Low levels of microplastics (MP) in wild mussels indicate that MP ingestion by humans is minimal compared to exposure via household fibres fallout during a meal

Microplastics (MPs) are the most numerous debris reported in marine environments and assessment of the amounts of MPs that accumulate in wild organisms is necessary for risk assessment. Our objective was to assess MP contamination in mussels collected around the coast of Scotland (UK) to identify characteristics of MPs and to evaluate risk of human exposure to MPs via ingestion of mussels. We deployed caged mussels (Mytilus edulis) in an urbanised estuary (Edinburgh, UK) to assess seasonal changes in plastic pollution, and collected mussels (Mytilus spp and subtidal Modiolus modiolus) from eight sampling stations around Scotland to enumerate MP types at different locations. We determined the potential exposure of humans to household dust fibres during a meal to compare with amounts of MPs present in edible mussels. The mean number of MPs in M. modiolus was 0.086 ± 0.031 (SE, n = 6)/g ww (3.5 ± 1.29 (SE) per mussel). In Mytilus spp, the mean number of MPs/g ww was 3.0 ± 0.9 (SE, n = 36) (3.2 ± 0.52 (SE) per mussel), but weight dependent. The visual accuracy of plastic fibres identification was estimated to be between 48 and 50%, using Nile Red staining and FT-IR methodologies, respectively, halving the observed amounts of MPs in wild mussels. We observed an allometric relationship between the number of MPs and the mussels wet weight. Our predictions of MPs ingestion by humans via consumption of mussels is 123 MP particles/y/capita in the UK and can go up to 4620 particles/y/capita in countries with a higher shellfish consumption. By comparison, the risk of plastic ingestion via mussel consumption is minimal when compared to fibre exposure during a meal via dust fallout in a household (13,731–68,415 particles/Y/capita).

A. I. Catarino, V. Macchia, W. G. Sanderson and al., Environmental Pollution, Volume 237, June 2018, Pages 675–684

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Application of an enzyme digestion method reveals microlitter in Mytilus trossulus at a wastewater discharge area

The ingestion of microlitter by blue mussels (450) was studied at a wastewater recipient area in the Baltic Sea. The mussel soft tissues were digested using enzymatic detergents and the detected litter particles characterized with FT-IR imaging spectroscopy. Microlitter concentration in seawater and WWTP effluent were also measured. Microlitter was found in 66% of the mussels. Mussels from the WWTP recipient had higher microlitter content compared to those collected at the reference site. Plastics made up 8% of all the analysed microlitter particles. The dominating litter types were fibres (~90% of all microlitter), 42% of which were cotton, 17% linen, 17% viscose and 4% polyester. The risk of airborne contamination during laboratory work was lowered when mussels were digested with their shells on instead of dissecting them first. The approach was found applicable and gentle to both non-synthetic and synthetic materials including fragile fibres.

Saana Railo, Julia Talvitie, Outi Setälä and al., Marine Pollution Bulletin, Volume 130, May 2018,  Pages 206–214

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Evaluation of uptake and chronic toxicity of virgin polystyrene microbeads in freshwater zebra mussel Dreissena polymorpha (Mollusca: Bivalvia)

Microplastics (MPs), plastic debris smaller than 5 mm, are widely found in both marine and freshwater ecosystems. However, few studies regarding their hazardous effects on inland water organisms, have been conducted. For this reason, the aim of our research was the evaluation of uptake and chronic toxicity of two mixtures (MIXs) of virgin polystyrene microbeads (PMs) of 10 μm and 1 μm in size (MIX 1, with 5 × 105 of 1 μm size PMs/L and 5 × 105 of 10 μm size PMs/L, and MIX 2 with 2 × 106 of 1 μm size PMs/L and 2 × 106 of 10 μm size PMs/L) on freshwater zebra mussel Dreissena polymorpha (Mollusca: Bivalvia) during 6 exposure days. The PM uptake in the mussel body and hemolymph was assessed using confocal microscopy, while the chronic toxicity of PMs was evaluated on exposed mussels using a comprehensive battery of biomarkers of cellular stress, oxidative damage and neuro- genotoxicity. Confocal microscopy analyses showed that MPs concentrated in the gut lumen of exposed mussels, absorbed and transferred firstly in the tissues and then in the hemolymph. The results revealed that PMs do not produce oxidative stress and genetic damage, with the exception of a significant modulation of catalase and glutathione peroxidase activities in mussels exposed to MIX 1. Regarding neurotoxicity, we observed only a significant increase of dopamine concentration in mussels exposed to both MIXs, suggesting a possible implication of this neurotransmitter in an elimination process of accumulated PMs. This research represents a first study about the evaluation of virgin MP toxicity in zebra mussel and more research is warranted concerning the long term neurological effects of virgin MPs.

Stefano Magni, François Gagné, Chantale André and al., Science of The Total Environment, Volumes 631–632, 1 August 2018, Pages 778–788

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Weathering impacts the uptake of polyethylene microparticles from toothpaste in Mediterranean mussels (M. galloprovincialis)

Mediterranean mussels (Mytilus galloprovincialis) were exposed over 21 days to polyethylene (PE) particles (0.01 mg ml−1; 50–570 μm) isolated from toothpaste. PE was deployed in the Outer Oslofjord (Norway) for 21 days, before exposing the mussels to both virgin (PE-V) and weathered PE (PE-W) particles. The mussels ingested both types of particles, but significantly more weathered particles were ingested than virgin (p = .0317), based on PE dosed by weight (mg ml−1) but not when considering particle number (PE-V: 1.18 ± 0.16 particles ml−1; PE-W 1.86 ± 0.66 particles ml-1;). PE particle ingestion resulted in structural changes to the gills and digestive gland, as well as necrosis in other tissues such as the mantle. No differences were found regarding the degree of tissue alteration between PE-virgin and PE-weathered exposures. This current study illustrates the importance of using weathered particles in microplastic exposure studies to reflect the behaviour of plastic particles after entering the marine environment. The observed tissue alterations demonstrate the potential adverse effects to mussels exposed to microplastic particles.

Inger Lise N. Brate, Mercedes Blazquez, Steven J. Brooks, Kevin V. Thomas, Science of The Total Environment, Volume 626, 1 June 2018, Pages 1310–1318

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Continuous Exposure to Microplastics Does Not Cause Physiological Effects in the Cultivated Mussel Perna perna

The environmental impact of microplastics is a challenging theme, especially under realistic experimental conditions. We investigated physiological responses to 0.1–1.0 μm PVC particles intake by the mussel Perna perna after a relative long-term exposure (90 days) at a less extreme concentration compared with previous studies (0.125 g/L). Microplastic intake was inferred by the presence of PVC in the feces of mussels, and physiological damages were assessed through ingestion rate, assimilation efficiency, growth rate, cellular and molecular biomarkers (lysosomal integrity, lipid peroxidation, and DNA damage), and condition index. All physiological responses showed nonsignificant effects of the microplastics on the exposed mussels. We suggest that, despite the experimental concentration of microplastics, mussels were able to acclimate to the exposure through their abilities for long-term recovery and tolerance to stresses. These data have positive implications for environmental health and in terms of human food resource because mussel farming is a worldwide practice that heavily relies on plastic materials, increasing the chances of microplastic exposure and mussels contamination.

Marina F. M. Santana,Fabiana T. Moreira, Camilo D. S. Pereira, Denis M. S. Abessa, Alexander Turra, Archives of Environmental Contamination and Toxicology, P; 1-11, 19/01/2018

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Plastic found in mussels from Arctic to China – enters human food

Tiny bits of plastic are contaminating mussels from the European Arctic to China in a sign of the global spread of ocean pollution that can end up on people’s dinner plates.

Mussels in apparently pristine Arctic waters had most plastic of any tested along the Norwegian coast, according to a study this month by the Norwegian Institute for Water Research (NIVA).

Plastics may be getting swept north by ocean currents and winds from Europe and America, ending up swirling around the Arctic Ocean, NIVA researcher Amy Lusher told Reuters.

“Microplastics have been found in mussels everywhere scientists have looked,” she said.

Past surveys have found microplastics off nations including China, Chile, Canada, Britain and Belgium. Off Norway, the molluscs contained on average 1.8 bits of microplastic – defined as smaller than 5 mm long (0.2 inch) – with 4.3 in the Arctic. (…) (reuters.com, 20/12/2017)

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Assessing the relationship between the abundance and properties of microplastics in water and in mussels

Microplastic pollution is increasingly becoming a great environmental concern worldwide. Microplastics have been found in many marine organisms as a result of increasing plastic pollution within marine environments. However, the relationship between micoplastics in organisms and their living environment is still relatively poorly understood. In the present study, we investigated microplastic pollution in the water and the mussels (Mytilus edulis, Perna viridis) at 25 sites along the coastal waters of China. We also, for the first time, conducted an exposure experiment in parallel on the same site using M. edulis in the laboratory. A strong positive linear relationship was found between microplastic levels in the water and in the mussels. Fibers were the dominant microplastics. The sizes of microplastics in the mussels were smaller than those in the water. During exposure experiments, the abundance of microbeads was significantly higher than that of fibers, even though the nominal abundance of fibers was eight times that of microbeads. In general, our results supported positive and quantitative correlations of microplastics in mussels and in their surrounding waters and that mussels were more likely to ingest smaller microplastics. Laboratory exposure experiment is a good way to understand the relative impacts of microplastics ingested by marine organisms. However, significant differences in the results between exposure experiments and field investigations indicated that further efforts are needed to simulate the diverse environmentally relevant properties of microplastics.

Xiaoyun Qu, Lei Su, Hengxiang Li, Mingzhong Liang, Huahong Shi, Science of The Total Environment, Volume 621, 15 April 2018, Pages 679–686

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