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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.
    Ahlinder, Jon
    et al.
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden.
    Eriksson, Karolina Ida Anna
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hellmér, Maria
    Department of Biology, Science Division, Swedish Food Agency, Sweden.
    Salomonsson, Emelie
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden.
    Granberg, Malin
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden.
    Dacklin, Ingrid
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden.
    Elving, Josefine
    Department of Chemistry, Environment and Feed Hygiene, National Veterinary Institute, Sweden.
    Brindefalk, Björn
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden.
    Upstream land use with microbial downstream consequences: iron and humic substances link to Legionella spp.Manuscript (preprint) (Other academic)
  • 3.
    Ahlinder, Jon
    et al.
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden; Department of Tree Breeding, Skogforsk, Sävar, Sweden.
    Eriksson, Karolina Ida Anna
    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).
    Hellmér, Maria
    Department of Biology, Science Division, Swedish Food Agency, Sweden.
    Salomonsson, Emelie
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden.
    Granberg, Malin
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden.
    Dacklin, Ingrid
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden.
    Elving, Josefine
    Department of Chemistry, Environment and Feed Hygiene, Swedish Veterinary Agency, Sweden.
    Brindefalk, Björn
    Division of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Sweden; Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Sweden.
    Upstream land use with microbial downstream consequences: iron and humic substances link to Legionella spp2024In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 256, article id 121579Article in journal (Refereed)
    Abstract [en]

    Intensified land use can disturb water quality, potentially increasing the abundance of bacterial pathogens, threatening public access to clean water. This threat involves both direct contamination of faecal bacteria as well as indirect factors, such as disturbed water chemistry and microbiota, which can lead to contamination. While direct contamination has been well described, the impact of indirect factors is less explored, despite the potential of severe downstream consequences on water supply. To assess direct and indirect downstream effects of buildings, farms, pastures and fields on potential water sources, we studied five Swedish lakes and their inflows. We analysed a total of 160 samples in a gradient of anthropogenic activity spanning four time points, including faecal and water-quality indicators. Through species distribution modelling, Random Forest and network analysis using 16S rRNA amplicon sequencing data, our findings highlight that land use indirectly impacts lakes via inflows. Land use impacted approximately one third of inflow microbiota taxa, in turn impacting ∌20–50 % of lake taxa. Indirect effects via inflows were also suggested by causal links between e.g. water colour and lake bacterial taxa, where this influenced the abundance of several freshwater bacteria, such as Polynucleobacter and Limnohabitans. However, it was not possible to identify direct effects on the lakes based on analysis of physiochemical- or microbial parameters. To avoid potential downstream consequences on water supply, it is thus important to consider possible indirect effects from upstream land use and inflows, even when no direct effects can be observed on lakes. Legionella (a genus containing bacterial pathogens) illustrated potential consequences, since the genus was particularly abundant in inflows and was shown to increase by the presence of pastures, fields, and farms. The approach presented here could be used to assess the suitability of lakes as alternative raw water sources or help to mitigate contaminations in important water catchments. Continued broad investigations of stressors on the microbial network can identify indirect effects, avoid enrichment of pathogens, and help secure water accessibility.

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  • 4. Aho, Kelly S.
    et al.
    Fair, Jennifer H.
    Hosen, Jacob D.
    Kyzivat, Ethan D.
    Logozzo, Laura A.
    Rocher-Ros, Gerard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Arctic Research Centre at Umeå University.
    Weber, Lisa C.
    Yoon, Byungman
    Raymond, Peter A.
    Distinct concentration-discharge dynamics in temperate streams and rivers: CO2 exhibits chemostasis while CH4 exhibits source limitation due to temperature control2021In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 66, no 10, p. 3656-3668Article in journal (Refereed)
    Abstract [en]

    Streams and rivers are significant sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the magnitudes of these fluxes are uncertain, in part, because dissolved greenhouse gases (GHGs) can exhibit high spatiotemporal variability. Concentration-discharge (C-Q) relationships are commonly used to describe temporal variability stemming from hydrologic controls on solute production and transport. This study assesses how the partial pressures of two GHGs—pCO2 and pCH4—vary across hydrologic conditions over 4 yr in eight nested streams and rivers, at both annual and seasonal timescales. Overall, the range of pCO2 was constrained, ranging from undersaturated to nine times oversaturated, while pCH4 was highly variable, ranging from 3 to 500 times oversaturated. We show that pCO2 exhibited chemostatic behavior (i.e., no change with Q), in part, due to carbonate buffering and seasonally specific storm responses. In contrast, we show that pCH4 generally exhibited source limitation (i.e., a negative relationship with Q), which we attribute to temperature-mediated production. However, pCH4 exhibited chemostasis in a wetland-draining stream, likely due to hydrologic connection to the CH4-rich wetland. These findings have implications for CO2 and CH4 fluxes, which are controlled by concentrations and gas transfer velocities. At high Q, enhanced gas transfer velocity acts on a relatively constant CO2 stock but on a diminishing CH4 stock. In other words, CO2 fluxes increase with Q, while CH4 fluxes are modulated by the divergent Q dynamics of gas transfer velocity and concentration.

  • 5. Ala-aho, P.
    et al.
    Soulsby, C.
    Pokrovsky, O. S.
    Kirpotin, S. N.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Serikova, Svetlana
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Manasypov, R.
    Lim, A.
    Krickov, I.
    Kolesnichenko, L. G.
    Laudon, H.
    Tetzlaff, D.
    Permafrost and lakes control river isotope composition across a boreal Arctic transect in the Western Siberian lowlands2018In: Environmental Research Letters, E-ISSN 1748-9326, Vol. 13, no 3, p. =20-=20, article id 034028Article in journal (Refereed)
    Abstract [en]

    The Western Siberian Lowlands (WSL) store large quantities of organic carbon that will be exposed and mobilized by the thawing of permafrost. The fate of mobilized carbon, however, is not well understood, partly because of inadequate knowledge of hydrological controls in the region which has a vast low-relief surface area, extensive lake and wetland coverage and gradually increasing permafrost influence. We used stable water isotopes to improve our understanding of dominant landscape controls on the hydrology of the WSL. We sampled rivers along a 1700 km South-North transect from permafrost-free to continuous permafrost repeatedly over three years, and derived isotope proxies for catchment hydrological responsiveness and connectivity. We found correlations between the isotope proxies and catchment characteristics, suggesting that lakes and wetlands are intimately connected to rivers, and that permafrost increases the responsiveness of the catchment to rainfall and snowmelt events, reducing catchment mean transit times. Our work provides rare isotope-based field evidence that permafrost and lakes/wetlands influence hydrological pathways across a wide range of spatial scales (10-105 km2) and permafrost coverage (0%-70%). This has important implications, because both permafrost extent and lake/wetland coverage are affected by permafrost thaw in the changing climate. Changes in these hydrological landscape controls are likely to alter carbon export and emission via inland waters, which may be of global significance.

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  • 6. Ala-aho, P.
    et al.
    Soulsby, C.
    Pokrovsky, O. S.
    Kirpotin, S. N.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Serikova, Svetlana
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vorobyev, S. N.
    Manasypov, R. M.
    Loiko, S.
    Tetzlaff, D.
    Using stable isotopes to assess surface water source dynamics and hydrological connectivity in a high-latitude wetland and permafrost influenced landscape2018In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 556, p. 279-293Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to alter hydrological and biogeochemical processes in high-latitude inland waters. A critical question for understanding contemporary and future responses to environmental change is how the spatio-temporal dynamics of runoff generation processes will be affected. We sampled stable water isotopes in soils, lakes and rivers on an unprecedented spatio-temporal scale along a 1700 km transect over three years in the Western Siberia Lowlands. Our findings suggest that snowmelt mixes with, and displaces, large volumes of water stored in the organic soils and lakes to generate runoff during the thaw season. Furthermore, we saw a persistent hydrological connection between water bodies and the landscape across permafrost regions. Our findings help to bridge the understanding between small and large scale hydrological studies in high-latitude systems. These isotope data provide a means to conceptualise hydrological connectivity in permafrost and wetland influenced regions, which is needed for an improved understanding of future biogeochemical changes.

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  • 7.
    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.

  • 8.
    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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  • 9.
    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).
    Hajdu, Susanna
    Stockholms universitet.
    Höglander, Helena
    Stockholms universitet.
    Skjevik, Ann-Turi
    SMHI.
    Pelagial biologi / växtplankton2010In: Havet: om miljötillståndet i svenska havsområden. 2010 / [ed] Kristina Viklund (huvudredaktör) Ulrika Brenner, Annika Tidlund, Marie Svärd, Stockholm: Naturvårdsverket, 2010, p. 32-33Chapter in book (Other academic)
  • 10.
    Andersson, Agneta
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Meier, Markus
    SMHI och Stockholms universitet.
    Hur påverkas Östersjön?2010In: Sverige i nytt klimat: våtvarm utmaning / [ed] Birgitta Johansson, Stockholm: Forskningsrådet Formas, 2010, p. 117-132Chapter in book (Other academic)
  • 11.
    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.

  • 12.
    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.
  • 13.
    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 svenska havsområden. 2015/2016, Göteborg: Havs- och vattenmyndigheten , 2016, p. 25-28Chapter in book (Other academic)
  • 14.
    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)
  • 15.
    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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  • 16.
    Ask, Jenny
    et al.
    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.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Net ecosystem production in clear-water and brown-water lakes2012In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 26, p. GB1017-Article in journal (Refereed)
    Abstract [en]

    We studied 15 lakes in northern Sweden with respect to primary production and respiration in benthic and pelagic habitats. The lakes were characterized by different concentrations of colored dissolved organic carbon (DOC) of terrestrial origin, forming a gradient ranging from clear-water to brown-water lakes. Primary production decreased and respiration increased on a whole-lake scale along the gradient of increasing DOC. Thus, the lakes became more net heterotrophic, i.e., had lower net ecosystem production (NEP = gross primary production - community respiration), with increasing terrestrial DOC and this change coincided with increasing partial pressure of carbon dioxide (pCO(2)) in the surface waters. The single most important process for the increasing net heterotrophy along the DOC gradient was pelagic respiration of terrestrial organic carbon. In spite of high metabolic activity in the benthic habitat, benthic primary production and benthic respiration decreased simultaneously with increasing DOC, showing that the benthic habitat was in metabolic balance throughout the gradient. Therefore, the net heterotrophic states of the lakes depended on the terrestrial DOC export to lakes and the concomitant respiration of terrestrial organic carbon in the pelagic habitat.

  • 17. Attermeyer, Katrin
    et al.
    Casas-Ruiz, Joan Pere
    Fuss, Thomas
    Pastor, Ada
    Cauvy-Fraunie, Sophie
    Sheath, Danny
    Nydahl, Anna C.
    Doretto, Alberto
    Portela, Ana Paula
    Doyle, Brian C.
    Simov, Nikolay
    Roberts, Catherine Gutmann
    Niedrist, Georg H.
    Timoner, Xisca
    Evtimova, Vesela
    Barral-Fraga, Laura
    Basic, Tea
    Audet, Joachim
    Deininger, Anne
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Busst, Georgina
    Fenoglio, Stefano
    Catalan, Nuria
    de Eyto, Elvira
    Pilotto, Francesca
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mor, Jordi-Rene
    Monteiro, Juliana
    Fletcher, David
    Noss, Christian
    Colls, Miriam
    Nagler, Magdalena
    Liu, Liu
    Gonzalez-Quijano, Clara Romero
    Romero, Ferran
    Pansch, Nina
    Ledesma, Jose L. J.
    Pegg, Josephine
    Klaus, Marcus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Freixa, Anna
    Ortega, Sonia Herrero
    Mendoza-Lera, Clara
    Bednarik, Adam
    Fonvielle, Jeremy A.
    Gilbert, Peter J.
    Kenderov, Lyubomir A.
    Rulik, Martin
    Bodmer, Pascal
    Carbon dioxide fluxes increase from day to night across European streams2021In: Communications Earth & Environment, E-ISSN 2662-4435, Vol. 2, no 1, article id 118Article in journal (Refereed)
    Abstract [en]

    Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1mmolm(-2) h(-1) at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams. Diel patterns can greatly impact total stream carbon dioxide emissions, with 39% greater carbon dioxide flux during the night-time relative to the day-time, according to a study of 34 streams across Europe.

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  • 18. Bach, Lydia L.
    et al.
    Freer, Jennifer J.
    Kamenos, Nicholas A.
    School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom.
    In situ Response of Tropical Coralline Algae to a Novel Thermal Regime2017In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 4, article id 212Article in journal (Refereed)
    Abstract [en]

    Coralline algae provide important ecosystem services. In situ observations of how they respond to different environmental conditions can help us to understand (i) their ability to adapt to their local environment and (0 their capacity to acclimatize to a novel thermal regime. Here, individuals of the tropical coralline algae, Lithophyllum kotschyanum, were translocated on a coral reef from thermally stable areas to areas characterized by natural temperature variability. Changes in their photosynthetic efficiency were determined using pulse amplitude modulation (PAM) chlorophyll fluorescence. Despite an initial stress response, algae exposed to increases in thermal variation recovered within 24 hours, indicating a rapid, short-term acclimatization capacity. Algae naturally inhabiting thermally variable areas of the reef showed no change in photosynthetic efficiency throughout the study suggesting longer-term adaptation to living in a variable environment also occurs. However, coralline algae living in thermally stable reef areas were abundant and marginally larger, suggesting physiological trade-offs are used to survive in variable environments. Thus, our results suggest that while coralline algae can survive in environmentally variable conditions, there may be structural and ecosystem costs.

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  • 19.
    Bastias, Elliot
    et al.
    Integrative Freshwater Ecology Group, Centre d’Estudis Avançats de Blanes, Blanes, Girona, Spain.
    Ribot, Miquel
    Jonsson, Micael
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sabater, Francesc
    Martí, Eugènia
    Chemical and optical properties of leachates from different riparian particulate organic matter sources influence instream microbial activity2020In: Freshwater Science, ISSN 2161-9549, E-ISSN 2161-9565, Vol. 39, no 4, p. 812-823Article in journal (Refereed)
    Abstract [en]

    The release of soluble compounds (i.e., leachates) from allochthonous coarse particulate organic matter (CPOM) into stream water can be an important source of dissolved organic matter (DOM) and nutrients for instream microbial activity. Here, we assessed variability in the chemistry and the composition of DOM of leachates from different CPOM sources and examined how these characteristics influenced the activity of microbial assemblages in streams. Specifically, we considered leaf litter from 6 tree species that are broadly distributed in riparian zones of the Mediterranean region, a mixture of fruits from some of these species, and a mixture of twigs. We analyzed the leachates from each CPOM source for the concentration of dissolved forms of carbon, nitrogen, and phosphorus, as well as for the composition of DOM based on optical indices associated with the degree of aromaticity and molecular weight. Under laboratory conditions, we used the Resazurin–Resorufin system to estimate the microbial metabolic activity associated with each leachate type. Microbial metabolic activity varied among leachates from different CPOM sources and was positively related to the degree of aromaticity and the NO3 concentration of leachates. Hence, certain types of riparian CPOM inputs can constitute sources of high-quality DOM and dissolved nutrients for instream microbial assemblages. Thus, management of riparian vegetation should consider variation in leachate properties among plant species, as they can influence dissolved organic carbon and nutrient dynamics and heterotrophic activity in stream ecosystems.

  • 20. Bejarano, Maria Dolores
    et al.
    Garcia-Palacios, Jaime H.
    Sordo-Ward, Alvaro
    Garrote, Luis
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden.
    A New Tool for Assessing Environmental Impacts of Altering Short-Term Flow and Water Level Regimes2020In: Water, E-ISSN 2073-4441, Vol. 12, no 10, article id 2913Article in journal (Refereed)
    Abstract [en]

    The computational tool InSTHAn (indicators of short-term hydrological alteration) was developed to summarize data on subdaily stream flows or water levels into manageable, comprehensive and ecologically meaningful metrics, and to qualify and quantify their deviation from unaltered states. The pronunciation of the acronym refers to the recording interval of input data (i.e., instant). We compared InSTHAn with the tool COSH-Tool in a characterization of the subdaily flow variability of the Colorado River downstream from the Glen Canyon dam, and in an evaluation of the effects of the dam on this variability. Both tools captured the hydropeaking caused by a dam operation, but only InSTHAn quantified the alteration of key flow attributes, highlighting significant increases in the range of within-day flow variations and in their rates of change. This information is vital to evaluate the potential ecological consequences of the hydrological alteration, and whether they may be irreversible, making InSTHAn a key tool for river flow management.

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  • 21. Bejarano, Maria Dolores
    et al.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gonzales del Tanago, Marta
    Marchamalo, Miguel
    Responses of riparian trees and shrubs to flow regulationalong a boreal stream in northern Sweden2011In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 56, no 5, p. 853-866Article in journal (Refereed)
    Abstract [en]

    1. Flow dynamics is a major determinant of riparian plant communities. Therefore, flowregulation may heavily affect riparian ecosystems. Despite the large number of damsworldwide, little specific information is available on the longitudinal impacts of dams onvegetation, for example how far downstream and at what degree of regulation a dam on ariver can influence riparian woodlands.

    2. We quantified the long-term responses of riparian trees and shrubs to flow regulation byidentifying their lateral distribution and habitat conditions along a boreal river in northernSweden that has been regulated by a single dam since 1948. The regulation has reducedannual flow fluctuations, this effect being largest at the dam, downstream from which itprogressively decreases following the entrance of free-flowing tributaries.

    3. We related changes in the distribution patterns, composition, abundance and richness oftree and shrub species to the degree of regulation along the river downstream from thedam. Regulation has triggered establishment of trees and shrubs closer to the channel,making it possible to measure ecological impacts of flow regulation as differences invegetation attributes relative to the positions of tree and shrub communities establishedbefore and after regulation.

    4. Trees and shrubs had migrated towards the mid-channel along the entire study reach,but the changes were largest immediately downstream of the dam. Shrubs were mostimpacted by flow regulation in terms of lateral movement, but the effect on trees extendedfurthest downstream.

    5. The species composition of trees progressively returned to its pre-regulation state withdistance downstream, but entrance of free-flowing tributaries and variation in channelmorphology and substratum caused local deviations. Species richness after regulationincreased for trees but decreased for shrubs. The changes in species composition andrichness of trees and shrubs showed no clear downstream patterns, suggesting that otherfactors than the degree of regulation were more important in governing life form.

  • 22.
    Bejarano, Maria Dolores
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sordo-Ward, Alvaro
    Alonso, Carlos
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Characterizing effects of hydropower plants on sub-daily flow regimes2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 550, p. 186-200Article in journal (Refereed)
    Abstract [en]

    A characterization of short-term changes in river flow is essential for understanding the ecological effects of hydropower plants, which operate by turning the turbines on or off to generate electricity following variations in the market demand (i.e., hydropeaking). The goal of our study was to develop an approach for characterizing the effects of hydropower plant operations on within-day flow regimes across multiple dams and rivers. For this aim we first defined ecologically meaningful metrics that provide a full representation of the flow regime at short time scales from free-flowing rivers and rivers exposed to hydropeaking. We then defined metrics that enable quantification of the deviation of the altered short-term flow regime variables from those of the unaltered state. The approach was successfully tested in two rivers in northern Sweden, one free-flowing and another regulated by cascades of hydropower plants, which were additionally classified based on their impact on short-term flows in sites of similar management. The largest differences between study sites corresponded to metrics describing sub-daily flow magnitudes such as amplitude (i.e., difference between the highest and the lowest hourly flows) and rates (i.e., rise and fall rates of hourly flows). They were closely followed by frequency-related metrics accounting for the numbers of within-day hourly flow patterns (i.e., rises, falls and periods of stability of hourly flows). In comparison, between-site differences for the duration-related metrics were smallest. In general, hydropeaking resulted in higher within-day flow amplitudes and rates and more but shorter periods of a similar hourly flow patterns per day. The impacted flow feature and the characteristics of the impact (i.e., intensity and whether the impact increases or decreases whatever is being described by the metric) varied with season. Our approach is useful for catchment management planning, defining environmental flow targets, prioritizing river restoration or dam reoperation efforts and contributing information for relicensing hydropower dams. 

  • 23. Beldowski, Jacek
    et al.
    Klusek, Zygmunt
    Szubska, Marta
    Turja, Raisa
    Bulczak, Anna I.
    Rak, Daniel
    Brenner, Matthias
    Lang, Thomas
    Kotwicki, Lech
    Grzelak, Katarzyna
    Jakacki, Jaromir
    Fricke, Nicolai
    Ostin, Anders
    Olsson, Ulf
    Fabisiak, Jacek
    Garnaga, Galina
    Nyholm, Jenny Rattfelt
    Majewski, Piotr
    Broeg, Katja
    Soderstrom, Martin
    Vanninen, Paula
    Popiel, Stanislaw
    Nawala, Jakub
    Lehtonen, Kari
    Berglind, Rune
    Umeå University, Faculty of Science and Technology, European CBRNE Center.
    Schmidt, Beata
    Chemical Munitions Search & Assessment-An evaluation of the dumped munitions problem in the Baltic Sea2016In: Deep-sea research. Part II, Topical studies in oceanography, ISSN 0967-0645, E-ISSN 1879-0100, Vol. 128, p. 85-95Article in journal (Refereed)
    Abstract [en]

    Chemical Munitions Search & Assessment (CHEMSEA) project has performed studies on chemical weapon (CW) detection, sediment pollution and spreading as well as biological effects of chemical warfare agents (CWAs) dumped in the Baltic Sea. Results suggest that munitions containing CWAs are more scattered on the seafloor than suspected, and previously undocumented dumpsite was discovered in Gdansk Deep. Pollution of sediments with CWA degradation products was local and close to the detected objects; however the pollution range was larger than predicted with theoretical models. Bottom currents observed in the dumpsites were strong enough for sediment re-suspension, and contributed to the transport of polluted sediments. Diversity and density of the faunal communities were poor at the dumping sites in comparison to the reference area, although the direct effects of CWA on benthos organisms were difficult to determine due to hypoxic or even anoxic conditions near the bottom. Equally, the low oxygen might have affected the biological effects assessed in cod and caged blue mussels. Nonetheless, both species showed significantly elevated molecular and cellular level responses at contaminated sites compared to reference sites.

  • 24. Berggren, M.
    et al.
    Bengtson, P.
    Soares, A. R. A.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC).
    Terrestrial support of zooplankton biomass in northern rivers2018In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 63, no 6, p. 2479-2492Article in journal (Refereed)
    Abstract [en]

    The contribution of terrestrially derived carbon to micro-crustacean zooplankton biomass (i.e., allochthony) has been previously studied in lakes, reservoirs, and estuaries, but little is known about zooplankton allochthony in rivers. In lacustrine environments, allochthony is regulated by distinct selective feeding behavior of different taxa. However, we hypothesized that restricted possibility for selective grazing in turbulent environments such as rivers would decouple zooplankton from specific microbial and algal food resources, such that their allochthony would mirror the terrestrial contribution to the surrounding bulk particle pool. We tested this idea by analyzing allochthony in 13 widely distributed Swedish rivers, using a dual-isotope mixing model. Zooplankton biomasses were generally low, and allochthony in different micro-crustacean groups (Cladocera, Cyclopoida, Calanoida) varied from 2% to 77%. As predicted, there were no correlations between allochthony and variables indicating the supply of algal and microbial food resources, such as chlorophyll a and bacterial production. Instead, the allochthony was generally similar to the share allochthonous contribution in bulk particulate organic matter, with relationships close to the 1 : 1 line. The zooplankton community allochthony was strongly regulated by the ecosystem metabolic balance between production and respiration, which in turn was dependent upon the ratio between total autochthonous organic carbon concentrations and water color. Our study for the first time shows that micro-crustacean allochthony is regulated differently in rivers compared to in lacustrine systems, and points to inefficient support of zooplankton biomass by algal resources in turbulent waters.

  • 25. Berggren, Martin
    et al.
    Gudasz, Cristian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Guillemette, Francois
    Hensgens, Geert
    Ye, Linlin
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Systematic microbial production of optically active dissolved organic matter in subarctic lake water2020In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 65, no 5Article in journal (Refereed)
    Abstract [en]

    The ecology and biogeochemistry of lakes in the subarctic region are particularly sensitive to changes in the abundance and optical properties of dissolved organic matter (DOM). External input of colored DOM to these lakes is an extensively researched topic, but little is known about potential reciprocal feedbacks between the optical properties of DOM and internal microbial processes in the water. We performed 28-day dark laboratory incubation trials on water from 101 subarctic tundra lakes in northern Sweden, measuring the microbial decay of DOM and the resulting dynamics in colored (CDOM) and fluorescent (FDOM) DOM components. While losses in dissolved oxygen during the incubations corresponded to a 20% decrease in mean DOM, conversely the mean CDOM and total FDOM increased by 22% and 30%, respectively. However, the patterns in microbial transformation of the DOM were not the same in all lakes. Notably, along the gradient of increasing ambient CDOM (water brownness), the lakes showed decreased microbial production of protein-like fluorescence, lowered DOM turnover rates and decreasing bacterial growth per unit of DOM. These trends indicate that browning of subarctic lakes systematically change the way that bacteria interact with the ambient DOM pool. Our study underscores that there is no unidirectional causal link between microbial processes and DOM optical properties, but rather reciprocal dependence between the two.

  • 26. Berggren, Martin
    et al.
    Sponseller, Ryan A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Soares, Ana R. Alves
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Toward an ecologically meaningful view of resource stoichiometry in DOM-dominated aquatic systems2015In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 37, no 3, p. 489-499Article in journal (Refereed)
    Abstract [en]

    Research on nutrient controls of planktonic productivity tends to focus on a few standard fractions of inorganic or total nitrogen (N) and phosphorus (P). However, there is a wide range in the degree to which land-derived dissolved organic nutrients can be assimilated by biota. Thus, in systems where such fractions form a majority of the macronutrient resource pool, including many boreal inland waters and estuaries, our understanding of bacterio-and phytoplankton production dynamics remains limited. To adequately predict aquatic productivity in a changing environment, improved standard methods are needed for determining the sizes of active (bioavailable) pools of N, P and organic carbon (C). A synthesis of current knowledge suggests that variation in the C:N:P stoichiometry of bioavailable resources is associated with diverse processes that differentially influence the individual elements across space and time. Due to a generally increasing organic nutrient bioavailability from C to N to P, we hypothesize that the C:N and N:P of bulk resources often vastly overestimates the corresponding ratios of bioavailable resources. It is further proposed that basal planktonic production is regulated by variation in the source, magnitude and timing of terrestrial runoff, through processes that have so far been poorly described.

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  • 27.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hydrological controls on pelagic food structure: From shunts to chemostats as caused by runoff magnitudes and frequency of episodes2020In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 34, no 22, p. 4150-4155Article in journal (Refereed)
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  • 28.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Seasonal dynamics of bacteria and mixotrophic flagellates as related to input of allochthonous dissolved organic carbon2009In: International association of theoretical and applied limnology, vol 30, pt 6: proceedings / [ed] Jones, J & Faaborg, J, Stuttgart: Schweizerbart , 2009, p. 923-928Conference paper (Refereed)
  • 29.
    Bergström, Ann-Kristin
    et al.
    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.
    Karlsson, Daniel
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vrede, Tobias
    Contrasting plankton stoichiometry and nutrient regeneration in northern arctic and boreal lakes2018In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 80, no 2, article id 24Article in journal (Refereed)
    Abstract [en]

    Contrasting carbon: nitrogen: phosphorus (C: N: P) stoichiometry between phytoplankton and zooplankton affect consumer growth and phytoplankton nutrient limitation via nutrient recycling by zooplankton. However, no study has assessed how regional differences in terrestrial loadings of organic matter affect plankton N: P stoichiometry and recycling in systems with low N deposition and N-limited phytoplankton. We address this question by using data from 14 unproductive headwater arctic and boreal lakes. We found that boreal lakes had higher lake water-and seston C, N and P concentrations than arctic lakes, whereas seston C: N, C: P and N: P ratios did not differ among regions. Boreal zooplankton were also richer in N and P relative to C, with lower somatic N: P ratios, compared to arctic lakes. Consequently, the estimated N: P imbalances between seston and zooplankton were negative in arctic lakes, indicating zooplankton feeding on phytoplankton of suboptimal N content, resulting in low consumer driven N: P recycling (medians arctic sub-mid and high altitude lakes: 11 and 13). In boreal lakes, estimated N: P imbalance did not differ from zero, with a seston N: P stoichiometry matching the N: P requirements of zooplankton, which resulted in higher consumer driven N: P recycling (median 18). Our results imply that regional climate induced catchment differences, through enhanced terrestrial nutrient inputs, affect plankton stoichiometry by raising consumer N: P recycling ratio and changing zooplankton from being mainly N-(arctic) to NP co-limited (boreal). Browning of lakes, in regions with low N deposition, may therefore promote large-scale regional changes in plankton nutrient limitation with potential feedbacks on pelagic food webs.

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  • 30.
    Bergström, Ann-Kristin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lau, Danny C. P.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Isles, Peter D. F.
    Watershed Management Division, Vermont Department of Environmental Conservation, VT, Montpelier, United States.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Creed, Irena F.
    Department of Physical and Environmental Sciences, University of Toronto – Scarborough Campus, ON, Toronto, Canada.
    Biomass, community composition and N:P recycling ratios of zooplankton in northern high-latitude lakes with contrasting levels of N deposition and dissolved organic carbon2022In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 67, no 9, p. 1508-1520Article in journal (Refereed)
    Abstract [en]
    1. Global changes are causing decreases in inorganic nitrogen (N) concentrations, increases in coloured dissolved organic carbon (DOC) concentrations, and decreases in dissolved inorganic N to total phosphorus ratios (DIN:TP) in northern lakes. The effects of these changes on phytoplankton and zooplankton biomass and the N:P recycling ratio of zooplankton remain unresolved.
    2. In 33 Swedish headwater lakes across subarctic-to-boreal gradients with different levels of N deposition (low N in the north [Västerbotten, boreal; Abisko, subarctic] vs. high N in the south [Värmland, boreal; Jämtland, subarctic]), we measured water chemistry, phytoplankton biomass (chlorophyll-a [Chl-a], Chl-a:TP), seston mineral quality (C:P, N:P), as well as zooplankton biomass, community composition, and C:N:P stoichiometry. We estimated nutrient imbalances and the N:P recycling ratios of zooplankton using ecological stoichiometry models.
    3. There was a large-scale gradient from low lake DIN and DIN:TP in the north to high DIN and DIN:TP in the south, with lower DIN:TP in lakes coinciding with higher DOC within each region. Lower lake DIN was associated with lower phytoplankton biomass (lower Chl-a:TP). Lower lake DIN:TP was associated with richer seston mineral quality (lower seston C:P and N:P) and higher zooplankton biomass.
    4. Zooplankton community composition differed in the north vs. south, with a dominance of N-requiring calanoid copepods with high N:P in the north and P-requiring cladocerans with low N:P in the south. Also, greater differences in zooplankton community composition were found between subarctic regions (with lower DOC) than between boreal regions (with higher DOC), suggesting that increases in lake DOC and associated declines in lake DIN:TP reduce differences in zooplankton community composition.
    5. The combination of lower lake DIN, higher lake DOC, and lower lake DIN:TP led to reduced zooplankton N:P recycling ratios, possibly by reducing seston N:P and/or by enhancing calanoid copepod dominance in the zooplankton community.
    6. Our findings suggest that the combination of declining N deposition and increasing lake browning in northern high-latitude lakes will reduce phytoplankton biomass, but will concurrently enhance seston mineral quality and probably also zooplankton biomass and their recycling efficiency of P relative to N.
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  • 31. Bijmans, Martijn FM
    et al.
    van Helvoort, Pieter-Jan
    Dar, Shabir A
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Dopson, Mark
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Lens, Piet NL
    Buisman, Cees JN
    Selective recovery of nickel over iron from a nickel-iron solution using microbial sulfate reduction in a gas-lift bioreactor2009In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 43, no 3, p. 853-861Article in journal (Refereed)
    Abstract [en]

    Process streams with high concentrations of metals and sulfate are characteristic for the mining and metallurgical industries. This study aims to selectively recover nickel from a nickel-iron-containing solution at pH 5.0 using a single stage bioreactor that simultaneously combines low pH sulfate reduction and metal-sulfide formation. The results show that nickel was selectively precipitated in the bioreactor at pH 5.0 and the precipitates consisted of >= 83% of the nickel content. The nickel-iron precipitates were partly crystalline and had a metal/sulfur ratio of 1, suggesting these precipitates were NiS and FeS. Experiments focusing on nickel recovery at pH 5.0 and 5.5 reached a recovery of >99.9%, resulting in a nickel effluent concentration <0.05 mu M. The mixed microbial population included known sulfate reducers and acetogens. This study shows that selective metal precipitation in a single stage sulfate reducing bioreactor operated at low pH has the potential to produce metal-sulfides that can be used by the metallurgical industry as a resource for metal production.

  • 32.
    Bindler, Richard
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Beyond the peat: synthesizing peat, lake sediments and soils in studies of the Swedish environment2006In: Peatlands: basin evolution and depository of records on global environmental and climatic changes / [ed] I.P. Martini, A. Martínez Cortizas and W. Chesworth, Elsevier, 2006, p. 431-448Chapter in book (Other academic)
    Abstract [en]

    This chapter illustrates on comparing peat and lake sediment records and linking the quantitative record of metals in peat to contemporary environmental problems. Quantifying metal records in peat has been an important step, but new research needs to move beyond this and consider how to apply these data. Lead analyses, including stable isotopes, are now fairly routine and based on these analyses the historical trends of lead deposition are now well established in peat, lake sediments and even glacial ice. The biogeochemical cycling of lead has also been well researched, which allows making this link between the historical lead record and soil biogeochemistry. Because peat and lake sediments seem to record the same changes in mercury deposition, there is similar promise in linking the long-term peat record of mercury and other metals with biogeochemical cycling of mercury and other important metals in forests and soils.

  • 33. Björk, G
    et al.
    Nohr, C
    Gustafsson, BG
    Lindberg, Amund E. B.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ice dynamics in the Bothnian Bay inferred from ADCP measurements2008In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 60, no 1, p. 178-188Article in journal (Refereed)
    Abstract [en]

    A bottom mounted ADCP has monitored the ice motion and thickness in Bothnian Bay, Baltic Sea during the entire winter season 2004. The ADCP was deployed at 20 m depth at Falkensgrund well outside the land fast ice zone. The data shows that the ice motion is primarily driven by the wind but with a clear influence of internal ice stresses. The ice stresses become more dominant as the ice grow thicker with increasing number of observations with nearly stationary ice for relatively high wind speeds. A clear dependence of the ice/wind speed ratio to wind shifts is detected with higher ratio in the new wind direction. The effect of strain hardening is also seen in several events as decreasing ice speed, sometimes to zero, in spite of constant wind speed and wind direction. A rough force balance computation gives a compressive ice strength of about  9 × 104 N m−2 , which is much larger than normally used in numerical ice models. The ice thickness data show numerous ice ridges with ice draft well above 1 m passing the instrument. The ridges make up a large portion, 30–50%, of the total ice volume showing that dynamical processes are important for the total ice production in the Bothnian Bay.

  • 34.
    Blackburn, Nicholas
    et al.
    MicroWISE, Ebeltoft, Denmark.
    Haecky, Pia
    MicroWISE, Ebeltoft, Denmark.
    Jurgensone, Iveta
    Latvian Institute of Aquatic Ecology, Riga, Latvia.
    Griniene, Evelina
    Marine Research Institute, Klaipėda University, Klaipėda, Lithuania.
    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).
    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.
    Carstensen, Jacob
    Department of Ecoscience, Aarhus University, Roskilde, Denmark.
    The use of an automated organism tracking microscope in mesocosm experiments2022In: Limnology and Oceanography: Methods, E-ISSN 1541-5856, Vol. 20, no 12, p. 768-780Article in journal (Refereed)
    Abstract [en]

    A method for automatically counting and measuring sizes and motility behavior of zooplankton and phytoplankton in water samples is presented. Two video cameras are focused on separate optical chambers of different sizes. The chambers are filled and emptied repeatedly by synchronized pumps. Real-time motion analysis is performed by computer on the respective video feeds. Fluorescence from chlorophyll a (Chl a) is imaged at single pixel resolution. Measured parameters for individual organisms include size, swimming velocity, motility patterns, and chlorophyll fluorescence density. The system was tested during a mesocosm experiment where it was mounted on one of several mesocosm columns. The results were validated against Chl a measurements and microscopy counts. A sampling interval of 1 per day revealed detailed dynamics of chlorophyll activity as well as shifts in both the phytoplankton and zooplankton community structure over the course of a month. A helix coefficient, a metric related to organism motility behavior, showed substantial variation over time, consistent with changing plankton communities. Sampling rates as frequent as 1 per hour enables detailed analysis of diurnal vertical migration and similar phenomena at fixed sampling points.

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  • 35. Block, Benjamin D.
    et al.
    Denfeld, Blaize A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Stockwell, Jason D.
    Flaim, Giovanna
    Grossart, Hans-Peter F.
    Knoll, Lesley B.
    Maier, Dominique B.
    North, Rebecca L.
    Rautio, Milla
    Rusak, James A.
    Sadro, Steve
    Weyhenmeyer, Gesa A.
    Bramburger, Andrew J.
    Branstrator, Donn K.
    Salonen, Kalevi
    Hampton, Stephanie E.
    The unique methodological challenges of winter limnology2019In: Limnology and Oceanography: Methods, E-ISSN 1541-5856, Vol. 17, no 1, p. 42-57Article, review/survey (Refereed)
    Abstract [en]

    Winter is an important season for many limnological processes, which can range from biogeochemical transformations to ecological interactions. Interest in the structure and function of lake ecosystems under ice is on the rise. Although limnologists working at polar latitudes have a long history of winter work, the required knowledge to successfully sample under winter conditions is not widely available and relatively few limnologists receive formal training. In particular, the deployment and operation of equipment in below 0 degrees C temperatures pose considerable logistical and methodological challenges, as do the safety risks of sampling during the ice-covered period. Here, we consolidate information on winter lake sampling and describe effective methods to measure physical, chemical, and biological variables in and under ice. We describe variation in snow and ice conditions and discuss implications for sampling logistics and safety. We outline commonly encountered methodological challenges and make recommendations for best practices to maximize safety and efficiency when sampling through ice or deploying instruments in ice-covered lakes. Application of such practices over a broad range of ice-covered lakes will contribute to a better understanding of the factors that regulate lakes during winter and how winter conditions affect the subsequent ice-free period.

  • 36. Bonk, Alicja
    et al.
    Kinder, Małgorzata
    Enters, Dirk
    Grosjean, Martin
    Meyer-Jacob, Carsten
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tylmann, Wojciech
    Sedimentological and geochemical responses of Lake Żabińskie (north-eastern Poland) to erosion changes during the last millennium2016In: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 56, no 2-3, p. 239-252Article in journal (Refereed)
    Abstract [en]

    Increased erosion triggered by land-use changes is a major process that influences lake sedimentation. We explored the record of erosion intensity in annually laminated sediments of Lake Żabińskie, northeast Poland. A 1000-year-long, annually resolved suite of sedimentological (varve thickness, sediment accumulation rate) and geochemical data (scanning XRF, loss on ignition, biogenic silica) was analyzed with multivariate statistics. PCA indicated erosion was a major process responsible for changes in the chemical composition of the sediments. Analysis of sedimentary facies enabled identification of major phases of erosion that influenced lake sedimentation. These phases are consistent with the history of land use, inferred from pollen analysis. From AD 1000 to 1610, conditions around and in Lake Żabińskie were relatively stable, with low erosion intensity in the catchment and a dominance of carbonate sedimentation. Between AD 1610 and 1740, higher lake productivity and increased delivery of minerogenic material were caused by development of settlements in the region and widespread deforestation. The most prominent changes were observed between AD 1740 and 1880, when further land clearance and increased agricultural activity caused intensified soil erosion and higher lake productivity. Landscape clearance also created better conditions for water column mixing, which led to changes in redox conditions in the hypolimnion. The most recent period (AD 1880–2010) was characterized by partial reforestation and a gradual decrease in the intensity of erosional processes.

  • 37.
    Brum, Mauro
    et al.
    Department of Natural Resources & the Environment, University of New Hampshire, 56 College Rd, Durham, United States.
    Vadeboncoeur, Matthew
    Earth Systems Research Center, University of New Hampshire, 8 College Rd, Durham, United States.
    Asbjornsen, Heidi
    Department of Natural Resources & the Environment, University of New Hampshire, 56 College Rd, Durham, United States; Earth Systems Research Center, University of New Hampshire, 8 College Rd, Durham, United States.
    Puma Vilca, Beisit L.
    Facultad de Ciencias Biológicas, Universidad Nacional de San Antonio Abad del Cusco, Av. de La Cultura 773, Cusco Province 08000, Cusco, Peru; Asociación Civil Sin Fines De Lucro Para La Biodiversidad, Investigación Y Desarrollo Ambiental En Ecosistemas Tropicales (ABIDA), Avenida Argentina F-9, Cusco, Peru.
    Galiano, Darcy
    Facultad de Ciencias Biológicas, Universidad Nacional de San Antonio Abad del Cusco, Av. de La Cultura 773, Cusco Province 08000, Cusco, Peru; Asociación Civil Sin Fines De Lucro Para La Biodiversidad, Investigación Y Desarrollo Ambiental En Ecosistemas Tropicales (ABIDA), Avenida Argentina F-9, Cusco, Peru.
    Horwath, Aline B.
    Asociación Civil Sin Fines De Lucro Para La Biodiversidad, Investigación Y Desarrollo Ambiental En Ecosistemas Tropicales (ABIDA), Avenida Argentina F-9, Cusco, Peru.
    Metcalfe, Daniel B.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ecophysiological controls on water use of tropical cloud forest trees in response to experimental drought2023In: Tree Physiology, ISSN 0829-318X, E-ISSN 1758-4469, Vol. 43, no 9, p. 1514-1532Article in journal (Refereed)
    Abstract [en]

    Tropical montane cloud forests (TMCFs) are expected to experience more frequent and prolonged droughts over the coming century, yet understanding of TCMF tree responses to moisture stress remains weak compared with the lowland tropics. We simulated a severe drought in a throughfall reduction experiment (TFR) for 2 years in a Peruvian TCMF and evaluated the physiological responses of several dominant species (Clusia flaviflora Engl., Weinmannia bangii (Rusby) Engl., Weinmannia crassifolia Ruiz & Pav. and Prunus integrifolia (C. Presl) Walp). Measurements were taken of (i) sap flow; (ii) diurnal cycles of stem shrinkage, stem moisture variation and water-use; and (iii) intrinsic water-use efficiency (iWUE) estimated from foliar δ13C. In W. bangii, we used dendrometers and volumetric water content (VWC) sensors to quantify daily cycles of stem water storage. In 2 years of sap flow (Js) data, we found a threshold response of water use to vapor pressure deficit vapor pressure deficit (VPD) > 1.07 kPa independent of treatment, though control trees used more soil water than the treatment trees. The daily decline in water use in the TFR trees was associated with a strong reduction in both morning and afternoon Js rates at a given VPD. Soil moisture also affected the hysteresis strength between Js and VPD. Reduced hysteresis under moisture stress implies that TMCFs are strongly dependent on shallow soil water. Additionally, we suggest that hysteresis can serve as a sensitive indicator of environmental constraints on plant function. Finally, 6 months into the experiment, the TFR treatment significantly increased iWUE in all study species. Our results highlight the conservative behavior of TMCF tree water use under severe soil drought and elucidate physiological thresholds related to VPD and its interaction with soil moisture. The observed strongly isohydric response likely incurs a cost to the carbon balance of the tree and reduces overall ecosystem carbon uptake.

  • 38. Buffam, Ishi
    et al.
    Laudon, Hjalmar
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Seibert, Jan
    Mörth, Carl-Magnus
    Bishop, Kevin
    Spatial heterogeneity of the spring flood acid pulse in a boreal stream network.2008In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 407, no 1, p. 708-22Article in journal (Refereed)
    Abstract [en]

    Spatial and temporal patterns in streamwater acidity are ecologically important, but difficult to measure in parallel. Here we present the spatial distribution of streamwater chemistry relevant to acidity from 60 stream sites distributed throughout a 67 km(2) boreal catchment, sampled during a period of winter baseflow (high pH) and during a spring flood episode (low pH). Sites were grouped based on pH level and pH change from winter baseflow to spring flood. The site attributes of each pH group were then assessed in terms of both stream chemistry and subcatchment landscape characteristics. Winter baseflow pH was high throughout most of the stream network (median pH 6.4), but during the spring flood episode stream sites experienced declines in pH ranging from 0-1.6 pH units, resulting in pH ranging from 4.3-6.3. Spring flood pH was highest in larger, lower altitude catchments underlain by fine sorted sediments, and lowest in small, higher altitude catchments with a mixture of peat wetlands and forested till. Wetland-dominated headwater catchments had low but stable pH, while the spring flood pH drop was largest in a group of catchments of intermediate size which contained well-developed coniferous forest and a moderate proportion of peat wetlands. There was a trend with distance downstream of higher pH, acid neutralizing capacity (ANC) and base cation concentrations together with lower dissolved organic carbon (DOC, strongly negatively correlated with pH). This apparent scale-dependence of stream chemistry could be explained by a number of environmental factors which vary predictably with altitude, catchment area and distance downstream-most notably, a shift in surficial sediment type from unsorted till and peat wetlands to fine sorted sediments at lower altitudes in this catchment. As a result of the combination of spatial heterogeneity in landscape characteristics and scale-related processes, boreal catchments like this one can be expected to experience high spatial variability both in terms of chemistry at any given point in time, and in the change experienced during high discharge episodes. Although chemistry patterns showed associations with landscape characteristics, considerable additional variability remained, suggesting that the modeling of dynamic stream chemistry from map parameters will continue to present a challenge. (C) 2008 Elsevier B.V. All rights reserved.

  • 39.
    Bunse, Carina
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Bacterioplankton in the light of seasonality and environmental drivers2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bacterioplankton are keystone organisms in marine ecosystems. They are important for element cycles, by transforming dissolved organic carbon and other nutrients. Bacterioplankton community composition and productivity rates change in surface waters over spatial and temporal scales. Yet, many underlying biological processes determining when, why and how bacterioplankton react to changes in environmental conditions are poorly understood. Here, I used experiments with model bacteria and natural assemblages as well as field studies to determine molecular, physiological and ecological responses allowing marine bacteria to adapt to their environment.

    Experiments with the flavobacterium Dokdonia sp. MED134 aimed to determine how the metabolism of bacteria is influenced by light and different organic matter. Under light exposure, Dokdonia sp. MED134 expressed proteorhodopsin and adjusted its metabolism to use resources more efficiently when growing with lower-quality organic matter. Similar expression patterns were found in oceanic datasets, implying a global importance of photoheterotrophic metabolisms for the ecology of bacterioplankton.

    Further, I investigated how the composition and physiology of bacterial assemblages are affected by elevated CO2 concentrations and inorganic nutrients. In a large-scale experiment, bacterioplankton could keep productivity and community structure unaltered by adapting the gene expression under CO2 stress. To maintain pH homeostasis, bacteria induced higher expression of genes related to respiration, membrane transport and light acquisition under low-nutrient conditions. Under high-nutrient conditions with phytoplankton blooms, such regulatory mechanisms were not necessary. These findings indicate that open ocean systems are more vulnerable to ocean acidification than coastal waters.

    Lastly, I used field studies to resolve how bacterioplankton is influenced by environmental changes, and how this leads to seasonal succession of marine bacteria. Using high frequency sampling over three years, we uncovered notable variability both between and within years in several biological features that rapidly changed over short time scales. These included potential phytoplankton-bacteria linkages, substrate uptake rates, and shifts in bacterial community structure. Thus, high resolution time series can provide important insights into the mechanisms controlling microbial communities.

    Overall, this thesis highlights the advantages of combining molecular and traditional oceanographic methodological approaches to study ecosystems at high resolution for improving our understanding of the physiology and ecology of microbial communities and, ultimately, how they influence biogeochemical processes.

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  • 40.
    Burdett, Heidi L.
    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.
    Cautious positivity for the future of aquatic conservation in Europe2024In: Aquatic conservation, ISSN 1052-7613, E-ISSN 1099-0755, Vol. 34, no 7, article id e4222Article in journal (Other academic)
  • 41.
    Burdett, Heidi L.
    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.
    Looking forward in aquatic conservation2024In: Aquatic conservation, ISSN 1052-7613, E-ISSN 1099-0755, Vol. 34, no 2, article id e4110Article in journal (Other academic)
  • 42. Burdett, Heidi L.
    et al.
    Perna, Gabriela
    McKay, Lucy
    Broomhead, Gemma
    Kamenos, Nicholas A.
    King Abdullah University for Science and Technology, Thuwal, Saudi Arabia.
    Community-level sensitivity of a calcifying ecosystem to acute in situ CO2 enrichment2018In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 587, p. 73-80Article in journal (Refereed)
    Abstract [en]

    The rate of change in ocean carbonate chemistry is a vital determinant in the magnitude of effects observed. Benthic marine ecosystems are facing an increasing risk of acute CO2 exposure that may be natural or anthropogenically derived (e.g. engineering and industrial activities). However, our understanding of how acute CO2 events impact marine life is restricted to individual organisms, with little understanding for how this manifests at the community level. Here, we investigated in situ the effect of acute CO2 enrichment on the coralline algal ecosystem - a globally ubiquitous, ecologically and economically important habitat, but one which is likely to be sensitive to CO2 enrichment due to its highly calcified reef-like structures engineered by coralline algae. Most notably, we observed a rapid community-level shift to favour net dissolution rather than net calcification. Smaller changes from net respiration to net photosynthesis were also observed. There was no effect on the net flux of DMS/DMSP (algal secondary metabolites), nor on the nutrients nitrate and phosphate. Following return to ambient CO2 levels, only a partial recovery was seen within the monitoring timeframe. This study highlights the sensitivity of biogenic carbonate marine communities to acute CO2 enrichment and raises concerns over the capacity for the system to 'bounce back' if subjected to repeated acute high-CO2 events.

  • 43. Cael, B. B.
    et al.
    Seekell, David A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The size-distribution of Earth's lakes2016In: Scientific Reports, E-ISSN 2045-2322, Vol. 6, article id 29633Article in journal (Refereed)
    Abstract [en]

    Globally, there are millions of small lakes, but a small number of large lakes. Most key ecosystem patterns and processes scale with lake size, thus this asymmetry between area and abundance is a fundamental constraint on broad-scale patterns in lake ecology. Nonetheless, descriptions of lake size-distributions are scarce and empirical distributions are rarely evaluated relative to theoretical predictions. Here we develop expectations for Earth's lake area-distribution based on percolation theory and evaluate these expectations with data from a global lake census. Lake surface areas >= 8.5 km(2) are power-law distributed with a tail exponent (T = 1.97) and fractal dimension (d = 1.38), similar to theoretical expectations (T = 2.05; d = 4/3). Lakes <8.5 km(2) are not power-law distributed. An independently developed regional lake census exhibits a similar transition and consistency with theoretical predictions. Small lakes deviate from the power-law distribution because smaller lakes are more susceptible to dynamical change and topographic behavior at sub-kilometer scales is not self-similar. Our results provide a robust characterization and theoretical explanation for the lake size-abundance relationship, and form a fundamental basis for understanding and predicting patterns in lake ecology at broad scales.

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  • 44.
    Cael, B.B.
    et al.
    National Oceanography Centre, Southampton, United Kingdom.
    Seekell, David A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Simple model of morphometric constraint on carbon burial in boreal lakes2023In: Frontiers in Environmental Science, E-ISSN 2296-665X, Vol. 11, article id 1101332Article in journal (Refereed)
    Abstract [en]

    A geometric theory was developed to explain the empirical relationship between carbon burial and lake shape in boreal lakes. The key feature of this model is an attenuation length scale, analogous to models of marine organic carbon fluxes. This length scale is the ratio of how fast carbon is displaced vertically versus how fast it is respired and engenders a simple model with a single easily constrained free parameter. Lake depths are modeled based on fractal area–volume relationships that reflect the approximate scale invariance of Earth’s topography on idealized lake geometries. Carbon burial is estimated by applying the attenuation length scale to these depths. Using this model, we demonstrate the relationship between the dynamic ratio—a metric of lake morphometry calculated by dividing the square root of surface area by the mean depth—and carbon burial. We use scaling relationships to predict how dynamic ratio, and by extension carbon burial, varies across the lake size spectrum. Our model also provides a basis for generalizing empirical studies to the biome scale. By applying our model to a boreal lake census, we estimate boreal lake carbon burial to be 1.8 (Formula presented.) 0.5 g C/m2/yr or 1.1 (Formula presented.) 0.3 Tg C/yr among all boreal lakes.

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  • 45.
    Cael, Brendan B.
    et al.
    National Oceanography Centre, Southampton, United Kingdom.
    Seekell, David
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    A theory for the relationship between lake surface area and maximum depth2022In: Limnology and Oceanography Letters, E-ISSN 2378-2242, Vol. 7, no 6, p. 527-533Article in journal (Refereed)
    Abstract [en]

    Maximum depth is crucial for many lake processes and biota, but attempts to explain its variation have achieved little predictive power. In this paper, we describe the probability distribution of maximum depths based on recent developments in the theory of fractal Brownian motions. The theoretical distribution is right-tailed and adequately captures variations in maximum depth in a dataset of 8164 lakes (maximum depths 0.1–135 m) from the northeastern United States. Maximum depth increases with surface area, but with substantial random variation—the 95% prediction interval spans more than an order of magnitude for lakes with any specific surface area. Our results explain the observed variability in lake maximum depths, capture the link between topographic characteristics and lake bathymetry, and provide a means to upscale maximum depth-dependent processes, which we illustrate by upscaling the diffusive flux of methane from northern lakes to the atmosphere.

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  • 46. Cai, Minggang
    et al.
    Hong, Qingquan
    Sun, Jionghui
    Sundqvist, Kristina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wiberg, Karin
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Aquatic Sciences and Environmental Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Chen, Kai
    Wang, Yun
    Qiu, Cangrong
    Huang, Shuiying
    Concentrations, distribution and sources of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls in coastal sediments from Xiamen, China2016In: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 185, p. 74-81Article in journal (Refereed)
    Abstract [en]

    Xiamen and its surroundings are representative areas suffering from intense anthropogenic turbulence and contamination in southeast coast of China during rapid industrialization and urbanization period, thus relevant organic pollutants research is necessary to assess the coastal environmental quality and generate management strategy. Contamination status of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin like polychlorinated biphenyls (DL-PCBs) was investigated for 7 surface sediment samples collected in these areas in January 2007. The given data were used to evaluate the contamination and their potential risks of the pollutants. Concentrations of PCDD/Fs were in the range of 60 to 4089 pg g(-1) (dry weight) with an average of 1706 pg g(-1) and DL-PCBs in the range of 3 to 76 pg g(-1) with an average of 28 pg g(-1). Octa-chlorinated dibenzo-p-dioxin (OCDD) and PCBs 105 and 118 were the main congeners of the PCDD/F and DL-PCB, respectively. The toxicity equivalent concentrations (TEQs) were in the range of 0.15 to 5.2 pg g(-1) (average: 3.0 pg g(-1)) for PCDD/Fs, while in the range of <limit of quantitation (LOQ) to 0.09 pg g(-1) (average: 0.05 pg g(-1)) for DL-PCBs. Congener pattern analysis showed a dominance of OCDD, suggesting main sources were current or historical use of chlorophenol, current use of dioxin contaminated pesticides or atmospheric deposition. Due to the current levels of PCDD/Fs and DL-PCBs in this area, it is necessary to further research their biogeochemical processes and ecological influences in the future.

  • 47.
    Callisto Puts, Isolde
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Myrstener, Maria
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Contrasting impacts of warming and browning on periphyton2023In: Limnology and Oceanography Letters, E-ISSN 2378-2242, Vol. 8, no 4, p. 628-638Article in journal (Refereed)
    Abstract [en]

    We tested interactive effects of warming (+2°C) and browning on periphyton accrual and pigment composition when grown on a synthetic substrate (plastic strips) in the euphotic zone of 16 experimental ponds. We found that increased colored dissolved organic matter (cDOM) and associated nutrients alone, or in combination with warming, resulted in a substantially enhanced biomass accrual of periphyton, and a comparatively smaller increase in phytoplankton. This illustrates that periphyton is capable of using nutrients associated with cDOM, and by this may affect nutrient availability for phytoplankton. However, warming weakened the positive impact of browning on periphyton accrual, possibly by thermal compensation inferred from altered pigment composition, and/or changes in community composition. Our results illustrate multiple impacts of climate change on algal growth, which could have implications for productivity and consumer resource use, especially in shallow areas in northern lakes.

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  • 48.
    Capo, Eric
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Marine Biology, Institut de Ciències del Mar, CSIC, Barcelona, Spain.
    Barouillet, CéciliaINRAE, Université Savoie Mont Blanc CARRTEL, Thonon-les-Bains, France.Smol, John P.Paleoecological Environmental Assessment and Research Lab (PEARL) Department of Biology, Queen’s University, Kingston, Canada.
    Tracking environmental change using lake sediments: volume 6: sedimentary DNA2023Collection (editor) (Refereed)
    Abstract [en]

    This book, entitled Tracking Environmental Change Using Lake Sediments: Volume 6 – Sedimentary DNA, provides an overview of the applications of sedimentary DNA-based approaches to paleolimnological studies. These approaches have shown considerable potential in providing information about the long-term changes of overall biodiversity in lakes and their watersheds in response to natural and anthropogenic changes, as well as tracking human migrations over the last thousands of years.

    Although the first studies investigating the preservation of these molecular proxies in sediments originate from the late-1990s, the number of scientific publications on this topic has increased greatly over the last five years. Alongside numerous ecological findings, several sedimentary DNA studies have been dedicated to understanding the reliability of this approach to reconstruct past ecosystem changes.  Despite the major surge of interest, a comprehensive compilation of sedimentary DNA approaches and applications has yet to be attempted. The overall aim of this DPER volume is to fill this knowledge gap. 

  • 49. Catalán, N.
    et al.
    Casas-Ruiz, J. P.
    Arce, M. I.
    Abril, M.
    Bravo, A. G.
    del Campo, R.
    Estévez, E.
    Freixa, A.
    Giménez-Grau, P.
    González-Ferreras, A. M.
    Gómez-Gener, Luís
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lupon, A.
    Martinez, A.
    Palacin-Lizarbe, C.
    Poblador, S.
    Rasines-Ladero, R.
    Reyes, M.
    Rodriguez-Castillo, T.
    Rodriguez-Lozano, P.
    Sanpera-Calbet, I.
    Tornero, I.
    Pastor, A.
    Behind the Scenes: mechanisms Regulating Climatic Patterns of Dissolved Organic Carbon Uptake in Headwater Streams2018In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 32, no 10, p. 1528-1541Article in journal (Refereed)
    Abstract [en]

    Large variability in dissolved organic carbon (DOC) uptake rates has been reported for headwater streams, but the causes of this variability are still not well understood. Here we assessed acetate uptake rates across 11 European streams comprising different ecoregions by using whole-reach pulse acetate additions. We evaluated the main climatic and biogeochemical drivers of acetate uptake during two seasonal periods. Our results show a minor influence of sampling periods but a strong effect of climate and dissolved organic matter (DOM) composition on acetate uptake. In particular, mean annual precipitation explained half of the variability of the acetate uptake velocities (Vf(Acetate)) across streams. Temperate streams presented the lowest Vf(Acetate), together with humic-like DOM and the highest stream respiration rates. In contrast, higher Vf(Acetate) were found in semiarid streams, with protein-like DOM, indicating a dominance of reactive, labile compounds. This, together with lower stream respiration rates and molar ratios of DOC to nitrate, suggests a strong C limitation in semiarid streams, likely due to reduced inputs from the catchment. Overall, this study highlights the interplay of climate and DOM composition and its relevance to understand the biogeochemical mechanisms controlling DOC uptake in streams. Plain Language Summary Headwater streams receive and degrade organic carbon and nutrients from the surrounding catchments. That degradation can be assessed by measuring the uptake of simple compounds of carbon or nitrogen such as acetate or nitrate. Here we determine the variability in acetate and nitrate uptake rates across headwater streams and elucidate the mechanisms behind that variability. The balance between nutrients, the composition of the organic materials present in the streams, and the climatic background is at interplay.

  • 50.
    Cherif, Mehdi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Arnott, Russell N.
    Department of Architecture and Civil Engineering, Centre for Climate Adaptation and Environment Research, University of Bath, Bath, United Kingdom; Aquatic Ecosystems and Global Change Research Unit, National Research Institute for Agriculture, Food and the Environment, Cedex, Cestas, France; Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom; Bristol Water (South West Water Ltd), Bristol, United Kingdom.
    Wain, Danielle J.
    Department of Architecture and Civil Engineering, Centre for Climate Adaptation and Environment Research, University of Bath, Bath, United Kingdom; Aquatic Ecosystems and Global Change Research Unit, National Research Institute for Agriculture, Food and the Environment, Cedex, Cestas, France; Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom; Bristol Water (South West Water Ltd), Bristol, United Kingdom.
    Bryant, Lee D.
    Department of Architecture and Civil Engineering, Centre for Climate Adaptation and Environment Research, University of Bath, Bath, United Kingdom.
    Larsson, Henrik
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Slavin, Emily I.
    Department of Architecture and Civil Engineering, Centre for Climate Adaptation and Environment Research, University of Bath, Bath, United Kingdom; Aquatic Ecosystems and Global Change Research Unit, National Research Institute for Agriculture, Food and the Environment, Cedex, Cestas, France; Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom; Bristol Water (South West Water Ltd), Bristol, United Kingdom.
    Using convective mixing in mesocosms to study climate-driven shifts in phytoplankton community distributions2023In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 10, article id 1204922Article in journal (Refereed)
    Abstract [en]

    With climate change predicted to alter water column stability and mixing across the world’s oceans, a mesocosm experiment was designed to ascertain how a natural phytoplankton community would respond to these changes. As a departure from other mesocosm experiments, we used heating and cooling to produce four different climate-inspired mixing scenarios ranging from well-mixed water columns representative of typical open turbulence (ϵ = 3 x 10-8 m2/s3) through to a quiescent water column with stable stratification (ϵ = 5 x 10-10 m2/s3). This method of turbulence generation is an improvement on previous techniques (e.g., grid, shaker, and aeration) which tend to produce excessive dissipation rates inconsistent with oceanic turbulence observations. Profiles of classical physical parameters used to describe turbulence and mixing (turbulent dissipation rate, buoyancy frequency, turbulent eddy diffusivity, Ozmidov scale) were representative of the profiles found in natural waters under similar mixing conditions. Chlorophyll-a profiles and cell enumeration showed a clear biological response to the different turbulence scenarios. However, the responses of specific phytoplankton groups (diatoms and dinoflagellates) did not conform to the usual expectations: diatoms are generally expected to thrive under convective, turbulent regimes, while dinoflagellates are expected to thrive in converse conditions, i.e., in stable, stratified conditions. Our results suggest that responses to mixing regimes are taxon-specific, with no overwhelming physical effect of the turbulence regime. Rather, each taxon seemed to very quickly reach a given vertical distribution that it managed to hold, whether actively or passively, with a high degree of success. Future studies on the effects of climate change on phytoplankton vertical distribution should thus focus on the factors and mechanisms that combine to determine the specific distribution of species within taxa. Our convection-based mesocosm approach, because it uses a primary physical force that generates turbulence in open waters, should prove a valuable tool in this endeavor.

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