Relative influence of chemical and non-chemical stressors on invertebrate communities: a case study in the Danube River

Four decades of region- and species-specific trends in lowland stream Ephemeroptera abundance

Lowland stream ecosystems are under threat from climate change, industrialization, urbanization, and intensive agriculture. Since the 1980s, improvements in water quality have led to an increase in lowland stream biodiversity. Despite restoration efforts, however, further recovery is often hampered by the presence of region-specific (combinations of) stressors, and species-specific stressor responses. Identification of these stressors may not be achieved by the analysis of abundance data over large areas for entire communities or species assemblages. Therefore, our study introduces an alternative in-depth approach, selecting Ephemeroptera as a model organism group and analyzing 41 years of species abundance data across distinct geographical regions. Our findings revealed that 15 Ephemeroptera species had already disappeared before 1985, emphasizing the importance of evaluating an extended historical period when analyzing biodiversity trends. While biodiversity was generally characterized by an initial recovery that stagnated over time, the analysis of the past 41 years of Ephemeroptera abundance data revealed strong differences in species' abundance trends between periods, regions, and species. Certain species were likely to have benefitted from local restoration measures in specific geographical regions, while others may have declined due to the presence of region-specific stressors. Our approach underscores the importance of studying the development of region- and species-specific stream biodiversity trends over time to aid the selection of the appropriate restoration measures to recover lowland stream biodiversity.

Water quality deterioration remains a major stressor for macroinvertebrate, diatom and fish communities in German rivers

About 60 % of Europe's rivers fail to meet ecological quality standards derived from biological criteria. The causes are manifold, but recent reports suggest a dominant role of hydro-morphological and water quality-related stressors. Yet, in particular micropollutants and hydrological stressors often tend to be underrepresented in multiple-stressor studies. Using monitoring data from four Federal States in Germany, this study investigated the effects of 19 stressor variables from six stressor groups (nutrients, salt ions, dissolved oxygen/water temperature, mixture toxicity of 51 micropollutants, hydrological alteration and morphological habitat quality) on three biological assemblages (fishes, macroinvertebrates, benthic diatoms). Biological effects were analyzed for 35 community metrics and quantified using Random Forest (RF) analyses to put the stressor groups into a hierarchical context. To compare metric responses, metrics were grouped into categories reflecting important characteristics of biological communities, such as sensitivity, functional traits, diversity and community composition as well as composite indices that integrate several metrics into one single index (e.g., ecological quality class). Water quality-related stressors - but not micropollutants - turned out to dominate the responses of all assemblages. In contrast, the effects of hydro-morphological stressors were less pronounced and stronger for hydrological stressors than for morphological stressors. Explained variances of RF models ranged 23-64 % for macroinvertebrates, 16-40 % for benthic diatoms and 18-48 % for fishes. Despite a high variability of responses across assemblages and stressor groups, sensitivity metrics tended to reveal stronger responses to individual stressors and a higher explained variance in RF models than composite indices. The results of this study suggest that (physico-chemical) water quality deterioration continues to impact biological assemblages in many German rivers, despite the extensive progress in wastewater treatment during the past decades. To detect water quality deterioration, monitoring schemes need to target relevant physico-chemical stressors and micropollutants. Furthermore, monitoring needs to integrate measures of hydrological alteration (e.g., flow magnitude and dynamics). At present, hydro-morphological surveys rarely address the degree of hydrological alteration. In order to achieve a good ecological status, river restoration and management needs to address both water quality-related and hydro-morphological stressors. Restricting analyses to just one single organism group (e.g., macroinvertebrates) or only selected metrics (e.g., ecological quality class) may hamper stressor identification and its hierarchical classification and, thus may mislead river management.

Understanding Ecological Complexity in a Chemical Stress Context: A Reflection on Recolonization, Recovery, and Adaptation of Aquatic Populations and Communities

Recovery, recolonization, and adaptation in a chemical stress context are processes that regenerate local populations and communities as well as the functions these communities perform. Recolonization, either by species previously present or by new species able to occupy the niches left empty, refers to a metacommunity process with stressed ecosystems benefiting from the dispersal of organisms from other areas. A potential consequence of recolonization is a limited capacity of local populations to adapt to potentially repeating events of chemical stress exposure when their niches have been effectively occupied by the new colonizers or by new genetic lineages of the taxa previously present. Recovery, instead, is an internal process occurring within stressed ecosystems. More specifically, the impact of a stressor on a community benefits less sensitive individuals of a local population as well as less sensitive taxa within a community. Finally, adaptation refers to phenotypic and, sometimes, genetic changes at the individual and population levels, allowing the permanence of individuals of previously existing taxa without necessarily changing the community taxonomic composition (i.e., not replacing sensitive species). Because these processes are usually operating in parallel in nature, though at different degrees, it seems relevant to try to understand their relative importance for the regeneration of community structure and ecosystem functioning after chemical exposure. In the present critical perspective, we employed case studies supporting our understanding of the underlying processes with the hope to provide a theoretical framework to disentangle the relevance of the three processes for the regeneration of a biological community after chemical exposure. Finally, we provide some recommendations to experimentally compare their relative importance so that the net effects of these processes can be used to parameterize risk-assessment models and inform ecosystem management. Environ Toxicol Chem 2023;42:1857-1866. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effects of multiple stressors on benthic invertebrates using Water Framework Directive monitoring data

Multiple stressors affect freshwater systems and cause a deficient ecological status according to the European Water Framework Directive (WFD). To select effective mitigation measures and improve the ecological status, knowledge on the stressor hierarchy and individual and joined effects is necessary. However, compared to common stressors like nutrient enrichment and morphological degradation, the relative importance of micropollutants such as pesticides and pharmaceuticals is largely unaddressed. We used WFD monitoring data from Saxony (Germany) to investigate the importance of 85 environmental variables (including 34 micropollutants) for 18 benthic invertebrate metrics at 108 sites. The environmental variables were assigned to five groups (natural factors, nutrient enrichment, metals, micropollutants and morphological degradation) and were ranked according to their relative importance as group and individually within and across groups using Principal Component Analyses (PCAs) and Boosted Regression Trees (BRTs). Overall, natural factors contributed the most to the total explained deviance of the models. This variable group represented not only typological differences between sampling sites but also a gradient of human impact by strongly anthropogenically influenced variables such as electric conductivity and dissolved oxygen. These large-scale effects can mask the individual importance of the other variable groups, which may act more specifically at a subset of sites. Accordingly, micropollutants were not represented by a few dominant variables but rather a diverse palette of different chemicals with similar contribution. As a group, micropollutants contributed similarly as metals, nutrient enrichment and morphological degradation. However, the importance of micropollutants might be underestimated due to limitations of the current chemical monitoring practices.

Identifying the impact of toxicity on stream macroinvertebrate communities in a multi-stressor context based on national ecological and ecotoxicological monitoring databases

In situ bioassays are used to measure the harmful effects induced by mixtures of toxic chemicals in watercourses. In France, national-scale biomonitoring data are available including invertebrate surveys and in-field chemical toxicity measures with caged gammarids to assess environmental toxicity of mixtures of chemicals. The main objective of our study is to present a proof-of-concept approach identifying possible links between in-field chemical toxicity, stressors and the ecological status. We used two active biomonitoring databases comprising lethal toxicity (222 in situ measures of gammarid mortality) and sublethal toxicity (101 in situ measures of feeding inhibition). We measured the ecological status of each active biomonitoring site using the I₂M₂ metric (macroinvertebrate-based multimetric index), accounted for known stressors of nutrients and organic matter, hydromorphology and chemical toxicity. We observed a negative relationship between stressors (hydromorphology, nutrients and organic matter, and chemical toxicity) and the good ecological status. This relationship was aggravated in watercourses where toxicity indicators were degraded. We validated this hypothesis for instance with nutrients and organic matter like nitrates or hydromorphological conditions like percentage of vegetation on banks. Future international assesments concerning the role of in-field toxic pollution on the ecological status in a multi-stressor context are now possible via the current methodology.

Two constructed wetlands within a Mediterranean natural park immersed in an agrolandscape reduce most heavy metal water concentrations and dampen the majority of pesticide presence

The water concentrations of 12 heavy and other metals/metalloids were analyzed seasonally along two horizontal-flow constructed wetlands (CWs) (Tancat Mília-TM and Tancat l'Illa-TLI) located within the Mediterranean Albufera de València Natural Park during 2020-2021. A wide-scope screening of pesticides present in waters was also performed. The two CWs were created to improve water quality and increase biodiversity. They currently receive effluent waters from two different tertiary-treatment wastewater plants, and the water flows along the CWs before being discharged into the main lagoon and a smaller lagoon in TM and TLI, respectively. TLI manages to reduce (Mn) or maintain the concentration of most of the studied elements (Zn, Ni, Hg, Cr, Fe Cd, Cu) at the same level as outside (67%). Only Al, Pb, B, and As remain at a higher concentration. TM also reduces Zn and Cu and keeps the concentration of Cr, Cd, and Hg (representing 42%). Al, Pb, B, and As remain at higher concentrations, as in TLI, but Ni, Fe, and Mn are also at higher concentrations. Although both CWs vary in their ability to remove elements, no risks to human health or the environment have been detected due to the low metal concentration in their outlets, all of them (except Hg) below the legal limits for environmental quality in the European Union. With the detection of 71 compounds in water in each CW area (26 herbicides, 26 insecticides, and 19 fungicides in TLI, and 29 herbicides, 23 insecticides, and 19 fungicides in TM), we also provide evidence of the impact of pesticides, which depends on the application method (helicopter, tractor), originated from areas with high agricultural pressure (chiefly rice crops) on systems (mainly TM) created to preserve biodiversity. Nevertheless, both systems provide crucial environmental services in water quality in this agrolandscape.

Contribution of sediment contamination to multi-stress in lowland waters

Water bodies in densely populated lowland areas are often impacted by multiple stressors. At these multi-stressed sites, it remains challenging to quantify the contribution of contaminated sediments. This study, therefore, aimed to elucidate the contribution of sediment contamination in 16 multi-stressed drainage ditches throughout the Netherlands. To this end an adjusted TRIAD framework was applied, where 1) contaminants and other variables in the sediment and the overlying water were measured, 2) whole-sediment laboratory bioassays were performed using larvae of the non-biting midge Chironomus riparius, and 3) the in situ benthic macroinvertebrate community composition was determined. It was hypothesized that the benthic macroinvertebrate community composition would respond to all jointly present stressors in both water and sediment, whereas the whole-sediment bioassays would only respond to the stressors present in the sediment. The benthic macroinvertebrate community composition was indeed related to multiple stressors in both water and sediment. Taxa richness was positively correlated with the presence of PO₄-P in the water, macrophyte cover and some pesticides. Evenness, the number of Trichoptera families and the SPEAR_pesticides were positively correlated to the C:P ratios in the sediment, whilst negative correlations were observed with various contaminants in both the water and sediment. The whole-sediment bioassays with C. riparius positively related to the nutrient content of the sediment, whereas no negative relations to the sediment-associated contaminants were observed, even though the lowered SPEAR_pesticides index indicated contaminant effects in the field. Therefore, it was concluded that sediment contamination was identified as one of the various stressors that potentially drove the benthic macroinvertebrate community composition in the multi-stressed drainage ditches, but that nutrients may have masked the adverse effects caused by low and diverse sediment contaminants on C. riparius in the bioassays.

Benthic Macroinvertebrate Diversity as Affected by the Construction of Inland Waterways along Montane Stretches of Two Rivers in China

Building inland waterways affects the natural structure, formation, and extent of the riverbed and riparian zone. It alters the hydrology and sediment deposition conditions and hence damages the aquatic ecosystem. To address the effects of the construction of inland waterways on the riverine biome, benthic macroinvertebrate communities were compared at different building stages of inland waterways along a gradient of shipping traffic density at two montane rivers in China. The Shannon–Wiener diversity index of the benthic macroinvertebrate communities ranged from 0.4 to 1.6; the lowest value was recorded in the completed inland waterway, while the highest value was recorded in the unaffected stretch. Principal component analysis and canonical correlation analysis showed the communities in the inland waterways to be distinct from those in the natural riparian habitats. Our results suggest that benthic macroinvertebrate communities can reflect the damage done by the hydromorphological modifications caused by building inland waterways. Benthic macroinvertebrate diversity and abundance should therefore be included when assessing the impact of building and operating inland waterways.

The effect of habitat restoration on macroinvertebrate communities in Shaoxi rivers, China

In recent decades, the biodiversity of freshwater environments has decreased sharply due to anthropogenic disturbances that damaged ecosystem structures and functions. Habitat restoration has emerged as an important method to mitigate the degradation of river ecosystems. Although in many cases a post-project monitoring has been promoted to access the restoration progress, it is still unclear how aquatic community changes following river habitat restoration in China. Macroinvertebrate communities intermediately positioned within ecosystem food webs play a key role in ecosystem processes within river ecosystem, driving energy flow and nutrient cycling. Here, benthic macroinvertebrates are used as bio-indicators to assess the ecosystem health of degraded urban rivers, restored urban rivers, and undisturbed rivers. This study aims to determine (i) how habitat restoration influences macroinvertebrates diversity and how this compared to degraded and reference conditions; (ii) how did macroinvertebrate community compositions differ in restored, degraded, and reference sites; and (iii) the environmental factors shaping macroinvertebrate communities. Habitat restoration significantly increased the diversity and richness of macroinvertebrate community and intolerant species and shifted the community composition towards reference status. Habitat characteristics and water chemistry, including substrate diversity, water velocity, and both nutrients (TN) and organic pollutants (TOC), appeared to shape the turnover of these communities. Habitat characteristics contributed to most of the variation of the entire macroinvertebrate community. Our research indicates that habitat restoration is an efficient approach to restore the aquatic community and hence improve river ecosystem health for freshwater conservation and sustainable management in Zhejiang province. This study strengthens our understanding of the changes of macroinvertebrate community after habitat restoration and important controlling variables that attribute to these changes, which provides an important guidance for future freshwater management.

The Eco-Exposome Concept: Supporting an Integrated Assessment of Mixtures of Environmental Chemicals

Organisms are exposed to ever-changing complex mixtures of chemicals over the course of their lifetime. The need to more comprehensively describe this exposure and relate it to adverse health effects has led to formulation of the exposome concept in human toxicology. Whether this concept has utility in the context of environmental hazard and risk assessment has not been discussed in detail. In this Critical Perspective, we propose-by analogy to the human exposome-to define the eco-exposome as the totality of the internal exposure (anthropogenic and natural chemicals, their biotransformation products or adducts, and endogenous signaling molecules that may be sensitive to an anthropogenic chemical exposure) over the lifetime of an ecologically relevant organism. We describe how targeted and nontargeted chemical analyses and bioassays can be employed to characterize this exposure and discuss how the adverse outcome pathway concept could be used to link this exposure to adverse effects. Available methods, their limitations, and/or requirement for improvements for practical application of the eco-exposome concept are discussed. Even though analysis of the eco-exposome can be resource-intensive and challenging, new approaches and technologies make this assessment increasingly feasible. Furthermore, an improved understanding of mechanistic relationships between external chemical exposure(s), internal chemical exposure(s), and biological effects could result in the development of proxies, that is, relatively simple chemical and biological measurements that could be used to complement internal exposure assessment or infer the internal exposure when it is difficult to measure. Environ Toxicol Chem 2022;41:30-45. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Sensitivity and specificity of macroinvertebrate responses to gradients of multiple agricultural stressors

Environmental degradation of rivers in agricultural landscapes is typically caused by multiple co-occurring stressors, but how interactions among stressors affect freshwater ecosystems is poorly understood. Therefore, we investigated the sensitivity and specificity of several measures of benthic macroinvertebrate community response to the individual and combined effects of the pesticide sulfoxaflor (SFX), increased sand sedimentation and elevated nutrients using outdoor recirculating mesocosms. Among the single stressor treatments, nutrients had no observable impact and sand only affected one community response measure compared to controls. High SFX levels had the largest effects on benthic macroinvertebrate communities, negatively affecting six of seven macroinvertebrate response measures. Sulfoxaflor had similar adverse effects on biota when in combination with sand and nutrients in the multi-stressor treatment, suggesting that generally SFX has overwhelming and pervasive effects irrespective of the presence of the other stressors. In contrast to SFX, elevated nutrients had no detectable effect on macroinvertebrate communities, likely as a consequence of nutrients being rapidly taken up by bacteria rather than by benthic algae. Elevated sand sedimentation increased the negative effects of SFX on sediment sensitive taxa, but generally had limited biological effects. This was despite the levels of sedimentation in our treatments being at concentrations that have caused large impacts in other studies. This research points to direct and rapid toxic effects of SFX on stream macroinvertebrates, contrasting with effects of the other stressors. This study emphasises that pesticide effects could be misattributed to other common freshwater stressors, potentially focussing restoration actions on a stressor of lesser importance.

Sub-organism (acetylcholinesterase activity), population (survival) and chemical concentration responses reinforce mechanisms of antagonism associated with malathion toxicity

Within human modified ecosystems the effects of individual stressors are difficult to establish amid co-occurring biological processes, environmental gradients and other stressors. Coupled examination of several endpoints across different levels of organisation may help elucidate the individual and combined effects of stressors and interactions. Malathion is a commonly used organophosphate pesticide that contaminates freshwaters and has strong negative effects on aquatic biota. However, both other stressors (e.g. increased sediment) and common ecosystem components (e.g. macrophytes and variable pH) can reduce the aqueous concentrations of malathion, reducing its toxic effects. We conducted a fully orthogonal bioassay to examine how pH (at 7 and 7.8) and sorptive processes (across two levels of kaoline clay 0 and 24 g L^-1) affected aqueous malathion concentrations and toxicity in an aquatic invertebrate genus. Survival and acetylcholinesterase activity as a sub-organism response were examined in the mayfly Coloburiscoides spp. (Ephemeroptera; Coluburiscidae). Measured aqueous malathion concentrations decreased with increased pH and in the presence of kaolin clay. Survival declined with increasing malathion concentrations and exposure period. Results further identify that antagonism of malathion toxicity was associated with both pH (alkaline hydrolysis) and effects associated with sediment independent of pH (driven by sorptive processes). However, model predictions varied associated with target and measured concentrations and concentrations examined. Antagonistic effects were most apparent using subset target malathion concentrations because of the dominant effect of malathion at high concentrations. Acetylcholinesterase activity, identified repression occurred across all treatments and did not identify antagonistic interactions, but these results were similar to survival responses at the time points examined (i.e. 120 h). Examination of chemistry, acetylcholinesterase, and survival, affords greater understanding of stressor effects and their interactions. Measured malathion concentrations may underestimate effects on aquatic biota; not because of synergism among stressors, but because of strong effects despite antagonism.

Trends of nutrients and metals in precipitation in northern Germany: the role of emissions and meteorology

We analyzed the precipitation chemistry for a maritime region in northern Germany (Schleswig-Holstein) from 1997 to 2017 in order to reveal temporal and spatial patterns and to evaluate the role of meteorological factors relative to emission reductions in Germany and Europe. Therefore, we applied several statistical methods such as time series decomposition, principal component, and redundancy analysis. We extracted two main groups: (i) a marine group (Cl, Na, Mg) that was related to natural processes like sea spray input and (ii) an anthropogenic group (Pb, Cd, As, Zn, and nitrogen species) with a terrestrial subgroup (Fe, Al, Mn), which were both related to emissions. These groups were valid for the spatial, seasonal, and annual trend data. Other elements, like Ca, K, total P, and sulfate, were influenced by natural and anthropogenic processes. The seasonal variation of ammonium deposition was caused primarily by ammonia emissions and ancillary by precipitation. Most heavy metals as well as sulfate, nitrate, and ammonium showed decreasing trends in concentrations and deposition fluxes. Only Hg did not show any trend. The decreasing depositions of sulfate and total nitrogen were correlated to emission reductions in Germany. The deposition of most heavy metals was influenced by emission reductions on European scale and meteorological factors such as wind speed and humidity. Hg did not show any correlation with the emission time series in Europe. Instead, it was correlated to the NAO index and wind, implying that global emissions and transport pathways determine the temporal development of Hg depositions. Overall, the study reveals that emission reductions positively influence regional depositions for most investigated substances. The regional spatial patterns of depositions were also influenced by local meteorological factors.

Effects of anthropogenic pollution and hydrological variation on macroinvertebrates in Mediterranean rivers: A case-study in the upper Tagus river basin (Spain)

Seasonal hydrological variation and chemical pollution represent two main drivers of freshwater biodiversity change in Mediterranean rivers. We investigated to what extent low flow conditions can modify the effects of chemical pollution on macroinvertebrate communities. To that purpose, we selected twelve sampling sites in the upper Tagus river basin (central Spain) having different sources of chemical pollution and levels of seasonal hydrological variation. The sites were classified as natural (high flow variation, low chemical impact), agricultural (high flow variation, high agricultural chemical inputs) and urban (limited flow variation, high urban chemical inputs). In these sites, we measured daily water discharge, nutrients, and contaminant concentrations, and we sampled benthic macroinvertebrates, in spring, summer and autumn. Significant differences related to toxic pressure and nutrient concentrations were observed between the three groups of sites. Seasonal patterns were found for some water quality parameters (e.g. nitrites, ammonia, suspended solids, metal toxicity), particularly in agricultural sites. Taxonomic and functional richness were slightly lower in the polluted sites (agricultural and urban), particularly during low flow periods (summer and early autumn). Functional diversity was significantly lower in sites with seasonal flow variation (agricultural sites) as compared to the more constant ones (urban sites). The frequency of traits such as large size, asexual reproduction, aquatic passive dispersion and the production of cocoons increased in response to pollution during low flow periods. This study shows that the impacts of anthropogenic chemical pollution on taxonomic and functional characteristics of macroinvertebrate communities seem to be larger during low flow periods. Therefore, further studies and monitoring campaigns assessing the effects of chemical pollution within these periods are recommended.

Can SPEcies At Risk of pesticides (SPEAR) indices detect effects of target stressors among multiple interacting stressors?

Pesticides are increasingly recognised as a threat to freshwater biodiversity, but their specific ecological effects remain difficult to distinguish from those of co-occurring stressors and environmental gradients. Using mesocosms we examined the effects of an organophosphate insecticide (malathion) on stream macroinvertebrate communities concurrently exposed to a suite of stressors typical of streams in agricultural catchments. We assessed the specificity of the SPEcies At Risk index designed to determine pesticide effects in mesocosm trials (SPEAR_mesocosm). This index determines the log abundance proportion of taxa that are considered physiologically sensitive to pesticides. Geographic variation in pesticide sensitivity within taxa, coupled with variation between pesticides and the effects of co-occurring stressors may decrease the accuracy of SPEAR_mesocosm. To examine this, we used local pesticide sensitivity assessments based on rapid toxicity tests to develop two new SPEAR versions to compare to the original SPEAR_mesocosms index using mesocosm results. We further compared these results to multivariate analyses and community indices (e.g. richness, abundance, Simpson's diversity) commonly used to assess stressor effects on biota. To assess the implications of misclassifying species sensitivity on SPEAR indices we used a series of simulations using artificial data. The impacts of malathion were detectable using SPEAR_mesocosm, and one of two new SPEAR indices. All three of the SPEAR indices also increased when exposed to other agricultural non-pesticide stressors, and this change increased with greater pesticide concentrations. Our results support that interactions between other non-pesticide stressors with pesticides can affect SPEAR performance. Multivariate analysis and the other indices used here identified a significant effect of malathion especially at high concentrations, with little or no evidence of effects from the other agricultural stressors.

Double constrained ordination for assessing biological trait responses to multiple stressors: A case study with benthic macroinvertebrate communities

Benthic macroinvertebrate communities are used as indicators for anthropogenic stress in freshwater ecosystems. To better understand the relationship between anthropogenic stress and changes in macroinvertebrate community composition, it is important to understand how different stressors and species traits are associated, and how these associations influence variation in species occurrence and abundances. Here, we show the capacity of the multivariate technique of double constrained correspondence analysis (dc-CA) to analyse trait-environment relationships, and we compare it with the redundancy analysis method on community weighted mean values of traits (CWM-RDA), which is frequently used for this type of analysis. The analyses were based on available biomonitoring data for macroinvertebrate communities from the Danube River. Results from forward selection of traits and environmental variables using dc-CA analyses showed that aquatic stages, reproduction techniques, dispersal tactics, locomotion and substrate relations, altitude, longitudinal and transversal distribution, and substrate preferendum were significantly related to habitat characteristics, hydromorphological alterations and water quality measurements such as physico-chemical parameters, heavy metals, pesticides and pharmaceuticals. Environmental variables significantly associated with traits using the CWM-RDA method were generally consistent with those found in dc-CA analysis. However, the CWM-RDA does neither test nor explicitly select traits, while dc-CA tests and selects both traits and environmental variables. Moreover, the dc-CA analysis revealed that the set of environmental variables was much better in explaining the community data than the available trait set, a kind of information that can neither be obtained from CWM-RDA nor from RLQ (Environment, Link and Trait data), which is a close cousin of dc-CA but not regression-based. Our results suggest that trait-based analysis based on dc-CA may be useful to assess mechanistic links between multiple anthropogenic stressors and ecosystem health, but more data sets should be analysed in the same manner.

Preliminary investigation of lower Danube pollution caused by potentially toxic metals

The current study aims to assess the pollution status of the European river-sea system lower Danube River-Danube Delta-North West Black Sea, through an integrated analysis of metal concentrations in water, sediments and fish community. The Danube flows through numerous industrial cities and receives a significant amount of pollutants due to the reception of urban and industrial emissaries, as well as agricultural land runoff. Samples of water, sediments and fish (10 species) were collected from 7 representative sites along Danube River, Danube Delta and Black Sea shore. For the analysed fish species, potentially toxic and essential elements (Pb, Cd, As, Cu, Fe, Zn, Mg, Ca, Na, K) from muscle and liver samples were measured and discussed. Measurement of elements and other environmental quality parameters were determined for water and sediments. The Black Sea area, represented by S6 and S7, received sediments from Danube with the lowest concentrations of Cd (0.05 ± 0.01 μg g^-1, respectively 0.01 ± 0.001 μg g^-1), Pb (3 ± 0.03 μg g^-1, respectively 2 ± 0.03 μg g^-1), As (2 ± 0.02 μg g^-1, respectively 1.4 ± 0.3 μg g^-1), Ni (8.9 ± 0.1 μg g^-1, respectively 5.2 ± 0.2 μg g^-1), Cr (8 ± 0.7 μg g^-1, respectively 5 ± 0.2 μg g^-1), Cu (3 ± 0.1 μg g^-1, respectively 2 ± 0.04 μg g^-1), Fe(6 ± 0.3 μg g^-1, respectively 3 ± 0.1 μg g^-1) and Zn (0.03 ± 0.003 μg g^-1, respectively 0.017 ± 0.001 μg g^-1). These results suggest that the Danube Delta system plays an important role in filtering the pollutants. Based on the biota and water analysis, there was no correlation observed between Cd, respectively Pb concentration in the environment and fish body (Person Coef. = -0.02 in muscle tissue and -0.01 in liver tissue, respectively Pearson Coeff. = -0.06 in muscle tissue and 0.1 in liver tissue). Cadmium remained an active element in the pollution of the Danube area (S1 and S2), with high concentration in the water matrix (0.14 ± 0.02 μg L^-1, respectively 0.05 ± 0.01 μg L^-1) and fish muscle (0.15 ± 0.03 μg g^-1f.w. in C. carpio - S2). This fact was confirmed by several other studies.

A mechanistic effect modeling approach to the prioritization of hidden drivers in chemical cocktails

Exposure to a single chemical does not exist in reality. Mixtures, which are the ecological norm, are often characterized by numerous intrinsic driving factors with unknown combined effects. Interactions between heterogeneous chemicals, or chemical and nonchemical stressors, could alter their toxicity traits relative to single exposure. Hence, revealing the hidden environmental effects affecting multiple stressor interactions is essential to expand our knowledge about uncertainty sources in chemical risk-based decision contexts. Global sensitivity analysis (GSA) techniques involving Morris method sampling and elementary effects (EE) sensitivity analysis was applied to investigate the driving factors underlying the combined effects on Scenedesmus obliquus, and identify the mode of interaction in mixtures at environmentally-relevant concentrations. One hundred mixed-exposure formulas were generated with 9 variables (8 chemicals and temperature) via the Morris method, representing environmental perspective in the field. Subsequently, EE sensitivity analysis combined with quantitative high-throughput screening (q-HTS) was adopted to identify the most critical mixture and its primary drivers. Combined exposure exerted significantly increased effects on S. obliquus compared to the effects of individual exposure. The critical drivers were identified and validated by the control variate method. For the mode of combined action, mixture toxicity did not match the additivity relationship, and a strong interaction existed among chemicals. Collectively, the data provides evidence that a combination of specific pesticides and emerging brominated flame retardants can produce comparable, or even stronger, bionegative effects than pure chemicals due to complicated interactions. The method used offers direct comparison of multifarious factors in a unified standard scale, bridges the actual interaction scenarios in the field to toxicity simulations in the laboratory, and fill a gap in ecotoxicology.

Hierarchical response of littoral macroinvertebrates to altered hydromorphology and eutrophication

The composition of littoral macroinvertebrate communities in lakes is governed by multiple natural and anthropogenic environmental influences interacting at different spatial scales. Since ecological assessment methods using littoral macroinvertebrates should respond specifically to a single stressor, knowledge on the unique effects of a given stressor is necessary. To effectively disentangle the effects of hydromorphology and trophic state requires analysing macroinvertebrate communities at lake sites with the full range of both stressors. We used a dataset of 98 lakes encompassing the entire gradient of geographical locations, lake types, hydromorphological degradation and trophic states in Central European lakes. We studied the unique and joint effects of hydromorphology and trophic state on macroinvertebrate richness, community composition and the Littoral Invertebrate Multimetric Index based on Composite Sampling (LIMCO). Variation partitioning analyses were conducted to test the importance of hydromorphology relative to trophic state across and within hydromorphological states (natural shorelines, hard and soft shore modifications) and trophic states (oligotrophic to hypertrophic states). At natural, hard and soft modification sites, hydromorphology explained 10, 16 and 19%, respectively, of the average unique variation of diversity, community composition and the LIMCO index, whereas trophic state explained on average 2, 5 and 5%, respectively. Similarly, in low, medium and high trophic state lakes, hydromorphology explained 10, 15 and 7%, respectively, of the average unique variation of diversity, community composition and the LIMCO index, whereas trophic state explained on average 0.3, 3 and 6%, respectively. Our results demonstrate that littoral hydromorphology was a more important driver of macroinvertebrate diversity, community composition and LIMCO than trophic state across hydromorphological states and trophic states. This indicates that multiple stressors in lakes act hierarchically on littoral macroinvertebrate communities and that the hydromorphological degradation of littoral zones is the primary driver for altered communities.

Occurrence and ecological risks of pharmaceuticals in a Mediterranean river in Eastern Spain

Pharmaceuticals are biologically active molecules that may exert toxic effects to a wide range of aquatic organisms. They are considered contaminants of emerging concern due to their common presence in wastewaters and in the receiving surface waters, and the lack of specific regulations to monitor their environmental occurrence and risks. In this work, the environmental exposure and risks of pharmaceuticals have been studied in the Mijares River, Eastern Mediterranean coast (Spain). A total of 57 surface water samples from 19 sampling points were collected in three monitoring campaigns between June 2018 and February 2019. A list of 40 compounds was investigated using a quantitative target UHPLC-MS/MS method. In order to complement the data obtained, a wide-scope screening of pharmaceuticals and metabolites was also performed by UHPLC-HRMS. The ecological risks posed by the pharmaceutical mixtures were evaluated using species sensitivity distributions built with chronic toxicity data for aquatic organisms. In this study, up to 69 pharmaceuticals and 9 metabolites were identified, out of which 35 compounds were assessed using the quantitative method. The highest concentrations in water corresponded to acetaminophen, gabapentin, venlafaxine, valsartan, ciprofloxacin and diclofenac. The compounds that were found to exert the highest toxic pressure on the aquatic ecosystems were principally analgesic/anti-inflammatory drugs and antibiotics. These were: phenazone > azithromycin > diclofenac, and to a lower extent norfloxacin > ciprofloxacin > clarithromycin. The monitored pharmaceutical mixtures are expected to exert severe ecological risks in areas downstream of WWTP discharges, with the percentage of aquatic species affected ranging between 65% and 82% in 3 out of the 19 evaluated sites. In addition, five antibiotics were found to exceed antibiotic resistance thresholds, thus potentially contributing to resistance gene enrichment in environmental bacteria. This work illustrates the wide use and impact of pharmaceuticals in the area under study, and the vulnerability of surface waters if only conventional wastewater treatments are applied. Several compounds included in this study should be incorporated in future water monitoring programs to help in the development of future regulations, due to their potential risk to the aquatic environment.

How to quantify the links between bioavailable contamination in watercourses and pressures of anthropogenic land cover, contamination sources and hydromorphology at multiple scales?

Active biomonitoring permits the quantification of biological exposure to chemicals through measurements of bioavailable concentrations in biota and biological markers of toxicity in organisms. It enables respective comparison of the levels of contamination between sites and sampling campaigns. Caged gammarids are recently proposed as relevant probes for measuring bioavailable contamination in freshwater systems. The purpose of the present study was to develop a multi-pressure and multiscale approach, considering metallic contamination levels (from data based on active biomonitoring) as a response to pressures (combination of individual stressors). These pressures were anthropogenic land cover, industry density, wastewater treatment plant density, pressures on stream hydromorphological functioning, riverside vegetation and bioavailability factors. A dataset combining active biomonitoring and potentially related pressures was established at the French national scale, with 196 samplings from 2009 to 2016. The links between pressures and metallic contamination were defined and modelled via structural equation modeling (more specifically partial least squares - path modeling). The model enabled the understanding of the respective influences of pressures on metallic bioconcentration in caged sentinel organisms. Beyond validating the local influence of industries and wastewater treatment plants on metallic contamination, this model showed a complementary effect of driving forces of anthropogenic land cover (leading to human activities). It also quantified a significant influence of pressures on stream hydromorphological functioning, presence of vegetation and physico-chemical parameters on metal bioconcentration. This hierarchical multi-pressure approach could serve as a concept on how pressures and contamination (assessed by active biomonitoring) can be connected. Its future application will enable better understanding of environmental pressures leading to contamination in freshwater ecosystems.

Benthic invertebrate and microbial biodiversity in sub-tropical urban rivers: Correlations with environmental variables and emerging chemicals

Urban rivers often function as sinks for various contaminants potentially placing the benthic communities at risk of exposure. We performed a comprehensive biological survey of the benthic macroinvertebrate and bacterial community compositions in six rivers from the suburb to the central urban area of Guangzhou city (South China), and evaluated their correlations with emerging organic contaminants, heavy metals and nutrients. Overall, the benthic macroinvertebrate community shifted from molluscs to oligochaete from the suburban to the central urban rivers that receive treated and untreated sewage. An exception was the site in the Sha River where chironomids were most abundant. The differences in macroinvertebrate community assemblages were significantly associated with chromium, total phosphorus, galaxolide, triclosan and sand content in the sediment. There was no significant difference in benthic macroinvertebrate composition between the dry and wet season. As assessed by double constrained ordination, sexual reproduction was the only trait of benthic macroinvertebrates that showed a significant correlation with pollution variables, as it was significantly positively correlated with chromium and total phosphorus. This suggests that r-strategist occurs in polluted sampling sites. The benthic bacterial community composition showed a significant difference between seasons and among the Liuxi River, Zhujiang River and central urban rivers. The differences in community composition of the benthic bacteria were significantly correlated with galaxolide, total phosphorus, lead and triclosan. These results suggest that input of treated and untreated sewage significantly altered the benthic macroinvertebrate and bacterial community compositions in urban rivers.

Is the Effect Assessment Approach for Fungicides as Laid Down in the European Food Safety Authority Aquatic Guidance Document Sufficiently Protective for Freshwater Ecosystems?

In Europe, the European Food Safety Authority aquatic guidance document describes the procedures for the derivation of regulatory acceptable concentrations (RACs) for pesticides in edge-of-field surface waters on the basis of tier-1 (standard test species), tier-2 (geometric mean and species sensitivity distributions [SSDs]), and tier-3 (model ecosystem studies) approaches. In the present study, the protectiveness of such a tiered approach was evaluated for fungicides. Acute and chronic RACs for tier-1 and tier-2B (SSDs) were calculated using toxicity data for standard and additional test species, respectively. Tier-3 RACs based on ecological thresholds (not considering recovery) could be derived for 18 fungicides. We show that tier-1 RACs, in the majority of cases, are more conservative than RACs calculated based on model ecosystem experiments. However, acute tier-2B RACs do not show a sufficient protection level compared with tier-3 RACs from cosm studies that tested a repeated pulsed exposure regime or when relatively persistent compounds were tested. Chronic tier-2B RACs showed a sufficient protection level, although they could only be evaluated for 6 compounds. Finally, we evaluated the suitability of the calculated RACs for 8 compounds with toxicity data for fungi. The comparison shows that the current RACs for individual fungicides, with a few exceptions (e.g., tebuconazole), show a sufficient protection level for structural and functional fungal endpoints. However, more data are needed to extend this comparison to other fungicides with different modes of action. Environ Toxicol Chem 2019;38:2279-2293. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Identification of contaminants of concern in the upper Tagus river basin (central Spain). Part 2: Spatio-temporal analysis and ecological risk assessment

This study provides a description of the water quality status in the tributaries of the upper Tagus River and a preliminary risk assessment for freshwater organisms. A wide range of physico-chemical parameters, nutrients, metals and organic contaminants (20 pesticides, and 32 point source chemicals, mainly pharmaceuticals) were monitored during spring, summer and autumn of 2016. Monitoring of organic contaminants was performed using conventional grab sampling and passive samples (POCIS). The variation of the different groups of parameters as regards to land use and sampling season was investigated. The prioritization of organic and inorganic contaminants was based on the toxic unit (TU) approach, using toxicity data for algae, invertebrates and fish. Finally, the compliance with the Environmental Quality Standards (EQS) set as part of the Water Framework Directive (WFD) was evaluated for the listed substances. This study shows that the land use characteristics had a large influence on the spatial distribution of the contaminants and other water quality parameters, while temporal trends were only significant for physico-chemical parameters, and marginally significant for insecticides. Acute toxicity is likely to occur for some metals (copper and zinc) in the most impacted sites (TU values close to or above 1). Low acute toxicity was determined for organic contaminants (individual compounds and mixtures) on the basis of grab samples. However, the assessment performed with POCIS samples identified diuron, chlorpyrifos and imidacloprid as potentially hazardous compounds. Several contaminant mixtures that may cause chronic toxicity and that should be considered in future regional chemical monitoring plans were identified. Our study also shows that some metals and pesticides exceeded the WFD regulatory thresholds and that only 30% of the sampled sites had a good chemical status. Further research is needed to identify chemical emission sources and to design proper abatement options in the Tagus river basin.

Identification of contaminants of concern in the upper Tagus river basin (central Spain). Part 1: Screening, quantitative analysis and comparison of sampling methods

Pesticides and point source contaminants (primarily pharmaceuticals) were monitored in 16 sampling sites of the upper Tagus river basin during spring, summer and autumn of 2016. A qualitative screening analysis was performed using a library of 430 compounds. Next, a novel method was implemented for the selection and quantification of contaminants with LC-MS/MS. The method is based on the frequency of detection in the screening, ecotoxicity data and the potential use in the watershed. Moreover, the efficacy of grab samples and passive samples (POCIS) in detecting compound-specific exposure patterns was compared during the summer sampling campaign. The screening method detected the presence of 268 compounds in the study area, out of which 52 were selected for the quantitative analysis (20 pesticides and 32 point source chemicals). Although very helpful in the prioritization exercise, the qualitative screening demonstrated some biases and the need for improvement by using more effective instruments for confirming positive results. Grab samples proved not to be fully suitable for contaminants with discontinuous exposure such as pesticides, which may be underestimated, but offer a sufficient basis for the characterization of contaminants coming from urban wastewaters. All selected chemicals showed a very high concentration variability due to differences among sampling sites, which are related to agricultural intensity and demographic pressure. Some insecticides (chlorpyrifos, dimethoate, imidacloprid), herbicides (diuron, metribuzine, simazine, terbuthylazine), and fungicides (carbendazim) were measured at concentrations exceeding 100 ng/L; while paracetamol, ibuprofen, some antibiotics (azithromycin, sulfamethoxazole, trimethoprim) and life-style compounds (caffeine, paraxanthine, nicotine) were found at very high concentrations (up to several μg/L). The results of this work represent the basis for the development of an ecological risk assessment for the aquatic ecosystem in the upper Tagus river basin and for the identification of basin-specific contaminant mixtures of environmental concern.

Agriculture versus wastewater pollution as drivers of macroinvertebrate community structure in streams

Water pollution is ubiquitous globally, yet how the effects of pollutants propagate through natural ecosystems remains poorly understood. This is because the interactive effects of multiple stressors are generally hard to predict. Agriculture and municipal wastewater treatment plants (WWTPs) are often major sources of contaminants for streams, but their relative importance and the role of different pollutants (e.g. nutrients or pesticides) are largely unknown. Using a 'real world experiment' with sampling locations up- and downstream of WWTPs, we studied how effluent discharges affected water quality and macroinvertebrate communities in 23 Swiss streams across a broad land-use gradient. Variation partitioning of community composition revealed that overall water quality explained approximately 30% of community variability, whereby nutrients and pesticides each independently explained 10% and 2%, respectively. Excluding oligochaetes (which were highly abundant downstream of the WWTPs) from the analyses, resulted in a relatively stronger influence (3%) of pesticides on the macroinvertebrate community composition, whereas nutrients had no influence. Generally, the macroinvertebrate community composition downstream of the WWTPs strongly reflected the upstream conditions, likely due to a combination of efficient treatment processes, environmental filtering and organismal dispersal. Wastewater impacts were most prominently by the Saprobic index, whereas the SPEAR index (a trait-based macroinvertebrate metrics reflecting sensitivity to pesticides) revealed a strong impact of arable cropping but only a weak impact of wastewater. Overall, our results indicate that agriculture can have a stronger impact on headwater stream macroinvertebrate communities than discharges from WWTP. Yet, effects of wastewater-born micropollutants were clearly quantifiable among all other influence factors. Improving our ability to further quantify the impacts of micropollutants requires highly-resolved water quality and taxonomic data with adequate spatial and temporal sampling. These improvements would help to better account for the underlying causal pathways that drive observed biological responses, such as episodic contaminant peaks and dispersal-related processes.

Critical review: Grand challenges in assessing the adverse effects of contaminants of emerging concern on aquatic food webs

Much progress has been made in the past few decades in understanding the sources, transport, fate, and biological effects of contaminants of emerging concern (CECs) in aquatic ecosystems. Despite these advancements, significant obstacles still prevent comprehensive assessments of the environmental risks associated with the presence of CECs. Many of these obstacles center around the extrapolation of effects of single chemicals observed in the laboratory or effects found in individual organisms or species in the field to impacts of multiple stressors on aquatic food webs. In the present review, we identify 5 challenges that must be addressed to promote studies of CECs from singular exposure events to multispecies aquatic food web interactions. There needs to be: 1) more detailed information on the complexity of mixtures of CECs in the aquatic environment, 2) a greater understanding of the sublethal effects of CECs on a wide range of aquatic organisms, 3) an ascertaining of the biological consequences of variable duration CEC exposures within and across generations in aquatic species, 4) a linkage of multiple stressors with CEC exposure in aquatic systems, and 5) a documenting of the trophic consequences of CEC exposure across aquatic food webs. We examine the current literature to show how these challenges can be addressed to fill knowledge gaps. Environ Toxicol Chem 2019;38:46-60. © 2018 SETAC.

Biological interactions mediate context and species-specific sensitivities to salinity

Toxicants have both sub-lethal and lethal effects on aquatic biota, influencing organism fitness and community composition. However, toxicant effects within ecosystems may be altered by interactions with abiotic and biotic ecosystem components, including biological interactions. Collectively, this generates the potential for toxicant sensitivity to be highly context dependent, with significantly different outcomes in ecosystems than laboratory toxicity tests predict. We experimentally manipulated stream macroinvertebrate communities in 32 mesocosms to examine how communities from a low-salinity site were influenced by interactions with those from a high-salinity site along a gradient of salinity. Relative to those from the low-salinity site, organisms from the high-salinity site were expected to have greater tolerance and fitness at higher salinities. This created the potential for both salinity and tolerant-sensitive organism interactions to influence communities. We found that community composition was influenced by both direct toxicity and tolerant-sensitive organism interactions. Taxon and context-dependent responses included: (i) direct toxicity effects, irrespective of biotic interactions; (ii) effects that were owing to the addition of tolerant taxa, irrespective of salinity; (iii) toxicity dependent on sensitive-tolerant taxa interactions; and (iv) toxic effects that were increased by interactions. Our results reinforce that ecological processes require consideration when examining toxicant effects within ecosystems.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Community-level and phenological responses of emerging aquatic insects exposed to 3 neonicotinoid insecticides: An in situ wetland limnocorral approach

Seasonal aquatic insect emergence represents a critical subsidy link between aquatic and terrestrial ecosystems. Early and late instar larvae developing in wetlands near neonicotinoid-treated cropland can be at risk of chronic insecticide exposure. In the present study, an in situ wetland limnocorral experiment compared emergent insect community responses to imidacloprid, clothianidin, and thiamethoxam. Twenty-one limnocorrals were dosed weekly for 9 wk to target peak nominal doses of 0.0, 0.05, or 0.5 μg/L, followed by a 6-wk recovery period. Thirty-nine aquatic insect taxa were recorded but 11 taxa groups made up 97% of the community composition. Principal response curves (PRCs) indicated that during the dosing period, community composition among the treatments resembled the controls. During the 6-wk recovery period, significant deviance was observed in the high imidacloprid treatment with similar trends in the clothianidin treatment, suggesting that community effects from neonicotinoid exposure can be delayed. Non-biting midges (Diptera: Chironomidae) and damselflies (Odonata: Zygoptera) emerged 18 to 25 d earlier than controls in the imidacloprid and clothianidin neonicotinoid treatments, with no effects from thiamethoxam treatments. These data suggest that phenology and subtle community effects can occur at measured neonicotinoid concentrations of 0.045 (imidacloprid) and 0.038 μg/L (clothianidin) under chronic repeated exposure conditions. Synchronization and community dynamics are critical to aquatic insects and consumers; thus, neonicotinoids may have broad implications for wetland ecosystem function. Environ Toxicol Chem 2018;37:2401-2412. © 2018 SETAC.

Reconciling monitoring and modeling: An appraisal of river monitoring networks based on a spatial autocorrelation approach - emerging pollutants in the Danube River as a case study

Rivers extend in space and time under the influence of their catchment area. Our perception largely relies on discrete spatial and temporal observations carried out at certain sites located throughout the catchment (monitoring networks, MN). However, MNs are constrained by (a) the distribution of sampling sites, (b) the dynamics of the variable considered and (c) the river hydrological conditions. In this study, all three aspects were captured and quantified by applying a spatial autocorrelation modeling approach. We exemplarily studied its application to 235 emerging contaminants (pesticides, pharmaceuticals, and personal care products [PPCP], industrial and miscellaneous) measured at 55 sampling sites in the Danube River. 22 out of the 235 compounds monitored were present at all sites and 125 were found in at least 50%.We first calculated the Moran Index (MI) to characterize the spatial autocorrelation of the compound set. 59 compounds showed MI≤0, which can be interpreted as 'no spatial correlation'. Next, spatial autocorrelation models were set for each compound. From the autocorrelation parameter ρ, catchment average correlation lengths were derived for each compound. MN optimality was examined and compounds were classified into three groups: (a) those with ρ≤0 [25%]; (b) those with ρ>0 and correl. length<average distance between consecutive sites [ 2%] and (c) those with ρ>0 and correl. length>average distance between consecutive sites [73%]. The MN was considered optimal only for the latter class. Networks with the larger average distance between consecutive sites resulted in a decreasing number of optimally monitored compounds. Furthermore, neighbors vs. local relative contributions were quantified based on the spatial autocorrelation model for all the measured compounds. The results of this study show how autocorrelation models can aid water managers to improve the design of river MNs, which are a key aspect of the Water Framework Directive.

Environmental stressors as a driver of the trait composition of benthic macroinvertebrate assemblages in polluted Iberian rivers

We used the trait composition of macroinvertebrate communities to identify the effects of pesticides and multiple stressors associated with urban land use at different sites of four rivers in Spain. Several physical and chemical stressors (high metal pollution, nutrients, elevated temperature and flow alterations) affected the urban sites. The occurrence of multiple stressors influenced aquatic assemblages at 50% of the sites. We hypothesized that the trait composition of macroinvertebrate assemblages would reflect the strategies that the assemblages used to cope with the respective environmental stressors. We used RLQ and fourth corner analysis to address the relationship between stressors and the trait composition of benthic macroinvertebrates. We found a statistically significant relationship between the trait composition and the exposure of assemblages to environmental stressors. The first RLQ dimension, which explained most of the variability, clearly separated sites according to the stressors. Urban-related stressors selected taxa that were mainly plurivoltine and fed on deposits. In contrast, pesticide impacted sites selected taxa with high levels of egg protection (better egg survival), indicating a potentially higher risk for egg mortality. Moreover, the trait diversity of assemblages at urban sites was low compared to that observed in pesticide impacted sites, suggesting the homogenization of assemblages in urban areas.

Water quality variables and pollution sources shaping stream macroinvertebrate communities

In 2015, over 90 percent of German rivers failed to reach a good ecological status as demanded by the EU Water Framework Directive (WFD). Deficits in water quality, mainly from diffuse pollution such as agricultural run-off, but also from wastewater treatment plants (WWTPs), have been suggested as important drivers of this decline in ecological quality. We modelled six macroinvertebrate based metrics indicating ecological quality for 184 streams in response to a) PCA-derived water quality gradients, b) individual water quality variables and c) catchment land use and wastewater exposure indices as pollution drivers. The aim was to evaluate the relative importance of key water quality variables and their sources. Indicator substances (i.e. carbamazepine and caffeine indicating wastewater exposure; herbicides indicating agricultural run-off) represented micropollutants in the analyses and successfully related water quality variables to pollution sources. Arable and urban catchment land covers were strongly associated with reduced ecological quality. Electric conductivity, oxygen concentration, caffeine, silicate and toxic units with respect to pesticides were identified as the most significant in-stream predictors in this order. Our results underline the importance to manage diffuse pollution, if ecological quality is to be improved. However, we also found a clear impact of wastewater on ecological quality through caffeine. Thus, improvement of WWTPs, especially preventing the release of poorly treated wastewater, will benefit freshwater communities.

Macroinvertebrate community in relation to water quality and riparian land use in a substropical mountain stream, China

Exploring how water quality and land use shape the benthic macroinvertebrate community composition is of widespread interest in biodiversity conservation and environmental management. In this study, we investigated the structures of benthic macroinvertebrate assemblages and their environmental controls in terms of water quality and riparian land use in the Jinshui River, China. We carried out three campaigns including wet season (August 2009), dry season (November 2009), and normal season (April 2010) based on the hydrological regime in Jinshui basin. The result showed that macroinvertebrate assemblage variations were better explained by water quality factors than land use based on variance partitioning procedure. The land use of 2 km upstream from the sampling sites had explained more variation than that of the whole riparian zone in upstream catchment on macroinvertebrate community, and land use of 2 km upstream also had more interactions with water quality. Canonical correspondence analysis (CCA) indicated that the elements or nutrient of magnesium (Mn), selenium (Se), strontium (Sr), silicon (Si), dissolved inorganic nitrogen (DN), sulfur (S), total organic carbon (TOC), and total nitrogen (TN) in water exhibited a strong relationship with macroinvertebrate assemblages. However, the variance in water quality explained by land use was lower than that explained by water quality in rivers using redundancy analysis. Our study suggested that proximate factors (i.e., water quality) were more important to interpret the macroinvertebrate community compared to ultimate factors (i.e., land use) for macroinvertebrate assemblages in river system.

An expanded conceptual framework for solution-focused management of chemical pollution in European waters

BACKGROUND

This paper describes a conceptual framework for solutions-focused management of chemical contaminants built on novel and systematic approaches for identifying, quantifying and reducing risks of these substances.

METHODS

The conceptual framework was developed in interaction with stakeholders representing relevant authorities and organisations responsible for managing environmental quality of water bodies. Stakeholder needs were compiled via a survey and dialogue. The content of the conceptual framework was thereafter developed with inputs from relevant scientific disciplines.

RESULTS

The conceptual framework consists of four access points: Chemicals, Environment, Abatement and Society, representing different aspects and approaches to engaging in the issue of chemical contamination of surface waters. It widens the scope for assessment and management of chemicals in comparison to a traditional (mostly) perchemical risk assessment approaches by including abatement- and societal approaches as optional solutions. The solution-focused approach implies an identification of abatement- and policy options upfront in the risk assessment process. The conceptual framework was designed for use in current and future chemical pollution assessments for the aquatic environment, including the specific challenges encountered in prioritising individual chemicals and mixtures, and is applicable for the development of approaches for safe chemical management in a broader sense. The four access points of the conceptual framework are interlinked by four key topics representing the main scientific challenges that need to be addressed, i.e.: identifying and prioritising hazardous chemicals at different scales; selecting relevant and efficient abatement options; providing regulatory support for chemicals management; predicting and prioritising future chemical risks. The conceptual framework aligns current challenges in the safe production and use of chemicals. The current state of knowledge and implementation of these challenges is described.

CONCLUSIONS

The use of the conceptual framework, and addressing the challenges, is intended to support: (1) forwarding sustainable use of chemicals, (2) identification of pollutants of priority concern for cost-effective management, (3) the selection of optimal abatement options and (4) the development and use of optimised legal and policy instruments.

Effects of water scarcity and chemical pollution in aquatic ecosystems: State of the art

Water scarcity is an expanding climate and human related condition, which drives and interacts with other stressors in freshwater ecosystems such as chemical pollution. In this study we provide an overview of the existing knowledge regarding the chemical fate, biological dynamics and the ecological risks of chemicals under water scarcity conditions. We evaluated a total of 15 studies dealing with the combined effects of chemicals and water scarcity under laboratory conditions and in the field. The results of these studies have been elaborated in order to evaluate additive, synergistic or antagonistic responses of the studied endpoints. As a general rule, it can be concluded that, in situations of water scarcity, the impacts of extreme water fluctuations are much more relevant than those of an additional chemical stressor. Nevertheless, the presence of chemical pollution may result in exacerbated ecological risks in some particular cases. We conclude that further investigations on this topic would take advantage on the focus on some specific issues. Experimental (laboratory and model ecosystem) studies should be performed on different biota groups and life stages (diapausing eggs, immature stages), with particular attention to those including traits relevant for the adaptation to water scarcity. More knowledge on species adaptations and recovery capacity is essential to predict community responses to multiple stressors and to assess the community vulnerability. Field studies should be performed at different scales, particularly in lotic systems, in order to integrate different functional dynamics of the river ecosystem. Combining field monitoring and experimental studies would be the best option to reach more conclusive, causal relationships on the effects of co-occurring stressors. Contribution of these studies to develop ecological models and scenarios is also suggested as an improvement for the prospective aquatic risk assessment of chemicals in (semi-)arid areas.