Anion-Exchange Membrane Water Electrolyzers.

This Review provides an overview of the emerging concepts of catalysts, membranes, and membrane electrode assemblies (MEAs) for water electrolyzers with anion-exchange membranes (AEMs), also known as zero-gap alkaline water electrolyzers. Much of the recent progress is due to improvements in materials chemistry, MEA designs, and optimized operation conditions. Research on anion-exchange polymers (AEPs) has focused on the cationic head/backbone/side-chain structures and key properties such as ionic conductivity and alkaline stability. Several approaches, such as cross-linking, microphase, and organic/inorganic composites, have been proposed to improve the anion-exchange performance and the chemical and mechanical stability of AEMs. Numerous AEMs now exceed values of 0.1 S/cm (at 60-80 °C), although the stability specifically at temperatures exceeding 60 °C needs further enhancement. The oxygen evolution reaction (OER) is still a limiting factor. An analysis of thin-layer OER data suggests that NiFe-type catalysts have the highest activity. There is debate on the active-site mechanism of the NiFe catalysts, and their long-term stability needs to be understood. Addition of Co to NiFe increases the conductivity of these catalysts. The same analysis for the hydrogen evolution reaction (HER) shows carbon-supported Pt to be dominating, although PtNi alloys and clusters of Ni(OH)2 on Pt show competitive activities. Recent advances in forming and embedding well-dispersed Ru nanoparticles on functionalized high-surface-area carbon supports show promising HER activities. However, the stability of these catalysts under actual AEMWE operating conditions needs to be proven. The field is advancing rapidly but could benefit through the adaptation of new in situ techniques, standardized evaluation protocols for AEMWE conditions, and innovative catalyst-structure designs. Nevertheless, single AEM water electrolyzer cells have been operated for several thousand hours at temperatures and current densities as high as 60 °C and 1 A/cm2, respectively.

High-Voltage Induced Surface and Intragranular Structural Evolution of Ni-Rich Layered Cathode.

Layered Ni-rich lithium transition metal oxides are promising cathode materials for high-energy-density lithium-ion batteries. These cathodes, however, suffer from rapid performance decay under high-voltage operation. In this work, the electrochemical properties and structural evolution of the LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cathode upon high-voltage cycling are investigated. The results show that the NMC811 cathode not only experiences surface evolution with the formation of Li-deficient rock-salt layers, but also suffers from drastic intragranular structural changes inside bulk grains after high-voltage cycling. Direct evidence for the formation of transition-metal/Li disordering domains with uneven Li content and lattice plane distortion at the internal grains of 4.6 V-cycled NMC811 are provided with their atomic ordering and spatial distribution clearly resolved. The complex intragranular structural changes impede Li+ diffusion inside bulk material, resulting in kinetic limitation and capacity loss. The results demonstrate that the high-voltage cycling would induce severe structural degradation at the grain interior of the cathode material beyond surface evolution, which contributes significantly to the rapid performance decay of the NMC811 cathode. The findings provide new insights for developing effective countermeasures to mitigate this degradation pathway.

Factors shaping community patterns of protists and bacteria on a European scale.

Factors shaping community patterns of microorganisms are controversially discussed. Physical and chemical factors certainly limit the survival of individual taxa and maintenance of diversity. In recent years, a contribution of geographic distance and dispersal barriers to distribution patterns of protists and bacteria has been demonstrated. Organismic interactions such as competition, predation and mutualism further modify community structure and maintenance of distinct taxa. Here, we address the relative importance of these different factors in shaping protists and bacterial communities on a European scale using high-throughput sequencing data obtained from lentic freshwater ecosystems. We show that community patterns of protists are similar to those of bacteria. Our results indicate that cross-domain organismic factors are important variables with a higher influence on protists as compared with bacteria. Abiotic physical and chemical factors also contributed significantly to community patterns. The contribution of these latter factors was higher for bacteria, which may reflect a stronger biogeochemical coupling. The contribution of geographical distance was similar for both microbial groups.

Trade-off between taxon diversity and functional diversity in European lake ecosystems.

Inferring ecosystem functioning and ecosystem services through inspections of the species inventory is a major aspect of ecological field studies. Ecosystem functions are often stable despite considerable species turnover. Using metatranscriptome analyses, we analyse a thus-far unparalleled freshwater data set which comprises 21 mainland European freshwater lakes from the Sierra Nevada (Spain) to the Carpathian Mountains (Romania) and from northern Germany to the Apennines (Italy) and covers an altitudinal range from 38 m above sea level (a.s.l) to 3110 m a.s.l. The dominant taxa were Chlorophyta and streptophytic algae, Ciliophora, Bacillariophyta and Chrysophyta. Metatranscriptomics provided insights into differences in community composition and into functional diversity via the relative share of taxa to the overall read abundance of distinct functional genes on the ecosystem level. The dominant metabolic pathways in terms of the fraction of expressed sequences in the cDNA libraries were affiliated with primary metabolism, specifically oxidative phosphorylation, photosynthesis and the TCA cycle. Our analyses indicate that community composition is a good first proxy for the analysis of ecosystem functions. However, differential gene regulation modifies the relative importance of taxa in distinct pathways. Whereas taxon composition varies considerably between lakes, the relative importance of distinct metabolic pathways is much more stable, indicating that ecosystem functioning is buffered against shifts in community composition through a functional redundancy of taxa.

Generation of Complex Azabicycles and Carbobicycles from Two Simple Compounds in a Single Operation through a Metal-Free Six-Step Domino Reaction.

Aza- and carbobicyclic compounds possess favorable pharmaceutical properties, but they are difficult to access. Herein, we demonstrate an unprecedented organocatalytic two component six-step chemodivergent domino reaction, which provides a straightforward, sustainable and atom economical route to difficult-to-access complex bicyclic architectures: azabicycles and carbobicycles, whose ratios can be controlled by the applied electrophiles and catalysts. Detailed NMR and X-ray studies on the structures and relative stereochemistry of selected compounds are presented. Mechanistic investigations of the chemoselective branching step have been carried out with DFT methods in conjunction with semiempirical van der Waals interactions. This new domino reaction opens up a new vista of generating, in a single operation, new bioactive compounds with strong antiviral properties (EC50 up to 0.071 µM for human cytomegalovirus (HCMV)) outperforming clinically used ganciclovir (EC50 2.6 µM).

Small but Manifold - Hidden Diversity in "Spumella-like Flagellates".

Colourless, nonscaled chrysophytes comprise morphologically similar or even indistinguishable flagellates which are important bacterivors in water and soil crucial for ecosystem functioning. However, phylogenetic analyses indicate a multiple origin of such colourless, nonscaled flagellate lineages. These flagellates are often referred to as "Spumella-like flagellates" in ecological and biogeographic studies. Although this denomination reflects an assumed polyphyly, it obscures the phylogenetic and taxonomic diversity of this important flagellate group and, thus, hinders progress in lineage- and taxon-specific ecological surveys. The smallest representatives of colourless chrysophytes have been addressed in very few taxonomic studies although they are among the dominant flagellates in field communities. To overcome the blurred picture and set the field for further investigation in biogeography and ecology of the organisms in question, we studied a set of strains of specifically small, colourless, nonscaled chrysomonad flagellates by means of electron microscopy and molecular analyses. They were isolated by a filtration-acclimatisation approach focusing on flagellates of around 5 µm. We present the phylogenetic position of eight different lineages on both the ordinal and the generic level. Accordingly, we describe the new genera Apoikiospumella, Chromulinospumella, Segregatospumella, Cornospumella and Acrispumella Boenigk et Grossmann n. g. and different species within them.

Casting shadows on the prevalence of tanning dependence: an assessment of mCAGE criteria.

Recently more and more studies have reported high prevalence rates for a 'tanning dependence' among tanning bed users. The authors of these studies base their argumentation on a modified (m) version of the CAGE (Cut-down, Annoyed, Guilty and Eye-opener) Criteria, initially used for alcohol addiction. By means of cognitive interviews and a large population survey, we tested the validity of the mCAGE Criteria and the above-mentioned prevalence that was deduced on the basis of rather small collectives. Firstly, it seems that the mCAGE Criteria wording used so far is inconsistent, misleading and intrinsically invalid. Secondly, our population-based data show a much lower percentage (15%) of current sunbed users with potential dependence symptoms than the above-mentioned previously published studies. Thirdly, the usage parameters for most of the supposed 'addicts' do not indicate a substance addiction: 38% of the users with positive scores reported not having visited a tanning studio at all in the previous month, 39% did not use sunbeds regularly and 89% did not show signs of tolerance to UV radiation. The mCAGE Criteria do not seem suitable for assessing tanning dependence.

Dietary counselling for cardiovascular disease prevention in primary care settings: results from a German physician survey.

BACKGROUND: Primary care physicians (PCPs) play an important role in the promotion of healthy dietary behaviour. However, little is known about the practice of and factors associated with the provision of dietary counselling in primary health care in Germany. OBJECTIVES: To explore the attitudes towards and factors associated with the routine provision of dietary counselling in Germany using data from the nationwide, representative sample of the Physician Survey on Cardiovascular Disease Prevention. METHODS: A total of 4074 randomly selected PCPs (response rate: 33.9%) provided data on dietary counselling for prevention of cardiovascular disease (CVD) based on the 5 A's (Assess, Advise, Agree, Assist, Arrange), attitudes towards dietary counselling and patients' and practice characteristics. RESULTS: While the majority of PCPs (86%) reported having high levels of competence in providing dietary advice, only 49% felt they had been successful in counselling their patients on nutrition. PCPs routinely asked (68%) and advised patients to change their dietary habits more frequently (77%) compared to other counselling techniques based on the 5 A's. Female physicians and those with a higher percentage of privately insured patients and patients at higher risk of CVD were more likely to use the 5 A's to routinely counsel their patients on nutrition. CONCLUSIONS: The data showed high levels of involvement by German PCPs in CVD prevention and dietary counselling. The rather low perceived success of dietary intervention and differences with respect to patients' health insurance status indicate a need to address both communication skills in medical training and appropriate reimbursement of preventive services.

Walking, bicycling, and sports in postmenopausal breast cancer survivors--results from a German patient cohort study.

OBJECTIVES: Physical activity (PA) is increasingly discussed as a means to achieve both physical and psychological benefits for breast cancer patients and survivors. However, little is known about activity-specific PA behavior following diagnosis. Our objectives were to describe sports and active transportation in the course of breast cancer and to identify factors associated with these activities. METHODS: We used data from a German cohort study including 1067 postmenopausal breast cancer survivors aged 50-75 years. Data were collected about walking and bicycling for transportation purposes and sports before diagnosis, during therapy, and 1 year after surgery. Associations between these activities and clinical, behavioral, and social characteristics were analyzed with logistic regression. RESULTS: The proportions of physically active women decreased significantly during therapy compared with before diagnosis (walking: 75.1% vs. 89.7%; bicycling: 19.3% vs. 56.5%; sports: 14.8% vs. 64.5%; all p < 0.001). Calisthenics, swimming, and walking for exercise were the most frequent types of sport. Chemotherapy/radiotherapy was negatively associated with sports (odds ratio [OR]: 0.35 [0.17-0.73]) but positively associated with walking during therapy (OR: 2.08 [1.04-4.15]). Although sociodemographic factors showed weak associations with PA, participation in rehabilitation increased the likelihood for bicycling (OR: 1.48 [1.06-2.09]) and sports (OR: 1.88 [1.38-2.58]) 1 year after surgery. CONCLUSIONS: The majority of women stopped exercising and bicycling during breast cancer therapy. Interventions promoting in particular moderate activities after breast cancer diagnosis are required for this population. Increasing participation in rehabilitation might help to increase the proportion of women who bicycle and engage in sports after breast cancer diagnosis.

Building awareness of the health risks of sunbed use: identification of target groups for prevention.

PURPOSE: Sunbed use, a recognized risk factor for skin cancer development, is common in developed countries. Cost-efficient interventions to reduce the negative health consequences of sunbed use are needed. As a first step to identify what kind of intervention might be useful, we aimed to assess the awareness of potential health risks of sunbed use in current, former, and never users as well as in current users with differing risk profiles. METHODS: We assessed risk awareness using items addressing the potential health risks of sunbed use (e.g. skin damage) in a representative sample of 4851 individuals. The response format assessed agreement with each statement. Risk profiles were defined by a large number of birthmarks, a history of frequent childhood sunburn, or a (family) history of melanoma. RESULTS: Many individuals were not aware of potential risks (e.g. agreement to skin cancer risk 72.6%). Current users were less aware compared with former and never users [e.g. skin cancer risk (65.6% vs. 75.9% and 73.0%, respectively; P < 0.001]). Among current users, those with at least two risk factors showed the highest proportion of risk aware individuals. CONCLUSION: Low risk awareness among current users suggests the need for targeted interventions to reduce or discontinue sunbed use.

Exploring the efficacy of metabarcoding and non-target screening for detecting treated wastewater.

Wastewater treatment processes can eliminate many pollutants, yet remainder pollutants contain organic compounds and microorganisms released into ecosystems. These remainder pollutants have the potential to adversely impact downstream ecosystem processes, but their presence is currently not being monitored. This study was set out with the aim of investigating the effectiveness and sensitivity of non-target screening of chemical compounds, 18S V9 rRNA gene, and full-length 16S rRNA gene metabarcoding techniques for detecting treated wastewater in receiving waters. We aimed at assessing the impact of introducing 33 % treated wastewater into a triplicated large-scale mesocosm setup during a 10-day exposure period. Discharge of treated wastewater significantly altered the chemical signature as well as the microeukaryotic and prokaryotic diversity of the mesocosms. Non-target screening, 18S V9 rRNA gene, and full-length 16S rRNA gene metabarcoding detected these changes with significant covariation of the detected pattern between methods. The 18S V9 rRNA gene metabarcoding exhibited superior sensitivity immediately following the introduction of treated wastewater and remained one of the top-performing methods throughout the study. Full-length 16S rRNA gene metabarcoding demonstrated sensitivity only in the initial hour, but became insignificant thereafter. The non-target screening approach was effective throughout the experiment and in contrast to the metabarcoding methods the signal to noise ratio remained similar during the experiment resulting in an increasing relative strength of this method. Based on our findings, we conclude that all methods employed for monitoring environmental disturbances from various sources are suitable. The distinguishing factor of these methods is their ability to detect unknown pollutants and organisms, which sets them apart from previously utilized approaches and allows for a more comprehensive perspective. Given their diverse strengths, particularly in terms of temporal resolution, these methods are best suited as complementary approaches.

Raman and infrared spectroscopy of α and ß phases of thin nickel hydroxide films electrochemically formed on nickel.

The present work utilizes Raman and infrared (IR) spectroscopy, supported by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to re-examine the fine structural details of Ni(OH)(2), which is a key material in many energy-related applications. This work also unifies the large body of literature on the topic. Samples were prepared by the galvanostatic basification of nickel salts and by aging the deposits in hot KOH solutions. A simplified model is presented consisting of two fundamental phases (α and ß) of Ni(OH)(2) and a range of possible structural disorder arising from factors such as impurities, hydration, and crystal defects. For the first time, all of the lattice modes of ß-Ni(OH)(2) have been identified and assigned using factor group analysis. Ni(OH)(2) films can be rapidly identified in pure and mixed samples using Raman or IR spectroscopy by measuring their strong O-H stretching modes, which act as fingerprints. Thus, this work establishes methods to measure the phase, or phases, and disorder at a Ni(OH)(2) sample surface and to correlate desired chemical properties to their structural origins.

The prevalence of gestational diabetes in advanced economies.

AIMS: One of the first steps in optimizing future prevention and appropriately allocating resources to future diagnosis and treatment of Gestational diabetes (GDM) is to quantify its burden. The aim of this study was therefore to conduct a systematic review of current international literature on the prevalence of GDM with a focus on advanced economies. METHODS: Based on literature searches with the database "PubMed" we included studies with a publication date between 2000 and 2011. All studies were classified independently by two authors. In accordance with the PRISMA Statement we identified 27 original studies. RESULTS: The prevalence of GDM varies substantially between populations with a range of 1.7­11.6 %. Patient self-reports yield higher prevalence estimates than values that are based on medical diagnosis or clinical diagnostic tests. Prevalence seems to vary considerably within Europe with higher prevalence values being observed in Southern Europe than in Northern and Central Europe. Prevalence values from studies from Australia and North America were within this range. CONCLUSION: This review provides a comprehensive and sound summary of the current state of research on the prevalence of GDM in advances economies as a fi rst step in identifying starting points for future interventions.

An ultra-stable reference electrode for scaled all-vanadium redox flow batteries.

Redox flow batteries (RFBs) have been investigated as a promising energy storage system (ESS) for grid applications over the past several decades due to their unique features, which include the separation of energy and power output, high safety, and long cycle life. It is therefore vital but still in severe deficiency to understand the reliability of RFBs, and the mechanisms that cause degradation with time. One of the primary challenges involves the unseparated contributions from individual electrodes due to the absence of a stable reference electrode (RE), particularly for long-term cycle testing in a scaled cell. Herein, we first develop an ultra-stable RE for scaled all-vanadium RFBs. The newly developed RE, based on a dynamic hydrogen electrode (DHE) with a novel design on the area (size) and surface roughness of platinum electrodes, demonstrates high accuracy and long-term stability that enables in situ monitoring of individual electrode potentials throughout 500 cycles. By introducing the RE approach to decouple the cathode and anode in conjunction with the measurement of voltage profiles, overpotentials and polarization curves, the reliability and degradation mechanism of a scaled all-vanadium RFB are further explored, revealing the diverse behaviors of individual electrodes. This exploratory work will benefit the future design and development of a stable RE for a scaled ESS, as well as the fundamental understanding of the RFB's reliability and degradation mechanism.

UPDATING THE GENUS DICTYOSPHAERIUM AND DESCRIPTION OF MUCIDOSPHAERIUM GEN. NOV. (TREBOUXIOPHYCEAE) BASED ON MORPHOLOGICAL AND MOLECULAR DATA1.

Recent molecular analyses of Dictyosphaerium strains revealed a polyphyletic origin of this morphotype within the Chlorellaceae. The type species Dictyosphaerium ehrenbergianum Nägeli formed an independent lineage within the Parachlorella clade, assigning the genus to this clade. Our study focused on three different Dictyosphaerium species to resolve the phylogenetic position of remaining species. We used combined analyses of morphology; molecular data based on SSU and internally transcribed spacer region (ITS) rRNA sequences; and the comparison of the secondary structure of the SSU, ITS-1, and ITS-2 for species and generic delineation. The phylogenetic analyses revealed two lineages without generic assignment and two distinct clades of Dictyosphaerium-like strains within the Parachlorella clade. One clade comprises the lineages with the epitype strain of D. ehrenbergianum Nägeli and two additional lineages that are described as new species (Dictyosphaerium libertatis sp. nov. and Dictyosphaerium lacustre sp. nov.). An emendation of the genus Dictyosphaerium is proposed. The second clade comprises the species Dictyosphaerium sphagnale Hindák and Dictyosphaerium pulchellum H. C. Wood. On the basis of phylogenetic analyses, complementary base changes, and morphology, we describe Mucidosphaerium gen. nov with the four species Mucidosphaerium sphagnale comb. nov., Mucidosphaerium pulchellum comb. nov., Mucidosphaerium palustre sp. nov., and Mucidosphaerium planctonicum sp. nov.

Patterns of protist distribution and diversification in alpine lakes across Europe.

Biogeography in Europe is known to be crucially influenced by the large mountain ranges serving as biogeographical islands for cold-adapted taxa and geographical barriers for warm-adapted taxa. While biogeographical patterns are well-known for plants and animals in Europe, we here investigated diversity and distribution patterns of protist freshwater communities on a European scale (256 lakes) in the light of the well-studied post-glacial distribution patterns of macroorganisms. Thus, our study compared 43 alpine protist communities of lakes located in the Alps, Carpathians, Pyrenees, and the Sierra Nevada with that of surrounding lowland lakes. We verified altitudinal diversity gradients of freshwater protists with decreasing richness and diversity across altitudes similar to those observed for plants and animals. Alpine specialists and generalists could be identified differing significantly in richness and diversity, but hardly in occurrence and proportions of major taxonomic groups. High proportions of region-specific alpine specialists indicate an increased occurrence of distinct lineages within each mountain range and thus, suggested either separated glacial refugia or post-glacial diversification within mountain ranges. However, a few alpine specialists were shared between mountain ranges suggesting a post-glacial recolonization from a common lowland pool. Our results identified generalists with wide distribution ranges and putatively wide tolerance ranges toward environmental conditions as main drivers of protist diversification (specification) in alpine lakes, while there was hardly any diversification in alpine specialists.

Centers of endemism of freshwater protists deviate from pattern of taxon richness on a continental scale.

Here, we analyzed patterns of taxon richness and endemism of freshwater protists in Europe. Even though the significance of physicochemical parameters but also of geographic constraints for protist distribution is documented, it remains unclear where regional areas of high protist diversity are located and whether areas of high taxon richness harbor a high proportion of endemics. Further, patterns may be universal for protists or deviate between taxonomic groups. Based on amplicon sequencing campaigns targeting the SSU and ITS region of the rDNA we address these patterns at two different levels of phylogenetic resolution. Our analyses demonstrate that protists have restricted geographical distribution areas. For many taxonomic groups the regions of high taxon richness deviate from those having a high proportion of putative endemics. In particular, the diversity of high mountain lakes as azonal habitats deviated from surrounding lowlands, i.e. many taxa were found exclusively in high mountain lakes and several putatively endemic taxa occurred in mountain regions like the Alps, the Pyrenees or the Massif Central. Beyond that, taxonomic groups showed a pronounced accumulation of putative endemics in distinct regions, e.g. Dinophyceae along the Baltic Sea coastline, and Chrysophyceae in Scandinavia. Many other groups did not have pronounced areas of increased endemism but geographically restricted taxa were found across Europe.

Interaction-Specific Changes in the Transcriptome of Polynucleobacter asymbioticus Caused by Varying Protistan Communities.

We studied the impact of protist grazing and exudation on the growth and transcriptomic response of the prokaryotic prey species Polynucleobacter asymbioticus. Different single- and multi-species communities of chrysophytes were used to determine a species-specific response to the predators and the effect of chrysophyte diversity. We sequenced the mRNA of Pn. asymbioticus in communities with three single chrysophyte species (Chlorochromonas danica, Poterioochromonas malhamensis and Poteriospumella lacustris) and all combinations. The molecular responses of Pn. asymbioticus significantly changed in the presence of predators with different trophic modes and combinations of species. In the single-species samples we observed significant differences related to the relative importance of grazing and exudation in the protist-bacteria interaction, i.e., to the presence of either the heterotrophic Ps. lacustris or the mixotrophic C. danica. When grazing dominates the interaction, as in the presence of Ps. lacustris, genes acting in stress response are up-regulated. Further genes associated with transcription and translation are down-regulated indicating a reduced growth of Pn. asymbioticus. In contrast, when the potential use of algal exudates dominates the interaction, genes affiliated with iron transport are up-regulated. Rapid phototrophic growth of chrysophytes, with a high demand on soluble iron, could thus lead to iron-limitation and cause changes in the iron metabolism of Pn. asymbioticus. Additionally, we observe a benefit for Pn. asymbioticus from a more diverse protistan community, which could be due to shifts in the relative importance of phototrophy in the mixotrophic chrysophytes when competing for food with other species. Our study highlights the importance of biotic interactions and the specificity of such interactions, in particular the differential effect of grazing and algal exudation in the interaction of bacteria with mixotrophic protists.

Silver stress differentially affects growth of phototrophic and heterotrophic chrysomonad flagellate populations.

Silver ions are among the predominant anthropogenic introduced pollutants in aquatic systems. As silver has effects on species at all trophic levels the community composition in aquatic habitats can be changed as a result of silver stress. The response of planktonic protists to environmental stressors is particularly important as they act both as producers and consumers in complex planktonic communities. Chrysomonad flagellates are of major interest, since this group includes heterotrophic, mixotrophic and phototrophic taxa, and therefore allows analysis of silver stress in organisms with contrasting nutritional strategies independent of a potential taxonomic bias. In a series of lab experiments, we compared the response of different trophic chrysophyte strains to low (5 µg L-1), medium (10 µg L-1) and high (20 µg L-1) nominal Ag concentrations in combination with changes in temperature and light intensity (phototrophs), temperature and food concentration (heterotrophs), or a combination of the above settings (mixotrophs). All tested strains were negatively affected by silver in their growth rates. The phototrophic strains reacted strongly to silver stress, whereas light intensity and temperature had only minor effects on growth rates. For heterotrophic strains, high food concentration toned down the effect of silver, whereas temperatures outside the growth optimum had a combined stress effect. The mixotrophic strains reacted differently depending on whether their nutritional mode was dominated by heterotrophy or by phototrophy. The precise response pattern across all variables was uniquely different for every single species we tested. The present work contributes to a deeper understanding of the effects of environmental stressors on complex planktonic communities. It indicates that silver will negatively impact planktonic communities and may create shifts in their composition and functioning.

Synchrony of Eukaryotic and Prokaryotic Planktonic Communities in Three Seasonally Sampled Austrian Lakes.

Freshwater systems are characterized by an enormous diversity of eukaryotic protists and prokaryotic taxa. The community structures in different lakes are thereby influenced by factors such as habitat size, lake chemistry, biotic interactions, and seasonality. In our study, we used high throughput 454 sequencing to study the diversity and temporal changes of prokaryotic and eukaryotic planktonic communities in three Austrian lakes during the ice-free season. In the following year, one lake was sampled again with a reduced set of sampling dates to observe reoccurring patterns. Cluster analyses (based on SSU V9 (eukaryotic) and V4 (prokaryotic) OTU composition) grouped samples according to their origin followed by separation into seasonal clusters, indicating that each lake has a unique signature based on OTU composition. These results suggest a strong habitat-specificity of microbial communities and in particular of community patterns at the OTU level. A comparison of the prokaryotic and eukaryotic datasets via co-inertia analysis (CIA) showed a consistent clustering of prokaryotic and eukaryotic samples, probably reacting to the same environmental forces (e.g., pH, conductivity). In addition, the shifts in eukaryotic and bacterioplanktonic communities generally occurred at the same time and on the same scale. Regression analyses revealed a linear relationship between an increase in Bray-Curtis dissimilarities and elapsed time. Our study shows a pronounced coupling between bacteria and eukaryotes in seasonal samplings of the three analyzed lakes. However, our temporal resolution (biweekly sampling) and data on abiotic factors were insufficient to determine if this was caused by direct biotic interactions or by reacting to the same seasonally changing environmental forces.