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Alfred Johny Wüest

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Publications associées (118)

Particle dynamics in high-Alpine proglacial reservoirs modified by pumped-storage operation

Alfred Johny Wüest

Temperature and suspended particle distribution were surveyed and modeled in two high-Alpine reservoirs in Switzerland, connected by pumped-storage operations for similar to 30 years. Due to different glacier coverage of the catchments, the two reservoirs ...

Amer Geophysical Union2011

Impact of a large tropical reservoir on riverine transport of sediment, carbon, and nutrients to downstream wetlands

Bernhard Wehrli, Alfred Johny Wüest

Large dams can have major ecological and biogeochemical impacts on downstream ecosystems such as wetlands and riparian habitats. We examined sediment removal and carbon (C), nitrogen (N), and phosphorus (P) cycling in Itezhi-Tezhi Reservoir (ITT; area = 36 ...

Amer Geophysical Union2011

Spatial Heterogeneity of Methane Ebullition in a Large Tropical Reservoir

Bernhard Wehrli, Alfred Johny Wüest

Tropical reservoirs have been identified as important methane (CH4) sources to the atmosphere, primarily through turbine and downstream degassing. However, the importance of ebullition (gas bubbling) remains unclear. We hypothesized that ebullition is a di ...

Amer Chemical Soc2011

Sediment accumulation and carbon, nitrogen, and phosphorus deposition in the large tropical reservoir Lake Kariba (Zambia/Zimbabwe)

Bernhard Wehrli, Alfred Johny Wüest

Large dams affect the aquatic continuum from land to ocean by accumulating particles and nutrients in their reservoirs. We examined sediment cores to quantify sediment, organic carbon (OC), nitrogen (N), and phosphorous (P) accumulation, and to examine his ...

Amer Geophysical Union2011

Boundary mixing in lakes: 2. Combined effects of shear- and convectively induced turbulence on basin-scale mixing

Alfred Johny Wüest

A detailed comparison of results from a numerical three-dimensional hydrostatic lake model with high-resolution observations of the vertical structure of the turbulent bottom boundary layer (BBL) in a medium-size lake (Lake Alpnach, Switzerland) is provide ...

Amer Geophysical Union2011

Application of Oxygen Eddy Correlation in Aquatic Systems

Alfred Johny Wüest

The eddy correlation technique is rapidly becoming an established method for resolving dissolved oxygen fluxes in natural aquatic systems. This direct and noninvasive determination of oxygen fluxes close to the sediment by simultaneously measuring the velo ...

Amer Meteorological Soc2010

Variable sediment oxygen uptake in response to dynamic forcing

Alfred Johny Wüest

Seiche-induced turbulence and the vertical distribution of dissolved oxygen above and within the sediment were analyzed to evaluate the sediment oxygen uptake rate (J(O2)), diffusive boundary layer thickness (delta(DBL)), and sediment oxic zone depth (z(ma ...

American Society of Limnology and Oceanography2010

Carbonate sedimentation and effects of eutrophication observed at the Kalista subaquatic springs in Lake Ohrid (Macedonia)

Marco Matter, Alfred Johny Wüest

To date, little is known about the role of spring waters with respect to authigenic carbonate precipitation in a shallow lacustrine setting. Lake Ohrid, located in Southeastern Europe, is a large lake fed to over 50% by karstic springs of which half enter ...

Copernicus Gesellschaft Mbh2010

Hypolimnetic oxygen consumption by sediment-based reduced substances in former eutrophic lakes

Alfred Johny Wüest, Beat Mueller, Martin Schmid

We quantified the areal hypolimnetic mineralization rate (AHM; total areal hypolimnetic oxygen depletion including the formation of reduced substances) in two formerly eutrophic lakes based on 20 yr of water-column data collected during oligotrophication. ...

American Society of Limnology and Oceanography2010

Evaluating oxygen fluxes using microprofiles from both sides of the sediment-water interface

Alfred Johny Wüest

Sediment-water fluxes are influenced by both hydrodynamics and sediment biogeochemical processes. However, fluxes at the sediment-water interface (SWI) are almost always analyzed from either a water-or sediment-side perspective. This study expands on previ ...

Association for the Sciences of Limnology and Oceanography (ASLO)2010

Double-diffusive convection in Lake Kivu

Alfred Johny Wüest, Martin Schmid

Double-diffusive staircases with a total of 230-350 mixed layers and sharp interfaces were observed in nine microstructure temperature profiles measured during February 2004 in Lake Kivu. The presence of these staircases at depths. 120 m indicates that dia ...

American Society of Limnology and Oceanography2010

Physical and biogeochemical limits to internal nutrient loading of meromictic Lake Kivu

Bernhard Wehrli, Natacha Tofield-Pasche, Alfred Johny Wüest, Beat Mueller, Martin Schmid

Lake Kivu is one of the large African Rift lakes situated between the Democratic Republic of the Congo and Rwanda. In its permanently stratified hypolimnion, unusually high methane concentrations have increased further in recent decades. Because methanogen ...

American Society of Limnology and Oceanography2009

Balancing nutrient inputs to Lake Kivu

Natacha Tofield-Pasche, Alfred Johny Wüest, Beat Mueller, Martin Schmid

The primary production in meromictic Lake Kivu is sustained by external nutrient inputs and by internal loading due to upwelling caused by sub-aquatic sources. We present here the results of external loading of phosphorus (P), nitrogen (N) and silica (Si) ...

Elsevier Sci Ltd2009

Do Microscopic Organisms Feel Turbulent Flows?

Alfred Johny Wüest, Miki Hondzo

Microscopic organisms in aquatic environments are continuously exposed to a variety of physical and chemical conditions. Traditionally, it is accepted that due to their small size the physiology of microscopic organisms is not affected by the moving fluid ...

Amer Chemical Soc2009

Measurements of eddy correlation oxygen fluxes in shallow freshwaters: Towards routine applications and analysis

Alfred Johny Wüest

Benthic fluxes of dissolved oxygen are measured in a shallow reservoir using the eddy correlation technique. Flux variations depict the diurnal production-consumption cycle, with daytime oxygen release following the solar radiation trend. The average night ...

Amer Geophysical Union2008

Lake Baikal deepwater renewal mystery solved

Alfred Johny Wüest, Martin Schmid

Deepwater renewal by intrusions and turbulent diffusion in Lake Baikal is very effective despite the enormous depth of up to 1642 m and the permanently stable stratification below similar to 300 m depth. Temperature time series recorded at the bottom of a ...

Amer Geophysical Union2008

Intermittent oxygen flux from the interior into the bottom boundary of lakes as observed by eddy correlation

Bernhard Wehrli, Alfred Johny Wüest

Turbulent oxygen transport from the overlying stratified water column into the bottom boundary layer (BBL) on the slope of a medium-sized lake was investigated using the eddy correlation (EC) technique. The seicheinduced oscillatory flow of the BBL, with a ...

American Society of Limnology and Oceanography2008

Comparing effects of oligotrophication and upstream hydropower dams on plankton and productivity in perialpine lakes

Alfred Johny Wüest, Martin Schmid

In recent decades, many perialpine lakes have been affected by oligotrophication due to efficient sewage treatment and by altered water turbidity due to upstream hydropower operations. Such simultaneous environmental changes often lead to public debate on ...

Amer Geophysical Union2007

Effects of alpine hydropower operations on primary production in a downstream lake

Alfred Johny Wüest, Beat Mueller, Martin Schmid

During the past century, the construction of hydropower dams in the watershed of Lake Brienz has significantly altered the dynamics of turbidity, which has important implications for lake productivity. To assess these effects, we measured in situ carbon as ...

Birkhauser Verlag Ag2007

Eutrophication of ancient Lake Ohrid: Global warming amplifies detrimental effects of increased nutrient inputs

Alfred Johny Wüest, Beat Mueller, Martin Schmid

Lake Ohrid in southeastern Europe is one of the few ancient, long-lived lakes of the world, and contains more than 200 endemic species. On the basis of integrated monitoring of internal and external nutrient fluxes, a progressing eutrophication was detecte ...

American Society of Limnology and Oceanography2007

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