Munin: Browsing Doktorgradsavhandlinger (BFE-fak) by Title

Neuronal hypoxia tolerance in diving endotherms

Ludvigsen, Stian (Doctoral thesis; Doktorgradsavhandling, 20-Aug-2010)

[+]

Abstract:	The thesis “Neuronal hypoxia tolerance in diving endotherms” sheds light on mechanisms giving diving animals, such as the hooded seal, impressive dive capabilities of 1 hr duration down to 1000 m depth. In spite of enhanced capacity to store oxygen in their body and an ability to reduce their oxygen-consumption, these animals can resurface with blood oxygen values so low that a human being in the same situation would loose consciousness within seconds. This implies that the brain of diving animals tolerate lack of oxygen much better than the brain of non-diving animals. In the thesis it is demonstrated for the first time that this is actually the case. Electrophysiological recordings of isolated brain slices were used to investigate how neuronal activity changed in response to hypoxia in brain tissue from hooded seals (Cystophora cristata) (Folkow et al., 2008) and eider ducks (Somateria mollissima) (Ludvigsen & Folkow, 2009). Results showed a significant higher survival of brain tissue from the diving species relative to non-diving controls. Follow-up experiments were performed in order to investigate whether ATP-sensitive potassium channels (KATP-channels), that previously have been demonstrated to offer short-term protection against oxygen- and energy deprivation in other species, play a role in the neuronal hypoxia tolerance of the diving animals. The KATP-channels were pharmacologically blocked in hypoxic tissue, and comparison of responses to that of un-manipulated tissue indicated that the ion-channels offer some protection, but that they are not solely responsible for the high hypoxia tolerance in brain tissue from the divers. Investigating capillary density in the hooded seal brain, it was found that the hooded seal has a higher, or similar, capillary density compared to much smaller mammals. This is not expected from capillary density scaling laws, and may indicate that the hooded seal benefits from a higher capillary density than more similar sized mammals that may contribute to the hypoxia-tolerance of hooded seals. The electrophysiological investigations also gave new information on how coordinated network activity may arise in the mammalian brain. Earlier investigations have indicated that such rhythms are dependent upon neural connections between different brain regions and therefore can be studied only in the intact brain. Working with thick, isolated brain slices from hooded seals it was discovered that rhythmical activity may also arise within smaller neocortical areas, which may contribute to understanding how intrinsic brain activity is regulated.
Description:	The papers of the thesis are not available in Munin: 1. L.P. Folkow, J.M. Ramirez, S. Ludvigsen, N. Ramirez, A.S. Blix: "Remarkable neuronal hypoxia tolerance in the deep-diving adult hooded seal (Cystophora cristata)" Neuroscience Letters, vol 446 (2008), 147-150 (Elsevier - publisher's restrictions). Available at http://dx.doi.org/10.1016/j.neulet.2008.09.040 2. J.M. Ramirez, L.P. Folkow, S. Ludvigsen, N. Ramirez, A.S. Blix: "Spontaneous and persistent activity in thick neocortical slices of the deep-diving hooded seal" (manuscript) 3. S. Ludvigsen, L.P. Folkow: "Differences in in vitro cerebellar neuronal responses to hypoxia in eider ducks, chicken and rats", Journal of Comparative Physiology A, Vol 195 (2009), no 11, 1021-1030 (Springer - publisher's restrictions). Available at http://dx.doi.org/10.1007/s00359-009-0476-x 4. S. Geiseler, S. Ludvigsen, L.P. Folkow: "KATP-channels and their possible contribution to neuronal hypoxia tolerance in the cerebellum of eider ducks (Somateria mollissima)" (manuscript) 5. S. Ludvigsen, L.P. Folkow, E.B. Messelt: "Brain capillary density in the deepdiving hooded seal (Cystophora cristata)" (manuscript)
URI:	http://hdl.handle.net/10037/2788

File(s) in this item: 1

thesis.pdf (969.3Kb)

Planktonic food webs in the Arctic Ocean : structure and function in contrasting seasons and physical settings across Fram Strait

Seuthe, Lena (Doctoral thesis; Doktorgradsavhandling, 08-Dec-2011)

[+]

Abstract:	This thesis investigates the structure and function of planktonic food webs at two sites between Greenland and the Svalbard Archipelago, covering a coastal ecosystem influenced by Atlantic water masses (Kongsfjorden, 78º N) and a more oceanic system off the East Greenlandic shelf, influenced by the outflow of Arctic water and sea ice from the Arctic Ocean (northwest Fram Strait, 75 - 80º N). In Kongsfjorden, a seasonal study was conducted with sampling at six occasions between March and December 2006. Logistical constrains prohibited a similar extensive seasonal investigation in the ice-covered waters of northwest Fram Strait. Sampling fell into the onset (April-May 2008) and end (September 2006/2007) of the productive season. All four studies investigated the stocks of pico- to micro-sized autotrophs and heterotrophs, i.e. heterotrophic bacteria, proto- and metazooplankton. Production rates of autotrophs and heterotrophic bacteria were measured in Kongsfjorden. Ratios of heterotrophic and autotrophic biomass (H:A) and of specific bacterial and primary production (µBac:µPhyto) allowed to asses the overall structure and function of the investigated planktonic food webs and to compare them to published data from other Arctic regions. The emerging picture provides three distinct food web modes, where mode A is characterized by H:A < 1 and µBac:µPhyto > 1, new production, and large-celled phytoplankton. Mode B and C are characterized by dominance of heterotrophs (H:A > 1), more regenerated production, and small-celled phytoplankton. The difference between mode B and C is a difference in the specific production ratio, with µBac:µPhyto smaller and larger 1, respectively. According to this scheme, Arctic plankton communities appear to prevail under mode B and C most of the year. In Kongsfjorden, e.g. five of the six months sampled fell under mode B and C, with mode C being typical for light-limited winter communities. From own and literature data, it is suggested that the food web mode controlling physical factors are the amount of incident photosynthetically active radiation (PAR), ice cover, nutrient concentration, and water column stability. Due to an approximately latitudinal change in these physical settings, the relative prevalence of the three food web modes changes from the marginal seas to the central Arctic Ocean, with mode A most likely being absent from the highest latitude waters. In general, Arctic plankton communities appear to sustain on average a 3-fold higher H:A biomass ratio for a given phytoplankton stock than the world’s coastal oceans, which may mainly be due to extensive import of long-lived copepods from sub-Arctic European seas through advection. It is argued that the large stock of heterotrophs plays a crucial role in structuring Arctic plankton communities, with the potential to prohibit phytoplankton bloom formation (mode A) through extensive grazing.
Description:	Paper 3 and 4 of this thesis are not available in Munin: 3. Seuthe L, Töpper B, Reigstad M, Thyrhaug R and Vaquer-Sunyer R: 'Microbial communities and processes in ice-covered Arctic waters of the northwestern Fram Strait (75 – 80ºN) during the vernal pre-bloom phase', Aquatic Microbial Ecology (2011) 64:253-266. Available at http://dx.doi.org/10.3354/ame01525 4. Svensen C, Seuthe L, Vasilyeva Y, Pasternak A and Hansen E: 'Zooplankton communities across Fram Strait in autumn : are small copepods and protozooplankton important? (in press in Progress in Oceanography).
URI:	http://hdl.handle.net/10037/3777

File(s) in this item: 3

paper_1.pdf (1.039Mb)

paper_2.pdf (966.8Kb)

thesis.pdf (2.535Mb)

Plant regulatory networks : RNA binding proteins as mediators of communication between DNA containing compartments by dual targeting

Fuss, Janina (Doctoral thesis; Doktorgradsavhandling, 11-May-2012)

[+]

Abstract:	The endosymbiosis-derived organelles within a plant cell, plastids and mitochondria, have to be equipped with a certain set of proteins to be fully functional. This set of proteins is encoded by different genomes: the organellar genomes and the nuclear genomes. This setup poses some interesting challenges for the regulation of gene expression and protein transport. On the one hand, the targeting signals that transport proteins to the organelles have to be highly specific and on the other hand, the communication between the DNA containing compartments to coordinate their gene expression has to be transmitted somehow, not only from the nucleus but also from the organelles back to the nucleus. In this thesis, two prediction programs are introduced. One of them can predict dual targeted proteins to both organelles (ATP, ambiguous targeting predictor) and the other one is species- specific for Physcomitrella patens (GTP_Pp; green targeting predictor – P. patens-specific). The first predictor can help to gain a more complete picture of the proteins potentially present in the organelles. With the help of that predictor, we predicted that the amount of proteins with dual targeting signals is higher than anticipated and that we to date know only a minor part of actually dual targeted proteins. The second predictor can help to answer the question on the evolutionary consistency of targeting signals within the plant kingdom and the importance of having species-specific approaches in analyzing protein targeting. We actually observed a surprisingly big difference in composition and recognition of mitochondrial and dual-targeting protein signals, which led to the conclusion, that species-specific approaches always should be considered as the optimal option for both, in silico and in vivo experiments. The second part of this thesis focuses the mechanisms of communication between nucleus and the organelles, especially the plastid possibly mediated by dual targeting. We chose several plastid RNA-/DNA-binding proteins to analyze their sub-plastidic localization and their potential additional nuclear localization. Those candidates were AtWHY1 (Arabidopsis thaliana Whirly1), four members of the AtcpRNP (chloroplast ribonucleoprotein) family and AtEF-Tu (elongation factor thermo-unstable). The analyzed members of the AtcpRNP family reflect their described multiple functions within the plastid also in a multiple localization pattern. Furthermore, we were able to show interactions of different members of the AtcpRNP family by yeast-two-hybrid interaction assays. The localization pattern of AtEF-Tu was very similar to the one observed for the AtcpRNPs, which indicated, together with a confirmed localization within the transcriptionally active chromosome, a multiple function for AtEF-Tu. The sub-plastidic localization data suggest overlapping networks of activity for the proteins by observed co-localizations. This was also shown with respect to several marker proteins for plastid functions. For AtEF-Tu and the AtcpRNPs, we also showed experimentally that a second localization in the nucleus is possible for the mature protein, which makes them interesting candidates for a possible mediation of plastid signals to the nucleus next to AtWHY1. For AtWHY1, we were able to show an effect of the DNA binding domain on the known localization pattern which seemed to reflect an aberration in transport processes through the envelope. This offers a potential regulatory mechanism that needs to be explored in detail in the future.
Description:	Papers 1, 3, 4 and 5 are not available in Munin: 1. Mitschke J, Fuss J, Blum T, Hoglund A, Reski R, Kohlbacher O and Rensing SA.: 'Prediction of dual protein targeting to plant organelles', New Phytologist (2009), 183(1): 224-235. Available at http://dx.doi.org/10.1111/j.1469-8137.2009.02832.x 3. Herrmann U, Fuss J, Krupinska K and Krause K.: 'Moonlighting in plastids : translation elongation factor EF-Tu is a component of chloroplast transcriptionally active chromosomes' (manuscript I submitted to Current Genetics). 4. Fuss J, Krause K.: 'Co-Localization and interaction of ribonucleoproteins in chloroplasts of Arabidopsis thaliana' (manuscript II). 5. Fuss J, Liegmann O, Krause K and Rensing SA.: 'Can Arabidopsis thaliana read the messages from Physcomitrella patens and vice versa? : an analysis on the conservation of targeting signals' (manuscript III submitted to New Phytologist). 6. Fuss J, Krause K.: 'The DNA binding domain of a Whirly protein from Arabidopsis thaliana is engaged in protein translocation across the plastid envelope membrane' (manuscript IV).
URI:	http://hdl.handle.net/10037/4154

File(s) in this item: 2

paper_2.pdf (541.8Kb)

thesis.pdf (1.509Mb)

PLGA and PLA particles as vaccine delivery systems for Atlantic salmon : a study on formulation and use with an emphasis on immune responses

Fredriksen, Børge Nilsen (Doctoral thesis; Doktorgradsavhandling, 07-Jun-2012)

[+]

Abstract:	Vaccines are regarded as the safest and most cost-effective strategy to prevent infectious diseases. For some diseases, vaccine improvements are required as protection levels are still inadequate. The key to solving this challenge might lie in the development of more efficacious vaccine delivery systems and adjuvants. Poly (lactide-co-glycolide) (PLGA) is a biodegradable polymer which has an extensive safety record in biological systems and possesses immunological adjuvant properties as injectable particles. In the present work, micro- and nanoparticles of PLGA and PLA were explored as a vaccine delivery system in Atlantic salmon (Salmo salar). The overall objectives were to investigate their adjuvant abilities in provoking innate and adaptive immune responses, forming antigen depots and inducing protective immunity in a challenge test with infectious pancreatic necrosis virus (IPNV). Formulation parameters in preparation of polymeric particles were systematically optimized (paper IV) to achieve stable PLGA particle products containing co-entrapped model antigens and β-glucan (paper I and II), or virus particles of infectious pancreatic necrosis virus (IPNV) (paper III). Post immunization potency of nanoparticles (300-400 nm) was demonstrated by their ability to induce early innate responses (day 2, 4 and 8) at transcription levels equal to or higher than the oil-adjuvanted formulation (paper I). Temporal differences in expression levels of innate markers were observed, suggesting rapid systemic distribution of particles (paper I). By tracing of isotope labelled proteins, nanoparticles (˂ 1000 nm) were found to localize antigens in the head kidney while micro-sized (~ 8 µm) particles generally retained antigen at the injection site. Irrespective of size, particles made of polymers with high molecular weight (MW) generally had superior depot capabilities compared to their low MW counterparts (paper II). Adaptive immune responses to immunization were assessed by QPCR and ELISA. T cell markers were not differentially expressed at the selected early time points (paper I), but at day 60 and 75 antibody responses were found to be elevated (paper II and III). In a dose-response study, micro- but not nanoparticles were demonstrated to be equally potent compared to the oil-adjuvanted control group with regard to induction of antibody responses. Long-term antibody responses induced by particles were generally less robust and therefore declined towards the end of the experimental period (120 days), while responses induced by the oil-adjuvanted formulation progressively increased. Following immunization, antibody responses were not related to polymer qualities or the ability of particles to depot or distribute antigens. Scoring of side effects demonstrated excellent safety profiles for the particle formulations (paper II and discussed in paper V). In paper III, vaccine efficacy was tested in a cohabitation challenge with IPN. Survival rates for the nanoparticle vaccinated groups were comparable to the non-vaccinated control fish and demonstrated that their ability to induce protection against IPN was inferior to the oil-adjuvanted vaccines. Virus re-isolation from head kidney and blood during the challenge period did however demonstrate some level of protection as the nanoparticle vaccinated groups were able to delay the IPNV infection. In the presented studies, the principal adjuvant properties of PLGA particles in Atlantic salmon have been demonstrated to include their capacity to induce strong innate responses and provide antigen depots for long-term delivery of antigens. In addition, indication of particle presence in lymphoid organs was an interesting finding that could suggest a certain targeting effect to phagocytic cells. To achieve a better understanding of how PLGA particles may be used to direct immune responses in salmon, more detailed studies on particle qualities-cell interactions/responses are required.
Description:	Papers 1-4 of this thesis are not available in Munin: 1. B.N. Fredriksen, K. Sævareid, L. McAuley, M.E. Lane, J. Bøgwald and R.A. Dalmo.: 'Early immune responses in Atlantic salmon (Salmo salar L) after immunization with PLGA nanoparticles loaded with a model antigen and β-glucan', Vaccine (2011) 29(46):8338-8349. Available at http://dx.doi.org/10.1016/j.vaccine.2011.08.087 2. B.N. Fredriksen and J. Grip.: 'PLGA/PLA micro- and nanoparticle formulations serve as antigen depots and induce elevated humoral responses after immunization of Atlantic salmon (Salmo salar L)', Vaccine (2012) 30(3):656-667. Available at http://dx.doi.org/10.1016/j.vaccine.2011.10.105 3. H.M. Munang‟andu, B. N. Fredriksen, S. Mutoloki, B. Brudeseth, T.Y. Kuo, I. S. Marjara, R.A. Dalmo and Ø. Evensen.: 'Comparison of vaccine efficacy for different antigen delivery systems for infectious pancreatic necrosis virus vaccines in Atlantic salmon (Salmo salar L)' (submitted manuscript). 4. B.N. Fredriksen, L.B. Hølvold, J.Bøgwald and R.A. Dalmo.: 'Optimization of formulation variables to increase antigen entrapment in PLGA particles' (submitted manuscript).
URI:	http://hdl.handle.net/10037/4153

File(s) in this item: 2

paper_5.pdf (223.3Kb)

thesis.pdf (1.720Mb)

Polar bears (Ursus maritimus) in the Barents Sea area : population biology and linkages to sea ice change, human disturbance and pollution

Andersen, Magnus (Doctoral thesis; Doktorgradsavhandling, 16-Mar-2013)

[+]

Abstract:	Polar bears in the Barents Sea population have been protected from hunting in Russia since 1956 and following the signing of the international Polar Bear Agreement in 1973 in Norway. This thesis seeks to summarise current knowledge on key population biology issues four decades after the Norwegian protection and almost six after the Russian. Further, it discusses threats that have developed in the decades following protection against human harvesting. It concludes with a discussion of the effect of multiple stressors on the population, and some thoughts on future research, monitoring and management. Polar bears in Svalbard and the Barents Sea area have been studied during the last 40 years with the aim of gaining knowledge regarding population biology and to evaluate potential sources of impact on the population from anthropogenic activity and changes to their habitat. The initial threat to polar bears in the region was unquestionably overharvest. Polar bear numbers were reduced quite drastically and hunting was clearly not sustainable. After the harvesting was stopped, the population grew in size to an estimated 2650 (1900-3600) in 2004. We believe that population recovery led to a wider distribution of maternity denning in the Svalbard Archipelago, compared to the period just after the protection of the population in 1973. However, during recent decades, the population has faced challenges from a variety of new anthropogenic impacts. The population has been exposed to a range of pollutants and an increasing level of human presence and activity within their range. Contaminants are bioaccumulated through the trophic levels in the marine food web, culminating in this top predator that consumes primarily ringed, bearded and harp seals. Females with small cubs use the land-fast sea ice for hunting, and are vulnerable to human disturbance. Changes in sea ice conditions also affect polar bears in the region, and reduced access to denning areas on the eastern islands of Svalbard is currently a concern. A decrease in spring land-fast ice close to important denning areas could negatively affect the survival of cubs. Research and monitoring provides advice to management bodies both locally and globally. Information on the presence of toxic compounds in High Arctic systems has resulted in progress in recent decades in having better control of harmful substances and in some cases international bans on their production and use. This has resulted in declining contaminant burdens in polar bears. Unfortunately, new harmful substances are finding their way to the Arctic, while others, such as radionuclides, are stored locally (within Russian Territories) in large quantities, representing potential sources of pollution. The protection of important habitats locally with restrictions on motorized traffic may help reduce negative impacts from human activity on polar bears in the region. The fate of polar bears with regard to climate change is uncertain, but significant negative effects have been documented and these impacts are expected to increase in the coming decades. Relevant research and monitoring of polar bears is essential for future management of the species. The arctic environment should be managed in such a way that the combined effects of stressors on polar bear populations are minimized.
Description:	All but paper 5 of this thesis are not available in Munin: 1. Aars J, Marques T A, Buckland ST, Andersen M, Belikov S, Boltunov A & Wiig Ø.: 'Estimating the Barents Sea polar bear subpopulation size', Marine Mammal Science (2009), vol. 25(1):35-52. Available at http://dx.doi.org/10.1111/j.1748-7692.2008.00228.x 2. Andersen M, Derocher AE, Wiig Ø & Aars J.: 'Movements of two Svalbard polar bears recorded using geographical positioning system satellite transmitters', Polar Biology (2008), vol. 31:501-507. Available at http://dx.doi.org/10.1007/s00300-008-0428-x 3. Freitas C, Kovacs KM, Andersen M, Aars J, Sandven S, Mauritzen M, Pavlova O & Lydersen C.: 'Importance of fast ice and glacier fronts for female polar bears and their cubs during spring in Svalbard, Norway', Marine Ecology Progress Series (2012), 447:289-304. Available at http://dx.doi.org/10.3354/meps09516 4. Andersen M, Derocher AE, Wiig Ø & Aars J.: 'Polar bear (Ursus maritimus) maternity den distribution in Svalbard, Norway', Polar Biology (2012), vol.35:499-508. Available at http://dx.doi.org/10.1007/s00300-011-1094-y 6. Andersen M and Aars J.: 'Short-term behavioural responses of polar bears to disturbance by snowmobiles', Polar Biology (2008), vol.31:501-507. Available at http://dx.doi.org/10.1007/s00300-007-0376-x 7. Derocher AE, Wiig Ø & Andersen M.: 'Diet composition of polar bears in Svalbard and the western Barents Sea', Polar Biology (2002), vol.25:448-452. Available at http://dx.doi.org/10.1007/s00300-002-0364-0 8. Andersen M, Lie E, Derocher AE, Belikov SE, Bernhoft A, Boltunov AN, Garner GW, Skaare JU & Wiig Ø.: 'Geographic variation of PCB congeners in polar bears (Ursus maritimus), from Svalbard to the Chukchi Sea', Polar Biology (2001), vol. 24:231-238. Available at http://dx.doi.org/10.1007/s003000000201 9. Andersen M, Gwynn JP, Dowdall M, Lydersen C & Kovacs KM.: 'Radiocaesium in marine mammals from Svalbard, the Barents Sea and the North Greenland Sea', Science of the Total Environment (2006), vol. 363:87-94. Available at http://dx.doi.org/10.1016/j.scitotenv.2005.06.019
URI:	http://hdl.handle.net/10037/5069

File(s) in this item: 2

paper_5.pdf (300.8Kb)

thesis.pdf (1.746Mb)

Post mortem proteolytic degradation of myosin heavy chain in skeletal muscle of Atlantic cod

Wang, Pål Anders (Doctoral thesis; Doktorgradsavhandling, 28-Jan-2011)

[+]

Abstract:	One of the most important parameters of quality regarding meat both from mammals and fish is texture. The post mortem degradation of muscle and connective tissue proteins during tenderization of meat from warm-blooded animals is unwanted in fish due to a loss of product quality. Soft fillet and gaping are common problems both in wild and farmed cod and have huge impact on the quality and the consumers’ perception of the products. The underlying mechanisms responsible for the changes in texture are not known, but endogenous proteolytic enzymes seem to play an important role in the process. A muscle cell contains several proteolytic systems. Among these are the multicatalytic proteasome, lysosomal cathepsins, cytosolic calpains and metalloproteinases. It has been shown that calpains are important in the degradation process resulting in tender meat in warm-blooded animals. In fish, the calpains and cathepsins have been suggested to act in cooperation resulting in the observed post mortem degradation of muscle proteins. Many of the cathepsins and calpains have been shown to be able to degrade myofibrillar proteins in vitro systems. Such systems have traditionally been a main strategy when studying protein degradation post slaughter in fish muscle. A weakness in such systems is that grinding of muscle tissue and isolation of proteins from the homogenate leads to a loss of the internal control system in the muscle. Another problem by using such systems is that the conditions are often highly optimized and therefore very different from normal post mortem muscle. The temperature and pH is often different from normal post mortem muscle. In this thesis cathepsin D, one of the candidate enzymes being responsible for post mortem muscle degradation in cod has been studied. The enzyme was purified from cod liver, and an antibody specific against the enzyme was produced in mouse. The isolated enzyme had lower tolerance towards temperature than a similar commercial available enzyme isolated from bovine. The antibody detected cathepsin D in extracts from several other fish species. Further, the degradation of myosin heavy chain (MHC) was studied. The degradation of MHC in isolated myofibrils occurred at the highest rate at high temperature (20ºC) and low pH (5.5), but degradation occurred even when stored on ice and at relevant muscle-pH. For comparison, intact muscle was stored prior to isolation of myofibrils. The results showed that the MHCdegradation occurred in a similar pattern in intact muscle, however less prominent. It was also shown that cathepsin D was associated with the myofibrils, and the enzyme could not be completely removed even after several washing steps. A model system was established, that made it possible to study how small changes in pH and inhibitors of proteolytic enzymes influence on the MHC-degradation in intact muscle tissue post slaughter. A low muscle-pH (6.05-6.3) did lead to degradation of MHC, while the protein stayed unchanged at pH 6.9. Inhibitors of cysteine and aspartic acid proteinases were obviously more efficient in preventing MHC-degradation than inhibitors of serine and metalloproteinases. A surprising observation was that EDTA, an inhibitor of metalloproteinases, increased the degradation of MHC. The conlusion of this thesis is that lysosomal cathepsins of the cysteine- and aspartic acid-types are responsible for the MHC-degradation in intact muscle. The new model system will be suitable when studying how other muscle proteins are degraded in intact muscle tissue post slaughter, and which enzymes that are involved.
Description:	The papers in this thesis are not available due to publishers' restrictions: 1. Wang, P.A, Steinvik, J., Larsen, R., Mæhre, H and Olsen, R.L.:'Cathepsin D from Atlantic cod (Gadus morhua L.) liver. Isolation and comparative studies', Comparative Biochemistry and Physiology, Part B (2007), 147, 504–511. Available at http://dx.doi.org/10.1016/j.cbpb.2007.03.004 2. Wang, P.A., Martinez, I. and Olsen, R.L.:'Myosin heavy chain degradation during post mortem storage of Atlantic cod (Gadus morhua L.)', Food Chemistry (2009), 115, 1228–1233. Available at http://dx.doi.org/10.1016/j.foodchem.2009.01.031 3. Wang, P.A., Vang, B., Pedersen, A.M., Martinez, I. and Olsen R.L.: 'Postmortem degradation of myosin heavy chain in intact fish muscle: Effects of pH and enzyme inhibitors', Food Chemistry (2011), 124, 1090–1095. Available at http://dx.doi.org/10.1016/j.foodchem.2010.07.093
URI:	http://hdl.handle.net/10037/3337

File(s) in this item: 1

thesis.pdf (1.089Mb)

Poverty in Small-Scale Fisheries : Governance Challenges in Lake Victoria Fishing Communities, Tanzania

Onyango, Paul Ochieng (Doctoral thesis; Doktorgradsavhandling, 23-Aug-2011)

[+]

Abstract:	The pursuit of a world without poverty is without doubt among the leading global challenges not only for governments but also the poor themselves. This challenge is also in small-scale fishing communities where poverty is persistent and has become a thorny issue to the poor as well as governing actors. Strategies have been formulated and implemented but the results have not been up to the expectations. Why haven’t these strategies yielded expected results? This is the central question of this thesis. This study seeks to understand why poverty persists despite the good instruments that have been directed at its alleviation. It examines poverty through studying the underlying factors that determine relationships between and among the many variables that make poverty a multidimensional problem. It argues that the persistent poverty in small-scale fishing communities in Lake Victoria Tanzania finds explanation in the manner in which poverty and its challenges have been understood and addressed. By using Kooiman’s and Jentoft’s (2009) ‘meta-governance’ perspective, the study discusses how differences in, what people consider as important (values), what they believe is morally mandatory to do (norms) and what should direct behaviour or action (principles), explain the persistent poverty in fishing communities. The study shows that there is inconsistency in the way poor fishers’, riparian to the Lake and governing actors in Tanzania understand poverty in the fishing communities and how to confront it. This inconsistency exists at the meta-governance level i.e. with regards to values, norms and principles. The study proposes that to alleviate poverty, a solution to this difference should be sought from a governance mechanism that addresses the dissimilarity. This must be a process which provides governing actors and the poor opportunities to interact in order to influence policy.
Description:	Papers 1,3,4 and 5 of the thesis are not available in Munin: 1. Onyango, P. O.: 'Re-configuring Poverty: The Wickedness Perspective', African Journal of Tropical Hydrobiology and Fisheries (2009), 12, 37-46. Available at http://www.ajol.info/index.php/ajthf/article/view/58032 3. Onyango, P. O. and S. Jentoft: 'Assessing poverty in small-scale fisheries in Lake Victoria, Tanzania', Fish and Fisheries (2010), 11, 250-263. Available at http://dx.doi.org/10.1111/j.1467-2979.2010.00378.x 4. Onyango, P. O.: 'Occupation of last resort? Small-scale fishing in Lake Victoria, Tanzania', In Jentoft S. and A. Eide (Eds.). Poverty Mosaics: Realities and Prospects in Small-Scale Fisheries (2011) Springer Verlag. Available at http://dx.doi.org/10.1007/978-94-007-1582-0_6 5. Onyango, P. O. and S. Jentoft.: 'Climbing the Hill: Poverty Alleviation, Gender Relationships, and Women’s Social Entrepreneurship in Lake Victoria, Tanzania' (accepted paper in Maritime studies)
URI:	http://hdl.handle.net/10037/3551

File(s) in this item: 2

paper_2.pdf (159.8Kb)

thesis.pdf (1.466Mb)

Primary production and the relevance of small autotrophic and heterotrophic cells in marine arctic ecosystems

Hodal, Helene (Doctoral thesis; Doktorgradsavhandling, 02-Dec-2011)

[+]

Abstract:	The Arctic is one of the least studied regions in the world and large changes in marine ecosystem dynamic are expected here because of the increasing air and ocean temperature. The central Arctic Ocean has for a long time been considered as a very low productive ecosystem, but recent estimates of primary production gives relatively high values. The shelves surrounding the Arctic Ocean are highly productive areas, especially the Barents Sea region, and a large part of arctic primary production occurs in these seasonally ice-covered regions. The relevance of small cells in arctic ecosystems has received increased attention the last two decades, and it is now accepted that the microbial food web play an important role also in the Arctic. To increase the knowledge on primary production and the relevance of small autotrophic and heterotrophic cells in the Arctic different field studies were conducted. Spring bloom dynamics (nutrients, phytoplankton, protozoans and in situ primary production) were investigated in Kongsfjorden (Svalbard) in April and May in 2002. During the multidisciplinary CABANERA-project three field campaigns in 2003-2005 to the marginal ice zone of the northern Barents Sea were conducted. Primary production was measured in situ for 24 hours at different stages of ice-edge blooms. Primary production and chlorophyll a measurements were fractionated in small (<10µm) and large cells (>10µm). During an expedition across the Arctic Ocean in August and September 2005 different biological parameters were measured (chlorophyll a, biogenic silica, particulate carbon and nitrogen, few zooplankton samples) together with the distribution of autotrophic and heterotrophic microbial biomass. Bacteria abundance was estimated using flow-cytometry and protists abundance was analyzed by epifluorescence microscopy after staining with DAPI. Protists were divided in different size categorize: < 2µm, 2-5µm, 5-10µm and 10-20µm. A seasonally study (January-September) of bacteria community structure and activity was conducted in a cold high latitude fjord (Balsfjord, northern Norway) in 2009 using fluorescence in situ hybridization (FISH) combined with microautoradiography (micro-FISH). In Kongsfjorden we found that the onset of the spring bloom was linked to the hydrographical situation during the sea ice break up. The peak of the spring bloom was found to vary between different years in both timing and intensity but will most probably occur between the middle-end of April and the middle of May. Primary production in 2002 persisted for a long time due to mixing with nutrient rich water masses. The ice edge phytoplankton bloom in the marginal ice zone of the northern Barents Sea was very heterogenic and no patterns in integrated primary production could be assigned to stages or latitudes. Subsurface (20-60m) primary production contributed with 24% to the total integrated primary production during ice edge blooms in the marginal ice zone, illustrating the importance of sampling in subsurface maxima. Small cells contributed with 46% to total primary production during ice edge blooms underlining the important role small cells can play as primary producers. Picoplankton (<2µm) abundance was high in the Arctic Ocean, and in the central part heterotrophic cells dominated (72%). Bacteria abundance was very low in the central part of the Arctic Ocean, but it is unknown whether this was caused by low growth rates or by high predation pressure. Bacteria were found to be highly active during summer in the Balsfjord underlining the important role they play in carbon turnover in the ocean. Bacteria belonging to Roseobacter were very active in assimilating DOM but they were not very abundant. This suggests that species specific predation may regulate the abundance of active bacteria. The main conclusion from the work included in this synthesis is that small cells are an important component of arctic food webs. Small cells need to be considered as important primary producers, also during spring blooms and ice edge blooms. We also found that bacteria need to be studied on single cell level to understand the underlying reasons for the dynamics that are observed on community levels.
Description:	Papers 2,3 and 4 are not available in Munin: 2. Hodal H and Kristiansen S.: 'The importance of small-celled phytoplankton in spring blooms at the marginal ice zone in the northern Barents Sea', Deep-Sea Research Part II (2008) 55: 2176-2185. Available at http://dx.doi.org/10.1016/j.dsr2.2008.05.012 3. Kristiansen S, Hodal H and Reigstad M.: 'Autotrophic and heterotrophic microbial biomass across the Arctic Ocean' (manuscript) 4. Hodal H, Kirchman D, Kristiansen S, Straza T.: 'Bacteria diversity and single-cell activity in a cold high latitude fjord (Balsfjord) from winter to late summer 2009' (manuscript)
URI:	http://hdl.handle.net/10037/3783

File(s) in this item: 2

paper_1.pdf (838.0Kb)

thesis.pdf (1.114Mb)

På grensen til et eventyr : økonomisering av Snøhvit LNG

Tveiterås, Kathrine (Doctoral thesis; Doktorgradsavhandling, 29-Jun-2012)

[+]

Abstract:

Megaprosjekter er store investeringsprosjekter med betydelig innflytelse på samfunn, miljø og økonomi. Til tross for grundige utredninger og beregninger i forkant, presterer slike prosjekter sjelden i overenstemmelse med planene: de blir gjerne både forsinket og mye dyrere enn estimatene tilsa. Hva er det som skjer i megaprosjekter som gjør at planer om suksess blir til fortellinger om fiasko? Dette spørsmålet har fått stor oppmerksomhet både i offentlige institusjoner, i media og i faglitteraturen. De skisserte løsningene for å endre på den klassiske utviklingen har ofte dreiet seg om å forbedre bruken av styringsverktøy, med sterkere krav til nøyaktighet i beregninger og gjennomsiktighet i beslutningsprosessene. Denne avhandlingen problematiserer slike resepter, og argumenterer for at fokuset på mer nøyaktighet i megaprosjekter samtidig overser hvilken innvirkning dette kravet i seg selv har på hvordan prosjektene presterer. Studien flytter på denne måten fokuset fra bruken av styringsverktøy til verktøyene selv. Hva er deres rolle i megaprosjektenes dynamikk? Avhandlingen tar for seg utbyggingen av Snøhvit LNG. Prosjektet ble gjennomført i 2002-2007, mer enn 20 år etter at funnene ble gjort i Hammerfestbassenget. Den lange tiden skyldtes at var et nytt og usikkert prosjekt, og det var derfor vanskelig å finne en utbyggingsløsning som ble ansett både som gjennomførbar og lønnsom. Til slutt lyktes arbeidet med dette og Snøhvit ble realisert. Men til tross for omfattende forberedelser sluttet prosjektet seg likevel raskt til rekken av megaprosjekter som ikke presterer som forutsatt, med både forsinkelser og store kostnadsoverskridelser. Det ble anvendt en rekke styringsredskaper for å manøvrere i prosjektets usikre og komplekse omgivelser. Disse verktøyene baserer seg på økonomiske prinsipper: Oppfatningen er at tallene vil gi nøytrale svar. Avhandlingen anvender et STS-perspektiv og studerer bruken av to slike styringsredskaper i prosjektet. Først handler det om hvordan Snøhvit ble konstruert som et lønnsomt prosjekt. Det sentrale verktøyet for å vurdere dette er nettonåverdimodellen. Deretter handler det om hvordan kostnadsoverskridelsene ble håndtert. Det er inntjent verdistyring som hjelper til med dette. Ved å bruke disse instrumentene, kunne prosjektet tilpasses kalkylenes logikk. Dette kalles økonomisering. Ved å oversette usikre momenter til tall, blir kompleks informasjon mulig å sammenligne, håndtere og ta stilling til. Uten denne forenklingen er det vanskelig å ta beslutninger. Det er imidlertid den samme forenklingen som skaper problemer i gjennomføringen fordi de ikke favner kompleksiteten i utbyggingen. Studien gir nye innspill til megaprosjektforskningen. Det er ikke bare menneskelige aktører som spiller en rolle; hvordan prosjektverktøyene virker sier også noe om sammenhengen og dynamikken i et stort prosjekt. Jo mer nøyaktig omgivelsene tallfestes, jo mer sannsynlig er det at ting vil utvikle seg annerledes. Det kan således synes som at det nødvendige valget for megaprosjekter er et kostnadsoverskridende prosjekt eller ingen prosjekt over hode. En aksept for dette innebærer at framtidige forsknings- og samfunnsspørsmål bør stilles på en måte som er mer relevant for dynamikken i megaprosjekter. Hvilken type kunnskap er nødvendig for styring og evaluering av prosjekter, og hvilken type kunnskap koster mer enn den gir fordeler?

URI:

http://hdl.handle.net/10037/4299

File(s) in this item: 1

thesis.pdf (1.237Mb)

Quality of salted cod (Gadus morhua L.) as influenced by raw material and salt composition

Lauritzsen, Kristin (Doctoral thesis; Doktorgradsavhandling, 29-Mar-2004)

[+]

Abstract:

Hva påvirker kvaliteten på saltfisk? Saltfiskens lukt, farge, konsistens og smak bestemmer kvaliteten. Dersom torsken blir dødsstiv samtidig med at saltet strømmer inn i fiskekjøttet, oppnår man et lavere vektutbytte, vann- og saltinnhold på sluttproduktet. Fisken bør derfor saltes etter dødsstivheten for å oppnå et høyt vektutbytte. Ønsker man å minimere proteintapet fra salteprosessen og få en høy lyshet på sluttproduktet, bør fisken derimot saltes før dødsstivheten inntrer. Økt kalsium- og magnesiuminnhold samt lav pH i saltet, gir et hvitere og mer fast ferdigprodukt samt et lavere proteintap fra prosessen. Torskefilet har et høyt innhold av flerumettede fettsyrer, og er derfor spesielt utsatt for harskning og fargeendringer ved salting. Det er påvist at torskens muskel-pH (surhet) etter slakting, har betydning for evnen til å motvirke misfarging av ferdigproduktet i nærvær av kopper. Lav muskel-pH ga større misfarging samt lavere vanninnhold i fullsaltet muskel enn høy muskel-pH før salting. Kopper og jern er metaller som naturlig forekommer i fiskekjøtt, salt og drikkevann. Kopper-ioner framskynder harskning i fullsaltet torsk og gir kraftigere gul misfarging av ferdigproduktet sammenlignet med jern. Enverdig kopper er mer harskningsfremmende enn toverdig kopper. For å unngå harskning, er det vanlig å bruke antioksidanter i framstillingsprosessen. Når mer enn 0.1% natriumaskorbat blir tilsatt saltlaken, forhindrer den kopper i å fremme harskning av torskemuskelen. Antioksidantene sitronsyre og EDTA ble også undersøkt, men kun ved lav konsentrasjon sammen med kopper i saltlaken. EDTA var en effektiv antioksidant, mens sitronsyre derimot fremmet harskning i fullsaltet torsk. Doktorgradsarbeidet ble finansiert av næringsmiddelprogrammet ved Norges forskningsråd i perioden 1997-2001.

URI:

http://hdl.handle.net/10037/1819

File(s) in this item: 6

paper_1.pdf (3.960Mb)

paper_2.pdf (544.1Kb)

paper_3.pdf (667.7Kb)

paper_4.pdf (866.8Kb)

(more files)

Quantification and characterisation of residual blood in fish muscle : impact of slaughtering methods

Olsen, Stein Harris (Doctoral thesis; Doktorgradsavhandling, 17-Jun-2011)

[+]

Abstract:	Omorganisering i oppdrettsnæringen har ført til større og mer mekaniserte anlegg med høy slaktekapasitet. I dag kontrolleres normalt restblod i fiskefilet ved visuell inspeksjon. Dette er arbeidskrevende og innebærer subjektive evalueringer som muliggjør høy grad av unøyaktighet. Fargen på fiskemuskelen er også et viktig kriterium når kunder vurderer kvalitet, og disse fargeforandringene skyldes ofte restblod. Oppgaven belyser, i første omgang, de ulike enhetsoperasjonene ved slakting av fisk og hvilke effekter de har på selve utblødningen. I tillegg belyser den muligheten for å bruke en objektiv og hurtig målemetode for restblod i fiskemuskel, som er basert på visuell- og nærinfrarød spektroskopi. Restblod fører til store økonomiske tap for fiskeindustrien som følge av nedklassifisering. Området er lite belyst, og denne oppgaven søker å bidra med ny kunnskap rundt hvilke faktorer som påvirker mengden restblod i fiskemuskel. En kjemisk målemetode ble brukt som referanse og sammenlignet opp mot dagens visuelle inspeksjon samt en visuell- og nærinfrarød (VIS/NIR) spektroskopi metode. Sistnevnte innebærer måling av absorbsjon/refleksjon av lys fra bl.a. fargepigmentet hemoglobin, og metoden benyttes allerede i annen næringsmiddelindustri. Oppgaven viser at mengden blod i fiskemuskel påvirkes av stress før slakting, avlivingsmetoder, kjøling og lagring. Spesielt ble det funnet at bedøving ved bruk av slag før bløgging er optimalt med hensyn til restblod. Bruk av karbondioksid anbefales derimot ikke. VIS/NIR metoden anbefales ikke brukt industrielt, men metoden kan forbedres og automatiseres. Det foreslås å anvende avbildende VIS/NIR spektroskopi for å vurdere restblod i fiskefilet, med spektra fra fiske hemoglobin som referanse.
Description:	The papers of this thesis are not available in Munin: 1. Olsen, S.H., Sørensen, N.K., Stormo, S.K. and Elvevoll, E.O.: 'Effect of slaughter methods on blood spotting and residual blood in fillets of Atlantic salmon (Salmo salar)', Aquaculture (2006) 258, 462-469. Available at http://dx.doi.org/10.1016/j.aquaculture.2006.04.047 2. Olsen, S.H., Sørensen, N.K., Larsen, R., Elvevoll, E.O. and Nilsen, H.: 'Impact of pre-slaughter stress on residual blood in fillet portions of farmed Atlantic cod (Gadus morhua) - Measured chemically and by Visible and Near-infrared spectroscopy', Aquaculture (2008) 284, 90-97. Available at http://dx.doi.org/10.1016/j.aquaculture.2008.07.042 3. Olsen, S.H. and Elvevoll, E.O.: 'A pH induced shift in the haemoglobin spectra – A spectrophotometeric comparison of fish (Gadus morhua) and mammalian haemoglobin', Journal of Agriculture and Food Chemistry (2011) 59 (4), pp 1415–1422. Available at http://dx.doi.org/10.1021/jf1036273
URI:	http://hdl.handle.net/10037/3590

File(s) in this item: 1

thesis.pdf (748.0Kb)

Reproductive behaviour and sex trait allocations in an external fertilizer – the Charr (Salvelinus alpinus)

Figenschou, Lars (Doctoral thesis; Doktorgradsavhandling, 12-May-2010)

[+]

Abstract:	This thesis illuminates several aspects of mate choice and sexual selection in a species with external fertilization and no parental care. At a general level we have contributed to the basic framework within evolutionary biology and ecology and at a more specific level, as the proximate mechanisms controlling the associations between immune response, parasite intensities and traits indicative of sperm quality are not straightforward, we examined the effect of increased immunological activity on sperm traits. Our results have established the significance of male social status, and in the two inter-disciplinary studies, showed that parasitized and infected males seem to invest more in sperm quality, less in ornamental development and adapt to sperm competition (i.e., subordinate mating tactic). Thus, as reproductive decisions in charr seem to be strongly influenced by parasites and antigens, host parasite co-evolution may have been a significant mechanism in the maintenance and evolution of both male sexual behaviour and ornamentation.
Description:	Papers number 1, 3, 4, 5 and 6 of the thesis are not available in Munin: 1. Figenschou, L., Folstad, I. & Liljedal, S.: «Lek fidelity of male Arctic charr», Canadian Journal of Zoology, 82(2004): 1278-1284 (National Research Council Canada - publisher's restrictions). Available at http://dx.doi.org/10.1139/z04-106 3. Rudolfsen, G., Figenschou, L., Folstad, I., Tveiten, H. & Figenschou, M.: «Rapid adjustments of sperm characteristic in relation to social status», Proceedings of the Royal Society of London, Series B-Biological Sciences, 273(2006): 325-332 (publisher's restrictions). Available at http://dx.doi.org/10.1098/rspb.2005.3305 4. Figenschou, L., Rudolfsen, G., & Folstad, I.: «Female Arctic charr do not show apparent benefits from exposing their eggs to sperm from dominant males», Journal of Fish Biology, 71(2007): 284–289 (Wiley - publisher's restrictions). Available at http://dx.doi.org/10.1111/j.1095-8649.2007.01477.x 5. Figenschou, L., Skau, P.A., Folstad, I., Rudolfsen, G., Hanssen, S.A., Kortet, R., Killie, J.E., Oskam, I. & Strand, H.: «Parasite intensities and male social status as modifiers of sperm production and sperm swimming speed in the Arctic charr (Salvelinus alpinus)» (manuscript) 6. Figenschou, L., Skau, P.A., Folstad, I., Rudolfsen, G., Hanssen, S.A., Kortet, R., Killie, J.E. & Strand, H.: «Immune activation leads to reproductive compensation in Arctic charr (Salvelinus alpinus)» (manuscript)
URI:	http://hdl.handle.net/10037/2639

File(s) in this item: 2

paper_2.pdf (286.0Kb)

thesis.pdf (2.009Mb)

Risk sensitive reproductive strategies : the effect of environmental unpredictability

Bårdsen, Bård-Jørgen (Doctoral thesis; Doktorgradsavhandling, 13-Feb-2009)

[+]

Abstract:	A crucial task in ecology is to quantify trade offs between competing demographic processes for experienced by individuals that inhabit unpredictable environments. Perhaps the most widely studied trade off is that between current reproduction and future survival (‘the cost of reproduction’). While experimental studies have been widely used to quantify life history strategies in birds, virtually no experimental studies have been carried out on large and free ranging mammals. This thesis quantifies how female reindeer Rangifer tarandus subject to variability in food availability, trade their resources between reproduction and body mass to ensure own survival. By combining two experiments, one observational study and one theoretical model, this thesis show that: (1) Individuals subject to reduced food availability in one winter feeding promptly reduced their reproductive allocation the following summer to increased their autumn body mass. On the other hand, short-term improved conditions did not result in increased reproductive allocation. (2) Long-term improved winter feeding conditions did, however, result in increased reproductive allocation. (3) Reproduction was costly, especially for smaller females, as occasional harsh winters and high population density resulted in reduced reproduction and lowered female body mass. Moreover, a successfully reproducing female produced a smaller offspring in the coming year relative to a barren one. Reindeer also differ in their intrinsic quality as successfully reproducing females’ showed an increased probability of reproducing also in the following year. (4) In harsh and unpredictable winter conditions, the optimal reproductive strategy involved a low reproductive allocation per unit female spring body mass. Under such conditions females increased their autumn body mass to enhance their own survival. Conversely, the optimal reproductive strategy in benign and predictable conditions involved a higher reproductive allocation. (5) Reproductive strategies and environmental conditions had significant effects on population dynamics. Female reindeer do not to jeopardize their own survival and adjust their reproductive allocation in order to buffer periods of low food availability in a risk sensitive manner.
Description:	Papers number 1 and 2 of the thesis are not available in Munin, due to publishers' restrictions: 1. Bårdsen, B.-J., P. Fauchald, T. Tveraa, K. Langeland, N. G. Yoccoz, and R. A. Ims: "Experimental evidence for a risk sensitive reproductive allocation in a long-lived mammal", Ecology (2008)89:829-837 (Ecological Society of America). Available at http://dx.doi.org/10.1890/07-0414.1 2. Bårdsen, B.-J., P. Fauchald, T. Tveraa, K. Langeland, and M. Nieminen: "Experimental evidence of cost of lactation in a low risk environment for a long-lived mammal", Oikos (2009)118:837-852. Available at http://dx.doi.org/10.1111/j.1600-0706.2008.17414.x
URI:	http://hdl.handle.net/10037/2807

File(s) in this item: 3

paper_3.pdf (1.666Mb)

paper_4.pdf (2.045Mb)

thesis.pdf (1.924Mb)

Scavenging amphipods in the high Arctic : Studies of benthic and sympagic amphipods in the genera Onisimus and Anonyx

Nygård, Henrik (Doctoral thesis; Doktorgradsavhandling, 02-May-2011)

[+]

Abstract:	The main objective of this study was to increase our knowledge about the ecology of scavenging amphipods, particularly amphipods within the genera Onisimus and Anonyx. Specifically, the emphasis was to increase the knowledge of ice-associated (sympagic) Onisimus-species, but as these species are rather inaccessible, an approach using benthic congeners as proxies was chosen. By studying the shallow-water scavenging amphipods, a high temporal resolution in sampling could be achieved, resulting in detailed descriptions of life cycles and reproduction parameters of Onisimus caricus and O. litoralis. As seasonal studies on the amphipod scavenging guilds in the Arctic are rare, this study also includes a description of the seasonal variations in the amphipod scavenging guild in two fjords in Svalbard, Norway. Feeding strategies of the scavenging amphipods were studied using fatty acid composition and stable isotopes. Extrapolating the knowledge gained on benthic Onisimus-species to sympagic congeners showed that O. nanseni likely follows a similar life strategy as O. litoralis, being an income breeder. Additionally, the extended parental care by investing in a “start pack” of energy to the offspring is likely similar in these two species. Further, it could be hypothesized that O. nanseni and O. glacialis need a higher reproductive output in order to compensate for the high variation in the extent and loss of their sea ice habitat. However, further studies are needed to confirm this. A first step would be to obtain good winter samples, containing ovigerous females of O. nanseni and O. glacialis, that could give information on reproduction parameters and thus illuminate their life strategies and adaptations towards the sea ice habitat.
Description:	The papers of the thesis are not available in Munin: 1. Henrik Nygård, Mikko Vihtakari and Jørgen Berge:'Life history of Onisimus caricus (Amphipoda: Lysianassoidea) in a high Arctic fjord', Aquatic Biology (2009) 5:63-74. (Publisher's restriction). Available at http://dx.doi.org/10.3354/ab00142 2. Henrik Nygård, Jago Wallenschus, Lionel Camus, Øystein Varpe and Jørgen Berge:'Annual routines and life history of the amphipod Onisimus litoralis: seasonal growth, body composition and energy budget',Marine Ecology Progress Series (2010) 417:115-126. (Publisher's restriction) Available at http//dx.doi.org/10.3354/meps08798 3. Marek Zajączkowski, Henrik Nygård, Else Nøst Hegseth and Jørgen Berge:'Vertical flux of particulate matter in an Arctic fjord: the case of lack of the sea-ice cover in Adventfjorden 2006-2007',Polar Biology (2010), 33:223-239. (Publisher's restriction). Available at http://dx.doi.org/10.1007/s00300-009-0699-x 4. Henrik Nygård, Jørgen Berge, Janne E. Søreide, Mikko Vihtakari and Stig Falk-Petersen:'The amphipod scavenging guild in two Arctic fjords: seasonal variations, abundance and trophic interactions' (manuscript). 5. Henrik Nygård, Jørgen Berge, Bjørn Gulliksen and Lionel Camus:'The occurrence of Eualus gaimardii gibba Krøyer 1841 (Crustacea, Decapoda) in the sympagic habitat: an example of bentho-sympagic coupling', Polar Biology (2007) 30:1351-1354. (Publisher's restriction). Available at http://dx.doi.org/10.1007/s00300-007-0302-2
URI:	http://hdl.handle.net/10037/3382

File(s) in this item: 1

thesis.pdf (899.1Kb)

Seabirds, climate and prey. A population study of two seabird species.

Reiertsen, Tone Kristin (Doctoral thesis; Doktorgradsavhandling, 30-May-2013)

[+]

Abstract:	Many seabird populations have declined dramatically over recent decades, and studying the demography and population dynamic in seabird populations is important to gaining a better understanding of causes and mechanisms lying behind such changes and to identify targets for conservation and management. Climate and prey availability are known to affect demography and population dynamics of seabirds. Climate is now changing and a warming of the ocean may lead to changed availability of prey species and will affect seabirds through their demographic traits and ultimately their abundance and distribution. The main aim of this thesis was to study the impact of climate and prey abundance on seabird demography and population dynamics, using two seabird populations; the black-legged kittiwake Rissa tridactyla and the Common guillemot Uria aalge breeding on Hornøya in NE Norway whose populations are declining in Norway. The first question addressed in the thesis was how environmental conditions affect the demography and population variability of kittiwakes and guillemots. The non-breeding distribution of the kittiwakes has recently been documented using year-round light-based geolocators, and we investigated the relationship between environmental conditions in these non-breeding areas and the adult survival of kittiwakes breeding on Hornøya. We found for the kittiwakes that Thecosomata, a group of pteropods (also called sea butterflies), in the Grand Banks/Labrador Sea area in winter and the capelin Mallotus villosus stock in Barents Sea in the pre-breeding season together explained as much as 52 % of the yearly variation in adult survival rate. Further we found that the availability of 0-group cod Gadus morhua was a much more important factor affecting demography and determining the population dynamics of the common guillemot in the Barents Sea than previously considered. The second question was which demographic trait drives the population dynamics of the steeply declining kittiwake population on Hornøya. We showed, by using demographic matrix modeling and LTRE analyses, that both the variability in breeding success (and hence the recruitment to the population) and adult survival rate contributed to the steep decline in the kittiwake population on Hornøya. The strong reduction in breeding success (and hence a decline in recruitment to the population) had, however, the highest impact. The final question was whether populations can adapt to environmental changes through micro-evolutionary processes. This study found that adult survival of the two different genetic colour morphs (bridled and non-bridled morph) of the common guillemot responded differently to yearly variability in sea surface temperatures. Colour dimorphism may, in this case serve as a genetic marker in the guillemot population, and can potentially visualize the direction of selection and micro-evolutionary processes driven by climate. The studies in this thesis contribute to the understanding of the population dynamic of two declining seabird species which are both on the Norwegian Red List, and to the directions of future studies and conservation targets of both species.
Description:	Papers 1, 2 and 4 of this thesis are not available in Munin: 1. Reiertsen, T.K., Erikstad, K.E., Anker-Nilssen, T., Barrett, R.T., Boulinier, T., Frederiksen, M., González-Solís, J., Gremillet, D., Johns, D., Moe, B., Ponchon, A., Sandvik, H., Skern-Mauritzen, M. and Yoccoz, N.G.: 'Prey density in non-breeding areas affects adult survival of black-legged kittiwakes Rissa tridactyla breeding in the southern Barents Sea' (manuscript). 2. Reiertsen, T.K., Barrett, R.T. and Erikstad, K.E.: 'Kittiwakes on the cliff edge: a demographic analysis of a steeply declining arctic kittiwake population' (manuscript). 4. Reiertsen, T.K., Erikstad, K.., Barrett, R.obert T., Sandvik, H. and Yoccoz, N.: 'Climate fluctuations and differential survival of bridled and non-bridled Common Guillemots Uria aalge', Ecosphere (2013), vol. 3(6). Available at http://dx.doi.org/10.1890/ES12-00031R
URI:	http://hdl.handle.net/10037/5158

File(s) in this item: 2

paper_3.pdf (943.5Kb)

thesis.pdf (1.264Mb)

Species concepts and functional aspects of cold-water diatoms (Bacillariophyceae)

Degerlund, Maria (Doctoral thesis; Doktorgradsavhandling, 18-Oct-2011)

[+]

Abstract:	The choice of species concept when delineating phytoplankton species is decisive for our knowledge of species diversity and distribution, but will also affect our understanding of the functioning of marine ecosystems. This is particularly true for so-called cryptic species, which may show high degree of genetic and physiological heterogeneity although being morphologically similar. A precise species delimitation procedure appreciating the value of genotypic as well as phenotypic traits is therefore important. In this thesis, species concepts and functional aspects in abundant cold-water diatoms were investigated using biogeographic (species presence and abundance), taxonomic (morphological and molecular data), and functional (experimental physiological and metabolomics data) tools. A compilation of multiannual phytoplankton species abundance data gathered during the spring bloom period from north-east Atlantic and Arctic waters (68-80oN) revealed high similarities in associations of the most abundant species. Spring associations were dominated by the diatom Chaetoceros socialis and the prymnesiophyte Phaeocystis pouchetii. A corresponding investigation of the winter period in this area could not identify associations of actively growing, autotrophic phytoplankton species. Change in species composition and abundance in time could not be assessed due to lack of consistency and regularity in sampling. A high-resolution time series of phytoplankton distribution is therefore needed in this area. A case study of the so-called cosmopolitan diatom C. socialis was performed using strains from north-east Atlantic/Arctic and from Mediterranean waters. By applying a phylo-phenetic species concept the two geographical populations were found to be pseudo-cryptic. They were genetically distinct, but only slight morphological differences were observed, in this case in resting spore morphology. Furthermore, when cultivated at 2.5, 8 and 13oC, the two groups of strains were functionally different in terms of growth rates (doublings day-1), photosynthetic efficiency (maximum quantum yield), and metabolic profiles. Our results do not support the assumed cosmopolitan distribution of C. socialis and therefore the present taxonomy of this species will need revision. A taxonomic update of the pseudo-cryptic diatom formerly known as Skeletonema costatum indicated that the species present in northern Norwegian and Barents Sea waters is identical to S. marinoi. Due to reports of high genetic, metabolic, and physiological diversity within this species, a functional approach would be valuable for understanding the ecology of S. marinoi in this area. Integrated approaches combining taxonomic and functional variables are recommended for future taxonomic work on phytoplankton species. Similarly, phytoplankton ecologists are urged to acknowledge the high degree of hidden taxonomic and functional diversity present in several phytoplankton species. Functional diversity studies are suggested to be a useful spot for integration and eventual modelling phenotypic, genotypic and ecological species data. Ultimately, such an approach should be beneficial also at the ecosystem level.
Description:	The papers of this thesis are not available in Munin: 1. Degerlund M and Eilertsen HC: 'Main species characteristics of phytoplankton spring blooms in NE Atlantic and Arctic waters(68–80°N)', Estuaries and Coasts (2010) 33: 242-269. Available at http://dx.doi.org/10.1007/s12237-009-9167-7 2. Eilertsen HC and Degerlund M: 'Phytoplankton and light during the northern high-latitude winter', Journal of Plankton Research (2010) 32: 899-912. Available at http://dx.doi.org/10.1093/plankt/fbq017 3. Degerlund M, Huseby S, Zingone A, Sarno D and Landfald B: 'Functional diversity in cryptic species of Chaetoceros socialis Lauder (Bacillariophyceae)' (submitted paper to Journal of Plankton Research). 4. Huseby S, Degerlund M, Zingone A and Hansen, E: 'Metabolite fingerprinting and physiology of the cryptic diatom Chaetoceros socialis Lauder' (manuscript)
URI:	http://hdl.handle.net/10037/3679

File(s) in this item: 1

thesis.pdf (1.139Mb)

Browsing Doktorgradsavhandlinger (BFE-fak) by Title

DSpace/Manakin Repository

Browsing Doktorgradsavhandlinger (BFE-fak) by Title

Search Munin

Browse

All of Munin

This Collection

Help