| 1. |
- Kehoe, Laura, et al.
(författare)
-
Make EU trade with Brazil sustainable
- 2019
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 2. |
-
- 2019
-
Tidskriftsartikel (refereegranskat)
|
|
| 3. |
- Álvarez-Muñiz, Jaime, et al.
(författare)
-
The Giant Radio Array for Neutrino Detection (GRAND) : Science and design
- 2020
-
Ingår i: Science China Physics, Mechanics & Astronomy. - : Springer Science and Business Media LLC. - 1674-7348 .- 1869-1927. ; 63:1
-
Forskningsöversikt (refereegranskat)abstract
- The Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 108 GeV. Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays. To do this, GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity. GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere. Its design is modular: 20 separate, independent sub-arrays, each of 10000 radio antennas deployed over 10000 km(2). A staged construction plan will validate key detection techniques while achieving important science goals early. Here we present the science goals, detection strategy, preliminary design, performance goals, and construction plans for GRAND.
|
|
| 4. |
- Engel, Fabian, et al.
(författare)
-
A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters
- 2018
-
Ingår i: The Science of Nature. - : Springer. - 0028-1042 .- 1432-1904. ; 105
-
Tidskriftsartikel (refereegranskat)abstract
- The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO2) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO2 production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO2 production by mineralization as well as CO2 loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of 0.70(-0.31)(+0.27) 1.52(-0.90)(+1.09) Pg C yr(-1) depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO2 sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO2 sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.
|
|
| 5. |
- Engel, Fabian, et al.
(författare)
-
A simplified approach to detect a significant carbon dioxide reduction by phytoplankton in lakes and rivers on a regional and global scale
- 2020
-
Ingår i: The Science of Nature. - : Springer Science and Business Media LLC. - 0028-1042 .- 1432-1904. ; 107:4
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide (CO2) uptake by phytoplankton can significantly reduce the partial pressure of CO2 (pCO2) in lakes and rivers, and thereby CO2 emissions. Presently, it is not known in which inland waters on Earth a significant pCO2 reduction by phytoplankton is likely. Since detailed, comparable carbon budgets are currently not available for most inland waters, we modified a proxy to assess the pCO2 reduction by phytoplankton, originally developed for boreal lakes, for application on a global scale. Using data from 61 rivers and 125 lakes distributed over five continents, we show that a significant pCO2 reduction by phytoplankton is widespread across the temperate and sub-/tropical region, but absent in the cold regions on Earth. More specifically, we found that a significant pCO2 reduction by phytoplankton might occur in 24% of the lakes in the temperate region, and 39% of the lakes in the sub-/tropical region. We also showed that such a reduction might occur in 21% of the rivers in the temperate region, and 5% of the rivers in the sub-/tropical region. Our results indicate that CO2 uptake by phytoplankton is a relevant flux in regional and global carbon budgets. This highlights the need for more accurate approaches to quantify CO2 uptake by primary producers in inland waters, particularly in the temperate and sub-/tropical region.
|
|
| 6. |
- Engel, Fabian, et al.
(författare)
-
Effect of Thermal Stratification on Phytoplankton and Nutrient Dynamics in a Regulated River (Saar, Germany)
- 2017
-
Ingår i: Rivers Research and Applications. - : Wiley. - 1535-1459 .- 1535-1467. ; 33:1, s. 135-146
-
Tidskriftsartikel (refereegranskat)abstract
- The weir pool Serrig is the deepest one along the impounded river Saar. Damming caused massive changes in the river's hydrodynamics. We analyzed the spatio-temporal variability of thermal density stratification in the weir pool and its effect on phytoplankton and nutrient dynamics. In the analysis, continuous measurements from the years 2014 and 2015 were combined with three two-day sampling campaigns in spring 2015. Thermal stratification occurred regularly in the downstream section of the weir pool during spring and summer and showed a diurnal rhythm. Temperature differences >1 K between the 1 and 2 m water layer were observed during 34 out of 217 days (16%) in 2014, with maximum temperature gradients up to 3.71 K. Whereas the influence of thermal stratification on phytoplankton biomass and distribution was low during the algal bloom in early spring, stratification events between May and July promoted temporary algal blooms in the surface layer with chlorophyll a concentrations up to 98 µg Chla l−1and a maximum difference between the 1 and 2 m water layer of 36 µg Chla l−1. Some of the stratification events resulted in reduced concentrations of dissolved nutrients in the surface layer as a result of increased uptake by algae, with maximum gradients between the surface and the 8 m water layer of 0.070 mg ortho-PO43--P l−1, 0.136 mg NH4+−N l−1 and 0.24 mg NO3¯−N l−1. These vertical gradients should be considered in sampling protocols for the assessment of the water quality of temporarily stratified river sections.
|
|
| 7. |
- Engel, Fabian, et al.
(författare)
-
Environmental conditions for phytoplankton influenced carbon dynamics in boreal lakes
- 2019
-
Ingår i: Aquatic Sciences. - : SPRINGER BASEL AG. - 1015-1621 .- 1420-9055. ; 81:2
-
Tidskriftsartikel (refereegranskat)abstract
- The partial pressure of CO2 (pCO(2)) in lake water, and thus CO2 emissions from lakes are controlled by hydrologic inorganic carbon inputs into lakes, and in-lake carbon transformation (mainly organic carbon mineralization and CO2 uptake by primary producers). In boreal lakes, CO2 uptake by phytoplankton is often considered to be of minor importance. At present, however, it is not known in which and how many boreal lakes phytoplankton CO2 uptake has a sizeable influence on the lake water pCO(2). Using water physico-chemical and phytoplankton data from 126 widely spread Swedish lakes from 1992 to 2012, we found that pCO(2) was negatively related to phytoplankton carbon in lakes in which the phytoplankton share in TOC (C-phyto:TOC ratio) exceeded 5%. Total phosphorus concentration (TP) was the strongest predictor of spatial variation in the C-phyto:TOC ratio, where C-phyto:TOC ratios>5% occurred in lakes with TP>30 mu gl(-1). These lakes were located in the hemi-boreal zone of central and southern Sweden. We conclude that during summer, phytoplankton CO2 uptake can reduce the pCO(2) not only in warm eutrophic lakes, but also in relatively nutrient poor hemi-boreal lakes.
|
|
| 8. |
- Engel, Fabian, et al.
(författare)
-
Phytoplankton gross primary production increases along cascading impoundments in a temperate, low-discharge river : Insights from high frequency water quality monitoring
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Damming alters carbon processing along river continua. Estimating carbon transport along rivers intersected by multiple dams requires an understanding of the effects of cascading impoundments on the riverine metabolism. We analyzed patterns of riverine metabolism and phytoplankton biomass (chlorophyll a; Chla) along a 74.4-km river reach intersected by six low-head navigation dams. Calculating gross primary production (GPP) from continuous measurements of dissolved oxygen concentration, we found a maximum increase in the mean GPP by a factor of 3.5 (absolute difference of 0.45 g C m−3 d−1) along the first 26.5 km of the study reach, while Chla increased over the entire reach by a factor of 2.9 (8.7 µg l−1). In the intermittently stratified section of the deepest impoundment the mean GPP between the 1 and 4 m water layer differed by a factor of 1.4 (0.31 g C m−3 d−1). Due to the strong increase in GPP, the river featured a wide range of conditions characteristic of low- to medium-production rivers. We suggest that cascading impoundments have the potential to stimulate riverine GPP, and conclude that phytoplankton CO2 uptake is an important carbon flux in the river Saar, where a considerable amount of organic matter is of autochthonous origin.
|
|
| 9. |
- Engel, Fabian
(författare)
-
The role of freshwater phytoplankton in the global carbon cycle
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Water flowing through the landscape transports chemical substances including carbon. Along the way from upland soils to the ocean, carbon is transformed from organic carbon into inorganic carbon and vice versa. One such carbon transformation process is the uptake of carbon dioxide (CO2) from the water phase by phytoplankton. For some inland waters, it has been shown that phytoplankton can significantly reduce the amount of CO2 (measured as partial pressure of CO2, pCO2) in the water phase. However, the importance of this process for carbon budgets on a regional and global scale is not yet known.The aim of this thesis was to investigate the importance of CO2 uptake by phytoplankton for CO2 dynamics in lakes and rivers on a regional and global scale, and to explain its spatial variation. Conceptual models and the analysis of monitoring data together with statistical modeling and meta-analyses were used.Combining a conceptual lake model for carbon transformation with a mass balance approach showed that gross primary production in lakes is an important flux in the global dissolved inorganic carbon budget of inland waters. In a next step, a simple proxy to assess the phytoplankton influence on the pCO2 in individual lakes and rivers was tested and applied on a regional and global scale. The analysis showed that a significant pCO2 reduction by phytoplankton could be expected in about 20% to 40% of lakes in the temperate and sub-/tropical region. In 9% of the Swedish lakes analyzed, the proxy indicated a significant pCO2 reduction by phytoplankton during summer. The pCO2 can also be significantly reduced by phytoplankton in rivers, and such a reduction might occur in about 20% of the temperate rivers on Earth. In a temperate river that was studied in more detail, consecutive impoundments were found to stimulate phytoplankton production, which might be one explanation for a greater phytoplankton influence on the pCO2 in such systems.Taken together, these results suggest that CO2 uptake by phytoplankton is a significant flux in the global CO2 budget of inland waters. The importance of CO2 uptake by phytoplankton for CO2 dynamics in individual lakes and rivers was predictable by easily available water physico-chemical and biological variables and varied widely in relation to environmental conditions.
|
|
