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  • 1.
    Ahlgren, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). The Swedish Institute for the Marine Environment, PO Box 260, SE-40530 Göteborg, Sweden.
    Grimvall, Anders
    Omstedt, Anders
    Rolff, Carl
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). The Swedish Institute for the Marine Environment, PO Box 260, SE-40530 Göteborg, Sweden.
    Temperature, DOC level and basin interactions explain the declining oxygen concentrations in the Bothnian Sea2017In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 170, p. 22-30Article in journal (Refereed)
    Abstract [en]

    Hypoxia and oxygen deficient zones are expanding worldwide. To properly manage this deterioration of the marine environment, it is important to identify the causes of oxygen declines and the influence of anthropogenic activities. Here, we provide a study aiming to explain the declining oxygen levels in the deep waters of the Bothnian Sea over the past 20 years by investigating data from environmental monitoring programmes. The observed decline in oxygen concentrations in deep waters was found to be primarily a consequence of water temperature increase and partly caused by an increase in dissolved organic carbon (DOC) in the seawater (R-Adj(2). = 0.83) as well as inflow from the adjacent sea basin. As none of the tested eutrophication-related predictors were significant according to a stepwise multiple regression, a regional increase in nutrient inputs to the area is unlikely to explain a significant portion of the oxygen decline. Based on the findings of this study, preventing the development of anoxia in the deep water of the Bothnian Sea is dependent on the large-scale measures taken to reduce climate change. In addition, the reduction of the nutrient load to the Baltic Proper is required to counteract the development of hypoxic and phosphate-rich water in the Baltic Proper, which can form deep water in the Bothnian Sea. The relative importance of these sources to oxygen consumption is difficult to determine from the available data, but the results clearly demonstrate the importance of climate related factors such as temperature, DOC and inflow from adjacent basins for the oxygen status of the sea.

  • 2.
    Ahlgren, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Havsmiljöinstitutet.
    Rolff, Carl
    Stockholms universitet.
    Grimvall, Anders
    Havsmiljöinstitutet.
    Omstedt, Anders
    Göteborgs universitet.
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Havsmiljöinstitutet.
    Orsaker till minskande syrehalter i Bottenhavet2017Report (Refereed)
    Abstract [sv]

    Resultat från den nationella miljöövervakningen visar att syrehalterna i Bottenhavet har minskat sedan 1970-talet, en minskning som accelererat från 1990. För att ha möjlighet att på något sätt kunna åtgärda denna försämring av den marina miljön är det nödvändigt att identifiera orsakerna till denna syreminskning, eftersom olika orsaker kan kräva olika former av åtgärder. Om orsaken till exempel är ökad syreförbrukning beroende på regional övergödning, skulle detta innebära ökat behov av regionala reningsåtgärder. Målsättningen med projektet var därmed att ge en tillförlitlig förklaring till de sjunkande syrehalterna i Bottenhavet under de senaste 20 åren genom att använda data från de nationella miljöövervakningsprogrammen. De huvudhypoteser som undersöktes som orsaker till de sjunkande syrehalterna var:  • Ökad regional gödning av Bottenhavet och därmed ökad produktion.  • Tillförsel av syrefattigt och fosfatrikt från Egentliga Östersjön.  • Starkare haloklin och försämrad ventilation av Bottenhavets djupvatten.  • Ökad temperatur och ökad tillförsel av löst organiskt kol. Analys av tidsserier och modellanalyser utifrån miljöövervaknings- och forskningsdata visade att den observerade syrehaltsminskningen i Bottenhavets djupvatten främst beror på en ökning av vattentemperaturen och delvis på en ökning av löst organiskt kol i vattnet, samt tillflöde från Egentliga Östersjön. Dataanalysen visade däremot inget tydligt stöd för att ökad produktion av biomassa i Bottenhavet orsakat de minskande syrehalterna. Detta gäller indikatorer för växtplankton, sedimentation och bakterieplankton som alla förväntas öka vid ökad produktion och det finns således inga direkta indicier för att stödja hypotesen om ökad gödning av Bottenhavet.  Sammantaget visar de analyser som gjorts inom projektet att Bottenhavets framtida hälsa främst gynnas av en kombination av åtgärder för att motverka globala klimatförändringar, samt åtgärder för att förbättra vattenkvaliteten i Egentliga Östersjön. Näringstillförsel från Bottenhavets avrinningsområden bedöms främst ha haft betydelse för syresituationen i kustnära vattenförekomster. Den bedöms därför inte i betydande omfattning ha orsakat de minskande syrehalterna i Bottenhavets utsjöområden.  

  • 3.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Biologisk inventering av havsbottnar kring Örefjärden, Snöan och Bonden: Marinbiologisk inventering och naturvärdesbedömning av planerat marint naturreservat2009Report (Other academic)
  • 4.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Inventering och naturvärdesbedömning av fyra kustnära havsområden i Västerbotten - Tavasten, Ostnäs, Juviken/Lillhavet och Kinnbäcksfjärden2017Report (Other academic)
    Abstract [sv]

    En inventering och naturvärdesbedömning av fyra kustnära havsområden i Västerbottens län har genomförts. Inventeringen fokuserade på undervattensvegetation och består huvudsakligen av en visuell transektinventering genom video och dykning utförd av Umeå marina forskningscentrum 2007-2008. Kunskapsunderlaget har utökats genom att inkludera flera andra undersökningar. Totalt spänner underlaget över tidsperioden 1997-2012.

  • 5.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Miljöövervakning i Gaviksfjärden, Västernorrlands län: sammanställning och resultatanalys2014Report (Other academic)
  • 6.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Trophic interactions involving mysid shrimps (Mysidacea) in the near-bottom habitat in the Baltic Sea2004In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, Vol. 38, no 3, p. 457-469Article in journal (Refereed)
    Abstract [en]

    In a six month mesocosm tank experiment, hypotheses were tested concerning the role of benthopelagic mysid shrimps (Mysidacea) in the near-bottom food web of the Bothnian Sea, in the northern Baltic Sea. The first hypothesis tested was that the mysids interact, through predation, with benthic deposit-feeding Monoporeia affinis amphipods. A second hypothesis tested was that the sediment type is important for the overwintering success of the mysids. Changes in abundance and mass were recorded for M. affinis and mysids when separate and when coexisting, in two sediment types differing in organic content (food level); soft muddy clay (rich) and fine sand (poor). Despite the fact that newborn M. affinis offspring, a plausible target for predation by mysids, were present in substantial numbers in the tanks, no consistent evidence for any interaction between these taxa was found. The biomass of mysids was slightly higher in the muddy clay than in the sand tanks, and the mechanism behind this substrate effect is discussed. A third hypothesis, that the mysids interact with near-bottom zooplankton, was investigated. The tanks were continually supplied with in situ near-bottom sea-water containing a seminatural assemblage of near-bottom plankton. As a result of mysid predation, tanks with mysids had lower abundance and biomass of cyclopoid copepods than tanks without mysids. Thus, the major interaction found was predation on near-bottom zooplankton by mysids and it is suggested that this interaction could potentially be an important food link, especially during periods with low food availability in the pelagic system.

  • 7.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Undervattensvegetation i Holmöarnas naturreservat: Inventeringar och miljöövervakningar genomförda under åren 1997, 2004 och 20072008Report (Other academic)
  • 8.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Uppföljning av naturtypen 1140 blottade ler- och sandbottnar i Bottenviken och Södra Östersjön: En pilotstudie2016Report (Other (popular science, discussion, etc.))
  • 9.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Övervakning av makrovegetation i Bottniska viken: En utvärdering av pågående undersökningar och underlag för vidareutveckling2014Report (Other academic)
  • 10.
    Albertsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Leonardsson, K
    Deposit-feeding amphipods (Monoporeia affinis) reduce the recruitment of copepod nauplii from benthic resting eggs in the northern Baltic Sea2001In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 138, no 4, p. 793-801Article in journal (Refereed)
    Abstract [en]

    We experimentally investigated the effect of different densities of the burrowing, deposit-feeding amphipod Monoporeia affinis on the recruitment of zooplankton from benthic resting eggs. Intact sediment cores with in situ density and species composition of zooplankton resting eggs and benthic fauna were collected in the northern Bothnian Sea, part of the Baltic Sea. We removed as many M, affinis as possible from the cores and then added different numbers of ill. affinis to the cores to generate a range of densities. The cores were exposed to different densities of M. affinis for either 3 or 40 days, after which the hatched zooplankton was registered. One subset of the cores were initially incubated under low temperature (2-3 degreesC, to prevent hatching) for 37 days (the resting phase), to allow for effects of M. affinis on unhatched resting eggs. These cores were then incubated under higher temperature (13 degreesC) for 3 days (the hatching phase), to induce hatching and allow for effects on hatching or hatched specimens. In a second subset of cores with the same time and temperature schedule, the M. affinis density was experimentally reduced at the start of the hatching phase, to evaluate the effect of M. affinis during the hatching phase. To a third subset of cores, we immediately initiated the hatching phase, without an experimental resting phase, to evaluate the effects induced during the resting phase. The most common zooplankton species that hatched was Eurytemora affinis (Copepoda), followed by Bosmina longispina maritima (Cladocera). In all cores that were subjected to a resting phase, the numbers of hatched E. affinis were log-linearly negatively related to density of M. affinis. An increase of M. affinis density from 1,000 to 5,000 individuals m(-2), normal field densities, reduced the hatching by 60-70%. The negative impact was mainly exerted during the hatching phase, suggesting predation on, burial of or physical injury of hatching nauplii or eggs in a late development stage as likely mechanisms. Also, the number of B. longispina maritima that hatched was reduced by M. affinis during the hatching phase, but no clear relation to density of M. affinis could be identified. The results show that M. affinis can reduce recruitment to zooplankton from benthic resting eggs. Such impact by the benthos on resting stages of zooplankton is therefore a potentially significant link between the benthic and pelagic systems.

  • 11.
    Albertsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Leonardsson, K
    Impact of a borrowing deposit-feeder, Monoporeia affinis, on viable zooplankton resting eggs in the northern Baltic Sea2000In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 136, no 4, p. 611-619Article in journal (Refereed)
    Abstract [en]

    We investigated the effect of different densities of the burrowing deposit-feeding amphipod Monoporeia affinis on the potential for recruitment of zooplankton from benthic resting eggs. Hatching of resting eggs was induced in the laboratory on sliced and resuspended 1-cm depth-sections of sediment cores, collected at six stations ill an archipelago area of the Gulf of Bothnia, Baltic Sea. The uppermost 5 cm of the sediment was studied. The most common species that hatched was Eurytemor affinis (Copepoda). Individuals from another copepod genus, Acartia, hatched in significant numbers only in the cores from two stations with low amphipod abundance. Cores from stations with high amphipod densities showed a deeper distribution of emerging E. affinis nauplii compared with stations with few amphipods: the oxidised sediment layer was also deeper at high M. affinis densities than at low. Total (0 to 5 cm strata pooled) number of hatched E. affinis nauplii was independent of amphipod density. This indicates that the effect of M. affinis on E. affinis eggs involves deeper burial due to bioturbation, rather than predation. Decreased benthic recruitment of zooplankton at localities with high M. affinis density is suggested, since more deeply positioned eggs are less likely to hatch. When hatching was induced in intact, non-sliced cores from one station, the number of E. affinis nauplii that hatched was on average 43% of the number that hatched in the upper centimetre of the sliced cores from the same station. This fraction (43%), if applied to the other stations, implied a potential for benthic recruitment of up to 80000 ind m(-2) for E. affinis. Due to its high abundance, M. affinis is likely to greatly reduce benthic recruitment of zooplankton in this system.

  • 12.
    Algesten, Grete
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brydsten, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jonsson, Per
    Institute of Applied Environmental Research, Stockholm University, Stockholm, Sweden.
    Kortelainen, Pirkko
    Finnish Environment Institute, P.O. Box 140, FIN-00251, Helsinki, Finland.
    Löfgren, Stefan
    Department of Environmental Assessment, SLU, P.O. Box 7050, Uppsala, Sweden.
    Rahm, Lars
    Department of Water and Environmental Studies, Linköping University, SE-58183 Linköping, Sweden.
    Räike, Antti
    Finnish Environment Institute, P.O. Box 140, FIN-00251, Helsinki, Finland.
    Sobek, Sebastian
    Institute for Aquatic Sciences and Water Pollution Control, Swiss Federal Institute of Technology Zurich (ETH), Universitätsstr. 16, CH-8092 Zurich, Switzerland.
    Tranvik, Lars
    Department of Ecology and Evolution, EBC, Uppsala University, SE-752 36 Uppsala, Sweden.
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Organic carbon budget for the Gulf of Bothnia2006In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 63, no 3-4, p. 155-161Article in journal (Refereed)
    Abstract [en]

    We calculated input of organic carbon to the unproductive, brackish water basin of the Gulf of Bothnia from rivers, point sources and the atmosphere. We also calculated the net exchange of organic carbon between the Gulf of Bothnia and the adjacent marine system, the Baltic Proper. We compared the input with sinks for organic carbon; permanent incorporation in sediments and mineralization and subsequent evasion of CO2 to the atmosphere. The major fluxes were riverine input (1500 Gg C year− 1), exchange with the Baltic Proper (depending on which of several possible DOC concentration differences between the basins that was used in the calculation, the flux varied between an outflow of 466 and an input of 950 Gg C year 1), sediment burial (1100 Gg C year− 1) and evasion to the atmosphere (3610 Gg C year− 1). The largest single net flux was the emission of CO2 to the atmosphere, mainly caused by bacterial mineralization of organic carbon. Input and output did not match in our budget which we ascribe uncertainties in the calculation of the exchange of organic carbon between the Gulf of Bothnia and the Baltic Proper, and the fact that CO2 emission, which in our calculation represented 1 year (2002) may have been overestimated in comparison with long-term means. We conclude that net heterotrophy of the Gulf of Bothnia was due to input of organic carbon from both the catchment and from the Baltic Proper and that the future degree of net heterotrophy will be sensible to both catchment export of organic carbon and to the ongoing eutrophication of the Baltic Proper.

  • 13.
    Algesten, Grete
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Sobek, Sobek
    Department of Limnology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden .
    Tranvik, Lars T.
    Department of Limnology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden .
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Seasonal variation of CO2 saturation in the Gulf of Bothnia: Indications of marine net heterotrophy2004In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 18, p. 4021-4028Article in journal (Refereed)
    Abstract [en]

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

  • 14. Aljetlawi, A A
    et al.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Leonardsson, K
    Effect of food and sediment pre-treatment in experiments with a deposit-feeding amphipod, Monoporeia affinis2000In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 249, no 2, p. 263-280Article in journal (Refereed)
    Abstract [en]

    We experimentally investigated the effects of different pre-treatments of the sediment, and the effect of daily addition of fresh phytoplankton, on the growth and survival of 1-year-old (1 +) individuals of the deposit feeder Monoporeia affinis (Amphipoda). We used three different types of sieved sediment: pre-frozen muddy clay, non-pre-frozen muddy clay, and fine sand. The muddy clay contained phytoplankton originating from the surface sediment sampled in the field during the late spring bloom. No phytoplankton was initially present in sand. The experiment lasted for 18 days. M. affinis responded to the daily phytoplankton addition by increasing growth. Phytoplankton addition had no significant effects on the survival of M. affinis. Upon phytoplankton addition, the sandy and non-frozen muddy clay gave similar growth and survival responses. In contrast, the pre-frozen sediment resulted in significantly lower growth and survival. The growth was negative in all treatments without phytoplankton. Thus, the high initial chlorophyll content in the muddy clay was not of sufficient quality or concentration to allow a positive growth response in M. affinis. The growth of M. affinis was significantly correlated with the reduction of the chlorophyll. Our results indicated that M. affinis is capable of assimilating settled phytoplankton with no, or only a few days' time delay. (C) 2000 Elsevier Science BN: All rights reserved.

  • 15.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Ett ekosystem i ständig förändring2014In: Havsutsikt Tema Hav och Klimat, no 2, p. 9-11Article in journal (Other (popular science, discussion, etc.))
  • 16.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Ahlinder, J.
    Mathisen, Peter
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hagglund, M.
    Backman, S.
    Nilsson, E.
    Sjodin, A.
    Thelaus, J.
    Predators and nutrient availability favor protozoa-resisting bacteria in aquatic systems2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 8415Article in journal (Refereed)
    Abstract [en]

    The long co-existence of bacteria and protozoa has led to the development of bacterial protozoa resistance strategies, which are suggested to serve as drivers for the evolution of pathogenic bacteria. However, the ecological mechanisms underpinning selection for protozoa-resistance in aquatic bacteria are poorly known. To assess the role of nutrient availability and predation-pressure on selection for protozoa-resisting bacteria (PRB), an enrichment-dilution experiment was designed using laboratory microcosms containing natural lake water. PRB was monitored by screening 16S rRNA amplicon sequence data for reads assigned to bacteria that previously has been shown to resist degradation by amoebae. To estimate the effects of the microbial food web dynamics (microscopy of; heterotrophic bacteria, phytoplankton, protozoa and rotifers) and physicochemical variables on the PRB abundance in the study system, a joint species distribution modelling approach was used. The predation-pressure (ratio between predator and bacterial biomass) had a positive effect on the abundance of the PRB genus Mycobacterium, while perturbation (enrichment and dilution) favored the PRB genus Pseudomonas that dominated the bacterial community in the disturbed systems. Our results show that PRB with different ecological strategies can be expected in water of high and intermediate nutrient levels and after major disturbances of an aquatic system.

  • 17.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Brugel, Sonia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Paczkowska, Joanna
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Rowe, Owen F.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, University of Helsinki, Helsinki, Finland.
    Figueroa, Daniela
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Kratzer, S.
    Legrand, C.
    Influence of allochthonous dissolved organic matter on pelagic basal production in a northerly estuary2018In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 204, p. 225-235Article in journal (Refereed)
    Abstract [en]

    Phytoplankton and heterotrophic bacteria are key groups at the base of aquatic food webs. In estuaries receiving riverine water with a high content of coloured allochthonous dissolved organic matter (ADOM), phytoplankton primary production may be reduced, while bacterial production is favoured. We tested this hypothesis by performing a field study in a northerly estuary receiving nutrient-poor, ADOM-rich riverine water, and analyzing results using multivariate statistics. Throughout the productive season, and especially during the spring river flush, the production and growth rate of heterotrophic bacteria were stimulated by the riverine inflow of dissolved organic carbon (DOC). In contrast, primary production and photosynthetic efficiency (i.e. phytoplankton growth rate) were negatively affected by DOC. Primary production related positively to phosphorus, which is the limiting nutrient in the area. In the upper estuary where DOC concentrations were the highest, the heterotrophic bacterial production constituted almost 100% of the basal production (sum of primary and bacterial production) during spring, while during summer the primary and bacterial production were approximately equal. Our study shows that riverine DOC had a strong negative influence on coastal phytoplankton production, likely due to light attenuation. On the other hand DOC showed a positive influence on bacterial production since it represents a supplementary food source. Thus, in boreal regions where climate change will cause increased river inflow to coastal waters, the balance between phytoplankton and bacterial production is likely to be changed, favouring bacteria. The pelagic food web structure and overall productivity will in turn be altered.

  • 18.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Hajdu, Susanna
    Inst. f. Systemekologi, Stockholms universitet.
    Haecky, Pia
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Kuparinen, Jorma
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Succession and growth limitation of phytoplankton in the Gulf of Bothnia (Baltic Sea)1996In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 126, no 4, p. 791-801Article in journal (Refereed)
    Abstract [en]

    A one year field study of four stations in the Gulf of Bothnia during 1991 showed that the biomass was ca. two times, and primary productivity ca, four times, lower in the north (Bothnian Bay) than in the south (Bothnian Sea) during the summer. Nutrient addition experiments indicated phosphorus limitation of phytoplankton in the Bothnian Bay and the coastal areas in the northern Bothnian Sea, but nitrogen limitation in the open Bothnian Sea. A positive correlation between the phosphate concentration and the production/biomass ratio of phytoplankton was demonstrated, which partly explained the differences in the specific growth rate of the phytoplankton during the summer. Differences in photosynthetic active radiation between the stations also showed a covariation with the primary productivity. The relative importance of nutrient or light limitation for photosynthetic carbon fixation could not, however, be conclusively determined from this study. Marked differences in phytoplankton species composition from north to south were also observed. The number of dominating species was higher in the Bothnian Sea than in the Bothnian Bay. The distribution of some species could be explained as due to nutrient availability (e.g. Nodularia spumigena, Aphanizomenon sp.), while salinity probably limits the distribution of some limnic as well as marine species. The potentially toxic phytoplankton N. spumigena, Dinophysis acuminata and Chrysochromulina spp. were common in the Bothnian Sea but not in the Bothnian Bay. The pico- and nanoplankton biomass during late summer was higher than previously reported due to a revised carbon/volume ratio.

  • 19.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Hansen, W
    Wänstrand, I
    Huseby, S
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Strategi för kontrollerande övervakning av kustvatten i Bottenhavets vattendistrikt2008Report (Refereed)
  • 20.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Hansen, Wenche
    Länsstyrelsen Västernorrland.
    Wänstrand, Ingrid
    Länsstyrelsen Gävleborg.
    Huseby, Siv
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Strategi för kontrollerande övervakning av Bottenhavets vattendistrikt2008Report (Other academic)
    Abstract [sv]

    Ett pelagialprogram har tagits fram för övervakning i relativt opåverkade referensområden i kustvattentyperna 16 t.o.m.19 i Bottemhavet. Programmet bör kunna ligga till grund för uppföljning av internationella, nationella och regionala miljömål samt följa upp ekologisk status. Den rumsliga variationen samt mellanårsvariationen hos pelagiala variabler i Bottenhavsområdet har använts som utgångspunkt för att beräkna provtagningsbehovet. Det föreslagna programmet innebär att mellan 48 och 60 provtagningar årsperiod, varefter ekologisk status kan bedömas. Designen gör det möjligt att med 80 % säkerhet bedöma ekologisk status med mätdata som ligger minst 20 % från klassgränserna. Mätprogrammet är designat för provtagningar -årsperiod. Stationer har slumpats ut i de olika typerna, och förslag på årliga provtagningslokaler anges i rapporten. Eftersom djupet vid de olika stationerna varierar, bör de flesta pelagiala variablerna provtas vid ett diskret djup i övre delen av vattenmassan, t.ex. 1 m djup. Av vetenskapliga och ekonomiska skäl är det viktigt att pelagialprogrammet samordnas för hela Bottenhavet.

    För mjukbottenfauna bedöms det befintliga integrerade programmet för trendanalys i Bottenhavet kunna tillgodose Vattendirektivets behov för kontrollerande övervakning i distriktet. Detta under förutsättning att Sundsvallsbuktens program fortsätter och att de nya nationella och regionala provtagningsområdena i södra Bottenhavet (Gräsö) etableras och drivs. Dimensioneringen av nuvarande nationellt och regionalt bottenfaunaprogram och områdesövervakning men har även visat sig vara väl anpassat för bedömningar inom ramen för Vattendirektivet. Enligt bedömningsgrunden bör minst 5 stationer användas för klassning av ekologisk status. Dessa stationer måste dock inte ligga inom samma vattenförekomst, utan kan vara lokaliserade i angränsande vattenförekomster. Den ekologiska statusen för mjukbottenfauna i enskilda vattenförekomster klassas genom extrapolering med hjälp av data från närbelägna områden med liknande bottenmiljö och påverkansgrad.

    Befintlig fiskebeståndsövervakning föreslås fortlöpa för att möjliggöra uppföljning av förändringar. En utökning av antalet övervakningsområden föreslås dock för att upprätta minst ett referensområde per inre och yttre kustvattentyp. En kombination av stratifierad och slumpmässig övervakning av fiskebestånden enligt nuvarande strategi föreslås, där djupintervallen stratifieras medan stationerna slumpas ut i respektive djupintervall.

    Provfiske och provtagning för miljögiftsanalys av fisk bör samordnas till samma provtagningstillfälle. Vidare bör den modell för samfinansiering och samordning som idag tillämpas av kustlänen i Bottniska viken för övervakning av fiskbestånd, samt och miljögiftsövervakning av fisk, fortlöpa även framöver.

    De ämnen som ingår i det pågående nationella programmet för miljögifter i fisk bör mätas även i de nya föreslagna områdena. När EU:s dotterdirektiv för prioriterade ämnen är beslutat och Vattenmyndigheterna fastställt miljökvalitetsnormer för särskilda förorenande ämnen, bör en översyn göras och ytterligare ämnen som är aktuella för Bottenhavet införlivas i övervakningsprogrammet. Miljögiftsövervakning i fisk bedöms kunna mätas med ett maximalt avstånd på 75 km mellan stationsområdena. Bedömning och extrapolera mätvärdena.

    För samtliga delprogram har en grova uppskattningar av kostnader för genomförandet gjorts.

  • 21.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Höglander, Helena
    Karlsson, Chatarina
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Huseby, Siv
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Key role of phosphorus and nitrogen in regulating cyanobacterial community composition in the northern Baltic Sea2015In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 164, p. 161-171Article in journal (Refereed)
    Abstract [en]

    Despite cyanobacteria being a key phytoplankton group in the Baltic Sea, the factors governing their community structure are still poorly understood. Here, we studied the occurrence of the orders Chroococcales, Oscillatoriales and Nostocales, and potentially explanatory variables at five locations in the northern Baltic Sea from June–September, 1998–2012. Cyanobacteria constituted 1–36% of the total phytoplankton biomass along the north–south gradient. In the Bothnian Bay, Chroococcales and Oscillatoriales dominated the cyanobacterial community, whereas in the Bothnian Sea and northern Baltic Proper, Nostocales was the dominant group. The dominance of Chroococcales was coupled to low salinity and low total phosphorus, whereas Oscillatoriales correlated with high total nitrogen and low salinity. Nostocales correlated to high total phosphorus, inorganic phosphorus and salinity. Chroococcales showed an increase over time in the offshore Bothnian Bay, whereas Nostocales increased in the coastal Bothnian Sea and coastal Baltic Proper. The increase of Nostocales in the coastal Bothnian Sea was explained by a rise in total phosphorus and decrease in dissolved inorganic nitrogen compared to an increase of total nitrogen and phosphorus in the coastal Baltic Proper. No significant trends were observed in the cyanobacterial community in the offshore Bothnian Sea and the offshore northern Baltic Proper. We concluded that Chroococcales may be a useful indicator for increased phosphorus levels in waters with low phosphorus concentrations, whereas Nostocales could be used as a quality indicator for increasing phosphorus concentrations in waters with low inorganic N/P ratios (<20), such as in the coastal Bothnian Sea and Baltic Proper.

  • 22.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Jurgensone, Iveta
    Rowe, Owen F.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Simonelli, Paolo
    Bignert, Anders
    Lundberg, Erik
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Can Humic Water Discharge Counteract Eutrophication in Coastal Waters?2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 4, p. e61293-Article in journal (Refereed)
    Abstract [en]

    A common and established view is that increased inputs of nutrients to the sea, for example via river flooding, will cause eutrophication and phytoplankton blooms in coastal areas. We here show that this concept may be questioned in certain scenarios. Climate change has been predicted to cause increased inflow of freshwater to coastal areas in northern Europe. River waters in these areas are often brown from the presence of high concentrations of allochthonous dissolved organic carbon ( humic carbon), in addition to nitrogen and phosphorus. In this study we investigated whether increased inputs of humic carbon can change the structure and production of the pelagic food web in the recipient seawater. In a mesocosm experiment unfiltered seawater from the northern Baltic Sea was fertilized with inorganic nutrients and humic carbon (CNP), and only with inorganic nutrients (NP). The system responded differently to the humic carbon addition. In NP treatments bacterial, phytoplankton and zooplankton production increased and the systems turned net autotrophic, whereas the CNP-treatment only bacterial and zooplankton production increased driving the system to net heterotrophy. The size-structure of the food web showed large variations in the different treatments. In the enriched NP treatments the phytoplankton community was dominated by filamentous >20 mu m algae, while in the CNP treatments the phytoplankton was dominated by picocyanobacteria <5 mu m. Our results suggest that climate change scenarios, resulting in increased humic-rich river inflow, may counteract eutrophication in coastal waters, leading to a promotion of the microbial food web and other heterotrophic organisms, driving the recipient coastal waters to net-heterotrophy.

  • 23.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Karlsson, C
    Hajdu, S
    Höglander, H
    Skjevik, A-T
    Pelagial biologi / växtplankton2010In: Havet: Om miljötillståndet i svenska havsområden, Stockholm: Naturvårdsverket, 2010, p. 32-33Chapter in book (Refereed)
  • 24.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Karlsson, Chatarina
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Huseby, Siv
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Höglander, Helena
    Mer fosfor ger mer cyanobakterier i norra Östersjön2013In: Havet, p. 51-54Article, review/survey (Other academic)
    Abstract [sv]

    I flera områden i norra Östersjön har cyanobakterierna ökat under de senaste tio till femton åren. I Bottenhavets och Egentliga Östersjöns kustområden ökar de kvävefixerande cyanobakterierna. I Bottenvikens utsjö är det den småcelliga och kolonibildande gruppen Chroococcales som blir fler. Förändringarna beror i flera fall på ökande halter av fosfor.

  • 25.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Meier, H.E. Markus
    Ripszam, Matyas
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
    Rowe, Owen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Eilola, Kari
    Legrand, Catherine
    Figueroa, Daniela
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Paczkowska, Joanna
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lindehoff, Elin
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Elmgren, Ragnar
    Projected future climate change and Baltic Sea ecosystem management2015In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, no Suppl 3, p. S345-S356Article in journal (Refereed)
    Abstract [en]

    Climate change is likely to have large effectson the Baltic Sea ecosystem. Simulations indicate 2–4 Cwarming and 50–80 % decrease in ice cover by 2100.Precipitation may increase *30 % in the north, causingincreased land runoff of allochthonous organic matter(AOM) and organic pollutants and decreased salinity.Coupled physical–biogeochemical models indicate that, inthe south, bottom-water anoxia may spread, reducing codrecruitment and increasing sediment phosphorus release,thus promoting cyanobacterial blooms. In the north,heterotrophic bacteria will be favored by AOM, whilephytoplankton production may be reduced. Extra trophiclevels in the food web may increase energy losses andconsequently reduce fish production. Future managementof the Baltic Sea must consider the effects of climatechange on the ecosystem dynamics and functions, as wellas the effects of anthropogenic nutrient and pollutant load.Monitoring should have a holistic approach, encompassingboth autotrophic (phytoplankton) and heterotrophic (e.g.,bacterial) processes.

  • 26.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Meier, M
    Hur påverkas östersjön?2010In: Sverige i nytt klimat – våtvarm utmaning, Stockholm: Forskningsrådet Formas, 2010, p. 117-132Chapter in book (Refereed)
  • 27.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Samuelsson, K
    Haecky, P
    Albertsson, J
    Changes in the pelagic microbial food web due to artificial eutrophication2006In: Aquat Ecol, Vol. 40, p. 299-313Article in journal (Refereed)
  • 28. Andersson, Agneta
    et al.
    Samuelsson, Kristina
    Haecky, Pia
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Changes in the pelagic microbial food web due to artificial eutrophication2006In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, Vol. 40, no 3, p. 299-313Article in journal (Refereed)
    Abstract [en]

    The effect of nutrient enrichment on the structure and carbon flow in the pelagic microbial food web was studied in mesocosm experiments using seawater from the northern Baltic Sea. The experiments included food webs of at least four trophic levels; (1) phytoplankton-bacteria, (2) flagellates, (3) ciliates and (4) mesozooplankton. In the enriched treatments high autotrophic growth rates were observed, followed by increased heterotrophic production. The largest growth increase was due to heterotrophic bacteria, indicating that the heterotrophic microbial food web was promoted. This was further supported by increased growth of heterotrophic flagellates and ciliates in the high nutrient treatments. The phytoplankton peak in the middle of the experiments was mainly due to an autotrophic nanoflagellate, Pyramimonas sp. At the end of the experiment, the proportion of heterotrophic organisms was higher in the nutrient enriched than in the nutrient-poor treatment, indicating increased predation control of primary producers. The proportion of potentially mixotrophic plankton, prymnesiophyceans, chrysophyceans and dinophyceans, were significantly higher in the nutrient-poor treatment. Furthermore, the results indicated that the food web efficiency, defined as mesozooplankton production per basal production (primary production + bacterial production - sedimentation), decreased with increasing nutrient status, possibly due to increasing loss processes in the food web. This could be explained by promotion of the heterotrophic microbial food web, causing more trophic levels and respiration steps in the food web.

  • 29.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Hagström, Åke
    Vertical transport of lipid in seawater1993In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 98, no 1-2, p. 149-155Article in journal (Refereed)
    Abstract [en]

    Lipids in seawater act as solvents and transporters of lipophilic organic pollutants. To investigate a possible transport route of lipophilic pollutants, the vertical flux of lipid was quantified during an annual cycle in the northern Baltic Sea. The lipid content in both sedimenting material and different size fractions of seawater was analyzed. During the year, 8 g lipid m-2 sedimented out from the photic zone to the benthic system. The sedimentation of lipid accounted for 300 to 400 % of the average standing stock of pelagic lipid and was concentrated in the spring bloom period (April-June) when 70 % of the total lipid sedimentation occurred. About 30 % of the produced pelagic lipid settled out from the system. In seawater the lipid maximum occurred at the end of the spring bloom, shortly after nutrient depletion, indicating a stress response in the algae. Since lipid sedimentation is concentrated in the spring bloom, removal of lipophilic organic pollutants may be important during this period.

  • 30.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Tamminen, Timo
    Lehtinen, Sirpa
    Jürgens, Klaus
    Labrenz, Matthias
    Viitasalo, Markku
    The pelagic food web2017In: Biological oceanography of the Baltic sea / [ed] Pauline Snoeijs, Hendrik Schubert, Teresa Radziejewska, Dordrecht: Springer Netherlands, 2017, p. 281-332Chapter in book (Refereed)
    Abstract [en]
    1. Environmental drivers and food web structure in the pelagic zone vary from south to north in the Baltic Sea. 
    2. While nitrogen is generally the limiting nutrient for primary production in the Baltic Sea, phosphorus is the limiting nutrient in the Bothnian Bay. 
    3. In the Gulf of Bothnia the food web is to a large extent driven by terrestrial allochthonous material, while autochthonous production dominates in the other parts of the Baltic Sea. 
    4. Changes in bacterioplankton, protist and zooplankton community composition from south to north are mainly driven by salinity. 
    5. Bacteria are crucial constituents of the pelagic food web (microbial loop) and in oxygen-poor and anoxic bottom waters where they mediate element transformations. 
    6. Diatoms and dinoflagellates are the major primary producers in the pelagic zone. Summer blooms of diazotrophic (nitrogen-fixing) filamentous cyanobacteria are typical of the Baltic Sea, especially in the Baltic Sea proper and the Gulf of Finland. 
    7. The mesozooplankton (mainly copepods and cladocerans) channel energy from primary producers and the microbial food web to fish and finally to the top predators in the pelagic system (waterbirds and mammals). 
    8. Herring and sprat populations are affected by the foraging intensity of their main predator (cod), and therefore the environmental conditions that affect cod may also influence mesozooplankton due to food web effects "cascading down the food web". 
    9. Anthropogenic pressures, such as overexploitation of fish stocks, eutrophication, climate change, introduction of non-indigenous species and contamination of top predators by hazardous substances, cause changes in the pelagic food web that may have consequences for the balance and stability of the whole ecosystem.
  • 31.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Klimatförändringar kan leda till mindre fisk i havet2016In: Havet: om miljötillståndet i i svenska havsområden. 2015/2016, Göteborg: Havs- och vattenmyndigheten , 2016, p. 25-28Chapter in book (Other academic)
  • 32.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Pelagisk biologi2004In: Bottniska viken: årsrapport från den marina miljöövervakningen. 2003, Skydd av havsområden gagnar fisken, Hörnefors: Umeå marina forskningscentrum (UMF) , 2004, p. 11-13Chapter in book (Refereed)
  • 33.
    Ask, Jenny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rowe, Owen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brugel, Sonia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Strömgren, Mårten
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Importance of coastal primary production in the northern Baltic Sea2016In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 45, no 6, p. 635-648Article in journal (Refereed)
    Abstract [en]

    In this study, we measured depth-dependent benthic microalgal primary production in a Bothnian Bay estuary to estimate the benthic contribution to total primary production. In addition, we compiled data on benthic microalgal primary production in the entire Baltic Sea. In the estuary, the benthic habitat contributed 17 % to the total annual primary production, and when upscaling our data to the entire Bothnian Bay, the corresponding value was 31 %. This estimated benthic share (31 %) is three times higher compared to past estimates of 10 %. The main reason for this discrepancy is the lack of data regarding benthic primary production in the northern Baltic Sea, but also that past studies overestimated the importance of pelagic primary production by not correcting for system-specific bathymetric variation. Our study thus highlights the importance of benthic communities for the northern Baltic Sea ecosystem in general and for future management strategies and ecosystem studies in particular.

  • 34.
    Bartels, Pia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Giesler, Reiner
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Allochthonous Organic Matter Supports Benthic but Not Pelagic Food Webs in Shallow Coastal Ecosystems2018In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, no 7, p. 1459-1470Article in journal (Refereed)
    Abstract [en]

    Rivers transport large amounts of allochthonous organic matter (OM) to the ocean every year, but there are still fundamental gaps in how allochthonous OM is processed in the marine environment. Here, we estimated the relative contribution of allochthonous OM (allochthony) to the biomass of benthic and pelagic consumers in a shallow coastal ecosystem in the northern Baltic Sea. We used deuterium as a tracer of allochthony and assessed both temporal variation (monthly from May to August) and spatial variation (within and outside river plume). We found variability in allochthony in space and time and across species, with overall higher values for zoobenthos (26.2 +/- 20.9%) than for zooplankton (0.8 +/- 0.3%). Zooplankton allochthony was highest in May and very low during the other months, likely as a result of high inputs of allochthonous OM during the spring flood that fueled the pelagic food chain for a short period. In contrast, zoobenthos allochthony was only lower in June and remained high during the other months. Allochthony of zoobenthos was generally higher close to the river mouth than outside of the river plume, whereas it did not vary spatially for zooplankton. Last, zoobenthos allochthony was higher in deeper than in shallower areas, indicating that allochthonous OM might be more important when autochthonous resources are limited. Our results suggest that climate change predictions of increasing inputs of allochthonous OM to coastal ecosystems may affect basal energy sources supporting coastal food webs.

  • 35.
    Berglund, Johnny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Jürgens, Klaus
    Bruchmüller, Iris
    Wedin, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Use of group-specific PCR primers for identification of chrysophytes by denaturing gradient gel electrophoresis2005In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, ISSN 0948-3055, Vol. 39, no 2, p. 171-182Article in journal (Refereed)
    Abstract [en]

    The chrysophytes Chrysophyceae and Synurophyceae are ecologically important groups of autotrophic, mixotrophic and heterotrophic flagellates. The smallest forms are difficult to identify by classical microscopy but have important functions both as primary producers and as consumers of bacteria in the aquatic food chain. Group-specific primers for amplification of the 18S small sub-unit rRNA gene were developed for analysis of chrysophyte diversity by denaturing gradient gel electrophoresis (DGGE). Two different primer pairs were tested. The first primer pair (EukC1-F–Chryso-R) primarily targeted Paraphysomonadaceae and Ochromonadales, which generally have heterotrophic or mixotrophic nutrition. The second primer pair (EukC2-F–Chryso-R) targeted both Chrysophyceae and Synurophyceae. The primer pairs were tested for PCR amplification of the 18S rRNA gene of 25 cultured chrysophyte species and 6 other closely related nanoplanktonic species. Both primer pairs performed well, since PCR products were obtained for the corresponding chrysophyte cultures. None of the non-chrysophyte species were amplified with these primers. PCR products of chrysophyte cultures could be separated by DGGE in a denaturing gradient from 40 to 60%. In order to test this PCR-DGGE system for natural planktonic systems, we used field samples from a brackish water area (Baltic Sea) and a freshwater lake. The most intense DGGE bands were excised, sequenced and compared to sequences in GenBank. All obtained sequences grouped within the chrysophytes. Thus, the method seems to be promising for examining chrysophyte diversity in planktonic systems.

  • 36.
    Berglund, Johnny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Müren, Umut
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Efficiency of a phytoplankton-based and a bacterial-based food web in a pelagic marine system2007In: Limnology and Oceanography, Vol. 52, no 1, p. 121-131Article in journal (Refereed)
    Abstract [en]

    he food web efficiency in two contrasting food webs, one phytoplankton based and one bacteria based, was studied in a mesocosm experiment using seawater from the northern Baltic Sea. Organisms included in the experiment were bacteria, phytoplankton, protozoa, and mesozooplankton (copepods). A phytoplankton-based food web was generated by incubating at a high light level with the addition of nitrogen and phosphorus (NP). A bacteria-based food web was created by adding carbon, nitrogen, and phosphorus (CNP) and incubating at a lower light level. In the CNP treatment bacteria dominated the productivity (91%), while in the NP treatment phytoplankton were dominant producers (74%). The phytoplankton community in the NP treatment was dominated by autotrophic nanoflagellates. The food web efficiency, defined as mesozooplankton productivity per basal productivity (phytoplankton + bacteria), was 22% in the phytoplankton-based food web and 2% in the bacteria-based food web. This discrepancy could be explained by 1�xtra trophic levels in the bacteria-based food web where carbon passed through flagellates and ciliates before reaching mesozooplankton, while in the phytoplankton-based food web there was a direct pathway from phytoplankton to mesozooplankton. The results were supported by stable isotope analysis of mesozooplankton. We propose that climate change, with increased precipitation and river runoff in the Baltic Sea, might favor a bacteria-based food web and thereby reduce pelagic productivity at higher trophic levels.

  • 37.
    Berglund, Johnny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Samuelsson, Kristina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Kull, Tomas
    Muren, Umut
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Relative strength of resource and predation limitation of heterotrophic nanoflagellates in a low-productive sea area2005In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 27, no 9, p. 923-935Article in journal (Refereed)
    Abstract [en]

    The magnitude of resource and predation limitation of heterotrophic nanoflagellates (HNF) was studied in two short-term enclosure experiments performed in a low-productive sea area in the northern Baltic Sea in 2001. A cross-factorial design was used to simultaneously assess the relative importance of the two factors. Resource limitation was removed by adding bacteria, and predation limitation was eliminated by selective filtration. The first experiment was performed in June just after the spring bloom decline and the second in September at the end of the productive season. Resource limitation prevailed during both experiments, contributing to 60% of the net growth increase in June and 74% in September. Removal of predators had a significant effect only in June. Evidence for simultaneous resource and predation limitation was thus found only during the post-bloom situation. The results were applied to a model on resource and predation control of HNF abundances. To evaluate seasonal differences, field data on HNF and bacteria from a whole year study were applied to the model. Except for a few occasions during spring, the model indicated prevailing resource control of HNF at two locations with slightly different productivity.

  • 38. Bergström, Lena
    et al.
    Albertsson, Jan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Undervattensvegetation i Kronörens naturreservat, Västerbottens län: Inventeringar genomförda under åren 1996, 1997 och 20012003Report (Other academic)
  • 39. Bertilsson, Stefan
    et al.
    Stepanauskas, Ramonas
    Cuadros-Hansson, Rocio
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Graneli, Wilhelm
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Tranvik, Lars
    Photochemically induced changes in bioavailable carbon and nitrogen pools in a boreal watershed1999In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 19, no 1, p. 47-56Article in journal (Refereed)
    Abstract [en]

    In several recent studies, a net stimulation of bacterial growth has been demonstrated after exposing humic surface waters to solar radiation or artificial ultraviolet radiation. This stimulation has been attributed to a photochemical release of bioavailable carbon or nitrogen compounds (ammonium). In a synoptic experiment, we exposed 0.2 mu m filtered water from 12 different habitats in a river system, dominated by allochthonous carbon input, to mild artificial UV radiation. A significant photochemical release of carboxylic acids of low molecular weight occurred. Furthermore, the exposure increased carbon-limited bacterial yield on average by a factor of 1.7. No photochemical production of free ammonium could be detected, which was in accordance with the lack of effects of radiation on bacterial growth yield under nitrogen-limited conditions. We conclude that, in boreal systems dominated by allochthonous carbon input, photochemical production of bioavailable carbon rather than nitrogen compounds is likely to positively influence the total substrate pool available for bacterial utilization.

  • 40.
    Blackburn, Nicholas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Hagström, Åke
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Cuadros, Rocio
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Bjornsen, Peter K
    Rapid determination of bacterial abundance, biovolume, morphology, and growth by neural network-based image analysis1998In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 64, no 9, p. 3246-3255Article in journal (Refereed)
    Abstract [en]

    Annual bacterial plankton dynamics at several depths and locations in the Baltic Sea were studied by image analysis. Individual bacteria were classified by using an artificial neural network which also effectively identified nonbacterial objects, Cell counts and frequencies of dividing cells were determined, and the data obtained agreed well with visual observations and previously published values. Cell volumes were measured accurately by comparison with bead standards. The survey included 690 images from a total of 138 samples. Each image contained approximately 200 bacteria. The images were analyzed automatically at a rate of 100 images per h, Bacterial abundance exhibited coherent patterns with time and depth, and there were distinct subsurface peaks in the summer months. Four distinct morphological classes were resolved by the image analyzer, and the dynamics of each could be visualized. The bacterial growth rates estimated from frequencies of dividing cells were different from the bacterial growth rates estimated by the thymidine incorporation method. With minor modifications, the image analysis technique described here can be used to analyze other planktonic classes.

  • 41. Blomqvist, Peter
    et al.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Drakare, Stina
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brydsten, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Effects of additions of DOC on pelagic biota in a clearwater system: results from a whole lake experiment in northern Sweden2001In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 42, no 3, p. 383-394Article in journal (Refereed)
    Abstract [en]

    An oligotrophic clearwater lake, initially characterized by a pronounced dominance of autotrophic phytoplankton and mostly by one species, the green alga Botryococcus, was subject to additions of dissolved organic carbon in the form of white sugar (sucrose) during two consecutive years. The hypothesis tested was that it is organic carbon per se, and not other possible effects of humic substances, that determines the differences in structure of the planktonic ecosystem between humic and clearwater lakes. The additions of DOC resulted in a significant increase in bacterial biomass and a decrease in the biomass of autotrophic phytoplankton. The biomass of mixotrophic and heterotrophic flagellates instead increased significantly, whereas no effects were found to propagate to higher trophic levels. As a result of the changes among biota, total planktonic biomass also decreased to a level typical of nearby humic lakes. We suggest that it is the carbon component of humic material and its utilization by bacterioplankton that determines the structure and function of the pelagic food web in humic lakes.

  • 42.
    Båmstedt, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Blomqvist, Sven
    Konsekvenser för Östersjöns biologi av förändrat klimat under 21:a århundradet2007Report (Other academic)
  • 43.
    Båmstedt, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Brugel, Sonia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    A cost-precision model for marine environmental monitoring, based on time-integrated averages2017In: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 189, no 7, article id 354Article in journal (Refereed)
    Abstract [en]

    Ongoing marine monitoring programs are seldom designed to detect changes in the environment between different years, mainly due to the high number of samples required for a sufficient statistical precision. We here show that pooling over time (time integration) of seasonal measurements provides an efficient method of reducing variability, thereby improving the precision and power in detecting inter-annual differences. Such data from weekly environmental sensor profiles at 21 stations in the northern Bothnian Sea was used in a cost-precision spatio-temporal allocation model. Time-integrated averages for six different variables over 6 months from a rather heterogeneous area showed low variability between stations (coefficient of variation, CV, range of 0.6-12.4%) compared to variability between stations in a single day (CV range 2.4-88.6%), or variability over time for a single station (CV range 0.4-110.7%). Reduced sampling frequency from weekly to approximately monthly sampling did not change the results markedly, whereas lower frequency differed more from results with weekly sampling. With monthly sampling, high precision and power of estimates could therefore be achieved with a low number of stations. With input of cost factors like ship time, labor, and analyses, the model can predict the cost for a given required precision in the time-integrated average of each variable by optimizing sampling allocation. A following power analysis can provide information on minimum sample size to detect differences between years with a required power. Alternatively, the model can predict the precision of annual means for the included variables when the program has a pre-defined budget. Use of time-integrated results from sampling stations with different areal coverage and environmental heterogeneity can thus be an efficient strategy to detect environmental differences between single years, as well as a long-term temporal trend. Use of the presented allocation model will then help to minimize the cost and effort of a monitoring program.

  • 44.
    Båmstedt, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Larsson, Henrik
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    An indoor pelagic mesocosm facility to simulate multiple water-column characteristics2018In: International Aquatic Research, ISSN 2008-4935, E-ISSN 2008-6970, Vol. 10, no 1, p. 13-29Article in journal (Refereed)
    Abstract [en]

    Mesocosms are important research tools in aquatic ecology because they close the gap between laboratory studies at the individual or lower organization level and field studies at the population and ecosystem level. However, most mesocosm studies regarding the pelagic environment do not consider the effects of physical factors like water-column stratification, turbulence and mixing. Neglecting such factors might bias the results compared to the natural system. Using a unique indoor mesocosm facility, we present results on how different water-column stratifications can be made and how they act as barriers for exchange between water layers. Turbulent mixing, simulated by vertically rotating incubation vessels, is shown to be of high importance for primary production, generating up to nine times higher production in humus-rich water than incubation vessels at fixed depths. Convective stirring is shown to be an attractive method for generating different turbulence conditions, and different temperature settings can be used to get turnover times from 84 h or more down to 17 min for a 5-m water parcel. We also demonstrate how an anoxic bottom layer can be achieved by stimulating heterotrophic bacteria through addition of bioavailable organic carbon.

  • 45.
    Båmstedt, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Martinussen, Monica B.
    Institute of Marine Research, Bergen, Norway .
    Ecology and behavior of Bolinopsis infundibulum (Ctenophora; Lobata) in the Northeast Atlantic2015In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 759, no 1, p. 3-14Article in journal (Refereed)
    Abstract [en]

    Results from field surveys with net sampling and video profiling, combined with laboratory experiments on feeding and growth, revealed the ecological function of Bolinopsis infundibulum in northern temperate coastal waters. B. infundibulum reaching a peak abundance of around 250 ctenophores m(-2), in mid-May, followed by a dramatic reduction over the next few weeks, presumably explained by predation from the ctenophore Beroe cucumis. The field data on maximum individual body height in the population indicated an instantaneous growth rate of 0.129 d(-1). Newly hatched cydippid larvae showed an average instantaneous growth rate of 0.240 d(-1) over 4 weeks, whereas ctenophores in the size range of 4.4-9.8 mm height gave instantaneous growth rates between 0.10 and 0.20 d(-1). B. infundibulum disappeared from surface water in mid-June, but big individuals were found in deeper water, where they preyed on copepods. The results indicate that the new generation of the year was recruited from February onwards. Laboratory predation and digestion experiments showed a continuous increase in predation rate with increased prey abundance, throughout the tested range of 5-400 copepods l(-1), and a digestion time increasing from 39 min with a single copepod ingested to 73 min with 8 copepods ingested.

  • 46.
    Båmstedt, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Mixing depth and allochthonous dissolved organic carbon: controlling factors of coastal trophic balance2016In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 561, p. 17-29Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: The interacting effects of different mixing depths and increased allochthonous dissolved organic carbon (DOC) on the ratio of heterotrophic to autotrophic production (i.e. trophic balance) was evaluated in a mesocosm study with a stratified water column. An autumn plankton community from the northern Bothnian Sea showed significantly decreased phytoplankton production and somewhat increased bacterial production with added DOC. In addition, increased mixing depth further reduced phytoplankton production. With a deep pycnocline and added DOC, the system became net-heterotrophic, with an average bacteria-to-phytoplankton production ratio of 1.24. With a deep pycnocline without added DOC, the trophic balance was changed to 0.44 (i.e. autotrophic). With a shallow pycnocline, the system remained net-autotrophic irrespective of DOC addition. We propose that increased precipitation in northern Europe due to climate change may result in changed density stratification and increased allochthonous DOC transport to the sea, leading to more heterotrophic coastal aquatic ecosystems. Such a scenario may entail reduced biological production at higher trophic levels and enhanced CO2 emission to the atmosphere.

  • 47. COCHLAN, William P
    et al.
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Steward, Grieg F
    Smith, David C
    Azam, Farooq
    SPATIAL-DISTRIBUTION OF VIRUSES, BACTERIA AND CHLOROPHYLL-A IN NERITIC, OCEANIC AND ESTUARINE ENVIRONMENTS1993In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 92, no 1-2, p. 77-87Article in journal (Refereed)
    Abstract [en]

    The spatial distribution of viruses was investigated in the coastal and oceanic waters of the Southern California Bight, USA, and the brackish waters of the Gulf of Bothnia, Sweden, using the direct harvesting technique and transmission electron microscopy. The vertical and horizontal distributions of viruses were examined in relation to bacterial abundance and chlorophyll a. Total virus abundances ranged from 0.3 to 52 X 10(9) l-1; higher concentrations of viruses were found in the upper 50 m of the water column and in coastal environments. Viruses with capsid diameters less than 60 nm dominated the virus community, were morphologically characterized as bacteriophages and were responsible for most of the observed spatial variability. Bacteria abundance alone explained 67 % of the spatial variability in virus numbers, thereby suggesting that bacteria constituted the major host organisms for viruses in these physically diverse habitats.

  • 48.
    Dahlgren, Kristin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Larsson, Ulf
    Department of Systems Ecology, Stockholm University, 10691 Stockholm, Sweden.
    Hajdu, Susanna
    Department of Systems Ecology, Stockholm University, 10691 Stockholm, Sweden.
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Planktonic production and carbon transfer efficiency along a north-south gradient in the Baltic sea2010In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 409, p. 77-94Article in journal (Refereed)
    Abstract [en]

    A 1 yr study was conducted along a brackish-water production gradient to enhance the understanding of factors governing pelagic food web function. This was achieved by measuring carbon transfer efficiency (TE) from the basal resource to an intermediate trophic level. TE was defined as mesozooplankton carbon consumption rate divided by production at the basal trophic level, which is composed of phytoplankton and bacteria. A north–south transect in the Baltic Sea was used as a model system, with 2 stations each in the Bothnian Bay, Bothnian Sea and Baltic Proper being sampled 5 to 8× during 2006. In addition, data from monitoring programmes were used, which comprised 10 to 22 samplings stn–1. TE was expected to be governed by the size distribution of phytoplankton and due to the nutrient gradient, we expected to find an optimal cell size, and thus also a high TE, in the intermediate-productive Bothnian Sea. The basal production during summer/autumn increased 5-fold from north to south, while the mesozooplankton carbon consumption rate exhibited a peak inthe Bothnian Sea, being ~3× higher than in both Bothnian Bay and Baltic Proper. TE was found to be intermediate in the Bothnian Bay (average: 0.8), highest in the Bothnian Sea (1.6), and lowest in the Baltic Proper (0.2). We suggest that the variation in carbon transfer efficiency can be explained by the composition of the phytoplankton community, the abundance balance between copepods and cladocerans, as well as the species composition of mesozooplankton in relation to the size structure of phytoplankton.

  • 49.
    Dahlgren, Kristin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Eriksson Wiklund, Ann-Kristin
    Department of Applied Environmental Science, ITM, Stockholm University, 106 91 Stockholm, Sweden.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Influence of plankton structure and temperature on pelagic food web efficiency in a brackish water system2011In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, Vol. 45, p. 307-323Article in journal (Refereed)
    Abstract [en]

    As part of one climate change scenario, water temperature as well as the ratio between heterotrophic and autotrophic production is expected to increase; the latter at least in higher latitudes. In order to test how this scenario would affect organisms, such as metazooplankton, at higher trophic levels and carbon transfer up the food chain, a mesocosm experiment was performed at two different temperatures; 5 and 10°C, with two food webs; one phytoplankton-based (NP; autotrophic) and one bacteria-based (CNP; heterotrophic).  The groups of pelagic organisms included in the mesocosms were bacteria, flagellates, ciliates, phytoplankton and metazooplankton. Metazooplankton production was observed to increase with temperature, but was not significantly affected by food web structure. A change in food web structure, i.e. increased heterotrophy, did however lead to decreased fatty acid content and lower individual weight of the metazooplankton. Food web efficiency (FWE), defined as metazooplankton production divided by basal production, increased with autotrophy and temperature: 5CNP (0.2%) < 10CNP (0.4%) < 5NP (1.2%) < 10NP (7.3%). Our results indicate that in the climate change scenario under consideration, the temperature will have a positive effect on FWE whereas the increase in heterotrophy will have a negative effect on FWE. Furthermore, the quality, in terms of fatty acid content and individual weight of the metazooplankton, will be reduced with possible negative effects on higher trophic levels.

  • 50.
    Dahlgren, Kristin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olsen, Bernt Rydland
    Troedsson, Christofer
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Seasonal variation in wax ester concentration and gut content in a Baltic Sea copepod [Limnocalanus macrurus (Sars 1863)]2012In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 34, no 4, p. 286-297Article in journal (Refereed)
    Abstract [en]

    Limnocalanus macrurus from Bothnian Bay in the northern part of the Baltic Sea was studied during the ice-free period (AprilDecember) in order to understand its life history and feeding biology. Our data on the population dynamics indicated that reproduction occurred during the ice-covered period, during which lipid storage was reduced to a minimum. From spring to late summer, the lipid reserve increased by a factor of 3, while the gonads of adult females were immature during this period, continuing to December as indicated by the small size of the eggs. Average stomach fullness was always ca. 50 indicating continuous feeding activity. A newly developed denaturing high-performance liquid chromatography method was used to analyse the gut contents over the study period. More than 30 taxa (at different taxonomic levels) could be identified. However, phytoplankton was only represented by one taxon (Diatomophycea), and was restricted to July. Thus, adult L. macrurus seems to have a strongly carnivorous feeding preference in the northern Baltic Sea.

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