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  • 51. Hajdu, Susanna
    et al.
    Larsson, Ulf
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Huseby, Siv
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Skjevik, Ann-Turi
    Sommarens växtplanktonsamhälle har förändrats2007Ingår i: Havet 2007, Naturvårdsverket, 2007Kapitel i bok, del av antologi (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    Växtplanktonsamhällets sammansättning under sommaren har förändrats i alla havsområden under senare år. Exempelvis har filamentösa cyanobakterier ökat i Egentliga Östersjön. Den troligaste förklaringen är ändrade hydrografiska förutsättningar, så som ökad humustillförsel från land, försämrat ljusklimat, minskad salinitet och ökad temperatur orsakad av ändringar i klimatet.

  • 52. Harvey, E. Therese
    et al.
    Kratzer, Susanne
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Relationships between colored dissolved organic matter and dissolved organic carbon in different coastal gradients of the Baltic Sea2015Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, nr Suppl 3, s. S392-S401Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to high terrestrial runoff, the Baltic Sea is rich in dissolved organic carbon (DOC), the light-absorbing fraction of which is referred to as colored dissolved organic matter (CDOM). Inputs of DOC and CDOM are predicted to increase with climate change, affecting coastal ecosystems. We found that the relationships between DOC, CDOM, salinity, and Secchi depth all differed between the two coastal areas studied; the W Gulf of Bothnia with high terrestrial input and the NW Baltic Proper with relatively little terrestrial input. The CDOM: DOC ratio was higher in the Gulf of Bothnia, where CDOM had a greater influence on the Secchi depth, which is used as an indicator of eutrophication and hence important for Baltic Sea management. Based on the results of this study, we recommend regular CDOM measurements in monitoring programmes, to increase the value of concurrent Secchi depth measurements.

  • 53. Harvey, E. Therese
    et al.
    Walve, Jakob
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlson, Bengt
    Kratzer, Susanne
    The Effect of Optical Properties on Secchi Depth and Implications for Eutrophication Management2019Ingår i: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 5, s. 1-19, artikel-id 496Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Successful management of coastal environments requires reliable monitoring methods and indicators. Besides Chlorophyll-a concentration (Chl-a), water transparency measured as Secchi Depth (ZSD) is widely used in Baltic Sea management for water quality assessment as eutrophication indicator. However, in many coastal waters not only phytoplankton but also coloured dissolved organic matter (CDOM) and suspended particulate matter (SPM) influence the under-water light field, and therefore the ZSD. In this study all three main optical variables(CDOM, Chl-a and SPM [organic and inorganic]) as well as ZSD were measured in three Swedish regions: the Bothnian Sea, the Baltic Proper and the Skagerrak in 2010-2014. Regional multiple regressions with Chl-a, CDOM and inorganic SPM as predictors explained the variations in ZSD well (R2adj = 0.53-0.84). Commonality analyses of the regressions indicated considerable differences between regions regarding the contribution of each factor to the variance, R2adj, in ZSD. CDOM explained most of the variance in the Bothnian Sea and the Skagerrak; in general, Chl-a contributed only modestly to the ZSD. In the Baltic Proper the largest contribution was from the interaction of all three variables. As expected, the link between Chl-a and ZSD was much weaker in the Bothnian Sea with high CDOM absorption and SPM concentration. When applying the Swedish EU Water Framework Directive threshold for Good/Moderate Chl-a status in the models it was shown that ZSD is neither a sufficient indicator for eutrophication, nor for changes in Chl-a. Natural coastal gradients in CDOM and SPM influence the reference conditions for ZSD and other eutrophication indicators, such as the depth distribution of macro-algae. Hence, setting targets for these indicators based on reference Chl-a concentrations and simple Chl-a to ZSD relationships might in some cases be inappropriate and misleading due to overestimation of water transparency under natural conditions.

  • 54. Höglander, Helena
    et al.
    Hajdu, Susanna
    Skjevik, Ann-Turi
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Karlsson, Chatarina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Pelagial biologi /växtplankton2011Ingår i: Havet: om miljötillståndet i svenska havsområden. 2011 / [ed] Maria Lewander (huvudredaktör), Malin Karlsson, Karin Lundberg, Stockholm: Naturvårdsverket, 2011, s. 32-33Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 55. Höglander, Helena
    et al.
    Hajdu, Susanna
    Skjevik, Ann-Turi
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Chatarina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Pelagial biologi/växtplankton2012Ingår i: Havet: om miljötillståndet i svenska havsområden. 2012, Stockholm: Naturvårdsverket, 2012, s. 48-49Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 56. Jaanus, A
    et al.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Hajdu, S
    Huseby, S
    Jurgensone, I
    Olenina, I
    Wasmund, N
    Toming, K
    Shifts in the Baltic Sea summer phytoplankton communities in 1992-20062007Rapport (Övrig (populärvetenskap, debatt, mm))
  • 57. Jaanus, A
    et al.
    Hajdu, H
    Kaitala, S
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Kaljurand, K
    Ledaine, I
    Lips, I
    Olenina, I
    Distribution patterns of isomorphic cold-water dinoflagellates (Scrippsiella/Woloszynskia complex). causing `red tides in the Baltic Sea2006Ingår i: Hydrobiologia, Vol. 554, s. 137-146Artikel i tidskrift (Refereegranskat)
  • 58. Jaanus, Andres
    et al.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Olenina, Irina
    Toming, Kaire
    Kaljurand, Kaire
    Changes in phytoplankton communities along a north–south gradient in the Baltic Sea between 1990 and 20082011Ingår i: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 16, s. 191-208Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Evaluation of changes in Baltic Sea phytoplankton communities has been hampered by a lack of quantitative long-term data. We investigated changes in biomass of summer (June–September) phytoplankton over the last two decades (1990–2008) along a north–south gradient in the Baltic Sea. The areas were characterized by different temperature, salinity and nutrient conditions. Thirty taxonomic groups were selected for the statistical analysis. Increases in total phytoplankton, particularly cyanobacterial, biomass were observed in the Gulfs of Bothnia and Finland. In these two areas over the study period cyanobacteria also became abundant earlier in the season, and in the Curonian Lagoon Planktothrix agardhii replaced Aphanizomenon flos-aquae as the most abundant cyanobacterium. In general, water temperature was the most influential factor affecting the summer phytoplankton communities. Our data suggest that temperature increases resulting from climate change are likely to cause basin-specific changes in the phytoplankton communities, which in turn may affect overall ecosystem functioning in the Baltic Sea.

  • 59.
    Jansson, Mats
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jonsson, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Biomass and structure of planktonic communities along an air temperature gradient in subarctic Sweden2010Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 55, nr 3, s. 691-700Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Air temperature will probably have pronounced effects on the composition of plankton communities in northern lake ecosystems, either via indirect effects on the export of essential elements from catchments or through direct effects of water temperature and the ice-free period on the behaviour of planktonic organisms.

    2. We assessed the role of temperature by comparing planktonic communities in 15 lakes along a 6 °C air temperature gradient in subarctic Sweden.

    3. We found that the biomass of phytoplankton, bacterioplankton and the total planktonic biomass were positively related to air temperature, probably as a result of climatic controls on the export of nitrogen from the catchment (which affects phytoplankton biomass) and dissolved organic carbon (affecting bacterioplankton biomass).

    4. The structure of the zooplankton community, and top down effects on phytoplankton, were apparently not related to temperature but mainly to trophic interactions ultimately dependent on the presence of fish in the lakes.

    5. Our results suggest that air temperature regimes and long-term warming can have strong effects on the planktonic biomass in high latitude lakes. Effects of temperature on the structure of the planktonic community might be less evident unless warming permits the invasion of fish into previous fishless lakes.

  • 60.
    Jonsson, Sofi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Nilsson, Mats B
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Skyllberg, Ulf
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Schaefer, Jeffra K
    Department of Geosciences, Princeton University.
    Åkerblom, Staffan
    Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Impact of nutrient and humic matter loadings on methylmercury formation and bioaccumulation in estuarine ecosystemsManuskript (preprint) (Övrigt vetenskapligt)
  • 61.
    Jonsson, Sofi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Nilsson, Mats B.
    Skyllberg, Ulf
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Schaefer, Jeffra K.
    Åkerblom, Staffan
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Terrestrial discharges mediate trophic shifts and enhance methylmercury accumulation in estuarine biota2017Ingår i: Science Advances, Vol. 3, nr 1, artikel-id e1601239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The input of mercury (Hg) to ecosystems is estimated to have increased two- to fivefold during the industrial era, and Hg accumulates in aquatic biota as neurotoxic methylmercury (MeHg). Escalating anthropogenic land use and climate change are expected to alter the input rates of terrestrial natural organic matter (NOM) and nutrients to aquatic ecosystems. For example, climate change has been projected to induce 10 to 50% runoff increases for large coastal regions globally. A major knowledge gap is the potential effects on MeHg exposure to biota following these ecosystem changes. We monitored the fate of five enriched Hg isotope tracers added to mesocosm scale estuarine model ecosystems subjected to varying loading rates of nutrients and terrestrial NOM. We demonstrate that increased terrestrial NOM input to the pelagic zone can enhance the MeHg bioaccumulation factor in zooplankton by a factor of 2 to 7 by inducing a shift in the pelagic food web from autotrophic to heterotrophic. The terrestrial NOM input also enhanced the retention of MeHg in the water column by up to a factor of 2, resulting in further increased MeHg exposure to pelagic biota. Using mercury mass balance calculations, we predict that MeHg concentration in zooplankton can increase by a factor of 3 to 6 in coastal areas following scenarios with 15 to 30% increased terrestrial runoff. The results demonstrate the importance of incorporating the impact of climate-induced changes in food web structure on MeHg bioaccumulation in future biogeochemical cycling models and risk assessments of Hg.

  • 62.
    Jonsson, Sofi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Skyllberg, Ulf
    Nilsson, Mats B.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Differentiated availability of geochemical mercury pools controls methylmercury levels in estuarine sediment and biota2014Ingår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, s. 4624-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Neurotoxic methylmercury (MeHg) formed from inorganic divalent mercury (HgII) accumulates in aquatic biota and remains at high levels worldwide. It is poorly understood to what extent different geochemical Hg pools contribute to these levels. Here we report quantitative data on MeHg formation and bioaccumulation, in mesocosm water-sediment model ecosystems, using five HgII and MeHg isotope tracers simulating recent Hg inputs to the water phase and Hg stored in sediment as bound to natural organic matter or as metacinnabar. Calculations for an estuarine ecosystem suggest that the chemical speciation of HgII solid/adsorbed phases control the sediment Hg pool's contribution to MeHg, but that input of MeHg from terrestrial and atmospheric sources bioaccumulates to a substantially greater extent than MeHg formed in situ in sediment. Our findings emphasize the importance of MeHg loadings from catchment runoff to MeHg content in estuarine biota and we suggest that this contribution has been underestimated.

  • 63.
    Jonsson, Sofi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Skyllberg, Ulf
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Nilsson, Mats B
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Differentiated reactivity of geochemical mercury pools control methylmercury levels in sediment and biotaManuskript (preprint) (Övrigt vetenskapligt)
  • 64. Karlsson, Bengt
    et al.
    Hajdu, Susanna
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Huseby, Siv
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Skadliga algblomningar2008Ingår i: Havet: om miljötillståndet i svenska havsområden. 2008, Stockholm: Naturvårdsverket, 2008, s. 46-49Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 65. Kuparinen, J
    et al.
    Kuosa, H
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Autio, R
    Granskog, MA
    Ikävalko, J
    Kaartokallio, H
    Karell, K
    Leskinen, E
    Piiparinen, J
    Rintala, J-M
    Tuomainen, J
    Role of sea-ice biota in nutrient and organic material cycles in the northern Baltic Sea2007Ingår i: Ambio, Vol. 36, s. 149-154Artikel i tidskrift (Refereegranskat)
  • 66. Kuuppo, Pirjo
    et al.
    Samuelsson, Kristina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Ekologi och geovetenskap.
    Lignell, Risto
    Seppälä, Jorma
    Tamminen, Timo
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Fate of increased production due to nutrient enrichment in late-summer plankton communities of the Baltic Proper2003Ingår i: Aquatic Microbial Ecology, ISSN 0948-3055, Vol. 32, nr 1, s. 47-60Artikel i tidskrift (Refereegranskat)
  • 67. Larsson, U
    et al.
    Hajdu, S
    Walve, J
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Larsson, P
    Edler, L
    Bedömningsgrunder för kust och hav: Växtplankton, näringsämnen, klorofyll, siktdjup2016Rapport (Refereegranskat)
  • 68.
    Lefebure, Robert
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Degerman, Rickard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Larsson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Eriksson, Lars-Ove
    Department of Wildlife, Fish and Environmental Studies, SLU, Umeå, Sweden.
    Båmstedt, Ulf
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Impacts of elevated terrestrial nutrient loads and temperature on pelagic food-web efficiency and fish production2013Ingår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, nr 5, s. 1358-1372Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Both temperature and terrestrial organic matter have strong impacts on aquatic food-web dynamics and production. Temperature affects vital rates of all organisms, and terrestrial organic matter can act both as an energy source for lower trophic levels, while simultaneously reducing light availability for autotrophic production. As climate change predictions for the Baltic Sea and elsewhere suggest increases in both terrestrial matter runoff and increases in temperature, we studied the effects on pelagic food-web dynamics and food-web efficiency in a plausible future scenario with respect to these abiotic variables in a large-scale mesocosm experiment. Total basal (phytoplankton plus bacterial) production was slightly reduced when only increasing temperatures, but was otherwise similar across all other treatments. Separate increases in nutrient loads and temperature decreased the ratio of autotrophic:heterotrophic production, but the combined treatment of elevated temperature and terrestrial nutrient loads increased both fish production and food-web efficiency. CDOM: Chl a ratios strongly indicated that terrestrial and not autotrophic carbon was the main energy source in these food webs and our results also showed that zooplankton biomass was positively correlated with increased bacterial production. Concomitantly, biomass of the dominant calanoid copepod Acartia sp. increased as an effect of increased temperature. As the combined effects of increased temperature and terrestrial organic nutrient loads were required to increase zooplankton abundance and fish production, conclusions about effects of climate change on food-web dynamics and fish production must be based on realistic combinations of several abiotic factors. Moreover, our results question established notions on the net inefficiency of heterotrophic carbon transfer to the top of the food web.

  • 69. Legrand, Catherine
    et al.
    Fridolfsson, Emil
    Bertos-Fortis, Mireia
    Lindehoff, Elin
    Larsson, Per
    Pinhassi, Jarone
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Interannual variability of phyto-bacterioplankton biomass and production in coastal and offshore waters of the Baltic Sea2015Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, nr Suppl 3, s. S427-S438Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microbial part of the pelagic food web is seldom characterized in models despite its major contribution to biogeochemical cycles. In the Baltic Sea, spatial and temporal high frequency sampling over three years revealed changes in heterotrophic bacteria and phytoplankton coupling (biomass and production) related to hydrographic properties of the ecosystem. Phyto- and bacterioplankton were bottom-up driven in both coastal and offshore areas. Cold winter temperature was essential for phytoplankton to conform to the successional sequence in temperate waters. In terms of annual carbon production, the loss of the spring bloom (diatoms and dinoflagellates) after mild winters tended not to be compensated for by other taxa, not even summer cyanobacteria. These results improve our ability to project Baltic Sea ecosystem response to short- and long-term environmental changes.

  • 70.
    Liem-Nguyen, Van
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Jonsson, Sofi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Skyllberg, Ulf
    Nilsson, Mats B.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lundberg, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Effects of Nutrient Loading and Mercury Chemical Speciation on the Formation and Degradation of Methylmercury in Estuarine Sediment2016Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 50, nr 13, s. 6983-6990Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Net formation of methylmercury (MeHg) in sediments is known to be affected by the availability of inorganic divalent mercury (HgII) and by the activities of HgII methylating and MeHg demethylating bacteria. Enhanced autochthonous organic matter deposition to the benthic zone, following increased loading of nutrients to the pelagic zone, has been suggested to increase the activity of HgII methylating bacteria and thus the rate of net methylation. However, the impact of increased nutrient loading on the biogeochemistry of mercury (Hg) is challenging to predict as different geochemical pools of Hg may respond differently to enhanced bacterial activities. Here, we investigate the combined effects of nutrient (N and P) supply to the pelagic zone and the chemical speciation of HgII and of MeHg on MeHg formation and degradation in a brackish sediment-water mesocosm model ecosystem. By use of Hg isotope tracers added in situ to the mesocosms or ex situ in incubation experiments, we show that the MeHg formation rate increased with nutrient loading only for HgII tracers with a high availability for methylation. Tracers with low availability did not respond significantly to nutrient loading. Thus, both microbial activity (stimulated indirectly through plankton biomass production by nutrient loading) and HgII chemical speciation were found to control the MeHg formation rate in marine sediments. 

  • 71. Lindh, Markus V.
    et al.
    Figueroa, Daniela
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sjostedt, Johanna
    Baltar, Federico
    Lundin, Daniel
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Legrand, Catherine
    Pinhassi, Jarone
    Transplant experiments uncover Baltic Sea basin-specific responses in bacterioplankton community composition and metabolic activities2015Ingår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 6, artikel-id 223Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anthropogenically induced changes in precipitation are projected to generate increased river runoff to semi enclosed seas, increasing loads of terrestrial dissolved organic matter and decreasing salinity. To determine how bacterial community structure and functioning adjust to such changes, we designed microcosm transplant experiments with Baltic Proper (salinity 7.2) and Bothnian Sea (salinity 3.6) water. Baltic Proper bacteria generally reached higher abundances than Bothnian Sea bacteria in both Baltic Proper and Bothnian Sea water, indicating higher adaptability. Moreover, Baltic Proper bacteria growing in Bothnian Sea water consistently showed highest bacterial production and beta-glucosidase activity. These metabolic responses were accompanied by basin specific changes in bacterial community structure. For example, Baltic Proper Pseudomonas and Limnobacter populations increased markedly in relative abundance in Bothnian Sea water, indicating a replacement effect. In contrast, Roseobacter and Rheinheknera populations were stable or increased in abundance when challenged by either of the waters, indicating an adjustment effect. Transplants to Bothnian Sea water triggered the initial emergence of particular Burkholderiaceae populations, and transplants to Baltic Proper water triggered Alteromonadaceae populations. Notably, in the subsequent re transplant experiment, a priming effect resulted in further increases to dominance of these populations. Correlated changes in community composition and metabolic activity were observed only in the transplant experiment and only at relatively high phylogenetic resolution. This suggested an importance of successional progression for interpreting relationships between bacterial community composition and functioning. We infer that priming effects on bacterial community structure by natural episodic events or climate change induced forcing could translate into long-term changes in bacterial ecosystem process rates.

  • 72. Lindh, Markus V.
    et al.
    Lefébure, Robert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Marine Stewardship Council, London EC1A 2DH, England.
    Degerman, Rickard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lundin, Daniel
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Pinhassi, Jarone
    Consequences of increased terrestrial dissolved organic matter and temperature on bacterioplankton community composition during a Baltic Sea mesocosm experiment2015Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, nr Suppl 3, s. S402-S412Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Predicted increases in runoff of terrestrial dissolved organic matter (DOM) and sea surface temperatures implicate substantial changes in energy fluxes of coastal marine ecosystems. Despite marine bacteria being critical drivers of marine carbon cycling, knowledge of compositional responses within bacterioplankton communities to such disturbances is strongly limited. Using 16S rRNA gene pyrosequencing, we examined bacterioplankton population dynamics in Baltic Sea mesocosms with treatments combining terrestrial DOM enrichment and increased temperature. Among the 200 most abundant taxa, 62 % either increased or decreased in relative abundance under changed environmental conditions. For example, SAR11 and SAR86 populations proliferated in combined increased terrestrial DOM/temperature mesocosms, while the hgcI and CL500-29 clades (Actinobacteria) decreased in the same mesocosms. Bacteroidetes increased in both control mesocosms and in the combined increased terrestrial DOM/temperature mesocosms. These results indicate considerable and differential responses among distinct bacterial populations to combined climate change effects, emphasizing the potential of such effects to induce shifts in ecosystem function and carbon cycling in the future Baltic Sea.

  • 73. Lindh, Markus V.
    et al.
    Sjostedt, Johanna
    Ekstam, Borje
    Casini, Michele
    Lundin, Daniel
    Hugerth, Luisa W.
    Hu, Yue O. O.
    Andersson, Anders F.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Legrand, Catherine
    Pinhassi, Jarone
    Metapopulation theory identifies biogeographical patterns among core and satellite marine bacteria scaling from tens to thousands of kilometers2017Ingår i: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 19, nr 3, s. 1222-1236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Metapopulation theory developed in terrestrial ecology provides applicable frameworks for interpreting the role of local and regional processes in shaping species distribution patterns. Yet, empirical testing of metapopulation models on microbial communities is essentially lacking. We determined regional bacterioplankton dynamics from monthly transect sampling in the Baltic Sea Proper using 16S rRNA gene sequencing. A strong positive trend was found between local relative abundance and occupancy of populations. Notably, the occupancy-frequency distributions were significantly bimodal with a satellite mode of rare endemic populations and a core mode of abundant cosmopolitan populations (e.g. Synechococcus, SAR11 and SAR86 clade members). Temporal changes in population distributions supported several theoretical frameworks. Still, bimodality was found among bacterioplankton communities across the entire Baltic Sea, and was also frequent in globally distributed datasets. Datasets spanning waters with widely different physicochemical characteristics or environmental gradients typically lacked significant bimodal patterns. When such datasets were divided into subsets with coherent environmental conditions, bimodal patterns emerged, highlighting the importance of positive feedbacks between local abundance and occupancy within specific biomes. Thus, metapopulation theory applied to microbial biogeography can provide novel insights into the mechanisms governing shifts in biodiversity resulting from natural or anthropogenically induced changes in the environment.

  • 74. Lindh, Markus V.
    et al.
    Sjöstedt, Johanna
    Casini, Michele
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Legrand, Catherine
    Pinhassi, Jarone
    Local Environmental Conditions Shape Generalist But Not Specialist Components of Microbial Metacommunities in the Baltic Sea2016Ingår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 7, artikel-id 2078Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Marine microbes exhibit biogeographical patterns linked with fluxes of matter and energy. Yet, knowledge of the mechanisms shaping bacterioplankton community assembly across temporal scales remains poor. We examined bacterioplankton 16S rRNA gene fragments obtained from Baltic Sea transects to determine phylogenetic relatedness and assembly processes coupled with niche breadth. Communities were phylogenetically more related over time than expected by chance, albeit with considerable temporal variation. Hence, habitat filtering, i.e., local environmental conditions, rather than competition structured bacterioplankton communities in summer but not in spring or autumn. Species sorting (SS) was the dominant assembly process, but temporal and taxonomical variation in mechanisms was observed. For May communities, Cyanobacteria, Actinobacteria, Alpha- and Betaproteobacteria exhibited SS while Bacteroidetes and Verrucomicrobia were assembled by SS and mass effect. Concomitantly, Gammaproteobacteria were assembled by the neutral model and patch dynamics. Temporal variation in habitat filtering and dispersal highlights the impact of seasonally driven reorganization of microbial communities. Typically abundant Baltic Sea populations such as the NS3a marine group (Bacteroidetes) and the SAR86 and SAR11 clade had the highest niche breadth. The verrucomicrobial Spartobacteria population also exhibited high niche breadth. Surprisingly, variation in bacterioplankton community composition was regulated by environmental factors for generalist taxa but not specialists. Our results suggest that generalists such as NS3a, SAR86, and SAR11 are reorganized to a greater extent by changes in the environment compared to specialists and contribute more strongly to determining overall biogeographical patterns of marine bacterial communities.

  • 75.
    Mathisen, Peter
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Forsman, Mats
    Division of CBRN Defence and Security, Swedish Defence Research Agency, FOI, SE-901 82 Umeå, Sweden.
    Noppa, Laila
    Division of CBRN Defence and Security, Swedish Defence Research Agency, FOI, SE-901 82 Umeå, Sweden.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi.
    Thelaus, Johanna
    Division of CBRN Defence and Security, Swedish Defence Research Agency, FOI, SE-901 82 Umeå, Sweden.
    Francisella tularensis subspecies holarctica´s adaptation to protozoan and mammal hostsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The long co-existence of bacteria and protozoa in natural ecosystems has led to the evolution of different bacterial predation-resistance mechanisms1, which in turn may have triggered development of mammal pathogens2, such as the tularemia bacterium Francisella tularensis3. We studied links between environmental persistence and pathogenicity of Francisella tularensis subsp. holarctica (F. t. holarctica), by comparing its growth in association with an aquatic amoeba and a murine macrophage. A virulent wild-type strain and four isogenic mutations with different functional protein deletions were compared; DsbA4, 5 a membrane lipoprotein with disulfide oxidoreductase activity important for proper folding in Francisella tularensis; Hfq6 a pleiotropic regulatory RNA binding protein; PilA7, 8 a type IV pilus subunit and PglA9 a protein involved in O-linked protein glycosylation. DsbA was found to be essential for bacterial growth in association with both amoeba and macrophage, while PglA did not affect bacterial persistence in any of the hosts. Absence of PilA and Hfq had marked negative effect on the bacterial cell counts in amoeba, while growth was only slightly impaired in the macrophage. Functional similarities for bacterial persistence in both hosts highlight eco-evolutionary links between persistence of intracellular pathogenic bacteria in aquatic systems and mammal hosts.

  • 76.
    Mathisen, Peter
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Thelaus, J
    Sjöstedt de Luna, Sara
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rapid adaptation of predation resistance in bacteria isolated from a seawater microcosm2016Ingår i: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 78, nr 2, s. 81-92Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bacterial defense against protozoan grazing has been shown to occur in many different bacteria. Predation resistance traits may however be plastic, making bacterial com munities resilient or resistant to predation perturbations. We studied the adaptation of pre dation resistance traits in bacteria isolated from a microcosm experiment. In the initial microcosm ex periment the predation pressure on bacteria varied markedly, while changes in the bacterial community composition could not be verified. Seven bacteria were isolated from the microcosm (Micrococcus sp., Rhodobacter sp., Paracoccus sp., Shewanella sp., Rhizobium sp. and 2 un identified species) and these were repeatedly exposed to high predation by the ciliate Tetrahymena pyriformis. High variations in edibility and rate of adaptation of predation resistance traits were observed among the strains. The initial mortality rate of the different bacterial taxa and the change over time varied by a factor of 7 and 24, respectively. Rhodobacter sp. was already predation resistant at the start of the experiment and did not change much over time, while Micrococcus sp., Paracoccus sp. and Shewanella sp. initially were relatively edible and later developed predation resistance. In conclusion, we show that rapid adaptation of predation resistance traits is common among bacteria in an aquatic microbial community, and that a single test of a bacterium’s edibility will in many cases not be enough to fully understand its ecological role, as it will not reveal the potential adaptive response. The results suggest the potential of rapid changes of predation resistance as a mechanism for bacterial communities to be resilient to variations in predation disturbances.

  • 77.
    Meunier, Cédric L.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Liess, Antonia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Rydberg Laboratory of Applied Science, School of Business, Science and Engineering, Halmstad University, Halmstad, Sweden.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Brugel, Sonia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Paczkowska, Joanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Rahman, Habib
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Skoglund, Björn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rowe, Owen F.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Allochthonous carbon is a major driver of the microbial food web: a mesocosm study simulating elevated terrestrial matter runoff2017Ingår i: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 129, s. 236-244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climate change predictions indicate that coastal and estuarine environments will receive increased terrestrial runoff via increased river discharge. This discharge transports allochthonous material, containing bioavailable nutrients and light attenuating matter. Since light and nutrients are important drivers of basal production, their relative and absolute availability have important consequences for the base of the aquatic food web, with potential ramifications for higher trophic levels. Here, we investigated the effects of shifts in terrestrial organic matter and light availability on basal producers and their grazers. In twelve Baltic Sea mesocosms, we simulated the effects of increased river runoff alone and in combination. We manipulated light (clear/shade) and carbon (added/not added) in a fully factorial design, with three replicates. We assessed microzooplankton grazing preferences in each treatment to assess whether increased terrestrial organic matter input would: (1) decrease the phytoplankton to bacterial biomass ratio, (2) shift microzooplanlcton diet from phytoplankton to bacteria, and (3) affect microzooplankton biomass. We found that carbon addition, but not reduced light levels per se resulted in lower phytoplanlcton to bacteria biomass ratios. Microzooplankton generally showed a strong feeding preference for phytoplanlcton over bacteria, but, in carbon-amended mesocosms which favored bacteria, microzooplankton shifted their diet towards bacteria. Furthermore, low total prey availability corresponded with low microzooplankton biomass and the highest bacteria/phytoplankton ratio. Overall our results suggest that in shallow coastal waters, modified with allochthonous matter from river discharge, light attenuation may be inconsequential for the basal producer balance, whereas increased allochthonous carbon, especially if readily bioavailable, favors bacteria over phytoplankton. We conclude that climate change induced shifts at the base of the food web may alter energy mobilization to and the biomass of microzooplankton grazers.

  • 78.
    Müren, U
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Berglund, J
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Samuelsson, K
    Andersson, A
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Potential effects of elevated sea-water temperature on pelagic food webs2005Ingår i: Hydrobiologia, Vol. 545, s. 153-166Artikel i tidskrift (Refereegranskat)
  • 79. Olenina, I
    et al.
    Hajdu, S
    Edler, L
    Andersson, A
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Wasmund, N
    Busch, S
    Göbel, J
    Gromisz, S
    Huseby, Siv
    Huttunen, M
    Jaanus, A
    Kokkonen, P
    Ledaine, I
    Niemkiewicz, E
    Biovolumes and size-classes of phytoplankton in the Baltic Sea2006Ingår i: HELCOM, Balt. Sea Environ. Proc, Vol. 106, s. 1-144Artikel i tidskrift (Refereegranskat)
  • 80. Olenina, I
    et al.
    Hajdu, S
    Edler, L
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Wasmund, N
    Göbel, J
    Huttunen, M
    Jaanus, A
    Ledaine, I
    Huseby, S
    Niemkiewicz, E
    Biovolumes and size-classes of phytoplankton in the Baltic Sea2006Ingår i: Baltic Sea Environment proceedings, ISSN 0357-2994, nr 106Artikel i tidskrift (Refereegranskat)
  • 81.
    Paczkowska, Joanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Brugel, Sonia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rowe, Owen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lefébure, Robert
    Brutemark, Andreas
    ARONIA Research and Development Institute, Novia University of Applied Sciences and Åbo Akademi University, Raseborgsvägen 9, FI-10600 Ekenäs, Finland.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Influence of allochthonous dissolved organic matter on a coastal phytoplankton communityManuskript (preprint) (Övrigt vetenskapligt)
  • 82.
    Paczkowska, Joanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Centro para el Estudiode Sistemas Marinos CESIMAR-CONICET, Blvd. Brown 2915, U9120ACD, Puerto Madryn, Chubut, Argentina .
    Rowe, Owen F.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Guest researcher: Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, Viikki Biocenter 1, University of Helsinki, Helsinki, Finland; Helsinki Commission, HELCOM Secretariat, Baltic Marine Environment Protection Commission, Helsinki, Finland.
    Figueroa, Daniela
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Swedish Meteorological and Hydrological Institute, SMHI, Göteborg, Sweden.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Drivers of phytoplankton production and community structure in nutrient-poor estuaries receiving terrestrial organic inflow2019Ingår i: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 151, artikel-id 104778Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of nutrient availability and light conditions on phytoplankton size-structure, nutritional strategy and production was studied in a phosphorus-poor estuary in the northern Baltic Sea receiving humic-rich river water. The relative biomass of mixotrophic nanophytoplankton peaked in spring when heterotrophic bacterial production was high, while autotrophic microphytoplankton had their maximum in summer when primary production displayed highest values. Limiting substance (phosphorus) only showed small temporal variations, and the day light was at saturating levels all through the study period. We also investigated if the phytoplankton taxonomic richness influences the production. Structural equation modelling indicated that an increase of the taxonomic richness during the warm summer combined with slightly higher phosphorus concentration lead to increased resource use efficiency, which in turn caused higher phytoplankton biomass and primary production. Our results suggest that climate warming would lead to higher primary production in northerly shallow coastal areas, which are influenced by humic-rich river run-off from un-disturbed terrestrial systems.

  • 83.
    Paczkowska, Joanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rowe, Owen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Figueroa, Daniela
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Drivers of phytoplankton production and community structure in a sub-arctic estuary influenced by seasonal river dischargeManuskript (preprint) (Övrigt vetenskapligt)
  • 84.
    Paczkowska, Joanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. UMEÅ MARINE SCIENCE CENTRE, SE-905 71 HÖRNEFORS, SWEDEN.
    Rowe, Owen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. UMEÅ MARINE SCIENCE CENTRE, SE-905 71 HÖRNEFORS, SWEDEN; DEPARTMENT OF FOOD AND ENVIRONMENTAL SCIENCES, DIVISION OF MICROBIOLOGY AND BIOTECHNOLOGY, VIIKKI BIOCENTER I, UNIVERSITY OF HELSINKI, HELSINKI, FINLAND.
    Schlüter, Louise
    DHI, Environment and Toxicology, Agern Allé 5, 2970 Hørsholm, Denmark.
    Legrand, Catherine
    Center of Ecology and Evolution in Microbial Model Systems, EEMiS, Department of Biology and Environmental Sciences, Linnaeus University, SE-391 82 Kalmar, Sweden.
    Karlson, Bengt
    Swedish Meteorological and Hydrological Institute, Oceanography SE-426 71 Västra Frölunda, Sweden.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. UMEÅ MARINE SCIENCE CENTRE, SE-905 71 HÖRNEFORS, SWEDEN.
    Allochthonous matter: an important factor shaping the phytoplankton community in the Baltic Sea2017Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 39, nr 1, s. 23-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is well-known that nutrients shape phytoplankton communities in marine systems, but in coastal waters allochthonous dissolved organic matter (ADOM) may also be of central importance. We studied how humic substances (proxy of ADOM) and other variables influenced the nutritional strategies, size structure and pigment content of the phytoplankton community along a south-north gradient in the Baltic Sea. During the summer, the proportion of mixotrophs increased gradually from the phosphorus-rich south to the ADOM-rich north, probably due to ADOM-fueled microbes. The opposite trend was observed for autotrophs. The chlorophyll a (Chl a): carbon (C) ratio increased while the levels of photoprotective pigments decreased from south to north, indicating adaptation to the darker humic-rich water in the north. Picocyanobacteria dominated in phosphorusrich areas while nanoplankton increased in ADOM- rich areas. During the winter-spring the phytoplankton biomass and concentrations of photoprotective pigments were low, and no trends with respect to autotrophs and mixotrophs were observed. Microplankton was the dominant size group in the entire study area. We conclude that changes in the size structure of the phytoplankton community, the Chl a: C ratio and the concentrations of photoprotective pigments are indicative of changes in ADOM, a factor of particular importance in a changing climate.

  • 85.
    Ripszám, Mátyás
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Gallampois, Christine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Berglund, Åsa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Larsson, Henrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Haglund, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Effects of predicted climatic changes on distribution of organic contaminants in brackish water mesocosms2015Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 517, nr 1 June 2015, s. 10-21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Predicted consequences of future climate change in the northern Baltic Sea include increases in sea surface temperatures and terrestrial dissolved organic carbon (DOC) runoff. These changes are expected to alter environmental distribution of anthropogenic organic contaminants (OCs). To assess likely shifts in their distributions, outdoor mesocosms were employed to mimic pelagic ecosystems at two temperatures and two DOC concentrations, current: 15 degrees C and 4 mg DOC L-1 and, within ranges of predicted increases, 18 degrees C and 6 mg DOC L-1, respectively. Selected organic contaminants were added to the mesocosms to monitor changes in their distribution induced by the treatments. OC partitioning to particulate matter and sedimentation were enhanced at the higher DOC concentration, at both temperatures, while higher losses and lower partitioning of OCs to DOC were observed at the higher temperature. No combined effects of higher temperature and DOC on partitioning were observed, possibly because of the balancing nature of these processes. Therefore, changes in OCs' fates may largely depend on whether they are most sensitive to temperature or DOC concentration rises. Bromoanilines, phenanthrene, biphenyl and naphthalene were sensitive to the rise in DOC concentration, whereas organophosphates, chlorobenzenes (PCBz) and polychlorinated biphenyls (POs) were more sensitive to temperature. Mitotane and diflufenican were sensitive to both temperature and DOC concentration rises individually, but not in combination. (C) 2015 Elsevier B.V. All rights reserved.

  • 86. Rodríguez, Juanjo
    et al.
    Gallampois, Christine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Timonen, Sari
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sinkko, Hanna
    Haglund, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Berglund, Åsa M. M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ripszam, Matyas
    Figueroa, Daniela
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Rowe, Owen
    Effects of Organic Pollutants on Bacterial Communities Under Future Climate Change Scenarios2018Ingår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 9, artikel-id 2926Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coastal ecosystems are highly dynamic and can be strongly influenced by climate change, anthropogenic activities (e.g. pollution) and a combination of the two pressures. As a result of climate change, the northern hemisphere is predicted to undergo an increased precipitation regime, leading in turn to higher terrestrial runoff and increased river inflow. This increased runoff will transfer terrestrial dissolved organic matter (tDOM) and anthropogenic contaminants to coastal waters. Such changes can directly influence the resident biology, particularly at the base of the food web, and can influence the partitioning of contaminants and thus their potential impact on the food web. Bacteria have been shown to respond to high tDOM concentration and organic pollutants loads, and could represent the entry of some pollutants into coastal food webs. We carried out a mesocosm experiment to determine the effects of: 1) increased tDOM concentration, 2) organic pollutant exposure, and 3) the combined effect of these two factors, on pelagic bacterial communities. This study showed significant responses in bacterial community composition under the three environmental perturbations tested. The addition of tDOM increased bacterial activity and diversity, while the addition of organic pollutants led to an overall reduction of these parameters, particularly under concurrent elevated tDOM concentration. Furthermore, we identified 33 bacterial taxa contributing to the significant differences observed in community composition, as well as 35 bacterial taxa which responded differently to extended exposure to organic pollutants. These findings point to the potential impact of organic pollutants under future climate change conditions on the basal coastal ecosystem, as well as to the potential utility of natural bacterial communities as efficient indicators of environmental disturbance.

  • 87.
    Rowe, Owen F.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, University of Helsinki, Helsinki, Finland; Helsinki Commission, HELCOM Secretariat, Baltic Marine Environment Protection Commission, Helsinki, Finland.
    Dinasquet, Julie
    Paczkowska, Joanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Figueroa, Daniela
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Riemann, Lasse
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Major differences in dissolved organic matter characteristics and bacterial processing over an extensive brackish water gradient, the Baltic Sea2018Ingår i: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 202, s. 27-36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dissolved organic matter (DOM) in marine waters is a complex mixture of compounds and elements that contribute substantially to the global carbon cycle. The large reservoir of dissolved organic carbon (DOC) represents a vital resource for heterotrophic bacteria. Bacteria can utilise, produce, recycle and transform components of the DOM pool, and the physicochemical characteristics of this pool can directly influence bacterial activity; with consequences for nutrient cycling and primary productivity. In the present study we explored bacterial transformation of naturally occurring DOM across an extensive brackish water gradient in the Baltic Sea. Highest DOC utilisation (indicated by decreased DOC concentration) was recorded in the more saline southerly region where waters are characterised by more autochthonous DOM. These sites expressed the lowest bacterial growth efficiency (BGE), whereas in northerly regions, characterised by higher terrestrial and allochthonous DOM, the DOC utilisation was low and BGE was highest. Bacterial processing of the DOM pool in the south resulted in larger molecular weight compounds and compounds associated with secondary terrestrial humic matter being degraded, and a processed DOM pool that was more aromatic in nature and contributed more strongly to water colour; while the opposite was true in the north. Nutrient concentration and stoichiometry and DOM characteristics affected bacterial activity, including metabolic status (BGE), which influenced DOM transformations. Our study highlights dramatic differences in DOM characteristics and microbial carbon cycling in sub-basins of the Baltic Sea. These findings are critical for our understanding of carbon and nutrient biogeochemistry, particularly in light of climate change scenarios.

  • 88.
    Rowe, Owen F.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, Viikki Biocenter 1, University of Helsinki, Helsinki, Finland.
    Guleikova, Liudmyla
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Institute of Hydrobiology National Academy of Sciences of Ukraine, UA-04210, Kyiv, Ukraine.
    Brugel, Sonia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    A potential barrier to the spread of the invasive cladoceran Cercopagis pengoi (Ostroumov 1891) in the Northern Baltic Sea2016Ingår i: Regional Studies in Marine Science, ISSN 0080-0694, E-ISSN 2168-1376, Vol. 3, s. 8-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spread of the invasive cladoceran Cercopagis pengoi has been well documented in southern areas of the Baltic Sea, however, little research on this invasive species (nor the zooplankton community) has focused on the Gulf of Bothnia (Bothnian Sea and Bay). We analysed data collected over a 12–13 year period at two main stations, one coastal and one offshore, to examine the occurrence of C. pengoi, invasion dynamics, effects on natural zooplankton communities and associated environmental factors. Nine other stations in the Gulf of Bothnia were also examined and the contribution to three-spined stickleback (Gasterosteus aculeatus) diet was quantified. The zooplankton community response apparently differed between coastal and offshore stations with Bosmina, Eurytemora, and Acartia populations being influenced during peak abundances of C. pengoi. It appears that the native zooplankton community has some resilience, returning to its prior structure outside of peak invasion periods. C. pengoi, where present, contributed significantly to stickleback diet. We explored possible barriers for C. pengoi in the Bothnian Bay, suggesting that the low productive Bothnian Bay ecosystem may be incapable of supporting such a predator. This highlights the need for further studies, especially in the light of global climate change.

  • 89. Samuelsson, K
    et al.
    Berglund, J
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Andersson, A
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Factors structuring the heterotrophic flagellate and ciliate community along a brackish water primary production gradient.2006Ingår i: J Plankton Research, Vol. 28, s. 345-359Artikel i tidskrift (Refereegranskat)
  • 90. Samuelsson, K
    et al.
    Edler, L
    Hajdu, S
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Bedömningsgrunder för kust och hav enligt EUs ramdirektiv. Växtplankton.2004Rapport (Refereegranskat)
  • 91.
    Sandberg, Johannes
    et al.
    1Department of Systems Ecology, Stockholm University, Stockholm, Sweden.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Johansson, S
    Swedish Environmental Protection Agency, Stockholm, Sweden.
    Wikner, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Pelagic food web structure and carbon budget in the northern Baltic Sea: Potential importance of terrigenous carbon2004Ingår i: Marine Ecology Progress Series, ISSN Print ISSN: 0171-8630; Online ISSN: 1616-1599, Vol. 268, s. 13-29Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this study was to quantitatively assess the relative importance of terrigenous dissolved organic material (TDOC) as a carbon source for secondary producers (e.g. bacteria) and as a structuring factor for the pelagic food web in the Gulf of Bothnia, northern Baltic Sea. The 3 study sites, situated in Bothnian Bay (BB), the Öre Estuary (ÖE) and the Bothnian Sea (BS), had markedly different freshwater loads and water-residence times. In Bothnian Bay, bacterial biomass and production were higher than expected from the levels of phytoplankton biomass and productivity there, suggesting an uncoupling of bacterial productivity from phytoplankton production. Phytoplankton size structure and size-fractionated production were, however, relatively similar among areas. A simplified carbon budget model suggested that bacterioplankton dominated organic carbon consumption in all of the food webs studied, but was most marked in BB. The model showed that the available autochthonous primary production could not alone support the heterotrophic carbon demand in BB. The most likely explanation of this discrepancy was that the total annual input of terrigenous dissolved organic carbon was bioavailable, resulting in a budget closer to balance with the heterotrophic carbon demand. BB, receiving 38% of the carbon input from land, was consequently a net heterotrophic ecosystem. A sensitivity analysis showed that the bacterial carbon demand, and growth efficiency in particular, had the greatest influence on the resulting budget. TDOC was the dominant carbon source in ÖE, but the losses of carbon through advection to offshore areas and sedimentation was high. The evidence of net heterotrophy in ÖE was therefore weaker than in BB. In BS the input of TDOC was less important, and the carbon used for secondary production originated mainly from autochthonous primary production. Our results suggest that the supply of TDOC is of great importance for the abundance of plankton and as a structuring factor for the aquatic food webs in the Gulf of Bothnia.

  • 92.
    Talyzina, Nina M
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ingvarsson, Pär K
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Zhu, J
    Wai, Sun N
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Molecular diversification in the quorum-sensing system of vibrio cholerae: role of natural selection in the emergence of pandemic strains2009Ingår i: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 75, s. 3808-3812Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two haplotypes of the Vibrio cholerae quorum-sensing system regulator hapR are described: hapR1, common among nonpandemic, non-O1, non-O139 strains, and hapR2, associated with pandemic O1 and O139 and epidemic O37 V. cholerae strains. The hapR2 has evolved under strong natural selection, implying that its fixation was influenced by conditions that led to cholera pandemics.

  • 93.
    Thelaus, Johanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Mathisen, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Forslund, A-L
    Forsman, Mats
    Influence of nutrient status and grazing pressure on the fate of Francisella tularensis in lake water2009Ingår i: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 67, nr 1, s. 69-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The natural reservoir of Francisella tularensis, the causative agent of tularaemia, is yet to be identified. We investigated the possibility that Francisella persists in natural aquatic ecosystems between outbreaks. It was hypothesized that nutrientrich environments, with strong protozoan predation, favour the occurrence of the tularaemia bacterium. To investigate the differences in adaptation to aquatic environments of the species and subspecies of Francisella, we screened 23 strains for their ability to survive grazing by the ciliate Tetrahymena pyriformis. All the Francisella strains tested were consumed at a low rate, although significant differences between subspecies were found. The survival and virulence of gfp-labelled F. tularensis ssp. holarctica were then studied in a microcosm experiment using natural lake water, with varying food web complexities and nutrient availabilities. High nutrient conditions in combination with high abundances of nanoflagellates were found to favour F. tularensis ssp. holarctica. The bacterium was observed both free-living and within the cells of a nanoflagellate. Francisella tularensis entered a viable but nonculturable state during the microcosm experiment. When studied over a longer period of time, F. tularensis ssp. holarctica survived in the lake water, but loss of virulence was not prevented by either high nutrient availability or the presence of predators.

  • 94.
    Thelaus, Johanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Mathisen, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Forslund, Anna-Lena
    Forsman, Mats
    Influence of nutrient status and microbial food web structure on the fate of Francisella tularensis in lake waterIngår i: Artikel i tidskrift (Refereegranskat)
  • 95.
    Thelaus, Johanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Forsman, Mats
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Role of productivity and protozoan abundance for the occurrence of predation-resistant bacteria in aquatic systems.2008Ingår i: Microbial Ecology, ISSN 0095-3628, Vol. 56, nr 1, s. 18-28Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Top–down control of lower trophic levels, e.g., bacteria, has been suggested to increase along aquatic productivity gradients. The response by the bacterial community may be to become more predation resistant in highly productive environments. To test this hypothesis, samples were taken from 20 aquatic systems along a productivity gradient (dissolved organic carbon from 7 to 71 mg/L), during late summer. The results showed that the biomass of bacteria, phytoplankton, and ciliates increased along the gradient (r 2 = 0.532, 0.426, and 0.758, P < 0.01, respectively). However, the organisms did not increase equally, and the ratio of protozoan to bacterial biomass showed a 100-fold increase along the gradient. Ciliates dominated the protozoan biomass in the more nutrient-rich waters. The edibility of colony-forming bacteria was tested using a ciliate predator, Tetrahymena pyriformis. Bacterial edibility was found to decrease with increases in nutrient richness and ciliate biomass in the aquatic systems (r 2 = 0.358, P < 0.01; r 2 = 0.242, P < 0.05, respectively). Quantile regression analysis indicated that the selection pressures on edible bacteria were increasing along the productivity gradient. Thus, inedible forms of bacteria were selected for in the transition from oligotrophic to eutrophic conditions. Isolated bacteria were distributed among the α-, β-, and γ- Proteobacteria and the Actinobacteria and Firmicutes taxa. We conclude that bacterial predation resistance increases in nutrient-rich waters with high protozoan predation.

  • 96.
    Thelaus, Johanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Haecky, Pia
    Forsman, Mats
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Predation pressure on bacteria increases along aquatic productivity gradients2008Ingår i: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 52, s. 45-55Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To elucidate how predation pressure on bacteria is affected by increasing productivity in aquatic systems, we ran model simulations of a microbial food web. In addition, we conducted a meta-analysis of data from studies in seas and lakes. The model was run as a flow-through system simulating conditions ranging from oligotrophic to hypertrophic. The organisms included in the model were heterotrophic bacteria, phytoplankton, 3 size classes of protozoa and metazooplankton. Predation pressure was defined as flagellate and ciliate grazing per bacterial biomass. The food-web model simulations showed increasing predation pressure on bacteria with increasing productivity (estimated chlorophyll a concentration 0.2 to 112 µg l–1). This was explained by an increase in bacterial production and the ratio of protozoan to bacterial biomass with increasing productivity. The results of the model simulation were supported by the meta-analysis, which showed increasing protozoan predation pressure on bacteria with increasing productivity in aquatic systems (chlorophyll a concentration 0.1 to 250 µg l–1). The ratio of protozoan to bacterial biomass also increased with productivity in the meta-analysis of field data. Our results suggest that protozoa control the bacterial community by predation in high-productivity environments.

  • 97. Traving, Sachia J.
    et al.
    Rowe, Owen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Jakobsen, Nina M.
    Sorensen, Helle
    Dinasquet, Julie
    Stedmon, Colin A.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Riemann, Lasse
    The Effect of Increased Loads of Dissolved Organic Matter on Estuarine Microbial Community Composition and Function2017Ingår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 8, artikel-id 351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Increased river loads are projected as one of the major consequences of climate change in the northern hemisphere, leading to elevated inputs of riverine dissolved organic matter (DOM) and inorganic nutrients to coastal ecosystems. The objective of this study was to investigate the effects of elevated DOM on a coastal pelagic food web from the coastal northern Baltic Sea, in a 32-day mesocosm experiment. In particular, the study addresses the response of bacterioplankton to differences in character and composition of supplied DOM. The supplied DOM differed in stoichiometry and quality and had pronounced effects on the recipient bacterioplankton, driving compositional changes in response to DOM type. The shifts in bacterioplankton community composition were especially driven by the proliferation of Bacteroidetes, Gemmatimonadetes, Planctomycetes, and Alpha-and Betaproteobacteria populations. The DOM additions stimulated protease activity and a release of inorganic nutrients, suggesting that DOM was actively processed. However, no difference between DOM types was detected in these functions despite different community compositions. Extensive release of re-mineralized carbon, nitrogen and phosphorus was associated with the bacterial processing, corresponding to 25-85% of the supplied DOM. The DOM additions had a negative effect on phytoplankton with decreased Chl a and biomass, particularly during the first half of the experiment. However, the accumulating nutrients likely stimulated phytoplankton biomass which was observed to increase towards the end of the experiment. This suggests that the nutrient access partially outweighed the negative effect of increased light attenuation by accumulating DOM. Taken together, our experimental data suggest that parts of the future elevated riverine DOM supply to the Baltic Sea will be efficiently mineralized by microbes. This will have consequences for bacterioplankton and phytoplankton community composition and function, and significantly affect nutrient biogeochemistry.

  • 98.
    Tysklind, Mats
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Haglund, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Bidleman, Terry F.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    A Baltic mystery2014Övrigt (Refereegranskat)
    Abstract [en]

    HNPs are produced by macroalgae (seaweeds), phytoplankton, worms, sponges and other marine organisms. HNPs in the Baltic comprise halocarbons, bromophenols and their transformation products, and other compounds with diverse chemical structures. The HNPs derived from bromophenols are widespread in Baltic algae, fi sh and mussels, and include bromoanisoles, hydroxylated and methoxylated bromodiphenyl ethers (OH- and MeO-BDEs) and polybrominated dibenzo-p-dioxins (PBDDs). Some of these also have anthropogenic origins; bromophenols are used as industrial compounds, while MeO-BDEs and OH-BDEs are metabolites and photolysis products of polybrominated diphenyl ether fl ame retardants. Nonetheless, radiocarbon-14 dating has shown that most of the OH-BDEs and MeO-BDEs found in marine mammals and sponges are natural. The bromophenolderived HNPs have toxic properties which add to the ‘soup’ of anthropogenic toxic chemicals present in the Baltic.

  • 99.
    Vaitkevicius, Karolis
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Lindmark, Barbro
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Ou, Gangwei
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi.
    Song, Tianyan
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Toma, Claudia
    Division of Bacterial Pathogenesis, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan.
    Iwanaga, Masaaki
    Division of Bacterial Pathogenesis, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan.
    Zhu, Jun
    Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Hammarström, Marie-Louise
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi.
    Tuck, Simon
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå centrum för molekylär patogenes (UCMP).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    A Vibrio cholerae protease needed for killing of Caenorhabditis elegans has a role in protection from natural predator grazing2006Ingår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 103, nr 24, s. 9280-9285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrio cholerae is the causal bacterium of the diarrheal disease cholera, and its growth and survival are thought to be curtailed by bacteriovorous predators, e.g., ciliates and flagellates. We explored Caenorhabditis elegans as a test organism after finding that V. cholerae can cause lethal infection of this nematode. By reverse genetics we identified an extracellular protease, the previously uncharacterized PrtV protein, as being necessary for killing. The killing effect is associated with the colonization of bacteria within the Caenorhabditis elegans intestine. We also show that PrtV is essential for V. cholerae in the bacterial survival from grazing by the flagellate Cafeteria roenbergensis and the ciliate Tetrahymena pyriformis. The PrtV protein appears to have an indirect role in the interaction of V. cholerae with mammalian host cells as judged from tests with tight monolayers of human intestinal epithelial cells. Our results demonstrate a key role for PrtV in V. cholerae interaction with grazing predators, and we establish Caenorhabditis elegans as a convenient organism for identification of V. cholerae factors involved in host interactions and environmental persistence.

  • 100. Villafane, Virginia E.
    et al.
    Paczkowska, Joanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Duran Romero, Cristina
    Valinas, Macarena S.
    Walter Helbling, E.
    Dual role of DOM in a scenario of global change on photosynthesis and structure of coastal phytoplankton from the South Atlantic Ocean2018Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 634, s. 1352-1361Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We evaluated the dual role of DOM (i.e., as a source of inorganic nutrients and as an absorber of solar radiation) on a phytoplankton community of the western South Atlantic Ocean. Using a combination of microcosms and a cluster approach, we simulated the future conditions of some variables that are highly influenced by global change in the region. We increased nutrients (i.e., anthropogenic input) and dissolved organic matter (DOM), and we decreased the pH, to assess their combined impact on growth rates (mu), species composition/abundance and size structure, and photosynthesis (considering in this later also the effects of light quality i.e., with andwithout ultraviolet radiation). We simulated two Future conditions (Fut) where nutrients and pHwere similarly manipulated, but in one the physical role of DOM (Fut(out)) was assessed whereas in the other (Fut(in)) the physicochemical role was evaluated; these conditions were compared with a control (Present condition, Pres). The mu significantly increased in both Fut conditions as compared to the Pres, probably due to the nutrient addition and acidification in the former. The highest mu were observed in the Fut(out), due to the growth of nanoplanktonic flagellates and diatoms. Cells in the Fut(in) were photosynthetically less efficient as compared to those of the Fut(out) and Pres, but these physiological differences, also between samples with or without solar UVR observed at the beginning of the experiment, decreased with time hinting for an acclimation process. The knowledge of the relative importance of both roles of DOM is especially important for coastal areas that are expected to receive higher inputs and will be more acidified in the future.

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