Habilitationsschrift--Tübingen. / Bibliography: p. [106]-109.

Issued also as thesis, Kiel, 1963. / Offa-Bücher, Bd. 19.

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on Mar. 23, 2009). Includes bibliographical references.

Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on Dec. 23, 2009). Includes bibliographical references.

Akademisk avhandling--Uppsala. / "Källor och litteratur": p. [x]-xx.

Thesis (doctoral)--Stockholms Universitet, 2003. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 304-317).

Biogeochemical processes in the marine biosphere are important in global element cycling and greatly influence the gas composition of the Earth’s atmosphere. The nitrogen cycle is a key component of marine biogeochemical cycles. Nitrogen is an essential constituent of living organisms, but bioavailable nitrogen is often short in supply thus limiting primary production. The largest input of nitrogen to the marine environment is by N2-fixation, the transformation of inert N2 gas into bioavailable ammonium by a distinct group of microbes. Hence, N2-fixation bypasses nitrogen limitation and stimulates productivity in oligotrophic regions of the marine biosphere. Extensive blooms of N2-fixing cyanobacteria occur regularly during summer in the Baltic Sea. N2-fixation during these blooms adds several hundred kilotons of new nitrogen into the Baltic Proper, which is similar in magnitude to the annual nitrogen load by riverine discharge and more than twice the atmospheric nitrogen deposition in this area. N2-fixing cyanobacteria are therefore a critical constituent of nitrogen cycling in the Baltic Sea. In this thesis N2 fixation of common cyanobacteria in the Baltic Sea and the direct fate of newly fixed nitrogen in otherwise nitrogen-impoverished waters were investigated. Initially, the commonly used 15N-stable isotope assay for N2-fixation measurements was evaluated and optimized in terms of reliability and practicality (Paper I), and later applied for N2-fixation assessments (Paper II–IV). N2 fixation in surface waters of the Baltic Sea was restricted to large filamentous heterocystous cyanobacteria (Aphanizomenon sp., Nodularia spumigena, Dolichospermum spp.) and absent in smaller filamentous cyanobacteria such as Pseudanabaena sp., and unicellular and colonial picocyanobacteria (Paper II-III). Most of the N2-fixation in the Northern Baltic Proper was contributed by Aphanizomenon sp. due to its high abundance throughout the summer and similar rates of specific N2-fixation as Dolichospermum spp. and N. spumigena. Specific N2 fixation was substantially higher near the coast than in an offshore region (Paper II). Half of the fixed nitrogen was released as ammonium at the site near the coast and taken up by non-N2-fixing organisms including phototrophic and heterotrophic, prokaryotic and eukaryotic planktonic organisms. Newly fixed nitrogen was thereby rapidly turned-over in the nitrogen-depleted waters (Paper III). In colonies of N. spumigena even the potential for a complete nitrogen cycle condensed to a microcosm of a few millimeters could be demonstrated (Paper IV). Cyanobacterial colonies can therefore be hot-spots of nitrogen transformation processes potentially including nitrogen gain, recycling and loss processes. In conclusion, blooms of cyanobacteria are instrumental for productivity and CO2 sequestration in the Baltic Sea. These findings advance our understanding of biogeochemical cycles and ecosystem functioning in relation to cyanobacterial blooms in the Baltic Sea with relevance for both ecosystem-based management in the Baltic Sea, and N2-fixation and nitrogen cycling in the global ocean. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.</p>

Climate change is a pressing issue caused by the systematic increase of greenhouse gasses (GHG). One way to avoid higher GHG emissions is through an increased use of public transportation, transitioning society away from the personal automobile. Public transportation is more sustainable than the personal automobile as its emissions per person are less and it takes up significantly less space. Sustainability is defined through the principle-based definition of the Framework for Strategic Sustainable Development (FSSD). This research studied barriers and best practices to the use of public transportation in the South Baltic Sea Region (SBSR), in cooperation with the EU funded InterConnect Project. The research team was able to use the resources of the InterConnect Project for their methods in order to discover perceived barriers and potential best practices and ideas to overcome these barriers through the stakeholder perspective. The research team concludes that by addressing the perceived barriers, a first step towards transitioning society within the SBSR towards more sustainable transportation can be done. As transportation is complex and connected to other systems, the need for a systems perspective and a strategic and collaborative approach was identified. This could be achieved through using the FSSD in the SBSR.

Lina Mire, Gotland, is an area of archaeological significance and has a complex history of shoreline displacement. Archaeologists suspect that Lina Mire was once part of an important inland water system which connected the Littorina Sea with central Gotland. This study investigates vegetational and palaeoenvironmental changes of the Lina Mire area between 6900 – 400 BC (8850 – 2350 cal years BP) in order to better understand how the area has developed and how humans have impacted the vegetation. Pollen analysis, C/N ratios, organic matter and carbon content measurements were conducted. The chronology was based on 14C AMS dating of terrestrial macrofossils and bulk sediments. A transgression of the Littorina Sea at about 6550 BC (8500 cal years BP) inundated the Lina Mire basin, which was a lake at the time. The onset of cultivation was indicated by the presence of Hordeum (Barley or Wild Barley) during the Late Neolithic, 2630 BC (4580 cal years BP). Hordeum continued to grow during the Bronze Age when Cereals appeared at about 970 BC (2920 cal years BP). During the onset of cultivation during the Late Neolithic, the Lina Mire basin was a bay of the Littorina Sea. The Lina Mire basin remained connected with the Littorina Sea until isostatic uplift caused it to become isolated at about 1870 BC (3820 cal years BP). The lake overgrew and became a mire about 820 BC (2770 cal years BP).

Thiamine (vitamin B1) is involved in several basal metabolic processes. It is an essential compound for many organisms and in aquatic systems it is mainly produced by phytoplankton and prokaryotes and transferred to higher trophic levels through grazing and predation. The occurrence of thiamine deficiency in top predators has been reported from several aquatic systems. In the Baltic populations of the Atlantic salmon (Salmo salar) this has been observed since 1974 and recently thiamine deficiency has also been reported for Baltic sea birds. This thesis aims at investigating what processes that governs the flow of thiamine from the primary producers to top predators via zooplankton grazers and planktivoric fish. Paper I showed that abiotic stress factors such as salinity, temperature and light conditions can alter the thiamine content of phytoplankton. Paper II showed that abiotic factors indirectly can affect the stress resistance of zooplankton grazers by changing the nutritional quality of their food. In Paper III we found that the in situ thiamine content of zooplankton grazers was directly affected by that of the phytoplankton diet. In Paper IV we found a similar connection between the thiamine contents of Baltic salmon and herring, one of the major salmon prey species. In Paper V we looked at the thiamine content of the pelagic food web of the Baltic Sea as a whole and found a pattern of trophic dilution; the higher the trophic level of an organism (i.e. the further away from the source of thiamine in the food web), the lower was its thiamine content. In all, the results of this thesis suggests a bottom up effect on the thiamine status of the higher trophic levels of  the Baltic Sea and that external factors, both natural and man-made, have the capability to affect the thiamine status of the plankton communities and thereby the whole Baltic ecosystem. Thiamine and other micronutrients are not something generally considered in the environmental management of aquatic systems but the results of this thesis suggest that ecological disturbances indirectly can have negative effects on top predators via a disrupted supply of essential substances. / <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. Paper 5: Manuscript.</p>