cultures. Genistein and quercetin inhibited cell proliferation in the cultures while 8-prenylnarigenin had no effect. In a second series of experiments the addition of genistein (10 µg/ml) to primary cultures significantly inhibited both cell proliferation and cell differentiation as determined by flow cytometry using CFSE/PI labeling.

In cultured medaka testis fragments, cells remained viable for the entire culture period (17h), and spermatids that developed from spermatocytes were viable and motile. Primary cultures were characterized over a period of two days with respect to cell viability and the distribution of adherent and suspended cells. These two cell populations were maintained in dynamic equilibrium in vitro for several days. Proliferating cells were predominant among clusters of suspended cells, as determined by BrdU labeling, and CFSE and propidium iodide PI labeling. Based on cytological criteria, the proliferating cells were mostly spermatogonia and possibly also preleptotene spermatocytes. Differentiation of spermatocytes into spermatids or spermatozoa was also observed, mainly among the suspended cells. These results suggest that the organ and primary culture systems are suitable systems for studying the effects of substances that interfere with spermatogenesis in the medaka, a model vertebrate. The organ and primary culture systems were used to analyze the effects of a synthetic estrogen, EE2, on cell proliferation in medaka testis. Both organ and primary culture were suitable for this purpose consistently small concentrations (0.01 and 1 nM) of EE2 stimulated cell proliferation slightly, while higher concentrations (100 nM) had an inhibitory effect. To investigate the effect of phytoestrogens on cell proliferation in spermatogenesis, selected flavonoids [genistein (1, 10, 100 µg/ml), quercetin (0.01, 1, 100 µM), and 8-prenylnarigenin (0.001, 0.1, 1, 10 µM)] were added to medaka testis primary cultures. Genistein and quercetin inhibited cell proliferation in the cultures while 8-prenylnarigenin had no effect. In a second series of experiments the addition of genistein (10 µg/ml) to primary cultures significantly inhibited both cell proliferation and cell differentiation as determined by flow cytometry using CFSE/PI labeling.