uu.seUppsala universitets publikationer
Ändra sökning
Avgränsa sökresultatet
1 - 9 av 9
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Alonso-Saez, Laura
    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 genetik, Limnologi.
    Unanue, Marian
    Latatu, Ainhoa
    Azua, Inigo
    Ayo, Begona
    Artolozaga, Itxaso
    Iriberri, Juan
    Changes in marine prokaryotic community induced by varying types of dissolved organic matter and subsequent grazing pressure2009Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 31, nr 11, s. 1373-1383Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We analysed changes in the abundance, biomass, activity and composition of coastal marine prokaryotic communities after the addition of organic substrates, such as glucose, leucine and yeast extract, and the effect of grazing pressure exerted by nanoflagellates. The addition of a carbon source (i.e. glucose) promoted the growth of Gammaproteobacteria, while a combined source of C and N (i.e. leucine) favoured the development of Alphaproteobacteria. The addition of yeast extract, a complex substrate rich in N and growth factors, promoted the proliferation of Alphaproteobacteria and Gammaproteobacteria. Grazing pressure exerted by nanoflagellates produced marked differences on the size structure of the prokaryotic biomass. A pronounced tendency to filamentation and aggregation was observed in the glucose treatment, while in the case of yeast extract, small and mainly freely dispersed prokaryotes were maintained throughout the incubations. Thus, the final community in the yeast extract treatment showed a high percentage of edible biomass, while an important fraction of potentially grazing-resistant prokaryotes (more than 50% of total prokaryotic biomass) was detected in the microcosms enriched with glucose. These results suggest a marked effect of DOM sources on the development of grazing-resistant prokaryotes.

  • 2.
    Holeton, Clare
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Ekologisk botanik.
    Lindell, Kristin
    Holmborn, Towe
    Högfors, Hedvig
    Gorokhova, Elena
    Decreased astaxanthin at high feeding rates in the calanoid copepod Acartia bifilosa2009Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 31, nr 6, s. 661-668Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In marine food webs, copepods are the major producers of a carotenoid  pigment astaxanthin, which is an important antioxidant. The availability of astaxanthin for higher trophic levels can be affected by changes in phytoplankton stocks and copepod feeding; however, the functional relationship between food availability and astaxanthin production is poorly understood. We hypothesized that with a given food  type and quality, astaxanthin content in copepods is positively related  to feeding and egg production rates. The hypothesis was tested by  measuring astaxanthin accumulation in concert with ingestion and egg production rates in the copepod Acartia bifilosa exposed to different algal concentrations (Tetraselmis suecica; 0 to 1200 mu g C L-1). Egg production and ingestion rates increased with increasing food availability and reached a plateau at >= 400-600 mu g C L-1. In contrast, increasing accumulation of astaxanthin with increasing food availability was observed only at concentrations <= 150 mu g C L-1. Contrary to our hypothesis, at 600-1200 mu g C L-1 copepods had maximal ingestion and egg production rates, but low astaxanthin contents. It is suggested that this low accumulation of astaxanthin at high food concentrations results from a food-dependant decrease in assimilation efficiency. These findings are important for the understanding of astaxanthin dynamics within marine food webs, where increases in phytoplankton biomass may translate to a trade-off between zooplankton quantity and its nutritional quality for zooplanktivores.

  • 3. Hylander, Samuel
    et al.
    Jephson, Therese
    Lebret, Karen
    Lund University.
    von Einem, Jessica
    Fagerberg, Tony
    Balseiro, Esteban
    Modenutti, Beatriz
    Sol Souza, Maria
    Laspoumaderes, Cecilia
    Joensson, Mikael
    Ljungberg, Peter
    Nicolle, Alice
    Nilsson, Per Anders
    Ranaker, Lynn
    Hansson, Lars-Anders
    Climate-induced input of turbid glacial meltwater affects vertical distribution and community composition of phyto- and zooplankton2011Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 33, nr 8, s. 1239-1248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Receding glaciers are among the most obvious changes caused by global warming, and glacial meltwater entering lakes generally forms plumes of particles. By taking vertical samples along a horizontal gradient from such a particle source, we found that photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) attenuated 20-25% faster close to the inflow of suspended particles compared with the more transparent part of the gradient. All sampled stations had a deep chlorophyll a (Chl a) maximum at 15-20 m which was more distinct in the transparent part of the horizontal gradient. Picocyanobacteria increased in abundance in more transparent water and their numbers were tightly correlated with the intensity of the deep Chl a maxima. Motile species of phytoplankton had a deeper depth distribution in transparent versus less transparent water. Yet other species, like Chrysochromulina parva, that can withstand high PAR intensities and low nutrient concentrations, increased in abundance as the water became more transparent. Also copepods increased in abundance, indicating that they are more successful in transparent water. We conclude that sediment input into lakes creates horizontal gradients in PAR and UVR attenuation which strongly affect both distribution and behavior of phyto-and zooplankton. The input of glacial flour creates a sub-habitat that can function as a refuge for species that are sensitive to high PAR and UVR exposure. When the glacier has vanished, this habitat may disappear. During the melting period, with heavy sediment input, we predict that competitive species in transparent waters, like Chrysocromulina, picocyanobacteria and copepods, will become less common. The deep Chl a maxima is also likely to become less developed. Hence, glacier melting will probably have profound effects on both species composition and behavior of several planktonic taxa with potential effects on the food web.

  • 4.
    Isaksson, Anneli
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Bergström, Ann-Kristin
    Blomqvist, Peter
    Jansson, Mats
    Bacterial grazing by phagotrophic phytoflagellates in a deep humic lake in northern Sweden1999Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 21, nr 2, s. 247-268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bacterial grazing was measured from June to August 1995 in Lake Örträsket, a deep brown-water lake in northern Sweden. Mixotrophic chrysophytes were the dominating bacterivores at all times, grazing 3-14% of bacterial standing stock daily. The effects of altered nutrient supply and light availability on grazing activity and growth were studied in two mesocosm experiments. Incubation in the dark did not stimulate phagotrophy, which would otherwise be expected if bacteria were mainly being used as an energy source. Furthermore, clearance rates were not reduced after alleviation of nutrient limitation conditions. Rather, phagotrophy may work as a relatively fixed attribute of the mixotrophic community in this lake. When availability of dissolved nutrients is restricted, phagotrophy permits the mixotrophs to outcompete other phytoplankton, but they become less competitive at high nutrient concentrations. The relative share of mixotrophs in relation to total phytoplankton decreased considerably after enrichment with nitrogen + phosphorus.

  • 5.
    Karlsson-Elfgren, Irene
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för evolutionsbiologi, Limnologi.
    Hyenstrand, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Rydin, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Pelagic growth and colony division of Gloeotrichia echinulata in Lake Erken2005Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 27, nr 2, s. 145-151Artikel i tidskrift (Refereegranskat)
    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.

  • 6. Lischke, Betty
    et al.
    Weithoff, Guntram
    Wickham, Stephen
    Attermeyer, Katrin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Grossart, Hans-Peter
    Scharnweber, Kristin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
    Hilt, Sabine
    Gaedke, Ursula
    Large biomass of small feeders: Ciliates may dominate herbivory in eutrophic lakes2016Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 38, nr 1, s. 2-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The importance of ciliates as herbivores and in biogeochemical cycles is increasingly recognized. An opportunity to observe the potential consequences of zooplankton dominated by ciliates arose when winter fish kills resulted in strong suppression of crustaceans by young planktivorous fish in two shallow lakes. On an annual average, ciliates made up 38-76% of the total zooplankton biomass in both lakes during two subsequent years. Consequently, ciliate biomass and their estimated grazing potential were extremely high compared with other lakes of various trophic states and depths. Grazing estimates based on abundance and size suggest that ciliates should have cleared the water column of small (<5 mu m) and intermediate (5-50 mu m) sized phytoplankton more than once a day. Especially, small feeders within the ciliates were important, likely exerting a strong top-down control on small phytoplankton. Particle-attached bacteria were presumably strongly suppressed by intermediate-sized ciliate feeders. In contrast to other lakes, large phytoplankton was proportionately very abundant. The phytoplankton community had a high evenness, which may be attributed to the feeding by numerous fast growing and selective ciliate species. Our study highlights ciliates as an important trophic link and adds to the growing awareness of the role of winter processes for plankton dynamics.

  • 7.
    Peter, Hannes
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Sommaruga, Ruben
    An evaluation of methods to study the gut bacterial community composition of freshwater zooplankton.2008Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 30, nr 9, s. 997-1006Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The occurrence of gut bacteria in freshwater and marine zooplankton has long been recognized, but knowledge about the composition of the gut "microflora" and its permanent presence in different zooplankters is still inadequate. In this study, we tested the suitability of fluorescence in situ hybridization (FISH), catalysed reporter deposition (CARD)-FISH, cultivation and transmission electron microscopy (TEM) on homogenates and whole-specimen sections to assess the presence and identity of gut bacteria in several freshwater copepod and cladoceran species. Unambiguous results about the presence of a permanent gut "microflora" were obtained for freshly caught Daphnia pulex by TEM. CARD-FISH on gut homogenates from Acanthodiaptomus denticornis and D. pulex revealed a very similar bacterial composition to that present in the water column. Major bacterial groups found in cladocerans and copepods were alpha-, beta-, gamma-Proteobacteria and Cytophaga–Flavobacteria. The high contribution of alpha-Proteobacteria in A. denticornis suggested a specific niche for this group, but probably in association with its carapace. FISH on paraffin semithin sections had the potential to provide quantitative and qualitative information about the composition of the gut "microflora", but loss of bacteria and gut content was significant.

  • 8. Winter, Amos
    et al.
    Henderiks, Jorijntje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Beaufort, Luc
    Rickaby, Rosalind E. M.
    Brown, Christopher W.
    Poleward expansion of the coccolithophore Emiliania huxleyi2014Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 36, nr 2, s. 316-325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coccolithophores are one of the most abundant eukaryotic phytoplankton in the oceans and are distinguished by their ability to build calcitic platelets (coccoliths). Of the numerous species, Emiliania huxleyi is considered one of the major calcifiers in the pelagic ocean. There is growing concern that increasing levels of CO2 in the atmosphere and the subsequent acidification of the ocean may disrupt the production of coccoliths. Furthermore, any change in the global distribution and abundance of E. huxleyi relative to non-calcifying groups of phytoplankton (e.g. diatoms) will have important effects on the biogeochemical cycling of carbon and climatic feedbacks. We review different lines of evidence that suggest E. huxleyi is increasingly expanding its range into the polar oceans. These observations contribute to the debate on the climatic effects on natural coccolithophore populations. We postulate that E. huxleyi may be more sensitive to recent environmental changes such as increasing sea surface temperature and salinity than to changing ocean carbonate chemistry, partly because increased availability of CO2(aq) likely alleviates a carbon limitation for the inefficient Rubisco enzyme in these algae. Any potentially important climatic feedbacks of coccolithophores need a better knowledge of the mechanisms and rates of adaptation by natural populations. As more data and modelling work become available, the real significance of this poleward expansion will become clear.

  • 9.
    Šupraha, Luka
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ljubešić, Zrinka
    Univ Zagreb, Fac Sci, Dept Biol, Rooseveltov Trg 6, Zagreb 10000, Croatia.
    Mihanović, Hrvoje
    Inst Oceanog & Fisheries, Setaliste Ivana Mestrov 63, Split 21000, Croatia.
    Henderiks, Jorijntje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Inst Oceanog & Fisheries, Setaliste Ivana Mestrov 63, Split 21000, Croatia [Show the Organization-Enhanced name(s)] [ 4 ] Univ Oslo, Dept Biosci, CEES, POB 1066 Blindern, N-0316 Oslo, Norway.
    Coccolithophore life-cycle dynamics in a coastal Mediterranean ecosystem: seasonality and species-specific patterns2016Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 38, nr 5, s. 1178-1193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coccolithophores (calcifying haptophyte algae) commonly exhibit a heteromorphic life cycle, alternating between morphologically distinct heterococcolith (diploid) and holococcolith (haploid) phases. The prevalence of each life phase in a coccolithophore community defines its overall ecological and biogeochemical performance due to differences in physiology, biomass and calcification. The main drivers of life-cycle dynamics and ecological preferences of the two life-phases are still unclear and field data of high taxonomic resolution are needed. We investigated the distribution and abundance patterns of the life-phases of 14 coccolithophore species. The study was conducted along the strong environmental gradients of the Krka River estuary (Eastern Adriatic Sea) during winter (February) and summer (July) 2013. The results reveal characteristic life-phase seasonality with an overall dominance of the heterococcolith phase during winter and a holococcolith phase during summer. However, we also detected exceptions to the strictly seasonal patterns as well as species-specific ecological preferences. Our findings provide new insights into coccolithophore life-phase dynamics in the Mediterranean Sea that will further advance the understanding of ecology and evolution of the group.

1 - 9 av 9
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf