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  • Rosenfeldt, Ricki  (23)
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  • 1
    Language: English
    In: 2012, Vol.7(11), p.e48956
    Description: The nanoparticle industry is expected to become a trillion dollar business in the near future. Therefore, the unintentional introduction of nanoparticles into the environment is increasingly likely. However, currently applied risk-assessment practices require further adaptation to accommodate the intrinsic nature of engineered nanoparticles. Combining a chronic flow-through exposure system with subsequent acute toxicity tests for the standard test organism Daphnia magna , we found that juvenile offspring of adults that were previously exposed to titanium dioxide nanoparticles exhibit a significantly increased sensitivity to titanium dioxide nanoparticles compared with the offspring of unexposed adults, as displayed by lower 96 h-EC 50 values. This observation is particularly remarkable because adults exhibited no differences among treatments in terms of typically assessed endpoints, such as sensitivity, number of offspring, or energy reserves. Hence, the present study suggests that ecotoxicological research requires further development to include the assessment of the environmental risks of nanoparticles for the next and hence not directly exposed generation, which is currently not included in standard test protocols.
    Keywords: Research Article ; Agriculture ; Biology ; Materials Science ; Biotechnology ; Neuroscience
    E-ISSN: 1932-6203
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  • 2
    Language: English
    In: Environmental Pollution, July 2016, Vol.214, pp.840-846
    Description: Although nanoparticles are increasingly investigated, their impact on the availability of food (i.e., algae) at the bottom of food chains remains unclear. It is, however, assumed that algae, which form heteroagglomerates with nanoparticles, sediment quickly limiting the availability of food for primary consumers such as As a consequence, it may be hypothesized that this scenario – in case of fundamental importance for the nanoparticles impact on primary consumers – induces a similar pattern in the life history strategy of daphnids relative to situations of food depletion. To test this hypothesis, the present study compared the life-history strategy of experiencing different degrees of food limitation as a consequence of variable algal density with daphnids fed with heteroagglomerates composed of algae and titanium dioxide nanoparticles (nTiO ). In contrast to the hypothesis, daphnids’ body length, weight, and reproduction increased when fed with these heteroagglomerates, while the opposite pattern was observed under food limitation scenarios. Moreover, juvenile body mass, and partly length, was affected negatively irrespective of the scenarios. This suggests that daphnids experienced – besides a limitation in the food availability – additional stress when fed with heteroagglomerates composed of algae and nTiO Potential explanations include modifications in the nutritious quality of algae but also an early exposure of juveniles to nTiO . Impact of nTiO -algae heteroagglomerates in 's life history strategy cannot exclusively be explained by food depletion.
    Keywords: Energy Budget ; Heteroagglomerates ; Trophic Interaction ; Physiology ; Food Quality ; Nanomaterials ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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  • 3
    In: Freshwater Biology, December 2016, Vol.61(12), pp.2185-2196
    Description: Ecotoxicology is often criticised for its simplistic approach, which does not normally consider the complexity of field conditions. Simple laboratory experiments can still be useful, however, especially for assessing effects of emerging stressors such as nanoparticles, which exhibit fates, exposure profiles and modes of action substantially different from those of traditional chemicals. Here we argue that it is important to understand the potential effects of environmental conditions (e.g. UV radiation, dissolved organic matter, chemical stressors) on the fate and ecotoxicological potential of nanoparticles by using simple and well‐controlled experiments, while aiming to mimic realistic environmental conditions as closely as possible. The observation that increasingly complex test systems may yield lower effect thresholds for nanoparticles than standardised tests suggests that current approaches require modification. Specifically, research is encouraged on interactions among trophic levels, community composition and ecosystem and evolutionary processes, so that effects observed in complex environmental settings can be explained mechanistically. We highlight recent discoveries in ecotoxicology and ecology that suggest nanoparticle‐induced consequences on evolutionary and ecosystem processes as well as their potential transfer across ecosystem boundaries. These insights may encourage further research on nanoparticle effects informed by ecological theory.
    Keywords: Environmental Variables ; Mechanism Of Toxicity ; Mixture Toxicity ; Nanomaterial ; Trophic Interaction
    ISSN: 0046-5070
    E-ISSN: 1365-2427
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  • 4
    Language: English
    In: Chemosphere, 2011, Vol.85(10), pp.1563-1567
    Description: ► Effects of nTiO and ambient UV-irradiation affect representatives of detrital food webs. ► Accumulation of nTiO at the bottom of the test vessel seems to affect ecotoxicity. ► nTiO and ambient UV-irradiation increases ecotoxicity due to the formation of ROS. Production and use of engineered nanoparticles, such as titanium dioxide nanoparticles (nTiO ), is increasing worldwide, enhancing their probability to enter aquatic environments. However, direct effects of nTiO as well as ecotoxicological consequences due to the interactions of nTiO with environmental factors like ultraviolet (UV) irradiation on representatives of detrital food webs have not been assessed so far. Hence, the present study displayed for the first time adverse sublethal effects of nTiO at concentrations as low as 0.2 mg L on the leaf shredding amphipod both in presence and absence of ambient UV-irradiation following a 7-d exposure. In absence of UV-irradiation, however, the effects seemed to be driven by accumulation of nTiO at the bottom of the test vessels to which the gammarids were potentially exposed. The adverse sublethal and lethal effects on gammarids caused by the combined application of nTiO and ambient UV-irradiation are suggested to be driven by the formation of reactive oxygen species. In conclusion, both the accumulation of nTiO at the bottom of the test vessel and the UV induced formation of reactive oxygen species clearly affected its ecotoxicity, which is recommended for consideration in the environmental risk assessment of nanoparticles.
    Keywords: Nanoparticle ; Titanium Dioxide ; Ultraviolet Irradiation ; Gammarus Fossarum ; Accumulation ; Reactive Oxygen Species ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 5
    Language: English
    In: Science of the Total Environment, 15 September 2014, Vol.493, pp.891-897
    Description: Nanoparticle toxicity depends amongst others on particle characteristics and nanoparticle behavior during their aquatic life cycle. Aquatic organisms may be exposed to nanoparticle agglomerates of varying size, while lager agglomerates after settling rather affect benthic organisms. In this context, the present study systematically examined the role of particle characteristics, i.e. crystalline structure composition (anatase as well as mixture of anatase-rutile), initial particle size (55-, 100-, and 140-nm) and surface area, in the toxicity of titanium dioxide nanoparticles (nTiO ) to the pelagic filter feeder (n = 4) and the benthic amphipod (n = 30). Smaller initial particle sizes (i.e. 55-nm) and anatase based particles showed an approximately 90% lower EC -value compared to its respective counterpart. Most importantly, particle surface normalized EC -values significantly differed for nanoparticles equal to or below 100 nm in size from 140-nm sized particles. Hence, these data suggest that the reactive initial surface area may explain the ecotoxicological potential of different particle size classes only if their size is smaller or around 100 nm. In contrast to , was not affected by nTiO concentrations of up to 5.00 mg/L, irrespective of their characteristics. This indicates fundamental differences in the toxicity of nTiO during its aquatic life cycle mediated by alterations in their characteristics over time.
    Keywords: Daphnia Magna ; Gammarus Fossarum ; Crystallinity ; Toxicity ; Crustacea ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 6
    Language: English
    In: PLoS ONE, 01 January 2015, Vol.10(5), p.e0126021
    Description: During their aquatic life cycle, nanoparticles are subject to environmentally driven surface modifications (e.g. agglomeration or coating) associated with aging. Although the ecotoxicological potential of nanoparticles might be affected by these...
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 7
    Language: English
    In: PLoS ONE, 01 January 2013, Vol.8(11), p.e80960
    Description: Due to their surface characteristics, nanosized titanium dioxide particles (nTiO2) tend to adhere to biological surfaces and we thus hypothesize that they may alter the swimming performance and behavior of motile aquatic organisms. However, no suitable approaches to address these impairments...
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 8
    Language: English
    In: Environmental Pollution, January 2015, Vol.196, pp.276-283
    Description: Interactions with environmental parameters may alter the ecotoxicity of nanoparticles. The present study therefore assessed the (in)direct effects of nanoparticulate titanium dioxide (nano-TiO ) towards , considering nano-TiO 's photocatalytic properties at ambient UV-intensities. Gammarids' habitat selection was investigated using its feeding preference on leaf discs either exposed to or protected from UV-irradiation in presence of nano-TiO as proxy (  = 49). UV-irradiation alone induced a significant preference for UV-protected habitats, which was more pronounced in simultaneous presence of nano-TiO . This behaviour may be mainly explained by the UV-induced formation of reactive oxygen species (ROS) by nano-TiO . Besides their direct toxicity, ROS may have lowered the leaf-quality in UV-exposed areas contributing (approximately 30%) to the observed behavioural pattern. Since the predicted no effect concentration of nano-TiO in combination with UV-irradiation falls below the predicted environmental concentration this study underpins the importance of considering environmental parameters during the risk assessment of nanoparticles. Results revealed for the first time a PNEC of nano-TiO falling below the PEC indicating a substantial risk for aquatic ecosystems already nowadays.
    Keywords: Gammarus ; Uv-Irradiation ; Interaction Effect ; Reactive Oxygen Species ; Behavioural Response ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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  • 9
    In: Journal of Applied Ecology, April 2015, Vol.52(2), pp.310-322
    Description: The application of fungicides is considered an indispensable measure to secure crop production. These substances, however, may unintentionally enter surface waters via run‐off, potentially affecting the microbial community. To assess such risks adequately, authorities recently called for suitable test designs involving relevant aquatic micro‐organisms. We assessed the structural and functional responses of leaf‐associated microbial communities, which play a key role in the breakdown of allochthonous leaf material in streams, towards the inorganic fungicides copper (Cu) and elemental sulphur (S). These substances are of particular interest as they are authorized for both conventional and organic farming in many countries of the world. We used the food choice of the amphipod shredder Gammarus fossarum (indicative for micro‐organism‐mediated leaf palatability) as well as microbial leaf decomposition as functional endpoints. Moreover, the leaf‐associated microbial communities were characterized by means of bacterial density, fungal biomass and community composition facilitating mechanistic understanding of the observed functional effects. While Gammarus preferred Cu‐exposed leaves over unexposed ones, microbial leaf decomposition was reduced by both Cu and S (up to 30%). Furthermore, Cu exposure decreased bacterial densities (up to 60%), stimulated the growth of leaf‐associated fungi (up to 100%) and altered fungal community composition, while S did not affect any of the assessed structural endpoints. Synthesis and applications. We observed both structural and functional changes in leaf‐associated microbial communities at inorganic fungicide concentrations realistic for surface water bodies influenced by conventional and organic farming. Our data hence justify a careful re‐evaluation of the environmental safety of the agricultural use of these compounds. Moreover, inclusion of an experimental design similar to the one used in this study in lower tier environmental risk assessments of antimicrobial compounds may aid to safeguard the integrity of aquatic microbial communities and the functions they provide. We observed both structural and functional changes in leaf‐associated microbial communities at inorganic fungicide concentrations realistic for surface water bodies influenced by conventional and organic farming. Our data hence justify a careful re‐evaluation of the environmental safety of the agricultural use of these compounds. Moreover, inclusion of an experimental design similar to the one used in this study in lower tier environmental risk assessments of antimicrobial compounds may aid to safeguard the integrity of aquatic microbial communities and the functions they provide.
    Keywords: Antagonistic Effect ; Antimicrobial ; Aquatic Hyphomycetes ; Bacteria ; Biofilm ; Ecosystem Functioning ; Environmental Risk Assessment ; Heavy Metal ; Leaf Litter Breakdown ; Mixture Toxicity
    ISSN: 0021-8901
    E-ISSN: 1365-2664
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  • 10
    Language: English
    In: Environmental Pollution, March 2014, Vol.186, pp.136-140
    Description: Although nanoparticle production and application increases continuously, their implications in species interactions, especially in combination with other environmental stressors, are rarely assessed. Therefore, the present study investigated the influence of 2 mg/L titanium dioxide nanoparticles (nTiO ; 〈100 nm) on the interaction between the prey (Ephemeroptera) and the predator (Amphipoda) over 96 h considering UV-irradiation at field relevant levels (approximately 11.4 W/m ) as an additional environmental factor (  = 16). At the same time, gammarid's consumption of an alternative food source, i.e. leaf discs, was assessed. All endpoints covered were not affected by nTiO alone, while the combination of nTiO and UV caused a reduction in gammarid's predation (68%), leaf consumption (60%) and body weight (22%). These effects were most likely triggered by the UV-induced formation of reactive oxygen species by nTiO . The present study, hence, highlights the importance to cover UV-irradiation during the risk assessment of nanoparticles. UV-irradiation influences nanoparticles' ecotoxicity rising concerns about adverse effects in trophic interactions and ecosystem functions.
    Keywords: Gammarid ; Mayfly ; Energy Transfer ; Ecosystem Functioning ; Sunlight ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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