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  • 1.
    Blenckner, Thorsten
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Climate Related Impacts on a Lake : From Physics to Biology2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Climatic variation and change affect the dynamics of organisms and ecosystem processes. This thesis examines phytoplankton as a target variable to trace climatic impacts on Lake Erken (Sweden) with special emphasis on the spring bloom.

    A strong correlation between the timing of the spring bloom and the North Atlantic Oscillation (NAO) illustrates the link between atmospheric pressure variations and local biological processes. The predictive power increased by applying a recently established regional Scandinavian Circulation Index (SCI). Changes to an earlier timing of the spring bloom and elevated water temperature were induced by the global warming trend. The climate signal was still persistent in summer manifested by an enhanced summer phytoplankton biomass.

    Between spring and summer, the phytoplankton was mainly controlled by phosphorus limitation. The application of a new method to measure alkaline phosphatase activity revealed that P-limitation varied between species and among individual cells.

    Combining the above knowledge and literature data, the impact of the NAO on the timing of life history events, biomass and trophic cascade in aquatic and terrestrial ecosystems was quantitatively tested with a meta-analysis. In all environments, pronounced effects of the NAO were apparent, indicating the generality of climate effects found in different ecosystems.

    Finally, a regional climate model was applied, forcing a physical lake model from which future lake conditions were simulated. The simulation revealed a one-month shorter ice cover period with two years out of ten being completely ice free. Internal eutrophication is one of the expected consequences.

    In conclusion, the strong influences of global and regional climate are apparent in local physical, chemical and biological variables and will most probably also in future affect the structure and function of processes in lakes.

  • 2. Blomqvist, P.
    et al.
    Jansson, M.
    Drakare, S.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Bergström, A.-K.
    Brydsten, L.
    Effects of additions of DOC on pelagic biota in a clearwater system: Results from a whole lake experiment in northern Sweden2001In: Microbial Ecology, Vol. 42, p. 383-394Article in journal (Refereed)
  • 3.
    Brunberg, Anna-Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Nilsson, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Blomqvist, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Characteristics of oligotrophic hardwater lakes in a postglacial land-rise area in mid-Sweden2002In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 47, no 8, p. 1451-1462Article in journal (Refereed)
    Abstract [en]

    1. We describe some remarkable ephemeral, oligotrophic hardwater lakes formed becauseof land rise in the coastal areas of the Baltic Sea, that are unique in Sweden and probablyalso worldwide. Two younger, coastal lakes were studied by regular sampling for 1 yearand compared with an older (i.e. greater altitude) lake, that passed through theoligotrophic hardwater stage some 3–4000 years ago.

    2. Despite some differences in composition of the catchment, the two younger lakes weresimilar with regard to water chemistry and plankton community composition. Theconcentration of phosphorus was low while nitrogen was high, resulting in very high N/Pquotients (101 and 131). Although water colour was moderate, the concentration of organiccarbon was extremely high (average values of ‡ 20 lg TOC L–1), consisting mainly ofdissolved compounds (DOC).

    3. While the plankton was poorly developed, sediments in both lakes were covered by alayer of photosynthesising micro-organisms. This substantial 'microbial mat', which hasnot been described in detail before, was up to 15 cm thick and dominated by cyanobacteriaand purple sulphur bacteria. The concentration of sediment phosphorus was extremelylow (352 lg g–1 dw) in one of the lakes and dominated by organic-bound (residual)phosphorus.

    4. Deep sediments in the older lake, representing its oligotrophic hardwater period,differed in phosphorus composition from the currently oligotrophic hardwater lakes byhaving a strong dominance of HCl-extractable (Ca-bound) phosphorus. This indicates thatphosphorus, initially organic-bound within the microbial mat, is subsequently bound tocalcium. We hypothesise that this is promoted by the environmental conditions created bythe benthic photosynthetic activity, in combination with the prevailing hardwaterconditions.

    5. The rich and flourishing microbial community on the sediments may also explain thehigh concentration of DOC in the lake.

  • 4.
    Drakare, S.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Blomqvist, P.
    Bergström, A.-K.
    Jansson, M.
    Primary production and phytoplankton composition in relation to DOC input and bacterioplankton production in Lake Örträsket2002In: Freshwater Biology, Vol. 47, no 1, p. 41-52Article in journal (Refereed)
  • 5.
    Drakare, S.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Blomqvist, P.
    Bergström, A.-K.
    Jansson, M.
    Relationships between picophytoplankton and their environment along a gradient of lakes of different water colour and nutrient contentIn: Freshwater BiologyArticle in journal (Refereed)
  • 6.
    Drakare, Stina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Competition between picoplanktonic cyanobacteria and heterotrophic bacteria along crossed gradients of glucose and phosphate2002In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 44, no 4, p. 327-335Article in journal (Refereed)
    Abstract [en]

    A laboratory experiment was performed to test whether differences in nutrient and energy demands between picophytoplankton and heterotrophic bacteria can explain the apparent inverse biomass relationship between these organisms in lakes along gradients of organic carbon and nutrients. Growth rates and final yield of cells were analyzed in crossed gradients of glucose and phosphate. Concentrations of phosphate (10, 25, and 60 microg P L(-1)) and glucose (0, 0.3, and 3 mg C L(-1)) were used in all possible combinations giving 9 different treatments. Heterotrophic bacteria had higher maximum growth rates in all treatments and became larger than picophytoplankton in many treatments. The variance in abundance of heterotrophic bacteria between treatments could almost completely be explained by the combined effects of glucose and P. In treatments where carbon limitation slowed down the growth of heterotrophic bacteria, picophytoplankton became abundant and these organisms showed a positive response to P in combination with a negative response to glucose. The negative effect of glucose on picophytoplankton is suggested to be indirect and caused by competition with bacteria that are favored by organic C. The results suggest that competition for phosphate between phytoplankton and bacteria is not size-dependent, that heterotrophic bacteria are superior competitors for P, and that organic C produced by picophytoplankton was of minor importance for heterotrophic bacteria.

  • 7.
    Drakare, Stina
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    The Role of Picophytoplankton in Lake Food Webs2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Picophytoplankton were inferior competitors for inorganic phosphorus compared to heterotrophic bacteria. This may be due to the source of energy available for the heterotrophs, while cell-size was of minor importance. However, picophytoplankton were superior to large phytoplankton in the competition for nutrients at low concentrations.

    Biomass of picophytoplankton was low in brownwater lakes and high in clearwater lakes, compared to the biomass of heterotrophic bacteria. The results suggest that picophytoplankton are inferior to heterotrophic bacteria in the competition for inorganic nutrients in brownwater lakes, where the production of heterotrophic bacteria is subsidized by humic dissolved organic carbon (DOC)

    Relative to large phytoplankton, picophytoplankton were most important in lakes with intermediate water colour, despite the fact that the lowest nutrient concentrations were found in the clearwater lakes. Large phytoplankton in the clearwater lakes may be able to overcome nutrient competition with picophytoplankton by vertical migration.

    In conclusion, changes in nutrient content, light availability and concentrations of DOC affect the interactions of heterotrophic bacteria, picophytoplankton and large phytoplankton and are therefore important factors for the structure of the food web in the pelagic zones of lakes.

    Picophytoplankton (planktonic algae and cyanobacteria, < 2 µm) constitute an important component of pelagic food webs. They are linked to larger phytoplankton and heterotrophic bacteria through complex interactions including competition, commensalism and predation. In this thesis, field and laboratory studies on the competitive ability of picophytoplankton are reported.

    List of papers
    1. Competition between picoplanktonic cyanobacteria and heterotrophic bacteria along crossed gradients of glucose and phosphate
    Open this publication in new window or tab >>Competition between picoplanktonic cyanobacteria and heterotrophic bacteria along crossed gradients of glucose and phosphate
    2002 (English)In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 44, no 4, p. 327-335Article in journal (Refereed) Published
    Abstract [en]

    A laboratory experiment was performed to test whether differences in nutrient and energy demands between picophytoplankton and heterotrophic bacteria can explain the apparent inverse biomass relationship between these organisms in lakes along gradients of organic carbon and nutrients. Growth rates and final yield of cells were analyzed in crossed gradients of glucose and phosphate. Concentrations of phosphate (10, 25, and 60 microg P L(-1)) and glucose (0, 0.3, and 3 mg C L(-1)) were used in all possible combinations giving 9 different treatments. Heterotrophic bacteria had higher maximum growth rates in all treatments and became larger than picophytoplankton in many treatments. The variance in abundance of heterotrophic bacteria between treatments could almost completely be explained by the combined effects of glucose and P. In treatments where carbon limitation slowed down the growth of heterotrophic bacteria, picophytoplankton became abundant and these organisms showed a positive response to P in combination with a negative response to glucose. The negative effect of glucose on picophytoplankton is suggested to be indirect and caused by competition with bacteria that are favored by organic C. The results suggest that competition for phosphate between phytoplankton and bacteria is not size-dependent, that heterotrophic bacteria are superior competitors for P, and that organic C produced by picophytoplankton was of minor importance for heterotrophic bacteria.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-90042 (URN)10.1007/s00248-002-1013-4 (DOI)12399896 (PubMedID)
    Available from: 2002-10-23 Created: 2002-10-23 Last updated: 2017-12-14Bibliographically approved
    2. Effects of additions of DOC on pelagic biota in a clearwater system: Results from a whole lake experiment in northern Sweden
    Open this publication in new window or tab >>Effects of additions of DOC on pelagic biota in a clearwater system: Results from a whole lake experiment in northern Sweden
    Show others...
    2001 In: Microbial Ecology, Vol. 42, p. 383-394Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90043 (URN)
    Available from: 2002-10-23 Created: 2002-10-23Bibliographically approved
    3. Primary production and phytoplankton composition in relation to DOC input and bacterioplankton production in Lake Örträsket
    Open this publication in new window or tab >>Primary production and phytoplankton composition in relation to DOC input and bacterioplankton production in Lake Örträsket
    2002 In: Freshwater Biology, Vol. 47, no 1, p. 41-52Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90044 (URN)
    Available from: 2002-10-23 Created: 2002-10-23Bibliographically approved
    4. Relationships between picophytoplankton and their environment along a gradient of lakes of different water colour and nutrient content
    Open this publication in new window or tab >>Relationships between picophytoplankton and their environment along a gradient of lakes of different water colour and nutrient content
    In: Freshwater BiologyArticle in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-90045 (URN)
    Available from: 2002-10-23 Created: 2002-10-23Bibliographically approved
  • 8.
    Höglund, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Kolm, Niclas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Animal Ecology.
    Winberg, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Comparative Physiology. Jämförande fysiologi.
    Stress-induced changes in brain serotonergic activity, plasma cortisol and aggressive behavior in Arctic charr (Salvelinus alpinus) is counteracted by L-DOPA2001In: Physiology and Behavior, ISSN 0031-9384, E-ISSN 1873-507X, Vol. 74, no 3, p. 381-389Article in journal (Refereed)
    Abstract [en]

    Arctic charr (Salvelinus alpinus) were tested for aggressive behavior using intruder tests, before and after 2 days of dyadic social interaction. Following social interaction, half of the dominant and half of the subordinate fish were given l-DOPA (10 mg/kg, orally), whereas the remaining dominant and subordinate fish were given vehicle. One hour following drug treatment, the fish were tested for aggressive behavior again in a third and final intruder test, after which blood plasma and brain tissue were sampled for analysis of plasma cortisol concentrations and brain levels of monoamines and monoamine metabolites. Subordinate fish showed a reduction in the number of attacks launched against the intruder, as well as an increase in attack latency, as compared to prior to dyadic social interactions. Social subordination also resulted in an elevation of brain serotonergic activity. Fish receiving l-DOPA prior to the final intruder test showed shorter attack latency than vehicle controls. Drug treatment was a stressful experience and vehicle controls showed elevated plasma cortisol levels and longer attack latency as compared to before treatment. l-DOPA-treated fish showed lower plasma levels of cortisol and lower serotonergic activity in certain brain areas than vehicle controls. These results suggest that l-DOPA counteracts the stress-induced inhibition of aggressive behavior, and at the same time inhibits stress-induced effects on brain serotonergic activity and plasma cortisol concentrations.

  • 9.
    Karlsson Elfgren, Irene
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Studies on the Life Cycles of Akinete Forming Cyanobacteria2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cyanobacteria which can form resting cells (in this case akinetes) are common in meso-eutrophic lakes in temperate regions, often dominating the phytoplankton communities during summer. The life cycles of akinete-forming cyanobacteria has been studied with Gloeotrichia echinulata as a model organism. Anabaena and Aphanizomenon were also included in a migration study. The focus of this thesis has been the factors influencing the processes of germination and subsequent growth, the factors influencing migration from the sediment, and the amount of growth occurring in the water.

    Germination of G. echinulata was strongly favoured by light, and recruitment was highest from organic-rich sediments in shallow, sheltered littoral areas, between 0-3 m. Recruitment of Anabaena and Aphanizomenon was less light dependent, yet the highest recruitment occurred from shallow sediments (0-2 m). This means that organic-rich sediments (0-3 m) in shallow areas are the most important seed-banks of akinete-forming cyanobacteria. The inocula contributed only to a minor extent to the maximum pelagic populations. 4% for G. echinulata in the mesotrophic Lake Erken, and 0.03% for both Anabaena and Aphanizomenon in the eutrophic Lake Limmaren. This implies that processes of growth and division in the water are important for the maximum size of the pelagic population. Prolonged recruitment from the sediment strongly promoted establishment of the species in the water, especially G. echinulata.

    List of papers
    1. On the germination of the akinete-forming cyanobacterium Gloeotrichia echinulata, in Lake Erken, Sweden
    Open this publication in new window or tab >>On the germination of the akinete-forming cyanobacterium Gloeotrichia echinulata, in Lake Erken, Sweden
    1999 In: Algological Studies, Vol. 94, p. 175-180Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-90423 (URN)
    Available from: 2003-05-14 Created: 2003-05-14Bibliographically approved
    2. Benthic growth of Gloeotrichia echinulata
    Open this publication in new window or tab >>Benthic growth of Gloeotrichia echinulata
    2003 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 506, no 1, p. 189-193Article in journal (Refereed) Published
    Abstract [en]

    Gloeotrichia echinulata is an akinete forming cyanobacterium with both a pelagic and a benthic phase. After germination of the akinete there is a short phase of growth on the sediment before the filaments develop gas vacuoles and migrate up into the water. It has been indicated that during the time of growth on the sediment surface the germlings take up nutrients. Those nutrients would be used during the pelagic phase as the pelagic colonies do not have a very efficient nutrient uptake. To test the length of the initial growth period `akinete colonies' were picked out of sediment samples from Lake Erken, Sweden, and placed on a thin layer of sediment in wellplates (Nunclon multidish, 48 wells) in an incubator with 17 °C and a light:dark cycle of 16:8 h. The plates were then studied under a stereomicroscope and pictures were taken one or two times per day for 20 days. Germination occurred in one third of the wells and the growth was recorded. The germlings formed bundles on the surface of the old akinete colony during the experiment. Several bundles were found on the same akinete colony. In the migration traps colonies and filament bundles were found. The morphology of filament bundles found in the migration traps was similar to the filament bundles found in the germination experiment which had reached a stage of development where they would soon be considered colonies.

    National Category
    Ecology
    Identifiers
    urn:nbn:se:uu:diva-90424 (URN)10.1023/B:HYDR.0000008570.03256.00 (DOI)
    Available from: 2003-05-14 Created: 2003-05-14 Last updated: 2017-12-14Bibliographically approved
    3. Factors regulating recruitment from the sediment to the water column in the bloom-forming cyanobacterium Gloeotrichia echinulata
    Open this publication in new window or tab >>Factors regulating recruitment from the sediment to the water column in the bloom-forming cyanobacterium Gloeotrichia echinulata
    2004 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 49, no 3, p. 265-273Article in journal (Refereed) Published
    Abstract [en]

    Summary

    1. The influence of light, temperature, sediment mixing and sediment origin (water depth) on the recruitment of the cyanobacterium Gloeotrichia echinulata was examined in the laboratory.

    2. Light and temperature were the most important factors initiating germination in G. echinulata.

    3. The extent of germination (recruited biovolume) was mainly regulated by temperature and sediment mixing. Furthermore, sediment mixing significantly enhanced the frequency of observed heterocysts and colonies.

    4. Despite the fact that the deep and shallow sediments contained a similar number of akinete colonies, the highest recruitment occurred from shallow sediments, indicating that akinetes from shallow sediments have a higher viability than those from deeper parts of the lake.

    5. Our results support the hypothesis that shallow sediments are more important than profundal sediments for the recruitment of G. echinulata to the pelagic zone.

    National Category
    Ecology
    Identifiers
    urn:nbn:se:uu:diva-90425 (URN)10.1111/j.1365-2427.2004.01182.x (DOI)
    Available from: 2003-05-14 Created: 2003-05-14 Last updated: 2017-12-14Bibliographically approved
    4. Recruitment and pelagic growth of Gloeotrichia echinulata (Chyanophyceae) in Lake Erken
    Open this publication in new window or tab >>Recruitment and pelagic growth of Gloeotrichia echinulata (Chyanophyceae) in Lake Erken
    2003 (English)In: Journal of Phycology, ISSN 0022-3646, E-ISSN 1529-8817, Vol. 39, no 6, p. 1050-1056Article in journal (Refereed) Published
    Abstract [en]

    Different parameters in the life cycle of the colony forming cyanobacterium Gloeotrichia echinulata (J.E. Smith) Richter was evaluated in Lake Erken, Sweden. Recruitment of colonies from the sediments and pelagic abundance were measured during 2 years. These data were then used in a model to evaluate and estimate parameters of the life cycle. In our study, recruitment alone only contributed to a small part (<5%) of the maximum G. echinulata abundance that occurred during late summer. However, recruitment from shallow sediments forms the important seed for the pelagic population. Together with measured rates of migration from the sediment, variations in either pelagic colony division rate or pelagic residence time could explain variations in the measured abundance of G. echinulata in situ.

    National Category
    Ecology
    Identifiers
    urn:nbn:se:uu:diva-90426 (URN)10.1111/j.0022-3646.2003.03-030.x (DOI)
    Available from: 2003-05-14 Created: 2003-05-14 Last updated: 2017-12-14Bibliographically approved
    5. Pelagic growth and colony division of Gloeotrichia echinulata in Lake Erken
    Open this publication in new window or tab >>Pelagic growth and colony division of Gloeotrichia echinulata in Lake Erken
    2005 (English)In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 27, no 2, p. 145-151Article in journal (Refereed) Published
    Abstract [en]

    Gloeotrichia echinulata colony development was monitored in Lake Erken, Sweden and studied inenclosure experiments. Significant colonial division did not occur in mesh bags, although the abundance ofthe pelagic population in the lake increased during the experimental periods. On the basis of these findings,it is suggested that circulation of G. echinulata to deeper nutrient rich water supports pelagic growth. Insupport of this, a large part of the buoyant G. echinulata colonies in Lake Erken was found at severalmeters depth. In an experiment with nutrient additions, the only treatment that favoured G. echinulatadevelopment was additions of phosphate, nitrate and iron. Trace element additions had a negative effecton the development of G. echinulata. On the basis of these findings, the nutritional requirements ofG. echinulata are discussed.

    National Category
    Ecology
    Identifiers
    urn:nbn:se:uu:diva-90427 (URN)10.1093/plankt/fbh165 (DOI)
    Available from: 2003-05-14 Created: 2003-05-14 Last updated: 2017-12-14Bibliographically approved
    6. The Importance of Shallow Sediments in the Recruitment of Anabaena and Aphanizomenon (Cyanophyceae)
    Open this publication in new window or tab >>The Importance of Shallow Sediments in the Recruitment of Anabaena and Aphanizomenon (Cyanophyceae)
    2004 (English)In: Journal of Phycology, ISSN 0022-3646, E-ISSN 1529-8817, Vol. 40, no 5, p. 831-836Article in journal (Refereed) Published
    Abstract [en]

    Recruitment of Anabaena and Aphanizomenon from the sediments to the water column was investigated in shallow (1-2 m) and deep (6-7 m) areas of Lake Limmaren, central Sweden. Recruitment traps attached to the bottom were sampled weekly throughout the summer season (June through September). A comparison between the two sites shows that the largest part of the recruited cells originated from the shallow site, although recruitment occurred at all depths in the lake. There were also differences between the species, regarding the site as well as the timing of the recruitment. The contribution of the inoculum to the pelagic population was calculated to vary between 0.003% and 0.05% for the different species. From these results we conclude that shallow sediments are more important than deep ones for the recruitment and that the inoculum in Lake Limmaren is small but may still be an important factor in the population dynamics.

    National Category
    Ecology
    Identifiers
    urn:nbn:se:uu:diva-90428 (URN)10.1111/j.1529-8817.2004.04070.x (DOI)
    Available from: 2003-05-14 Created: 2003-05-14 Last updated: 2018-06-05Bibliographically approved
  • 10.
    Karlsson, Irene
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Benthic growth of Gloeotrichia echinulata2003In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 506, no 1, p. 189-193Article in journal (Refereed)
    Abstract [en]

    Gloeotrichia echinulata is an akinete forming cyanobacterium with both a pelagic and a benthic phase. After germination of the akinete there is a short phase of growth on the sediment before the filaments develop gas vacuoles and migrate up into the water. It has been indicated that during the time of growth on the sediment surface the germlings take up nutrients. Those nutrients would be used during the pelagic phase as the pelagic colonies do not have a very efficient nutrient uptake. To test the length of the initial growth period `akinete colonies' were picked out of sediment samples from Lake Erken, Sweden, and placed on a thin layer of sediment in wellplates (Nunclon multidish, 48 wells) in an incubator with 17 °C and a light:dark cycle of 16:8 h. The plates were then studied under a stereomicroscope and pictures were taken one or two times per day for 20 days. Germination occurred in one third of the wells and the growth was recorded. The germlings formed bundles on the surface of the old akinete colony during the experiment. Several bundles were found on the same akinete colony. In the migration traps colonies and filament bundles were found. The morphology of filament bundles found in the migration traps was similar to the filament bundles found in the germination experiment which had reached a stage of development where they would soon be considered colonies.

  • 11.
    Karlsson, Irene
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    On the germination of the akinete-forming cyanobacterium Gloeotrichia echinulata, in Lake Erken, Sweden1999In: Algological Studies, Vol. 94, p. 175-180Article in journal (Refereed)
  • 12.
    Karlsson-Elfgren, Irene
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Brunberg, Anna-Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    The Importance of Shallow Sediments in the Recruitment of Anabaena and Aphanizomenon (Cyanophyceae)2004In: Journal of Phycology, ISSN 0022-3646, E-ISSN 1529-8817, Vol. 40, no 5, p. 831-836Article in journal (Refereed)
    Abstract [en]

    Recruitment of Anabaena and Aphanizomenon from the sediments to the water column was investigated in shallow (1-2 m) and deep (6-7 m) areas of Lake Limmaren, central Sweden. Recruitment traps attached to the bottom were sampled weekly throughout the summer season (June through September). A comparison between the two sites shows that the largest part of the recruited cells originated from the shallow site, although recruitment occurred at all depths in the lake. There were also differences between the species, regarding the site as well as the timing of the recruitment. The contribution of the inoculum to the pelagic population was calculated to vary between 0.003% and 0.05% for the different species. From these results we conclude that shallow sediments are more important than deep ones for the recruitment and that the inoculum in Lake Limmaren is small but may still be an important factor in the population dynamics.

  • 13.
    Karlsson-Elfgren, Irene
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Hyenstrand, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Rydin, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Pelagic growth and colony division of Gloeotrichia echinulata in Lake Erken2005In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 27, no 2, p. 145-151Article in journal (Refereed)
    Abstract [en]

    Gloeotrichia echinulata colony development was monitored in Lake Erken, Sweden and studied inenclosure experiments. Significant colonial division did not occur in mesh bags, although the abundance ofthe pelagic population in the lake increased during the experimental periods. On the basis of these findings,it is suggested that circulation of G. echinulata to deeper nutrient rich water supports pelagic growth. Insupport of this, a large part of the buoyant G. echinulata colonies in Lake Erken was found at severalmeters depth. In an experiment with nutrient additions, the only treatment that favoured G. echinulatadevelopment was additions of phosphate, nitrate and iron. Trace element additions had a negative effecton the development of G. echinulata. On the basis of these findings, the nutritional requirements ofG. echinulata are discussed.

  • 14.
    Karlsson-Elfgren, Irene
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Rengefors, Karin
    Gustafsson, Susanne
    Factors regulating recruitment from the sediment to the water column in the bloom-forming cyanobacterium Gloeotrichia echinulata2004In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 49, no 3, p. 265-273Article in journal (Refereed)
    Abstract [en]

    Summary

    1. The influence of light, temperature, sediment mixing and sediment origin (water depth) on the recruitment of the cyanobacterium Gloeotrichia echinulata was examined in the laboratory.

    2. Light and temperature were the most important factors initiating germination in G. echinulata.

    3. The extent of germination (recruited biovolume) was mainly regulated by temperature and sediment mixing. Furthermore, sediment mixing significantly enhanced the frequency of observed heterocysts and colonies.

    4. Despite the fact that the deep and shallow sediments contained a similar number of akinete colonies, the highest recruitment occurred from shallow sediments, indicating that akinetes from shallow sediments have a higher viability than those from deeper parts of the lake.

    5. Our results support the hypothesis that shallow sediments are more important than profundal sediments for the recruitment of G. echinulata to the pelagic zone.

  • 15.
    Karlsson-Elfgren, Irene
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Rydin, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Hyenstrand, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Pettersson, Kurt
    Recruitment and pelagic growth of Gloeotrichia echinulata (Chyanophyceae) in Lake Erken2003In: Journal of Phycology, ISSN 0022-3646, E-ISSN 1529-8817, Vol. 39, no 6, p. 1050-1056Article in journal (Refereed)
    Abstract [en]

    Different parameters in the life cycle of the colony forming cyanobacterium Gloeotrichia echinulata (J.E. Smith) Richter was evaluated in Lake Erken, Sweden. Recruitment of colonies from the sediments and pelagic abundance were measured during 2 years. These data were then used in a model to evaluate and estimate parameters of the life cycle. In our study, recruitment alone only contributed to a small part (<5%) of the maximum G. echinulata abundance that occurred during late summer. However, recruitment from shallow sediments forms the important seed for the pelagic population. Together with measured rates of migration from the sediment, variations in either pelagic colony division rate or pelagic residence time could explain variations in the measured abundance of G. echinulata in situ.

  • 16.
    Kolm, Niclas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Animal Ecology.
    Olsson, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Differential investment in the Banggai cardinalfish: can females adjust egg size close to egg maturation to match the attractiveness of a new partner?2003In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 63, no S1, p. 144-151Article in journal (Refereed)
    Abstract [en]

    To test whether females can change their egg investment according to the different attractiveness ( i.e. size as measured by standard length, Ls) of a new mate after eggs have already matured in response to an earlier mate, female Banggai cardinalfish Pterapogon kauderni were first allowed to produce eggs for small (unattractive) or large (attractive) males. Then, when spawning was initiated, but prior to actual spawning, their partner was switched to either a significantly larger or a significantly smaller partner, respectively. A strong positive correlation between egg size and days until spawning with the second male was found for the females initially paired to a small and then a large male. Within a few days, these females apparently increased their egg size to match the attractiveness of their new male. No correlation between days until spawning and egg size in females initially paired to a large and then a small male, however was found, so apparently females were unable to adjust egg size in response to a decrease in mate attractiveness. Consequently, it is suggested that females can increase their egg size investment even after the onset of egg maturation and that this change can be quite rapid.

  • 17.
    Vrede, Katarina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Vrede, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Isaksson, Anneli
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Karlsson, Ann-Louise
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Limnology.
    Effects of nutrients (phosphorous, nitrogen, and carbon) and zooplankton on bacterioplankton and phytoplankton: a seasonal study1999In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 44, no 7, p. 1616-1624Article in journal (Refereed)
1 - 17 of 17
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