The rise in global energy demand has motivated the exploration and production of oil and gas in increasingly challenging marine environments and there is a continuous risk of accidental oil spills. One of the many fates of spilled oil is deposition on the seabed, which has been extensively studied following the Deepwater Horizon oil spill. However, post-depositional fates of oil in sediments are not well understood. Similarly, the effects of chemical dispersant on oil fate are currently under investigation as their overall contribution to mitigating oil spills environmental impacts remains debated. This project aimed to evaluate the potential for spilled oil to entrain marine sediments and the effects dispersant application had on the process under three transport regimes; (1) post-depositional transport via oil-sediment aggregate deposition in deep-sea sediments, (2) percolative transport in intertidal sands and (3) advective pore-water transport in intertidal and subtidal sands. Investigations into the sorption dynamics of two polyaromatic hydrocarbons in sediment-dispersantseawater systems were also undertaken to evaluate the influence of dispersant application on sorption of hydrocarbons to sediments. Finally, the effects of oil exposure at in situ conditions of pressure and temperature on sediment bacterial community composition were investigated. Oil transport experiments revealed that the tested regimes resulted in significant entrainment of hydrocarbons in marine sediments. Dispersant application resulted in enhanced oil entrainment into sands but not in silts and this effect depended on the water-solubility of hydrocarbons. Watersoluble components were less affected by dispersant than less water-soluble ones. Investigations into sediment bacterial responses to oil exposure at in situ conditions of pressure and temperature revealed a significant effect of both variables on diversity and community composition, highlighting the importance of conducting deep-sea microbial studies at conditions as close to in situ as possible.

Seagrasses provide an important habitat for gillfish, crustacea and migratory birds. Extensive losses of seagrass in the Northern Hemisphere have occurred since the 1930's in what has been described as a 'wasting disease'. More recently, point-source contamination by nutrient inflows, herbicides (anti-fouling agents used on commercial shipping), heavy metals and fresh water inflows have helped explain localised losses of seagrass amounting to 20% in the case of Adelaide's metropolitan coastline, South Australia. However, losses of seagrass acreage have also occurred in regions that are far removed from anthropogenic activity and these are less easily explained by pointsource contamination. Intertidal seagrasses, such as Zostera muelleri, are subjected to environmental pressures imposed on them by the marine and terrestrial environments. For the purpose of this thesis, the intertidal environment is regarded as a complex of several components or micro-environments, each imposing a selective pressure or stress upon seagrass. The many stress factors create a tolerance zone in which Z. muelleri can survive. Zostera muelleri has adapted its physiology and biochemistry to the selective pressures that operate within the intertidal region. Zostera muelleri's internal leaf morphology has many gas storage compartments (lacunae) that extend from the leaves to the roots of the plants and its photosynthetic biochemistry has also adapted to the intertidal region enabling the sequestering of carbon under conditions of high irradiance and temperatures. It is evident from the literature that the survival of intertidal seagrasses requires effective photosynthesis. It is also evident that events that interfere with the synthesis, translocation and release of photosynthesised oxygen from the roots of Z. muelleri will compromise seagrass survival. The present study has revealed that herbicides, used in broad- acre farming, can be transported to the intertidal environment and negatively impact upon Z. muelleri. Extensive studies by others have shown that transport mechanisms, such as 'spray drift' and 'run-off', can move herbicides from their point of usage. However, 'dust' (wind-eroded soil ) as a transport mechanism for herbicides to the intertidal environment is less well studied. This is surprising, inasmuch as there is a known rate of pedogenesis in Adelaide of five to ten tonnes per km2 per annum from the accretion of dust. Results of the present study suggest that farmed soils of the Yorke Peninsula have a range of potentials to form fine particulate matter ('dust') and this potential is likely determined by the soil type and farming practices. Soil surface applied herbicides, such as 2,4-D, are 'lost' from land at 5% of the applied rate while soil-incorporated herbicides, such as treflan (trifluralin), are lost at 1.5% of the applied rate. Indeed, such herbicides can be transported as dust for tens to thousands of kilometres. Instrumental analytical techniques used in the present study have detected 2,4-D, trifluralin and sulfonylurea herbicides on whole soil. Additionally, 2,4-D- like chemicals have also been detected in whole soil and in dust obtained from whole soil. Bioassay techniques using Z. muelleri have shown that its photosynthetic pathways are negatively impacted upon by micromolar concentrations of 2,4-D that are similar to the known losses of this herbicide from land. It is concluded that, at these concentrations, 2,4-D acts as an auxin, up-regulating growth in affected plants. Such up-regulation is unlikely to be problematic in terrestrial plants since gas flows to the external environment are largely controlled by stomata. However, seagrasses lack stomata and the auxin-like activity of 2,4-D appears to have a negative impact on Z. muelleri. This is probably caused by an up - regulation in oxygen production and a subsequent oxygen-inhibition of a key enzyme ( ribulose 1,5- bisphosphate carboxylase, RUBISCO ) used in the carbon-sequestering photosynthetic process. The proposed inhibition of RUBISCO is then likely to cause a carbon deficit and a subsequent energy deficit within affected plants. One interpretation of the results presented is that Z. muelleri simply outgrows its intertidal environment after a transient exposure to an auxin-like concentration of 2,4-D. With increasing use of auxin-like herbicides, and the associated increasing stress imposed on photosynthetic processes, it is likely that further negative impacts will occur on intertidal seagrass species. Continued depletion of seagrass acreage will further adversely affect fishing yields unless appropriate measures are not taken. Closer collaboration between regulators, farm managers and herbicide manufacturers is now necessary in order to minimise the negative impact of herbicides on intertidal species. / Thesis (M.App.Sc.)--School of Earth and Environmental Sciences, 2005.

Samples of benthic organisms off the coast of Oregon, taken from depths varying from 50 to 2900 meters, have been analyzed in terms of diversity at a given station, and similarity and ecological distance to other stations. Estimates of epifauna abundance were also made. In the analysis an important distinction is made between diversity, abundance, and variety indices; the three measures are considered independent pieces of information relevant to the ecological structure of the population of interest. Two types of sampling gear were used. Large epifauna were sampled with a beam trawl. Polychaetous infauna were sampled with an anchor-box dredge. The diversity index chosen is Simpson's index; the measures of similarity and ecological distance are related. These measures are preferred because of their ease in calculation and basic simplicity. In addition these measures may be interpreted as estimates of well-defined population parameters (as Simpson has pointed out) which have straightforward probabilistic interpretation. A valid measure of diversity is one piece of relevant information necessary for elucidating the sufficient parameters of ecological systems. Therefore the methodology presented has broad application to studies of population structure. / Graduation date: 1970

This thesis is an account of my explorations into the field of natural products chemistry. These investigations led to the discovery of several novel secondary metabolites isolated from the marine cyanobacterium Lyngbya majuscula. In addition, biosynthetic investigations were undertaken using stable isotope-labeled precursors. The dominant role that NMR spectroscopy plays in the field of natural products chemistry has led to the development of several novel pulse sequences. Hectochlorin was discovered during a phytochemical investigation of a cultured L. majuscula originally collected off the coast of the Caribbean Island, Jamaica. The absolute stereochemistry was determined by X-ray crystallography. Through a series of biological evaluations, this compound was found to stimulate actin polymerization. The jamaicamide class of compound was isolated from the same organism that yielded hectochlorin. The structures were elucidated utilizing a variety of NMR methods, including a newly developed pulse sequence. Because the producing organism was in culture, a biosynthetic pathway investigation ensued to elucidate the carbon framework in jamaicamide A. The marine natural product barbamide is intriguing due to the incorporation of a trichloromethyl group into its molecular constitution. Further investigation into the timing of the chlorination reaction has been pursued. In addition, the isolation of dechlorobarbamide and the determination of the absolute stereochemistry assignment of barbamide was accomplished. A reevaluation of the stereochemistry of antillatoxin necessitated a correction in the original assignment. Four antillatoxin stereoisomers were obtained from a collaborator and found to possess differing levels of biological activity. The three dimensional solution structures of these isomers were evaluated in an effort to understand the role these stereochemical features play in the observed bioactivity. The structures were determined utilizing NMR-derived constraints applied to molecular modeling calculations. The development of two new pulse sequences for the determination of long-range heteronuclear coupling constants was also accomplished. The 1,1 ADEQUATE experiment was modified to yield an ACCORDIAN experiment which can be optimized to observe of a wide range of ��J[subscript cc] couplings. This new experiment is demonstrated for a model compound as well as for the new marine natural product jamaicamide A. / Graduation date: 2002

My investigations of the natural products of marine algae have resulted in the discovery of several new secondary metabolites. Bioassay-guided fractionation led to the isolation of these new compounds and spectroscopic analysis was utilized in their structural characterization. Two new and potent antimitotic metabolites, curacins B and C, were isolated from a Curacao collection of Lyngbya majuscula. In addition, four curacin A analogs were prepared by semisynthetic methods. The structures of the new curacins and the curacin A analogs were determined by spectroscopic analysis in comparison with curacin A. The biological properties of the new natural products and synthetic derivatives of curacin A were examined. Investigations of another Curacao collection of L. majuscula revealed a new cytotoxic lipopeptide, microcolin C. Microcolin C was found to have an interesting profile of cytotoxicity to human cancer-derived cell lines. A new metabolite, vidalenolone, was isolated from an Indonesian red alga Vidalia sp. The structure of this new cyclopentenolone-containing compound was determined by a combination of spectroscopic methods. Filamentous cells isolated from female gametophytes of the brown alga Laminaria saccharina were cultured in flasks or bioreactors. These cultures produced a variety of w6-lipoxygenase metabolites: 13-hydroxy-9,11-octadecadienoic acid (13-HODE), 13-hydroxy-6,9,11,15-octadecatetraenoic acid (13-HODTA), and 15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE). Five oxidized anandamide derivatives were prepared from anandamide through autoxidation in an exploration of ligand binding to the cannabinoid receptor. Their structures were determined by a combination of NMR spectroscopy and GC-MS. The cannabinoid receptor binding affinity of these derivatives was evaluated. This study revealed the following trend in activity: anandamide > 15- > 9- > 8- > 11- > 5-hydroxyanandamide. / Graduation date: 1998

Marine algae have been recognized as a rich resource of new and unusual organic molecules with diverse biological properties. The current need to develop new antifungal, anticancer, antibiotic and antiviral drugs has led to an intense research effort into the discovery, isolation and structure determination of potential medicinal agents from marine algae. In the past two years, I have participated in a drug discovery program designed for antitumor, antifungal and other agents of potential pharmaceutical utility from the marine cyanobacterium Lyngbya majuscula. This research utilized modern chromatographic and spectrochemical techniques including 2D NMR spectroscopy. Brine shrimp toxicity guided the fractionation that led to the discovery of the biologically active compound kalkitoxin from a Curacao Lyngbya majuscula extract. The structure of this new thiazoline ring-containing lipid was determined spectroscopically by interpretation of 2D-NMR experiments, including heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple-bond coherence spectroscopy (HMBC) and ��H-��H COSY at room temperature and elevated temperature. Kalkitoxin shows modest molluscicidal toxicity, good brine shrimp toxicity and extremely potent ichthyotoxicity. From the same extract of Lyngbya majuscula, I also isolated two other secondary metabolites, malyngamide J and malyngamide L. The structures of these new compounds, including stereochemistry, were determined by spectroscopic techniques including 2D-NMR experiments and by comparison with other known malyngamides. / Graduation date: 1997

I have participated in a drug discovery program designed to screen marine algae for inhibitors of cancer-related enzymes, antitumor compounds, antiinflammatory substances, and other agents of potential pharmaceutical utility. Over 1,500 lipid and aqueous extracts of marine plants and animals were surveyed for biomedical potential. Assays designed to screen extracts for new types of marine toxins have served to guide the isolation and identification of biologically active compounds. Extracts of the Oregon marine alga Constantinea simplex were found to contain a mixture of constanolactones, and lactonized cyclopropyl-containing oxylipin metabolites that logically derive from arachidonic and eicosapentaenoic acids. Spectroscopic analysis and chiroptical measurements of the natural products and various synthetically produced derivatives afforded the structures of seven structurally related compounds. Nakienones A-C and nakitriol, a series of reactive cytotoxic metabolites, were isolated from dead and necrotic branches of stony coral (Acropora sp.) which were completely covered with a gray-black mat of cyanobacteria (Synechocystis sp.). Their structures were determined spectroscopically by interpretation of 2D-NMR experiments, including heteronuclear multiple-bond coherence spectroscopy (HMBC) and 2-D nuclear Overhauser exchange spectroscopy (NOESY), and by comparison with model compounds. Bioassay-guided fractionation of the organic extract of a Curacao Lyngbya majuscula organic extract led to the isolation of an extremely potent brine shrimp toxin with antiproliferative activity. The structure of this new thiazoline ring-containing lipid, curacin A, was deduced from spectroscopic information and comparison of products obtained from chemical degradation of the natural product with the same substances prepared by synthesis. Curacin A is an antimitotic agent that inhibits microtubule assembly and the binding of colchicine to tubulin. In addition to curacin A, a potent new ichthyotoxic depsipeptide (antillatoxin), a new malyngamide derivative, and an unusual molluscicidal compound have been isolated from this alga. / Graduation date: 1995

Oil and gas exploration and production activities in deep and ultra deep waters in hostile environments necessitates the need to develop innovative riser systems capable of ensuring transfer of fluids from the seabed to a floating vessel and vice versa, with little or no issues with respect to influences of environmental loads and vessel motions.The design of the riser system must focus on different types of loading and load effects than for traditional water-depth. A variety of different riser concepts are proposed, both with respect to geometric shape and selection of materials.In the last few years, steel catenary risers have been a preferred riser solution for deep-water field developments due to its simple engineering concept, cost effective, flexibility in using different host platform and flexibility in geographical and environmental conditions. In this report, a case study considering a steel catenary riser operating in 1000 m water depth was conducted. The riser was subjected to extreme environmental conditions and static and dynamic response analyses were performed by the computer program RIFLEX.Last, parametric study is carried out to investigate the effects of parameter variation based on some parameters like current profiles, mesh density, wall thickness and so on. These parameters have significant effect on the structural response, especially in the touch down region.

Subject of the present study was the investigation of the wake behind stepped circular cylinders. Experiments were performed using particle image velocimetry (PIV). Cylinder models with diameter ratios D/d=1, D/d=6/5 and D/d=2 were investigated at Reynolds numbers Re_{D}=2243.6, Re_{D}=12820.5 and Re_{D}=51282.1 with respect to the large diameter. Of main interest were the influences of step size and Reynolds number on the formation of vortex shedding cells. Mean flow characteristics and instantaneous captures of the flow field were analyzed in order to gain insight into vortex development in the wake. Spectral analysis was applied to obtain information on the number of forming vortex shedding cells.It was found that an increase in Re_D leads to a decrease in eddy formation length $L_f$. At the largest investigated Reynolds number, turbulence gained strong influence on the flow characteristics. An increase in stepsize leads to the development of a large and a small diameter wake with distinct eddy formation lengths L_{f,L} and L_{f,S}.Due to a mismatch in vortex shedding frequencies in the two wakes, vortices that come out of phase connect to subsequent vortices on the same side of the step. This occurs more frequently for a higher diameter ratio.Several vortex shedding cells were found in the wake of the step cylinders, their number increasing with the step size and differing for different Reynolds numbers.The wake behind step cylinders was discovered to be strongly three-dimensional. I order to complete the information about flow characteristics, measurements were performed in several parallel vertical and horizontal planes along the cylinder.PIV proved to be a good method for the investigation of flow features in the wake of step cylinders for the chosen model dimensions and Reynolds numbers.

Due to the substantial increase in oil and gas activities in Polar areas the demand for ice strengthen vessel has increased greatly. This increase in demand has highlighted the importance of designing ice strengthened ship structures that are more producible and maintain adequate safety and integrity. In order to encounter these new challenges, the international association of classification societies (IACS) has developed unified regulations for the designing of ice strengthened ship. In addition to these requirements, most of the classification societies have their regulation for design of polar ships. Stiffened plates are the basic structural building blocks of ships. So, the study mainly explores the plastic response of stiffened plate subject to lateral ice loads. The Non Linear Finite Element Method (NLFEM) is extensively used to study the plastic behavior of stiffened plates. The Abaqus non linear finite element program is used in this study.The aims of the study are to investigate the validity of the limit state equation employed in the IACS new Unified Requirements for Polar Ships [6], investigate the membrane effect at large deformation, determine the ALS design load, and assess limit loads when fracture in plating likely to take place. The study also focuses on the warping effect of unsymmetrical sections and the effect of end brackets on the lateral load carrying capacity of the stiffener. The effect of mid-span tripping bracket on the load deflection behavior of L and T stiffeners is also studied. In particular, the study focuses on the behavior of inclined T and L stiffener. As ships move forward by crushing ice, sides of ships’ bow come across with ice initially. To design ice strengthen vessel, it’s very important to understand the behavior of ships’ side structure subjected to ice loads. So, this study extensively focuses on the non-linear finite element analysis of ships’ side structure subjected to ice loads. Normally, ship design rules are based on the behavior of single frame subjected to loads. It’s reasonable to consider frames singly under the uniform loading but in case of ice loading which is non uniform, the behavior of the structure obtained from single frame based design does not accurately represent the true behavior of the structure. The load-deflection characteristic of frames in isolation, frames as part of a ½+1+½ frames and frames as part of a grillage subjected to unsymmetrical loading is studied. As, stiffeners in the side structure of ships’ bow are not normally perpendicular with shell plate, the lateral capacity of frames as part of a ½+1+½ frames and as part of a grillage is obtained for inclined stiffener.The analyses in this study cover the full range of stiffener behavior from elastic, through yield, through the formation of initial mechanisms, through large deformations. The parameters considered for the analyses are: •frame profile: Angle, Tee•frame span•load length: patch (transverse), uniform (longitudinal)•web thickness•end brackets: with, without•Angle of inclination of stiffener web with the plate flange•Tripping bracket at mid span