Lake Geneva Research Articles

Calcite precipitation: The forgotten piece of lakes' carbon cycle.

Lakes emit substantial amounts of carbon dioxide (CO2) into the atmosphere, but why they do remains debated. The long-standing vision of lakes as solely respirators of the organic matter leaking from the soils has been challenged by evidence that inorganic carbon produced by weathering of the catchment bedrock could also support lake CO2 emissions. How inorganic carbon inputs ultimately generate lake CO2 outgassing remains a blind spot. We develop and introduce a calcite module in a coupled one-dimensional physical-biogeochemical model that we use to simulate the carbon cycle of the large Lake Geneva over the past 40 years. We mechanistically demonstrate how the so-far neglected process of calcite precipitation boosts net CO2 emissions at the annual scale. Far from being anecdotal, we show that calcite precipitation could explain CO2 outgassing across various lakes globally, including some of the largest lakes in the world.

Unraveling Lake Geneva's hypoxia crisis in the Anthropocene

AbstractDespite global evidence of lake deoxygenation, its duration, timing, and impacts over decadal to centennial timescales remain uncertain. This study introduces a novel model approach using 150 yr of limnological and paleolimnological data to evaluate the anthropogenic impacts on deep oxygen in Lake Geneva. Results highlight an increase in oxygen consumption rates due to cultural eutrophication, initially triggering historical hypoxia, subsequently exacerbated by reduced winter mixing induced by climate change. Simulations of pre‐eutrophication conditions and future climate scenarios define safe operating spaces for the lake to thrive without severe hypoxia risk. Complete winter mixing and O2 recharge once every 3 yr can compensate the oxygen demand in Lake Geneva, even when exceeding 1.5 g O2 m−2 d−1. However, when complete winter mixing becomes less frequent, even consumption rates similar to those observed before eutrophication can cause persistent hypoxia, posing a significant threat to the survival of hypolimnetic aquatic life.

Strong bottom currents in large, deep Lake Geneva generated by higher vertical-mode Poincaré waves

Although internal seiches are ubiquitous in large, deep lakes, little is known about the effect of higher vertical-mode seiches on deepwater dynamics. Here, by combining entire summer season current and temperature observations and 3D numerical modeling, we demonstrate that previously undetected vertical mode-two and mode-three Poincaré waves in 309-meter deep Lake Geneva (Switzerland/France) generate bottom-boundary layer currents up to 4 cm s−1. Poincaré wave amphidromic patterns revealed three strong cells excited simultaneously. Weak hypolimnetic stratification (N2 ≈ 10−6s−2), typical of deep lakes, significantly modified the wave structure by shifting the lower vertical node in the lake’s center from ~75-meter depth (without stratification) to ~150-meter depth (with stratification). This shift induces shear in the middle of the hypolimnion and strengthens bottom currents, with important implications for hypolimnetic mixing and sediment-water exchange. Our findings demonstrate that classical concepts based on constant temperature layers cannot correctly characterize higher vertical-mode Poincaré seiches in deep lakes.

Adrien Rist (1841–1923), membre de la Société Médico-Psychologique (1881) et fondateur d’une maison de santé privée à Versailles « La Châtaigneraie » (1889) (Partie I)

Professor Edouard Rist (1871–1956), a former president of the Academy of Medicine (1948), wrote an unpublished text entitled “His Memories”. This text allows us to sketch the portrait of his father: Adrien Rist (1841–1923) and to review the professional career of this alienist doctor who always had a deep sense of loyalty and attachment to France and its culture. Coming from a family of surgeons, his grandfather Jean-Louis Rist (1769–1839) was a surgeon of the Grande-Armée like his uncle Côme Damien Rist (1760–1826) and their father Jean Népomucène Sébastien Rist (1725–1798) was too a surgeon in Wissembourg. It was under the July Monarchy that A. Rist (1841–1923) was born in Strasbourg. Raised in a Protestant family, he enrolled at the Military Health Service School in Strasbourg. He left the school after one year to enroll in the medical school of the same city. However, he finished his medical study in Paris. After his externship, he was accepted as an intern on December 26, 1864. Five years later (1869), he was a doctor of medicine and became the first one to make known in France the psychophysical law of Gustav Théodor Fechner (1801–1887), which bridges the gap between psychology and the exact sciences. Then, he returned to Strasbourg where he opened a medical practice and started to prepare for the aggregation in physics at the University of Göttingen (Germany). He stayed there long enough to fall in love with Emma Cornelia Gess (1848–1928), a native of Württemberg, to whom he married on April 5, 1870. Three months after his marriage, the war with Prussia broke out. During the conflict, his wife gave birth in Strasbourg to a boy named Edouard (1871–1956). Thus, his new family life and the Franco-Prussian war and its outcome deterred him from passing the aggregation. But also, A. Rist chooses to leave Alsace so as not to renounce his French nationality. After a brief stay in Le Havre (Normandy), he decided to expatriate to Switzerland. In order to be able to practice in this country, A. Rist passed the examinations in the canton of Vaud where he provided an important memorandum on the legislation of insane persons. In 1867, the Champ de l’Air Hospital for the insane was transferred to the Bois-de-Cery located near Lausanne where six years later (1873) a new hospital called “Asile de Cery” was inaugurated. Authorized to practice in Switzerland, A. Rist became in 1873 the first doctor-director of the Bois-de-Cery. A few years earlier, the first private psychiatric clinic in Romanisch Switzerland opened: La Métairie. In 1877, he became the director of this establishment located not far from the previous one at about forty kilometers away still on the banks of Lake Geneva. Board of Directors of this private establishment composed of a majority of Geneva bankers was able to receive about forty patients of well-to-do condition who came from all over the world. A. Rist lived there with his family and the organization at La Métairie was based on the participation of the insane in the family life of the doctor. A. Rist's children (Edouard, Charles, Elisabeth and Eve) founded the “Children's Society” which aimed to give concerts and theatrical performances to the patients of La Métairie. Also, they contributed when patients ran away. At the Métairie, A. Rist received the visit of Alexandrovitch Herzen (1839–1906) who was a professor of physiology at the medical faculty of Lausanne (1881) and whose father, Alexander Ivanovich Herzen (1812–1870) was the father of Russian populist socialism. However, the separation from his children who were studying in France and the tragic death of his daughter Elisabeth at the age of 17 were two factors that led to his return to France. In 1889, A. Rist and his wife decided to leave La Métairie. Rudolf Friedreich Fetscherin (1829–1892), a former assistant physician at the Waldau (Bern; 1859) succeeded him. A. Rist moved to Versailles near Paris where he opened a nursing home at 11 rue des Deux-Moulins: La Châtaigneraie.

Long‐range transport of littoral methane explains the metalimnetic methane peak in a large lake

AbstractIn large and stratified lakes, substantial methane stocks are often observed within the metalimnion. The origin of the methane (CH4) accumulated in the metalimnion during stratification, which can sustain significant emissions during convective mixing, is still widely debated. While commonly attributed to the transport of methane produced anaerobically ex situ, recent evidence suggests that oxic in situ methane production could also contribute to metalimnetic methane peaks. Here, we assessed the origin, that is, pelagic CH4 production or transport of sublittoral CH4 through the interflow, of metalimnetic methane in Lake Geneva, the largest lake in Western Europe. Microbial diversity data do not support the hypothesis of oxic methane production in the metalimnion. In contrast, both spatial and temporal surveys of methane show that maxima occur at depths and sites most affected by the Rhône River inflow. Methane δ13C values point to an anaerobic sublittoral methane source, within a biogeochemical hotspot close to the river delta region, and an efficient transport across several kilometers in a vertically well‐constrained metalimnion. Our current findings emphasize the indirect role of river interflows for the long‐range transport of CH4 produced in sediment biogeochemical hotspots, even for large lakes where sublittoral habitats represent a fairly limited fraction of the lake volume.

Genetic identification, morphology and distribution of Natrixhelvetica subspecies in southern and western Switzerland (Reptilia, Squamata, Serpentes).

Most of Switzerland is inhabited by the nominotypical subspecies of the barred grass snake (Natrixhelveticahelvetica), which is characterized by mitochondrial DNA lineage E. Only in the northeast of the country, the common grass snake (N.natrix) occurs and hybridizes with N.h.helvetica in a narrow contact zone. However, we discovered that in southern and western Switzerland barred grass snakes representing another mtDNA lineage (lineage C) are widely distributed. Lineage C is typical for Alpine populations of the southern subspecies N.h.sicula. Our microsatellite analyses of the Swiss samples revealed differences between the two subspecies and also a substructure with two clusters in each subspecies. Furthermore, we discovered a contact and hybrid zone of N.h.helvetica and N.h.sicula along the northern shore of Lake Geneva and also confirm that interbreeding with alien common grass snakes (N.n.moreotica, mtDNA lineage 7) occurs there. This finding is of concern for nature conservation and measures should be taken to prevent further genetic pollution. Using morphometrics, we found no differences between the two subspecies of N.helvetica, while N.natrix was slightly distinct from N.helvetica.

Combining multi-species connectivity modelling with expert knowledge to inform the green infrastructure design

The Canton of Geneva is currently working on defining and mapping its green infrastructure (GI), in order to implement its biodiversity protection directives by 2030. Ecological connectivity is considered in the definition of the GI, as it is a key factor in managing the species extinction risk. It is considered a vital aspect of the landscape, because it can indicate how landscape facilitates or influences wildlife movement. In order to assess connectivity, animal movement data is essential as it provides precise behavioral information on the movements of organisms. Unfortunately, this kind of data is often missing or available only at local scales. Ecologists therefore must deal with a lack of data when trying to supply useful spatially explicit ecological models for conservation planning. To help managers in their efforts to define the GI, an alternative is to rely on local expert knowledge. We have thus applied a structured analytical framework to parameterize an ecological connectivity model combining expert opinion with three of the most used methods to assess ecological connectivity: graph theory, circuit theory and cumulative costs algorithm. By considering a selection of focal species representative of the different ecological requirements and movement behaviour of the regional wildlife, maps of priority areas for the promotion of ecological connectivity were obtained for red deer, roe deer, brown hare and common toad. We estimated the principal cross-border corridors at the scale of the Greater Geneva region, between France and Switzerland. Three transboundary high priority areas were highlighted in our maps. The localization of these areas is principally characterized by natural habitats such as forests, grasslands and freshwater ecosystems, but depends also on the agricultural areas. The principal natural barrier to animal movement is Lake Geneva, and the principal human barriers to movement are human settlements and highways that impede the regional displacements for all of the species. Considering the highways, the barrier effect could be diminished thanks to the recent construction of wildlife overpasses. We have seen that a close collaboration between local experts and ecological modelers is necessary when interpreting the conservation value of land potentially capable of promoting wildlife ecological connectivity. When implementing the GI, it will be useful to combine our models with field campaigns to measure the real functionality of the estimated priority areas, in order to guarantee the success of conservation actions.

Combined Earth observations reveal the sequence of conditions leading to a large algal bloom in Lake Geneva

Freshwater algae exhibit complex dynamics, particularly in meso-oligotrophic lakes with sudden and dramatic increases in algal biomass following long periods of low background concentration. While the fundamental prerequisites for algal blooms, namely light and nutrient availability, are well-known, their specific causation involves an intricate chain of conditions. Here we examine a recent massive Uroglena bloom in Lake Geneva (Switzerland/France). We show that a certain sequence of meteorological conditions triggered this specific algal bloom event: heavy rainfall promoting excessive organic matter and nutrients loading, followed by wind-induced coastal upwelling, and a prolonged period of warm, calm weather. The combination of satellite remote sensing, in-situ measurements, ad-hoc biogeochemical analyses, and three-dimensional modeling proved invaluable in unraveling the complex dynamics of algal blooms highlighting the substantial role of littoral-pelagic connectivities in large low-nutrient lakes. These findings underscore the advantages of state-of-the-art multidisciplinary approaches for an improved understanding of dynamic systems as a whole.

Short-Term Coastal Impact Of Lakeshore For Natural Reserve Protection

The site of Grangettes, which is registered as a natural reserve of national and international importance for waterowl and migratory birds (i.e. OROEM site), is considered the last part of the Swiss lakeshore of Lake Geneva that remains natural. This area hosts a wide variety of coastal ecosystems, containing significant natural values located both in aquatic and in terrestrial areas of the reserve. Because of repetitive localized dredging activities of the lake bottom since the last century, a severe withdraw of the shoreline and its associated natural values has been observed between 1964 and 2001 close to the « Gros Brasset » dredge pit.

Deepwater Renewal in a Large, Deep Lake (Lake Geneva): Identifying and Quantifying Winter Cooling Processes Using Heat Budget Decomposition

AbstractWintertime deepwater renewal, which is important for heat–oxygen–nutrient exchange in lakes, is traditionally considered to be mainly driven by 1D vertical convective cooling. However, differential cooling between shallow and deep waters can produce density currents that flow into deep layers. In order to determine the role that these two cooling processes play in deepwater renewal, field measurements and 3D numerical modeling were combined to investigate heat content dynamics in Lake Geneva's large basin, the Grand Lac (maximum depth 309 m), during an exceptionally cold air spell in early 2012 where complete overturning had been reported. In a novel approach, the heat budget of the lake was decomposed, which allowed the identification and quantification of the heat budget components. The heat budget decomposition revealed that vertical convective cooling only penetrated to 200 m and that lateral advection was not only caused by density currents being discharged from the shallow littoral zone of the Grand Lac, but also from the Lake's shallow Petit Lac basin (maximum depth 75 m); the latter was found to be the main driver of heat content decrease in the deep layers of the Grand Lac below ∼200‐m depth. These findings provide unique insight into heat exchange processes that cannot be obtained from field data or numerical simulations alone. Heat budget decomposition proved to be a powerful, universally applicable tool for quantifying the contribution of alternative deepwater renewal processes. This is important, since deepwater renewal by convective cooling is weakening due to persistent global warming.

Influence of Concentration, Surface Charge, and Natural Water Components on the Transport and Adsorption of Polystyrene Nanoplastics in Sand Columns.

Information about the influence of surface charges on nanoplastics (NPLs) transport in porous media, the influence of NPL concentrations on porous media retention capacities, and changes in porous media adsorption capacities in the presence of natural water components are still scarce. In this study, laboratory column experiments are conducted to investigate the transport behavior of positively charged amidine polystyrene (PS) latex NPLs and negatively charged sulfate PS latex NPLs in quartz sand columns saturated with ultrapure water and Geneva Lake water, respectively. Results obtained for ultrapure water show that amidine PS latex NPLs have more affinity for negatively charged sand surfaces than sulfate PS latex NPLs because of the presence of attractive electrical forces. As for the Geneva Lake water, under natural conditions, both NPL types and sand are negatively charged. Therefore, the presence of repulsion forces reduces NPL's affinity for sand surfaces. The calculated adsorption capacities of sand grains for the removal of both types of NPLs from both types of water are oscillating around 0.008 and 0.004 mg g-1 for NPL concentrations of 100 and 500 mg L-1, respectively. SEM micrography shows individual NPLs or aggregates attached to the sand and confirms the limited role of the adsorption process in NPL retention. The important NPL retention, especially in the case of negatively charged NPLs, in Geneva Lake water-saturated columns is related to heteroaggregate formation and their further straining inside narrow pores. The presence of DOM and metal cations is then crucial to trigger the aggregation process and NPL retention.

Time-first approach for land cover mapping using big Earth observation data time-series in a data cube – a case study from the Lake Geneva region (Switzerland)

ABSTRACT Accurate, consistent, and high-resolution Land Use & Cover (LUC) information is fundamental for effectively monitoring landscape dynamics and better apprehending drivers, pressures, state, and impacts on land systems. Nevertheless, the availability of such national products with high thematic accuracy is still limited and consequently researchers and policymakers are constrained to work with data that do not necessarily reflect on-the-ground realities impending to correctly capture details of landscape features as well as limiting the identification and quantification of drivers and rate of change. Hereafter, we took advantage of the Switzerland’s official LUC statistical sampling survey and dense time-series of Sentinel-2 data, combining them with Machine and Deep Learning methods to produce an accurate and high spatial resolution land cover map over the Lake Geneva region. Findings suggest that time-first approach is a valuable alternative to space-first approaches, accounting for the intra-annual variability of classes, hence improving classification performances. Results demonstrate that Deep Learning methods outperform more traditional Machine Learning ones such as Random Forest, providing more accurate predictions with lower uncertainty. The produced land cover map has a high accuracy, an improved spatial resolution, while at the same time preserving the statistical significance (i.e. class proportion) of the official national dataset. This work paves the way towards the objective to produce a yearly high resolution land cover map of Switzerland and potentially implement a continuous land change monitoring capability. However further work is required to properly address challenges such as the need for increased temporal resolution for LUC information or the quality of training samples.

The uneven distribution of refugial endemics across the European Alps suggests a threefold role of climate in speciation of refugial populations

AbstractA little more than 10% of the vascular plant flora native to the European Alps is endemic to this area. It has long been noticed that the distribution of endemics across the Alps is very uneven. While most endemics are found along the southern edge of the Alps, with some also on its western, eastern, and northeastern edges, the northern edge of the Alps more or less between Lake Geneva in the west and Lake Traun in the east harbours almost no endemics. The distribution of endemics in the Alps has often been related to the location of glacial refugia. Accordingly, the virtual absence of endemics from the northern edge of the Alps has been explained with the unsuitability of climatic conditions for glacial survival of alpine plants there. After discussing evidence for the existence of glacial refugia for alpine species along the northern edge of the Alps and north of the Alps, I will examine how these refugia differed from refugia along the southern edge of the Alps. I conclude that the uneven distribution of endemics in the Alps is best explained by the different climate through time north and south of the Alps. These climatic differences affected the spatial structure and extent of refugia, the length of isolation of refugial populations, and selective conditions in refugia.

From Particles to Flocs: Revealing Where Flocculation Occurs in the Nearfield of a Negatively‐Buoyant River Plume in a Large Lake (Lake Geneva)

AbstractThe dynamics of sediments entering lakes in river plumes is virtually unknown. This field study provides unprecedented evidence of the initiation and evolution of suspended sediment flocculation in the nearfield of the negatively‐buoyant Rhône River plume, flowing as interflow in the thermocline of stratified Lake Geneva. Sediment floc property changes (formation, size, composition, shape) with depth and distance from the mouth, were determined by combining digital holographic camera LISST‐HOLO data with full‐depth in situ profiles of particle size (LISST‐100X), density, turbidity, currents and water samples taken along the plume path. The total suspended matter volume of inflowing Rhône River waters (∼155 mg l−1) mostly consisted of clays (<4 μm), very fine silts (4–8 μm) and small contributions of microflocs (20–100 μm). This composition was also found in the interflow plume core. Above the plume, in the epilimnion, fine silts, microflocs and numerous phytoplanktonic organisms (∼200 μm) were observed, representative of the lake background. High levels of shear (15–27 s−1) and turbulence occurred in the shear layer that formed between the interflow bottom and the hypolimnion below. It was found that macroflocs only formed in this shear layer. In the hypolimnion, sediment load was the lowest and macroflocs (up to ∼300 μm) composed of inorganic particles were dominant. The size of the largest flocs was limited by the size of the smallest turbulent eddies determined by the Kolmogorov microscale. Floc 3D fractal dimensions of ∼2.1–2.5 suggest an intermediate shape complexity between marine snow and sludge flocs.

Waterborne Virus Transport and Risk Assessment in Lake Geneva Under Climate Change

AbstractClimate changes influence lake hydrodynamics and radiation levels and thus may affect the fate and transport of waterborne pathogens in lakes. This study examines the impact of climate change on the fate, transport, and associated risks of four waterborne viruses in Lake Geneva. We used a coupled water quality‐microbial risk assessment model to estimate virus concentrations and associated risks to recreational water users for each month in 2019 and 2060. Long‐term hydrodynamic simulations suggested that although the annual hydrodynamic transport pattern of Lake Geneva will remain relatively stable, a 1.9°C increase of lake surface water temperature can be expected, while a slight decrease in lake current velocity may occur. The subsequent effect on the fate and transport of the four enteric viruses was found to vary by time of year. During warmer periods, the increase of virus inactivation due to higher water temperature and stronger solar radiation at the earth's surface will compensate for the additional virus discharge brought about by population growth over the time period considered, whereas during winter the virus concentration near the lake shore and the associated infection probabilities risks are likely to increase due to population growth. Additionally, the current estimation of virus inactivation rate shows significant variability, which has a more substantial effect on enteric virus concentrations in the lake compared with changing climate parameters. Overall, the study suggests that future risks posed by enteric viruses with recreational water users near popular beaches around Lake Geneva will likely remain similar to current risks and accurate estimation of the environmental inactivation of viruses is crucial for predicting the fate of enteric viruses in the aquatic system.

Impact of fishing activities on the population dynamics of European whitefish in four peri-alpine lakes

Inland fisheries play a crucial role in socio-economic activities and food production. However, these fisheries are often less intensively monitored and studied than marine fisheries. In the past two decades, important fluctuations in European whitefish (Coregonus lavaretus) landings have been observed in four peri-alpine lakes in France and Switzerland. To better gauge the impact of fishing removal, a multi-lakes Delay-Difference model was developed and adapted to these fisheries. A hierarchical state-space Bayesian framework was used to integrate stochasticity for each process and incorporate diverse data. The model gave estimates of time series for biomass, recruitment, stage-structured landings, and fishing mortality, as well as estimates of natural mortality rate, Brody growth coefficient and mean recruitment productivity. Differences in the estimates of variables predicted by the model were observed among lakes. Negative impacts of exploitation have been highlighted for Lakes Geneva, Bourget, and Annecy. Low levels of biomass under high fishing mortality rates were observed, while landings tended to increase under lower mortality rates. Lakes Geneva and Bourget outputs suggest stocks were impacted by fishing activities and that fishing effort reduction could ultimately increase yields. Lake Annecy abundance and landings trends increased after 2010, suggesting management strategies that focused on effort reduction were successful. Lake Neuchâtel stock abundance was low after 2017 and probably more fragile due to low biomass levels and recruitment. The observed changes in European whitefish biomass cannot be attributed solely to fishing, suggesting that environmental factors may also influence recruitment success alongside the impacts of fishing pressure.

Winter is not coming: evaluating impacts of changing winter conditions on coregonine reproductive phenology

Fishes in northern latitude lakes are at risk from climate-induced warming because the seasonality in water temperature is degrading, which can change ecosystem properties and the phenology of life-history events. Temperature-dependent embryo development models were developed for a group of cold, stenothermic fishes (Salmonidae Coregoninae) to assess the potential impacts of climate-induced changes in water temperature on cisco (Coregonus artedi) from two populations in Lake Superior (Apostle Islands [USA] and Thunder Bay [Canada]) and one in Lake Ontario (USA), vendace (C. albula) in Lake Southern Konnevesi (Finland), and European whitefish (C. lavaretus) in lakes Southern Konnevesi, Constance (Germany), Geneva (France), and Annecy (France). Water temperatures for each study group were simulated and changes in reproductive phenology across historic (1900–2006) and three future climatic-warming scenarios (2007–2099) were investigated. Models predicted that increases in water temperatures are likely to cause delayed spawning, shorter embryo incubation durations, and earlier larval hatching. Relative changes increased as warming scenarios increased in severity and were higher for littoral as compared to pelagic populations. Our simulations demonstrated that slower cooling in the autumn and (or) more rapid warming in spring can translate into substantial changes in the reproductive phenology of coregonines among our study groups. We expect that the changes in reproductive phenology predicted by our models, in the absence of thermal or behavioral adaptation, will have negative implications for population sustainability.

Assessment of Potential Threats to Arctic Char in Lake Geneva: Bacterial Kidney Disease (BRD)

Evaluating the Impact of Bacterial Kidney Disease on Arctic Char Populations in Lake Geneva: A Critical Analysis – This study investigates a significant ecological concern: the notable reduction in Arctic char harvests from Lake Geneva since 1998. This decline is particularly perplexing given the consistent application of existing fishing regulations and ongoing restocking initiatives. Central to this research is the exploration of the hypothesis that Bacterial Kidney Disease (BKD) plays a pivotal role in escalating mortality rates among these fish populations. Utilizing advanced epistemological methodologies, our investigation rigorously identified the presence of BKD through laboratory analyses. Notably, the incidence of BKD in Lake Geneva’s Arctic char was found to be relatively minimal, with a prevalence of merely 0.6\% in 2004, diminishing to 0\% by 2005. Consequently, this study concludes that the presence of BKD, in isolation, is insufficient to account for the substantial decrease in Arctic char catches observed in the region. These findings prompt further research into alternative factors that might be influencing the decline of the Arctic char in Lake Geneva.

The Guardian of Lake Geneva: From Glacial Epochs to the Era of Global Warming

The manuscript presents an in-depth exploration of the Arctic char, a native species in Lake Geneva, tracing its lineage back to the post-glacial era approximately 13,000 years ago. This study delves into the historical documentation of the species, starting from a notable manuscript in 1150, and continuing through various historical records, including acts and laws. The systematic classification of the Arctic char in Lake Geneva has been a topic of considerable scientific discourse, marked by differing species descriptions over time. Current consensus recognizes Salvelinus alpinus as the sole species inhabiting the lake. The research also examines the socio-economic aspects of Arctic char fishing in the region, highlighting its dual role as both an economic resource and a recreational pursuit. Notably, the manuscript addresses the significant surge in fishing yields during the 1990s, followed by a persistent decline in recent years. This study not only provides a historical perspective on the Arctic char but also underscores the dynamic interplay between environmental changes and fishing activities in Lake Geneva.

Temporal Changes in the Physico chemical Composition of Lake Geneva from 1957 to the Present

This manuscript presents an exhaustive analysis of a physicochemical dataset collected from Lake Geneva since 1957, offering a detailed exploration of its long-term environmental evolution. This study encompasses an array of cycles and trophic states that the lake has undergone. A critical finding is the significant influence of human activities within the catchment area, notably the introduction of substantial quantities of nutrients, especially phosphorus, into the lake’s ecosystem. This anthropogenic impact culminated in a marked ecological decline between the 1960s and 1970s, characterized by a phase of eutrophication. This period saw a surge in algal blooms and a consequent decrease in water transparency. In the 1970s, strategic interventions were implemented to address this environmental challenge. These measures, including the enhancement of phosphorus treatment at sewage facilities in the catchment area and the nationwide ban on phosphated detergents in Switzerland, proved instrumental in reducing the influx of nutrients. Consequently, a significant reduction in the lake’s phosphorus levels was observed by the 1980s. The lake is currently undergoing a re-oligotrophication process, with phosphorus concentrations indicating a mesotrophic state. However, it is noteworthy that the biological components of the lake are exhibiting a slower recovery rate in adapting to reduced nutrient levels, in contrast to the more immediate response noted during the eutrophication phase. Despite the progress achieved, ongoing vigilance and efforts are essential to continuously monitor, identify, and manage potential sources of phosphorus pollution. This proactive approach is vital for maintaining the lake’s ecological balance and ensuring it remains free from significant algal proliferation.