Density-driven current between reed belts and open water in a shallow lake

2008 ◽  
Vol 44 (10) ◽  
Author(s):  
Charlotta Borell Lövstedt ◽  
Lars Bengtsson
Keyword(s):  
Shallow Lake ◽  
Open Water

Notable increases in nutrient concentrations in a shallow lake during seasonal ice growth

2016 ◽  
Vol 74 (12) ◽  
pp. 2773-2783 ◽  
Author(s):  
Yang Fang ◽  
Li Changyou ◽  
Matti Leppäranta ◽  
Shi Xiaonghong ◽  
Zhao Shengnan ◽  
...  
Keyword(s):  
Liquid Water ◽  
Shallow Lake ◽  
Water Environment ◽  
Open Water ◽  
Middle Layer ◽  
Nutrient Concentrations ◽  
Unfrozen Water ◽  
Total N ◽  
Water And Sediment ◽  
Increased Risk

Nutrients may be eliminated from ice when liquid water is freezing, resulting in enhanced concentrations in the unfrozen water. The nutrients diluted from the ice may contribute to accumulated concentrations in sediment during winter and an increased risk of algae blooms during the following spring and summer. The objective of this study was to evaluate the influence of ice cover on nitrogen (N) and phosphorus (P) concentrations in the water and sediment of a shallow lake, through an examination of Ulansuhai Lake, northern China, from the period of open water to ice season in 2011–2013. The N and P concentrations were between two and five times higher, and between two and eight times higher, than in unfrozen lakes, respectively. As the ice thickness grew, contents of total N and total P showed C-shaped profiles in the ice, and were lower in the middle layer and higher in the bottom and surface layers. Most of the nutrients were released from the ice to liquid water. The results confirm that ice can cause the nutrient concentrations in water and sediment during winter to increase dramatically, thereby significantly impacting on processes in the water environment of shallow lakes.

scholarly journals High net CO<sub>2</sub> and CH<sub>4</sub> release at a eutrophic shallow lake on a formerly drained fen

2016 ◽  
Vol 13 (10) ◽  
pp. 3051-3070 ◽  
Author(s):  
Daniela Franz ◽  
Franziska Koebsch ◽  
Eric Larmanou ◽  
Jürgen Augustin ◽  
Torsten Sachs
Keyword(s):  
Global Warming ◽  
Shallow Lake ◽  
Typha Latifolia ◽  
Open Water ◽  
Emergent Vegetation ◽  
Lake Ecosystem ◽  
Co2 Uptake ◽  
Mild Winter ◽  
Ch4 Emissions ◽  
Northeastern Germany

Abstract. Drained peatlands often act as carbon dioxide (CO2) hotspots. Raising the groundwater table is expected to reduce their CO2 contribution to the atmosphere and revitalise their function as carbon (C) sink in the long term. Without strict water management rewetting often results in partial flooding and the formation of spatially heterogeneous, nutrient-rich shallow lakes. Uncertainties remain as to when the intended effect of rewetting is achieved, as this specific ecosystem type has hardly been investigated in terms of greenhouse gas (GHG) exchange. In most cases of rewetting, methane (CH4) emissions increase under anoxic conditions due to a higher water table and in terms of global warming potential (GWP) outperform the shift towards CO2 uptake, at least in the short term.Based on eddy covariance measurements we studied the ecosystem–atmosphere exchange of CH4 and CO2 at a shallow lake situated on a former fen grassland in northeastern Germany. The lake evolved shortly after flooding, 9 years previous to our investigation period. The ecosystem consists of two main surface types: open water (inhabited by submerged and floating vegetation) and emergent vegetation (particularly including the eulittoral zone of the lake, dominated by Typha latifolia). To determine the individual contribution of the two main surface types to the net CO2 and CH4 exchange of the whole lake ecosystem, we combined footprint analysis with CH4 modelling and net ecosystem exchange partitioning.The CH4 and CO2 dynamics were strikingly different between open water and emergent vegetation. Net CH4 emissions from the open water area were around 4-fold higher than from emergent vegetation stands, accounting for 53 and 13 g CH4 m−2 a−1 respectively. In addition, both surface types were net CO2 sources with 158 and 750 g CO2 m−2 a−1 respectively. Unusual meteorological conditions in terms of a warm and dry summer and a mild winter might have facilitated high respiration rates. In sum, even after 9 years of rewetting the lake ecosystem exhibited a considerable C loss and global warming impact, the latter mainly driven by high CH4 emissions. We assume the eutrophic conditions in combination with permanent high inundation as major reasons for the unfavourable GHG balance.

scholarly journals Characterization of sediment layer composition in a shallow lake: from open water zones to reed belt areas

2014 ◽  
Vol 11 (11) ◽  
pp. 12627-12657
Author(s):  
I. Kogelbauer ◽  
W. Loiskandl
Keyword(s):  
Shallow Lake ◽  
Open Water ◽  
Penetration Resistance ◽  
Measuring System ◽  
High Water Content ◽  
Sediment Layer ◽  
Soil Physics ◽  
Layer Composition

Abstract. Lake sediment characterization, a pre-requirement for the vulnerability assessment of lake ecosystems, demands reliable in situ methods for the characterization of the sediment layer composition. A unified characterization of lake sediments within different lake ecotopes (open water, open water patches within the reed, and the reed) is still a challenge. Each ecotope is covered by different classical scientific disciplines (hydrography and terrestrial remote sensing to soil physics) with their specific characterization methods. However, a complementary tool that bridges the gap between land- and hydrographic surveying methods is still missing. Therefore a combination of soil physical sensors (a capacitive sensor and a cone penetrometer) in a measuring system (CSPS) was introduced. CSPS is a non-acoustic device for the rapid in situ delineation of water-mud-consolidated lakebed interfaces. The system was successfully applied across the different ecotopes at the Neusiedler See, a well-mixed shallow lake rich in fine-grained sediments. The geo-referenced vertical CSPS profiles show ecotope-specific layer composition. The effect of wind induced turbidity, particle size, and electrical conductivity were analysed. The water–mud interface was precisely delineated at the open water due to a persistent high water content gradient, equivalent to a lutocline. The penetration resistance for open water showed either a shallow and highly-compacted consolidated lakebed or a consolidated lakebed with a partially compacted layer above; while in the reed the penetration resistance smoothly increased until reaching the deepest penetration depths.

scholarly journals High net CO<sub>2</sub> and CH<sub>4</sub> release at a eutrophic shallow lake on a formerly drained fen

2016 ◽  
Author(s):  
D. Franz ◽  
F. Koebsch ◽  
E. Larmanou ◽  
J. Augustin ◽  
T. Sachs
Keyword(s):  
Global Warming ◽  
Shallow Lake ◽  
Typha Latifolia ◽  
Open Water ◽  
Emergent Vegetation ◽  
Lake Ecosystem ◽  
Co2 Uptake ◽  
Mild Winter ◽  
Ch4 Emissions ◽  
Ne Germany

Abstract. Drained peatlands often act as carbon dioxide (CO2) hotspots. Raising the groundwater table is expected to reduce their CO2 contribution to the atmosphere and revitalize their function as carbon (C) sink in the long term. Without strict water management rewetting often results in partial flooding and the formation of spatially heterogeneous, nutrient-rich shallow lakes. Uncertainties remain as to when the intended effect of rewetting is achieved, as this specific ecosystem type has hardly been investigated in terms of greenhouse gas exchange (GHG) exchange. In most cases, methane (CH4) emissions increase under anoxic conditions due to a higher water table and in terms of global warming potential (GWP) outperform the shift towards CO2 uptake, at least in the short-term. Based on eddy covariance measurements we studied the ecosystem–atmosphere exchange of CH4 and CO2 (NEE) at a shallow lake situated on a former fen grassland in Northeast (NE) Germany. The lake evolved shortly after flooding, 9 years previous to our investigation period. The ecosystem consists of two main surface types: open water (inhabited by submerged and floating vegetation) and emergent vegetation (particularly including the eulittoral zone of the lake, dominated by Typha latifolia). To determine the individual contribution of the two main surface types to the net CO2 and CH4 exchange of the whole lake ecosystem, we combined footprint analysis with CH4 modelling and NEE partitioning. The CH4 and CO2 dynamics were strikingly different between open water and emergent vegetation. Net CH4 emissions from the open water area were around 4-fold higher than from emergent vegetation stands, accounting for 53 and 13 g CH4 m−2 a−1, respectively. In addition, both surface types were net CO2 sources with 158 and 750 g CO2 m−2 a−1, respectively. Unusual meteorological conditions in terms of a warm and dry summer and a mild winter might have facilitated high respiration rates. In sum, even after 9 years of rewetting the lake ecosystem exhibited a considerable C loss and global warming impact, the latter mainly driven by high CH4 emissions. We assume the eutrophic conditions in combination with permanent high inundation as major reasons for the unfavourable GHG balance.

scholarly journals Characterization of sediment layer composition in a shallow lake: from open water zones to reed belt areas

2015 ◽  
Vol 19 (3) ◽  
pp. 1427-1438 ◽  
Author(s):  
I. Kogelbauer ◽  
W. Loiskandl
Keyword(s):  
Shallow Lake ◽  
Open Water ◽  
Measuring System ◽  
High Water Content ◽  
Sediment Layer ◽  
Soil Physics ◽  
Lake Ecosystems ◽  
Layer Composition

Abstract. Lake sediment characterization, a prerequisite for the vulnerability assessment of lake ecosystems, demands reliable in situ methods for the characterization of the sediment layer composition. A unified characterization of lake sediments within lake ecotopes (open water, open water patches within the reed, and the reed) is still a challenge. Each ecotope is covered by different classical scientific disciplines (hydrography and terrestrial remote sensing to soil physics) with their specific characterization methods. Recently, a complementary tool that bridges the gap between land and hydrographic surveying methods was introduced. It is a non-acoustic device that combines two soil physical sensors (a capacitive sensor and a cone penetrometer) and GNSS-positioning in a measuring system (CSPS). The CSPS enables rapid in situ delineation of water–mud–consolidated lakebed interfaces. The system was successfully applied across ecotopes at the Neusiedler See, a well-mixed shallow lake rich in fine-grained sediments. The geo-referenced vertical CSPS profiles show ecotope-specific layer composition. The effects of wind-induced turbidity, particle size, and electrical conductivity were analysed. The water–mud interface was precisely delineated at the open water due to a persistent high water content gradient, equivalent to a lutocline. The penetration resistance (PR) for open water showed either a shallow and highly compacted consolidated lakebed or a consolidated lakebed with a partially compacted layer above, while in the reed the PR smoothly increased until reaching the deepest penetration depths.

scholarly journals RESPONSE OF A SHALLOW LAKE TO WIND LOAD DURING THE OPEN WATER PERIOD (3D NUMERICAL EXPERIMENTS)

2020 ◽  
pp. 5
Author(s):  
Илья Сергеевич Зверев ◽  
Роман Эдуардович Здоровеннов ◽  
Галина Эдуардовна Здоровеннова ◽  
Николай Иннокентьевич Пальшин ◽  
Сергей Рэмович Богданов ◽  
...  
Keyword(s):  
Shallow Lake ◽  
Numerical Experiments ◽  
Open Water ◽  
Wind Load
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