uu.seUppsala University Publications
Change search
Refine search result
1234567 1 - 50 of 473
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Abrahamsson, K.
    et al.
    Pakhomovc,, E.A.
    Loréna, A.
    Fronemanc,, P.W.
    Bertilsson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Chiericia,, M.
    Franssona, A.
    Variations of biochemical parameters along a transect in the Southern Ocean, with special emphasis on volatile halogenated organic compounds2004In: Deep Sea Research Part II:: Topical Studies in Oceanography, Vol. 51,, no 22-24, p. 2745-2756Article in journal (Refereed)
    Abstract [en]

    A number of parameters of biogeochemical interest were monitored along a north–southerly transect (S 43–S 63°) in the Atlantic Sector of the Southern Ocean from the 8th to the 20th of December 1997. Changes in total dissolved inorganic carbon (CT) and total alkalinity (AT) were mostly dependent on temperature and salinity until the ice edge was reached. After this point only a weak correlation was seen between these. Highest mean values of CT and AT were observed in the Winter Ice Edge (WIE) (2195 and 2319 μmol kg−1, respectively). Lowest mean AT (2277 μmol kg−1) was observed in the Sub-Antarctic Front (SAF), whereas lowest mean CT concentration (2068 μmol kg−1) was associated with the Sub-Tropical Front (STF). The pH in situ varied between 8.060 and 8.156 where the highest values were observed in the southern part of the Antarctic Polar Front (APF) and in the Summer Ice Edge (SIE) Region . These peaks were associated with areas of high chlorophyll a (chl a) and tribromomethane values. In the other areas the pH in situ was mainly dependent on hydrography. Bacterial abundance decreased more than one order of magnitude when going from north to south. The decrease appeared to be strongly related to water temperature and there were no elevated abundances at frontal zones. Microphytoplankton dominated in the SAF and APF, whereas the nano- and picoplankton dominated outside these regions.

    Volatile halogenated compounds were found to vary both with regions, and with daylight. For the iodinated compounds, the highest concentrations were found north of the STF. Brominated hydrocarbons had high concentrations in the STF, but elevated concentrations were also found in the APF and SIE regions. No obvious correlation could be found between the occurrence of individual halocarbons and chl a. On some occasions trichloroethene and tribromomethane related to the presence of nano- and microplankton, respectively.

  • 2.
    Admassu, Demeke
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Ahlgren, Ingemar
    Department of Ecology and Evolution, Limnology.
    Growth of juvenile tilapia, Oreochromis niloticus L. from Lakes Zwai, Langeno and Chamo (Ethiopian rift valley) based on otolith microincrement analysis2000In: Ecology of Freshwater Fish, Vol. 9, no 3, p. 127-137Article in journal (Refereed)
    Abstract [en]

    Age and growth of juvenile tilapia, Oreochromis niloticus, from Lakes Zwai, Langeno and Chamo (Ethiopia) were studied from microincrements in otoliths. Growth in length was best described by the Gompertz model. Average growth rate of the fish was most rap

  • 3. Adrian, Rita
    et al.
    O`Reilly, Catherine M.
    Zagarese, Horacio
    Baines, Stephen B.
    Hessen, Dag O.
    Keller, Wendel
    Livingstone, David M.
    Sommaruga, Ruben
    Straile, Dietmar
    Van Donk, Ellen
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Winder, Monika
    Lakes as sentinels of climate change2009In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 54, no 6(2), p. 2283-2297Article in journal (Refereed)
    Abstract [en]

    While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.

  • 4.
    Ahlgren, G
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Ahlgren, I
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Hernández, S
    Mejia, M.
    Fatty acid quality of seston and its effects on small fish in the lakes Xolotlán and Cocibolca, Nicaragua.2002In: Verh. Internat. Verein. Limnol., Vol. 28, p. 786-791Article in journal (Refereed)
  • 5.
    Ahlgren, G.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Van Niewerburgh, L
    Wänstrand, I.
    Pedersén, M.
    Boberg, M.
    Medicinska vetenskapsområdet, Faculty of Medicine, Department of Public Health and Caring Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Imbalance of fatty acids in the base of the Baltic sea food web - a mesocosm study.2005In: Canadian Journal of Fisheries and Aquatic Sciences ., Vol. 62:, p. 2240-2253Article in journal (Refereed)
    Abstract [en]

    A reproductive disturbance in Baltic Sea Atlantic salmon (Salmo salar), the M74 syndrome, has been reported since early 1970s and has occasionally caused up to 90% mortality for newborn fry. Previous research has revealed that the M74 syndrome may be due to reduced levels of the vitamin thiamin, the carotenoid astaxanthin, and elevated ratios of 3/ 6 fatty acids in salmon eggs. Using mesocosm experiments, we compared the quantity (µg•L–1) and quality (mg•g–1 C) of fatty acids in microalgae and copepods in the southern Baltic Sea where the M74 syndrome is common with those in a habitat in the Norwegian Sea where the syndrome has not been observed. Daily additions were made of the nutrients N and P or N, P, and Si, copepods were added after 6–7 days, and nutrient additions were stopped after 9–10 days. Flagellates dominated completely in the Baltic Sea, whereas higher phytoplankton diversity was found in the Norwegian Sea. We found elevated 3/ 6 ratios in phytoplankton and abnormally high docosahexaenoic acid/arachidonic acid ratios (22:6 3/20:4 6) in copepods in the Baltic Sea mesocosms compared with those in the Norwegian Sea. Our results suggest that imbalance in fatty acid composition may prevail in the basic food web of the Baltic Sea.

    On a signalé depuis le début des années 1970 une perturbation de la reproduction, le syndrome M74, chez le saumon atlantique (Salmo salar) de la Baltique qui, à l’occasion, cause une mortalité pouvant atteindre 90 % chez les alevins néonates. Les études antérieures ont montré que le syndrome M74 peut être dû à des concentrations faibles de la vitamine thiamine et du caroténoïde l’astaxanthine et à des rapports élevés des acides gras 3/ 6 dans les oeufs de saumons. Dans des expériences de mésocosmes, nous avons comparé la quantité (µg•L–1) et la qualité (mg•g–1 C) des acides gras dans les microalgues et les copépodes dans le sud de la Baltique où le syndrome M74 est répandu à celles d’un habitat de la mer de Norvège où le syndrome n’a pas été observé. Nous avons ajouté quotidiennement les nutriments N et P ou alors N, P et Si, introduit des copépodes au bout de 6–7 jours et arrêté les additions de nutriments après 9–10 jours. Dans la Baltique, les flagellés sont dominants, alors que, dans la mer de Norvège, le phytoplancton est plus diversifié. Dans les mésocosmes de la Baltique, les rapports 3/ 6 du phytoplancton sont élevés et les rapports acide docosahexanoïque/acide arachidonique (22:6 3/20:4 6) anormalement grands chez les copépodes, par comparaison aux mésocosmes de la mer de Norvège. Nos résultats laissent croire qu’il peut y avoir un déséquilibre dans la composition en acides gras dans le réseau alimentaire de base de la Baltique.

  • 6.
    Ahlgren, Gunnel
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology. Limnologi.
    Goedkoop, Willem
    Markensten, Hampus
    Department of Ecology and Evolution, Limnology. Limnologi.
    Sonesten, Lars
    Boberg, Mats
    Seasonal variations in food quality for pelagic and benthic invertebrates in Lake Erken - the role of fatty acids1997In: FRESHWATER BIOLOGY, ISSN 0046-5070, Vol. 38, no 3, p. 555-570Article in journal (Refereed)
    Abstract [en]

    1. Plankton net samples and sedimenting matter in traps from mesotrophic Lake Erken, Sweden, were analysed for carbon (C), nitrogen (N) phosphorus (P), total lipids and fatty acid (FA) content to determine what differences and seasonal changes might exist

  • 7.
    Ahlgren, Gunnel
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Hyenstrand, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Nitrogen limitation effects of different nitrogen sources on nutritional quality of two freshwater organisms, Scenedesmus Quadricauda (Clorophyceae) and Synechococcus sp. (Cyanophyceae)2003In: J. Phycol., Vol. 39, p. 906-917Article in journal (Refereed)
  • 8.
    Ahlgren, Gunnel
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Hyenstrand, Per
    Vrede, Tobias
    Department of Ecology and Evolution, Limnology.
    Karlsson, E
    Zetterberg, S.
    Nutritional quality of Scenedesmus quadricauda (Chlorophyceae) grown in different nitrogen regimes and tested on Daphnia2001In: International Association of Theoretical and Applied Limnology, Vol. 27, no 3, p. 1234-1238Article in journal (Refereed)
  • 9.
    Ahlgren, Gunnel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tilahun, Girma
    Fatty acid quality of the basic food web in the Ethiopian lakes Awassa, Chamo, and Ziway2008In: INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, VOL 30, PT 4, PROCEEDINGS / [ed] Jones J, Faaborg J, 2008, Vol. 30, no 4, p. 581-586Conference paper (Refereed)
  • 10.
    Ahlgren, Gunnel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Vrede, Tobias
    Goedkoop, Willem
    Fatty acid ratios in freshwater fish, zooplankton and zoobenthos - Are there specific optima?2009In: Lipids in aquatic ecosystems / [ed] Michael T. Arts, Michael T. Brett, Martin J. Kainz, London: Springer , 2009, p. 147-178Chapter in book (Other (popular science, discussion, etc.))
  • 11.
    Ahlgren, Ingemar
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Drakare, Stina
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Factors controlling pelagic and sediment heterotrophic bacterial numbers and production in lakes.2002In: Verh. Internat. Verein. Limnol, Vol. 28, p. 792-797Article in journal (Refereed)
  • 12.
    Ahlgren, Ingemar
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology. Limnologi.
    Eriksson, R
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology. Limnologi.
    Moreno, L
    Pacheco, L
    Montenegro-Guillén, S
    Vammen, K
    Pelagic food web interactions in Lake Cocibolca, Nicaragua2001In: Verh. Internat. Verein. Limnol., Vol. 27, no 4, p. 1740-1746Article in journal (Refereed)
  • 13.
    Ahlgren, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Reitzel, Kasper
    Danielsson, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Rydin, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Biogenic phosphorus in oligotrophic mountain lake sediments: Differences in composition measured with NMR spectroscopy2006In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, no 20, p. 3705-3712Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) composition in alkaline sediment extracts from three Swedish oligotrophic mountain lakes was investigated using P-31-NMR spectroscopy. Surface sediments from one natural lake and two mature reservoirs, one of which has received nutrient additions over the last 3 years, were compared with respect to biogenic P composition. The results show significant differences in the occurrence of labile and biogenic P species in the sediments of the different systems. The P compound groups that varied most between these three systems were pyrophosphate and polyphosphates, compound groups known to play an important role in sediment P recycling. The content of these compound groups was lowest in the reservoirs and may indicate a coupling between anthropogenic disturbances (i.e., impoundment) to a water system and the availability of labile P species in the sediment. A statistical study was also conducted to determine the accuracy and reliability of using P-31-NMR spectroscopy for quantification of sediment P forms.

  • 14.
    Ahlgren, Joakim
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry.
    Reitzel, Kasper
    Danielsson, Rolf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry.
    Gogoll, Adolf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Rydin, Emil
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Biogenic phosphorus in oligotropic mountain lake sediments: Differences in composition measured with NMR spectroscopy2006In: Water Research, no 40, p. 3705-3712Article in journal (Refereed)
  • 15.
    Ahlgren, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Reitzel, Kasper
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Rydin, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments: A P-31 nuclear magnetic resonance study2006In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 51, no 5, p. 2341-2348Article in journal (Refereed)
    Abstract [en]

    The composition and abundance of phosphorus extracted by NaOH-ethylenediaminetetraacetic acid from anoxic Northwest Baltic Sea sediment was characterized and quantified using solution P-31 nuclear magnetic resonance. Extracts from sediment depths down to 55 cm, representing 85 yr of deposition, contained 18.5 g m(-2) orthophosphate. Orthophosphate monoesters, teichoic acid P, microbial P lipids, DNA P, and pyrophosphate corresponded to 6.7, 0.3, 1.1, 3.0, and 0.03 g P m(-2), respectively. The degradability of these compound groups was estimated by their decline in concentration with sediment depth. Pyrophosphate had the shortest half-life (3 yr), followed by microbial P lipids with a half-life of 5 yr, DNA P (8 yr), and orthophosphate monoesters (16 yr). No decline in concentration with sediment depth was observed for orthophosphate or teichoic acid P.

  • 16.
    Ahlgren, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Waldebäck, Monica
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Rydin, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Sediment Depth Attenuation of Biogenic Phosphorus Compounds Measured by 31P NMR2005In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 3, p. 867-872Article in journal (Refereed)
    Abstract [en]

    Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using 31P NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.

  • 17. Algesten, Grete
    et al.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bergström, Ann-Kristin
    Jonsson, Anders
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Jansson, Mats
    Contribution of sediment respiration to summer CO2 emission from low productive 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 (CO2) and methane (CH4) and the net flux of CO2 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 CO2 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 CO2 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 CO2 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.

  • 18. Algesten, Grete
    et al.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bergström, Ann-Kristin
    Ågren, Anneli
    Tranvik, Lars J.
    Jansson, Mats
    Role of lakes for organic carbon cycling in the boreal zone2004In: Global Change Biology, Vol. 10, p. 141-147Article in journal (Refereed)
  • 19. Algesten, Grete
    et al.
    Wikner, Johan
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Jansson, Mats
    Seasonal variation of CO2 saturation in the Gulf of Bothnia: indications of marine net heterotrophy2004In: Global Biogeochemical Cycles, ISSN 1944-9224 EISSN, Vol. 18, no 4, p. GB4021-Article in journal (Refereed)
    Abstract [en]

    [1] Seasonal variation of pCO2 and primary and bacterioplankton production were measured in the Gulf of Bothnia during an annual cycle. Surface water was supersaturated with CO2 on an annual basis, indicating net heterotrophy and a source of CO2 to the atmosphere. However, the Gulf of Bothnia oscillated between being a sink and a source of CO2 over the studied period, largely decided by temporal variation in bacterial respiration (BR) and primary production (PP) in the water column above the pycnocline. The calculated annual respiration-production balance (BR-PP) was very similar to the estimated CO2 emission from the Gulf of Bothnia, which indicates that these processes were major determinants of the exchange of CO2 between water and atmosphere. The southern basin (the Bothnian Sea) had a lower net release of CO2 to the atmosphere than the northern Bothnian Bay (7.1 and 9.7 mmol C m−2 d−1, respectively), due to higher primary production, which to a larger extent balanced respiration in this basin.

  • 20.
    Alonso-Saez, Laura
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Galand, Pierre E.
    Casamayor, Emilio O.
    Pedros-Alio, Carlos
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    High bicarbonate assimilation in the dark by Arctic bacteria2010In: ISME Journal, ISSN 1751-7362, Vol. 4, no 12, p. 1581-1590Article in journal (Refereed)
    Abstract [en]

    Although both autotrophic and heterotrophic microorganisms incorporate CO2 in the dark through different metabolic pathways, this process has usually been disregarded in oxic marine environments. We studied the significance and mediators of dark bicarbonate assimilation in dilution cultures inoculated with winter Arctic seawater. At stationary phase, bicarbonate incorporation rates were high (0.5-2.5 mu gC L-1 d(-1)) and correlated with rates of bacterial heterotrophic production, suggesting that most of the incorporation was due to heterotrophs. Accordingly, very few typically chemoautotrophic bacteria were detected by 16S rRNA gene cloning. The genetic analysis of the biotin carboxylase gene accC putatively involved in archaeal CO2 fixation did not yield any archaeal sequence, but amplified a variety of bacterial carboxylases involved in fatty acids biosynthesis, anaplerotic pathways and leucine catabolism. Gammaproteobacteria dominated the seawater cultures (40-70% of cell counts), followed by Betaproteobacteria and Flavobacteria as shown by catalyzed reporter deposition fluorescence in situ hybridization (CARDFISH). Both Beta-and Gammaproteobacteria were active in leucine and bicarbonate uptake, while Flavobacteria did not take up bicarbonate, as measured by microautoradiography combined with CARDFISH. Within Gammaproteobacteria, Pseudoalteromonas-Colwellia and Oleispira were very active in bicarbonate uptake (ca. 30 and 70% of active cells, respectively), while the group Arctic96B-16 did not take up bicarbonate. Our results suggest that, potentially, the incorporation of CO2 can be relevant for the metabolism of specific Arctic heterotrophic phylotypes, promoting the maintenance of their cell activity and/or longer survival under resource depleted conditions.

  • 21.
    Amcoff, P
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Elofsson, U O E
    Börjesson, H
    Norrgren, L
    Nilsson, G
    Alterations of dopaminergic and serotonergic activity in the brain of sea-run Baltic salmon suffering a thiamine deficiency-related disorder.2002In: J. Fish Biol, Vol. 60, p. 1407-1416Article in journal (Refereed)
  • 22.
    Ammenberg, P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Centre for Image Analysis. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis.
    Flink, P
    Lindell, T.
    Strömbeck, N.
    Bio-optical Modelling Combined with Remote Sensing to Assess Water Quality2002In: International Journal of Remote Sensing, ISSN 0143-1161, Vol. 23, no 8, p. 1621-1638Article in journal (Refereed)
  • 23.
    Anderson, NJ
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Blomqvist, Peter
    Renberg, I
    An experimental and palaeoecological study of algal responses to lake acidification and liming in three central Swedish lakes1997In: EUROPEAN JOURNAL OF PHYCOLOGY, ISSN 0967-0262, Vol. 32, no 1, p. 35-48Article in journal (Refereed)
    Abstract [en]

    Contemporary phytoplankton and palaeolimnological studies were made of the algal response to acidification and liming in three lakes in Halsingland, central Sweden (Njupfatet, Sjosjon, Djuptjarn). Surveys and experimental studies of the phytoplankton resp

  • 24.
    Andersson, Anders F.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Banfield, Jillian F.
    Virus population dynamics and acquired virus resistance in natural microbial communities.2008In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 320, no 5879, p. 1047-1050Article in journal (Refereed)
    Abstract [en]

    Viruses shape microbial community structure and function by altering the fitness of their hosts and by promoting genetic exchange. The complexity of most natural ecosystems has precluded detailed studies of virus-host interactions. We reconstructed virus and host bacterial and archaeal genome sequences from community genomic data from two natural acidophilic biofilms. Viruses were matched to their hosts by analyzing spacer sequences that occur among clustered regularly interspaced short palindromic repeats (CRISPRs) that are a hallmark of virus resistance. Virus population genomic analyses provided evidence that extensive recombination shuffles sequence motifs sufficiently to evade CRISPR spacers. Only the most recently acquired spacers match coexisting viruses, which suggests that community stability is achieved by rapid but compensatory shifts in host resistance levels and virus population structure.

  • 25.
    Andersson, Anders F.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lindberg, Mathilda
    Jakobsson, Hedvig
    Bäckhed, Fredrik
    Nyrén, Pål
    Engstrand, Lars
    Comparative analysis of human gut microbiota by barcoded pyrosequencing2008In: PloS one, ISSN 1932-6203, Vol. 3, no 7, p. e2836-Article in journal (Refereed)
    Abstract [en]

    Humans host complex microbial communities believed to contribute to health maintenance and, when in imbalance, to the development of diseases. Determining the microbial composition in patients and healthy controls may thus provide novel therapeutic targets. For this purpose, high-throughput, cost-effective methods for microbiota characterization are needed. We have employed 454-pyrosequencing of a hyper-variable region of the 16S rRNA gene in combination with sample-specific barcode sequences which enables parallel in-depth analysis of hundreds of samples with limited sample processing. In silico modeling demonstrated that the method correctly describes microbial communities down to phylotypes below the genus level. Here we applied the technique to analyze microbial communities in throat, stomach and fecal samples. Our results demonstrate the applicability of barcoded pyrosequencing as a high-throughput method for comparative microbial ecology

  • 26.
    Andersson, Anders F
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Riemann, Lasse
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Pyrosequencing reveals contrasting seasonal dynamics of taxa within Baltic Sea bacterioplankton communities2010In: ISME J, ISSN 1751-7362, Vol. 4, no 2, p. 171-181Article in journal (Refereed)
    Abstract [en]

    Variation in traits causes bacterial populations to respond in contrasting ways to environmental drivers. Learning about this will help us understand the ecology of individual populations in complex ecosystems. We used 454 pyrosequencing of the hypervariable region V6 of the 16S rRNA gene to study seasonal dynamics in Baltic Sea bacterioplankton communities, and link community and population changes to biological and chemical factors. Surface samples were collected from May to October 2003 and in May 2004 at the Landsort Deep in the central Baltic Sea Proper. The analysis rendered, on average, 20 200 sequence reads for each of the eight samples analyzed, providing the first detailed description of Baltic Sea bacterial communities. Community composition varied dramatically over time, supporting the idea of strong temporal shifts in bacterioplankton assemblages, and clustered according to season (including two May samples from consecutive years), suggesting repeatable seasonal succession. Overall, community change was most highly correlated with change in phosphorus concentration and temperature. Individual bacterial populations were also identified that tightly co-varied with different Cyanobacteria populations. Comparing the abundance profiles of operational taxonomic units at different phylogenetic distances revealed a weak but significant negative correlation between abundance profile similarity and genetic distance, potentially reflecting habitat filtering of evolutionarily conserved functional traits in the studied bacterioplankton.

  • 27.
    Andersson, Eva
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Swedish Nuclear Fuel and Waste Management.
    Brunberg, Anna-Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Inorganic nutrient acquisition in a shallow clearwater lake: dominance of benthic microbiota2006In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 68, no 2, p. 172-180Article in journal (Refereed)
    Abstract [en]

    This mesocosm study from the oligotrophic Lake Eckarfjärden in Sweden shows, in contrast to many previous studies, that benthic microbiota dominated production following elevated nutrient concentrations in the water. Increased nutrient concentrations favoured microphytobenthos, whereas phytoplankton biomass remained roughly the same. Microphytobenthos biomass and production were clearly stimulated by nitrogen addition, while phytoplankton showed signs of phosphorus limitation. There were tight interactions between pelagic and benthic habitats and between organisms, and pelagic as well as benthic heterotrophic bacteria were disfavoured when microphytobenthos had access to nitrogen.

    We conclude that increased nutrient concentrations in the water column may trigger immediate responses in both habitats, altering the tight interactions between microbiota, but not necessarily resulting in a shift towards pelagic production.

  • 28.
    Andersson, Eva
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Brunberg, Anna-Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Net autotrophy in an oligotrophic lake rich in dissolved organic carbon and with high benthic primary production2006In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 43, no 1, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Biomass and production of microbiota—primary producers as well as heterotrophic bacteria—were studied both in the pelagial and in the benthic habitat over 2 yr in the shallow oligotrophic Lake Eckarfjärden, Sweden. Both biomass and production of microbiota were concentrated in the benthic habitat. Despite a high dissolved organic carbon (DOC) concentration of about 25 mg C l–1 in the water, the total bacterial production was lower than the total primary production. Moreover, measurements of DOC concentrations in the in- and outflow, and CO2-saturation measurements, indicate that the system is net autotrophic. Generally, low-productive systems (<100 µg C l–1 d–1) tend to be net heterotrophic. In contrast, we found a low-productive (55 µg C l–1 d–1) but net autotrophic system, the conditions of which were largely influenced by benthic production. Many lakes in the world are shallow and may provide substantial benthic areas suitable for primary production. Hence, it is important to include this habitat when evaluating whether lakes are autotrophic or heterotrophic systems.

  • 29.
    Andersson, Eva
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Kumblad, Linda
    A carbon budget for an oligotrophic clearwater lake in mid-Sweden2006In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 68, no 1, p. 52-64Article in journal (Refereed)
    Abstract [en]

    In this study, a whole-lake carbon budget for the oligotrophic, clearwater Lake Eckarfjärden was established both on an annual and seasonal basis. For budget calculations, the lake was divided into three habitats (pelagial, littoral and benthic) and the biota into 19 functional groups. In the lake, major parts of biomass (97%) and primary production (91%) are concentrated in benthic and littoral habitats and to a few functional groups. Respiration on the other hand, is focused on benthic and pelagial habitats where 60% and 39%, respectively, of the respiration took place. Our conceptual model indicates strong interactions between habitats. For instance, the pelagial is fed with carbon fixed by primary producers in the benthic and littoral zones. On an annual basis, total primary production exceeds total respiration and the lake is net autotrophic. However, there are clear differences between habitats and between seasons. For instance, the littoral is net autotrophic during spring, summer and autumn, the benthic habitat is net autotrophic only during summer, and the pelagial is always net heterotrophic. Our results demonstrate clear couplings between habitats and organisms and the importance of a holistic view when studying lake ecosystems.

  • 30.
    Andersson, Eva
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Tudorancea, M.-M.
    Tudorancea, C.
    Brunberg, Anna-Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Blomqvist, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. limnologi.
    Water chemistry, biomass and production in Lake Eckarfjärden during 2002.2003Report (Other academic)
  • 31.
    Andrén, Cecilia
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ger alla ALI-analyser ALI – monomert oorganiskt aluminium?2007In: Norsk-Svensk Konferanse om forsurning og kalkning 2007: Bergen, Norge, 18-20 sept 2007, 2007Conference paper (Other (popular scientific, debate etc.))
  • 32.
    Andrén, Cecilia
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Inorganic Aluminium in streams - bioavailability and toxicity: Litteratursammanställning2003Report (Other scientific)
  • 33.
    Andrén, Cecilia
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Provningsjämförelser av aluminiumfraktioner 2001 & 20022003Report (Other scientific)
  • 34.
    Andrén, Cecilia
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Studier av episodisk försurning i IKEU-projektet2005Report (Other (popular scientific, debate etc.))
  • 35.
    Andrén, Cecilia
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Andersson, Paul
    Fröberg, Elisabeth
    Temporal variations of aluminum fractions in streams in the Delsbo area, central Sweden2001In: Water, Air and Soil Pollution, Vol. 130, no 1-4, p. 1715-1720Article in journal (Refereed)
  • 36.
    Andrén, Cecilia
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bergquist, Björn
    Biological indicators of episodic acidification2004In: SIL Lahti 8-14 augusti 2004, 2004Conference paper (Other scientific)
  • 37.
    Andrén, Cecilia
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bergquist, Björn
    Can the stream community predict its acidity regime?2005In: Acid Rain 2005, Prag, Tjeckoslovakien, 12-17 juni, 2005, 2005Conference paper (Other (popular scientific, debate etc.))
  • 38.
    Andrén, Cecilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Jarlman, Amelie
    Benthic diatoms as indicators of acidity in streams.2008In: Fundamental and Applied Limnology, Vol. 173, no 3, p. 237-253Article in journal (Refereed)
    Abstract [en]

    As acidification changes from chronic to more episodic in nature, study focus shifts from lakes, where the basin moderates acidity, to streams where acid episodes occur. To assess the effects of acid stress, several macroinvertebrate indices have been used in Scandinavia and elsewhere, based on the presence or absence of species. Benthic diatoms are strongly linked to water quality with small spatial influence, and display a broad spectrum of species. An acidity index for streams based on benthic diatoms could refine assessment resolution, which is required as the acidification declines. During the autumns of 2004 and 2005, 99 benthic diatom samples were collected from 75 humic streams in Sweden that were monitored by monthly water sampling. The relationships between benthic diatoms and measured environmental variables were explored using canonical correspondence analysis. Acidity was the principal factor influencing the diatoms, with the highest eigenvalues noted for pH, alkalinity, and inorganic aluminium. Several weighted averaging (WA) models were developed to infer stream pH, both using 50 streams from 2004 as a calibration dataset cross-validated with 49 streams from 2005 as an independent dataset, and by modeling all 99 streams. The predictive power of the WA models was good. The model with all streams showed a high correlation for mean pH (r2 = 0.85) and minimum pH (r2 = 0.74) values. An acidity index for diatoms, ACID, was proposed. The correlations to mean and minimum pH values were strong, at r2 = 0.85 and 0.77, respectively. Our results confirmed a strong link between benthic diatoms and water quality, particularly acidity. By employing different approaches we demonstrated that diatoms are excellent acidity indicators. The proposed ACID index can be used to assess the acidity state of a stream. ACID is more convenient to use than a WA model for pH and has equal precision.

  • 39.
    Andrén, Cecilia
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Jarlman, Amelie
    Bentiska kiselalger som surhetsindikatorer i rinnande vatten2006Report (Other (popular scientific, debate etc.))
  • 40.
    Andrén, Cecilia
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Jarlman, Amelie
    Stream water quality and acidity classified by benthic diatoms2005In: Acid Rain 2005, Prag, Tjeckoslovakien, 12-17 juni, 2005, 2005Conference paper (Other (popular scientific, debate etc.))
  • 41.
    Andrén, Cecilia
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Kroglund, Frode
    Teien, Hans-Christian
    Controlled exposure of brown trout to a limed acid and aluminium-rich humic water2004In: SIL Lahti 8-14 augusti 2004, 2004Conference paper (Other (popular scientific, debate etc.))
  • 42.
    Andrén, Cecilia
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Kroglund, Frode
    Teien, Hans-Christian
    Controlled exposure of brown trout to a limed acid and aluminium-rich humic water2006In: Verh. Internat. Verein. Limnol., Vol. 29, p. 1548-1552Article in journal (Refereed)
  • 43. Andrén, Cecilia M.
    et al.
    Rydin, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Which aluminium fractionation method will give true inorganic monomeric Al results in fresh waters (not including colloidal Al)?2009In: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 11, no 9, p. 1639-1646Article in journal (Refereed)
    Abstract [en]

    Aluminium solubility and toxicity increase with acidification. There is no standardized analytical method for the determination of inorganic monomeric Al (Alim), which is the form that causes toxicity to fish. Separation by cation exchange is commonly combined with other analytical methods, such as complexation with pyrochatechol violet (PCV) or 8-hydroxyquinoline (HQ) and total quantification using graphite furnace or inductively-coupled plasma emission. Data from 14 laboratories were obtained for a dilution series of Alim samples; the results of the Alim analysis were statistically evaluated. The Alim levels were altered through pH, which was controlled by the addition of calcium hydroxide. Confounding parameters such as total organic carbon (TOC) or fluoride (F) were controlled. The total determination and HQ methods yielded significantly higher Alim concentrations than the PCV method. Pretreatment by passage through a 0.45 µm filter and pH-adjustment of the ion exchange column had no apparent effect on the Alim yield. However, ultra filtration (<10 kDa) caused a significant reduction in the Alim concentration using the HQ method. The ultra filtrated Alim fraction was similar to the PCV results in the interlaboratory comparison. Retention of colloidal bound Al in the cation exchange column may result in overestimation of Alim when the total and HQ methods are used. Estimated Alim concentrations derived from two equilibrium models were similar to PCV-derived Alim concentrations, as well as the HQ method using ultra filtrated water. The fact that the PCV method does not detect colloidal Al, neither before nor after ion exchange, makes this a preferred technique for Alim analysis. Because of the variability in the reported Alim concentrations that can arise when different analytical procedures are used, the adoption of a single, reliable technique will facilitate inter-study comparisons and provide consistency in the detection of trends in environmental monitoring programs.

  • 44.
    Anesio, Alexandre M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Denward, C Måns T
    Tranvik, Lars J
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Graneli, Wilhelm
    Decreased bacterial growth on vascular plant detritus due to photochemical modification1999In: AQUATIC MICROBIAL ECOLOGY, ISSN 0948-3055, Vol. 17, no 2, p. 159-165Article in journal (Refereed)
    Abstract [en]

    We investigated the effects of UV radiation on abiotic decomposition and dissolution of leaf Litter from the aquatic macrophyte Phragmites australis. Dead leaves were autoclaved and incubated in quartz tubes with autoclaved Milli-Q water, in darkness, und

  • 45.
    Anesio, Alexandre M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, Lars J
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Granéli, Wilhelm
    Production of inorganic carbon from aquatic macrophytes by solar radiation1999In: Ecology, Vol. 80, no 6, p. 1852-1859Article in journal (Refereed)
  • 46. Araújo, M.S.
    et al.
    Guimarães, P.R.
    Svanbäck, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Pinheiro, A.
    Guimarães, P.
    Dos Reis, S.F.
    Bolnick, D.I.
    Network analysis reveals contrasting effects of intraspecific competition on individual versus population diets2008In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 89, no 7, p. 1981-1993Article in journal (Refereed)
    Abstract [en]

    Optimal foraging theory predicts that individuals should become more opportunistic when intraspecific competition is high and preferred resources are scarce. This density-dependent diet shift should result in increased diet breadth for individuals as they add previously unused prey to their repertoire. As a result, the niche breadth of the population as a whole should increase. In a recent study, R. Svanback and D. I. Bolnick confirmed that intraspecific competition led to increased population diet breadth in threespine stickleback (Gasterosteus aculeatus). However, individual diet breadth did not expand as resource levels declined. Here, we present a new method based on complex network theory that moves beyond a simple measure of diet breadth, and we use the method to reexamine the stickleback experiment. This method reveals that the population as a whole added new types of prey as stickleback density was increased. However, whereas foraging theory predicts that niche expansion is achieved by individuals accepting new prey in addition to previously preferred prey, we found that a subset of individuals ceased to use their previously preferred prey, even though other members of their population continued to specialize on the original prey types. As a result, populations were subdivided into groups of ecologically similar individuals, with diet variation among groups reflecting phenotype-dependent changes in foraging behavior as prey density declined. These results are consistent with foraging theory if we assume that quantitative trait variation among consumers affects prey preferences, and if cognitive constraints prevent individuals from continuing to use their formerly preferred prey while adding new prey.

  • 47. Baker, Kate L.
    et al.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Nicol, Graeme W.
    Ricketts, Dean
    Killham, Kenneth S.
    Campell, Colin D.
    Prosser, James I.
    Environmental and spatial characterisation of microbial community composition to inform sampling strategies2009In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 41, no 11, p. 2292-2298Article in journal (Refereed)
    Abstract [en]

    Soil physicochemical properties and microbial communities are highly heterogeneous and vary widely over spatial scales, necessitating careful consideration of sampling strategies to provide representative and reproducible soil samples across field sites. To achieve this, the study aimed to establish appropriate sampling methodology and to determine links between the variability of parameters, utilising two sampling strategies. The first (design 1) involved extracting 25 cores from random locations throughout the field and pooling them into five sets of five cores. The second (design 2) involved a further 25 cores within five 1 m2 sub-plots. Sub-samples from each sub-plot were pooled in order to determine between and within sub-plot variability. All samples were analysed independently and as pooled sub-samples. Results indicate that pooling spatially separated samples significantly reduced the variability in pH, compared to individual samples. Pooling samples from a small area resulted in lower within sub-plot variability than between sub-plots for pH and bacterial community composition assessed by terminal-restriction fragment length polymorphism analysis. Following multivariate statistical analysis, a large amount of variation in community composition was explained by soil pH, which is remarkable given the relatively small size of the sampling area and minor differences in pH. Moisture content was also important in determining bacterial communities in the random design (design 1). In the 1 m2 sub-plot design (design 2), the spatial location of the plots explained a large degree of the variation in bacterial community composition between plots, which was due to spatial autocorrelation of pH and possible additional environmental parameters. This study emphasises the importance of sampling design for obtaining representative samples from soil.

  • 48. Bastviken, D
    et al.
    Cole, J
    Pace, M
    Tranvik, L
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Methane emissions from lakes: Dependence of lake characteristics, two regional assessments, and a global estimate2004In: Global Biogeochemical Cycles, Vol. 18, p. GB4009-Article in journal (Refereed)
  • 49. Bastviken, D.
    et al.
    Ejlertsson, J.
    Sundh, I.
    Tranvik, L. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Methane oxidation in lakes: Implications for methane emission and energy transfer to pelagic food webs2003In: Ecology, Vol. 84, p. 969-981Article in journal (Refereed)
  • 50. Bastviken, D.
    et al.
    Olsson, M.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Simultaneous measurements of bacterial production and organic carbon mineralization in oxic and anoxic lake sediment2003In: Microbial Ecology: Simultaneous measurement of bacterial production and organic carbon mineralization in oxic and anoxic lake sediment, Vol. 46, p. 73-82Article in journal (Refereed)
1234567 1 - 50 of 473
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf