uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Alternative names
Publications (10 of 75) Show all publications
Almeida, R. M., Paranaíba, J. R., Barbosa, Í., Sobek, S., Kosten, S., Linkhorst, A., . . . Barros, N. (2019). Carbon dioxide emission from drawdown areas of a Brazilian reservoir is linked to surrounding land cover. Aquatic Sciences, 81, Article ID 68.
Open this publication in new window or tab >>Carbon dioxide emission from drawdown areas of a Brazilian reservoir is linked to surrounding land cover
Show others...
2019 (English)In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 81, article id 68Article in journal (Refereed) Published
Abstract [en]

Reservoir sediments exposed to air due to water level fluctuations are strong sources of atmospheric carbon dioxide (CO2). The spatial variability of CO2 fluxes from these drawdown areas are still poorly understood. In a reservoir in southeastern Brazil, we investigated whether CO2 emissions from drawdown areas vary as a function of neighboring land cover types and assessed the magnitude of CO2 fluxes from drawdown areas in relation to nearby water surface. Exposed sediments near forestland (average = 2733 mg C m−2 day−1) emitted more CO2 than exposed sediments near grassland (average = 1261 mg C m−2 day−1), congruent with a difference in organic matter content between areas adjacent to forestland (average = 12.2%) and grassland (average = 10.9%). Moisture also had a significant effect on CO2 emission, with dry exposed sediments (average water content: 13.7%) emitting on average 2.5 times more CO2 than wet exposed sediments (average water content: 23.5%). We carried out a systematic comparison with data from the literature, which indicates that CO2 efflux from drawdown areas globally is about an order of magnitude higher than CO2 efflux from adjacent water surfaces, and within the range of CO2 efflux from terrestrial soils. Our findings suggest that emissions from exposed sediments may vary substantially in space, possibly related to organic matter supply from uphill vegetation, and that drawdown areas play a disproportionately important role in total reservoir CO2 emissions with respect to the area they cover.

National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-392337 (URN)10.1007/s00027-019-0665-9 (DOI)000482233400001 ()
Funder
EU, European Research Council, 336642
Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-30Bibliographically approved
Harrison, J. A., Barros, N., Bastviken, D., Deemer, B., Evans, C., Grinham, A., . . . Tranvik, L. (2019). Dams: weigh pros and cons case by case [Letter to the editor]. Nature, 568(7751), 171-171
Open this publication in new window or tab >>Dams: weigh pros and cons case by case
Show others...
2019 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 568, no 7751, p. 171-171Article in journal, Letter (Other (popular science, discussion, etc.)) Published
National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-384037 (URN)10.1038/d41586-019-01137-2 (DOI)
Note

Author in publication: John A. Harrison on behalf of 13 signatories (see go.nature.com/f41tt1 for full list)

Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2019-10-30Bibliographically approved
Pasche, N., Hofmann, H., Bouffard, D., Schubert, C. J., Lozovik, P. A. & Sobek, S. (2019). Implications of river intrusion and convective mixing on the spatial and temporal variability of under-ice CO2. INLAND WATERS, 9(2), 162-176
Open this publication in new window or tab >>Implications of river intrusion and convective mixing on the spatial and temporal variability of under-ice CO2
Show others...
2019 (English)In: INLAND WATERS, ISSN 2044-2041, E-ISSN 2044-205X, Vol. 9, no 2, p. 162-176Article in journal (Refereed) Published
Abstract [en]

Ice-covered periods might significantly contribute to lake emissions at ice-melt, yet a comprehensive understanding of under-ice carbon dioxide (CO2) dynamics is still lacking. This study investigated the processes driving spatiotemporal patterns of under-ice CO2 in large Lake Onego. In March 2015 and 2016, under-ice CO2, dissolved inorganic carbon (DIC), and dissolved organic carbon (DOC) distributions were measured along a river to an open-lake transect. CO2 decreased from 120/129 μmol L−1 in the river to 51/98 μmol L−1 in the bay, and 34/36 μmol L−1 in the open lake, while DOC decreased from 1.18/1.55 mmol L−1 in the river to 0.67/1.04 mmol L−1 in the bay in 2015 and 2016, respectively. These decreases in concentrations with increasing distance from the river mouth indicate that river discharge modulates spatial patterns of under-ice CO2. The variability between the 2 years was mainly driven by river discharge and ice transparency affecting the extent of under-ice convection. Higher discharge during winter 2016 resulted in higher CO2 concentrations in the bay. By contrast, intensive under-ice convection led to lower, more homogeneously distributed CO2 in 2015. In conclusion, the river-to-bay transition zone is characterized by strong CO2 variability and is therefore an important zone to consider when assessing the CO2 budget of large lakes.

Keywords
carbon dioxide, convective mixing, humic lake, river intrusion, spatial distribution, under-ice
National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-384042 (URN)10.1080/20442041.2019.1568073 (DOI)000482317700004 ()
Funder
EU, FP7, Seventh Framework Programme, 336642
Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2019-10-02Bibliographically approved
Isidorova, A., Grasset, C., Mendonca, R. & Sobek, S. (2019). Methane formation in tropical reservoirs predicted from sediment age and nitrogen. Scientific Reports, 9, Article ID 11017.
Open this publication in new window or tab >>Methane formation in tropical reservoirs predicted from sediment age and nitrogen
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 11017Article in journal (Refereed) Published
Abstract [en]

Freshwater reservoirs, in particular tropical ones, are an important source of methane (CH4) to the atmosphere, but current estimates are uncertain. The CH4 emitted from reservoirs is microbially produced in their sediments, but at present, the rate of CH4 formation in reservoir sediments cannot be predicted from sediment characteristics, limiting our understanding of reservoir CH4 emission. Here we show through a long-term incubation experiment that the CH4 formation rate in sediments of widely different tropical reservoirs can be predicted from sediment age and total nitrogen concentration. CH4 formation occurs predominantly in sediment layers younger than 6-12 years and beyond these layers sediment organic carbon may be considered effectively buried. Hence mitigating reservoir CH4 emission via improving nutrient management and thus reducing organic matter supply to sediments is within reach. Our model of sediment CH4 formation represents a first step towards constraining reservoir CH4 emission from sediment characteristics.

National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-387547 (URN)10.1038/s41598-019-47346-7 (DOI)000477702400001 ()31358820 (PubMedID)
Funder
EU, FP7, Seventh Framework Programme, 336642
Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-09-24Bibliographically approved
Isidorova, A., Mendonca, R. & Sobek, S. (2019). Reduced Mineralization of Terrestrial OC in Anoxic Sediment Suggests Enhanced Burial Efficiency in Reservoirs Compared to Other Depositional Environments. Journal of Geophysical Research - Biogeosciences, 124(3), 678-688
Open this publication in new window or tab >>Reduced Mineralization of Terrestrial OC in Anoxic Sediment Suggests Enhanced Burial Efficiency in Reservoirs Compared to Other Depositional Environments
2019 (English)In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 124, no 3, p. 678-688Article in journal (Refereed) Published
Abstract [en]

Freshwater reservoirs are important sites of organic carbon (OC) burial, but the extent to which reservoir OC burial is a new anthropogenic carbon sink is currently unclear. While burial of aquatic OC (by, e.g., phytoplankton) in reservoirs may count as a new C sink, the burial of terrestrial OC in reservoirs constitutes a new C sink only if the burial is more efficient in reservoirs than in other depositional environments. We carried out incubation experiments that mimicked the environmental conditions of different depositional environments along the land‐sea continuum (oxic and anoxic freshwater, oxic and anoxic seawater, oxic river bedload, and atmosphere‐exposed floodplain) to investigate whether reservoirs bury OC more efficiently compared to other depositional environments. For sediment OC predominantly of terrestrial origin, OC degradation rates were significantly lower, by a factor of 2, at anoxic freshwater and saltwater conditions compared to oxic freshwater and saltwater, river, and floodplain conditions. However, the transformation of predominantly terrestrial OC to methane was one order of magnitude higher in anoxic freshwater than at other conditions. For sediment OC predominantly of aquatic origin, OC degradation rates were uniformly high at all conditions, implying equally low burial efficiency of aquatic OC (76% C loss in 57 days). Since anoxia is more common in reservoirs than in the coastal ocean, these results suggest that reservoirs are a depositional environment in which terrestrial OC is prone to become buried at higher efficiency than in the ocean but where also the terrestrial OC most efficiently is transformed to methane.

Abstract [en]

Plain Language Summary

The widespread construction of dams disrupts the transport of sediment particles by rivers and traps sediment in reservoirs. The sediment contains organic carbon (OC) that can be degraded into greenhouse gas (carbon dioxide and methane) or buried in the sediment. In the absence of dams, sediment would be deposited in other environments, such as rivers, floodplains, or sea. In our study, we investigated through incubation experiments if the construction of reservoirs creates an environment that stores sediment OC more efficiently than other environments. We found that OC from terrestrial origin is buried more efficiently in anoxic conditions than in oxic conditions. Slowing down of water and high primary production makes reservoirs prone to anoxia, implying that they may be sites of highly efficient OC burial. However, anoxic reservoir conditions were also characterized by higher methane emissions than other environments. OC from aquatic origin was degraded extensively in all studied conditions. Our results suggest that the ~50% of the terrestrial OC that escapes degradation if it gets trapped in an anoxic reservoir may be accounted as a new carbon sink; however, whole‐system studies that account for site‐specific environmental conditions are necessary to calculate the magnitude of this effect.

Keywords
sediment, burial, carbon, anoxic, reservoir, methane
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-375404 (URN)10.1029/2018JG004823 (DOI)000464653200016 ()
Funder
EU, FP7, Seventh Framework Programme, 336642
Available from: 2019-01-30 Created: 2019-01-30 Last updated: 2019-05-21Bibliographically approved
Grasset, C., Abril, G., Mendonca, R., Roland, F. & Sobek, S. (2019). The transformation of macrophyte-derived organic matter to methane relates to plant water and nutrient contents. Limnology and Oceanography, 64(4), 1737-1749
Open this publication in new window or tab >>The transformation of macrophyte-derived organic matter to methane relates to plant water and nutrient contents
Show others...
2019 (English)In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 64, no 4, p. 1737-1749Article in journal (Refereed) Published
Abstract [en]

Macrophyte detritus is one of the main sources of organic carbon (OC) in inland waters, and it is potentially available for methane (CH4) production in anoxic bottom waters and sediments. However, the transformation of macrophyte‐derived OC into CH4 has not been studied systematically, thus its extent and relationship with macrophyte characteristics remains uncertain. We performed decomposition experiments of macrophyte detritus from 10 different species at anoxic conditions, in presence and absence of a freshwater sediment, in order to relate the extent and rate of CH4 production to the detritus water content, C/N and C/P ratios. A significant fraction of the macrophyte OC was transformed to CH4 (mean = 7.9%; range = 0–15.0%) during the 59‐d incubation, and the mean total C loss to CO2 and CH4 was 17.3% (range = 1.3–32.7%). The transformation efficiency of macrophyte OC to CH4 was significantly and positively related to the macrophyte water content, and negatively to its C/N and C/P ratios. The presence of sediment increased the transformation efficiency to CH4 from an average of 4.0% (without sediment) to 11.8%, possibly due to physicochemical conditions favorable for CH4 production (low redox potential, buffered pH) or because sediment particles facilitate biofilm formation. The relationship between macrophyte characteristics and CH4 production can be used by future studies to model CH4 emission in systems colonized by macrophytes. Furthermore, this study highlights that the extent to which macrophyte detritus is mixed with sediment also affects CH4 production.

National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-384036 (URN)10.1002/lno.11148 (DOI)000474301200022 ()
Funder
EU, FP7, Seventh Framework Programme, 336642
Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2019-09-16Bibliographically approved
Chmiel, H., Hofmann, H., Sobek, S., Efremova, T. & Pasche, N. (2019). Where does the river end ?: Drivers of spatiotemporal variability in CO2 concentration and flux in the inflow area of a large boreal lake. Limnology and Oceanography
Open this publication in new window or tab >>Where does the river end ?: Drivers of spatiotemporal variability in CO2 concentration and flux in the inflow area of a large boreal lake
Show others...
2019 (English)In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590Article in journal (Refereed) Epub ahead of print
Abstract [en]

River inflow affects the spatiotemporal variability of carbon dioxide (CO2) in the water column of lakes and may locally influence CO2 gas exchange with the atmosphere. However, spatiotemporal CO2 variability at river inflow sites is often unknown leaving estimates of lake‐wide CO2 emission uncertain. Here, we investigated the CO2 concentration and flux variability along a river‐impacted bay and remote sampling locations of Lake Onego. During 3 years, we resolved spatial CO2 gradients between river inflow and central lake and recorded the temporal course of CO2 in the bay from the ice‐covered period to early summer. We found that the river had a major influence on the spatial CO2 variability during ice‐covered periods and contributed ~ 35% to the total amount of CO2 in the bay. The bay was a source of CO2 to the atmosphere at ice‐melt each year emitting 2–15 times the amount as an equally sized area in the central lake. However, there was large interannual variability in the spring CO2 emission from the bay related to differences in discharge and climate that affected the hydrodynamic development of the lake during spring. In early summer, the spatial CO2 variability was unrelated to the river signal but correlated negatively with dissolved oxygen concentrations instead indicating a stronger biological control on CO2. Our study reveals a large variability of CO2 and its drivers at river inflow sites at the seasonal and at the interannual time scale. Understanding these dynamics is essential for predicting lake‐wide CO2 fluxes more accurately under a warming climate.

National Category
Ecology Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-397518 (URN)10.1002/lno.11378 (DOI)
Available from: 2019-11-21 Created: 2019-11-21 Last updated: 2019-11-26Bibliographically approved
Wallin, M., Campeau, A., Audet, J., Bastviken, D., Bishop, K., Kokic, J., . . . Grabs, T. J. (2018). Carbon dioxide and methane emissions of Swedish low-order streams: a national estimate and lessons learnt from more than a decade of observations. Limnology and Oceanography: Letters, 3(3), 156-167
Open this publication in new window or tab >>Carbon dioxide and methane emissions of Swedish low-order streams: a national estimate and lessons learnt from more than a decade of observations
Show others...
2018 (English)In: Limnology and Oceanography: Letters, ISSN 2378-2242, Vol. 3, no 3, p. 156-167Article in journal (Refereed) Published
Abstract [en]

Low‐order streams are suggested to dominate the atmospheric CO2 source of all inland waters. Yet, many large‐scale stream estimates suffer from methods not designed for gas emission determination and rarely include other greenhouse gases such as CH4. Here, we present a compilation of directly measured CO2 and CH4 concentration data from Swedish low‐order streams (> 1600 observations across > 500 streams) covering large climatological and land‐use gradients. These data were combined with an empirically derived gas transfer model and the characteristics of a ca. 400,000 km stream network covering the entire country. The total stream CO2 and CH4 emission corresponded to 2.7 Tg C yr−1 (95% confidence interval: 2.0–3.7) of which the CH4 accounted for 0.7% (0.02 Tg C yr−1). The study highlights the importance of low‐order streams, as well as the critical need to better represent variability in emissions and stream areal extent to constrain future stream C emission estimates.

National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-357196 (URN)10.1002/lol2.10061 (DOI)000456696200012 ()
Funder
Knut and Alice Wallenberg Foundation, KAW 2013.0091Swedish Research Council Formas, 214-2009-872; 2015-1559Swedish Research Council, 2012-00048; 201604829Swedish Nuclear Fuel and Waste Management Company, SKBEU, European Research Council, 725546Swedish Environmental Protection AgencySwedish Agency for Marine and Water ManagementSwedish Energy Agency
Available from: 2018-08-13 Created: 2018-08-13 Last updated: 2019-02-19Bibliographically approved
Hastie, A., Lauerwald, R., Weyhenmeyer, G. A., Sobek, S., Verpoorter, C. & Regnier, P. (2018). CO2 evasion from boreal lakes: Revised estimate, drivers of spatial variability, and future projections. Global Change Biology, 24(2), 711-728
Open this publication in new window or tab >>CO2 evasion from boreal lakes: Revised estimate, drivers of spatial variability, and future projections
Show others...
2018 (English)In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 2, p. 711-728Article in journal (Refereed) Published
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.

Keywords
Boreal, CO2, Carbon budget, Climate change, Future projections, Lake, Precipitation, Terrestrial NPP
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-335068 (URN)10.1111/gcb.13902 (DOI)000423994700043 ()28892578 (PubMedID)
Funder
EU, Horizon 2020, 643052, 703813Swedish Research Council, 2016-04153Knut and Alice Wallenberg FoundationEU, FP7, Seventh Framework Programme, 336642
Available from: 2017-11-30 Created: 2017-11-30 Last updated: 2018-05-17Bibliographically approved
Kosten, S., van den Berg, S., Mendonça, R., Paranaíba, J. R., Roland, F., Sobek, S., . . . Barros, N. (2018). Extreme drought boosts CO2 and CH4 emissions from reservoir drawdown areas. INLAND WATERS, 8(3), 329-340
Open this publication in new window or tab >>Extreme drought boosts CO2 and CH4 emissions from reservoir drawdown areas
Show others...
2018 (English)In: INLAND WATERS, ISSN 2044-2041, E-ISSN 2044-205X, Vol. 8, no 3, p. 329-340Article in journal (Refereed) Published
Abstract [en]

Although previous studies suggest that greenhouse gas (GHG) emissions from reservoir sediment exposed to the atmosphere during drought may be substantial, this process has not been rigorously quantified. Here we determined carbon dioxide (CO 2) and methane (CH 4) emissions from sediment cores exposed to a drying and rewetting cycle. We found a strong temporal variation in GHG emissions with peaks when the sediment was drained (C emissions from permanently wet sediment and drained sediments were, respectively, 251 and 1646 mg m −2 d −1 for CO 2 and 0.8 and 547.4 mg m −2 d −1 for CH 4) and then again during rewetting (C emissions from permanently wet sediment and rewetted sediments were, respectively, 456 and 1725mg m −2 d −1 for CO 2 and 1.3 and 3.1 mg m −2 d −1 for CH 4). To gain insight into the importance of these emissions at a regional scale, we used Landsat satellite imagery to upscale our results to all Brazilian reservoirs. We found that during the extreme drought of 2014-2015, an additional 1299 km 2 of sediment was exposed, resulting in an estimated emission of 8.5 × 10 11 g of CO 2-eq during the first 15 d after the overlying water disappeared and in the first 33 d after rewetting, the same order of magnitude as the year-round GHG emissions of large (∼mean surface water area 454 km 2) Brazilian reservoirs, excluding the emissions from the draw-down zone. Our estimate, however, has high uncertainty, with actual emissions likely higher. We therefore argue that the effects of drought on reservoir GHG emissions merits further study, especially because climate models indicate an increase in the frequency of severe droughts in the future. We recommend incorporation of emissions during drying and rewetting into GHG budgets of reservoirs to improve regional GHG emission estimates and to enable comparison between GHG emissions from hydroelectric and other electricity sources. We also emphasize that peak emissions at the onset of drought and the later rewetting should be quantified to obtain reliable emission estimates. ARTICLE HISTORY

Keywords
drought, emission peaks, greenhouse gases, reservoirs, rewetting, sediment
National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-371238 (URN)10.1080/20442041.2018.1483126 (DOI)000456214100008 ()
Funder
EU, European Research Council, 336642
Note

Corresponding author: R. Mendonca

Available from: 2018-12-19 Created: 2018-12-19 Last updated: 2019-11-25Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1351-9277

Search in DiVA

Show all publications