User:Hez28/Lake Lucerne

Limnology: Lake Lucerne.

Background Information
Lake Lucerne is located in Switzerland, which is one of the largest freshwater lakes in Central Europe. Lake Lucerne is an open and oligotrophic lake, which is different from most eutrophic lakes in Europe. Lake Lucerne is also a fjord lake. Lake Lucerne has a surface area of ​​116 square kilometers, a volume of 12 cubic kilometers, and a maximum depth of 214 meters (Thevenon, F, 2012). The average depth is 119.8 meters, and the average discharge is 93.135m. Lake Lucerne is about 39 kilometers long, with a maximum width of about 3 kilometers, and is located at an altitude of 434 m. The basin of this lake includes Four basins, which are injected by four mountain rivers and flow through most of the catchment area. Lake Lucerne is a meromictic lake, and it completely overturns every 3 to 6 years (Thevenon, F, 2012). Lake Lucerne’s complex shape and the surrounding historically significant landscape provide unique insights into the structure and landform development of the high mountains and mountains in the area. The irregular shape of Lake Lucerne is related to the underlying and surrounding geological structures, such as basins and alpine valleys (Keller B, 2021).

"The Lake of the Four Forested Cantons"
Lake Lucerne is called "the lake of the four forested cantons" because it borders the original Uri, Schwyz, Unterwalden, and the canton of Lucerne in Switzerland. Lake Lucerne is located between steep limestone mountains and there are many peaks in the waters of Lake Lucerne, such as Horn on the West, Meggenhorn on the North, Burgenstock, and Seelisberg on the South (LakePedia).

Water Bodies of Lake Lucerne
Several important water bodies of Lake Lucerne are connected by narrow and tortuous passages, and a deep trench interrupts the western end of the main branch of Lake Lucerne. The main source of water for Lake Lucerne is the Reuss River, which flows into Lake Lucerne in Fluelen and flows out in the town of Lucerne. In order to prevent Lake Lucerne from being affected by changes in water level and causing flooding along the shoreline, a dam was built in the Reuss River between 1859 and 1860. In addition, three rivers flow into Lake Lucerne, the Muota River flows in Brunnen, the Engelberger Aa River flows in Buochs, and the Sarner As River flows into Alpnachstad.

Lake Type
Lake Lucerne is a poorly nutritious lake (oligotrophic lake), the lake is very clear and cold. The nutrient level of the lake water is very low, and there are relatively few fish, aquatic plants, algae, zooplankton, and phytoplankton in the lake. Lake Lucerne is a monomictic lake that only flips completely once every six years, and the intensity of water turnover depends on temperature conditions and strong winds. The Light Intensity of Lake Lucerne is better, and the Euphotic zone will be deeper.

The Genesis of Lake Lucerne
The landform of Lake Lucerne is complex, and its irregular shape is related to the underlying geological structure, including multiple arms, bays, and basins. The genesis of Lake Lucerne is mainly related to the decline of glaciers in the Ice Age, and the erosion and deposition processes of glaciers are related to this Related. The complex shape of Lake Lucerne is the product of macro-geological structure, and it was formed after being eroded by glaciers in the subsequent ice age. During the period of glacier melting, Lake Lucerne increasingly became a large-scale sedimentary trap and was filled with glacial turbidity sediments. During the Neolithic period, the water level of Lake Lucerne rose due to sediments brought by the approaching torrent. The weir built in the Middle Ages promoted a further rise in the water level of Lake Lucerne. The many parts of Lake Lucerne that extend in different directions have caused controversy over the explanation of its causes by previous scientists. Penck and Brückner believed that glacial erosion gave Lake Lucerne a complex shape; Heim believed that Lake Lucerne and its tributaries were paleo-river valleys, and they were submerged due to subsidence in the later stages of the formation of the mountains (Keller B, 2021).

The Changes of Trophic State
In the past few decades, Lake Lucerne has been in four different periods of main nutritional status. From 1955 to 1969, Lake Lucerne was oligotrophic. Due to the discharge of industrial wastewater, water pollution by toxic metals reached a peak in the mid-twentieth century. Between 1970 and 1977, Lake Lucerne was in a period of eutrophication. In the 1960s, the phytoplankton community was Cyanobacteria (mainly Planktothrix rubescens) and pinnate diatoms. As the number of phosphorus increases, algae plants multiply. Subsequently, between 1978 and 1988, the lake became mesotrophic again, and finally became oligotrophic (1989-2001) because the improvement of sewage, and treatment and phosphate detergents were banned, the phosphorus decreased significantly. In the second half of the 20th century, with the implementation of sewage treatment plants, the metal pollution of Lake Lucerne also decreased. During the lean phase, the biomass of cyanobacteria and green algae declines. Today, the community structure of Lake Lucerne is mainly Rhodomonas in winter, pennate diatoms (Fragilaria) in summer, and blue-green algae in autumn.

Studies on Lake Lucerne
Many studies on Lake Lucerne have made people better understand this lake. From high-resolution seismic imaging of Lake Lucerne and piston coring, researcher Schnellmann et al, discovered surprisingly deformed structures in the flat loose sediments at the foot of the underwater slope (Schnellmann et al, 2005). Therefore, they studied the influence of fjord-type Lake Lucerne's unique sedimentation and bottom topography conditions on the movement of materials and the resulting sediments(Schnellmann et al, 2005). This research focuses on the three external basins that are separated from the major deltas by subaqueous sills, including the Chrüztrichter, Vitznau and Küssnacht basins. Like many alpine lakes, a primarily Holocene drape covers large parts of Lake Lucerne. Only in very steep There is no or very little sediment accumulation on the seismic sections on slopes and cliffs (Schnellmann et al, 2005). Chrüztrichter Slide(is located on the north-western edge of the Chrüztrichter Basin), Zinnen Slide(is located in the southern part of the Küssnacht Basin), Weggis Slide(is located on the northern slope of the Vitznau Basin), and St Niklausen Slide (is located in the western Chrüztrichter Basin) is the four slides being studied, they will increase sediment deposition. Triggering events such as earthquakes and tsunamis will affect the state and thickness of sediments. Mass movement in these sediments will cause folds and thrust belt structures. This study also shows that the lateral sliding of Lake Lucerne caused deep and profound deformation of the basin-plain basement sediment adjacent to the slope, which is also the reason for the unique shape of Lake Lucerne. Historical reports from the 17th century documented two destructive tsunamis that spanned more than 5 m, affecting the proximal basin of Lake Lucerne (Hilbe et al, 2014). The research by Hilbe et al. also believes that earthquakes and tsunamis are significant as a common sedimentation process and as a natural hazard in fjord-type lakes and similar environments (Hilbe et al, 2014).