Jorunn Larsen

• Eide, Ingvar; Berg, Toril; Thorvaldsen, Bodil; Christensen, Guttorm N.; Savinov, Vladimir & Larsen, Jorunn (2011). Polycyclic Aromatic Hydrocarbons in Dated Freshwater and Marine Sediments Along the Norwegian Coast. Water, Air and Soil Pollution. ISSN 0049-6979. 218(1-4), p. 387–398. doi: 10.1007/s11270-010-0653-0.
• Paasche, Øyvind & Larsen, Jorunn (2010). Changes in lake stratification and oxygen distribution inferred from two contrasting records of magnetotactic bacteria and diatoms. Journal of Geophysical Research (JGR): Biogeosciences. ISSN 2169-8953. 115. doi: 10.1029/2009JG001081. Show summary

  Magnetotactic bacteria (MTB) and diatoms produce hard parts on seasonal timescales that continuously becomes embedded in various soft sediment archives. Consequently, they can, and are, frequently used to reconstruct past environmental conditions in oceans, fjords, and freshwater basins. In this study, we observe how these two cosmopolitan creatures can be used to track vertical shifts in the distribution of oxygen in a small mountain lake situated in western Norway. Several short and long sediment cores have been retrieved from the lake, allowing for a detailed reconstruction that spans the last 2500 years. During periods of enhanced runoff from the catchment the Oxic-Anoxic Transition Zone (OATZ) is lowered down to the lake-sediment interface, due to increased convection. We posit that this condition reduces the concentration of microaerophilic magnetite-producing MTB, an interpretation partly supported by rock magnetic analyzes. Preservation of diatom frustules is, however, improved whenever this oxygen-rich scenario prevails. Similarly, when runoff is low, and the OATZ is lifted above the lake-sediment interface, MTB concentration seems to increase, whereas dissolution of diatoms is more common. This consistent antiphase relationship between MTB concentration and diatom preservation, occurring on a multidecadal timescale during lowest reconstructed lake-water pH in the lake's history, suggest a coupled response to subtle changes in external environmental variables that affect catchment and lake hydrology.

• Velle, Gaute; Bjune, Anne Elisabeth; Larsen, Jorunn & Birks, Harry John Betteley (2010). Holocene climate and environmental history of Brurskardstjørni, a lake in the catchment of Øvre Heimdalsvatn, south-central Norway. Hydrobiologia. ISSN 0018-8158. 642(1), p. 13–34. doi: 10.1007/s10750-010-0153-7.
• Dahlø Jarbu, Aina; Larsen, Jorunn & Talbot, Michael (2009). Jarbu A.D., LarsenCombining carbonate δ13C and δ18O and diatom data to interpret the Holocene palaeoenvironment of Lake Ulltvedttjern, southern Norway. In Jarbu A.D (2009). Stable isotopic studies of carbonates and organic matter from selected Norwegian lakes. Stable isotopic studies of carbonates and organic matter from selected Norwegian lakes : implications for palaeoenvironmental reconstructions. Universitetet i Bergen. ISSN 978-82-308-0910-5. Show summary

  PhD-avhandling

• Larsen, Jorunn; Paasche, Øyvind; Andersen, Dag Olav; Bjune, Anne Elisabeth & De la Riva Caballero, Argutitxu (2006). Sedimentary diatom assemblages in a small alpine west Norwegian lake: evidence for metal release and precipitation? In Withowski, Andrzej (Eds.), Proceedings of the 18th International Diatom Symposium - Miedzyzdroje, Poland, 2nd-7th September, 2004. Andrzej Withowski. ISSN 0-948737-75-1. p. 221–234.
• Paus, Aage; Velle, Gaute; Larsen, Jorunn; Nesje, Atle & Lie, Øyvind (2006). Lateglacial nunataks in central Scandinavia: Biostratigraphical evidence for ice thickness from Lake Flafattjonn, Tynset, Norway. Quaternary Science Reviews. ISSN 0277-3791. 25(11-12), p. 1228–1246.
• Larsen, Jorunn; Jones, V.J. & Eide, Wenche (2006). Climatically driven pH changes in two Norwegian alpine lakes. Journal of Paleolimnology. ISSN 0921-2728. 36(2), p. 175–187. doi: 10.1007/s10933-006-0013-7.
• Larsen, Jorunn; Bjune, Anne Elisabeth & De La Riva, Arguitxu Caballero (2006). Holocene environmental and climate history of Trettetjørn, a low-alpine lake in western Norway, based on subfossil pollen, diatoms, oribatid mites, and plant macrofossils. Arctic, Antarctic and Alpine research. ISSN 1523-0430. 38(4), p. 571–583.
• Velle, Gaute; Larsen, Jorunn; Eide, Wenche; Peglar, Sylvia Margaret & Birks, Harry John Betteley (2005). Holocene environmental history and climate of Råtåsjøen, a low-alpine lake in south-central Norway. Journal of Paleolimnology. ISSN 0921-2728. 33, p. 129–153. Show summary

  The Holocene environmental history and climate are reconstructed for Råtåsjøen, a low-alpine lake in south-central Norway. The reconstructions are based on chironomids, diatoms, pollen, plant macrofossils, and sediment characteristics. From plant macrofossil evidence, birch trees (Betula pubescens) immigrated ca. 10,000 cal BP. The chironomid-inferred mean July air temperature was high, but may be unreliable during the early stages of the lakes history due to the high abundance of Chironomus anthracinus type, a taxon that may include several species. From ca. 9000 cal BP the inferred mean July temperature was lower (ca. 9 °C). Temperatures increased towards 8000 cal BP and pine (Pinus sylvestris) reached its upper limit near the lake. July temperature may have become a significant factor controlling long-term pH in the lake, starting shortly after 8000 cal BP. High pH values were associated with periods of warm summers and lower pH values occurred during periods of colder summers. Alkalinity processes within the lake and/or the catchment are possible factors controlling this relationship. A temperature decline at ca. 5400 cal BP separated two 10.6 °C temperature maxima around 6400 and 4500 cal BP. The 1.5 °C decline in July air temperatures from ca. 4400 cal BP was paralleled by a decrease of pH from 7.2 to 6.8. Following the temperature drop, first pine and then birch trees declined and disappeared from the catchment and organic accumulation in the lake increased. The increased organic accumulation rate had a positive effect on diatom production. At ca. 2700 cal BP the temperature reached a minimum (ca. 9.2 °C) and correspondingly a second pH minimum was reached. Temperature decreased again slightly at ca. 400 cal BP during the Little Ice Age, before increasing by about 0.5 °C towards the present. Percentage organic carbon as estimated by loss-on-ignition appears to be better correlated with chironomid-inferred July temperatures than organic accumulation rates, at least for the last 9000 years. Accumulation rates of organic sediments are more coupled with catchment-related processes, such as erosion and major changes in vegetation, than is percentage organic carbon.

• Larsen, Jorunn (2003). Size distributions and concentrations of spheroidal carbonaceous fly-ash particles (SCPs) in lake sediments as an aid to detecting locally deposited atmospheric pollution. Water, Air and Soil Pollution. ISSN 0049-6979. 149, p. 163–175.
• Larsen, Jorunn (2000). Recent changes in diatom-inferred pH, heavy metals, and spheroidal carbonaceous particles in lake sediments near an oil refinery at Mongstad, western Norway. Journal of Paleolimnology. ISSN 0921-2728. 23(4), p. 343–363. Show summary

  Sediments from two naturally acid lakes have been used to inevstigate whether there is any local impact of atmospheric pollution from an oil refinery at Mongstad in western Norway. the refinery started started production in 1975 and expanded in 1987. One lake was selected as a reference site as it only receives long-transported air pollution, whereas a second lake was selected as it was expected to receive both long-range transported and local air pollution from the refinery. Heavy metal (Pb, Ni, and Zn) and spheroidal carbonaceous particles (SCP) concentrations and accumulation rates have been estimated and lake-water pH has been reconstructed by weighted averaging partial least squares regression and calibration from the fossil diatom assemblages. Heavy metals that are in the size range for which atmospheric residence time is greatest do not show any enhanced levels in the sediments after 1975 that could be associated with local impacts from the refinery. SCPs in the sediments that are in the size range thought to be effectively removed by dry deposition, and thus have a more local deposition pattern, show an increase after 1975 and an additional large increase after 1987 that can be explained by impacts from the local oil refinery. After 1975 the SCP diameter distribution changed from being dominated by SCPs with a small diameter to SCPs with larger diameters.The sulphur dioxid emission from the oil refinery seems to have had no significant effect on lake pH. The reconstructed lake pH history is complex, possibly related to land-use changes and long-range transported air pollution.

• Larsen, Jorunn; Boyle, John F. & Birks, Harry John Betteley (1996). Variation in the geochemistry of recent lake sediments along a west-east pollution gradient in the Bergen area, Norway. Water, Air and Soil Pollution. ISSN 0049-6979. 0088(1-2), p. 47–81. Show summary

  Twenty nine lakes were sampled on a 62 km long west-east transect nea r Bergen, Norway from Sotra in the west to Norheimsund in the east. T op bottom samples of 29 sediment cores, 20-40 cm long, were collected and 17 chemical elements were measured. Sphaeroidal carbonaceous par ticles from fossil fuel origin were counted in the surface sediments. The study was designed to answer two questions: (1) Does lake-sedime nt composition reflect variations in local atmospheric pollution? (2) What factors explain the observed variation in concentration of chem ical elements along this transect? Ca, Cr, Mg, and Ni concentrations along the transect appear to result from differences in the content o f these elements in bedrock. Hg, Pb, and Zn concentrations in the top sediments are dominated by input from anthropogenic sources. Variati on of Cd, Fe, and Zn in the top sediments seems to be dependent on va riation in lake-water pH. Hg and Zn from anthropogenic sources probab ly result from long-transported pollution. Pb and carbonaceous partic les from anthropogenic sources possibly have a local origin.

• Larsen, Jorunn; Birks, Harry John Betteley; Raddum, Gunnar & Fjellheim, Arne (1996). Quantitative relationships of invertebrates to pH in Norwegian river systems. Hydrobiologia. ISSN 0018-8158. 328(1), p. 57–74. Show summary

  The invertebrate fauna has been surveyed for twenty one unlimed gener ally acidic river systems in Norway. The data consist of 180 samples and 127 invertebrate taxa and associated water chemistry data (pH, ca lcium, acid neutralizing capacity, total aluminium, and conductivity) . Multivariate numerical methods are used to quantify the relationshi ps between aquatic invertebrates and water chemistry. Detrended canon ical correspondence analysis (DCCA) shows one dominant axis of variat ion with high correlations for pH and aluminium. DCCA axis 2 is signi ficantly correlated with calcium. The predictive abilities of inverte brates to pH are explored by means of weighted averaging (WA) regress ion and calibration and weighted averaging partial-least-squares regr ession (WA-PLS). The performance of the methods is reported in terms of the root mean square error of prediction (RMSEP) of (observed pH-i nferred pH). Bootstrapping and leave-one-out jackknifing are used as cross-validation procedures. The predictive abilities of invertebrate s are good (RMSEP( boot) for WA = 0.309 pH units). Comparison of the invertebrates with diatom studies shows that invertebrates are as goo d predictors of modern pH as diatoms are. RMSEP(jack) shows that WA-P LS improves the predictive abilities . Indicator taxa for pH are foun d by Gaussian regression. Anisoptera, Agrypnia obsoleta, Leptophlebia marginata, Sialis lutaria, and Zygoptera have significant sigmoidal curves where abundances increase with decreasing pH. Cyrnus flavidus shows a significant unimodal response and has an estimated optimum in the acid part of the gradient. These results suggest that a combined use of Gaussian regression and direct gradient analysis is needed to get a full overview of potential indicator taxa.

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• Larsen, Jorunn (2023). Vil at sjelden skog skal stanse byggingen av 270 boliger. Byggeindustrien bygg.no.
• Larsen, Jorunn & Fiskvatn, Kari (2023). Her skal det bygges boliger og kontorbygg. Det bekymrer Kari og Jorunn. Fædrelandsvennen. ISSN 0805-3790.
• Larsen, Jorunn; Korslund, Lars & Fiskvatn, Kari (2023). Fortellingen om enda en skog som forsvinner. Fædrelandsvennen. ISSN 0805-3790.
• Larsen, Jorunn; Nygaard, Malene; Halvorsen, Kirsti Vindal; Borg-Stoveland, Stian; Sørdalen, Tonje Knutsen & Fiskvatn, Kari [Show all 7 contributors for this article] (2023). Når natur forsvinner: Bærekraftig utvikling eller bare kraftig utvikling i Kristiansand kommune? Fædrelandsvennen. ISSN 0805-3790.
• Lien, Anne; Nygård, Malene Østreng; Laugen, Ane Timenes; Lie, Asbjørn; Slettan, Audun & Johansen, Beate Strøm [Show all 33 contributors for this article] (2023). Utbygging vil ødelegge for biologisk mangfold på campus Gimlemoen. NB! 34 forfattere totalt. Fædrelandsvennen. ISSN 0805-3790. p. 19–19.
• Svingen-Austestad, Anna; Lipka Falck, Åsa; Enberg, Cecilia; Lien, Anne; Larsen, Jorunn & Fiskvatn, Kari (2019). MOBILE DIORAMA TOUR 2019.
• Lipka Falck, Åsa; Enberg, Cecilia; Svingen-Austestad, Anna; Lien, Anne; Fiskvatn, Kari & Larsen, Jorunn (2019). LAB (Skala 1:1) – Hva er observasjon? .
• Svingen-Austestad, Anna; Lien, Anne; Larsen, Jorunn; Fiskvatn, Kari; Lipka Falck, Åsa & Enberg, Cecilia [Show all 7 contributors for this article] (2019). LAB (skala 1:1) – Hva er observasjon? .
• Larsen, Jorunn & Hjelle, Kari Loe (2013). Moderne gårdsdrift betyr gjødsling av åker og eng, dyrking av monokulturer, ugrasbekjemping og maskinell høsting. Hjelle K. og Larsen L. i Nord, S., Solhøy, T. & Helland-Hansen, W. Ei halvøy i Hardanger. Natur- og kulturforteljingar frå Neshalvøya. Nord 4, Kvinnherad 2013. In Nord, Svein (Eds.), Ei halvøy i Hardanger, Natur- og kulturforteljingar frå Neshalvøya. Nord 4. ISSN 978-82-7326-104-5.
• Larsen, Jorunn (2008). Diatoméer - naturens fremste teknologer og miljøindikatorer. . Naturen. ISSN 0028-0887.
• Larsen, Jorunn (2008). Elever blant krystaller av mineraler. . Årbok (Agder naturmuseum og botaniske hage). ISSN 0333-3124.
• Larsen, Jorunn (2007). Før snakket vi om været – nå gjør vi noe med det. . Fædrelandsvennen. ISSN 0805-3790.
• Larsen, Jorunn (2007). Før snakket vi om været – nå gjør vi noe med det. . Fædrelandsvennen. ISSN 0805-3790.
• Larsen, Jorunn & Fiskvatn, Kari (2006). Naturforsker – prosjektet. Årbok (Agder naturmuseum og botaniske hage). ISSN 0333-3124.
• Larsen, Jorunn; Paasche, Øyvind; Andersen, Dag Olav; Bjune, Anne E. & Caballero, Arguitxu (2004). Sedimentary diatom assemblages in a small alpine west Norwegian lake: evidence for metal release and precipitation.
• Bjune, Anne Elisabeth & Larsen, Jorunn (2003). Arkivet i innsjøen. AKA. ISSN 1503-3368. 9, p. 13–14.
• Larsen, Jorunn (2003). The contribution of freshwater diatom studies to climate research in some Norwegian alpine lakes.
• Larsen, Jorunn (2003). Diatom responses to climate or other environmental changes during the last centuries in the alpine region of southern Norway.
• Larsen, Jorunn (2003). Detecting local-deposited atmospheric pollution using size and concentrations of spheroidal carbonaceous fly-ash particles (SCPs).
• Larsen, Jorunn (2002). Diatom changes through Holocene in alpine lakes in Southern Norway.
• Holmstad, Per Ragnvald; Østenstad, Petter; Larsen, Jorunn & Fjellanger, Inger Johanne (2002). Videre studier ved Universitetet i Bergen ?
• Larsen, Jorunn (2002). Holocene productivity changes in a present oligotrophic alpine lake.
• Larsen, Jorunn (2002). Innsjøer - arkiv for forsurings-og forurensningshistorie.
• Larsen, Jorunn (2000). Innsjøbunnen avslører tidligere pH. pH-status : forum for sur nedbør og kalking. ISSN 0808-4882. 6(2). Show summary

  To estimate average pH in a lake can be time consuming and expensive. In most lakes it is impossible to find the lake-water pH that existed before the Industrial Revolution as pH measurements have not been taken. Reconstruction of average lake-water pH can be done by taking a sediment core from the lake bottom and by simple laboratory techniques analyse the sediments for a group of plant alga called diatoms.

• Lindstrøm, Eli-Anne; Brettum, Pål; Halvorsen, Godtfred Anker; Halvorsen, Gunnar; Johansen, Stein W. & Larsen, Jorunn [Show all 7 contributors for this article] (2005). Effekter av kalking på biologisk mangfold. Undersøkelser i Tovdalsvassdraget 1999-2001. Direktoratet for naturforvaltning. ISSN 82-7072-597-8. 2005(5).
• Larsen, Jorunn (2004). Prøvetaking av sediment fra Svartatjønn ved Mongstad og Kattatjønn på Sotra. Natur i Sør, Agder naturmuseums rapportserie.
• Johansen, S.W.; Lindstrøm, Eli-Anne; Larsen, Jorunn & Romstad, R. (2003). Årsrapporter 2002 - biologiske forhold. Stakraft SF. ISSN 82-554-0607-7.
• Larsen, Jorunn (2000). The detection of environmental change in lakes and rivers of western Norway using biological and chemical data. Universitetet i Bergen. ISSN 82-7460-003-7.

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