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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Rezente submarine Barytbildung im Derugin-Becken (Ochotskisches Meer) geochemische Prozesse an aktiven Fluidaustrittsstellen /

Bollwerk, Sandra Marianne. Unknown Date (has links) (PDF)
Universiẗat, Diss., 2002--Kiel.
2

Reproductive Patterns of Cold-Seep Mussels in the Gulf of Mexico and Northwestern Atlantic

Plowman, Caitlin 06 September 2017 (has links)
Continuous or semi-continuous reproduction is the norm in deep-sea animals, with exceptions explained by seasonal pulses of surface-derived phytodetritus. Chemosynthesis-based ecosystems such as cold seeps have an independent nutritional supply and are often thought of as decoupled from surface productivity. This thesis explores reproductive patterns of four bathymodiolin mussel species from 14 cold seeps (320 to 3300 m depth) in the Gulf of Mexico (2014) and the northwestern Atlantic (2015). Using paraffin histology, I determined maturity stages for male and oocyte sizes for female mussels. All species at all sites reproduced periodically and synchronously, with geographic synchrony among sites. This suggests that mussels rely on a site-independent cue such as seasonal phytodetrital flux to synchronize reproduction, providing evidence for a stronger coupling between surface productivity and chemosynthesis-based fauna than previously expected. Mature oocytes were of similar size for all species at all depths, suggesting that egg size is phylogenetically constrained.
3

Macrobenthic community structure and total sediment respiration at cold hydrocarbon seeps in the northern Gulf of Mexico

Nunnally, Clifton Charles 15 November 2004 (has links)
Cold seeps are areas of high biomass in the deep-sea, the impacts of these food-rich environments upon the sediment community is unknown in the Gulf of Mexico. The structure and function of benthic communities was investigated at food-rich and food-limited sites on the northern Gulf of Mexico continental slope. Cold seeps were richer in macrofauna densities and total sediment respiration, but were poorer in biomass and taxa diversity than normal slope communities. Decreased diversity is seen at most chemosynthetic communities and suggests a competition for resources. The spatial extent of these results at seeps is unknown and may be a localized, bioenhancement effect caused by seeping fluids.
4

Macrobenthic community structure and total sediment respiration at cold hydrocarbon seeps in the northern Gulf of Mexico

Nunnally, Clifton Charles 15 November 2004 (has links)
Cold seeps are areas of high biomass in the deep-sea, the impacts of these food-rich environments upon the sediment community is unknown in the Gulf of Mexico. The structure and function of benthic communities was investigated at food-rich and food-limited sites on the northern Gulf of Mexico continental slope. Cold seeps were richer in macrofauna densities and total sediment respiration, but were poorer in biomass and taxa diversity than normal slope communities. Decreased diversity is seen at most chemosynthetic communities and suggests a competition for resources. The spatial extent of these results at seeps is unknown and may be a localized, bioenhancement effect caused by seeping fluids.
5

Microbial diversity in sediments and gas hydrates associated with cold seeps in the Gulf of Mexico

Mills, Heath Jordan 08 July 2004 (has links)
A molecular phylogenetic approach was used to characterize the composition of microbial communities from two gas hydrate sedimentary systems in the Gulf of Mexico. Nucleic acids were extracted from three distinct locales on surface breaching gas hydrate mounds, i.e., sediment overlaying gas hydrate, sediment/hydrate interface and sediment-free hydrate, and from three sediment depths, i.e., 0-2, 6-8 and 10-12 cm, in Beggiatoa sp. mat-associated sediments located several meters from exposed gas hydrate. Samples were collected from a research submersible (water depth 550-575 m) during two research cruises aboard the R/V Seward Johnson I and II funded by the NSF Life in Extreme Environments program. The 16S rRNA gene and 16S rRNA were amplified using PCR and reverse transcription-PCR, respectively, from DNA and RNA extracted from the total microbial community. The primers targeted microorganisms at the domain-specific, i.e., Bacteria and Archaea, and group-specific, i.e., sulfate-reducing bacteria (SRB) and putative anaerobic methane-oxidizing (ANME) archaea, level. Sequence analysis of the Bacteria clones revealed that the microbial communities were primarily dominated by Deltaproteobacteria. Other Proteobacteria classes, including Epsilon- and Gammaproteobacteria, represented a large fraction of the total microbial community isolated from the sediment overlying hydrate sample and the metabolically active fraction of the 0-2 cm sediment depth sampled from the Beggiatoa sp. mat-associated sediments. Sequence analysis indicated the majority of the archaeal clones were most closely related to Methanosarcinales, Methanomicrobiales and distinct lineages within the ANME groups. Several novel lineages were identified including a fourth ANME-2 clade, i.e., ANME-2D, and three clades with no closely related previously sequenced 16S rRNA gene clones or isolates, i.e., Unclassified Bacteria groups 1 and 2 and Unclassified Euryarchaeota. These studies represent the first 16S rRNA gene and 16S rRNA phylogenetic-based description of microbial communities extant in sediment-free gas hydrate and in methane-rich hydrate-associated and Beggiatoa sp.-associated sediments from a hydrocarbon seep region in the Gulf of Mexico.
6

REDOX VARIATIONS AT COLD SEEPS RECORDED BY RARE EARTH ELEMENTS IN SEEP CARBONATES

Feng, Dong, Chen, Duofu, Lin, Zhijia, Peckmann, Jörn, Bohrmann, Gerhard, Roberts, Harry H. 06 1900 (has links)
Understanding the formation conditions of seep carbonate is crucial to better constrain the dynamic fluid flow and chemical fluxes associate with cold seeps on the seafloor. Rare earth element (REE) in seep carbonates collected from modern cold seeps of Gulf of Mexico, Black Sea, Congo Fan, ancient seeps of Beauvoisin (Oxfordian, J3, Southeastern France) and Marmorito (Miocene, Northern Italy) were studied. Our focus has been on 5% HNO3-treated solution (authigenic carbonate minerals) of carbonates. Several crystalline forms of carbonate minerals have been selected for analysis. Total REE (ΣREE) contents in seep carbonates varies widely, from 0.068 to 43.655 ppm, but the common trend is that the ΣREE in microcrystalline phases is highest and lowest of in sparite, suggesting that the ΣREE of seep carbonates may be a function of diagenesis. The shale-normalized REE patterns of the seep carbonates show varied Ce anomalies across several seep sites and even within one site, suggesting that the formation condition of seep carbonate is variable and complex. Overall, our results show that apart from anoxic, oxic formation condition is also common at hydrocarbon seep environments.
7

Sulfidaufnahme von Calyptogena pacifica im Vergleich mit geochemischen Untersuchungen in Cold-Seep-Sedimenten vor Makran und West-Java

Mirbach, Nikolaus von. January 2000 (has links) (PDF)
Kiel, Universiẗat, Diss., 2000.
8

Origin of methane at ancient methane seeps inferred from organic geochemical signatures in seep carbonates / 冷湧水炭酸塩岩の有機地球化学分析による古冷湧水メタンの起源推定

Miyajima, Yusuke 26 March 2018 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20926号 / 理博第4378号 / 新制||理||1629(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 生形 貴男, 教授 酒井 治孝, 教授 田上 高広 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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