| 1. |
- Abbott, Benjamin W., et al.
(författare)
-
Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment
- 2016
-
Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 11:3
-
Tidskriftsartikel (refereegranskat)abstract
- As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.
|
|
| 2. |
- Algesten, Grete, et al.
(författare)
-
Organic carbon budget for the Gulf of Bothnia
- 2006
-
Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 63:3-4, s. 155-161
-
Tidskriftsartikel (refereegranskat)abstract
- We calculated input of organic carbon to the unproductive, brackish water basin of the Gulf of Bothnia from rivers, point sources and the atmosphere. We also calculated the net exchange of organic carbon between the Gulf of Bothnia and the adjacent marine system, the Baltic Proper. We compared the input with sinks for organic carbon; permanent incorporation in sediments and mineralization and subsequent evasion of CO2 to the atmosphere. The major fluxes were riverine input (1500 Gg C year(-1)), exchange with the Baltic Proper (depending on which of several possible DOC concentration differences between the basins that was used in the calculation, the flux varied between an outflow of 466 and an input of 950 Gg C year(-1)), sediment burial (1100 Gg C year) and evasion to the atmosphere (3610 Gg C year(-1)). The largest single net flux was the emission of CO2 to the atmosphere, mainly caused by bacterial mineralization of organic carbon. Input and output did not match in our budget which we ascribe uncertainties in the calculation of the exchange of organic carbon between the Gulf of Bothnia and the Baltic Proper, and the fact that CO2 emission, which in our calculation represented 1 year (2002) may have been overestimated in comparison with long-term means. We conclude that net heterotrophy of the Gulf of Bothnia was due to input of organic carbon from both the catchment and from the Baltic Proper and that the future degree of net heterotrophy will be sensible to both catchment export of organic carbon and to the ongoing eutrophication of the Baltic Proper.
|
|
| 3. |
- Algesten, Grete, 1974-
(författare)
-
Regulation of carbon dioxide emission from Swedish boreal lakes and the Gulf of Bothnia
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The global carbon cycle is subject to intense research, where sources and sinks for greenhouse gases, carbon dioxide in particular, are estimated for various systems and biomes. Lakes have previously been neglected in carbon balance estimations, but have recently been recognized to be significant net sources of CO2. This thesis estimates emission of carbon dioxide (CO2) from boreal lakes and factors regulating the CO2 saturation from field measurements of CO2 concentration along with a number of chemical, biological and physical parameters. Concentration of dissolved organic carbon (DOC) was found to be the most important factor for CO2 saturation in lake water, whereas climatic parameters such as precipitation, temperature and global radiation were less influential. All lakes were supersaturated with and, thus, sources of CO2. Sediment incubation experiments indicated that in-lake mineralization processes during summer stratification mainly occurred in the pelagial. Approximately 10% of the CO2 emitted from the lake surface was produced in epilimnetic sediments. The mineralization of DOC and emission of CO2 from freshwaters was calculated on a catchment basis for almost 80,000 lakes and 21 major catchments in Sweden, together with rates of sedimentation in lakes and export of organic carbon to the sea. The total export of terrestrial organic carbon to freshwaters could thereby be estimated and consequently also the importance of lakes for the withdrawal of organic carbon export from terrestrial sources to the sea. Lakes removed 30-80% of imported terrestrial organic carbon, and mineralization and CO2 emission were much more important than sedimentation of carbon. The carbon loss was closely related to water retention time, where catchments with short residence times (<1 year) had low carbon retentions, whereas in catchments with long residence times (>3 years) a majority of the imported TOC was removed in the lake systems. The Gulf of Bothnia was also studied in this thesis and found to be a net heterotrophic system, emitting large amounts of CO2 to the atmosphere on an annual basis. The rate of CO2 emission was depending on the balance between primary production and bacterial respiration, and the system was oscillating between being a source and a sink of CO2.
|
|
| 4. |
- Bergström, Ann-Kristin, 1968-, et al.
(författare)
-
Declining calcium concentration drives shifts toward smaller and less nutritious zooplankton in northern lakes
- 2024
-
Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 30:3
-
Tidskriftsartikel (refereegranskat)abstract
- Zooplankton community composition of northern lakes is changing due to the interactive effects of climate change and recovery from acidification, yet limited data are available to assess these changes combined. Here, we built a database using archives of temperature, water chemistry and zooplankton data from 60 Scandinavian lakes that represent broad spatial and temporal gradients in key parameters: temperature, calcium (Ca), total phosphorus (TP), total organic carbon (TOC), and pH. Using machine learning techniques, we found that Ca was the most important determinant of the relative abundance of all zooplankton groups studied, while pH was second, and TOC third in importance. Further, we found that Ca is declining in almost all lakes, and we detected a critical Ca threshold in lake water of 1.3 mg L−1, below which the relative abundance of zooplankton shifts toward dominance of Holopedium gibberum and small cladocerans at the expense of Daphnia and copepods. Our findings suggest that low Ca concentrations may shape zooplankton communities, and that current trajectories of Ca decline could promote widespread changes in pelagic food webs as zooplankton are important trophic links from phytoplankton to fish and different zooplankton species play different roles in this context.
|
|
| 5. |
- Creed, Irena F., et al.
(författare)
-
Global change-driven effects on dissolved organic matter composition : Implications for food webs of northern lakes
- 2018
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 24:8, s. 3692-3714
-
Forskningsöversikt (refereegranskat)abstract
- Northern ecosystems are experiencing some of the most dramatic impacts of global change on Earth. Rising temperatures, hydrological intensification, changes in atmospheric acid deposition and associated acidification recovery, and changes in vegetative cover are resulting in fundamental changes in terrestrial-aquatic biogeochemical linkages. The effects of global change are readily observed in alterations in the supply of dissolved organic matter (DOM)-the messenger between terrestrial and lake ecosystems-with potentially profound effects on the structure and function of lakes. Northern terrestrial ecosystems contain substantial stores of organic matter and filter or funnel DOM, affecting the timing and magnitude of DOM delivery to surface waters. This terrestrial DOM is processed in streams, rivers, and lakes, ultimately shifting its composition, stoichiometry, and bioavailability. Here, we explore the potential consequences of these global change-driven effects for lake food webs at northern latitudes. Notably, we provide evidence that increased allochthonous DOM supply to lakes is overwhelming increased autochthonous DOM supply that potentially results from earlier ice-out and a longer growing season. Furthermore, we assess the potential implications of this shift for the nutritional quality of autotrophs in terms of their stoichiometry, fatty acid composition, toxin production, and methylmercury concentration, and therefore, contaminant transfer through the food web. We conclude that global change in northern regions leads not only to reduced primary productivity but also to nutritionally poorer lake food webs, with discernible consequences for the trophic web to fish and humans.
|
|
| 6. |
- de Wit, Heleen A., et al.
(författare)
-
Current Browning of Surface Waters Will Be Further Promoted by Wetter Climate
- 2016
-
Ingår i: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS. - : American Chemical Society (ACS). - 2328-8930. ; 3:12, s. 430-435
-
Tidskriftsartikel (refereegranskat)abstract
- Browning of surface waters because of increasing terrestrial dissolved organic carbon (OC) concentrations is a concern for drinking water providers and can impact land carbon storage. We show that positive trends in OC in 474 streams, lakes, and rivers in boreal and subarctic ecosystems in Norway, Sweden, and Finland between 1990 and 2013 are surprisingly constant across climatic gradients and catchment sizes (median, +1.4% year(-1); interquartile range, +0.8-2.0% year(-1)), implying that water bodies across the entire landscape are browning. The largest trends (median, +1.7% year(-1)) were found in regions impacted by strong reductions in sulfur deposition, while subarctic regions showed the least browning (median, +0.8% year(-1)). In dry regions, precipitation was a strong and positive driver of OC concentrations, declining in strength moving toward high rainfall sites. We estimate that a 10% increase in precipitation will increase mobilization of OC from soils to freshwaters by at least 30%, demonstrating the importance of climate wetting for the carbon cycle. We conclude that upon future increases in precipitation, current browning trends will continue across the entire aquatic continuum, requiring expensive adaptations in drinking water plants, increasing land to sea export of carbon, and impacting aquatic productivity and greenhouse gas emissions.
|
|
| 7. |
- Denfeld, Blaize, et al.
(författare)
-
Regional Variability and Drivers of Below Ice CO2 in Boreal and Subarctic Lakes
- 2016
-
Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 19:3, s. 461-476
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 8. |
- Humborg, Christoph, et al.
(författare)
-
Environmental Impacts - Freshwater Biogeochemistry
- 2015
-
Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - Cham : Springer. - 9783319160054 - 9783319160061 ; , s. 307-336
-
Bokkapitel (refereegranskat)abstract
- Climate change effects on freshwater biogeochemistry and riverine loads of biogenic elements to the Baltic Sea are not straight forward and are difficult to distinguish from other human drivers such as atmospheric deposition, forest and wetland management, eutrophication and hydrological alterations. Eutrophication is by far the most well-known factor affecting the biogeochemistry of the receiving waters in the various sub-basins of the Baltic Sea. However, the present literature review reveals that climate change is a compounding factor for all major drivers of freshwater biogeochemistry discussed here, although evidence is still often based on short-term and/or small-scale studies.
|
|
| 9. |
- Humborg, Christoph, et al.
(författare)
-
Environmental Impacts—Freshwater Biogeochemistry
- 2015
-
Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - Cham : Springer. - 9783319160054 - 9783319160061 ; , s. 307-336
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 10. |
- Isles, Peter D. F., et al.
(författare)
-
Widespread synchrony in phosphorus concentrations in northern lakes linked to winter temperature and summer precipitation
- 2023
-
Ingår i: Limnology and Oceanography Letters. - : John Wiley & Sons. - 2378-2242. ; 8:4, s. 639-648
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, unexplained declines in lake total phosphorus (TP) concentrations have been observed at northern latitudes (> 42°N latitude) where most of the world's lakes are found. We compiled data from 389 lakes in Fennoscandia and eastern North America to investigate the effects of climate on lake TP concentrations. Synchrony in year-to-year variability is an indicator of climatic influences on lake TP, because other major influences on nutrients (e.g., land use change) are not likely to affect all lakes in the same year. We identified significant synchrony in lake TP both within and among different geographic regions. Using a bootstrapped random forest analysis, we identified winter temperature as the most important factor controlling annual TP, followed by summer precipitation. In Fennoscandia, TP was negatively correlated with the winter East Atlantic Pattern, which is associated with regionally warmer winters. Our results suggest that, in the absence of other overriding factors, lake TP and productivity may decline with continued winter warming in northern lakes.
|
|
| 11. |
- Jantze, Elin, 1983-
(författare)
-
Waterborne Carbon in Northern Streams : Controls on dissolved carbon transport across sub-arctic Scandinavia
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Waterborne carbon (C) forms an active and significant part of the global C cycle, which is important in theArctic where greater temperature increases and variability are anticipated relative to the rest of the globe withpotential implications for the C cycle. Understanding and quantification of the current processes governing themovement of C by connecting terrestrial and marine systems is necessary to better estimate future changes ofwaterborne C. This thesis investigates how the sub-arctic landscape influences the waterborne carbon exportby combining data-driven and modeling methods across spatial and temporal scales. First, a study of the stateof total organic carbon monitoring in northern Scandinavia was carried out using national-scale monitoringdata and detailed data from scientific literature. This study, which highlights the consistency in land cover andhydroclimatic controls on waterborne C across northern Scandinavia, was combined with three more detailedstudies leveraging field measurements and modeling. These focused on the Abisko region to provide insightto processes and mechanisms across scales. The thesis highlights that the governing transport mechanismsof dissolved organic and inorganic carbon (DOC and DIC respectively) are fundamentally different due todifferences in release rates associated with the nature of their terrestrial sources (geogenic and organic matterrespectively). As such, the DIC mass flux exhibits a high flow-dependence whereas DOC is relatively flowindependent.Furthermore, these investigations identified significant relationships between waterborne C andbiogeophysical as well as hydroclimatic variables across large to small spatial scales. This thesis demonstratesthat both surface and sub-surface hydrological processes (such as flow pathway distributions) in combinationwith distributions of C sources and associated release rates are prerequisite for understanding waterborne Cdynamics in northern streams.
|
|
| 12. |
- Palstev, Aleksey, et al.
(författare)
-
Phytoplankton biomass in northern lakes reveals a complex response to global change
- 2024
-
Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 940
-
Tidskriftsartikel (refereegranskat)abstract
- Global change may introduce fundamental alterations in phytoplankton biomass and community structure that can alter the productivity of northern lakes. In this study, we utilized Swedish and Finnish monitoring data from lakes that are spatially (135 lakes) and temporally (1995-2019, 110 lakes) extensive to assess how phytoplankton biomass (PB) of dominant phytoplankton groups related to changes in water temperature, pH and key nutrients [total phosphorus (TP), total nitrogen (TN), total organic carbon (TOC), iron (Fe)] along spatial (Fennoscandia) and temporal (25 years) gradients. Using a machine learning approach, we found that TP was the most important determinant of total PB and biomass of a specific species of Raphidophyceae - Gonyostomum semen - and Cyanobacteria (both typically with adverse impacts on food-webs and water quality) in spatial analyses, while Fe and pH were second in importance for G. semen and TN and pH were second and third in importance for Cyanobacteria. However, in temporal analyses, decreasing Fe and increasing pH and TOC were associated with a decrease in G. semen and an increase in Cyanobacteria. In addition, in many lakes increasing TOC seemed to have generated browning to an extent that significantly reduced PB. The identified discrepancy between the spatial and temporal results suggests that substitutions of data for space-for-time may not be adequate to characterize long-term effects of global change on phytoplankton. Further, we found that total PB exhibited contrasting temporal trends (increasing in northern- and decreasing in southern Fennoscandia), with the decline in total PB being more pronounced than the increase. Among phytoplankton, G. semen biomass showed the strongest decline, while cyanobacterial biomass showed the strongest increase over 25 years. Our findings suggest that progressing browning and changes in Fe and pH promote significant temporal changes in PB and shifts in phytoplankton community structures in northern lakes.
|
|
| 13. |
- Raymond, Peter A., et al.
(författare)
-
Global carbon dioxide emissions from inland waters
- 2013
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 503:7476, s. 355-359
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide (CO2) transfer from inland waters to the atmosphere, known as CO2 evasion, is a component of the global carbon cycle. Global estimates of CO2 evasion have been hampered, however, by the lack of a framework for estimating the inland water surface area and gas transfer velocity and by the absence of a global CO2 database. Here we report regional variations in global inland water surface area, dissolved CO2 and gas transfer velocity. We obtain global CO2 evasion rates of 1.8(-0.25)(+0.25) petagrams of carbon (Pg C) per year from streams and rivers and 0.32(-0.26)(+0.52) Pg C yr(-1) from lakes and reservoirs, where the upper and lower limits are respectively the 5th and 95th confidence interval percentiles. The resulting global evasion rate of 2.1 Pg C yr(-1) is higher than previous estimates owing to a larger stream and river evasion rate. Our analysis predicts global hotspots in stream and river evasion, with about 70 per cent of the flux occurring over just 20 per cent of the land surface. The source of inland water CO2 is still not known with certainty and new studies are needed to research the mechanisms controlling CO2 evasion globally.
|
|
| 14. |
- Sobek, Sebastian, et al.
(författare)
-
Patterns and regulation of dissolved organic carbon : An analysis of 7,500 widely distributed lakes
- 2007
-
Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 52:3, s. 1208-1219
-
Tidskriftsartikel (refereegranskat)abstract
- Dissolved organic carbon (DOC) is a key parameter in lakes that can affect numerous features, including microbial metabolism, light climate, acidity, and primary production. In an attempt to understand the factors that regulate DOC in lakes, we assembled a large database (7,514 lakes from 6 continents) of DOC concentrations and other parameters that characterize the conditions in the lakes, the catchment, the soil, and the climate. DOC concentrations were in the range 0.1-332 mg L-1, and the median was 5.71 mg L-1. A partial least squares regression explained 48% of the variability in lake DOC and showed that altitude, mean annual runoff, and precipitation were negatively correlated with lake DOC, while conductivity, soil carbon density, and soil C:N ratio were positively related with lake DOC. A multiple linear regression using altitude, mean annual runoff, and soil carbon density as predictors explained 40% of the variability in lake DOC. While lake area and drainage ratio (catchment:lake area) were not correlated to lake DOC in the global data set, these two factors explained significant variation of the residuals of the multiple linear regression model in several regional subsets of data. These results suggest a hierarchical regulation of DOC in lakes, where climatic and topographic characteristics set the possible range of DOC concentrations of a certain region, and catchment and lake properties then regulate the DOC concentration in each individual lake.
|
|
| 15. |
- Tranvik, Lars J., et al.
(författare)
-
Lakes and reservoirs as regulators of carbon cycling and climate
- 2009
-
Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 54:6:2, s. 2298-2314
-
Forskningsöversikt (refereegranskat)abstract
- We explore the role of lakes in carbon cycling and global climate, examine the mechanisms influencing carbon pools and transformations in lakes, and discuss how the metabolism of carbon in the inland waters is likely to change in response to climate. Furthermore, we project changes as global climate change in the abundance and spatial distribution of lakes in the biosphere, and we revise the estimate for the global extent of carbon transformation in inland waters. This synthesis demonstrates that the global annual emissions of carbon dioxide from inland waters to the atmosphere are similar in magnitude to the carbon dioxide uptake by the oceans and that the global burial of organic carbon in inland water sediments exceeds organic carbon sequestration on the ocean floor. The role of inland waters in global carbon cycling and climate forcing may be changed by human activities, including construction of impoundments, which accumulate large amounts of carbon in sediments and emit large amounts of methane to the atmosphere. Methane emissions are also expected from lakes on melting permafrost. The synthesis presented here indicates that (1) inland waters constitute a significant component of the global carbon cycle, (2) their contribution to this cycle has significantly changed as a result of human activities, and (3) they will continue to change in response to future climate change causing decreased as well as increased abundance of lakes as well as increases in the number of aquatic impoundments.
|
|
| 16. |
|
|
| 17. |
- Weyhenmeyer, Gesa, et al.
(författare)
-
Carbon Dioxide in Boreal Surface Waters : A Comparison of Lakes and Streams
- 2012
-
Ingår i: Ecosystems (New York. Print). - : Springer-Verlag. - 1432-9840 .- 1435-0629. ; 15:8, s. 1295-1307
-
Tidskriftsartikel (refereegranskat)abstract
- The quantity of carbon dioxide (CO2) emissions from inland waters into the atmosphere varies, depending on spatial and temporal variations in the partial pressure of CO2 (pCO2) in waters. Using 22,664 water samples from 851 boreal lakes and 64 boreal streams, taken from different water depths and during different months we found large spatial and temporal variations in pCO2, ranging from below atmospheric equilibrium to values greater than 20,000 μatm with a median value of 1048 μatm for lakes (n = 11,538 samples) and 1176 μatm for streams (n = 11,126). During the spring water mixing period in April/May, distributions of pCO2 were not significantly different between stream and lake ecosystems (P > 0.05), suggesting that pCO2 in spring is determined by processes that are common to lakes and streams. During other seasons of the year, however, pCO2 differed significantly between lake and stream ecosystems (P < 0.0001). The variable that best explained the differences in seasonal pCO2 variations between lakes and streams was the temperature difference between bottom and surface waters. Even small temperature differences resulted in a decline of pCO2 in lake surface waters. Minimum pCO2 values in lake surface waters were reached in July. Towards autumn pCO2 strongly increased again in lake surface waters reaching values close to the ones found in stream surface waters. Although pCO2 strongly increased in the upper water column towards autumn, pCO2 in lake bottom waters still exceeded the pCO2 in surface waters of lakes and streams. We conclude that throughout the year CO2 is concentrated in bottom waters of boreal lakes, although these lakes are typically shallow with short water retention times. Highly varying amounts of this CO2 reaches surface waters and evades to the atmosphere. Our findings have important implications for up-scaling CO2 fluxes from single lake and stream measurements to regional and global annual fluxes.
|
|
