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  • 201. Alfimov, V
    et al.
    Aldahan, A
    Possnert, G
    Winsor, P
    Anthropogenic iodine-129 in seawater along a transect from the Norwegian coastal current to the North Pole2004In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 49, no 11-12, p. 1097-1104Article in journal (Refereed)
    Abstract [en]

    Variation in the concentrations of iodine-129 (I-129, T-1/2 = 15.7 Myr), a low-level radioactive component of nuclear fuel waste, is documented in surface waters and depth profiles collected during 2001 along a transect from the Norwegian Coastal Current to the North Pole. The surface waters near the Norwegian coast are found to have 20 times higher I-129 concentration than the surface waters of the Arctic Ocean. The depth profiles of I-129 taken in the Arctic Ocean reveal a sharp decline in the concentration to a depth of about 300-500m followed by a weaker gradient extending down to the bottom. A twofold increase in the I-129 concentration is observed in the upper 1000m since 1996. Based on known estimates of marine transient time from the release sources (the nuclear reprocessing facilities at La Hague, France, and Sellafield, UK), a doubling in the I-129 inventory of the top 1000m of the Arctic Ocean is expected to occur between the years 2001 and 2006. As I-129 of polar mixed layer and Atlantic layer of the Arctic Ocean is ventilated by the East Greenland Current into the Nordic Seas and North Atlantic Ocean, further dispersal and increase of the isotope concentration in these regions will be encountered in the near future. (C) 2004 Elsevier Ltd. All rights reserved.

  • 202. Alfimov, V
    et al.
    Possnert, G
    Aldahan, A
    Anthropogenic iodine-129 in the Arctic Ocean and Nordic Seas: Numerical modeling and prognoses2006In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 52, no 4, p. 380-385Article in journal (Refereed)
    Abstract [en]

    A numerical model simulation has been used to predict extent and variability in the anthropogenic I-129 pollution in the Arctic Ocean and Nordic Seas region over a period of 100 years. The source function of I-129 used in the model is represented by a well-known history of discharges from the Sellafield and La Hague nuclear reprocessing facilities. The simulations suggest a fast transport and large inventory of the anthropogenic I-129 in the Arctic and North Atlantic Oceans. In a fictitious case of abrupt stop of the discharges, a rapid decline of inventories is observed in all compartments except the North Atlantic Ocean, the deep Nordic Seas and the deep Arctic Ocean. Within 15 years after the stop of releases, the model prediction indicates that near-equilibrium conditions are reached in all compartments. (c) 2005 Elsevier Ltd. All rights reserved.

  • 203. Alfimov, Vasily
    et al.
    Aldahan, Ala
    Possnert, Goran
    Water masses and I-129 distribution in the Nordic Seas2013In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 294, p. 542-546Article in journal (Refereed)
    Abstract [en]

    The application of the radioactive isotope iodine-129 as a tracer of water circulation in the oceans has provided interesting information with respect to sources and mixing of different water masses. We here present results of I-129 distribution in water profiles located in the Nordic Seas and use the isotope to fingerprint water masses in the region. The samples were collected by the US research vessel Knorr in May-June 2002. I-129 signatures along the Norwegian Sea reflect a mixing of I-129-rich surface water along the Scandinavian continental slope and I-129-poor North Atlantic surface water. These two water masses become less segregated along the Fram Strait where apparent I-129 enrichment penetrates the return Arctic flow into the East Greenland Current. The I-129 data further suggest existence of a water mass that is not entirely labeled with respect to origin at the Denmark Strait bottom water. This water parcel probably originates from the Iceland Sea. I-129 data also shed light on the major deep water outflow from the Nordic Seas located at the Faeroe Bank Channel. (C) 2012 Elsevier B.V. All rights reserved.

  • 204.
    Algesten, Grete
    Umeå universitet, Ekologi och geovetenskap.
    Regulation of carbon dioxide emission from Swedish boreal lakes and the Gulf of Bothnia2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The global carbon cycle is subject to intense research, where sources and sinks for greenhouse gases, carbon dioxide in particular, are estimated for various systems and biomes. Lakes have previously been neglected in carbon balance estimations, but have recently been recognized to be significant net sources of CO2.

    This thesis estimates emission of carbon dioxide (CO2) from boreal lakes and factors regulating the CO2 saturation from field measurements of CO2 concentration along with a number of chemical, biological and physical parameters. Concentration of dissolved organic carbon (DOC) was found to be the most important factor for CO2 saturation in lake water, whereas climatic parameters such as precipitation, temperature and global radiation were less influential. All lakes were supersaturated with and, thus, sources of CO2. Sediment incubation experiments indicated that in-lake mineralization processes during summer stratification mainly occurred in the pelagial. Approximately 10% of the CO2 emitted from the lake surface was produced in epilimnetic sediments.

    The mineralization of DOC and emission of CO2 from freshwaters was calculated on a catchment basis for almost 80,000 lakes and 21 major catchments in Sweden, together with rates of sedimentation in lakes and export of organic carbon to the sea. The total export of terrestrial organic carbon to freshwaters could thereby be estimated and consequently also the importance of lakes for the withdrawal of organic carbon export from terrestrial sources to the sea. Lakes removed 30-80% of imported terrestrial organic carbon, and mineralization and CO2 emission were much more important than sedimentation of carbon. The carbon loss was closely related to water retention time, where catchments with short residence times (<1 year) had low carbon retentions, whereas in catchments with long residence times (>3 years) a majority of the imported TOC was removed in the lake systems.

    The Gulf of Bothnia was also studied in this thesis and found to be a net heterotrophic system, emitting large amounts of CO2 to the atmosphere on an annual basis. The rate of CO2 emission was depending on the balance between primary production and bacterial respiration, and the system was oscillating between being a source and a sink of CO2.

  • 205.
    Algesten, Grete
    et al.
    Umeå universitet, Ekologi och geovetenskap.
    Sobek, Sebastian
    Bergström, Ann-Kristin
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Jonsson, Anders
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Tranvik, Lars J
    Jansson, Mats
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Contribution of sediment respiration to summer CO2 emission from boreal and subarctic lakes2005In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 50, no 4, p. 529-535Article in journal (Refereed)
    Abstract [en]

    We measured sediment production of carbon dioxide (CO(2)) and methane (CH(4)) and the net flux of CO(2) across the surfaces of 15 boreal and subarctic lakes of different humic contents. Sediment respiration measurements were made in situ under ambient light conditions. The flux of CO(2) between sediment and water varied between an uptake of 53 and an efflux of 182 mg C m(-2) day(-1) from the sediments. The mean respiration rate for sediments in contact with the upper mixed layer (SedR) was positively correlated to dissolved organic carbon (DOC) concentration in the water (r(2) = 0.61). The net flux of CO(2) across the lake surface [net ecosystem exchange (NEE)] was also closely correlated to DOC concentration in the upper mixed layer (r(2) = 0.73). The respiration in the water column was generally 10-fold higher per unit lake area compared to sediment respiration. Lakes with DOC concentrations <5.6 mg L(-1) had net consumption of CO(2) in the sediments, which we ascribe to benthic primary production. Only lakes with very low DOC concentrations were net autotrophic (<2.6 mg L(-1)) due to the dominance of dissolved allochthonous organic carbon in the water as an energy source for aquatic organisms. In addition to previous findings of allochthonous organic matter as an important driver of heterotrophic metabolism in the water column of lakes, this study suggests that sediment metabolism is also highly dependent on allochthonous carbon sources.

  • 206. Al-Handal, Adil Y
    et al.
    Riaux-Gobin, C.
    Romero, O.
    Wulff, Angela
    Two new marine species of the diatom genus Cocconeis Ehrenberg: C. melchioroides sp. nov. and C. dallmannii sp. nov., from King George Island, Antarctica2008Chapter in book (Other academic)
  • 207.
    Al-Handal, Adil Y.
    et al.
    Univ Gothenburg, Dept Marine Ecol, SE-40530 Gothenburg, Sweden..
    Wulff, Angela
    Univ Gothenburg, Dept Marine Ecol, SE-40530 Gothenburg, Sweden..
    Marine benthic diatoms from Potter Cove, King George Island, Antarctica2008In: Botanica Marina, ISSN 0006-8055, E-ISSN 1437-4323, Vol. 51, no 1, p. 51-68Article in journal (Refereed)
    Abstract [en]

    Antarctic benthic marine diatoms from the Potter Cove region, King George Island were studied in samples collected during the austral summer 2003. A floristic list was made to add information on the Antarctic benthic diatom distribution. A total of 84 species was identified from four localities in Potter Cove, the majority of which are of cosmopolitan distribution. The most common taxa encountered were Cocconeis spp., Gyrosigma fasciola, Navicula cf. cancellata, N. cf. perminuta, Petroneis plagiostoma and Pleurosigma obscurum. Both G. fasciola and P. obscurum are recorded for the first time from Antarctica with such common occurrence. The overall diatom population in Potter Cove appeared rather different from other diatom populations observed in Antarctic marine habitats.

  • 208. Al-Handal, Adil Y
    et al.
    Wulff, Angela
    Marine epiphytic diatoms of the shallow littoral zone in Potter Cove, King George Island, Antarctica2008Chapter in book (Other academic)
  • 209.
    Al-Handal, Adil Yousif
    et al.
    Univ Gothenburg, Dept Marine Ecol, SE-40530 Gothenburg, Sweden..
    Riaux-Gobin, Catherine
    Univ Paris 06, CNRS, UMR7621, Lab Oceanog Biol, FR-66650 Banyuls Sur Mer, France..
    Wulff, Angela
    Univ Gothenburg, Dept Marine Ecol, SE-40530 Gothenburg, Sweden..
    COCCONEIS POTTERCOVEI SP NOV AND COCCONEIS PINNATA VAR. MATSII VAR. NOV., TWO NEW MARINE DIATOM TAXA FROM KING GEORGE ISLAND, ANTARCTICA2010In: Diatom Research, ISSN 0269-249X, E-ISSN 2159-8347, Vol. 25, no 1, p. 1-11Article in journal (Refereed)
    Abstract [en]

    Details of two new small marine taxa of the genus Cocconeis Ehrenberg are described; C. pottercovei sp. nov. and C. pinnata var. matsii var. nov., which were observed as epipelic and epiphytic in Potter Cove, King George Island, Antarctica. Descriptions are based on both light and scanning electron microscope observations. C. pottercovei belongs to the group of Cocconeis taxa that bear very short and marginal striae on the rapheless valve while C. pinnata var. matsii belongs to the C. costata Gregory complex. They are mainly differentiated from the other similar taxa by stria number, stria arrangement and structure on both raphe and rapheless valves. A comparison with closely resembling taxa is given.

  • 210. Ali, Arshad
    et al.
    Molau, Ulf
    Bai, Yang
    Jägerbrand, Annika K.
    Alatalo, Juha M.
    Diversity-productivity dependent resistance of an alpine plant community to different climate change scenarios2016In: Ecological research, ISSN 0912-3814, E-ISSN 1440-1703, Vol. 31, no 6, p. 935-945Article in journal (Refereed)
    Abstract [en]

    Here we report from a experiment imposing different warming scenarios [control with ambient temperature, constant level of moderate warming for 3 years, stepwise increase in warming for 3 years, and one season of high level warming (pulse) simulating an extreme summer event] on an alpine ecosystem to study the impact on species diversity–biomass relationship, and community resistance in terms of biomass production. Multiple linear mixed models indicate that experimental years had stronger influence on biomass than warming scenarios and species diversity. Species diversity and biomass had almost humpback relationships under different warming scenarios over different experimental years. There was generally a negative diversity–biomass relationship, implying that a positive diversity–biomass relationship was not the case. The application of different warming scenarios did not change this tendency. The change in community resistance to all warming scenarios was generally negatively correlated with increasing species diversity, the strength of the correlation varying both between treatments and between years within treatments. The strong effect of experimental years was consistent with the notion that niche complementarity effects increase over time, and hence, higher biomass productivity over experimental years. The strongest negative relationship was found in the first year of the pulse treatment, indicating that the community had weak resistance to an extreme event of one season of abnormally warm climate. Biomass production started recovering during the two subsequent years. Contrasting biomass-related resistance emerged in the different treatments, indicating that micro sites within the same plant community may differ in their resistance to different warming scenarios.

  • 211. Allen, C.E.
    The influence of schistocity on soil weathering on large boulder tops, Kärkevagge, Sweden.2002In: Catena, Vol. 49, p. 157-169Article in journal (Other academic)
  • 212.
    Allen, C.E.
    Department of Geography..
    Weathering regimes and pedogenic variability on large boulders, Kärkevagge, Northern Scandinavia.2001Student thesis
  • 213. Allen, C.E.
    et al.
    Darmody, R.G.
    Thorn, C.E.
    Dixon, J.C.
    Schlyter, P.
    Clay mineralogy, chemical weathering and landscape evolution in Arctic-Alpine Sweden.2001In: Geoderma, Vol. 99, p. 277-294Article in journal (Other academic)
  • 214. Alling, Vanja
    Terrestrial organic carbon dynamics in Arctic coastal areas2010Doctoral thesis, monograph (Other academic)
  • 215. Alling, Vanja
    et al.
    Humborg, Christoph
    Morth, Carl-Magnus
    Rahm, Lars
    Pollehne, Falk
    Tracing terrestrial organic matter by delta(34)S and delta(13)C signatures in a subarctic estuary2008In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 53, no 6, p. 2594-2602Article in journal (Refereed)
    Abstract [en]

    A key issue to understanding the transformations of terrestrial organic carbon in the ocean is to disentangle the latter from marine-produced organic matter. We applied a multiple stable isotope approach using delta(34)S and delta(13)C isotope signatures from estuarine dissolved organic matter (DOM), enabling us to constrain the contribution of terrestrial-derived DOM in an estuarine gradient of the northern Baltic Sea. The stable isotope signatures for dissolved organic sulfur (delta(34)S(DOS)) have twice the range between terrestrial and marine end members compared to the stable isotope signatures for dissolved organic carbon (delta(13)C(DOC)); hence, the share of terrestrial DOM in the total estuarine DOM can be calculated more precisely. DOM samples from the water column were collected using ultrafiltration on board the German RV Maria S Merian during a winter cruise, in the Bothnian Bay, Bothnian Sea, and Baltic proper. We calculated the terrestrial fraction of the estuarine DOC (DOC(ter)) from both delta(13)C(DOC) and delta(34)S(DOS) signatures and applying fixed C: S ratios for riverine and marine end members to convert S isotope signatures into DOC concentrations. The delta(34)S(DOS) signature of the riverine end member was +7.02 parts per thousand, and the mean signatures from Bothnian Bay, Bothnian Sea, and Baltic proper were +10.27, +12.51, and +13.67 parts per thousand, respectively, showing an increasing marine signal southwards (d34SDOS marine end member = 18.1 parts per thousand). These signatures indicate that 87%, 75%, and 67%, respectively, of the water column DOC is of terrestrial origin (DOC(ter)) in these basins. Comparing the fractions of DOC(ter) in each basin-that are still based on few winter values only-with the annual river input of DOC, it appears that the turnover time for DOC(ter) in the Gulf of Bothnia is much shorter than the hydraulic turnover time, suggesting that high-latitude estuaries might be efficient sinks for DOC(ter).

  • 216. Alling, Vanja
    et al.
    Humborg, Christoph
    Mörth, Carl-Magnus
    Rahm, Lars
    Pollehne, Falk
    Tracing terrestrial organic matter by sigma34S and sigma13C signatures in a subarctic estuary2008In: Limnology and Oceanography, Vol. 53, no 6, p. 2594-2602Article in journal (Refereed)
  • 217. Alling, Vanja
    et al.
    Porcelli, Don
    Mörth, Carl-Magnus
    Anderson, Leif G.
    Andersson, Per
    Humborg, Christoph
    Degradation of terrestrial organic carbon, primary production and out-gassing of CO2 along the Laptev and East Siberian Seas as inferred from sigma 13C values of DIC2010In: Terrestrial organic carbon dynamics in Arctic coastal areas, Stockholm Univ., Dept. of Environmental Science , 2010, , p. 43Chapter in book (Other academic)
  • 218. Alling, Vanja
    et al.
    Sanchez-Garcia, Laura
    Porcelli, Don
    Pugach, Sveta
    Vonk, Jorien E.
    van Dongen, Bart
    Morth, Carl-Magnus
    Anderson, Leif G.
    Sokolov, Alexander
    Andersson, Per
    Humborg, Christoph
    Semiletov, Igor
    Gustafsson, Orjan
    Nonconservative behavior of dissolved organic carbon across the Laptev and East Siberian seas2010In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 24Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to have a strong effect on the Eastern Siberian Arctic Shelf (ESAS) region, which includes 40% of the Arctic shelves and comprises the Laptev and East Siberian seas. The largest organic carbon pool, the dissolved organic carbon (DOC), may change significantly due to changes in both riverine inputs and transformation rates; however, the present DOC inventories and transformation patterns are poorly understood. Using samples from the International Siberian Shelf Study 2008, this study examines for the first time DOC removal in Arctic shelf waters with residence times that range from months to years. Removals of up to 10%-20% were found in the Lena River estuary, consistent with earlier studies in this area, where surface waters were shown to have a residence time of approximately 2 months. In contrast, the DOC concentrations showed a strong nonconservative pattern in areas with freshwater residence times of several years. The average losses of DOC were estimated to be 30%-50% during mixing along the shelf, corresponding to a first-order removal rate constant of 0.3 yr(-1). These data provide the first observational evidence for losses of DOC in the Arctic shelf seas, and the calculated DOC deficit reflects DOC losses that are higher than recent model estimates for the region. Overall, a large proportion of riverine DOC is removed from the surface waters across the Arctic shelves. Such significant losses must be included in models of the carbon cycle for the Arctic Ocean, especially since the breakdown of terrestrial DOC to CO2 in Arctic shelf seas may constitute a positive feedback mechanism for Arctic climate warming. These data also provide a baseline for considering the effects of future changes in carbon fluxes, as the vast northern carbon-rich permafrost areas draining into the Arctic are affected by global warming.

  • 219. Alling, Vanja
    et al.
    Sanchez-Garcia, Laura
    Porcelli, Don
    Pugach, Sveta
    Vonk, Jorien E.
    van Dongen, Bart
    Mörth, Carl-Magnus
    Anderson, Leif G.
    Sokolov, Alexander
    Andersson, Per
    Humborg, Christoph
    Semiletov, Igor
    Gustafsson, Örjan
    Non-conservative behaviour of dissolved organic carbon across Laptev and East Siberian Seas2010In: Terrestrial organic carbon dynamics in Arctic coastal areas, Stockholm Univ., Dept. of Environmental Science , 2010, , p. 49Chapter in book (Other academic)
  • 220. Alm, C.G.
    Botaniska trädgården vid Abisko turiststation.1924In: Svenska Turistföreningens Årsskrift, Vol. 1924, p. 302-304Article in journal (Other academic)
  • 221. Alm, C.G.
    Fjällväxter vid Abisko Turiststation.1924Report (Other academic)
  • 222. Alm, C.G.
    Floristiska anteckningar från Torneträskområdet.1921In: Svensk Botanisk Tidskrift, Vol. 15, no 2-4, p. 263-265Article in journal (Other academic)
  • 223. Alm, C.G.
    Gyrophora rugifera (Nyl. ) Th. Fr. funnen i Torne Lappmark.1920In: Svensk Botanisk Tidskrift, Vol. 14, no 4, p. 344-345Article in journal (Other academic)
  • 224. Alm, C.G.
    Meddelande angående frostskadade björkar å Nuolja.1923In: Svensk Botanisk Tidskrift, Vol. 17, no 1, p. 120-Article in journal (Other academic)
  • 225. Alm, C.G.
    Några ord om Braya glabella Richards.1923In: Botaniska Notiser, Vol. 1923, p. 111-114Article in journal (Other academic)
  • 226. Alm, C.G.
    Om Braya glabella Richards. och dess utbredning i Skandinavien.1921In: Acta Florae Sueciae, Vol. 1, p. 245-264Article in journal (Other academic)
  • 227. Alm, C.G.
    Om Carex macloviana d'Urv. och dess utbredning i Nordeuropa.1944In: The Svedberg 1884 - 1944, Festskrift 1944, Uppsala, 1944, p. 578-600Chapter in book (Other academic)
  • 228. Alm, C.G.
    Plantanthera parvula Schltr. , en nybeskriven svensk växt.1923In: Svensk Botanisk Tidskrift, Vol. 17, no 2, p. 224-227Article in journal (Other academic)
  • 229. Alm, C.G.
    Skogsfrublomman i Torne Lappmark.1921In: Sveriges Natur, Vol. 12, p. 163-164Article in journal (Other academic)
  • 230. Alm, C.G.
    Vår sällsyntaste orkidé och dess öden.1929In: Sveriges Natur, Vol. 20, p. 134-137Article in journal (Other academic)
  • 231. Alm, C.G.
    et al.
    Fries, Th.C.E.
    Botanische Exkursionen in Torne Lappmark. Kurzer Führer über das Gebiet von Kiruna und der Umgebung des Torneträsk.1925Report (Other academic)
  • 232. Alm, G.
    Monographie der Schwedischen Süsswasser-Ostracoden nebst systematischen Besprechungen der tribus Podocopa1916Report (Other academic)
  • 233. Alm, G.
    Ostracoden aus den nordschwedischen Hochgebirgen1914Report (Other academic)
  • 234. Alm, Göran
    Ice detection during cloudly conditions over the Arctic region using NOAA AVHR satellite imagery1991In: Geografiska annaler A, no 3/4, p. 155-166Article in journal (Refereed)
  • 235. Alm, T.
    Noen fugletuer i fjellet.1993In: Polarflokken, Vol. 17, no 1, p. 131-137Article in journal (Other academic)
  • 236. Almquist, E.
    Järnvägsfloristiska notiser. Ett apropos till järnvägsjubileet.1957In: Svensk Botanisk Tidskrift, Vol. 51, no 1, p. 223-263Article in journal (Other academic)
  • 237. Almquist, E.
    Växtlokaler från Torne och Lule Lappmarker.1917In: Svensk Botanisk Tidskrift, Vol. 11, no 1, p. 125-130Article in journal (Other academic)
  • 238. Almroth, B. C.
    et al.
    Asker, N.
    Wassmur, B.
    Rosengren, M.
    Jutfelt, F.
    Grans, A.
    Sundell, K.
    Axelsson, M.
    Sturve, J.
    Warmer water temperature results in oxidative damage in an Antarctic fish, the bald notothen2015In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 468, p. 130-137Article in journal (Refereed)
    Abstract [en]

    Global climate change is predicted to result in increases in water temperature in the polar regions, but the full consequences of this for marine fish species are not understood, especially with regard to cellular mechanisms underlying oxidative stress. Warmer temperatures could potentially result in increased oxidative stress, and it is not known whether stenothermal fish can cope with this on a cellular and physiological level. In order to address this, we exposed bald notothen (Pagothenta borchgrevinki), a fish species endemic to Antarctica, to an increase in temperature from -1.6 degrees C to 4 degrees C and measured the effects on oxidative stress including antioxidant defenses, oxidative damage in proteins and lipids, and transcriptional regulation of involved genes. We show that the fish responds to an acute (12 h) temperature increase with increased antioxidant defenses. However, these antioxidant defenses were similar to basal levels following long-term (3 weeks) exposure to the higher temperature and moreover, these individuals also had higher levels of oxidative damage. These results indicate that this species has the ability to alter levels of endogenous antioxidants, but that this response is transient and insufficient to protect against oxidative damage. These effects may have serious consequences for these fish in a warmer future since long-term consequences of this accumulation of damaged lipids and proteins are associated with aging and known to include decreased cellular function, disease and eventually cell death. (C) 2015 Elsevier B.V. All rights reserved.

  • 239. Alonso-Saez, Laura
    et al.
    Andersson, Anders
    Heinrich, Friederike
    Bertilsson, Stefan
    High archaeal diversity in Antarctic circumpolar deep waters2011In: Environmental Microbiology Reports, ISSN 1758-2229, E-ISSN 1758-2229, Vol. 3, no 6, p. 689-697Article in journal (Refereed)
    Abstract [en]

    Archaea are abundant in polar oceans but important ecological aspects of this group remain enigmatic, such as patterns of diversity and biogeography. Here, we provide the first high-throughput sequencing population study of Antarctic archaea based on 198 bp fragments of the 16S rRNA gene, targeting different water masses across the Amundsen and Ross Seas. Our results suggest that archaeal community composition is strongly shaped by hydrography and significantly influenced by environmental parameters. Archaeal communities from cold continental shelf waters (SW) of the Ross Sea were similar over depth with a single thaumarchaeal phylotype dominating Antarctic surface waters (AASW) and deeper SW (contributing up to 80% of reads). However, this phylotype contributed less than 8% of reads in circumpolar deep waters (CDW). A related thaumarchaeon (98% identity) was almost absent in AASW, but contributed up to 30% of reads in CDW, suggesting ecological differentiation of closely related phylotypes. Significantly higher archaeal richness and evenness were observed in CDW, with Shannon indices (c. 2.5) twice as high as for AASW, and high contributions of Group II Euryarchaeota. Based on these results, we suggest that CDW is a hotspot of archaeal diversity and may play an important role in the dispersal of archaeal phylotypes to other oceanic water masses.

  • 240. Alonso-Saez, Laura
    et al.
    Waller, Alison S.
    Mende, Daniel R.
    Bakker, Kevin
    Farnelid, Hanna
    Yager, Patricia L.
    Lovejoy, Connie
    Tremblay, Jean-Eric
    Potvin, Marianne
    Heinrich, Friederike
    Estrada, Marta
    Riemann, Lasse
    Bork, Peer
    Pedros-Alio, Carlos
    Bertilsson, Stefan
    Role for urea in nitrification by polar marine Archaea2012In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 44, p. 17989-17994Article in journal (Refereed)
    Abstract [en]

    Despite the high abundance of Archaea in the global ocean, their metabolism and biogeochemical roles remain largely unresolved. We investigated the population dynamics and metabolic activity of Thaumarchaeota in polar environments, where these microorganisms are particularly abundant and exhibit seasonal growth. Thaumarchaeota were more abundant in deep Arctic and Antarctic waters and grew throughout the winter at surface and deeper Arctic halocline waters. However, in situ single-cell activity measurements revealed a low activity of this group in the uptake of both leucine and bicarbonate (<5% Thaumarchaeota cells active), which is inconsistent with known heterotrophic and autotrophic thaumarchaeal lifestyles. These results suggested the existence of alternative sources of carbon and energy. Our analysis of an environmental metagenome from the Arctic winter revealed that Thaumarchaeota had pathways for ammonia oxidation and, unexpectedly, an abundance of genes involved in urea transport and degradation. Quantitative PCR analysis confirmed that most polar Thaumarchaeota had the potential to oxidize ammonia, and a large fraction of them had urease genes, enabling the use of urea to fuel nitrification. Thaumarchaeota from Arctic deep waters had a higher abundance of urease genes than those near the surface suggesting genetic differences between closely related archaeal populations. In situ measurements of urea uptake and concentration in Arctic waters showed that small-sized prokaryotes incorporated the carbon from urea, and the availability of urea was often higher than that of ammonium. Therefore, the degradation of urea may be a relevant pathway for Thaumarchaeota and other microorganisms exposed to the low-energy conditions of dark polar waters.

  • 241. Alsander, J.
    et al.
    Hill, A.
    Nilsson, I.
    Paktajokk. Vattenföring, fluvial transport och denudation.1978Report (Other academic)
  • 242. Alsos, I G
    et al.
    Engelskjon, T
    Gielly, L
    Taberlet, P
    Brochmann, C
    Impact of ice ages on circumpolar molecular diversity: insights from an ecological key species2005In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 14, no 9, p. 2739-2753Article in journal (Refereed)
    Abstract [en]

    We address the impact of the ice age cycles on intraspecific cpDNA diversity, for the first time on the full circumboreal-circumarctic scale. The bird-dispersed bog bilberry (or arctic blueberry, Vaccinium uliginosum) is a key component of northern ecosystems and is here used to assess diversity in previously glaciated vs. unglaciated areas and the importance of Beringia as a refugium and source for interglacial expansion. Eighteen chloroplast DNA haplotypes were observed in and among 122 populations, grouping into three main lineages which probably diverged before, and thus were affected more or less independently by, all major glaciations. The boreal ‘Amphi-Atlantic lineage’ included one haplotype occurring throughout northern Europe and one occurring in eastern North America, suggesting expansion from at least two bottlenecked, glacial refugium populations. The boreal ‘Beringian lineage’ included seven haplotypes restricted to Beringia and the Pacific coast of USA. The ‘Arctic-Alpine lineage’ included nine haplotypes, one of them fully circumpolar. This lineage was unexpectedly diverse, also in previously glaciated areas, suggesting that it thrived on the vast tundras during the ice ages and recolonized deglaciated terrain over long distances. Its largest area of persistence during glaciations was probably situated in the north, stretching from Beringia and far into Eurasia, and it probably also survived the last glaciation in southern mountain ranges. Although Beringia apparently was important for the initial divergence and expansion of V. uliginosum as well as for continuous survival of both the Beringian and Arctic-Alpine lineages during all ice ages, this region played a minor role as a source for later interglacial expansions.

  • 243. Alsos, Inger Greve
    et al.
    Eidesen, Pernille Bronken
    Ehrich, Dorothee
    Skrede, Inger
    Westergaard, Kristine
    Jacobsen, Gro Hilde
    Landvik, Jon Y.
    Taberlet, Pierre
    Brochmann, Christian
    Frequent long-distance plant colonization in the changing Arctic2007In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 316, no 5831, p. 1606-1609Article in journal (Refereed)
    Abstract [en]

    The ability of species to track their ecological niche after climate change is a major source of uncertainty in predicting their future distribution. By analyzing DNA fingerprinting ( amplified fragment-length polymorphism) of nine plant species, we show that long-distance colonization of a remote arctic archipelago, Svalbard, has occurred repeatedly and from several source regions. Propagules are likely carried by wind and drifting sea ice. The genetic effect of restricted colonization was strongly correlated with the temperature requirements of the species, indicating that establishment limits distribution more than dispersal. Thus, it may be appropriate to assume unlimited dispersal when predicting long-term range shifts in the Arctic.

  • 244. Alstrup, V.
    Lichens and lichenicolous fungi from the Torneträsk area.1991In: Graphis Scripta, Vol. 3, p. 54-67Article in journal (Other academic)
  • 245. Alstrup, V.
    Lichens from Björkliden, Northern Sweden.1986In: Graphis Scripta, Vol. 1, no 1, p. 3-6Article in journal (Other academic)
  • 246. Alverson, K.
    et al.
    Bradley, R.
    Briffa, K.
    Cole, J.
    Hughes, M.
    Larocque, I.
    Pedersen, T.
    Thompson, L.
    Tudhope, S.
    Disappearing Evidence: the Need for a Global Paleoclimate Observing System.2001In: Global Change NewsLetter, Vol. 46, p. 2-6Article in journal (Other academic)
  • 247.
    Amnéus, E.
    Naturgeografiska institutionen, Avdelningen för Naturgeografi.
    Markanvändningsförändringar i Torneträskområdet.1989Student thesis
  • 248. Amon, D. J.
    et al.
    Wiklund, H.
    Dahlgren, T. G.
    Copley, J. T.
    Smith, C. R.
    Jamieson, A. J.
    Glover, A. G.
    Molecular taxonomy of Osedax (Annelida: Siboglinidae) in the Southern Ocean2014In: Zoologica Scripta, ISSN 0300-3256, E-ISSN 1463-6409, Vol. 43Article in journal (Refereed)
    Abstract [en]

    We report the discovery of three new species of Osedax in the deep Southern Ocean, expanding the diversity and geographical range of this genus of bone-eating worms. Osedax rogersi sp. n. and Osedax crouchi sp. n. were found on a whale skeleton at 1444m in the Kemp Caldera in the East Scotia Sea during the Chemosynthetic Ecosystems of the Southern Ocean (ChEsSo) project. The recently described species, Osedax antarcticus, found on whale bones implanted at a depth of 550-650m off Smith Island in the Bransfield Strait, was also found inhabiting the whale skeleton in the Kemp Caldera. Osedax crouchi as well as another new species Osedax nordenskjoeldi sp. n. have also been found on the implanted whale bones off Smith Island. These two localities are approximately 1800km apart demonstrating a wide distribution of species within the genus. We describe the three new species, O.rogersi, O.crouchi and O.nordenskjoeldi and report the second record of O.antarcticus. We also present a new phylogenetic analysis for Osedax, including data examining genetic connectivity between the Scotia Arc and the Bransfield Strait.

  • 249. Amon, Rainer M. W.
    A river runs through it: dissolved organic matter in the Arctic Ocean2006In: Polarforskningssekretariatets årsbok 2005, Stockholm: Swedish Polar Research Secretariat , 2006, , p. 85 - 86Chapter in book (Other academic)
  • 250. Ampomah, O. Y.
    et al.
    James, E. K.
    Iannetta, P. P. M.
    Kenicer, G.
    Sprent, J. I.
    Huss-Danell, K.
    Nodulation and ecological significance of indigenous legumes in Scotland and Sweden2012In: Symbiosis, ISSN 0334-5114, E-ISSN 1878-7665, Vol. 57Article in journal (Refereed)
    Abstract [en]

    The ability of wild indigenous legumes to form root nodules capable of biological nitrogen (N-2) fixation has rarely been demonstrated for species in natural ecosystems in large parts of Europe. In order to understand and manage these ecosystems, it is important to demonstrate nodulation across a diverse range of environments, sites and climates. This study surveyed nodulation at a number of sites in Scotland and Sweden. Presence of nodules was noted and nodule structure and indicators of nitrogen fixation capacity were assessed using light and transmission electron microscopy. Soils from several sites were also sampled for carbon and nitrogen analysis. The collections comprised 24 species in Scotland, and 30 taxa in Sweden; 17 of these in common for both countries. Highest species numbers occurred in meadows, farmland margins, hedgerows, roadsides and wasteland. Coastal sites and sites in the mountainous region above the Arctic Circle hosted several rare species. All sampled species had features of N-2-fixing nodules such as pink colour (leghaemoglobin) when dissected and bacteroids. Nodule structure for a number of species is here reported for the first time and presence of the N-2-fixing enzyme nitrogenase is demonstrated in three previously not studied Swedish legume species. North European legumes may make significant contributions to the N-budgets of their ecosystems. Such species (and their symbionts) represent unique germplasm that may be adopted to empower advances in agriculture and conservation aimed at mitigation and adaptation to the effects of climate change.

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