Depuis de nombreuses années, l'industrie microélectronique s'est engagée dans une course à l'augmentation des performances et à la diminution des coûts de ses dispositifs grâce à la miniaturisation de ces derniers. La génération de ces structures de petites dimensions repose essentiellement sur l'étape de lithographie. Dans cette optique, plusieurs techniques de lithographie nouvelle génération (NGL) sont en cours de développement afin de pouvoir répondre aux besoins de l'industrie pour les nœuds technologiques inférieurs à 20 nm. Parmi elles, les solutions de lithographie à faisceaux d'électrons multiples semblent très prometteuses grâce à leur écriture directe sans masque (ML2), ainsi que leur coût et encombrement réduits. Le CEA-LETI s'est associé à l'entreprise Mapper Lithography basée aux Pays-Bas afin d'aider au développement d'une technologie de lithographie électronique à faisceaux d'électrons multiples basse énergie (d'énergie 5 keV). Les travaux de thèse de ce manuscrit visent à contribuer au développement de cette technologie qui pourrait à terme permettre de réaliser des dispositifs CMOS pour les nœuds technologiques actuels et futurs. L'intégration d'une nouvelle technique de lithographie dans l'industrie repose sur 3 grands critères du procédé lithographique, la production horaire (sensibilité), la résolution (taille minimale des structures réalisées) et la rugosité de ligne. La rugosité de ligne est devenue l'un des paramètres les plus critiques limitant à l'heure actuelle la miniaturisation et pour cause cette dernière impacte de manière négative les performances des dispositifs. Alors que l'ITRS préconise une rugosité de ligne inférieure à 1.7 nm pour les futurs nœuds technologiques inférieurs à 20 nm, les lithographies actuelles ne permettent pas d'obtenir des rugosités inférieures à 4-5 nm. Les travaux de cette thèse visent la minimisation de la rugosité de ligne de résine imprimée par lithographie électronique en proposant des stratégies alternatives d'écriture ou en modifiant les empilements de matériaux sous-jacents la résine, ou encore par l'introduction de traitements post-lithographiques tels que des recuits thermiques ou des traitements plasma. Les études ont montré qu'en combinant une stratégie d'écriture et un traitement plasma à base de dihydrogène une réduction de 41% du LWR pouvait être obtenue. / For decades, the growth of the Semiconductor Industry (SI) has been driven by the paramount need for faster devices at a controlled cost primarily due to the shrinkage of chip transistors. The performances of future CMOS technology generations still rely on the decrease of the device dimensions. However, the photolithography is, today, the limiting factor for pattern miniaturization and the technology has been at a standstill since the development of 193-nm water-based immersion lithography. Moreover, another parameter limiting further semiconductor scaling is the transistor gate linewidth roughness (LWR), i.e. the standard deviation of the gate critical dimension (CD) along the line. The LWR needs to be controlled at the nanometer range to ensure good electrical performances of the future CMOS device. The lithography step is again identified as the root cause of the gate LWR. Indeed, the significant LWR (4-5 nm) of the patterns printed by photolithography is transferred into the gate during the subsequent plasma etching steps, resulting in a final gate LWR far above the sub-2 nm LWR targeted for the sub-20 nm technological nodes. In order to continue scaling down feature sizes of devices, the semiconductor industry is waiting for the maturity of next generation lithographies (NGL). Among NGL, one can find the promising mask-less direct-write techniques (ML2) in which multiple electron beam lithography (multibeam lithography) is regarded as a serious candidate for providing high resolution structures at a low cost. The firm MAPPER Lithography, associated with CEA-LETI is working on the development of such a technology. The aim of this work is to contribute to the development of a low energy (5 keV) multibeam technology and to focus on the improvement of the LWR of the printed patterns. Several process parameters have been investigated to decrease the LWR: the effect of a specific writing strategy, the influence of the under layers and the introduction of post-lithographic treatments such as plasma treatments or thermal annealing. This work has shown that by combining a biased writing strategy with H2 plasma treatment, a 41% LWR decrease could be obtained. Although this performance is still above the ITRS requirements, this work opens the pace for LWR optimization with multi-beam lithography.

Tidally-influenced sandwaves are common coastal features present in various settings, including shipping channels. The main shipping channel in Tampa Bay under the Bob Graham Sunshine Skyway Bridge (a.k.a. the Skyway Bridge) contains such sandwave bedforms. Between the years 2000 and 2017, these bedforms have been surveyed with multibeam echosounders (MBES) on 21 occasions with ranging coverage and quality of returns. Surveys between 2000 and 2009 used a 300 kHz Kongsberg EM3000; surveys between 2015 and 2017 used a 400 kHz Reson Seabat 7125. For comparable surveys, bathymetry, backscatter, slope, curvature, planform curvature, and profile curvature maps were created and analyzed. Spectral analyses were completed on the same cross-section for usable surveys, providing a period and amplitude for the bedforms. Sediment samples were taken in September 2015 using a Shipek grab. The sediment samples were analyzed for grain size and carbonate content. A bottom-mounted ADCP recorded velocity data semi-continuously over the same time period. These data were analyzed in an effort to investigate the forcing mechanisms that influence the bedform morphology. Mean grain sizes in the shipping channel under the Skyway Bridge range from 0.01 φ (0.99 mm, coarse sand) to 1.55 φ (0.34 mm, medium sand). Calcium carbonate content ranges from 25% to 87%. The sediment sample site most representative of the sandwave bedforms has a mean grain size of 0.01 φ and a calcium carbonate content of 87%. The calculated mean current velocity required to initiate transport of the D50 and D84 grain size percentile of the representative sediment sample site is 0.70 m/s and 1.05 m/s, respectively. Analysis of the ADCP-recorded velocity data shows that the calculated D50 critical velocity is frequently reached by peak flood and peak ebb currents except during neap tides, while the D84 critical velocity is reached only intermittently, mostly during spring tides. Analysis of MBES backscatter shows similar spatial patterns in two larger MBES surveys in 2004 and 2015. Bathymetric analysis of the sandwaves shows consistent characteristics through time. Wave crest analysis reveals that bedforms migrate in both the ebb and flood directions. Spectral analysis shows primary wave spatial frequencies range from 0.13 m-1 to 0.22 m-1, and primary wave periods range from 4.5 m to 6.0 m. The predominant wavelength of sandwaves within the study area is about 5 m, with an average wave height of 0.47 m. The maximum wave height along the axial cross-section analyzed is 0.8 m, observed in April 2017. The sediments comprising the sandwave bedforms are likely winnowed by tidal currents resulting in larger grain size and carbonate content than other areas of the shipping channel and surrounding bay. Consistent patterns in MBES backscatter over time indicate that the sediment distribution pattern in the study area have not significantly changed. The size and shape of the bedforms in the shipping channel beneath the Skyway Bridge are have been in a quasi-dynamic equilibrium over the past 13 years. The bedforms are shown to migrate in both the ebb and flood directions despite an average faster ebb current velocity than a flood current velocity. More frequent and consistent MBES surveys as well as more continuous ADCP data availability would allow for better understanding of sediment transport via bedform migration in tidally-influenced environments.

abstract: Worldwide, rivers and streams make up dense, interconnected conveyor belts of sediment– removing carved away earth and transporting it downstream. The propensity of alluvial river beds to self-organize into complex trains of bedforms (i.e. ripples and dunes) suggests that the associated fluid and sediment dynamics over individual bedforms are an integral component of bedload transport (sediment rolled or bounced along the river bed) over larger scales. Generally speaking, asymmetric bedforms (such as alluvial ripples and dunes) migrate downstream via erosion on the stoss side of the bedform and deposition on the lee side of the bedform. Thus, the migration of bedforms is intrinsically linked to the downstream flux of bedload sediment. Accurate quantification of bedload transport is important for the management of waters, civil engineering, and river restoration efforts. Although important, accurate qualification of bedload transport is a difficult task that continues t elude researchers. This dissertation focuses on improving our understanding and quantification of bedload transport on the two spatial scales: the bedform scale and the reach (~100m) scale. Despite a breadth of work investigating the spatiotemporal details of fluid dynamics over bedforms and bedload transport dynamics over flat beds, there remains a relative dearth of investigations into the spatiotemporal details of bedload transport over bedforms and on a sub-bedform scale. To address this, we conducted two sets of flume experiments focused on the two fundamental regions of flow associated with bedforms: flow separation/reattachment on the lee side of the bedform (Chapter 1; backward facing-step) and flow reacceleration up the stoss side of the next bedform (Chapter 2; two-dimensional bedform). Using Laser and Acoustic Doppler Velocimetry to record fluid turbulent events and manual particle tracking of high-speed imagery to record bedload transport dynamics, we identified the existence and importance of “permeable splat events” in the region proximal to flow reattachment. These coupled turbulent and sediment transport events are integral to the spatiotemporal pattern of bedload transport over bedforms. Splat events are localized, high magnitude, intermittent flow features in which fluid impinges on the bed, infiltrates the top portion of bed, and then exfiltrates in all directions surrounding the point of impingement. This initiates bedload transport in a radial pattern. These turbulent structures are primarily associated with quadrant 1 and 4 turbulent structures (i.e. instantaneous fluid fluctuations in the streamwise direction that bring fluid down into the bed in the case of quadrant 1 events, or up away from the bed in the case of quadrant 4 events) and generate a distinct pattern of bedload transport compared to transport dynamics distal to flow reattachment. Distal to flow reattachment, bedload transport is characterized by relatively unidirectional transport. The dynamics of splat events, specifically their potential for inducing significant magnitudes of cross-stream transport, has important implications for the evolution of bedforms from simple, two dimensional features to complex, three-dimensional features. New advancements in sonar technology have enabled more detailed quantification of bedload transport on the reach scale, a process paramount to the effective management of rivers with sand or gravel-dominated bed material. However, a practical and scalable field methodology for reliably estimating bedload remains elusive. A popular approach involves calculating transport from the geometry and celerity of migrating bedforms, extracted from time-series of bed elevation profiles (BEPs) acquired using echosounders. Using two sets of repeat multibeam sonar surveys from the Diamond Creek USGS gage station in Grand Canyon National Park with large spatio-temporal resolution and coverage, we compute bedload using three field techniques for acquiring BEPs: repeat multi-, single-, and multiple single-beam sonar. Significant differences in flux arise between repeat multibeam and single beam sonar. Mulitbeam and multiple single beam sonar systems can potentially yield comparable results, but the latter relies on knowledge of bedform geometries and flow that collectively inform optimal beam spacing and sampling rate. These results serve to guide design of optimal sampling, and for comparing transport estimates from different sonar configurations. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018

The United States of Army Corp of Engineers (USACE) closely monitors the changing depths of navigation channels throughout the U.S. and Western Europe. The main issue with their surveying methodology is that the USACE surveys in linear cross sections, perpendicular to the channel direction. Depending on the channel length and width, these cross sections are spaced 100 - 400 feet apart, which produces large unmapped areas within each cross section of a survey. Using a variety of spatial interpolation methods, depths of these unmapped areas were produced. The choice of spatial interpolator varied upon which method adequately produced surfaces from large hydrographic survey data sets with the lowest amount of prediction error. The data used for this research consisted of multibeam and singlebeam surveys. These surveys were taken in a systematic manner of linear cross-sections that produced tens of thousands of data points. Nine interpolation techniques (inverse distance weighting, completely regularized spline, spline with tension, thin plate spline, multiquadratic spline, inverse multiquadratic spline, ordinary kriging, simple kriging, and universal kriging) were compared for their ability to accurately produce bathymetric surfaces of navigation channels. Each interpolation method was tested for effectiveness in determining depths at "unknown" areas. The level of accuracy was tested through validation and cross validation of training and test data sets for a particular hydrographic survey. By using interpolation, grid surfaces were created at 15, 30, 60, and 90-meter resolution for each survey of the study site, the Atlantic Ocean Channel. These surfaces are used to produce shoaling amounts, which are taken in the form of volumes (yd.³). Because the Atlantic Ocean Channel is a large channel with a small gradual change in depth, a comparison of grid resolution was conducted to determine what difference, if any, exists between the calculated volumes from varying grid resolutions. Also, a comparison of TIN model volume calculations was compared to grid volume estimates. Volumes are used to determine the amount of shoaling and at what rate shoaling is occurring in a navigation channel. Shoaling in each channel was calculated for the entire channel length. Volumes from varying grid resolutions were produced from the Atlantic Ocean Channel over a seven-year period from 1994-2001. Using randomly arranged test and training datasets, spline with tension and thin plate spline produced the mean total error when interpolating using singlebeam and multibeam hydrographic data respectively. Thin plate spline and simple kriging produced the lowest mean total error in full cross validation testing of entire singlebeam and multibeam hydrographic datasets respectively. Volume analysis of varying grid resolution indicates that finer grid resolution provides volume estimates comparable to TIN modeling, the USACE's technique for determining sediment volume estimates. The coarser the resolution, the less similar the volume estimates are in comparison to TIN modeling. All grid resolutions indicate that the Atlantic Ocean Channel is shoaling. Using a plan depth of 53 feet, TIN modeling displayed an annual average increase of 928,985 cubic yards of sediment from 1994 - 2001. / Master of Science

Underwater navigation is a key technology for exploring the oceans and exploiting their resources. For autonomous underwater vehicles (AUVs) to explore the marine environment efficiently and securely, underwater simultaneous localization and mapping (SLAM) systems are often indispensable due to the lack of the global positioning system (GPS). In an underwater SLAM system, an AUV maps its surroundings and estimates its own pose at the same time. The pose of the AUV can be predicted by dead reckoning, but navigation errors accumulate over time. Therefore, sensors are needed to calibrate the state of the AUV. Among various sensors, the multibeam echosounder (MBES) is one of the most popular ones for underwater SLAM since it can acquire bathymetric point clouds with depth information of the surroundings. However, there are difficulties in data association for seabeds without distinct landmarks. Previous studies have focused more on traditional computer vision methods, which have limited performance on bathymetric data. In this thesis, a novel method based on deep learning is proposed to facilitate underwater perception. We conduct two experiments on place recognition and point cloud registration using data collected during a survey. The results show that, compared with the traditional methods, the proposed neural network is able to detect loop closures and register point clouds more efficiently. This work provides a better data association solution for designing underwater SLAM systems. / Undervattensnavigering är en viktig teknik för att utforska haven och utnyttja deras resurser. För att autonoma undervattensfordon (AUV) ska kunna utforska havsmiljön effektivt och säkert är underwater simultaneous localization and mapping (SLAM) system ofta oumbärliga på grund av bristen av det globala positioneringssystemet (GPS). I ett undervattens SLAM-system kartlägger ett AUV sin omgivning och uppskattar samtidigt sin egen position. AUV:s position kan förutsägas med hjälp av dödräkning, men navigeringsfel ackumuleras med tiden. Därför behövs sensorer för att kalibrera AUV:s tillstånd. Bland olika sensorer är multibeam ekolod (MBES) en av de mest populära för undervattens-SLAM eftersom den kan samla in batymetriska punktmoln med djupinformation om omgivningen. Det finns dock svårigheter med dataassociation för havsbottnar utan tydliga landmärken. Tidigare studier har fokuserat mer på traditionella datorvisionsmetoder som har begränsad prestanda för batymetriska data. I den här avhandlingen föreslås en ny metod baserad på djup inlärning för att underlätta undervattensuppfattning. Vi genomför två experiment på punktmolnregistrering med hjälp av data som samlats in under en undersökning. Resultaten visar att jämfört med de traditionella metoderna kan det föreslagna neurala nätverket upptäcka slingförslutningar och registrera punktmoln mer effektivt. Detta arbete ger en bättre lösning för dataassociation för utformning av undervattens SLAM-system.

L'objectif de la thèse est de développer une méthode de modélisation 3D des tunnels canaux en service, afin de les documenter de manière précise. Le levé des structures est effectué en dynamique depuis un bateau, avec un ensemble de caméras au-dessus de l'eau et un sonar pour la partie immergée. La construction du modèle 3D doit combiner des données acquises dans deux milieux différents, en l'absence de signal GPS pour la localisation du système de mesure. L'approche proposée exploite pleinement les capacités du calcul photogrammétrique, à la fois pour construire le modèle 3D de la voûte et pour estimer la trajectoire du bateau, laquelle permet de géoréférencer les profils de points sonar. L'application du procédé en vraie grandeur dans le tunnel de Niderviller a permis d'obtenir un premier modèle 3D. L'analyse de la méthode a mis en jeu une technologie innovante de mesure sonar statique, nécessitant le développement de traitements appropriés. Elle a permis de jauger les capacités du sonar à numériser les canaux, d'évaluer les trajectoires estimées par photogrammétrie et de comparer quantitativement le modèle obtenu à un modèle de référence préalablement construit. / The aim of this thesis is to develop a 3D modeling method for canal-tunnels in service, in order to document them accurately. The survey of the structures is carried out dynamically from a boat, with a set of cameras above the water and a sonar for the submerged part. The construction of the 3D model must combine data acquired in two different environments, in the absence of a GPS signal to locate the measurement system. The proposed approach makes full use of the capabilities of photogrammetric computation, both to build the 3D model of the vault and to estimate the trajectory of the boat, which allows georefencing of sonar point profiles. The application of the process to field test data acquired in the Niderviller tunnel allowed a first 3D model to be obtained. The analysis of the method involved an innovative static sonar measurement technology, requiring the development of appropriate treatments. It enabled to assess the capacity of the sonar for canal surveying, to evaluate the trajectories estimated using photogrammetry and to compare quantitatively the obtained model with a previously constructed reference mode

Sistemas estuarinos são locais de transição entre ambientes marinhos e fluviais, cujas forçantes influenciam a dinâmica e a distribuição das propriedades químicas, biológicas e sedimentares. Aproximadamente 60 % de todas as grandes cidades se desenvolveram ao redor de estuários que, por serem ambientes abrigados, favorecem a navegação e instalação de portos. O objetivo geral do trabalho foi de identificar os processos sedimentares atuantes em um trecho do canal de acesso ao Porto de Santos (Trecho 1 do Porto organizado), compreendendo 12 km de comprimento desde a embocadura da baía de Santos até a entrada no Canal do Porto, utilizando um conjunto de dados de diferentes períodos (entre 2010 e 2016), provenientes de diferentes fontes acústicas, visando contribuir para a melhor compreensão da dinâmica sedimentar do Sistema Estuarino de Santos. Foram utilizados dados obtidos com um duplo chirp (frequências entre 2-8 kHz e 10-20 kHz) e dados de batimetria multifeixe. A metodologia consistiu na comparação de levantamentos batimétricos (executados em diferentes períodos) e de forma complementar foram utilizados os dados obtidos com a fonte acústica chirp. As análises proporcionaram a identificação de indícios de erosão e de assoreamento no Trecho 1 do canal do Porto de Santos. Em alguns locais, foi possível relacionar os padrões de erosão e de assoreamento com a hidrodinâmica local e, assim, sugerir tendências nos processos sedimentares atuantes na área de estudo. Sem dragagem a tendência do Trecho 1 do Porto de Santos é de assoreamento. O Trecho 1 foi divido em 2 setores com comportamento distintos. O setor A (próximo à embocadura do canal) é, naturalmente, mais profundo, o sedimento de fundo não é depositado em grande quantidade nesse local devido à intensidade da velocidade das correntes que ocorrem no setor. Há indícios de instabilidade das encostas no trecho mais estreito do canal, da ocorrência de lama fluida e de gás raso nesse local. O setor B era, naturalmente, mais raso em 1960, período em que o canal passou a ter a sua configuração atual, sugerindo a formação de um delta de maré vazante no setor, onde a velocidade das correntes são mais lentas, quando comparadas com o setor A. / Estuarine systems are sites of transition between marine and fluvial environments, whose forcing influences the dynamics and distribution of chemical, biological and sedimentary properties. Approximately 60% of all large cities have developed around estuaries because they are sheltered environments, allowed the navigation and harbors installation. The objective of the study was to identify the sedimentary processes in a section of Santos Harbor channel, comprising 12 km in length from the mouth of the bay to the entrance in the Port Channel. It was used a data set from different periods (2010-2016), from different acoustic sources, aiming to contribute to a better understanding the sedimentary dynamics in the Santos Estuary System. It was used a double chirp data with frequencies between 2-8 kHz and 10-20 kHz and multibeam bathymetry data. The methodology consisted in the comparison of bathymetric surveys performed in different periods and in a complementary way used the data obtained from a double chirp. The analyzes allowed an identification of erosion and silting in Section 1 of Santos Port Channel. It was possible to relate erosion and silting patterns to local hydrodynamics and to suggest trends in sedimentary processes in the study region. Without dredging, the trend of Section 1 from the Santos Harbor was of silting. The Section 1 it was divided into 2 sectors with different behavior. Sector A is naturally deeper; the sediment is not deposited in large quantities at this location because of the currents velocities that occurring there. In this site there is evidence of instability of the slopes in the channel\'s narrowest section, the occurrence of fluid mud and shallow gas. Sector B was naturally shallower in 1960, when the canal became its current configuration, suggesting the formation in this site of an ebb tide delta, where the currents velocities are slower when compared to sector A.

Using a towed underwater video camera system, benthic habitats were classified along transects in a popular offshore fishing area on the West Florida Shelf (WFS) known as “The Elbow.” Additionally, high resolution multibeam bathymetry and co-registered backscatter data were collected for the entire study area. Using these data, full coverage geologic and biotic habitat maps were developed using both unsupervised and supervised statistical classification methodologies. The unsupervised methodology used was k-means clustering, and the supervised methodology used a random forest algorithm. The two methods produced broadly similar results; however, the supervised methodology outperformed the unsupervised methodology. The results of the supervised classification demonstrated “substantial agreement” (κ>0.6) between observations and predictions for both geologic and biotic habitat, while the results of the unsupervised classification demonstrated “moderate agreement” (κ>0.4) between observations and predictions for both geologic and biotic habitat. Comparisons were made with the previously existing map for this area created by Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute (FWC-FWRI). Some features are distinguishable in both maps, but the FWC-FWRI map shows a greater extent of low relief hard bottom features than was predicted in our habitat maps. The areas predicted as low relief hard-bottom by FWC-FWRI often coincide with areas of higher uncertainty in the supervised map of geologic habitat from this study, but even when compared with ground-truth points from the towed video rather than predictions, the low relief hard bottom in FWC-FWRI’s map still corresponds to what was identified as sand in the video 73% of the time. The higher uncertainty might be a result of the presence of mixed habitats, differing morphology of hard-bottom, or the presence of sand intermixed with gravel or debris. More ground-truth samples should be taken in these areas to increase the confidence of these classifications and resolve discrepancies between the two maps. Data from the towed video system were also used to assess differences in fish communities among habitat types and to calculate habitat-specific densities for each taxa. Fish communities were found to significantly differ between soft and hard bottom habitats as well as among the hard-bottom habitats with different vertical relief (flat hard-bottom vs more steeply sloping areas). Additionally, significant differences were found between the fish communities in habitats with attached fauna such as sponges and gorgonians, and areas without attached fauna; however, attached fauna require rock to attach to and the rock habitats rarely lacked attached fauna, so this difference may just reflect the difference between fish communities in sand and rock habitats without the consideration of vertical relief. Moreover, the species driving the differences in the fish communities were identified. Fish were more likely to be present and assemblages were more species rich in more complex habitats (rockier, higher relief, presence of attached fauna). Habitat specific densities were calculated for each species, and general trends are discussed. Lastly the habitat-specific densities were extrapolated to the total area of habitat type (sand vs rock) as predicted by the supervised geologic habitat map. There is predicted to be approximately 111,000 fish (95% CI [67015, 169405]) within the study area based on this method, with ~47,000 (~43%) predicted to be within the sand habitat and ~64,000 (~57%) in the rock habitat. This demonstrates the potential of offshore rocky reefs as “critical habitats” for demersal fish in the offshore environment as rock accounts for just 4% of the study area but is expected to contain over half of the total abundance. The value of sand habitats is also shown, as due to their large area they are able to contribute substantially to the total number of fish despite sustaining comparatively low densities.

The former Viking settlement Birka is located on Björkö Island in Lake Mälaren, the third largest lake in Sweden. Birka is a well-known archeological site that onshore has been carefully examined. The lake floor of the waters surrounding the island has been less investigated but has a great potential to host not yet discovered archeological objects from this former hub for seafarers. Therefore, a geophysical survey including multibeam sonar mapping and subbottom profiling was carried out mainly along the shores of western Björkö Island. Processing and analysis of these collected data form the basis of this thesis. The main aims of this study are to produce a suite of geological maps and stratigraphic profiles that are used to geologically interpret the uppermost sediment stratigraphy and the bathymetry of the area. In addition, the processed data are investigated for archeological objects. The result shows that the acoustic records of the sediment stratigraphy reaches back to glacial clay formed as a consequence of the retreat of the Late Weichselian ice sheet, and that the uppermost sediment units probably are from the time after the isolation of Lake Mälaren from the Baltic Sea. The bathymetry and backscatter results have revealed that this relatively shallow study area contains several objects that potentially could be of interest from an archeological point of view. These objects include several unidentified objects in the Björkö strait and two unregistered shipwrecks where ground truthing data need to be collected to determine their respective origin.

Resolving diversity patterns and their underlying drivers has application for both ecological theory and ocean management. Because seafloor characteristics are often used to assess bottom habitat, I examined the relationship between deep-sea benthic (bottom-living) diversity and multi-scale topographic heterogeneity. Most work occurred on the Canadian Pacific continental shelf at Learmonth Bank with additional sites in Strait of Georgia (BC) and Gulf of Maine (Atlantic shelf). High-resolution species distribution and seafloor data were annotated from remotely operated vehicle benthic imagery surveys while large-scale seafloor data were derived from multibeam sonar. New method development to address problems of current methods and to facilitate comparison among ecosystems is a major outcome. My new MiLS method (microtopographic laser scanning) can profile the deep seafloor at a resolution of ~1-2 cm with high accuracy and precision. I also developed a new ACR (arc-chord ratio) rugosity index as a measure of 3-D topographic heterogeneity that is simple, accurate and highly versatile. Model systems and scales vary among my studies but results consistently yield a positive relationship between diversity and topographic heterogeneity and identify bottom hydrodynamics as an important underlying driver. Rockfish Sebastes spp. associate with higher seafloor rugosity non-randomly and select for deep-sea corals and sponges over inert substrata alone. Data indicate that degradation of biogenic structures is a long-term detriment to rockfish species. Gorgonian coral- and sponge-dominant biotopes strongly associate with a single substratum type. These relationships were used to map coral and sponge distributions. This work, which collectively adds new information on the ecological relevance and distribution of corals and sponges, is pertinent to the conservation and management of fish stocks and vulnerable marine ecosystems. Epibenthic community variables abundance, richness, and Shannon diversity positively correlated with both the local microtopographic heterogeneity on a scale of 10 m2 and with the surrounding regional large-scale topographic heterogeneity on scales of 25 to 250,000 m2. Relationships were strongest between epibenthic community variables and the largest scale rugosity and were used to generate and test predictive diversity models. Where management strategies rely on surrogate measures in data-poor areas, mapping benthic diversity using ACR rugosity will provide good indicators. Although bottom hydrodynamics is consistently identified as an underlying driver of epibenthic patterns related to topographic heterogeneity, data suggest the nature of the relationship varies across spatial scales. At small scales, high topographic heterogeneity likely increases diversity by increasing the number of available niches (including hydrodynamic gradients; e.g., the abrupt vertical rugosity created by tall corals and sponges provides rockfish refuge from currents) while at large scales, high topographic heterogeneity increases local diversity less directly through distant hydraulic events that alter bottom flow hydrodynamics. / Graduate / 0329 / 0416 / 0799 / cdupreez@uvic.ca