Transfer of benzo[a]pyrene from microplastics to Artemia nauplii and further to zebrafish via a trophic food web experiment: CYP1A induction and visual tracking of persistent organic pollutants

Soil microplastics inhibit the movement of springtail species

Previous studies have indicated the means by which micro-sized plastic particles may affect the soil environment, and this could be linked to the behavior of plastics in the soil system and how these particles are influenced by biological responses. Soil-dwelling organisms play a key role in modifying the soil system by constructing bio-pores, and these structural changes are potentially related to the behavior of plastic particles. In this study, we found that micro-sized plastic particles moved into bio-pores within seconds, and that this influx disrupted the movement of springtails (Lobella sokamensis). The springtails moved to avoid becoming trapped, and this behavior created bio-pores in the soil system. The influx of plastic particles into these cavities subsequently immobilized the springtails within. This phenomenon was observed at low a concentration of plastic particles (8 mg/kg), and it likely occurs in actual soil environments. The findings of this study indicate that the behavior of plastic particles in the soil not only disrupts the movement of springtails but also has wider implications for effective management of soils.

Co-exposure to polystyrene plastic beads and polycyclic aromatic hydrocarbon contaminants in fish gill (RTgill-W1) and intestinal (RTgutGC) epithelial cells derived from rainbow trout (Oncorhynchus mykiss)

Microscopic plastic (MP) particles are a ubiquitous contaminant in aquatic environments, which may bind hydrophobic chemicals, such as polycyclic aromatic hydrocarbons (PAHs), altering their environmental fate and interactions with biota. Using rainbow trout gill (RTgill-W1) and intestinal (RTgutGC) epithelial cells we investigated the effects of polystyrene microbeads (PS-MBs; 220 nm) on the cyto- and genotoxicity of the environmental pollutants benzo[a]pyrene (BaP) and 3-nitrobenzanthrone (3-NBA) over 48 h (0, 0.1, 1 and 10 μM). The Alamar Blue bioassay, used to assess cytotoxicity, showed that both pollutants significantly decreased cell viability by 10-20% at 10 μM in both cell lines after 48 h whereas PS-MBs (5 or 50 μg mL^-1) were non-toxic. Cytotoxicity in cells treated with PS-MBs together with BaP or 3-NBA were similar to those observed after exposure to BaP or 3-NBA alone. Using the formamidopyrimidine-DNA glycosylase (FPG)-modified comet assay 3-NBA, but not BaP, induced DNA damage in RTgutGC cells at 10 μM (∼10% tail DNA in the absence and ∼15% tail DNA in the presence of FPG versus ∼1% in controls), whereas PS-MBs alone showed no detrimental effects. Interestingly, comet formation was substantially increased (∼4-fold) when RTgutGC cells were exposed to PS-MBs (50 μg mL^-1) and 10 μM 3-NBA compared to cells treated with 3-NBA alone. Further, using ³²P-postlabelling we observed strong DNA adduct formation in 3-NBA-exposed RTgutGC cells (∼900 adducts/10⁸ nucleotides). 3-NBA-derived DNA adduct formation was significantly decreased (∼20%) when RTgutGC cells were exposed to MB and 3-NBA compared to cells treated with 3-NBA alone. Our results show that PS-MBs impact on the genotoxicity of 3-NBA, causing a significant increase in DNA damage as measured by the comet assay in the intestinal cell line, providing proof of principle that MPs may alter the genotoxic potential of PAHs in fish cells.

Abundance, characteristics and surface degradation features of microplastics in beach sediments of five coastal areas in Tamil Nadu, India

This study undertook to investigate the occurrence of microplastics (MPs) in the high and low-tide sediments of five coastal areas in Tamil Nadu, India. The abundance of microplastics vary from 439 ± 172 to 119 ± 72 (HTL) and 179 ± 68 to 33 ± 30 (LTL) items kg^-1 of sediments. The MP polymers found in the study sites are Polyethylene (73.2%), polypropylene (13.8%), nylon (8.2%), polystyrene (2.8%) and polyester (2%). The weathered surfaces might act as high-capacity carriers and this was confirmed by SEM-EDAX. The results of an analysis of the textures of the sediments do not ascribe any influence on microplastic abundance. The recreation, religious and fishing activities are the major contributors to plastic pollution in these beaches, which is borne out by the high abundance of MPs in the study sites. A regular and permanent waste management system should be put in place for the protection of beaches.

Microplastic pollution in estuaries across a gradient of human impact

Microplastic (MP) pollution is an emerging issue in aquatic sciences. Little comparative information currently exists about the problem in coastal systems exposed to different levels of human impact. Here we report a year-long study on the abundance of MP in the water column of three estuaries on the east-coast of Australia. The estuaries are subject to different scales of human impact; the Clyde estuary has little human modification, the Bega estuary has a small township and single wastewater treatment works discharging to its waters, and the Hunter estuary which has multiple townships, multiple wastewater treatment plants, and heavy industry. MP abundance followed an expected pattern with the lowest abundance in the low-impact Clyde estuary (98 part. m³), moderate levels of MP in the moderately impacted Bega estuary (246 part. m³), and high MP abundance in the highly impacted Hunter estuary (1032 part. m³). The majority of particles were <200 μm and fragment-like rather than fiber-like. MP abundance was positively related to maximum antecedent rainfall in the Bega estuary, however there are no clear environmental factors that could explain MP variation in the other systems. MP were generally higher in summer and following freshwater inflow events. On the Hunter estuary MP abundance was at times as high as zooplankton abundance, and within the range of numbers reported in other highly impacted systems globally. The results confirm that higher levels of human impact lead to greater plastic pollution and highlight the need to examine aquatic ecosystems under a range of conditions in order to adequately characterize the extent of MP pollution in rivers and coastal systems.

Microplastics and associated PAHs in surface water from the Feilaixia Reservoir in the Beijiang River, China

Microplastics have been a prevalent and persistent contamination problem in the global aquatic environment. In particular, microplastics that can adsorb persistent organic pollutants (POPs) and therefore transfer these POPs to organisms in the aquatic environment have received much attention. In this study, an investigation of microplastics in the surface water of the Feilaixia Reservoir (Guangdong Province, China), which is an important part of people's daily lives in Guangdong Province was carried out, mainly focusing on the characteristics and spatial distribution of microplastics, as well as microplastics and their adsorded PAHs in the surface water of the Feilaixia Reservoir were investigated. The average abundance of microplastics in the surface water of the Feilaixia Reservoir was 0.56 ± 0.45 items/m³. Six kinds of polymers, including polyethylene (PE), polypropylene (PP), polystyrene (PS), expanded polystyrene (EPS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET), were identified, among which PP (52.31%) and PE (27.39%) were the major compositions. Four shapes of microplastics, i.e., foams, films, fragments and fibers were found, and films (37.78%) being the main shape. The most common typical size of the plastic particles ranged from 0.6 to 2 mm (41.36%). The total concentration of the sixteen PAHs carried on the EPS, PE and PP microplastics ranged from 282.4 to 427.3 ng/g; chrysene, benzo [ghi] perylene, and phenanthrene were abundant in the samples, at concentrations of 39.5-89.6 ng/g, 34.6-56.8 ng/g and 25.6-45.6 ng/g, respectively. Based on the ratios of the PAH isomers (Flut/Py < 1 and Phe/Ant >10), it was speculated that the source of the PAHs may be derived from the imperfect combustion of fossil fuels.

Spatial distribution and source identification of hydrophobic organic compounds (HOCs) on sedimentary microplastic in Hong Kong

The spatial distribution, composition and source of hydrophobic organic compounds (HOCs) including polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorinated pesticides (OCPs) of the sedimentary microplastics (0.25-5 mm) in Hong Kong were investigated. The concentration of ΣPAHs ranged between 70.8 and 1509 ng g^-1 with inter-site differences although the regional difference was insignificant, indicating localised pyrolytic and petrogenic input of PAHs. The concentration of ΣPCBs (13-1083 ng g^-1) varied with both study sites and regions with higher concentrations obtained in the western waters, possibly due to the input from Pearl River. Significantly higher concentrations of OCPs on eastern shores highlighted fishing and aquaculture activities in South China Sea a potential major source of OCPs. DDT and its metabolites (DDX, ranged from 1.96 to 626 ng g^-1) were the dominant forms of OCPs (45%-80%). Since most of the DDX existed as DDT, this suggested that there was a fresh input of DDT into the microplastics. As microplastics and HOCs cannot be removed effectively from the environment, reduction of potential ecotoxicological risks should rely on minimizing the use of plastics and HOCs.

The influence of microplastics on trophic interaction strengths and oviposition preferences of dipterans

Microplastic (MP) pollution continues to proliferate in freshwater, marine and terrestrial environments, but with their biotic implications remaining poorly understood. Biotic interactions such as predation can profoundly influence ecosystem structuring, stability and functioning. However, we currently lack quantitative understandings of how trophic interaction strengths and associated behaviours are influenced by MP pollution, and how transference of MPs between trophic levels relates to consumptive traits. We also lack understanding of key life-history effects of MPs, for example, reproductive strategies such as oviposition. The present study examines the predatory ability of non-biting midge larvae, Chaoborus flavicans, towards larvae of Culex pipiens mosquitoes when the latter are exposed to MPs, using a functional response (FR) approach. Transfer of MPs occurred from larval mosquitoes to larval midges via predation. Microplastics transfer was significantly positively related to predation rates. Predation by C. flavicans followed a Type II FR, with average maximum feeding rates of 6.2 mosquito larvae per hour. These and other FR parameters (attack rates and handling times) were not significantly influenced by the presence of MPs. Further, C. pipiens adults did not avoid ovipositing in habitats with high concentrations of MPs. We thus demonstrate that MPs can move readily through freshwater food webs via biotic processes such as predation, and that uptake correlates strongly with consumption rates. Further, as MPs do not deter adult mosquitoes from ovipositing, our experiments reveal high potential for MP exposure and transference through ecosystems.

Zebrafish can recognize microplastics as inedible materials: Quantitative evidence of ingestion behavior

This study investigated the ingestion behavior of zebrafish exposed to microplastic particles (MPs) at different concentrations, presented alone or in a mix with food particles. Zebrafish showed spitting behavior after ingesting micro-sized (247.5 μm) polyethylene particles (i.e., MPs), with prey-capture time increasing when food and MPs were supplied simultaneously. Fish were compelled to ingest MPs with food, and the accumulation percentage (ingested particles/supplied particles) was quantified as 0.5 to 9.4% with increasing food volume. However, the accumulation percentage was determined as 0.0 to 1.0% under exposure to MPs only, and as 3.8 to 4.3% at high MP concentrations when the food concentration was fixed. Overall, these results demonstrate that small freshwater organisms can recognize that MPs are not food items. Under laboratory conditions, zebrafish rarely discriminate between food and MPs when both are presented together, and the indiscriminate feeding behavior becomes clearer as more food is available.

Determination of the microplastics emission in the effluent of a municipal waste water treatment plant using Raman microspectroscopy

Samples from the secondary clarifier effluent of a waste water treatment plant (serving 98500 inhabitants) were analyzed to determine the microplastics (MP) emission. The samples were collected using a stainless steel centrifugal pump and filtered through a 10 μm stainless steel cartridge filter. Microplastics particles (MPPs) and microplastics fibers (MPFs) were recovered by chemical and physical sample purification. To remove natural organic matter, the samples were first subjected to oxidative treatment with H₂O₂ and NaClO. Inorganic materials were subsequently removed by density separation in ZnCl₂ (ρ = 1.9 g/cm³) using a centrifuge. Special centrifuge tubes were developed for this purpose. Sample analysis was performed on a Si filter by Raman micro-spectroscopy. Particles with a diameter (d_p) ≥ 10 μm were analyzed. The results were differentiated by dry and wet weather samples. On average, 5900 MPPs m^-3 were identified in the effluent on wet weather days compared to 3000 MPPs m^-3 on dry weather days. Most of the MPPs detected were in the 30 μm < d_p < 100 μm size range. The MPFs ranged between 100 μm and 1000 μm in length. While most of the MPFs were of PET origin, the MPPs consisted mainly of PET, PP, PE and PS.

Effect of salinity and humic acid on the aggregation and toxicity of polystyrene nanoplastics with different functional groups and charges

Studies regarding the effect of environmental factors on the environmental behaviour and potential toxicity of nanoplastics (NPs) are limited but important. In this study, four polystyrene NPs with different functional groups and charges (PS, PS-COOH, n-PSNH₂, p-PSNH₂) were selected to investigate the effect of humic acid (HA) and salinity on their aggregation behaviour and toxicity. The results showed that salinity significantly accelerated the aggregation of the four NPs, while HA mainly exerted a stabilizing effect on the three negatively charged NPs. In contrast, the positively charged p-PSNH₂ aggregated significantly at first but remained stable as HA concentration further increased. The joint effect mainly depended on their concentration ratio. The aggregation phenomena can be explained by the Derjaguin - Landau - Verwey - Overbeek (DLVO) theory. Also, the acute toxicity of NPs on Daphnia magna was affected by the surface charge of NPs, and the positively charged p-PSNH₂ showed the lowest toxicity among the selected NPs. Furthermore, the presence of HA effectively alleviated the toxicity of PS and p-PSNH₂, as the survival rates increased from 15% to 45%-95% and 100% respectively. Our results demonstrate that the surface properties of NPs significantly influence their aggregation and toxicity.

Interactive effects of polystyrene microplastics and roxithromycin on bioaccumulation and biochemical status in the freshwater fish red tilapia (Oreochromis niloticus)

There are hundreds of thousands metric tons of microplastics (MPs) present in aquatic environments. The MPs coexist with other pollutants in water bodies, such as pharmaceuticals, and may carry and transfer them into aquatic organisms, consequently causing unpredictable ecological risks. The purpose of the present study was to evaluate the effect of the presence of polystyrene microplastics (PS-MPs) on the distribution and bioaccumulation of roxithromycin (ROX) in freshwater fish red tilapia (Oreochromis niloticus) as well as their interactive biochemical effects in red tilapia. PS-MPs were found to enhance the bioaccumulation of ROX in fish tissues compared to ROX-alone exposure. In the treatment of PS-MPs (100 μg L^-1) combined with ROX (50 μg L^-1), the highest concentrations of ROX reached 39,672.9 ± 6311.4, 1767.9 ± 277.8, 2907.5 ± 225.0, and 4307.1 ± 186.5 μg kg^-1 in gut, gills, brain, and liver, respectively. Furthermore, compared to the ROX alone, the neurotoxicity caused by ROX was alleviated due to the presence of MPs after 14 d of exposure. The activities of cytochrome P450 (CYP) enzymes [7-ethoxyresorufin O-deethylase (EROD) and 7-benzyloxy-4-trifluoromethyl-coumarin O-dibenzyloxylase (BFCOD)] in fish livers exposed to all co-exposure treatments exhibited great variability compared to ROX alone after 14 d of exposure, suggesting that the presence of MPs may affect the metabolism of ROX in tilapia. Compared with ROX alone, the superoxide dismutase (SOD) activity increased significantly, and malondialdehyde (MDA) contents decreased in the co-exposure treatments, showing that oxidative damage in situations of co-exposure to MPs and ROX was mitigated in fish livers after 14 d of exposure. Collectively, the presence of MPs could affect the fate and toxicity of other organic pollutants in fish. The results emphasize the importance to study the interactions between MPs and other organic pollutants in aquatic environments.

Effects of ingested polystyrene microplastics on brine shrimp, Artemia parthenogenetica

Microplastics are a contaminant of emerging concern which enter the marine environment from a variety of sources. The ingestion and toxic effects of microplastics on marine life, especially for filter feeders, are a cause of concern in view of their ubiquitous nature and their similar size as food sources. To assess the toxic effects of microspheres ingested by brine shrimp larvae, we exposed Artemia parthenogenetica to 10 μm polystyrene microspheres at different concentrations. These concentrations were approximate to the extrapolated marine aquatic environmentally relevant concentrations. The lowest polystyrene concentrations at which ingestion was visualized in A. parthenogenetica were 12 ± 0.57 particles/mL (6.7 ± 0.32 μg/L) and 1.1 ± 0.16 particles/mL (0.61 ± 0.088 μg/L), respectively. There were no significant impacts on the survival, growth or development in A. parthenogenetica occurring over the 14-d exposure across a range of polystyrene nominal concentrations (1-1000 particles/mL or 0.55-550 μg/L). However, abnormal ultrastructures of intestinal epithelial cells were observed upon exposure to polystyrene microspheres, including fewer and disordered microvilli, an increased number of mitochondrion and the appearance of autophagosome. These phenomena could affect nutrition absorption and energy metabolism. Although no major acute or chronic toxicity effects on A. parthenogenetica were observed over 24-h or 14-d exposures, this study provides evidence that the ingestion of polystyrene microplastics at extrapolated environmentally relevant concentrations can be visualized through a microscope to be causing a series of responses in intestinal epithelial cells.

The interactive effects of stratospheric ozone depletion, UV radiation, and climate change on aquatic ecosystems

Summary of current knowledge about effects of UV radiation in inland and oceanic waters related to stratospheric ozone depletion and climate change.

Evaluating exposure of northern fur seals, Callorhinus ursinus, to microplastic pollution through fecal analysis

Environmental microplastics are widely documented in marine life and bioaccumulation may present risks to marine predators. Investigations of microplastics in marine mammals are increasing, though none have examined animals routinely consumed by humans. Here, we investigate microplastic exposure in the northern fur seal (Callorhinus ursinus), a species consumed by humans, using fecal material. We examined 44 feces (scat) at sites encompassing the seals' eastern Pacific range. Multiple contamination control measures were implemented, including field and laboratory controls. Fragments were the most common microplastic recovered, in 55% (24/44) of scat and no controls (range 1 to 86 fragments/scat, mean 16.6, sd 19.1). Microplastic fibers were recovered from 41% of scats (18/44), though some controls contained fibers confounding fiber results. Fecal analysis documented northern fur seal exposure to microplastics throughout their eastern Pacific range.

Distribution and potential health impacts of microplastics and microrubbers in air and street dusts from Asaluyeh County, Iran

While the distribution and effects of microplastics (MPs) have been extensively studied in aquatic systems, there exits little information on their occurrence in the terrestrial environment and their potential impacts on human health. In the present study, street dust and suspended dust were collected from the city and county of Asaluyeh, Iran. Samples were characterized by various microscopic techniques (fluorescence, polarized light, SEM) in order to quantify and classify MPs and microrubbers (MRs) in the urban and industrial environments that are potentially ingestible or inhalable by humans. In < 5-mm street dust retrieved from 15 sites, there were an average of 900 MPs and 250 MRs per 15 g of sample, with MPs exhibiting a range of colours and sizes (<100 to >1000 μm). Most street dust samples were dominated by spherical and film-like particles and MRs largely made up of different sizes of black fragments and fibrous particulates. Airborne dust collected daily over an eight-day period at two locations revealed the ubiquity of fibrous MPs of sizes ranging from about 2 μm to 100 μm and an abundance of about 1 per m^-3. These samples contained small MR fragments whose precise characteristics were more difficult to define. Based on the median concentrations in street dust, estimates of acute exposure through ingestion are about 5 and 15 MP d^-1 and 2 and 7 MR d^-1 for construction workers and young children, respectively. Quantities of inhalable particulates were more difficult to define but the potential toxicity of MPs and MRs taken in by this route was evaluated from assays performed using particulates isolated from street dusts in the presence of an artificial lung fluid. Both types of particle exhibited oxidative potential, with MPs displaying consumptions of different antioxidants that were comparable with corresponding values for a reference urban particulate dust but lower than those for London ambient particulate matter. Thus, MPs and MRs contribute towards the health impacts of urban and industrial dusts but their precise roles remain unclear and warrant further study.

Rainbow Trout Maintain Intestinal Transport and Barrier Functions Following Exposure to Polystyrene Microplastics

Ingestion has been proposed as a prominent exposure route for plastic debris in aquatic organisms, including fish. While the consequences of ingestion of large plastic litter are mostly understood, the impacts resulting from ingestion of microplastics (MPs) are largely unknown. We designed a study that aimed to assess impacts of MPs on fish intestinal physiology and examined integrity of extrinsic, physical and immunological barriers. Rainbow trout were exposed to polystyrene (PS) MPs (100-400 μm) via feed for a period of 4 weeks. Fish were fed four types of diets: control, diets containing virgin PS particles, or particles exposed to two different environmental matrices (sewage or harbor effluent). Extrinsic barrier disturbance in intestinal tissue was evaluated via histology. The paracellular permeability toward ions and molecules was examined using Ussing chambers and mRNA expression analysis of tight junction proteins. Active transport was monitored as transepithelial potential difference, short-circuits current and uptake rate of amino acid ³H-lysine. Immune status parameters were measured through mRNA expression level of cytokines, lysozyme activity, and hematological analysis of immune cells. We could not show that PS MPs induced inflammatory responses or acted as physical or chemical hazards upon ingestion. No measurable effects were exerted on fish intestinal permeability, active transport or electrophysiology.

Presence of microplastics in benthic and epibenthic organisms: Influence of habitat, feeding mode and trophic level

The exponential production and use of plastics has generated increasing environmental release over the past decades, and microplastics (MPs) have been reported across all the oceans. Field studies have documented the occurrence of MPs in several species, but important knowledge gaps still remain. In the present study, we characterized the distribution of MPs in ten sediment-dwelling and epibenthic species representative of different habitat, feeding modes and trophic levels within the inner Oslofjord (Oslo, Norway), an area subjected to moderate anthropogenic pressures. Analysed species included fish, bivalves, echinoderms, crustaceans and polychaetes. MPs were present in all the species with a frequency up to 65% of positive individuals for some species. In most cases, 1 or 2 MPs were found per individual, but some organisms contained up to 7 particles. A total of 8 polymer typologies were identified, with PE and PP being the most common according to our extraction protocol. MP sizes ranged from 41 μm to lines as long as 9 mm. Our results indicate that occurrence of MPs in analysed biota is not influenced by organism habitat or trophic level, while characteristics and typology of polymers might be significantly affected by feeding mode of organisms.

Occurrence, sources, human health impacts and mitigation of microplastic pollution

The presence and accumulation of plastic and microplastic (MP) debris in the natural environment is of increasing concern and has become the focus of attention for many researchers. Plastic debris is a prolific, long-lived pollutant that is highly resistant to environmental degradation, readily adheres hydrophobic persistent organic pollutants and is linked to morbidity and mortality in numerous aquatic organisms. The prevalence of MPs within the natural environment is a symptom of continuous and rapid growth in synthetic plastic production and mismanagement of plastic waste. Many terrestrial and marine-based processes, including domestic and industrial drainage, maritime activities agricultural runoff and wastewater treatment plants (WWTPs) effluent, contribute to MP pollution in aquatic environments. MPs have been identified in food consumed by human and in air samples, and exposure to MPs via ingestion or inhalation could lead to adverse human health effects. Regulations in many countries have already been established or will soon be implemented to reduce MPs in aquatic environments. This review focuses on the occurrence, sources, and transport of MPs in terrestrial and aquatic environments to highlight potential human health effects, and applicable regulations to mitigate impacts of MPs. This study also highlights the importance of personality traits and cognitive ability in reducing the entry of MPs into the environment.

Effects of nanoplastics on Mytilus galloprovincialis after individual and combined exposure with carbamazepine

Plastic pollution is a worldwide problem, highlighted by the fact that plastic materials degrade into nano-size particles (<100 nm), potentially becoming more bioavailable as well as a source of entry of other contaminants into organisms. The present study aimed to assess the effects of polystyrene nanoplastics (PS), individually or combined with carbamazepine (Cbz), on the Mediterranean mussel, Mytilus galloprovincialis. For this purpose, mussels were exposed for 96 h to a concentration range of PS (from 0.05 up to 50 mg L^-1), to Cbz (6.3 μg L^-1) alone and to the mixture of PS + Cbz (0.05 mg L^-1+ 6.3 μg L^-1). Molecular and biochemical biomarkers were assessed in the digestive glands, gills and haemolymph. The abundance of mRNA in the digestive glands and gills revealed significant alterations in the expression of genes associated with biotransformation, DNA repair, cell stress-response and innate immunity. Combined exposure of PS + Cbz induced significant downregulation in gene expression (e.g., hsp70) when compared to individual exposure. Total oxidant status increased in digestive glands after exposure to 0.5 mg L^-1 PS. Moreover, increased total antioxidant capacity and esterase activity were observed for PS 50 mg L^-1, in digestive glands and gills, respectively. The PS induced effects on neurotransmission, measured as inhibition of cholinesterase activity in haemolymph. Genotoxicity was found in haemocytes after exposure to PS, Cbz and their mixture. Moreover, lipid peroxidation was observed for 0.05 mg L^-1 PS exposure, showing that nanoplastics can induce oxidative damage. The present study demonstrated that PS, even at low concentrations, led to alterations on the assessed mussels' endpoints.

Microplastic in marine organism: Environmental and toxicological effects

Microplastics are tiny ubiquitous plastic particles present in marine environments. They are not an individual entity, but constitute a cocktail of polymers and additives that can absorb substances from the surrounding environment, including living substances, nutrients and marine pollutants. Given their small size (< 5 μm), microplastics can be ingested by a wide range of marine organisms with the potential to cause harms. Microplastics are a growing threat for marine biota and ecosystem. For organisms, the risks associated with microplastic ingestion are not only due to the material itself, but also to its ability to absorb and concentrate environmental contaminants in seawater and subsequently transfer them through food chains. Moreover, microplastics could influence ecological processes. Recently, plastic debris are recognized as emerging pollutants and represent a great risk for marine biodiversity worldwide. Here, we summarize the main effects of plastics and microplastics on some marine organisms and ecosystem.

Transcriptional effects of polyethylene microplastics ingestion in developing zebrafish (Danio rerio)

Over the last few decades, plastic waste has become an increasing environmental concern as it accumulates in every environment on our planet. Though traditionally seen as a macroscopic problem (i.e., large plastic debris), plastic pollution is also evident at smaller scales. Indeed, the intentional industrial production of small plastic particles and the physical degradation of larger plastic debris have overtime resulted in an increased environmental prevalence of smaller plastic particles, including microplastics. While the effects of these small polymers on marine biota have been an important research focus, recent global surveys indicate that our freshwater lakes and rivers are also plagued by microplastics. However, despite these discoveries we currently have a limited understanding of the impact these particles may have on freshwater animals, particularly on vertebrate species. Thus, the aim of the present study was to assess the impact of high concentrations of microplastics (5 and 20 mg.L^-1) on the early life stages in zebrafish, a model freshwater vertebrate model. To do this, we exposed embryonic and larval zebrafish to fluorescently labelled polyethylene microspheres for up to 14 days and assessed their microplastic content, growth, hatching and oxygen consumption rates. We then explored the molecular underpinnings of the microplastic response by RNA sequencing. Over the course of the exposure, we observed a consistent accumulation of microplastics in the gastrointestinal tract of the fish in a concentration dependent manner, but could not detect any detrimental effects of these particles on larval development, growth or metabolism. However, whole animal transcriptomics revealed that microplastics induced a transient and extensive change in larval gene expression within 48 h exposure, which largely disappeared by 14 days. However, as these transcriptional changes occurred during a critical period of larval development, we suggest that an evaluation of the potential long-term impact of these particles is warranted.

Ingested microplastic as a two-way transporter for PBDEs in Talitrus saltator

The presence and accumulation of plastic waste into the marine environment are well known environmental issues. Microplastics (MPs) end up in sea waters and, due to their hydrophobicity and high surface/volume ratio, POPs tend to sorb and accumulate to their surface. The supralittoral amphipod Talitrus saltator (T. saltator) was selected to study the role of MPs in the transfer of organic pollutants and to investigate if ingested MPs could either transfer contaminants to biota or clean it adsorbing pollutants taken from the diet. T. saltator is an established POPs (Persistent Organic Pollutants) biomonitor in coastal environments and it is able to swallow microplastics in natural condition. Two laboratory experiments were performed and T. saltator was exposed to a labelled polybrominated diphenyl ether (¹³C-labelled BDE-47) to investigate the opposite gradient role of MPs. X Ray Micro-CT (Micro-Computed Tomography) analyses were also performed on sandhopper samples to evaluate the uptake of MPs via digestive tract. The results showed that MPs ingestion could whether transfer and remove contaminants from T. saltator, indicating a partial balance among positive and negative effects. This study has underlined MP potential double role demonstrating that MP can act both as a carrier and scavenger for the bioaccumulation of organic pollutants (i.e. PBDEs), suggesting that chemicals leaching from MPs could have a limited impact to biota.

Dietary uptake, biodistribution, and depuration of microplastics in the freshwater diving beetle Cybister japonicus: Effects on predacious behavior

Microplastics (MPs) have adverse effects on aquatic organisms in marine environments; however, there is a lack of information on freshwater environments. This study investigated the dietary uptake, and biodistribution and depuration of MPs in the freshwater diving beetle Cybister japonicus (Coleoptera: Dytiscidae) after consumption of zebrafish (Danio rerio) exposed to MPs. The transfer of MPs in diving beetles after consumption of zebrafish was assessed to determine whether the presence of MPs affected diving beetle behavior and predation. We found that diving beetles that consumed MP-exposed fish had a significantly lower ingestion rate than the control. In addition, the trophic transfer rate of MPs was 13-18%. However, MPs were found only in the crop and proventriculus of the beetles, and all particles were depurated within 48 h, likely via regurgitation. As diving beetle is a top predator in freshwater ecosystems and could facilitate transfer from aquatic to terrestrial ecosystems via predation, its behavior towards indigestible MPs in its digestive organs (i.e., filtering and vomiting) could represent a meaningful phenomenon as a potential vector for MP transport. This is the first report of the trophic transfer of MPs from fish to dytiscid species, which helps clarify the effects and mechanisms of MPs in freshwater systems.

Microplastics in the intestinal tracts of East Asian finless porpoises (Neophocaena asiaeorientalis sunameri) from Yellow Sea and Bohai Sea of China

The direct evidences for the ingestion of microplastics by cetaceans, especially the cetaceans in Asian marine areas are limited. In this study, residue of microplastics in the intestinal tracts of East Asian finless porpoises (Neophocaena asiaeorientalis sunameri) was investigated. Microplastics were detected in all specimens, with mean abundance of 19.1 ± 7.2 items/individual. With respect to microplastics properties, fibers, blue items, and polypropylene were predominant in shapes, colors, and plastic materials, respectively. Trophic transfer and unintentional ingestion might be the potential pathways for microplastics ingested by finless porpoise. The specific intestinal structure might account for the predominance of fibers and the accumulation of microplastics at the beginning portion of intestines. This study indicates that cetaceans in Chinese marine areas also suffer from microplastics pollution. Further studies on the fate and ecological effects of microplastics should be conducted to reveal their potential risks to cetaceans.

Double trouble in the South Pacific subtropical gyre: Increased plastic ingestion by fish in the oceanic accumulation zone

Fish are an important food source for South Pacific (SP) island countries, yet there is little information on contamination of commercial marine fish species by plastic. The aim of our study was to perform a broad-scale assessment of plastic ingestion by fish common in the diet of SP inhabitants. We examined 932 specimens from 34 commercial fish species across four SP locations, and some of the prey they ingested, for the presence of marine plastics. Plastic was found in 33 species, with an average ingestion rate (IR) of 24.3 ± 1.4% and plastic load of 2.4 ± 0.2 particles per fish. Rapa Nui fish exhibited the greatest IR (50.0%), significantly greater than in other three locations. Rapa Nui is located within the SP subtropical gyre, where the concentration of marine plastics is high and food is limited. Plastic was also found in prey, which confirms the trophic transfer of microplastics.

Characterization, source, and retention of microplastic in sandy beaches and mangrove wetlands of the Qinzhou Bay, China

Severe microplastic pollution from anthropogenic activities in coastal zones presents an imminent risk to marine ecosystems. In this study, abundant microplastics (15-12,852 items kg^-1) with sizes ranging between 0.16 and 5.0 mm were extracted from 17 sediment samples collected in sandy beaches and mangrove wetlands of the Qinzhou Bay, Guangxi Province, Southwest China. Three types of microplastics (i.e. polystyrene, polypropylene, and polyethylene) were identified with Fourier transform infrared (FTIR) spectroscopy analysis. These detected microplastics were characterized by different colors (white, transparent, yellow, green, red, and blue) and shapes (fragment, fiber, and sphere). Microplastics were concentrated on supratidal beaches and wetlands outside of mangrove, and less abundant on intertidal beaches and inside of mangrove wetlands. Meanwhile, high microplastic concentrations were observed near mollusk farms. The spatial distribution and chemical speciation indicated that microplastics were derived from disintegration of large plastic debris (e.g., Styrofoam buoys used to support mollusk rafts) abandoned by aquaculture industry. Further, coastal vegetation (e.g. mangrove) could trap microplastic particles.

Ecotoxicological effects of polystyrene microbeads in a battery of marine organisms belonging to different trophic levels

The aim of this study was to detect ecotoxicological effects of 0.1 μm polystyrene microbeads in marine organisms belonging to different trophic levels. MP build up, lethal and sub-lethal responses were investigated in the bacterium Vibrio anguillarum (culturability), in the green microalga Dunaliella tertiolecta (growth inhibition), in the rotifer Brachionus plicatilis (mortality and swimming speed alteration) and in the sea urchin Paracentrotus lividus (immobility and swimming speed alteration) exposed to a wide range of microplastic (MP) concentrations (from 0.001 to 10 mg L^-1). Survival was not affected in all organisms up to 10 mg L^-1, while algal growth inhibition, rotifer and sea urchin larvae swimming behaviour alterations were observed after exposure to MPs. Ingestion was only observed in rotifers and it was directly correlated with sub-lethal effects. These results account for the ecotoxicological risk associated to the polystyrene microbeads, which are able to affect different endpoints in primary producers and consumers (rotifers and sea urchins) since no effects were observed in decomposers. This study points out the importance of using a battery of marine organisms belonging to different trophic levels by studying acute toxicity of MPs at low and high contamination levels, and investigating sub-lethal responses. Further investigations aimed at studying the transfer of these materials through the web are particularly recommended.

Microplastics disturb the anthozoan-algae symbiotic relationship

World production of plastic has dramatically increased from the 1950's and now it reaches approximately 311 million tons per year. The resulting accumulation of small plastic detritus less than 5 mm in size, termed "microplastics", has started threatening the life cycles of marine organisms. Here we show the first evidence that microplastics disturb the initiation of symbiotic relationships in anthozoan-algae symbiosis. We found in both the aposymbiotic sea-anemone Aiptasia sp. and the coral Favites chinensis that the infectivity of symbiotic algae into the host is severely suppressed by microspheres fed either directly or indirectly through microsphere-fed Artemia sp. Similar trends were seen when microplastics collected from commercial facewash were used instead of microspheres. Therefore, ongoing accumulation of microplastics in the ocean might disturb the healthy anthozoan-algae symbiotic relationships, which are cornerstones of the biologically enriched coral reef ecosystem.

Screening study of four environmentally relevant microplastic pollutants: Uptake and effects on Daphnia magna and Artemia franciscana

This study investigated four different environmentally relevant microplastic (MP) pollutants which were derived from two facial cleansers, a plastic bag and polyethylene textile fleece. The mean size range of the particles (according to number distribution) was 20-250 μm when measured as a powder and 0.02-200 μm in suspension. In all MP exposures, plastic particles were found inside the guts of D. magna and A. franciscana, but only in the case of daphnids a clear exponential correlation between MP uptake in the gut and the size of the MP was identified. Exposure tests in which the majority of the MP particles were below 100 μm in size also had higher numbers of daphnids displaying evidence of MP ingestion. As the average MP particle size increased, the percentage of daphnids which had MP in their gut decreased. Using a number distribution value to measure particle size when in a suspension is more experimentally relevant as it provides a more realistic particle size than when samples are measured as a powder. Generally, artemias had fewer MP particles in the gut, than the daphnids, which could be explained by their different food size preferences. No acute effects on D. magna were found, but the growth of A. franciscana was affected. We conclude that zooplankton crustacean can ingest various MPs but none of the exposures tested were highly acutely hazardous to the test species. In addition, no delayed lethal effects in a 24 h post-exposure period were found.

Impact of emerging, high-production-volume graphene-based materials on the bioavailability of benzo(a)pyrene to brine shrimp and fish liver cells

With increasing commercialization of high volume, two-dimensional carbon nanomaterials comes a greater likelihood of environmental release. In aquatic environments, black carbon binds contaminants like aromatic hydrocarbons, leading to changes in their uptake, bioavailability, and toxicity. Engineered carbon nanomaterials can also adsorb pollutants onto their carbon surfaces, and nanomaterial physicochemical properties can influence this contaminant interaction. We used 2D graphene nanoplatelets and isometric carbon black nanoparticles to evaluate the influence of particle morphology and surface properties on adsorption and bioavailability of benzo(a)pyrene, a model aromatic hydrocarbon, to brine shrimp (Artemia franciscana) and a fish liver cell line (PLHC-1). Acellular adsorption studies show that while high surface area carbon black (P90) was most effective at a given concentration, 2D graphene nanoplatelets (G550) adsorbed more benzo(a)pyrene than carbon black with comparable surface area (M120). In both biological models, co-exposure to nanomaterials lead to reduced bioavailability, with G550 graphene nanoplatelets cause a greater reduction in bioavailability or response than the M120 carbon black nanoparticles. However, on a mass basis the high surface area P90 carbon black was most effective. The trends in bioavailability and adsorption were consistent across all biological and acellular studies, demonstrating the biological relevance of these results in different models of aquatic organisms. While adsorption is limited by surface area, 2D graphene nanoplatelets adsorb more benzo(a)pyrene than carbon black nanoparticles of similar surface area and charge, demonstrating that both surface area and shape play important roles in the adsorption and bioavailability of benzo(a)pyrene to carbon nanomaterials.

A meta-analysis of the effects of exposure to microplastics on fish and aquatic invertebrates

Microplastics are present in aquatic ecosystems the world over and may influence the feeding, growth, reproduction, and survival of freshwater and marine biota; however, the extent and magnitude of potential effects of microplastics on aquatic organisms is poorly understood. In the current study, we conducted a meta-analysis of published literature to examine impacts of exposure to microplastics on consumption (and feeding), growth, reproduction, and survival of fish and aquatic invertebrates. While we did observe within-taxa negative effects for all four categories of responses, many of the effects summarized in our study were neutral, indicating that the effects of exposure to microplastics are highly variable across taxa. The most consistent effect was a reduction in consumption of natural prey when microplastics were present. For some taxa, negative effects on growth, reproduction and even survival were also evident. Organisms that serve as prey to larger predators, e.g., zooplankton, may be particularly susceptible to negative impacts of exposure to microplastic pollution, with potential for ramifications throughout the food web. Future work should focus on whether microplastics may be affecting aquatic organisms more subtly, e.g., by influencing exposure to contaminants and pathogens, or by acting at a molecular level.

Plastic pellets, meso- and microplastics on the coastline of Northern Crete: Distribution and organic pollution

Plastic pollution in the marine environment is one of the foremost environmental problems of our time, as it affects wildlife and human health both directly and indirectly through the effects of contaminants carried by microplastics. This study investigates the temporal and spatial distribution of plastic pellets and fragments in sandy beaches along the coastline of Northern Crete, during 2013. Their densities varied throughout the year in each beach, with highest densities during the summer and towards the upper parts of the beaches. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) sorbed on microplastics sampled from nine sandy beaches of Northern Crete was quantified using Gas chromatography - Ion Trap Mass Spectrometry (GC-ITMS). PAHs concentrations ranged from non-detectable levels to 1592 ng/g and fluctuated between sampling periods. Based on the observed patterns of meso- and microplastics distribution, practical guidelines are proposed to minimize the entrance of microplastics into the seawater wherefrom they are exceptionally difficult to collect, if mitigation actions are to be applied.

The effects of trophic transfer and environmental factors on microplastic uptake by plaice, Pleuronectes plastessa, and spider crab, Maja squinado

Microplastic pollution is apparent throughout the marine environment from deep ocean sediments to coastal habitats. Most of this is believed to originate on land, although marine activities, such as fishing and shipping, also contribute to the release and redistribution of microplastic. The relative importance of these maritime plastic sources, the manner by which they are distributed in the environment, and their effect on uptake by marine organisms are yet to be fully quantified. In this study, the relative impact of fishing activities on microplastic uptake by demersal fish and crustaceans was explored. Local fishing intensity, proximity to land and mean water velocity are compared to microplastic uptake in plaice, Pleuronectes platessa, and spider crab, Maja squinado, from the Celtic Sea. Observations were also made of microplastic contamination in ingested sand eels, Ammodytes tobianus, to establish a potential route of trophic transfer. This study is the first to identify microplastic contamination in spider crab and to document trophic transfer in the wild. Individuals were sampled from sites of varied fishing intensity in the Celtic Sea, and their stomach contents examined for the presence of microplastic. Contamination was observed in 50% of P. platessa, 42.4% of M. squinado, and 44.4% of A. tobianus. Locations of highest plastic abundance varied between P. platessa and M. squinado, indicating that different factors influence the uptake of microplastic in these two taxa. No significant link was observed between fishing effort and microplastic abundance; however, proximity to land was linked to increased abundance in M. squinado and Observations of whole prey demonstrate ongoing trophic transfer from A. tobianus to P. platessa. The lack of significant difference in microplastic abundance between predator and prey suggests that microplastic is not retained by P. platessa.

The implications of water extractable organic matter (WEOM) on the sorption of typical parent, alkyl and N/O/S-containing polycyclic aromatic hydrocarbons (PAHs) by microplastics

Microplastics sorption of persistent organic pollutants (POPs) was the core processes that cause negative effects to biota, and their influencing factors and related mechanisms are poorly understood. In this study, we explored the impacts of water extractable organic matter (WEOM), an important source of endogenous dissolved organic matter in mangrove sediment, on the sorption coefficients of typical parent, alkyl and N/O/S-containing polycyclic aromatic hydrocarbons (PAHs) by microplastics. The presence of L-WEOM (D) impeded the PAHs sorption as the coefficients (K_f) decreased to 10.17 (μg/kg)/(μg/L)ⁿ and to 8.39 (μg/kg)/(μg/L)ⁿ for fluorene (Flu) and 1-methyl-fluorene (1-M-Flu), respectively. The K_f exhibited good linear relationships with the aliphaticity of L-WEOM (p < 0.05) rather than the aromatic carbon/alkyl carbon content (p > 0.05). Under the presences of L-WEOM (D), (S) and (K), the lone pair electrons of N/O/S-containing PAHs was the dominant factor contributing to the obvious difference of the K_f values from the other groups. Moreover, the largest impact of L-WEOM (D) on the Flu sorption was in the case of PVC microplastics, while almost no effect was in the case of PS microplastics. The findings of our work may be helpful in improving our understanding of the role of WEOM on the sorption of PAHs to microplastics in the field mangrove sediment.

Investigating microplastic trophic transfer in marine top predators

Microplastics are highly bioavailable to marine organisms, either through direct ingestion, or indirectly by trophic transfer from contaminated prey. The latter has been observed for low-trophic level organisms in laboratory conditions, yet empirical evidence in high trophic-level taxa is lacking. In natura studies face difficulties when dealing with contamination and differentiating between directly and indirectly ingested microplastics. The ethical constraints of subjecting large organisms, such as marine mammals, to laboratory investigations hinder the resolution of these limitations. Here, these issues were resolved by analysing sub-samples of scat from captive grey seals (Halichoerus grypus) and whole digestive tracts of the wild-caught Atlantic mackerel (Scomber scombrus) they are fed upon. An enzymatic digestion protocol was employed to remove excess organic material and facilitate visual detection of synthetic particles without damaging them. Polymer type was confirmed using Fourier-Transform Infrared (FTIR) spectroscopy. Extensive contamination control measures were implemented throughout. Approximately half of scat subsamples (48%; n = 15) and a third of fish (32%; n = 10) contained 1-4 microplastics. Particles were mainly black, clear, red and blue in colour. Mean lengths were 1.5 mm and 2 mm in scats and fish respectively. Ethylene propylene was the most frequently detected polymer type in both. Our findings suggest trophic transfer represents an indirect, yet potentially major, pathway of microplastic ingestion for any species whose feeding ecology involves the consumption of whole prey, including humans.

Accumulation, tissue distribution, and biochemical effects of polystyrene microplastics in the freshwater fish red tilapia (Oreochromis niloticus)

While the presence of microplastics (MPs) in marine environments has been detected worldwide, the importance of MPs pollution in freshwater environments has also been emphasized in recent years. However, the body of knowledge regarding the biological effects of MPs on freshwater organisms is still much more limited than on marine organisms. The aim of the present study was to evaluate the accumulation and tissue distribution of MPs in the freshwater fish red tilapia (Oreochromis niloticus), as well as the biochemical effects of MPs on O. niloticus. During 14 days of exposure to 0.1 μm polystyrene-MPs at concentrations of 1, 10, and 100 μg L^-1, the MPs concentrations in various tissues of O. niloticus generally increased over time following the order gut > gills > liver ≈ brain. Moreover, the acetylcholinesterase (AChE) activity in the fish brain was inhibited by MPs exposure, with a maximum inhibition rate of 37.7%, suggesting the potential neurotoxicity of MPs to freshwater fish. The activities of cytochrome P450 (CYP) enzymes [7-ethoxyresorufin O-deethylase (EROD) and 7-benzyloxy-4-trifluoromethyl-coumarin O-dibenzyloxylase (BFCOD)] in the fish liver exhibited clear temporal variabilities, with significant decreases followed by elevations compared to the control. The alterations of the EROD and BFCOD activities indicate the potential involvement of CYP enzymes for the metabolism of MPs. The activity of antioxidative enzyme superoxide dismutase (SOD) in the liver was significantly induced throughout the exposure period, while the malondialdehyde (MDA) content did not vary with MPs exposure, suggesting that the antioxidative enzymatic system in O. niloticus could prevent oxidative damage. These results highlight the ingestion and accumulation of MPs in different tissues of freshwater fish, which lead to perturbations in fish biological systems and should be considered in environmental risk assessment.

Trophic transfer of microplastics and mixed contaminants in the marine food web and implications for human health

Plastic litter has become one of the most serious threats to the marine environment. Over 690 marine species have been impacted by plastic debris with small plastic particles being observed in the digestive tract of organisms from different trophic levels. The physical and chemical properties of microplastics facilitate the sorption of contaminants to the particle surface, serving as a vector of contaminants to organisms following ingestion. Bioaccumulation factors for higher trophic organisms and impacts on wider marine food webs remain unknown. The main objectives of this review were to discuss the factors influencing microplastic ingestion; describe the biological impacts of associated chemical contaminants; highlight evidence for the trophic transfer of microplastics and contaminants within marine food webs and outline the future research priorities to address potential human health concerns. Controlled laboratory studies looking at the effects of microplastics and contaminants on model organisms employ nominal concentrations and consequently have little relevance to the real environment. Few studies have attempted to track the fate of microplastics and mixed contaminants through a complex marine food web using environmentally relevant concentrations to identify the real level of risk. To our knowledge, there has been no attempt to understand the transfer of microplastics and associated contaminants from seafood to humans and the implications for human health. Research is needed to determine bioaccumulation factors for popular seafood items in order to identify the potential impacts on human health.

Adsorption of antibiotics on microplastics

Microplastics and antibiotics are two classes of emerging contaminants with proposed negative impacts to aqueous ecosystems. Adsorption of antibiotics on microplastics may result in their long-range transport and may cause compound combination effects. In this study, we investigated the adsorption of 5 antibiotics [sulfadiazine (SDZ), amoxicillin (AMX), tetracycline (TC), ciprofloxacin (CIP), and trimethoprim (TMP)] on 5 types of microplastics [polyethylene (PE), polystyrene (PS), polypropylene (PP), polyamide (PA), and polyvinyl chloride (PVC)] in the freshwater and seawater systems. Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD) analysis revealed that microplastics have different surface characterizes and various degrees of crystalline. Adsorption isotherms demonstrated that PA had the strongest adsorption capacity for antibiotics with distribution coefficient (K_d) values ranged from 7.36 ± 0.257 to 756 ± 48.0 L kg^-1 in the freshwater system, which can be attributed to its porous structure and hydrogen bonding. Relatively low adsorption capacity was observed on other four microplastics. The adsorption amounts of 5 antibiotics on PS, PE, PP, and PVC decreased in the order of CIP > AMX > TMP > SDZ > TC with K_f correlated positively with octanol-water partition coefficients (Log K_ow). Comparing to freshwater system, adsorption capacity in seawater decreased significantly and no adsorption was observed for CIP and AMX. Our results indicated that commonly observed polyamide particles can serve as a carrier of antibiotics in the aquatic environment.

Comparison of six digestion methods on fluorescent intensity and morphology of the fluorescent polystyrene beads

Effect of digestion methods on fluorescence intensity of fluorescent polystyrene (PS) beads was poorly understood, which may affect the accuracy of toxicity test of the fluorescent PS beads exposed to marine organisms. Therefore, six digestion approaches were compared on fluorescence intensities and properties of three commercial fluorescent PS beads. Among all the protocols, the digestion using KOH (10% w/v, 60 °C) (KOH-digestion) had no effect on the fluorescence intensity, morphology and composition of the three fluorescent PS beads. Moreover, the extraction efficiency ≥ 95.3 ± 0.2% of fluorescent PS beads in Daphnia magna and zebrafish, confirming its feasibility in fluorescent PS beads quantitative analysis. However, the fluorescence intensities of fluorescent PS beads digested by other five protocols were significantly decreased, as well as the change of morphology and composition on fluorescent PS beads. Overall, the KOH-digestion is an optimal protocol for extracting fluorescent PS beads in biological samples.

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).

Ecotoxicological effects of microplastics on biota: a review

The ubiquitous presence of microplastics in the environment has drawn the attention of ecotoxicologists on its safety and toxicity. Sources of microplastics in the environment include disintegration of larger plastic items (secondary microplastics), personal care products like liquid soap, exfoliating scrubbers, and cleaning supplies etc. Indiscriminate usage of plastics and its poor waste disposal management pose serious concern on ecosystem quality at global level. The present review focused on the ecological impact of microplastics on biota at different trophic levels, its uptake, accumulation, and excretion etc., and its plausible mechanistic toxicity with risk assessment approaches. Existing scientific evidence shows that microplastics exposure triggers a wide variety of toxic insult from feeding disruption to reproductive performance, physical ingestion, disturbances in energy metabolism, changes in liver physiology, synergistic and/ or antagonistic action of other hydrophobic organic contaminants etc. from lower to higher trophics. Thus, microplastic accumulation and its associated adverse effects make it mandatory to go in for risk assessment and legislative action. Subsequent research priorities, agenda, and key issues to be addressed are also acknowledged in the present review.

Virgin microplastics are not causing imminent harm to fish after dietary exposure

Among aquatic organisms, fish are particularly susceptible to ingesting microplastic particles due to their attractive coloration, buoyancy, and resemblance to food. However, in previous experimental setups, fish were usually exposed to unrealistically high concentrations of microplastics, or the microplastics were deliberately contaminated with persistent organic chemicals; also, in many experiments, the fish were exposed only during the larval stages. The present study investigated the effects of virgin microplastics in gilt-head seabream (Sparus aurata) after 45 days' exposure at 0.1 g kg^-1 bodyweight day^-1 to 6 common types of microplastics. The overall growth, biochemical analyses of the blood, histopathology, and the potential of the microplastics to accumulate in gastrointestinal organs or translocate to the liver and muscles were monitored and recorded. The results revealed that ingestion of virgin microplastics does not cause imminent harm to the adult gilt-head seabream during 45 days of exposure and an additional 30 days of depuration. The retention of virgin microplastics in the gastrointestinal tract was fairly low, indicating effective elimination of microplastics from the body of the fish and no significant accumulation after successive meals. Therefore, both the short- and the long-term retention potential of microplastics in the gastrointestinal tract of fish is close to zero. However, some large particles remained trapped in the liver, and 5.3% of all the livers analyzed contained at least one microplastic particle. In conclusion, the dietary exposure of S. aurata to 6 common types of virgin microplastics did not induce stress, alter the growth rate, cause pathology, or cause the microplastics to accumulate in the gastrointestinal tract of the fish.

Comparative live-imaging of in vivo EROD (ethoxyresorufin-O-deethylase) induction in zebrafish (Danio rerio) and fathead minnow (Pimephales promelas) embryos after exposure to PAHs and river sediment extracts

The measurement of EROD (ethoxyresorufin-O-deethylase) activity to determine the induction of CYP1A after exposure to dioxin-like substances is a well-established biomarker in fish. For reasons of animal welfare and implementations of new chemicals regulations (REACh), in vivo methods using zebrafish (Danio rerio) and medaka (Oryzias latipes) embryos have recently been developed to quantify CYP1A induction, which is visualized as mean intensity of the autofluorescent resorufin formed in living anaesthetized embryos. In the present study, concentration ranges of three PAHs (benzo[a]pyrene, β-naphthoflavone, benzo[k]fluoranthene) as examples of known CYP1A inducers as well as extracts of two well-characterized sediment samples of the lower Neckar river (Southern Germany) were used to determine the suitability of the fathead minnow (Pimephales promelas) embryo for the in vivo EROD assay. Data for zebrafish embryos were generated for comparison. Fathead minnow embryos were principally suitable to show in vivo EROD induction via live-imaging. Since in fathead minnow embryos both signal area and fluorescence intensities are lower than in zebrafish embryos, the induction potentials of the three model PAHs and the environmental samples proved to be species-dependent. Among the three PAHs tested, benzo[k]fluoranthene lead to the strongest EROD signal followed by β-naphthoflavone and benzo[a]pyrene in comparison to the positive control. Whereas benzo[k]fluoranthene and β-naphthoflavone showed a dose-response relationship for the EROD induction, benzo[a]pyrene failed to induce a significant signal in fathead minnow embryos. If compared to the model PAHs, the extracts of both sediments from the lower Neckar River induced stronger EROD signals in both fathead minnow and zebrafish embryos. Observations thus documented fathead minnow embryos to be as suitable for biomonitoring purposes as are zebrafish embryos.

Microplastic accumulation patterns and transfer of benzo[a]pyrene to adult zebrafish (Danio rerio) gills and zebrafish embryos

Since only a few studies have investigated effects of microplastics (MPs) by routes other than ingestion, this study was designed to analyze the accumulation patterns and transfer of toxic substances associated with microplastic exposure by simple attachment to (1) adult zebrafish (Danio rerio) gills and (2) zebrafish embryos. Two sizes of fluorescently labelled polymers (1-5 and 10-20 μm) loaded with the model polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BaP) were used to analyze fate, accumulation and transfer of microplastic-associated persistent organic pollutants (POPs) on gills and embryos. Results indicate that microplastics did not permanently accumulate at high amounts in adult zebrafish gills after 6 nor 24 h of incubation: Most particles only superficially adhered to the mucus layer on the filaments, which is constantly being excreted. In contrast, the smaller and heavier MPs (1-5 μm) accumulated in high numbers on the surface of zebrafish egg chorions. In both exposure scenarios, transfer of BaP could be visualized with fluorescence microscopy: A prominent BaP signal was visible both in gill filaments and arches after 6 and 24 h incubation and in zebrafish embryos after exposure to BaP-spiked microplastics. Furthermore, the gill EROD (Ethoxyresorufin-O-deethylase) assay showed a clear trend to CYP 1A (Cytochrom P450 1 A) induction via exposure to BaP-spiked microplastics. However, BaP from spiked microplastics did not reach sufficiently high concentrations to be able to induce morphological effects in the fish embryo toxicity test (FET). In contrast, control exposure to waterborne BaP did induce effects in the FET. As a conclusion, microplastics can also transfer POPs not only via ingestion, but also by simple attachment to epithelia or via the water column. However, further studies are needed to clarify if these interactions are of environmental concern relative to waterborne exposure to toxic substances.

In vitro effects of virgin microplastics on fish head-kidney leucocyte activities

Microplastics are well-documented pollutants in the marine environment that result from production or fragmentation of larger plastic items. The knowledge about the direct effects of microplastics on immunity, including fish, is still very limited. We investigated the in vitro effects of microplastics [polyvinylchloride (PVC) and polyethylene (PE)] on gilthead seabream (Sparus aurata) and European sea bass (Dicentrarchus labrax) head-kidney leucocytes (HKLs). After 1 and 24 h of exposure of HKLs with 0 (control), 1, 10 and 100 mg mL^-1 MPs in a rotatory system, cell viability, innate immune parameters (phagocytic, respiratory burst and peroxidase activities) and the expression of genes related to inflammation (il1b), oxidative stress (nrf2, prdx3), metabolism of xenobiotics (cyp1a1, mta) and cell apoptosis (casp3) were studied. Microplastics failed to affect the cell viability of HKLs. In addition, they provoke very few significant effects on the main cellular innate immune activities, as decrease on phagocytosis or increase in the respiratory burst of HKLs with the highest dose of microplastics tested. Furthermore, microplastics failed to affect the expression of the selected genes on sea bass or seabream, except the nrf2 which was up-regulated in seabream HKLs incubated with the highest doses. Present results seem to suggest that continue exposure of fish to PVC or PE microplastics could impair fish immune parameters probably due to the oxidative stress produced in the fish leucocytes.

Uptake and Depuration Kinetics Influence Microplastic Bioaccumulation and Toxicity in Antarctic Krill ( Euphausia superba)

The discarding of plastic products has led to the ubiquitous occurrence of microplastic particles in the marine environment. The uptake and depuration kinetics of ingested microplastics for many marine species still remain unknown despite its importance for understanding bioaccumulation potential to higher trophic level consumers. In this study, Antarctic krill ( Euphausia superba) were exposed to polyethylene microplastics to quantify acute toxicity and ingestion kinetics, providing insight into the bioaccumulation potential of microplastics at the first-order consumer level. In the 10 day acute toxicity assay, no mortality or dose-dependent weight loss occurred in exposed krill, at any of the exposure concentrations (0, 10, 20, 40, or 80% plastic diet). Krill exposed to a 20% plastic diet for 24 h displayed fast uptake (22 ng mg^-1 h^-1) and depuration (0.22 h^-1) rates, but plastic uptake did not reach steady state. Efficient elimination also resulted in no bioaccumulation over an extended 25 day assay, with most individuals completely eliminating their microplastic burden in less than 5 days post exposure. Our results support recent findings of limited acute toxicity of ingested microplastics at this trophic level, and suggest sublethal chronic end points should be the focus of further ecotoxicological investigation.