Biological Quality Elements Research Articles

Benthic Diatoms in River Biomonitoring—Present and Future Perspectives within the Water Framework Directive

The European Water Framework Directive 2000/60/EC (WFD) has been implemented over the past 20 years, using physicochemical, biological and hydromorphological elements to assess the ecological status of surface waters. Benthic diatoms (i.e., phytobenthos) are one of the most common biological quality elements (BQEs) used in surface water monitoring and are particularly successful in detecting eutrophication, organic pollution and acidification. Herein, we reviewed their implementation in river biomonitoring for the purposes of the WFD, highlighting their advantages and disadvantages over other BQEs, and we discuss recent advances that could be applied in future biomonitoring. Until now, phytobenthos have been intercalibrated by the vast majority (26 out of 28) of EU Member States (MS) in 54% of the total water bodies assessed and was the most commonly used BQE after benthic invertebrates (85% of water bodies), followed by fish (53%), macrophytes (27%) and phytoplankton (4%). To meet the WFD demands, numerous taxonomy-based quality indices have been developed among MS, presenting, however, uncertainties possibly related to species biogeography. Recent development of different types of quality indices (trait-based, DNA sequencing and predictive modeling) could provide more accurate results in biomonitoring, but should be validated and intercalibrated among MS before their wide application in water quality assessments.

Indicative value of benthic foraminifera for biomonitoring: Assignment to ecological groups of sensitivity to total organic carbon of species from European intertidal areas and transitional waters

This work contributes to the ongoing work aiming at confirming benthic foraminifera as a biological quality element. In this study, benthic foraminifera from intertidal and transitional waters from the English Channel/European Atlantic coast and the Mediterranean Sea were assigned to five ecological groups using the weighted-averaging optimum with respect to TOC of each species. It was however not possible to assign typical salt marsh species due to the presence of labile and refractory organic matter that hampers TOC characterization. Tests of this study species' lists with Foram-AMBI on two independent datasets showed a significant correlation between Foram-AMBI and TOC, confirming the strong relation between foraminifera and TOC. For one of the validation datasets, associated macrofaunal data were available and a significant correlation was found between the foraminiferal Foram-AMBI and the macrofaunal AMBI. The here proposed lists should be further tested with sensitivity-based indices in different European regional settings.

Assessing the Ecological Status of European Rivers and Lakes Using Benthic Invertebrate Communities: A Practical Catalogue of Metrics and Methods

The Water Framework Directive requires that the ecological status of surface waters be monitored and managed if necessary. A central function in ecological status assessment has the Biological Quality Elements—organisms inhabiting surface waters—by indicating human impact on their habitat. For benthic invertebrates, a wide array of national methods are used, but to date no comprehensive summary of metrics and methods is available. In this study, we summarize the benthic invertebrate community metrics used in national systems to assess the ecological status of rivers, (very) large rivers, and lakes. Currently, benthic invertebrate assemblages are used in 26 national assessment systems for rivers, 13 assessment systems for very large rivers, and 21 assessment systems for lakes in the EU. In the majority of systems, the same metrics and modules are used. In the Red Queen’s race of ecosystem management this may be a disadvantage as these same metrics and module likely depict the same stressors but there is growing evidence that aquatic ecosystems are subject to highly differentiated, complex multiple stressor impacts. Method development should be fostered to identify and rank impacts in multi-stressor environments. DNA-based biomonitoring 2.0 offers to detect stressors with greater accuracy—if new tools are calibrated.

Integration of DNA-Based Approaches in Aquatic Ecological Assessment Using Benthic Macroinvertebrates

Benthic macroinvertebrates are among the most used biological quality elements for assessing the condition of all types of aquatic ecosystems worldwide (i.e., fresh water, transitional, and marine). Current morphology-based assessments have several limitations that may be circumvented by using DNA-based approaches. Here, we present a comprehensive review of 90 publications on the use of DNA metabarcoding of benthic macroinvertebrates in aquatic ecosystems bioassessments. Metabarcoding of bulk macrozoobenthos has been preferentially used in fresh waters, whereas in marine waters, environmental DNA (eDNA) from sediment and bulk communities from deployed artificial structures has been favored. DNA extraction has been done predominantly through commercial kits, and cytochrome c oxidase subunit I (COI) has been, by far, the most used marker, occasionally combined with others, namely, the 18S rRNA gene. Current limitations include the lack of standardized protocols and broad-coverage primers, the incompleteness of reference libraries, and the inability to reliably extrapolate abundance data. In addition, morphology versus DNA benchmarking of ecological status and biotic indexes are required to allow general worldwide implementation and higher end-user confidence. The increased sensitivity, high throughput, and faster execution of DNA metabarcoding can provide much higher spatial and temporal data resolution on aquatic ecological status, thereby being more responsive to immediate management needs.

Impacts of Extreme Weather Events on Hydromorphology of UK Rivers

In this study, we assessed the effects of extreme weather events on Hydro-morphological Quality Elements in rivers of the United Kingdom alongside other pressures that will provide significant challenges for the implementation of the Water Framework Directive in the UK in terms of cost-effectiveness and sustainability. While observed meteorological data and river data sets were used for assessing changes in river systems and weather patterns, for future assessments, UK Climate Projections 2018 data was used. The studies in the literature have shown that during periods of extreme events, the river hydro-morphology is affected especially in terms of river flows, sediments and riparian zones such as draughts, and intense and heavy rainfall leading to reduced or exceptionally high flow respectively. Reduced flows can lead to the loss of habitat of aquatic organisms and an increase in fish deaths. Whilst increased river flows lead to changes of the hydro-morphology of rivers including changes to sediment dynamics and channels, rivers are also under negative effects of anthropogenic hydro-morphological pressures such as building dams and water abstractions. Furthermore, changes in river hydro-morphology can cause other problems such as increasing water temperature and decreasing dissolved oxygen, and thereby degrading Biological Quality Elements and Physico-Chemical Quality Elements. To deal with and mitigate these problems, a holistic view of water policy that considers climate change projections, reduces water demand, changes agricultural and urban land use practices, improves water availability and quality is required.

Marmara denizi körfezlerinin baskı–etki durumu ve ötrofikasyon açısından değerlendirilmesi

Closed or semi-enclosed bays in the Marmara Sea, which have long residence time, can be exposed to eutrophication as a result of organic matter enrichment from land-based pollutants. The Pressure Index method was tested for the first time in this study in order to reveal the pressure exerted by land-based sources on Izmit, Gemlik, Bandırma and Erdek Bays. As a result of the evaluation of the pressures, it was determined that the pressures on Izmit, Gemlik inner and Bandırma Bay were high, whereas Erdek and Gemlik Outer Bays were under moderate pressure. In terms of eutrophication, the nutrient, chlorophyll-a and secchi disk data of the monitoring studies carried out in the bays were compared with the limit values of the “Urban Wastewater Treatment Regulation Sensitive” and “Less Sensitive Areas Declaration and the Surface Water Quality Regulation”. Although there are differences according to the regulations, it has been determined that Izmit, Gemlik (Inner) and Bandırma Bays have eutrophic-hypertrophic conditions, Erdek and Gemlik (Outer) Bays have mesotrophic conditions. There are differences in the results due to the use of different variables and limit values in the evaluation of coastal waters by regulations. In addition to collecting regulations under a single heading, it is recommended to include biological quality elements in the eutrophication assessment.

Water quality and macrophytes in the Danube River: Artificial neural network modelling

Ecological assessment of large rivers such as the Danube is a challenging task. Eutrophication was reported as one of the main drivers that structure aquatic communities in the Danube basin. Due to their sedentary nature, relatively slow growth/ long life spans, and engineering role in aquatic ecosystems, macrophytes are widely used in the detection of nutrient enrichment. In this study, macrophyte presence-absence data within the 3 km long reaches obtained from the Joint Danube Survey (JDS3) were used to predict the water quality of the Danube river and its main tributaries. For each water quality variable (dissolved oxygen, nitrate-nitrogen, and orthophosphates), a multi-layer feed-forward artificial neural network model (ANN) was constructed using the macrophytes as explanatory variables. Despite the limited number of samples (123) along the wide trophic gradient of the Danube, the model showed good predictive performances for the main river channel. The highest discrepancy between observed and predicted water quality was obtained for the samples collected in the tributaries or downstream from the tributaries' mouth, where the model predicted better trophic conditions compared to measured ones. From 64 analysed macrophyte species, 28 were selected by sensitivity analysis as key water quality indicators (KIS) for at least one environmental variable. KIS mainly belonged to the eutrophic tolerant submerged or emerged species with broad ecological amplitude, which reflects the significance of the developed model for use on rivers subjected to nutrient pollution. However, the use of the developed predictive model is restricted to the river sections having a water velocity suitable for macrophytes growth. The developed ANN architecture represents the modelling approach which could be applied to other lotic systems and biological quality elements.

Reconstruction of the palaeo-ecological quality status in an impacted estuary using benthic foraminifera: The Santos Estuary (São Paulo state, SE Brazil)

The Santos Estuary (SE Brazil) is a coastal ecosystem with a high ecological importance and has been strongly impacted by human activities over the last century. A multiproxy analysis of sediment core dated by 137Cs, 210Pb and 226Ra activities and based on sediment geochemistry and benthic foraminifera is here used to reconstruct the environmental changes and the variations of the Palaeo-Ecological Quality Status (Palaeo-EcoQS) during the last ~120 years. The Palaeo-EcoQS was reconstructed by applying the diversity index Exp(H'bc) based on the benthic foraminiferal fauna. Specifically, the Ecological Quality Ratio (EQR) allowed to assess the Palaeo-EcoQS during the last ~120 years using local reference conditions. Based on our data, the pre-industrial period (~1883–1902) represents the reference conditions with “Good” Palaeo-EcoQS. The ~1902–1972 period coincides with the beginning of industrial operations and intensification of coastal urbanization leading to a deterioration of the environmental quality and Palaeo-EcoQS shifting to “Moderate” conditions. Dredging operations in 1972 led to increase the influences of adjacent sea that ultimately resulted in a “Good” Palaeo-EcoQS persisting up to the 1990s. Despite the preservation actions and recovery programs, the 1993–2012 period was characterized by an overall deterioration of the environmental conditions. Indeed, the reconstructed “Poor” to “Bad” Palaeo-EcoQS suggest the ineffectiveness of the remediation actions. This work confirmed that benthic foraminifera are reliable to evaluate EcoQS and Palaeo-EcoQS in estuarine ecosystems. Based on the present findings and previous studies showing the potential of fossil foraminifera to define in situ reference conditions, we recommend the inclusion of foraminifera in the list of biological quality elements within legislations concerning transitional and marine habitats.

Benthic foraminifera to assess ecological quality statuses: The case of salmon fish farming

The “Rade de Cherbourg” (RdC, Cotentin) hosts the only marine salmon fish farm along the French coasts. High hydrodynamic regime would limit, there, organic matter (OM) accumulation directly under the cages, and enhance the transport of OM in the surrounding of the cages. This study was aiming at (1) monitoring the impact of a salmon fish farm on ecological quality statuses (EcoQs) of the RdC based on a benthic foraminiferal biotic index, (2) comparing EcoQs assessment results between foraminifera and macrofauna, and (3) in fine assessing the potential for benthic foraminifera to become an alternate biological quality element. In 2014 and 2015, bottom sediments of the RdC were sampled at 13 stations under and outside the farm for sedimentary (grain size and OM), and living foraminiferal and macrofaunal analyses. For benthic foraminifera, Exp(H’bc) was used to determine EcoQs, while H’, AMBI and BO2A indices were used for benthic macrofauna. Rank-frequency distributions (RFDs) were calculated for both groups. Ecological quality statuses based on foraminifera and macrofauna indicated a moderate degradation of the environmental conditions, shifting from excellent outside the farm to poor under the cages for foraminifera and from excellent to moderate for macrofauna. This study showed that benthic foraminifera are as reliable as macrofauna to assess EcoQs in the RdC. It offers interesting perspectives to monitor the health of marine systems based on benthic foraminifera. Furthermore, results obtained with RFDs suggested that this approach should be considered in the assessment of the good environmental status within the European marine strategic framework directive. Finally, diversity proved to be efficient in monitoring the health of the RdC, suggesting that it should not be set aside for the benefit of sensitivity-based indices.

Re-evaluating expectations for river phytobenthos assessment and understanding the relationship with macrophytes

Abstract The reference model underlying the UK phytobenthos (diatom) tool for Water Framework Directive assessments is revisited and a new approach is proposed which uses quantile regression to predict the lowest values of the Trophic Diatom Index (equating to the best available condition) at any level of alkalinity . Whilst a reference model based on least disturbed or minimally impacted conditions would be preferable in theory, in practice the absence of lowland high alkalinity streams in a minimally impacted condition in the UK precludes the use of these approaches. Having proposed a revised reference model for phytobenthos, we then go on to examine the relationship between phytobenthos and macrophytes. These two groups respond to nutrients and other stressors in different ways with phytobenthos being more sensitive to nutrients whilst macrophytes better reflect the extent to which secondary effects are likely. We argue that averaging the two sub-elements of the “macrophytes and phytobenthos” biological quality element is a more realistic option than the current approach of taking the lower of the two assessments. It is, however, possible, to predict the value of the combined quality element from either sub-element, though we recognize that this also risks misclassifications.

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.

Macrophytes as biological indicators of organic pollution in the Lepenci River Basin in Kosovo

Macrophytes represent one part of the biological quality elements defined by the European Water Framework Directive (WFD) as ‘macrophytes and phytobenthos’. The aim of this study was to evaluate the reliability of ecological status classification by the use of macrophytes for lowland rivers with different habitat conditions, corresponding to EWFD requirements. The classification of water quality is based on the Ecological Quality Ratios (EQRs) which is proposed for the purpose of macrophyte-based classification for the WFD. To determine the ecological quality ratio, we calculated the following indices: River Macrophyte Nutrient Index (RMNI), River Macrophyte Hydraulic Index (RMHI), Macrophyte Index for Rivers (MIR), Number of macrophyte taxa which are not helophytes (NTAXA). Water sources that supply Lepenci River are located in alpine and subalpine areas of the Sharri mountain, which are considered as ecologically clean. Our results show that the water in spring area is clean but as a result of the anthropogenic activities downstream, the river becomes polluted by different pollution substances. This fact is also confirmed by the presence or absence of macrophytes that we used in this work as a biological indicator of water pollution. River Macrophyte Hydraulic Index (RMHI), has shown the highest value at SP6-Gërlicë, with a value of 8.74 that classifies this station downstream the river as the most polluted. The water flow velocity in this station is smooth and as such it is characterized with Macrophyte species associated with this type of water flow. According to the assessment of ecological status with RMNI index, the stations SP7-Kaçanik and SP8-Hani i Elezit, have good water quality and high ecological status and belong to first class (I), whereas the station with poorest water quality (fourth class) and poorest ecological status is rated SP5-Nikë. MIR index classify the quality of water as very good at S8-Hani i Elezit, whereas the values of this index at stations S5-Nikë and S6- Gërlicë indicate the bad water quality and poor ecological status. The largest number of macrophyte species that were not heliophytes was recorded in SP8-Hani i Elezit. We can conclude that the presence of macrophyte species in river varies from nutrient levels in water. Our results show that values of macrophyte based indices reflect the water quality in sampling stations therefore we can consider them as a reliable instrument for the assessment of the ecological status of the rivers.

Controlled Reservoir Drawdown—Challenges for Sediment Management and Integrative Monitoring: An Austrian Case Study—Part A: Reach Scale

For Europe, a reduction of 80% of the potential storage volume due to reservoir sedimentation is predicted by 2080. Sedimentation processes trigger the decrease of the storage volume and a related restriction in hydropower production. Further, the artificial downstream flushing of deposited fines has manifold effects on the aquatic ecology, including changes in morphology and sediment quality, as well as increased turbidity and subsequent stress for aquatic species. However, it is common to lower the water surface of reservoirs for technical inspections, which is not comparable to reservoir flushing operations. The presented case study deals with such a controlled drawdown beyond the operational level of the Gepatsch reservoir (Tyrol, Austria). Based on the awareness of possible ecological consequences, an advanced set of measures and an integrative monitoring design, consisting of a detailed event-based quantification of suspended sediments, changes in the morphology, especially with respect to fine sediments, and analyses of the biological quality element fish on the reach scale along the Inn River have been developed.

A taxonomy-free approach based on machine learning to assess the quality of rivers with diatoms

Diatoms are a compulsory biological quality element in the ecological assessment of rivers according to the Water Framework Directive. The application of current official indices requires the identification of individuals to species or lower rank under a microscope based on the valve morphology. This is a highly time-consuming task, often susceptible of disagreements among analysts. In alternative, the use of DNA metabarcoding combined with High-Throughput Sequencing (HTS) has been proposed. The sequences obtained from environmental DNA are clustered into Operational Taxonomic Units (OTUs), which can be assigned to a taxon using reference databases, and from there calculate biotic indices. However, there is still a high percentage of unassigned OTUs to species due to the incompleteness of reference libraries. Alternatively, we tested a new taxonomy-free approach based on diatom community samples to assess rivers. A combination of three machine learning techniques is used to build models that predict diatom OTUs expected in test sites, under reference conditions, from environmental data. The Observed/Expected OTUs ratio indicates the deviation from reference condition and is converted into a quality class. This approach was never used with diatoms neither with OTUs data. To evaluate its efficiency, we built a model based on OTUs lists (HYDGEN) and another based on taxa lists from morphological identification (HYDMORPH), and also calculated a biotic index (IPS). The models were trained and tested with data from 81 sites (44 reference sites) from central Portugal. Both models were considered accurate (linear regression for Observed and Expected richness: R2 ≈ 0.7, interception ≈ 0.8) and sensitive to global anthropogenic disturbance (Rs2 > 0.30 p < 0.006 for global disturbance). Yet, the HYDGEN model based on molecular data was sensitive to more types of pressures (such as, changes in land use and habitat quality), which gives promising insights to its use for bioassessment of rivers.

Ecological quality status of the Turkish coastal waters by using marine macrophytes (macroalgae and angiosperms)

Marine macrophytes (macroalgae and angiosperms) were defined as one of the biological quality elements to assess the ecological quality status of transitional and coastal waters by the European Water Framework Directive (WFD, 2000/60/EC). In the present study, the Ecological Evaluation Index (EEI-c) was tested to assess the anthropogenic impact by using marine benthic macrophytes (macroalgae and angiosperms) and pressures by using MA-LUSI in the Turkish marine waters. Macrophyte samples were collected from 56 stations on the coasts of Turkey (at 17 Black Sea, 15 Marmara Sea, 13 Aegean Sea and 11 Mediterranean coastal water bodies) in the summer period between 2014 and 2016. In total, 209 marine macrophytes (macroalgae and angiosperms) taxa were found in all stations. The study revealed high ecological status class for 15 sites, good for 21 sites, moderate for 6 sites, poor for 10 sites, and bad for 4 sites. The MA-LUSI index was tested from the Corine land cover map which affects 1.5 km buffer zone around the sampling sites. The relationship between the pressure index MA-LUSI and EEI-ceqr (eqr: ecological quality ratio) was also tested, and a negative linear relationship was found between MA-LUSI and EEI-ceqr in the Turkish sites. The present study supports the use of the EEI-c index for ecological quality state classification in a wide area of Turkish coastal waters.

Potential Use of Zooplankton as Ecological Quality Indicator According to Water Framework Directive (WFD) in Central Brazilian Reservoir

Zooplankton species have high sensibility to environmental changes and impacts, leading to shifts in composition and diversity of the communities and associated to increase of biodiversity, with a high potential to endemism. With the implementation of the European Water Framework Directive (WFD), there was the ecological status classification of surface waters based on the assessment of series of biological quality elements (BQE) and supported by a set of chemical and hydro morphological quality data. Despite zooplankton have being considered a key component in pelagic food web, with a significant biological indicator of water quality, this group was not included at the first moment for the WFD evaluation.

Aquatic Macrophytes as a Biological Quality Element in Lake Abant

Bu çalışmada, Abant Gölü’nde sucul makrofitlere göre ekolojik kalitenin tahmin edilmesi amaçlanmıştır. Makrofitler, 6 istasyonda Nisan, Haziran, Eylül ve Aralık 2015 tarihlerinde incelenmiştir. Gölün litorali kısmen Phragmites australis (Cav.) Trin. ex Steud, Schoenoplectus lacustris (L.) Palla türlerinin oluşturduğu bir kemer ile çevrilidir. Yüzen yapraklı makrofitlerden Nuphar lutea (L.) Sm. ve Nymphaea alba (L.) komüniteleri bulunmaktadır. Ayrıca gölde Potamogeton natans (L.), Myriophyllum spicatum (L.), Lemna minor (L.), Juncus articulatus (L.) ve M. verticillatum (L.) türleri belirlenmiştir. Gölde P. australis, S. lacustris, N. lutea ve N. alba türlerinin dağılımı yaz ve sonbahar dönemlerinde artış göstermiştir. PCA analizine göre makrofit bolluğunun, su sıcaklığı, çözünmüş oksijen, iletkenlik, alkalinite, pH, askıda katı madde, ortofosfat ve toplam fosfor derişimi ile ilişkili olduğu belirlenmiştir. Abant Gölü’nde makrofit indeksi 2,57 Referans İndekse göre hesaplanan Ekolojik Kalite Oranı ise 0,52 olarak belirlenmiştir. Buna göre Abant Gölü’nde ekolojik kalitenin iyi ve besin zenginleşmesinin orta olduğu tahmin edilmiştir.

Stream water quality assessment by metabarcoding of invertebrates

Abstract Stream water quality assessments are conducted by analysing invertebrate communities as a biological quality element (BQE). In Denmark, water quality assessments of streams are often estimated according to the Danish Stream Fauna Index (DSFI). The conventional DSFI method is time consuming and requires highly specialized expertise for species identification of the relevant indicator invertebrates. Furthermore, conventional species identification of relevant indicators may be hampered by differences in, or lack of, developmental stages or due to damages during the sampling process. Metabarcoding has the potential to overcome the challenges associated with conventional morphology-based species identification. Using high-throughput DNA sequencing, metabarcoding of invertebrates collected from stream water provides an alternative to the expertise of taxonomic experts. The present study applies metabarcoding using universal invertebrate primers targeting the mitochondrial cytochrome oxidase I (COI) gene to determine stream water qualities. The obtained community profiles were compared to conventional water quality assessments according to the Danish Stream Fauna Index (DSFI). Multivariate data analysis of obtained sequences resulted in distinct clusters of taxonomic units, which reflected the stream water quality as defined by the DSFI. In conclusion, the present study supports the knowledge that invertebrates are efficient as BQE for stream water quality assessment. DNA sequencing by metabarcoding provided a unique fingerprint of the studied communities of invertebrates and was successful in describing the stream water quality.

Predicting the ecological status of rivers and streams under different climatic and socioeconomic scenarios using Bayesian Belief Networks

Freshwater systems have increasingly been subjected to a multitude of human pressures and the re-establishment of their ecological integrity is currently a major worldwide challenge. Expected future climate and socioeconomic changes will most probably further exacerbate such challenges. Modelling techniques may provide useful tools to help facing these demands, but their use is still limited within ecological quality assessment of water resources due to its technical complexity.We developed a Bayesian Belief Network (BBN) framework for modelling the ecological quality of rivers and streams in two European river basins located in two distinct European climatic regions: the Odense Fjord basin (Denmark) and the Sorraia basin (Portugal). This method enabled us to integrate different data sources into a single framework to model the effect of multiple stressors on several biological indicators of river water quality and, subsequently, on their ecological status. The BBN provided a simple interactive user interface with which we simulated combined climate and socioeconomic changes scenarios to assess their impacts on river ecological status.According to the resulting BBNs the scenarios demonstrated small impacts of climate and socioeconomic changes on the biological quality elements analysed. This yield a final ecological status similar to the baseline in the Odense case, and slightly worse in Sorraia. Since the present situation already depicts a high percentage of rivers and streams with moderate or worse ecological status in both basins, this means that many of them would not fulfil the Water Framework Directive target in the future. Results also showed that macrophytes and fish indices were mainly responsible for a non-desirable overall ecological status in Odense and Sorraia, respectively. The approach followed in this study is novel, since BBN modelling is used for the first time for assessing the ecological status of rivers and streams under future scenarios, using an ensemble of biological quality elements. An important advantage of this tool is that it may easily be updated with new knowledge on the nature of relationships already established in the BBN or even by introducing new causal links. By encompassing two case studies of very different characteristics, these BBN may be more easily adapted as decision-making tools for water management of other river basins.

EDNA metabarcoding in zooplankton improves the ecological status assessment of aquatic ecosystems

Aquatic ecosystems are monitored worldwide using a range of biological quality elements that are morphologically identified. The environmental DNA (eDNA)-based approach has unprecedented advantages (e.g., high throughput, high efficiency and low cost) for biodiversity surveys in both freshwater and marine ecosystems compared with traditional sampling and image recognition. The use of eDNA has been mostly limited to biodiversity estimation, how to apply the eDNA approach in assessing the ecological health status is largely unexplored. Here, using zooplankton as an example, we examined the application of eDNA monitoring for ecological status assessment in an aquatic ecosystem. The results showed that eDNA monitoring reflected the spatial and temporal variations in zooplankton structure. Both species composition and bio-interactions varied significantly between sampling seasons (dry, normal and wet). A total of 60 different zooplankton indices were calculated based on eDNA monitoring and most of these indices were highly correlated with the level of water pollution, which was indicated by the water quality index in one or all three seasons. Both qualitative and quantitative eDNA-based biological indices were correlated with water quality. The season-dependent eDNA zooplankton integrity index (IZI) reflected the ecological status, and this method improves the timeliness of bioassessment.