Stranded in the high tide line: Spatial and temporal variability of beached microplastics in a semi-enclosed embayment (Arcachon, France)

Juveniles at risk: behaviour and colour changes in sole juveniles (Solea solea) after exposure to estuarine ragworms (Hediste diversicolor) contaminated with microplastics

Due to strong anthropogenic pressures and their location at the interface between continental and oceanic environments, estuarine areas are affected by significant diverse pollution and species that live in these areas are particularly exposed. Microplastic (MPs) pollution is a worldwide issue and causes substantiated trouble in estuaries where sometimes the number of MPs equal or exceed the number of fish larvae which suggest a high risk of contamination of biota especially in benthic organisms and demersal fish. There are growing evidence that, beyond intrinsic toxicity, MPs can transfer chemicals (additives or pollutants). In order to get closer to environmental situations, in this study we tackled an issue that is rarely dealt with, namely the trophic transfer of MPs and chemicals through the food chain between a sediment- and a benthic-feeder. To take into account these specificities, we used an emblematic and common species of the European coastlines, the common sole (Solea solea) and its annelid prey. Sole juveniles were fed with estuarine ragworms (Hediste diversicolor) previously exposed to MPs via enriched MPs sediment. The MPs used were either a mixture of micronized plastics collected from the Seine Estuary (eMPs, two environmental concentrations at 1 or 100 mg/kg of sediment, median size range 52-77 μm) or model MPs of PVC particles (at 1 g/kg of sediment, size range 125-250 μm), either uncontaminated or contaminated with Benzo(a)Pyrene (BaP, 11.5 μg/g MPs) or benzophenone-3 (BP3, 66 ng/g MPs). Several indicators of health status such as survival, growth, behaviour, energy metabolism, and histopathology were studied. Sole individuals fed ragworms exposed to eMPs or PVC MPs displayed a change in behaviour (place preference between black/white background). Seine Estuary eMPs lead to an increase in body colour chroma for the highest concentration and behaviour was modified with an increase in time spent on white bottom and transition number for the highest concentration when distance moved increased only at the lowest concentration. Sole exposed to BaP-PVC-MPs displayed the lowest time spent on white background compared to control and BP3-PVC-MPs group. Soles exposed to BP3-PVC MPs displayed a significant skin colour increase in chroma and a wider combination of value/chroma reflecting more diverse skin colours. Finally, lipid content in muscle and DNA damage were significantly higher in BP3-MPs. Although the exact mechanisms underpinning such changes are largely unknown, these observations are indicative of physiological stress which may have a significant impact on survival by increasing predation risks for fish juveniles, hence the ecosystem health and calls for further trophic transfer experimental research.

Mapping marine debris hotspots on Boa Vista Island, Cabo Verde

Coastal ecosystems are under increasing threat, with the accumulation of marine debris-particularly plastics-posing significant ecological risks. Oceanic islands are especially vulnerable due to ocean currents depositing marine debris on their exposed shores. This study presents the first assessment of marine debris accumulation on sandy beaches of Boa Vista Island, Cabo Verde. Using a combination of drone-based aerial imagery and sand sampling, we quantified micro-, meso-, and macro-debris densities across 29 beaches. North- and east-facing beaches of the island showed the highest accumulation of marine debris (>85 % plastics), driven by ocean currents. Mean drone-based densities varied between 5 and 2371 macro-debris items per 100 m of beach length, totalling 23,085 items. As for sand samples, mean densities ranged from 0 to 1639 items/m2, totalling 4272 large microplastics, 1221 mesoplastics and 350 macroplastics. The easternmost beach, Ponta de Roque, alone accounted for 31 % of the total debris recorded across all locations, with sand samples averaging 1639 items/m2 (1453 microplastics larger than 1 mm), and drone-based surveys averaging 68 macro-debris items/100 m2. Fishing-related items comprised ∼24 % of drone-surveyed debris, suggesting input from the Northwest African coast. Plastic fragments predominated, with significant correlations between drone-surveyed macro-plastics and sand-sampled large microplastic densities. Drone surveys effectively identified marine debris hotspots, aligning with ground-based data. This study provides important baseline data for long-term monitoring in the archipelago and offers a transferable methodology for assessing plastic pollution in other island systems.

Mission Tara Microplastics: a holistic set of protocols and data resources for the field investigation of plastic pollution along the land-sea continuum in Europe

The Tara Microplastics mission was conducted for 7 months to investigate plastic pollution along nine major rivers in Europe-Thames, Elbe, Rhine, Seine, Loire, Garonne, Ebro, Rhone, and Tiber. An extensive suite of sampling protocols was applied at four to five sites on each river along a salinity gradient from the sea and the outer estuary to downstream and upstream of the first heavily populated city. Biophysicochemical parameters including salinity, temperature, irradiance, particulate matter, large and small microplastics (MPs) concentration and composition, prokaryote and microeukaryote richness, and diversity on MPs and in the surrounding waters were routinely measured onboard the French research vessel Tara or from a semi-rigid boat in shallow waters. In addition, macroplastic and microplastic concentrations and composition were determined on river banks and beaches. Finally, cages containing either pristine pieces of plastics in the form of films or granules, and others containing mussels were immersed at each sampling site, 1 month prior to sampling in order to study the metabolic activity of the plastisphere by meta-OMICS and to run toxicity tests and pollutants analyses. Here, we fully described the holistic set of protocols designed for the Mission Tara Microplastics and promoted standard procedures to achieve its ambitious goals: (1) compare traits of plastic pollution among European rivers, (2) provide a baseline of the state of plastic pollution in the Anthropocene, (3) predict their evolution in the frame of the current European initiatives, (4) shed light on the toxicological effects of plastic on aquatic life, (5) model the transport of microplastics from land towards the sea, and (6) investigate the potential impact of pathogen or invasive species rafting on drifting plastics from the land to the sea through riverine systems.

Spatiotemporal response of microplastics to natural and anthropogenic factors in estuarine waters

Riverine outflow is the primary pathway for transporting microplastics from terrestrial to marine environments, making estuaries hotspots for microplastics pollution. However, how and to what extent natural and anthropogenic factors affect the distribution of microplastics in estuarine waters remains largely unknown. A meta-analysis of 126 estuaries from 93 studies revealed a global median microplastics abundance of 196.9 items/m3, with a range from 0.007 ± 0.003 to 792,000 ± 138,000 items/m3. Microplastics were more abundant in estuaries in Asia and Oceania compared to Europe and South America. The microplastic abundance in estuarine waters was positively correlated with regional population density, per capita plastic waste, agricultural land proportion, and silt content, while the human development index (HDI) and mean annual precipitation displayed negative effects on microplastic abundance. Notably, HDI was the dominant factor influencing microplastic abundance in estuarine waters. In developing countries, microplastic abundance in estuarine waters showed positive changes, whereas it remained stable in developed countries over time. This study offers critical insights into the effects of natural and anthropogenic factors on the distribution patterns of microplastics in estuarine waters, providing important support for future management of microplastics pollution in estuaries.

Occurrence and migration patterns of microplastics in different tidal zones of tourist beaches: A case study in the Bohai Bay, North China

Coastal areas are acknowledged to be significant reservoirs of microplastics, while limited research on their presence and migration in the intertidal zones. This study investigated in a tourist beach in northern China, to reveal the occurrence of microplastics at different intertidal heights, elucidates their migration patterns, and discusses the impact of tourist activities on microplastics. Results showed that the mean microplastic abundance was 2114.8 ± 933.2 items/kg in sediments and 30,670.8 ± 15,094.9 items/m3 in seawater. Fibers were the most common shape; transparent, blue, green and black prevailed in color; and cellulose and PET were the most common components. Microplastic abundances decreased from high tide zone to low tide zone, and the abundances of microplastics in seawater were positively correlated with those in the high tide zone and negatively correlated with those in the low tide zone. Compared to wave disturbance, human activities have a relatively limited impact on microplastic abundance. However, intensive tourist activities contribute to a higher diversity of microplastic types on tourist beaches. This study enhances the understanding of the occurrence and migration patterns of microplastics in tourist beaches, and provides a valuable dataset and theoretical basis for subsequent research on microplastic pollution in coastal areas.

New insights into the impact of leachates from in-field collected plastics on aquatic invertebrates and vertebrates

The impact of leachates from micronized beached plastics of the Mediterranean Sea and Atlantic Ocean on coastal marine ecosystems was investigated by using a multidisciplinary approach. Chemical analysis and ecotoxicological tests on phylogenetically distant species were performed on leachates from the following plastic categories: bottles, pellets, hard plastic (HP) containers, fishing nets (FN) and rapido trawling rubber (RTR). The bacteria Alivibrio fischeri, the nauplii of the crustaceans Amphibalanus amphitrite and Acartia tonsa, the rotifer Brachionus plicatilis, the embryos of the sea urchin Paracentrotus lividus, the ephyrae of the jellyfish Aurelia sp. and the larvae of the medaka Oryzias latipes were exposed to different concentrations of leachates to evaluate lethal and sub-lethal effects. Thirty-one additives were identified in the plastic leachates; benzophenone, benzyl butyl phthalate and ethylparaben were present in all leachates. Ecotoxicity of leachates varied among plastic categories and areas, being RTR, HP and FN more toxic than plastic bottles and pellets to several marine invertebrates. The ecotoxicological results based on 13 endpoints were elaborated within a quantitative weight of evidence (WOE) model, providing a synthetic hazard index for each data typology, before their integrations in an environmental risk index. The WOE assigned a moderate and slight hazard to organisms exposed to leachates of FN and HP collected in the Mediterranean Sea respectively, and a moderate hazard to leachates of HP from the Atlantic Ocean. No hazard was found for pellet, bottles and RTR. These findings suggest that an integrated approach based on WOE on a large set of bioassays is recommended to get a more reliable assessment of the ecotoxicity of beached-plastic leachates. In addition, the additives leached from FN and HP should be further investigated to reduce high concentrations and additive types that could impact marine ecosystem health.

Microplastic abundance in the semi-enclosed Osaka Bay, Japan

Anthropogenic particles in sea surface water of the semi-enclosed Osaka Bay were identified using stereomicroscopy, classified according to polymer type using Fourier-transform infrared spectroscopy (FTIR), and categorized according to their physical characteristics. A total of 565.1 particles were detected in the water samples. However, plastic particles accounted for only 22.4% of the particles. Microplastic abundance in Osaka Bay showed seasonal variance from 8.9 ± 1.4 (in May) to 22.8 ± 6.5 particles/L (in July), which is consistent with previous reports in other semi-enclosed bays. Microplastics were mainly fragmented and fiber shaped, with gray and colorless/white coloration. The dominant polymer types were polypropylene, poly(methylmethacrylate), polyester, polyethylene, and polyethylene terephthalate. Generally, there were considerably higher abundances of microplastics at offshore sites compared with nearshore sites. The results of this study suggest that local river effluents and marine-related activities are probable sources of microplastics in Osaka Bay.

Marine litter and microplastic pollution in mangrove sediments in the Sea of Oman

Marine litter and microplastic pollution in mangroves pose significant threats. This study of litter in Omani mangroves revealed an average density of 0.83 to 21.92 items/m2. Quriyat lagoon emerged as the most contaminated area, hosting 133 items/m2, while Qurum Natural Reserve lagoon showed the least contamination at 10 items/m2. Plastics constituted 73-96 % of the litter, with microplastic levels in sediment ranging from 6 to 256 pieces/kg. Al-Sawadi's lagoon had the highest microplastic abundance (27.52 ± 5.32 pieces/kg), in contrast to Al Qurum's Marine Protected Area with the lowest (0.60 ± 1.12 pieces/kg). Microplastics, categorized as fragments, pellets, and fibers, were distributed across zones 40.05 % landward, 30.97 % seaward, and 28.98 % in the middle mangrove zones. Primary plastic polymers identified were Polyethylene (PE) at 40 % and High-Density Polyethylene (HDPE) at 28 %, along with others found in specific areas. Our findings provide essential baseline data for future monitoring efforts and management strategies in Oman and other countries.

Lost and found: Patterns of marine litter accumulation on the remote Island of Santa Luzia, Cabo Verde

Santa Luzia, an uninhabited island in the archipelago of Cabo Verde, serves as a natural laboratory and important nesting site for loggerhead turtles Carettacaretta. The island constitutes an Integral Natural Reserve and a Marine Protected Area. We assessed marine litter accumulation on sandy beaches of the island and analysed their spatial patterns using two sampling methods: at a fine scale, sand samples from 1 × 1 m squares were collected, identifying debris larger than 1 mm; at a coarse scale, drone surveys were conducted to identify visible marine debris (>25 mm) in aerial images. We sampled six points on three beaches of the island: Achados (three points), Francisca (two points) and Palmo Tostão (one point). Then, we modelled the abundance of marine debris using topographical variables as explanatory factors, derived from digital surface models (DSM). Our findings reveal that the island is a significant repository for marine litter (>84% composed of plastics), with up to 917 plastic items per m2 in the sand samples and a maximum of 38 macro-debris items per m2 in the drone surveys. Plastic fragments dominate, followed by plastic pellets (at the fine-scale approach) and fishing materials (at the coarse-scale approach). We observed that north-facing, higher-elevation beaches accumulate more large marine litter, while slope and elevation affect their spatial distribution within the beach. Achados Beach faces severe marine debris pollution challenges, and the upcoming climate changes could exacerbate this problem.

Spatial distribution of anthropogenic particles and microplastics in a meso-tidal lagoon (Arcachon Bay, France): A multi-compartment approach

Assessment of microplastic (MP) contamination is still needed to evaluate this threat correctly and tackle this issue. Here, MP contamination was assessed for a meso-tidal lagoon of the Atlantic coast (Arcachon Bay, France). Sea surface, water column, intertidal sediments and wild oysters were sampled. Five different stations were studied to assess the spatial distribution of the contamination. Two were outside of the bay and three were inside the bay (from the inlet to the back). A distinction was made between all anthropogenic particles (AP, i.e. visually sorted) and MP (i.e. plastic polymer confirmed by ATR-FTIR spectroscopy). The length of particles recovered in this study ranged between 17 μm and 5 mm. Concentration and composition in sea surface and water column samples showed spatial variations while sediment and oyster samples did not. At outside stations, the sea surface and the water column presented a blended composition regarding shapes and polymers and low to high concentrations (e.g. 0.16 ± 0.08 MP.m-3 and 561.7 ± 68.5 MP.m-3, respectively for sea surface and water column), which can be due to coastal processes and nearby input sources. The inlet station displayed a well-marked pattern only at the sea surface. High AP and MP concentrations were recorded, and fragments along with polyethylene overwhelmed (respectively 76.0 % and 73.2 %). Higher surface currents could explain this pattern. At the bay back, AP and MP concentrations were lower and fibers were mainly recorded. Weaker hydrodynamics in this area was suspected to drive this contamination profile. Overall, fragments and buoyant particles were mainly detected at the sea surface while fibers and negatively buoyant particles prevailed in other compartments. Most of the studied samples presented an important contribution of fiber-shaped particles (from 31.5 % to 94.2 %). Finally, contamination was ubiquitous as AP and MP were found at all stations in all sample types.

A global snapshot of microplastic contamination in sediments and biota of marine protected areas

Microplastics (MPs) become ubiquitous contaminants in Marine Protected Areas (MPA) that have been planned as a conservation strategy. The present study provides a comprehensive overview of the occurrence, abundance, and distribution of MPs potentially affecting MPA worldwide. Data on MP occurrence and levels in sediment and biota samples were collected from recent peer-reviewed literature and screened using a GIS-based approach overlapping MP records with MPA boundaries. MPs were found in 186 MPAs, with levels ranging from 0 to 9187.5 items/kg in sediment and up to 17,461.9 items/kg in organisms. Peaked MPs concentrations occurred within multiple-use areas, and no-take MPAs were also affected. About half of MP levels found within MPA fell into the higher concentration quartiles, suggesting potential impacts on these areas. In general, benthic species were likely more affected than pelagic ones due to the higher concentrations of MP reported in the tissues of benthic species. Alarmingly, MPs were found in tissues of two threatened species on the IUCN Red List. The findings denote urgent concerns about the effectiveness of the global system of protected areas and their proposed conservation goals.

Microplastic levels on sandy beaches: Are the effects of tourism and coastal recreation really important?

This study assessed the effect of tourism and other recreational activities on microplastic (MP) levels and their characteristics in the sand and surf zone of the seawater. Six sites were chosen belonging to three sandy beaches with similar geomorphologic and morphodynamic characteristics but with different tourism activities. On average, a concentration of 1133.3 ± 811.3 items/kg dry weight (d.w.) and 12.7 ± 14.9 items/m³ were found in the sand and seawater samples, respectively. Fibers and films predominated and were less than 1 mm in length. In the sand, the films mainly matched the PE polymer spectra and the fibers matched PET polymer, cotton, and indigo blue dye; in the seawater samples, PP films and PET fibers prevailed. At the Pehuén-Co - Monte Hermoso Coastal Marine MPA where the flow of tourists is low, the MP levels were the lowest and the largest particles were found, mainly blue or black fibers, with less polymer diversity, cotton and PET being the most prevalent suggesting a recent input of textile fibers to this site. Moreover, the highest concentration of MPs was found on the southern site of a beach considered to be more pristine due to negligible human activity, including the smallest size pattern, mostly composed of white films or fibers with a greater diversity of polymers, predominantly PE > PET > PP. A great occurrence of PVC white films was also found in the surf zone at this site. Proximity to the mouth of a river, littoral drift, and other point sources were identified as the main sources, indicating that, apart from the local tourism and recreational activities, other sources might play a major role in the input of MPs to sandy beaches, such as extensive/intensive agricultural land use and irrigation areas.

Effects of Biofilms and Particle Physical Properties on the Rising and Settling Velocities of Microplastic Fibers and Sheets

Vertical dynamics of microplastics (MPs) in the water column are complex and not fully understood due to the diversity of environmental MPs and the impact of weathering and biofouling on their dynamical properties. In this study, we investigate the effects of the particle properties and biofilm on the vertical (settling or rising) velocity of microplastic sheets and fibers under laboratory conditions. The experiments focus on three types of MPs (polyester PES fibers, polyethylene terephthalate PET sheets, and polypropylene PP sheets) of nine sizes and two degrees of biological colonization. Even though pristine PES fibers and PET sheets had a similar density, the sinking velocity of fibers was much smaller and independent of their length. The settling or rising velocity of sheets increased with the particle size up to a threshold and then decreased in the wake of horizontal oscillations in large particles. Biofilms had unexpected effects on vertical velocities. Irregular biofilm distributions can trigger motion instabilities that decrease settling velocities of sheets despite the increase in density. Biofilms can also modify the orientation of fibers, which may increase their settling velocity. Finally, we selected the most performant theoretical formulation for each type of particle and proposed modifications to consider the effect of biofilm distribution.

Hydrometeorological assessments of the transport of microplastic pellets in the Eastern Mediterranean

Microplastic pellets were sampled in May and November 2018 during one-week surveys at 13 coastal beaches in Iskenderun Bay/Turkey. Pellet pollution index (PPI) was calculated for the beaches as a tool to assess beach pollution by microplastic pellets. Hydrometeorological conditions, including wind, current, wave, surface run-off, and precipitation, were examined during 2018 to reveal the effect on the transport of microplastic pellets within the study area. Sea-surface heights, including the astronomical tide and the storm surge and the wave runup heights, were also considered in the analysis to study the extent of hydrodynamic forcing on the beach. Hydrometeorological assessments indicated that the pellet concentrations in the coastal zone are mostly related to wind-induced transport. Three major river discharges are considered as the main source of microplastic pellets effluents. A Lagrangian particle transport model was conducted to reveal the possible beaching hotspots of microplastic pellets released from these river mouths. Average microplastic pellets were calculated as 126.04 ± 54.08 items/m² for May 2018 and 70.22 ± 18.25 items/m² for November 2018. An overall mean PPI for May 2018 was calculated as 1.13, indicating a moderate degree of pellet pollution, and 0.56 for November 2018, indicating a low degree of pellet pollution. The simulations showed that Orontes River effluents affected the inner Iskenderun Bay coasts more than the Seyhan and Ceyhan River.

Seasonal Distribution, Composition, and Inventory of Plastic Debris on the Yugang Park Beach in Zhanjiang Bay, South China Sea

Plastic debris contamination in marine environments is a global problem that poses a considerable threat to the sustainability and health of coastal ecosystems. Marine beaches, as the key zones where terrestrial plastic debris reach coastal waters, are faced with the increasing pressures of human activities. In this study, we explored the distribution, composition, and inventory of plastic debris over seasonal and tidal zones at the Yugang Park Beach (YPB) in Zhanjiang Bay, South China Sea, to provide a baseline for plastic debris on a marine beach. The results showed mean abundance of plastic debris in summer (6.00 ± 2.10 items/m2) was significantly greater than that in winter (3.75 ± 2.12 items/m2). In addition, the composition of plastic debris ranged in size mainly from 1 to 5 mm and 0.5 to 2.5 cm in winter and summer, respectively. In terms of composition, white plastic debris was the most common (81.1%), and foam was the most abundant (64.4%). Moreover, there was a significant relationship between the abundance of plastic debris and sand grain size fraction (p < 0.05), implying the abundances of microplastic debris were more easily impacted by sand grain size (>2 mm). In total inventory, there were about 1.18 × 105 and 2.95 × 105 items of plastic debris on the YPB in winter and summer, respectively. The tidal variation and human activities are responsible for the plastic debris accumulation. This study provided a method to quantify the inventory of plastic debris on a beach and could be helpful to consider regional tidal variations and critical source areas for effective plastic debris clean-up.