Neutral microsatellite markers were used to analyse genetic variation in three demersal finfish species, whiting (<i>Merlangius merlangus</i>) haddock (<i>Melanogrammus aeglefinus</i>) and anglerfish (<i>Lophius piscatorius</i>) in the north east Atlantic.  For each species samples were collected from the North Sea and west of the British Isles while geographically distant samples were also collected from Icelandic waters.  In the case of the anglerfish study samples were also taken from the Bay of Biscay and the Mediterranean Sea. Whiting appears to show the highest level of structuring in the north east Atlantic with samples from Icelandic waters being significantly divergent from samples on the continental shelf.  Just one of the continental shelf haddock samples, the Irish Sea, showed evidence of divergence from the Icelandic samples.  This general lack of divergence between Icelandic and continental shelf haddock is most likely reflective of a combination of relatively recent isolation and large effective population sizes (N_e).  Apart from a few significant results (P&lt;0.05) continental shelf haddock and whiting conspecific populations tended to show little divergence.  This would also appear to be due primarily to large effective population sizes and a relatively recent isolation.  <i>L. piscatorius </i>showed a total absence of genetic differentiation between all the Atlantic samples which is consistent with the long distance movements associated with this species.  There was however strong evidence of divergence between the Atlantic and Mediterranean anglerfish samples. Comparing the results of the molecular studies presented here with non molecular approaches to determining population structure highlights the importance of combining information from several approaches if a sustainable management plan is to be put in place for commercial species.

Although the deep seafloor represents the largest biome on the planet, its benthos has remained understudied because of logistical difficulties and the cost of access. Long-term, time-series information is needed to understand the small-scale and inter-annual variations required to build predictive models of ecological processes. In this thesis, we employed three newly developed observatory systems, which coupled in situ imagery with environmental data to examine ecological processes in three deep-sea benthic habitats: 1) Megabenthic surface bioturbation on the upper continental slope (400m depth) near Barkley Canyon, off Vancouver Island, 2) Thermal response in polynoid taxa at Main Endeavour Hydrothermal Vent Field (2,100m depth) on the Juan de Fuca Ridge and 3) Behavioural rhythms and bacterial mat growth in Saanich Inlet (100m), a fjord in southern Vancouver Island. To ensure that the imagery collected was useful for quantitative hypothesis testing by a single observer, we employed a step-wise methodological approach, taking advantage of previously acquired knowledge and, in two cases, the interactive nature of cabled observatories, to tailor the sampling frequency to the variables of interest. The application of a diverse array of image analysis techniques and statistical models, easily extendable to other systems, was also demonstrated. The results obtained while conducting the protocol optimization phase described organism and community level responses to environmental variations. Using a remotely operated camera connected to the NEPTUNE Canada cabled observatory, we estimated that total surface sediment turnover by sea urchins and flatfish, the two most important megafaunal contributors, within the field of view required 93 to 125 days in the absence of phytodetrital accumulations. When employing a camera-temperature array system, the most frequently observed mobile megafaunal species, two polynoid taxa, were not found to exploit the recorded temperature gradients suggesting that they employed a thermoconforming strategy to cope with thermal variability. In the aphotic, mostly hypoxic benthos of Saanich Inlet, strong behavioural entrainment, neither diel nor tidal, was not observed. However, significant changes in species composition and bacterial mat substratum coverage were observed following intrusion of oxygenated waters, a yearly event resulting from specific bathymetric features and oceanographic dynamics of this fjord. A Bayesian approach to data modeling was found to be particularly well suited to protocol optimization purposes as complex models could be more easily and intuitively implemented. The further application of our multi-disciplinary step-wise approach will reduce the time required to approach new ecological questions and improve integration of studies carried in different locations. By carefully choosing ecosystem functions which can be used as indicators of change, the current baseline state of the system can be described. Informed long-term monitoring initiatives can then be implemented in order to quantify global ocean responses to anthropogenic factors such as climate change, resource extraction or eutrophication. / Graduate

Thesis (Ph.D.)--University of Western Australia, 2005.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 75-80).

Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on July 20, 2009). Includes bibliographical references.

Deep-sea systems are understudied compared to any other ecological system on Earth, but they are important for ecosystem functioning and services. The deep sea is important in the climatic regulation of Earth, and it is a new frontier for resource provisioning for humanity. Impacts, such as increased carbon emissions and deep-sea fishing and mining will likely influence the system, but these effects are not well understood. To recognise these impacts, common patterns in community structure need to be understood. This study aims to assess community structure in the deep sea by looking at patterns in body size and biodiversity. It uses polychaetes (bristle worms) as a study group as they are the most abundant group in the benthic macrofauna in terms of density and play key roles in the food web. Body size is an important component of the community structure, as body size is correlated with many other traits of the organism, from physiological rates (e.g. heart or breathing rates) to population dynamics (e.g. production rates or population abundances) and species richness. It is thought that body size of deep-sea (endo)benthic organisms declines with increasing depth, which is often related to food availability which itself declines with increasing depth. Many contradictory results on body-size change with increasing depth, however, have been reported, including no change, increasing, or a parabolic relationship. It is demonstrated here (Chapter 2) that there is much variety in body-size estimates between different geographic regions and taxonomic groups. These differences can ultimately influence the predictions of other traits, and might hint at what might happen in changing climatic conditions. It sets the basis to argue that there should be a focus on explaining why there are differences, instead of focusing on finding a general trend for organisms in all geographical regions. Furthermore, it is unlikely that food availability alone can explain a change in body size. An alternative explanation is offered (Chapter 3), where habitat complexity is shown to influence body size. Sponge density, in the form of habitat complexity, can have a structuring effect on the community potentially through the loss of spicules that add complexity to soft-sediments, and this in turn can influence body size of organisms. Deep-sea community structure in terms of family richness has been studied at local spatial scale. Fewer studies have been performed on regional spatial scale and these studies lack extensive sampling coverage of environmental gradients. Here (Chapter 4), the first study is presented on the maintenance of deep-sea family composition on regional scale with high sampling coverage along a variety of environmental gradients. It is shown that energy (food) availability, habitat complexity, and long-term temperature are important in influencing the polychaete distribution in this region. It is shown that there is an unusual high proportion of an opportunistic group, the Capitellidae, present in the study area. Biodiversity is important for the maintenance of ecosystem functioning, but human impacts result in the restructuring of biodiversity. The first deep-sea biodiversity - ecosystem functioning relationship for macrofauna is presented (Chapter 5). It is shown that there is a positive and saturating relationship between biodiversity and ecosystem functioning. However, fishing intensity seems to influence this relationship by potentially affecting secondary biomass production, abundance and taxonomic and functional diversity measures. It is suggested that as the disturbance of fishing negatively impacts taxonomic and functional evenness, a system is created where opportunistic species are dominant, like communities found in disturbed areas such as under fish farms. This will have consequences for the state of the system and energy transfer to trophic levels higher up.

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.

During July 1974, two reversed deep seismic sounding (DSS) profiles extending about 75 km were recorded in the Explorer Ridge region of the northeastern Pacific, one parallel and the other perpendicular to the ridge. A two-ship operation was used to record near-vertical incidence to wide-angle reflected waves and refracted waves with penetration from the ocean bottom to the upper mantle. Signals from six individual hydrophones suspended at 45 m depth from a 600 m cable trailed behind the receiving ship were recorded in digital form. The shooting ship detonated charges ranging from 2.3 kg to 280 kg and recorded the direct arrival plus the WWVB time code. Processing of the data recorded at distances beyond 4 km included demultiplexing, stacking, and filtering. Before the data were presented in record section form, traveltime corrections were made for topography and shot distance, and amplitude corrections were made for amplifier gain, charge size, and spherical spreading. The interpretation procedure consisted of two steps. A homogeneous, layered velocity-depth model was initially constructed from first arrival traveltime data. The p-A curve corresponding to this model was then altered until an amplitude fit was obtained using synthetic seismograms. Weichert-Herglotz integration of the resultant p-A curve produced the final velocity-depth model. This traveltime and amplitude interpretation required the introduction of velocity gradients into the model. The profile run across the ridge showed no anomalous behaviour as the ridge was crossed; the profile on the Juan de Fuca plate, paralleling the ridge, exhibited traveltime branch offsets and delays. These have been interpreted as due to faulting with a. vertical component of offset of about 5 km. The reversed upper mantle velocities are 7.8 and 7.3 km/s in directions perpendicular and parallel to the ridge. Anisotropy is proposed to explain these different velocities. Compared with crustal sections from other ridge areas, the data require a thick "layer 3" (up to 7 km) near the ridge crest. The total depth to the base of the oceanic crust varies between 10 and 12 km except in the faulted region. The results of this study favor the hypothesis that Explorer Ridge is presently an inactive spreading center. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Chemosynthetic ecosystems in the deep sea hold vast amounts of untapped energy that until recent decades have been largely unobtainable. With the growing demand for resources and constant advancements in technology, these ecosystems and the diverse communities that inhabit them now face increasing pressure from anthropogenic exploitation activities. Thus, employing effective management and conservation strategies to avoid devastating these long-lived communities is imperative. However, effective protection hinges on a thorough understanding of these ecosystems. Here, I present a number of studies conducted on methane seeps along the Pacific Costa Rican Margin (CRM), exploring various ecological dynamics and highlighting the unique biodiversity thriving there. These studies aim to address gaps in our knowledge regarding the “sphere of influence” surrounding chemosynthetic methane seeps, providing insights into the flow of energy within these ecosystems, their spatial dynamics and how they interact with background deep-sea habitats. In Chapter 2, I employ a novel seascape approach using systematic surveys of several actively seeping areas to characterize the seep communities and delineate distinct seep zones, testing for inter- and intraspecific differences in community structure. Our results reveal nuanced patterns in α and β diversity between sites and across different zones, driven largely by depth. Additionally, I identify transitional zones extending the spatial extent of the seeps by up to 300 meters, emphasizing the “sphere of influence” surrounding these ecosystems. / Biology

Efficient exploitation and conservation of the oceans poses great technological challenges for scientists and engineers who must develop materials, structures and equipment for use in harsh environment of the oceans. For the applications of materials in marine environment, knowledge of the corrosion properties is essential for selection purposes. Presently, effort is being devoted to exploit deep-sea mineral resources. Deterioration of materials in the deep sea is due to the cumulative effect hydrostatic pressure, temperature, pH, dissolved oxygen, salinity and sea current. For the first time, in-situ corrosion measurements on the effect of deep sea environment on some metallic and composite materials were carried out at depths of 500,1200,3500, and 5100 m for 168,174 and 174 days of exposure in the Indian Ocean. Corrosion rate was obtained from weight loss measurements (mm/year) and surface morphology of as-exposed and cleaned specimens of the above materials was studied under scanning electron microscope and ED AX. Galvanic coupling of steel with zinc, magnesium and aluminium were also studied.. Tensile on metal and alloys and tensile, compressive, flexure and ILSS tests on carbon fibre reinforced composite specimen were performed on exposed specimens. XRD studies were conducted on the corrosion product of materials. In order to correlate the performance of materials in deep-sea environment, seawater current and temperature data were also collected at same period Results reveal that the corrosion behaviour of steels is controlled by dissolved oxygen prevailing and corrosion rate corresponds to dissolved oxygen available at these depth levels. This is due to the fact that oxygen acts as a cathodic deploarizer during corrosion reaction of steels in seawater. Corrosion rate of aluminium increases as the depth increases. This is due to the effect of hydrostatic pressure, which reduces the ionic radii of chlorine ions and facilitates easy penetration of these ions into surface layer. Titanium, titanium alloy (Ti-6A1-4V) and stainless steels did not show any deterioration at all depths studied. Morphology of as exposed and corroded coupons reveal different features. EDS analyses on exposed specimens are analyzed in light of seawater parameters. Carbon fibre reinforced composite did not show any change in properties like tensile, compression flexural and ILSS compared to control (unexposed) specimens. The deposition of calcium carbonate on galvanically coupled mild steel with zinc, aluminium and magnesium corresponds to availability of calcium in the deep ocean. EDS analyses on exposed coupons did not reveal calcium element below the calcium carbonate compensation depth (CCD) at 3800 m in Indian Ocean. Potentiodynamic polarization studies on some metals and alloys indicate that the behaviour of materials in deep-sea environment is a cumulative effect of all oceanographic parameters. Tensile test results on stainless steels SS-304 & SS-316L), titanium and titanium alloy (exposed) specimens did not show any significant change in their tensile properties and is again attributed to the passive film formed on its surface and nearly zero corrosion rate observed. Microbiological investigations on the exposed materials indicate that except carbon fibre reinforced composite all other metals and alloys harboured bacterial colonies. Results have been used to recommend structural materials suitable for the deep-sea applications.