Dissertations / Theses on the topic 'Side scan sonars'

In underwater environments, the perception and navigation systems are heavily dependent on the acoustic wave based sonar technology. Side-scan sonar (SSS) provides high-resolution, photo-realistic images of the seafloor at a relatively cheap price. These images could be considered potential candidates for place recognition and navigation of autonomous underwater vehicles (AUVs). Local feature correspondence matching, or the detection, description and matching of keypoints in overlapping images is a necessary building block for AUV navigation. Recent deep learning based research has resulted in state-of-the-art local correspondence models for camera images. For SSS images, however, deep learning based studies are limited and handcrafted methods such as SIFT and RootSIFT still dominate the field. In this study, SSS images taken from a seafloor area with bottom trawling marks were used for correspondence matching. D2-Net, a detect-and-describe VGG16 based network architecture designed for and tested on camera image correspondence was fine-tuned for SSS image correspondence. Using triplet margin ranking loss, the network was trained to simultaneously detect salient keypoints and produce similar descriptors for corresponding pixels and dissimilar descriptors for non-corresponding pixels. When evaluated on the nontrivial SSS images pairs in the test dataset, the best performing D2-Net based network was found to outperform the RootSIFT baseline in terms of number of detected keypoints, keypoint repeatability and mean matching accuracy at above 10 pixel threshold.<br>I undervattensmiljöer så är perception och navigationssystem ofta beroende av ekolodsteknik. Side scan sonar (SSS) ger högupplösta, fotorealistiska bilder av havsbottnen till en relativt låg kostnad. Dessa bilder kan användas för områdesigenkänning och navigation av autonoma undervattensfordon (AUV). Lokal kännerteckensmatchning består av detektion, beskrivning och matchning av nyckelpunkter på överlappande bilder. Detta är en viktig byggsten för AUV navigation. Nya metoder baserade på djupinlärning har varit i framkant för kännerteckensmatching av kamerabilder. Däremot är kännerteckensmatchning av SSS bilder fortfarande dominerat av traditionella metoder så som SIFT och RootSIFT. Denna rapport använder SSS bilder av havsbottnen där bottentrålning har förekommit för kännerteckensmatching. D2-Net är en detect-and-describe VGG16 baserad nätverksarkitektur designad och testad på kännerteckensmatching av kamerabilder. I denna rapport anpassas denna metod till SSS bilder. Kostnadsfunktionen använder sig av trippelmarginalsrankning så att nätverket ska kunna detektera distinkta nyckelpunkter samt producera liknande deskriptorer för matchande pixlar. Metoden utvärderades på icke-triviala SSS bildpar och uppnådde bättre resultat än RootSIFT.

The size and organization of bed material, bed texture, is a fundamental attribute of channels and is one component of the physical habitat of aquatic ecosystems. Multiple discipline-specific definitions of texture exist and there is not a universally accepted metric(s) to quantify the spectrum of possible bed textures found in aquatic environments. Moreover, metrics to describe texture are strictly statistical. Recreational-grade side scan sonar systems now offer the possibility of imaging submerged riverbed sediment at resolutions potentially sufficient to identify subtle changes in bed texture with minimal cost,expertise in sonar, or logistical effort. However, inferring riverbed sediment from side scan sonar data is limited because recreational-grade systems were not designed for this purpose and methods to interpret the data have relied on manual and semi-automated routines. Visual interpretation of side scan sonar data is not practically applied to large volumes of data because it is labor intensive and lacks reproducibility. This thesis addresses current limitations associated with visual interpretation with two objectives: 1) objectively quantify side scan sonar imagery texture, and 2) develop an automated texture segmentation algorithm for broad-scale substrate characterization. To address objective 1), I used a time series of imagery collected along a 1.6 km reach of the Colorado River in Marble Canyon, AZ. A statistically based texture analysis was performed on georeferenced side scan sonar imagery to identify objective metrics that could be used to discriminate different sediment types. A Grey Level Co-occurrence Matrix based texture analysis was found to successfully discriminate the textures associated with different sediment types. Texture varies significantly at the scale of ≈ 9 m2 on side scan sonar imagery on a regular 25 cm grid. A minimum of three and maximum of five distinct textures could be observed directly from side scan sonar imagery. To address objective 2), linear least squares and a Gaussian mixture modeling approach were developed and tested. Both sediment classification methods were found to successfully classify heterogeneous riverbeds into homogeneous patches of sand, gravel, and boulders. Gaussian mixture models outperformed the least squares models because they classified gravel with the highest accuracies.Additionally, substrate maps derived from a Gaussian modeling approach were found to be able to better estimate reach averaged proportions of different sediments types when they were compared to similar maps derived from multibeam sonar.

Underwater navigation using Autonomous Underwater Vehicles (AUVs), which is significant for marine science research, highly depends on the acoustic method, sonar. Typically, AUVsare equipped with side-scan sonars and multibeam sonars at the same time since they both have their advantages and limitations. Side-scan sonars have a much wider range than multibeamsonars and at the same time are much cheaper, yet they could not provide accurate depth measurements. This thesis is aiming at investigating if a machine-interpreted method could beused to translate side-scan sonar data to multibeam data with high accuracy so that underwater navigation could be done by AUVs equipped only with side-scan sonars. The approaches considered in this thesis are based on Machine Learning methods, including generative models and discriminative models. The objective of this thesis is to investigate the feasibility of machine learning based models to infer the depth based on side-scan sonar images. Different models, including regression and Generative Adversarial Networks, are tested and compared. Different CNN based architectures such as U-Net and ResNet are tested andcompared as well. As an experiment trial, this project has already shown the ability and great potential of machine learning based methods extracting latent representations from side-scansonars and inferring the depth with reasonable accuracy. Further improvement could be madeto improve the performance and stability to be potentially verified on the AUV platforms inreal-time.<br>Undervattensnavigering med autonoma undervattensfordon (AUV från engelskans Autonomous Underwater Vehicle), är betydelsefull för marinvetenskaplig forskning, och beror starkt på vilken typ av sonar som används. Vanligtvis är AUV:er utrustade med både sidescansonar och multibeamsonar eftersom båda har sina fördelar och begränsningar. Sidescansonar har större omfång än multibeam-sonar och är samtidigt mycket billigare, men kan inte ge exakta mätningar av djupet. Detta examensarbete syftar till att undersöka om maskininlärningsmetoder skulle kunna användas för att översätta sidescandata till multibeamdata med hög noggrannhet så att undervattensnavigering skulle kunna göras av AUV:er utrustade endast med sidescansonar. Tillvägagångssättet i examensarbetet är baserat på olika maskininlärningsmetoder, däribland generativa modeller och diskriminerande modeller. Syftet är att undersöka om olika maskininlärningsbaserade modeller kan dra slutsatser om havsdjupet baserat endast på sidescandata. De modeller som testas och jämförs inkluderar regression och generativa adversativt nätverk. Även olika CNN-baserade arkitekturer som U-Net och ResNet testas och jämförs. Som ett experimentförsök har detta projekt redan visat förmågan och den stora potentialen för maskininlärningsbaserade metoder som extraherar latenta representationer från sidescansonar och kan estimera djupet med en rimlig noggrannhet. Ytterligare förbättringar skulle kunna göras för att förbättra prestanda och stabilitet som potentiellt kan verifieras på AUV-plattformar i realtid.

Knowledge of surface sediment distribution in Galveston Bay is important because it allows us to better understand how the bay works and how human activities impact the bay and its ecosystems. In this project, six areas of bay bottom were surveyed using acoustic techniques to make maps of bay bottom types and to investigate the types and extent of anthropogenic impacts. A total of 31 km2 was surveyed in six areas, one in Bolivar Roads (6.1 km2), one near Redfish Bar (3.1 km2), two in East Bay (12 km2), one southeast of the Clear Lake entrance (5.3 km2), and one in Trinity Bay (4.3 km2). Sidescan sonars (100 kHz and 600 kHz) were used to image the bay bottom, and a chirp sonar (2-12 kHz) was used to image subsurface sediment layers and bottom topography. In the side-scan records, objects as small as a few meters in extent were visible, whereas the chirp sonar records show a vertical resolution of a few tens of centimeters. The sidescan images display strong backscatter in some areas due to coarse sediments in addition to weak backscatter in areas of fine sediment. The bay bottom was classified using three levels of sonar backscatter ranging from high to low. Areas of differing sonar backscatter intensity were sampled with cores and grab-samples. High backscatter corresponded to coarse shell debris and oyster reefs, medium backscatter corresponded to a sand-silt-shell mixture, and low backscatter corresponded to silty loam. Chirp sonar records were classified as one of nine different bottom reflection types based on changes in amplitude and stratigraphy. Parallel, layered sediments are seen filling the bay valley and resting atop a sharp contact at which the acoustic signal fades out. Along the flanks of the valley fill the acoustic response revealed an absent or weakly laminated stratigraphy, whereas areas of high oyster productivity produced mounds, strong surface returns, and strong, shallow subsurface reflectors surrounding current oyster reefs. Anthropogenic features imaged with the sonar included sediment disruptions, such as the ship channels, dredge holes, gouges, and trawl marks, as well as debris, such as submerged boats, pipes, and unidentified objects.

While side-scan sonar has become a valuable geophysical tool for forensic water searches, controlled research is paramount to determine the best practices for searches in aquatic environments as it provides a structured environment in which to investigate variables that influence the effectiveness of the technology and provides valuable experience for sonar operators. The purpose of this research is to conduct controlled research in order to evaluate the applicability of side-scan sonar to searches involving submerged firearms and proxy cadavers. In addition, the best practices for employing this technology in forensic searches in freshwater ponds and lakes in a humid, subtropical environment in Central Florida would be developed. Five street-level firearms were submerged in a pond, and two sets of three pig carcasses (Sus scrofa), utilized as proxies for human bodies, were staked to the bottom of a pond for this research. Transects were conducted over the firearms and the pig carcasses utilizing side-scan sonar. The first set of pig carcasses represented a child size (30-32 kg) and the second set a small adult size (51-54 kg). Results show that firearms were not detected due to the terrain and small size. However, this technology successfully located small to medium-sized proxy carcasses on a flat, sandy lake bottom when experienced operators were conducting the search. Conversely, vegetation obscured submerged bodies. While the smaller carcasses were difficult to detect throughout the data collection, medium-sized carcasses were easily discerned. Moreover, the medium-sized carcasses decomposed at the same rate as previous studies and were visible throughout each stage of decomposition. Finally, employing a 900 kHz frequency with a 20 m swath-width provided the best search parameters. Therefore, in the appropriate conditions,side-scan sonar is an effective tool for locating submerged bodies in freshwater lakes and ponds in a humid, subtropical environment.<br>M.A.<br>Masters<br>Anthropology<br>Sciences<br>Anthropology

Simpson Bay is a turbid, outwash fjord located in northeastern Prince William Sound, Alaska. A high ratio of watershead:basin surface area combined with high precipitation and an easily erodable catchment create high sediment inputs. Fresh water from heavy precipitation and meltwater from high alpine glaciers enter Simpson Bay through bay head rivers and small shoreline creeks that drain the catchment. Side scan sonar, seismic profiling, and high resolution bathymetry were used to investigate the record of modern sedimentary processes. Four bottom types and two seismic faces were described to delineate the distribution of sediment types and sedimentary processes in Simpson Bay. Sonar images showed areas of high backscatter (coarse grain sediment, bedrock outcrops and shorelines) in shallow areas and areas of low backscatter (estuarine mud) in deeper areas. Seismic profiles showed that high backscatter areas reflected emergent glacial surfaces while low backscatter areas indicated modern estuarine mud deposition. The data show terminal morainal bank systems and grounding line deposits at the mouth of the bay and rocky promontories, relict medial moraines, that extend as terrestrial features through the subtidal and into deeper waters. Tidal currents and mass wasting are the major influences on sediment distribution. Hydrographic data showed high spatial variability in surface and bottom currents throughout the bay. Bottom currents are tide dominated, and are generally weak (5-20 cm s-1) in the open water portions of the bay while faster currents are found associated with shorelines, outcrops, and restrictive sills. Tidal currents alone are not enough to cause the lack of estuarine mud deposition in shallow areas. Bathymetric data showed steep slopes throughout the bay suggesting sediment gravity flows. Central Alaska is a seismically active area, and earthquakes are most likely the triggering mechanism of the gravity flows.

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro<br>Os estuários são ambientes altamente dinâmicos e concentram a maior parte da população mundial em seu entorno. São ambientes complexos que necessitam de uma gama de estudos. Nesse contexto, este trabalho visa contribuir para o entendimento dos estuários lagunares, tendo como objetivo comparar duas ferramentas geofísicas acústicas no mapeamento de uma porção submersa do Mar de Cananéia que está inserido no Sistema Estuarino Lagunar de Cananéia-Iguape (SP). Os equipamentos utilizados nesta pesquisa são o Sonar de Varredura Lateral e o Sistema Acústico de Classificação de Fundo RoxAnn, através da parametrização de amostras de fundo. A comparação do padrão acústico do Sonar de Varredura Lateral com as amostras de fundo da região permitiu o reconhecimento de 6 tipos distintos de padrões acústicos e a relação positiva com o diâmetro médio do grão foi de 50%. A comparação da resposta acústica do Sistema Acústico de Classificação de Fundo RoxAnn com o diâmetro médio do grão foi igualmente de 50%. Isto deve-se ao fato de que os valores produzidos pelo eco 1 e pelo eco 2 deste equipamento mostram que, por ser um mono-feixe e por analisar valores de intensidade do retorno acústico, o equipamento em questão pode responder a outros fatores ambientais que não seja somente o diâmetro médio do grão. Ao comparar a resposta acústica do Sonar de Varredura Lateral com o Sistema Acústico de Classificação de fundo RoxAnn obteve-se um resultado positivo de 93%. Isto pode ser explicado pelo fato de o Sonar de Varredura Lateral gerar uma imagem acústica do fundo. Em locais onde tem-se amostra e os valores do eco 1 e do eco 2 do Sistema Acústico de Classificação de Fundo RoxAnn são altos, pode-se associar a esses locais a influência da compactação dos sedimentos finos através da análise das imagens do Sonar de Varredura Lateral. Por meio da comparação destes dois métodos foi possível estabelecer um intervalo de valores para o eco 1 que pode ser associado ao diâmetro médio do grão. Assim, valores entre 0.170 a 0.484 milivolts podem ser associados a sedimentos finos com granulometria até areia fina. Valores entre 0.364 a 0.733 podem ser associados a sedimentos de granulometria entre areia fina a média. Valores acima de 0.805 milivolts até 1.585 milivolts podem ser associados a sedimentos mais grossos como carbonatos biodetríticos ou areias grossas. E, por fim, valores acima de 2.790 milivolts podem ser associados a afloramentos rochosos.<br>Estuaries are highly dynamic environments which concentrate the largest part of the world`s population in it`s surroundings. They are complex environments which need a variety of studies. The objective of this work is to contribute to a better understanding of the estuarine system, having as a main objective the comparison between two geophysical acoustic methods in the mapping of a submersed portion of the Cananéia Sea, located in the Estuarine System of Cananéia Iguape (SP). The equipment used in this research were the Side Scan Sonar and the RoxAnn Acoustic Ground Discrimination System, through the correlation of the geological bottom samples. The comparison of the acoustic pattern between the Side Scan Sonar and the geological bottom samples enabled the recognition of 6 distinct acoustic patterns and the positive correlation between the medium diameters of the sediments was 50%. The correlation of the acoustic feedback of the RoxAnn Acoustic Ground Discrimination System and the medium diameter of the sediments was equally 50%. This is due to the fact that the data produced by the echo 1 and echo 2 of this system show that because it is a single beam and because it analyses acoustic intensity feedback data, the equipment may also respond to other environmental factors which are not only related to the medium diameter of sediments. When comparing the acoustic feedback taken from the Side Scan Sonar and the RoxAnn Acoustic Ground Discrimination System a positive result of 93% was obtained. This may be explained due to the fact that the Side Scan Sonar generates an acoustic ground image. In areas where one has high value samples from echo 1 and echo 2 and also from the RoxAnn Acoustic Ground Discrimination System, one may correlate to these places the influence of fine sediment compression through the analysis of the images taken from the Side Scan Sonar. By comparing these two methods it was possible to establish an interval of values for echo 1 which can be associated to the medium diameter of the sediments. In this way, values between 0,170 to 0.484 milivolts can be associated to fine sediments with granulometry variating up to very fine sediments. Values between 0.364 to 0.733 can be associated to fine sediments with granulometry variating from medium to fine sediments. Values above 0.805 milivolts to 1.585 milivolts can be associated to coarser sediments such as biodetritic carbonates or thick sediments. Finally, values above 2.790 milivolts can be associated to rocky emergences.

Natural hydrocarbon seeps harbor distinctive geological, chemical, and biological features in the marine environment. This thesis verified remote sensing signatures of seeps using in-situ observation and repeated collections of satellite imagery. Bubble streams in the Gulf of Mexico water column from four natural seep sites on the upper continental slope were imaged by a side-scan sonar, which was operated from a submarine near the seafloor, and by acoustic profilers, which were operated from surface ships. These data were correlated with sea surface slicks imaged by Synthetic Aperture Radar (SAR) on the RADARSAT satellite. Comparing non-oily bubble streams from rapidly venting mud volcanoes with oily bubble streams from shallow deposits of gas hydrate showed that they produced notably different signatures. Non-oily bubbles produced high backscatter on the side-scan sonar records, but were difficult to detect with the acoustic profilers. Oily bubbles from hydrate deposits produced acoustic shadows on the side-scan sonar records. The oily bubbles generated clear signatures extending from the seafloor to the near surface on the acoustic profile records. RADARSAT SAR images verified the presence of surface oil slicks over the hydrate deposits, but not over the mud volcanoes. This indicates that SAR imagery will not be able to capture every oil and gas seep in a region because non-oily bubble streams do not create surface oil slicks. A total of 113 natural oily seep sources were identified based on surface slicks in eleven SAR images collected over the northern continental slope. A persistence analysis verified that SAR is a dependable tool for capturing oil slicks because 93.5% of the slick sources identified in the 2001 images were corroborated with slicks in the 2002 images. The sources ranged in depth from 100 to 2000 m and 79% of the sources were in 900 meters or greater of water. Seventy-six percent of the seep sources were associated with salt less than 1500 m below the seafloor and none of the sources were located in the bottom of salt withdrawal basins. Geographical Information Systems (GIS) proved to be a useful tool in these analyses.

Substantial hunting pressure and habitat destruction caused by oil extraction has critically endangered the Amazonian manatee in Ecuador. The current population status is unknown because an effective method to observe them in the wild has yet to be developed. This study explored whether the Amazonian manatee persists or has been extirpated in the eastern Ecuadorian Amazon utilizing side-scan sonar to increase odds of detection. Spatial differences in probability of detection were quantified if manatees were observed. The level of chemical contamination was determined and compared spatially and temporally against historical data. Data were collected using opportunistic transect surveys and grab sampling of surface water in Yasuni National Park, Lagartococha, and Cuyabeno Wildlife Reserve. Surveys confirmed that the manatee population is extant. Manatees were encountered more often in Cuyabeno Wildlife Reserve than in Lagartococha and Yasuni. Side-scan sonar detected more manatees than previously reported in 1996-1999. Side-scan sonar is a viable method for detection of manatees in the Ecuadorian Amazon system and resulted in greater detection as a function of effort. All future population studies should incorporate side-scan sonar. Lead, arsenic, mercury, polynuclear aromatic hydrocarbons [PAHs], and volatile organic compounds [VOCs] were not detected in the waters of the study region. High total petroleum hydrocarbon [TPH] levels were measured in 7 samples from Yasuni National Park. The concentrations of TPH were higher in Yasuni National Park than in Lagartococha and Cuyabeno. TPHs were detected only in the study region with a recent oil spill; there was no evidence that TPHs were higher near oil production wells and pipelines. The concentrations of TPH were significantly different than those measured in 1998 (z =3.01710, p=0.0026). A dedicated study should be performed to develop a protocol for monitoring persistent oil contaminants in the Ecuadorian Amazon and determine their sink.

Made available in DSpace on 2015-03-13T17:08:34Z (GMT). No. of bitstreams: 1 CamilaHCS_DISSERT.pdf: 5199158 bytes, checksum: 3fe566edfdb484ed92ea990061bd1ccd (MD5) Previous issue date: 2012-02-28<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior<br>The aim of this study was the seasonal characterization of the morphology, sedimentology and hydrodynamic of the A?u, Cavalos and Conchas estuaries. These estuaries are inserted in a semi-arid climate area and form the mouth of the hydrographic basin of the Piranhas-A?u river, that represent the discharge of the largest watershed in the state. They are embedded in an environment consisting of a fluvial-marine floodplain, mangrove ecosystem, sandbanks, fields of dunes, spits and sandy beaches. Adjacent to the natural units are the main local socioeconomic activities (oil industry, salt industry, shrimp farming, fishing and tourism) are dependent on this river and its conservation. The environmental monitoring is necessary because it is an area under constant action of coastal processes and at high risk of oil spill. The acquisition and interpretation of hydrodynamic, sonographic and sediment data was conducted in two campaigns, dry season (2010) and rainy season (2011), using respectively the current profiler ADCP Doppler effect, the side-scan sonar and Van Veen sampler. In these estuaries: A?u, Cavalos and Conchas were identified the following types of bedforms: flatbed and Dunes 2-D and 3-D (small to medium size), generated at lower flow regime (Froude number <1). Structures such as ripples were observed in the A?u estuary mouth. The higher values of flow discharge and velocity were recorded in the A?u estuary (434,992 m?.s-? and 0,554 m.s-?). In rainy season, despite the record of highest values of discharge and flow velocities at the mouth, the energy rates upstream did not differ much from the data of the dry season. However, in all estuaries were recorded an increase in speed and flow, with reservation to the flow in the A?u estuary and flow at the mouth of the Conchas estuary. Sediment grain sizes tend to increase towards the mouth of the estuary and these ranged from very fine sand to very coarse sand, medium sand fraction being the most recurrent. Based on the data acquired and analyzed, the estuaries A?u, Cavalos and Conchas are classified as mixed , dominated by waves and tides. According to their morphology, they are classified as estuaries constructed by bar and according to the classification by salinity, estuaries Conchas and Cavalos were ranked as hypersaline estuaries, and A?u as hypersaline and vertically well mixed type C<br>Este trabalho teve como objetivo a caracteriza??o sazonal da morfologia, sedimentologia e hidrodin?mica dos estu?rios A?u, Cavalos e Conchas. Estes estu?rios est?o inseridos numa regi?o semi-?rida e comp?e a desembocadura do Rio Piranhas-A?u, maior bacia hidrogr?fica do Estado do Rio Grande do Norte. Compreendem um ambiente constitu?do por plan?cie de inunda??o fl?vio-marinha, ecossistema de manguezal, bancos arenosos, campos de dunas, pontais e praias arenosas, onde os processos costeiros atuantes s?o ressaltados principalmente pela din?mica das modifica??es nas estruturas morfol?gicas ali presentes. Adjacente as unidades naturais, as principais atividades socioecon?micas locais s?o constituidas pela ind?stria petrol?fera, salineira, carcinicultura, pesqueira e tur?stica, tamb?m dependentes deste rio e da sua conserva??o. O monitoramento ambiental desta regi?o se faz portanto necess?rio por se tratar de uma ?rea sob constante a??o dos processos costeiros e com alto risco ao derramamento de ?leo. A aquisi??o de dados hidrodin?micos, sonogr?ficos e sedimentol?gicos foi realizada em duas campanhas: uma no per?odo seco de 2010 e outra no per?odo chuvoso de 2011, utilizando respectivamente, perfilador de correntes por efeito Doppler- ADCP, sonar de varredura lateral e amostrador pontual Van Veen. Nestes estu?rios foram identificadas fei??es de fundo do tipo Leito Plano e Dunas 2-D e 3-D (pequeno a m?dio porte), geradas em regime de fluxo inferior (n?mero de Froude <1). Estruturas do tipo marcas onduladas (ripples) foram observadas somente na foz do estu?rio A?u. Os maiores valores de vaz?o e velocidade do fluxo foram registrados no estu?rio A?u (434,992 m?.s-? e 0,554 m.s-?). No per?odo chuvoso foram registrados os maiores valores de descarga e velocidades do fluxo na regi?o da foz. Entretanto, na montante as taxas de energia n?o diferenciaram muito dos dados obtidos no per?odo seco. Contudo, foi registrado nos tr?s estu?rios um aumento na velocidade e na vaz?o durante o per?odo chuvoso, com ressalva na vaz?o no estu?rio A?u e na vaz?o na foz do estu?rio Conchas. Os sedimentos presentes nos estu?rios variaram de areia muito fina a areia muito grossa, sendo a fra??o areia m?dia a mais recorrente. Em geral a granulometria aumentou em dire??o a foz dos estu?rios. Com base na an?lise e interpreta??o dos dados adquiridos os estu?rios A?u, Cavalos e Conchas foram classificados como dominados por processos misto de ondas e mar?s. De acordo com a morfologia foram classificados como estu?rios constru?dos por barra e segundo a classifica??o por salinidade, os estu?rios A?u, Cavalos e Conchas foram classificados como estu?rios hipersalinos. Adicionalmente o estu?rio A?u tamb?m foi classificado como verticalmente bem misturado do tipo C

Orientador: Francisco Sekiguchi de Carvalho e Buchmann<br>Resumo: Estuários são ambientes heterogêneos, altamente complexos, e condicionados por diversos fatores ambientais. Nenhum estuário é igual a outro, e é esta diversidade que os torna tão importantes do ponto de vista da conservação. A grande quantidade de recursos naturais disponíveis nesses ambientes favorece o desenvolvimento de assentamentos urbanos nas suas margens, podendo comprometer o equilíbrio natural. A partir do conhecimento detalhado dos sistemas estuarinos é possível traçar metas assertivas para a conservação e gestão destes ambientes tão singulares. O presente estudo visa a caracterização e comparação dos estuários dos rios Itaguaré e Guaratuba (Bertioga, SP) quanto aos seus parâmetros geo-físico-químicos. A área de estudo está localizada na planície costeira da Bacia Hidrográfica da Baixada Santista e inserida no Parque Estadual Restinga de Bertioga. Foram realizados levantamentos semestrais de batimetria e imageamento com sonar de varredura lateral, com o intuito de conhecer as profundidades e feições de fundo dos estuários, avaliando a dinâmica de processos erosivos e deposicionais. Medições mensais de salinidade, temperatura e turbidez foram realizadas ao longo de um ano, visando avaliar o comportamento sazonal da intrusão salina e da zona de máxima turbidez. Para verificar variações na granulometria, foram coletadas amostras de sedimentos nos mesmos pontos de medição das variáveis físico-químicas da água. Os resultados foram avaliados de forma integrada, utilizando... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: Estuaries are highly complex heterogeneous environments, conditioned by different environmental factors. Every estuary has particular characteristics, and this diversity makes them so important for conservation. The great amount of available natural resources in these environments contributes to urban settlement developments on their surroundings, which may compromise their natural balance. Detailed knowledge of estuarine systems helps establish assertive goals for the conservation and management of these unique environments. This study aims to characterize and compare Itaguaré and Guaratuba estuaries (Bertioga, SP) regarding their geophysical-chemical characteristics. The study area is located on the Baixada Santista Basin’s coastal plain, and inserted in the Restinga of Bertioga State Park. Biannual bathymetry and side scan sonar surveys were carried in order to evaluate erosive and depositional processes affecting depths and bottom features of the estuaries. Salinity, temperature and turbidity measurements were carried out monthly over a period of one year to evaluate seasonal behavior of saline intrusion and the estuarine turbidity maximum. Sediment samples were collected in order to verify granulometry variations. Results were evaluated in an integrated manner, using geoprocessing and spatial analysis techniques, coupled with secondary data of mareography and precipitation, analyzing the influence of meteoceanographic factors in the water column and the background config... (Complete abstract click electronic access below)<br>Mestre

Small scale protected zones are valuable for helping the health and productivity of fisheries at Lake Tanganyika (East Africa). Spatial placement of protected areas relies on accurate maps of benthic habitats, consisting of detailed bathymetry data and information on lake-floor substrates. This information is unknown for most of Lake Tanganyika. Fish diversity is known to correlate with rocky substrates in ≤ 30 m water depth, which provide spawning grounds for littoral and pelagic species. These benthic habitats form important targets for protected areas, if they can be precisely located. At the NMVA, echosounding defined the position of the 30-m isobath and side-scan sonar successfully discriminated among crystalline basement, CaCO3-cemented sandstones, mixed sediment, and shell bed substrates. Total area encompassed from the shoreline to 30 m water depth is ~21 km2 and the distance to the 30-m isobath varies with proximity to deltas and rift-related faults. Total benthic area defined by crystalline basement is ~1.6 km2, whereas the total area of CaCO3-cemented sandstone is 0.2 km2. Crystalline basement was present in all water depths (0-30 m), whereas CaCO3-cemented sandstones were usually encountered in water ≤ 5 m deep. Spatial organization of rocky substrates is chiefly controlled by basin structure and lake level history.

Made available in DSpace on 2015-03-13T17:08:32Z (GMT). No. of bitstreams: 1 WernerFT.pdf: 4981794 bytes, checksum: 659d4c7e2270b32fa3929a5b6a5ab459 (MD5) Previous issue date: 2002-02-26<br>This dissertation the results of a research developed in the area of S?o Bento do Norte and Cai?ara do Norte, northern coast of the State of Rio Grande do Norte, during the period of June of 2000 to August of 2001, in the ambit of the projects MAMBMAR? (CNPq/CTPETRO) and PROBRAL (CAPES/DAAD).The objective principal of this research was the characterization of the sedimentary dynamics of this coast, with base in data of coastal process (winds, currents, waves and tides), with topographical risings (beach profiles and dunes), satellite images and sedimentary analyses. The more specific objectives were accomplished the coastal monitoring of this coast, to verify the maintenance of an erosive tendency or progradacional after the groynes construction for contention of the erosion in the beach of Cai?ara do Norte, as well as to verify the influence of the features of bottom of the platform interns adjacent on the pole petroliferous of Guamar?. The executed monitoramento allowed to identify that the movement of the sediments, along the year, in that area, is cyclical, reaching the largest oscillations during the months of winter (deposition) and they will summer (erosion). The sedimentologic studies indicated a general tendency for sands quartzosas, with gravel presence, moderately to good selected, with asymmetry predominantly negative. In agreement with the parameter of Dean (1957), used in the identification of the state morfodin?mico of the beaches, monitored beaches, are basically reflectivas with tendency to middlemen, what frames that space of the coast norteriograndense, as a space strongly vulnerable to erosive processes. The studies developed in the platform, it interns of this area, allowed to visualize for the first time, in large scale, the distribution of the features of the submarine bottom to the batom?trico coat of 25 meters. Being pointed out the presence of a high one topographical submerged, with about 5 meters of height, 1 km of width and more than 24 meters of extension, located in the platform it interns in front of S?o Bento do Norte; coincident with the trend of the system of flaws of Carnaubais. This feature relay an important paper on the control of the sedimentary processes and oceanographic, as well as in the coastal evolution of this area of the RN state, and they affect the area of the pole petroliferous of Guamar? directly. These results contribute to a better knowledge of the processes in the area, and consequently as subsidies implantation of measures of coastal and environmental protection for the cities of S?o Bento do Norte and Cai?ara do Norte, as well as to understand how the geological-sedimentary processes and oceanographic, in this area, are influencing the characteristics geoambientais of the pole petroliferous of Guamar?<br>Esta disserta??o apresenta os resultados de uma pesquisa desenvolvida na regi?o de S?o Bento do Norte e Cai?ara do Norte, litoral setentrional do Estado do Rio Grande do Norte, durante o per?odo de Junho de 2000 a Agosto de 2001, no ?mbito dos projetos MAMBMAR? (CNPq/CTPETRO) e PROBRAL (CAPES/DAAD). O objetivo principal da pesquisa foi a caracteriza??o da din?mica sedimentar do litoral em quest?o, com base em dados relativos ? din?mica costeira (ventos, correntes, ondas e mar?s), levantamentos topogr?ficos (perfis de praia e dunas), imagens de sat?lite e an?lises sedimentol?gicas. Como objetivos espec?ficos foram realizados o monitoramento deste litoral, com o fim de verificar a manuten??o de uma tend?ncia erosiva ou progradacional ap?s a constru??o de gabi?es para conten??o da eros?o na praia de Cai?ara do Norte, bem como verificar a influ?ncia das fei??es de fundo da plataforma interna adjacente sobre o p?lo petrol?fero de Guamar?. O monitoramento executado permitiu identificar que a movimenta??o dos sedimentos, ao longo do ano, nessa regi?o, exibe um padr?o c?clico, atingindo as maiores oscila??es durante os meses de inverno (deposi??o) e ver?o (eros?o). Os estudos sedimentol?gicos indicaram uma tend?ncia geral para areias quartzosas, com presen?a de cascalho, moderadamente a bem selecionadas, com assimetria predominantemente negativa. De acordo com o par?metro de Dean (1957), as praias monitoradas s?o basicamente reflectivas com tend?ncia a intermedi?rias, o que enquadra esse trecho da costa norteriograndense como fortemente vulner?vel a processos erosivos. Os estudos desenvolvidos na plataforma interna desta regi?o permitiram visualizar pela primeira vez, em macroescala, a distribui??o das fei??es do fundo submarino at? a is?bata de 25 metros. Ressaltando-se a presen?a de um alto topogr?fico submerso, com cerca de 5 metros de altura, 1 km de largura e mais de 24 metros de extens?o, localizado na plataforma interna em frente a cidade de S?o Bento do Norte, coincidente com o trend do Sistema de Falhas de Carnaubais. Esta fei??o exerce um papel importante no controle dos processos sedimentares e oceanogr?ficos, bem como na evolu??o costeira desta regi?o do Estado do RN, que afetam diretamente a regi?o do p?lo petrol?fero de Guamar?. Estes resultados contribuem para um melhor conhecimento dos processos atuantes na regi?o e, conseq?entemente, fornece subs?dios para a implementa??o de medidas de prote??o costeira e ambiental para as cidades de S?o Bento do Norte e Cai?ara do Norte, bem como para o melhor entendimento de modo como os processos geol?gicos e oceanogr?ficos atuantes nesta ?rea, v?m influenciando nas caracter?sticas geoambientais do p?lo petrol?fero de Guamar?

La marge Ligure est une marge passive soumise à une déformation tectonique compressive associée à la tectonique salifère messinienne. La reprise en compression de la marge s’accompagne d’une sismicité modérée récurrente ponctuée d’évènements plus forts. La marge Ligure est le siège d’une sédimentation importante au Plio-Quaternaire. Elle constitue un environnement propice à l’étude des déstabilisations gravitaires. L’objectif principal de ce travail était de décrire et caractériser les principaux mouvements en masse ayant affecté la marge continentale Ligure au cours du Plio-Quaternaire, de localiser les principales zones sujettes aux déstabilisations et d’identifier les facteurs pré-conditionnant et déclenchant les ruptures dans le but de mieux évaluer l’aléa gravitaire. Une large couverture de données bathymétriques, géophysiques et des carottages acquis sur l’ensemble de la marge a permis de réaliser une étude multi-échelles des processus de ruptures gravitaires et des facteurs déclenchant associés. Près de 1500 glissements ont été identifiés. L’étude de leur répartition spatio-temporelle illustre que l’ensemble de la marge a toujours été affectée par des déstabilisations de pente mais que les principales zones de ruptures auraient migré vers l’ouest au cours du Plio-Quaternaire. Les grandes ruptures sous-marines sont préférentiellement associées aux zones de déformation maximale, cette dernière étant contrôlée par la tectonique crustale et/ou la tectonique salifère. Il apparaît que les ruptures résultent plus généralement d’une association de facteurs distincts qui ont participé à fragiliser la stabilité des dépôts de la pente et qui ont pu provoquer leur rupture<br>The Ligurian margin is a passive margin characterized by high sedimentation rates during the Plio-Quaternary. It is affected by a compressive tectonic deformation leading to the inversion of the margin, together with a salt tectonic. The present-day moderate seismic activity is punctuated by stronger seismic events. Thus, this margin offers a good natural laboratory to study submarine landslides and their triggering factors. Although the Var Turbidite System has been well investigated over the last 20 years, the morphology and tectonics/sedimentary processes affecting the whole margin remained poorly known. This study aims to describe and to characterize the main types of mass movements, their preferential locations along the Ligurian margin during the Plio-Quaternary and their triggering factors to improve geohazards assessment related to landslides. A dataset including bathymetric and geophysical data and cores allowed to realize a multi-scale study of submarine failures and their associated triggering factors. About 1500 landslides were identified on the margin and in the basin. The study of their spatio-temporal distribution revealed that the margin has always been affected by mass-wasting processes and that the main zones of landsliding migrated westward during the Plio-Quaternary. The largest submarine landslides are preferentially associated with the highest deformation rates and their location is controlled by crustal tectonics and/or salt tectonics. The initiation of failures results from the combination of several factors including the margin deformation, earthquakes, salt tectonics and sediment under-consolidation

Les marges continentales, passives ou actives, sont la principale voie de transfert sédimentaire entre le plateau continental et le bassin océanique profond et les plaines abyssales. Les pentes continentales sont le siège de processus d'érosion/dépôt sous le contrôle de transfert de flux particulaires continentaux chenalisés par des structures érosives, telles que les canyons sous‐marins, puis redistribues à l'ensemble de la marge. Les canyons érodent fortement les pentes continentales et contribuent à l'évolution de leur morphologie au cours du temps. On retrouve cependant des canyons sous‐marins qui ne sont pas en relation avec la présence d'un réseau fluviatile. De ce fait, la formation et l'évolution des canyons sous‐marins sont encore peu comprises. Ce travail de thèse s'intéresse aux processus de formation et d'évolution de six canyons sous-marins sur la Marge Ouest du Bassin Ligure et à dix systèmes de canyons sur la Marge Calabro-Ionienne. Le but de cette étude est de contraindre les principales caractéristiques morphométriques (longueur, largeur, profondeur, inclinaison, sinuosité), morphologique (éléments architecturaux, configuration) des canyons, de caractériser leur évolution amont‐aval et d'analyser leur structure interne, afin de mieux comprendre l'origine des canyons sous‐marins, leurs mécanismes de construction et leur évolution au cours du temps en relation avec le contexte géologique régional et leurs potentiels bassins versants subaérien. Pour cela, une approche basée sur une analyse morpho-bathymétrique et géophysiques a été mise en œuvre à partir de relevés bathymétriques complets des marges, de profils de sismiques, de Chirp et de SAR.

碩士<br>國立臺灣大學<br>工程科學及海洋工程學研究所<br>96<br>This work presents the development of a side-scan sonar images simulator by considering the image formation processes of a side-scan sonar acoustic model and properties of terrain. The simulator involved acoustic propagation through the water medium, seabed scattering and towfish motion characteristics. Synthetic images are obtained by applying the bistatic scattering model. The seabed is generated using the fractal theory and the terrain is represented as a random fractal terrain. The outcome of the simulator has two aspects: the synthetic side-scan sonar signal and synthetic side-scan images. The simulator can be used as a tool to generate simulated side-scan signals for underwater exploration tasks.

碩士<br>國立中山大學<br>海洋環境及工程學系研究所<br>99<br>Abstract The interpretation and identification of information from the side-scan sonar imagery are mainly depended on visual observation and personal experiences. Recent studies tended to increase the identification efficiency by using numerical analysis methods. This can reduce the error that cause by the differences of observer’s experience as well as by extended time observation. The position around the center line of the slant range corrected side-scan sonar imagery might result in the degradation of the ability of numerical methods to successfully detect artificial objects. Theoretically, this problem could be solved by using a specific characteristic function to identify the existence of concrete reefs, and then filtering the noise of the central line area with a threshold value. This study was intended to develop fully automatic sonar imagery processing system for the identification of cubic concrete and cross-type protective artificial reefs in Taiwan offshore area. The procedures of the automatic sonar imagery processing system are as follows: (1) Image Acquisition：500kHz with slant range of 75m. (2) Feature Extraction：grey level co-occurrence matrix (i.e., Entropy, Homogeneity and Mean) (3) Classification：unsupervised Bayesian classifier. (4) Object Identification：by characteristic feature (i.e., Entropy). (5) Object’s Status Analysis：object’s circumference、area、center of mass and quantity. This study used the sonar images collected at Chey-Ding artificial reef site in Kaohsiung City as a case study, aiming to verify the automatic sonar imagery processing system and find out the optimum window size. The image characteristic functions include one set of first order parameter (i.e., mean) and two sets of second order parameter (i.e., entropy and homogeneity). Eight(8) sonar images with 1-8 sets of cubic concrete and cross-type protective artificial reefs where used in this step. The identification efficiency of the system, in terms of the produce’s accuracy, is 79.41%. The results illustrated that there were 16~28 sets of artificial reefs being detected in this case which is comparable with the actual amount of 17 sets. Based on this investigation, the optimum window size was concluded to be 12×12 pixels with sliding size of 4 pixel. Imagery collected at Fang-Liau artificial reef site of Pingtung County was tested. For the purpose of applicability, the original imagery (2048×2800 pixels) was divided into 8 consecutive smaller sized imagery frames(2048×350 pixels). The influence of using a two-fold classification procedure and a central filtering method to reduce the noise that caused by slant range correction were discussed. The results showed that central line filtering method is applicable. The results of object’s status analysis showed that there are 156-236 sets of reefs existed. Automatic determination of the target using the characteristic function of entropy is feasible. If the value is larger than 1.45, it represents positive identification of concrete artificial reefs. It can be classified as muddy sand seabed type if the value is smaller than 1.35. If the value is between 1.35~1.45, it illustrates the existence of a transition zone where objects of smaller in dimensions might exist. To achieve the purpose of automatic operation, firstly, we have to identify the existence of the concrete reefs by using the specific characteristic function. Based on the result of existing concrete reefs, suture line filtering method will hence be used to filter the noise from the image information. For that all of the procedures are automatically operated without human intervention. Key word: side-scan sonar ; characteristic function ; gray level co-occurrence matrix ; Bayesian classification ;entropy ; homogeneity ; mean

Daniel T. Cobra.<br>Also issued as Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1990.<br>Includes bibliographical references (p. 137-141).<br>Supported in part by the Defense Advanced Research Projects Agency monitored by the Office of Naval Research. N00014-89-J-1489 Supported in part by the National Science Foundation. MIP-87-14969 Supported in part by Lockheed Sanders, Inc.

碩士<br>國立高雄應用科技大學<br>電子工程系<br>106<br>Side scan sonar system is a acoustic explorer, widely applied below underwater. Because of receiving unvaild data before the first bottom return, it generates blind zone in the side scan sonar image. It’s the disadvantage for auto underwater target detection and image analysis. Correct blind zone detection can remove unnecessary noise, increase the efficiency of image analysis. Accuracy in the current method of blind zone detection is easily affected by seabed topography and interference of echo. Moreover, it relies on assisted detection by people. It not only causes labor wasting, but influencing the reliability. In order to enhance the efficiency in blind zone detection, this study propose an adaptive blind zone detection algorithm for side scan sonar images, basing on image processing technology. This algorithm design is according to the features of blind zone. It takes advantages of image thresholding method, image edge enhancement method, image connected component method and so on to complete the purpose. The experiment result, applying in various side scan sonar images by seabed topography and interference of echo, reveals that this algorithm in processing blind zone detection is similar with artificial detection. Besides, this algorithm only has 2.65% percentage error in average in forty sheets of side scan sonar images. It’s less than 16.49% and 10.96% of the current methods. Therefore, this algorithm break through currently technological difficulties by image processing technology and reach the high efficiency blind zone detection.

碩士<br>國立臺灣大學<br>海洋研究所<br>97<br>In this study, side-scan signals were displayed as sonograph, and different morphological images were classified using digital image processing methods. The data of side-scan sonar image was collected in the project of “Disposal plan of the Keelung Harbor dredging material” in June and October 2007, respectively. Two kinds of method to analysis image are: Wavelet Packet Feature (WPF) and Gray Level Co-occurrence Matrix (GLCM). WPF constructs the signals into seven bands to calculate their respective statistics, and each morphological feature poses their represented trend of statistics among the bands; GLCM produces 16 by 16 grayscale matrix based on the grayscale value which is derived from the pairs of each of 8 peripheral elements matching with the central pixel, respectively, in a sequence of 3 by 3 matrix. GLCM matrix is to establish the characteristics or distribution for each specified image. In the follow, this study also tries to recognize texture composed by side-scan image using automatically identification method instead of manually approach, especially to identify some specific sediment properties. Results of morphological recognition using side-scan images show WPF distribution among the bands and GLCM entropy and homogeneity patterns provide successful differentiation on different morphological images. In addition, for automatic identification, this method can identify their respective locations for those specific sediment properties. In the final, the study brings up some discussions regarding to error judgment to the images resulted from data processing and data quality.

碩士<br>國立中山大學<br>海洋環境及工程學系研究所<br>92<br>About the investigation method of the present situation of coral reef at present, the main choice is scuba diving investigation no matter domestic and foreign countries. Take the coral reef of physical examination in Taiwan as example, divers use transects as basic methods to calculate the coverage rate of coral reef and characteristic of the seabed environment and to survey specific fish and quantity of the invertebrate in order to judge the influence that the human activity causes to the coral reef. In above-mentioned methods can really make full and accurate investigation to the coral reef of monitor area, so the method has already been adopted and walked for many years by the domestic and international relevant organization. But its shortcomings are slower investigating speed and lack accurate fixed position methods, and the divers also have hiding danger. However, some characteristics of side-scan sonar system just can mend the weak points of them. For the speed of investigating, our side-scan sonar''s survey range can reach the belt area of hundred meters wide in both route sides, so it can substantially improve the speed of investigating. For the accuracy of fixed position, the side-scan sonar system match to GPS can obtain certain longitude and latitude of targets（the precision about 10 m）. So, this research is using side-scan sonar system to survey the seabed around LIU-CHIEU YU（the survey area about 2.6 km2）, the steps contain: mapping the distribute condition（sand, mud and rock）of seabed bottom, then identifying growing coral reef of rocky area, final assessing its feasibility by the process and result of survey. The ultimate purpose is an attempt to provide a new method for coral reef survey. The result of study shows: the seabed bottom around LIU-CHIEU YÜ can be divided into several parts by the difference of acoustics reflectivity. Among them, coral reef covers maximum area, and the area can reach to 1,133,670m2（46.4% of effective survey area）. In the part of identifying growing coral reef in the acoustics image, this study compares with optics images of TOV and acoustics images of side-scan sonar to establish the characteristics of growing coral reef in the acoustics image. Among them, the tree-like corals have some characteristics about high backscatter, individual risings, tree-like figures and acoustics shadows, unregulated reflection surfaces and complicated color tones in the reflection surface, but the cover-form reefs do not have tree-like figures and acoustics shadows. Then, using the above-mentioned characteristics to identify survey area seabed shows：The cover area of growing coral reef is 547,438 m2（22.4% of effective survey area）, and the growing coral reef distributes in the southwest, southern and eastern sea area of LIU-CHIEU YÜ. And the optics images of the TOV shows the growth state of growing coral reef in the southeast sea area is superior to the southwest sea area, Finally, assessed by the process and result of this research, basically it is feasible to map the distribute condition of growing coral reef by side-scan sonar system.

碩士<br>國立臺灣大學<br>海洋研究所<br>99<br>In order to objectively analyze side-scan sonar image, we use SwathView which produced by QTC in Canada to process acoustic classification. We also use SwathView to analyze the data of area between Taiwan and Penghu Island. The main feature of SwathView is segmentation method; it combines many statistic algorithms and is useful to process large dataset. Every data has its own acoustic property; we classify the data which has the same acoustic property as one class and the others are so on. Firstly, we load each file and compensate it. Secondly, we segment sonar image by small rectangle, each small rectangle area has many backscatter intensity information. Thirdly, we calculate each rectangle area’s intensity value by statistic algorithms; each rectangle area has 29 statistic values. The last, we reduce 29 values to 3 principle values which called Q1, Q2, Q3 by PCA, according to these Q values we can define each rectangle area’s acoustic property and use K-means cluster method to classify each data. After classification by software, the result seems not well because some class has fake information. The most common fake information is along-track feature. Therefore we must process quality control. I devise the process of quality control by two steps: filter data before analysis and process data after analysis. After quality control we can get a good acoustic classification image. Then we can define each class by real habitat samples.

Η παρούσα διδακτορική διατριβή αποτελεί ένα συνδυαστικό ερευνητικό προϊόν που στοιχειοθετείται από την ανάπτυξη υπολογιστικών εργαλείων επεξεργασίας και ανάλυσης θαλάσσιων γεωφυσικών δεδομένων και την εφαρμογή τους σε πρωτογενή δεδομένα, συλλεγμένα από το Εργαστήριο Θαλάσσιας Γεωλογίας και Φυσικής Ωκεανογραφίας (Ε.ΘΑ.ΓΕ.Φ.Ω) του πανεπιστημίου Πατρών, κατά το διάστημα 2005 – 2011. Τα πεδία στα οποία συγκεντρώνεται το κέντρο βάρους της διατριβής είναι: 1) τα συστήματα ακουστικής ταξινόμησης πυθμένα και 2) η χαρτογράφηση και παραμετροποίηση εμφανίσεων των πολύ σημαντικών θαλάσσιων ενδιαιτημάτων της Ποσειδώνιας και των κοραλλιογενών σχηματισμών στο Ιόνιο και στο Αιγαίο πέλαγος. Έτσι αναπτύχθηκαν και παρουσιάστηκαν εκτενώς τα λογισμικά εργαλεία SonarClass και TargAn, που αναφέρονται αντίστοιχα στην αυτόματη ακουστική ταξινόμηση πυθμένα και την παραμετροποίηση περιοχών ενδιαφέροντος σε εικόνες ηχοβολιστών ευρείας σάρωσης και εφαρμόστηκαν για την χαρτογράφηση λειμώνων ποσειδώνιας στη Ζάκυνθο και κοραλλιογενών σχηματισμών (τραγάνας) στις Κυκλάδες νήσους. Παράλληλα και επεκτείνοντας το εύρος των ερευνητικών προϊόντων αυτής της διατριβής, αναπτύχθηκαν επίσης: 1) το λογισμικό SBP-Im-An για τη γεωαναφορά και ψηφιοποίηση παλαιών αναλογικών καταγραφών τομογράφων υποδομής πυθμένα, 2) το λογισμικό χωροστάθμησης θαλάσσιων γεωμαγνητικών δεδομένων MagLevel και 3) το λογισμικό ποσοτικοποίησης αλιευτικών ιχνών σε δεδομένα ηχοβολιστών ευρείας σάρωσης PgStat, με αντίστοιχες σημαντικές εφαρμογές σε πρωτογενή δεδομένα. Η παρούσα διατριβή επιδεικνύει πρωτοτυπία τόσο σε επίπεδο ανάπτυξης νέων μεθόδων ανάλυσης και επεξεργασίας γεωφυσικών δεδομένων όσο και σε επίπεδο παρουσίασης εφαρμογών τους σε περιοχές μελέτης με ιδιαίτερο περιβαλλοντικό ενδιαφέρον αλλά και σε πεδία έρευνας για τα οποία το ενδιαφέρον της σύγχρονης θαλάσσιας επιστημονικής κοινότητας βρίσκεται στο απόγειό του.<br>The present PhD thesis is a combinational research product concerning the development of software tools for the processing and analysis of marine geophysical data and their application to original data, collected by the Laboratory of Marine Geology and Physical Oceanography (L.M.G.P.O), university of Patras, Greece, during the period 2005-2011. The fields that this thesis focuses on are: 1) the Acoustic Seabed Classification Systems and 2) the mapping and quantification of very important marine habitats that specifically are the Posidonia Oceanica Prairies and the Coralline formations in the Aegean and Ionian seas. The software tools SonarClass and TargAn, that respectively refer to the Acoustic Seabed Classification and the quantification of Regions Of Interest in swath sonar imagery are presented and applied to the cases of Posidonia Oceanica in Zakinthos Isl. (Ionian Sea) and Coralline formations in Cyclades Isl. (Aegean Sea). Additionally and extending the range of the research products of this thesis, other software tools that are presented are: 1) the SBP-Im-An for the recreation (georeferencing and digitization) of old analog Sub Bottom Profiler recordings, 2) the MagLevel for the tie line leveling of marine geomagnetic data and 3) the PGStat for the quantification of trawl marks in swath sonar imagery, all of them with significant applications to original data. This thesis demonstrates originality due to both the development of new methods for the analysis and processing of marine geophysical data and the applications to study areas with particular environmental interest and research fields for which the attention of the marine scientists is at its peak.

<p>Manatees (Mammalia: Sirenia), along with the closely related dugongs, are the only herbivorous marine mammals. Manatees consume a wide variety of vascular plants and algae in both marine and freshwater habitats. However, little is known about what characteristics influence diet and food selectivity, especially in freshwater habitats, which represent a large portion of the available habitat for the endangered Antillean manatee, <italic>Trichechus manatus manatus</italic>, in Central and South America. Understanding foraging ecology is an important element of effective conservation strategies.</p><p>This dissertation investigated various aspects of the foraging ecology of the Antillean manatee in a freshwater habitat, specifically: 1) how plant availability (i.e. species richness, diversity, and abundance) varied seasonally with changes in water depths, 2) manatee food selectivity from a representative set of plant species from that freshwater habitat, and 3) the relationship of plant nutritive compounds and availability with manatee food selectivity. In addition, this dissertation describes the multiple uses of sonar technology for studying manatees and habitat characteristics in freshwater.</p><p>Plant availability to manatees was evaluated by conducting monthly plant surveys from July 2010-July 2011 in four contact lakes in the wetlands of Tabasco, Mexico. Manatee food selectivity was examined by conducting food selection experiments on a wild adult manatee during the low water season with 54 plant species representing 25+ genera. The nutritive components (i.e. crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HC), and ash) and plant availability values for selected and non-selected plants species were evaluated to determine their relationship with manatee food selectivity. The applicability of using side-scan sonar for manatee research was tested in various freshwater and estuarine habitats in Honduras, Costa Rica, Panama, and the wetlands of Tabasco, Mexico between 2006-2011.</p><p>The major findings of this dissertation are as follows. Plant species richness, diversity, and abundance were greatest during the rising water season (July-August) and lowest during the low water season (March-June). No plants were available in April-June, which represented the majority of the low water season. The wild manatee</p><p>selected 27 (11+ genera) of the 54 species examined during the feeding experiments. Of the plant characteristics tested (i.e. nutritive components and plant availability), only digestible fiber (HC) was significantly related to manatee food selection, with manatees</p><p>selecting plants with higher HC content. Four unique applications were identified for the use of side-scan sonar to facilitate manatee research in freshwater habitats: 1) confirmation of visual sightings and determination of group size, 2) determination of mother-calf pairs, 3) habitat characterization, and 4) assisting manatee captures.</p><p>Results from this study reveal that manatees living in the freshwater wetlands of Tabasco, Mexico have to cope with a highly seasonal availability of plants and that while manatees consume plants from a wide variety of genera, they are highly selective. Unlike other herbivorous mammals, manatee food selectivity was not influenced by CP, NDF, or ADF, but rather by digestible fiber. A unique suit of anatomical and physiological characteristics suggests that manatees may be fiber digestion specialists. Both seasonal plant availability and the manatee's large dietary breadth must be considered when developing 1) conservation strategies for wild manatees in freshwater habitats and 2) protocols for captive rehabilitation of orphaned and stranded manatees that will be reintroduced into the wild.</p><br>Dissertation

Η παρούσα εργασία εκπονήθηκε στα πλαίσια του Διατμηματικού Προγράμματος Μεταπτυχιακών σπουδών στις περιβαλλοντικές Επιστήμες. Οι θαλάσσιες γεωφυσικές έρευνες εκτελέστηκαν από το Εργαστήριο Θαλάσσιας Γεωλογίας και Φυσικής Ωκεανογραφίας (Ε.ΘΑ.ΓΕ.Φ.Ω) του Τμήματος Γεωλογίας του Πανεπιστημίου Πατρών. Οι έρευνες του Οκτωβρίου του 2011 αποτελούν συνέχεια αυτών του Οκτωβρίου του 2010 με σκοπό να καλυφθεί το σύνολο της θαλάσσιας περιοχής για την οποία υπάρχει αδειοδότηση. Αντικείμενο της έρευνας είναι η γεωφυσική διασκόπηση του πυθμένα με τη χρήση ηχοβολιστή πλευρικής σάρωσης (side scan sonar) στις περιοχές της Νεάπολης και της Ελαφονήσου με σκοπό: α) την αποτύπωση της μορφολογίας του πυθμένα και β) τον εντοπισμό βιολογικών πόρων (λιβάδια Posidonia oceanica και ασβεστιτικά ροδοφύκη). Τα λιβάδια της Posidonia oceanica και τα ασβεστιτικά ροδοφύκη αποτελούν ενδημικά είδη της Μεσογείου των οποίων ο ρυθμός αύξησής τους θεωρείται εξαιρετικά αργός ενώ παράλληλα ο ρυθμός καταστροφής τους είναι τεράστιος και κρίνεται απαραίτητη η χαρτογράφηση τους ώστε να παρθούν καλύτερα μέτρα προστασίας.Η εμφάνιση των δύο βιολογικών σχηματισμών συμπίπτει με την βιβλιογραφία καθώς για την περιοχή μελέτης της Νεάπολης η Posidonia oceanica εμφανίζεται σε βάθη 0-35 m και στην Ελαφόνησο 0-25 m.Οι σχηματισμοί των ασβεστιτικών ροδοφυκών-ροδόλιθων εμφανίζονται σε βάθη 50-100 m για την Νεάπολη και 20-100 m για την Ελαφόνησο.<br>This present study was conducted for the Interdepartmental program of postgraduate studies in environmental sciences, Department of Geology. Marine geophysical survey took place in October 2011 by the Laboratory of Marine Geology and Physical Oceanography. The current research follows the survey of October 2010 in order to cover the entire sea area for which license was given. The purpose of this thesis is to have a full bottom analysis for the areas Neapoli and Elafonisos , using side scan sonar, and mapping Posidonia oceanica and Coralligene formations which are two very important species for the marine environment.

Στα πλαίσια της παρούσας έρευνας, μελετήθηκε η προστατευόμενη περιοχή του Οικολογικού Δικτύου Natura 2000: «Λιμνοθάλασσα Πύλου (Διβάρι), Νήσος Σφακτηρία, Αγ. Δημήτριος» με κωδικό GR2550004. Διεξάχθηκαν δύο εποχικές δειγματοληψίες, στις 31 Αυγούστου του 2012 και στις 21 Απριλίου του 2013. Η λιμνοθάλασσα της Γιάλοβας έχει έκταση περίπου 2,5 Km2, μέγιστο βάθος 1 m και επικοινωνεί με τον κόλπο του Ναυαρίνου μέσω ενός τεχνητού διαύλου. Αρχικά, πραγματοποιήθηκε η ηχοβολιστική αποτύπωση του πυθμένα, με χρήση ηχοβολιστή πλευρικής σάρωσης (Side Scan Sonar, SSS) με σκοπό να αποκαλυφθεί, τόσο η μορφολογία του βυθού, όσο και η παρουσία, η αφθονία και η χωρική κατανομή των υδρόβιων μακροφύτων. Κατόπιν, σε 9 προεπιλεγμένους δειγματοληπτικούς σταθμούς, πραγματοποιήθηκε καταγραφή των φυσικοχημικών παραμέτρων και συλλέχθηκαν δείγματα υδρόβιας χλωρίδας. Με τη βοήθεια του ηχοβολιστή πλευρικής σάρωσης μελετήθηκε, περίπου, το 37% της έκτασης της λιμνοθάλασσας. Μέσω αυτής της διαδικασίας, προέκυψαν 6 διαφορετικοί ακουστικοί τύποι που αντιστοιχούν σε 6 διαφορετικά ποσοστά φυτοκάλυψης: πυκνή (76-100%), λιγότερο πυκνή (51-75%), αραιή (26-50%), πολύ αραιή (6-25%), σπάνια (1-5%) και καθόλου (<1%). Αφού κατασκευάστηκε το μωσαϊκό του πυθμένα, με τη χρήση των λογισμικών Triton Isis και TritonMap (Delphmap) της Triton Imaging Inc., διαπιστώθηκε ότι, η λιμνοθάλασσα καλύπτεται από βλάστηση σε ποσοστό περίπου 25% ενώ, περίπου, το 75% δεν καταλαμβάνεται από κάποιο είδος υδρόβιας βλάστησης, και το υπόστρωμα είναι αμμώδες/ ιλυοαμμώδες (Μπούζος et al., 2002a). Τα αποτελέσματα του Αυγούστου έδειξαν ότι, η πυκνή φυτοκάλυψη φτάνει περίπου στο 2% της υπό μελέτη έκτασης, και χωρικά περιορίζεται κοντά στο δίαυλο επικοινωνίας με τη θάλασσα. Η υδρόβια χλωρίδα που απαντά στους σταθμούς αυτούς αποτελείται από τα είδη Ruppia cirrhosa σε μίξη με την Cymodocea nodosa, με κυρίαρχο είδος τη Ruppia cirrhosa. Όσο απομακρυνόμαστε από το δίαυλο, η πυκνή φυτοκάλυψη εναλλάσσεται με λιγότερο πυκνή, σε ποσοστό 1% επί του συνόλου, και αποτελείται από τα ίδια είδη. Η αραιή φυτοκάλυψη, απαντά σε ποσοστό 3% και χωρικά κατανέμεται στο δίαυλο επικοινωνίας, αλλά και στα νοτιοδυτικά της λιμνοθάλασσας, όπου, εκτός από τη Ruppia cirrhosa, απαντά και η Cladophora glomerata. To ποσοστό της πολύ αραιής φυτοκάλυψης κυμαίνεται γύρω στο 15% και χωρικά κατανέμεται, κυρίως, στα βορειοανατολικά της λιμνοθάλασσας, όπου απαντά μόνο η Ruppia cirrhosa, ενώ, σε ποσοστό 4%, η φυτοκάλυψη είναι σπάνια και απαντά στα βορειοδυτικά και στα κεντρικά σημεία της λιμνοθάλασσας. Τον Απρίλιο, η χωρική κατανομή των υδρόβιων μακροφύτων είναι ακόμα πιο περιορισμένη, με συμμετοχή μόνο της Ruppia cirrhosa, η οποία συγκεντρώνεται κυρίως, κοντά στο δίαυλο επικοινωνίας με τον κόλπο του Ναυαρίνου, καθώς εκεί ευνοείται η ανανέωση του νερού και οι περιβαλλοντικές συνθήκες είναι κατάλληλες για την ανάπτυξή τους. Τονίζεται επίσης ότι, τον Απρίλιο, συλλέχθηκε από τα βόρεια της λιμνοθάλασσας ένα είδος του γένους Ulva spp, που αποτελεί δείκτη ευτροφικών συνθηκών (Orfanidis et al., 2005, Aliaume et al., 2007). Γενικά, το κυρίαρχο είδος στη λιμνοθάλασσα, και τις δύο δειγματοληπτικές περιόδους, είναι το κοσμοπολίτικο είδος Ruppia cirrhosa το οποίο έχει καταγραφεί ξανά στην περιοχή (Tiniakos et al., 1997). Σε όλους τους δειγματοληπτικούς σταθμούς, καταγράφηκαν οι παράμετροι: θερμοκρασία, αλατότητα, pH και διαλυμένο οξυγόνο, αλλά και το βάθος της λιμνοθάλασσας, η διαφάνεια του νερού και η ένταση της φωτοσυνθετικά ενεργής ακτινοβολίας (PAR). Επιπλέον, υπολογίστηκαν οι συγκεντρώσεις της χλωροφύλλης-α, τα ολικά αιωρούμενα στερεά (TSS), οι συγκεντρώσεις των ανόργανων ενώσεων αζώτου και φωσφόρου, καθώς και τα επίπεδα της ολικής αλκαλικότητας των ανθρακικών και όξινων ανθρακικών ιόντων. Τα αποτελέσματα έδειξαν χωρική και χρονική διακύμανση όλων των παραμέτρων, με πιο σημαντικές τις διακυμάνσεις της θερμοκρασίας, της αλατότητας και της συγκέντρωσης των θρεπτικών ενώσεων αζώτου και φωσφόρου. H εποχική διακύμανση των περιβαλλοντικών παραμέτρων προκαλεί φυσικό stress στους υδρόβιους οργανισμούς επηρεάζοντας την αφθονία και εξάπλωσή τους (Crouzet et al., 1999). O έλεγχος των στατιστικώς σημαντικών διαφορών των φυσικοχημικών παραμέτρων, πραγματοποιήθηκε με τον έλεγχο Mann-Whitney U, ο οποίος έδειξε ότι υπάρχουν στατιστικώς σημαντικές διαφορές, μεταξύ των δύο εποχών, που αφορούν στις παραμέτρους: διαφάνεια, αλατότητα, θερμοκρασία, pH, TSS, NO2, CO3ˉ και HCO3=. Αντίθετα, δεν εντοπίστηκαν στατιστικώς σημαντικές διαφορές μεταξύ των δύο εποχικών δειγματοληψιών στις παραμέτρους: βάθος, διαλυμένο οξυγόνο, χλωροφύλλη-α, NO3, NH4 και PO4. Ενδεικτικά, η θερμοκρασία παρουσίασε μεγάλη εποχική διακύμανση, σημειώνοντας πολύ υψηλές τιμές τον Αύγουστο (28,80 C - 30,50 C), και πολύ χαμηλότερες τον Απρίλιο (19,0 0C - 20,40C). Η αλατότητα παρουσίασε μεγάλες διακυμάνσεις από σταθμό σε σταθμό, κυρίως τον Αύγουστο, αλλά και από εποχή σε εποχή. Συγκεκριμένα τον Αύγουστο, κυμάνθηκε από 42,73‰ έως 54,42‰ ενώ τον Απρίλιο κυμάνθηκε γύρω στο 31‰ σε όλη την έκταση της λιμνοθάλασσας. Επιπρόσθετα, το pH παρουσίασε στατιστικώς σημαντικές διαφορές, καθώς τον Αύγουστο κυμάνθηκε στο 8,23 κατά μέσο όρο, αναφορικά για όλη τη λιμνοθάλασσα, ενώ τον Απρίλιο παρουσίασε πτωτική τάση, αφού η μέση του τιμή ήταν 6,99. Όσον αφορά στις συγκεντρώσεις των θρεπτικών, τα αμμωνιακά ιόντα ήταν η κυρίαρχη μορφή αζώτου, καθώς παρουσίασε υψηλές τιμές και τις δύο δειγματοληπτικές περιόδους, ενώ, τα νιτρώδη ιόντα, παρόλο που διέφεραν στατιστικώς σημαντικά, σε γενικές γραμμές, κυμάνθηκαν σε χαμηλά επίπεδα και τους δύο μήνες (έως 0,010 mg/l). Το διαλυμένο οξυγόνο παρέμεινε σε φυσιολογικά επίπεδα και τους δύο μήνες, όπου η μέση τιμή του ήταν 8 mg/l. Το βάθος δεν μεταβλήθηκε σημαντικά, ενώ τα επίπεδα της χλωροφύλλης-α, ήταν υψηλά και τις δύο χρονικές περιόδους. Η ανάλυση Spearman έδειξε σαφείς συσχετίσεις μεταξύ των περιβαλλοντικών παραμέτρων. Ανάμεσα στις πιο σημαντικές συγκαταλέγονται, η αρνητική συσχέτιση της διαφάνειας με την εποχή και το βάθος. Επιπλέον, σημαντική είναι η αρνητική συσχέτιση της αλατότητας και της θερμοκρασίας με την εποχή, αλλά και η θετική συσχέτιση μεταξύ των δύο πρώτων. Στη συνέχεια, εξίσου σημαντική είναι η θετική συσχέτιση του pH με την αλατότητα και τη θερμοκρασία, αλλά αξιοσημείωτες είναι και οι θετικές συσχετίσεις που παρουσιάζουν τα TSS με τη θερμοκρασία και το pH, και η χλωροφύλλη-α με τη διαφάνεια. Σύμφωνα με τα κριτήρια που έθεσε η Οργάνωση για Συνεργασία και Ανάπτυξη (ΟΕCD) για τα στάσιμα ύδατα, προέκυψε η τροφική κατάσταση της λιμνοθάλασσας, με βάση τις μέσες και οριακές τιμές των παραμέτρων: TP, χλωροφύλλη-α και διαφάνεια (Secchi depth) (OECD, 1982). Έτσι, με βάση τη μέση συγκέντρωση του ολικού φωσφόρου χαρακτηρίζεται ως υπερτροφική τον Αύγουστο και ως ευτροφική τον Απρίλιο. Όσον αφορά στη χλωροφύλλη-α, με βάση τις μέσες και μέγιστες τιμές που σημειώθηκαν τον Αύγουστο, η λιμνοθάλασσα χαρακτηρίζεται ως ευτροφική, ενώ τον Απρίλιο χαρακτηρίζεται ως ευτροφική, με βάση τη μέση τιμή, αλλά ως μεσοτροφική, με βάση τη μέγιστη τιμή που καταγράφηκε. Τέλος, όσον αφορά στη διαφάνεια, σύμφωνα με τις μέσες και ελάχιστες τιμές της, η λιμνοθάλασσα, και τους δύο μήνες, χαρακτηρίζεται ως υπερτροφική. Με χρήση των Γεωγραφικών Συστημάτων Πληροφοριών (ΓΣΠ), και με υπόβαθρο ένα μωσαϊκό ορθοφωτοχαρτών της Κτηματολόγιο Α.Ε., που αποκτήθηκαν κατά το διάστημα 2007-2009, κατασκευάστηκε ο χάρτης των καλύψεων/ χρήσεων γης του συστήματος ταξινόμησης Corine Land Cover 2000, για ολόκληρη την προστατευόμενη περιοχή. Ακολούθως, έγινε η αντιστοίχηση των κατηγοριών καλύψεων/ χρήσεων γης που προέκυψαν, με τους τύπους οικοτόπων του Παραρτήματος Ι της Οδηγίας 92/43/ΕΚ, στο 3ο επίπεδο ταξινόμησης. Επιπλέον, πραγματοποιήθηκε μια ποιοτική σύγκριση μεταξύ του νέου χάρτη και του χάρτη του Corine Land Cover, που κατασκευάστηκε για την περιοχή το 2000. Με βάση το χάρτη που κατασκευάστηκε διαπιστώθηκε ότι, υπάρχει ποικιλία φυσικών τύπων οικοτόπων, που προσδίδουν στην περιοχή ιδιαίτερη οικολογική και αισθητική αξία. Περιμετρικά της λιμνοθάλασσας απαντούν μεσογειακά αλίπεδα (Juncetalia maritimi), καλαμώνες, μεσογειακοί λειμώνες υψηλών χόρτων και βούρλων (Molinio Holochoenion), παρόχθια δάση-στοές και λόχμες (Nerio-Tamaricetea και Securinegion tinctoriae), σχηματισμοί με αρκεύθους (Juniperus spp.), υποτυπώδεις κινούμενες θίνες, κινούμενες θίνες της ακτογραμμής με Ammophila arenaria και μονοετή βλάστηση μεταξύ των ορίων πλημμυρίδας και αμπώτιδας. Επιπλέον, στη νήσο Σφακτηρία, στους λόφους του Παλαιόκαστρου και του Πετροχωρίου, απαντούν απόκρημνες βραχώδεις ακτές με βλάστηση στη Μεσόγειο (με ενδημικά Limonium spp.), Garrigues της Ανατολικής Μεσογείου και φρύγανα ενώ, οι όχθες του ποταμού Σελά χαρακτηρίζονται από δάση ανατολικής πλατάνου (Platanus orientalis). Τονίζεται η σημειακή συμμετοχή του τύπου προτεραιότητας των θινών των παραλιών με αρκεύθους (Juniperus spp). Επιπλέον, σε μεγάλη έκταση, απαντούν οι αγροτικές καλλιέργειες, με κυρίαρχους τους ελαιώνες, περιοχές αστικού πρασίνου, δρόμοι αλλά και οικισμοί. Τα αποτελέσματα της παρούσας εργασίας όπως η αποτύπωση της μορφολογίας του πυθμένα της λιμνοθάλασσας και των καλύψεων/ χρήσεων γης, στα όρια της προστατευόμενης περιοχής και η περαιτέρω εκτίμηση της οικολογικής κατάστασης της λιμνοθάλασσας θα συμβάλλουν περαιτέρω στην ορθολογική διαχείριση της.<br>In the context of this research, the protected area of the «Natura 2000» ecological network: "Pylos Lagoon, Sfaktiria island, St. Dimitrios" with the sitecode GR2550004, has been studied. Two sampling campaigns were carried out, οn August 31st 2012 and on April 21st 2013. Gialova lagoon covers an area of 2.5 Km2 with a maximum depth of 1 m and is connected with the adjoining Navarino Bay, via a small channel. Firstly, side scan sonar bottom interpretation was carried out, in order to investigate, not only the morphology of the lagoon’s bottom, but also the presence, abundance and spatial distribution of aquatic macrophytes. In addition, physicochemical parameters were recorded in 9 different sampling stations. Furthermore, samplings of aquatic vegetation were carried out as well. Initially, with the use of SSS, roughly 37% of the lagoon’s surface has been studied. Side scan sonar imagery resulted in 6 different acoustic types, which correspond to 6 different percentages of plant cover: thick (76-100%), less than thick (51-75%), sparse (26-50%), too sparse (6-25%), rare (1-5%) and absent (<1%). Having built the mosaic of the bottom of the lagoon, with the use of software Triton Isis and Triton Map (Delphmap) of Triton Imaging Inc., it was found that, the lagoon is covered by vegetation at 25%, while 75% is not occupied by any kind of aquatic vegetation, but the substrate is sandy/mudsandy (Bouzos et al., 2002a). The results of August showed that the thick plant cover reaches approximately 2% of the study area, and it is spatially restricted near the communication channel with the sea. The aquatic flora which responds to these stations is Ruppia cirrhosa in mixing with the Cymodocea nodosa, with the Ruppia cirrhosa as the dominant species. When we move away from the communication channel, the thick plant cover alternates with less than thick, representing 1% of the total, and consists of the same species. The sparse plant cover responds to 3% and is spatially distributed in the communication channel, but also in the southwest of the lagoon, where, apart from the Ruppia cirrhosa, Cladophora glomerata is found as well. The percentage of too sparse vegetation is around 15%, and it is spatially distributed mainly in the north-east of the lagoon, where only Ruppia cirrhosa is found, while, the vegetation is rare at 4%, and responds to the northwest and the central points of the lagoon. In April, the spatial distribution of aquatic macrophytes is even more limited, involving only the Ruppia cirrhosa, which is mainly concentrated near the communication channel with the adjoining Navarino Bay, which favored the renewal of water and where the environmental conditions are suitable for their development. It should be also noted that, in April, an occasional species of the genus Ulva spp., was collected from the northern section of the lagoon. This species is an indicator of eutrophic conditions (Orfanidis et al., 2005, Aliaume et al., 2007). In general, the dominant species in the lagoon, in both sampling periods, is the cosmopolitan species Ruppia cirrhosa, which has been recorded before in the region (Tiniakos et al., 1997). The following parameters were recorded in all the sampling stations: temperature, salinity, pH and dissolved oxygen, but also the depth of the lagoon, the transparency of the water’s column and the volume of photosynthetically active radiation (PAR). Furthermore, chlorophyll-a, total suspended solids (TSS), inorganic nitrogen and phosphorus compounds, as well as the levels of total alkalinity of carbonates and acid carbonates were calculated. The results showed spatial and temporal variability of all parameters, and the most significant fluctuations were observed in temperature, salinity and in nitrogen and phosphorus concentrations. This seasonal variation of environmental parameters causes natural stress on aquatic organisms affecting their abundance and their spatial distribution (Crouzet et al., 1999). The control of the statistically significant differences in physicochemical parameters was carried out with the Mann-Whitney U test, which has shown that, there are statistically significant differences between the two seasons, relating to parameters: transparency, salinity, temperature, pH, TSS, NO2, CO3ˉ and HCO3=. In contrast, there were not statistically significant differences between the two sampling periods for parameters: depth, dissolved oxygen, Chl-a, NO3, NH4 and PO4. More specifically, the temperature has large seasonal variation, noting very high values in August (28.8ᵒ C – 30.5ᵒ C) and much lower in April (19.0ᵒ C – 20.4ᵒ C). The salinity showed large fluctuations from station to station, especially in August, but also from season to season. Specifically in August, it ranged from 42.73‰ to 54.42‰ and in April fluctuated around 31‰ throughout the lagoon. In addition, the pH values presented statistically significant differences. In August, pH ranged from around 8.23 on average, with respect to the entire lagoon, while in April showed a downward trend, when the average value was around 6.99. With regard to the concentrations of nutrients, ammonium ions were the dominant form of nitrogen, as it presented high values in both sampling periods, while the nitrite ions, although differed statistically significantly, in general, varied in low levels both months. Dissolved oxygen, remained at normal levels in both sampling periods, where the average value was around 8 mg/l. The depth did not change significantly, while the levels of Chl-a, were very high in both time periods. The Spearman analysis showed clear correlations between environmental parameters. Among the most important is, the negative correlation of transparency with season and depth. In addition, significant is the negative correlation of salinity and temperature with season, but also the positive correlation between the first two. Of course, equally important is the positive correlation of pH with salinity and temperature, but also significant are the positive correlations of the TSS with temperature and pH, and Chl-a with transparency. Finally, it is mentioned that there is negative correlation of total phosphorus with season and acid carbonates, and positive correlation with salinity, temperature, pH and TSS. In accordance with the standards set by the Organization for Cooperation and Development (OECD) for stagnant water, the trophic status of the lagoon has been established, on the basis of the average and maximum values of parameters: TP, Chl-a and transparency (Secchi depth) (OECD, 1982). So, on the basis of the average concentration of total phosphorus, it is characterized as hypereutrophic in August and as eutrophic in April. As regards the Chl-a, on the basis of the average and maximum values occurred in August, the lagoon is characterised as eutrophic, while in April it is characterized as eutrophic, based on the average value, but as mesotrophic, on the basis of the maximum value recorded. Finally, with regard to transparency, in accordance with the average and minimum values, the lagoon is characterized as hypereutrophic in both seasons. With the use of Geographical Information Systems (GIS) and with the help of ortho-corrected aerial photographs, acquired during 2007 and 2009, a Land Cover Land Use map was constructed. Subsequently, the categories of Corine Land Cover that came up, matched with the habitat types included in the Annex I of the Directive 92/43/EC, according to the 3rd classification level. Furthermore, the land cover/ land use categories of the new map compared with those of the map that constructed in 2000 for the same area, in order to estimate the changes during the years that have passed. The map, which was constructed in the context of this research, showed that there is a variety of natural habitat types, which gives the area special ecological and aesthetic value. In particular, around the lagoon, we found mediterranean salt meadows (Juncetalia maritimi), reedbeds, mediterranean grassland with high grass and rush (Molinio Holochoenion), southern riparian forest-arcades and scrubs galleries (Nerio-tamaricetea and Securinegion tinctoriae), formations with juniper thickets (Juniperus spp.), embryonic dunes, shifting dunes along the shoreline with Ammophila Arenaria and vegetation of drift lines. In addition, on the Sfaktiria island, in Paleokastro and Petrochori hills respond vegetated sea cliffs of the Mediterranean coasts (with endemic Limonium spp.), Garrigues of eastern Mediterranean and phrygana, while the banks of the river Selas are characterized by oriental plane woods (Platanus orientalis). The spot presence of dune juniper thickets is emphasized (Juniperus spp), which is a priority habitat. In addition, to a large extent, there are agricultural crops with olive groves, urban areas, roads and different kinds of settlements. The ultimate aim of this study is the visual interpretation of the morphology of the bottom of the lagoon and the Land Cover Land Uses, within the limits of the protected area and the further assessment of the ecological status of the lagoon.

Η περιοχή μελέτης είναι η λιμνοθάλασσα Καϊάφα.Η μελέτη αυτή βασίστηκε στη συλλογή και ανάλυση γεωφυσικών δεδομένων, στην ανάλυση πυρήνων ιζήματος καθώς και σε μικροβιολογική ανάλυση δειγμάτων νερού της λιμνοθάλασσας. Τέλος ελήφθησαν δείγματα υδρόβιων φυτών από τον πυθμένα της λιμνοθάλασσας για τον έλεγχο των γεωφυσικών δεδομένων. Η γεωφυσική έρευνα-δειγματοληψία και η κοκκομετρική ανάλυση έδειξαν δυο περιοχές στον πυθμένα με διαφορετική κοκκομετρική σύσταση (αμμώδης-ιλυώδης πυθμένας) και διαφορετική βλάστηση (Chara hispida f. corfuensis και Potamogeton pectinatus). Επίσης χαρτογραφήθηκαν περιοχές του πυθμένα όπως, κρατηρόμορφοι σχηματισμοί, ουλές και μέτωπα. Η μικροβιολογική ανάλυση έδειξε περιοχές με έντονη μόλυνση κοπρανώδους προέλευσης καθώς και περιοχές χωρίς σημαντική βακτηριακή επιβάρυνση. Οι περιοχές όπου παρατηρείται η μεγαλύτερη μόλυνση είναι τα λουτρά του Καϊάφα και η περιοχή απέναντι από τις στις τουριστικές εγκαταστάσεις του Ε.Ο.Τ (προβλήτα). Η μικρότερη μόλυνση παρατηρείται στο κέντρο της λιμνοθάλασσας όπου ο αριθμός ολικών βακτηρίων και κολοβακρτηρίων είναι μηδενικός. Τέλος η γεωχημική ανάλυση έδειξε παρόμοιες συγκεντρώσεις βαρέων μετάλλων στα ιζήματα με άλλες παράκτιες περιοχές του ελληνικού χώρου.<br>The study area is Kaiafas lagoon, West Peloponnese. For this study it was collected and analyzed digital geophysical data (side scan sonar echographs), two cores of sediment and samples of water for microbiological examination. It was also collected samples of marine plants for groundtruthing. The geophysical survey-grain size analysis revealed different grain size composition in the South and North part of the lagoon (sandy-silty seabed correspondingly), which was covered with different marine plants species (Chara hispida –Potamogeton pectinatus. The mapping of seabed showed crater-like formations, scars and fronts. The microbiological analysis showed that the pollution (from fecal bacteria) was restricted in the South part of the lagoon near the pipe of the biological treatment plant. In a lower extend, fecal pollution was tracked in the western part of the lagoon near the touristic settlement of E.O.T. The greater part of the lagoon is unpolluted. Geochemistry analysis showed similar levels of heavy metals in sediment with other coastal areas in Greece.

Η παρούσα μεταπτυχιακή διατριβή επικεντρώνεται στην μελέτη της παράκτιας ζώνης της νήσου Λέρου στο Νοτιοανατολικό Αιγαίο, παρουσιάζοντας τα αποτελέσματα της ερμηνείας των γεωφυσικών στοιχείων που συλλέχθηκαν από το Εργαστήριο Θαλάσσιας Γεωλογίας και Φυσικής Ωκεανογραφίας (Ε.ΘΑ.ΓΕ.Φ.Ω.) τον Ιούνιο του 2011. Η έρευνα φιλοδοξεί να συνεισφέρει στην ανάδειξη της υποθαλάσσιας πολιτιστικής και φυσικής κληρονομιάς του νησιού, καθώς η συλλογή, επεξεργασία και ερμηνεία του συνόλου των δεδομένων επέτρεψε την αναγνώριση και την λεπτομερή χαρτογράφηση υποθαλάσσιων στόχων μεγάλης ιστορικής και περιβαλλοντικής σημασίας. Ως εκ τούτου, η διατριβή κινείται σε δύο κατευθύνσεις. Η πρώτη κατεύθυνση αφορά στον εντοπισμό στόχων πιθανής ιστορικής σπουδαιότητας που εντοπίστηκαν στην επιφάνεια του πυθμένα ενώ η δεύτερη κατεύθυνση αφορά στον εντοπισμό και την αποτύπωση βιογενών σχηματισμών και συγκεκριμένα λειμώνων P. Oceanica και ασβεστιτικών ροδοφυκών (corallegene formations). Οι θαλάσσιες έρευνες πραγματοποιήθηκαν σε δύο διακριτά στάδια, στην συστηματική αποτύπωση του πυθμένα με ηχοβολιστή πλευρικής σάρωσης (EG&G 272 TD) και την οπτική επιβεβαίωση των αποτελεσμάτων της ηχοβολιστικής αποτύπωσης με σύστημα συρόμενης υποβρύχιας κάμερας. Η ανάλυση και επεξεργασία των ηχογραφιών οδήγησε στον εντοπισμό ναυαγίων που συνδέονται με τη Μάχη της Λέρου (9-10/1943), ένα από τα σημαντικότερα πολεμικά γεγονότα που έλαβαν χώρα κατά τη διάρκεια του Δευτέρου Παγκοσμίου πολέμου, στην ανατολική Μεσόγειο και τα οποία αποτελούν πολύτιμα ιστορικά στοιχεία σε παγκόσμια κλίμακα, μεταξύ των οποίων το βυθισμένο ελληνικό αντιτορπιλικό Βασίλισσα ‘Ολγα (D15). Στο πλαίσιο της δεύτερης κατεύθυνσης εντοπίστηκαν και χαρτογραφήθηκαν οι λειμώνες P. Oceanica και οι σχηματισμοί των ασβεστιτικών ροδοφυκών σχεδόν ανά όρμο περιμετρικά της νήσου. Η σχεδίαση των αντιστοίχων υποθαλάσσιων θεματικών χαρτών της παράκτιας ζώνης της Λέρου αναμένεται να αποτελέσουν ένα σημαντικό εργαλείο στην προστασία και στην ανάδειξη της σημαντικής υποθαλάσσιας ιστορικής και φυσικής κληρονομιάς του νησιού<br>The present study describes the submarine geophysical survey which was carried out in Leros Island, Aegean Sea and presents the results of the geophysical data analysis. The data were collected by the Laboratory of Marine Geology & Physical Oceanography, department of Geology, University of Patras during the period 11-17 June 2011. The research aims to contribute to the enhancement of underwater cultural and natural heritage of the island, as the collection, processing and interpretation of all of the data has allowed the identification of underwater targets of great historic and environmental importance. Geophysical survey in Leros Island, using a side scan sonar (EG&G 272 TD), coupled with ground-truthing by deploying a Towing Camera System of historic shipwrecks from World War II and of the major seabed habitats, namely Posidonia oceanica and coralligène formations. The survey revealed a great number of shipwrecks associated with the Battle of Leros (9-10/1943), one of the most important military events that took place during the World War II, in the Eastern Mediterranean which are considered as valuable historic data on a global scale, including the sunken Greek destroyer Queen Olga (D15). The design of the thematic maps of the coastal zone of Leros is expected to become an important tool in both protecting and promoting the significant underwater cultural and natural heritage of the island.