Salinization is a global threat to freshwater habitats that has been intensified by climate change. Monitoring, assessment and management of salinity is therefore essential. The first step is to set criteria that are sufficiently stringent to protect ecosystem health. However, many countries have not yet defined criteria, and there are substantial differences between criteria. This has been noted in the EU, where salinity is a required “supporting element” for ecological status in inland waters but also for implementation of UN Sustainable Development Goal (SDG) indicator 6.3.2. for “good ambient water quality” where different approaches and widely different threshold values were reported for salinity criteria. Much of this information has not been published and is difficult to access, hindering further efforts to address the problem. We first discuss the implications of salinization for freshwater ecological health. We go on to discuss the principles and guidelines on how salinity criteria to protect ecology should be established. Next, we review salinity criteria submitted as part of implementation of SDG indicator 6.3.2 and the EU Water Framework Directive. Finally, we discuss setting salinity thresholds in an already‐warming world and the challenges facing anyone trying to develop salinity criteria to protect freshwater ecosystems. This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness Science of Water > Water Quality

Shallow lakes provide a multitude of ecosystem functions, but they are particularly vulnerable to natural and anthropogenic disturbances. Understanding the driving factors determining the fate and spatial distribution of nutrients and pollutants in such systems is fundamental to assess the impact of ongoing or future external pressures endangering their ecological integrity. This study investigates the fate of trace contaminants transported into the large shallow Lake Neusiedl, including contaminants representative of different patterns of sources and emission pathways and of environmental behavior, namely metals, pharmaceuticals, an artificial sweetener and perfluoroalkyl substances. Further, it examines the horizontal spatial distribution of nutrients, ions and physico-chemical parameters with an unprecedented detailed focus on the internal variability within the large reed belt. As described in the past e.g. for chloride, evaporation was identified as the process leading to a substantial concentration enrichment of the industrial chemical PFOA and the sweetener acesulfame K from the tributary river into the open lake. This is particularly relevant in view of the predicted future increase of evapotranspiration due to climate change. In contrast, the observed loss of diclofenac, but also of PFOS and carbamazepine suggests that the well-mixed, humic-rich and alkaline Lake Neusiedl offers favorable conditions for the photodegradation of otherwise very persistent chemicals. Another important finding, in the context of possible modifications in lake water levels due to climate change, is the fundamental role played by the connectivity between open lake and reed belt but also by the presence and characteristics of inner water areas within the reed belt region in determining the hydrochemistry of the lake system. By revealing systematic spatial patterns and by focusing on the underlying factors and processes, the understanding offered by this study is of high value for the conservation of shallow lakes.

Fish are important elements of aquatic ecosystems. Their communities naturally follow the river continuum and have been well described in the western European freshwater watersheds. In regions of higher endemism, such as the Balkan Peninsula, the widely accepted fish zonation of Illies is doubtfully relevant. In this study, a more suitable categorization of lotic and lentic freshwater ecosystems in Bulgaria is proposed, based on 389 multimethodological and multihabitat fish sampling occasions. Referent-type communities have been determined for 33 types of recognized water bodies. Adapted zonation of Illies is a rough estimation of the real distribution of fish assemblances in the country; moreover, sensitive and/or endemic species are generally of restricted distribution and abundance. In view of the lentic ecosystems, they can be divided into salmonid and cyprinid, at approximately 1500 m above sea level.

Nutrient targets based on pressure-response models are essential for defining ambitions and managing eutrophication. However, the scale of biogeographical variation in these pressure-response relationships is poorly understood, which may hinder eutrophication management in regions where lake ecology is less intensively studied. In this study, we derive ecology-based nutrient targets for five major ecoregions of Europe: Northern, Central-Baltic, Alpine, Mediterranean and Eastern Continental. As a first step, we developed regressions between nutrient concentrations and ecological quality ratios (EQR) based on phytoplankton and macrophyte communities. Significant relationships were established for 13 major lake types; in most cases, these relationships were stronger for phosphorus than for nitrogen, and stronger for phytoplankton than for macrophytes. Using these regressions, we estimated the total phosphorus (TP) and total nitrogen (TN) concentrations at which lakes of different types are likely to achieve good ecological status. However, in the very shallow lakes of the Eastern Continental region, relations between nutrient and biological communities were weak or non-significant. This can be attributed to high nutrient concentrations (in the asymptotic zone of phosphorus-phytoplankton models) suggesting other factors (light, grazing) limit primary production. However, we also show that fish stocking is a major pressure on Eastern Continental lakes, negatively affecting ecological status: lakes with low fish stocking show low chlorophyll-a concentrations and good ecological status despite high nutrient levels, while the lakes with high fish stocking show high chlorophyll-a and low ecological status. This study highlights the need to better understand lakes in biogeographic regions that have been, for historical reasons, less studied. This, in turn, helps reveal factors that challenge the dominant paradigms of lake assessment and management.

Lake Neusiedl is the largest endorheic lake in Central Europe, straddling the Austrian–Hungarian border. The lake has an area of 315 km2, 52% of which is covered by a reed belt representing the second largest contiguous reed population in Europe. The lake's drainage basin has an area of about 1,120 km2 and is strongly impacted by intensive agricultural production and urban settlements, especially in the catchment of the main inflow River Wulka. On average, the lake's surface lies 115.45 m above the Adriatic Sea and the lake is no more than 1.8 m deep. Due to its chemical composition Lake Neusield can be characterized as soda lake with typical pH values of 9.0-9.3 in the open lake.In this contribution, we present results from investigations on selected PAH (Benzo(a)pyrene, Fluoranthene) and PFAS (PFOS and PFOA) in the lake with specific focus on sediment associated transport and legacy processes. We apply a holistic approach, by combining emission modelling, targeted monitoring, adsorption and mobilization experiments as well as a lake’s mass balance. We describe the current state of contamination of River Wulka and the lake, we identify the main emission pathways into both river and lake and we shed light on the complex environmental behavior within the coupled system lake - reed belt.While PFOA and PFOS emissions into the river are dominated by effluents from waste water treatment plants, atmospheric deposition on the lake surface adds a significant contribution to the contamination of the lake. On the contrary, agricultural erosion is the dominant pathway of the contamination of river and lake for Benzo(a)pyrene, Fluoranthene. Our results show that the reed belt at the entrance of River Wulka to the lake acts as a significant sink for these substances due to suspended solid sedimentation.Persistent chemicals entering the lake may undergo different fates. They may concentrate in water, because in this peculiar lake evaporation exceeds precipitation. They may also be stored in the sediments of the reed belt, from where they might be later re-mobilized. The fate of Benzo(a)pyrene and Fluoranthene is clearly dominated by the latter processes. While these processes cannot be neglected for PFOS and PFOA as well, PFOA shows a strong enrichment in the lake water. The behavior of PFOS is even more complex. Though highly persistent, its removal from the lake water cannot be explained by suspended solid associated transport to and sedimentation in the reed belt. It is removed from the lake water through degradation or conversion to metabolites to a significant extent as well.

Zusammenfassung Im vorliegenden Artikel wird auf Basis unterschiedlicher Datenquellen in einem ersten Schritt die Belastung des Neusiedler Sees mit national oder gemeinschaftlich geregelten anthropogenen Spurenstoffen dargestellt. Darüber hinaus werden für ausgewählte Stoffe Eintragspfade in Wulka und Neusiedler See identifiziert und für weitere Stoffe wird ein mögliches Umweltverhalten im See dargestellt. Auch wenn derzeit ein umfassendes Monitoring von allen national oder gemeinschaftlich geregelten Spurenstoffen im Neusiedler See fehlt, kann für den überwiegenden Teil dieser Stoffe auf Basis von Untersuchungen in der Wulka bzw. Fischuntersuchungen im See eine Einhaltung der UQN angenommen werden. Für einzelne Stoffe ist eine Zielverfehlung geben oder anzunehmen. Für andere Stoffe ist zurzeit aufgrund analytischer Schwierigkeiten ein eindeutiger Befund nicht möglich. In Abhängigkeit vom Stoff und der Betrachtungsebene können sowohl Kläranlagenabläufe, landwirtschaftliche Erosion als auch die atmosphärische Deposition auf die Oberfläche des Sees die Einträge dominieren. Mit Bedachtnahme auf die große Zahl der in die aquatische Umwelt emittierten anthropogenen Spurenstoffe muss unabhängig von der Betrachtung von Einzelstoffen für den Neusiedler See eine ganz besondere Vulnerabilität für diese Form der Belastung diagnostiziert werden. Dies liegt vor allem an der Funktion des Sees als Stoffsenke. Persistente Spurenstoffe, die in den See gelangen, werden im Freiwasser aufkonzentriert oder in den Sedimentbereichen des Schilfs gespeichert, von wo sie allenfalls wieder mobilisiert werden können. Selbst wenn eine Vielzahl von schwer abbaubaren Spurenstoffen durch Ab- oder Umbau aus dem Freiwasser des Sees eliminiert wird, ist über die Endprodukte eines solchen Umbaus noch wenig bekannt bzw. sind diese aufgrund der Vielzahl möglicher Stoffe nicht gänzlich zu überwachen. Als Grundlage zur Entwicklung von Strategien für ein langfristiges und effizientes Management des Sees wäre ein regelmäßiges Monitoring von Spurenstoffen in See und Schilfgürtel deutlich zu verstärken, um Fehlentwicklungen im See frühzeitig erkennen zu können.

Die vorliegende Arbeit behandelt die Nährstoffdynamik am Neusiedler See, ein Thema, das untrennbar mit den Einträgen und Austauschprozessen der Fest- oder Schwebstoffe verbunden ist. Es werden zusammenfassend ältere Untersuchungen von Anfang der 1980er-Jahre diskutiert und neueren Erkenntnissen aus einem laufenden EU-INTERREG-Projekt (REBEN) gegenübergestellt. Der Beitrag behandelt zunächst die Schwebstoff- und Nährstofffrachten in den Neusiedler See über den größten Zubringer des Sees, die Wulka. In einem zweiten Abschnitt werden Veränderungen durch Umsetzungsprozesse beim Durchtritt der Wulka durch den Schilfgürtel-Mündungsbereich Höhe Donnerskirchen beschrieben. Die Langzeitentwicklung der Nährstoffe im offenen See bildet den dritten Abschnitt, während abschließend die horizontale Verteilung von Schweb- und Nährstoffen im Schilfgürtel und Rückschlüsse auf horizontale Strömungen und Austauschprozesse behandelt werden. Der wichtigste Befund der Datenanalysen ist der Rückgang der Phosphorfrachten der Wulka in den letzten Jahrzehnten, eine entsprechende Reaktion der trophischen Verhältnisse im See selbst sowie die Bedeutung horizontaler Austauschprozesse zwischen offenem See und Schilfgürtel für den langfristigen Erhalt einer guten Wasserqualität im Freiwasser und eines guten ökologischen Zustands des Neusiedler Sees.

This paper deals with nutrient dynamics at Lake Neusiedl, an issue that is inseparable from the inputs and exchange processes of suspended matter. Older studies from the early 1980s are summarised, discussed and compared with new findings from an ongoing EU INTERREG project (REBEN). The article first deals with the suspended matter and nutrient loads in Lake Neusiedl via the largest tributary of the lake, the river Wulka. In a second section changes due to chemical processes during the passage of the river Wulka through the reed belt at Donnerskirchen are described. The long-term development of nutrients in the open lake are discussed in the third part of the paper, which closes with the description of the horizontal distribution of suspended matter and nutrients in the reed belt and conclusions about horizontal currents and exchange processes. The most important finding of the data analysis is the decline of the phosphorus load of the river Wulka in recent decades, a corresponding reaction of the trophic conditions in the lake itself and the importance of horizontal exchange processes between the open lake and the reed belt for the preservation of a good water quality in the open water zone and a good ecological status of Lake Neusiedl.

Bulgaria has joined the official intercalibration (IC) in order to complete the state commitments for the classification of rivers based on Biological Quality Elements (BQE). The objective of this paper was to verify whether the present Bulgarian classification method for ecological status of large lowland (national type R7) and medium-sized lowland (national type R8) rivers was compliant with the normative definitions of the Water Framework Directive. Thus, a two-year study (2014 2015) on macroinvertebrate communities was conducted at 43 sites (18 from R7 and 25 from R8). Differences in qualitative and quantitative composition in the abovementioned river types, as well as indicative potential of BQE in relation to different anthropogenic pressures were analysed. Based on alternative benchmark sites (identified using the criteria defined by the EU), the High/Good boundary and a reference value for the Biotic index were defined. Class boundaries were in line with the results of the completed intercalibration exercise. We found a significant association between the biotic index and all three groups of pressures (land use, chemistry and hydro-morphology) and these results could be used for assessment of the ecological status. The national assessment method (based on our data) was in good agreement with the accepted methods from other member states who share the same river types within the Eastern Continental Geographical Intercalibration Group (EC-GIG).

Short-term impacts of aerial application of Bacillus thuringiensis israelensis (Bti) on Culicidae and Chironomidae were investigated over several years in temporary waters of the Dyje and Morava floodplains in Eastern Austria. The sampling followed a Before-After-Control-Impact (BACI) approach with sampling dates immediately before and shortly after the application and was repeated for 3 years. To test for effects of the Bti treatment on the two Diptera families, linear mixed-effects models were used. Data analysis included the factors Before-After and Control-Impact as fixed effects, while general temporal and spatial variables were random effects. One hundred sixteen taxa of chironomids were identified. Abundance varied between 2 and 1125 larvae per m2, while culicid densities reached values of several 100 ind. per liter. Total culicid abundance significantly decreased after the Bti treatment, whereas no significant effects were found on the abundance of total chironomids and dominant chironomid subfamilies, tribes, and genera, on relative proportions of chironomid feeding guilds, diversity, and species composition. Further studies from this area are needed to extend the investigation over a period of several weeks in order to reveal possible delayed effects of the larvicide application.

.......................................................................................................... 4 Introduction ...................................................................................................... 5 2 Part A: National assessment methods ................................................................ 5 2.1. Overview of national assessment methods for large rivers using phytoplankton .. 5 2.2. Pressure-impact relationships of national methods .......................................... 6 2.3. Checking of compliance with the WFD requirements ....................................... 23 2.4. Methods’ intercalibration feasibility check ...................................................... 38 3 Part B: Intercalibration exercise ....................................................................... 39 3.1. Global intercalibration exercise (option 2) ..................................................... 39 3.2. Intercalibration exercise (option 3) ............................................................... 53 4 Conclusions ................................................................................................... 61 References ...................................................................................................... 62 List of figures ................................................................................................... 63 List of tables .................................................................................................... 64 Annexes .......................................................................................................... 65 Annex I: Completed questionnaires of phytoplankton methods ........................ 65 Annex II: Description of national assessment methods in detail ...................... 114 Annex III: Overview of chlorophyll a boundaries of all countries ................... 139 Annex IV: R-script computing intercept offsets with linear mixed models .......... 141 Annex V: List of national delegates participating in the intercalibration exercise142 Annex VI: Offsets in single common metrics per IC river type gained from benchmark standardising the common metrics against the pressure index .......... 143 Annex VII: Offsets in national EQR units gained from benchmark standardising the national EQR scores against the CM12b .......................................................... 144 Annex VIII: Partial regressions within typeand pressure-parameter .............. 146 Annex IX: Complete list of sites and number of annual averages used in the IC exercise for phytoplankton ............................................................................ 156 Annex X: Justification for excluding specific BQE or sub-BQE (Gap 4) for the countries Sweden, Finland and Norway ........................................................... 164 Annex XI: Justification for excluding specific BQE or sub-BQE (Gap 4) for Italy . 170

The proposed new index BFBI-L5 was developed by using the data from 15 years ichthyological investigations in the Srebarna Lake (Danube floodplain). The method is based on the comparison of composition and structure of the fish community with the reference model ichthyocenosis as defined by historical data and data of specific hydromorphological features of the water body. Fish sampling shall be performed twice a year with standard bottom multi-mesh gillnets (NORDIC type) covering proportionally all main fish biotopes. Eleven indicators calculated through seven ichthyological parameters characterizing both fish community and type specific guilds are used to assess the ecological status of the lake. Each indicator is converted to score values according to its significance and to the specific metrics. The total sum of scores of all 11 indicators is used to calculate the ecological quality ratio (EQR) as the ratio of calculated sum of scores and the reference total score. The normalized EQR values equal the BFBI-L5, with equidistant class boundaries from 0 to 1. Although the index was developed for the lakes of type L5/L-EC1, the methodology for ecological assessment could be adapted also for other lowland natural lakes in Bulgaria, such as the lakes along the Black Sea coast.

The Water Framework Directive is the first international legislation to require European countries to establish comparable ecological assessment schemes for their freshwaters. A key element in harmonising quality classification within and between Europe's river basins is an "Intercalibration" exercise, stipulated by the WFD, to ensure that the good status boundaries in all of the biological assessment methods correspond to similar levels of anthropogenic pressure. In this article, we provide a comprehensive overview of this international comparison, focusing on the assessment schemes developed for freshwater lakes. Out of 82 lake ecological assessment methods reported for the comparison, 62 were successfully intercalibrated and included in the EC Decision on intercalibration, with a high proportion of phytoplankton (18), macrophyte (17) and benthic fauna (13) assessment methods. All the lake assessment methods are reviewed in this article, including the results of intercalibration. Furthermore, the current gaps and way forward to reach consistent management objectives for European lakes are discussed. (C) 2015 The Authors. Published by Elsevier Ltd.

We investigated the chemical characteristics of the astatic soda pans in the Carpathian Basin based on comprehensive new and archive data. Analysed parameters were salinity and ionic composition. The most frequent type of soda waters was the basic alkaline type (Na-HCO3) that represented more than half of the natural soda pans. Besides 11 subtypes occurred. The second and third most frequent types were the chloride (13%) and sulphate subtypes (11%), with the secondary dominance of these anions. The other subtypes meant <4% of the pans. Magnesium sometimes occurred as a secondary dominant cation beside sodium. Until now, this subtype of soda waters has not been published in any part of the world, because of the general rule of soda lake formation (depending on low levels of magnesium and calcium). We found a regionally constant correction factor [Salinity (mg.L-1) = 0.8 x E1.Cond. (mu S.cm(-1))] for confidentially estimating salinity from electrical conductivity in these habitats. Salinity varied between sub- (0.5-3 g.L-1) and hypersaline (>50 g.L-1) ranges, with its mean value (similar to 4 g.L-1) in the hyposaline range (3-20 g.L-1). The basic alkaline type had random geographical distribution, while the other subtypes were restricted to certain regions of the Basin. The high number of subtypes reflects the high chemical diversity of alkaline soda pans in the relatively small territory of the Carpathian Basin.

We review the severe water-management problems of the Nile Basin, where physical water scarcity is associated with high demographic growth, leading to a sharply rising demand for competing water uses such as hydropower and large-scale irrigation. Rapid economic growth is perceived as the means to emerge from the poverty trap that afflicts livelihoods in the Upper Basin and vital wetland ecosystem services such as fish biomass, freshwater biodiversity, groundwater recharge, flow regulation and local climate moderation are threatened by the water-development schemes and pollution that follow from this policy. Their cumulative impacts remain unaddressed. The High Aswan Dam's impacts on freshwater biodiversity are incompletely understood; a significant number of species may have become threatened as a result of its construction. Today the reservoir water quality is high, it is thought to support 47 fish species, its local human activities are restricted by central government regulations and recent estimates indicate that eutrophication threats are unlikely. Sediment and nutrient inputs coming into it from upstream will, however, continue to decrease in the near future as a result of newly built and planned dams in the upper basin. The dams will also reduce discharge and cause further loss of connectivity between the river and its floodplain, exacerbated by the possible completion of the Jonglei Canal bypassing the Sudd swamps. These impacts will affect the Nile's vulnerable aquatic biodiversity and regulatory services that are likely to affect local climate conditions. Under the current geopolitical scenario, management decisions that could favour participatory and sustainable options are over-ruled by high-level political trade-offs between the numerous riparian states. The financing of major hydropower developments by vested interests creates a scenario that is unlikely to favour sustainable resource management and conflict resolution.