Search

The paper analyses the developments in the EU state aid policy as a result of the COVID-19 pandemic breakout. The general framework for state aid in the EU was presented. Based on a case study analysis of selected airlines that benefited from state aid following the COVID-19 crisis, changes in the European Commission approach were identified. In general, investigation of arrangements between the state aid cases is a complex (and thus often lengthy) process. The outbreak of the COVID-19 pandemic was a challenge for EU member states and the European Commission as well due to the unexpected, turbulent, and very profound nature of the crisis. It made it necessary to look for new or revised policies for state aid to respond quickly and keep airlines afloat in times when the flow of revenue was practically stopped. One of the key issues that needed to be addressed was inflexibility and lengthiness of state aid approval processes. To this end, additional guidelines were introduced to make the state aid policy of the EU more flexible. This way member states could respond to the ongoing developments in a more targeted and objective-oriented approach, which possibly made state aid more efficient. It should be stressed that it could have been achieved without changes to pre-existing legislation and by adjusting executive guidelines instead.

Our study explores the variability of chlorophyll a and phycocyanin as well as the taxonomic and functional structure of phytoplankton in epilimnetic and metalimnetic strata regarding the main environmental features of the water column. The maximum phytoplankton pigment concentrations are located differently depending on the type of thermal stratification and light availability. In general, there were three situations observed during the summer stratification: the euphotic zone did not extend to the thermocline and the highest chlorophyll concentration developed above the thermocline level, at the bottom of the euphotic zone (type I); the euphotic zone reached beyond the thermocline, and the maximum chlorophyll concentration occurred above the thermocline (type II); or the euphotic zone was much greater than the thermocline depth and the peak phytoplankton density was located below the thermocline (type III). In metalimnetic samples, the most dominant cyanobacteria belonged to the Reynolds Functional Groups (RFG) H1, S1, and Lo; their occurrence differed depending on the types of light and thermal regimes. It was assumed that vertical heterogeneity affects the ecological status assessment based on phytoplankton. Calculating the two applied indices (TI index and Q index) based on metalimnetic and epilimnetic data (as opposed to only epilimnetic data) yielded worse ecological status in > 70% of cases.

Since 2000, after the Water Framework Directive came into force, aquatic ecosystems’ bioassessment has acquired immense practical importance for water management. Currently, due to extensive scientific research and monitoring, we have gathered comprehensive hydrobiological databases. The amount of available data increases with each subsequent year of monitoring, and the efficient analysis of these data requires the use of proper mathematical tools. Our study challenges the comparison of the modelling potential between four indices for the ecological status assessment of lakes based on three groups of aquatic organisms, i.e. phytoplankton, phytobenthos and macrophytes. One of the deep learning techniques, artificial neural networks, has been used to predict values of four biological indices based on the limited set of the physicochemical parameters of water. All analyses were conducted separately for lakes with various stratification regimes as they function differently. The best modelling quality in terms of high values of coefficients of determination and low values of the normalised root mean square error was obtained for chlorophyll a followed by phytoplankton multimetric. A lower degree of fit was obtained in the networks for macrophyte index, and the poorest model quality was obtained for phytobenthos index. For all indices, modelling quality for non-stratified lakes was higher than this for stratified lakes, giving a higher percentage of variance explained by the networks and lower values of errors. Sensitivity analysis showed that among physicochemical parameters, water transparency (Secchi disk reading) exhibits the strongest relationship with the ecological status of lakes derived by phytoplankton and macrophytes. At the same time, all input variables indicated a negligible impact on phytobenthos index. In this way, different explanations of the relationship between biological and trophic variables were revealed.

The purpose of the study was to ascertain the effect of cyanobacterial abundance and its taxonomic structure on the results of measurements made by a fluorometric device designed to detect in situ chlorophyll a and phycocyanin. A multiparameter water quality probe was tested at 10 lakes located in the Wel River catchment. We found a strong correlation between the chlorophyll a concentration determined by laboratory procedure (CHL-a) and that obtained as a result of the probe measurements (YSI CHL-a) (R=0.78) as well as between the YSI CHL-a and the total phytoplankton biomass (R=0.73), whereas YSI CHL-a was not a good predictor of cyanobacterial biomass (R=0.24). The phycocyanin recorded by the probe was proportional to the total biomass of cyanobacteria (R=0.86); however, this cyanobacterial taxonomic structure influenced the fluorometric signal. Nevertheless, our study showed significant differentiation of phycocyanin measurement distribution at different levels of cyanobacterial abundance (−1, between 2 and 10 mg L−1, and >10 mg L−1), which indicates that the PC-YSI measurements are valuable in the detection of increased risk of exceeding health alert thresholds recommended by the WHO.

The authors acknowledge COST Action ES 1105 "CYANOCOST Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management" and COST Action Global Change Biology ES 1201 NETLAKE -Networking Lake Observatories in Europe" for contributing to this study through networking and knowledge sharing with European experts in the field. We acknowledge the members of the Global Lake Ecological Observatory Network (GLEON) for their collaborative spirit and enthusiasm that inspired the grassroots effort of the EMLS. E.M. was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis. We thank Pieter Slot for assisting with the pigment analysis. We thank Dr. Ian Jones for valuable feedback on an earlier version of the manuscript. We thank the Leibniz Institute of Freshwater Ecology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart, and the Leibniz Association for financial support. H.P. was supported by the US National Science Foundation (1840715, 1831096). A.C.'s work was funded by the Spanish Agencia Estatal de Investigacion and EU funds through the project CLIMAWET (CGL2015-69557-R). The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland. We are grateful to Kristiina Vuorio from the Freshwater Centre of the Finnish Environment institute for her help in organizing, collecting and analysing samples by the University of Jyvaskyla and to Gerald Dorflinger from the Water Development Department of Cyprus for his assistance with the sampling in Cyprus and for granting the CUT team permission to use WDD's equipment. Finally, we would like to thank the numerous other assistants that helped realizing each local survey. Open access funding provided by Universite de Geneve., To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L-1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 degrees C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature., European Cooperation in Science and Technology (COST) ES 1105 ES 1201, Swiss State Secretariat for Education, Research and Innovation, University of Geneva, Leibniz Association, National Science Foundation (NSF) 1840715 1831096, Spanish Agencia Estatal de Investigacion, European Commission CGL2015-69557-R, Department of Agriculture, Environment and Rural Affairs, Northern Ireland

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains., Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe; 1105

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains. © 2018 by the authors. Licensee MDPI, Basel, Switzerland., The authors acknowledge COST Action ES 1105 “CYANOCOST—Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE—Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from the University of Geneva. We thank Clare Ahnlund, Ena Suarez and Irene Gallego for helping out with the Swiss survey. We thank Wendy Beekman and Els J. Faassen for the nutrient and toxin analysis.

The abiotic typology of Polish lakes, compliant with the requirements of the EU Directive 2000/60/EC (Water Framework Directive), was developed in 2004 under the commission of the Ministry of the Environment. Based on the combination of the obligatory typological criteria from Annex II of the WFD and one additional factor, all Polish lakes larger than 0.5 km 2 were assigned to 13 abiotic types. This typology reflected the diversity of abiotic conditions and was assumed to be tested and validated for its ecological relevance on the basis of biological data obtained thereafter. The first ten years of its application proved the high usability of this typology for lake classification of ecological status on the one hand, while on the other hand, it allowed to gather experiences and to detect deficiencies and errors considered in the verification process. In 2015, the abiotic typology of Polish lakes was verified. Above all, verification involved an analysis of the justification of lake eco-regional division and refinement of water stratification criteria, as these two issues have been questioned in the current typology. Data on physicochemical properties, phytoplankton, macrophytes and benthic diatoms obtained from the state lake monitoring conducted in the years 2007–2013 were used to verify the ecological relevance of the typological criteria. Typological criteria used in the verified lake typological scheme were essentially the same as those used in 2004. However, the number of lake types has been reduced from the previous 13 to seven, mainly due to the withdrawal from the lake division based on eco-regions. Moreover, the more specific criteria for determining the water mixing type were established. The new lake typology is expected to be implemented in routine monitoring and water management in Poland in the forthcoming River Basin Management Plan 2021–2027.

The Water Framework Directive introduces the requirement for ecological status assessment based primarily on aquatic organisms and supporting physico-chemical elements, including oxygen conditions. The criteria for assessing oxygen conditions applied in routine lake monitoring in Poland are based on the mean hypolimnetic saturation with oxygen at the peak of summer stagnation in stratified lakes, and on the oxygen content at the bottom in the summer in polimictic lakes. The currently used oxygen criteria usually cause dismay, particularly if biological elements indicate at least good ecological status and the oxygen conditions are the only reason for lowering status class. The aim of the article is to present the scale of variability of oxygen conditions in selected lakes within the last two decades and to analyse the limitations and conditions of applying this indicator in routine monitoring, assessment and classification of Polish lakes. Data from the years 1999–2015 on oxygen and thermal conditions in a set of nine benchmark lakes in Poland were examined and the reasons for changeability in water oxygenation from year to year were discussed. Alternative oxygen indicators were considered as well as oxygen standards based on fish protection requirements that have been adopted in some European countries. It was suggested that when assessing lake ecological status, data on the oxygen conditions from a number of years must be taken into consideration, e.g., for the analysis of trends in lake trophy changes or for documenting the effects of remedial actions in lake catchment areas in long time frames.

The lake monitoring programme compliant with the Water Framework Directive has been implemented in Poland since 2007. Currently, the methods for three biological quality elements (BQEs): phytoplankton (the Phytoplankton Multimetric for Polish Lakes, PMPL), macrophytes (the Ecological State Macrophyte Index, ESMI) and phytobenthos (the Diatom Index for Lakes, IOJ) are officially applied and internationally intercalibrated. Based on the monitoring data from 256 lakes surveyed in 2010–2013 and assessed for all the three BQEs, we tested whether the assessment results obtained by the three biological methods were consistent and we searched for the causes of inconsistencies which we found. The lake classifications obtained from the PMPL and ESMI were highly consistent and the relationship between these metrics was relatively strong (R = 0.66, p a concentrations and were accompanied by a better status of phytoplankton (higher values of PMPL) than in deep lakes that can be explained by a synergistic effect of inorganic suspended solids and algal growth on water transparency. As a consequence, the positions of phytoplankton and macrophytes as early warning indicators in the eutrophication gradient in shallow lakes were inverted compared to those in deep lakes. Compared to the PMPL and ESMI, the IOJ method gave the least stringent assessment results, with 22% of lakes failing to meet the environmental objectives. The relationships between IOJ and PMPL, and ESMI were relatively weak (R = 0.17, p = 0.008 and R = 0.17, p = 0.007, respectively). Moreover, the phytobenthos index IOJ correlated significantly more weakly with all the water quality indicators than either PMPL or ESMI did. The poor performance of the phytobenthos method in this study may suggest a limited indicator value of this BQE for lake assessment or inappropriate sampling design.

Celem artykułu było przedstawienie oceny i postrzegania inwestycji w infrastrukturę transportową przez lokalne podmioty. Badania ankietowe przeprowadzono w 2014 roku na terenie powiat wołomińskiego na grupie 20 losowo wybranych przedsiębiorstw. Lokalne przedsiębiorstwa w większości dobrze i bardzo dobrze oceniały rozwój infrastruktury transportowej w powiecie. Lepiej były postrzegane inwestycje drogowe niż kolejowe. Przyczyną takiego stanu jest przewaga inwestycji drogowych oraz większa ich użyteczność w prowadzonej działalności przedsiębiorstw.

Although the phytoplankton indices describing the response of phytoplankton to the eutrophication have been developed and used for many years in the routine lake monitoring programme in some countries, the implementation of the Water Framework Directive (WFD) [EC, 2000] stimulated the development and improvement of quite a number of the current WFD-compliant phytoplankton-based methods. This paper is a review of the current phytoplankton-based methods for assessing the ecological status of European lakes. The particular attention was paid to the ways of solving problems arising from the need to reflect the complex and dynamic plankton algal communities on a numerical scale in order to gain reliable information about the state of the ecosystem.

situ Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment., The authors acknowledge COST Action ES 1105 “CYANOCOST – Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE – Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis and the University of Wageningen for covering the costs of this analysis from the personal funding of dr. Miquel Lürling. We thank Pieter Slot for assisting with the pigment analysis and the University of Amsterdam for covering the costs of the analysis through funding from the group of Prof. Jef Huisman and dr. Petra Visser (IBED). We would like to thank the Environmental Data Initiative for covering the cost of archiving the EMLS dataset. We would like to thank the Leibniz Institute of Freshwater Ecology and Inland Fisheries, Dept. of Experimental Limnology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart; and the Leibniz Association for financial support. The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland.

Embargo until 13 July 2019 Blooms of cyanobacteria are a current threat to global water security that is expected to increase in the future because of increasing nutrient enrichment, increasing temperature and extreme precipitation in combination with prolonged drought. However, the responses to multiple stressors, such as those above, are often complex and there is contradictory evidence as to how they may interact. Here we used broad scale data from 494 lakes in central and northern Europe, to assess how cyanobacteria respond to nutrients (phosphorus), temperature and water retention time in different types of lakes. Eight lake types were examined based on factorial combinations of major factors that determine phytoplankton composition and sensitivity to nutrients: alkalinity (low and medium‐high), colour (clear and humic) and mixing intensity (polymictic and stratified). In line with expectations, cyanobacteria increased with temperature and retention time in five of the eight lake types. Temperature effects were greatest in lake types situated at higher latitudes, suggesting that lakes currently not at risk could be affected by warming in the future. However, the sensitivity of cyanobacteria to temperature, retention time and phosphorus varied among lake types highlighting the complex responses of lakes to multiple stressors. For example, in polymictic, medium‐high alkalinity, humic lakes cyanobacteria biovolume was positively explained by retention time and a synergy between TP and temperature, while in polymictic, medium‐high alkalinity, clear lakes only retention time was identified as an explanatory variable. These results show that, although climate change will need to be accounted for when managing the risk of cyanobacteria in lakes, a “one‐size fits‐all” approach is not appropriate. When forecasting the response of cyanobacteria to future environmental change, including changes caused by climate and local management, it will be important to take this differential sensitivity of lakes into account.

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment. The authors acknowledge COST Action ES 1105 “CYANOCOST – Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE – Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis and the University of Wageningen for covering the costs of this analysis from the personal funding of dr. Miquel Lürling. We thank Pieter Slot for assisting with the pigment analysis and the University of Amsterdam for covering the costs of the analysis through funding from the group of Prof. Jef Huisman and dr. Petra Visser (IBED). We would like to thank the Environmental Data Initiative for covering the cost of archiving the EMLS dataset. We would like to thank the Leibniz Institute of Freshwater Ecology and Inland Fisheries, Dept. of Experimental Limnology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart; and the Leibniz Association for financial support. The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland. The authors acknowledge COST Action ES 1105 “CYANOCOST – Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE – Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis and the University of Wageningen for covering the costs of this analysis from the personal funding of dr. Miquel Lürling. We thank Pieter Slot for assisting with the pigment analysis and the University of Amsterdam for covering the costs of the analysis through funding from the group of Prof. Jef Huisman and dr. Petra Visser (IBED). We would like to thank the Environmental Data Initiative for covering the cost of archiving the EMLS dataset. We would like to thank the Leibniz Institute of Freshwater Ecology and Inland Fisheries, Dept. of Experimental Limnology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart; and the Leibniz Association for financial support. The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland.

This study identifies the ecological status of lakes which are significant water bodies located within Polish national and landscape parks. The assessment carried out on the basis of data from the National Environmental Monitoring System coming from 2010-12 took into account the requirements of the Water Framework Directive (WFD). Half of the lakes analyzed were characterized by at least good status, while the others were in moderate or even poor or bad status, although they were situated in protected areas. The study shows multi-aspect (morphometric, hydrological, and catchment-related) factors that determine the water quality and the status of the lake ecosystem. A strong correlation was found between eutrophication indicators (chlorophyll a concentration, water transparency, nutrient concentrations in water) and the majority of limnological parameters of lakes. There was no direct relationship between the percentage shares of the major land uses of lake catchments and the ecological status of lakes, but the nitrogen and phosphorus load theoretically emerging in the catchment correlated with the nutrient concentrations in water, as well as with chlorophyll a and water transparency. On the basis of data available, it proved impossible to identify a positive impact of covering lakes with protection within a national or landscape park on their ecological status.