How tolerances, competition and dispersal shape benthic invertebrate colonisation in restored urban streams

Biotic communities often respond poorly to river restoration activities and the drivers of community recovery after restoration are not fully understood. According to the Asymmetric Response Concept (ARC), dispersal capacity, species tolerances to stressors, and biotic interactions are three key drivers influencing community recovery of restored streams. However, the ARC remains to be tested. Here we used a dataset on benthic invertebrate communities of eleven restored stream sections in a former open sewer system that were sampled yearly over a period of eleven years. We applied four indices that reflect tolerance against chloride and organic pollution, the community's dispersal capacity and strength of competition to the benthic invertebrate taxa lists of each year and site. Subsequently, we used generalised linear mixed models to analyse the change of these indices over time since restoration. Dispersal capacity was high directly after restoration but continuously decreased over time. The initial communities thus consisted of good dispersers and were later joined by more slowly dispersing taxa. The tolerance to organic pollution also decreased over time, reflecting continuous improvement of water quality and an associated increase of sensitive species. On the contrary, chloride tolerances did not change, which could indicate a stable chloride level throughout the sampling period. Lastly, competition within the communities, reflected by interspecific trait niche overlap, increased with time since restoration. We show that recovery follows a specific pattern that is comparable between sites. Benthic communities change from tolerant, fast dispersing generalists to more sensitive, slowly dispersing specialists exposed to stronger competition. Our results lay support to the ARC (increasing role of competition, decreasing role of dispersal) but also underline that certain tolerances may still shape communities a decade after restoration. Disentangling the drivers of macroinvertebrate colonisation can help managers to better understand recovery trajectories and to define more realistic restoration targets.

Scrutinizing the Role of Venoarterial Extracorporeal Membrane Oxygenation: Has Clinical Practice Outpaced the Evidence?

The use of venoarterial extracorporeal membrane oxygenation (VA-ECMO) for temporary mechanical circulatory support in various clinical scenarios has been increasing consistently, despite the lack of sufficient evidence regarding its benefit and safety from adequately powered randomized controlled trials. Although the ARREST trial (Advanced Reperfusion Strategies for Patients with Out-of-Hospital Cardiac Arrest and Refractory Ventricular Fibrillation) and a secondary analysis of the PRAGUE OHCA trial (Prague Out-of-Hospital Cardiac Arrest) provided some evidence in favor of VA-ECMO in the setting of out-of-hospital cardiac arrest, the INCEPTION trial (Early Initiation of Extracorporeal Life Support in Refractory Out-of-Hospital Cardiac Arrest) has not found a relevant improvement of short-term mortality with extracorporeal cardiopulmonary resuscitation. In addition, the results of the recently published ECLS-SHOCK trial (Extracorporeal Life Support in Cardiogenic Shock) and ECMO-CS trial (Extracorporeal Membrane Oxygenation in the Therapy of Cardiogenic Shock) discourage the routine use of VA-ECMO in patients with infarct-related cardiogenic shock. Ongoing clinical trials (ANCHOR [Assessment of ECMO in Acute Myocardial Infarction Cardiogenic Shock, NCT04184635], REVERSE [Impella CP With VA ECMO for Cardiogenic Shock, NCT03431467], UNLOAD ECMO [Left Ventricular Unloading to Improve Outcome in Cardiogenic Shock Patients on VA-ECMO, NCT05577195], PIONEER [Hemodynamic Support With ECMO and IABP in Elective Complex High-risk PCI, NCT04045873]) may clarify the usefulness of VA-ECMO in specific patient subpopulations and the efficacy of combined mechanical circulatory support strategies. Pending further data to refine patient selection and management recommendations for VA-ECMO, it remains uncertain whether the present usage of this device improves outcomes.

Multi-decadal improvements in the ecological quality of European rivers are not consistently reflected in biodiversity metrics

Humans impact terrestrial, marine and freshwater ecosystems, yet many broad-scale studies have found no systematic, negative biodiversity changes (for example, decreasing abundance or taxon richness). Here we show that mixed biodiversity responses may arise because community metrics show variable responses to anthropogenic impacts across broad spatial scales. We first quantified temporal trends in anthropogenic impacts for 1,365 riverine invertebrate communities from 23 European countries, based on similarity to least-impacted reference communities. Reference comparisons provide necessary, but often missing, baselines for evaluating whether communities are negatively impacted or have improved (less or more similar, respectively). We then determined whether changing impacts were consistently reflected in metrics of community abundance, taxon richness, evenness and composition. Invertebrate communities improved, that is, became more similar to reference conditions, from 1992 until the 2010s, after which improvements plateaued. Improvements were generally reflected by higher taxon richness, providing evidence that certain community metrics can broadly indicate anthropogenic impacts. However, richness responses were highly variable among sites, and we found no consistent responses in community abundance, evenness or composition. These findings suggest that, without sufficient data and careful metric selection, many common community metrics cannot reliably reflect anthropogenic impacts, helping explain the prevalence of mixed biodiversity trends.

River ecological status is shaped by agricultural land use intensity across Europe

Agriculture impacts the ecological status of freshwaters through multiple pressures such as diffuse pollution, water abstraction, and hydromorphological alteration, strongly impairing riverine biodiversity. The agricultural effects, however, likely differ between agricultural types and practices. In Europe, agricultural types show distinct spatial patterns related to intensity, biophysical conditions, and socioeconomic history, which have been operationalised by various landscape typologies. Our study aimed at analysing whether incorporating agricultural intensity enhances the correlation between agricultural land use and the ecological status. For this, we aggregated the continent's agricultural activities into 20 Areas of Farming-induced Freshwater Pressures (AFFP), specifying individual pressure profiles regarding nutrient enrichment, pesticides, water abstraction, and agricultural land use in the riparian zone to establish an agricultural intensity index and related this intensity index to the river ecological status. Using the agricultural intensity index, nearly doubled the correlative strength between agriculture and the ecological status of rivers as compared to the share of agriculture in the sub-catchment (based on the analysis of more than 50,000 sub-catchment units). Strongest agricultural pressures were found for high intensity cropland in the Mediterranean and Temperate regions, while extensive grassland, fallow farmland and livestock farming in the Northern and Highland regions, as well as low intensity mosaic farming, featured lowest pressures. The results provide advice for pan-European management of freshwater ecosystems and highlight the urgent need for more sustainable agriculture. Consequently, they can also be used as a basis for European Union-wide and global policies to halt biodiversity decline, such as the post-2027 renewal of the Common Agricultural Policy.

Effects of agriculture on river biota differ between crop types and organism groups

While the general effects of agricultural land use on riverine biota are well documented, the differential effects of specific crop types on different riverine organism groups, remain largely unexplored. Here we used recently published land use data distinguishing between specific crop types and a Germany-wide dataset of 7748 sites on the ecological status of macroinvertebrates, macrophytes and diatoms and applied generalized linear mixed models to unravel the associations between land use types, crop types, and the ecological status. For all organism groups, associations of specific crop types with biota were stronger than those of urban land use. For macroinvertebrates and macrophytes, strong negative associations were found for pesticide intensive permanent crops, while intensively fertilized crops (maize, intensive cereals) affected diatoms most. These differential associations highlight the importance of distinguishing between crop types and organism groups and the urgency to buffer rivers against agricultural stressors at the catchment scales and to expand sustainably managed agriculture.

Stressors affecting the ecological status of temporary rivers in the Mediterranean region

Temporary rivers are widespread in the Mediterranean region and impose a challenge for the implementation of the Water Framework Directive (WFD) and other environmental regulations. Surprisingly, an overarching analysis of their ecological status and the stressors affecting them is yet missing. We compiled data on the ecological status of 1504 temporary rivers in seven European Mediterranean region countries and related their ecological status (1) to publicly available data on pressures from the European WISE-WFD dataset, and (2) to seven more specific stressors modelled on a sub-catchment scale. More than 50 % of the temporary water bodies in the Mediterranean countries reached good or even high ecological status. In general, status classes derived from phytobenthos and macrophyte assessment were higher than those derived from the assessment of benthic invertebrates or fish. Of the more generally defined pressures reported to the WISE-WFD database, the most relevant for temporary rivers were 'diffuse agricultural' and 'point urban waste water'. Of the modelled more specific stressors, agricultural land use best explained overall ecological status, followed by total nitrogen load, and urban land use, while toxic substances, total phosphorus load and hydrological stressors were less relevant. However, stressors differed in relevance, with total nitrogen being most important for macrophytes, and agricultural land use for phytobenthos, benthic invertebrates and fish. For macrophytes, ecological quality increased with stressor intensity. The results underline the overarching effect of land use intensity for the ecological status of temporary water bodies. However, assessment results do not sufficiently reflect hydrological stress, most likely as the biological indicators used to evaluate these systems were designed for perennial water bodies and thus mainly target land use and nutrient impacts. We conclude that biomonitoring systems need to be updated or newly developed to better account for the specific situation of temporary water bodies.

Quality Analysis of Radiation Therapy for Hodgkin Lymphoma in the HD 16/17 Trials: A Final Report By the Reference Radiation Oncology Panel of the German Hodgkin Study Group

PURPOSE/OBJECTIVE(S)

The HD 16 and 17 trials by the German Hodgkin Study Group (GHSG) have evaluated the use of consolidative radiotherapy (RT) in early-favorable and -unfavorable stage Hodgkin lymphoma (HL), respectively (1, 2). Quality of RT planning and execution is pivotal for treatment outcome in HL with protocol violations jeopardizing prognosis (3). Consequently, the present work aims at a decisive analysis of quality and dosimetry in the modern era.

MATERIALS/METHODS

Random samples of 100 involved-field RT (IFRT) plans in HD16 and 176 plans in HD17 (134 involved-node RT (INRT) and 42 IFRT) were selected for analysis. Evaluation was performed systematically by the reference radiation oncology panel using pre-chemotherapy imaging, recommendation by the reference radiation oncology and RT planning imaging and graded as "correct", "minor" or "major deviation", respectively. RT doses to the target volume and organs at risks (OAR) were analyzed using dose-volume histograms.

RESULTS

Median RT doses were 20 Gy (19.8 Gy-21.6 Gy) in HD16 and 30 Gy in HD17 (IFRT: 18-30.6 Gy, INRT: 14 Gy-40 Gy). Overall, 84.0%, 69.0%, and 76.1% of RT series in HD16, the IFRT-group of HD17 and the INRT-group of HD17, respectively, were planned correctly. The main reason for major deviation was an insufficient coverage of an involved region (11 %-14.3 %). There was no significant difference in quality between IFRT and INRT in HD17 (p = 0.418 for any deviations; p = 0.466 for major deviations). In comparison to previous GHSG studies in the respective stages, a significant increase in correct RT-series (p<0.001) and decrease in major deviations (p<0.001) occurred. However, doses to OAR varied individually with median values of 4.3 Gy (0.2 Gy-9.2 Gy), 4.7 Gy (0.2 Gy-15.2 Gy) and 3.8 Gy (0.0 Gy-16.0 Gy) for mean doses to the right lung, left lung and heart in HD16, respectively. Correspondingly, values were 9.8 Gy (0.3 Gy-20.0 Gy), 10.5 Gy (0.2 Gy-26.5 Gy) and 13.1 Gy (0.5 Gy-30.4 Gy) for mean doses to the right lung, left lung and heart in HD17, respectively. The size of the planning target volume decreased significantly with INRT compared to IFRT (median values: 1163.1 ml vs. 1464.3 ml; p = 0.043). However, only some OAR-parameters (V25 of the right and left lung, respectively, thyroid and spinal cord) showed significant differences between INRT and IFRT in HD17. The use of intensity-modulated techniques in HD 17 resulted in an increase in V5 and V10 of the lungs with a concomitant decrease in V20-V30.

CONCLUSION

Quality of RT in the planning and treatment of HL has improved significantly with the latest GHSG study generation. Future analyses will focus on a further individualization of treatment fields.

LITERATURE

MRI, FDG-PET/CT and Image-Guidance for Re-Irradiation of Locoregionally Recurrent or Second Primary Head-and-Neck Squamous Cell Carcinoma Patients - Results of a Multicenter Cohort Study

PURPOSE/OBJECTIVE(S)

To investigate patterns of care and prognostic benefits of MRI, FDG-PET/CT and image-guidance in re-irradiation of locoregionally recurrent or second primary head-and-neck squamous cell carcinomas (r/s HNSCCs) within a multicenter cohort study.

MATERIALS/METHODS

Patients receiving re-irradiation for r/s HNSCC between 2009 and 2020 at 16 tertiary cancer centers in Germany were retrospectively analyzed in terms of MRI and FDG-PET/CT usage for treatment planning and regarding image-guidance frequency during re-irradiation. Patterns of use of these modalities over time were analyzed by binary logistic regression analysis, and the association between the usage of these modalities and best locoregional treatment response was analyzed with chi-square tests. Cumulative incidence analyses of locoregional failures with death as competing event were performed.

RESULTS

In the total cohort of 297 patients, 226 (76%) were male, median age was 62 years (IQR, 56-70), and median ECOG was 1 (IQR, 1-2). There were 260 locoregionally recurrent HNSCCs, and 37 second primary HNSCCs; 44 patients (15%) had distant metastases at the time of re-irradiation. MRI and FDG-PET/CT was used for re-irradiation planning in 117 (39%) and 71 patients (24%), respectively. In median, image guidance (IGRT) was performed twice weekly (IQR, 1-5), usually with cone beam CTs or megavolt-CTs, and 85 patients (29%) received daily IGRT during re-irradiation. Usage of MRI (OR = 0.967; 95% CI, 0.892-1.048; p = .416), FDG-PET/CT (OR = 1.053; 95% CI, 0.960-1.156; p = .274), or daily IGRT (OR = 1.057; 95% CI, 0.968-1.115; p = .218) did not increase in frequency over time within the analyzed time span but was significantly dependent on the treatment center (χ2(15), P<.001 for all modalities). Daily IGRT was associated with a higher rate of at least stable disease after re-irradiation as assessed by RECIST criteria (χ2(1) = 4.011, p<.05). There was a trend towards better RECIST-assessed treatment response for MRI (χ2(1) = 3.223, p = .073) and FDG-PET/CT (χ2(1) = 2.792, p = .095) as part of the re-irradiation planning process. Incidence of locoregional failures was not dependent on MRI (SHR = 0.94; 95% CI, 0.67-1.33; p = 0.741, Fine-Gray), FDG-PET/CT (SHR = 0.88; 95% CI, 0.59-1.33; p = 0.552) or daily IGRT (SHR = 0.76; 95% CI, 0.51-1.14, p = 0.182), There was a trend towards lower acute grade 3/4-toxicities in patients receiving daily IGRT (χ2(1) = 3.354, p = 0.067).

CONCLUSION

Our data suggest that daily IGRT may increase disease control and should be regularly applied for re-irradiation of r/s HNSCCs. MRI and FDG-PET/CT usage were not associated with the incidence of locoregional failures after re-irradiation. However, prospective trials with multiparametric MRI and/or FDG-PET/CT for optimal re-irradiation planning are warranted.

Of causes and symptoms: using monitoring data and expert knowledge to diagnose the causes of stream degradation

Ecological status assessment under the European Water Framework Directive (WFD) often integrates the impact of multiple stressors into a single index value. This hampers the identification of individual stressors being responsible for status deterioration. As a consequence, management measures are often disentangled from assessment results. To close this gap and to support river basin managers in the diagnosis of stressors, we linked numerous macroinvertebrate assessment metrics and one diatom index with potential causes of ecological deterioration through Bayesian belief networks (BBNs). The BBNs were informed by WFD monitoring data as well as regular consultation with experts and allow to estimate the probabilities of individual degradation causes based upon a selection of biological metrics. Macroinvertebrate metrics were shown to be stronger linked to hydromorphological conditions and land use than to water quality-related parameters (e.g., thermal and nutrient pollution). The modeled probabilities also allow to order the potential causes of degradation hierarchically. The comparison of assessment metrics showed that compositional and trait-based community metrics performed equally well in the diagnosis. The testing of the BBNs by experts resulted in an agreement between model output and expert opinion of 17-92% for individual stressors. Overall, the expert-based validation confirmed a good diagnostic potential of the BBNs; on average 80% of the diagnosed causes were in agreement with expert judgement. We conclude that diagnostic BBNs can assist the identification of causes of stream and river degradation and thereby inform the derivation of appropriate management decisions.

The recovery of European freshwater biodiversity has come to a halt

Owing to a long history of anthropogenic pressures, freshwater ecosystems are among the most vulnerable to biodiversity loss1. Mitigation measures, including wastewater treatment and hydromorphological restoration, have aimed to improve environmental quality and foster the recovery of freshwater biodiversity2. Here, using 1,816 time series of freshwater invertebrate communities collected across 22 European countries between 1968 and 2020, we quantified temporal trends in taxonomic and functional diversity and their responses to environmental pressures and gradients. We observed overall increases in taxon richness (0.73% per year), functional richness (2.4% per year) and abundance (1.17% per year). However, these increases primarily occurred before the 2010s, and have since plateaued. Freshwater communities downstream of dams, urban areas and cropland were less likely to experience recovery. Communities at sites with faster rates of warming had fewer gains in taxon richness, functional richness and abundance. Although biodiversity gains in the 1990s and 2000s probably reflect the effectiveness of water-quality improvements and restoration projects, the decelerating trajectory in the 2010s suggests that the current measures offer diminishing returns. Given new and persistent pressures on freshwater ecosystems, including emerging pollutants, climate change and the spread of invasive species, we call for additional mitigation to revive the recovery of freshwater biodiversity.

The Asymmetric Response Concept explains ecological consequences of multiple stressor exposure and release

Our capacity to predict trajectories of ecosystem degradation and recovery is limited, especially when impairments are caused by multiple stressors. Recovery may be fast or slow and either complete or partial, sometimes result in novel ecosystem states or even fail completely. Here, we introduce the Asymmetric Response Concept (ARC) that provides a basis for exploring and predicting the pace and magnitude of ecological responses to, and release from, multiple stressors. The ARC holds that three key mechanisms govern population, community and ecosystem trajectories. Stress tolerance is the main mechanism determining responses to increasing stressor intensity, whereas dispersal and biotic interactions predominantly govern responses to the release from stressors. The shifting importance of these mechanisms creates asymmetries between the ecological trajectories that follow increasing and decreasing stressor intensities. This recognition helps to understand multiple stressor impacts and to predict which measures will restore communities that are resistant to restoration.

Freshwater-related species richness in Natura 2000 sites strongly depends on the surrounding land use besides local habitat conditions

The Birds and Habitats Directive are the cornerstones of Europe's nature conservation policy and the resulting Natura 2000 (N2k) sites form the largest coordinated network of protected areas in the world. Despite the ambitious targets of these directives and decades of efforts, biodiversity, especially of freshwater-related species, continues to decline in Europe. While multiple stressors at larger spatial scales are known to limit the effect of river restoration projects, the importance of surrounding land use outside the N2k sites for freshwater-related species richness inside N2k sites has rarely been studied. Conditional inference forests were used to assess the importance of land use in the surrounding and upstream of the German N2k sites compared to local habitat conditions inside. Freshwater-related species richness depended on land use in the surrounding besides local habitat conditions. Results indicated that this was especially true for birds in small N2k sites embedded in a wet, diverse, and patchy landscape and for non-birds due to the provision of additional habitats outside the N2k sites. Given that most N2k sites in Europe are rather small, the surrounding habitat conditions and land use potentially influences and affects freshwater-related species in many N2k sites across Europe. The additional conservation and restoration areas to be designated under the EU Biodiversity Strategy and upcoming EU restoration law should either be large enough or surrounded by extensive land use to optimize their effect on freshwater-related species.

Perceived multiple stressor effects depend on sample size and stressor gradient length

Multiple stressors are continuously deteriorating surface waters worldwide, posing many challenges for their conservation and restoration. Combined effect types of multiple stressors range from single-stressor dominance to complex interactions. Identifying prevalent combined effect types is critical for environmental management, as it helps to prioritise key stressors for mitigation. However, it remains unclear whether observed single and combined stressor effects reflect true ecological processes unbiased by sample size and length of stressor gradients. Therefore, we examined the role of sample size and stressor gradient lengths in 158 paired-stressor response cases with over 120,000 samples from rivers, lakes, transitional and marine ecosystems around the world. For each case, we split the overall stressor gradient into two partial gradients (lower and upper) and investigated associated changes in single and combined stressor effects. Sample size influenced the identified combined effect types, and stressor interactions were less likely for cases with fewer samples. After splitting gradients, 40 % of cases showed a change in combined effect type, 30 % no change, and 31 % showed a loss in stressor effects. These findings suggest that identified combined effect types may often be statistical artefacts rather than representing ecological processes. In 58 % of cases, we observed changes in stressor effect directions after the gradient split, suggesting unimodal stressor effects. In general, such non-linear responses were more pronounced for organisms at higher trophic levels. We conclude that observed multiple stressor effects are not solely determined by ecological processes, but also strongly depend on sampling design. Observed effects are likely to change when sample size and/or gradient length are modified. Our study highlights the need for improved monitoring programmes with sufficient sample size and stressor gradient coverage. Our findings emphasize the importance of adaptive management, as stress reduction measures or further ecosystem degradation may change multiple stressor-effect relationships, which will then require associated changes in management strategies.

GPR55 in B cells limits atherosclerosis development and regulates plasma cell maturation

Dissecting the pathways regulating the adaptive immune response in atherosclerosis is of particular therapeutic interest. Here we report that the lipid G-protein coupled receptor GPR55 is highly expressed by splenic plasma cells (PC), upregulated in mouse spleens during atherogenesis and human unstable or ruptured compared to stable plaques. Gpr55-deficient mice developed larger atherosclerotic plaques with increased necrotic core size compared to their corresponding controls. Lack of GPR55 hyperactivated B cells, disturbed PC maturation and resulted in immunoglobulin (Ig)G overproduction. B cell-specific Gpr55 depletion or adoptive transfer of Gpr55-deficient B cells was sufficient to promote plaque development and elevated IgG titers. In vitro, the endogenous GPR55 ligand lysophsophatidylinositol (LPI) enhanced PC proliferation, whereas GPR55 antagonism blocked PC maturation and increased their mitochondrial content. Collectively, these discoveries provide previously undefined evidence for GPR55 in B cells as a key modulator of the adaptive immune response in atherosclerosis.

GPR55 deficiency in B-cells promotes atherosclerosis and regulates plasma cell maturation

 

Atherosclerosis is a chronic and multifactorial disease accompanied by an imbalance between resolving and pro-inflammatory lipid mediators. Targeting lipid signaling might offer new therapeutical targets for improving the clinical outcome in cardiovascular disease patients. We considered lysophosphatidylinositol (LPI) and its receptor G protein-coupled receptor (GPR)55 as a potential modulator of atherosclerosis. Its role in regulating atherosclerosis and B cell function is unknown.

We hypothesize that GPR55 signaling affects atherosclerosis by regulating B cell function.

Atherosclerotic plaques were compared between apolipoprotein-E-deficient (ApoE−/−) and ApoE−/−Gpr55−/− mice after 4 to 16 weeks Western Diet (WD; 0.15% cholesterol; n=12–15 per group). To test the role of B cell GPR55, we generated mixed chimeras by irradiating low density lipoprotein receptor deficient (Ldlr−/−) mice and reconstituting with a mixture of μMT and wildtype or μMT and Gpr55−/− bone marrow cells. Circulating B cells were sorted and bulk RNA sequencing analysis was performed. We performed atheroma plaque characterization, qPCR and ELISA of tissue lysates and measure plasma immunoglobulins. Circulating and tissue leukocyte counts were determined.

We confirmed Gpr55 expression on circulating B cells, which was higher compared to T and myeloid cells. ApoE−/−Gpr55−/− mice had significantly larger plaques after 4 & 16 weeks WD compared to ApoE−/−, with increased body weight & cholesterol levels. In addition, global Gpr55 deficiency resulted in enhanced aortic pro-inflammatory cytokine mRNA expression, a massively upregulated IgG levels and increased counts of splenic germinal center and plasma cells. ApoE−/−Gpr55−/− B-cell RNA-seq analysis showed 460 differential expressed genes compared to ApoE−/−. The main pathways affected were calcium ion transport, immunoglobulin production, T & B cell activation, and cellular response to stress. B cell specific Gpr55 deficiency blunted the metabolic effects but still translated in larger atherosclerotic plaques and elevated plasma IgG levels.

Both global and B cell-restricted Gpr55 deficiency promotes atherosclerosis and is associated with a pro-inflammatory phenotype.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The authors received funds from the Deutsche Forschungsgemeinschaft (STE1053/6-1, STE1053/8-1 to S.S. and SFB1123 to S.S., C.W. and L.M.), the German Ministry of Research and Education (DZHK FKZ 81Z0600205 to S.S.) and the LMU Medical Faculty FöFoLe program (1061 to R.G.P.). I.H. is supported by the DFG (HI1573/2 and CRC1425 #422681845).

A strategy for successful integration of DNA-based methods in aquatic monitoring

Recent advances in molecular biomonitoring open new horizons for aquatic ecosystem assessment. Rapid and cost-effective methods based on organismal DNA or environmental DNA (eDNA) now offer the opportunity to produce inventories of indicator taxa that can subsequently be used to assess biodiversity and ecological quality. However, the integration of these new DNA-based methods into current monitoring practices is not straightforward, and will require coordinated actions in the coming years at national and international levels.

To plan and stimulate such an integration, the European network DNAqua-Net (COST Action CA15219) brought together international experts from academia, as well as key environmental biomonitoring stakeholders from different European countries. Together, this transdisciplinary consortium developed a roadmap for implementing DNA-based methods with a focus on inland waters assessed by the EU Water Framework Directive (2000/60/EC). This was done through a series of online workshops held in April 2020, which included fifty participants, followed by extensive synthesis work.

The roadmap is organised around six objectives: 1) to highlight the effectiveness and benefits of DNA-based methods, 2) develop an adaptive approach for the implementation of new methods, 3) provide guidelines and standards for best practice, 4) engage stakeholders and ensure effective knowledge transfer, 5) support the environmental biomonitoring sector to achieve the required changes, 6) steer the process and harmonise efforts at the European level.

This paper provides an overview of the forum discussions and the common European views that have emerged from them, while reflecting the diversity of situations in different countries. It highlights important actions required for a successful implementation of DNA-based biomonitoring of aquatic ecosystems by 2030.

Environmental ranges discriminating between macrophytes groups in European rivers

Riverine macrophytes form distinct species groups. Their occurrence is determined by environmental gradients, e.g. in terms of physico-chemistry and hydromorphology. However, the ranges of environmental variables discriminating between species groups (“discriminatory ranges”) have rarely been quantified and mainly been based on expert judgement, thus limiting options for predicting and assessing ecosystem characteristics. We used a pan-European dataset of riverine macrophyte surveys obtained from 22 countries including data on total phosphorus, nitrate, alkalinity, flow velocity, depth, width and substrate type. Four macrophyte species groups were identified by cluster analysis based on species’ co-occurrences. These comprised Group 1) mosses, such as Amblystegium fluviatile and Fontinalis antipyretica, Group 2) shorter and pioneer species such as Callitriche spp., Group 3) emergent and floating species such as Sagittaria sagittifolia and Lemna spp., and Group 4) eutraphent species such as Myriophyllum spicatum and Stuckenia pectinata. With Random Forest models, the ranges of environmental variables discriminating between these groups were estimated as follows: 100–150 μg L-1 total phosphorus, 0.5–20 mg L-1 nitrate, 1–2 meq L-1 alkalinity, 0.05–0.70 m s-1 flow velocity, 0.3–1.0 m depth and 20–80 m width. Mosses were strongly related to coarse substrate, while vascular plants were related to finer sediment. The four macrophyte groups and the discriminatory ranges of environmental variables fit well with those described in literature, but have now for the first time been quantitatively approximated with a large dataset, suggesting generalizable patterns applicable at regional and local scales.

A metric-based analysis on the effects of riparian and catchment landuse on macroinvertebrates

Woody riparian vegetation along rivers and streams provides multiple functions beneficial for aquatic macroinvertebrate communities. They retain fine sediments, nutrients and pesticides, improve channel hydromorphology, control water temperature and primary production through shading and provide leaves, twigs and large wood. In a recent conceptual model (Feld et al., 2018), woody riparian functions were considered either independent from large-scale landuse stressors (e.g. shading, input of organic matter), or dependent on landuse at larger spatial scales (e.g. fine sediment, nutrient and pesticide retention). We tested this concept using high-resolution data on woody riparian vegetation cover and empirical data from 1017 macroinvertebrate sampling sites in German lowland and mountain streams. Macroinvertebrate metrics indicative for individual functions were used as response variables in structural equation models (SEM), representing the hierarchical structure between the different considered stressors at different spatial scales: catchment, upstream riparian, local riparian and local landuse cover along with hydromorphology and water quality. The analysis only partly confirmed the conceptual model: Biotic integrity and water quality were strongly related to large-scale stressors as expected (absolute total effect 0.345-0.541), but against expectations, fine sediments retention, considered scale-dependent in the conceptual model, was poorly explained by large-scale stressors (absolute total effect 0.027-0.231). While most functions considered independent from large-scale landuse were partly explained by riparian landuse cover (absolute total effect 0.023-0.091) they also were nonetheless affected by catchment landuse cover (absolute total effect 0.017-0.390). While many empirical case studies at smaller spatial scales clearly document the positive effects of restoring woody riparian vegetation, our results suggest that most effects of riparian landuse cover are possibly superimposed by larger-scale stressors. This does not negate localized effects of woody riparian vegetation but helps contextualize limitations to successful restoration measures targeting the macroinvertebrate community.

A global agenda for advancing freshwater biodiversity research

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation.

The interplay of nutrients, dissolved inorganic carbon and algae in determining macrophyte occurrences in rivers

Nitrogen and phosphorous concentrations are widely considered to drive macrophyte assemblages in rivers. However, Dissolved Inorganic Carbon (DIC) - available for plants as CO₂ and HCO₃^- - is also of major relevance. Based on literature, we present a conceptual model on the interaction between algae, macrophytes, DIC, pH, light, N, P and the surface water and sedimental compartment. Analysing two separate datasets (i) on river physico-chemistry and chlorophyll-a, and (ii) on river physico-chemistry and macrophytes we quantify three connections within this concept: (1) the correlation of chlorophyll-a versus pH, (2) the correlation of TP versus chlorophyll-a and (3) the occurrence of HCO₃-users and CO₂-only-users among macrophytes along the DIC gradient. Chlorophyll-a correlated positively with pH (R-squared = 77%, p < .001) due to increased carbon dioxide uptake of phytoplankton. Surface water TP did not linearly correlate with chlorophyll-a concentrations. Obligate and optionally submerged macrophyte species that utilise HCO₃^- were separated from CO₂-only-users by HCO₃^- concentrations, with an area under the curve (AUC) of 68% and 70% (both p < .001) between groups. Obligate and optionally submerged macrophyte assemblages only composed of HCO₃-users and those exclusively composed of CO₂-only-users showed an even stronger separation based on the HCO₃^- concentration, with both an AUC of 82% and 78% (both p < .001). Our results underline that DIC can greatly affect riverine macrophytes. However, absolute concentrations of HCO₃^- are less relevant, while the connection to pH is more important, reflecting CO₂ concentrations. River monitoring and management should consider the interaction between nutrients DIC, surface water and sedimental compartment as important factors affecting macrophyte occurrence, rather than solely focussing on surface water nutrients.

Multiple stressors determine river ecological status at the European scale: Towards an integrated understanding of river status deterioration

The biota of European rivers are affected by a wide range of stressors impairing water quality and hydro-morphology. Only about 40% of Europe's rivers reach 'good ecological status', a target set by the European Water Framework Directive (WFD) and indicated by the biota. It is yet unknown how the different stressors in concert impact ecological status and how the relationship between stressors and status differs between river types. We linked the intensity of seven stressors to recently measured ecological status data for more than 50,000 sub-catchment units (covering almost 80% of Europe's surface area), which were distributed among 12 broad river types. Stressor data were either derived from remote sensing data (extent of urban and agricultural land use in the riparian zone) or modelled (alteration of mean annual flow and of base flow, total phosphorous load, total nitrogen load and mixture toxic pressure, a composite metric for toxic substances), while data on ecological status were taken from national statutory reporting of the second WFD River Basin Management Plans for the years 2010-2015. We used Boosted Regression Trees to link ecological status to stressor intensities. The stressors explained on average 61% of deviance in ecological status for the 12 individual river types, with all seven stressors contributing considerably to this explanation. On average, 39.4% of the deviance was explained by altered hydro-morphology (morphology: 23.2%; hydrology: 16.2%), 34.4% by nutrient enrichment and 26.2% by toxic substances. More than half of the total deviance was explained by stressor interaction, with nutrient enrichment and toxic substances interacting most frequently and strongly. Our results underline that the biota of all European river types are determined by co-occurring and interacting multiple stressors, lending support to the conclusion that fundamental management strategies at the catchment scale are required to reach the ambitious objective of good ecological status of surface waters.

Multiple stressors determine river ecological status at the European scale: Towards an integrated understanding of river status deterioration

The biota of European rivers are affected by a wide range of stressors impairing water quality and hydro-morphology. Only about 40% of Europe's rivers reach 'good ecological status', a target set by the European Water Framework Directive (WFD) and indicated by the biota. It is yet unknown how the different stressors in concert impact ecological status and how the relationship between stressors and status differs between river types. We linked the intensity of seven stressors to recently measured ecological status data for more than 50,000 sub-catchment units (covering almost 80% of Europe's surface area), which were distributed among 12 broad river types. Stressor data were either derived from remote sensing data (extent of urban and agricultural land use in the riparian zone) or modelled (alteration of mean annual flow and of base flow, total phosphorous load, total nitrogen load and mixture toxic pressure, a composite metric for toxic substances), while data on ecological status were taken from national statutory reporting of the second WFD River Basin Management Plans for the years 2010-2015. We used Boosted Regression Trees to link ecological status to stressor intensities. The stressors explained on average 61% of deviance in ecological status for the 12 individual river types, with all seven stressors contributing considerably to this explanation. On average, 39.4% of the deviance was explained by altered hydro-morphology (morphology: 23.2%; hydrology: 16.2%), 34.4% by nutrient enrichment and 26.2% by toxic substances. More than half of the total deviance was explained by stressor interaction, with nutrient enrichment and toxic substances interacting most frequently and strongly. Our results underline that the biota of all European river types are determined by co-occurring and interacting multiple stressors, lending support to the conclusion that fundamental management strategies at the catchment scale are required to reach the ambitious objective of good ecological status of surface waters.

Trait-based ecology at large scales: Assessing functional trait correlations, phylogenetic constraints and spatial variability using open data

The growing use of functional traits in ecological research has brought new insights into biodiversity responses to global environmental change. However, further progress depends on overcoming three major challenges involving (a) statistical correlations between traits, (b) phylogenetic constraints on the combination of traits possessed by any single species, and (c) spatial effects on trait structure and trait-environment relationships. Here, we introduce a new framework for quantifying trait correlations, phylogenetic constraints and spatial variability at large scales by combining openly available species' trait, occurrence and phylogenetic data with gridded, high-resolution environmental layers and computational modelling. Our approach is suitable for use among a wide range of taxonomic groups inhabiting terrestrial, marine and freshwater habitats. We demonstrate its application using freshwater macroinvertebrate data from 35 countries in Europe. We identified a subset of available macroinvertebrate traits, corresponding to a life-history model with axes of resistance, resilience and resource use, as relatively unaffected by correlations and phylogenetic constraints. Trait structure responded more consistently to environmental variation than taxonomic structure, regardless of location. A re-analysis of existing data on macroinvertebrate communities of European alpine streams supported this conclusion, and demonstrated that occurrence-based functional diversity indices are highly sensitive to the traits included in their calculation. Overall, our findings suggest that the search for quantitative trait-environment relationships using single traits or simple combinations of multiple traits is unlikely to be productive. Instead, there is a need to embrace the value of conceptual frameworks linking community responses to environmental change via traits which correspond to the axes of life-history models. Through a novel integration of tools and databases, our flexible framework can address this need.

B cell-specific GPR55 deficiency promotes atherosclerosis

Background

Atherosclerosis is accompanied by an imbalance between resolving and pro-inflammatory lipid mediators. Targeting lipid signaling pathways might offer a new anti-inflammatory therapy for improving the clinical outcome in cardiovascular disease patients. We considered lysophosphatidylinositol (LPI) and its receptor G protein-coupled receptor (GPR)55 as a potential modulator of atherosclerosis. Its role in regulating atherosclerosis and B cell function is unknown.

Hypothesis

We assessed the hypothesis that GPR55 signaling causally affects atherosclerosis and whether it has a specific role in regulating B cell function in this disease.

Methods

Atherosclerotic plaques were compared between apolipoprotein E deficient (ApoE−/−) and ApoE−/−Gpr55−/− mice after 4 to 16 weeks Western Diet (WD; 0.15% cholesterol; n=12–15 per group). To specifically test the role of B cell GPR55 in atherosclerosis, we generated mixed chimeras by lethally irradiating low density lipoprotein receptor deficient (Ldlr−/−) mice and reconstituting with a mixture of μMT and wildtype (control) or μMT and Gpr55−/− bone marrow cells. Circulating B cells were sorted and bulk RNA sequencing analysis was performed. We performed lipid and immunostainings of murine aortic root plaques, qPCR and ELISA of tissue lysates, as well as multiplex analysis of plasma immunoglobulins. Leukocyte plasma and tissue counts were determined by flow cytometry.

Results

GPR55 expression in mouse and human atherosclerotic plaques was detected by immunostaining. Furthermore, we confirmed murine Gpr55 mRNA expression on sorted circulating B220+B cells via qPCR, which was higher compared to CD3+ T cells, while CD11+ myeloid cells as well as NK cells had only low Gpr55 mRNA levels. ApoE−/−Gpr55−/− mice had significantly larger plaques after 4&16 weeks WD compared to ApoE−/− controls, with more pronounced body weight increases and higher cholesterol levels at the 16 weeks WD time point. In addition, global Gpr55 deficiency resulted in enhanced aortic pro-inflammatory cytokine mRNA expression (IL-1β, IL-6, TNFα) and a massively upregulated IgG1 plasma levels and increased percentages of splenic germinal center and plasma cells. B-cell RNA-seq analysis showed 460 differential expressed regulated genes in the ApoE−/−Gpr55−/− compared to ApoE−/−. The main pathways affected were calcium ion transport, immunoglobulin production, negative regulation of phosphorylation, and cellular component morphogenesis, suggesting a dsysregulation of B cell function. B cell specific Gpr55 deficiency blunted the metabolic effects on body weight and cholesterol, but still translated in larger atherosclerotic plaques and elevated plasma IgG levels compared to the respective controls.

Conclusion

Both global and B cell-restricted Gpr55 deficiency promotes atherosclerosis and is associated with a more pro-inflammatory phenotype. Our findings suggest a novel role for GPR55 in regulating B cell development and function.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG)

2-Arachidonoylglycerol mobilizes myeloid cells and worsens heart function after acute myocardial infarction

AIMS

Myocardial infarction (MI) leads to an enhanced release of endocannabinoids and a massive accumulation of neutrophils and monocytes within the ischaemic myocardium. These myeloid cells originate from haematopoietic precursors in the bone marrow and are rapidly mobilized in response to MI. We aimed to determine whether endocannabinoid signalling is involved in myeloid cell mobilization and cardiac recruitment after ischaemia onset.

METHODS AND RESULTS

Intravenous administration of endocannabinoid 2-arachidonoylglycerol (2-AG) into wild type (WT) C57BL6 mice induced a rapid increase of blood neutrophil and monocyte counts as measured by flow cytometry. This effect was blunted when using cannabinoid receptor 2 knockout mice. In response to MI induced in WT mice, the lipidomic analysis revealed significantly elevated plasma and cardiac levels of the endocannabinoid 2-AG 24 h after infarction, but no changes in anandamide, palmitoylethanolamide, and oleoylethanolamide. This was a consequence of an increased expression of 2-AG synthesizing enzyme diacylglycerol lipase and a decrease of metabolizing enzyme monoacylglycerol lipase (MAGL) in infarcted hearts, as determined by quantitative RT-PCR analysis. The opposite mRNA expression pattern was observed in bone marrow. Pharmacological blockade of MAGL with JZL184 and thus increased systemic 2-AG levels in WT mice subjected to MI resulted in elevated cardiac CXCL1, CXCL2, and MMP9 protein levels as well as higher cardiac neutrophil and monocyte counts 24 h after infarction compared with vehicle-treated mice. Increased post-MI inflammation in these mice led to an increased infarct size, an impaired ventricular scar formation assessed by histology and a worsened cardiac function in echocardiography evaluations up to 21 days. Likewise, JZL184-administration in a myocardial ischaemia-reperfusion model increased cardiac myeloid cell recruitment and resulted in a larger fibrotic scar size.

CONCLUSION

These findings suggest that changes in endocannabinoid gradients due to altered tissue levels contribute to myeloid cell recruitment from the bone marrow to the infarcted heart, with crucial consequences on cardiac healing and function.

Analysis of 13,312 benthic invertebrate samples from German streams reveals minor deviations in ecological status class between abundance and presence/absence data

Benthic invertebrates are the most commonly used organisms used to assess ecological status as required by the EU Water Framework Directive (WFD). For WFD-compliant assessments, benthic invertebrate communities are sampled, identified and counted. Taxa × abundance matrices are used to calculate indices and the resulting scores are compared to reference values to determine the ecological status class. DNA-based tools, such as DNA metabarcoding, provide a new and precise method for species identification but cannot deliver robust abundance data. To evaluate the applicability of DNA-based tools to ecological status assessment, we evaluated whether the results derived from presence/absence data are comparable to those derived from abundance data. We analysed benthic invertebrate community data obtained from 13,312 WFD assessments of German streams. Broken down to 30 official stream types, we compared assessment results based on abundance and presence/absence data for the assessment modules “organic pollution” (i.e., the saprobic index) and “general degradation” (a multimetric index) as well as their underlying metrics.

In 76.6% of cases, the ecological status class did not change after transforming abundance data to presence/absence data. In 12% of cases, the status class was reduced by one (e.g., from good to moderate), and in 11.2% of cases, the class increased by one. In only 0.2% of cases, the status shifted by two classes. Systematic stream type-specific deviations were found and differences between abundance and presence/absence data were most prominent for stream types where abundance information contributed directly to one or several metrics of the general degradation module. For a single stream type, these deviations led to a systematic shift in status from ‘good’ to ‘moderate’ (n = 201; with only n = 3 increasing). The systematic decrease in scores was observed, even when considering simulated confidence intervals for abundance data. Our analysis suggests that presence/absence data can yield similar assessment results to those for abundance-based data, despite type-specific deviations. For most metrics, it should be possible to intercalibrate the two data types without substantial efforts. Thus, benthic invertebrate taxon lists generated by standardised DNA-based methods should be further considered as a complementary approach.

Taming the Wild West of Molecular Tools Application in Aquatic Research and Biomonitoring

Modern high-throughput sequencing technologies are becoming a game changer in many fields of aquatic research and biomonitoring. To unfold their full potential, however, the independent development of approaches has to be streamlined. This discussion must be fuelled by stakeholders and practitioners and, scientific results collaboratively filtered to identify the most promising avenues. Furthermore, aspects such as time, budget, skills and the application context have to be considered, finally communicating good practice strategies to target audiences.

Since 2016, the EU COST Action DNAqua-Net is taming the wild west of molecular tools application in aquatic research and biomonitoring. After nucleating available knowledge by the formation of a highly international and transdisciplinary network of scientists, stakeholders, practitioners and enterprises, fields of high methodological diversity were identified. Relevant aspects are currently ground truthed, thereby reducing the plethora of pipelines, parameters and protocols to a subset of good practices or standardisations. To effectively bridge the science-application interface, the very same network is exploited for the dissemination of results (Leese et al. 2018).

The internal working group structure of DNAqua-Net is used to provide an overview of existing methodological fields of diversity in DNA-based aquatic biomonitoring:

WG1 -DNA Barcode References: Different marker systems are targeted for the same organism group. Even in case the same molecular marker is investigated, different primer pairs are frequently applied for DNA metabarcoding. Both aspects challenge the further development of high-quality and complete DNA barcode reference libraries (Weigand et al. 2019).

WG2 -Biotic Indices &amp; Metrics: Index systems are developed from molecular data in various ways: from the estimation of species' biomass (as a proxy for abundance) from sequence reads, to the correlation of presence/absence data of molecular operational taxonomic units (MOTUs) with environmental parameters (Pawlowski et al. 2018).

WG3 -Field &amp; Lab Protocols: Using environmental DNA (eDNA) metabarcoding as an example, diverse sampling techniques based on varying water volumes, different filter systems and collection devices as well as a multitude of laboratory protocols for PCR, replication and sequencing are considered.

WG4 -Data Analysis &amp; Storage: During the process of MOTU identification, varying threshold values and conceptually different pipelines are used, potentially impacting the final list of MOTUs or species retrieved. Furthermore, routine storage concepts for big biodiversity data are only in development and some sample types (e.g. eDNA) have no sophisticated metadata descriptions.

WG5 -Implementation Strategy &amp; Legal Issues: The working group picks up collaboratively filtered good practice strategies and generates room for discussions at the science-policy interface (Hering et al. 2018). The CEN working group WG28 "DNA methods" has been initiated and the development of standardisations is fostered.

Protecting and restoring Europe's waters: An analysis of the future development needs of the Water Framework Directive

The Water Framework Directive (WFD) is a pioneering piece of legislation that aims to protect and enhance aquatic ecosystems and promote sustainable water use across Europe. There is growing concern that the objective of good status, or higher, in all EU waters by 2027 is a long way from being achieved in many countries. Through questionnaire analysis of almost 100 experts, we provide recommendations to enhance WFD monitoring and assessment systems, improve programmes of measures and further integrate with other sectoral policies. Our analysis highlights that there is great potential to enhance assessment schemes through strategic design of monitoring networks and innovation, such as earth observation. New diagnostic tools that use existing WFD monitoring data, but incorporate novel statistical and trait-based approaches could be used more widely to diagnose the cause of deterioration under conditions of multiple pressures and deliver a hierarchy of solutions for more evidence-driven decisions in river basin management. There is also a growing recognition that measures undertaken in river basin management should deliver multiple benefits across sectors, such as reduced flood risk, and there needs to be robust demonstration studies that evaluate these. Continued efforts in 'mainstreaming' water policy into other policy sectors is clearly needed to deliver wider success with WFD goals, particularly with agricultural policy. Other key policy areas where a need for stronger integration with water policy was recognised included urban planning (waste water treatment), flooding, climate and energy (hydropower). Having a deadline for attaining the policy objective of good status is important, but even more essential is to have a permanent framework for river basin management that addresses the delays in implementation of measures. This requires a long-term perspective, far beyond the current deadline of 2027.

Development and validation of a macroinvertebrate-based biomonitoring tool to assess fine sediment impact in small mountain streams

Increased fine sediment deposition is recognised as one of the major causes of biological impairment of rivers and streams influencing all components of aquatic communities. Notably, stream macroinvertebrates are affected showing changes in abundance and community composition. This makes macroinvertebrates an attractive choice for biomonitoring fine sediment stress. However, there are substantial knowledge gaps regarding the quantification of deposited fine sediment and the identification of taxa sensitive to fine sediment deposition, which could serve as indicators. In this study, we developed a stream type-specific index based on the taxon-specific response of macroinvertebrates to deposited fine sediment in small, coarse substrate-dominated mountain streams. We sampled fine sediment at 73 sampling sites in Western Germany (Europe) in spring 2014 and 2015 using a sediment remobilization technique. Macroinvertebrate taxalists originating from WFD monitoring surveys were available for all sites. We applied Threshold Indicator Taxa ANalysis (TITAN) on the fine sediment mass of the sampling sites and the corresponding macroinvertebrate taxalists to identify indicator taxa, which were then used for index development. In total, TITAN identified 95 reliable indicator taxa, of which some taxa tolerated large amounts of fine sediment (e.g., Gammarus roeselii and Tubificidae Gen. sp.), while others were found to be highly sensitive to increased fine sediment mass (e.g., Elodes sp. and Limnius perrisi). The newly developed index was tested on an independent data set and performed well in detecting fine sediment stress (Spearman's r = 0.63). Furthermore, the index was better related to the deposited fine sediment mass as compared to other fine sediment indices and standard metrics used for monitoring purposes under the Water Framework Directive (WFD). The diagnostic index can be a cost-effective biomonitoring tool for stream managers and can be used as a proxy for the impact of deposited fine sediment on the reach scale.

Diverging response patterns of terrestrial and aquatic species to hydromorphological restoration

Although experiences with ecological restoration continue to accumulate, the effectiveness of restoration for biota remains debated. We complemented a traditional taxonomic analysis approach with information on 56 species traits to uncover the responses of 3 aquatic (fish, macroinvertebrates, macrophytes) and 2 terrestrial (carabid beetles, floodplain vegetation) biotic groups to 43 hydromorphological river restoration projects in Germany. All taxonomic groups responded positively to restoration, as shown by increased taxonomic richness (10-164%) and trait diversity (habitat, dispersal and mobility, size, form, life history, and feeding groups) (15-120%). Responses, however, were stronger for terrestrial than aquatic biota, and, contrary to our expectation, taxonomic responses were stronger than those of traits. Nevertheless, trait analysis provided mechanistic insights into the drivers of community change following restoration. Trait analysis for terrestrial biota indicated restoration success was likely enhanced by lateral connectivity and reestablishment of dynamic processes in the floodplain. The weaker response of aquatic biota suggests recovery was hindered by the persistence of stressors in the aquatic environment, such as degraded water quality, dispersal constraints, and insufficient hydromorphological change. Therefore, river restoration requires combined local- and regional-scale approaches to maximize the response of both aquatic and terrestrial organisms. Due to the contrasting responses of aquatic and terrestrial biota, the planning and assessment of river restoration outcomes should consider effects on both components of riverine landscapes.

Freshwater species distributions along thermal gradients

The distribution of a species along a thermal gradient is commonly approximated by a unimodal response curve, with a characteristic single optimum near the temperature where a species is most likely to be found, and a decreasing probability of occurrence away from the optimum. We aimed at identifying thermal response curves (TRCs) of European freshwater species and evaluating the potential impact of climate warming across species, taxonomic groups, and latitude. We first applied generalized additive models using catchment-scale global data on distribution ranges of 577 freshwater species native to Europe and four different temperature variables (the current annual mean air/water temperature and the maximum air/water temperature of the warmest month) to describe species TRCs. We then classified TRCs into one of eight curve types and identified spatial patterns in thermal responses. Finally, we integrated empirical TRCs and the projected geographic distribution of climate warming to evaluate the effect of rising temperatures on species' distributions. For the different temperature variables, 390-463 of 577 species (67.6%-80.2%) were characterized by a unimodal TRC. The number of species with a unimodal TRC decreased from central toward northern and southern Europe. Warming tolerance (WT = maximum temperature of occurrence-preferred temperature) was higher at higher latitudes. Preferred temperature of many species is already exceeded. Rising temperatures will affect most Mediterranean species. We demonstrated that freshwater species' occurrence probabilities are most frequently unimodal. The impact of the global climate warming on species distributions is species and latitude dependent. Among the studied taxonomic groups, rising temperatures will be most detrimental to fish. Our findings support the efforts of catchment-based freshwater management and conservation in the face of global warming.

Evaluating riparian solutions to multiple stressor problems in river ecosystems - A conceptual study

Rivers are among the most sensitive of all ecosystems to the effects of global change, but options to prevent, mitigate or restore ecosystem damage are still inadequately understood. Riparian buffers are widely advocated as a cost-effective option to manage impacts, but empirical evidence is yet to identify ideal riparian features (e.g. width, length and density) which enhance ecological integrity and protect ecosystem services in the face of catchment-scale stressors. Here, we use an extensive literature review to synthesise evidence on riparian buffer and catchment management effects on instream environmental conditions (e.g. nutrients, fine sediments, organic matter), river organisms and ecosystem functions. We offer a conceptual model of the mechanisms through which catchment or riparian management might impact streams either positively or negatively. The model distinguishes scale-independent benefits (shade, thermal damping, organic matter and large wood inputs) that arise from riparian buffer management at any scale from scale-dependent benefits (nutrient or fine sediment retention) that reflect stressor conditions at broader (sub-catchment to catchment) scales. The latter require concerted management efforts over equally large domains of scale (e.g. riparian buffers combined with nutrient restrictions). The evidence of the relationships between riparian configuration (width, length, zonation, density) and scale-independent benefits is consistent, suggesting a high certainty of the effects. In contrast, scale-dependent effects as well as the biological responses to riparian management are more uncertain, suggesting that ongoing diffuse pollution (nutrients, sediments), but also sources of variability (e.g. hydrology, climate) at broader scales may interfere with the effects of local riparian management. Without concerted management across relevant scales, full biological recovery of damaged lotic ecosystems is unlikely. There is, nevertheless, sufficient evidence that the benefits of riparian buffers outweigh potential adverse effects, in particular if located in the upstream part of the stream network. This supports the use of riparian restoration as a no-regrets management option to improve and sustain lotic ecosystem functioning and biodiversity.

Implementation options for DNA-based identification into ecological status assessment under the European Water Framework Directive

Assessment of ecological status for the European Water Framework Directive (WFD) is based on "Biological Quality Elements" (BQEs), namely phytoplankton, benthic flora, benthic invertebrates and fish. Morphological identification of these organisms is a time-consuming and expensive procedure. Here, we assess the options for complementing and, perhaps, replacing morphological identification with procedures using eDNA, metabarcoding or similar approaches. We rate the applicability of DNA-based identification for the individual BQEs and water categories (rivers, lakes, transitional and coastal waters) against eleven criteria, summarised under the headlines representativeness (for example suitability of current sampling methods for DNA-based identification, errors from DNA-based species detection), sensitivity (for example capability to detect sensitive taxa, unassigned reads), precision of DNA-based identification (knowledge about uncertainty), comparability with conventional approaches (for example sensitivity of metrics to differences in DNA-based identification), cost effectiveness and environmental impact. Overall, suitability of DNA-based identification is particularly high for fish, as eDNA is a well-suited sampling approach which can replace expensive and potentially harmful methods such as gill-netting, trawling or electrofishing. Furthermore, there are attempts to replace absolute by relative abundance in metric calculations. For invertebrates and phytobenthos, the main challenges include the modification of indices and completing barcode libraries. For phytoplankton, the barcode libraries are even more problematic, due to the high taxonomic diversity in plankton samples. If current assessment concepts are kept, DNA-based identification is least appropriate for macrophytes (rivers, lakes) and angiosperms/macroalgae (transitional and coastal waters), which are surveyed rather than sampled. We discuss general implications of implementing DNA-based identification into standard ecological assessment, in particular considering any adaptations to the WFD that may be required to facilitate the transition to molecular data.

Abstract 185: G-protein Coupled Receptor 55 Deficiency Promotes Atherosclerosis and Inflammation in Mice

Background: The endocannabinoid system plays a pathophysiological role in metabolic and cardiovascular disorders. G protein-coupled receptor (GPR) 55 is a novel cannabinoid receptor expressed by various lymphocyte subsets, in particular γδT cells, innate lymphoid cells and B1 cells. Its role in regulating immune functions and atherosclerosis is unknown.

Methods: We studied early and advanced atherosclerotic plaques and inflammatory parameters in apolipoprotein E deficient (ApoE-/-) and ApoE-/-GPR55-/- mice after 4 or 16 weeks Western Diet (WD), respectively (n=12-15 per group). GPR55 mRNA expression was assessed in human carotid artery plaques (n=29) and healthy control vessels (left internal thoracic arteries; n=28).

Results: ApoE-/-GPR55-/- mice had significantly 1.9 to 2.3-fold increased plaque sizes after 4 and 16 weeks WD compared to ApoE-/- controls with higher macrophage content at early stage, but less macrophage and more collagen content at advanced stage. This was accompanied by enhanced aortic pro-inflammatory cytokine mRNA expression (IL-6, TNFα, IL-1β, iNOS) as well as massively upregulated IgG1 plasma levels. Moreover, GPR55 deficiency was associated with increased circulating, splenic and aortic lymphocyte counts after 4 and 16 weeks WD. The most striking (2 to 4-fold) increase was found in γδT cells, with less pronounced increases in the total CD3+ T cell population and CD4+ and CD8+ subsets. This was paralleled by systemic increases in blood monocyte and neutrophil counts, likely due to enhanced myelopoiesis as suggested by enhanced bone marrow myeloid cell counts. At advanced atherosclerosis, ApoE-/-GPR55-/- had significantly higher NK cell numbers in blood and lymphoid organs, suggesting a possible regulation of cytotoxic lymphocyte responses. In view of a potential relevance for human pathophysiology, GPR55 mRNA levels were significantly higher in human plaque samples compared to non-atherosclerotic control vessels.

Conclusion: GPR55 deficiency promotes atherosclerosis associated with a more pro-inflammatory phenotype. We may speculate that GPR55 negatively regulates the proatherogenic activity of lymphocyte subsets such as γδT cells, which deserves further investigation.

Revisiting restored river reaches - Assessing change of aquatic and riparian communities after five years

Hydromorphological restructuring of river sections, i.e. river restoration measures, often has little effects on aquatic biota, even in case of strong habitat alterations. It is often supposed that the biotic response is simply delayed as species require additional time to recolonize the newly generated habitats and to establish populations. To identify and specify the supposed lag time between restoration and biotic response, we investigated 19 restored river reaches twice in a five-year interval. The sites were restored one to ten years prior to the first sampling. We sampled three aquatic (fish, benthic invertebrates, macrophytes) and two riparian organism groups (ground beetles and riparian vegetation) and analyzed changes in assemblage composition and biotic metrics. With the exception of ground beetle assemblages, we observed no significant changes in richness and abundance metrics or metrics used for biological assessment. However, indicator taxa for near-natural habitat conditions in the riparian zone (indicators for regular inundation in plants and river bank specialists in beetles) improved significantly in the five-year interval. Contrary to general expectations in river restoration planning, we neither observed a distinct succession of aquatic communities nor a general trend towards "good ecological status" over time. Furthermore, multiple linear regression models revealed that neither the time since restoration nor the morphological status had a significant effect on the biological metrics and the assessment results. Thus, the stability of aquatic assemblages is strong, slowing down restoration effects in the aquatic zone, while riparian assemblages improve more rapidly. When defining restoration targets, the different timelines for ecological recovery after restoration should be taken into account. Furthermore, restoration measures should not solely focus on local habitat conditions but also target stressors acting on larger spatial scales and take other measures (e.g. species reintroduction) into consideration.

Application and validation of a new approach for modelling benthic invertebrate dispersal: First colonisation of a former open sewer system

Within a heavily modified catchment, formerly polluted streams are now free of untreated wastewater. Additionally, the morphology of streams has been improved by physical habitat restoration. Both water quality and structural improvements offered a unique opportunity to investigate the recolonisation of restored sections by benthic macroinvertebrates. As dispersal is a key mechanism for recolonisation, we developed a method to predict the dispersal of 18 aquatic insect taxa to 35,338 river sections (section length: 2m) within the catchment. Source populations of insect taxa were sampled at 33 sites. In addition, 14 morphologically restored sites were sampled and constituted the validation dataset. We applied a "least-cost" modelling approach within a raster-based GIS model, combining taxon-specific aquatic and terrestrial dispersal capabilities with the "friction" that physical migration barriers impose on dispersal of aquatic and terrestrial stages. This taxon-specific modelling approach was compared to a conservative modelling approach, assuming a Euclidean distance of 5km as the maximum dispersal distance for any source population regardless of dispersal barriers. Least-cost modelling showed a significantly better performance in terms of the correct classification rate (CCR) and true predicted absences (specificity), with on average 37% points higher CCR and 42% points higher specificity. Sensitivity was 18% points lower. At 71% of the validation sites, recolonisation was predicted with at least a modest goodness of fit (CCR>70%). Conversely, the conservative modelling approach achieved a modest goodness of fit for only 14% of the validation sites. For 44% of the taxa, least-cost modelling showed a high CCR (=100%), whereas the conservative approach showed a high CCR for none of the taxa. Our approach can help water managers select appropriate sites for restoration to increase recolonisation and biological recovery.

Additive effects prevail: The response of biota to multiple stressors in an intensively monitored watershed

Freshwater ecosystems are impacted by a range of stressors arising from diverse human-caused land and water uses. Identifying the relative importance of single stressors and understanding how multiple stressors interact and jointly affect biology is crucial for River Basin Management. This study addressed multiple human-induced stressors and their effects on the aquatic flora and fauna based on data from standard WFD monitoring schemes. For altogether 1095 sites within a mountainous catchment, we used 12 stressor variables covering three different stressor groups: riparian land use, physical habitat quality and nutrient enrichment. Twenty-one biological metrics calculated from taxa lists of three organism groups (fish, benthic invertebrates and aquatic macrophytes) served as response variables. Stressor and response variables were subjected to Boosted Regression Tree (BRT) analysis to identify stressor hierarchy and stressor interactions and subsequently to Generalised Linear Regression Modelling (GLM) to quantify the stressors standardised effect size. Our results show that riverine habitat degradation was the dominant stressor group for the river fauna, notably the bed physical habitat structure. Overall, the explained variation in benthic invertebrate metrics was higher than it was in fish and macrophyte metrics. In particular, general integrative (aggregate) metrics such as % Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa performed better than ecological traits (e.g. % feeding types). Overall, additive stressor effects dominated, while significant and meaningful stressor interactions were generally rare and weak. We concluded that given the type of stressor and ecological response variables addressed in this study, river basin managers do not need to bother much about complex stressor interactions, but can focus on the prevailing stressors according to the hierarchy identified.

A polymorphism in the norepinephrine transporter gene is associated with affective and cardiovascular disease through a microRNA mechanism

Norepinephrine released from sympathetic nerves is removed from the neuroeffector junction via the action of the norepinephrine transporter (NET). NET impairment is evident in several clinically important conditions including major depressive disorder (MDD), panic disorder (PD), essential hypertension and the postural orthostatic tachycardia syndrome (POTS). We aimed to determine whether a single nucleotide polymorphism (SNP) in the 3' untranslated region (UTR) of the NET gene is associated with NET impairment and to elucidate the mechanisms involved. The analyses were carried out in two cohorts of European ancestry, which included healthy controls and MDD, PD, hypertensive and POTS patients. Compared with controls, cases had significantly higher prevalence of the T allele of rs7194256 (C/T), arterial norepinephrine, depression and anxiety scores, larger left ventricular mass index, higher systolic and diastolic blood pressures, and heart rate. Bioinformatic analysis identified that the microRNA miR-19a-3p could bind preferentially to the sequence created by the presence of the T allele. This was supported by results of luciferase assays. Compared with controls, cases had significantly lower circulating miR-19a-3p, which was associated with pathways related to blood pressure and regulation of neurotransmission. In vitro norepinephrine downregulated miR-19a-3p. In conclusion, the T allele of the rs7194256 SNP in the 3'UTR of the NET gene is more prevalent in diseases where NET impairment is evident. This might be explained by the creation of a binding site for the microRNA miR-19a-3p. A defect in NET function may potentiate the sympathetic neurochemical signal, predisposing individuals with affective diseases to increased risk of cardiovascular disease development.