Biotests für ein effektbasiertes Monitoring: Schadstoffe - Ermittlung von Belastungspfaden

Die Belastung von Oberflächengewässern kann mit unterschiedlichen Methoden erfasst werden. Bioteste ergänzen die Ergebnisse der chemischen Analyse. Mit dem effektbasierten Monitoring lassen sich Risikopotentiale erfassen. Es sind Rückschlüsse auf die Art der Belastung möglich. Der Bericht enthält erste Ergebnisse für ausgewählte sächsische Fließgewässer. Redaktionsschluss: 29.07.201

Mixed messages from benthic microbial communities exposed to nanoparticulate and ionic silver: 3D structure picks up nano-specific effects, while EPS and traditional endpoints indicate a concentration-dependent impact of silver ions

Silver nanoparticles (AgNP) are currently defined as emerging pollutants in surface water ecosystems. Whether the toxic effects of AgNP towards freshwater organisms are fully explainable by the release of ionic silver (Ag+) has not been conclusively elucidated. Long-term effects to benthic microbial communities (periphyton) that provide essential functions in stream ecosystems are unknown. The effects of exposure of periphyton to 2 and 20 μg/L Ag+ (AgNO3) and AgNP (polyvinylpyrrolidone stabilised) were investigated in artificial indoor streams. The extracellular polymeric substances (EPS) and 3D biofilm structure, biomass, algae species, Ag concentrations in the water phase and bioassociated Ag were analysed. A strong decrease in total Ag was observed within 4 days. Bioassociated Ag was proportional to dissolved Ag indicating a rate limitation by diffusion across the diffusive boundary layer. Two micrograms per liter of AgNO3 or AgNP did not induce significant effects despite detectable bioassociation of Ag. The 20-μg/L AgNO3 affected green algae and diatom communities, biomass and the ratio of polysaccharides to proteins in EPS. The 20-μg/L AgNO3 and AgNP decreased biofilm volume to about 50 %, while the decrease of biomass was lower in 20 μg/L AgNP samples than the 20-μg/L AgNO3 indicating a compaction of the NP-exposed biofilms. Roughness coefficients were lower in 20 μg/L AgNP-treated samples. The more traditional endpoints (biomass and diversity) indicated silver ion concentration-dependent effects, while the newly introduced parameters (3D structure and EPS) indicated both silver ion concentration-dependent effects and effects related to the silver species applied

Isolation, purification, and characterization of new Daphnia-toxic compound from axenic Microcystis flos-aquae strain PCC7806

A new compound, that is toxic to Daphnia, called the Daphnia-toxic compound (DTC), was isolated and purified from water extracts of Microcystis PCC7806. An established Daphnia-bioassay was used as a detection system for the DTC in purified actions. Temperature and pH stability were used to separate DTC from unstable compounds by changing the pH while the temperature was kept at 90 degrees C. This was followed oy ultracentrifugation at 100,000 g. A molecular cutoff filtration technique was used to separate compounds with a molecular weight > 100,000 Da and to reduce the volume of the fraction that was > 500 Da. Evaporation in a vacuum led to a fraction that had a suitable volume for further characterization procedures. DTC was resistant to degradation by two bacteria that were isolated from a laboratory culture. DTC was not inactivated by incubation with protease K or pronase E. A strong anion-exchange resin at the stationary phase of the FPLC equipment was used to purify and concentrate the DTC. The molecular weight determined by gel filtration was between 1.0 and 3.1 kDa, A UV spectrum from this purified fraction exhibited absorption maxima at 220, 260, and 360 nm. The ecological and analytical relevance of the DTC is compared with microcystin

Toxicity to Daphnia of a compound extracted from laboratory and natural Microcystis spp., and the role of microcystins

1. The microcystin content of a variety of Microcystis spp., from both laboratory strains and natural blooms, was analysed by HPLC. The microcystin content of laboratory strains ranged from 1.6 to 4.3 mug mg-1 dry weight. Yearly and seasonal variation was detected in an analysis of bloom material collected from Bautzen Reservoir over a 3-year period. The microcystin concentration in bloom material ranged from undetectable to 1.16 mug ml-1 dry weight. 2. Toxicity of laboratory and natural Microcystis to Daphnia pulicaria was determined using an established LC50 technique. Partially purified water extracts from different Microcystis samples exhibited a wide range of toxicity. The highest activity was found in natural Microcystis samples, with an LC50 of 36 mug ml-1 dry weight of Microcystis, whereas one strain did not appear toxic at 1600 mug ml-1. 3. No correlation was found between the concentrations of microcystins of different laboratory and natural Microcystis strains and the toxicity of extracts to Daphnia pulicaria from the same strains. Therefore, we discriminated between hepatotoxic microcystins and the compound(s) that is toxic to Daphnia, here termed DTC (Daphnia-toxic compound), which is independent of microcystins

Direct and indirect effects of pesticides on a benthic grazer during its life cycle

Abstract Background Macroinvertebrates in aquatic ecosystems are repeatedly exposed to pesticides during their life cycle. Effects of consecutive exposure during different life stages and possible synergistic effects are not addressed in the standardized hazard assessment. The present study investigated two environmentally relevant exposure scenarios in batch (microcosm) and artificial indoor stream (mesocosm) experiments using the larvae of the mayfly Rhithrogena semicolorata (grazer) and natural aufwuchs. Grazers were analysed regarding growth, physiological condition, and drift behaviour, while the aufwuchs was analysed in terms of biomass using the particulate organic carbon as well as the chlorophyll a content. The aim was to reveal direct and indirect effects of an herbicide exposure during autumn on juvenile grazers and an insecticide exposure during spring on semi-juvenile grazers. Results Direct and indirect effects were found in both exposure scenarios at environmentally relevant concentrations. In the herbicide exposure scenario with terbutryn, clear direct effects on the aufwuchs community with a LOEC of 0.38 µg L−1 were found. Effect levels of grazers due to indirect effects were equal, with the overnight drift being the most sensitive grazer endpoint. In the insecticide exposure scenario, clear lethal and sub lethal effects of lambda-cyhalothrin were evident. Derived LC50 values for the artificial indoor stream and batch experiment were 2.42 µg g−1 OC (69 days) and 1.2 µg g−1 OC (28 days), respectively. Sub lethal effects in terms of increased drift as well-reduced growth and triglyceride levels were found at concentrations of 1.4 and 0.09 µg g−1 OC (LOECs). These results were confirmed by the batch experiment, which revealed effect values in the similar range. Finally, a clear indirect effect of the insecticide on the aufwuchs was evident in the batch experiment with an LOEC at 0.9 µg g−1 OC. Conclusion Toxicity Exposure Ratios calculated with the derived effect values indicate a risk for the investigated grazer by both pesticides. Moreover, observed indirect effects during the herbicide exposure seem to be able to affect the grazers during a second exposure with an insecticide, due to reduced physiological conditions. We suggest further research with time-shifted exposure scenarios to gain a better understanding of the complex interactions of pesticides with the life cycle and the food webs of macroinvertebrates

Biotests für ein effektbasiertes Monitoring: Schadstoffe - Ermittlung von Belastungspfaden

Die Belastung von Oberflächengewässern kann mit unterschiedlichen Methoden erfasst werden. Bioteste ergänzen die Ergebnisse der chemischen Analyse. Mit dem effektbasierten Monitoring lassen sich Risikopotentiale erfassen. Es sind Rückschlüsse auf die Art der Belastung möglich. Der Bericht enthält erste Ergebnisse für ausgewählte sächsische Fließgewässer. Redaktionsschluss: 29.07.201

Biotests für ein effektbasiertes Monitoring: Schadstoffe - Ermittlung von Belastungspfaden

Die Belastung von Oberflächengewässern kann mit unterschiedlichen Methoden erfasst werden. Bioteste ergänzen die Ergebnisse der chemischen Analyse. Mit dem effektbasierten Monitoring lassen sich Risikopotentiale erfassen. Es sind Rückschlüsse auf die Art der Belastung möglich. Der Bericht enthält erste Ergebnisse für ausgewählte sächsische Fließgewässer. Redaktionsschluss: 29.07.201