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Found 891 results.

Effect of temperature on growth, survival and respiratory rate of larval Allis shad Alosa alosa

An ecotoxicological view on neurotoxicity assessment

The numbers of potential neurotoxicants in the environment are raising and pose a great risk for humans and the environment. Currently neurotoxicity assessment is mostly performed to predict and prevent harm to human populations. Despite all the efforts invested in the last years in developing novel in vitro or in silico test systems, in vivo tests with rodents are still the only accepted test for neurotoxicity risk assessment in Europe. Despite an increasing number of reports of species showing altered behaviour, neurotoxicity assessment for species in the environment is not required and therefore mostly not performed. Considering the increasing numbers of environmental contaminants with potential neurotoxic potential, eco-neurotoxicity should be also considered in risk assessment. In order to do so novel test systems are needed that can cope with species differences within ecosystems. In the field, online-biomonitoring systems using behavioural information could be used to detect neurotoxic effects and effect-directed analyses could be applied to identify the neurotoxicants causing the effect. Additionally, toxic pressure calculations in combination with mixture modelling could use environmental chemical monitoring data to predict adverse effects and prioritize pollutants for laboratory testing. Cheminformatics based on computational toxicological data from in vitro and in vivo studies could help to identify potential neurotoxicants. An array of in vitro assays covering different modes of action could be applied to screen compounds for neurotoxicity. The selection of in vitro assays could be guided by AOPs relevant for eco-neurotoxicity. In order to be able to perform risk assessment for eco-neurotoxicity, methods need to focus on the most sensitive species in an ecosystem. A test battery using species from different trophic levels might be the best approach. To implement eco-neurotoxicity assessment into European risk assessment, cheminformatics and in vitro screening tests could be used as first approach to identify eco-neurotoxic pollutants. In a second step, a small species test battery could be applied to assess the risks of ecosystems. Quelle: Verlagsinformation

Culture experiments on the environmental controls of trace metal ratios (Mg/Ca, B/Ca, U/Ca) recorded in calcareous tests of bipolar deep-sea benthic foraminifera

Das Projekt "Culture experiments on the environmental controls of trace metal ratios (Mg/Ca, B/Ca, U/Ca) recorded in calcareous tests of bipolar deep-sea benthic foraminifera" wird vom Umweltbundesamt gefördert und von Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung durchgeführt. The Polar eans are our most important climate amplifiers: First, the production of polar deep waters drives the Global Thermohaline Conveyer Belt, and thus, climate. Second, the Antarctic deep water during glacial time was, disputably still is, the largest marine sink of atmospheric CO2. Employment of effective and fossilisable proxies on changes in the physical and geochemical properties is essential to assess glacial-interglacial variabilities, modern and future changes in bipolar deep-waters. In this respect, analyses on trace metal (Mg/Ca, U/Ca, B/Ca) ratios recorded in tests of foraminifers to estimate calcification temperatures, alkalinity, carbonate ion saturation, and pH are common methods. However, for the Arctic and Southern Ocean deep-sea benthic foraminifera calibration curves constrained by either core-top samples or culture experiments are lacking. Newly developed high-pressure aquaria have recently facilitated the first efficient cultivation (producing offspring) of our most trusted palaeodeep-water recorders Fontbotia wuellerstorfi and Uvigerina peregrina. In different experimental set-ups the same facilities will be used to cultivate these foraminifera and associated species at different temperatures and in waters with different carbonate chemistries to establish the first species-specific trace metal calibration curves for both Polar Oceans. Core top analyses on more than 150 core sites from both oceans will verify the experimental results.

Sub project: Climate induced changes in phenology of lake plankton communities: Implications for the match / mismatch of species interactions

Das Projekt "Sub project: Climate induced changes in phenology of lake plankton communities: Implications for the match / mismatch of species interactions" wird vom Umweltbundesamt gefördert und von Forschungsverbund Berlin, Leibniz-Institut für Gewässerökologie und Binnenfischerei durchgeführt. Long term studies suggest that seasonal succession in aquatic ecosystems is currently advancing in temperate latitudes. Those changes are likely to generate complex, and possibly time lagged responses leading to a decoupling (mismatch) of so far tightly coupled (matched) processes. Previous studies have basically focussed on individual species' responses to warming, while neglecting inter-specific interactions. Within AQUASHIFT we aim to identify past phase shifts and time-lagged responses in phyto- and zooplankton communities, and subsequent changes in species interaction induced by observed and projected climate warming. Our methodological approach is focussed on statistical data exploration, time series analysis, and modelling, based upon long-term records (24 years) of plankton, physical and chemical data from shallow, polymictic, eutrophic Müggelsee (Berlin). We anticipate to separate direct temperature driven responses from indirect responses through changes in thermal regime and species interaction. A stochastic and/or deterministic model will be created to describe the linkage between winter and spring meteorological conditions and vernal phytoplankton development in Müggelsee. Model development builds on previous statistical analysis and will be complemented by stochastic terms resulting from the parallel time series analysis. The model will be coupled to an existing lake physics model. This offline-coupled model system will be used to project changes in the timing and intensity of the phytoplankton spring blooms under a range of climate change scenarios.

Field and laboratory studies of aerosol formation from halogenated precursor gases

Das Projekt "Field and laboratory studies of aerosol formation from halogenated precursor gases" wird vom Umweltbundesamt gefördert und von Technische Universität Berlin, Institut für Technischen Umweltschutz durchgeführt. This project was part of the HaloProc research unit on natural halogenation processes, and explored the impact of reactive halogen species on aerosol formation in field and laboratory experiments. Field studies were focused on the Lake King salt lake area in Western Australia. New particle formation events were frequently observed and characterized by measuring the temporal evolution of the submicron aerosol size distributions, and collecting aerosol samples for subsequent chemical analysis. 9 out of 11 measurement days in 2013 showed secondary aerosol formation with particle growth rates from 2.9 to 25.4 nm h^-1. Raman spectroscopy and ultrahigh resolution mass spectrometry revealed a contribution of organohalogen compounds (mostly organochlorine) to the secondary organic aerosol, however, organosulfate and organonitrate formation seemed to play a larger role in the studied environment. Nevertheless, a new experimental approach that made use of a mobile Teflon chamber set up above the salt crust and the organic-rich mud layer of various salt lakes directly linked new particle formation to the hypersaline environment of Western Australia. For more detailed process studies, these field results provided realistic scenarios and constraints for simulation experiments in the laboratory. Salt lake conditions were successfully simulated in aerosol chamber experiments and showed secondary aerosol formation in the presence of light and organic precursor compounds. The particle formation dynamics and the chemical speciation of aerosol samples, which were collected from the chamber experiments and analyzed by Raman spectroscopy and mass spectrometry, indicated a coupling of aqueous phase chemistry and secondary aerosol formation. In particular, the Fe(II) concentrations of the simulated salt lakes were a key control for the intensity of new particle formation. In saline environments with low pH values and high solar radiation, Fe(II) might be converted to Fe(III) in the presence of organic matter in a Fenton-like reaction, which can act as a major source for highly reactive OH radicals in the aqueous phase. On the one hand, this expands the potential oxidation pathways for organic compounds, which led to a larger chemical diversity. On the other hand, Fe(II)-controlled aqueous phase chemistry competes with secondary aerosol formation in the gas phase, which led to reduced particle formation in our experiments. While it is premature to fully incorporate these findings in chemistry box models, additional laboratory studies provided experimental data that will guide the development of model parameterizations, e.g., for the organic aerosol yield from the oxidation of organic compounds by chlorine and bromine, or for reactive bromine loss due to uptake in secondary organic aerosol. In conclusion, this project bridged gaps between field studies of halogen-influenced new particle formation in the real world and laboratory experiments within the HaloProc research u

Glufosinat: Metabolismus in transgenen und nicht-transgenen Pflanzengeweben sowie Schicksal im Boden

Das Projekt "Glufosinat: Metabolismus in transgenen und nicht-transgenen Pflanzengeweben sowie Schicksal im Boden" wird vom Umweltbundesamt gefördert und von RWTH Aachen University, Institut für Umweltforschung, Biologie V, Lehrstuhl für Umweltbiologie und -chemodynamik durchgeführt. Glufosinat (oder Phosphinotricin) ist ein vergleichsweise modernes Herbizid, das seit etwa 25 Jahren in Gebrauch ist. Bei der Verbindung handelt es sich um eine Aminosäure; üblicherweise bezeichnet man das DL-Racemat als Glufosinat, das L-Enantiomer als Phosphinothricin. Die Verbindung ist Teilstruktur eines von den Pilzen Streptomyces viridochromogenes und Streptomyces hygroscopicus produzierten natürlichen Antibiotikums (Tripeptid: L-Alanin-L-Alanin-L-Phosphinothricin). Neben seiner antibakteriellen Wirkung zeigt Glufosinat eine nicht-selektive herbizide Wirkung. Der antibakterielle und herbizide Effekt geht nur vom L-Enantiomer aus; das D-Enantiomer ist inaktiv. Sowohl Glufosinat (Racemat) als auch das Tripeptid (Bialaphos oder Bilanaphos; mit L-Enantiomer) werden als Herbizide vermarktet. Die herbizide Wirkung von Phosphinothricin beruht auf einer Inhibition der Glutaminsynthetase. Glufosinat weist günstige ökotoxikologische Eigenschaften auf, z.B. bezüglich Versickerung, Abbau sowie Toxizität gegenüber Tier und Mensch. Auf Grund dieser Eigenschaften ist Glufosinat ein geeigneter Kandidat zur Herstellung gentechnisch modifizierter Herbizid-resistenter Pflanzen, um Glufosinat auch selektiv - im Nachauflauf - einsetzen zu können. Dazu wurden verschiedene Spezies, wie z.B. die Zuckerrübe, mit dem bar-Gen aus Streptomyces hygroscopicus transformiert. Das bar-Gen codiert für eine Phosphinothricin-N-acetyltransferase, die Phosphinothricin zum nicht herbizid-wirksamen, stabilen N-Acetylderivat umsetzt. Bei entsprechend hoher Expression des bar-Gens resultiert eine Glufosinat-resistente Pflanze. Ein Ziel unseres Forschungsvorhabens war es, den Metabolismus von Glufosinat und der einzelnen Enantiomere (L- und D-Phyosphinothricin) in transgenen und nicht transgenen Pflanzenzellkulturen zu untersuchen. Die transgenen Kulturen, die von der Zuckerrübe (Beta vulgaris) stammten, waren mit dem bar-Gen transformiert, exprimierten demnach die Phosphinothricin-N-acetyltransferase. Sie wurden aus entsprechenden Sprosskulturen initiiert. Daneben wurden nicht-transgene Kulturen von Zuckerrübe, Karotte (Daucus carota), Fingerhut (Digitalis purpurea) und Stechapfel (Datura stramonium) untersucht. In einer zweiten Versuchsserie wurden abgetrennte Sprosse und Blätter von 20 Wildpflanzen auf den Metabolismus von Glufosinat untersucht. Es sollte überprüft werden, ob qualitative und quantitative Unterschiede im Umsatz des Herbizids im Pflanzenreich vorkommen und möglicherweise eine natürliche (teilweise) Resistenz gegenüber Glufosinat existiert. Schließlich wurde das Schicksal des Herbizids im Boden (Abbau, Versickerung) nach Aufbringung des Wirksstoffs in einer handelsüblichen Formulierung auf ein bewachsenes Versuchsfeld im Freiland untersucht.

Steady-State Dilution and Mixing-Controlled Reactions in Three-Dimensional Heterogeneous Porous

Das Projekt "Steady-State Dilution and Mixing-Controlled Reactions in Three-Dimensional Heterogeneous Porous" wird vom Umweltbundesamt gefördert und von Eberhard Karls Universität Tübingen, Zentrum für Angewandte Geowissenschaften (ZAG), Arbeitsgruppe Hydrogeology durchgeführt. Understanding transport of contaminants is fundamental for the management of groundwater re-sources and the implementation of remedial strategies. In particular, mixing processes in saturated porous media play a pivotal role in determining the fate and transport of chemicals released in the subsurface. In fact, many abiotic and biological reactions in contaminated aquifers are limited by the availability of reaction partners. Under steady-state flow and transport conditions, dissolved reactants come into contact only through transverse mixing. In homogeneous porous media, transverse mixing is determined by diffusion and pore-scale dispersion, while in heterogeneous formations these local mixing processes are enhanced. Recent studies investigated the enhancement of transverse mixing due to the presence of heterogeneities in two-dimensional systems. Here, mixing enhancement can solely be attributed to flow focusing within high-permeability inclusions. In the proposed work, we will investigate mixing processes in three dimensions using high-resolution laboratory bench-scale experiments and advanced modeling techniques. The objective of the proposed research is to quantitatively assess how 3-D heterogeneity and anisotropy of hydraulic conductivity affect mixing processes via (i) flow focusing and de-focusing, (ii) increase of the plume surface, (iii) twisting and intertwining of streamlines and (iv) compound-specific diffusive/dispersive properties of the solute species undergoing transport. The results of the experimental and modeling investigation will allow us to identify effective large-scale parameters useful for a correct description of conservative and reactive mixing at field scales allowing to explain discrepancies between field observations, bench-scale experiments and current stochastic theory.

European Union Basin-scale Analysis, Synthesis and Integration (EURO-BASIN)

Das Projekt "European Union Basin-scale Analysis, Synthesis and Integration (EURO-BASIN)" wird vom Umweltbundesamt gefördert und von Danmarks Tekniske Universitet durchgeführt. Objective: EURO-BASIN is designed to advance our understanding on the variability, potential impacts, and feedbacks of global change and anthropogenic forcing on the structure, function and dynamics of the North Atlantic and associated shelf sea ecosystems as well as the key species influencing carbon sequestering and ecosystem functioning. The ultimate goal of the program is to further our capacity to manage these systems in a sustainable manner following the ecosystem approach. Given the scope and the international significance, EURO-BASIN is part of a multidisciplinary international effort linked with similar activities in the US and Canada. EURO-BASIN focuses on a number of key groups characterizing food web types, e.g. diatoms versus microbial loop players; key species copepods of the genus Calanus; pelagic fish, herring (Clupea harengus), mackerel (Scomber scombrus), blue whiting (Micromesistius poutassou) which represent some of the largest fish stocks on the planet; piscivorous pelagic bluefin tuna (Thunnus thynnus) and albacore (Thunnus alalunga) all of which serve to structure the ecosystem and thereby influence the flux of carbon from the euphotic zone via the biological carbon pump. In order to establish relationships between these key players, the project identifies and accesses relevant international databases and develops methods to integrate long term observations. These data will be used to perform retrospective analyses on ecosystem and key species/group dynamics, which are augmented by new data from laboratory experiments, mesocosm studies and field programs. These activities serve to advance modelling and predictive capacities based on an ensemble approach where modelling approaches such as size spectrum; mass balance; coupled NPZD; fisheries; and ?end to end? models and as well as ecosystem indicators are combined to develop understanding of the past, present and future dynamics of North Atlantic and shelf sea ecosystems and their living marine resources.

Frozen Ark Projekt

Das Projekt "Frozen Ark Projekt" wird vom Umweltbundesamt gefördert und von Zoologisches Forschungsmuseum Alexander König - Leibniz-Institut für Biodiversität der Tiere durchgeführt. Over the next thirty years it is predicted that more than 1000 species of mammals, a quarter of the world's total, and a similar proportion of birds, amphibians and marine animals (both invertebrates and vertebrates) will go extinct. Thousands of invertebrate species have already disappeared after the destruction of their habitats. The Frozen Ark Project is a strategy to conserve the genetic resources of the world's endangered species. It is the animal equivalent of the the 'Millennium Seed Bank' created by Kew Gardens to conserve the seeds of the world's plants. The Ark's consortium is a network of research and conservation bodies, including zoos, aquaria, natural history museums and research laboratories around the world. The charity's office and laboratory is based within the University of Nottingham.

The influence of Fe on the distribution and kinetic speciation of Zn, Cd, Co and Ni in the Southern Ocean

Das Projekt "The influence of Fe on the distribution and kinetic speciation of Zn, Cd, Co and Ni in the Southern Ocean" wird vom Umweltbundesamt gefördert und von Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), Forschungsbereich 2: Marine Biogeochemie, Forschungseinheit Chemische Ozeanographie durchgeführt. The role of Fe as the key limiting nutrient for the growth of phytoplankton in the high-nitrate-low-chlorophyll (HNLC) waters of the Southern Ocean is now without question after a series of mesoscale Fe enrichment experiments conducted there over the last few years. Through its influence on phytoplankton physiology changes in Fe have an effect on the biological demand and the distribution of other nutrients. Some of the other key bio-elements have the potential to co-limit the growth of plankton species and in turn influence the phytoplankton community structure and the drawdown of macronutrients. In this context the trace metals Zn, Cd, Co and Ni are needed for the uptake and metabolisation of the macronutrients N, Si, C and P (Figure 1) and have been identified as prime candidates for further studies. While Zn, Co and Ni are important cofactors in various enzymes the role of Cd is ambivalent as it is toxic in relatively low concentrations. However recently it could be shown that a variety of marine diatoms have the ability to use Cd as a substitute for Zn in isoforms of the Carbonic Anhydrase. Furthermore a deepened knowledge regarding the biogeochemistry of Zn and Cd is fundamental to establish their use as paleo-tracers for carbon-export (Zn) and primary productivity (Cd).

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