Torbjørn Severinsen

• Stien, A; Loe, L.E.; Mysterud, A; Severinsen, T; Kohler, Jack & Langvatn, Rolf (2010). Icing events trigger range displacement in a high-arctic ungulate. Ecology. ISSN 0012-9658. 91(3), p. 915–920. doi: 10.1890/09-0056.1. Full text in Research Archive
• Loe, Leif Egil; Bonenfant, C; Mysterud, Atle; Severinsen, T.; Øritsland, N. A. & Langvatn, Rolf [Show all 11 contributors for this article] (2007). Activity pattern of arctic reindeer in a predator-free environment: no need to keep a daily rhythm. Oecologia. ISSN 0029-8549. 152, p. 617–624. doi: 10.1007/s00442-007-0681-7. Full text in Research Archive
• Chan, Kung-Sik; Mysterud, Atle; Øritsland, Nils Are; Severinsen, Torbjørn & Stenseth, Nils Christian (2005). Continuous and discrete extreme climatic events affecting the dynamics of a high arctic reindeer population. Oecologia. ISSN 0029-8549. 145, p. 556–563. Full text in Research Archive
• Kleivane, L.; Severinsen, Torbjørn; Lydersen, C.; Berg, V & Skaare, J.U. (2004). Total blubber burden of organochlorine pollutants in phocid seals; methods and suggested standardization. Science of the Total Environment. ISSN 0048-9697. 320(2-3), p. 109–119. Full text in Research Archive
• Lydersen, C.; Wolkers, H.; Severinsen, Torbjørn; Nordøy, E.S.; Kleivane, L. & Skaare, Janneche Utne (2002). Blood is a poor substrate for monitoring pollution burdens in phocid seals. Science of the Total Environment. ISSN 0048-9697. 292(3), p. 193–203. Full text in Research Archive Show summary

  The present study investigated how concentrations of different organochlorines (OCs) vary with nutritional condition in adult harp seal (Phoca groenlandica) females in a captive fasting experiment and in the wild. During the first part of this study seals in good condition (N=5) were fasted for a period of 28 days and blood and blubber samples were collected at days 1, 14 and 28. Blubber OC concentrations remained unchanged throughout the experimental period, and were consistently significantly higher than concentrations in the blood. In contrast to blubber OC levels, blood OC levels showed a significant time-dependant increase. During the fasting experiment the seals lost an average of 24 kg of body mass, which is less than half the natural annual variation in this species in the wild. The second part of this study compared OC concentrations in blood and blubber from seals collected at prime condition before the breeding season (N=10) with animals collected during molt when condition is poor (N=7). The average mass difference between the two groups was more than 40 kg. Blood levels of most OCs were significantly higher in the thin seals compared with the levels found in the fat seals. These differences in blood OC concentrations were much greater than what was found during the fasting experiment. For example PCB levels in the blood during the fasting experiment increased by ~83%, while the corresponding increase in blood levels of PCB between the two other samples was 720% (from 201 to 1447 ng/g lipid). Blubber levels of OCs from the animals in the wild were significantly higher in the thin seals compared with the fat animals. In addition, the blubber levels of OCs were significantly higher than blood levels of OCs only for the fat seals. This study demonstrates the extreme variability present in the concentrations of OCs in blood of seals in response to change in condition. Since the natural variation in condition is extreme during phocid seals' annual cycles, we recommend that blood should not be used in studies of OCs where the aim of the study is to monitor OC levels for comparative purposes or time-trend analysis. Keywords: Monitoring; Organochlorines; Blood; Blubber; Sampling methods; Marine mammals; Harp seals; Phoca groenlandica

• Foreid, S; Severinsen, Torbjørn; Rundberget, T; Wiig, Øystein & Skaare, Janneche Utne (2000). Determination of toxaphenes in fish and marine mammals. Chemosphere. ISSN 0045-6535. 41(4), p. 521–528. Full text in Research Archive
• Muir, D.; Riget, F.; Cleemann, M.; Skaare, Janneche Utne; Kleivane, L. & Nakata, H. [Show all 9 contributors for this article] (2000). Circumpolar trends of PCBs and organochlorine pesticides in the arctic marine environment inferred from levels in ringed seals. Environmental Science and Technology. ISSN 0013-936X. 34(12), p. 2431–2438. Full text in Research Archive
• Severinsen, Torbjørn; Skaare, Janneche Utne & Lydersen, C. (2000). Spatial distribution of persistent organochlorines in ringed seal (Phoca hispida) blubber. Marine Environmental Research. ISSN 0141-1136. 49(3), p. 291–302. Full text in Research Archive Show summary

  Blubber samples, taken through the entire blubber column, were collected from three different anatomical locations on ringed seals (Phoca hispida). The outer and inner layers of these samples were analysed for concentrations of PCBs (sum of the analysed congeners, polychlorinated biphenyls) and p,p'-DDE (4,4'-dichlorodiphenyldichloroethylene). No significant differences were found in blubber thickness or in per cent extractable lipid when comparing age- and sex-groups, or in extractable lipid content when comparing anatomical locations of the blubber or blubber depth. No significant differences were found between the three different anatomical locations with respect to the concentrations of PCBs or p,p'-DDE. However, the concentrations of both PCB and p,p'-DDE were significantly higher in the outer blubber layer compared to the inner. Higher levels of both PCB and p,p'-DDE were found in males compared to females and juveniles in both the inner and outer parts of the blubber column. The most commonly used blubber sampling devices are biopsy tools that penetrate only the outer layer of the blubber. Analyses of such samples will not reflect the real body burden of organochlorines. Standard methods for sampling blubber of marine mammals should be developed so that comparative studies and longitudinal monitoring programs of pollutants in marine mammals can be conducted in a meaningful way. Author Keywords: Persistent organochlorines; Ringed seal; Phoca hispida; Blubber; Arctic; DDE; Marine mammals; monitoring; PLBs

• Kleivane, L.; Severinsen, Torbjørn & Skaare, Janneche Utne (2000). Biological transport and mammal to mammal transfer of organochlorines in Arctic fauna. Marine Environmental Research. ISSN 0141-1136. 49(4), p. 343–357. Full text in Research Archive Show summary

  Ringed seal (Phoca hispida) is assumed to be the most important and common prey of polar bears (Ursus maritimus). However, during a scientific survey in the ice area of the northern Barents Sea east of Svalbard in June 1995, an unexpectedly high number of polar bears were observed feeding on harp seal (Phoca groenlandica) carcasses. Samples of both harp and ringed seals were obtained and organochlorine (OC) occurrence and pattern in these two potential polar bear prey species were determined. Significantly higher OC concentrations were found in harp seals, as compared to the ringed seals. All animals in the northern harp seal group were lean specimens in late moult. The industrial chemicals, polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB), and the OC pesticides bis-2,2,(chlorophenyl)-1,1,1-trichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and chlordanes (CHLORs) were analysed in blubber. The concentrations of PCB (sum of concentrations of 16 PCB congeners) and DDT (sum of concentrations of p,p'-DDT and p,p'-DDE) in the northern harp seal group ranged from 2093 to 20,382 and 1460 to 10,381 ng g-1 lipid weight, with mean concentrations of 11,133 and 6847 ng g-1 lipid weight, respectively. The mean concentrations of the CHLORs, oxychlordane and trans-nonachlor, were 1311 and 3743 ng g-1 lipid weight, respectively, while the mean concentrations of HCB and HCH isomers (-, - and -HCH) were all <500 ng g-1 lipid weight. No significant difference was found in the mean total blubber mass between the two seal species when collected in June. This indicates that polar bears preying on harp seals instead of ringed seals at this time of the year could accumulate significantly higher PCB concentrations. We suggest that polar bears feeding along the ice-edge east of Svalbard in May and June preferentially prey on harp seals instead of ringed seals, and that this may partly explain the variation in PCB concentrations among polar bears from the Norwegian Arctic. An hypothesis is that the harp seal may function as a transport vector of OCs into the high Arctic environment. Author Keywords: Polar bear; Harp seal; Ringed seal; PCBS; Organochlorines

• Severinsen, Torbjørn & Munch, Ingunn C. (1999). Body core temperature during food restriction in rats. Acta Physiologica Scandinavica. ISSN 0001-6772. 165(3), p. 299–305. Full text in Research Archive Show summary

  Deep body temperature and locomotor activity of rats fed a reduced food amount (n = 9) and of starved rats (n = 9), were measured by implanted transmitters. Both groups were then refed ad libitum. The reduction in body temperature was significant for both groups, but larger in the starved rats than in the food restricted rats. There was a displacement of the circadian temperature rhythm in the starved rats. There were no significant differences in locomotor activity between groups until the start of refeeding. Rats fed reduced food amounts rapidly increased their activity, while the starved group retained a low activity for several days. Thermal conductance was reduced by 30% in both groups. This reduction in thermal conductance may explain how starving and semistarving rats are able to maintain core temperatures close to normal, even if resting metabolic rates are drastically reduced. The measured reduction in body core temperature signifies a change in the thermoregulatory `set-point' during starvation.

• Severinsen, Torbjørn & Øritsland, Nils Are (1993). Resting metabolism during the stable phase of fever in rats. Journal of Thermal Biology. ISSN 0306-4565. 18(1), p. 7–11. Full text in Research Archive
• Severinsen, Torbjørn & Øritsland, Nils Are (1991). Endotoxin induced prolonged fever in rats. Journal of Thermal Biology. ISSN 0306-4565. 16(3), p. 167–171. Full text in Research Archive

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• Bengtson, S. -A.; Mehlum, F. & Severinsen, T. (1999). Svalbardtundraens økologi. Norsk Polarinstitutt Meddelelser. 1 p. Full text in Research Archive

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• Kohler, Jack; Aanes, Ronny; Hansen, Brage; Loe, Leif Egil; Severinsen, Torbjørn & Stien, Audun (2008). Parsimonious snow model explains reindeer population dynamics and ranging behavior. Full text in Research Archive
• Bengtson, Sven-Axel; Mehlum, Fridtjof & Severinsen, Torbjørn (1999). Terrestrisk økologisk forskningsprogram på Svalbard. Svalbardtundraens Økologi. Norsk Polarinstitutt Meddelelser, Tromsø. ISSN 9788276661392. Full text in Research Archive
• Bengtson, Sven-Axel; Mehlum, Fridtjof & Severinsen, Torbjørn (1999). Terrestrisk økologisk forskningsprogram på Svalbard. Svalbardtundraens økologi. Norsk Polarinstitutt Meddelelser, Tromsø. ISSN 9788276661392. Full text in Research Archive
• Bengtson, Sven-Axel; Mehlum, Fridtjof & Severinsen, Torbjørn (1999). Terrestrisk økologisk forskning på Svalbard. Svalbardtundraens økologi. Norsk Polarinstitutt, Medd. nr. 150, Tromsø. Full text in Research Archive

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