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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

Target strength variability in Atlantic herring (Clupea harengus) and its effect on acoustic abundance estimates

Fässler, Sascha M. M. January 2010 (has links)
Acoustic survey techniques are widely used to quantify abundance and distribution of a variety of pelagic fish such as herring (Clupea harengus). The information provided is becoming increasingly important for stock assessment and ecosystem studies, however, the data collected are used as relative indices rather than absolute measures, due to the uncertainty of target strength (TS) estimates. A fish’s TS is a measure of its capacity to reflect sound and, therefore, the TS value will directly influence the estimate of abundance from an acoustic survey. The TS is a stochastic variable, dependent on a range of factors such as fish size, orientation, shape, physiology, and acoustic frequency. However, estimates of mean TS, used to convert echo energy data from acoustic surveys into numbers of fish, are conveniently derived from a single metric - the fish length (L). The TS used for herring is based on TS-L relationships derived from a variety of experiments on dead and caged fish, conducted 25-30 years ago. Recently, theoretical models for fish backscatter have been proposed to provide an alternative basis for exploring fish TS. Another problem encountered during acoustic surveys is the identification of insonified organisms. Trawl samples are commonly collected for identification purposes, however, there are several selectivity issues associated with this method that may translate directly into biased acoustic abundance estimates. The use of different acoustic frequencies has been recognised as a useful tool to distinguish between different species, based on their sound reflection properties at low and high frequencies. In this study I developed theoretical models to describe the backscatter of herring at multiple frequencies. Data collected at four frequencies (18, 38, 120 and 200 kHz) during standard acoustic surveys for herring in the North Sea were examined and compared to model results. Multifrequency backscattering characteristics of herring were described and compared to those of Norway pout, a species also present in the survey area. Species discrimination was attempted based on differences in backscatter at the different frequencies. I examined swimbladder morphology data of Baltic and Atlantic herring and sprat from the Baltic Sea. Based on these data, I modelled the acoustic backscatter of both herring stocks and attempted to explain differences previously observed in empirical data. I investigated the change in swimbladder shape of herring, when exposed to increased water pressures at deeper depths, by producing true shapes of swimbladders from MRI scans of herring under pressure. The swimbladder morphology representations in 3-D were used to model the acoustic backscatter at a range of frequencies and water pressures. I developed a probabilistic TS model of herring in a Bayesian framework to account for uncertainty associated with TS. Most likely distributions of model parameters were determined by fitting the model to in situ data. The resulting probabilistic TS was used to produce distributions of absolute abundance and biomass estimates, which were compared to official results from ICES North Sea herring stock assessment. Modelled backscatter levels of herring from the Baltic Sea were on average 2.3 dB higher than those from herring living in northeast Atlantic waters. This was attributed to differences in swimbladder sizes between the two herring stocks due to the lower salinity Baltic Sea compared to Atlantic waters. Swimbladders of Baltic herring need to be bigger to achieve a certain degree of buoyancy. Morphological swimbladder dimensions of Baltic herring and sprat were found to be different. Herring had a significantly larger swimbladder height at a given length compared to sprat, resulting in a modelled TS that was on average 1.2 dB stronger. Water depth, and therefore the increase in ambient pressure, was found to have a considerable effect on the size and shape of the herring swimbladder. Modelled TS values were found to be around 3 dB weaker at a depth of 50 m compared to surface waters. At 200 m, this difference was estimated to be about 5 dB. The Bayesian model predicted mean abundances and biomass were 23 and 55% higher, respectively, than the ICES estimates. The discrepancy was linked to the depth-dependency of the TS model and the particular size-dependent bathymetric distribution of herring in the survey area.
382

Validation of the WAM-model over the Baltic Sea

Berg, Caroline January 2008 (has links)
<p>In order to understand how waves influence the exchange of momentum, latent heat and other parameters, between the ocean surface and the atmosphere, one can use models. A coupling between a wave model and an atmospheric regional climate model, for the Baltic Sea, will be performed at the Meteorology Institute in Uppsala University. The wave model is a state of the art, third generation wave model called WAM.</p><p>The new version of the WAM model (cycle 4) needs to be validated. The aim of this thesis is to perform this validation and also to investigate what meteorological forcing one should use to achieve best results. Two different types of forcing are analyzed, ERA40 reanalysis and the RCA climate model. In order to do this, observations from six different buoys in the Baltic Sea will be compared with the model output from WAM. The parameters that will be compared in this study are significant wave height, direction and peak period.</p><p>A consistent phenomenon for all the buoys is a slightly overestimation by the model of what the rate of this increases with increasing wave height. If one compares the model output when WAM are forced with the RCA climate model and when it is forced with ERA40 reanalysis, the differences between them are notable but not large. ERA40 is slightly better.</p><p>Significant wave height is quite good and gives a reasonably result. Some buoys and periods are better and some are worse. There are some differences for the significant wave height between the east coast and the west coast of Sweden, when forcing the model with RCA. It is slightly better on the west coast. On the contrary, the results from ERA40 are very coherent. The quality of the hindcast for the direction and the peak period, in contrast to the significant wave height, is not that good. The results are not bad, but it only gives a rough picture of the sea state.</p>
383

European Union communication policy and its implementation on the national level: Case of the Baltic States / Europos Sąjungos komunikacijos politika ir jos įgyvendinimas nacionaliniu lygmeniu: Baltijos šalių atvejis

Vinciūnienė, Aušra 26 November 2010 (has links)
Dissertation focuses on qualitative aspects of EU communication strategies applied in two new EU member states, young democracies – Lithuania and Estonia. The overall goal of the research was twofold: to gain a better understanding about the reasons that determine implementation of EU Communication Policy in different national contexts as well as to propose possible solutions how to reshape and adapt it to specific cultures and conditions. Dissertation deals with the normative approach, that EU communication can provide a basis for the formation of the European public sphere and can help to bridge the ‘gap‘ between EU institutions and citizens on the national level. Generally, this comparative study performed in two Baltic countries has shown that while analysing European political communication, it is crucially important to examine strategic-organisational, as well as contextual factors (socio-cultural, political, economic conditions, local particularities of histories and traditions of communication) and values of those communicating (institutional communication officers and journalists) that influence their relationship (political communication culture) and have an impact on messages produced. / Disertacijoje analizuojama, kaip vyksta politikos komunikacijos sistemų europeizacijos procesai naujosiose narėse, jaunos demokratijos valstybėse (Lietuvoje ir Estijoje), apie kurių kontekstą ir patirtis Europos moksliniame diskurse pernelyg mažai yra žinoma. Mokslinė problema formuluojama tokiu klausimu: kokiu būdu ir kokiomis priemonėmis galima būtų užtikrinti efektyvią politikos komunikaciją tarp ES lygmens bei nacionalinių institucijų ir piliečių, ir taip pasiūlyti efektyvių sprendimų, kaip institucinė ES komunikacijos politika, pritaikyta prie skirtingų ES šalių narių ar jų grupių (tokių kaip Baltijos šalys) kontekstų, galėtų padėti spręsti ES demokratijos stygiaus problemą bei paspartinti bendros politinės viešosios erdvės formavimąsi Europoje? Darbe siekta parodyti, kad veiksniai, lemiantys Europos viešosios erdvės formavimąsi, yra daugialypiai bei kompleksiški. Remiantis Lietuvos ir Estijos atvejo analize galima daryti prielaidą, kad ES komunikacijos politikos įgyvendinimą nacionaliniu lygmeniu ir viešosios erdvės europeizacijos galimybes „iš viršaus“ apsprendžia bent trys skirtingos grupės veiksnių: strateginiai-organizaciniai, politikos komunikacijos kultūros (politikos-žiniasklaidos santykio) ir sociokultūriniai (priklausomybė nuo politinio, ekonominio, socialinio ir kt. konteksto).
384

Audito pasiūlos Baltijos šalių kapitalo rinkoms tyrimas / The research of audit supply for the capital markets of Baltic countries

Černelis, Vidmantas 14 June 2011 (has links)
Šiame darbe yra atskleidžiama ir analizuojama audito pasiūla tenkanti kapitalo rinkoms, nagrinėjama jos nepakankamumo problema. Darbo tikslas yra, įvertinus globalius audito pasiūlos pokyčius ir jų įtaką kapitalo rinkoms, atlikti audito pasiūlos ir auditoriaus pasirinkimo veiksnių Baltijos šalių kapitalo rinkoms tyrimą. Darbas skirstomas į tris pagrindines dalis. Pirmojoje dalyje apibūdinamas auditoriaus vaidmuo bei jo reikšmė ekonomikai, atskleidžiamas sisteminės rizikos, kylančios iš audito rinkos pasiūlos nepakankamumo, mastas, aptariamos pagrindinės priežastys, lemiančios esamą audito pasiūlos struktūrą. Antrojoje darbo dalyje analizuojamas darbo objektas – išorinio nepriklausomo finansinio audito pasiūla kapitalo rinkoms, pateikiama darbo tyrimo metodologija. Trečiojoje darbo dalyje aprašomi atlikto tyrimo rezultatai, iškeltų darbe hipotezių tikrinimas, pateikiamos rekomendacijos tyrimo metu nustatytose probleminėse srityse bei tyrimo rezultatų taikymo ir tyrimo plėtotės galimybės. Gauti darbo rezultatai parodė, jog audito rinkos koncentracija visose trijose Baltijos akcijų biržose yra aukšta ir kelia sisteminės kapitalo rinkų rizikos pavojų. Pagrindiniais auditoriaus pasirinkimo veiksniais buvo priimti audituojamos įmonės dydis bei kapitalo kilmė. / This paper discloses and analyses the audit supply for the capital markets and examines its insufficiency problem. The aim of this paper is to evaluate the global changes in the audit supply and to perform a research of audit supply and influencing factors when choosing the auditor in the capital markets of Baltic countries. The paper consists of three main parts. The first part presents the role of the auditor and its significance to the economy, the extent of the systemic risk entailed by the insufficiency of the audit supply, discusses the main causes of the current structure of the audit market. In the second part of this paper the external independent financial audit supply for the capital markets, which is the object of this paper, is analyzed. Also, the research methodology is presented. In the third part of this paper the results of the research and hypothesis testing are presented. It also provides the guideline on the identified problem areas as well as applicability and development capabilities of the research made. The main conclusions showed that the audit market concentration in all three Baltic stock exchanges is high and poses a systemic risk to the capital markets. The key factors when choosing the auditor in the capital markets of Baltic countries is the size and the capital origin of the company.
385

Būsto paskolų portfelis Baltijos šalyse: portfelį veikiančių veiksnių tyrimas / Mortgage portfolio in the baltic countries: analysis of main factors

Klupšaitė, Almantė 25 June 2014 (has links)
Per paskutinį dešimtmetį Baltijos šalys išgyveno pilną ekonomikos ciklą - lėtą atsigavimą, spartų augimą ir staigų kritimą. Itin sparčiai vystėsi būsto paskolų ir nekilnojamojo turto rinka, todėl jau 2007 - 2008 metais buvo svarstoma dėl nekilnojamojo turto rinkos perkaitimo, nors dauguma gyventojų vis dar džiaugėsi galimybe be didesnių kliūčių gauti kreditą brangstančio būsto įsigijimui. Būgštavimai dėl ekonomikos ir jos atskirų sektorių perkaitimo buvo pagrįsti – Baltijos šalių ekonomikos 2009 m. smuko daugiausiai tarp visų ES valstybių. Taigi, įvykus nekilnojamojo turto sektoriaus ir būsto paskolų rinkos pakilimui bei nuosmukiui, galima ištirti būsto paskolų portfelį viso ekonominio ciklo periodu. Įvardinus veiksnius, labiausiai įtakojančius būsto paskolų portfelio augimą, būtų galima juos stebėti, bandyti pakeisti, ir taip ateityje išvengti potencialios ekonominės krizės arba sušvelninti galimus neigiamus ekonominio nuosmukio padarinius. Darbo tyrimo tikslas – ištirti makroekonominius veiksnius, darančius poveikį Lietuvos, Latvijos ir Estijos šalių būsto paskolų portfelio dinamikai. Darbo objektas yra Baltijos šalių būsto paskolų portfelis ir jį įtakojantys makroekonominiai veiksniai. Siekiant užsibrėžto tikslo, yra sprendžiami uždaviniai: 1) Išnagrinėti ekonominėje literatūroje pateikiamus modelius, tiriančius būsto paskolų portfelį. 2) Apibrėžti makroekonominius veiksnius, įtakojančius būsto paskolų portfelį. 3) Išanalizuoti būsto paskolų portfelio pokyčius Baltijos... [toliau žr. visą tekstą] / During the last decade Baltic countries experienced a full economic cycle – slow recovery, fast growth and sharp deterioration of whole economy. On the growth period the portfolio of mortgage loans and real estate market developed extremely rapidly, thus, since 2007 - 2008 there was discussions about the overheating of economies and bubbles of the real estate prices in the Baltic countries. However, the majority of the citizens were still taking advantage of easy accessible mortgage loans for the acquisition of desired real estate even prices were going upwards. Unfortunately, doubts about overheating of the separate parts of economies were reasonable and economies of the Baltic countries contracted the most among all EU. Therefore, with a full picture of economic cycle the analysis of portfolio of mortgage loans is being developed. Identification of the main factors that are determining growth of the portfolio of mortgage loans is important for developing a strategy to avoid possible economic crises in the future or to ease the negative effects of economic downturn. The aim of the paper – to find out the most important macroeconomic factors that are determining the dynamic of mortgage portfolio in Lithuania, Latvia and Estonia. The object of the paper – the mortgage portfolio of the three Baltic countries and macroeconomic factors of the mortgage portfolio. To reach the aim of the paper such tasks were developed: 1) Examine the theory and the models that are analyzing the... [to full text]
386

Dioxinkontaminering i Gävleborgs län : Utbredning, orsaker och åtgärdsanalys / Dioxin contamination i Gävleborg County : Distribution, causes and analysis of measures

Robertsson, Jonas January 2014 (has links)
Detta examensarbete syftade till att ta fram ett underlag för en regional åtgärdsplan avseende dibenso-p-dioxiner och dibensofuraner, gemensamt benämnda som PCDD/F eller dioxiner, i Gävleborgs län. Länet har historiskt varit ett av de mest utsatta områdena i Sverige beträffande dessa föroreningar och höga koncentrationer i bland annat strömming har medfört att denna inte får saluföras i övriga EU.   I arbetet har resultaten från den rådande forskningen på området studerats för att få kunskap om nuvarande källor och möjliga förklaringar till de fortsatt förhöjda koncentrationerna av dioxiner. Därefter har data från tidigare undersökningar av dioxinkoncentrationer i Gävleborgs län samlats in, sammanställts och använts för att studera hur koncentrationerna varierar geografiskt inom länet. Principalkomponentanalys (PCA) av specifika dioxinkongeners koncentrationer har sedan använts för att försöka identifiera verksamhetstyper som potentiellt kan ha bidragit till föroreningarna på olika platser - en analys som dock är behäftad med stora osäkerheter. De insamlade provresultaten har även använts för att genom massbalansmodellering undersöka återhämtningen i två känt förorenade fjärdar i länet; Norrsundet och Gårdsfjärden. Utifrån resultaten av ovanstående analyser diskuterades även nyttan av att genomföra eventuella åtgärder för att reducera halterna i kraftigt förorenade områden.   Proverna som sammanställts visade klara geografiska skillnader i sedimentkoncentration, och till viss del även i koncentration i muskel från abborre, vilket visar på en stark betydelse av lokala källor i vissa områden. Bland strömmingsproverna kunde inget liknande samband ses. Detta kan förklaras av att det migrerande beteendet hos strömming gör att fisken under sin livstid exponeras för varierande föroreningsnivåer i olika områden, medan abborren är mer stationär även som vuxen. Principalkomponentanalysen gav, för vissa prover, indikationer kring vilken typ av verksamhet som bidragit till de uppmätta koncentrationerna. Dessa resultat är dock mycket osäkra och bör inte på egen hand användas som underlag för att fastställa föroreningskällor. Massbalansmodelleringen visade att PCDD/F-koncentrationen i sediment inte har någon betydelse för koncentrationen i vattenmassan utan att inflödet från omgivande hav dominerar även i avgränsade fjärdar. De modellerade jämviktskoncentrationerna mellan sediment och vattenmassa indikerade även att koncentrationerna i sediment kommer fortsätta överskrida somliga gränsvärden tills koncentrationen i vattenmassan reducerats, vilket även stöds av att dessa gränsvärden överskreds i majoriteten av de sammanställda proverna.   Baserat på samtliga ovannämnda resultat drogs slutsatsen att lokala saneringsåtgärder sannolikt inte ger någon effekt på PCDD/F-koncentrationerna i strömming, samt att de inte är tillräckliga för att erhålla sedimentkoncentrationer under samtliga gränsvärden. De kan däremot effektivt minska den exponering som mer stationära organismer som abborre utsätts för i områden med kraftigt förorenade sediment, och kan även ha positiva effekter på förekomsten av andra miljöfarliga ämnen i området. För- och nackdelar måste således övervägas i varje enskilt fall. / The aim of this Master’s Thesis was to provide a basis for a regional plan of action regarding dibenzo-p-dioxins and dibenzofurans, commonly referred to as PCDD/F or dioxins, in Gävle-borg County. This region has historically been one of the Swedish areas most affected by these pollutants, and high concentrations in for example Atlantic herring (Clupea harengus) have resulted in restrictions where some fish species cannot be sold in other EU countries.   In this work, results of current research on the subject were studied in order to gain knowledge about current sources and possible explanations to the continued high concentrations of dioxins. Thereafter, data from earlier investigations of dioxin levels in Gävleborg County have been gathered, compiled and used to study the regional geographic variation of the concentrations. Principal component analysis (PCA) was then used on the concentrations of specific congeners in an attempt to identify source types that might have contributed to the contamination in various sites; this analysis is however marred by uncertainties. The gathered data have also been used to investigate the recovery in two bays with known contaminations, Norrsundet and Gårdsfjärden, using mass balance modelling. The benefits of implementing measures to reduce the PCDD/F-concentrations in highly polluted areas were then discussed based on the results of the above-mentioned analyses.   The measured sediment concentrations, and partly also the concentrations in European perch (Perca fluviatilis), of the compiled samples showed distinct geographic differences, which indicates a strong influence from local sources in some areas. Among the herring samples, no such connection could be seen. This could be explained by the migrating behaviour of adult herring, resulting in an exposure to various levels of contamination in different areas as they migrate, while adult perch has a more stationary behaviour. For some samples, the principal component analysis gave indications on source types that might have contributed to the local contamination levels. These results are however very uncertain and they should not be used as the sole basis when determining emission sources. The mass balance modelling showed that the PCDD/F-concentrations in sediments have no influence on the concentrations in the water body; the inflow from the surrounding sea is predominant also in enclosed bays. The modelled equilibrium concentrations between sediments and water body also indicated that the sediment concentrations will continue to exceed the guideline values until the water concentrations have decreased. This is also supported by the fact that the majority of the samples showed concentrations exceeding these guideline values.   Based on all of the abovementioned results it was concluded that local remediation measures would most likely not affect the PCDD/F-concentrations in herring. It was also concluded that such measures would not suffice to obtain sediment concentrations that fall below all guideline values. They can however be used to lessen the exposure that stationary organisms are subjected to in areas with highly contaminated sediments, and can also have positive effects on the levels of other hazardous substances in the area. Thus, the benefits and disadvantages need to be considered in each specific case.
387

Bio-optics, satellite remote sensing and Baltic Sea ecosystems : Applications for monitoring and management

Harvey, Therese January 2015 (has links)
Earth observation satellites cover large areas with frequent temporal repetition and provide us with new insight into ocean and coastal processes. Ocean colour measurements from satellite remote sensing are linked to the bio-optics, which refers to the light interactions with living organisms and dissolved and suspended constituents in the aquatic environment. Human pressures have changed the aquatic ecosystems, by, for example, the increased input of nutrient and organic matter leading to eutrophication. This thesis aims to study and develop the link between bio-optical data and the remote sensing method to the monitoring and management of the Baltic Sea. The results are applied to the European Union’s Water Directives, and the Baltic Sea Action Plan from the Helsinki commission. In paper I indicators for eutrophication, chlorophyll-a concentration and Secchi depth were evaluated as a link to remote sensing observations. Chlorophyll-a measurements from an operational satellite service (paper I) were compared to conventional ship-based monitoring in paper II and showed high correlations to the in situ data. The results in paper I, II and IV show that the use of remote sensing can improve both the spatial and temporal monitoring of water quality. The number of observations increased when also using satellite data, thus facilitating the assessment of the ecological and environmental status within the European Union’s water directives. The spatial patterns make it possible to study the changes of e.g. algae blooms and terrestrial input on larger scales. Furthermore, the water quality products from satellites can offer a more holistic and easily accessible view of the information to decision makers and end-users. In paper III variable relationships between in situ bio-optical parameters, such as coloured dissolved organic matter (CDOM), dissolved organic carbon, salinity and Secchi depth, were found in different parts of the Baltic Sea. In paper IV an in situ empirical model to retrieve suspended particulate matter (SPM) from turbidity was developed and applied to remote sensing data. The use of Secchi depth as an indicator for eutrophication linked to the concentrations of chlorophyll-a and SPM and CDOM absorption was investigated in paper V. The variations in Secchi depth were affected differently by the mentioned parameters in the different regions. Therefore, one must also consider those when evaluating changes in Secchi depth and for setting target levels for water bodies. This thesis shows good examples on the benefits of incorporating bio-optical and remote sensing data to a higher extent within monitoring and management of the Baltic Sea. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.</p>
388

Remote sensing in optically complex waters : water quality assessment using MERIS data

Beltrán-Abaunza, José M. January 2015 (has links)
This PhD study focusses on the use of MEdium Resolution Imaging Spectrometer (MERIS) data for reliable and quantitative water-quality assessment of optically-complex waters (lake, brackish and coastal waters). The thesis is divided into two parts: A. intercalibration of reflectance measurements in different optically-complex water bodies (Paper I), and validation of various satellite processing algorithms for the coastal zone (Paper II). B. Applications: the use of MERIS data in integrated coastal zone management mostly using Himmerfjärden bay as an example. Himmerfjärden bay is one of the most frequently monitored coastal areas in the world and it is also the recipient of a large urban sewage treatment plant, where a number of full-scale nutrient management experiments have been conducted to evaluate the ecological changes due to changes in nutrient schemes in the sewage plant. Paper I describes the development and assessment of a new hyperspectral handheld radiometer for in situ sampling and validation of remote sensing reflectance.  The instrument is assessed in comparison with readily available radiometers that are commonly used in validation. Paper II has a focus on the validation of level 2 reflectance and water products derived from MERIS data. It highlights the importance of calibration and validation activities, and the current accuracy and limitations of satellite products in the coastal zone.  Bio-optical in situ data is highlighted as one of the key components for assessing the reliability of current and future satellite missions. Besides suspended particulate matter (SPM), the standard MERIS products have shown to be insufficient to assure data quality retrieval for Baltic Sea waters. Alternative processors and methods such as those assessed and developed in this thesis therefore will have to be put in place in order to secure the success of future operational missions, such as Sentinel-3. The two presented manuscripts in the applied part B of the thesis (paper III and IV), showed examples on the combined use of in situ measurements with optical remote sensing to support water quality monitoring programs by using turbidity and suspended particulate matter as coastal indicators (manuscript III). The article also provides  a new turbidity algorithm for the Baltic Sea and a robust and cost-efficient method for research and management.  A novel approach to improve the quality of the satellite-derived products in the coastal zone was demonstrated in manuscript IV. The analysis included, the correction for adjacency effects from land and an improved pixel quality screening.  The thesis provides the first detailed spatio-temporal description of the evolution of phytoplankton blooms in Himmerfjärden bay  using quality-assured MERIS data, thus forwarding our understanding of ecological processes in in Swedish coastal waters. It must be noted that monitoring from space is not a trivial matter in these optically-complex waters dominated by the absorption of coloured dissolved organic matter (CDOM). These types of coastal waters are especially challenging for quantitative assessment from space due to their low reflectance.  Papers III and IV thus also provide tools for a more versatile use in other coastal waters that are not as optically-complex as the highly absorbing Baltic Sea waters. The benefits of the increased spatial-temporal data coverage by optical remote sensing were presented, and also compared to in situ sampling methods (using chlorophyll-a as indicator). / <p>Research funders:</p><p>European Space Agency (ESA, contract no.21524/08/I-OL)</p><p>NordForsk funding: Nord AquaRemS Ref. no. 80106</p><p>NordForsk funding:  NordBaltRemS Ref.no. 42041</p><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>
389

Acoustic survey of sea floor features in Asköfjärden

Lundmark, Kim January 2017 (has links)
Marine geological surveys in Asköfjärden in the southern Stockholm Archipelago hasrevealed step like features in the sediments on the Baltic sea floor. The aim of this project is toanalyse the steps and possible formation processes from the survey data. The data used aretaken from the acoustic instruments multibeam echosunder and Chirp sonar sediment profiler.The multibeam reveal the seafloor topography and can detect water column features. TheChirp sonar produce sub-bottom profiles showing the sediments down to some tens of metersunderneath the sea floor. The multibeam data show multiple crescent shaped steps as well aselliptically shaped “pockmarks”. Water column data show what could be interpreted as seepsfrom the sea floor under these features. The sub bottom profile show deformation and fluidsignatures under the steps. Gas signatures and what could be other fluids are present. Theinterpretation concludes that the formation could be from either gas or groundwater seeps. Nodefinitive conclusions can be made from the data available for the present study, andapetrophysical or geochemical study of the study area cold provide further understanding ofthe formation of the steps.
390

Baltic shore-lands facing climate change

Strandmark, Alma January 2017 (has links)
This thesis provides new insight concerning drivers behind differences in arthropod diversity and abundance in Baltic shore ecosystems and how the arthropod communities might be affected when the conditions in the Baltic Sea are altered due to climate change.  The focus has been on climate related changes that are unique for coastal ecosystems, especially sea level rise and changes in the inflow of marine nutrients. As sea levels rise, features in coastal landscapes will be altered, islands and habitats will be flooded and diminished, and structural connectivity within the island landscape will therefore change. This thesis shows that arthropod diversity within the two arthropod groups, spiders and beetles, increases with island size but also that diversity is positively influenced by a high number of islands in the surroundings. A changed distribution and occurrence of marine species, due to climate change or eutrophication, can also affect terrestrial organisms on the shore.  In the Baltic Sea the new conditions following climate change will decrease the prevalence of bladder-wrack and benefit filamentous algae. Algal deposits on shores reflect the marine species composition and a decreased prevalence of bladder-wrack in the Baltic Sea will also be visible on the shores.  This thesis shows that a lower proportion of bladder-wrack in the algal deposits will decrease the diversity and abundance of arthropods in these deposits. Changes in the marine environment may also affect the inflow of insects with aquatic life stages and terrestrial adult stages.  On Baltic shores, prey species with aquatic life stages, especially chironomids, constitute a large proportion of the diet of the terrestrial predatory group, wolf spiders. In freshwater system, the inflow of chironomids is known to decrease with elevated water temperatures if this is true in the Baltic Sea prey availability of wolf spiders would decrease.  This thesis supports the importance of chironomids as a prey for coastal wolf spiders, but also shows that the diet varies over season with dominance of terrestrial prey in early summer shifting to a dominance of marine prey in late summer and autumn. This seasonal variation is primarily due to a gradual increase in the consumption of chironomids over season. Climate change has the potential to alter the biogeographical conditions in coastal landscapes as well as the density and quality of marine nutrient inflow. Sea level rise will diminish and flood islands and this thesis shows that a moderate sea level rise of 0.5 meters would make the total number of islands in the outer part of Stockholm archipelago decrease with about 25 %. Sea level rise could thus have consequences for arthropod diversity in Baltic shore meadows in the near future. The combined effects of sea level rise and changed prevalence of marine species in the Baltic Sea will affect the abundance and diversity of arthropods substantially. The abundance and diversity of spiders and beetles will decrease on shores that today have a high occurrence of bladder-wrack and prey availability for coastal predators might decrease due to a decreased inflow of chironomids. Changes in the arthropod communities could have consequences also further up in the food chain, such as for shore birds feeding on these arthropods. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p>

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