The Russian annexation of Crimea in 2014 was the start of the increasing tensions inthe Baltic sea. According to the Swedish government, the threats against the Nordic-Baltic countries have increased and this study will examine the Swedishgovernment’s security measures during the period of 2014 - 2020. Our methodselection is based on a qualitative text analysis. To review Sweden’s arrangements,we will analyse one proposition from a theoretical framework that is constituted ofthe Constructivism theory and the Securitization theory. The conclusion of the studyis that the Swedish government looks at the situation in the Baltic sea as amultidimensional security process. In order to protect the Swedish territory, thecountry must expand and strengthen both its national and international militarypower.

The Baltic Sea is the most polluted sea in the world. Its hydrological conditions and ongoing eutrophication are a high threat for marine biodiversity and ecosystems. Additionally, eutrophication has negative effects on the wellbeing of countries and their societies in the Baltic Sea Region (BSR). Actions to mitigate eutrophication in the Baltic Sea have been implemented through on-land measures in the last 40 years. Although the improvement in the marine environment is notable, it happens very slowly. In order to combat eutrophication, there is a need for a combination of on-land and in-situ measures. In this study, blue mussel farming practices are presented as one of the in-situ measures to combat eutrophication in the Baltic Sea. Blue mussel farming has been implemented in Sweden since the 1980s and has potential to not only mitigate the amounts of nutrients that accumulate in the sea but also brings a circular approach to resource use. In this study, stakeholders from four different sectors that are closely related to blue mussel farming practices and Baltic Sea issues have been interviewed with the aim of making a comprehensive analysis of stakeholder perceptions of blue mussel farming practices in the BSR. Interviewed stakeholders represent four different sectors - academia, entrepreneurs, municipalities and NGOs. A comprehensive analysis of stakeholders’ perceptions on blue mussel farming practises from environmental, social and economic perspective is presented. All interviewed stakeholders are actors in Sweden and represent Swedish perspective on blue mussel farming activities. Potential causes for different perceptions across sectors are discussed.

Carbon dioxide (CO2) is an important greenhouse gas, and the atmospheric concentration of CO2 has increased by more than 100 ppm since prior to the industrial revolution.  The global oceans are considered an important sink of atmospheric CO2, since approximately one third of the anthropogenic emissions are absorbed by the oceans. To be able to model the global carbon cycle and the future climate, it is important to have knowledge of the processes controlling the air-sea exchange of CO2. In this thesis, measurements as well as a model is used in order to increase the knowledge of the exchange processes. The air-sea flux of CO2 is estimated from high frequency measurements using three methods; one empirical method, and two methods with a solid theoretical foundation. The methods are modified to be applicable for various atmospheric stratifications, and the agreement between methods is good in average. A new parameterization of the transfer velocity (the rate of transfer across the air-sea interface), is implemented in a Baltic Sea model. The new parameterization includes also the mechanism of water-side convection. The impact of including the new parameterization is relatively small due to feedback processes in the model. The new parameterization is however more representative for flux calculations using in-situ measurement or remote sensing products. When removing the feedback to the model, the monthly average flux increases by up to 20% in some months, compared to when water-side convection is not included. The Baltic Sea carbon budget was estimated using the Baltic Sea model, and the Baltic Sea was found to be a net sink of CO2. This is consistent with some previous studies, while contradictory to others. The dissimilarity between studies indicates the difficulty in estimating the carbon budget mainly due to variations of the CO2 uptake/release in time and space. Local variations not captured by the model, such as coastal upwelling, give uncertainties to the model. Coastal upwelling can alter the uptake/release of CO2 in a region by up to 250%. If upwelling would be included in the model, the Baltic Sea might be considered a smaller sink of CO2.

No description available.

A sediment core from Himmerfjärden estuary, south of Stockholm, was examined to detect records of eutrophication on the site since the opening of the sewage treatment plant Himmerfjärdsverket in 1974. The core was analysed with respect to the diatom record and lithology. Four macrofossil that were found in the sediment were dated using 14C-dating.    This study aims to detect changes in the environment of Himmerfjärden by using the diatom stratigraphy record. The results have been interpreted and discussed regarding natural environmental and climate change and/or anthropogenic impact, and detected changes will be associated with the history of the sampling site. The results show that the lowermost zone started to deposit around 1300-1490 cal yr BP and the homogeneous sediment indicates that the area was not suffering from hypoxia at that time. There is a successive transition towards more distinct lamination further up in the core which show that the environment in Himmerfjärden have changed and become hypoxic. This may have to do with factors such as the opening of heavily trafficked Södertälje Canal, and also the increased nutrient input from Himmerfjärdsverket.    This study could be a part of the process of working towards a “good environmental status” in the Baltic Sea. However, continued and improved work is needed for further and more accurate interpretations.

Convective snow bands develop commonly over the open water surface of lakes or seas when cold airgets advected from a continent. Enhanced heat and moisture fluxes from the comparatively warm waterbody trigger shallow convection and an unstable boundary layer builds up. Relatively strong wind canorganize this convection into wind-parallel quasi-stationary cloud bands with moving individual cells.Depending on various factors like the horizontal wind, the vertical shear or the shape of the coast, thosecloud bands can form of different strength and structure. When the air mass meets the coast orographicforcing causes horizontal convergence and vertical lifting intensifies the precipitation at the coast. If thewind direction stays constant for several days a single snow band would accumulate its precipitation ina very restricted region and cause locally a significant increase in snow depth. This process leads in thecold season repeatedly to severe precipitation events at the Swedish east coast. Large amounts of snowalong with strong wind speeds can cause serious problems for traffic and infrastructure.Two different cases of convective snow bands in the Baltic Sea area were selected to simulate theassociated atmospheric conditions with a total of five different model systems. The atmosphere climatemodel RCA has been used independently at default settings as well as with increased resolution on avertical and a horizontal scale and furthermore coupled either to the ice-ocean model NEMO or the wavemodel component WAM.Comparing all models the crucial parameters like wind, temperature, heat fluxes, and precipitationvary generally in a reasonable range. However, the model systems show systematical differences amongthemselves. The strongest 10 meter wind speeds can be observed for both RCA models with increasedresolution. The RCA-WAM simulation shows its wind enhancement during the snow band event witha time shift to the other models by several hours. The mean directional wind shear above the Gulf ofBothnia, the snow band’s region of origin, is for all models small. The warmest sea surface temperaturesare reached by the RCA-NEMO simulation, which as a result also stands out for its most intense heatfluxes in both sensible and latent heat. Both high resolution RCA models as well as RCA-NEMO givethe most remarkable local precipitation rates. The original RCA and RCA-WAM simulate significantlyless snowfall. Local comparison with SMHI station measurements show that the models represent thetrend of wind, temperature and precipitation evolution well. However, all models decelerate the air masstoo rapidly when meeting the coast. Moreover, it remains a challenge to simulate the exact time andlocation of the extreme precipitation.The coupling of the atmosphere model with the ice-ocean model as well as the increased resolution ofthe atmospheric component have been observed to show great improvements in the model performanceand are suggested for future research work to be used in combination with each other for the regionalmodelling of convective snow bands in the Baltic Sea area.

The costal populations of perch (Perca fluviatilis) in some parts of the Baltic Sea have been in decline for about two decades. Recruitment failure in the early larval stages has been put forward as a possible cause and the decline has also been suggested to coincide with increases in three-pined stickleback (Gasterosteus aculeatus) densities. The aim of this study was to study the effects of growth and survival of newly hatched perch larvae in the presence of the three-pined stickleback, and if possible determine the main mechanism behind any negative effects the perch may suffer under such conditions. Using large scale experimental ponds as a controlled habitat, an experiment was conducted where perch larvae were being exposed to sticklebacks under four different stages of their development. Results showed that the three- spine stickleback can have a strong negative effect on the survival of young perch. This effect was strongest in the earliest stage of perch development and decreased as they grew bigger. The zooplankton densities didn't differ between the controls and stickleback treatments, suggesting that the young perch didn't suffer from food limitation. Instead predation was identified as the main mechanism behind the high mortality. The results of this study highlight the potential danger of the observed patterns of decreasing predator populations in conjunction with increasing populations of smaller prey species in the Baltic Sea.

Earth mean surface temperature has increased by 1 °C since the industrial revolution, and this has already had considerable effects on animal and plant species. Ecological responses to the warming climate – often facilitated via phenotypic plasticity – are ubiquitous. However, even though evolution can occur rapidly there are only few examples of genetic adaptation to climate change. In my thesis, I used a near-natural system to study if and how organisms have adapted to 30 years of warming, and how this has affected competitive species interactions. I investigated Baltic Sea populations of the aquatic snails Galba truncatula and Theodoxus fluviatilis, which had been subjected to cooling water discharge from power plants, resulting in water temperatures 4 to 10 °C higher than in the surrounding sea. G. truncatula had high upper thermal limits and large acclimation potential. This plasticity may have helped the species to survive under the new conditions, allowing evolution through natural selection to take place. I found that the populations of the two thermal origins had diverged in SNP markers associated with warmer temperature, whereas divergence in selectively neutral markers was mainly related to geographical distance. Adaptation occurred from standing genetic variation, emphasizing the importance of genetic diversity and population size in enabling the persistence of populations. Changes in thermal sensitivity of growth and survival were subtle yet significant, and complied with theoretical models of thermal adaptation in ectotherms. At the community level, pre-adaptation to warmer conditions aided the native T. fluviatilis when competing with the alien Potamopyrgus antipodarum. However, interspecific competition limited the snails most in those traits favored under warming, highlighting the challenge of adapting to different selecting forces during global change. The persistence of species and populations under climate change depends on several factors - plasticity allowing for initial survival, evolvability in allowing the genetic changes, and species interactions affecting the new ecological niches. The results of my thesis indicate that persistence under climate change is possible when these factors align, but the relative roles of ecology and plasticity may explain why there are so few observed instances of evolution in response to climate change.

The overall aim of the study was to provide better insights to the ecological role and impact of cyanobacteria in Baltic Sea (BS) bay, coastal and open sea areas. Biomass and heterocyst development of diazotrophic, heterocystous cyanobacteria were monitored over several years simultaneously as physical parameters such as nutrients and temperature. Nitrogen fixation was estimated as well as its transfer in the BS food web. Even after decades of debate there is still controversy whether eutrophication of lakes and estuaries/coastal areas should be managed by reducing phosphorus only or also nitrogen. Central to this debate is whether nitrogen fixation by cyanobacteria can replace shortages of combined nitrogen quickly enough to make phosphorus the limiting nutrient and nitrogen removal pointless or even harmful. Also, it is not clear if available combined nitrogen inhibits heterocystous cyanobacterial nitrogen fixation and if it is used for their growth in situ. A large ecosystem-wide experiment started in Himmerfjärden bay in year 1997, where the N-loadings and release depth from a modern sewage treatment plant (STP), located in the inner part of the bay, were modulated. The STP creates a steep gradient of nutrients and stable nitrogen isotopes, which can be used to study uptake of combined nitrogen, as well as biomass development and primary productivity. A 35-year long data series was used to achieve good insights into phytoplankton development and primary productivity in the Baltic Sea over the last couple of decades. These in vivo long time series, based on monitoring data, in combination with shorter series (2-3 seasons, including measurements of colony stoichiometry and stable isotopes), have resulted in a unique meta-dataset, allowing for high-resolution observations into the role of the cyanobacteria in the Baltic Sea ecosystem. / <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>

No description available.