Microplastic pollution in sublittoral coastal sediments of a North Atlantic island: The case of La Palma (Canary Islands, Spain)

The potential use of birds as bioindicators of suspended atmospheric microplastics and artificial fibers

Microplastics (MPs) and artificial fibers (AFs) have been detected suspended tens of meters above ground level in the atmosphere, yet empirical data on them remain scarce. This study aimed to investigate the presence of MPs and AFs in the digestive and respiratory systems of two abundant bird species, the Common House Martin (Delichon urbicum) and the Common Swift (Apus apus), within the Community of Madrid, Spain. Given that these birds spend the majority of their lives airborne, engaging in activities such as mating and sleeping during flight, the research sought to assess the potential of using these bird species as bioindicators for suspended atmospheric MPs and AFs. Samples were obtained from necropsies of birds (N = 24) collected primarily between spring and summer from 2021 to 2023. Only individuals that died within the initial 24-hour period and had not been fed were selected for examination to avoid contamination. MPs and AFS were identified by micro-FTIR, characterized and quantified. Results revealed that 75 % of the sampled birds exhibited at least one MPs in their respiratory and/or digestive system. All identified MPs were fibers, with polyester (PES) being the most predominant (48 %), followed by acrylic fibers (ACR; 28 %), and polyethylene (PE; 18 %). The average concentrations in the respiratory system were 1.12 ± 0.45 MPs/specimen and 2.78 ± 1.04 AFs/specimen for Common Swift and 0.75 ± 0.30 MPs/specimen and 0.75 ± 0.36 AFs/specimen for House Martin. In the digestive system, these were 1.92 ± 0.72 MPs/specimen and 3.42 ± 0.69 AFs/specimen for Common Swift, and 1.34 ± 0.50 MPs/specimen and 1.39 ± 0.47 AFs/specimen for House Martin. Birds collected areas with high population density located in the direction of the prevailing winds showed a concentration of MPs significantly higher in the digestive system. Taken together, these findings confirmed the potential use of these birds as bioindicators for monitoring of suspended atmospheric MPs and AFs.

Understanding and addressing microplastic pollution: Impacts, mitigation, and future perspectives

Improper disposal of household and industrial waste into water bodies has transformed them into de facto dumping grounds. Plastic debris, weathered on beaches degrades into micro-particles and releases chemical additives that enter the water. Microplastic contamination is documented globally in both marine and freshwater environments, posing a significant threat to aquatic ecosystems. The small size of these particles makes them susceptible to ingestion by low trophic fauna, a trend expected to escalate. Ingestion leads to adverse effects like intestinal blockages, alterations in lipid metabolism, histopathological changes in the intestine, contributing to the extinction of vulnerable species and disrupting ecosystem balance. Notably, microplastics (MPs) can act as carriers for pathogens, potentially causing impaired reproductive activity, decreased immunity, and cancer in various organisms. Studies have identified seven principal sources of MPs, including synthetic textiles (35%) and tire abrasion (28%), highlighting the significant human contribution to this pollution. This review covers various aspects of microplastic pollution, including sources, extraction methods, and its profound impact on ecosystems. Additionally, it explores preventive measures, aiming to guide researchers in selecting techniques and inspiring further investigation into the far-reaching impacts of microplastic pollution, fostering effective solutions for this environmental challenge.

The distribution of sediment microplastics assemblages is driven by location and hydrodynamics, not sediment characteristics, in the Gulf of Maine, USA

Microplastics (MP) are found in marine sediments across the globe, but we are just beginning to understand their spatial distribution and assemblages. In this study, we quantified MP in Gulf of Maine, USA sediments. MP were extracted from 20 sediment samples, followed by polymer identification using Raman spectroscopy. We detected 27 polymer types and 1929 MP kg-1 wet sediment, on average. Statistical analyses showed that habitat, hydrodynamics, and station proximity were more important drivers of MP assemblages than land use or sediment characteristics. Stations closer to one another were more similar in their MP assemblages, tidal rivers had higher numbers of unique plastic polymers than open water or embayment stations, and stations closer to shore had higher numbers of MP. There was little evidence of relationships between MP assemblages and land use, sediment texture, total organic carbon, or contaminants.

Microplastic and mesoplastic pollution in surface waters and beaches of the Canary Islands: A review

The Canary Archipelago is a group of volcanic islands located in the North Atlantic Ocean with high marine biodiversity. This archipelago intercepts the Canary Current, the easternmost branch of the Azores Current in the North Atlantic Subtropical Gyre, which brings large amounts of litter from remote sources via oceanic transportation. It is, therefore, particularly vulnerable to marine plastic pollution. Here, we present a review of the available studies on mesoplastics and microplastics in the Canary Islands over the last decade to evaluate the level and distribution of plastic pollution in this archipelago. Specifically, we focused on data from beaches and surface waters to assess the pollution level among the different islands as well as between windward and leeward zones, and the main characteristics (size, type, colour, and polymer) of the plastics found in the Canary Islands. The concentrations of meso- and MPs on beaches ranged from 1.5 to 2972 items/m2 with a mean of 381 ± 721 items/m2. The concentration of MPs (>200 μm) in surface waters was highly variable with mean values of 998 × 103 ± 3364 × 103 items/km2 and 10 ± 31 items/m3. Plastic pollution in windward beaches was one order of magnitude significantly higher than in leeward beaches. The accumulation of MPs in surface waters was higher in the leeward zones of the high-elevation islands, corresponding to the Special Areas of Conservation (ZECs) and where the presence of marine litter windrows (MLW) has been reported. Microplastic fragments of polyethylene of the colour category "white/clear/uncoloured" were the most common type of plastic reported in both beaches and surface waters. More studies on the occurrence of MLW in ZECS and plastic pollution in the water column and sediments, including small-size fractions (<200 μm), are needed to better assess the level of plastic pollution and its fate in the Canary Islands. Overall, this review confirms that the Canary Archipelago is a hotspot of oceanic plastic pollution, with concentrations of MPs in surface waters in the highest range reported for oceanic islands and one of the highest recorded mean concentrations of beached meso- and microplastics in the world.

Beneath the water column: Uncovering microplastic pollution in the sublittoral coastal sediments of the Canary Islands, Spain

Marine ecosystems pollution by microplastics (MPs) is a global problem of special concern. The present study examines the prevalence and distribution of MPs and cellulosic particles in sublittoral coastal sediments of the Canary Islands archipelago (Spain). At twenty-six different locations alongside seven islands, three samples were taken parallel to the shoreline between 1 and 10 m depth (n = 78). Sediment samples were primarily digested with a H2O2 solution followed by four flotations in a saturated NaCl solution. The mean concentration obtained was 3.9 ± 1.6 items/g of dry weight. A similar distribution pattern was observed across all islands concerning particles morphology, color, size and composition: mainly colorless/translucent and blue fibers (60.0%). Additionally, fragments were also found, and to a much lesser extent microbeads, films and tangled messes. MicroFourier Transform Infrared spectroscopy analysis of 12.5% of the fibers, showed that they were mainly cellulosic (54.5%) -either natural or semisynthetic- followed by polyester (22.7%) and acrylic (4.5%). The potential correlation between particle distribution in nearshore sediments and wave intensity was also explored. This work provides the first comprehensive report on the current MPs content of the seabed of the region.

Tracking anthropogenic microparticles in wildlife of an alpine insular environment

Despite the isolation of remote natural regions, it has been discovered that they are experiencing the accumulation of anthropogenic microparticles (i.e., microplastics or natural or semisynthetic cellulosic particles). Teide National Park (Canary Islands, Spain) is a high-mountain protected area known for its rich biodiversity. This study aims to assess the occurrence of coloured anthropogenic particles in the faecal matter of wild mammals, specifically rabbits and mouflons, residing in the park. With this purpose, faeces were collected from 68 systematically distributed sampling points. A stereomicroscopy-guided grinding process allowed a chemical-free and quick visual inspection of 616 individual excreta, revealing that 96% were particle-free. However, 37 anthropogenic particles were found, which correspond to 0.79 ± 0.20 items per gram of dry faecal matter. The archetypical particle was a cellulosic blue microfibre of 2721 ± 407 µm, though poly(ethylene-vinyl acetate) and polypropylene were also identified via micro Fourier-transform infrared spectroscopic analysis. Atmospheric deposition and touristic pressure may be the sources of the anthropogenic particles, as they were randomly found in 36% of the sampling points. These findings represent the first evidence of anthropogenic particle ingestion by wild rabbits and mouflons, signifying the introduction of microplastics into terrestrial food chains in a remote high-mountain environment.

Lakes with or without urbanization along their coasts had similar level of microplastic contamination, but significant differences were seen between sampling methods

The influence of sampling method on microplastic (MP) quantification and the impact of population density on the levels of MP contamination in surface waters from Patagonian lakes were investigated. Six lakes located in Northern Patagonia (Argentina) were studied using two different sampling protocols widely reported in the literature: water collected in glass bottles vs. water collected using a 50 μm mesh size net. To assess the influence of population density on MP contamination, lakes with urbanization at shores (Nahuel Huapi, Gutierrez and Moreno) and lakes without urbanization on their shores (Espejo, Espejo Chico and Mascardi) were considered. We identified contamination with secondary MP at all the freshwater lakes studied, with predominance (>90 %) of textile-based microfibers (MF). Remarkably the levels of contamination were similar in all the lakes, independently of whether they were impacted by urbanization along their coasts or not, which supports the notion that there is atmospheric transport of MP. The greatest variability found was among sampling methods, with differences above of three orders magnitude. Samples collected directly in 1-l bottles had an average of 5257 MP/m³ in comparison to 1.57 MP/m³ in the samples that were collected with a 50 μm net. Interestingly, Nahuel Huapi lake samples collected with bottles where the WWTP discharges effluents were significantly more contaminated (SD 9400 ± 4351 MP/MF per m³) than samples collected 5 km west of the plant (2100 ± 1197 MP/MF per m³). Results highlight the significance of textile microfibers as microplastic contaminants of freshwater, and the need to address mesh size when looking for textile microfibers and to develop standardized sampling protocols to make studies on freshwater MF contamination comparable.

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 abundance, distribution, and characterization in freshwater sediments in Iran: a case study in Kermanshah city

This paper focuses on abundance, distribution, and characteristics of microplastics (MPs) in freshwater sediments of Sarab Niloofar Lake, Kermanshah, Iran. After selecting an appropriate method for extraction of MPs, the characterization such as polymer types, surface morphology, and trace elements has been determined using Fourier transform infrared spectroscopy, scanning electron microscopic, and energy-dispersive X-ray spectroscopic analysis, respectively. The results highlighted that all sampling locations were contaminated by MP abundance ranged from 1733.33 to 4400 items kg^-1 d.w with an average of 2483.59 ± 805.30 items kg^-1 d.w. MPs with a size range of 0.025 to 1 mm (25-1000 μm) were the most frequently detected MPs in size (62%). Furthermore, the MPs found in this area mainly contain fiber (61%), fragment (19%), film (9%), foam (6%), and pallet (5%). The main color for detected MPs in sampling stations was black (51%) and followed by white/transparent (27%), red (11%), blue (7%), and yellow (4%). The results of polymer identification revealed that the polyethylene, polystyrene, polyurethane, and polypropylene were the principal polymers. This research work emphasized that various types of MPs have been distributed in freshwater sediments of Sarab Niloofar Lake, which is a first useful data for MPs in one the most important Kermanshah's tourist area.

Deep Sea Microplastic Pollution Extends Out to Sediments in the Northeast Atlantic Ocean Margins

Microplastics are ubiquitous emerging contaminants found in every habitat surveyed, building upon international databases globally. Costs and accessibility often correlate to few deep sea sediment surveys, restricting the number of stations within a given sampling area. An extensive survey of the Porcupine Seabight, Porcupine Bank, the Goban Spur, and south-western canyons resulted in identifying microplastics in deep sea sediment surface layers from 33 of the 44 stations sampled (75%), with a total of 83 particles (74 synthetic and 9 natural) recorded. No microplastic hotspots were identified, and abundances (kg d.w.^-1) were not correlated with distance from land, depth, or the presence of macrolitter on the seafloor. Understanding the sources of deep sea microplastics, such as marine traffic, is crucial to developing effective mitigation strategies as well as further monitoring campaigns targeting microplastic pollution in areas with significant deep sea biodiversity such as the Porcupine Seabright.

Hidden problems in geological heritage sites: The microplastic issue on Saint Mary's Island, India, Southeast Arabian Sea

Microplastics (MPs) have become a dominant constituent of several oceanic islands. This study focuses on the occurrence and distribution of MPs present in the beach sediments of Saint Mary's Island (SMI), a geological heritage site located in the south-eastern part of the Arabian Sea. The average (standard deviation) abundance of MPs on this island was 97.18 (80.49) particles/kg. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy revealed that MPs are composed of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyamide (PA). Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) highlighted the presence of Cr, As, Pb, and Cd (harmful pollutants) on MP surfaces. The MPs in the SMI are largely contributed by the nearby fishing harbour, touristic beaches and estuaries. The results of this study, act as a starting point for continuous environmental monitoring in this unique region of the world.

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.

Ageing and fragmentation of marine microplastics

The generation of small fragments from the environmental ageing of microplastics (MPs) is still a poorly known process. This work addresses the fragmentation of MPs obtained from marine debris consisting of polyethylene and polypropylene (PE and PP in environmental mixture) and polystyrene (PS) after exposure to accelerated ageing by irradiation and mechanical stirring. Number particle size distribution in the 1-100 μm range was assessed by combining laser diffractometry with particle counts from flow cytometry. The results showed the generation of a high number of small MP particles, which reached 10⁵-10⁶ items/mg of plastic with most fragments <2 μm. The results showed that environmentally aged MPs give rise to a larger number of small MPs in a pattern consistent with progressive fragmentation in the three spatial dimensions. The proportion of small MPs was much higher than that found in current sampling campaigns, suggesting a severe underestimation of the environmental presence of small MPs. We also demonstrated the generation of nanoplastics (NPs) in the fraction <1 μm from irradiated runs. The results showed that the mechanism that produced nanoplastics (NPs) from MPs was irradiation, which yielded up to 10¹¹-10¹³ NPs/g with particle size in the few hundreds of nm range. Our results are relevant for the assessment of fate and risk of plastic debris in the environment showing that the number of small plastic fragments produced during the ageing of MPs is much larger than expect from the extrapolation of larger size populations.

Occurrence, spatial distribution, and risk assessment of microplastics in surface water and sediments of Saint Martin Island in the Bay of Bengal

Microplastics (MPs) are emerging contaminants in aquatic and terrestrial ecosystems and have caused substantial concern worldwide. This study surveyed the presence of MPs in surface water and sediments across the coastal area of Saint Martin Island in the Bay of Bengal. MPs were collected following the standard protocol and identified as various types like expanded polystyrene, foam, filaments, fragments, lines, fibres, and paint flakes. Total MPs pollution in beach sediment was 317 particles/kg across 14 sampling sites, varied from 11 to 10589 particles/m² of dry sediment and 0.95 particles/m³, having ~2 to 19 particles/30 min trawl in coastal surface water samples. Most of the frequent MPs in beach sediments ranged from 1.0 to 2.0 mm, whereas the fragments were predominant in sediment and surface water samples. MPs distribution revealed that different shapes were dominant at different sites within the Island. The calculated pollution risk index due to the presence of MPs indicated that the sediment and surface water samples were under the low-risk category. However, polymeric risk assessment and contamination factors suggest that the coastline is significantly polluted, as high pollution load indices (PLI >1) were observed for sediments and coastal surface water samples. This work provides the detailed MPs data in the coastal environment of Saint Martin Island for the first time; hence it may be helpful to develop proper strategies to deal with environmental problems.

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.

Microplastics Determination in Gastrointestinal Tracts of European Sea Bass (Dicentrarchus labrax) and Gilt-Head Sea Bream (Sparus aurata) from Tenerife (Canary Islands, Spain)

Microplastic pollution has an extremely widespread distribution, to the extent that microplastics could be ingested by aquatic organisms, including species of commercial importance for fisheries and aquaculture. In this work, the anthropogenic particles content of the gastrointestinal tracts of 86 individuals of cultivated European sea bass (Dicentrarchus labrax, n = 45) and gilt-head sea bream (Sparus aurata, n = 41) from Tenerife (Canary Islands, Spain) was determined. Samples were bought at local markets and directly transported to the laboratory. After the dissection of the fishes and digestion of the gastrointestinal tracts in 10% KOH (w/v) at 60 °C for 24 h, the digests were filtered (50 µm stainless-steel mesh) and visualized under a stereomicroscope, finding that most of the items were colourless (47.7% for Dicentrarchus labrax and 60.9% for Sparus aurata) and blue (35.3% vs. 24.8%) microfibers, with an average length of 1957 ± 1699 µm and 1988 ± 1853 µm, respectively. Moreover, 15.3% of the microfibres were analysed by Fourier transform infrared spectroscopy, showing the prevalence of cellulosic fibres together with polyester, polyacrylonitrile, and poly(ether-urethane). This pattern (microplastics shapes, colours, sizes, and composition) clearly agrees with previous studies carried out in the Canary Islands region regarding the determination of microplastics in the marine environment.

Recycled wastewater as a potential source of microplastics in irrigated soils from an arid-insular territory (Fuerteventura, Spain)

In this work, the occurrence of microplastics (MPs) in irrigation recycled wastewaters (RWWs) and a desalinated brackish water (DBW) from the arid territory of Fuerteventura (Canary Islands, Spain) was studied. Besides, the presence of MPs in two types of soils (sandy-loam and clay-loamy; with no mulch film or fertilization with sewage sludge applied) irrigated with both water qualities was addressed. Results showed the prevalence presence of cellulosic and polyester microfibers (between 84.4 and 100%) of blue and transparent colors (up to 55.6 and 33.3%, respectively), with an average length of 786.9 ± 812.1 μm in the water samples. DBW had the lowest MP concentration (2.0 ± 2.0 items·L^-1) while RWW showed concentrations up to 40.0 ± 19.0 items·L^-1. Similarities were also observed between the MPs types and sizes found in both soils top layer (0-5 cm), with an average concentration three times greater in soil irrigated with RWW than in soil under DBW irrigation (159 ± 338 vs. 46 ± 92 items·kg^-1, respectively). In addition, no MPs were extracted from non-irrigated/non-cultivated soils, suggesting agricultural activities as the unique source of MPs in soils of this arid area. Results show that RWWs constitute a potential source of MPs in irrigated soils that should be considered among other pros and cons linked to the use of this water quality in agricultural arid lands.

The micro-, submicron-, and nanoplastic hunt: A review of detection methods for plastic particles

Plastic particle pollution has been shown to be almost completely ubiquitous within our surrounding environment. This ubiquity in combination with a variety of unique properties (e.g. density, hydrophobicity, surface functionalization, particle shape and size, transition temperatures, and mechanical properties) and the ever-increasing levels of plastic production and use has begun to garner heightened levels of interest within the scientific community. However, as a result of these properties, plastic particles are often reported to be challenging to study in complex (i.e. real) environments. Therefore, this review aims to summarize research generated on multiple facets of the micro- and nanoplastics field; ranging from size and shape definitions to detection and characterization techniques to generating reference particles; in order to provide a more complete understanding of the current strategies for the analysis of plastic particles. This information is then used to provide generalized recommendations for researchers to consider as they attempt to study plastics in analytically complex environments; including method validation using reference particles obtained via the presented creation methods, encouraging efforts towards method standardization through the reporting of all technical details utilized in a study, and providing analytical pathway recommendations depending upon the exact knowledge desired and samples being studied.