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  • 1. Adrian, Rita
    et al.
    O`Reilly, Catherine M.
    Zagarese, Horacio
    Baines, Stephen B.
    Hessen, Dag O.
    Keller, Wendel
    Livingstone, David M.
    Sommaruga, Ruben
    Straile, Dietmar
    Van Donk, Ellen
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Winder, Monika
    Lakes as sentinels of climate change2009In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 54, no 6(2), p. 2283-2297Article in journal (Refereed)
    Abstract [en]

    While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.

  • 2. Andersson, B
    et al.
    Eriksson, L
    Herlitz, E
    Persson, G
    Weyhenmeyer, Gesa
    SLU.
    Wiederholm, A-M
    Miljöövervakning i Mälarens fjärdar och sund 19992000Report (Other academic)
  • 3. Andersson, B
    et al.
    Herlitz, E
    Persson, G
    Weyhenmeyer, Gesa
    SLU.
    Wiederholm, A-M
    Miljöövervakning i Mälarens fjärdar och sund 20002001Report (Other academic)
  • 4. Andersson, B
    et al.
    Weyhenmeyer, Gesa
    SLU.
    Miljöövervakning i Mälaren 20012002Report (Other academic)
  • 5. Arvola, Lauri
    et al.
    George, Glen
    Livingstone, David M.
    Järvinen, Marko
    Blenckner, Thorsten
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Dokulil, Martin T.
    Jennings, Eleanor
    Aonghusa, Caitriona Nic
    Nõges, Peeter
    Nõges, Tiina
    Weyhenmeyer, Gesa. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The impact of changing climate on the thermal characteristics of lakes2010In: The impact of climate change on European lakes / [ed] D.G. George, Springer , 2010, p. 85-101Chapter in book (Other academic)
  • 6. Benson, Barbara J.
    et al.
    Magnuson, John J.
    Jensen, Olaf P.
    Card, Virginia M.
    Hodgkins, Glenn
    Korhonen, Johanna
    Livingstone, David M.
    Stewart, Kenton M.
    Weyhenmeyer, Gesa
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Granin, Nick G.
    Extreme events, trends, and variability in Northern Hemisphere lake-ice phenology (1855-2005)2012In: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 112, no 2, p. 299-323Article in journal (Refereed)
    Abstract [en]

    Often extreme events, more than changes in mean conditions, have the greatest impact on the environment and human well-being. Here we examine changes in the occurrence of extremes in the timing of the annual formation and disappearance of lake ice in the Northern Hemisphere. Both changes in the mean condition and in variability around the mean condition can alter the probability of extreme events. Using long-term ice phenology data covering two periods 1855-6 to 2004-5 and 1905-6 to 2004-5 for a total of 75 lakes, we examined patterns in long-term trends and variability in the context of understanding the occurrence of extreme events. We also examined patterns in trends for a 30-year subset (1975-6 to 2004-5) of the 100-year data set. Trends for ice variables in the recent 30-year period were steeper than those in the 100- and 150-year periods, and trends in the 150-year period were steeper than in the 100-year period. Ranges of rates of change (days per decade) among time periods based on linear regression were 0.3-1.6 later for freeze, 0.5-1.9 earlier for breakup, and 0.7-4.3 shorter for duration. Mostly, standard deviation did not change, or it decreased in the 150-year and 100-year periods. During the recent 50-year period, standard deviation calculated in 10-year windows increased for all ice measures. For the 150-year and 100-year periods changes in the mean ice dates rather than changes in variability most strongly influenced the significant increases in the frequency of extreme lake ice events associated with warmer conditions and decreases in the frequency of extreme events associated with cooler conditions.

  • 7.
    Björnerås, C.
    et al.
    Lund University, Lund, Sweden.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Evans, C. D.
    Environm Ctr Wales, Bangor, Wales.
    Gessner, M. O.
    Leibniz Inst Freshwater Ecol & Inland Fisheries I, Stechlin, Germany; TU Berlin, Berlin, Germany.
    Grossart, H. P.
    Potsdam Univ, Potsdam, Germany.
    Kangur, K.
    Estonian Univ Life Sci, Rannu, Estonia.
    Kokorite, I.
    Univ Latvia, Riga, Latvia.
    Kortelainen, P.
    Finnish Environm Inst, Helsinki, Finland.
    Laudon, H.
    Swedish Univ Agr Sci, Umeå, Sweden.
    Lehtoranta, J.
    Finnish Environm Inst, Helsinki, Finland.
    Lottig, N.
    Univ Wisconsin, Madison, USA.
    Monteith, D. T.
    Lancaster Environm Ctr, Lancaster, England.
    Nõges, P.
    Estonian Univ Life Sci, Tartu, Estonia.
    Nõges, T.
    Estonian Univ Life Sci, Tartu, Estonia.
    Oulehle, F.
    Czech Geol Survey, Prague, Czech Republic.
    Riise, G.
    Norwegian Univ Life Sci NMBU, As, Norway.
    Rusak, J. A.
    Ontario Minist Environm & Climate Change, Dorset, Canada.
    Räike, A.
    Finnish Environm Inst, Helsinki, Finland.
    Sire, J.
    Latvian Environm Geol & Meteorol Ctr, Riga, Latvia.
    Sterling, S.
    Dalhousie Univ, Halifax, Canada.
    Kritzberg, E. S.
    Lund University, Lund, Sweden.
    Widespread Increases in Iron Concentration in European and North American Freshwaters2017In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 31, no 10, p. 1488-1500Article in journal (Refereed)
    Abstract [en]

    Recent reports of increasing iron (Fe) concentrations in freshwaters are of concern, given the fundamental role of Fe in biogeochemical processes. Still, little is known about the frequency and geographical distribution of Fe trends or about the underlying drivers. We analyzed temporal trends of Fe concentrations across 340 water bodies distributed over 10 countries in northern Europe and North America in order to gain a clearer understanding of where, to what extent, and why Fe concentrations are on the rise. We found that Fe concentrations have significantly increased in 28% of sites, and decreased in 4%, with most positive trends located in northern Europe. Regions with rising Fe concentrations tend to coincide with those with organic carbon (OC) increases. Fe and OC increases may not be directly mechanistically linked, but may nevertheless be responding to common regional-scale drivers such as declining sulfur deposition or hydrological changes. A role of hydrological factors was supported by covarying trends in Fe and dissolved silica, as these elements tend to stem from similar soil depths. A positive relationship between Fe increases and conifer cover suggests that changing land use and expanded forestry could have contributed to enhanced Fe export, although increases were also observed in nonforested areas. We conclude that the phenomenon of increasing Fe concentrations is widespread, especially in northern Europe, with potentially significant implications for wider ecosystem biogeochemistry, and for the current browning of freshwaters.

  • 8.
    Blenckner, Thorsten
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Adrian, Rita
    Arvola, Lauri
    Järvinen, Marko
    Nõges, Peeter
    Nõges, Tiina
    Pettersson, Kurt
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The impact of climate change on lakes in northern Europe2010In: The impact of climate change on European lakes / [ed] D.G. George, Springer , 2010, p. 339-358Chapter in book (Other academic)
  • 9.
    Blenckner, Thorsten
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Adrian, Rita
    Livingstone, David
    Jennings, Eleanor
    Weyhenmeyer, Gesa
    George, Glen
    Jankowski, Thomas
    Ärviken, Marko
    Aonghusa, Caitriona
    Noges, Tiina
    Straile, Dietmar
    Teubner, Katrin
    Large-scale climatic signatures in lakes across Europe: A meta-analysis2007In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 13, no 7, p. 1314-1326Article in journal (Refereed)
    Abstract [en]

    Recent studies have highlighted the impact of the winter North Atlantic Oscillation (NAO) on water temperature, ice conditions, and spring plankton phenology in specific lakes and regions in Europe. Here, we use meta-analysis techniques to test whether 18 lakes in northern, western, and central Europe respond coherently to winter climate forcing, and to assess the persistence of the winter climate signal in physical, chemical, and biological variables during the year. A meta-analysis approach was chosen because we wished to emphasize the overall coherence pattern rather than individual lake responses. A particular strength of our approach is that time-series from each of the 18 lakes were subjected to the same robust statistical analysis covering the same 23-year period. Although the strongest overall coherence in response to the winter NAO was exhibited by lake water temperatures, a strong, coherent response was also exhibited by concentrations of soluble reactive phosphorus and soluble reactive silicate, most likely as a result of the coherent response exhibited by the spring phytoplankton bloom. Lake nitrate concentrations showed significant coherence in winter. With the exception of the cyanobacterial biomass in summer, phytoplankton biomass in all seasons was unrelated to the winter NAO. A strong coherence in the abundance of daphnids during spring can most likely be attributed to coherence in daphnid phenology. A strong coherence in the summer abundance of the cyclopoid copepods may have been related to a coherent change in their emergence from resting stages. We discuss the complex nature of the potential mechanisms that drive the observed changes.

  • 10.
    Blenckner, Thorsten
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Järvinen, Marko
    Dep. of Ecology and Systematic, University of Helsinki.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Atmospheric circulation and its impact on ice phenology in Scandinavia2004In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 9, no 5, p. 371-380Article in journal (Refereed)
    Abstract [en]

    Atmospheric circulation is important in affecting surface climate and ecosystems. In this study, we compared the impact of north-atlantic and regional atmospheric circulation, as represented by the North Atlantic Oscillation (NAO) index and a set of regional circulation indices, on ice phenology of 50 Scandinavian lakes. Both ice freeze and ice break-up dates were coherent over the whole region and were significantly correlated with both types of circulation indices. Correlations were especially strong for regional circulation indices. The application of regional indices, here for the first time related with ice data over a large area, allowed the determination of the type (i.e. meridional/ zonal wind and cyclonic/anticyclonic conditions) of atmospheric circulation influencing the ice phenology. The results suggest that regional circulation indices are very useful tools, in addition to global circulation, to improve the understanding of the interaction between ecosystem processes and climate.

  • 11. Bloch, Ina
    et al.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Long-term changes in physical and chemical conditions of nutrient-poor lakes along a latitudinal gradient: is there a coherent phytoplankton community response?2012In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 74, no 1, p. 77-85Article in journal (Refereed)
    Abstract [en]

    To evaluate climate and atmospheric deposition induced physical and water chemical changes and their effects on phytoplankton communities, we used complete time series (14 years, monthly measurements during the growing season) of 18 physical and chemical variables and phytoplankton data from 13 nutrient-poor Swedish reference lakes along a latitudinal gradient. We found numerous strong significant changes over time that were most coherent among lakes for sulfate concentrations, conductivity, calcium, magnesium, chloride, potassium, water color, surface water temperature and the intensity of thermal stratification. Despite these pronounced coherent physical and water chemical changes over Sweden, the phytoplankton biomass and species richness of six phytoplankton groups, measured at the same time as the water chemical variables, showed only few and weak significant changes over time. The only coherent significant change over Sweden, occurring in seven lakes, was observed in the species richness of chlorophytes. The number of chlorophyte taxa significantly declined over Sweden. Using a partial least square model for each lake, we attributed the decline primarily to an increase in water temperatures and water color, which were among the most important variables for the model performance of each lake. All other taxonomic groups were driven primarily by non-coherent changes in nutrient concentrations, pH and probably also non-coherent grazing pressure. We concluded that coherent phytoplankton responses can only be achieved for taxonomic groups that are driven primarily by coherent physical/chemical changes. According to our study, chlorophytes belong to such a group, making them possible global change indicators. Our findings give new insights into global change effects on different phytoplankton taxonomic groups in nutrient-poor lakes.

  • 12. Daneshvar, Atlasi
    et al.
    Aboulfadl, Khadija
    Viglino, Liza
    Broseus, Romain
    Sauve, Sebastien
    Madoux-Humery, Anne-Sophie
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Prevost, Michele
    Evaluating pharmaceuticals and caffeine as indicators of fecal contamination in drinking water sources of the Greater Montreal region2012In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 88, no 1, p. 131-139Article in journal (Refereed)
    Abstract [en]

    We surveyed four different river systems in the Greater Montreal region, upstream and downstream of entry points of contamination, from April 2007 to January 2009. The studied compounds belong to three different groups: PPCPs (caffeine, carbamazepine, naproxen, gemfibrozil, and trimethoprim), hormones (progesterone, estrone, and estradiol), and triazine herbicides and their metabolites (atrazine, deethylatrazine, deisopropylatrazine, simazine, and cyanazine). In the system A. B, and C having low flow rate and high TOC, we observed the highest detection frequencies and mass flows of PPCPs compared to the other compounds, reflecting discharge of urban contaminations through WWTPs and CSOs. However, in River D, having high flow rate and low TOC, comparable frequency of detection of triazine and their by-products and PPCPs, reflecting cumulative loads of these compounds from the Great Lakes as well as persistency against natural attenuation processes. Considering large differences in the removal efficiencies of caffeine and carbamazepine, a high ratio of caffeine/carbamazepine might be an indicative of a greater proportion of raw sewage versus treated wastewater in surface waters. In addition, caffeine appeared to be a promising indicator of recent urban fecal contaminations, as shown by the significant correlation with FC (R-2 = 0.45), while carbamazepine is a good indicator of cumulative persistence compounds.

  • 13. Daneshvar, Atlasi
    et al.
    Svanfelt, Jesper
    Kronberg, Leif
    Prévost, Michele
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Seasonal variations in the occurrence and fate of basic and neutral pharmaceuticals in a Swedish river-lake system2010In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 80, no 3, p. 301-309Article in journal (Refereed)
    Abstract [en]

    The seasonal variations in the occurrence of carbamazepine, atenolol, metoprolol, sotalol, and acebutolol were studied at seven sites along River Fyris from December 2007 to December 2008. Samples were collected from the effluent of a waste water treatment plant (WWTP), at one upstream site, and five downstream sites of the WWTP). During one occasion in May 2008, water samples were collected at different locations and depths in the recipient lake. All analytes except of acebutolol were present in both the river and the lake at quantifiable amounts at all sampling occasions. Carbamazepine was found in similar concentrations (about 90 ng L-1) at all sampling sites and all studied depths (0.5-40 m) in the lake, indicating high environmental persistence of this compound. A clear seasonal pattern was observed for the natural attenuation of the beta-blockers in the river, with the highest attenuation occurring in summer and the lowest in winter. The loss of beta-blockers on a distance of 1320 m reached up to 75% during summer time but was insignificant during winter. The seasonal variations in the loss followed the seasonal variations in water temperature and chlorophyll a mass flow suggesting that biotransformation and adsorption are the main processes responsible for the loss of the studied pharmaceuticals in River Fyris downstream the WWTP.

  • 14. Daneshvar, Atlasi
    et al.
    Svanfelt, Jesper
    Kronberg, Leif
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Neglected sources of pharmaceuticals in river water: footprints of a Reggae festival2012In: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 14, no 2, p. 596-603Article in journal (Refereed)
    Abstract [en]

    Wastewater treatment plants (WWTPs) are commonly considered as the main source of pharmaceuticals in surface waters. Here, however, we show that an open-air festival, attracting approximately 10 000 visitors per year at the shores of River Fyris upstream of Uppsala WWTP, can temporarily result in a higher pharmaceutical input into the river water than the WWTP. Studying the influence of Uppsala Reggae festival on the occurrence of ten commonly used acidic and basic pharmaceuticals upstream, in the effluent, and downstream of the Uppsala WWTP, we found that occasional heavy rainfalls during the festival in 2008 severely increased the mass flows of all pharmaceuticals at the WWTP upstream site. Also, strong increases in ammonium (210-fold), nitrate (21-fold), and total nitrogen (21-fold) mass flows were observed. The pharmaceutical mass flows at the upstream site were up to 3.4 times higher than those observed in the WWTP effluent. In contrast, in 2009, the festival was not accompanied with rainfalls and no major additional input of pharmaceuticals and nitrogen was observed. The findings of this study give new insights into risk assessments and are relevant for monitoring programmes.

  • 15. Daneshvar, Atlasi
    et al.
    Svanfelt, Jesper
    Kronberg, Leif
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Winter accumulation of acidic pharmaceuticals in a Swedish river2010In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 17, no 4, p. 908-916Article in journal (Refereed)
    Abstract [en]

    In this study, seasonal variations in the concentration profile of four analgesics and one lipid regulator were monitored on their way from a wastewater treatment plant (WWTP) effluent, along a river, and into a lake. From December 2007 to December 2008, water samples were collected monthly (n = 12) from an upstream point, the effluent, four downstream points of the WWTP, and at the point where the river merges with the lake, and the concentrations of ibuprofen, naproxen, bezafibrate, diclofenac, and ketoprofen were determined. The analytical methodology involved solid-phase extraction of the target compounds from water samples followed by liquid chromatography coupled with tandem mass spectrometry for compound separation and detection. The studied pharmaceuticals were found in the effluent at concentrations ranging from 31 to 1,852 ng l(-1) depending on the season. In the river and lake, the concentrations were much lower (6-400 ng l(-1)) mainly due to dilution but also to a season-dependent contribution from natural transformation processes. The mean mass flow of all analgesics was highest during winter while the highest mean mass flow of the lipid regulator bezafibrate was observed in spring. The WWTP is the main source of the target compounds in the aquatic environment. The observed winter accumulation signifies the importance of natural transformation processes, which can only be estimated based on mass flow data, on the fate of pharmaceuticals in the environment.

  • 16.
    Denfeld, Blaize A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wallin, Marcus B.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sahlée, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Kokic, Jovana
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Chmiel, Hannah E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Temporal and spatial carbon dioxide concentration patterns in a small boreal lake in relation to ice cover dynamics2015In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 20, no 6, p. 679-692Article in journal (Refereed)
    Abstract [en]

    Global carbon dioxide (CO2) emission estimates from inland waters commonly neglect the ice-cover season. To account for CO2 accumulation below ice and consequent emissions into the atmosphere at ice-melt we combined automatically-monitored and manually- sampled spatially-distributed CO2 concentration measurements from a small boreal ice-covered lake in Sweden. In early winter, CO2 accumulated continuously below ice, whereas, in late winter, CO2 concentrations remained rather constant. At ice-melt, two CO2 concentration peaks were recorded, the first one reflecting lateral CO2 transport within the upper water column, and the second one reflecting vertical CO2 transport from bottom waters. We estimated that 66%–85% of the total CO2 accumulated in the water below ice left the lake at ice-melt, while the remainder was stored in bottom waters. Our results imply that CO2 accumulation under ice and emissions at ice-melt are more dynamic than previously reported, and thus need to be more accurately integrated into annual CO2 emission estimates from inland waters.

  • 17.
    Denfeld, Blaize
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Kortelainen, Pirkko
    Finnish Environment Institute.
    Rantakari, Miitta
    Department of Environmental Sciences, University of Helsinki.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Weyhenmeyer, Gesa
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Regional Variability and Drivers of Below Ice CO2 in Boreal and Subarctic Lakes2016In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 19, no 3, p. 461-476Article in journal (Refereed)
    Abstract [en]

    Northern lakes are ice-covered for considerable portions of the year, where carbon dioxide (CO2) can accumulate below ice, subsequently leading to high CO2 emissions at ice-melt. Current knowledge on the regional control and variability of below ice partial pressure of carbon dioxide (pCO(2)) is lacking, creating a gap in our understanding of how ice cover dynamics affect the CO2 accumulation below ice and therefore CO2 emissions from inland waters during the ice-melt period. To narrow this gap, we identified the drivers of below ice pCO(2) variation across 506 Swedish and Finnish lakes using water chemistry, lake morphometry, catchment characteristics, lake position, and climate variables. We found that lake depth and trophic status were the most important variables explaining variations in below ice pCO(2) across the 506 lakes(.) Together, lake morphometry and water chemistry explained 53% of the site-to-site variation in below ice pCO(2). Regional climate (including ice cover duration) and latitude only explained 7% of the variation in below ice pCO(2). Thus, our results suggest that on a regional scale a shortening of the ice cover period on lakes may not directly affect the accumulation of CO2 below ice but rather indirectly through increased mobility of nutrients and carbon loading to lakes. Thus, given that climate-induced changes are most evident in northern ecosystems, adequately predicting the consequences of a changing climate on future CO2 emission estimates from northern lakes involves monitoring changes not only to ice cover but also to changes in the trophic status of lakes.

  • 18.
    Denfeld, Blaize
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Umea Univ, Dept Ecol & Environm Sci, Umea, Sweden.
    Ricão Canelhas, Monica
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Weyhenmeyer, Gesa
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bastviken, David
    Linköping University, Department of Thematic Studies – Environmental Change .
    Constraints on methane oxidation in ice-covered boreal lakes2016In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, no 7, p. 1924-1933Article in journal (Refereed)
    Abstract [en]

    Boreal lakes can be ice covered for a substantial portion of the year at which time methane (CH4) can accumulate below ice. The amount of CH4 emitted at ice melt is partially determined by the interplay between CH4 production and CH4 oxidation, performed by methane-oxidizing bacteria (MOB). Yet the balance between oxidation and emission and the potential for CH4 oxidation in various lakes during winter is largely unknown. To address this, we performed incubations at 2 degrees C to screen for wintertime CH4 oxidation potential in seven lakes. Results showed that CH4 oxidation was restricted to three lakes, where the phosphate concentrations were highest. Molecular analyses revealed that MOB were initially detected in all lakes, although an increase in type I MOB only occurred in the three lake water incubations where oxidation could be observed. Accordingly, the increase in CO2 was on average 5 times higher in these three lake water incubations. For one lake where no oxidation was measured, we tested if temperature and CH4 availability could trigger CH4 oxidation. However, regardless of incubation temperatures and CH4 concentrations, ranging from 2 to 20 degrees C and 1-500M, respectively, no oxidation was observed. Our study indicates that some lakes with active wintertime CH4 oxidation may have low emissions during ice melt, while other and particularly nutrient poor lakes may accumulate large amounts of CH4 below ice that, in the absence of CH4 oxidation, will be emitted following ice melt. This variability in CH4 oxidation rates between lakes needs to be accounted for in large-scale CH4 emission estimates.

  • 19.
    Eklöf, Karin
    et al.
    SLU Department of Aquatic Sciences and Assessment.
    Kraus, Andrea
    SLU Department of Aquatic Sciences and Assessment.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Meili, Markus
    Stockholm University.
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Forestry Influence by Stump Harvest and Site Preparation on Methylmercury, Total Mercury and Other Stream Water Chemistry Parameters Across a Boreal Landscape2012In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 15, no 8, p. 1308-1320Article in journal (Refereed)
    Abstract [en]

    Forestry has been reported to cause elevated mercury (Hg) concentrations in runoff water. However, the degree to which forestry operations influence Hg in runoff varies among sites. A synoptic study, covering 54 catchments distributed all over Sweden, subjected to either stump harvest (SH), site preparation (SP) or no treatment (Ref), was undertaken to reveal the degree of forestry impact and causes of eventual variation. All streams were sampled twice, in autumn 2009 and summer 2010. There were no significant differences in total mercury (THg) and methylmercury (MeHg) concentrations between the three treatments in either 2009 or 2010. However, when pooling the treated catchments (that is, SH and SP) and taking catchment properties such as latitude into account, the treatment had a significant influence on the THg and MeHg concentrations. Although the treatment effect on THg and MeHg did not differ between SH and SP, the study did reveal significant forestry effects on potassium (K) and total nitrogen (TN) that were greater in the SH catchments and lower in the SP catchments. Partial least square (PLS) regressions indicated that organic matter was the most important variable influencing both the THg and MeHg concentrations. There were no significant differences between the treatment groups when comparing the ratios of THg/total organic carbon (TOC) and MeHg/TOC, suggesting that the high concentrations of THg and MeHg observed at some of the treated catchments are associated with increased concentrations of TOC rather than new methylation or increased mobilization caused by factors other than TOC.

  • 20. Erlandsson, Martin
    et al.
    Buffam, Ishi
    Folster, Jens
    Laudon, Hjalmar
    Temnerud, Johan
    Weyhenmeyer, Gesa A.
    Bishop, Kevin
    Thirty-five years of synchrony in the organic matter concentrations of Swedish rivers explained by variation in flow and sulphate2008In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 14, no 5, p. 1191-1198Article in journal (Refereed)
  • 21.
    Erlandsson, Martin
    et al.
    University of Reading, UK.
    Cory, Neil
    SLU.
    Fölster, Jens
    SLU Department of Aquatic Sciences and Assessment.
    Köhler, Stephan
    SLU Department of Aquatic Sciences and Assessment.
    Laudon, Hjalmar
    SLU Department of Forest Ecology and Management.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Bishop, Kevin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Increasing Dissolved Organic Carbon Redefines the Extent of Surface Water Acidification and Helps Resolve a Classic Controversy2011In: BioScience, ISSN 0006-3568, E-ISSN 1525-3244, Vol. 61, no 8, p. 614-618Article in journal (Refereed)
    Abstract [en]

    Concentrations of organic acids in freshwaters have increased significantly during recent decades across large parts of Europe and North America. Different theories of the causes (e.g., recovery from acidification, climate change, land use) have different implications for defining the preindustrial levels for dissolved organic carbon (DOC), which are crucial for assessing acidification and other aspects of water quality. We demonstrate this by classifying the acidification status of 66 lakes with long-term observations, representative of about 12,700 acid-sensitive lakes in nemoral and boreal Sweden. Of these lakes, 47% are classified as significantly acidified (Delta pH >= 0.4), assuming preindustrial DOC levels were equal to those observed in 1990. But if instead, the higher DOC levels observed in 2009 define preindustrial conditions, half as many lakes are acidified (24%). This emphasizes the need to establish reference levels for DOC and casts new light on the classic controversy about natural versus anthropogenic acidification.

  • 22. Erlandsson, Martin
    et al.
    Folster, Jens
    Laudon, Hjalmar
    Weyhenmeyer, Gesa A.
    Bishop, Kevin
    Natural variability in lake pH on seasonal, interannual and decadal time scales: Implications for assessment of human impact2008In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 42, no 15, p. 5594-5599Article in journal (Refereed)
  • 23.
    Farkas, Julia
    et al.
    Norwegian Univ Sci & Technol, Dept Biol, N-7491 Trondheim, Norway..
    Peter, Hannes
    Univ Innsbruck, Inst Ecol, A-6020 Innsbruck, Austria..
    Ciesielski, Tomasz M.
    Norwegian Univ Sci & Technol, Dept Biol, N-7491 Trondheim, Norway..
    Thomas, Kevin V.
    Norwegian Inst Water Res, N-0349 Oslo, Norway..
    Sommaruga, Ruben
    Univ Innsbruck, Inst Ecol, A-6020 Innsbruck, Austria..
    Salvenmoser, Willi
    Univ Innsbruck, Inst Zool, A-6020 Innsbruck, Austria..
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Jenssen, Bjorn M.
    Norwegian Univ Sci & Technol, Dept Biol, N-7491 Trondheim, Norway..
    Impact of TiO2 nanoparticles on freshwater bacteria from three Swedish lakes2015In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 535, p. 85-93Article in journal (Refereed)
    Abstract [en]

    Due to the rapidly rising production and usage of nano-enabled products, aquatic environments are increasingly exposed to engineered nanoparticles (ENPs), causing concerns about their potential negative effects. In this study we assessed the effects of uncoated titanium dioxide nanoparticles (TiO(2)NPs) on the growth and activity of bacterial communities of three Swedish lakes featuring different chemical characteristics such as dissolved organic carbon (DOC) concentration, pH and elemental composition. TiO2NP exposure concentrations were 15, 100, and 1000 mu g L-1, and experiments were performed in situ under three light regimes: darkness, photosynthetically active radiation (PAR), and ambient sunlight including UV radiation (UVR). The nanoparticles were most stable in lake water with high DOC and low chemical element concentrations. At the highest exposure concentration (1000 mu g L-1 TiO2NP) the bacterial abundance was significantly reduced in all lake waters. In the medium and high DOC lake waters, exposure concentrations of 100 mu g L-1 TiO2NP caused significant reductions in bacterial abundance. The cell-specific bacterial activity was significantly enhanced at high TiO2NP exposure concentrations, indicating the loss of nanoparticle-sensitive bacteria and a subsequent increased activity by tolerant ones. No UV-induced phototoxic effect of TiO2NP was found in this study. We conclude that in freshwater lakes with high DOC and low chemical element concentrations, uncoated TiO(2)NPs show an enhanced stability and can significantly reduce bacterial abundance at relatively low exposure concentrations.

  • 24.
    Grubisic, Lorena M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Brutemark, Andreas
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wikner, Johan
    Bamstedt, Ulf
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Effects of stratification depth and dissolved organic matter on brackish bacterioplankton communities2012In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 453, p. 37-48Article in journal (Refereed)
    Abstract [en]

    Bacterioplankton growth is often directly or indirectly controlled by external energy subsidies via organic matter inputs or solar radiation. We carried out a mesocosm experiment to assess how bacterioplankton communities responded to elevated levels of dissolved organic matter (DOM) and experimentally controlled stratification depth. The month-long experiment consisted of 2500 l mesocosms subjected to 4 experimental manipulations in triplicate: the stratification depth was set to either 1.5 or 3.5 m, with or without experimental addition of ambient levels of chromophoric DOM. DOM addition had a significant effect on bacterial community composition as assessed by terminal restriction fragment length polymorphism of amplified 16S rRNA genes. In contrast, there were no effects of the DOM amendment on bacterial biomass or production. Mixing depth and the coupled effective light climate in the photic zone also had a significant effect on bacterial community composition. Furthermore, shallow mixing depth was associated with enhanced primary production, whereas DOM addition had a negative effect on phyto plankton biomass and productivity. Our results suggest that bacterial community composition is coupled to primary production under the studied coastal nutrient regime, and point to a key role of DOM quality in controlling bacterioplankton communities.

  • 25. Hampton, Stephanie E.
    et al.
    Galloway, Aaron W. E.
    Powers, Stephen M.
    Ozersky, Ted
    Woo, Kara H.
    Batt, Ryan D.
    Labou, Stephanie G.
    O’Reilly, Catherine M.
    Sharma, Sapna
    Lottig, Noah R.
    Stanley, Emily H.
    North, Rebecca L.
    Stockwell, Jason D.
    Adrian, Rita
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Arvola, Lauri
    Baulch, Helen M.
    Bertani, Isabella
    Bowman, Larry L.
    Carey, Cayelan C.
    Catalan, Jordi
    Colom-Montero, William
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Domine, Leah M.
    Felip, Marisol
    Granados, Ignacio
    Gries, Corinna
    Grossart, Hans-Peter
    Haberman, Juta
    Haldna, Marina
    Hayden, Brian
    Higgins, Scott N.
    Jolley, Jeff C.
    Kahilainen, Kimmo K.
    Kaup, Enn
    Kehoe, Michael J.
    MacIntyre, Sally
    Mackay, Anson W.
    Mariash, Heather L.
    McKay, Robert M.
    Nixdorf, Brigitte
    Nõges, Peeter
    Nõges, Tiina
    Palmer, Michelle
    Pierson, Don C.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Post, David M.
    Pruett, Matthew J.
    Rautio, Milla
    Read, Jordan S.
    Roberts, Sarah L.
    Rücker, Jacqueline
    Sadro, Steven
    Silow, Eugene A.
    Smith, Derek E.
    Sterner, Robert W.
    Swann, George E. A.
    Timofeyev, Maxim A.
    Toro, Manuel
    Twiss, Michael R.
    Vogt, Richard J.
    Watson, Susan B.
    Whiteford, Erika J.
    Xenopoulos, Marguerite A.
    Ecology under lake ice2017In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 20, no 1, p. 98-111Article, review/survey (Refereed)
    Abstract [en]

    Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experience periods of snow and ice cover. Relatively little is known of winter ecology in these systems, due to a historical research focus on summer ‘growing seasons’. We executed the first global quantitative synthesis on under-ice lake ecology, including 36 abiotic and biotic variables from 42 research groups and 101 lakes, examining seasonal differences and connections as well as how seasonal differences vary with geophysical factors. Plankton were more abundant under ice than expected; mean winter values were 43.2% of summer values for chlorophyll a, 15.8% of summer phytoplankton biovolume and 25.3% of summer zooplankton density. Dissolved nitrogen concentrations were typically higher during winter, and these differences were exaggerated in smaller lakes. Lake size also influenced winter-summer patterns for dissolved organic carbon (DOC), with higher winter DOC in smaller lakes. At coarse levels of taxonomic aggregation, phytoplankton and zooplankton community composition showed few systematic differences between seasons, although literature suggests that seasonal differences are frequently lake-specific, species-specific, or occur at the level of functional group. Within the subset of lakes that had longer time series, winter influenced the subsequent summer for some nutrient variables and zooplankton biomass.

  • 26. Hastie, Adam
    et al.
    Lauerwald, Ronny
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Verpoorter, Charles
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Univ Lille, Univ Littoral Cole Opale, CNRS, LOG,UMR 8187, Wimereux, France.
    Regnier, Pierre
    CO2 evasion from boreal lakes: Revised estimate, drivers of spatial variability, and future projections2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 2, p. 711-728Article in journal (Refereed)
    Abstract [en]

    Lakes (including reservoirs) are an important component of the global carbon (C) cycle, as acknowledged by the 5th assessment report of the IPCC. In the context of lakes, the boreal region is disproportionately important contributing to 27% of the worldwide lake area, despite representing just 14% of global land surface area. In this study, we used a statistical approach to derive a prediction equation for the partial pressure of CO2 (pCO2) in lakes as a function of lake area, terrestrial net primary productivity (NPP) and precipitation (r2 = 0.56), and to create the first high resolution, circumboreal map (0.5) of lake pCO2. The map of pCO2 was combined with lake area from the recently published GLOWABO database and three different estimates of the gas transfer velocity k to produce a resulting map of CO2 evasion (FCO2). For the boreal region we estimate an average, lake area weighted,pCO2 of 966 (678- 1325) μatm and a total FCO2 of 189 (74-347) Tg C yr−1, and evaluate the corresponding uncertainties based on Monte Carlo simulation. Our estimate of FCO2 is approximately twofold greater than previous estimates, as a result of methodological and data source differences. We use our results along with published estimates of the other C fluxes through inland waters to derive a C budget for the boreal region, and find that FCO2 from lakes is the most significant flux of the land-ocean aquatic continuum, and of a similar magnitude as emissions from forest fires. Using the model and applying it to spatially resolved projections of terrestrial NPP and precipitation while keeping everything else constant, we predict a 107% increase in boreal lake FCO2 under emission scenario RCP8.5 by 2100. Our projections are largely driven by increases in terrestrial NPP over the same period, showing the very close connection between the terrestrial and aquatic C cycle.

  • 27. Humborg, Christoph
    et al.
    Andersen, Hans Estrup
    Blenckner, Thorsten
    Gadegast, Mathias
    Giesler, Reiner
    Hartmann, Jens
    Hugelius, Gustaf
    Hürdler, Jens
    Kortelainen, Pirkko
    Blicher-Mathiesen, Gitte
    Venohr, Markus
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Environmental Impacts—Freshwater Biogeochemistry2015In: Second Assessment of Climate Change for the Baltic Sea Basin, Cham: Springer, 2015, p. 307-336Chapter in book (Other academic)
  • 28. Jankowski, Thomas
    et al.
    Weyhenmeyer, Gesa A.
    The role of spatial scale and area in determining richness-altitude gradients in Swedish lake phytoplankton communities2006In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 115, no 3, p. 433-442Article in journal (Refereed)
  • 29. Jennings, Eleanor
    et al.
    Jones, Stuart
    Arvola, Lauri
    Staehr, Peter A.
    Gaiser, Evelyn
    Jones, Ian D.
    Weathers, Kathleen C.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Chiu, Chih-Yu
    De Eyto, Elvira
    Effects of weather-related episodic events in lakes: an analysis based on high-frequency data2012In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 57, no 3, p. 589-601Article in journal (Refereed)
    Abstract [en]

    1. Weather-related episodic events are typically unpredictable, and their duration is often short. Abiotic and biological responses are often missed in routine monitoring. These responses are, however, now of particular relevance given projected changes in extreme weather conditions.

    2. We present data from high-frequency monitoring stations from lakes in Europe, North America and Asia that illustrate two classes of abiotic effects of weather events: (i) generally short-lived effects of storms on lake thermal structure and (ii) the more prolonged effects of high rainfall events on dissolved organic matter levels and water clarity. We further relate these abiotic effects to changes in dissolved oxygen or in chlorophyll a levels.

    3. Three differing causes for weather-related decreases in surface dissolved oxygen levels were observed: (i) entrainment of anoxic water from depth, (ii) reduction in primary productivity and (iii) increased mineralisation of organic carbon delivered from the catchment.

    4. The duration of in-lake effects tended to be longer for events driven by weather conditions with a longer return period, that is, conditions that were relatively more severe and less frequent at a site. While the susceptibility of lakes to change was related in part to the severity of the meteorological drivers, the impacts also depended on site-specific factors in some cases.

    5. The availability of high-frequency data at these sites provided insight into the capacity of the lakes to absorb current and future pressures. Several of the changes we observed, including increases in carbon availability, decreases in photosynthetically active radiation and increased disturbance, have the capacity to shift lakes towards an increased degree of heterotrophy. The magnitude and direction of any such change will, however, also depend on the magnitude and direction of climate change for a given location and on lake and catchment characteristics.

  • 30. Jennings, Eleanor
    et al.
    Järvinen, Marko
    Allott, Norman
    Arvola, Lauri
    Moore, Karen
    Naden, Pam
    Aonghusa, Caitriona Nic
    Nõges, Tiina
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The impact of the changing climate on the flux of dissolved organic carbon from catchments2010In: The impact of climate change on European lakes / [ed] Glen George, Springer , 2010, p. 199-220Chapter in book (Other academic)
  • 31.
    Kasurinen, Ville
    et al.
    Univ Helsinki, Dept Forest Sci, Helsinki, Finland; Norwegian Univ Sci & Technol, Dept Hydraul & Environm Engn, Trondheim, Norway.
    Alfredsen, Knut
    Norwegian Univ Sci & Technol, Dept Hydraul & Environm Engn, Trondheim, Norway.
    Ojala, Anne
    Univ Helsinki, Dept Forest Sci, Helsinki, Finland; Univ Helsinki, Dept Environm Sci, Helsinki, Finland.
    Pumpanen, Jukka
    Univ Helsinki, Dept Forest Sci, Helsinki, Finland.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Futter, Martyn N.
    Swedish Univ Agr Sci, Dept Aquat Sci & Assessment, Uppsala, Sweden.
    Laudon, Hjalmar
    Swedish Univ Agr Sci, Dept Forest Ecol & Management, Uppsala, Sweden.
    Berninger, Frank
    Univ Helsinki, Dept Forest Sci, Helsinki, Finland.
    Modeling nonlinear responses of DOC transport in boreal catchments in Sweden2016In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, no 7, p. 4970-4989Article in journal (Refereed)
    Abstract [en]

    Stream water dissolved organic carbon (DOC) concentrations display high spatial and temporal variation in boreal catchments. Understanding and predicting these patterns is a challenge with great implications for water quality projections and carbon balance estimates. Although several biogeochemical models have been used to estimate stream water DOC dynamics, model biases common during both rain and snow melt-driven events. The parsimonious DOC-model, K-DOC, with 10 calibrated parameters, uses a nonlinear discharge and catchment water storage relationship including soil temperature dependencies of DOC release and consumption. K-DOC was used to estimate the stream water DOC concentrations over 5 years for eighteen nested boreal catchments having total area of 68 km2 (varying from 0.04 to 67.9 km2). The model successfully simulated DOC concentrations during base flow conditions, as well as, hydrological events in catchments dominated by organic and mineral soils reaching NSEs from 0.46 to 0.76. Our semimechanistic model was parsimonious enough to have all parameters estimated using statistical methods. We did not find any clear differences between forest and mire-dominated catchments that could be explained by soil type or tree species composition. However, parameters controlling slow release and consumption of DOC from soil water behaved differently for small headwater catchments (less than 2 km2) than for those that integrate larger areas of different ecosystem types (10–68 km2). Our results emphasize that it is important to account for nonlinear dependencies of both, soil temperature, and catchment water storage, when simulating DOC dynamics of boreal catchments.

  • 32. Khalili, Maria I.
    et al.
    Temnerud, Johan
    Fröberg, Mats
    Karltun, Erik
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Nitrogen and carbon interactions between boreal soils and lakes2010In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 24, no 4, p. GB4011-Article in journal (Refereed)
    Abstract [en]

    In this study, we used a large data set on nitrogen (N) and carbon (C) from Swedish boreal soils and lake waters to investigate N and C interactions between soils and lake waters. To link thousands of soils sites with hundreds of lake sites distributed all over Sweden, we gridded the data and found a significant relation between gridded C:N ratios of the organic soil layer and the ones of lake waters. We also found evidence of N deposition having depressed the C:N ratios of lake waters more than the ones of organic soil layers. In lake waters N strongly increased toward southern Sweden, mainly in the form of nitrate-nitrogen (NO3--N) which we primarily attribute to an increased NO3--N input from the boreal soils into the lakes. In contrast to N we found a much weaker direct relationship for C between soils and lake waters over Sweden. Instead, lake C was strongly related to lake morphometry and catchment characteristics. Our results indicate that large-scale variations in soil C content are not directly linked to C concentrations in lake waters, whereas soil N seems to leach in small amounts from the soils directly into the lakes in form of NO3--N. Such differences in N and C interactions between soils and lake waters give important insights into the global biogeochemical cycling of N and C.

  • 33. Khalili, Maria I.
    et al.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Growing season variability of nitrate along a trophic gradient: contrasting patterns between lakes and streams2009In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 71, no 1, p. 25-33Article in journal (Refereed)
    Abstract [en]

    We studied the growing season (May to October) variability of NO3-N across Swedish lakes and streams. We found that NO3-N concentrations showed the highest growing season variability among all water chemical variables tested, both in lakes and in streams. However, the growing season variability of NO3-N increased with increasing trophic status in lakes while it decreased in streams. We attributed the contrasting pattern between lakes and streams to the relative importance of biological uptake and denitrification with increasing trophic status. Our results highlight the relation between growing season NO3-N variability and trophic status, which is positive in lakes but negative in streams. The findings of this study have important ramifications for ecosystem studies as well as water management. We suggest that the assessment of growing season variability of NO3-N in aquatic systems can be improved by considering the effect of trophic status.

  • 34.
    Koehler, Birgit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Landelius, Tomas
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Machida, Nanako
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Sunlight-induced carbon dioxide emissions from inland waters2014In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 28, no 7, p. 696-711Article in journal (Refereed)
    Abstract [en]

    The emissions of carbon dioxide (CO2) from inland waters are substantial on a global scale. Yet, the fundamental question remains open which proportion of these CO2 emissions is induced by sunlight via photochemical mineralization of dissolved organic carbon (DOC), rather than by microbial respiration during DOC decomposition. Also, it is unknown on larger spatial and temporal scales how photochemical mineralization compares to other C fluxes in the inland water C cycle. We combined field and laboratory data with atmospheric radiative transfer modeling to parameterize a photochemical rate model for each day of the year 2009, for 1086 lakes situated between latitudes from 55 to 69°N in Sweden. The sunlight-induced production of dissolved inorganic carbon (DIC) averaged 3.8 ± 0.04 g C m-2 yr-1, which is a flux comparable in size to the organic carbon burial in the lake sediments. Countrywide, 151 ± 1 kt C yr-1 was produced by photochemical mineralization, corresponding to about 12% of total annual mean CO2 emissions from Swedish lakes. With a median depth of 3.2 m, the lakes were generally deep enough that incoming, photochemically active photons were absorbed in the water column. This resulted in a linear positive relationship between DIC photoproduction and the incoming photon flux, which correspond to the absorbed photons. Therefore, the slope of the regression line represents the wavelength- and depth-integrated apparent quantum yield of DIC photoproduction. We used this relationship to obtain a first estimate of DIC photoproduction in lakes and reservoirs worldwide. Global DIC photoproduction amounted to 13 and 35 Mt C yr-1 under overcast and clear sky, respectively. Consequently, these directly sunlight-induced CO2 emissions contribute up to about one tenth to the global CO2 emissions from lakes and reservoirs, corroborating that microbial respiration contributes a substantially larger share than formerly thought, and generate annual C fluxes similar in magnitude to the C burial in natural lake sediments worldwide.

  • 35.
    Kothawala, Dolly
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Murphy, Kathleen R.
    Stedmon, Colin A.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Inner filter correction of dissolved organic matter fluorescence2013In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 11, p. 616-630Article in journal (Refereed)
    Abstract [en]

    The fluorescence of dissolved organic matter (DOM) is suppressed by a phenomenon of self-quenching known as the inner filter effect (IFE). Despite widespread use of fluorescence to characterize DOM in surface waters, the advantages and constraints of IFE correction are poorly defined. We assessed the effectiveness of a commonly used absorbance-based approach (ABA), and a recently proposed controlled dilution approach (CDA) to correct for IFE. Linearity between corrected fluorescence and total absorbance (ATotal; the sum of absorbance at excitation and emission wavelengths) across the full excitation-emission matrix (EEM) in dilution series of four samples indicated both ABA and CDA were effective to an absorbance of at least 1.5 in a 1 cm cell, regardless of wavelength positioning. In regions of the EEMs where signal to background noise (S/N) was low, CDA correction resulted in more variability than ABA correction. From the ABA algorithm, the onset of significant IFE (>5%) occurs when absorbance exceeds 0.042. In these cases, IFE correction is required, which was the case for the vast majority (97%) of lakes in a nationwide survey (n= 554). For highly absorbing samples, undesirably large dilution factors would be necessary to reduce absorbance below 0.042. For rare EEMs with ATotal > 1.5 (3.0% of the lakes in the Swedish survey), a 2-fold dilution is recommended followed by ABA or CDA correction. This study shows that for the vast majority of natural DOM samples the most commonly applied ABA algorithm provides adequate correction without prior dilution.

  • 36.
    Kothawala, Dolly N.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Stedmon, Colin A.
    Müller, Roger A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Köhler, Stephan J.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Controls of dissolved organic matter quality: evidence from a large-scale boreal lake survey2014In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 20, no 4, p. 1101-1114Article in journal (Refereed)
    Abstract [en]

    Inland waters transport large amounts of dissolved organic matter (DOM) from terrestrial environments to the oceans, but DOM also reacts en route, with substantial water column losses by mineralization and sedimentation. For DOM transformations along the aquatic continuum, lakes play an important role as they retain waters in the landscape allowing for more time to alter DOM. We know DOM losses are significant at the global scale, yet little is known about how the reactivity of DOM varies across landscapes and climates. DOM reactivity is inherently linked to its chemical composition. We used fluorescence spectroscopy to explore DOM quality from 560 lakes distributed across Sweden and encompassed a wide climatic gradient typical of the boreal ecozone. Six fluorescence components were identified using parallel factor analysis (PARAFAC). The intensity and relative abundance of these components were analyzed in relation to lake chemistry, catchment, and climate characteristics. Land cover, particularly the percentage of water in the catchment, was a primary factor explaining variability in PARAFAC components. Likewise, lake water retention time influenced DOM quality. These results suggest that processes occurring in upstream water bodies, in addition to the lake itself, have a dominant influence on DOM quality. PARAFAC components with longer emission wavelengths, or red-shifted components, were most reactive. In contrast, protein-like components were most persistent within lakes. Generalized characteristics of PARAFAC components based on emission wavelength could ease future interpretation of fluorescence spectra. An important secondary influence on DOM quality was mean annual temperature, which ranged between −6.2 and +7.5 °C. These results suggest that DOM reactivity depends more heavily on the duration of time taken to pass through the landscape, rather than temperature. Projected increases in runoff in the boreal region may force lake DOM toward a higher overall amount and proportion of humic-like substances.

  • 37. Livingstone, D
    et al.
    et al, (14 more authors)
    Weyhenmeyer, Gesa
    SLU.
    Long-term supra-regional coherence2005Report (Other academic)
  • 38. Livingstone, D
    et al.
    et al, (6 more authors)
    Weyhenmeyer, Gesa
    SLU.
    Long-term regional coherence2004Report (Other academic)
  • 39. Livingstone, D
    et al.
    George, DG
    Järvinen, M
    Noges, P
    Noges, T
    Weyhenmeyer, Gesa
    SLU.
    Short-term coherence2004Report (Other academic)
  • 40. Livingstone, David M.
    et al.
    Adrian, Rita
    Arvola, Lauri
    Blenckner, Thorsten
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Dokulil, Martin T.
    Hari, Renata E.
    George, Glen
    Jankowski, Thomas
    Järvinen, Marko
    Jennings, Eleanor
    Nõges, Peeter
    Nõges, Tiina
    Straile, Dietmar
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Regional and supra-regional coherence in limnological variables2010In: The impact of climate change on European lakes / [ed] Glen George, Dordrecht: Springer , 2010, p. 311-338Chapter in book (Other academic)
  • 41. Livingstone, David M.
    et al.
    Adrian, Rita
    Blenckner, Thorsten
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    George, Glen
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lake ice phenology2010In: The impact of climate change on European lakes / [ed] Glen George, Dordrecht: Springer , 2010, p. 51-62Chapter in book (Other academic)
  • 42. Lundin, L
    et al.
    Khalili, M
    Weyhenmeyer, Gesa
    SLU.
    Fölster, J
    Löfgren, S
    Kyllmar, K
    Aastrup, M
    Thunholm, B
    Whitlock, H
    Konsekvenser för sötvattnen av ändrad utlakning från skogs- och jordbruksmark inkluderande ändringar i grundvatten orsakade av klimatpåverkad hydrologi och temperatur2009Report (Other academic)
  • 43. Marcé, Rafael
    et al.
    George, Glen
    Buscarinu, Paola
    Deidda, Melania
    Dunalska, Julita
    de Eyto, Elvira
    Flaim, Giovanna
    Grossart, Hans-Peter
    Istvanovics, Vera
    Lenhardt, Mirjana
    Moreno-Ostos, Enrique
    Obrador, Biel
    Ostrovsky, Ilia
    Pierson, Don
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Potužák, Jan
    Poikane, Sandra
    Rinke, Karsten
    Rodríguez-Mozaz, Sara
    Staehr, Peter A.
    Šumberová, Kateřina
    Waajen, Guido
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Weathers, Kathleen C.
    Zion, Mark
    Ibelings, Bas W.
    Jennings, Eleanor
    Automatic High Frequency Monitoring for Improved Lake and Reservoir Management2016In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 50, no 20, p. 10780-10794Article, review/survey (Refereed)
    Abstract [en]

    Recent technological developments have increased the number of variables being monitored in lakes and reservoirs using automatic high frequency monitoring (AHFM). However, design of AHFM systems and posterior data handling and interpretation are currently being developed on a site-by-site and issue-by-issue basis with minimal standardization of protocols or knowledge sharing. As a result, many deployments become short-lived or underutilized, and many new scientific developments that are potentially useful for water management and environmental legislation remain underexplored. This Critical Review bridges scientific uses of AHFM with their applications by providing an overview of the current AHFM capabilities, together with examples of successful applications. We review the use of AHFM for maximizing the provision of ecosystem services supplied by lakes and reservoirs (consumptive and non consumptive uses, food production, and recreation), and for reporting lake status in the EU Water Framework Directive. We also highlight critical issues to enhance the application of AHFM, and suggest the establishment of appropriate networks to facilitate knowledge sharing and technological transfer between potential users. Finally, we give advice on how modern sensor technology can successfully be applied on a larger scale to the management of lakes and reservoirs and maximize the ecosystem services they provide.

  • 44.
    Moore, Karen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Pierson, Donald
    Weyhenmeyer, Gesa
    Pettersson, Kurt
    High-frequency monitoring of colored dissolved organic matter (CDOM) fluorescence in the Swedish river HedströmmenManuscript (Other academic)
  • 45. Moss, Brian D.
    et al.
    Hering, Daniel
    Green, Andy J.
    Adoud, Ahmed
    Becares, Eloy
    Beklioglu, Meryem
    Bennion, Helen
    Boix, Dani
    Brucet, Sandra
    Carvalho, Laurence
    Clement, Bernard
    Davidson, Tom
    Declerck, Steven
    Dobson, Michael
    van Donk, Ellen
    Dudley, Bernard
    Feuchtmayr, Heidrun
    Friberg, Nikolai
    Grenouillet, Gael
    Hillebrand, Helmut
    Hobaek, Anders
    Irvine, Kenneth
    Jeppesen, Erik
    Johnson, Richard
    Jones, Iwan
    Kernan, Martin
    Lauridsen, Torben L.
    Manca, Marina
    Meerhof, Mariana
    Olafsson, Jon
    Ormerod, Steve
    Papastergiadou, Eva
    Penning, W.Ellis
    Ptacnik, Robert
    Quintana, Xavier
    Sandin, Leonard
    Seferlis, Miltiadis
    Simpson, Gavin
    Trigal, Cristina
    Verdonschot, Piet
    Verschoor, Antonie M.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Climate change and the future of freshwater biodiversity in Europe: a primer for policy-makers2009In: Freshwater Reviews, ISSN 1755-084X, Vol. 2, no 2, p. 103-130Article in journal (Refereed)
    Abstract [en]

    Earth's climate is changing, and by the end of the 21st century in Europe, average temperatures are likely to have risen by at least 2 °C, and more likely 4 °C with associated effects on patterns of precipitation and the frequency of extreme weather events. Attention among policy-makers is divided about how to minimise the change, how to mitigate its effects, how to maintain the natural resources on which societies depend and how to adapt human societies to the changes. Natural systems are still seen, through a long tradition of conservation management that is largely species-based, as amenable to adaptive management, and biodiversity, mostly perceived as the richness of plant and vertebrate communities, often forms a focus for planning. We argue that prediction of particular species changes will be possible only in a minority of cases but that prediction of trends in general structure and operation of four generic freshwater ecosystems (erosive rivers, depositional floodplain rivers, shallow lakes and deep lakes) in three broad zones of Europe (Mediterranean, Central and Arctic-Boreal) is practicable. Maintenance and rehabilitation of ecological structures and operations will inevitably and incidentally embrace restoration of appropriate levels of species biodiversity. Using expert judgement, based on an extensive literature, we have outlined, primarily for lay policy makers, the pristine features of these systems, their states under current human impacts, how these states are likely to alter with a warming of 2 °C to 4 °C and what might be done to mitigate this. We have avoided technical terms in the interests of communication, and although we have included full referencing as in academic papers, we have eliminated degrees of detail that could confuse broad policy-making

     

  • 46.
    Müller, Roger A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Futter, Martyn N.
    Swedish University of Agricultural Sciences (SLU).
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Nisell, J.
    Swedish University of Agricultural Sciences (SLU).
    Bishop, Kevin
    Swedish University of Agricultural Sciences (SLU).
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Water renewal along the aquatic continuum offsets cumulative retention by lakes: implications for the character of organic carbon in boreal lakes2013In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 75, no 4, p. 535-545Article in journal (Refereed)
    Abstract [en]

    The character of organic carbon (OC) in lake waters is strongly dependent on the time water has spent in the landscape as well as in the lake itself due to continuous biogeochemical OC transformation processes. A common view is that upstream lakes might prolong the water retention in the landscape, resulting in an altered OC character downstream. We calculated the number of lakes upstream for 24,742 Swedish lakes in seven river basins spanning from 56º to 68º N. For each of these lakes, we used a lake volume to discharge comparison on a landscape scale to account for upstream water retention by lakes (Tn tot). We found a surprisingly weak relationship between the number of lakes upstream and Tn tot. Accordingly, we found that the coloured fraction of organic carbon was not related to lake landscape position but significantly related to Tn tot when we analysed lake water chemical data from 1,559 lakes in the studied river basins. Thus, we conclude that water renewal along the aquatic continuum by lateral water inputs offsets cumulative retention by lakes. Based on our findings, we suggest integrating Tn tot in studies that address lake landscape position in the boreal zone to better understand variations in the character of organic carbon across lake districts.

  • 47.
    Müller, Roger A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Kothawala, Dolly N.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Podgrajsek, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sahlée, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Köhler, Birgit
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Hourly, daily, and seasonal variability in the absorption spectra of chromophoric dissolved organic matter in a eutrophic, humic lake2014In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 119, no 10, p. 1985-1998Article in journal (Refereed)
    Abstract [en]

    The short-term (hourly and daily) variation in chromophoric dissolved organic matter (CDOM) in lakes is largely unknown. We assessed the spectral characteristics of light absorption by CDOM in a eutrophic, humic shallow mixed lake of temperate Sweden at a high-frequency (30 min) interval and during a full growing season (May to October). Physical time series, such as solar radiation, temperature, wind, and partial pressures of carbon dioxide in water and air, were measured synchronously. We identified a strong radiation-induced summer CDOM loss (25 to 50%) that developed over 4 months, which was accompanied by strong changes in CDOM absorption spectral shape. The magnitude of the CDOM loss exceeded subhourly to daily variability by an order of magnitude. Applying Fourier analysis, we demonstrate that variation in CDOM remained largely unaffected by rapid shifts in weather, and no apparent response to in-lake dissolved organic carbon production was found. In autumn, CDOM occasionally showed variation at hourly to daily time scales, reaching a maximum daily coefficient of variation of 15%. We suggest that lake-internal effects on CDOM are quenched in humic lake waters by dominating effects associated with imported CDOM and solar exposure. Since humic lake waters belong to one of the most abundant lake types on Earth, our results have important implications for the understanding of global CDOM cycling.

  • 48. Noges, Peeter
    et al.
    Noges, Tiina
    Adrian, Rita
    Weyhenmeyer, Gesa A.
    Silicon load and the development of diatoms in three river-lake systems in countries surrounding the Baltic Sea2008In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 599, p. 67-76Article in journal (Refereed)
  • 49.
    Nydahl, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wallin, Marcus B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    No long-term trends in pCO2 despite increasing organic carbon concentrations in boreal lakes, streams and rivers2017In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 31, no 6, p. 985-995Article in journal (Refereed)
    Abstract [en]

    Concentrations of dissolved organic carbon (DOC) from terrestrial sources have been increasing in freshwaters across large parts of the boreal region. According to results from large-scale field and detailed laboratory studies, such a DOC increase could potentially stimulate carbon dioxide (CO2) production, subsequently increasing the partial pressure of CO2 (pCO2) in freshwaters. However, the response of pCO2 to the presently observed long-term increase in DOC in freshwaters is still unknown. Here we tested whether the commonly found spatial DOC-pCO2 relationship is also valid on a temporal scale. Analyzing time series of water chemical data from 71 lakes, 30 streams, and 4 river mouths distributed across all of Sweden over a 17 year period, we observed significant DOC concentration increases in 39 lakes, 15 streams, and 4 river mouths. Significant pCO2 increases were, however, only observed in six of these 58 waters, indicating that long-term DOC increases in Swedish waters are disconnected from temporal pCO2 trends. We suggest that the uncoupling of trends in DOC concentration and pCO2 are a result of increased surface water runoff. When surface water runoff increases, there is likely less CO2 relative to DOC imported from soils into waters due to a changed balance between surface and groundwater flow. Additionally, increased surface water runoff causes faster water flushing through the landscape giving less time for in situ CO2 production in freshwaters. We conclude that pCO2 is presently not following DOC concentration trends, which has important implications for modeling future CO2 emissions from boreal waters.

  • 50. Nõges, Peeter
    et al.
    Adrian, Rita
    Anneville, Orlane
    Arvola, Lauri
    Blenckner, Thorsten
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    George, Glen
    Jankowski, Thomas
    Järvinen, Marko
    Maberly, Stephen
    Padisák, Judit
    Straile, Dietmar
    Teubner, Katrin
    Weyhenmeyer, Gesa A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The impact of the changing climate on seasonal dynamics of phytoplankton2010In: The impact of climate change on European lakes / [ed] Glen George, Dordrecht: Springer , 2010, p. 253-274Chapter in book (Other academic)
123 1 - 50 of 142
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