Lake States Research Articles

Multiple signs of ecosystem change in the zooplankton community of a large temperate lake

Large lakes, such as Lake Simcoe, Ontario, Canada, are undergoing significant change due to local and global stressors. Uni- and multivariate analyses of Lake Simcoe's zooplankton community from 1986 to 2012 indicated multiple events of ecosystem change that were synchronous across three lake stations . In the mid-1990s, shifts in zooplankton species abundance and richness, and total cladoceran body size were strongly correlated with the invasion of the zooplanktivore, Bythotrephes cederstroemii. In the early 2000s, additional shifts in zooplankton abundance, as well as copepod body size, coincided with increased water clarity (linked to filter feeding by the invader Dreissena polymorpha) and hypolimnetic water temperature. Further community changes occurred in the 2000s when Bythotrephes declined and many vulnerable cladoceran species recovered. However, the Lake Simcoe community did not fully return to its pre-invasion state as the cold-water herbivores, Daphnia longiremis and Daphnia pulicaria, remained absent. The Lake Simcoe zooplankton community illustrates ongoing ecosystem change that propagated throughout the lake food web and may be reflected in other lakes experiencing global stressors of climate change and species invasions.

Eco-assessment of phytoplankton composition in relation to environmental conditions of saltwater and freshwater lakes in the Konya Closed Basin (Türkiye)

Eco-assessment of phytoplankton composition in relation to environmental conditions of saltwater and freshwater lakes in the Konya Closed Basin (Türkiye)

Comparative Study on the Determination of Chlorophyll-a in Lake Phytoplankton by a YSI Multi-Parameter Water Quality Meter and Laboratory Spectrophotometric Method

Algal blooms caused by eutrophication are a major global problem, and the monitoring and prediction of algal densities in lakes are important indicators of eutrophication management. However, the reliability of the commonly used chlorophyll-a (Chl-a) to characterize phytoplankton density in lake environments needs to be further investigated. In this paper, we sampled and analyzed 365 samples from nine plateau lakes in Yunnan Province during the dry and rainy seasons. The Chl-a data measured by the laboratory spectrophotometric method and the portable YSI multi-parameter water quality meter (YSI) directly used in the field were compared, and regression analysis and correlation analysis with phytoplankton density were performed. Most of the Chl-a values measured by the laboratory instrument were greater than those measured by the YSI, and the correlation between the two methods was weak (0.492, p < 0.001). The correlation between Chl-a and phytoplankton density measured by the YSI reached 0.67 (p < 0.001) in the dry season, while the laboratory methods used to measure Chl-a to characterize phytoplankton density may have led to an overestimation of phytoplankton density due to nonspecific sources of Chl-a. However, both methods are relatively inaccurate for characterizing phytoplankton density. For different trophic states of lakes, nutrient concentration changes affect the Chl-a concentration of phytoplankton. During different seasons, changes in the fluorescence intensity of phytoplankton in response to environmental conditions prevent the YSI results from reflecting the authentic phytoplankton density. Furthermore, high species diversity can lead to inconsistent changes in Chl-a and phytoplankton because the content of Chl-a in individual cells of different phytoplankton is different. The relationship between Chl-a and phytoplankton density was species specific. Therefore, when applying Chl-a to characterize phytoplankton density in lakes, it is necessary to consider environmental conditions, phytoplankton community structure and other practical conditions. In addition, laboratory analytical methods and instrumental techniques and instruments need to be improved.

Cladocera and Geochemical Variables from Core Sediments Show Different Conditions of Hungarian Lakes

Cladocera and Geochemical Variables from Core Sediments Show Different Conditions of Hungarian Lakes

Size Distributions of Microplastics in the St Louis Estuary and Western Lake Superior.

Identifying the sources and fate of microplastics in natural systems has garnered a great deal of attention because of their implications for ecosystem health. This work characterizes the size fraction, morphology, color, and polymer composition of microplastics in western Lake Superior and its adjacent harbor sampled in August and September 2021. The results reveal that the overall microplastic counts are similar, with the harbor stations ranging from 0.62 to 3.32 microplastics per liter and the lake stations ranged from 0.83 to 1.4 microplastics per liter. However, meaningful differences between the sample locations can be seen in the size fraction trends and polymer composition. Namely, the harbor samples had relatively larger amounts of the largest size fraction and more diversity of polymer types, which can be attributed to the urbanized activity and shorter water residence time. Power law size distribution modeling reveals deviations that help in the understanding of potential sources and removal mechanisms, although it significantly underpredicts microplastic counts for smaller-sized particles (5-45 μm), as determined by comparison with concurrently collected microplastic samples enumerated by Nile Red staining and flow cytometry.

Investigating the Impact of Large Lakes on Local Precipitation: Case Study of Lake Urmia, Iran

Large lakes face considerable challenges due to human activities and climate change, impacting local weather conditions and ecosystem sustainability. Lake Urmia, Iran’s largest lake and the world’s second-largest saltwater lake, has undergone a substantial reduction in water levels, primarily due to drought, climate change, and excessive irrigation. This study focuses on the potential repercussions on local climate conditions, particularly investigating the impact of moisture sources, evaporation from lake surfaces, and evapotranspiration from agricultural activities, on local convection rainfall. The prevailing westerly winds in the basin suggest a hypothesis that this moisture is transported eastward within the basin, potentially leading to local precipitation as it ascends to higher altitudes near the eastern basin border. To validate this hypothesis, climate data from 1986 to 2017 from the Sarab meteorological station (east of the lake basin, influenced by local precipitation) and Saqez meteorological station (south of the basin, unaffected by local precipitation) were analyzed. The impact of lake water level reduction was assessed by categorizing data into periods of normal lake conditions (1986–1995) and water level reduction (1996–2017). Additionally, the MSWEP global precipitation product was used to examine the precipitation distribution in the entire basin over the entire period and sub-periods. The findings indicate Lake Urmia’s significant influence on convective rainfall in the eastern basin, especially during the summer. Despite decreasing lake levels from 1996 to 2017, convective rainfall in the eastern basin increased during the summer, suggesting intensified agricultural irrigation, particularly in hot seasons.

COMPARATIVE ANALYSIS OF PRISMA HYPERSPECTRAL AND SENTINEL-2 MULTISPECTRAL IMAGES FOR CHLOROPHYLL-A AND TURBIDITY MAPPING OF TAAL LAKE

Abstract. Freshwater bodies like Taal Lake play a pivotal role in providing essential resources like fresh drinking water and in supporting local livelihoods. This study aimed to examine the environmental conditions of Taal Lake by quantifying chlorophyll-a (chl-a) and turbidity levels with Water Colour Simulator (WASI) and water quality indices, specifically with Sentinel-2 and PRISMA imagery. The results from the satellite image-derived data revealed discernible variations in chlorophyll-a and turbidity concentrations across different regions of Taal Lake. Higher chlorophyll-a was consistently observed in the western regions (1.3–5.9 μg/L for Sentinel-2; 1.4–5.4 μg/L for PRISMA), while lower concentrations were found in the south (1.7–3.4 μg/L for Sentinel-2; 1.9–3.3 μg/L for PRISMA). Meanwhile, turbidity values were higher in the eastern and northeastern parts (0.15–0.59 mg/L for Sentinel-2; 0.13–0.51 mg/L for PRISMA). Water quality indices (NDTI & NDCI) also supported these findings. The findings of this comparative analysis between PRISMA hyperspectral and Sentinel-2 multispectral imagery demonstrate the potential of both satellite systems in providing valuable insights into the spatial distribution of water quality parameters in Taal Lake. Nonetheless, discrepancies observed in the scatter plots and inversion failures in PRISMA underscore the need for further research and refinement in utilizing PRISMA data with the WASI model. This study highlights the significance of freshwater bodies and the importance of monitoring their health for the well-being of communities and the environment.

An innovative method based on Gaussian cloud distribution and sample information richness for eutrophication assessment of Yangtze's lakes and reservoirs under uncertainty.

The precise assessment of a water body's eutrophication status is essential for making informed decisions in water environment management. However, conventional approaches frequently fail to consider the randomness, fuzziness, and inherent hidden information of water quality indicators. These would result in an unreliable assessment. An enhanced method was proposed for the eutrophication assessment under uncertainty in this study. The multi-dimension gaussian cloud distribution was introduced to capture the randomness and fuzziness. The Shannon entropy based on various sample size and trophic levels was proposed to maximize valuable information hidden in the datasets. Twenty-seven significant lakes and reservoirs located in the Yangtze River Basin were selected to demonstrate the proposed method. The sensitivity and consistency were used to evaluate the accuracy of the proposed method. Results indicate that the proposed method has the capability to effectively assess the eutrophication status of lakes and reservoirs under uncertainty and that it has a better sensitivity since it can identify more than 33-50% trophic levels compared to the traditional methods. Further scenario experiments analysis revealed that the sample information richness, i.e., sample size and the number of trophic levels is of great significance to the accuracy/robustness of the method. Moreover, a sample size of 60 can offer the most favorable balance between accuracy/robustness and the monitoring expenses. These findings are crucial to optimizing the eutrophication assessment.

Breeding waterbird species as ecological indicators of shifts from turbid to clear water conditions in northwest European shallow eutrophic lakes

AbstractWe used biological and physical responses at 71 shallow waterbodies with contrasting nutrient levels undergoing recovery from eutrophication to predict potential changes in waterbird species abundance, an important component of lake ecosystems. These general predictions were tested using 28 years of breeding waterbird data from three Danish shallow eutrophic lakes, comparing species-specific responses to improved nutrient and water transparency in two lakes with a third where conditions remained constantly suitable for breeding waterbirds. We predicted positive responses to improved water quality from pursuit diving predators (three grebe species), a specialist zooplankton feeder (northern shoveler Anas clypeata) and waterbirds feeding on (common pochard Aythya ferina) or within (tufted duck A. fuligula) submerged macrophyte underwater canopies. These species were characterised by positive waterbird community composition changes (using Principal Components Analysis) associated with decreasing nutrient loading and increasing water transparency at two lakes, with no change in breeding waterbird community at the third. Secchi depth explained 73–95% of variance in both PC axes at both restored lakes, but not at the third, suggesting water transparency was the major factor driving waterbird community composition. These examples show predicting waterbird species-specific responses to management can usefully direct the use of breeding waterbirds as indicator species.

Long-term monitoring chlorophyll-a concentration using HJ-1 A/B imagery and machine learning algorithms in typical lakes, a cold semi-arid region.

Chlorophyll a (Chl-a) in lakes serves as an effective marker for assessing algal biomass and the nutritional level of lakes, and its observation is feasible through remote sensing methods. HJ-1 (Huanjing-1) satellite, deployed in 2008, incorporates a CCD capable of a 30 m resolution and has a revisit interval of 2 days, rendering it a superb choice or supplemental sensor for monitoring trophic state of lakes. For effective long-term and regional-scale mapping, both the imagery and the evaluation of machine learning algorithms are essential. The several typical machine learning algorithms, i.e., Support Vector Regression (SVR), Gradient Boosting Decision Trees (GBDT), XGBoost (XGB), Random Forest (RF), K-Nearest Neighbor (KNN), Kernel Ridge Regression (KRR), and Multi-Layer Perception Network (MLP), were developed using our in-situ measured Chl-a. A cross-validation grid to identify the most effective hyperparameter combinations for each algorithm was used, as well as the selected optimal superparameter combinations. In Chl-a mapping of three typical lakes, the R2 of GBDT, XGB, RF, and KRR all reached 0.90, while XGB algorithm also exhibited stable performance with the smallest error (RMSE = 3.11 μg/L). Adjustments were made to align the Chl-a spatial-temporal patterns with past data, utilizing HJ1-A/B CCD images mapping through XGB algorithm, which demonstrates its stability. Our results highlight the considerable effectiveness and utility of HJ-1 A/B CCD imagery for evaluation and monitoring trophic state of lakes in a cold arid region, providing the application cases contribute to the ongoing efforts to monitor water qualities.

Characterizing the Impact of Cyanobacterial Blooms on the Photoreactivity of Surface Waters from New York Lakes: A Combined Statewide Survey and Laboratory Investigation.

Cyanobacterial blooms introduce autochthonous dissolved organic matter (DOM) into aquatic environments, but their impact on surface water photoreactivity has not been investigated through collaborative field sampling with comparative laboratory assessments. In this work, we quantified the apparent quantum yields (Φapp,RI) of reactive intermediates (RIs), including excited triplet states of dissolved organic matter (3DOM*), singlet oxygen (1O2), and hydroxyl radicals (•OH), for whole water samples collected by citizen volunteers from more than 100 New York lakes. Multiple comparisons tests and orthogonal partial least-squares analysis identified the level of cyanobacterial chlorophyll a as a key factor in explaining the enhanced photoreactivity of whole water samples sourced from bloom-impacted lakes. Laboratory recultivation of bloom samples in bloom-free lake water demonstrated that apparent increases in Φapp,RI during cyanobacterial growth were likely driven by the production of photoreactive moieties through the heterotrophic transformation of freshly produced labile bloom exudates. Cyanobacterial proliferation also altered the energy distribution of 3DOM* and contributed to the accelerated transformation of protriptyline, a model organic micropollutant susceptible to photosensitized reactions, under simulated sunlight conditions. Overall, our study provides insights into the relationship between the photoreactivity of surface waters and the limnological characteristics and trophic state of lakes and highlights the relevance of cyanobacterial abundance in predicting the photoreactivity of bloom-impacted surface waters.

The Antarctic Subglacial Hydrological Environment and International Drilling Projects: A Review

Subglacial lakes and hydrological systems play crucial roles in Antarctic subglacial hydrology, water balance, subglacial geomorphology, and ice dynamics. Satellite altimetry has revealed that some recurrent water exchange occurs in subglacial lakes. They are referred to as ’active lakes’, which prominently influence a majority of subglacial hydrological processes. Our analysis indicates that active subglacial lakes are more likely to be situated in regions with higher surface ice flow velocities. Nevertheless, the origin of subglacial lakes still remains enigmatic and uncertain. They could have potential associations with geothermal heat, ice sheets melting, and ice flow dynamics. Subglacial lake drilling and water sampling have the potential to provide valuable insights into the origin of subglacial lakes and subglacial hydrological processes. Moreover, they could also offer unique opportunities for the exploration of subglacial microbiology, evolution of the Antarctic ice sheets, and various fundamental scientific inquiries. To date, successful drilling and sampling has been accomplished in Lake Vostok, Lake Mercer, and Lake Whillans. However, the use of drilling fluids caused the water sample contamination in Lake Vostok, and the drilling attempt at Lake Ellsworth failed due to technical issues. To explore more of the conditions of the Antarctic subglacial lakes, the Lake Centro de Estudios Científicos (Lake CECs) and Lake Snow Eagle (LSE) drilling projects are upcoming and in preparation. In this study, we aim to address the following: (1) introduce various aspects of Antarctic subglacial lakes, subglacial hydrological elements, subglacial hydrology, and the interactions between ice sheets and the ocean; and (2) provide an overview and outlook of subglacial lakes drilling projects.

Effects of constant high water levels in winter on waterbird diversity in Caizi Lakes: A functional perspective

The middle and lower Yangtze River floodplain lakes are important stopover and wintering sites for migratory birds on the East Asian–Australasian Flyway. The periodic water level fluctuation of the lakes plays a critical role in the aggregation of waterbirds. However, the construction of a series of gates and dams has impeded the hydrological connectivity between rivers and lakes and disrupted the natural water level fluctuation patterns of lakes. The water level status of lakes influences habitat utilization by waterbirds. In recent years, Caizi Lakes, the gate-controlled lakes connected to the Yangtze River due to the need for water level regulation requirements, has experienced sustained high water levels in winter, which can reduce habitat quality and in turn influence waterbirds activity. In the present study, wintering waterbirds in Caizi Lakes were surveyed during the 2021–2022 (W1) and 2022–2023 (W2) wintering periods. Moreover, we explored the effects of constant high water levels in winter on waterbird assemblages by comparing species richness, abundance, and functional alpha and beta diversity. Correlation analyses were then performed to elucidate the relationship between habitat factors and water level changes during the wintering period of migratory waterbirds and between changes in various habitat factors and wintering waterbird assemblages under different hydrological conditions. The results showed that functional beta diversity was more sensitive to changes in waterbird assemblages in Caizi Lakes than functional alpha diversity. Moreover, constant high water levels in the mid-wintering period decreased suitable habitats for wintering waterbirds, increased functional turnover among waterbird assemblages, increased total dissimilarity among assemblages significantly, and decreased the level of functional nestedness significantly. Additionally, the areas of the three wetland habitats in Caizi Lakes were significantly correlated with water level changes during W1 and relatively less affected by water level changes under constant high water level conditions during W2. The changes in habitat area were influenced primarily by anthropogenic activities, with an increase in meadow area favorable for species richness and abundance, as well as functionally nested components. Water level regulation should take into consideration the natural hydrological rhythms of the declining water level to ensure that adequate and suitable habitats are provided for wintering waterbirds.

The theory of the regional security complex — Case study, the riparian states of the Black Sea

Known in Antiquity as the Pontus Euxinus, the Black Sea has been the bridge between European and Eastern civilizations since ancient times. Possessing a multi-varied mosaic of cultures, the Black Sea area has facilitated over the centuries, both the development of commercial and political relations and the maintenance and production of conflicts, being like the Sword of Damocles. Located at the intersection of three security zones (Euro-Atlantic, Russian, and Eastern), the Black Sea is currently a vulnerable space in terms of security. Heir to Byzantine culture, most of the riparian states have a complicated internal and external policy, being caught between the idealism of the Western world and the realism of the Eastern European space. At the same time, the revisionism of the Russian Federation and Turkey in terms of foreign policy will also mean a change in the dynamics of the relations between the states bordering the Black Sea, which could result either in its return to the status of a Russian lake or in a division of the spheres of influence between the Russian Federation and Turkey. In this sense, in order to analyze the future security dynamics of the riparian states, we used the theory of the regional security complex, which we consider very appropriate in our study of the Black Sea region.

The Dialectics of Nature–Human Conflicts for Sustainable Water Security

How humans use and manage water resources under climate change conditions threatens water security, which means risking the availability of enough good-quality water for everybody and for nature’s flora and fauna. Integrated Water Resources Management is a state-of-the-art water management model. After 20 years in use, the application of this model failed to achieve its primary goal in many countries, i.e., ensuring the good ecological status of rivers, lakes, and aquifers. This paper shows that because the model is more human-centered than nature-oriented or anthropocentric, it generates severe environmental damages called “externalities.” From a historical analysis of the human–nature interplay, three main results were obtained: (1) the nature–human interaction is always in a state of contradictory confrontation, being composed of two opposite human behaviors of conflict and cooperation with nature; (2) this contradiction is assumed as a general ontological principle and epistemic hypothesis, called “dialectical”; and (3) historically, in the balance of power between nature and humans, three clusters are identified: (i) naturalistic, (ii) dualistic, and (iii) anthropocentric. A theory of a novel behaviorist conflict resolution model is suggested to dialectically resolve conflicts between stakeholders and natural laws. This model provides a harmonic symbiosis of humans and nature, removes environmental externalities, and can lead to sustainable water security. Three case studies illustrate the merits of the new dialectical model in real applications.

Human activities caused lake ecological transitions in the Chinese Loess Plateau over the past 1400 years

The combined effects of climate change and human disturbance has degraded lake ecosystems worldwide in recent times, but there are few studies that explore the relative impact of these factors over long timescales. In this paper, we use sedimentary pigment data to reveal variations in algal abundance and the lake ecological environment of a typical subalpine lake (Beilianchi Lake) in the southwestern Chinese Loess Plateau, to distinguish the relative effects of natural climate change and human disturbance over the past 5000 years. Our data show that between 5000 and 1400 cal yr BP, algal abundance exhibited a slow decline without obvious fluctuations, mainly driven by a gradually drying and cooling climate. After 1400 cal yr BP, algal abundance showed large and rapid fluctuations characterized by a pattern of a decline, then increase, and then decline again. During this period, human activities began to affect lake ecology and gradually overshadowed the role of climatic changes as the main driving factor. Enhanced human disturbances caused a rapid and synchronous decline in algal abundance due to increases in soil erosion and reductions in water transparency. Algal biomass levels recovered when the soil erosion intensity decreased during 800–500 cal yr BP corresponding to the period from Southern Song to Yuan Dynasties. Thereafter (during the period of Ming and Qing Dynasties), as human activities became further enhanced and the soil erosion intensity became very high, the lake ecosystem rapidly transitioned to a stable state of low algal growth. This indicates that the lake ecosystem may have had the capacity to recover from moderate external disturbances in the early stages of human activity, but the resilience of the lake ecosystem began to decrease under stronger human disturbances. Our findings provide important empirical evidence for evaluating the current state of lakes and for sound lake management in the future.

Lacustrine deposition in response to the middle eocene climate evolution and tectonic activities, Bohai Bay Basin, China

The lower unit of the third member of the Eocene Shahejie Formation (Es3L, 42.5 to ∼40Ma) is one of the most important petroleum exploration targets in the Bohai Bay Basin. Lacustrine deposits are widely distributed in the Es3Lunit of the Shulu Sag and display strong vertical and horizontal variations in lithofacies and geochemical characteristics. Based on core data, thin-section petrography, stable δ13C isotope analyses, and organic geochemistry data, eight lithofacies and six evolutionary lake stages are identified. Combining the results of the astronomical time scale (ATS) and the radiometric age, the correlation between the evolutionary lake stages of Es3Land the Eocene global climate curve was illustrated. Tectonic movement caused the basin to subside and resulted in shallow lake formation (Stage 1) during the cooling phase prior to the Middle Eocene Climatic Optimum (MECO); then, the lake level began to rise (Stage 2) with an increasingly warm and humid climate. Stage 3 corresponds to the peak of the MECO and was influenced by the warm and humid climate during the thermal maximum period, forming a deep, freshwater lake. This stage was followed by highly turbulent lake conditions (Stage 4), which were influenced by both the cooling climate and intensive tectonic activity. Subsequently, a stable lake (Stage 5) was formed, which was mainly controlled by the slightly warming climate since the tectonic movement was relatively stable, followed by another stage of turbulent lake conditions (Stage 6). The results show that the global mid-Eocene climate played an important role on the relative lake level changes and TOC enrichment. The MECO led to a rise in the relative sea-level and the obviously rise in relative lake-level in the Bohai Bay Basin. The evolution of the depositional settings was controlled by both global climate and tectonic activities and accounted for the deposition and distribution of lithofacies with distinctly different characteristics and origins.

Assessing physical and biological lake oxygen indicators using simulated environmental variables and machine learning algorithms

We integrate observations and simulated data from physics-based models with observations and machine learning (ML) algorithms to assess and predict lake dissolved oxygen (DO) and Apparent Oxygen Utilization (AOU). DO is a proxy of hypoxia, and AOU a proxy of respiration processes and biological activity. Weather, hydrology, and agroecosystem data were used to understand how various environmental drivers impact hypoxic conditions in Lake Erie for a 15-year period. We utilized outputs from various physics-based models and developed ML models with Random Forest (RF) and eXtreme Gradient Boosting (XGBoost) to predict DO and AOU and rank the importance of influential explanatory variables. The ML models were able to accurately predict bottom DO and AOU, and identified thermal stratification as the most influential environmental variable, followed by mineralized phosphorus soil content. RF and XGBoost were not statistically different, therefore, we recommend the use of either ML algorithm to study hypoxic lake conditions.

Challenge to Lake Ecosystems: Changes in Thermal Structure Triggered by Climate Change

Human activities, global warming, frequent extreme weather events, and changes in atmospheric composition affect the solar radiation reaching the Earth’s surface, affect mass and heat transfer at the air–water interface, and induce oscillations in wind-driven internal waves. This leads to changes in the spatiotemporal characteristics of thermal stratification in lakes, altering lake circulation patterns and vertical mass transfer. However, thermal stratification structures are often overlooked. The intensification of lake thermal stratification due to warming may lead to increased release of bottom pollutants, spreading through the dynamic behavior of the thermocline to the epilimnion. Moreover, the increased heat storage is beneficial for the growth and development of certain phytoplankton, resulting in rapid transitions of the original steady state of lakes. Consequently, water quality deterioration, ecological degradation, and declining biodiversity may occur. Conventional surface water monitoring may not provide comprehensive, accurate, and timely assessments. Model simulations can better predict future thermal stratification behaviors, reducing financial burdens, providing more refined assessments, and thus preventing subsequent environmental issues.

Obtaining accurate population estimates with reduced workload and lower fish mortality in multi-mesh gillnet sampling of a large pre-alpine lake.

The EU Water Framework Directive requires monitoring of the ecological status of lakes, with fish as a relevant class of biotic quality indicator, but monitoring fish populations in large lakes is demanding. This study evaluated use in Lake Constance of a novel multi-mesh gillnet modified to reduce catch numbers. In direct comparison with conventional European Committee for Standardization (CEN) nets we achieved 48% reduction in fish mortality with 38% less labour for tasks directly influenced by fish catch numbers, while maintaining comparable species composition and catch per unit effort. Comparison of mesh sizes indicated no significant reduction in species detection in area-reduced panels of the small mesh sizes, while total observed species richness was greater when using the modified nets. Differences in benthic species communities among depth strata were common, while those of pelagic zones were more homogeneous and did not differ significantly with depth. Catches of different net types from the same depth stratum did not exhibit significant differences. The dominance structure of the most common species, relevant to lake assessment, was similar in catches of both net types, suggesting overall superiority of the modified nets in Lake Constance. Sampling conducted according to standard European CEN protocol, while deploying 60% fewer nets, yielded sufficiently precise abundance estimates for monitoring shallow areas of the benthic zone. A 50% difference in the abundance of dominant species was detected among sampling events with a certainty of 95%. The sample did not provide comparable accuracy in deep benthic strata or the pelagic zone, but was adequate to record complete inventories of species present. Based on this trial data, a new stratified sampling design is proposed for monitoring large lake fish communities for ecological assessment. Depth-dependent fish communities were used to calculate the required number of nets, which resulted in a 69% reduction for the entire lake compared to the CEN calculation method. Using the modified nets increases the feasibility of performing WFD surveys, by reducing effort and cost, while the simultaneous halving of fish mortality minimises the negative impact of fish surveys.