| 21. |
- 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.
|
|
| 22. |
- Jansen, Joachim, 1989-, et al.
(författare)
-
Global increase in methane production under future warming of lake bottom waters
- 2022
-
Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 28:18, s. 5427-5440
-
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.
|
|
| 23. |
- Münzner, Karla, 1989-
(författare)
-
Causes and consequences of Gonyostomum semen blooms
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aquatic ecosystems provide essential ecosystem services, but are also highly vulnerable to global change. Climate change, eutrophication and browning, for example, collectively drive the increase of harmful algal blooms in freshwaters. While cyanobacterial blooms have been intensively studied, blooms caused by other algal species have received far less attention.The aim of my thesis was to increase our understanding of the causes and consequences of the freshwater raphidophyte Gonyostomum semen (Ehrenberg) Diesing, which forms high biomass blooms in lakes all over the world. I used laboratory experiments, field studies and lake monitoring data to investigate how G. semen growth is affected by environmental factors related to water color, and how G. semen blooms affect carbon cycling in lakes.High iron concentration (>200 µg L-1) was found to be a requirement for G. semen growth, but not for bloom formation. Rather, increase in dissolved organic carbon (DOC) concentration may drive bloom formation, possibly by a combination of providing additional nutrients to lakes as DOC is imported from terrestrial sources, and by reducing light availability for other competing phytoplankton species. Gonyostomum semen can possibly avoid light limitation and form blooms over a wide range of DOC concentration (8 – 20 mg L-1) due to its diel vertical migration and special pigment composition, although there likely exists a DOC threshold at which also G. semen growth becomes light limited.By fixing CO2 through photosynthesis, G. semen did considerably reduce the partial pressure of CO2 (pCO2) in the studied lakes. Furthermore, the relationship between pCO2 and G. semen became stronger with decreasing DOC concentration, suggesting that reduction in pCO2 caused by G. semen is highest in moderately colored lakes (8 – 12 mg DOC L-1). This resulted in temporary reduction in CO2 emission to the atmosphere during summer, though it is unlikely that it changes annual carbon emissions. Organic matter (OM) generated by G. semen was transported to the sediments, though this did not appear to affect carbon burial rates. However, G. semen increased the fraction of autochthonous OM that sank to the sediment, which may result in altered CO2 and methane (CH4) production on a short-term basis.In summary, G. semen growth is dependent on sufficient iron concentrations, while bloom formation is likely controlled by DOC. Blooms temporarily affect in-lake carbon dynamics through increased rates of CO2 fixation via photosynthesis, transport of autochthonous OM to the sediment and subsequent changes in CO2 and CH4 production. Thus, G. semen may contribute to changes in ecosystem functioning in lakes experiencing browning.
|
|
| 24. |
- Nydahl, Anna C., et al.
(författare)
-
Groundwater carbon within a boreal catchment : spatiotemporal variability of a hidden aquatic carbon pool
- 2020
-
Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 125:1
-
Tidskriftsartikel (refereegranskat)abstract
- Groundwater is an essential resource providing water for societies and sustaining surface waters. Although groundwater at intermediate depth could be highly influential at regulating lake and river surface water chemistry, studies quantifying organic and inorganic carbon (C) species in intermediate depth groundwater are still rare. Here, we quantified dissolved and gaseous C species in the groundwater of a boreal catchment at 3- to 20-m depth. We found that the partial pressure of carbon dioxide (pCO(2)), the stable carbon isotopic composition of dissolved inorganic carbon (delta C-13-DIC), and pH showed a dependency with depth. Along the depth profile, a negative relationship was observed between pCO(2) and delta C-13-DIC and between pCO(2) and pH. We attribute the negative pCO(2)-pH relationship along the depth gradient to increased silicate weathering and decreased soil respiration. Silicate weathering consumes carbon dioxide (CO2) and release base cations, leading to increased pH and decreased pCO(2). We observed a positive relationship between delta C-13-DIC and depth, potentially due to diffusion-related fractionation in addition to isotopic discrimination during soil respiration. Soil CO2 may diffuse downward, resulting in a fractionation of the delta C-13-DIC. Additionally, the dissolved organic carbon at greater depth may be recalcitrant consisting of old degraded material with a greater fraction of the heavier C isotope. Our study provides increased knowledge about the C biogeochemistry of groundwater at intermediate depth, which is important since these waters likely contribute to the widespread CO2 oversaturation in boreal surface waters.
|
|
| 25. |
- Nydahl, Anna, et al.
(författare)
-
Diverse drivers of long-term pCO2 increases across thirteen boreal lakes and streams
- 2020
-
Ingår i: Inland Waters. - : Informa UK Limited. - 2044-2041 .- 2044-205X. ; 10:3, s. 360-372
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the mechanisms driving carbon dioxide (CO2) concentrations in inland waters is important to foresee CO(2)responses to environmental change, yet knowledge gaps persist regarding which processes are the key drivers. Here we investigated possible drivers across 13 Swedish lakes and streams where the partial pressure of CO2(pCO(2)) has increased over a 21-year period. Overall, we could not identify a single dominating mechanism responsible for the observedpCO(2)increase. In the 8 lakes, we found thatpCO(2)increased, driven either by a possible dissolved organic carbon (DOC) stimulation of microbial mineralization or by water color primary production suppression. In streams, the dominating mechanism for apCO(2)increase was either a change in the carbonate system distribution or a possible nutrient-driven decrease in primary production. This is the first study to demonstrate and explain consistent positivepCO(2)temporal trends in freshwater ecosystems, and our results should be taken into account when predicting future emission of CO(2)from inland waters.
|
|
| 26. |
- Sharma, Sapna, et al.
(författare)
-
Long-term ice phenology records spanning up to 578 years for 78 lakes around the Northern Hemisphere
- 2022
-
Ingår i: Scientific Data. - : Springer Nature. - 2052-4463. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- In recent decades, lakes have experienced unprecedented ice loss with widespread ramifications for winter ecological processes. The rapid loss of ice, resurgence of winter biology, and proliferation of remote sensing technologies, presents a unique opportunity to integrate disciplines to further understand the broad spatial and temporal patterns in ice loss and its consequences. Here, we summarize ice phenology records for 78 lakes in 12 countries across North America, Europe, and Asia to permit the inclusion and harmonization of in situ ice phenology observations in future interdisciplinary studies. These ice records represent some of the longest climate observations directly collected by people. We highlight the importance of applying the same definition of ice-on and ice-off within a lake across the time-series, regardless of how the ice is observed, to broaden our understanding of ice loss across vast spatial and temporal scales.
|
|
| 27. |
- Sharma, Sapna, et al.
(författare)
-
Loss of Ice Cover, Shifting Phenology, and More Extreme Events in Northern Hemisphere Lakes
- 2021
-
Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 126:10
-
Tidskriftsartikel (refereegranskat)abstract
- Long-term lake ice phenological records from around the Northern Hemisphere provide unique sensitive indicators of climatic variations, even prior to the existence of physical meteorological measurement stations. Here, we updated ice phenology records for 60 lakes with time-series ranging from 107-204 years to provide the first re-assessment of Northern Hemispheric ice trends since 2004 by adding 15 additional years of ice phenology records and 40 lakes to our study. We found that, on average, ice-on was 11.0 days later, ice-off was 6.8 days earlier, and ice duration was 17.0 days shorter per century over the entire record for each lake. Trends in ice-on and ice duration were six times faster in the last 25-year period (1992-2016) than previous quarter centuries. More extreme events in recent decades, including late ice-on, early ice-off, shorter periods of ice cover, or no ice cover at all, contribute to the increasing rate of lake ice loss. Reductions in greenhouse gas emissions could limit increases in air temperature and abate losses in lake ice cover that would subsequently limit ecological, cultural, and socioeconomic consequences, such as increased evaporation rates, warmer water temperatures, degraded water quality, and the formation of toxic algal blooms.
|
|
| 28. |
- Wang, Jinling, et al.
(författare)
-
Urbanization in developing countries overrides catchment productivity in fueling inland water CO2 emissions
- 2022
-
Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 29:1, s. 1-4
-
Tidskriftsartikel (refereegranskat)abstract
- We compiled a nationwide dataset of carbon dioxide (CO2) efflux from 1405 measurements, and found that lakes, reservoirs, and rivers emit a total of 61.9 ± 55.3 TgC as CO2 each year, corresponding to 6.3% of the annual total national CO2 emission in 2020. Our analysis showed that the presence of anthropogenic disturbances in catchments strongly influences the emission of CO2 from these waters in the non-pristine areas, masking the catchment productivity effect on the emission of CO2. Our results highlight the need for adjusting climate change models for taking into account anthropogenic effects on CO2 emissions from inland waters.
|
|
| 29. |
|
|
| 30. |
- Woolway, R. Iestyn, et al.
(författare)
-
Winter inverse lake stratification under historic and future climate change
- 2022
-
Ingår i: Limnology and Oceanography Letters. - : John Wiley & Sons. - 2378-2242. ; 7:4, s. 302-311
-
Tidskriftsartikel (refereegranskat)abstract
- Millions of lakes inversely stratify during winter. Seemingly subtle variations in the duration of winter stratification can have major ecological effects by, for example, altering the vertical distribution of oxygen and nutrients in lakes. Yet, the influence of climate change on winter stratification has been largely unexplored. To fill this knowledge gap, here we used a lake-climate model ensemble to investigate changes in winter stratification from 1901 to 2099 across 12,242 representative lakes situated throughout the Northern Hemisphere. By the end of the 21st century, winter stratification duration is projected to shorten by an average of 18.5–53.9 d under Representative Concentration Pathways (RCPs) 2.6–8.5. Projected changes are faster in warmer geographical regions, in which 35–69% of lakes will no longer inversely stratify by 2070–2099 under RCPs 2.6–8.5. This shortening and loss of winter stratification will likely have numerous implications for lakes, including the misalignment of lifecycle events causing shifts in biodiversity.
|
|
