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  • 1.
    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.

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  • 2.
    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.
    Grinienė, Evelina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Marine Research Institute, Klaipėda University, Klaipėda, Lithuania.
    Berglund, Åsa M. M.
    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. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Gorokhova, Elena
    Department of Environmental Science, Stockholm University, Stockholm, Sweden.
    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).
    Gallampois, Christine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ripszam, Matyas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Microbial food web changes induced by terrestrial organic matter and elevated temperature in the coastal northern Baltic Sea2023In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 10, article id 1170054Article in journal (Refereed)
    Abstract [en]

    Climate change has been projected to cause increased temperature and amplified inflows of terrestrial organic matter to coastal areas in northern Europe. Consequently, changes at the base of the food web favoring heterotrophic bacteria over phytoplankton are expected, affecting the food web structure. We tested this hypothesis using an outdoor shallow mesocosm system in the northern Baltic Sea in early summer, where the effects of increased temperature (+ 3°C) and terrestrial matter inputs were studied following the system dynamics and conducting grazing experiments. Juvenile perch constituted the highest trophic level in the system, which exerted strong predation on the zooplankton community. Perch subsequently released the microbial food web from heavy grazing by mesozooplankton. Addition of terrestrial matter had a stronger effect on the microbial food web than the temperature increase, because terrestrial organic matter and accompanying nutrients promoted both heterotrophic bacterial production and phytoplankton primary production. Moreover, due to the shallow water column in the experiment, terrestrial matter addition did not reduce the light below the photosynthesis saturation level, and in these conditions, the net-autotrophy was strengthened by terrestrial matter enrichment. In combination with elevated temperature, the terrestrial matter addition effects were intensified, further shifting the size distribution of the microbial food web base from picoplankton to microphytoplankton. These changes up the food web led to increase in the biomass and proportion of large-sized ciliates (>60 µm) and rotifers. Despite the shifts in the microbial food web size structure, grazing experiments suggested that the pathway from picoplankton to nano- and microzooplankton constituted the major energy flow in all treatments. The study implies that the microbial food web compartments in shallow coastal waters will adjust to climate induced increased inputs of terrestrial matter and elevated temperature, and that the major energy path will flow from picoplankton to large-sized ciliates during the summer period.

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  • 3.
    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.

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  • 4.
    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.
    Zhao, Li
    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. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    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).
    Huseby, Siv
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Metabarcoding vs Microscopy - comparison of methods to monitor phytoplankton communities2023In: ACS - ES & T Water, E-ISSN 2690-0637, Vol. 3, no 8, p. 2671-2680Article in journal (Other academic)
    Abstract [en]

    Phytoplankton are used worldwide to monitor environmental status in aquatic systems. Long-time series of microscopy-analyzed phytoplankton are available from many monitoring stations. The microscopy-method is however time consuming and has short-comings. DNA metabarcoding has been suggested as an alternative method, but the consistency between different methods need further investigation. We performed a comparative study of microscopy and metabarcoding analyzing micro- and nanophytoplankton. For metabarcoding, 25-1000 ml seawater were filtered, DNA extracted and the 18S and 16S rRNA gene amplicons sequenced. For microscopy, based on the Utermöhl method we evaluated the use of three metrics: abundance, biovolume and carbon biomass. At the genus, species, and unidentified taxa level, metabarcoding generally showed higher taxonomic diversity than microscopy, and diversity was already captured at the lowest filtration volume tested, 25 ml. Metabarcoding and microscopy displayed relatively similar distribution pattern at the group level. The results showed that the relative abundances of the 18S rRNA amplicon at the group level best fitted the microscopy carbon biomass metric. The results are promising for implementing DNA metabarcoding as a complement to microscopy in phytoplankton monitoring, especially if databases would be improved and group level indexes could be applied to classify the environmental state of water bodies.

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  • 5.
    Berglund, Åsa M. M.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gallampois, Christine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ripszam, Matyas
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy.
    Larsson, Henrik
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Figueroa, Daniela
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Griniene, Evelina
    Marine Research Institute, Klaipėda University, Klaipėda, Lithuania.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gorokhova, Elena
    Department of Environmental Science, Stockholm University, Stockholm, Sweden.
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    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.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Effects on the food-web structure and bioaccumulation patterns of organic contaminants in a climate-altered Bothnian Sea mesocosms2023In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 10, article id 1244434Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to alter global temperature and precipitation patterns resulting in complex environmental impacts. The proposed higher precipitation in northern Scandinavia would increase runoff from land, hence increase the inflow of terrestrial dissolved organic matter (tDOM) in coastal regions. This could promote heterotrophic bacterial production and shift the food web structure, by favoring the microbial food web. The altered climate is also expected to affect transport and availability of organic micropollutants (MPs), with downstream effects on exposure and accumulation in biota. This study aimed to assess climate-induced changes in a Bothnian Sea food web structure as well as bioaccumulation patterns of MPs. We performed a mesocosms-study, focusing on aquatic food webs with fish as top predator. Alongside increased temperature, mesocosm treatments included tDOM and MP addition. The tDOM addition affected nutrient availability and boosted both phytoplankton and heterotrophic bacteria in our fairly shallow mesocosms. The increased tDOM further benefitted flagellates, ciliates and mesozooplankton, while the temperature increase and MP addition had minor effect on those organism groups. Temperature, on the other hand, had a negative impact on fish growth and survival, whereas tDOM and MP addition only had minor impact on fish. Moreover, there were indications that bioaccumulation of MPs in fish either increased with tDOM addition or decreased at higher temperatures. If there was an impact on bioaccumulation, moderately lipophilic MPs (log Kow 3.6 - 4.6) were generally affected by tDOM addition and more lipophilic MPs (log Kow 3.8 to 6.4) were generally affected by increased temperature. This study suggest that both increased temperatures and addition of tDOM likely will affect bioaccumulation patterns of MPs in shallow coastal regions, albeit with counteracting effects.

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  • 6.
    Figueroa, Daniela
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bacterioplankton in the Baltic Sea: influence of allochthonous organic matter and salinity2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Climate change is expected to increase the precipitation ~30% in higher latitudes during the next century, increasing the land runoff via rivers to aquatic ecosystems. The Baltic Sea will receive higher river discharges, accompanied by larger input of allochthonous dissolved organic matter (DOM) from terrestrial ecosystems. The salinity will decrease due to freshwater dilution. The allochthonous DOM constitute a potential growth substrate for microscopic bacterioplankton and phytoplankton, which together make up the basal trophic level in the sea. The aim of my thesis is to elucidate the bacterial processing of allochthonous DOM and to evaluate possible consequences of increased runoff on the basal level of the food web in the Baltic Sea. I performed field studies, microcosm experiments and a theoretical modeling study.

    Results from the field studies showed that allochthonous DOM input via river load promotes the heterotrophic bacterial production and influences the bacterial community composition in the northern Baltic Sea. In a northerly estuary ~60% of bacterial production was estimated to be sustained by terrestrial sources, and allochthonous DOM was a strong structuring factor for the bacterial community composition. Network analysis showed that during spring the diversity and the interactions between the bacteria were relatively low, while later during summer other environmental factors regulate the community, allowing a higher diversity and more interactions between different bacterial groups. The influence of the river inflow on the bacterial community allowed “generalists” bacteria to be more abundant than “specialists” bacteria.   

    Results from a transplantation experiment, where bacteria were transplanted from the northern Baltic Sea to the seawater from the southern Baltic Sea and vice versa, showed that salinity, as well as the DOM composition affect the bacterial community composition and their enzymatic activity. The results showed that α-proteobacteria in general were favoured by high salinity, β-proteobacteria by low salinity and terrestrial DOM compounds and γ-proteobacteria by the enclosure itself. However, effects on the community composition and enzymatic activity were not consistent when the bacterial community was retransplanted, indicating a functional redundancy of the bacterial communities. 

    Results of ecosystem modeling showed that climate change is likely to have quite different effect on the north and the south of the Baltic Sea. In the south, higher temperature and internal nutrient load will increase the cyanobacterial blooms and expand the anoxic or suboxic areas. In the north, climate induced increase in riverine inputs of allochthonous DOM is likely to promote bacterioplankton production, while phytoplankton primary production will be hampered due to increased light attenuation in the water. This, in turn, can decrease the production at higher trophic levels, since bacteria-based food webs in general are less efficient than food webs based on phytoplankton. However, complex environmental influences on the bacterial community structure and the large redundancy of metabolic functions limit the possibility of predicting how the bacterial community composition will change under climate change disturbances.

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  • 7.
    Figueroa, Daniela
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Capo, Eric
    Lindh, Markus
    Rowe, Owen
    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.
    Pinhassi, Jarone
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Coupling between bacterial community composition and allochthonous organic matter in a sub-arctic estuaryManuscript (preprint) (Other academic)
    Abstract [en]

    Climate change is expected to cause increased precipitation in boreal and subarctic zones, leading to increased runoff of allochthonous dissolved organic matter (ADOM) from land to the sea. ADOM has been shown to be a major driver of bacterioplankton production in a sub-arctic estuary in the northern Baltic Sea, the Råne estuary. By using a network approach we here analyzed how the bacterial community is affected by ADOM and other environmental factors in the same estuary. β-proteobacteria were observed to be dominant in spring when the river runoff and the ADOM concentrations were high. Planctomycetes and Verrucomicrobia become more abundant later during the summer when the ADOM discharge was low. The diversity and evenness in the bacterioplankton community increased as the runoff decreased during the summer. During this period Verrucomicrobia, β-proteobacteria, Bacteriodetes, γ-proteobacteria and Planctomycetes became more abundant. Overall more complex population interactions were established in summer than in spring. β-proteobacteria and Bacteriodetes formed clusters, showing similar responses to different environmental factors, which suggest a functional connection between these groups. The bacterial community consisted of as much as ~60% of generalists, which reflected the large variation of the environmental conditions in the estuary.

  • 8.
    Figueroa, Daniela
    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).
    Capo, Eric
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lindh, Markus V.
    Ecology and Evolution in Microbial Model Systems, EEMiS, Linnaeus University, Kalmar, Sweden.
    Rowe, Owen F.
    Baltic Marine Environment Protection Commission HELCOM, Helsinki, Finland.
    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).
    Pinhassi, Jarone
    Ecology and Evolution in Microbial Model Systems, EEMiS, Linnaeus University, Kalmar, 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).
    Terrestrial dissolved organic matter inflow drives temporal dynamics of the bacterial community of a subarctic estuary (northern Baltic Sea)2021In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 23, no 8, p. 4200-4213Article in journal (Refereed)
    Abstract [en]

    Climate change is projected to cause increased inflow of terrestrial dissolved organic matter to coastal areas in northerly regions. Estuarine bacterial community will thereby receive larger loads of organic matter and inorganic nutrients available for microbial metabolism. The composition of the bacterial community and its ecological functions may thus be affected. We studied the responses of bacterial community to inflow of terrestrial dissolved organic matter in a subarctic estuary in the northern Baltic Sea, using a 16S rRNA gene metabarcoding approach. Betaproteobacteria dominated during the spring river flush, constituting ~ 60% of the bacterial community. Bacterial diversity increased as the runoff decreased during summer, when Verrucomicrobia, Betaproteobacteria, Bacteroidetes, Gammaproteobacteria and Planctomycetes dominated the community. Network analysis revealed that a larger number of associations between bacterial populations occurred during the summer than in spring. Betaproteobacteria and Bacteroidetes populations appeared to display similar correlations to environmental factors. In spring, freshly discharged organic matter favoured specialists, while in summer a mix of autochthonous and terrestrial organic matter promoted the development of generalists. Our study indicates that increased inflows of terrestrial organic matter-loaded freshwater to coastal areas would promote specialist bacteria, which in turn might enhance the transformation of terrestrial organic matter in estuarine environments.

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  • 9.
    Figueroa, Daniela
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lindh, Markus
    Murphy, Kathleen
    Sjöstedt, Johanna
    Legrand, Catherine
    Pinhassi, Jarone
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Selective degradation of different dissolved organic matter compounds by regionally transplanted bacteria.Manuscript (preprint) (Other academic)
    Abstract [en]

    Climate change projections indicate that precipitation will increase by ~30% in the Baltic Sea within the next hundred years. This will lead to lowered salinity and increased inputs of dissolved organic matter (DOM) to the sea. The interactive effects of these changes on bacterial communities and DOM degradation are virtually unknown. We studied the selective degradation of different DOM compounds by regionally transplanted bacterial communities. Bacteria from the northern Baltic Sea were transplanted and re-transplanted to the southern Baltic Sea and vice versa. Three fractions of DOM were identified; two allochthonous fractions, originating from terrestrial systems and one autochthononous constituting the protein building blocks tryptophan/tyrosine. The largest decrease of dissolved organic carbon was observed in seawater from the Bothnian Sea (northern Baltic Sea), and the bacteria performing this degradation were those transplanted from the Baltic Proper (southern Baltic Sea). The native bacteria from the Bothnian Sea degraded both allochthonous and autochthonous DOM, while, bacteria from the Baltic Proper consumed mainly the autochthonous part of the DOM. Both autochthonous and allochthonous components of the DOM were found to shape the bacterioplankton community, Cyanobacteria and γ-proteobacteria were favored by all three DOM components, while α-proteobacteria and Bacteroidetes were favored by autochthonous DOM and β-proteobacteria by terrestrial DOM. However, no clear connection between different DOM components, specific bacterial groups and metabolic processes could be identified. Our study thus indicates that climate change can cause unforeseen adjustments of the bacterial community composition and function, governed by complex interactions between bacteria and their chemical environment.

  • 10.
    Figueroa, Daniela
    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).
    Rowe, Owen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, University of Helsinki, Helsinki, Finland.
    Paczkowska, Joanna
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Legrand, Catherine
    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).
    Allochthonous Carbon - a major driver of bacterioplankton production in the subarctic Northern Baltic Sea2016In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 71, no 4, p. 789-801Article in journal (Refereed)
    Abstract [en]

    Heterotrophic bacteria are, in many aquatic systems, reliant on autochthonous organic carbon as their energy source. One exception is low-productive humic lakes, where allochthonous dissolved organic matter (ADOM) is the major driver. We hypothesized that bacterial production (BP) is similarly regulated in subarctic estuaries that receive large amounts of riverine material. BP and potential explanatory factors were measured during May–August 2011 in the subarctic Råne Estuary, northern Sweden. The highest BP was observed in spring, concomitant with the spring river-flush and the lowest rates occurred during summer when primary production (PP) peaked. PLS correlations showed that ∼60 % of the BP variation was explained by different ADOM components, measured as humic substances, dissolved organic carbon (DOC) and coloured dissolved organic matter (CDOM). On average, BP was threefold higher than PP. The bioavailability of allochthonous dissolved organic carbon (ADOC) exhibited large spatial and temporal variation; however, the average value was low, ∼2 %. Bioassay analysis showed that BP in the near-shore area was potentially carbon limited early in the season, while BP at seaward stations was more commonly limited by nitrogen-phosphorus. Nevertheless, the bioassay indicated that ADOC could contribute significantly to the in situ BP, ∼60 %. We conclude that ADOM is a regulator of BP in the studied estuary. Thus, projected climate-induced increases in river discharge suggest that BP will increase in subarctic coastal areas during the coming century.

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  • 11. Lindh, Markus V.
    et al.
    Figueroa, Daniela
    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.
    Sjostedt, Johanna
    Baltar, Federico
    Lundin, Daniel
    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).
    Legrand, Catherine
    Pinhassi, Jarone
    Transplant experiments uncover Baltic Sea basin-specific responses in bacterioplankton community composition and metabolic activities2015In: Frontiers in Microbiology, E-ISSN 1664-302X, Vol. 6, article id 223Article in journal (Refereed)
    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.

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  • 12.
    Paczkowska, Joanna
    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). Centro para el Estudiode Sistemas Marinos CESIMAR-CONICET, Blvd. Brown 2915, U9120ACD, Puerto Madryn, Chubut, Argentina .
    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). 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 University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Swedish Meteorological and Hydrological Institute, SMHI, Göteborg, Sweden.
    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.
    Drivers of phytoplankton production and community structure in nutrient-poor estuaries receiving terrestrial organic inflow2019In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 151, article id 104778Article in journal (Refereed)
    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.

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  • 13. Rodríguez, Juanjo
    et al.
    Gallampois, Christine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Timonen, Sari
    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.
    Sinkko, Hanna
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Berglund, Åsa M. M.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ripszam, Matyas
    Figueroa, Daniela
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rowe, Owen
    Effects of Organic Pollutants on Bacterial Communities Under Future Climate Change Scenarios2018In: Frontiers in Microbiology, E-ISSN 1664-302X, Vol. 9, article id 2926Article in journal (Refereed)
    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.

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  • 14.
    Rowe, Owen F.
    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). 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 University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    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).
    Riemann, Lasse
    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).
    Major differences in dissolved organic matter characteristics and bacterial processing over an extensive brackish water gradient, the Baltic Sea2018In: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 202, p. 27-36Article in journal (Refereed)
    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.

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