Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (p. 168-204).

Thesis (D.Min.)--Liberty University, 2009. / Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Six maps included in back pocket. Vita. Abstract. Includes bibliographical references (leaves 115-116). Also available via the Internet.

Thesis (Doctoral)--Umeå University, Sweden, 1995. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008. / Lowell, Robert, Committee Chair ; Newman, Andrew, Committee Member ; Peng, Zhigang, Committee Member.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 155-174). Also available on the World Wide Web.

Ultra-slow spreading ridges have a full spreading rate of less than 20 mm/yr, and show deviations from the fundamental characteristics identified at faster spreading rates; however, they are poorly studied compared to faster spreading ridges. In this thesis we aim to build on previous studies in order to further characterise the unique processes occurring at the ultra-slow spreading Southwest Indian ridge (SWIR). This is an exploratory study utilising novel and existing bathymetry, gravity, video imagery data to understand tectonic and volcanic processes along the ridge crest from triple junction to triple junction. We conduct a series of studies which focus on the axial valley morphology, large seamount morphology, the distribution of small seamounts and large seamounts on the ridge, and admittance studies. We show that the long wavelength trends in geophysical data, geochemical data, and axial valley morphology are well correlated. These variations reflect along-axis changes in the crustal and mantle structure, governed by the thermal structure of the ridge. Seamounts provide important morphological evidence of the volcanic and tectonic processes beneath the Earth's surface. We use detailed morphological investigations to show that volcanic and erosional processes on six large seamounts are controlled by the local faulting and melt migration mechanisms. We investigate the distribution of seamounts on the ridge using a numerical algorithm, and demonstrate a lower seamount density than faster spreading ridges. We show that the seamount population statistics vary along the ridge due to changes in the degree of partial melting, magma conduit availability, and melt focussing mechanisms; the locations of three proximal hotspots coincide with increases in the estimated magmatic flux. Finally, best fit elastic thicknesses are determined using a 3D windowed admittance technique, which was tested using synthetic data. We construct a combined convection-flexure model to account for misfits between the observed data and existing flexural theoretical models. The average elastic thickness varies between 7 km and 12 km, and we show a strong dependence on spreading rate.

Hydrothermal vents are deep-sea hot springs. Vents are home to luxuriant assemblages of animals that colonize the warm venting fluids. High biomass is fed by microbes that use hydrogen sulphide and other reduced chemicals in the vent fluid as an energy source to fix inorganic carbon. Individual vents may persist for a few years to several decades. The specialized animals must find new vents, cope with changing fluid conditions and foster their offspring. The composition and structure of vent communities vary in space and time. My research at Axial Volcano, a seamount on the Juan de Fuca Ridge (JdFR) in the northeast Pacific, aims to find pattern in this variation and to propose viable hypotheses of the mechanisms driving the patterns. Axial is an ideal location as it supports mature vent fields (venting for over 15 years) and young, developing vents initiated by a volcanic eruption in 1998. Thus, I was able to study both temporal and spatial variation in vent communities at the same site and relate patterns of developing assemblages to patterns observed at longer-lived vents. Pattern detection is the first critical step in any community ecology study as it justifies and focuses the search for process. I have refined existing statistical methods and developed novel techniques to test for pattern in vent species distributions and abundances. I modified an existing null model approach and showed that species distributions among sixteen vents differ from random in a long-lived (>15 years) vent field. I also developed a novel null model to confirm that initial patterns of community assembly seven months following the Axial eruption differ from random recruitment of species and individuals to new vents. My description of the community response to the Axial eruption is the first quantitative report of patterns of vent colonization and succession. My work documents that new vents are colonized quickly (within months) and that initial assemblages are variable. However, rapid community transitions and species replacements within the first few years cause new assemblages to resemble mature vents by 2.5 years post-eruption. Three habitat factors correlate with the development of nascent vent assemblages: the recruitment timing of the tubeworm Ridgeia piscesae post-eruption, vent age and vent fluid hydrogen sulphide content. I also describe a new polynoid polychaete discovered colonizing the new vents in high densities. My major contribution to vent community ecology is revealing species patterns through extensive sampling and rigorous statistical methods. These patterns are a necessary step towards understanding the processes that structure vent communities: they direct future research effort towards the key species and generate hypotheses to be experimentally tested. My work also elucidates how vent species respond to habitat destruction and creation, which is critical information for effectively managing Canada's only hydrothermal vent Marine Protected Area on the JdFR. / Graduate

This thesis presents inference for the multiple linear regression model Y = beta_1 x_1 + ... + beta_p x_p + e after model or variable selection, including prediction intervals for a future value of the response variable Y_f, and testing hypotheses with the bootstrap. If n is the sample size, most results are for n/p large, but prediction intervals are developed that may increase in average length slowly as p increases for fixed n if the model is sparse: k predictors have nonzero coefficients beta_i where n/k is large.

This work seeks to explore current ecological theory through application to communities inhabiting hydrothermal vents. This thesis aims to: (1) add to and synthesise knowledge of species and their distributions at the intra- and intersegment scale; and (2) evaluate vent community patterns and speculate on processes. Samples used are submersible grabs of low temperature (<60°C) tubeworm assemblages on basalt and sulphide surfaces. Species abundances and distributions on three segments of the Juan de Fuca Ridge (Axial, Cleft, and CoAxial) are described. Community descriptors such as species density, Simpson's and the Shannon-Wiener diversity indices, evenness, species richness, species abundance-distribution models, species percent-average relative abundance and density are used. Vent community structure is compared among segments using these descriptors, visual descriptions, pairwise correlations, Friedman tests of distributions, cluster and correspondence analysis, rarefaction, complementarity, a test for saturation, and Whittaker's beta diversity. Vent community composition on Axial, north Cleft, and CoAxial is similar at the segment and inter-segment scale. The limpet Lepetodrilus fucensis is the most abundant species at all sites. Differences among communities are best seen temporally, not spatially. Senescent communities can be distinguished from active vent assemblages. Pioneer communities, however, are statistically indistinguishable from intermediate communities when sampled two or more years post-eruption. Axial and Cleft species dispersion fits the core-satellite hypothesis. The exceptions are the polynoids Branchinotogluma sp., Lepidonotopodium piscesae, and Levensteiniella kincaidi, which are widespread and present in low local abundances. Both local and mesoscale regional mechanisms explain observed local diversity. Spatial isolation, not habitat differences, influences between-habitat diversity (beta diversity) on Axial, Cleft, and all three segments combined. Meiofauna are important for species richness estimates, identifying differences among structurally similar communities, and understanding input/output between vents and the deep-sea. Measurements such as species richness and diversity indices may be poor at distinguishing among vent communities because vents are species poor and uneven. The Michaelis-Menten, Jackknife 2, and Chao 2 nonparametric vent species richness estimators perform well with small samples. Vent communities should be compared to habitats of similar diversity and evenness as well as disturbance and productivity regimes. Candidate comparison communities include communities in early successional states, selected taxocenes such as carabid beetles on fungi, or high disturbance and/or low diversity systems like the rocky intertidal, organically polluted sediments and oxygen minimum zones below upwelling regions in the deep-sea. / Graduate