The deep sea is a major sink for microplastic debris

Seasonal patterns of microplastics in surface sediments of a Mediterranean lagoon heavily impacted by human activities (Bizerte lagoon, Northern Tunisia)

In this paper, we investigated seasonal variations in concentrations of microplastics (MPs) in surface sediments of a lagoon heavily impacted by human activities, located in northern Tunisia (the Bizerte lagoon, southern Mediterranean Sea). Analyses of 112 sediment samples collected from 28 stations between May 2019 and February 2020 revealed significant seasonal variation in concentrations of total MPs, with the highest levels recorded in August 2019 (109.6 ± 59.8 items kg^-1 DS (dry sediment)) and the lowest in February 2020 (33.2 ± 22.0 items kg^-1 DS). In terms of polymer types, polyethylene particles were the most abundant throughout the year, followed by polypropylene, polyvinyl chloride, and polyethylene terephthalate. Spatial variations in total MP concentrations were found to depend on several environmental factors, including proximity to the coastline, level of anthropogenic pressure, location inside the lagoon, and presence/absence of vegetation. The upper 5-cm surface sediment layer of the lagoon was found to contain ~ 9.96 × 10¹⁰ MP particles, equal to ~ 248.97 t of plastic. Similar patterns of microplastic composition and structure were found throughout the year, revealing the same plastic pollution hotspots during all seasons. This indicates that sources of plastic pollution are land-based and originate from coastal urban, industrial, and agricultural areas, as well as from major freshwater streams. The findings of the present work can help to develop an efficient environmental management plan aiming to reduce and/or stop the spread of plastic pollution and its impacts on the socially and economically important ecosystem of the Bizerte lagoon.

Microplastics in ASEAN region countries: A review on current status and perspectives

A literature assessment was conducted to determine the current state of microplastics research in ASEAN countries focusing on 1) microplastics in water, sediment, and water organisms; 2) microplastics' sources and dispersion; and 3) microplastics' environmental consequences, including human toxicity. ASEAN countries contributed only about 5 % of the global scholarly papers on microplastics, with Indonesia contributing the most followed by Malaysia and Thailand. The lack of standard harmonized sampling and processing methodologies made comparisons between research difficult. ASEAN contributes the most to plastic trash ending up in the ocean, indicating a need for more work in this region to prevent plastic pollution. Microplastics are found in every environmental compartment; however, their distribution and environmental consequences have not been sufficiently investigated. There are very few studies on microplastics in the human blood system as well as respiratory organs like the lungs, indicating that more research is needed.

Implications for the seafood industry, consumers and the environment arising from contamination of shellfish with pharmaceuticals, plastics and potentially toxic elements: A case study from Irish waters with a global orientation

Shellfish are a rich source of minerals, B-vitamins and omega-3 to the human diet. The global population is expected to reach 9.6 billion people by 2050 where there will be increased demand for shellfish and for sustained improvements in harvesting. The production of most consumed species of shellfish is sea-based and are thus susceptible to in situ environmental conditions and water quality. Population growth has contributed to expansion of urbanization and the generation of effluent and waste that reaches aquatic environments, potentially contaminating seafood by exposure to non-treated effluents or inappropriately discarded waste. Environmental contaminants as microplastics (MP), pharmaceuticals (PHAR) and potentially toxic contaminants (PTE) are being identified in all trophic levels and are a current threat to both shellfish and consumer safety. Immunotoxicity, genotoxicity, fertility reduction, mortality and bioaccumulation of PTE are representative examples of the variety of effects already established in contaminated shellfish. In humans, the consumption of contaminated shellfish can lead to neurological and developmental effects, reproductive and gastrointestinal disorders and in extreme cases, death. This timely review provides insights into the presence of MP, PHAR and PTE in shellfish, and estimate the daily intake and hazard quotient for consumption behaviours. Alternatives approaches for seafood depuration that encompass risk reduction are addressed, to reflect state of the art knowledge from a Republic of Ireland perspective. Review of best-published literature revealed that MP, PHAR and PTE contaminants were detected in commercialised species of shellfish, such as Crassostrea and Mytilus. The ability to accumulate these contaminants by shellfish due to feeding characteristics is attested by extensive in vitro studies. However, there is lack of knowledge surrounding the distribution of these contaminants in the aquatic environment their interactions with humans. Preventive approaches including risk assessment are necessary to safeguard the shellfish industry and the consumer.

Effects of organic matter on interaction forces between polystyrene microplastics: An experimental study

The aggregation and deposition processes of marine microplastics are extremely important in marine ecosystems. The main effect of these two physical processes is the transfer of surface microplastics to the deep sea, and the underlying kinetics can be significantly affected by the organic matter in the ocean. The morphology of and interaction force on 20-μm polystyrene microplastics in the presence of organic matter were studied by using environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM), respectively. Experiments were performed using organic matter of various concentrations, and the results showed that humic acid formed a translucent organic film around polystyrene microplastics. With increasing total organic content (TOC), the average overall size of the microplastic coated with biofilm increased up to 11 % (at a TOC of 50 mg/L) and then decreased slightly. The biofilm formed by humic acid decreases the repulsion force between two particles and thus could promote the aggregation process significantly. A modified formulation of eXtended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, describing the interaction force of microplastics with the influences of biofilms was proposed based on the measured results.

Testing citizen science as a tool for monitoring surface water microplastics

The use of citizen science in the collection of surface water marine microplastics (MP) samples with manta trawl was tested in the Baltic Sea, where the collection of surface water samples is often hampered by environmental conditions. Sampling was carried out at 7 locations around the Baltic Sea with a custom-made manta trawl which was operated onboard a sailing boat. The total concentrations of ≥ 0.3 mm MP in the samples ranged from 0.45 to 1.98 MP m^-3. Based on the results and experiences from this study, citizen science could be introduced into the toolbox of monitoring large MP. When the common basic constraints of surface water sampling within a regional sea are defined and agreed upon, citizen science could be used for strengthening the power of assessments on the state of the marine environment by increasing the spatial coverage of the monitored area.

Microplastics in aquatic systems, a comprehensive review: origination, accumulation, impact, and removal technologies

Although the discovery of plastic in the last century has brought enormous benefits to daily activities, it must be said that its use produces countless environmental problems that are difficult to solve. The indiscriminate use and the increase in industrial production of cleaning, cosmetic, packaging, fertilizer, automotive, construction and pharmaceutical products have introduced tons of plastics and microplastics into the environment. The latter are of greatest concern due to their size and their omnipresence in the various environmental sectors. Today, they represent a contaminant of increasing ecotoxicological interest especially in aquatic environments due to their high stability and diffusion. In this regard, this critical review aims to describe the different sources of microplastics, emphasizing their effects in aquatic ecosystems and the danger to the health of living beings, while examining, at the same time, those few modelling studies conducted to estimate the future impact of plastic towards the marine ecosystem. Furthermore, this review summarizes the latest scientific advances related to removal techniques, evaluating their advantages and disadvantages. The final purpose is to highlight the great environmental problem that we are going to face in the coming decades, and the need to develop appropriate strategies to invert the current scenario as well as better performing removal techniques to minimize the environmental impacts of microplastics.

Assessment of metals associated with virgin pre-production and freshwater microplastics collected by an Italian river

Recently, microplastics (MPs) have been detected in almost all environmental matrices (water, soil, air, biota). Their presence is of concern due to high environmental persistence and their ability to release or bind pollutants. In light of this, the present work aimed to quantify a poorly studied pollutant category associated with MPs: metals. This analysis was conducted on virgin MPs, used as raw materials in the plastics' production process and on environmental MPs taken from the Ofanto river in Southern Italy. The MP samples were initially grouped for colour, shape and ageing and following mineralised by a microwave digestor. The metals and metalloids Pb, Ba, Sb, Sn, Cd, Mo, Se, Zn, Cu, Ni, Co, Cr, Fe, Mn, Ti, Al, V, Ca, K, Mg, Na were subsequently quantified with ICP-MS. All the analysed elements were found on both types of samples (virgin and environmental MPs), with higher concentrations detected on environmental samples (above 14,400 μg/g^-1) rather than on pristine ones (above 5000 μg/g^-1). Many of these inorganic compounds are probably adsorbed by the surrounding environment, and others are intentionally added during the plastic production process to improve their properties (e.g. additives). Noticeable differences were detected concerning the metal's distribution and amount observed in the two types of MP particles analysed. Moreover, trace element concentrations were also linked to the colour and shape of the environmental particles analysed. Most abundant levels of metals were quantified on aged black fragments, followed by coloured and transparent fragments and black pellets. Our concluding remarks underline the role of MPs as a vehicle for the transport of metals, with significant differences between the high abundance of these pollutants examined in our particles collected in a freshwater environment and the significantly lower concentrations revealed previously in marine MPs.

Variance and precision of microplastic sampling in urban rivers

Microplastics (MPs), plastic particles <5 mm in diameter, have become an emerging ubiquitous concern for the environment. Rivers are the primary pathways that transport MPs from the land to the ocean; however, standardized methodologies for in-situ sampling in freshwater environments remain undefined. Notably, uncertainties in MP sampling methods lead to errors in estimating MP discharge through rivers. In the present study, the inter-sample variance of plankton net-obtained MP concentrations for two urban rivers in Japan was investigated. Numerical concentrations, expressed in particles·m^-3, revealed that variance s² was proportional to the mean m of replicated estimates of numerical concentrations. A derived statistical model suggested that river MPs disperse according to purely random processes; that is, Poisson point processes. Accordingly, a method was established to project the "precision," the ratio of the standard error to m, of numerical concentrations based on the number of net sampling repetitions. It was found that the mean of two replicates maintained sufficient precision of <30% for conditions with high concentrations of ≥3 particles·m^-3. Projected precisions under different levels of MP concentrations are also presented to help design future field campaigns.

Assessment of the health status of the European anchovy (Engraulis encrasicolus) in the NW Mediterranean Sea from an interdisciplinary approach and implications for food safety

The European anchovy (Engraulis encrasicolus) is a small pelagic fish with an outstanding commercial value supporting important fisheries and is a key component of pelagic ecosystems in the Mediterranean Sea. Progressive reductions in the population size of this species has been observed in the Mediterranean Sea during recent decades, accompanied by a decline in the body condition, as well as the size/age of maturation. Nonetheless, the health status has not been yet assessed using a holistic approach. Herein, we analyse the health status of the European anchovy, integrating distinct indicators from fish condition, enzymatic biomarkers, presence of tissue alterations, and parasite descriptors. In addition, we analyse the presence of anthropogenic items (AIs) in the digestive tract of fish and their potential impact on health status. Additionally, we assess the differences between current AIs values and those recorded over 12 years ago. None of the health indicators studied provided evidence of relevant pathologic conditions affecting this fish species in the studied area. However, changes in the pattern of liver parenchyma were found. Compared with anchovy populations from other distribution areas, no zoonotic parasites were recorded in this study, demonstrating a reduced risks associated with foodborne transmission to humans. AIs, such as fibres and plastic particles, were found in the digestive tract of half of the fish analysed. A significant increase was detected in AIs prevalence between 2007 (40 %) and 2019 (70 %), alongside differences in the abundance and typology of the AIs, though this does not seem to have impacted fish health yet. Therefore, our work underscores the importance of implementing a regular program to monitor the health status of this key species to better understand population dynamics and their drivers.

Presence of microplastics in six bivalve species (Mollusca, Bivalvia) commercially exploited at the Pacific coast of Costa Rica, Central America

Microplastic pollution represents a serious threat to coastal marine systems. We evaluated the presence of microplastics (MPs) in 168 specimens of six commercially exploited bivalve species in the Golfo de Nicoya, Costa Rica. MPs were present in 100 % of the specimens of Leukoma asperrima and L. ecuadoriana, 74 % of Mytella strigata, 82 % of M. guyanensis, 84 % of Asthenometis asthenodon, and 82 % of Tagelus affinis. When considering all specimens, we found on average 4.8 ± 8.0 pieces per individual and 2.1 ± 3.3 items g^-1 of wet tissue. There were significant differences between species with L. asperrima and L. ecuadoriana containing the highest number of pieces. Fibers and particles comprised 92 % and 8 %, respectively. This is the first study from the Central America's Pacific region showing the presence of MPs in bivalve species.

First evidence of microplastics isolated in European citizens' lower airway

Microplastics (MPs) have been detected in all environmental locations, including the atmosphere. However, few studies have investigated the presence of airborne MPs in the human respiratory system. Our research purpose was to investigate these pollutants in the lower human airways of 44 adult European citizens, using bronchoalveolar lavage fluid (BALF) collection as a minimally invasive method, that enables the detection of these pollutants in living patients. We studied the relationship between the patients' life habits and physiological parameters, based on background information and medical and occupational history, and the concentration of MPs isolated from their respiratory systems. Our results indicate that most MPs were in the form of microfibers (MFs) (97.06%), with an average concentration of 9.18 ± 2.45 items/100 mL BALF, and only 5.88% (0.57 ± 0.27 items/100 mL BALF) were particulate MPs, without a significant relationship with environmental, physiological, or clinical factors. The average size was 1.73 ± 0.15 mm, with the longest dimension (9.96 mm) corresponding to a polyacrylic fiber. Taken together, the results demonstrated the occurrence of MPs in the lower human airway, although more studies are necessary to elucidate the negative effects these pollutants could induce in the human respiratory system and its associated diseases.

Distribution pattern and influencing factors for the microplastics in continental shelf, slope, and deep-sea surface sediments from the South China Sea

Marine microplastic pollution has become a major global concern in recent years and the fate of microplastics in the ocean is a hot issue of research. We investigated microplastic pollution in surface sediments in the northern South China Sea to explore its distribution characteristics and influencing factors across the continental shelf, continental slope, and deep-sea environments. It was found that the microplastic abundance of surface sediments was 130.56 ± 40.48 items/kg. The average abundance of microplastics in all three topographic areas gradually decreased with increasing distance offshore. However, the differences in microplastic diversity indices between the three areas were not significant and were higher than those in other seas of the world, indicating that the waters of the northern South China Sea are rich in microplastics from complex sources, with more pollution input channels. In the continental shelf, fibrous and low density microplastics accounted for the largest amount, with a low degree of microplastic aging, and were mostly transported by suspended-load. These microplastics were mainly influenced by human activities. In the deep sea, microplastics with higher density were the most abundant and the number of fibrous microplastics was fewer, while the average size was larger, mainly influenced by the bottom currents. These microplastics underwent long-term bedload transport. In the continental slope, the main factors affecting the distribution of microplastics were more complex. In addition to pollution by human activities, the slope also receives microplastic materials carried by bottom currents; therefore, the composition of microplastics in the slope combines those characteristics of microplastics in both the continental shelf and deep-sea areas. The findings of this study indicate that the South China Sea is affected by complex pollution sources under the dual effects of human activities and natural conditions; in particular, the pollution situation in the deep-sea area needs extensive attention.

Comparison of pre-treatment methods and heavy density liquids to optimize microplastic extraction from natural marine sediments

The ubiquitous occurrence of anthropogenic particles, including microplastics in the marine environment, has, over the last years, gained worldwide attention. As a result, many methods have been developed to estimate the amount and type of microplastics in the marine environment. However, there are still no standardized protocols for how different marine matrices should be sampled or how to extract and identify these particles, making meaningful data comparison hard. Buoyant microplastics are influenced by winds and currents, and concentrations could hence be expected to be highly variable over time. However, since both high density and most of the initially buoyant microplastics are known to eventually sink and settle on the seafloor, marine sediments are proposed as a suitable matrix for microplastics monitoring. Several principles, apparatuses, and protocols for extracting microplastics from marine sediments have been presented, but extensive comparison of the different steps in the protocols using real environmental samples is lacking. Thus, in this study, different pre-treatment and subsequent density separation protocols for extraction of microplastics from replicate samples of marine sediment were compared. Two pre-treatment methods, one using inorganic chemicals (NaClO + KOH + Na₄P₂O₇) and one using porcine pancreatic enzymes, as well as one with no pre-treatment of the sediment, were compared in combination with two commonly used high-density saline solutions used for density separation, sodium chloride (NaCl) and zinc chloride (ZnCl₂). Both pre-treatment methods effectively removed organic matter, and both saline solutions extracted lighter plastic particles such as polyethylene (PE) and polypropylene (PP). The most efficient combination, chemical pre-treatment and density separation with ZnCl₂, was found to extract > 15 times more particles (≥ 100 µm) from the sediment than other treatment combinations, which could largely be explained by the high presence and efficient extraction of PVC particles.

Microplastic contamination in the sediments of Qarasu estuary in Gorgan Bay, south-east of Caspian Sea, Iran

Given the important ecological role of estuaries and implications of microplastics (MPs) in ecosystems, we assessed the occurrence, abundance, size, and polymer types of MPs present in the sediments of the Qarasu estuary in 2019. MPs were extracted from sediments by density separation, after which they were detected under a stereomicroscope and considered according to shape, size and color. Identification was implemented using Fourier-Transform Infrared Spectroscopy (FT-IR). The abundance and size of MPs in the samples ranged between 40 and 460 particles/kg and 200-5000 μm, respectively. The dominant shape of MPs was fiber (72%), followed by fragment (26%) and film (2%). Black and white were the most abundant colors with 48% and 29%, respectively. In total, 4 MPs polymers including polypropylene (33%), polyethylene (24%), polyamide (21%), and polystyrene (14%) were identified. Results from PCA showed that stations with a high abundance of microplastics had a significant correlation with the amount of clay.

Interactions of microplastics with organic, inorganic and bio-pollutants and the ecotoxicological effects on terrestrial and aquatic organisms

As emerging contaminants, microplastics (MPs) have attracted global attention. They are a potential risk to organisms, ecosystems and human health. MPs are characterized by small particle sizes, weak photodegradability, and are good environmental carriers. They can physically adsorb or chemically react with organic, inorganic and bio-pollutants to generate complex binary pollutants or change the environmental behaviors of these pollutants. We systematically reviewed the following aspects of MPs: (i) Adsorption of heavy metals and organic pollutants by MPs and the key environmental factors affecting adsorption behaviors; (ii) Enrichment and release of antibiotic resistance genes (ARGs) on MPs and the effects of MPs on ARG migration in the environment; (iii) Formation of "plastisphere" and interactions between MPs and microorganisms; (iv) Ecotoxicological effects of MPs and their co-exposures with other pollutants. Finally, scientific knowledge gaps and future research areas on MPs are summarized, including standardization of study methodologies, ecological effects and human health risks of MPs and their combination with other pollutants.

Distribution characteristics of microplastics in surface and subsurface Antarctic seawater

Microplastics have attracted worldwide attention due to their potential threat to the marine ecosystem, with such pollutants even detected in the polar seas. Although in-depth research on microplastics has increased in recent years, studies in Antarctic waters remain relatively scarce compared with coastal waters and open oceans. In this study, microplastics in surface and subsurface Antarctic waters were investigated. The average microplastic abundance in the surface water was 0.10 ± 0.14 items/m³, with highest abundance in the Ross Sea, and the average microplastic abundance in the subsurface water was 1.66 ± 1.20 items/m³, with highest abundance in the Dumont d'Urville Sea. Polyester was the main microplastic in the surface waters (87.3%), while polypropylene (33.1%), polyester (28.7%), and polyethylene (22.8%) were the dominant microplastics in the subsurface waters. Results indicate that microplastic pollution in Antarctic waters may come from the Antarctic continent as well as southward transport from the ocean at mid- and low latitudes.

Alcohol Pretreatment to Eliminate the Interference of Micro Additive Particles in the Identification of Microplastics Using Raman Spectroscopy

Raman spectroscopy is an indispensable tool in the analysis of microplastics smaller than 20 μm. However, due to its limitation, Raman spectroscopy may be incapable of effectively distinguishing microplastics from micro additive particles. To validate this hypothesis, we characterized and compared the Raman spectra of six typical slip additives with polyethylene and found that their hit quality index values (0.93-0.96) are much higher than the accepted threshold value (0.70) used to identify microplastics. To prevent this interference, a new protocol involving an alcohol treatment step was introduced to successfully eliminate additive particles and accurately identify microplastics. Tests using the new protocol showed that three typical plastic products (polyethylene pellets, polyethylene bottle caps, and polypropylene food containers) can simultaneously release microplastic-like additive particles and microplastics regardless of the plastic type, daily-use scenario, or service duration. Micro additive particles can also adsorb onto and modify the surfaces of microplastics in a manner that may potentially increase their health risks. This study not only reveals the hidden problem associated with the substantial interference of additive particles in microplastic detection but also provides a cost-effective method to eliminate this interference and a rigorous basis to quantify the risks associated with microplastic exposure.

Acute and multigenerational effects of petroleum- and cellulose-based microfibers on growth and photosynthetic capacity of Lemna minor

Comparative toxicological assessment studies on the effects of petroleum- and cellulose-based microfibers on aquatic plants are limited. Therefore, we evaluated the acute and 10-generational toxicological effects of two types of petroleum- and cellulose-based microfibers on the duckweed Lemna minor. Plant growth and photosynthesis parameters were monitored as bioindicators. The multigenerational test revealed the following ranking of the microfibers according to the severity of their effects on L. minor: polypropylene > lyocell > viscose > polyethylene terephthalate. The acute tests revealed a significant increase in the energy required to initiate photosynthesis, although the growth of L. minor was not adversely affected by any microfiber. Both petroleum- and cellulose-based microfibers induced adverse effects on the growth and photosynthesis of L. minor in multigenerational tests. The results of the generational tests contribute to the understanding of the long-term adverse effects of microfibers on aquatic plants.

Fate of river-derived microplastics from the South China Sea: Sources to surrounding seas, shores, and abysses

Microplastics (MPs) in the ocean have been widely recognized as causing global marine environmental problems. To gain a quantitative and comprehensive understanding of oceanic MP contamination, detailed numerical Lagrangian particle tracking experiments were conducted to evaluate the regional oceanic transport and dispersal of MPs in the South China Sea (SCS) derived from three major rivers, Pearl (China), Mekong (Vietnam), and Pasig (the Philippines), which are known to discharge large amounts of plastic waste into the SCS. As previous field surveys have suggested, MP contamination spreads from the surface to the deeper ocean in the water column, we thus considered three types of MPs: (1) positively buoyant (light) MPs, (2) positively buoyant (light) MPs with random walk diffusion, and (3) full 3-D tracking of non-buoyant MPs that are passively transported by ambient currents. Transport patterns of these MPs from the three rivers clearly showed the intra-annual variability associated with seasonally varying circulations driven by the Asian monsoons in the SCS. Many MPs floating during the prevailing southwest monsoon are transported to the northwest Pacific Ocean and the East China Sea through the Luzon Strait and the Taiwan Strait to form MP hotspots. Non-buoyant MPs are broadly transported from the surface layer to depths of approximately 100 m or deeper, where in situ observations are rare. In addition, the buoyant MPs drifting on the continental shelf originating from southern China tend to be pushed toward the shore and beached by northward wind-induced currents more pronouncedly than the non-buoyant MPs. Therefore, the river-derived MPs to the SCS were found to serve as sources to adjacent basins and oceans, to be distributed not only in the upper layer but also in the abyssal ocean (non-buoyant MPs), and to be transported to the shores (buoyant MPs).

Effect of biological and environmental factors on microplastic ingestion of commercial fish species

Marine litter is an emerging pollution all over the world. In addition to the macro sized plastics, ongoing scientific efforts revealed risks of micro and nano sized plastic particles in marine environment. In the past decades, an increasing number of studies have been carried out to understand the dynamics of this pollution. The aim of the present study was to investigate the microplastic (MPs) ingestion in commercially important fish species and to evaluate biological and environmental factors influencing the ingestion status. Gastrointestinal tract content of a total of 2222 individuals belonging to 17 species were examined for MPs existence. Out of 17 species evaluated, 13 of them was detected to ingest MPs. Our results showed that 18.1% of investigated fishes ingested MPs and the average length of the detected particles was 1.26 ± 1.38 (±SD) mm. The most dominant MP type was fiber (90.1%), while the most common particle colours were black (46.9%) and blue (29.4%). Polypropylene (85%) was the most common polymer type detected. Our evaluations indicated that the exposure of fish distributed in coastal areas to microplastic pollution is corelated to physical (precipitation and distance to nearest shore) and biological (functional trophic group, habitat of the species) factors. In order to design a more effective control mechanism, these impacts should be included in the assessments in future practices to reveal the effects of microplastic pollution on biota.

Seafloor litter generated by coastal and offshore fisheries operations in the South Sea of Korea

Seafloor litter sources, distribution and density were assessed in a bottom trawl survey of the South Sea around Jeju Island by the Ara-ho training ship of Jeju National University. Samples were taken from 14 transects at a depth range of 60-120 m in areas with sandy and muddy substratum. Generally, mean densities varied from 26.9 items/km² to 62.4 items/km² and 104.8 kg/km² to 370.9 kg/km². Mean densities of total litter sampled was 46.3 items/km² and 228.6 kg/km². Derelict gears were the most common litter items (92 % of total litter) with mean densities of 44.3 items/km² and 228.1 kg/km². Gillnets and traps were the most derelict with densities reaching 4.9 items/km² and 99.2 kg/km² and 25.0 items/km² and 89.1 kg/km² respectively. The results of this study indicate that significant level of pollution in the South Sea are generated from commercial fishing activities and gillnets and traps being high risk derelict gears.

Effects of Weathering on Microplastic Dispersibility and Pollutant Uptake Capacity

Microplastics are ubiquitous in the environment, leading to a new form of plastic pollution crisis, which has reached an alarming level worldwide. Micron and nanoscale plastics may get integrated into ecological cycles with detrimental effects on various ecosystems. Commodity plastics are widely considered to be chemically inert, and alterations in their surface properties due to environmental weathering are often overlooked. This lack of knowledge on the dynamic changes in the surface chemistry and properties of (micro)plastics has impeded their life-cycle analysis and prediction of their fate in the environment. Through simulated weathering experiments, we delineate the role of sunlight in modifying the physicochemical properties of microplastics. Within 10 days of accelerated weathering, microplastics become dramatically more dispersible in the water column and can more than double the surface uptake of common chemical pollutants, such as malachite green and lead ions. The study provides the basis for identifying the elusive link between the surface properties of microplastics and their fate in the environment.

Metabolic impacts of polystyrene microplastics on the freshwater microalga Microcystis aeruginosa

Microplastics (plastic particles < 5 mm; MPs) are ubiquitous in aquatic environments but their potential adverse ecological effects on biota remain poorly understood. This is in part because in typical ecotoxicology tests the toxic effects of MPs were found to be limited. To capture the potential find-scale effects of MPs on freshwater organisms, we employed ultra-performance liquid chromatography-tandem mass spectrometry based untargeted metabolomics to investigate the metabolic impact of polystyrene microbeads microplastics (PS-MPs) of different sizes (0.1, 1, 10, 100 μm) and concentrations (1, 10, 100 mg/L) on a common freshwater microalga, Microcystis aeruginosa, after a 96-h exposure test. The phenotype-based results illustrated that while PS-MPs had no discernible effects on microalgal growth and photosynthesis, both oxidative stress and microcystin production were slightly increased. Metabolomics analysis revealed that the PS-MPs altered the global metabolic profile of the microalga. Specially, PS-MPs of larger size and higher concentration induced a larger number of differentially expressed metabolites. The PS-MPs significantly disturbed metabolisms involved in amino acid synthesis, membrane formation, nitrogen storage, and antioxidant defense of the microalga, consistent with the phenotypic observations. These results suggested several perturbed metabolic pathways, especially arginine-related pathways, as the mechanism. Our study showed that the insights provided by metabolomics-based approaches can enhance assessments of the ecological impacts of MPs on freshwater organisms.

Uptake of microplastics by the snakelocks anemone (Anemonia viridis) is commonplace across environmental conditions

Microplastics (<1 mm) are ubiquitous in our oceans and widely acknowledged as concerning contaminants due to the multi-faceted threats they exert on marine organisms and ecosystems. Anthozoans, including sea anemones and corals, are particularly at risk of microplastic uptake due to their proximity to the coastline, non-selective feeding mechanisms and sedentary nature. Here, the common snakelocks anemone (Anemonia viridis) was used to generate understanding of microplastic uptake in the relatively understudied Anthozoa class. A series of microplastic exposure and multi-stressor experiments were performed to examine particle shape and size selectivity, and to test for the influence of food availability and temperature on microplastic uptake. All A. viridis individuals were found to readily take up microplastics (mean 142.1 ± 83.4 particles per gram of tissue) but exhibited limited preference between different particle shapes and sizes (n = 32). Closer examination identified that uptake involved both ingestion and external tissue adhesion, where microplastics were trapped in secreted mucus. Microplastic uptake in A. viridis was not influenced by the presence of food or elevated water temperature (n = 40). Furthermore, environmental sampling was performed to investigate microplastic uptake in A. viridis (n = 8) on the coast of southwest England, with a mean of 17.5 ± 4.0 particles taken up per individual. Fibres represented the majority of particles (91%) followed by fragments (9%), with 87% either clear, blue or black in colour. FTIR analysis identified 70% of the particles as anthropogenic cellulosic or plastic polymers. Thus, this study provides evidence of microplastic uptake by A. viridis in both laboratory exposures experiments and in the marine environment. These findings support recent literature suggesting that external adhesion may be the primary mechanism in which anthozoans capture microplastics from the water column and highlights the potential role anemones can play as environmental microplastic bioindicators.

Acrylic fabrics as a source of microplastics from portable washer and dryer: Impact of washing and drying parameters

Increasing uses of synthetic textiles are now a concerning issue as these synthetic textiles are shedding microfibers during the laundering of the fabrics and are considered as a potential source of microplastics (size <5 mm). In addition, manmade fibers like polyester, acrylic, and nylon represent 60% of the worldwide consumption of textile fibers. The novelty of this study is to assess the releasing trends of microfibers from acrylic fabrics during washing and drying under different conditions from a portable washer and dryer machine. Washing and drying effluents were filtered out which were further quantified with gravimetric analysis to determine the net weight of the released microfibers. Among different washing parameters, the mean length and diameter of the released microfibers were found to be approximately 2411 ± 1500 μm and 18 ± 4 μm, respectively. The results indicate that the release of microfibers increased by 2 and 1.4 times respectively when washing and drying time increased from 30 min to 60 min due to high mechanical stresses and longer rotational forces on the fabrics. The use of detergent during washing also promoted more microfiber release (162.49 ± 44.21 mg/kg) when compared to without detergent (60.22 ± 13.32 mg/kg). Moreover, microfibers were released approximately 1.8 times higher from washing when washed with 40 °C of water than with 20 °C of water. However, subsequent washing and drying cycles showed decreasing patterns of microfiber release as microfiber released 45% and 67% less during the 7th washing and drying cycle, respectively, compared to the 1st cycle. Results of this study would help to understand the releasing patterns of microfibers which can help to improve the existing systems to reduce the microplastic emissions from laundering.

Global qualitative and quantitative distribution of micropollutants in the deep sea

Micropollutants (MPs) include a wide range of biological disruptors that can be toxic to wildlife and humans at very low concentrations (<1 μg/L). These mainly anthropogenic pollutants have been widely detected in different areas of the planet, including the deep sea, and have impacts on marine life. Because of this potential toxicity, the global distribution, quantity, incidence, and potential impacts of deep-sea MPs were investigated in a systematic review of the literature. The results showed that MPs have reached different zones of the ocean and are more frequently reported in the Northern Hemisphere, where higher concentrations are found. MPs are also concentrated in depths up to 3000 m, where they are also more frequently studied, but also extend deeper than 10,000 m. Potentially toxic metals (PTMs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDTs), organotins, and polycyclic aromatic hydrocarbons (PAHs) were identified as the most prevalent and widely distributed MPs at ≥200 m depth. PTMs are widely distributed in the deep sea in high concentrations; aluminum is the most prevalent up to 3000 m depth, followed by zinc and copper. PCBs, organotins, hexachlorocyclohexanes (HCHs), PAHs, and phenols were detected accumulated in both organisms and environmental samples above legislated thresholds or known toxicity levels. Our assessment indicated that the deep sea can be considered a sink for MPs.

Investigating transport kinetics of polystyrene nanoplastics in saturated porous media

Understanding the fate and transport of polystyrene nanoparticles (PSNPs) in porous media under various conditions is necessary for evaluating and predicting environmental risks caused by microplastics. The transport kinetics of PSNPs are investigated by column experiment and numerical model. The surface of DLVO interaction energy is calculated to analyze and predict the adsorption and aggregation of PSNPs in porous media, which the critical ionic strength of PSNPs can be accurately investigated. The results of the DLVO energy surface suggest that when the concentration of Na⁺ increases from 1 mM to 50 mM, the DLVO energy barrier of PSNPs-silica sand (SS) decreases from 78.37 kT to 5.46 kT. As a result, PSNPs are easily adsorbed on the surface of SS and the mobility of PSNPs is reduced under the condition of a high concentration of Na⁺ (PSNPs recovery rate decreases from 62.16% to 3.65%). When the concentration of Ca²⁺ increases from 0.1 mM to 5 mM, the DLVO energy barrier of PSNPs-SS decreases from 12.10 kT to 1.90 kT, and PSNPs recovery rate decreases from 82.46% to 4.27%. Experimental and model results showed that PSNPs mobility is enhanced by increasing initial concentration, flow velocity and grain size of SS, while the mobility of PSNPs with larger particle diameter is lower. Regression analysis suggests that kinetic parameters related to PSNPs mobility are correlated with DLVO energy barriers. The environmental behavior and mechanism of PSNPs transport in porous media are further investigated in this study, which provides a scientific basis for the systematic and comprehensive evaluation of the environmental risk and ecological safety of nano-plastic particles in the groundwater system.

Quantitative assessment of microplastic in sandy beaches of Gujarat state, India

The present study was carried out to quantify microplastic prevalence among 20 sandy beaches on the Gujarat coast. Beaches were categorised into three different classes, viz. low-impacted sites, moderately impacted sites, and highly impacted sites based on anthropogenic pressure. Microplastic (MP) (≤ 5 mm) contamination on the beaches varied with an average of 1.4 MPs/kg to 26 MPs/kg sediment. Sutrapada site-1 and Porbandar showed the highest and lowest mean abundance of microplastics, respectively, among 20 selected beaches. Out of the total assessed microplastics, threads were the maximum (89.98%), followed by the films (4.75%), fragments (3.36%) and foam (1.89%). In terms of colour and size, different microplastics were recorded in this study. The chemical composition of microplastics was identified by ATR-FTIR as polypropylene (47.5%), polyethylene (26%), and polystyrene (25%). Tourism and fishing activities are the possible sources of higher microplastic contamination at highly impacted sites.

Environmentally relevant concentrations of microplastics modulated the immune response and swimming activity, and impaired the development of marine medaka Oryzias melastigma larvae

Microplastics (MPs), due to their impacts on the ecosystem and their integration into the food web either through trophic transfer or ingestion directly from the ambient environment, are an emerging class of environmental contaminants posing a great threat to marine organisms. Most reports on the toxic effects of MPs exclusively focus on bioaccumulation, oxidative stress, pathological damage, and metabolic disturbance in fish. However, the collected information on fish immunity in response to MPs is poorly defined. In particular, little is known regarding mucosal immunity and the role of mucins. In this study, marine medaka (Oryzias melastigma) larvae were exposed to 6.0 µm beads of polystyrene microplastics (PS-MPs) at three environmentally relevant concentrations (10² particles/L, 10⁴ particles/L, and 10⁶ particles/L) for 14 days. The experiment was carried out to explore the developmental and behavioural indices, the transcriptional profiles of mucins, pro-inflammatory, immune, metabolism and antioxidant responses related genes, as well as the accumulation of PS-MPs in larvae. The results revealed that PS-MPs were observed in the gastrointestinal tract, with a concentration- and exposure time-dependent manner. No significant difference in the larval mortality was found between the treatment groups and the control, whereas the body length of larvae demonstrated a significant reduction at 10⁶ particles/L on 14 days post-hatching. The swimming behaviour of the larvae became hyperactive under exposure to 10⁴ and 10⁶ particles/L PS-MPs. In addition, PS-MP exposure significantly up-regulated the mucin gene transcriptional levels of muc7-like and muc13-like, however down-regulated the mucin gene expression levels of heg1, muc2, muc5AC-like and muc13. The immune- and inflammation and metabolism-relevant genes (jak, stat-3, il-6, il-1β, tnf-а, ccl-11, nf-κb, and sod) were significantly induced by PS-MPs at 10⁴ and 10⁶ particles/L compared to the control. Taken together, this study suggests that PS-MPs induced inflammation response and might obstruct the immune functions and retarded the growth of the marine medaka larvae even at environmentally relevant concentrations.

Plastic burial by flash-flood deposits in a prodelta environment (Gulf of Patti, Southern Tyrrhenian Sea)

Plastic pollution affects all oceans and sequestration of plastics in sediments is considered its ultimate sink. We report evidence of macroplastic burial retrieved within a sediment core collected at 38 m depth at the mouth of the Mazzarrà River, a torrential river able to carry a large amount of sediment during seasonal flash-floods. Two macroplastic items were found at 68 and 255 cm below the core top (corresponding to the seafloor). Their association with terrestrial vegetal debris and their inclusion in decimetre-thick sandy/silty intervals showing coarsening- and fining-upward trends, suggest that they were deposited by hyperpycnal flows possibly triggered by flood events. These findings testify the potential of sedimentary flows in burying macroplastic at depth below the seafloor, especially in nearshore prodelta environments. Furthermore they raise the quest on the magnitude of macroplastic storage in the subsurface and on the lack of specific devices and strategies for their reckoning.

Anthropogenic microfibers are highly abundant at the Burdwood Bank seamount, a protected sub-Antarctic environment in the Southwestern Atlantic Ocean

Microplastics debris in the marine environment have been widely studied across the globe. Within these particles, the most abundant and prevalent type in the oceans are anthropogenic microfibers (MFs), although they have been historically overlooked mostly due to methodological constraints. MFs are currently considered omnipresent in natural environments, however, contrary to the Northern Hemisphere, data on their abundance and distribution in Southern Oceans ecosystems are still scarce, in particular for sub-Antarctic regions. Using Niskin bottles we've explored microfibers abundance and distribution in the water column (3-2450 m depth) at the Burdwood Bank (BB), a seamount located at the southern extreme of the Patagonian shelf, in the Southwestern Atlantic Ocean. The MFs detected from filtered water samples were photographed and measured using ImageJ software, to estimate length, width, and the projected surface area of each particle. Our results indicate that small pieces of fibers are widespread in the water column at the BB (mean of 17.4 ± 12.6 MFs.L^-1), from which, 10.6 ± 5.3 MFs.L^-1 were at the surface (3-10 m depth), 20 ± 9 MFs.L^-1 in intermediate waters (41-97 m), 24.6 ± 17.3 MFs.L^-1 in deeper waters (102-164 m), and 9.2 ± 5.3 MFs.L^-1 within the slope break of the seamount. Approximately 76.1% of the MFs were composed of Polyethylene terephthalate, and the abundance was dominated by the size fraction from 0.1 to 0.3 mm of length. Given the high relative abundance of small and aged MFs, and the oceanographic complexity of the study area, we postulate that MFs are most likely transported to the BB via the Antarctic Circumpolar Current. Our findings imply that this sub-Antarctic protected ecosystem is highly exposed to microplastic pollution, and this threat could be spreading towards the highly productive waters, north of the study area.

Repulsive Interactions of Eco-corona-Covered Microplastic Particles Quantitatively Follow Modeling of Polymer Brushes

The environmental fate and toxicity of microplastic particles are dominated by their surface properties. In the environment, an adsorbed layer of biomolecules and natural organic matter forms the so-called eco-corona. A quantitative description of how this eco-corona changes the particles' colloidal interactions is still missing. Here, we demonstrate with colloidal probe-atomic force microscopy that eco-corona formation on microplastic particles introduces a compressible film on the surface, which changes the mechanical behavior. We measure single particle-particle interactions and find a pronounced increase of long-range repulsive interactions upon eco-corona formation. These force-separation characteristics follow the Alexander-de Gennes (AdG) polymer brush model under certain conditions. We further compare the obtained fitting parameters to known systems like polyelectrolyte multilayers and propose these as model systems for the eco-corona. Our results show that concepts of fundamental polymer physics, like the AdG model, also help in understanding more complex systems like biomolecules adsorbed to surfaces, i.e., the eco-corona.

Prevalence of small-sized microplastics in coastal sediments detected by multipoint confocal micro-Raman spectrum scanning

Microplastics have become global emerging issue and received widespread attention in recent years. Due to their chemical persistence, plastic particles can be broken into smaller items but accumulated for long time in the environment like sediment. However, limited by current detection technologies, the distribution and characteristics of small-sized microplastics in coastal sediment remain uncertain. In this study, we established a new method based on micro-Raman spectroscopy for detecting small-sized microplastics, namely multipoint confocal micro-Raman spectrum scanning (MCmRSS). The MCmRSS was first applied in detecting microplastics in the sediment samples collected from three bays of the East China Sea. The minimum size of microplastics was 4 μm and average microplastics concentration was 91 ± 55 items /g dry weight sediment, with fragment and polyethylene as the most common shape and polymer type, respectively. The spatial variation of microplastics was in accordance with the strength of coastal human activities and marine dynamics. In all the microplastic items, the small-sized ones (<10 μm) accounted for 67%; and the relationship between microplastic concentration and its size followed a power-exponential equation. Compared with previous studies, the number of microplastics in coastal sediments detected by the MCmRSS increased by 2 orders of magnitude, which was benefited from the advantages of multipoint scanning in the fixed identification areas and high resolution of micro-Raman spectrum. Our findings would summon the re-evaluation of the potential risks of small-sized microplastics in the coastal environment.

First long-term evidence of microplastic pollution in the deep subtropical Northeast Atlantic

No anthropogenic pollutant is more widespread in the aquatic and terrestrial environment than microplastic; however, there are large knowledge gaps regarding its origin, fate, or temporal variations in the oceans. In this study, we analyzed sediment trap material from the deep subtropical Northeast Atlantic (2000 m) in a long-term record (2003-2015) to assess the role of the deep ocean as a potential sink of microplastics. Microplastic particles were identified in all 110 analyzed samples with flux rates of 1.13-3146.81 items d^-1 m^-2. Calculated microplastic mass fluxes ranged between 0.10 and 1977.96 μg d^-1 m^-2, representing up to 8% of the particle flux. Between years, the composition of the different polymers changed significantly, dominated by polyethylene, whose amount was correlated with the lithogenic input. The correlation between polyethylene and the lithogenic fraction was attributed to an air transport pathway from northeast Africa and surrounding regions. The second most abundant polymer detected in our study was polyvinyl chloride, which is not correlated with lithogenic or biogenic particle flux fractions. Instead, we observed seasonality for polyvinyl chloride with recurring high fluxes in winter before the plankton bloom and significantly lower amounts in summer. Other polymers identified were polypropylene, polyethylene terephthalate, and lower numbers of polystyrene and polymethyl methacrylate. The average microplastic particle size for all samples and polymers was 88.44 ± 113.46 μm, with polyethylene and polyvinyl chloride having the highest proportion of small particles (<100 μm). Our findings provide first insights into temporal variations of sinking microplastics, which are crucial for understanding the fate of plastic in the oceans.

Bacterial colonisation of plastic in the Rockall Trough, North-East Atlantic: An improved understanding of the deep-sea plastisphere

Plastic pollution has now been found within multiple ecosystems across the globe. Characterisation of microbial assemblages associated with marine plastic, or the so-called 'plastisphere', has focused predominantly on plastic in the epipelagic zone. Whether this community includes taxa that are consistently enriched on plastic compared to surrounding non plastic surfaces is unresolved, as are the ecological implications. The deep sea is likely a final sink for most of the plastic entering the ocean, yet there is limited information on microbial colonisation of plastic at depth. The aim of this study was to investigate deep-sea microbial communities associated with polystyrene (PS) and polyurethane (PU) with Bath stone used as a control. The substrates (n = 15) were deployed in the Rockall Trough (Atlantic), and recovered 420 days later from a depth of 1796 m. To characterise the bacterial communities, 16S rRNA genes were sequenced using the Illumina MiSeq platform. A dominant core microbiome (taxa shared across all substrates) comprised 8% of total ASVs (amplicon sequence variant) and accounted for 92% of the total community reads. This suggests that many commonly reported members of the plastisphere are simply opportunistic which freely colonise any hard surface. Transiently associated species consisted of approximately 7% of the total community. Thirty genera were enriched on plastic (P < 0.05), representing 1% of the total community. The discovery of novel deep-sea enriched taxa included Aurantivirga, Algivirga, IheB3-7, Spirosoma, HTCC5015, Ekhidna and Calorithrix on PS and Candidatus Obscuribacter, Haloferula, Marine Methylotrophic Group 3, Aliivibrio, Tibeticola and Dethiosulfatarculus on PU. This small fraction of the microbiome include taxa with unique metabolic abilities and show how bacterial communities can be shaped by plastic pollution at depth. This study outlines a novel approach in categorising the plastisphere to elucidate the ecological implications of enriched taxa that show an affinity for colonising plastic.

Integrated effects of polymer type, size and shape on the sinking dynamics of biofouled microplastics

Sinking of microplastics (MPs) after biofouling is considered an important mechanisms responsible for the downward transport/sedimentation of MPs in the ocean and freshwaters. Previous studies demonstrated MP sinking caused by an increase in the composite density of MPs after biofouling, while MPs with smaller size or shapes with higher surface area to volume ratios (SA:V), such as films, are speculated to sink faster. In this study, we designed an in situ microcosm to simulate the ambient environmental conditions experienced by floating MPs to elucidate the biofouling and sinking of polyethylene (PE), polypropylene (PP), and expanded-polystyrene (EPS) MPs of various sizes and shapes. Our results showed smaller PE and PP MP granules sank faster than large ones. Even EPS granules of 100 μm diameter, having a much lower density (0.02 mg/mm³) than water, started to sink after 2 weeks of biofouling. Moreover, PE film and fiber MPs with higher SA:V did not sink faster than PE MP granules of the same mass, implying that mechanisms other than SA:V, such as fouling contact area and drag coefficient, play a role in the regulation of biofouling and sinking of MPs.

Marine plastics in Mediterranean islands: Evaluating the distribution and composition of plastic pollution in the surface waters along four islands of the Western Sea Basin

To study the spatial distribution of sea surface plastics in marine protected and non-protected areas, 65 sea surface trawls were carried out using a Hydro-bios manta net coupled with a 335-μm mesh. A total of 19 sampling sites along the coastal waters of Mallorca, the "Parque Nacional Marítimo-Terrestre del Archipiélago de Cabrera" and Menorca in the Balearic Islands as well as along coastal waters of The Natural Park of Columbretes Islands (NW Mediterranean Sea) were sampled. A total of 10,637 plastic items were identified and a subset of these items was categorized by shape, color, size and polymer composition. Plastic particles were found at each sampling site and in all samples. No microscale nor mesoscale variability in floating marine plastics abundance (particles/m²) was encountered throughout the study area where similar values were found in protected areas with no local land-based contamination sources, such as Columbretes [0.04 (±0.03) particles/m²], and in high anthropized areas, such as the island of Mallorca [0.04 (±0.07) particles/m²]. However, differences were found in characteristics of plastic items (shape, polymer, and size range), with the protected area of Columbretes characterized by the presence of the highest density of very small plastic items composed mainly of fragments (93%). Quantified plastics from the marine environment were composed mainly of polyethylene (PE, 63.3%), polypropylene (PP; 24.9%), polycarbonate (PC; 4.6%) and polystyrene (PS, 3.3%). The polymer composition showed a homogenous composition between islands and differences were detected only amongst Columbretes and the other islands. Results from this study provide further evidence of the ubiquity of plastics in the marine environment and highlight that remote and protected areas, such as Columbretes, are not exempt from plastic pollution, but receptor areas for small and aged floating plastics composed mainly by fragments, which might have potentially harmful effects on protected ecosystems.

Occurrence of Natural and Synthetic Micro-Fibers in the Mediterranean Sea: A Review

Among microplastics (MPs), fibers are one of the most abundant shapes encountered in the aquatic environment. Growing attention is being focused on this typology of particles since they are considered an important form of marine contamination. Information about microfibers distribution in the Mediterranean Sea is still limited and the increasing evidence of the high amount of fibers in the aquatic environment should lead to a different classification from MPs which, by definition, are composed only of synthetic materials and not natural. In the past, cellulosic fibers (natural and regenerated) have been likely included in the synthetic realm by hundreds of studies, inflating “micro-plastic” counts in both environmental matrices and organisms. Comparisons are often hampered because many of the available studies have explicitly excluded the micro-fibers (MFs) content due, for example, to methodological problems. Considering the abundance of micro-fibers in the environment, a chemical composition analysis is fundamental for toxicological assessments. Overall, the results of this review work provide the basis to monitor and mitigate the impacts of microfiber pollution on the sea ecosystems in the Mediterranean Sea, which can be used to investigate other basins of the world for future risk assessment.

Spatial distribution of microplastics in volcanic lake water and sediments: Relationships with depth and sediment grain size

Microplastics (plastics <5 mm) are globally widespread pollutants of aquatic ecosystems. As microplastics contaminate both water and sediments, research on their spatial distribution in these different environmental matrices has increased. However, fresh waters are poorly studied and even less so are lentic ecosystems. To contribute filling this knowledge gap, this study analyses the distribution of microplastics in the water column and surface sediments of a volcanic lake, namely Lake Bracciano. Furthermore, it analyses in more detail the relationship between the concentration of microplastics in sediments, its grain size and the sampling depth (i.e. nearshore or deep). Water and sediment sampling was carried out in different sectors of the lake (northern, eastern, southern, western) using a plankton net and a van Veen grab sampler, respectively. Two sediment samples were collected at each station in order to analyse the abundance of microplastic and to perform grain size analysis. Results show a mean concentration of 2.4 items m^-3 in water and 42 items kg^-1 in sediments. The distribution of microplastics is uneven between the different sampling stations, with the northern sector being the most contaminated in both matrices. The chemical composition and shape of microplastics vary between water and sediment. In particular, polyethylene terephthalate and polyvinyl chloride are the most abundant polymers in water and sediments, respectively. Fibres are the main shape of microplastics in water while fragments are more abundant in sediments. In-depth analysis of sediment shows that sediments from deep stations are more contaminated than nearshore samples and have more fragment-shaped microplastics than fibre-shaped ones. Furthermore, there is a significant positive correlation between the concentration of microplastics and the abundance of silt, confirming data emerging from the scientific literature on marine and lotic ecosystems.

Surface water, sediment, and biota: The first multi-compartment analysis of microplastics in the Karnafully river, Bangladesh

The Karnafullly River, which flows through Chattogram and falls into the Bay of Bengal, Bangladesh, is vulnerable to microplastic contamination. In this study, we looked at microplastics in the Karnafully River's surface water (5 sites), sediment (9 sites), and biota (4 species). Microplastic concentrations ranged from 0.57 ± 0.07 to 6.63 ± 0.52 items/L in surface water, 143.33 ± 3.33 to 1240 ± 5.77 items/kg dry weight in sediment, and 5.93 ± 0.62 to 13.17 ± 0.76 items/species in biota. A significant difference (P < 0.05) was found in the concentration of MPs in the Karnafully River's sediment, biota, and surface water. High percentage of fiber-shaped and small-sized MPs (<1 mm) were detected throughout the samples. Water and sediment MPs were often transparent/white and blue, whereas biota MPs were mostly black and red, indicating a color preference during biological uptake. The Bay of Bengal received 61.3 × 10⁹ microplastic items per day. The feeding zone of biota influenced the level of microplastics, with a trend of pelagic > demersal > benthic > benthopelagic. Polyethylene and polyethylene terephthalate were the most abundant polymer. Using the average fish intake rate in Bangladesh, we computed a possible consumption of 4015-7665 items of MPs/person/year.

Can we quantify the aquatic environmental plastic load from aquaculture?

Aquaculture provides livelihoods for hundreds of millions of people, but it also forms a significant source of plastic litter that poses a serious hazard to aquatic ecosystems. How to assess and subsequently manage plastic loads from aquaculture is a pending and pressing issue for aquaculture sustainability, and an important concern for water environment monitoring and management. In this study, we developed the first framework for estimating plastic litter from aquaculture by combining data from satellite remote sensing, drones, questionnaires, and in situ measurements. By acquiring multidimensional (human and nature) and multiscale (centimeter to basin scale) data, this framework helped us understand the aquaculture farming patterns and its spatial and temporal evolution, and thus estimate the plastic load it generates and suggest effective management approaches. Applying this framework, we assessed the marine plastic load from oyster floating raft farming in the Maowei Sea, a typical mariculture bay in China, with an increasing farming area. Approximately 3840 tons of plastic waste is expected to be discharged into the sea in the next four years (the average service life of a floating raft) without improvements in aquaculture waste management. Strengthening governance, timely plastic removal, innovative replacement, and transforming farmers' behavior patterns are recommended as the subsequent measures for plastic management. This framework can be extended to other regions and other aquaculture patterns, and is applicable to local, regional, and global aquaculture plastic litter assessments. It is a source-based method for evaluating plastic pollution that is more conducive to subsequent plastic management than traditional post-contamination environmental monitoring. In the context of the global expansion of mariculture and the global commitment to action to combat plastic pollution, this approach could play a critical role in the investigation and management of plastic waste in aquatic environments.

Microplastics cause neurotoxicity and decline of enzymatic activities in important bioturbator Hediste diversicolor

Microplastics (MPs) tend to accumulate in marine sediments thus benthic fauna is particularly vulnerable to microplastic pollution. Hediste diversicolor is a widespread species in coastal marine sediments. It plays key ecological functions mostly related to bioturbation process which means sediment reworking due to the worm burrowing activity and building a network of galleries. Herein, we show that commercial plastic microspheres of two sizes (63-75 and 300-355 μm) have the potential to cause neurotoxicity in H. diversicolor. The whole-body acetylcholinesterase (AChE) activity - a common indicator of neurotoxic effect - was on average 60% lower in polychaetes exposed for 28 days to MPs served at environmentally relevant concentrations (0.08% sediment d. wt.), than in unexposed ones. Significantly reduced activities of antioxidant enzymes (SOD, CAT, GST) indicated suppression of the cellular antioxidative system in worms exposed to MPs. No changes were, however, observed in tGSH, lipid or protein oxidation measures (CBO, MDA), and in the energetic value of these polychaetes. The response was generally similar with no regard to MPs size. Only very few microspheres were found in polychaetes exposed to MPs spiked sediment. The potential role of MPs-associated pollutants as a factor responsible for observed biochemical effects, is discussed.

Characteristics and distribution of microplastics in shoreline sediments of the Yangtze River, main tributaries and lakes in China-From upper reaches to the estuary

Microplastics (MPs) pervade the environment and increasingly threaten both natural ecosystems and human health. In this study, we investigated MP particle concentrations in sediment samples collected from 54 sites along the banks of the Yangtze River and its major tributaries and on lakeshores. The main polymer types found in the samples were polypropylene (PP), polystyrene (PS) and polyethylene (PE). MP particle abundance in the various types of locations was 35-51,968 particles/kg dry weight (d.w.) on the banks of the main river, 52-1463 particles/kg (d.w.) on the banks of tributaries and 2574-23,685 particles/kg (d.w.) on lakeshores. Correlation between MP abundance and mean annual runoff of each upstream tributary was significant, which suggests that increased runoff brings more microplastic waste to streambank sediments. The most common shape of MP particles in all upstream samples was flake, and in downstream samples it was foam. Small microplastic particles (< 0.50 mm) were predominant at all sites in this study, and the minimum particle size in samples from the Yangtze river banks was 0.065 mm. Average abundance of MP particles on the shores of the source lake was 9069 particles/kg around the inlet but only 866 particles/kg around the outlet; the difference was due to interception associated with sedimentation and precipitation in the lake. Our study represents the large-scale study of MPs contamination in sediment along the Yangtze River and provides important data regarding the accumulation and distribution of MPs in shoreline sediments of the upper, middle and lower reaches of the Yangtze River, main tributaries and lakes in China.

Assessment, characterization, and quantification of microplastics from river sediments

Microplastic (MP), as a pollutant, is currently posing a biological hazard to the aquatic environment. The study aims to isolate, quantify, and characterize the MP pollutants in sediment samples from 14 study sites at Kaveri River, Killa Chinthamani, Tiruchirappalli, South India. With Sediment-MP Isolation (SMI) unit, density separation was done with a hydrogen peroxide solution. Four forms of MPs namely, fragments, films, foams, and fibers with orange, white, green, and saffron red were observed. The plenitude and distribution of four forms of MPs and natural substrates were geometrically independent, with large amounts of microfragments within the research region accounting for 79.72% variation by Principal Component Analysis. FT-IR analyses of MPs showed the presence of polyamide, polyethylene, polyethylene glycol, polyethylene terephthalate, polypropylene, and polystyrene. Additionally, the scanning electron microscopic analysis revealed that the MPs have differential surface morphology with rough surfaces, porous structures, fissures, and severe damage. Most MPs comprised Si, Mg, Cu, and Al, according to energy dispersive X-ray analyses. The combined SMI, instrumental analyses and evaluation (heat map) of MPs in river sediments help assess contamination levels and types of MPs. The findings might provide an insight into the status of MPs in Kavery River sediments that could help in formulating regulations for MPs reduction and contamination in rivers eventually to protect the environment.

An appraisal of early stage biofilm-forming bacterial community assemblage and diversity in the Arabian Sea, India

The community composition and distribution of early-stage (24 h) biofilm-forming bacteria on two different surfaces (glass slide and polystyrene plastic slide) at three different locations (Diu, Alang and Sikka) were studied using a culture-dependent and next-generation sequencing (NGS) approach in the Arabian Sea, Gujarat, India. The most dominant phyla observed using the NGS approach were the Proteobacteria among the sampling sites. Gammaproteobacteria class dominated both the surfaces among the sites and accounted for 46.7% to 89.2% of total abundance. The culture-dependent analysis showed Proteobacteria and Firmicutes as the dominant phyla on the surfaces within the sampling sites. During the initial colonization, hydrocarbon-degrading bacterial strains have also attached to the surfaces. The outcome of this study would be of great importance for targeting the early stage biofilm-forming and hydrocarbon-degrading bacterial isolates may help to degrade plastic in the marine environment.

Plastisphere community assemblage of aquatic environment: plastic-microbe interaction, role in degradation and characterization technologies

It is undeniable that plastics are ubiquitous and a threat to global ecosystems. Plastic waste is transformed into microplastics (MPs) through physical and chemical disruption processes within the aquatic environment. MPs are detected in almost every environment due to their worldwide transportability through ocean currents or wind, which allows them to reach even the most remote regions of our planet. MPs colonized by biofilm-forming microbial communities are known as the ''plastisphere". The revelation that this unique substrate can aid microbial dispersal has piqued interest in the ground of microbial ecology. MPs have synergetic effects on the development, transportation, persistence, and ecology of microorganisms. This review summarizes the studies of plastisphere in recent years and the microbial community assemblage (viz. autotrophs, heterotrophs, predators, and pathogens). We also discussed plastic-microbe interactions and the potential sources of plastic degrading microorganisms. Finally, it also focuses on current technologies used to characterize those microbial inhabitants and recommendations for further research.

Characteristics of Microplastics and Their Affiliated PAHs in Surface Water in Ho Chi Minh City, Vietnam

Microplastic pollution has become a worldwide concern. However, studies on the distribution of microplastics (MPs) from inland water to the ocean and their affiliated polycyclic aromatic hydrocarbons (PAHs) are still limited in Vietnam. In this study, we investigated the distribution of MPs and PAHs associated with MPs in canals, Saigon River, and Can Gio Sea. MPs were found at all sites, with the highest average abundance of MPs being 104.17 ± 162.44 pieces/m³ in canals, followed by 2.08 ± 2.22 pieces/m³ in the sea, and 0.60 ± 0.38 pieces/m³ in the river. Fragment, fiber, and granule were three common shapes, and each shape was dominant in one sampling area. White was the most common MP color at all sites. A total of 13 polymers and co-polymers were confirmed, and polyethylene, polypropylene, and ethylene-vinyl acetate were the three dominant polymers. The total concentration of MPs-affiliated PAHs ranged from 232.71 to 6448.66, from 30.94 to 8940.99, and from 432.95 to 3267.88 ng/g in Can Gio sea, canals, and Saigon River, respectively. Petrogenic sources were suggested as a major source of PAHs associated with MPs in Can Gio Sea, whereas those found in Saigon River and canals were from both petrogenic and pyrogenic sources.

Automatic quantification and classification of microplastics in scanning electron micrographs via deep learning

Microplastics quantification and classification are demanding jobs to monitor microplastic pollution and evaluate the potential health risks. In this paper, microplastics from daily supplies in diverse chemical compositions and shapes are imaged by scanning electron microscopy. It offers a greater depth and finer details of microplastics at a wider range of magnification than visible light microscopy or a digital camera, and permits further chemical composition analysis. However, it is labour-intensive to manually extract microplastics from micrographs, especially for small particles and thin fibres. A deep learning approach facilitates microplastics quantification and classification with a manually annotated dataset including 237 micrographs of microplastic particles (fragments or beads) in the range of 50 μm-1 mm and fibres with diameters around 10 μm. For microplastics quantification, two deep learning models (U-Net and MultiResUNet) were implemented for semantic segmentation. Both significantly outmatched conventional computer vision techniques and achieved a high average Jaccard index over 0.75. Especially, U-Net was combined with object-aware pixel embedding to perform instance segmentation on densely packed and tangled fibres for further quantification. For shape classification, a fine-tuned VGG16 neural network classifies microplastics based on their shapes with high accuracy of 98.33%. With trained models, it takes only seconds to segment and classify a new micrograph in high accuracy, which is remarkably cheaper and faster than manual labour. The growing datasets may benefit the identification and quantification of microplastics in environmental samples in future work.

Challenging the highstand-dormant paradigm for land-detached submarine canyons

Sediment, nutrients, organic carbon and pollutants are funnelled down submarine canyons from continental shelves by sediment-laden flows called turbidity currents, which dominate particulate transfer to the deep sea. Post-glacial sea-level rise disconnected more than three quarters of the >9000 submarine canyons worldwide from their former river or long-shore drift sediment inputs. Existing models therefore assume that land-detached submarine canyons are dormant in the present-day; however, monitoring has focused on land-attached canyons and this paradigm remains untested. Here we present the most detailed field measurements yet of turbidity currents within a land-detached submarine canyon, documenting a remarkably similar frequency (6 yr^-1) and speed (up to 5-8 ms^-1) to those in large land-attached submarine canyons. Major triggers such as storms or earthquakes are not required; instead, seasonal variations in cross-shelf sediment transport explain temporal-clustering of flows, and why the storm season is surprisingly absent of turbidity currents. As >1000 other canyons have a similar configuration, we propose that contemporary deep-sea particulate transport via such land-detached canyons may have been dramatically under-estimated.

Oceanic plastic pollution caused by Danish seine fishing in Norway

Wear and tear on fishing gear is a sparsely investigated source of microplastic pollution in the sea. In Norway, Danish seine ropes and trawls are the fishing gears that contribute most to this pollution. The main reason for this pollution is that the seine ropes are dragged along the seabed over a considerable distance, creating a friction force that results in high ropes wear. This note reports the findings after examining the wear of Danish seine ropes used in Norwegian fisheries. The results show that, in Norway alone, an average of 77 to 97 tons of plastic will be added to the sea annually due to this specific fishing gear. Aggregated to include all fly dragging, anchor seining, and pair seining globally, this number is estimated to be about 311 tons per year.