Ecological Status Of Lakes Research Articles

Application of Synchronous Evaluation-Diagnosis Model with Quantitative Stressor-Response Analysis (SED-QSR) to Urban Lake Ecological Status: A Proposed Multiple-Level System.

Ecological integrity assessment and degradation diagnosis are used globally to evaluate the health of water bodies and pinpoint critical stressors. However, current studies mainly focus on separate evaluation or diagnosis, leading to an inadequate exploration of the relationship between stressors and responses. Here, based on multiple data sets in an urban lake system, a synchronous evaluation-diagnosis model with quantitative stressor-response analysis was advanced, aiming to improve the accuracy of evaluation and diagnosis. The weights for key physicochemical stressors were quantitatively determined in the sequence of NDAVIadj > CODMn > TP > NH4+-N by the combination of generalized additive model and structural equation modeling, clarifying the most significant effects of aquatic vegetation on the degradation of fish assemblages. Then, sensitive biological metrics were screened by considering the distinct contributions of four key stressors to alleviate the possible deviation caused by common methods. Finally, ecological integrity was evaluated by summing the key physicochemical stressors and sensitive biological metrics according to the model-deduced weights instead of empirical weights. Our system's diagnosis and evaluation results achieved an accuracy of over 80% when predicting anthropogenic stress and biological status, which highlights the great potential of our multiple-level system for ecosystem management.

Performance of different modeling techniques in testing the impact of environmental variables on eel landing in Ichkeul Lake, a RAMSAR Wetland and UNESCO biosphere reserve

Advanced modeling techniques, including Random Forest (RF) and Cubist model (CB), were used to assess the relationship between environmental factors and European eels (Anguilla anguilla) abundance and to provide insights into the lake's ecological status while considering climate change and anthropogenic influences. A comprehensive dataset, attained through extensive environmental and biological monitoring for the period 2010–2020, was employed. The performance of the models is carried out using key metrics including the root mean square error (RMSE), coefficient of determination (R²), and mean estimation error (MAE). In addition, a sensitivity analysis was conducted to ascertain the relative significance of the thirteen input variables in shaping the predictions of the models. The precision of the CB and RF models in predicting eel landings surpassed that of Multiple Regression. In the training dataset, the CB model achieved R2=0.55, RMSE=7.68 tons, and MSE=6.20 tons, and the RF model achieved R2=0.56, RMSE=7.20 tons, and MSE=5.56 tons. High accuracy was maintained on the testing dataset, with CB achieving R2=0.73, RMSE=5.13 tons, and MSE=5.89 tons, and RF achieving R2=0.73, RMSE=5.81 tons, and MSE=4.67 tons. The scatter plot between predicted and measured eel landings indicated that the RF model tends to overestimate lower values and underestimate higher values of eel landings, while the CB model gave better performance in this context. Further, the carried sensitivity analysis using the CB model unequivocally identified three pivotal factors – water level, salinity, and turbidity level – as the most influential determinants governing the landing of eels in this ecosystem. Thus, the CB model is considered to be more promising for interpreting the relationship between environmental parameters and eel landings, which could be used by managers for an effective lake management strategy.

Functional ecological metrics of good ecological quality – Needs of managers and data from pristine lakes

Anthropogenic eutrophication and overfishing of top predators have put our lakes in danger, and coping mechanisms like The European Water Framework Directive have been put in place to mitigatetheireffects. However, the discussion on the means we employ to monitor lake ecosystems and establish their ecological status is ongoing. Importantly, it has been suggested that universal, functional indicators of healthy reference ecosystems could be identified, measured and used for comparison purposes across ecological types of lakes. An equally important issue is to develop such metrics that can be employed by lake managers, who are the end users of the scientific data when planning everyday management practices. We employed bioenergetic food web approach with Ecological Network Analysis to assess organic matter fluxes and food web structure in 13 lakes in Latvia – including 3 pristine bog lakes - and combined the acquired functional descriptors with simple and well-known ecological descriptors. We conclude that information on the functioning of pristine lakes provides a potentially valuable tool for setting functional reference conditions for lake management. We also found that the ecological parameters - the percentage of piscivorous fish and the abundance of cyanobacteria - correlate well with the functional food web descriptors. Thus, they could be valuable tools to both managers and scientists when evaluating lake ecological status across the boundaries of ecological types.

A new diatom-based multimetric index to assess lake ecological status

Eutrophication impairs lake ecosystems at a global scale. In this context, as benthic microalgae are well-established warnings for a large range of stressors, particularly nutrient enrichment, the Water Framework Directive required the development of diatom-based methods to monitor lake eutrophication. Here, we present the diatom-based index we developed for French lakes, named IBDL (Indice Biologique Diatomées en Lacs). Data were collected in 93 lakes from 2015 to 2020. A challenge arose from the discontinuous pressure gradient of our dataset, especially the low number of nutrient-impacted lakes. To analyze the data we opted for the so-called “Threshold Indicator Taxa ANalysis” method, which makes it possible to determine a list of “alert taxa.” We obtained a multimetric index based on specific pressure gradients (Kjeldahl nitrogen, suspended matter, biological oxygen demand, and total phosphorous). Considering the European intercalibration process, the very good correlation between IBDL and the common metric (R2 from 0.52 to 0.87 according to the lake alkalinity type) makes us very confident in our ability to match future IBDL quality thresholds with European standards. The IBDL proved at last to be particularly relevant as it has a twofold interest: an excellent relationship with total phosphorus (R2 from 0.63 to 0.83 according to the lake alkalinity type) and a possible application to any lake metatype. Its complementarity with macrophyte-based indices moreover justifies the use of at least two primary producer components for lake ecological status classification.

Assessing relationships between environmental stress and benthic diatoms in lentic habitats in the western Mediterranean basin (Turkey).

Hydrological (rainy and dry) periods can affect the water quality of lentic ecosystems, which may be useful for understanding their ecological condition in the watershed. Ecological status of various lentic ecosytems (both brackish and freshwater) in the western Mediterranean basin was evaluated by using various diatom metrics throughout rainy (May) and dry (August and October) periods to explain the diatom-stressor interactions using multivariate approaches. Canonical correspondence analysis separated freshwater habitats under the pressures of nitrate and total organic carbon from brackish ecosystems under the pressures of conductivity, nitrite, sulphate, calcium, and copper, which were characterized by different phytoplankton species. Ecological integrations of diatom species varied in the ecosystems throughout rainy and dry periods. Different ecological regional diatom indices were used to find the best index/indices indicating the ecological status of lakes and reservoirs in the basin during the two hydrological periods. The trophic diatom index developed for lakes was not found to be suitable for assessing lentic habitats. European diatom indices generally showed the distinction in the assessment of these ecosystems in the rainy and dry seasons, but others could not. Among the diatom indices, only the trophic index Turkey (TIT) showed a statistically significant correlation with TP. The TIT not only showed degradation of the water quality of ecosystems during the dry season compared to the rainy season, but it has also been successful in distinguishing the ecological conditions of lentic ecosystems.

Correlation between catchment land use/cover and macrophyte assessment of lake ecological status

The Water Framework Directive (WFD) provides the basis for developing a system to protect and restore the aquatic environment. Macrophytes are one of the groups of organisms for determining ecological status of lakes. Using partial least squares regression (PLS-R), we showed relationships between conductivity and chlorophyll a (to a lesser extent nutrient concentrations) and Ecological State Macrophyte Index (ESMI) values. However, catchment land use/cover (LU/LC) appears to be the important factor affecting macrophyte diversity as expressed by ESMI. The presence of significant correlations was found for the catchment area determined from surface runoff using the platform SCALGO Live, based on a permanently updated numerical terrain model and an accurate land use/cover database used in Poland BDOT10k. The Corine Land Cover (CLC) database commonly used in the EU appeared to be of insufficient resolution. We have shown a high positive impact of the presence of wetlands and reservoirs in the catchment on ESMI values and negative for agricultural and urbanized areas. Obtaining information on lake catchment land use and land cover is costless. Relating LU/LC to lake macrophyte assessment methods allows this no-cost method to be included in the set of biological methods for assessing lake condition. Understanding the factors that determine the condition of lakes is fundamental to managing them according to the requirements of the WFD. The results of our study indicate that the integration of lake catchment area planning with lake water management is imperative.

Phytoplankton metrics for trophic and ecological status assessment of a natural karstic lake

According to the Water Framework Directive (WFD), biological quality elements constitute the basis for assessing ecological status of surface waters. Biological communities are good indicators of water quality because they reflect environmental conditions over time and do not require frequent sampling. The main aims were to assess trophic and ecological status of the Lake Visovac (Krka River hydrosystem, South Croatia) using phytoplankton together with supportive physico-chemical parameters, eutrophication status and impact indicators. We also tested the viability of Chlorophyll-a (Chl-a) and Hungarian Lake Phytoplankton Index (HLPI) as proposed metrics in the standard regulatory monitoring procedure. The phytoplankton samples, Chl-a and physical- chemical parameters were taken on a monthly basis from April to September in 2016 and 2019. In 2016, the most dominant species was Pantocsekiella ocellata (Pantocsek) K.T.Kiss & Ács, while in 2019 it was accompanied by Ceratium hirundinella (O.F.Müller) Dujardin. According to Chl-a, Lake Visovac was within the limits of oligo- to mesotrophic status. Based on the HLPI index, the Lake ecological status was assessed as Good. Chl-a showed a statistically significant positive correlation with temperature, while HLPI was positively correlated with oxygen and Secchi depth. We propose the use of Chl-a for rapid bioassessment on a weekly basis, whilst more complex HLPI index should be applied monthly. Further improving the confidence level of the metrics used to assess the ecological status and a comprehensive revision of boundaries for included indicators is of fundamental importance.

Phytoplankton Composition and Ecological Status of Lakes with Cyanobacteria Dominance.

Phytoplankton is one of the five biological quality elements used in the assessment of the ecological status of surface waters according to the European Water Framework Directive established in 2000. In this study, we determined the ecological status of three small and shallow lakes in the Polesie Plain, Eastern Poland, by using indices based on phytoplankton assemblages. The predominant phytoplankton of all three lakes were filamentous cyanobacteria, both heterocystous and non-heterocystous, represented by the genera Aphanizomenon, Planktothrix, Limnothrix, and Planktolyngbya. We used the Hungarian Q index, German PSI (Phyto-See-Index), and recently developed PMPL (Phytoplankton Metrics for Polish Lakes) for Polish lakes. We compared the results from the calculation of the indices to physicochemical data obtained from the lake water and Carlson’s Trophy State Index (TSI). On the basis of TSI, Gumienek and Glinki lakes were classified as advanced eutrophic, whereas Czarne Lake had a better score and was classified as slightly eutrophic. The trophic state was generally confirmed by the ecological status based on phytoplankton indices and also showed the diverse ecological situation in the lakes studied. Based on the Polish PMPL, Gumienek Lake was classified as having bad status (ecological quality ratio (EQR) = 0.05), whereas Glinki and Czarne lakes were classified within the poor status range (EQR = 0.25 and 0.35, respectively). However, based on the German PSI, the lakes were classified in a different manner: the status of Gumienek and Czarne lakes was better, but unsatisfactory, because they were still below the boundary for the good status category recommended by the European Commission. The best ecological status for the studied lakes was obtained using the Q index: Gumienek Lake with EQR = 0.42 had a moderate status, and Czarne Lake with EQR = 0.62 obtained a good status. However, Glinki Lake, with EQR = 0.40, was classified at the boundary for poor and moderate status. Based on our study, it seems that the best index for ecological status assessment based on phytoplankton that can be used for small lakes is the Polish (PMPL) index.

Ecological status of lakes and estuaries, challenges and perspectives

Ecological status of lakes and estuaries, challenges and perspectives

The potential for colour to provide a robust alternative to high-cost sediment source fingerprinting: Assessment using eight catchments in England

Excess diffuse fine sediment losses from agriculture are associated with a reduction in the ecological status of lakes and rivers. Agri-environment initiatives aim to help reduce these excessive losses through targeted on-farm advice and capital grants. However, to deliver optimum cost-benefit such initiatives must target the most important sediment sources. Sediment source fingerprinting provides an approach by which sediment provenance data can be generated; however, conventional tracers are expensive and state-of-the-art data processing for source discrimination and apportionment requires significant expertise. In consequence, sediment fingerprinting is not routinely used for catchment management. Against this context, sediment colour measured using an ordinary document scanner is trialled as an inexpensive and accessible tracer in eight catchments classed as high priority for an agri-environment initiative in England. Colour is interpreted using simple scatter bi-plots of source and sediment samples and compared to the results produced by a conventional composite tracer sediment source fingerprinting methodology. It was found that in two study catchments, sediment colour was as effective as conventional sediment fingerprinting. In four catchments, sediment colour provided less source discrimination or minor differences in results but still identified the most important targets for sediment mitigation. In two catchments, colour was un-successful; however, significant challenges were also encountered with more conventional tracers due to specific local conditions. The findings suggest that use of low-cost colour tracers by non-experts has the potential to significantly increase the uptake of sediment source tracing to improve the cost-benefit of agri-environment initiatives combating the degradation of water quality and aquatic ecology by accelerated sediment losses.

Uncertainty in phytoplankton-based lake ecological status classification: Implications of sampling frequency and metric simplification

We examined the influence of sampling frequency and the elimination of selected metrics from the Phytoplankton Multimetric for Polish Lakes (PMPL index) on lake ecological status classification. The effect of sampling frequency was analysed by calculating the official PMPL index using data from four sampling periods (848 lake-years; 478 Polish lakes), and compared the Pmpl-based classification to that assessed from PMPL variants calculated using one, two and three sampling periods. The effect of metric elimination was analysed by comparing the official three-metric PMPL classification with two variants, a one-metric PMPL including only the concentration of chlorophyll-a and a two-metric variant including total phytoplankton biomass and summer cyanobacterial biomass. Correlation strength between the official PMPL and simplified variants weakened by reducing sampling frequency but varied by period combinations. Uncertainty of ecological status classification increased in both simplification types but it was greatest when using the one-metric (chlorophyll-a based) variant. Sampling reduction from four to three periods resulted in 0.5–6.5% of lakes being over- or under-classified (total lake-year misclassification: 3.7–6.7%). Highest uncertainty of classification to at least good status occurred when the spring sampling period was excluded (6.5%). The risk of misclassification increased to 4.2–14.9% when two sampling periods were used. When classification was based only on a one-period (late summer) PMPL, 12.1% of lake-years were misclassified to at least good and 9.3% to below-good ecological status. The risk of misclassification to at least good ecological status was 2% when the two-metric (biomass-based) PMPL index was used and 28.9% when the one-metric (chlorophyll-a based) was used. Lowest misclassification error (0.5%–5.2%) occurred when a three-period (spring-August-October), three-metric PMPL index was used, but as this 5.2% would result in substantial status under-classification, we recommend further research to possibly optimize a three-period PMPL variant to reduce the costs of lake ecological monitoring in Poland.

The use of eDNA and DNA metabarcoding in monitoring the ecological condition of Norwegian lakes

Biodiversity assessments using molecular identification of organisms through high-throughput sequencing techniques have been a game changer in ecosystem monitoring, providing increased taxonomic resolution, more objective identifications, potential cost reductions, and reduced processing times. The use of DNA metabarcoding of bulk samples and environmental DNA (eDNA) is now widespread but is not yet universally implemented in national monitoring programs. While bulk sample metabarcoding involves extraction of DNA from organisms in a sample, eDNA analysis involves obtaining DNA directly from environmental samples, which can include microorganisms, meiofauna-size taxa and macrofauna traces such as larval stages, skin and hair cells, gametes, faeces and free DNA bound to particles. In Norway, freshwater biomonitoring in compliance with the EU Water Framework Directive (WFD) is conducted on several administrative levels, including national monitoring programs for running water, small and large lakes. These programs typically focus on a fraction of the actual biodiversity present in the monitored habitats (Weigand 2019). DNA metabarcoding of both bulk samples and eDNA samples are relevant tools for future freshwater biomonitoring in Norway. The aim of this PhD project is to develop assessment protocols based on DNA-metabarcoding and eDNA of benthic invertebrates, microcrustaceans and fish that can be used as standard biomonitoring tools to assess the ecological condition of lakes. The main topics addressed will be: - Development of protocols throughout the eDNA-metabarcoding workflow (i.e. sampling, filtration, preservation, extraction, amplification and sequencing) suitable to execute biodiversity assessments and determine the ecological status of lakes. - Comparison of the results obtained using molecular tools and traditional morphology-based approaches in order to assess the feasibility of such techniques to be incorporated as standard biomonitoring tools, such as the ones implemented under the provisions of the WFD. - Evaluate the effect of improved taxonomic resolution from molecular techniques on determining the ecological status of lakes, both by broadening the number of taxa analyzed and by identifying more taxa to species level. - Assess the feasibility of using eDNA extracted from water samples, taken at different depths and fish densities, to measure fish abundance/biomass as a proxy to calculate the ecological quality indices regulated in the WFD. - Analyze the coverage and resolution provided by reference libraries for certain taxa, such as crustacea, in order to assess the reliability and precision of taxonomic assignments.

不同水位下拟建鄱阳湖水利枢纽对食块茎鸟类栖息地适宜性的影响研究

鄱阳湖为亚洲最大的候鸟栖息地，近十余年发生了枯水期提前且延长及湖区生态环境日益恶化的问题，对于此问题江西政府提出了一种科学的工程措施--鄱阳湖水利枢纽（简称枢纽）。然而，枢纽对越冬候鸟栖息地的影响尚无定量研究。以鄱阳湖食块茎鸟类--白鹤（Grus leucogeranus）、白枕鹤（Grus vipio）和小天鹅（Cygnus columbianus）的栖息地为研究对象，利用3S技术结合生态学知识，在ArcGIS平台上搭建了食块茎鸟类栖息地适宜性评价模型，使用二维水动力模型联合适宜性评价模型，生成鄱阳湖在兴建枢纽前、后的食块茎鸟类栖息地适宜性分布图。选取工程调度时期水位相对稳定时段，以鄱阳湖无枢纽状态下星子水位为基础，探究鄱阳湖在不同水位时，有拟建枢纽和无拟建枢纽状态下食块茎鸟类的栖息地适宜性的变化，定量分析拟建枢纽对候鸟栖息地适宜性造成的影响。研究发现：枢纽的调度规则具有一定的科学性，水位调度方案对湖泊食块茎鸟类越冬初期栖息产生的影响较小，但会牺牲一部分越冬后期适合食块茎鸟类栖息的区域。拟建枢纽选址处至都昌站的食块茎鸟类栖息地适宜性受枢纽的负面影响最为显著，各级自然保护区之中，北部省级候鸟自然保护区受其负面影响最大，此保护区将减少18.01-39.80 km²适合食块茎鸟类栖息的面积。但是枢纽的运行能增加湖泊土壤水含量，使食块茎鸟类更易于觅食，且能增加喜食块茎鸟类的食物丰富度。本研究可为为今后鄱阳湖湖区水环境规划和水生态管理维护提供一定的科学参考。;Poyang Lake is the largest wintering habitat for migratory birds in Asia. In the last decade, the Lake has experienced early-occurring and prolonged dry season that has deteriorated the lake's ecological status. To tackle this issue, the Chinese government has proposed the construction of the Poyang Lake Hydraulic Project. However, there is no quantitative study on the impact of the Hydraulic Project on wintering migratory bird habitats. The habitats of the Tuber-eating Birds including Grus leucogeranus, Grus vipio, and Cygnus columbianus, etc. were studied. The 3S technology combined with ecological knowledge were used to build a suitability evaluation model for the habitat of the Tuber-eating Birds on the ArcGIS platform. Then, we used the suitability evaluation model combined with a two-dimensional hydrodynamic model to generate the habitat suitability map of the Tuber-eating Birds, with and without the presence/operation of the hydraulic project. During the hydraulic project dispatch period, the period of stable water level was selected. Based on the Xingzi water level without the hydraulic project, we explored the habitat suitability changes of Poyang Lake in different water levels, with and without the presence/operation of the hydraulic project. The impact of the hydraulic project on the suitability of the Tuber-eating Birds habitats was quantitatively studied. The results showed that the scheduling rule of the hydraulic project were scientific. The scheduling rule had little impact on the habitat of the Tuber-eating Birds in the early winter, but still sacrificed some of the areas suitable for the Tuber-eating Birds in the late winter. The region of hydraulic project to Duchang station was significantly negatively affected by the hydraulic project. In the nature reserves at all levels, the northern provincial migratory bird nature reserve was most significantly negatively affected, and the area will reduce the area of 18.01-39.80 km² suitable for the Tuber-eating Birds. However, the operation of the hydraulic project could increase the soil water content, making it easier for the Tuber-eating Birds to eat and increase the food richness. Our study can provide a scientific reference for the future water environment planning and ecological management of the Poyang Lake.

A Retrospective Ecological Status Assessment of the Lakes Based on Historical and Current Maps of Submerged Vegetation—A Case Study from Five Stratified Lakes in Poland

This article presents and tests a new method for the retrospective assessment of ecological status assessment of the lakes in accordance with the Ecological State Macophyte Index (ESMI), which is formally used in biological monitoring in Poland. The proposed method is based on three metrics, the Z colonization index, the average maximum depth of lake vegetation Cmax, and the Secchi disk depth. Mathematical functions of ecological class were developed on the basis of the mean values of these three indicators in summer for different ecological status classes in 88 stratified lakes in northern Poland and the Łęczyńsko-Włodawskie Lake District and five lakes in the catchment area of the Wel River (published data). The new metrics were validated on the basis of literature data—ESMI, Cmax, Z and SD values from 11 lakes near Olsztyn (Poland). The obtained results are similar to those calculated based on macrophyte field surveys and can be an alternative of the Ecological State Macophyte Index (ESMI), which is formally used in biological monitoring in Poland. The proposed method makes it possible to compare long-term changes in the ecological state of lakes, because it enables an analogous assessment on the basis of data calculated from historical bathymetric maps showing the distribution of hydro macrophytes (parameters Z and Cmax) as well as contemporary data, collected, among others, during hydroacoustic research.

The Benthic Quality Index to Assess Water Quality of Lakes May Be Affected by Confounding Environmental Features

To assess if environmental differences other than water quality may affect the outcome of the Benthic Quality Index, a comparison of the application of four different methods (Benthic Quality Index—BQIES, Lake Habitat Modification Score—LHMS, Lake Habitat Quality Assessment—LHQA and Organisation for Economic Co-operation and Development—OECD) used to classify the lake ecological and hydro-morphological status of 10 Italian lakes was performed. Five lakes were natural and five were reservoirs belonging to both Alpine and Mediterranean Ecoregions. The 10 lakes were sampled using the Water Framework Directive compliant standardized national protocol, which includes sampling soft sediment in the littoral, sublittoral and deep layers along transects with a grab of 225 cm2 during spring and autumn. The application of Generalised Linear Mixed Effect Models both at the lake level and at the single station of each lake highlighted that, at the lake level, no significant correlations existed between any couple of hydro-morphological, ecological and trophic status assessments, with each metric representing a different facet of human impact on the environment. At the single site level, we found significant effects of depth on the metrics of biodiversity. The best approximation of single-site macroinvertebrates diversity among the metrics of overall lake quality was with the LHMS, but not with the BQIES. Our hypotheses that lake macroinvertebrates assemblages depend also on other potential confounding variables of habitat degradation and intrinsic differences between lakes were confirmed, with depth playing a major role. Therefore, the assessment of lakes with different depths may produce different whole-lake BQIES values, only because of the effect of depth gradient and not because of differences in lake quality.

Development of a periphyton-based index for biological integrity for lakes and reservoirs in Baiyangdian Watershed, China

A periphyton-based index for biological integrity was developed to assess the ecological status of lakes and reservoirs in Baiyangdian Watershed, China. Periphyton and environmental surveys were conducted at 20 sites during 2009-2010. A total of 22 surveyed metrics of periphyton, which were classified into 6 categories: biomass groups, community structure, pigment ratios, bacteria diversity, enzyme activities, and metabolism were evaluated in order to understand their responsiveness to environmental degradation. Out of these 22 metrics, six metrics were selected to constitute the periphyton-based index for biological integrity: chlorophyll b, chlorophyll c: chlorophyll a ratio, alkaline phosphatase activity, bacteria dominance, net daily metabolism, and autotrophic index by sensitivity and redundancy analysis. Then the periphyton-based index for biological integrity was verified by an independent validation-site data set. The test results indicated the index could not only discriminate disturbed sites from reference sites, but also be triggered by land use types. The scores of periphyton-based index for biological integrity were significantly correlated with the environmental parameters, especially ammonia nitrogen and total phosphorus. These results suggest that this index may be a potential tool for assessing the ecological status of lakes and reservoirs, polluted mainly by organic contaminants in Baiyangdian Watershed.

Changes in the diatom community in the great lake (Lurë National Park, Albania) from 2005 to 2017 and first steps towards assessment the water quality

Great Lake is the largest of 14 lakes situated in Lure National Park, in the eastern part of the Lure Mountains, Albania. To characterize lake ecological status, epiphytic and epilithic diatom samples were collected from the lakeshore in summer 2005, 2013, and 2017. However, in 2017 no macrophytes were present, such that only epilithic diatom samples could be collected. After laboratory analysis, 52 diatom taxa were identified in July 2005, 67 in June 2013, 111 in August 2013, and 126 in August 2017. The genera Diatoma, Epithemia, Fragilaria, and Surirella were not recorded in 2017, contrary to previous years. We applied two diatom indices to asses the ecological status of the Great Lake, IPS (Indice de Polluo–sensibilite), and TDIL (Trophic Diatom Index for lakes). The IPS index indicated very good water quality in all years, while the TDIL indicated moderate water quality in 2005 and 2013 and good water quality in 2017. Because more species have indicator values for calculating the IPS than the TDIL (valve number used to calculate the IPS was above 95%, while for TDIL was below 50% of 400 counted valves), the IPS may be a more promising tool for bioindication of lakes in Albania according to the demands of the Water Framework Directive.

The insight into diatom diversity, ecology, and biogeography of an extreme cold ultraoligotrophic Lake Labynkyr at the Pole of Cold in the northern hemisphere.

The freshwater ultraoligotrophic Lake Labynkyr is located near the Pole of Cold in the northern hemisphere (Yakutia, Russia). The lake is covered by ice during 240days a year. We undertook several expeditions to the lake during the ice and open water periods for sampling ice fouling, plankton and periphyton that were then analyzed by means of scanning electron microscopy. As a result, we identified a high biodiversity of diatoms-123 species and intraspecific taxa from 53 genera, among them 3 species were new for Russia and 26 taxa were new for the algal flora of Yakutia. The oligo- and xenosaprobionts and their variations dominate-71 taxa. 18 Species were evaluated as tolerant to cold oligotrophic waters, 12 occurred on the ice bottom, and 62 in the water column under ice (0-25m). 104 taxa were found during the open water period, 70 taxa were identified in the periphyton. We showed the diatom flora of Lake Labynkyr to be unique compared with other lakes of Yakutia and to share taxa with the diatom flora of Lake Baikal. The diatoms being indicators of the global climate changes and ecological status of lakes, our data can be used as an evidence of such changes as well as to be useful studies of biogeography and history of formation of flora in Arctic and Subarctic waters.

Biological, Chemical, and Ecotoxicological Assessments Using Benthos Provide Different and Complementary Measures of Lake Ecological Status

The Water Framework Directive (WFD) aims to monitor continental water bodies in Europe to achieve good ecological status. Indexes based on biological quality elements (BQEs), ecotoxicological tests, and chemical characterizations are commonly used with standardized protocols to assess sediment quality and the associated risks. Here, we compare the results of quality assessment of benthic macroinvertebrates as BQEs as required by the WFD with the results of ecotoxicological tests and assessment of selected persistent organic pollutants (POPs) in sediments of the same eight water bodies in Italy. The aim was to verify if the assessment of quality through macroinvertebrates through POPs analyses and ecotoxicological tools can yield comparable, overlapping, or complementary results. We used the Benthic Quality Index (BQIES) for macroinvertebrates (two different applications), legacy POPs (dichloro-diphenyl-trichloroethane and metabolites (DDTs) and polychlorinated-biphenyls (PCBs)), and the emergence ratio (ER) and development rate (DR) for ecotoxicology. The results showed that the two indices within each approach were highly correlated, but between approaches, each result can lead to a completely different scenario, with rather different results of the assessment of ecosystem quality. The most striking result was that very few significant correlations existed between sediment quality assessment through macroinvertebrates and the risk assessment through analyses of micropollutants and ecotoxicological tests. The highest absolute r-value (0.81) was for the correlation between the BQIESbottom index and PCBs for micropollutants, whereas all other pairwise comparisons between indices had r-values ranging between 0.07 and 0.53. Our analysis calls for a caveat in the blind application of one or only a few indices of water/sediment quality, as the results of a single index may not represent the complexity of a freshwater ecosystem.

Atmospheric stilling offsets the benefits from reduced nutrient loading in a large shallow lake

AbstractAs part of a global phenomenon, a 30% decrease in average wind speed since 1996 in southern Estonia together with more frequent easterly winds resulted in 47% decrease in bottom shear stress in the large (270 km2), shallow (mean depth 2.8 m), and eutrophic Lake Võrtsjärv. Following a peak in eutrophication pressure in the 1970s–80s, the concentrations of total nutrients were declining. Nonmetric Multidimensional Scaling (NMDS) ordination of a 54‐year phytoplankton community composition time‐series (1964–2017) revealed three distinct periods with breaking points coinciding with changes in wind and/or water level. Contrary to expectations, we detected no decrease in optically active substances that could be related to wind stilling, whereas phytoplankton biomass showed an increasing trend despite reduced nutrient levels. Here we show how opening of the “light niche,” caused by declining amount of suspended sediments, was capitalized and filled by the light‐limited phytoplankton community. We suggest that wind stilling is another global factor, complementary to climate warming that counteracts eutrophication mitigation in lakes and may provide a challenge to assessment of the lake ecological status.