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  • Jansen, Joachim, et al. (författare)
  • Global increase in methane production under future warming of lake bottom waters
  • 2022
  • Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486.
  • Tidskriftsartikel (refereegranskat)abstract
    • Lakes are significant emitters of methane to the atmosphere, and thus are important components of the global methane budget. Methane is typically produced in lake sediments, with the rate of methane production being strongly temperature dependent. Local and regional studies highlight the risk of increasing methane production under future climate change, but a global estimate is not currently available. Here, we project changes in global lake bottom temperatures and sediment methane production rates from 1901 to 2099. By the end of the 21st century, lake bottom temperatures are projected to increase globally, by an average of 0.86-2.60 degrees C under Representative Concentration Pathways (RCPs) 2.6-8.5, with greater warming projected at lower latitudes. This future warming of bottom waters will likely result in an increase in methane production rates of 13%-40% by the end of the century, with many low-latitude lakes experiencing an increase of up to 17 times the historical (1970-1999) global average under RCP 8.5. The projected increase in methane production will likely lead to higher emissions from lakes, although the exact magnitude of the emission increase requires more detailed regional studies.
  • Kasurinen, Ville, et al. (författare)
  • Modeling nonlinear responses of DOC transport in boreal catchments in Sweden
  • 2016
  • Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 52:7, s. 4970-4989
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
  • Khalili, Maria I., et al. (författare)
  • Growing season variability of nitrate along a trophic gradient : contrasting patterns between lakes and streams
  • 2009
  • Ingår i: Aquatic Sciences. - 1015-1621 .- 1420-9055. ; 71:1, s. 25-33
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
  • Khalili, Maria I., et al. (författare)
  • Nitrogen and carbon interactions between boreal soils and lakes
  • 2010
  • Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 24:4, s. GB4011-
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
  • Koehler, Birgit, 1980-, et al. (författare)
  • Sunlight-induced carbon dioxide emissions from inland waters
  • 2014
  • Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 28:7, s. 696-711
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
  • Livingstone, David M., et al. (författare)
  • Lake ice phenology
  • 2010
  • Ingår i: The impact of climate change on European lakes. - Dordrecht : Springer. - 9789048129447 - 9789048129454 ; , s. 51-62
  • Bokkapitel (övrigt vetenskapligt)
  • Moss, Brian D., et al. (författare)
  • Climate change and the future of freshwater biodiversity in Europe : a primer for policy-makers
  • 2009
  • Ingår i: Freshwater Reviews. - 1755-084X. ; 2:2, s. 103-130
  • Tidskriftsartikel (refereegranskat)abstract
    • 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  
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