Microplastics en route: Field measurements in the Dutch river delta and Amsterdam canals, wastewater treatment plants, North Sea sediments and biota

Environmental contamination by plastic particles, also known as ‘microplastics’, brings synthetic materials that are non-degradable and biologically incompatible into contact with ecosystems. In this paper we present concentration data for this emerging contaminant in wastewater treatment plants (WWTPs) and freshwater and marine systems, reflecting the routes via which these particles can travel and the ecosystems they potentially impact along their path. Raw sewage influents, effluents and sewage sludge from seven municipal WWTPs in the Netherlands contained mean particle concentrations of 68–910 L− 1, 51–81 L− 1 and 510–760 kg− 1 wet weight (ww), respectively (particle sizes between 10 and 5000 μm). Even after treatment, wastewater constitutes a source of microplastic pollution of surface waters, and via biosolids applications in farming and forestry, plastic retained in sewage sludge can be transferred to terrestrial environments. The WWTPs investigated here had a mean microplastics retention efficiency of 72% (s.d. 61%) in the sewage sludge. In the receiving waters of treated and untreated wastewaters, we detected high microplastic levels in riverine suspended particulate matter (1400–4900 kg− 1 dry weight (dw)) from the Rhine and Meuse rivers. Amsterdam canal water sampled at different urban locations contained microplastic concentrations (48–187 L− 1), similar to those observed in wastewater that is emitted from sewage treatment facilities in the area. At least partial settling of the particles occurs in freshwater as well, as indicated by microplastics in urban canal sediments (< 68 to 10,500 particles kg− 1 dw). Microplastics in suspension in the water column have the potential to be discharged into the sea with other riverine suspended particulates. We report microplastic concentrations from 100 up to 3600 particles kg− 1 dry sediment collected at 15 locations along the Dutch North Sea coast. The high microplastic enrichment in marine sediments compared to most literature data for seawater at the surface supports the hypothesis of a seabed sink for these materials. Marine species are heavily exposed to plastic particles. Body residues between 10 and 100 particles g− 1 dw were measured in benthic macroinvertebrate species inhabiting the Dutch North Sea coast: filter-feeding mussels and oysters (species for human consumption) as well as other consumers in the marine food chain.

H.A. Leslie, S.H. Brandsma, M.J.M. van Velzen, A.D. Vethaak, Environment International, Available Environment International, Volume 101, April 2017, Pages 133–142

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Microplastics Affect the Ecological Functioning of an Important Biogenic Habitat

Biological effects of microplastics on the health of bivalves have been demonstrated elsewhere, but ecological impacts on the biodiversity and ecosystem functioning of bivalve-dominated habitats are unknown. Thus, we exposed intact sediment cores containing European flat oysters (Ostrea edulis) or blue mussels (Mytilus edulis) in seawater to two different densities (2.5 or 25 μg L–1) of biodegradable or conventional microplastics in outdoor mesocosms. We hypothesized that filtration rates of the bivalves, inorganic nitrogen cycling, primary productivity of sediment dwelling microphytobenthos, and the structure of invertebrate benthic assemblages would be influenced by microplastics. After 50 days, filtration by M. edulis was significantly less when exposed to 25 μg L–1 of either type of microplastics, but there were no effects on ecosystem functioning or the associated invertebrate assemblages. Contrastingly, filtration by O. edulis significantly increased when exposed to 2.5 or 25 μg L–1 of microplastics, and porewater ammonium and biomass of benthic cyanobacteria decreased. Additionally the associated infaunal invertebrate assemblages differed, with significantly less polychaetes and more oligochaetes in treatments exposed to microplastics. These findings highlight the potential of microplastics to impact the functioning and structure of sedimentary habitats and show that such effects may depend on the dominant bivalve present.

Dannielle Senga Green, Bas Boots, Nessa E. O’Connor, and Richard Thompson, Environ. Sci. Technol., 2017, 51 (1), pp 68–77

Colonization of Polystyrene Microparticles by Vibrio crassostreae: Light and Electron Microscopic Investigation

Microplastics collected at sea harbor a high diversity of microorganisms, including some Vibrio genus members, raising questions about the role of microplastics as a novel ecological niche for potentially pathogenic microorganisms. In the present study, we investigated the adhesion dynamics of Vibrio crassostreae on polystyrene microparticles (micro-PS) using electronic and fluorescence microscopy techniques. Micro-PS were incubated with bacteria in different media (Zobell culture medium and artificial seawater) with or without natural marine aggregates. The highest percentage of colonized particles (38–100%) was observed in Zobell culture medium, which may be related to nutrient availability for production of pili and exopolysaccharide adhesion structures. A longer bacterial attachment (6 days) was observed on irregular micro-PS compared to smooth particles (<10 h), but complete decolonization of all particles eventually occurred. The presence of natural marine agreggates around micro-PS led to substantial and perennial colonization featuring monospecific biofilms at the surface of the aggregates. These exploratory results suggest that V. crassostreae may be a secondary colonizer of micro-PS, requiring a multispecies community to form a durable adhesion phenotype. Temporal assessment of microbial colonization on microplastics at sea using imaging and omics approaches are further indicated to better understand the microplastics colonization dynamics and species assemblages.

Valentin Foulon, Frédérique Le Roux, Christophe Lambert, Arnaud Huvet, Philippe Soudant, and Ika Paul-Pont, Environ. Sci. Technol., 2016, 50 (20), pp 10988–10996

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Reply to Lenz et al.: Quantifying the smallest microplastics is the challenge for a comprehensive view of their environmental impacts

Studies on impacts of emerging contaminants are challenging, as is the case for studying the smallest sizes (<100 µm) of microplastics, mainly because there is no clear view of their actual concentration and characteristics in the natural environment (1). Major developments are required to establish standardized procedures for collecting, fractionating, characterizing, and quantifying polymer particles; probably, the best promising method is in a liquid matrix. In our recent article on impacts of microplastics in oysters (2), the microplastic size tested was of 2 and 6 µm, the size range preferentially ingested by filter feeders, which is far below the size robustly characterized and quantified at sea. (…)

Arnaud Huvet, Ika Paul-Pont, Caroline Fabioux, Christophe Lambert, Marc Suquet, Yoann Thomas, Johan Robbens, Philippe Soudant, and Rossana Sussarellu, PNAS, July 19, 2016, vol. 113 no. 2

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Effects of microplastics on European flat oysters, Ostrea edulis and their associated benthic communities

Plastic pollution is recognised as an emerging threat to aquatic ecosystems, with microplastics now the most abundant type of marine debris. Health effects caused by microplastics have been demonstrated at the species level, but impacts on ecological communities remain unknown. In this study, impacts of microplastics on the health and biological functioning of European flat oysters (Ostrea edulis) and on the structure of associated macrofaunal assemblages were assessed in an outdoor mesocosm experiment using intact sediment cores. Biodegradable and conventional microplastics were added at low (0.8 μg L−1) and high (80 μg L−1) doses in the water column repeatedly for 60 days. Effects on the oysters were minimal, but benthic assemblage structures differed and species richness and the total number of organisms were ∼1.2 and 1.5 times greater in control mesocosms than in those exposed to high doses of microplastics. Notably, abundances of juvenile Littorina sp. (periwinkles) and Idotea balthica (an isopod) were ∼2 and 8 times greater in controls than in mesocosms with the high dose of either type of microplastic. In addition, the biomass of Scrobicularia plana (peppery furrow shell clam) was ∼1.5 times greater in controls than in mesocosms with the high dose of microplastics. This work indicates that repeated exposure to high concentrations of microplastics could alter assemblages in an important marine habitat by reducing the abundance of benthic fauna.

Dannielle Senga Green, Environmental Pollution, Volume 216, Pages 95–103, September 2016

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Microplastics damage oyster fertility

Oysters that consume the small pieces of plastic that are littering the world’s oceans produce fewer and less-healthy offspring, a study suggests — fuelling concern that the material may be damaging marine life. (…)

Arnaud Huvet, a scientist at France’s national marine research agency (Ifremer) in Plouzané, and his colleagues placed Pacific oysters (Crassostrea gigas) in water laced with micrometre-sized spheres of polystyrene, at levels similar to those that have been recorded in the wild in some locations. After two months, oysters exposed to the plastic produced fewer and smaller egg cells, less-mobile sperm and fewer offspring than did animals raised in water without the plastic. The offspring themselves grew more slowly, the researchers report. (…)

Daniel Cressey, Nature, 02 February 2016

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Oyster reproduction is affected by exposure to polystyrene microplastics

Plastics are persistent synthetic polymers that accumulate as waste in the marine environment. Microplastic (MP) particles are derived from the breakdown of larger debris or can enter the environment as microscopic fragments. Because filter-feeder organisms ingest MP while feeding, they are likely to be impacted by MP pollution. To assess the impact of polystyrene microspheres (micro-PS) on the physiology of the Pacific oyster, adult oysters were experimentally exposed to virgin micro-PS (2 and 6 µm in diameter; 0.023 mg·L−1) for 2 mo during a reproductive cycle. Effects were investigated on ecophysiological parameters; cellular, transcriptomic, and proteomic responses; fecundity; and offspring development. Oysters preferentially ingested the 6-µm micro-PS over the 2-µm-diameter particles. Consumption of microalgae and absorption efficiency were significantly higher in exposed oysters, suggesting compensatory and physical effects on both digestive parameters. After 2 mo, exposed oysters had significant decreases in oocyte number (−38%), diameter (−5%), and sperm velocity (−23%). The D-larval yield and larval development of offspring derived from exposed parents decreased by 41% and 18%, respectively, compared with control offspring. Dynamic energy budget modeling, supported by transcriptomic profiles, suggested a significant shift of energy allocation from reproduction to structural growth, and elevated maintenance costs in exposed oysters, which is thought to be caused by interference with energy uptake. Molecular signatures of endocrine disruption were also revealed, but no endocrine disruptors were found in the biological samples. This study provides evidence that micro-PS cause feeding modifications and reproductive disruption in oysters, with significant impacts on offspring.

 

Rossana Sussarellu, Marc Suquet, Yoann Thomas, Christophe Lambert, Caroline Fabioux, Marie Eve Julie Pernet, Nelly Le Goïc, Virgile Quillien, Christian Mingant, Yanouk Epelboin, Charlotte Corporeau, Julien Guyomarch, Johan Robbens, Ika Paul-Pont, Philippe Soudant, and Arnaud Huvet, PNAS, vol. 113 (9), 2430–2435, February 2016

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