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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.
71

Embryology, larval ecology, and recruitment of "Bathymodiolus" childressi, a cold-seep mussel from the Gulf of Mexico

Arellano, Shawn Michelle, 1977- 06 1900 (has links)
xx, 198 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / "Bathymodiolus" childressi is a mixotrophic mussel from Gulf of Mexico cold seeps. There is no genetic differentiation of mussels among the seeps, suggesting wide dispersal of their larvae. This dissertation describes larval biology, ecology, and recruitment dynamics for "B." childressi. Cleavage is spiral at a rate of one per 3-9 hours, with blastula larvae hatching by 40 hours at 7-8 à à °C. At 12-14 à à °C, D-shell veligers developed by day 8 without being fed. Egg size and shell morphology indicate planktotrophy, but feeding was not observed. Embryos developed normally from 7-15 à à °C and 35-45 ppt. Although survival of larvae declined with temperature, some survived at 25 à à °C. Larval survivorship was similar at 35 and 45 ppt. Oxygen consumption increased from blastulae to trochophores and was higher for "B." childressi than for shallow-water mussel trochophores. Estimated energy content of "B." childressi eggs was greater than the energy content of shallow-water mussel eggs. An energetic model predicts that the eggs provide sufficient energy for "B." childressi trochophores to migrate into the euphotic zone. In fact, "B." childressi veligers were found in plankton tows of surface waters. The influence of recruitment on fine-scale distributions of adults at the Brine Pool cold seep was examined through manipulative field experiments. The "Bathymodiolus" childressi population at this site has a distinct bimodal size structure that shifts across an environmental gradient. New recruits of "B." childressi are abundant in the inner zone, where methane and oxygen are high and sulfide is low, leading to the inference that larvae settle preferentially there. Experiments were placed in the inner and outer zones and 2-m away from the bed. The number of larvae collected in traps did not differ among the three zones, nor did settlement density. Juveniles survived and grew in all zones, but more caged than uncaged juveniles survived. Mortality of uncaged juveniles was similar in all zones, suggesting that predation does not cause the bimodal distribution. These results suggest that the bi-modal distribution cannot be attributed to settlement preferences or juvenile mortality, but instead to migration or early post-settlement mortality. This dissertation includes my co-authored materials. / Adviser: Craig M. Young
72

Computer graphic representation of remote environments using position tactile sensors

Fyler, Donald Charles January 1981 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by Donald Charles Fyler. / M.S.
73

Revisão taxonômica da família Serolidae Dana, 1853 (Crustacea: Isopoda) no oceano Atlântico (45°N - 60° S) / Taxonomic review of the family Serolidae Dana, 1853 (Crustacea: Isopoda) in the Atlantic Ocean (45N-60S)

Costa, Ingrid Ávila da 27 June 2017 (has links)
O presente estudo consiste na maior revisão taxonômica da família Serolidae já realizada no oceano Atlântico e constitui a primeira síntese sobre a taxonomia do grupo. A grande diversidade morfológica, definições genéricas imprecisas, descrições incompletas ou mal elaboradas e a ausência de ilustrações adequadas, resultaram em dificuldades que se acumularam ao longo de décadas para o reconhecimento de muitos gêneros e espécies. Portanto, os objetivos desse estudo foram: (i) redefinir o gênero Serolis com especial referência a sua espécie tipo e demais espécies americanas; (ii) redescrever e ilustrar Serolis paradoxa, espécie tipo de Serolis; (iii) examinar a validade dos gêneros Acantoserolis, Atlantoserolis, Cristaserolis, Glabroserolis e Leptoserolis; (iv) revisar as espécies cosmopolitas Acanthoserolis polaris e A. schythei; (v) rever o posicionamento taxonômico das espécies de Acutiserolis do Atlântico: A. margaretae, A. neaera e A. coineauae; (vi) rever a posição taxonômica de Brucerolis macdonnellae e B. maryannae; (vii) a partir de estudo de material inédito verificar a possível existência de espécies novas para a ciência e (viii) elaborar uma chave de identificação para gêneros e espécies do Oceano Atlântico. O estudo foi realizado com base em material depositado em coleções carcinológicas do Brasil, Estados Unidos e vários países da Europa. Ao término do presente estudo, a família inclui 53 espécies distribuídas em 15 gêneros. Foram identificadas e descritas 8 novas espécies: Ceratoserolis sp. nov., Neoserolis sp. nov. (1), Neoserolis sp. nov. (2), Serollela sp. nov., Serolis sp. nov. (1), Serolis sp. nov. (2), Serolis sp. nov. (3), Serolis sp. nov. (4). Foi estabelecido um novo gênero para abrigar uma nova espécie proveniente de águas rasas brasileiras. Os gêneros Atlantoserolis, Cristaserolis, Glabroserolis e Leptoserolis cuja validade era objeto de dúvida são confirmados como gêneros válidos. O gênero Acanthoserolis foi sinonimizado ao gênero Serolis, assim como suas espécies, Serolis polaris e Serolis scythei. O gênero Serolis foi redefinido e sua espécie tipo redescrita. As espécies atlânticas do gênero Brucerolis, B. maryannae e B. macdonannelae, cuja posição taxonômica em Brucerolis era duvidosa na medida em que o gênero foi caracterizado inicialmente com base nas espécies do oceano Pacífico, foram confirmadas em Brucerolis. A combinação original Serolis margaretae foi reestabelecida e, consequentemente, a inclusão da espécie em Acutiserolis rejeitada. Acutiserolis coineauae e A. neaera foram transferidas para o gênero Serolis. Septemserolis leachi [Serolis], também foi objeto de nova combinação. Treze outros novos registros e ampliações de distribuição geográfica foram efetuados, incluindo Heteroserolis mgrayi registrada pela primeira vez para o Hemisfério Sul. / The present study consists of the largest taxonomic revision of the family Serolidae carried out in the Atlantic Ocean and constitutes the first synthesis on the taxonomy of the group. The great morphological diversity, inaccurate generic definitions, incomplete or poorly elaborated descriptions and the absence of adequate illustrations resulted in difficulties that were accumulated over decades for the recognition of many genera and species. Therefore, the objectives of this study were: (i) to redefine the genus Serolis with special reference to its type species and other American species; (ii) to redescribe and illustrate Serolis paradoxa, type species of the genus; (iii) to examine the validity of the genera Acantoserolis, Atlantoserolis, Cristaserolis, Glabroserolis, and Leptoserolis; (iv) to review the cosmopolitan species Acanthoserolis polaris and A. schythei; (v) to review the taxonomic position of the Atlantic Acutiserolis species: A. margaretae, A. neaera and A. coineauae; (vi) to review the taxonomic position of Brucerolis macdonnellae and B. maryannae; (vii) to verify the existence of new species for science from unpublished material, and (viii) to provide an identification key for genera and species of the Atlantic Ocean. The study was carried out based on material deposited in crustacean collections from Brazil, the United States and several European countries. At the end of the present study, the family includes 53 species distributed in 15 genera. Eight new species were identified and described: Ceratoserolis sp. nov., Neoserolis sp. nov. (1), Neoserolis sp. nov. (2), Serollela sp. nov., Serolis sp. nov. (1), Serolis sp. nov. (2), Serolis sp. nov. (3), and Serolis sp. nov. (4). A new genus was established to accomodate a new species from Brazilian shallow waters. The genera Atlantoserolis, Cristaserolis, Glabroserolis, and Leptoserolis, whose validity was the object of doubt, are confirmed as valid genera. The genus Acanthoserolis was synonymized to Serolis, as well as its species, Serolis polaris and Serolis scythei. The genus Serolis was redefined and its type rediscovered. The Atlantic species of the genus Brucerolis, B. maryannae, and B. macdonannelae, whose taxonomic position was doubtful, was initially characterized based on the species of the Pacific Ocean, were confirmed in Brucerolis. The original combination Serolis margaretae was reestablished and, consequently, the inclusion of the species in Acutiserolis rejected. Acutiserolis coineauae and A. neaera were transferred to the genus Serolis. Septemserolis leachi [Serolis], was also the subject of a new combination. Thirteen other new records and extensions of geographical distribution were made, including Heteroserolis mgrayi first recorded for the Southern hemisphere.
74

Microbial Ecology and Functional Genomics of Deep-Water Coral-Associated Microbes

Galkiewicz, Julia Parker 01 January 2011 (has links)
Lophelia pertusa is a cosmopolitan cold-water coral, often found in aphotic waters (>200m). Aggregations of L. pertusa (reefs) provide important habitat to many invertebrate and fish species and act as biodiversity hotspots in the deep sea. The health and diversity of these reefs is of vital importance to deep-sea ecosystems, and the microbial consortia associated with L. pertusa form the most basic ecological level. Deciphering the diversity and function of these microbes provides insight into the roles they play in maintaining reef health. This dissertation takes microbiological techniques that are used in shallow-water coral microbial research and applies them to L. pertusa. A flaw in a primer set, which is commonly used in the molecular genetics method Polymerase Chain Reaction (PCR) to obtain data on coral-associated microbes, is discussed and an alternative approach is presented. In addition, two culture-based studies are employed to catalogue diversity and explore functional differences in strains of both bacteria and fungi. The cultured bacteria were tested for resistance against six antibiotics that affect a variety of cellular targets to elucidate strain level differences. The first cultured fungi ever described from L. pertusa were identified by molecular techniques and assayed using Biolog plates to test their metabolic capabilities. Preliminary data analysis on metagenomic libraries of the microbial-size fraction of L. pertusa is presented and discussed in the context of microbial diversity and function, bridging the gap between culture-based work on function and culture-independent work on diversity.
75

Species richness of deep-sea wood-boring clams (subfamily Xylophagainae) from the northeast Pacific

Stoeckle, Mathis 22 February 2010 (has links)
The deep sea. for a long time. had been perceived as a homogenous and stable environment, with little diversity. The discovery of island habitats such as hot vents. cold seeps and whale carcasses revealed the presence of high biomasses in the deep sea. Species richness on island habitats is low however, compared to the species richness on abyssal plains (Tunnicliffe 1991: Stecher et al. 2003). A study addressing species richness on abyssal plains concludes there to be tens of millions of new species (Grassle and Maciolek 1992). Other authors dispute these numbers and suggest a total deep-sea species richness of approximately half a million (May 1993). The discrepancy in these numbers by multiple orders of magnitude emphasize how under-sampled the deep sea is. The Northeast Pacific is recognized as a biogeographic species province both in the intertidal. shallow subtidal (Valentine 1966: Roy et al. 1994) as well as in hydrothermally active areas (Van Dover et al. 2002). The Northeast Pacific hydrothermally active areas are unique in that they appear to foster single dominant species within ecosystems: e.g. Ridgeia piscesae (Vestimentifera. Annelida) (Southward et al. 1995): Lepetodrilus fucensis (Gastropoda, Mollusca) (McLean 1993). Xylophaga washingiona BARTSCH (Bivalvia. Mollusca) is the only described species of deep-sea wood-boring clams in the Northeast Pacific (Bartsch 1921). We investigated the species richness of deep-sea wood-boring clams (Family Pholadidae. Subfamily Xylophagainae) in the Northeast Pacific by means of strategically placed, experimental wood blocks. The objective of the study was to a) assess the morphological diversity and separate the specimens into distinct morphological taxa: b) to use genetic markers (CO 1. 18S) to discern the genetic diversity within the morphological taxa and c) to elucidate the phylogenetic relationships among the new species. We discovered eight morphological taxa (B. F. G. M. R, T. U. X), defined by a set of characters. previously used to describe new pholad species. The most distinguishing characters were the morphologies of the siphon and mesoplax (accessory plates). The CO1 gene sequences showed little diversity within the morphological Taxa B. F, G. U and X. The 18S gene data split Taxa B and T into B1. B2 and T1, T2, respectively. There was no genetic diversity within 18S sequences of Taxon R. Thus. we discovered at least six new species: Xylophaga species B1. F. G, R. U and Xylopholas species X. I cannot confirm the statuses of Taxa M and T due to missing morphological characters as well as the unavailability of their CO1 sequences. The newly discovered species increase the number of deep-sea, wood-boring species from one to seven, in the Northeast Pacific. Globally, a total of 41 species have been described. Given the discoveries in this study, this number is likely an underestimate of the global species richness of the Xylophagainae. The phylogenetic relationships of the genus leveI remain inconclusive due to too few samples. Species relationships emerged. placing Species G and R as most closely related. as well as B1 and X washingtona. Additional samples from all ocean basins are necessary to further investigate the relationships and origins of the deep-sea woodborers. Future avenues that need to be explored are threefold: a) Ancestry: Has there been one or multiple invasions into the Northeast Pacific, with subsequent adaptive radiations? Where do this/these ancestor species come from? b) Support for Diversity: What mechanisms allow the deep-sea wood-boring clams to co-occur? What are the deep-sea wood-boring clams' micro-niches? c) Effects of Diversity : What is the role of the wood-boring clams in species communities inhabiting deep-sea wood?
76

Factors Shaping Macrofaunal Polychaete Communities in the Gulf of Mexico

Carvalho, Russell G 02 October 2013 (has links)
This dissertation addresses large-scale trends in composition, density, taxonomic and functional diversity in deep-sea benthic polychaete communities in the Gulf of Mexico (GoM). The study includes samples from two major sampling programs: the Deep Gulf of Mexico Benthos (DGoMB) program (2000–2002) (51 stations, 200-3700 m) and the SIGSBEE program (Universidad Nacional Autónoma de México), 2008-2010 (27 stations on the Sigsbee Abyssal Plain). Polychaete density decreased exponentially with depth. Alpha diversity did not show a mid-depth maximum and reached its peak near the Mississippi trough. Feeding guild diversity was also highest in the Mississippi trough. The environmental parameters that determine diversity and density of polychaete assemblages and species distribution ranges were examined. Depth, export flux of particulate organic carbon (POC), percent sand and silt were the best predictors of heterogeneity of polychaetes in the GoM. We performed an ecological niche modeling analysis (ENM) based on ‘presence-only’ data of four cosmopolitan species belonging to the Cirratulidae and Spionidae in the GoM. The GoM, being a semi-enclosed ocean basin, offers complex topographic features and hydrographic processes. Comparisons of the overall polychaete diversity and richness patterns from this study for this region indicate a strong geographic variation with increasing depth and distance from the shore. Additionally, the environmental gradients observed play a major role in shaping the spatial distribution of polychaete communities in this region.
77

Uniaxial behaviour of suction caissons in soft deposits in deepwater

Chen, Wen January 2005 (has links)
Suction caissons are a cost-effective alternative to traditional piles in deep to ultradeep waters. No design rule has been available on the axial capacity of suction caissons as part of the mooring system in soft sediments. In this research, a series of centrifuge tests were performed using instrumented model caissons, to investigate the axial capacity and radial stress changes around caissons during installation, consolidation and vertical pullout in normally consolidated, lightly overconsolidated and sensitive clays. Total pressure transducers instrumented on the caisson wall were calibrated for various conditions. The radial total stress acting on the external wall varied almost linearly during penetration and extraction of the caisson, with smaller gradients observed during post-consolidation pullout. Minimum difference was found in the penetration resistance and the radial total stress for caissons installed by jacking or by suction, suggesting that the mode of soil flow at the caisson tip is similar under these two types of installation. Observed soil heave showed that the soil particles at the caisson tip flow about evenly outside and inside the caisson during suction installation. Comparison was made between measurements and various theoretical predictions, on both the radial stress changes during caisson installation, and the radial effective stress after consolidation. Significant under-predictions on excess pore pressure changes, consolidation times and external shaft friction ratios were found for the NGI Method, based on the assumption that the caisson wall is accommodated entirely by inward motion of the clay during suction installation. Obvious over-predictions by the MTD approach were found in both stress changes and shaft capacity of the caissons. A simple form of cavity expansion method was found to give reasonable estimations of stress changes and post-consolidation external shaft friction. A model for predicting the penetration resistance of suction caissons in clay was evaluated. Upper and lower bound values of external shaft friction ratio during uplift loading after consolidation were derived. Uplift capacity of caissons under sustained loading and cyclic loading were investigated, revealing approximately 15 to 30% reduction of the capacity compared to that under monotonic loading. External shaft friction ratios and reverse end-bearing capacity factors were both found to be significantly lower than those under monotonic loading
78

Physiology and molecular ecology of chemolithoautotrophic nitrate reducing bacteria at deep sea hydrothermal vents

Voordeckers, James Walter. January 2007 (has links)
Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Microbiology and Molecular Genetics." Includes bibliographical references (p. 102-114).
79

Geologic history of the abyssal benthos evidence from trace fossils in Deep Sea Drilling Project cores /

Ekdale, Allan A. January 1974 (has links)
Thesis (Ph. D.)--Rice University, 1974. / Includes bibliographical references (leaves 112-125).
80

The role of marine renewable energy structures and biofouling communities in promoting self-sustaining populations of non-native species

Macleod, Adrian K. A. January 2013 (has links)
Novel environments and biological communities created by the large-scale deployment of Marine Renewable Energy Devices (MREDs) have the potential to promote the spread of non-native species (NNS). Knowledge of how community composition resident on MREDs is shaped by geography, local hydrodynamics and the duration of deployment, will clarify how these technologies will interact with natural habitats, including the provision of suitable habitat for NNS. A network of navigation buoys was used to study biofouling communities in areas proposed for MRED deployment. Significant differences in community structure were observed in different geographic areas. A significant reduction in number of taxa present and community wet-weight was observed where buoys were deployed in greater tidal flow rates. However, overall community composition was not significantly different between ‘high’ (>1 ms-1) and ‘low’ (<1 ms-1) flow areas and for buoys deployed for different time durations (1-7 years). These finding have important implications for the longevity of devices and their interaction with natural habitats, including proposed ‘artificial reef’ effects. In total five non-native species were identified on the buoys sampled, supporting the need to monitor MREDs as the industry grows. Hydrodynamic and biotic features of the epibenthic communities were used to predict the presence of the most prevalent NNS, the amphipod Caprella mutica, in addition to other native amphipod species. Caprella mutica presence was found to be significantly affected by increasing flow speed compared with the native amphipod Jassa herdmani. Behavioural flume studies investigating flow-related processes governing the presence of non-native amphipods supported these findings. This study details how the hydrodynamic and biological environments created by MREDs determine their suitability for the establishment of self-sustaining populations, and therefore their dispersal potential for NNS. These findings inform design criteria and management options to minimise the biosecurity risk that these structures will pose as the industry expands.

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