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Little is known about microplastics (MPs) in corals from the Indian Ocean. We compared MP concentrations, morphotypes, size, colours, and polymer compositions in six coral genera from three remote Mascarene islands (Rodrigues, St. Brandon's Atoll, and Agalega) of the Republic of Mauritius, on a 1200 km transect located in the South Equatorial Current (SEC). The mean MP concentration was 0.78 n/g (53 % fibres) with no significant differences between islands. Polymers were polypropylene (78 %) and polyethylene (18 %). We conclude that the SEC's MP concentrations and compositions have homogenized over thousands of kilometres across the Indian Ocean. We discuss the lack of hazardous polyurethane MPs in coral samples given obvious sources on St Brandon. To the best of our knowledge, this study is the first to report on MPs in coral from the Western Indian Ocean and the Mascarene Islands providing a baseline for further research, monitoring, mitigation, and policy development. [Display omitted] • Nothing is known about microplastics (MPs) in coral from the Western Indian Ocean. • We analysed MPs from hard and soft corals from three Mascarene islands, a 1200 km transect. • The mean concentration was 0.78 n/g (53 % fibres) with no significant differences between islands. • Polymers were polypropylene (78 %) and polyethylene (18 %). • Compositions homogenized over thousands of kilometres across the Indian Ocean. [ABSTRACT FROM AUTHOR]

The runoff from stormwater outlets are potential sources of microplastics (MPs) in coastal zones. The characteristics and concentrations of MPs in coastal water, sediment and biota (mussels, whelks and sea urchins) were measured in summer (2020/2021) (dry season) and winter (2021) (wet season) from three sites (Camps Bay, Mouille Point and Three Anchor Bay) in Cape Town. MPs were characterised visually using a stereo microscope and chemically using spectroscopy. MP concentrations were higher in water and sediment during winter, and higher in biota in summer. Compared to control sites, MPs were higher at all impact sites sampled. MPs extracted were mainly black polyester (PEST) fibres, 1000 to 2000 μm in length averaging 0.15 MPs/L in water, 52.11 MPs/kg dry weight in sediment and 1.35 MPs/g soft tissue wet weight in biota. The results indicate that coastal stormwater systems are potential sources of MPs in the coastal environment of Cape Town. • Microplastics were highest at coastal stormwater pipes during the wet season. • Dark fibres were the main shape recorded in water, sediment and invertebrates. • Polyester (PEST) was the dominant polymer recorded. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The ingestion of microplastics and natural fibres (<5 mm) was assessed for two commercial fish species in the western Mediterranean Sea: Sardina pilchardus and Engraulis encrasicolus . Gastrointestinal tracts from 210 individuals from 14 stations were examined with 14.28–15.24% of the small pelagic fish S. pilchardus and E. encrasicolus having ingested microplastics and natural fibres. A latitudinal increase in condition index (Fulton's K) of S. pilchardus gave an indication that larger individuals with better physical condition are less likely to ingest microplastics and natural fibres. Fibres were the most frequent particle type (83%) and Fourier Transform Infrared spectroscopy (FT-IR) analysis indicated polyethylene terephthalate was the most common microplastics material (30%). Results from this study show that both microplastics and natural fibres of anthropogenic origin are common throughout the pelagic environment along the Spanish Mediterranean coast. [ABSTRACT FROM AUTHOR]

Estimated plastic debris floating at the ocean surface varies depending on modelling approaches, with some suggesting unaccounted sinks for marine plastic debris due to mismatches between plastic predicted to enter the ocean and that accounted for at the surface. A major knowledge gap relates to the vertical sinking of oceanic plastic. We used an array of floating sediment traps combined with optical microscopy and Raman spectroscopy to measure the microplastic flux between 50 and 150 m water depth over 24 h within a natural harbour of the sub-Antarctic island of South Georgia. This region is influenced by fishing, tourism, and research activity. We found a 69 % decrease in microplastic flux from 50 m (306 pieces/m2/day) to 150 m (94pieces/m2/day). Our study confirms the occurrence of a vertical flux of microplastic in the upper water column of the Southern Ocean, which may influence zooplankton microplastic consumption and the carbon cycle. • Microplastic flux was measured in the Southern Ocean using a floating sediment trap. • Microplastic flux decreased by 69 % from 50 m to 150 m (306 and 94 pieces/m2/day). • Fibres dominated the microplastic flux at each depth (92 % of total microplastic). • Polyester was the dominant microplastic at each depth. • Positively/neutrally buoyant microplastic was observed at depth (150 m). [ABSTRACT FROM AUTHOR]

This study focused on quantifying the abundance of microplastics within the surface water of the River Thames, UK. Ten sites in eight areas were sampled within the tidal Thames, starting from Teddington and ending at Southend-on-Sea. Three litres of water was collected monthly at high tide from land-based structures from each site from May 2019 to May 2021. Samples underwent visual analysis for microplastics categorised based on type, colour and size. 1041 pieces were tested using Fourier transform spectroscopy to identify chemical composition and polymer type. 6401 pieces of MP were found during sampling with an average MP of 12.27 pieces L−1 along the river Thames. Results from this study show that microplastic abundance does not increase along the river. • Average MP along the River Thames decreased from 2019 (12.27 L−1) to 2021 (5.92 L−1). • Fibres made up 93.27 % of all MPs found within the river • The most commonly found polymers were polyvinyl chloride, polystyrene and polychloroprene. [ABSTRACT FROM AUTHOR]

Levels of marine debris, including microplastics, are largely un-documented in the Northeast Atlantic Ocean. Broad scale monitoring efforts are required to understand the distribution, abundance and ecological implications of microplastic pollution. A method of continuous sampling was developed to be conducted in conjunction with a wide range of vessel operations to maximise vessel time. Transects covering a total of 12,700 km were sampled through continuous monitoring of open ocean sub-surface water resulting in 470 samples. Items classified as potential plastics were identified in 94% of samples. A total of 2315 particles were identified, 89% were less than 5 mm in length classifying them as microplastics. Average plastic abundance in the Northeast Atlantic was calculated as 2.46 particles m −3 . This is the first report to demonstrate the ubiquitous nature of microplastic pollution in the Northeast Atlantic Ocean and to present a potential method for standardised monitoring of microplastic pollution. [ABSTRACT FROM AUTHOR]

An abundance of microplastics particles (0.2–5 mm, MPs) in bottom sediments is analyzed based on 53 samples (3 to 215 m deep) obtained in 8 cruises of research vessels across the Baltic Sea Proper in March–October 2015–2016. MPs content varied between stations from 103 up to 10,179 items kg−1 d.w., with the bulk mean of 863 ± 1371 items kg−1 d.w., showing a statistically significant increase with water depth. As many as 74.5% of MPs are of fibrous shape, followed by films (19.8%) and fragments (5.7%). The distributions of fibres, fragments, films, and different types of natural bottom sediments are significantly different, highlighting the specific behaviour of each of these kinds of bottom deposits. A statistically significant correlation between water depth and fibres content is found. Based on the analysis of oceanographic factors and sedimentological principles, an erosion/transition/accumulation pattern for fibres in the Baltic Sea Proper is outlined. Fibres can be considered as a specific type of "synthetic sediment", while principles of distribution of other MPs are not yet certain. [Display omitted] • Distribution of MPs differs from that of natural sediment types. • MPs abundance increases with depth/distance from the shore. • Deep-sea is a dead-end for synthetic fibres. • Erosion/transition/accumulation zones for fibres are indicated. [ABSTRACT FROM AUTHOR]

Bivalves are the focus of experimental research as they can filtrate a broad size range of microplastics (MPs) with negative consequences for their physiology. Studies use a range of MP shapes, materials, sizes and concentrations raising the question on whether these reflect environmental observations. We review experimental studies on the effects of MPs on marine bivalves and contrast the MP characteristics used with corresponding data from the environment. Mussels were the most common bivalve across experiments which reflect their high abundance and broad distribution in the field. Although fibres are the dominant shape of MPs in coastal systems, most studies focus on spherules and beads, and MP concentrations are often orders of magnitude higher than environmental levels. For higher relevance of experimental findings we recommend that maximum experimental concentrations of MPs are in the range of 100–1000 particles/L, that there is more focus on microfibers and that concentration is reported in particles/volume. [Display omitted] • Microplastic (MP) exposure studies on bivalves must reflect realistic exposure risks • The focus of experiments on mussels and nanoplastics is environmentally relevant. • Future experimental studies should focus on fibres instead of spherical MPs. • Lower MP concentration levels are recommended in long-term exposure studies. • Consensus on the environmental MPs sizes and concentrations is needed. [ABSTRACT FROM AUTHOR]

Litter is a well-known problem for marine species; however, we still know little about the extent to which they're affected by microplastics. In this study, we analyse the presence of this type of debris in Western Mediterranean striped dolphins' intestinal contents over three decades. Results indicated that frequency was high, as 90.5% of dolphins contained microplastics. Of these microplastics, 73.6% were fibres, 23.87% were fragments and 2.53% were primary pellets. In spite of the high frequency of occurrence, microplastic amount per dolphin was relatively low and highly variable (mean ± SD = 14.9 ± 22.3; 95% CI: 9.58–23.4). Through FT-IR spectrometry, we found that polyacrylamide, typically found in synthetic clothes, was the most common plastic polymer. Here, we establish a starting point for further research on how microplastics affect this species' health and discuss the use of striped dolphins as indicators of microplastics at sea. • First study quantifying microplastics in Mediterranean dolphins' digestive tract • Most dolphins (90.5%) presented microplastics although low amount of items/individual. • Most of the microplastics were fibres (73.6%). • The most abundant polymer found was polyacrylamide (40.9%). [ABSTRACT FROM AUTHOR]

We compare the toxicity of microplastics, microfibres and nanoplastics on mussels. Mussels (Mytilus spp.) were exposed to 500 ng mL-1 of 20 μm polystyrene microplastics, 10 × 30 μm polyamide microfibres or 50 nm polystyrene nanoplastics for 24 h or 7 days. Biomarkers of immune response, oxidative stress response, lysosomal destabilisation and genotoxic damage were measured in haemolymph, digestive gland and gills. Microplastics and microfibres were observed in the digestive glands, with significantly higher plastic concentrations after 7-days exposure (ANOVA, P < 0.05). Nanoplastics had a significant effect on hyalinocyte-granulocyte ratios (ANOVA, P < 0.05), indicative of a heightened immune response. SOD activity was significantly increased followed 24 h exposure to plastics (two-way ANOVA, P < 0.05), but returned to normal levels after 7-days exposure. No evidence of lysosomal destabilisation or genotoxic damage was observed from any form of plastic. The study highlights how particle size is a key factor in plastic particulate toxicity. Unlabelled Image • Mussels (Mytilus edulis) exposed to micro- and nanoplastics for 24 h and 7 days. • Microplastics and microfibres aggregated in the digestive glands. • Plastic exposure caused a short-lived increase in SOD activity. • Nanoplastics triggered an innate immune response. [ABSTRACT FROM AUTHOR]

Salt marshes in urban watersheds are prone to microplastics (MP) pollution due to their hydrological characteristics and exposure to urban runoff, but little is known about MP distributions in species from these habitats. In the current study, MP occurrence was determined in six benthic invertebrate species from salt marshes along the North Adriatic lagoons (Italy) and the Schelde estuary (Netherlands). The species represented different feeding modes and sediment localisation. 96% of the analysed specimens (330) did not contain any MP, which was consistent across different regions and sites. Suspension and facultative deposit-feeding bivalves exhibited a lower MP occurrence (0.5–3%) relative to omnivores (95%) but contained a much more variable distribution of MP sizes, shapes and polymers. The study provides indications that MP physicochemical properties and species' ecological traits could all influence MP exposure, uptake and retention in benthic organisms inhabiting European salt marsh ecosystems. Unlabelled Image • Quantification of microplastics in wild benthic invertebrates from European salt marshes • Species with different ecological traits were collected. • The 96% of the analysed specimens did not contain any MP. • Omnivores contained higher quantities of microplastics than suspension and deposit feeders. • Suspension and deposit-feeders exhibited greater variability of MP typologies than omnivores. [ABSTRACT FROM AUTHOR]