•We link ecological status of river diatom and macrophyte communities to nutrient levels.•We establish nutrient criteria for ‘good’ ecological status in several European river types.•We compare these ...values with the criteria used by countries and provide recommendations.•We provide a comprehensive overview of river nutrient criteria developed worldwide.
Nutrient pollution remains one of the leading causes of river degradation, making it important to set thresholds that support good ecological condition, which is the main objective of managing Europe's aquatic environment. A wide range of methods has been used by European member states to set river nutrient thresholds in the past, and these vary greatly among countries, even for similar river types. In some countries, thresholds have been set using expert judgement or the statistical distribution of nutrient concentrations. Application of such thresholds creates problems for planning strategies to achieve good ecological status and for managing transboundary river basins. An alternative approach is to examine the statistical relationship between nutrient concentration and one, or more, biological variables. Such relationships can then be used to inform decisions by water managers. We use such 'ecology-based' approaches (univariate regression and mismatch analyses) to derive nutrient thresholds for several river types in Central Europe. Our analysis focused on soluble reactive phosphorus (SRP) and total nitrogen (TN), two variables which were responsible for significant variation (40–55%) in river benthic floras. In this study, for the first time, river nutrient thresholds are estimated using both macrophytes and phytobenthos (EQRs) separately and in combination, calculated as the minimum and the average of the EQRs of the two sub-elements. The resulting thresholds supporting good ecological status range from 21 to 42 µg/L SRP and 0.9–3.5 mg/L TN for the low alkalinity lowland river type, and 32–90 µg/L SRP and 1.0–2.5 mg/L TN for the low alkalinity mid-altitude river type. These targets are compared to the values set by member states. We demonstrate that some national nutrient thresholds fall within the range of predicted values if uncertainty is taken into consideration; however, several threshold values considerably exceed this range. Adopting ecology-based nutrient targets should improve sustainable river management where nutrients are the major pressure preventing the achievement of good ecological status.
▸ We review 297 bioassessment methods of European surface waters. ▸ The overview includes methods for phytoplankton, benthic flora and fauna, and fish. ▸ Abundance and sensitivity metrics dominate, ...detecting organic and nutrient pollution. ▸ The pressure-impact relationship of >30% of methods is not tested empirically. ▸ Quality class boundaries were mostly set statistically lacking an ecological rationale.
According to the Water Framework Directive (WFD), the status of European surface waters is assessed using aquatic organism groups. Here we present an overview of 297 assessment methods, based on a questionnaire survey addressing authorities in all countries implementing the WFD. Twenty-eight countries reported on methods applied to rivers (30%), coastal waters (26%), lakes (25%) and transitional waters (19%). More than half of the methods are based on macroscopic plants (28%) or benthic invertebrates (26%); in addition, phytoplankton (21%), fish (15%) and phytobenthos (10%) were assessed. Countries of Central and Western Europe had developed almost all methods required for the WFD implementation. Two main sampling strategies were discernable: small-scale sampling of the taxonomically diverse groups of benthic invertebrates and phytobenthos that demand elaborate processing, versus large-scale sampling of vast, species-poor plant stands or the mobile fish fauna. About three-quarters of methods identified organisms to species-level while in particular phytoplankton-based methods used class- or phylum-level, or included no taxonomic information. Out of nine metric types distinguished, river methods used more sensitivity and trait metrics while for other water categories abundance metrics prevailed. Fish-based methods showed the highest number of metrics. Fifty-six percent of methods focussed on the detection of eutrophication and organic pollution, with shares decreasing from autotrophic to heterotrophic organism groups: phytoplankton>phytobenthos>macroscopic plants>benthic invertebrates>fish fauna. The order was almost reverse for hydrological or morphological deterioration: fish fauna and macroscopic plants>benthic invertebrates>phytoplankton>phytobenthos. These pressures were mainly assessed by methods applied to rivers and transitional waters. The pressure-impact relationship of about one-third of methods was not tested empirically with methods for transitional waters being the least validated. The strength of relationships differed significantly between organism groups and water categories. The correlation coefficients generally covered a broad range (<0.4 to >0.8), but on average with the pattern: phytoplankton>macroscopic plants>benthic invertebrates>phytobenthos and fish fauna. In terms of water categories the following order resulted: coastal waters>lakes>transitional waters>rivers. Status boundaries were mostly defined using statistical approaches. We advocate better reflection of the necessary sampling effort and precision, full validations of pressure-impact relationships and an implementation of more ecological components into classification.
A Partial Least Squares-Path Model (PLS-PM) was developed for the Ave River Basin (North of Portugal), and the results used in a scenario analysis. The data for PLS-PM comprised a set of ...anthropogenic pressures, water quality parameters, and a macroinvertebrate-based biodiversity index (IPtIN) used to assess the ecological status of streams. These groups of measured parameters (called latent variables) were given the names “Pressures”, “Contamination” and “Ecological Integrity”. Besides, latent variables were connected through path coefficients representing potential causal effects among them. In a large portion of Ave the ecological status of streams is currently bad or poor. Nitrate and coliforms were the most weighted measured variables of latent variable “Contamination”, with w ≈ 0.7 and w ≈ 0.2, respectively. The highest “Pressures” weights were ascribed to livestock farming (0.7) and population density (0.4). The connections “Pressures”—“Contamination” and “Contamination” — “Ecological Integrity” exposed a sequence of direct negative effects between the three variables, expressed in the corresponding path coefficients (pc = 0.87 and pc = −1.11). Paradoxically, a direct negative effect of “Pressures” over “Ecological Integrity” was absent (pc = 0.29). Therefore, the poor ecological status of local stream waters might not be directly related to the presence of potentially threatening contaminant sources (the “Pressures”), but to ineffective monitoring of livestock farming and wastewater treatment activities that potentiate (accidental) releases of contaminants into the streams. The lack of a direct link “Pressures” — “Ecological Integrity” supported the results of pressure change versus IPtIN change scenarios. Regardless of some significant reductions of anthropogenic activity and population density until 2027, announced by the Portuguese Environmental Agency, the scenarios could not predict improvement of ecological status beyond the “moderate” category. The study recommendations were therefore to prevent contamination through proper implementation and monitoring of existing watershed management plans. The adequate treatment of domestic effluents and the control of livestock farming residues are urgent.
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•Partial Least Squares – Path Modeling is used to connect environmental descriptors.•Poor ecological status in Ave streams is a direct consequence of water contamination.•Pollution of Ave streams is mostly caused by domestic sewage and livestock farming.
Creating a method to categorize the ecological status of streams according to their biological conditions and establishing scientifically defensible nutrient criteria to protect their biotic ...integrity poses significant challenges. Biomonitoring of least disturbed areas is an important issue to accurately assess the ecological status of surface waters and ensure their sustainability. The fuzzy logic as a novel approach was firstly applied to evaluate the biological condition gradient of 44 sampled streams in the Ceyhan River Basin, utilizing two diatom indices, total phosphorus (TP), electrical conductivity (EC), and CORINE data. The fuzzy logic was employed to examine variations in the diatom compositions and land cover based on biological condition gradients (BCGs) of various streams and to assess the suitability of BCG in evaluating the health of studied stream systems. A three-layer fuzzy logic was constructed to predict BCGs of steams based on input data, with diatom metrics, TP, and EC representing BCGdia and land cover variables contributing to BCGland. The effects of operating variables were studied to optimize BCG results. The highest BCG score (0.85) was determined in Aksu Spring Brook in the spring, whereas the lowest value (0.05) was calculated in Erkenez Stream3 in the summer. BCGs showed strong relationships with nutrients, altitude, and EC. Results of BCGs indicated that sampling stations have various ecological statuses ranging from bad to high in the Ceyhan River Basin. The BCGdia and BCGland made important contributions to determine the ecological status of streams in the Ceyhan River Basin. Results showed that the BCG approach allows a more reliable way to determine the ecological status of streams in the Ceyhan River Basin by combining biological and chemical assessments for the sustainability of the environment. It is recommended that the BCG will be applied and evaluated in future research studies across various river basins, both within and outside of Turkey.
Fuzzy logic as a novel approach to predict biological condition gradient of various streams in Ceyhan River Basin (Turkey). Abuzer Çelekli, Ömer Lekesiz, Mehmet Yavuzatmaca, Muzaffer Dügel. Display omitted
•First attempt to assess biological condition gradient (BCG) of streams in Ceyhan River Basin•BCG is a valuable tool for assessing, monitoring, and managing the sustainability of ecosystems.•BCG has successfully distinguished the ecological status of streams.•BCG is a more reliable way to determine ecological status of streams.•It is recommended to apply and evaluate the application of BCG in future research studies.
Ensuring a good ecological status of water bodies is one of the key challenges of communities and one of the objectives of the European Water Framework Directive. Although recent works identified the ...most significant stressors affecting the ecological quality of rivers, the ability to predict the overall ecological status of rivers based on a limited amount of easily accessible geospatial data has not been investigated so far. Most of the analyses focus on detailed local modelling and measurements which cannot be systematically applied at regional scales for the purposes of water resources management. The aim of this work is to understand the capabilities of five supervised machine learning classifiers of predicting the ecological status of rivers based on land use, climate, morphology, and water management parameters extracted over the river catchments corresponding to the ecological monitoring stations. Moreover, the performances of machine learning classifiers are compared to the results of the canonical correlation analysis. The method is applied to 360 catchments in Tuscany (central Italy) with a median size of 33.6 km2 and a Mediterranean climate. The results show (i) a significant correlation of ecological status with summer climate (i.e., maximum temperatures and minimum precipitation), land use and water exploitation, (ii) an 80 % precision of Random Forest algorithm to predict ecological status and (iii) higher capability of all classifiers to predict at least good ecological status. In perspective, such predictive capabilities can support decision making in the land and water resources management and highlight strategies for river eco-hydrological conservation.
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•Prediction of ecological status at large scales with few spatial data.•Performances of 5 Machine Learning classification algorithms are compared.•Ecological status is correlated to land use, summer climate and water exploitation.•Random Forest predicts ecological status with 80 % precision.
The paper reports the results obtained after 4 years of aquatic angiosperm transplants in areas of the Venice Lagoon (North Adriatic Sea, Mediterranean) where meadows almost disappeared due to ...eutrophication, pollution and overexploitation of clam resources. The project LIFE12 NAT/IT/000331-SeResto, funded by the European Union, allowed to recolonize the Habitat 1150* (coastal lagoons) in the northernmost part of the lagoon, by extensive manual transplants of small sods or single rhizomes of Zostera marina, Zostera noltei, Ruppia cirrhosa and, in some stations also of Cymodocea nodosa. Over the 4 years of the project more than 75,000 rhizomes were transplanted in 35 stations with the support of local stakeholders (fishermen, hunters and sport clubs). Plants took root in 32 stations forming extensive meadows on a surface of approx. 10 km2 even if some failures were recorded in areas affected by outflows of freshwater rich in nutrients and suspended particulate matter. The rapid recovery of the ecological status of the involved areas was the result of this meadow restoration, which was in compliance with Water Framework Directive (WFD 2000/60/EC) objectives. Moreover, the monitoring of environmental parameters in the water column and in surface sediments allowed to identify the best conditions for successful transplants. Small, widespread interventions and the participation of local stakeholders in the environmental recovery, make this action economically cheap and easily transposable in other similar environments.
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•The northern Venice Lagoon was restored by aquatic angiosperm transplants.•Areas characterized by low eutrophic status favoured aquatic angiosperm rooting.•Small sod and rhizome transplants were efficient and cheap rooting technique.•Fishermen and hunters actively participated in transplanting activities.•Aquatic angiosperms are indicators of good-high ecological status.
Understanding the effects of environmental stressors (e.g., potential changes in climate and land use) on ecological status is essential for freshwater management. The ecological response of rivers ...to stressors can be evaluated by several physico-chemical, biological, and hydromorphological elements as well as computer tools. In this study, an ecohydrological model based on SWAT (Soil and Water Assessment Tool) is used to investigate climate change impact on the ecological status of Albaida Valley Rivers. The predictions of five General Circulation Models (GCMs) each with four Representative Concentration Pathways (RCPs) are employed as input to the model for simulating several chemical and biological quality indicators (nitrate, ammonium, total phosphorus, and the IBMWP (Iberian Biological Monitoring Working Party) index) in three future periods (Near Future: 2025–2049, Mid Future: 2050–2074, and Far Future: 2075–2099). Based on chemical and biological status predicted with the model, the ecological status is determined at 14 representative sites. As a result of increased temperatures and decreased precipitations from most of GCMs projections, the model predicts decreased river discharge, increased concentrations of nutrients, and decreased values of IBMWP for future compared to the baseline period (2005–2017). While most representative sites have poor ecological status (10 sites with poor ecological status and four sites with bad ecological status) in the baseline, our model projects bad ecological status for most representative sites (four sites with poor ecological status and 10 sites with bad ecological status) under most emission scenarios in the future. It should be noted that the bad ecological status is projected for all 14 sites under the most extreme scenario (i.e., RCP8.5) in the Far Future. Despite the different emission scenarios, and all possible changes in water temperature and annual precipitation, our findings emphasize the urgent need for scientifically informed decisions to manage and preserve freshwaters.
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•A recently presented modeling framework is employed in different scenario simulations.•Climate change impact on ecological status is investigated.•Climate change influences hydrology, water quality, and ecological status.•In certain representative sites, ecological status is expected to downgrade.•Scientifically informed decisions are essential to manage and protect freshwaters.
In situ Chl-a data were used to perform empirical calibration and validation of Sentinel-3 level 2 product in Danish marine waters. Comparing in situ data with both same-day and ±5 days moving ...averaged Sentiel-3 Chl-a values yielded two similar positive correlations (p > 0.05) with rpearson values of 0.56 and 0.53, respectively. However, as the moving averaged values resulted in significantly more available data than daily matchups (N = 392 vs. N = 1292) at a similar quality of correlation with similar model parameters (slope (1.53 and 1.7) and intercept (−0.28 and −0.33) respectively), which were not significantly different (p > 0.05), the further analyses were focused on ±5 days moving averaged values. A thorough comparison of seasonal and growing season averages (GSA) also showed a very good agreement, except for a few stations characterized by very shallow depth. Overestimation by the Sentinel-3 occurred in shallow coastal areas and was attributed to the interferences from benthic vegetation and high levels of Colored Dissolved Organic matter (CDOM) interfering with the Chl-a signals. Underestimation observed in the inner estuaries with shallow Chl-a rich waters, however, seen as a result of self-shading at high Chl-a concentrations, reducing effective absorption by phytoplankton. Besides the observed minor disagreements, there was no significant difference when the GSA values from in situ and Sentinel-3 were compared for all three water types (p > 0.05, N = 110). Analyzing Chl-a estimates along a depth gradient showed significant (p < 0.001) non-linear trends of declining concentrations from shallow to deeper waters for both in situ (explaining 15.2 % of the variance (N = 109)) and Sentinel-3 data (explaining 36.3 % of the variance (N = 110)), with higher variability in shallow waters. Furthermore, Sentinel-3 enabled full spatial coverage of all 102 monitored water bodies providing GSA data at much higher spatial and temporal resolutions for good ecological status (GES) assessment compared to only 61 through in situ sampling. This underlines the potential of Sentinel-3 for substantially extending the geographical coverage of monitoring and assessment. However, the systematic over- and underestimation of Chl-a in shallow nutrient rich inner estuaries through Sentinel-3 requires further attention to enable routine application of the Sentinel-3 level 2 standard product in the operational Chl-a monitoring in Danish coastal waters. We provide methodological recommendations on how to improve the Sentinel-3 products' representation of in situ Chl-a conditions. Continued frequent in situ sampling remains important for monitoring as these measurements provide essential data for empirical calibration and validation of satellite based estimates to reduce possible systematic bias.
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•The suitability of Sentinel-3 in monitoring chlorophyll-a and assessing ecological status was evaluated.•In situ and Sentinel-3chlorophyll-a estimates showed very good seasonal agreement.•Challenges in chlorophyll-a rich shallow coastal areas•Synergistic use of in situ and Sentinel-3 satellites recommended
Karst ecosystems play a unique role as exceptional natural habitats in sustaining biodiversity. This study focuses on diatoms, a diverse group of microeukaryotes in the periphytic community of a ...karstic river. In a multi-microhabitat study along the Krka River (Croatia), our goal was to obtain a detailed overview of diatom diversity and community structure using morphological and molecular approaches, and to assess the applicability of eDNA metabarcoding as a reliable tool for biomonitoring assessment. The results revealed a relatively low agreement in the diatom community composition between the two approaches, but also provided complementary information, with no differences in beta diversity detected between microhabitats. The SIMPER analysis underlined the importance of the molecular approach in identifying diatom community composition, due to errors in distinguishing between deposited diatom cells that occurred in the morphological analysis. In contrast, the morphological approach indicated a clear diatom community separation along the river with a strong location effect. Despite certain differences, both approaches provided a feasible assessment of the ecological status according to the relationship to environmental pressures, classifying the Krka River as High (morphological approach) or Good (molecular approach) throughout the most of its course. Moreover, diatom diversity based on both approaches provides a reliable dataset applicable in routine monitoring assessment and offers a deeper understanding of the presented ecological status. The incompleteness of a reference database presents one major drawback of the molecular approach, which needs further updating in order to improve routine diatom metabarcoding.
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•Karst ecosystems play a unique role as exceptional natural habitats.•Periphytic diatom diversity was described by microscopy and eDNA metabarcoding.•Considerable differences in results were presented by both approaches.•Both approaches provided a feasible assessment of ecological status.
Invasive alien species (IAS) induce changes to community structure and functions which lead to a decline of endemic species and major irreversible changes to the local physical habitat. The ...distribution and the impacts of multiple freshwater IAS are not well known, and they have not been investigated simultaneously at catchment and at European scales.
This study provides an assessment of the distribution and cumulative impact of freshwater IAS over European catchments. IAS occurrences were retrieved from the European Alien Species Information Network geospatial dataset and updated with the most recent records from the literature. The Cumulative Impact Index of Invasive Alien Species (CIMPAL) was derived by aggregating the impacts of species and their occupied area at catchment level by following three steps: i) IAS were scored by both the magnitude of impacts on freshwater ecosystems and the strength of evidence in the literature, ii) scores were mapped over the catchment area, and iii) scores were summed across IAS over the catchment. The distribution of CIMPAL in the river ecological classes of the Water Framework Directive was examined and increasing/decreasing patterns identified across ecological statuses.
Results showed strong spatial variation in the documented distribution and impacts of IAS in Europe. Catchments with CIMPAL scores >40 (range 0–55) clustered in Western European countries (e.g. Belgium and France) were characterised by plant, invertebrate and vertebrate IAS that had both a large impact in magnitude and colonisation at local (catchment level) and large scale (across catchments). CIMPAL showed statistically significant and increasing values from high to bad ecological classes in eight countries only (Belgium, the Czech Republic, Germany, France, Hungary, Italy, Luxemburg, Poland). This study provides comprehensive evidence of the distribution and impact of IAS within freshwater environments that could be used to improve understanding of the ecological pressures at catchment scale.
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•Distribution and impacts of freshwater invasive species are assessed in Europe.•Impacts are calculated at catchment scale and related to river ecological status.•High variation of impact magnitude and spp. occupancy within and across catchments•Eleven countries on twenty-five show high impacts at poor and bad river status.•The approach can guide more effective catchment strategies to tackle invasive spp.
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