| 1. |
- Hansson, Lars-Anders, et al.
(författare)
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Experimental evidence for a mismatch between insect emergence and waterfowl hatching under increased spring temperatures
- 2014
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Ingår i: Ecosphere. - : Ecological Society of America. - 2150-8925 .- 2150-8925. ; 5:9, s. 120-
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Tidskriftsartikel (refereegranskat)abstract
- By combining a large-scale experimental assessment on timing of insect emergence with longtermmonitoring of waterfowl hatching date, we here show that insect emergence is mainly driven bytemperature, whereas there is only a weak effect of increasing spring temperatures on inter-annualvariability in observations of waterfowl chicks. Hence, a change in timing of the mass-emergence of insectsfrom lakes and wetlands, which is the crucial food source for waterfowl chicks, will likely result in aconsumer/resource mismatch in a future climate change perspective. Specifically, we experimentally showthat a moderate increase in temperature of 38C above ambient, expected to occur within 25–75 years, leadsto a considerably (2 weeks) earlier, and more pronounced, peak in insect emergence (Chironomus sp).Moreover, by utilizing long-term Citizen Science databases, ranging over several decades, we also showthat common waterfowl species are unable to significantly adjust their reproduction to fit futuretemperature increase. Hence, based on our data we predict a future mismatch between insect emergenceand waterfowl species basing their reproduction on temperature. This will have a profound impact onreproductive success and population dynamics of many aquatic birds, as well as on freshwaterbiodiversity.
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| 2. |
- Hansson, Lars-Anders, et al.
(författare)
-
Experimental evidence for a mismatch between insect emergence and waterfowl hatching under increased spring temperatures
- 2014
-
Ingår i: Ecosphere. - : Wiley-Blackwell. - 2150-8925. ; 5:9, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- By combining a large-scale experimental assessment on timing of insect emergence with long-term monitoring of waterfowl hatching date, we here show that insect emergence is mainly driven by temperature, whereas there is only a weak effect of increasing spring temperatures on inter-annual variability in observations of waterfowl chicks. Hence, a change in timing of the mass-emergence of insects from lakes and wetlands, which is the crucial food source for waterfowl chicks, will likely result in a consumer/resource mismatch in a future climate change perspective. Specifically, we experimentally show that a moderate increase in temperature of 3 degrees C above ambient, expected to occur within 25-75 years, leads to a considerably (2 weeks) earlier, and more pronounced, peak in insect emergence (Chironomus sp). Moreover, by utilizing long-term Citizen Science databases, ranging over several decades, we also show that common waterfowl species are unable to significantly adjust their reproduction to fit future temperature increase. Hence, based on our data we predict a future mismatch between insect emergence and waterfowl species basing their reproduction on temperature. This will have a profound impact on reproductive success and population dynamics of many aquatic birds, as well as on freshwater biodiversity.
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| 3. |
- Bianco, Giuseppe, et al.
(författare)
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Plankton 3D tracking: the importance of camera calibration in stereo computer vision systems
- 2013
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Ingår i: Limnology and Oceanography: Methods. - : Wiley. - 1541-5856. ; 11, s. 278-286
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Tidskriftsartikel (refereegranskat)abstract
- Computer vision applications are very useful to study animal movements, but due to their intrinsic complexity they are challenging to design, implement, and use properly. We here describe a calibration procedure for a laboratory stereo vision system for tracking zooplankton in three dimensions (3D). We demonstrate the crucial importance of using a correct calibration for proper interpretation of animal swimming tracks. We also address the effect of the air-water shift phase in the calibration procedure. Actually, not performing a proper calibration caused an average positional error of more than 25 body-lengths in the investigated animal Daphnia magna. Furthermore, we evaluate the different outcomes of using 2D and 3D tracks obtained with a calibrated stereo vision system and show that although 2D tracking might be sufficient in some cases, the method was in our study unable to give information of swimming path geometry and underestimated the speed by 25%. Finally, we discuss consequences for biologically relevant questions when an incorrect methodology is used and strongly recommend that future studies provide detailed descriptions of the framework used for calibration to allow for comparisons between different studies.
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| 4. |
- Book, Frida, 1989, et al.
(författare)
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Ecotoxicity screening of seven different types of commercial silica nanoparticles using cellular and organismic assays : Importance of surface and size
- 2019
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Ingår i: NanoImpact. - : Elsevier BV. - 2452-0748. ; 13, s. 100-111
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Tidskriftsartikel (refereegranskat)abstract
- We show that seven different types of commercial, biocide-free, colloidal silica products with mean particle sizes between 17 and 88 nm with 3 different surface chemistries (Na-stabilized, aluminized and silane-modified) are not toxic to the bacterium Pseudomonas putida, and the algae Raphidocelis subcapitata in the concentration range 5–500 mg/L. They are also not acutely toxic to Daphnia magna at concentrations up to 10,000 mg/L. Six silica particles are toxic to the gill cell line RTgill-W1 from Rainbow trout (Oncorhynchus mykiss), showing a clear concentration-response relationship with EC50 values between 13 and 92 mg/L. Toxicity in the fish cells decreases with increasing hydrodynamic size and is dependent on particle surface area. The average EC50 across the tested particles is 2.1 (±0.3) m2/L. Surface modifications clearly impact toxicity, with silane-modified particles showing no cytotoxicity. The reduced number of free silanol groups on the surface of the silane modified particle, in combination with an increased steric hindrance that prevents contact with the cells is a possible mechanism for the observed lack of toxicity. This is also in line with previous studies on silica nanoparticles in human toxicology. Overall, these findings show a generally low ecotoxicity of silica nanoparticles and indicate that silica particles of different sizes but identical surface chemistry could potentially be grouped into an assessment group under regulation such as REACH.
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| 5. |
- Cedervall, Tommy, et al.
(författare)
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Workshop on Environmental Nanosafety: Biological Interactions of Plastic Nanoparticles
- 2019
-
Ingår i: Journal of Chemical Education. - : American Chemical Society (ACS). - 0021-9584 .- 1938-1328. ; 96:9, s. 1967-1970
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Tidskriftsartikel (refereegranskat)abstract
- The one-hour workshop, containing both a demonstration and hands-on experiments on the topic of nanosafety, is based on current science on a topic of general interest. The workshop aims to provide a deeper knowledge and understanding of nanoparticles. The participants get an introduction to what nanoparticles are, why nanosized materials are interesting, how nanomaterials interact with biological molecules, and potential risks associated with nanoparticles. Furthermore, by participating in the workshop the audience gains insights into how research about nanoparticles is conducted. The participants carry out experiments to demonstrate that daily-used plastic products can be disintegrated into particles in the nanometer size range, which may have important implications for the environment.
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| 6. |
- Ekvall, Mikael, et al.
(författare)
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Diel vertical migration, size distribution and photoprotection in zooplankton as response to UV-A radiation
- 2015
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 60:6, s. 2048-2058
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Tidskriftsartikel (refereegranskat)abstract
- The transparency regulator hypothesis (TRH) proposes that ultraviolet radiation (UVR) is a main driving force behind diel vertical migration (DVM) of zooplankton in clearwater systems. While previous studies have mainly studied DVM in relation to the TRH on a spatial scale across systems we here focus on long-term trends in a single system in order to assess if UVR explains observed patterns in DVM. We show that the strength of DVM in Daphnia is to a large extent explained by UVR and we demonstrate a tipping point at which the UVR intensity drastically affects the strength of DVM in Daphnia. In contrast, the strength of DVM could not be explained by the level of UVR among calanoid copepods. The amount of photoprotective compounds did not differ between zooplankton found at different depths indicating that zooplankton do not change their vertical position in relation to the amount of accumulated photoprotective compounds. In addition, we show that both Daphnia and calanoid copepods display patterns of size structured migration.
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| 7. |
- Ekvall, Mikael
(författare)
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Multiple threat responses in zooplankton - from communities to individuals
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Most organisms on Earth live a life where they are exposed to multiple and variable threats. In order to maximise survival they need to be able to perceive and respond to these threats. Two common threats that crustacean zooplankton are faced with are predation and ultraviolet radiation (UVR). To cope with these threats zooplankton use different strategies such as diel vertical migration and the accumulation of photoprotective compounds. In this thesis I study the threat responses of zooplankton when exposed to predation and UVR. I explore both inter- and intraspecific differences in the response to these threat situations. In addition to field data I also developed a new technique for tracking zooplankton using fluorescent nanoparticles, which I use to track the individual responses of zooplankton. I investigate if accumulation of photoprotective pigmentation may affect the spatial distribution of species in nature and how individual size may affect the migratory behaviour of zooplankton. In addition I also explore how previous exposure to threats affect the behavioural responses and if some of the observed behavioural variance could be explained by consistent individual differences in behaviour. In summary, I show that even closely related species may show large differences in their response to UVR. Intraspecific differences in pigmentation could not be related to the spatial distribution of either Daphnia or calanoid copepods; however, both Daphnia and copepods were found to perform size structured migration. I also demonstrate that previous experiences of a threat can affect how the organism responds. Some evidence for consistent individual differences in the behavioural response of Daphnia to UVR is presented, suggesting that individual based studies could add further to our knowledge about behavioural responses in zooplankton. Given the variability both with respect to inter- and intraspecific differences in UVR response we need to keep these differences in mind when postulating new, more comprehensive theories explaining the behaviour of zooplankton exposed to everyday threats.
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| 8. |
- Ekvall, Mikael, 1977
(författare)
-
Production and Characterisation of Aquaporins and Proton-Translocating Transhydrogenase
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dissertation Abstract Water transport in eukaryotic cells is a highly regulated and fine-tuned process. Water channel protein known as aquaporins (AQPs), constitute the main cellular water transport system, preserving water homeostasis by maintaining specific selectivity-mechanisms. Dysfunctional AQPs induce a wide variety of diseases in humans thereby enhancing the clinical significance of structural and functional knowledge. Macromolecular structural research requires large amounts of pure, stable protein to initiate crystallization trials. To achieve this, genetic engineering and overproduction systems such as the methylotrophic yeast Pichia pastoris (P. pastoris) are employed. The next step, crystallization, involves arrangement of the macromolecule in a repetitive fashion. Once crystals have been obtained, these are exposed by synchrotron radiation (X-rays), producing a diffraction pattern. This reciprocal representation of the arrangement of atoms in the unit cell is converted back to real space by a Fourier transform, which generates a atomic model of the protein. This thesis is based on a comparative study of the production levels of all human AQPs, an production and purification analysis of eukaryotic transhydrogenases, and a structural and functional investigation of the spinach AQP SoPIP2;1 with associated mutants. The human AQPs produced in the study displayed a considerable variety in production yield. Although the production yield seamed to depend on multiple factors, a correlation could be drawn between the extent of protein inserted into the membrane and phylogenetic relationship, providing further insight into eukaryotic membrane protein production. Furthermore, zebrafish transhydrogenase was successfully produced in P. pastoris, but although the production yield was sufficient, further optimisation of purification conditions is required in order to obtain sample suitable for crystallization. Finally, crystal structures and water transport assays of SoPIP2;1 phosphomimicking mutants as well as of SoPIP2;1 in complex with mercury have given novel insights into the mechanism of plant AQP gating.
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| 9. |
- Ekvall, Mikael T., et al.
(författare)
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Adsorption of bio-organic eco-corona molecules reduces the toxic response to metallic nanoparticles in Daphnia magna
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- As the use of engineered nanomaterials increases, so does the risk of them spreading to natural ecosystems. Hitherto, knowledge regarding the toxic properties of nanoparticles (NP's) and their potential interactions with natural bio-organic molecules adsorbed to them, and thereby forming surface coronas, is limited. However, we show here that the toxic effect of NPs of tungsten carbide cobalt (WC-Co) and cobalt (Co) on the crustacean Daphnia magna is postponed in the presence of natural biological degradation products (eco-corona biomolecules). For Daphnia exposed to WC-Co NPs the survival time increased with 20-25% and for Co NPs with 30-47% after mixing the particles with a solution of eco-corona biomolecules before exposure. This suggests that an eco-corona, composed of biomolecules always present in natural ecosystems, reduces the toxic potency of both studied NPs. Further, the eco-coronas did not affect the particle uptake, suggesting that the reduction in toxicity was related to the particle-organism interaction after eco-corona formation. In a broader context, this implies that although the increasing use and production of NPs may constitute a novel, global environmental threat, the acute toxicity and long-term effects of some NPs will, at least under certain conditions, be reduced as they enter natural ecosystems.
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| 10. |
- Ekvall, Mikael T., et al.
(författare)
-
Behavioural responses to co-occurring threats of predation and ultraviolet radiation in Daphnia
- 2020
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 65:9, s. 1509-1517
-
Tidskriftsartikel (refereegranskat)abstract
- Organisms in the wild are faced with multiple threats and a common response is a change in behaviour. To disentangle responses to several threats, we exposed two differently sized species of the freshwater invertebrate Daphnia to solar ultraviolet radiation (UVR) and predation from either moving pelagic or benthic ambush predators. Using an advanced nanotechnology-based method, we tracked the three-dimensional movements of those mm-sized animals at the individual level. Each behavioural trial was performed both under conditions resembling night (no UVR) and day (UVR) and we examined patterns of the depth distribution and swimming speed by Daphnia across three treatments: no predator (control); bottom-dwelling damselfly (Calopteryx sp.); and fish (stickleback, Pungitius pungitius) predators. We also quantified the actual predation rate by the two predators on the two Daphnia species, Daphnia manga and Daphnia pulex. We show that individual Daphnia are able to identify predators with different feeding habitats, rank multiple and simultaneously occurring risks and respond in accordance with the actual threat; complex responses that are generally associated with larger animals. In a broader context, our results highlight and quantify how a cocktail of everyday threats is perceived and handled by invertebrates, which advances our understanding of species distribution in space and time, and thereby of population dynamics and ecosystem function in natural ecosystems.
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| 11. |
- Ekvall, Mikael T., et al.
(författare)
-
Environmental impact of nanoplastics from fragmentized consumer plastics : Final project report
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Misplaced plastics is an ongoing environmental problem. The breakdown of plastics into smaller pieces, microplastics, likely cause additional environmental burdens as they affect animals and plants at the beginning of the food chain. This may be even more true for the smallest of microplastics: the nano plastics as they will behave differently in nature and interact in new ways with organisms and potentially be taken up by the organisms and affect internal organs. The small size of nano plastics and their chemical resemblance with the surrounding environment makes them difficult to find, isolate and study. Most of what is known about nano plastics behavior in nature and their effect on nature derives from studies using commercially available polystyrene nanoparticles. These are probably different in many ways, such as structure, surface chemistry, and size distribution, compared to nano plastics broken down in nature from plastic debris. Despite this, we have used polystyrene nanoparticles to study knowledge gaps. The toxicity to zooplankton Daphnia magna (D. magna) of small positively charged amine-modified polystyrene nanoparticles is not affected by protein-induced aggregation. All tested polystyrene nanoparticles were toxic to D. magna regardless of their toxicity in acute tests. Proteins bound to polystyrene nanoparticles after filtration by D. magna were different on acutely and non-acutely toxic particles which may imply different mechanisms behind the toxicity. In order to study the effect of nano plastics that resemble what can be expected in nature we have mechanically broken down 8 different plastics and rubbers from 14 different consumer products and isolated the nano plastics. Careful characterization shows that the nano plastics are irregular in shape, have a slightly negative surface charge, and often have a strongly oxidized surface compared to the starting material. The nano sized fractions are not toxic to D. magna in the used concentrations. In contrary, for at least two plastics High Density Polyethylene (HDPE) and Polylactic acid (PLA) thoracoplasties increase the lifetime of the D. magna probably because the nano plastics can be utilized by bacteria which in turn serve as additional food for the zooplankton. However, leached additives and/or smaller polymers from HDPE are toxic to D. magna. We have also seen that UV irradiation further degrade polystyrene nanoparticles. The bacterial growth and the UV breakdown may imply that the nano plastics breakdown faster than believed in nature and that they with time may disappear.
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| 12. |
- Ekvall, Mikael T., et al.
(författare)
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Long-term effects of tungsten carbide (WC) nanoparticles in pelagic and benthic aquatic ecosystems
- 2018
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Ingår i: Nanotoxicology. - : Taylor & Francis. - 1743-5390 .- 1743-5404. ; 12:1, s. 79-89
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Tidskriftsartikel (refereegranskat)abstract
- As the production and usage of nanomaterials are increasing so are the concerns related to the release of the material into nature. Tungsten carbide (WC) is widely used for its hard metal properties, although its use, in for instance tyre studs, may result in nano-sized particles ending up in nature. Here, we evaluate the potential long-term exposure effects of WC nanoparticles on a pelagic (Daphnia magna) and a benthic (Asellus aquaticus) organism. No long-term effects were observed in the benthic system with respect to population dynamics or ecosystem services. However, long-term exposure of D. magna resulted in increased time to first reproduction and, if the particles were resuspended, strong effects on survival and reproductive output. Hence, the considerable differences in acute vs. long-term exposure studies revealed here emphasize the need for more long-term studies if we are to understand the effects of nanoparticles in natural systems.
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| 13. |
- Ekvall, Mikael T., et al.
(författare)
-
Nanoplastics formed during the mechanical breakdown of daily-use polystyrene products
- 2019
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 1:3, s. 1055-1061
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Tidskriftsartikel (refereegranskat)abstract
- Large amounts of plastics are released into the environment every day. These released plastics have a clearly documented negative effect on wildlife. Much research attention has been given to large plastic pieces and microplastics. However, if the breakdown of plastics is a continous process, eventually nanoplastics will be produced. Nanoplastics will affect wildlife differently from larger plastic pieces. We have studied the products formed by the mechanical breakdown of two commonly used polystyrene products, takeaway coffee cup lids and expanded polystyrene foam. After breakdown using a food processor, we characterized the breakdown products using seven different methods and found nanosized polystyrene particles with different shapes and negative or nearly neutral surface charges. These results clearly demonstrate that daily-use polystyrene products can break down into nanoparticles. Model polystyrene particles with different sizes and surface modifications have previously been shown to have different negative effects on wildlife. This indicates that breakdown nanoparticles might have the potential to cause cocktail effects in nature.
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| 14. |
- Ekvall, Mikael T., et al.
(författare)
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Nanoplastics released from daily used silicone and latex products during mechanical breakdown
- 2023
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Ingår i: PLoS ONE. - 1932-6203. ; 18:9
-
Tidskriftsartikel (refereegranskat)abstract
- Waste of polymer products, especially plastics, in nature has become a problem that caught the awareness of the general public during the last decade. The macro- and micro polymers in nature will be broken down by naturally occurring events such as mechanical wear and ultra-violet (UV) radiation which will result in the generation of polymeric particles in the nano-size range. We have recently shown that polystyrene and high-density polyethylene macroplastic can be broken down into nano-sized particles by applying mechanical force from an immersion blender. In this article, we show that particles in the nano-size range are released from silicone and latex pacifiers after the same treatment. Additionally, boiling the pacifiers prior to the mechanical breakdown process results in an increased number of particles released from the silicone but not the latex pacifier. Particles from the latex pacifier are acutely toxic to the freshwater filter feeding zooplankter Daphnia magna.
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| 15. |
- Ekvall, Mikael T, et al.
(författare)
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Size fractionation of high-density polyethylene breakdown nanoplastics reveals different toxic response in Daphnia magna
- 2022
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12, s. 3109-3109
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Tidskriftsartikel (refereegranskat)abstract
- Plastic litter is a growing environmental problem. Recently, microplastics and nanoplastics, produced during breakdown processes in nature, have been in focus. Although there is a growing knowledge concerning microplastic, little is still known about the effect of nanoplastics. We have showed that mechanical breakdown of high-density polyethylene (HDPE), followed by filtration through 0.8 µm filters, produces material toxic to the freshwater zooplankton Daphnia magna and affected the reproduction in life-time tests. However, further size fractionation and purification reveals that the nanoplastics fraction is non-toxic at these concentrations, whereas the fraction with smaller sizes, below ~ 3 nm, is toxic. The HDPE nanoplastics are highly oxidized and with an average diameter of 110 nm. We conclude that mechanical breakdown of HDPE may cause environmental problems, but that the fraction of leached additives and short chain HDPE are more problematic than HDPE nanoplastics.
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| 16. |
- Ekvall, Mikael T., et al.
(författare)
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The forgotten tonsils—does the immune active organ absorb nanoplastics?
- 2022
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Ingår i: Frontiers in Nanotechnology. - : Frontiers Media SA. - 2673-3013. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- Nanoplastics are defined as plastic particles broken down to extremely small sizes (1–100 nm) with unknown effects to the human body and immune system. Air and food exposure scenarios involving blood, lungs and intestine are considered in the literature. The fact that plastics also needs to pass the nose, oral cavity, and throat is so far ignored in the literature. The tonsils are immunologically important tissue in the oral cavity in which ingested and inhaled agents are incorporated through crypts with the capacity to capture agents and start early immunologic reactions. We argue that the tonsil is a very important tissue to study in regard to micro and nanoplastic human exposure and immunologic response. Nano-sized particles are known to be able to travel through the natural barriers and have different effects on biology compared to larger particle and the bulk material. It is therefore, although difficult, important to develop experimental methods to detect and identify nanoplastics in the tonsils. In preliminary experiments we have optimized the breakdown of tonsil tissues and tried to retrieve added polystyrene nanoparticles using density-based separation and concentration. The polystyrene was followed by FTIR spectrometry and could be detected in micro- and nano-size, in the tissue breakdown solution but not after density-based separation. When nanoplastics are incorporated in the human body, it is possible that the small plastic pieces can be detected in the tonsil tissue, in the lymph system and it is of importance for future studies to reveal the immunological effects for humans.
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| 17. |
- Ekvall, Mikael, et al.
(författare)
-
Three-dimensional tracking of small aquatic organisms using fluorescent nanoparticles.
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:11
-
Tidskriftsartikel (refereegranskat)abstract
- Tracking techniques are vital for the understanding of the biology and ecology of organisms. While such techniques have provided important information on the movement and migration of large animals, such as mammals and birds, scientific advances in understanding the individual behaviour and interactions of small (mm-scale) organisms have been hampered by constraints, such as the sizes of existing tracking devices, in existing tracking methods. By combining biology, chemistry and physics we here present a method that allows three-dimensional (3D) tracking of individual mm-sized aquatic organisms. The method is based on in-vivo labelling of the organisms with fluorescent nanoparticles, so-called quantum dots, and tracking of the organisms in 3D via the quantum-dot fluorescence using a synchronized multiple camera system. It allows for the efficient and simultaneous study of the behaviour of one as well as multiple individuals in large volumes of observation, thus enabling the study of behavioural interactions at the community scale. The method is non-perturbing - we demonstrate that the labelling is not affecting the behavioural response of the organisms - and is applicable over a wide range of taxa, including cladocerans as well as insects, suggesting that our methodological concept opens up for new research fields on individual behaviour of small animals. Hence, this offers opportunities to focus on important biological, ecological and behavioural questions never before possible to address.
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| 18. |
- Fernández, Carla E., et al.
(författare)
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Local adaptation to UV radiation in zooplankton : a behavioral and physiological approach
- 2020
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Ingår i: Ecosphere. - : Wiley. - 2150-8925. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- Ultraviolet radiation (UVR) is recognized as a driving force for phenotypic divergence. Here, we aim at assessing the ability of zooplankton to induce UVR tolerance and disentangle the relative importance of local adaptations behind the expression of such tolerance. Two populations of Daphnia pulex, derived from environments strongly differing in UVR conditions, were exposed to UVR for 70 d to induce production of photo-protective compounds and changes in behavioral responses. We expected greater tolerance to UVR in individuals from the high-UVR (H-U) environment as well as a refuge demand inversely related to the level of pigmentation. However, the complementarity between physiological and behavioral strategies was only observed on animals from the Low-UVR environment (L-U). L-U animals developed photo-protective compounds and decreased their refuge demand when re-exposed to UVR, that is, tolerated more UVR, compared to their control siblings. Conversely, UVR-exposed individuals from the H-U environment even having developed higher levels of photo-protective compounds increased their refuge demand staying deeper in the water column compared to the control animals, likely expressing an evolutionary memory to seek refuge in deeper waters irrespective of the UVR level. Stronger changes were observed in the H-U population compared to the L-U population; thus, our results suggest that although changes in tolerance after UVR exposure were evident for both populations, the strength of the inductions was more related to local adaptation independently of the rearing environment, showing that UVR tolerance is dependent on the evolutionary history of each population.
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| 19. |
- Frankel, Rebecca, et al.
(författare)
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Controlled protein mediated aggregation of polystyrene nanoplastics does not reduce toxicity towards Daphnia magna
- 2020
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Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry (RSC). - 2051-8153 .- 2051-8161. ; 7:5, s. 1518-1524
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Tidskriftsartikel (refereegranskat)abstract
- Microplastics have recently become a growing environmental issue, whereas the smaller fractions, nanoplastics, have received less attention. Due to their small size, nanoplastics may affect organisms differently and potentially more severely than larger microplastics. In natural environments nanoplastics also interact with organic material and form larger aggregates, which may, potentially, reduce their toxicity as they grow in size. We tested the change in toxicity towards Daphnia magna by controlling the size of the aggregates of positively charged 50 nm polystyrene nanoplastics, which are highly toxic as single particles. We show that although 200 to 500 nm nanoplastics are not toxic, aggregates of 50 nm nanoplastics in the same size range are at least as toxic as the free, 50 nm, nanoplastics. Hence, an increase in size through aggregation, a process likely to occur as nanoparticles enter natural ecosystems, does not reduce toxicity. In a broader context this finding provides a firm basis for societal decision making regarding the potency of nanoparticles as they enter natural ecosystems.
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| 20. |
- Frick, Anna, 1982, et al.
(författare)
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Mercury increases water permeability of a plant aquaporin through a non-cysteine-related mechanism
- 2013
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Ingår i: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 454:pt 3, s. 491-499
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Tidskriftsartikel (refereegranskat)abstract
- Water transport across cellular membranes is mediated by a family of membrane proteins known as AQPs (aquaporins). AQPs were first discovered on the basis of their ability to be inhibited by mercurial compounds, an experiment which has followed the AQP field ever since. Although mercury inhibition is most common, many AQPs are mercury insensitive. In plants, regulation of AQPs is important in order to cope with environmental changes. Plant plasma membrane AQPs are known to be gated by phosphorylation, pH and Ca2+. We have previously solved the structure of the spinach AQP SoPIP2;1 (Spinacia oleracea plasma membrane intrinsic protein 2; 1) in closed and open conformations and proposed a mechanism for how this gating can be achieved. To study the effect of mercury on SoPIP2; 1 we solved the structure of the SoPIP2;1-mercury complex and characterized the water transport ability using proteoliposomes. The structure revealed mercury binding to three out of four cysteine residues. In contrast to what is normally seen for AQPs, mercury increased the water transport rate of SoPIP2; 1, an effect which could not be attributed to any of the cysteine residues. This indicates that other factors might influence the effect of mercury on SoPIP2; 1, one of which could be the properties of the lipid bilayer.
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| 21. |
- Hansson, Lars Anders, et al.
(författare)
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Instantaneous threat escape and differentiated refuge demand among zooplankton taxa
- 2016
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 97:2, s. 279-285
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Tidskriftsartikel (refereegranskat)abstract
- Most animals, including aquatic crustacean zooplankton, perform strong avoidance movements when exposed to a threat, such as ultraviolet radiation (UVR). We here show that the genera Daphnia and Bosmina instantly adjust their vertical position in the water in accordance with the present UVR threat, i.e., seek refuge in deeper waters, whereas other taxa show less response to the threat. Moreover, Daphnia repeatedly respond to UVR pulses, suggesting that they spend more energy on movement than more stationary taxa, for example, during days with fluctuating cloud cover, illustrating nonlethal effects in avoiding UVR threat. Accordingly, we also show that the taxa with the most contrasting behavioral responses differ considerably in photoprotection, suggesting different morphological and behavioral strategies in handling the UVR threat. In a broader context, our studies on individual and taxa specific responses to UVR provide insights into observed spatial and temporal distribution in natural ecosystems.
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| 22. |
- Hedberg, Jonas, 1979-, et al.
(författare)
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Tungsten carbide nanoparticles in simulated surface water with natural organic matter : dissolution, agglomeration, sedimentation and interaction with Daphnia magna
- 2017
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Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry. - 2051-8153 .- 2051-8161. ; 4:4, s. 886-894
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Tidskriftsartikel (refereegranskat)abstract
- Even though anthropogenic nano-sized tungsten carbide nanoparticles (WC NPs) have been found in the environment, there are currently no investigations on their environmental fate. This work studies the interaction between natural organic matter (NOM) and WC NPs, as well as the potential uptake by the aquatic model organism Daphnia magna. We here show that the affinity between WC NPs and humic acid or dihydroxybenzoic acid (DHBA), which are model molecules of NOM, is very low with no observed surface adsorption. The lack of a stabilizing effect of these organic molecules, in combination with a relatively high effective density of WC NP agglomerates in humic acid, resulted in the substantial agglomeration and sedimentation of the WC NPs. A higher stability of the smaller sized WC NP agglomerates (<150 nm) means that this fraction is mobile and can be transported to other settings, suggesting that this particle fraction should be considered in further studies. The dissolution of tungsten from WC NPs was continuous and the relatively slow dissolution rate (on the order of 0.03 mg m-2 h-1) implies that particle transport will not be severely limited from a dissolution perspective. Uptake of tungsten (dissolved tungsten and WC particles) by D. magna was observed although this did not induce any acute toxic effects.
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| 23. |
- Heuschele, Jan, et al.
(författare)
-
Context-dependent individual behavioral consistency in Daphnia
- 2017
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Ingår i: Ecosphere. - : John Wiley & Sons. - 2150-8925 .- 2150-8925. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- The understanding of consistent individual differences in behavior, often termed “personality,” for adapting and coping with threats and novel environmental conditions has advanced considerably during the last decade. However, advancements are almost exclusively associated with higher-order animals, whereas studies focusing on smaller aquatic organisms are still rare. Here, we show individual differences in the swimming behavior of Daphnia magna, a clonal freshwater invertebrate, before, during, and after being exposed to a lethal threat, ultraviolet radiation (UVR). We show consistency in swimming velocity among both mothers and daughters of D. magna in a neutral environment, whereas this pattern breaks down when exposed to UVR. Our study also, for the first time, illustrates how the ontogenetic development in swimming and refuge-seeking behavior of young individuals eventually approaches that of adults. Overall, we show that aquatic invertebrates are far from being identical robots, but instead they show considerable individual differences in behavior that can be attributed to both ontogenetic development and individual consistency. Our study also demonstrates, for the first time, that behavioral consistency and repeatability, that is, something resembling “personality,” is context and state dependent in this zooplankter taxa.
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| 24. |
- Heuschele, Jan, et al.
(författare)
-
On the missing link in ecology : Improving communication between modellers and experimentalists
- 2017
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Ingår i: Oikos. - : Wiley. - 0030-1299. ; 126:8, s. 1071-1077
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Tidskriftsartikel (refereegranskat)abstract
- Collaboration between modellers and experimentalists is essential in ecological research, however, different obstacles linking both camps often hinder scientific progress. In this commentary, we discuss several issues of the current state of affairs in this research loop. Backed by an online survey amongst fellow ecologists, modellers and experimentalists alike, we identify two major areas that need to be mended. Firstly, differences in language and jargon lead to a lack of exchange of ideas and to unrealistic mutual expectations. And secondly, constraint data sharing, accessibility and quality limit the usage of empirical data and thereby the impact of ecological studies. We discuss ways to advance collaboration; how to improve communication and the design of experiments; and the sharing of data. We hope to start a much-needed conversation between modellers and experimentalists, to further future research collaboration and to increase the impact of single ecological studies alike.
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| 25. |
- Hua, Jing, et al.
(författare)
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Environmental risks of breakdown nanoplastics from synthetic football fields
- 2024
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Ingår i: Environmental Pollution. - 0269-7491. ; 347
-
Tidskriftsartikel (refereegranskat)abstract
- The widespread use of synthetic turf in sports has raised health concerns due to potential risks from nanoplastic inhalation or ingestion. Our research focused on detecting nanoplastics in drainage water from a synthetic football field and evaluating the toxicity of these materials after mechanical fragmentation. We collected and analysed drainage water samples for polymer content and subjected high-density polyethylene (HDPE) straws and ethylene propylene diene monomer (EPDM) granules used on synthetic football fields, to mechanical breakdown to create nanoplastics. The results indicated the presence of trace amounts of EPDM in the water samples. Furthermore, the toxicological assessment revealed that the broken-down nanoplastics and leachate from the surface of EPDM rubber granules exhibited high toxicity to Daphnia magna, while nanoplastics from the inner material exhibited no significant toxicity. The findings highlight the urgent need for future research to identify these specific toxic agents from the surface of EPDM granules.
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| 26. |
- Hylander, Samuel, et al.
(författare)
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Induced tolerance expressed as relaxed behavioural threat response in millimetre-sized aquatic organisms
- 2014
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 281:1788, s. Article ID: 20140364-
-
Tidskriftsartikel (refereegranskat)abstract
- Natural selection shapes behaviour in all organisms, but this is difficult to study in small, millimetre-sized, organisms. With novel labelling and tracking techniques, based on nanotechnology, we here show how behaviour in zooplankton (Daphnia magna) is affected by size, morphology and previous exposure to detrimental ultraviolet radiation (UVR). All individuals responded with immediate downward swimming to UVR exposure, but when released from the threat they rapidly returned to the surface. Large individuals swam faster and generally travelled longer distances than small individuals. Interestingly, individuals previously exposed to UVR (during several generations) showed a more relaxed response to UVR and travelled shorter total distances than those that were naive to UVR, suggesting induced tolerance to the threat. In addition, animals previously exposed to UVR also had smaller eyes than the naive ones, whereas UVR-protective melanin pigmentation of the animals was similar between populations. Finally, we show that smaller individuals have lower capacity to avoid UVR which could explain patterns in natural systems of lower migration amplitudes in small individuals. The ability to change behavioural patterns in response to a threat, in this case UVR, adds to our understanding of how organisms navigate in the ‘landscape of fear’, and this has important implications for individual fitness and for interaction strengths in biotic interactions.
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| 27. |
- Kelpsiene, Egle, et al.
(författare)
-
Long-term exposure to nanoplastics reduces life-time in Daphnia magna
- 2020
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- Plastics are widely used in todays society leading to an accelerating amount of plastic waste entering natural ecosystems. Over time these waste products degrade to micro- and, eventually, nanoplastic particles. Therefore, the break-down of plastics may become a critical threat to aquatic ecosystems and several short term studies have demonstrated acute toxicity of nanoplastics on aquatic organisms. However, our knowledge about effects of chronic or life-time exposure on freshwater invertebrates remains elusive. Here, we demonstrate results from life-time exposure (103 days) of a common freshwater invertebrate, Daphnia magna, exposed to sub-lethal concentrations of polystyrene nanoparticles. 53 nm positively charged aminated polystyrene particles were lethal at concentration of 0.32 mg/L which is two magnitudes lower than previously used concentrations in short-term (24 h) tests. At this concentration the life-time of individuals was shortened almost three times. Negatively charged carboxylated 26 and 62 nm polystyrene particles, previously demonstrated to be non-toxic at 25 and 50 mg/L concentrations in short-term tests, were toxic to D. magna at all concentrations used in our long-term study. Although total reproductive output was not significantly affected at increasing concentrations of polystyrene nanoparticles, there was a decreasing trend in the number of offspring over their life-time. Hence, in order to understand how the potential future environmental problem of nanoplastic particles may affect biota, long-term or life-time studies resembling environmental concentrations should be performed in order to provide information for predictions of future scenarios in natural aquatic environments.
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| 28. |
- Kelpsiene, Egle, et al.
(författare)
-
Prolonged survival time of Daphnia magna exposed to polylactic acid breakdown nanoplastics
- 2023
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Ingår i: PLoS ONE. - 1932-6203. ; 18:9
-
Tidskriftsartikel (refereegranskat)abstract
- Polylactic acid nanoparticles (PLA NPs) according to food and drug administration are biodegradable and biocompatible polymers that have received a lot of attention due to their natural degradation mechanism. Although there is already available information concerning the effects of PLA microplastic to aquatic organisms, the knowledge about PLA NPs is still vague. In the present study, we analyzed the chemical composition of engineered PLA NPs, daily used PLA items and their breakdown products. We show that PLA breakdown products are oxidized and may contain aldehydes and/or ketones. The breakdown produces nanosized particles, nanoplastics, and possibly other small molecules as lactide or cyclic oligomers. Further, we show that all PLA breakdown nanoplastics extended the survival rate in Daphnia magna in an acute toxicity assay, however, only PLA plastic cup breakdown nanoplastics showed a significant difference compared to a control group.
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| 29. |
- Kelpsiene, Egle, et al.
(författare)
-
Protein binding on acutely toxic and non-toxic polystyrene nanoparticles during filtration by Daphnia magna
- 2022
-
Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry (RSC). - 2051-8153 .- 2051-8161.
-
Tidskriftsartikel (refereegranskat)abstract
- Nanomaterials can adsorb biomolecules to their surface and form a protein corona. Here we investigated the protein profile bound to different sizes of aminated and carboxylated polystyrene (PS) nanoparticles after passing through the digestive tract of the freshwater zooplankter Daphnia magna. We found that acutely toxic aminated 53 nm PS nanoparticles bind a different set of proteins compared to other non-toxic PS nanoparticles. The aminated PS nanoparticles bind a higher number of proteins, which are smaller and more acidic, compared to the proteins which bind to the PS nanoparticles that are non-toxic in acute toxicity tests. The proteins bound to toxic nanoparticles can be divided into two groups. One group of proteins which function is related to the digestive system, whereas the other group of proteins can be related to the epithelium, intracellular structures and processes. Finally, we observed that not only proteins bind to the surfaces of the nanoparticles. Triglycerides effectively bind to 200 nm carboxylated PS nanoparticles but not to the other tested nanoparticles. These results provide information about the composition of the corona formed on surfaces of nanoparticles after a short-term incubation with D. magna and give insights to what underlies the acute toxicity caused by nanoparticles.
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| 30. |
- Kelpsiene, Egle, et al.
(författare)
-
Review of ecotoxicological studies of widely used polystyrene nanoparticles
- 2022
-
Ingår i: Environmental Science: Processes & Impacts. - 2050-7895. ; 24:1, s. 8-16
-
Forskningsöversikt (refereegranskat)abstract
- With polystyrene nanoparticles being widely used in various applications, there is a great need for deeper knowledge on the safety, fate and biological effects of these particles on both individual living organisms and the whole ecosystems. Due to this, there is a growing interest in performing ecotoxicological studies using model plastic nanoparticles, and consequently it generates an increasing number of published papers describing the negative impact on wildlife caused by such nanoparticles. Polystyrene is the most studied nanosized plastic, therefore this review focuses on research conducted with manufactured polystyrene nanoparticles. The aim of the present article is to provide a critical methodological outline of the existing ecotoxicological studies on the effects of polystyrene nanoparticles on aquatic organisms. Going through the published articles, we noted that particle characterization especially in the test medium, can be improved. The analysis also highlights the importance of purifying the polystyrene nanoparticles before studying its toxicity. Furthermore, the size characterization of such nanoparticles is underemphasized, and in future studies, authors should consider including more techniques to achieve this goal. Finally, short-term or direct exposure scenarios do not add the most environmentally relevant knowledge in terms of the toxicity caused by polystyrene nanoparticles.
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| 31. |
- Langer, Sina M., et al.
(författare)
-
A three-dimensional perspective of Daphnia’s swimming behavior with and without predator cues
- 2019
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Ingår i: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 64:4, s. 1515-1525
-
Tidskriftsartikel (refereegranskat)abstract
- Behavioral adaptations play an important role in predator–prey interactions as they reduce predation risk. Prey organisms have therefore evolved a tremendous variability in behavioral adaptations. In case of small crustaceans of the genus Daphnia, which are common and important herbivores transferring energy from primary producers to higher trophic levels, such as predatory fish, and insects, altered migration patterns, swarming, or adaptive swimming speeds may increase survival rates. However, hitherto it has been difficult to analyze predator-induced behavioral adaptations as the small body size, as well as the low contrast between the transparent animals and their environment, most often impede behavioral movement analysis of individual animals. Therefore, we worked with a newly established technique providing higher contrast. We tagged daphniids with fluorescent nanoparticles and used a three-dimensional movement analysis system. We analyzed behavioral defense strategies of Daphnia clones from three species against different types of predators by measuring their behavior in presence and absence of predator cues. We analyzed swimming speed, depth selection, and motion patterns of Daphnia, as well as swarming behavior. We observed differences in the general swimming behavior in all analyzed aspects and show that daphniids change their behavioral strategies in the presence of predator cues, e.g., decrease their swimming speed as well as their vertical position or increase their nearest neighbor distance. Based on the observed changes in behavioral patterns, we conclude that the swimming behavior of daphniids may play an important role as inducible defense strategy that has the potential to improve prey survival chances.
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| 32. |
- Mattsson, Karin, et al.
(författare)
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Altered Behavior, Physiology, and Metabolism in Fish Exposed to Polystyrene Nanoparticles
- 2015
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 1520-5851 .- 0013-936X. ; 49:1, s. 553-561
-
Tidskriftsartikel (refereegranskat)abstract
- The use of nanoparticles in consumer products, for example, cosmetics, sunscreens, and electrical devices, has increased tremendously over the past decade despite insufficient knowledge about their effects on human health and ecosystem function. Moreover, the amount of plastic waste products that enter natural ecosystems, such as oceans and lakes, is increasing, and degradation of the disposed plastics produces smaller particles toward the nano scale. Therefore, it is of utmost importance to gain knowledge about how plastic nanoparticles enter and affect living organisms. Here we have administered 24 and 27 nm polystyrene nanoparticles to fish through an aquatic food chain, from algae through Daphnia, and studied the effects on behavior and metabolism. We found severe effects on feeding and shoaling behavior as well as metabolism of the fish; hence, we conclude that polystyrene nanoparticles have severe effects on both behavior and metabolism in fish and that commonly used nanosized particles may have considerable effects on natural systems and ecosystem services derived from them.
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| 33. |
- Mattsson, Karin, et al.
(författare)
-
Translocation of 40 nm diameter nanowires through the intestinal epithelium of Daphnia magna
- 2016
-
Ingår i: Nanotoxicology. - : Informa UK Limited. - 1743-5390 .- 1743-5404. ; 10:8, s. 1160-1167
-
Tidskriftsartikel (refereegranskat)abstract
- Nanowires (NWs) have unique electrical and optical properties of value for many applications including lighting, sensing, and energy harnessing. Consumer products containing NWs increase the risk of NWs being released in the environment, especially into aquatic ecosystems through sewage systems. Daphnia magna is a common, cosmopolitan freshwater organism sensitive to toxicity tests and represents a likely entry point for nanoparticles into food webs of aquatic ecosystems. Here we have evaluated the effect of NW diameter on the gut penetrance of NWs in Daphnia magna. The animals were exposed to NWs of two diameters (40 and 80 nm) and similar length (3.6 and 3.8 μm, respectively) suspended in water. In order to locate the NWs in Daphnia, the NWs were designed to comprise one inherently fluorescent segment of gallium indium phosphide (GaInP) flanked by a gallium phosphide (GaP) segment. Daphnia mortality was assessed directly after 24 h of exposure and 7 days after exposure. Translocation of NWs across the intestinal epithelium was investigated using confocal fluorescence microscopy directly after 24 h of exposure and was observed in 89% of Daphnia exposed to 40 nm NWs and in 11% of Daphnia exposed to 80 nm NWs. A high degree of fragmentation was observed for NWs of both diameters after ingestion by the Daphnia, although 40 nm NWs were fragmented to a greater extent, which could possibly facilitate translocation across the intestinal epithelium. Our results show that the feeding behavior of animals may enhance the ability of NWs to penetrate biological barriers and that penetrance is governed by the NW diameter.
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| 34. |
- Mei, Nanxuan, et al.
(författare)
-
Transfer of Cobalt Nanoparticles in a Simplified Food Web : From Algae to Zooplankton to Fish
- 2021
-
Ingår i: Applied nano. - : MDPI. - 2673-3501. ; 2:3
-
Tidskriftsartikel (refereegranskat)abstract
- Cobalt (Co) nanoparticles (NPs) may be diffusely dispersed into natural ecosystems from various anthropogenic sources such as traffic settings and eventually end up in aquatic systems. As environmentally dispersed Co NPs may be transferred through an aquatic food web, this study investigated this transfer from algae (Scendesmus sp.) to zooplankton (Daphnia magna) to fish (Crucian carp, Carassius carassius). Effects of interactions between naturally excreted biomolecules from D. magna and Co NPs were investigated from an environmental fate perspective. ATR-FTIR measurements showed the adsorption of both algae constituents and excreted biomolecules onto the Co NPs. Less than 5% of the Co NPs formed heteroagglomerates with algae, partly an effect of both agglomeration and settling of the Co NPs. The presence of excreted biomolecules in the solution did not affect the extent of heteroagglomeration. Despite the low extent of heteroagglomeration between Co NPs and algae, the Co NPs were transferred to the next trophic level (D. magna). The Co uptake in D. magna was 300 times larger than the control samples (without Co NP), which were not influenced by the addition of excreted biomolecules to the solution. Significant uptake of Co was observed in the intestine of the fish feeding on D. magna containing Co NPs. No bioaccumulation of Co was observed in the fish. Moreover, 10–20% of the transferred Co NP mass was dissolved after 24 h in the simulated gut solution of the zooplankton (pH 7), and 50–60% was dissolved in the simulated gut solution of the fish (pH 4). The results elucidate that Co NPs gain different properties upon trophic transfer in the food web. Risk assessments should hence be conducted on transformed and weathered NPs rather than on pristine particles.
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| 35. |
- Mei, Nanxuan, et al.
(författare)
-
Transfer of Cobalt Nanoparticles in a Simplified Food Web : From Algae to Zooplankton to Fish
- 2021
-
Ingår i: Applied Nano. - : MDPI AG. - 2673-3501. ; 2:3, s. 184-205
-
Tidskriftsartikel (refereegranskat)abstract
- Cobalt (Co) nanoparticles (NPs) may be diffusely dispersed into natural ecosystems from various anthropogenic sources such as traffic settings and eventually end up in aquatic systems. As environmentally dispersed Co NPs may be transferred through an aquatic food web, this study investigated this transfer from algae (Scendesmus sp.) to zooplankton (Daphnia magna) to fish (Crucian carp, Carassius carassius). Effects of interactions between naturally excreted biomolecules from D. magna and Co NPs were investigated from an environmental fate perspective. ATR-FTIR measurements showed the adsorption of both algae constituents and excreted biomolecules onto the Co NPs. Less than 5% of the Co NPs formed heteroagglomerates with algae, partly an effect of both agglomeration and settling of the Co NPs. The presence of excreted biomolecules in the solution did not affect the extent of heteroagglomeration. Despite the low extent of heteroagglomeration between Co NPs and algae, the Co NPs were transferred to the next trophic level (D. magna). The Co uptake in D. magna was 300 times larger than the control samples (without Co NP), which were not influenced by the addition of excreted biomolecules to the solution. Significant uptake of Co was observed in the intestine of the fish feeding on D. magna containing Co NPs. No bioaccumulation of Co was observed in the fish. Moreover, 10–20% of the transferred Co NP mass was dissolved after 24 h in the simulated gut solution of the zooplankton (pH 7), and 50–60% was dissolved in the simulated gut solution of the fish (pH 4). The results elucidate that Co NPs gain different properties upon trophic transfer in the food web. Risk assessments should hence be conducted on transformed and weathered NPs rather than on pristine particles.
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| 36. |
- Nyblom, Anna Maria, 1975, et al.
(författare)
-
Structural and functional analysis of SoPIP2;1 mutants adds insight into plant aquaporin gating.
- 2009
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Ingår i: Journal of molecular biology. - : Elsevier BV. - 1089-8638 .- 0022-2836. ; 387:3, s. 653-68
-
Tidskriftsartikel (refereegranskat)abstract
- Plant plasma membrane aquaporins facilitate water flux into and out of plant cells, thus coupling their cellular function to basic aspects of plant physiology. Posttranslational modifications of conserved phosphorylation sites, changes in cytoplasmic pH and the binding of Ca(2+) can regulate water transport activity by gating the plasma membrane aquaporins. A structural mechanism unifying these diverse biochemical signals has emerged for the spinach aquaporin SoPIP2;1, although several questions concerning the opening mechanism remain. Here, we describe the X-ray structures of the S115E and S274E single SoPIP2;1 mutants and the corresponding double mutant. Phosphorylation of these serines is believed to increase water transport activity of SoPIP2;1 by opening the channel. However, all mutants crystallised in a closed conformation, as confirmed by water transport assays, implying that neither substitution fully mimics the phosphorylated state. Nevertheless, a half-turn extension of transmembrane helix 1 occurs upon the substitution of Ser115, which draws the C(alpha) atom of Glu31 10 A away from its wild-type conformation, thereby disrupting the divalent cation binding site involved in the gating mechanism. Mutation of Ser274 disorders the C-terminus but no other significant conformational changes are observed. Inspection of the hydrogen-bond interactions within loop D suggested that the phosphorylation of Ser188 may also produce an open channel, and this was supported by an increased water transport activity for the S188E mutant and molecular dynamics simulations. These findings add additional insight into the general mechanism of plant aquaporin gating.
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| 37. |
- Odnevall, Inger, 1965-, et al.
(författare)
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Characterization and Toxic Potency of Airborne Particles Formed upon Waste from Electrical and Electronic Equipment Waste Recycling : A Case Study
- 2023
-
Ingår i: ACS ENVIRONMENTAL AU. - : American Chemical Society (ACS). - 2694-2518. ; 3:6, s. 370-382
-
Tidskriftsartikel (refereegranskat)abstract
- Manual dismantling, shredding, and mechanical grinding of waste from electrical and electronic equipment (WEEE) at recycling facilities inevitably lead to the accidental formation and release of both coarse and fine particle aerosols, primarily into the ambient air. Since diffuse emissions to air of such WEEE particles are not regulated, their dispersion from the recycling plants into the adjacent environment is possible. The aim of this interdisciplinary project was to collect and characterize airborne WEEE particles smaller than 1 mu m generated at a Nordic open waste recycling facility from a particle concentration, shape, and bulk and surface composition perspective. Since dispersed airborne particles eventually may reach rivers, lakes, and possibly oceans, the aim was also to assess whether such particles may pose any adverse effects on aquatic organisms. The results show that WEEE particles only exerted a weak tendency toward cytotoxic effects on fish gill cell lines, although the exposure resulted in ROS formation that may induce adverse effects. On the contrary, the WEEE particles were toxic toward the crustacean zooplankter Daphnia magna, showing strong effects on survival of the animals in a concentration-dependent way.
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| 38. |
- Palmér, Tobias, et al.
(författare)
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Calibration, Positioning and Tracking in a Refractive and Reflective Scene
- 2017
-
Ingår i: Pattern Recognition (ICPR), 2016 23rd International Conference on. - 9781509048472 ; , s. 3810-3815
-
Konferensbidrag (refereegranskat)abstract
- We propose a framework for calibration, positioningand tracking in a scene viewed by multiple cameras, througha flat refractive surface and one or several flat reflective walls.Refractions are explicitly modeled by Snell’s law and reflectionsare handled using virtual points. A novel bundle adjustmentframework is introduced for solving the nonlinear equationsof refractions and the linear equations of reflections, which inaddition enables optimization for calibration and positioning. Thenumerical accuracy of the solutions is investigated on syntheticdata, and the influence of noise in image points for several settingsof refractive and reflective planes is presented. The performance ofthe framework is evaluated on real data and confirms the validityof the physical model. Examples of how to use the frameworkto back-project image coordinates, forward-project scene pointsand estimate the refractive and reflective planes are presented.Lastly, an application of the system on real data from a biologicalexperiment on small aquatic organisms is presented.
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| 39. |
- Öberg, Fredrik, 1982, et al.
(författare)
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Insight into factors directing high production of eukaryotic membrane proteins; production of 13 human AQPs in Pichia pastoris.
- 2009
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Ingår i: Molecular membrane biology. - : Informa UK Limited. - 1464-5203 .- 0968-7688. ; 26:4, s. 215-27
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Tidskriftsartikel (refereegranskat)abstract
- Membrane proteins are key players in all living cells. To achieve a better understanding of membrane protein function, significant amounts of purified protein are required for functional and structural analyses. Overproduction of eukaryotic membrane proteins, in particular, is thus an essential yet non-trivial task. Hence, improved understanding of factors which direct a high production of eukaryotic membrane proteins is desirable. In this study we have compared the overproduction of all human aquaporins in the eukaryotic host Pichia pastoris. We report quantitated production levels of each homologue and the extent of their membrane localization. Our results show that the protein production levels vary substantially, even between highly homologous aquaporins. A correlation between the extents of membrane insertion with protein function also emerged, with a higher extent of membrane insertion for pure water transporters compared to aquaporin family members with other substrate specificity. Nevertheless, the nucleic acid sequence of the second codon appears to play an important role in overproduction. Constructs containing guanine at the first position of this codon (being part of the mammalian Kozak sequence) are generally produced at a higher level, which is confirmed for hAQP8. In addition, mimicking the yeast consensus sequence (ATGTCT) apparently has a negative influence on the production level, as shown for hAQP1. Moreover, by mutational analysis we show that the yield of hAQP4 can be heavily improved by directing the protein folding pathway as well as stabilizing the aquaporin tetramer.
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