Quantitative investigation of the mechanisms of microplastics and nanoplastics toward zebrafish larvae locomotor activity

This study investigated the direct and indirect toxic effects of microplastics and nanoplastics toward zebrafish (Danio rerio) larvae locomotor activity. Results showed that microplastics alone exhibited no significant effects except for the upregulated zfrho visual gene expression; whereas nanoplastics inhibited the larval locomotion by 22% during the last darkness period, and significantly reduced larvae body length by 6%, inhibited the acetylcholinesterase activity by 40%, and upregulated gfap, α1-tubulin, zfrho and zfblue gene expression significantly. When co-exposed with 2 μg/L 17 α-ethynylestradiol (EE2), microplastics led to alleviation on EE2’s inhibition effect on locomotion, which was probably due to the decreased freely dissolved EE2 concentration. However, though nanoplastics showed stronger adsorption ability for EE2, the hypoactivity phenomenon still existed in the nanoplastics co-exposure group. Moreover, when co-exposed with a higher concentration of EE2 (20 μg/L), both plastics showed an enhanced effect on the hypoactivity. Principal component analysis was performed to reduce data dimensions and four principal components were reconstituted in terms of oxidative stress, body length, nervous and visual system related genes explaining 84% of total variance. Furthermore, oxidative damage and body length reduction were evaluated to be main reasons for the hypoactivity. Therefore, nanoplastics alone suppressed zebrafish larvae locomotor activity and both plastic particles can change the larvae swimming behavior when co-exposed with EE2. This study provides new insights into plastic particles’ effects on zebrafish larvae, improving the understanding of their environmental risks to the aquatic environment.

Qiqing Chen, Michael Gundlach, Shouye Yang and al., Science of The Total Environment, Volumes 584–585, 15 April 2017, Pages 1022–1031

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Influence of environmental and anthropogenic factors on the composition, concentration and spatial distribution of microplastics: A case study of the Bay of Brest (Brittany, France)

The concentration and spatial distribution of microplastics in the Bay of Brest (Brittany, France) was investigated in two surveys. Surface water and sediment were sampled at nine locations in areas characterized by contrasting anthropic pressures, riverine influences or water mixing. Microplastics were categorized by their polymer type and size class. Microplastic contamination in surface water and sediment was dominated by polyethylene fragments (PE, 53–67%) followed by polypropylene (PP, 16–30%) and polystyrene (PS, 16–17%) microparticles. The presence of buoyant microplastics (PE, PP and PS) in sediment suggests the existence of physical and/or biological processes leading to vertical transfer of lightweight microplastics in the bay. In sediment (upper 5 cm), the percentage of particles identified by Raman micro-spectroscopy was lower (41%) than in surface water (79%) and may explain the apparent low concentration observed in this matrix (0.97 ± 2.08 MP kg−1 dry sediment). Mean microplastic concentration was 0.24 ± 0.35 MP m−3 in surface water. We suggest that the observed spatial MP distribution is related to proximity to urbanized areas and to hydrodynamics in the bay. A particle dispersal model was used to study the influence of hydrodynamics on surface microplastic distribution. The outputs of the model showed the presence of a transitional convergence zone in the centre of the bay during flood tide, where floating debris coming from the northern and southern parts of the bay tends to accumulate before being expelled from the bay. Further modelling work and observations integrating (i) the complex vertical motion of microplastics, and (ii) their point sources is required to better understand the fate of microplastics in such a complex coastal ecosystem.

L. Frère, I. Paul-Pont, E. Rinnert, S. Petton, J. Jaffré, I. Bihannic, P. Soudant, C. Lambert, A. Huvet, Environmental Pollution, Volume 225, June 2017, Pages 211–222

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The use of potassium hydroxide (KOH) solution as a suitable approach to isolate plastics ingested by marine organisms

In studies of plastic ingestion by marine wildlife, visual separation of plastic particles from gastrointestinal tracts or their dietary content can be challenging. Earlier studies have used solutions to dissolve organic materials leaving synthetic particles unaffected. However, insufficient tests have been conducted to ensure that different categories of consumer products partly degraded in the environment and/or in gastrointestinal tracts were not affected. In this study 63 synthetic materials and 11 other dietary items and non-plastic marine debris were tested. Irrespective of shape or preceding environmental history, most polymers resisted potassium hydroxide (KOH) solution, with the exceptions of cellulose acetate from cigarette filters, some biodegradable plastics and a single polyethylene sheet. Exposure of hard diet components and other marine debris showed variable results. In conclusion, the results confirm that usage of KOH solutions can be a useful approach in general quantitative studies of plastic ingestion by marine wildlife.

Susanne Kühn, Bernike van Werven, Albert van Oyen, André Meijboom, Elisa L. Bravo Rebolledo, Jan A. van Franeker, Marine Pollution Bulletin, Volume 115, Issues 1–2, 15 February 2017, Pages 86–90

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The toxicity of plastic nanoparticles to green algae as influenced by surface modification, medium hardness and cellular adsorption

To investigate processes possibly underlying accumulation and ecological effects of plastic nano-particles we have characterized their interaction with the cell wall of green algae. More specifically, we have investigated the influence of particle surface functionality and water hardness (Ca2+ concentration) on particle adsorption to algae cell walls. Polystyrene nanoparticles with different functional groups (non-functionalized, −COOH and −NH2) as well as coated (starch and PEG) gold nanoparticles were applied in these studies. Depletion measurements and atomic force microscopy (AFM) showed that adsorption of neutral and positively charged plastic nanoparticles onto the cell wall of P. subcapitata was stronger than that of negatively charged plastic particles. Results indicated that binding affinity is a function of both inter-particle and particle-cell wall interactions which are in turn influenced by the medium hardness and particle concentration. Physicochemical modelling using DLVO theory was used to interpret the experimental data, using also values for interfacial surface free energies. Our study shows that material properties and medium conditions play a crucial role in the rate and state of nanoparticle bio-adsorption for green algae. The results show that the toxicity of nanoparticles can be better described and assessed by using appropriate dose metrics including material properties, complexation/agglomeration behavior and cellular attachment and adsorption. The applied methodology provides an efficient and feasible approach for evaluating potential accumulation and hazardous effects of nanoparticles to algae caused by particle interactions with the algae cell walls.

Tom M. Nolte , Nanna B. Hartmann, J. Mieke Kleijn, Jørgen Garnæs, Dik van de Meent, A. Jan Hendriks, Anders Baun, Aquatic Toxicology, Volume 183, February 2017, Pages 11–20

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Mumbai’s Most Popular Beaches Are Also The World’s Most Polluted Ones

According to the alarming facts brought out by a recent analysis of marine pollution around the world, seas near Mumbai are found to be the most polluted ones.

On analyzing the extent of plastic debris in the seas of Mumbai, it was found that there were an average of 68.83 items per sq m on the beaches of Juhu, Aksa, Dadar and Versova. The size of these micro-plastics varied between 1m to 5m. Also, of all the litter, about 41.85 percent was micro-plastic. The beach of Juhu has the highest quantity of micros-plastic litter, a whopping 55.33 percent, followed by Versova (28.8 percent), Dadar (18.6 percent) and Aksa (7.9 percent). (…) (topyaps.com, 4/04/2017)

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Microplastics in the environment (Microplastics issue)

  • On the harmonization of methods for measuring the occurrence, fate and effects of microplastics, Chelsea M. Rochman, Fiona Regan and Richard C. Thompson  
  • Analytical challenges associated with the determination of microplastics in the environment, Robert C. Hale
  • Improving microplastics source apportionment: a role for microplastic morphology and taxonomy? Paul A. Helm
  • Some problems and practicalities in design and interpretation of samples of microplastic waste, A. J. Underwood, M. G. Chapman and Mark Anthony Browne
  • Sampling, isolating and identifying microplastics ingested by fish and invertebrates, A. L. Lusher, N. A. Welden, P. Sobral and M. Cole  
and other 17 articles

Microplastics in freshwater and terrestrial environments: Evaluating the current understanding to identify the knowledge gaps and future research priorities

Plastic debris is an environmentally persistent and complex contaminant of increasing concern. Understanding the sources, abundance and composition of microplastics present in the environment is a huge challenge due to the fact that hundreds of millions of tonnes of plastic material is manufactured for societal use annually, some of which is released to the environment. The majority of microplastics research to date has focussed on the marine environment. Although freshwater and terrestrial environments are recognised as origins and transport pathways of plastics to the oceans, there is still a comparative lack of knowledge about these environmental compartments. It is highly likely that microplastics will accumulate within continental environments, especially in areas of high anthropogenic influence such as agricultural or urban areas. This review critically evaluates the current literature on the presence, behaviour and fate of microplastics in freshwater and terrestrial environments and, where appropriate, also draws on relevant studies from other fields including nanotechnology, agriculture and waste management. Furthermore, we evaluate the relevant biological and chemical information from the substantial body of marine microplastic literature, determining the applicability and comparability of this data to freshwater and terrestrial systems. With the evidence presented, the authors have set out the current state of the knowledge, and identified the key gaps. These include the volume and composition of microplastics entering the environment, behaviour and fate of microplastics under a variety of environmental conditions and how characteristics of microplastics influence their toxicity. Given the technical challenges surrounding microplastics research, it is especially important that future studies develop standardised techniques to allow for comparability of data. The identification of these research needs will help inform the design of future studies, to determine both the extent and potential ecological impacts of microplastic pollution in freshwater and terrestrial environments.

Alice A. Horton, Alexander Walton, David J. Spurgeon, Elma Lahive, Claus Svendsen, Science of The Total Environment, Volume 586, 15 May 2017, Pages 127–141

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