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The aim of the present study was to assess the impact of surrounding land use on the structure and functioning of lowland stream ecosystems. To this end, five different land use types were selected (forest, extensive grassland, intensive grassland, cropland and wastewater treatment plant) each represented by four replicate streams, in which diel dissolved oxygen concentrations were recorded, sediment and water quality parameters were measured and macroinvertebrate community composition was determined. Chironomus sp., Oligochaeta and Gastropoda dominated the cropland and wastewater treatment plant (WWTP) streams, while Plecoptera and most Trichoptera only occurred in forest and extensive grassland streams. Forest streams communities were related to a high oxygen saturation, a high C/N ratio in the sediment and woody debris and coarse particulate organic matter (CPOM) substrate cover. Macroinvertebrate communities in cropland and WWTP streams were related to a low oxygen saturation in water and sediment and high concentrations of dissolved nitrogen, phosphorus and carbon. It is concluded that land use specific impacts on lowland streams are likely exerted via fine sediment accumulation in deposition zones, affecting oxygen regimes, sediment oxygen demand and stream metabolism, ultimately changing macroinvertebrate community composition. This study supports therefore the importance of including the catchment scale in ecological stream quality assessments, combining structural and functional endpoints. [ABSTRACT FROM AUTHOR]

General colonization concepts consent that a slow process of microhabitat formation and subsequent niche realization occurs during early stages after new habitat is released. Subsequently, only few species are able to colonize new habitat in the early onset of succession, while species richness increases steadily over time. Although most colonization studies have been performed in terrestrial ecosystems, running water ecosystems are equally or even more prone to colonization after disturbance due to their dynamic nature. We question how invertebrate succession patterns reconcile with general colonization concepts. With this study we provide insight into the colonization process in newly created lowland stream trajectories and answer how within-stream bio- and functional diversity develops over time. Our results show a rapid influx of species, with a wide range of functional traits, during the first season after water flow commenced. During more than two years of regular monitoring, immigration rates were highest in autumn, marking the effects of seasonality on invertebrate dispersal. Biodiversity increased while abundance peaks of species alternated between seasons. Moreover, also days since start of the experiment explains a considerable part of the variability for taxa as well as traits. However, the relative trait composition remained similar throughout the entire monitoring period and only few specific traits had significantly higher proportions during specific seasons. This indicates that first phase colonization in freshwater streams can be a very rapid process that results in a high biodiversity and a large variety of species functional characteristics from the early onset of succession, contradicting general terrestrial colonization theory. [ABSTRACT FROM AUTHOR]

1. Phototrophic biofilms consist of a matrix of phototrophs, non-photosynthetic bacteria and extracellular polymeric substances (EPS) which is spatially structured. Despite widespread exploitation of algae and bacteria within phototrophic biofilms, for example by protozoans, the 'engineering' effects of these ciliates on the spatial heterogeneity of phototrophic biofilms are poorly studied. 2. We studied the potential engineering effects of two ciliates, Urostyla sp. and Paramecium bursaria, on the spatial heterogeneity of synthetic multispecies biofilms. Biomass of phototrophic organisms, EPS and bacteria was analysed three dimensionally using confocal laser scanning microscopy. Spatial heterogeneity and cover of the phototrophs, bacteria and EPS were determined at several depths within the biofilm. 3. Ciliate species did not interfere with the overall development of phototrophic microorganisms, because the thickness of the biofilm was equal whether the ciliates were present or not, even though their abundance did affect spatial heterogeneity of biofilm components. When Urostyla was present, it reduced aggregation in EPS and bacteria and increased EPS biovolume. This implies a local facilitating effect of ciliates on photosynthetic activity. Biofilms to which Paramecium was added did not differ from controls in terms of phototrophs, EPS cover and biovolume. Nevertheless, ciliates affected the spatial heterogeneity of these components as phototrophs and EPS became more evenly distributed. 4. This study shows that ecosystem engineering by organisms does not only occur at large spatial scales, as in grasslands and estuaries, but also plays a role at the microscopic scale of biofilms. This effect on spatial heterogeneity was not driven by substantial exploitation of biofilm components, but via the subtle engineering effects of ciliates. [ABSTRACT FROM AUTHOR]

In soils and sediments, the redox potential (Eh) is an important parameter controlling the persistence of many organic and inorganic compounds. Especially in wetlands, fluctuations in redox potential values can be very large and depth dependent. For this reason, field deployable logging systems have previously been developed, yet these systems were limited in several aspects. Here we report the development of an improved multichannel datalogger (HYPNOS) and two novel probes for continuous monitoring of Eh profiles, and briefly illustrate the potential applications. The combination of a multichannel logger with different types of probes allows characterisation of spatial and temporal variability of redox potential in relation to environmental and ecological parameters, and we expect this will greatly enhance our knowledge of the functioning of wetlands. [ABSTRACT FROM AUTHOR]

Many floodplains contain high concentrations of sediment associated contaminants that might be subjected to large changes in terms of mobility, transformation and bioavailability. Therefore, this study describes 1) changes in the redox conditions and the mobility of metals in artificially uncovered polluted floodplain sediments, 2) metal uptake by organisms and 3) colonization, succession and functioning of benthic algae on these sediments. Flooding caused long term changes in redox potential (Eh) profiles. In top layers strong gradients in redox potential established quickly, while in deeper layers changes occurred more gradually. The availability of copper as measured by Diffusive Gradients in Thinfilms (DGT) showed a consistent relationship with fluctuations in Eh. However, this relationship was restricted to deeper layers in the sediment. Within 1 week high amounts of total copper were immobilized. Differences in total copper concentrations between polluted and clean sediments became only partially apparent when comparing the available copper fraction (DGT-Cu). Introduced Tubifex shows only marginal differences in levels of accumulated Cu. Colonization, growth and succession of algal communities on polluted sediments was not impaired, most likely due to low bioavailability. It is concluded that changing environmental conditions, such as flooding, can result in stable chemical conditions with low a availability of metals and hence in a diminution of actual ecological risks. [Copyright &y& Elsevier]

The change in European distribution systems, exemplified by West Germany, represented a general change from a more cooperative towards a more competitive way of thinking and behaviour in everyday life. Substantial parts of the change towards a more competitive, more dynamic approach can be understood as Americanisation, an adapted and always selective process. Besides, in self-service we find Americanisation in supermarkets. These were no longer within walking distance but situated outside the cities, where customers needed a car in order to shop - a total break with European traditions. Mail-order business learned a lot concerning organisational matters. Channels of Americanisation were mainly travels by managers to the US and brochures, specially written for a distinctive branch of business. Americanisation also had its limits. Wholesale stayed neutral but unchanged. Other sectors, such as the institution of weekly private local markets, or of mobile retailers, resisted stubbornly. Some attempts failed utterly, for instance the attempt to introduce automats on a large scale. Also ignorance occurred: the discounter Aldi failed to recognise American experience in this sector, and consequently had to 'reinvent the wheel'. In spite of failures, ignorance and neutrality we have to acknowledge a wave of Americanisation in retail trade during the boom period of the 1950s which did not start to peter out before the late 1960s. [ABSTRACT FROM AUTHOR]

Americanisation is the (selected and adapted) transfer of values from the US to Europe. While this model is well established in cultural history, economist and economic historians had difficulties with this concept. However, the book's title 'Culture Matters!' is the latest insight of distinguished economists such as Michael E. Porter, Jeffrey Sachs, Francis Fukuyama and others.1 The contributors to this issue not only agree, but try to provide an answer to the question that is asked in the subtitle of the book: 'How Values Shape Human Progress'. More precisely, they ask how American values influenced European economic performance during the twentieth century. Europe experienced three major waves of Americanisation: in the 1920s, during the boom-phase 1949-1973, and finally from about 1985 until the present day. By using Americanisation as a cultural concept, as well as describing the waves, why they occurred can also be explained: the Europeans were eager to learn how to improve their economy during phases in which the US excelled not only in the economic field but also in others (politics, military strength, etc.). Thus, it can be understood how and why rationalisation swept over Europe as a wave in the 1920s, and why the US film industry became dominant; why during the boom European countries set up business schools; why firms changed their systems of government; and finally why since about 1985 Europeans have embarked on a process of privatisation and de-regulation. Thus, Americanisation gives us a better understanding of what has happened and is still happening with us Europeans - and why. The general trend was to become less cooperative and more competitive in all aspects. Why did Americanisation occur in waves? Already by 1914 some branches of American industry were superior to their European competitors. Selected European firms successfully adopted US standards. But what caused the three waves was not action by a couple of individual businesses: it needed a general feeling of American superiority. Cultural, political, military and financial strength provided the background for each of the waves, while they petered out when this background was no longer existent: during the world economic crisis of the 1930s, in the 1970s with the Vietnamese War, and at the time of the financial and oil crises. Americanisation started again when, with the breakdown of socialism, the US emerged as the world's sole hegemonic power, due to the US IT industry, and American ideas on private property and in the financial sector, all of which pressed for less cooperative and more exclusive, private ways of doing business and conducting one's personal life. The contribution shows how rationalisation spread in Europe during the 1920s. For the boom-period 1950-1973, the showcases are the Marshall Plan, mass distribution including the introduction of self-service and market research, management education, de-cartelisation, foreign direct investment and specific changes within internal organisation of enterprise. The last wave is explained by the changed role of finance, both in private life and in the economy, and in technological change. All these changes over time were entrenched in a handful of American values. It was the deepening of these values in the US themselves that, in combination with an upswing of political, military, cultural and economic power, prepared the next wave of Americanisation. [ABSTRACT FROM AUTHOR]

Introduces a series of articles on the impact of state intervention and cultural values on academia and industry.

In many large European rivers, the number of typical riverine insect species, such as mayflies, stoneflies, and caddisflies, is greatly reduced compared to historic records. This can no longer be explained by high concentrations of a relatively small number of dominant toxicants since many rivers have changed from heavily contaminated systems with a few selected key toxicants to systems with a complex contamination. This contamination consists of many substances in low concentrations coinciding with other unfavorable conditions, such as low oxygen concentrations. It was hypothesized that the joint adverse effects of such multiple stressors may be a steering factor in the distribution of riverine insect species. The aim of this study was therefore to determine the combined effects of toxicants and oxygen depletion. To this purpose, larvae of the indigenous riverine mayfly Ephoron virgo were exposed to two different model toxicants, copper and diazinon, under normoxia and hypoxia (50% air saturation) conditions. The median effective concentrations for mortality for copper were significantly lower in the hypoxia treatments than in the normoxia treatments. For diazinon, no differences were observed between two treatments differing in dissolved oxygen levels, and therefore we argue that interactions between multiple stressors may be compound specific. It is concluded that the combination of toxicants and lowered oxygen may have a stronger impact than can be expected based on the adverse effects of the individual factors and that standard toxicity tests may be insufficient alone to determine the impact of human activities on the ecological state of riverine communities. Instead, attention needs to be paid to more environmentally realistic nonoptimal conditions in toxicity testing to adequately fulfill the needs of ecological recovery programs.

The toxic unit concept is commonly applied for determining the effects of a mixture of toxicants. Use of this concept is, however, limited to compounds with similarly shaped dose-response relationships. In the present study, a method is proposed to gain insight regarding the influence of differences in the shapes of dose-response relationships on the applicability of the concentration-addition model by judging additivity at different effect levels. To this purpose, two model toxicants with different modes of action and dose-response relationships were selected: copper, and diazinon. Using mortality of the mayfly (Ephoron virgo) as the endpoint, it was demonstrated that the two compounds act in a less-than-concentration-additive manner. Application of the proposed calculation method revealed that the less-than-concentration-addition effect was independent of the effect level on which the mixture was judged. [ABSTRACT FROM AUTHOR]

Focuses on the economic and political constraints in Germany. Impact of the oil-price shocks on the economy; Recognition of coal refinement as a technological answer to economic and political constraints; Concern of the federal government on the rising effect of oil price.

Stream restoration efforts have increased, but the success rate is still rather low. The underlying reasons for these unsuccessful restoration efforts remain inconclusive and need urgent clarification. Therefore, the aim of the present study was to evaluate over 40 years of stream restoration to fuel future perspectives. To this purpose we evaluated the influence of policy goals on stream restoration efforts, biophysical restoration objectives, restoration measures applied including the scale of application and monitoring efforts. Information was obtained from five stream restoration surveys that were held among the regional water authorities in the Netherlands over the last 40 years and from an analysis of the international scientific publications on stream restoration spanning the same time period. Our study showed that there was a considerable increase in stream restoration efforts, especially motivated by environmental legislation. However, proper monitoring of the effectiveness of the measures was often lacking. Furthermore, a mismatch between restoration goals and restoration measures was observed. Measures are still mainly focused on hydromorphological techniques, while biological goals remain underexposed and therefore need to be better targeted. Moreover, restoration practices occur mainly on small scales, despite the widely recognized relevance of tackling multiple stressors acting over large scales for stream ecosystem recovery. In order to increase the success rate of restoration projects, it is recommended to improve the design of the accompanying monitoring programmes, allowing to evaluate, over longer time periods, if the measures taken led to the desired results. Secondly, we advise to diagnose the dominant stressors and plan restoration measures at the appropriate scale of these stressors, generally the catchment scale. • Legislation motivated the increase in stream restoration efforts. • A mismatch between restoration goals and measures was observed. • Proper stream restoration monitoring delays, acceleration is recommended. • Large scale processes need much more attention in restoration. [ABSTRACT FROM AUTHOR]

Eutrophication has been identified as the primary cause of water quality deterioration in inland waters worldwide, often associated with algal blooms or fish kills. Eutrophication can be controlled through watershed management and in-lake measures. An extreme heatwave event, through its impact on mineralization rates and internal nutrient loading (phosphorus—P, and nitrogen—N), could counteract eutrophication control measures. We investigated how the effectiveness of a nutrient abatement technique is impacted by an extreme heatwave, and to what extent biogeochemical processes are modulated by exposure to heatwaves. To this end, we carried out a sediment-incubation experiment, testing the effectiveness of lanthanum-modified bentonite (LMB) in reducing nutrients and greenhouse gas emissions from eutrophic sediments, with and without exposure to an extreme heatwave. Our results indicate that the effectiveness of LMB may be compromised upon exposure to an extreme heatwave event. This was evidenced by an increase in concentration of 0.08 ± 0.03 mg P/L with an overlying water volume of 863 ± 21 mL, equalling an 11% increase, with effects lasting to the end of the experiment. LMB application generally showed no effect on nitrogen species, while the heatwave stimulated nitrification, resulting in ammonium loss and accumulation of dissolved oxidized nitrogen species as well as increased dissolved nitrous oxide concentrations. In addition, carbon dioxide (CO2)-equivalent was more than doubled during the heatwave relative to the reference temperature, and LMB application had no effect on mitigating them. Our sediment incubation experiment indicates that the rates of biogeochemical processes can be significantly accelerated upon heatwave exposure, resulting in a change in fluxes of nutrient and greenhouse gas between sediment and water. The current efforts in eutrophication control will face more challenges under future climate scenarios with more frequent and intense extreme events as predicted by the IPCC. [ABSTRACT FROM AUTHOR]

Despite the widely acknowledged connection between terrestrial and aquatic ecosystems, the contribution of runoff to the sediment composition in lowland stream deposition zones and the subsequent effects on benthic invertebrates remain poorly understood. The aim of this study was therefore to investigate the mechanisms by which runoff affects sediment composition and macroinvertebrates in deposition zones of lowland stream ecosystems. To this end, sediment from runoff and adjacent instream deposition zones from streams with different land use was chemically characterized and the biological effects were assessed at the species, community and ecosystem level. Runoff and deposition zone sediment composition as well as biological responses differed clearly between forest and agricultural streams. The stream deposition zone sediment C/N ratio reflected the respective runoff sediment composition. Deposition zones in the forest stream had a higher C/N ratio in comparison to the agricultural streams. Growth of Hyalella azteca and reproduction of Asellus aquaticus were higher on forest stream sediment, whereas chironomids and worms suffered less mortality on the agricultural sediments containing only natural food. The forest stream deposition zones showed higher values for indices indicative of biological integrity and had a lower sediment oxygen demand. We concluded that agricultural land use affects lowland stream ecosystem deposition zones at the species, community and ecosystem level via altered food quality (C/N ratio) and higher oxygen demand of the sediment. [ABSTRACT FROM AUTHOR]

For several decades now, there has been an increase in the sources and types of chemicals in estuarine and coastal waters as a consequence of anthropogenic activities. This has led to considerable concern about the effects of these chemicals on the marine food chain. The fact is that estuarine and coastal waters are the most productive ecosystems with high primary production by microalgae. The toxic pressure of specific phytotoxic chemicals now poses a major threat to these ecosystems. In a previous study, six herbicides (atrazine, diuron, irgarol, isoproturon, terbutryn and terbutylazine) were identified as the main contaminants affecting photosynthesis in marine microalgae. The purpose of this study is to investigate the toxic pressure of these herbicides in the Dutch estuarine and coastal waters in relation to the effective photosystem II efficiency (ΦPSII) in microalgae. Temporal and spatial variations in the concentrations of these herbicides were analyzed based on monitoring data. Additionally, a field study was carried out in which chemical analysis of water was performed and also a toxicity assessment using the Pulse Amplitude Modulation (PAM) fluorometry assay that measures ΦPSII. The toxic pressure on ΦPSII in microalgae has decreased with 55–82% from 2003 to 2012, with the Western Scheldt estuary showing the highest toxic pressure. By combining toxicity data from the PAM assay with chemical analysis of herbicide concentrations, we have identified diuron and terbutylazine as the main contributors to the toxic pressure on microalgae. Although direct effects are not expected, the toxic pressure is close to the 10% effect level in the PAM assay. A compliance check with the current environmental legislation of the European Union revealed that the quality standards are not sufficient to protect marine microalgae. [ABSTRACT FROM AUTHOR]

Pulse Amplitude Modulation (PAM) fluorometry, based on chlorophyll a fluorescence, is a frequently used technique in algal bioassays to assess toxicity of single compounds or complex field samples. Several test conditions can influence the test results, and because a standardized test protocol is currently lacking, linking the results of different studies is difficult. Therefore, the aim of the present study was to gain insight into the effects of test conditions of laboratory algal bioassays using PAM fluorometry on the outcome of toxicity tests. To this purpose, we described the results from several pilot studies on test development in which information is provided on the effects of the main test factors during the pretest phase, the test preparation, the exposure period, and the actual measurement. The experiments were focused on individual herbicides and complex field samples and included the effects of culturing conditions, cell density, solvent concentration, exposure time, and the presence of actinic light. Several of these test conditions were found to influence the outcome of the toxicity test, and the presented information provides important background information for the interpretation of toxicity results and describes which test conditions should be taken into account when using an algal bioassay with PAM fluorometry. Finally, the application of PAM fluorometry in algal toxicity testing is discussed. Environ Toxicol Chem 2014;33:1017-1022. © 2014 SETAC [ABSTRACT FROM AUTHOR]

Abstract: Suspended particles are a major constituent of municipal wastewater and generally contain high levels of bacteria, including human pathogens. Discharge of these particles of anthropogenic nature can have profound effects on receiving aquatic ecosystems and mitigation of these effects requires additional polishing of treated municipal wastewater. Previously it was shown that surface flow constructed wetlands are effective in improving water quality by reducing the numbers of fecal indicator organisms. However, fecal indicator organisms represent only a minor fraction of the total planktonic bacterial community and knowledge on the effects of these constructed wetlands on the composition and functioning of the entire planktonic bacterial community is limited. The aim of this descriptive study was therefore to identify changes in the planktonic bacterial community during residence of secondary treated municipal wastewater in a full-scale surface flow constructed wetland. To this purpose water samples were taken in which the bacterial community composition and functioning were analyzed using FISH, DGGE and BIOLOG. Surprisingly, the bacterial abundance at the inflow of the constructed wetland was relatively low compared with more natural surface waters. However, the inflowing bacterial community showed high metabolic activity and functional diversity. During residence in the surface flow constructed wetland the bacterial abundance doubled, but decreased in metabolic activity and functional diversity. Shifts in the community composition indicate that these changes are related to turn-over of the bacterial community. The planktonic bacterial community in the effluent of the constructed wetland closely resembled natural bacterial communities in urban and agricultural ditches. Based on these observations we conclude that constructed wetlands are capable to mitigate possible impacts of the particle load in treated wastewaters by transforming the anthropological bacterial community to a bacterial community resembling more “natural” surface waters. [Copyright &y& Elsevier]

Abstract: Constructed wetlands (CWs) have been shown to improve the water quality of treated wastewater. The capacity of CWs to reduce nutrients, pathogens and organic matter and restore oxygen regime under normal operating conditions cannot be extrapolated to periods of incidental peak discharges. The buffering capacity of CWs during peak discharges is potentially a key factor for water quality in the receiving waters. Therefore, the aim of the present study was to investigate the behaviour of peak discharges of suspended particles, (associated) physiochemical parameters and pathogenic organisms from a wastewater treatment plant (WWTP) in a full scale constructed wetland (CW). By mixing clarified water and sludge rich water from the settlement tank of the WWTP, the suspended particle concentration was increased for 8 h from ±3.5 to ±230 mg L−1, and discharged into a full scale horizontal surface flow constructed wetland. An increase of suspended particle concentration following the peak discharge concurred with increases in turbidity and oxygen demand, total nutrient load (nitrogen, phosphorus and carbon) and pathogens (Escherichia coli and Enterococci). Temperature, pH, conductivity and dissolved nutrient concentrations (nitrogen, phosphorus and carbon) were however unaffected by the initial peak discharge. After retention in the unvegetated ponds (the first CW compartment) the applied suspended particle peak with a total load of 86.2 kg was reduced by >99%. Similar peak buffering was observed for the turbidity, oxygen demand and settable volume. Simultaneously dissolved nutrient concentrations increased, indicating partial mineralization of the suspended particles during retention in the unvegetated ponds. The peak buffering of pathogens was lower (40–84%), indicating differences in removal processes between other suspended particles and pathogens. The results indicated that the suspended particles were probably mostly removed by sedimentation and mineralization, where pathogens were more likely buffered by biofilm retainment, mortality and predation, mainly in reed ditches. After passing through the total CW the residuals of the suspended particle peak discharge were temporal increased concentrations of inorganic carbon (IC), NH4 and E. coli (respectively 11%, 17% and 160% higher than steady state concentrations). The observations support the positive role of CWs for effective buffering of wastewater discharge peaks. [Copyright &y& Elsevier]

Sponges are major epibionts of mangrove roots in the Caribbean. Mangrove sponge communities in the Caribbean mainly consist of species that are typical to this habitat and community compositions often differ from those found on coral reefs nearby. Heterogeneity in species distributions between locations and within locations between roots is often reported. This study quantifies the diversity and abundance of mangrove associated sponges in the inner bays of Curaçao and Aruba and correlates variability of regional sponge diversity with environmental variables measured along the surveyed sites. Tannin concentrations vary between mangrove roots, and were correlated to sponge cover as a possible cause for habitat heterogeneity on a smaller scale. A total of 22 species was observed. Heterogeneity in species richness and abundance was apparent, and several sponge species were restricted in their depth of occurrence. Statistical data reduction suggests that sponge diversity may be partly explained by the distance towards adjacent reefs and to the degree of eutrophication, in which the latter is comprised of rate of planktonic respiration, total carbon and turbidity. Tannin concentrations did not determine within locality species heterogeneity as a priori postulated, but were positively related to sponge cover for reasons not yet elucidated. [ABSTRACT FROM AUTHOR]

Newly constructed wetlands are created to provide a range of ecosystem services, including carbon sequestration. Our understanding of the initial factors leading to successful peat formation in such environments is, however, limited. In a new 100-ha wetland that was created north of Amsterdam (the Netherlands), we conducted an experiment to determine the best combination of abiotic and biotic starting conditions for initial peat-forming processes. Sediment conditions were the main driver of vegetation development, biomass production and elemental composition during the 3-year study period. Overall, helophytes (Typha spp.) dominated basins with nutrient-rich conditions, whereas nutrient-poor basins were covered by submerged vegetation, which produced about seven times less aboveground biomass than helophytes. The C/N ratios for all plant species and biomass components were generally lower under nutrient-rich conditions and were lower for submerged species than helophytes. Because total basin biomass showed five times higher shoot and ten times higher root and rhizome production for clay and organic than sand sediments, even with some differences in decomposition rates are the conditions in the nutrient-rich basins expected to produce higher levels of initial peat formation. The results suggest that addition of a nutrient-rich sediment layer creates the best conditions for initial peat formation by stimulating rapid development of helophytes. [ABSTRACT FROM AUTHOR]

Limnetic aggregates from a turbid delta lake with low dissolved nutrient availability were studied in relation to light and dissolved nutrient availability. Quick light‐attenuation restricts the euphotic zone to the top surface layer of the water column, whereas mineralization processes in the sediment specifically provide dissolved nutrients near the lakebed. This suggests neither the pelagic nor the benthic zone provides the combination of resources required for microalgal growth. Nutrient mineralization in aggregates could bridge this apparent spatial gap in light and nutrients by providing dissolved nutrients in the euphotic zone, promoting microalgal growth. To explore this, aggregates obtained from turbid and phosphate‐limited lake Markermeer (The Netherlands) were exposed in the laboratory to phosphate‐replete and phosphate depleted conditions, at high‐light and low‐light availability. Confocal microscopy revealed that aggregates exhibited alkaline phosphatase activity and contained microalgae, other microbes, and extracellular polymeric substances. The spatial distribution of the phosphatase activity in aggregates largely matched that of chlorophyll a (Chl a)‐lacking microbes, suggesting that these microbes were responsible for the activity. Colorimetric quantification revealed that aggregates exhibited over 1.9‐fold higher phosphatase activity than surrounding water. Two‐day exposure to different light and phosphate availabilities affected aggregate composition. Phosphate depleted conditions resulted in more Chl a‐lacking microbes and more phosphatase activity than phosphate‐replete conditions. Low‐light intensity resulted in higher abundance of extracellular polymeric substances than high‐light intensity. In contrast to aggregates from deep stratified systems, Markermeer aggregates were not enriched with dissolved phosphorus. These results suggest that P‐cycling in aggregates differs between shallow turbid and deep stratified ecosystems. [ABSTRACT FROM AUTHOR]

In densely populated delta regions, many freshwater shallow lakes constructed on top of marine deposits and their water tables are maintained at a fixed level. Reintroducing water table fluctuations in such lakes will stimulate emergent vegetation development, but potential alterations in nutrient fluxes are still largely unknown. In a mesocosm study, we investigated element fluxes between sediment and pore-water during water drawdown and over the sediment-water interface during subsequent rewetting using sediments from the Oostvaardersplassen (The Netherlands). Desiccation of lake sediment resulted in a decline in pore-water phosphate concentrations (up to 90%), while this was not observed for shore sediments with a desiccation history. Rewetting induced a strong flux of released sulphate and calcium over the sediment-water interface, while expected fluxes of phosphate and nitrogen to the surface water remained limited. In shore sediment, lower element fluxes were observed compared to lake sediments. While water drawdown in delta lakes on marine clay resulted in vegetation development, it can also induce in changes in buffering capacity of the sediment. This should be taken into account when applying water drawdown as a cyclic measure to regenerate emergent vegetation in constructed delta lakes. [ABSTRACT FROM AUTHOR]

Summary Annual sulfate mass balances have been constructed for four low-lying peat polders in the Netherlands, to resolve the origin of high sulfate concentrations in surface water, which is considered a water quality problem, as indicated amongst others by the absence of sensitive water plant species. Potential limitation of these plants to areas with low sulfate was analyzed with a spatial match-up of two large databases. The peat polders are generally used for dairy farming or nature conservation, and have considerable areas of shallow surface water (mean 16%, range 6–43%). As a consequence of continuous drainage, the peat in these polders mineralizes causing subsidence rates generally ranging between 2 and 10 mm y − 1 . Together with pyrite oxidation, this peat mineralization the most important internal source of sulfate, providing an estimated 96 kg SO 4 ha − 1 mm − 1 subsidence y − 1 . External sources are precipitation and water supplied during summer to compensate for water shortage, but these were found to be minor compared to internal release. The most important output flux is discharge of excess surface water during autumn and winter. If only external fluxes in and out of a polder are evaluated, inputs average 37 ± 9 and exports 169 ± 17 kg S ha − 1 y − 1 . During summer, when evapotranspiration exceeds rainfall, sulfate accumulates in the unsaturated zone, to be flushed away and drained off during the wet autumn and winter. In some polders, upward seepage from early Holocene, brackish sediments can be a source of sulfate. Peat polders export sulfate to the regional water system and the sea during winter drainage. The available sulfate probably only plays a minor role in the oxidation of peat: we estimate that this is less than 10% whereas aerobic mineralization is the most important. Most surface waters in these polders have high sulfate concentrations, which generally decline during the growing season when aquatic sediments are a sink. In the sediment, this sulfur is reduced and binds iron more strongly than phosphorus, which can be released to the overlying water and potentially fuels eutrophication. About 76% of the sampled vegetation-sites exceeded a threshold of 50 mg l − 1 SO 4 , above which sensitive species, such as Stratiotes aloides , and several species of Potamogeton were significantly less abundant. Thus high sulfate concentrations, mainly due to land drainage and consequent mineralization, appear to affect aquatic plant community composition. [ABSTRACT FROM AUTHOR]

Many wetlands are heavily modified and identifying the environmental drivers of indicator groups like aquatic insects is complicated by multiple stressors and co-varying environmental factors. Yet, incorporating data from other biological groups, such as microbial communities, potentially reveals which environmental factors are underpinning insect community composition. In the present study we investigated the application of benthic microbial community composition, as determined by phospholipid fatty acid (PLFA) analysis, alongside aquatic insect data in 25 peatland ditches in the province of North Holland, The Netherlands. We applied clustering and principal component analysis to a matrix of 26 PLFAs to group ditches by the microbial community. Generalized linear models were used to examine correlations between microbial PLFAs, insects, vegetation (emergent and submerged) and abiotic factors. The ratio of heterotrophic (e.g. sulphate reducing bacteria) to autotrophic (e.g. algae and cyanobacteria) derived PLFAs could be estimated as the ratio between saturated and branched to monounsaturated and polyunsaturated fatty acids (SB/MP). SB/MP was correlated with insect community composition, differences in water chemistry (in particular bicarbonate, sulphate and nutrients) and vegetation cover in the ditches. Moreover, ditches distinguished by their microbial communities differed in the number of insects they supported with differences most pronounced for Odonata, Trichoptera and Chironomus larvae. This study demonstrates that integrating microbial and aquatic insect community data provides insight into key environmental drivers in modified aquatic ecosystems and may facilitate the development of remediation strategies for degraded wetlands. [ABSTRACT FROM AUTHOR]

The extensive network of waters in the lower part of the Dutch delta is loaded with nutrients and accordingly a uniform ecological classification 'moderate' has been derived. The present study sets out to typify the diatom communities in this apparently homogenous environment via self-organizing maps of diatom species composition. Clusters of diatom communities were characterized through the representation of ecological guilds (high and low profile, motile and planktonic) and via a RDA analysis based on either species, genus or ecological guilds together with environmental drivers. Five clusters of diatom communities were identified despite the prominence of omnipresent species. The clusters had different profiles of ecological guilds and were associated with water transparency and sediment type (peat/clay) in addition to the well-established environmental drivers related to eutrophication, but with distinct roles for nitrogen and phosphate concentration. The clusters were interpreted as functional types of community, e.g. communities with a substantial share of planktonic diatom species were found in peat ditches with turbid water. The high consistency found between diatom community classification using species, genus or guilds may allow for a simplified water quality assessment while retaining valuable ecological information. The typology, based on species, genus and ecological guilds underpins the robust use of diatoms as water quality indicators in nutrient rich lentic waters and supports steps to improve ecological conditions. [ABSTRACT FROM AUTHOR]

This study describes in vivo cell turnover (the balance between cell proliferation and cell loss) in eight marine sponge species from tropical coral reef, mangrove and temperate Mediterranean reef ecosystems. Cell proliferation was determined through the incorporation of 5-bromo-2′-deoxyuridine (BrdU) and measuring the percentage of BrdU-positive cells after 6 h of continuous labeling (10 h for Chondrosia reniformis). Apoptosis was identified using an antibody against active caspase-3. Cell loss through shedding was studied quantitatively by collecting and weighing sponge-expelled detritus and qualitatively by light microscopy of sponge tissue and detritus. All species investigated displayed substantial cell proliferation, predominantly in the choanoderm, but also in the mesohyl. The majority of coral reef species (five) showed between 16.1±15.9% and 19.0±2.0% choanocyte proliferation (mean±SD) after 6 h and the Mediterranean species, C. reniformis, showed 16.6±3.2% after 10 h BrdU-labeling. Monanchora arbuscula showed lower choanocyte proliferation (8.1±3.7%), whereas the mangrove species Mycale microsigmatosa showed relatively higher levels of choanocyte proliferation (70.5±6.6%). Choanocyte proliferation in Haliclona vansoesti was variable (2.8–73.1%). Apoptosis was negligible and not the primary mechanism of cell loss involved in cell turnover. All species investigated produced significant amounts of detritus (2.5–18% detritus bodyweight−1·d−1) and cell shedding was observed in seven out of eight species. The amount of shed cells observed in histological sections may be related to differences in residence time of detritus within canals. Detritus production could not be directly linked to cell shedding due to the degraded nature of expelled cellular debris. We have demonstrated that under steady-state conditions, cell turnover through cell proliferation and cell shedding are common processes to maintain tissue homeostasis in a variety of sponge species from different ecosystems. Cell turnover is hypothesized to be the main underlying mechanism producing sponge-derived detritus, a major trophic resource transferred through sponges in benthic ecosystems, such as coral reefs. [ABSTRACT FROM AUTHOR]

The distance-decay relationship has been claimed to be a predictor for biological diversity because it unites several ecological phenomena such as dispersal ability and environmental structure. The effect of long-term disturbances on distance decay, however, has been widely overlooked, especially for microorganisms., We examine the effect of eutrophication on the distance-decay relationship in communities of attached diatoms in three peatland areas: mesotrophic, eutrophic and hypertrophic. The study follows a spatially explicit sampling scheme, collecting evenly spaced samples along 6-km sampling tracks., The three areas shared 24% of the total number of species, but the different nutrient levels in the three areas are reflected by the prominence of low profile and planktonic diatom species., Our study demonstrates that eutrophication can affect distance-decay relationships by decreasing turnover rates in microorganisms. Diatom communities are shown to be constrained by both environmental and spatial features, whose relative importance depends on the degree of eutrophication. Under eutrophic conditions, species are filtered from the regional species pool and community structure responds strongly to environmental factors (water chemistry variables and depth), while in mesotrophic environments, purely spatial processes play a prominent role in structuring diatom communities. These findings reveal that homogenisation of communities triggered by environmental disturbance is an ecological phenomenon of importance in the microbial world. [ABSTRACT FROM AUTHOR]

Agricultural peatlands and their associated drainage systems are often highly managed and exposed to anthropogenic pressures, such as eutrophication and stable water tables, maintained via drainage during periods of high rainfall and inlet of, alkaline-rich, waters during dry periods. These pressures promote peat degradation, resulting in the accumulation of fine-degraded peat particles that dramatically alter aquatic habitats by smothering surfaces and decreasing water quality. Consequential effects on benthic communities are expected but have not been investigated so far., We hypothesised that peat degradation can lead to the decline in submerged macrophytes, which are of critical importance to sustaining biodiversity of benthic invertebrate communities. To investigate this, we analysed decadal (1985-2007) changes in benthic species richness in 29 peat ditches in the Netherlands and, to determine patterns of macroinvertebrate habitat occupancy, carried out a complementary field experiment with submerged artificial macrophytes, natural sediments and emergent bank vegetation., Results from long-term monitoring indicate that chemical conditions in agricultural peat ditches have improved slightly over the last decades; however, there has been a simultaneous decline in benthic invertebrate species richness and densities corresponding to a decline in the numbers of submerged macrophytes. The apparent dependence of macroinvertebrates on macrophytes was reinforced by our field experiment which revealed that invertebrate density was highest in submerged artificial plants, while invertebrate species richness was highest in natural emergent vegetation. Conversely, degraded peat sediments supported extremely few invertebrates., Our results clearly illustrate the strong influence of submerged macrophyte loss on macroinvertebrate assemblages in peatland waters. Furthermore, this suggests that improvements in water quality alone will not benefit invertebrates in the absence of suitable vegetative habitats. [ABSTRACT FROM AUTHOR]

Highlights: [•] We monitored suspended particles characteristics in a surface flow CW. [•] CW residence did not cause removal of the net suspended particles concentrations. [•] We did observed removal of large dead organic particles and faecal indicators. [•] Simultaneously addition of inorganic particles and bacteria occurred. [•] CW residence resulted in the transition from an anthropological to a more natural particles assembly. [ABSTRACT FROM AUTHOR]

The article discusses research on partial degradation of organic matter from mangrove that are facilitating dissolved organic matter (DOM) assimilation in mangrove associated sponges. It references a study by Ellard R. Hunting et al. that tested the tannase activity and the ability for degrading mangrove-derived DOM in sponge species collected from reefs in Curacao. Results showed bacteria in mangrove roots capable of degrading mangrove-derived DOM and presence of recalcitrant organic compounds that can ecologically separate mangroves and reef sponges.

Ultrashort measurement-time resolution is traditionally obtained in pump–probe experiments, for which two ultrashort light pulses are required; the time resolution is then determined by the pulse duration. But although pulses of subfemtosecond duration are available, so far the energy of these pulses is too low to fully implement the traditional pump–probe technique. Here, we demonstrate ‘attosecond angular streaking’, an alternative approach to achieving attosecond time resolution. The method uses the rotating electric-field vector of an intense circularly polarized pulse to deflect photo-ionized electrons in the radial spatial direction; the instant of ionization is then mapped to the final angle of the momentum vector in the polarization plane. We resolved subcycle dynamics in tunnelling ionization by the streaking field alone and demonstrate a temporal localization accuracy of 24 as r.m.s. and an estimated resolution of ≈200 as. The demonstrated accuracy should enable the study of one of the fundamental aspects of quantum physics: the process of tunnelling of an electron through an energetically forbidden region. [ABSTRACT FROM AUTHOR]

Several variables determine the impact of a pesticide on aquatic invertebrates. In this study, aquatic insects were subjected to the common insecticide diazinon; we analyzed the variables taxon, developmental stage, and exposure time. Effects of diazinon on the caddis fly Hydropsyche angustipennis and the midge Chironomus riparius were determined in the laboratory during different exposure times (48 and 96 h) using mortality, activity, and growth as end points. Last instars of both species displayed a clear behavioral response at concentrations much lower than those affecting survival. Doubling the exposure time from 2 to 4 d decreased survival of midges and caddis flies by a factor 1.4 to 8.4. The 96-h 50% lethal concentrations were: 1.3 mug/L (first instar of the caddis fly), 29 mug/L (fifth instar of the caddis fly), 23 mug/L (first instar of the midge) and 167 mug/L (fourth instar of the midge). Within the spectrum of tested insects (nine species for which 48-h 50% lethal concentrations have been reported in the literature), H. angustipennis is the second most sensitive, and C. riparius the most tolerant species. However, the ranking of species strongly depends on the developmental stage; differences between species are often smaller than differences between instars of one species. Thelarge difference in sensitivities between young and old larvae implythat the impact of a pesticide strongly depends on the season of occurrence. Runoff from pesticide applications on crops is more likely to occur in spring and summer and may have a relatively greater impacton insect communities since young larvae prevail in these seasons. In addition, recovery of typical riverine insects such as H. angustipennis from incidental exposure will be slow, considering their relatively long life cycle. [ABSTRACT FROM AUTHOR]

• Lowland stream sediment food and habitat characteristics were land use specific. • Macroinvertebrate community composition was also land use specific. • EPT richness was positively related to the presence of woody debris. • Shannon-Wiener diversity was well explained by fatty acids origin. • Oligochaeta and Chironomus sp. abundances were explained by a low sediment C/N ratio. The input of land use specific organic matter into lowland streams may impact sediment characteristics in terms of food resources and habitat structure, resulting in differences in macroinvertebrate community composition. Therefore, we investigated to what extent land use specific sediment food and habitat characteristics structure macroinvertebrate communities. To this purpose linear multiple regression models were constructed, in which macroinvertebrate biotic indices were considered as response variables and sediment characteristics as predictor variables, analysed in 20 stream stretches running through five different land use types. Sediment characteristics and macroinvertebrate community composition were land use specific. The carbon/nitrogen (C/N) ratio, woody debris substrate cover and the origin of fatty acids influenced macroinvertebrate community composition. Shannon-Wiener diversity was better explained by fatty acids origin, such as in grassland streams, where a higher relative content of plant derived fatty acids related to a higher macroinvertebrate diversity. In cropland and wastewater treatment plant (WWTP) streams with a low C/N ratio and dominated by microbial derived fatty acids, higher abundances of Oligochaeta and Chironomus sp. were observed. Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness was positively related to woody debris substrate cover, which only occurred in forest streams. Hence, macroinvertebrate community composition was influenced by the origin of the organic material, being either allochthonous or autochthonous and when autochthonous being either autotrophic or heterotrophic. It is therefore concluded that sediment food and habitat characteristics are key ecological filters. [ABSTRACT FROM AUTHOR]