uu.seUppsala universitets publikasjoner
Endre søk
Begrens søket
45678910 301 - 350 of 473
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 301.
    Malmaeus, J. Mikael
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft- och vattenlära. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. LUVA.
    Rydin, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft- och vattenlära. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Limnologi.
    A time-dynamic phosphorus model for profundal sediments of Lake Erken, Sweden.2006Inngår i: Aquat. Sci.,, Vol. 68, s. 16-27Artikkel i tidsskrift (Fagfellevurdert)
  • 302.
    Malmaeus, J.M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft- och vattenlära. LUVA.
    Blenckner, T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft- och vattenlära. LUVA.
    Markensten, H.
    Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft- och vattenlära. Limnologi.
    Persson, I.
    Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft- och vattenlära. Limnologi.
    Lake phosphorus dynamics and climate warming: A mechanistic model approach.2006Inngår i: Ecol. Modelling, Vol. 190, s. 1-14Artikkel i tidsskrift (Fagfellevurdert)
  • 303.
    Markensten, Hampus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Climate effects on early phytoplankton biomass over three decades modified by the morphometry in connected lake basins2006Inngår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 559, nr 1, s. 319-329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A 30-year continuous record of chlorophyll a samples in May from six locations in the Swedish Lake Mälaren was tested for the correlation to air temperature, water temperature, precipitation, discharge, nutrients, yellow substance, dissolved phosphorous load, ice cover and NAO (North Atlantic Oscillation) index. In the deep basins subjected to stratification chlorophyll a concentration correlated with air temperature with equal or shorter delay than it did in the shallow basins. Both precipitation and discharge were significant negatively correlated with chlorophyll a concentration in many of the basins with varying retention times. However, discharge into flushed basins had a more immediate influence on chlorophyll a concentration, and precipitation was earlier correlated with chlorophyll a concentration in basins fed from the smaller and closer situated catchment.

  • 304.
    Markensten, Hampus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Climate Effects on Phytoplankton Biomass and Functional Groups2005Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Future climate in temperate regions is projected to get warmer and in many cases wetter. This poses questions about how phytoplankton in our lakes will respond. A dynamic modeling approach based on an allometric description of phytoplankton characteristics was used to investigate how the biomass of different functional groups of phytoplankton will respond to a changed future climate.

    Simulations based on a warmer future climate scenario suggest that we will experience an increase in phytoplankton biomass in northern temperate lakes. Moreover, phytoplankton groups are projected to shift towards a dominance of cyanobacteria at the expense of diatoms.

    Climate may affect phytoplankton, either via in-lake changes in temperature and stratification, or due to altered processes at the watershed level, which influence rates of nutrient export and water discharge. This study found that changes in lake temperature and stratification are the major causes of the projected increase in phytoplankton biomass, but that changes in the timing of nutrient export did influence the succession of diatoms.

    Variation in SPIM (suspended particulate inorganic matter) can have an important role in influencing the depth of the euphotic zone in a turbid lake, and hence the light climate experienced by phytoplankton. Wind and river discharge were found to regulate SPIM in this study, not only wind as in many other studies. Variations in SPIM could be adequately described by a few governing equations.

    This thesis suggests that, as a result of climate change, lakes close to the limit of becoming eutrophied may be pushed past a threshold beyond which water quality problems will become more prevalent. Finally it is important to bear in mind that all models are simplifications of the reality as we understand it. Still, the use of models can often give a good indication as to what might be expected in the future.

    Delarbeid
    1. Climate effects on early phytoplankton biomass over three decades modified by the morphometry in connected lake basins
    Åpne denne publikasjonen i ny fane eller vindu >>Climate effects on early phytoplankton biomass over three decades modified by the morphometry in connected lake basins
    2006 (engelsk)Inngår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 559, nr 1, s. 319-329Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A 30-year continuous record of chlorophyll a samples in May from six locations in the Swedish Lake Mälaren was tested for the correlation to air temperature, water temperature, precipitation, discharge, nutrients, yellow substance, dissolved phosphorous load, ice cover and NAO (North Atlantic Oscillation) index. In the deep basins subjected to stratification chlorophyll a concentration correlated with air temperature with equal or shorter delay than it did in the shallow basins. Both precipitation and discharge were significant negatively correlated with chlorophyll a concentration in many of the basins with varying retention times. However, discharge into flushed basins had a more immediate influence on chlorophyll a concentration, and precipitation was earlier correlated with chlorophyll a concentration in basins fed from the smaller and closer situated catchment.

    Emneord
    climate effect, temperature, precipitation, chlorophyll a, Lake Mälaren
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-93652 (URN)10.1007/s10750-005-1526-1 (DOI)
    Tilgjengelig fra: 2005-10-28 Laget: 2005-10-28 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    2. A dynamic model for flow and wind driven sediment resuspension in a shallow basin
    Åpne denne publikasjonen i ny fane eller vindu >>A dynamic model for flow and wind driven sediment resuspension in a shallow basin
    2003 (engelsk)Inngår i: Hydrobiologia, Vol. 494, s. 305-311Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-93653 (URN)
    Tilgjengelig fra: 2005-10-28 Laget: 2005-10-28 Sist oppdatert: 2009-03-30bibliografisk kontrollert
    3. Long and short term variations in suspended particulate material: the influence on light available to the phytoplankton community
    Åpne denne publikasjonen i ny fane eller vindu >>Long and short term variations in suspended particulate material: the influence on light available to the phytoplankton community
    2003 (engelsk)Inngår i: Hydrobiologia, Vol. 494, s. 299-304Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-93654 (URN)
    Tilgjengelig fra: 2005-10-28 Laget: 2005-10-28 Sist oppdatert: 2009-03-30bibliografisk kontrollert
    4. Weather driven influences on phytoplankton succession in a shallow lake during contrasting years: Application of PROTBAS
    Åpne denne publikasjonen i ny fane eller vindu >>Weather driven influences on phytoplankton succession in a shallow lake during contrasting years: Application of PROTBAS
    2007 (engelsk)Inngår i: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 207, nr 2-4, s. 128-136Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A dynamic model which simulates variations in the biomass of several phytoplankton functional groups (PROTECH) has been reconstructed into the PROTBAS (PROTech Based Algal Simulations) model, and was tested in a large (61 km(2)), shallow (mean depth 3.4 m) windexposed lake basin at the western end of Lake Malaren, Sweden. A subroutine was added to the model to estimate the variation in light extinction resulting from wind action and river discharge. Also the rate of regeneration of nitrogen and silica was modified. The model captured the overall magnitude and succession of phytoplankton during two contrasting years: a warm and calm calibration year, and a cold windy validation year. The model shows good behavior in the northern temperate climate, which includes ice cover during winter. However, there were discrepancies between measured and modeled spring growth and autumn decline of the phytoplankton.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-93655 (URN)10.1016/j.ecolmodel.2007.04.023 (DOI)000250167800005 ()
    Tilgjengelig fra: 2005-10-28 Laget: 2005-10-28 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    5. Lake phytoplankton response to a future climate scenario – a model approach
    Åpne denne publikasjonen i ny fane eller vindu >>Lake phytoplankton response to a future climate scenario – a model approach
    (engelsk)Manuskript (Annet (populærvitenskap, debatt, mm))
    Identifikatorer
    urn:nbn:se:uu:diva-93656 (URN)
    Tilgjengelig fra: 2005-10-28 Laget: 2005-10-28 Sist oppdatert: 2010-01-14bibliografisk kontrollert
  • 305.
    Markensten, Hampus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Moore, Karen
    Persson, Irina
    Lake phytoplankton response to a future climate scenario – a model approachManuskript (Annet (populærvitenskap, debatt, mm))
  • 306.
    Markensten, Hampus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Moore, Karen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Persson, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Simulated lake phytoplankton composition shifts toward cyanobacteria dominance in a future warmer climate2010Inngår i: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 20, nr 3, s. 752-767Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The climate is expected to become warmer and wetter in many temperate regions and is expected to affect the water quality in lakes and reservoirs. In this paper, we investigate the impacts of a regional climate scenario on lake productivity using three models in sequence and quantify the response in biomass of three phytoplankton groups. We used a watershed model (GWLE), a physical lake model (PROBE), and a phytoplankton model (PROTBAS) for simulations of a large (61 km(2)), shallow (mean depth 3.4 m), wind-exposed lake basin with a short water retention time (1 month) at the western end of Lake Malaren, Sweden. The results suggest that a future scenario with increased warming leads to a longer growing season for phytoplankton, slightly increased levels of total biomass, and a distinct shift in phytoplankton groups to favor nitrogen-fixing cyanobacteria at the expense of diatoms in this lake basin. The changes in the timing of nutrient export from the catchment are the primary cause of cyanobacteria dominance over diatoms, and elevated lake temperatures are responsible for the increase in total phytoplankton biomass.

  • 307.
    Markensten, Hampus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Pierson, Donald
    A dynamic model for flow and wind driven sediment resuspension in a shallow basin2003Inngår i: Hydrobiologia, Vol. 494, s. 305-311Artikkel i tidsskrift (Fagfellevurdert)
  • 308.
    Markensten, Hampus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Limnologi.
    Pierson, Donald C.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Limnologi.
    A dynamic model for flow and wind driven sediment resuspension in a shallow basin2003Inngår i: Hydrobiologia, Vol. 494, s. 1-3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model is presented, which describes the daily variations in suspended particulate inorganic matter (SPIM) in a large (61 km2), shallow (mean depth 3.4 m) wind-exposed lake basin at the western end of Lake Mälaren, Sweden. Field studies have shown that wind speed and river inflow are the two major factors leading to changes in SPIM. Wind speed and beam attenuation were measured at high (10 min) frequency, while river inflow were monitored at daily frequency to develop the model. From these field measurements, model-coefficients were determined for the SPIM transport, settling and resuspension. Large-scale variations in SPIM lasting many weeks could be explained by events of high river inflow with a correspondingly high particle load. The threshold for river transported SPIM to have effect on lake concentration was 150 m3 s-1, while wind induced resuspended SPIM was related to the square root of wind speed.

  • 309.
    Markensten, Hampus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Pierson, Donald C.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Weather driven influences on phytoplankton succession in a shallow lake during contrasting years: Application of PROTBAS2007Inngår i: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 207, nr 2-4, s. 128-136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A dynamic model which simulates variations in the biomass of several phytoplankton functional groups (PROTECH) has been reconstructed into the PROTBAS (PROTech Based Algal Simulations) model, and was tested in a large (61 km(2)), shallow (mean depth 3.4 m) windexposed lake basin at the western end of Lake Malaren, Sweden. A subroutine was added to the model to estimate the variation in light extinction resulting from wind action and river discharge. Also the rate of regeneration of nitrogen and silica was modified. The model captured the overall magnitude and succession of phytoplankton during two contrasting years: a warm and calm calibration year, and a cold windy validation year. The model shows good behavior in the northern temperate climate, which includes ice cover during winter. However, there were discrepancies between measured and modeled spring growth and autumn decline of the phytoplankton.

  • 310. Matrai, P.A.
    et al.
    Tranvik, L.J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Leck, C.
    Knulst, J.C.
    Are high Arctic surface microlayers a potential source of aerosol organic precursors?2008Inngår i: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 108, nr 1-2, s. 109-122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Particulate organic matter, including microorganisms, small water-insoluble particles and microaggregates, can form a substantial part of the summer aerosol over the open leads of the central Arctic Ocean. The increased presence of leads during the summer melt increases the biological activity of the region possibly resulting in accumulation of organic material, especially in the surface microlayer. Preferential microlayer enrichment of particulate and dissolved organic matter and gases might be reflected in derived aerosols. The subsurface seawater and microlayer concentrations were determined for dimethyl sulfide (DMS) and its biogenic precursor dimethylsulfoniopropionate (DMSP), dissolved combined amino acids (DCAA) and individual aminoacids, proteins, chlorophyll a (chl a) and bacterial cells as well as bacterial production. Enrichment factors and surface excess concentrations in the surface microlayer were calculated. Concentrations of particulate and dissolved DMSP, chl a-containing material, and bacterial cells were consistently enriched in arctic lead microlayers at 89°N in August 2001. DMS, protein and DCAA concentrations, however, were not in excess in surface microlayers, although proteins were occasionally enriched. The average mole % DCAA composition was similar in subsurface and microlayer water. Enrichment spikes and excess concentrations followed freezing events and did not co-occur with enhanced bacterial production.

  • 311.
    Meili, M
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Hylander, L D
    Human exposure to mercury from fish consumption in Latin America and Africa: effects of mercury-selenium interactions on mercury methylation rates in tropical waters.2002Inngår i: Co-ordinated Research Project (CRP) on Application of isotopic nuclear techniques in the study of nutrition-pollution interactions and their impact on the nutritional status of human subjects in developing country populations. Report on the First Research, 2002, s. 83-89Konferansepaper (Annet vitenskapelig)
  • 312. Metsamaa, Liisa
    et al.
    Kutser, Tilt
    Strömbeck, Niklas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Recognising cyanobacterial blooms based on their optical signature: a modelling study2006Inngår i: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 11, nr 6, s. 493-506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mass populations of cyanobacteria are increasingly attracting the attention of environment agencies, water authorities, and human and animal health organizations, since they can present a range of water quality and treatment problems as well as hazards to human and animal health. The problem is especially severe in the Baltic Sea where cyanobacterial blooms occur every summer covering areas of more than 100 000 km(2). We studied optical properties of several phytoplankton species (including cyanobacteria) present in the Baltic Sea region. The measurements results were used in a bio-optical model together with optical properties of other phytoplankton species from literature. Our results show that cyanobacteria have a characteristic double feature (peak at 650 nm and phycocyanin absorption feature near 630 nm) in their reflectance spectra which can be detected by remote sensing instruments. Our estimation for the open Baltic Sea waters shows that concentration of chlorophyll has to be 8-10 mg m(-3) before the double feature becomes detectable by remote sensing instruments which spectral resolution is 10 nm and signal-to-noise-ratio is 1000:1. Therefore, it is highly unlikely that remote sensing can be used for early warning of emerging potentially harmful blooms as chlorophyll concentrations higher than 4 mg m(-3) qualify as blooms here.

  • 313.
    Mille-Lindblom, C.,
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för evolutionsbiologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Tranvik, L. J.
    Antagonism between bacteria and fungi on decomposing aquatic plant litter2003Inngår i: Microbial Ecology, Vol. 45, s. 173-182Artikkel i tidsskrift (Fagfellevurdert)
  • 314.
    Mille-Lindblom, Cecilia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Fischer, Helmut
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Tranvik, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Antagonism between bacteria and fungi: substrate competition and a possible tradeoff between fungal growth and tolerance towards bacteria2006Inngår i: Oikos, Vol. 113, nr 2, s. 233-242Artikkel i tidsskrift (Fagfellevurdert)
  • 315.
    Mille-Lindblom, Cecilia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Fischer, Helmut
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Tranvik, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Litter-associated bacteria and fungi - a comparison of biomass and communities across lakes and plant species2006Inngår i: Freshwater biology, Vol. 51, nr 4, s. 730-741Artikkel i tidsskrift (Fagfellevurdert)
  • 316.
    Mille-Lindblom, Cecilia
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Limnologi.
    von Wachenfeldt, Eddie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Limnologi.
    Tranvik, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Limnologi.
    Ergosterol as a measure of living fungal biomass: persistence in environmental samples after fungal death2004Inngår i: Journal of Microbiological Methods, Vol. 59, nr 2, s. 253-262Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The membrane lipid ergosterol is found almost exclusively in fungi, and is frequently used by environmental microbiologists as an indicator of living fungal biomass, based on the assumption that ergosterol is labile, and therefore rapidly degraded after the death of fungal hyphae. We studied the degradation of ergosterol in environmental samples without living fungi. Under the conditions used in this study, ergosterol was very stable both when added as a pure compound and when associated with dead fungi. The decrease of ergosterol was at most 34% during 2 months when protected from sunlight. Presence of a natural bacterial assemblage did not enhance degradation over this time period, as compared to sterile controls. However, photochemical degradation was significant, and led to a 43% decrease of in ergosterol content during 24 h. These results suggest that ergosterol should be used cautiously as a biomarker for living fungi.

  • 317. Molau, Ulf
    et al.
    Kling, J.
    Lindblad, Karin
    Björk, Robert
    Dänhardt, Juliana
    Liess, Antonia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    A GIS assessment of alpine biodiversity at a range of scales2003Inngår i: Alpine Biodiversity in Europe: Ecological Studies, vol 167, Springer-Verlag, Berlin. , 2003Kapittel i bok, del av antologi (Fagfellevurdert)
  • 318.
    Moore, Karen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Climate Change Impacts on the Catchment Contribution to Lake Water Quantity and Quality2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A key question related to climate change projections is how will aquatic systems respond to changes in variables such as temperature and precipitation? This thesis uses GWLF, a simple catchment scale model to explore potential impacts of climate change on water quantity and quality.

    River discharge and nutrient loads were modelled for several warmer world scenarios. For one catchment in New York, USA changes in annual dissolved phosphorus loads decreased along with annual streamflow, and particulate phosphorus loads increased for a single future climate scenario. For the Galten catchment of Lake Mälaren, Sweden, the spring melt peak observed historically was reduced for six future scenarios. Peak runoff and dissolved phosphorus and nitrogen load maxima occurred in winter rather than early spring.

    A synthesis of model results for dissolved inorganic nitrogen (DIN) loadings for five European catchments showed changes in the timing and magnitude of peak DIN load for several future scenarios. In northern Europe, changes were largely due to increased winter streamflow and reduced snow pack and spring melt runoff. In western Europe, DIN loads increased in winter or early spring due to increased precipitation.

    The biological response for a warmer future scenario was modelled for the Galten basin of Lake Mälaren using GWLF coupled to a lake phytoplankton model and a physical lake model. An increase in cyanobacteria biomass accompanied by a decline in diatom biomass resulted from changes in the timing of nutrient export from the catchment. The projected increase in lake temperature favored an overall increase in total phytoplankton biomass.

    Lastly, a method based on hourly measurements of colored dissolved organic matter (CDOM) fluorescence provides the appropriate data for dissolved organic carbon (DOC) model parameterization and may also be used for surveillance of organic matter inputs to lakes.

    Delarbeid
    1. Impacts of projected climate change on phosphorus and sediment loadings for a New York City water supply reservoir
    Åpne denne publikasjonen i ny fane eller vindu >>Impacts of projected climate change on phosphorus and sediment loadings for a New York City water supply reservoir
    Vise andre…
    2006 Inngår i: Verh. Internat. Verein. Limnol., Vol. 29, s. 1829-1832Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-96262 (URN)
    Tilgjengelig fra: 2007-10-04 Laget: 2007-10-04bibliografisk kontrollert
    2. Effects of Warmer World Scenarios on Hydrologic Inputs to Lake Mälaren, Sweden and Implications for Nutrient Loads
    Åpne denne publikasjonen i ny fane eller vindu >>Effects of Warmer World Scenarios on Hydrologic Inputs to Lake Mälaren, Sweden and Implications for Nutrient Loads
    Vise andre…
    2008 (engelsk)Inngår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 599, s. 191-199Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A simple, rapid, and flexible modelling approach was applied to explore the impacts of climate change on hydrologic inputs and consequent implications for nutrient loading to Lake Malaren, Sweden using a loading function model (GWLF). The first step in the process was to adapt the model for use in a large and complex Swedish catchment. We focused on the Galten basin with four rivers draining into the western region of Malaren. The catchment model was calibrated and tested using long-term historical data for river discharge and dissolved nutrients (N, P). Then multiple regional climate model simulation results were downscaled to the local catchment level, and used to simulate possible hydrological and nutrient loading responses to warmer world scenarios. Climate change projections for the rivers of Galten basin show profound changes in the timing of discharge and nutrient delivery due to increased winter precipitation and earlier snow melt. Impacts on total annual discharge and load are minimal, but the alteration in river flow regime and the timing of nutrient delivery for future climate scenarios is strikingly different from historical conditions.

    Emneord
    catchment modeling, hydrologic transport, nutrient loading, climate impact assessment
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-96263 (URN)10.1007/s10750-007-9197-8 (DOI)000252890800024 ()
    Tilgjengelig fra: 2007-10-04 Laget: 2007-10-04 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    3. Lake phytoplankton response to a future climate scenario
    Åpne denne publikasjonen i ny fane eller vindu >>Lake phytoplankton response to a future climate scenario
    Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Identifikatorer
    urn:nbn:se:uu:diva-96264 (URN)
    Tilgjengelig fra: 2007-10-04 Laget: 2007-10-04bibliografisk kontrollert
    4. Modelling the Effects of Climate Change on Inorganic Nitrogen Transport from Catchments to Lakes
    Åpne denne publikasjonen i ny fane eller vindu >>Modelling the Effects of Climate Change on Inorganic Nitrogen Transport from Catchments to Lakes
    Vise andre…
    Manuskript (Annet vitenskapelig)
    Identifikatorer
    urn:nbn:se:uu:diva-96265 (URN)
    Tilgjengelig fra: 2007-10-04 Laget: 2007-10-04 Sist oppdatert: 2010-01-13bibliografisk kontrollert
    5. High-frequency monitoring of colored dissolved organic matter (CDOM) fluorescence in the Swedish river Hedströmmen
    Åpne denne publikasjonen i ny fane eller vindu >>High-frequency monitoring of colored dissolved organic matter (CDOM) fluorescence in the Swedish river Hedströmmen
    Manuskript (Annet vitenskapelig)
    Identifikatorer
    urn:nbn:se:uu:diva-96266 (URN)
    Tilgjengelig fra: 2007-10-04 Laget: 2007-10-04 Sist oppdatert: 2014-01-16
  • 319.
    Moore, Karen
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Pierson, Donald
    Pettersson, Kurt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Schneiderman, Elliot
    Samuelsson, Patrick
    Effects of Warmer World Scenarios on Hydrologic Inputs to Lake Mälaren, Sweden and Implications for Nutrient Loads2008Inngår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 599, s. 191-199Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple, rapid, and flexible modelling approach was applied to explore the impacts of climate change on hydrologic inputs and consequent implications for nutrient loading to Lake Malaren, Sweden using a loading function model (GWLF). The first step in the process was to adapt the model for use in a large and complex Swedish catchment. We focused on the Galten basin with four rivers draining into the western region of Malaren. The catchment model was calibrated and tested using long-term historical data for river discharge and dissolved nutrients (N, P). Then multiple regional climate model simulation results were downscaled to the local catchment level, and used to simulate possible hydrological and nutrient loading responses to warmer world scenarios. Climate change projections for the rivers of Galten basin show profound changes in the timing of discharge and nutrient delivery due to increased winter precipitation and earlier snow melt. Impacts on total annual discharge and load are minimal, but the alteration in river flow regime and the timing of nutrient delivery for future climate scenarios is strikingly different from historical conditions.

  • 320.
    Moore, Karen
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Rosenzweig, Cynthia
    Goldberg, Richard
    Pierson, Donald
    Pettersson, Kurt
    Schneiderman, Elliot
    Zion, Mark
    Impacts of projected climate change on phosphorus and sediment loadings for a New York City water supply reservoir.2006Inngår i: Verh. Internat. Verein. Limnol., Vol. 29, s. 1829-1832Artikkel i tidsskrift (Fagfellevurdert)
  • 321.
    Naddafi, R., R.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Abdoli,, A.
    Kiabi,, B.H.
    Amiri,, B.M.
    Karami, M.
    Age, growth and reproduction of the Caspian roach, Rutilus rutilus caspicus, in Gomishan and Anzali wetlands, North Iran.2005Inngår i: Journal of Applied Ichthyology, Vol. 21, s. 492-497Artikkel i tidsskrift (Fagfellevurdert)
  • 322.
    Naddafi, Rahmat
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    The Invasion of the Zebra Mussel - Effects on Phytoplankton Community Structure and Ecosystem Function2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Biological invasion has become a major threat to economy, ecology, global biodiversity and ecosystem function of aquatic ecosystems. The main aim of the thesis was to study the effects of the zebra mussel (Dreissena polymorpha), a versatile invasive species, on phytoplankton dynamics and ecosystem function of lakes.

    In a first attempt, I compared the density of Dreissena and the physicochemical data of ecosystems that it invaded among North American and European lakes to identify important factors in its invasion success. Secondly, I investigated the impact of zebra mussels on phytoplankton community composition in a natural lake. Thirdly, I evaluated whether zebra mussel feeding behavior were affected by the presence of predatory waterborne cues. Finally, I examined the effect of Dreissena on seston stoichiometry.

    A Generalized Additive Model revealed that a joint effect of surface area, mean depth, total phosphorus and calcium concentrations can explain the variability in Dreissena density. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics. Risk cues released by predators affected both feeding rate and prey selection of the mussels and had cascading indirect effects on phytoplankton biomass and community structure. I found that the flux in nutrients caused by differences in zebra mussel consumption lead to a variation in phytoplankton nutrient limitation.

    The flexibility of zebra mussel feeding behavior and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences. The results of this thesis contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. The results suggested that zebra mussel can indirectly both reduce and increase the energy transfer efficiency from primary producers to upper trophic levels in the pelagic and benthic food webs, respectively.

    Delarbeid
    1. Why is an invasive species more successful in some areas than others? A comparison of zebra mussel density in North American and European lakes
    Åpne denne publikasjonen i ny fane eller vindu >>Why is an invasive species more successful in some areas than others? A comparison of zebra mussel density in North American and European lakes
    Inngår i: Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Identifikatorer
    urn:nbn:se:uu:diva-96405 (URN)
    Tilgjengelig fra: 2007-11-14 Laget: 2007-11-14 Sist oppdatert: 2014-01-16
    2. The effect of seasonal variation in selective feeding by zebra mussels (Dreissena polymorpha) on phytoplankton community composition
    Åpne denne publikasjonen i ny fane eller vindu >>The effect of seasonal variation in selective feeding by zebra mussels (Dreissena polymorpha) on phytoplankton community composition
    2007 (engelsk)Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 52, nr 5, s. 823-842Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    To investigate the impact of zebra mussels (Dreissena polymorpha) on phytoplankton community composition, temporal variability in selective feeding by the mussels was determined from April to November 2005 in a natural lake using Delayed Fluorescence (DF) excitation spectroscopy. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics; mussels showed a consistent preference for cryptophytes and avoidance of chlorophytes and cyanobacteria. Diatoms, chrysophytes and dinoflagellates responded differentially to zebra mussel grazing depending on their size. Analysis of excreted products of the zebra mussels revealed that in addition to chlorophytes and cyanobacteria, phytoplankton >50 μm and very small phytoplankton (≤7 μm) were largely expelled in pseudofaeces. The zebra mussel is a selective filter-feeder that alters its feeding behaviour in relation to phytoplankton composition to capture and ingest high quality phytoplankton, especially when phytoplankton occur in preferred size ranges. Flexibility of zebra mussel feeding behaviour and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences.

    Emneord
    Delayed Fluorescence, Lake Erken, phytoplankton dynamics, selective feeding, Zebra mussel
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-96406 (URN)10.1111/j.1365-2427.2007.01732.x (DOI)000245987200005 ()
    Tilgjengelig fra: 2007-11-14 Laget: 2007-11-14 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    3. Non-lethal predator effects on the feeding rate and prey selection of the exotic zebra mussel (Dreissena polymorpha)
    Åpne denne publikasjonen i ny fane eller vindu >>Non-lethal predator effects on the feeding rate and prey selection of the exotic zebra mussel (Dreissena polymorpha)
    2007 (engelsk)Inngår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 116, nr 8, s. 1289-1298Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Predators may induce changes in prey feeding that indirectly influence both the impact of prey on resource abundances and their interactions with other species in their community. We evaluated whether clearance and excretion (faeces plus pseudofaeces) of phytoplankton by zebra mussels were affected by the presence of predatory cues from roach (Rutilus rutilus) and signal crayfish (Pasifastacus leniusculus). We found that non-lethal effects of predators can alter zebra mussel clearance rate and thus the impact of zebra mussels on phytoplankton. Risk cues released by both predators had similar negative effects on clearance rate of zebra mussels and cascading positive indirect effects on phytoplankton resources. Predation risk had a stronger effect on zebra mussels' clearance rate of cyanobacteria and diatoms than cryptophytes and chrysophytes. The presence of predators did not significantly affect the rate at which zebra mussels expelled and excreted phytoplankton, although there was a tendency for more chlorophyll to be expelled and excreted in the presence of predators. Our results contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. Our results suggest that exotic species such as zebra mussels can show behavioural responses to both native (e.g., roach) and exotic (e.g., crayfish) predators.

    Emneord
    Non-lethal effect of predator, Invasive species, Zebra mussel, Feeding rate, Prey selection, Trait-mediated indirect interaction, Phytoplankton community structure, Ecosystem function
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-96407 (URN)10.1111/j.2007.0030-1299.15695.x (DOI)000248681100004 ()
    Tilgjengelig fra: 2007-11-14 Laget: 2007-11-14 Sist oppdatert: 2017-12-14
    4. Effect of zebra mussel , an exotic freshwater species, on seston stoichiometry
    Åpne denne publikasjonen i ny fane eller vindu >>Effect of zebra mussel , an exotic freshwater species, on seston stoichiometry
    2008 (engelsk)Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590Artikkel i tidsskrift (Fagfellevurdert) Submitted
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-96408 (URN)
    Tilgjengelig fra: 2007-11-14 Laget: 2007-11-14 Sist oppdatert: 2017-12-14
  • 323.
    Naddafi, Rahmat
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Eklöv, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Pettersson, Kurt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Non-lethal predator effects on the feeding rate and prey selection of the exotic zebra mussel (Dreissena polymorpha)2007Inngår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 116, nr 8, s. 1289-1298Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Predators may induce changes in prey feeding that indirectly influence both the impact of prey on resource abundances and their interactions with other species in their community. We evaluated whether clearance and excretion (faeces plus pseudofaeces) of phytoplankton by zebra mussels were affected by the presence of predatory cues from roach (Rutilus rutilus) and signal crayfish (Pasifastacus leniusculus). We found that non-lethal effects of predators can alter zebra mussel clearance rate and thus the impact of zebra mussels on phytoplankton. Risk cues released by both predators had similar negative effects on clearance rate of zebra mussels and cascading positive indirect effects on phytoplankton resources. Predation risk had a stronger effect on zebra mussels' clearance rate of cyanobacteria and diatoms than cryptophytes and chrysophytes. The presence of predators did not significantly affect the rate at which zebra mussels expelled and excreted phytoplankton, although there was a tendency for more chlorophyll to be expelled and excreted in the presence of predators. Our results contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. Our results suggest that exotic species such as zebra mussels can show behavioural responses to both native (e.g., roach) and exotic (e.g., crayfish) predators.

  • 324.
    Naddafi, Rahmat
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Eklöv, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Pettersson, Kurt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Stoichiometric constraints do not limit successful invaders: zebra mussels in Swedish lakes2009Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 4, nr 4, s. e5345-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Elemental imbalances of carbon (C): nitrogen (N): phosphorus (P) ratios in food resources can constrain the growth of grazers owning to tight coupling between growth rate, RNA allocation and biomass P content in animals. Testing for stoichiometric constraints among invasive species is a novel challenge in invasion ecology to unravel how a successful invader tackles ecological barriers in novel ecosystems.Methodology/Principal Findings: We examined the C:P and N:P ratios and the condition factor of a successful invader in lakes, the zebra mussel (Dreissena polymorpha), collected from two Swedish lakes. Concurrently, we analyzed the elemental composition of the food (seston) and tissue of the mussels in which nutrient composition of food and mussels varied over time. Zebra mussel condition factor was weakly related to the their own tissue N:P and C:P ratios, although the relation with the later ratio was not significant. Smaller mussels had relatively lower tissue N:P ratio and higher condition factor. There was no difference in C:P and N:P ratios between seston and mussels' tissues. Our results indicated that the variation in nutrient stoichiometry of zebra mussels can be explained by food quality and quantity. Conclusions/Significance: Our study suggests that fitness of invasive zebra mussels is not constrained by nutrient stoichiometry which is likely to be important for their proliferation in novel ecosystems. The lack of imbalance in C:P and N:P ratios between seston and mussels along with high tissue C:P ratio of the mussel allow them to tolerate potential P limitation and maintain high growth rate. Moreover, zebra mussels are able to change their tissue C:P and N:P ratios in response to the variation in elemental composition of their food. This can also help them to bypass potential nutrient stoichiometric constraints. Our finding is an important step towards understanding the mechanisms contributing to the success of exotic species from stoichiometric principles.

  • 325.
    Naddafi, Rahmat
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Pettersson, Kurt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Eklöv, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Effects of the zebra mussel, an exotic freshwater species, on seston stoichiometry2008Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 53, nr 5, s. 1973-1987Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We examined the effect of the zebra mussel, Dreissena polymorpha, an exotic species, on seston stoichiometry by conducting laboratory experiments in which we varied nutrient composition of seston and mussels over time. Zebra mussels altered the stoichiometry of seston through removal of particulate organic nutrients and changed the stoichiometry of the dissolved nutrient pool through nutrient excretion. Grazers had stronger effects on carbon : phosphorus (C : P) and nitrogen (N) : P ratios than on the C:N ratio of seston. Elemental residence time in tissue and high mass-specific nutrient excretion by small mussels caused small mussels to be more efficient nutrient recyclers than larger mussels. Zebra mussels reduced P availability through enhancing C: P and N: P molar ratios of seston during the period extending from June to August, when P was limited in the lake, and increased the C:N molar ratio of seston in June, when N was at the minimum level in the lake. C: P and N: P molar ratios for zebra mussel tissue were higher in August and somewhat in September than in all other months. N was retained more efficiently than P in Dreissena tissue. Nutrient mass-specific uptake rate was higher than excretion rate by zebra mussels.

  • 326.
    Naddafi, Rahmat
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Pettersson, Kurt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Eklöv, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    The effect of seasonal variation in selective feeding by zebra mussels (Dreissena polymorpha) on phytoplankton community composition2007Inngår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 52, nr 5, s. 823-842Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To investigate the impact of zebra mussels (Dreissena polymorpha) on phytoplankton community composition, temporal variability in selective feeding by the mussels was determined from April to November 2005 in a natural lake using Delayed Fluorescence (DF) excitation spectroscopy. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics; mussels showed a consistent preference for cryptophytes and avoidance of chlorophytes and cyanobacteria. Diatoms, chrysophytes and dinoflagellates responded differentially to zebra mussel grazing depending on their size. Analysis of excreted products of the zebra mussels revealed that in addition to chlorophytes and cyanobacteria, phytoplankton >50 μm and very small phytoplankton (≤7 μm) were largely expelled in pseudofaeces. The zebra mussel is a selective filter-feeder that alters its feeding behaviour in relation to phytoplankton composition to capture and ingest high quality phytoplankton, especially when phytoplankton occur in preferred size ranges. Flexibility of zebra mussel feeding behaviour and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences.

  • 327. Olli, Kalle
    et al.
    Wassmann, Paul
    Reigstad, Marit
    Ratkova, Tatjana N.
    Arashkevich, Elena
    Pasternak, Anna
    Matrai, Patricia A.
    Knulst, Johan
    Tranvik, Lars J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Klais, Riina
    Jacobsen, A.
    The fate of production in the central Arctic ocean - top-down regulation by zooplankton expatriates?2007Inngår i: Progress in Oceanography, ISSN 0079-6611, E-ISSN 1873-4472, Vol. 72, nr 1, s. 84-113Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    We estimated primary and bacterial production, mineral nutrients, suspended chlorophyll a (Chl), particulate organic carbon (POC) and nitrogen (PON), abundance of planktonic organisms, mesozooplankton fecal pellet production, and the vertical flux of organic particles of the central Arctic Ocean (Amundsen basin, 89 88° N) during a 3 week quasi-Lagrangian ice drift experiment at the peak of the productive season (August 2001). A visual estimate of ≈15% ice-free surface, plus numerous melt ponds on ice sheets, supported a planktonic particulate primary production of 50 150 mg C m‑2 d‑1 (mean 93 mg C m‑2 d‑1, n = 7), mostly confined to the upper 10 m of the nutrient replete water column. The surface mixed layer was separated from the rest of the water column by a strong halocline at 20 m depth. Phototrophic biomass was low, generally 0.03 0.3 mg Chl m‑3 in the upper 20 m and <0.02 mg Chl m‑3 below, dominated by various flagellates, dinoflagellates and diatoms. Bacterial abundance (typically 3.7 5.3 × 105, mean 4.1 × 105 cells ml‑1 in the upper 20 m and 1.3 3.7 × 105, mean 1.9 × 105 cells ml‑1 below) and Chl concentrations were closely correlated (r = 0.75). Mineral nutrients (3 μmol NO3 l‑1, 0.45 μmol PO4 l‑1, 4 5 μmol SiO4 l‑1) were probably not limiting the primary production in the upper layer. Suspended POC concentration was ˜30 105 (mean 53) mg C m‑3 and PON ˜5.4 14.9 (mean 8.2) mg N m‑3 with no clear vertical trend. The vertical flux of POC in the upper 30 100 m water column was ˜37 92 (mean 55) mg C m‑2 d‑1 without clear decrease with depth, and was quite similar at the six investigated stations. The mesozooplankton biomass (≈2 g DW m‑2, mostly in the upper 50 m water column) was dominated by adult females of the large calanoid copepods Calanus hyperboreus and Calanus glacialis (≈1.6 g DW m‑2). The grazing of these copepods (estimated via fecal pellet production rates) was ≈15 mg C m‑2 d‑1, being on the order of 3% and 20% of the expected food-saturated ingestion rates of C. hyperboreus and C. glacialis, respectively. The stage structure of these copepods, dominated by adult females, and their unsatisfied grazing capacity during peak productive period suggest allochthonous origin of these species from productive shelf areas, supported by their long life span and the prevailing surface currents in the Arctic Ocean. We propose that the grazing capacity of the expatriated mesozooplankton population would match the potential seasonal increase of primary production in the future decreased ice perspective, diminishing the likelihood of algal blooms.

  • 328.
    Olsson, J.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Eklöv, P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Effects of habitat specific structure and feeding mode on phenotypic plasticity in Eurasian perch, Perca fluviatilis.2005Inngår i: Evolutionary Ecology Research, Vol. 7, s. 1109-1123.Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 329.
    Olsson, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Interplay Between Environment and Genes on Morphological Variation in Perch – Implications for Resource Polymorphisms2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Recent research has suggested that individual specialization within populations could be substantial and more common than previously acknowledged. Eurasian perch is one of many species of fish in lakes of postglacial origin that displays a morphological and dietary variation tightly coupled to the littoral and pelagic habitats of the lake. The occurrence of such resource polymorphisms might have important consequences for local adaptation and might also be an important initial step in speciation.

    I have investigated the importance of a number of factors for the development of resource polymorphisms using perch as a study organism. I found a weak genetic basis for morphological differences, and the environmental influence on morphology was of such a magnitude that an induced morphology could be reversed. The results nevertheless suggested that genetic differentiation could be substantial at small spatial and temporal scales, even within habitats. Several environmental factors were shown to influence the morphological development, and the results also suggest that behavioral differences could mediate a morphological response. I also found evidence for that competition-driven divergence might only occur when divergence in resource use is favoured at the same time as growth rates are kept sufficiently high for character divergence to be effective. The results finally indicate that divergence in the gut length of individuals might co-vary with habitat and diet use in resource polymorphic populations. This might enhance habitat fidelity and possibly also facilitate the persistence of resource polymorphisms since individuals should experience a cost of switching diets due to a too specific digestive system.

    Based on these findings I conclude that small scaled genetic differentiation might be more common than currently acknowledged, that more multi-factorial studies are needed if we are to fully understand the mechanisms behind trait diversity, and that competition not always favors divergence.

    Delarbeid
    1. Habitat structure, feeding mode and morphological reversibility: factors influencing phenotypic plasticity in perch
    Åpne denne publikasjonen i ny fane eller vindu >>Habitat structure, feeding mode and morphological reversibility: factors influencing phenotypic plasticity in perch
    2005 (engelsk)Inngår i: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 7, nr 8, s. 1109-1123Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Questions: Do both habitat structure and feeding mode contribute to morphological divergence within fish populations? To what extent may an induced morphology be reversed?

    Organism: Young-of-the-year Eurasian perch (Perca fluviatilis L.).

    Methods: An aquarium experiment with a 2 × 2 factorial design (two levels of habitat structure and two levels of feeding mode). The habitat structure and feeding mode were reversed for perch in two habitat treatments midway through the experiment.

    Results: Both habitat structure and feeding mode contributed to morphological divergence (40.7% and 4.9% of the total variation respectively), which suggests that both habitat complexity and prey type diversity influence morphological adaptations in this fish species. Perch morphology is highly plastic and can be reversed in as short a time as 4 weeks.

     

    Emneord
    feeding mode, geometric morphometrics, habitat structure, morphological reversibility, phenotypic plasticity, trophic polymorphism
    Identifikatorer
    urn:nbn:se:uu:diva-88665 (URN)
    Tilgjengelig fra: 2009-02-06 Laget: 2009-02-04 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    2. Small scale genetic and morphological differentiation in sympatric Eurasian perch
    Åpne denne publikasjonen i ny fane eller vindu >>Small scale genetic and morphological differentiation in sympatric Eurasian perch
    (engelsk)Manuskript (Annet (populærvitenskap, debatt, mm))
    Identifikatorer
    urn:nbn:se:uu:diva-95047 (URN)
    Tilgjengelig fra: 2006-11-07 Laget: 2006-11-07 Sist oppdatert: 2010-01-14bibliografisk kontrollert
    3. Effects of resource level and habitat type on behavioural and morphological plasticity in Eurasian perch
    Åpne denne publikasjonen i ny fane eller vindu >>Effects of resource level and habitat type on behavioural and morphological plasticity in Eurasian perch
    2007 (engelsk)Inngår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 152, nr 1, s. 48-56Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Spatial and temporal heterogeneity in the environment is a common feature affecting many natural populations. For example, both the resource levels and optimal habitat choices of individuals likely change over time. One way for organisms to cope with environmental variation is to display adaptive plasticity in traits such as behavior and morphology. Since trait plasticity is hypothesized to be a prerequisite for character divergence, studies of mechanisms behind such plasticity are warranted. In this study, we looked at the interaction of two potentially important environmental variables on behavioral and morphological plasticity in Eurasian perch (Perca fluviatilis L.). More specifically, the plastic responses in activity and morphology of perch exposed to different resource levels and simulated habitat types were studied in an aquarium experiment. The resource level experienced had a large influence on plasticity in both activity and morphology. Behavioral adaptations have been thought to mediate morphological transitions, and we suggest that the morphological response to the resource level was mediated by differences in activity and growth rates. The habitat type also affected morphological plasticity but to a lesser extent, and there was no effect on activity from habitat type. Based on these results, we suggest that it is essential to include several environmental factors acting in concert when studying mechanisms behind trait plasticity. We also propose that variation in resource levels might play a key role in fostering trait plasticity in at least fish populations, while other environmental variables such as divergent habitat complexities and prey types might be less influential. Dynamics in resource levels and optimal habitat choices might thus be important factors influencing character divergence in natural populations.

    Emneord
    Activity, Growth rate, Morphometric analyses, Morphological variation, Resource polymorphism
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-95048 (URN)10.1007/s00442-006-0588-8 (DOI)000245808100005 ()17431684 (PubMedID)
    Tilgjengelig fra: 2006-11-07 Laget: 2006-11-07 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    4. Growth rate constrain morphological divergence when driven by competition
    Åpne denne publikasjonen i ny fane eller vindu >>Growth rate constrain morphological divergence when driven by competition
    2006 (engelsk)Inngår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 115, nr 1, s. 15-22Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Resource competition has been hypothesized to be important in driving divergence by natural selection. The effect of competition on morphological divergence and plasticity has however rarely been investigated. Since low growth rates might constrain morphological modulation and individual growth rates usually are negatively related to the intensity of competition, there might be a connection between competition, growth rate and morphological divergence. We performed an aquarium experiment with young-of-the-year Eurasian perch (Perca fluviatilis L.) to investigate how individual growth rate affected morphological plasticity induced by contrasting habitat treatments. Furthermore, in a field study of 10 lakes we also related the degree of morphological differentiation between habitats to the intraspecific competitior biomass. In the aquarium experiment we found that morphological plasticity was growth rate dependent in that morphological differentiation between the habitat treatments was confined to high individual growth rates. In the field study we found that morphological differentiation between habitats decreased with increasing intraspecific competitior biomass. Since plasticity is hypothesized to be important in divergence and intraspecific biomass could serve as a proxy for the level of competition, we suggest that our results indicate that morphological divergence might be constrained during periods of intense intraspecific competition due to low growth rates. A possible scenario is that at low growth rates all energy available is used for metabolic maintenance and no surplus energy is therefore available for morphological modulation.

    HSV kategori
    Forskningsprogram
    Limnologi
    Identifikatorer
    urn:nbn:se:uu:diva-23508 (URN)10.1111/j.2006.0030-1299.14965.x (DOI)000240998300002 ()
    Tilgjengelig fra: 2008-11-17 Laget: 2008-11-17 Sist oppdatert: 2017-12-07bibliografisk kontrollert
    5. Gut length plasticity in perch: Into the bowels of resource polymorphisms
    Åpne denne publikasjonen i ny fane eller vindu >>Gut length plasticity in perch: Into the bowels of resource polymorphisms