Abstract
This study provides a transboundary evaluation of microplastic (MP) pollution across marine corridors primarily major shipping routes that link the Atlantic Ocean to the Arabian Gulf, navigating three of the most important choke points in international shipping – the Suez Canal, Bab-el-Mandeb, and the Strait of Hormuz as well as the Strait of Gibraltar. The research was conducted during the transfer voyage of the research vessel Jaywun from Spain to Abu Dhabi between November and December 2022. A total of 100 surface-water samples were collected from six major regions: the North Atlantic Ocean (Western Europe), Mediterranean Sea, Red Sea, Arabian Sea, Strait of Hormuz and UAE waters within the Arabian Gulf. MP concentrations (>500–5000 µm) varied widely, from 4 MPs L−1 in the Mediterranean to 290 MPs L−1 at the Western entrance to the Strait of Gibraltar, with an overall average of 34.7 ± 29.0 MPs L−1 across all sites. Regionally, the Arabian Sea recorded the highest mean concentrations (56.0 ± 31.6 MPs L−1), while lower values occurred in the Mediterranean (15.5 ± 9.6 MPs L−1 and Red Sea (24.5 ± 11.0 MPs L−1 UAE waters showed a moderate abundance (30.6 ± 21.4 MPs L−1 with localized hotspots near major ports and structured shipping routes. Polymer analyses revealed polyester (PES) and polyethylene terephthalate (PET) as dominant polymers (>57%), followed by polyamides (PA6/66), acrylonitrile butadiene styrene (ABS), with minor contributions from cellulose acetate (CA), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC), indicating inputs from textiles, packaging, fishing gear, and industrial sources. The Pollution Load Index (PLI) ranged from 1.00 to 8.51 (mean 2.85 ± 1.9). Furthermore, Kruskal–Wallis analysis revealed significant regional differences in microplastic concentrations (H = 20.93, p< 0.001), while Spearman correlation indicated no significant transect-wide trend (ρ = 0.033, p = 0.743). Spatial variability and polymer diversity underscore the influence of hydrodynamic transport and maritime activities on MP dispersion. This dataset provides an important baseline for large-scale monitoring of marine microplastics across interconnected oceans and serves as a valuable reference for comparative assessments within Abu Dhabi’s waters.
Graphical Abstract
1 Introduction
As the production and utilization of plastic materials have grown significantly over the last 7 decades to 464 Mt in 2020 (), the generation of plastic waste has increased in equal measure, much of it finding its way into the marine environment. Land-based plastic waste has been noted to be a major factor of marine pollution, although marine-based operations such as fishing, shipping in general, offshore oil production operations and tourism all contribute to plastic pollution (Karbalaei et al., 2019; Osman et al., 2023). Once in the ocean, plastic wastes can disperse passively over vast distances, driven by oceanic currents and wind-induced surface movement ().
As plastic resides in the marine environment, it tends to degrade with age, oftentimes fragmenting into smaller plastic particles, where frequently particles of sizes less than 5 mm are reached. These are defined as (secondary) microplastics (MPs) with even smaller particles of less than 1 µm (1000 nm) being classified as nanoplastics (NPs) (Gigault et al., 2018). While MPs can be created from larger plastics in the marine environment, as stated above, there are MPs intentionally manufactured in their small size that are directly released into the environment through products such as cosmetics (Habib et al., 2020) and synthetic textile fibers (Hossain et al., 2025) or through accidental spills of virgin plastic pellets (Gunawardhana et al., 2024). These are called primary MPs.
The occurrence of MPs in the marine environment is of concern due to their adverse impacts on aquatic organisms (Gola et al., 2021; Gundogdu et al., 2024). A study conducted on seven commercial species of fish in the Black Sea; reported the presence of MPs in all examined specimens (; Savuca et al., 2022). Also, humans are impacted through the consumption of seafood contaminated with MPs, which may lead to health risks (Smith et al., 2018; ). Further the fragments of smaller particles like MPs and nanoplastics (NPs) are likely pose a higher environmental impact and also more prone to adsorb organic contaminants and pathogens from surrounding media (Strungaru et al., 2019). Recent studies suggest that MP pollution has ecological impacts and may contribute to climate change by releasing greenhouse gases during plastic degradation (Li et al., 2024; Savuca et al., 2025).
Measurements of MP concentrations in as many locations as possible helps understand the distribution of MPs as well as their circulation and transport patterns within the marine environment. Ocean currents (Sterl et al., 2020) and wind-driven circulation () play key roles in redistributing plastics within marine systems after their entry, facilitating their movement between open waters and coastal zones. In some instances, these particles are carried back to shorelines (Kim and Kim, 2024), where they undergo further mechanical abrasion from wave action and break down into even smaller fragments (Hien et al., 2020; Yuan et al., 2022). In addition, there is the distribution of MPs between the water’s surface, the water column (Zhao et al., 2025) and the ocean floor, which is seen as one of MP sinks (Martin et al., 2022).
A circumpolar survey conducted during the Antarctic Circumnavigation Expedition (2016–2017) quantified floating macro- (>25 mm), meso- (5–25 mm), and microplastics (<5 mm), providing the first baseline of plastic abundance across the Southern Ocean and supporting global model validation and litter transport assessments (Suaria et al., 2020). The first dataset on MP occurrence, distribution, polymer types, and particle sizes in the tropical Indian Ocean was obtained during the expedition with the German research vessel Sonne from Hong Kong to Port Louis, using laser-based infrared imaging and microwave-assisted digestion (Hildebrandt et al., 2022). Li et al. (2022) carried out a MP survey along a cross-ocean transect during a 2019 expedition aboard the R.V. Shi Yan 3, spanning 11,750 nautical miles from Guangzhou across the Pearl River Estuary, the South China Sea, the Strait Zone, and into the eastern Indian Ocean. Here, a continuous pump-underway system (<5 m depth) was used, providing baseline data on cross-oceanic MP pollution between the Pacific and Indian Oceans. In addition, ten Hietbrink et al. (2025) measured NP concentrations on the 2020 R.V. Pelagia cruise across the North Atlantic, from the subtropical gyre to the northern European shelf, using TD-PTR-MS as an analytical method.
Despite significant advancements, current MP detection methods remain limited by the complexity of environmental matrices and the wide variation in MP size, shape, colour, and polymer composition. The detection and quantification of MPs particularly in seawater, sediment and biota remains technically demanding and often requires extensive sample preparation (Khanam et al., 2025). MP analysis using Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy provides accurate identifications, however, these techniques can be costly and time-consuming when applied to large environmental datasets (Hidalgo-Ruz et al., 2012; Khanam et al., 2025). To overcome these challenges adopting innovative monitoring and predictive strategies is needed (). The utility of Machine learning – domain of artificial intelligence has advance tools for data analytics and forecasting (Koelmans et al., 2019; Khanam et al., 2025). In machine learning the research extends beyond the MPs, biodiversity conservation, climate change modelling, pollution assessment and waste management (Zhang et al., 2017; Reichstein et al., 2019; Khanam et al., 2025). Recent studies have demonstrated that the machine learning algorithms enables more accurate predictions of MP dispersion, hotspots and movement trajectories (Su et al., 2023). Furthermore, computer vision and machine learning have enhanced MP analysis, enabling classification accuracies of over 99% regardless of particle size, shape, or polymer type (; ). In addition, understanding the hydrodynamic behaviour and transport pathways of MPs is very important, for effective environmental management and mitigation strategies (Saha et al., 2026).
Monitoring and reporting of MP concentrations in aquatic environments within the Middle East and North Africa (MENA) region began nearly fifteen years ago (Ouda et al., 2021; Pu et al., 2024). However, the region remains relatively new to systematic assessments of MP contamination in marine and coastal environments. Most available studies documenting MP concentrations in the Red Sea and along the Saudi Arabian and Egyptian coastlines have emerged only within the last decade (Habib and Thiemann, 2022), while measurements along the Yemeni and Omani coastlines in the Arabian Sea are missing, for the most part. No studies to date have compared MP contamination through equal assessments along the North African coast in the Mediterranean Sea, in the Red Sea, along the coast of Yemen and Oman in the Arabian Sea and along the coast of the United Arab Emirates (UAE) in the Arabian Gulf. The transfer of the research vessel Jaywun after its acquisition by the Environmental Agency Abu Dhabi from Vigo, Spain, to Abu Dhabi, UAE gave the chance to sample the surface waters along the journey for MPs. This allowed us to evaluate the distribution of MPs across regional and international marine environments, providing a glimpse into their spatial variability and transport patterns. The objective of this study was to quantify microplastic abundance (MPs L−1) in surface waters along a continuous transect connecting the Atlantic Ocean to the Arabian Gulf. Sampling was conducted aboard the above-named research vessel traveling from Spain to Abu Dhabi during November–December 2022. In total, 100 sea surface-water samples were collected across six major regions: the North Atlantic Ocean (Western Europe), Mediterranean Sea, Red Sea, Arabian Sea, Strait of Hormuz, and UAE waters within the Arabian Gulf, using a single standardized sampling and analytical protocol.
Because the ship followed a fixed schedule independent of the study, and due to ongoing hostilities in the southern Red Sea that restricted sampling to rapid methods because of safety concerns, 1 L grab samples were collected throughout. This consistent approach enables direct comparison of the data obtained in this study primarily from heavily trafficked shipping lanes (Marinetraffic, 2026) with available global marine MP datasets () generated using the same methodology.
The novelty of this study lies in its transboundary transect spanning multiple interconnected ocean basins, allowing for direct comparison of MP levels under consistent methodological conditions, despite the focus on major shipping routes. It was hypothesized that microplastic abundance would vary along the transect in response to differences in hydrodynamic conditions and anthropogenic pressures.
2 Materials and methods
2.1 Sampling area and sample collection
A total of 100 surface water samples were collected during the Jaywun research vessel expedition from Spain to Abu Dhabi (Figure 1) carried out between Nov. 25th and Dec. 20th, 2022. The expedition began near Vigo, Spain, and crossed multiple international and regional marine environments, encompassing the waters off the Portuguese North Atlantic coastline, the Mediterranean Sea, the Red Sea, the waters off the Yemeni and Omani coastlines in the Arabian Sea, Strait of Hormuz and the waters of the United Arab Emirates (UAE), both in the Arabian Sea and the Arabian Gulf (Supplementary Figures 2.1, 2.2). In the North Atlantic Ocean, off the coast of Spain and Portugal, five samples (MP-1 to MP-5) were taken, one of them near the Western entrance to the Strait of Gibraltar. Thirteen sites (MP-6 to MP-18) at varying distances from the coast of 41 km to 276 km were sampled across the Mediterranean Sea. This transect extended from the Strait of Gibraltar, following the coastlines of Algeria, Tunisia, Malta, Libya, and Egypt, reaching its eastern endpoint near the Suez Canal. Three samples were taken within the confines of the Suez Canal (MP-19 to MP-21). Sampling in the Red Sea was carried out at eight sites (MP-22 to MP-29) from the Southern entrance of the Suez Canal southward to the outlet of the Red Sea into the Arabian Sea. This stretch represents a critical maritime corridor linking the Mediterranean and Arabian Seas. One sampling (MP-30) was conducted directly at the Northern entry to the Bab el-Mandeb Strait. Twelve sites (MP-31 to MP-42) were sampled across the Arabian Sea, including in key transitional regions such as the Gulf of Aden and the Gulf of Oman, connecting the Arabian Sea with both the Red Sea and the wider Indian Ocean.
Figure 1
Twenty-four sites (MP-43 to MP-66) were sampled within the reaches of the Strait of Hormuz along the coasts of Iran and Oman. Finally, thirty-four sites (MP-67 to MP-100) were sampled within UAE waters, covering the Northern Emirates, Dubai, and Abu Dhabi. Sampling in UAE waters was conducted at high spatial resolution, with stations in the Northern Emirates and Dubai positioned at one-hour intervals along the transect and at 15-minute intervals within Abu Dhabi waters to capture fine-scale variability. This comprehensive sampling approach provided a robust, high-resolution dataset for comparing microplastic dynamics between international and regional marine waters. Detailed information on all sampling locations, including sampling dates, GPS coordinates, distance from shore, and station descriptions, is provided (Supplementary Figures 2.1, 2.2).
For this study, seawater samples were collected in amber-coloured 1-liter glass bottles (, ; Green et al., 2018; ) with foil-lined lids, where surface water up to a depth of 30 cm was obtained. Before sampling, all bottles were rinsed thoroughly three times with tap water onboard the vessel, immediately capped, and subsequently rinsed three times with ambient seawater at the sampling site. Following the final seawater rinse, a container-based sampling method was employed, using a stainless-steel bucket to collect surface seawater from the side of the research vessel. The seawater samples were collected from the side of the research vessel away from exhaust outlets, hull contact, and areas of water agitation to prevent contamination from the ship’s surfaces or from the ship’s emissions. The collected sea water samples were filled into the amber-coloured glass bottles and capped immediately to minimize air exposure and reduce the potential for airborne contamination. All samples were immediately stored in an ice-cooled container to maintain sample integrity and prevent degradation until the laboratory analysis.
2.2 Method of analysis
The collected samples were analysed at the Abu Dhabi Quality and Conformity Council (ADQCC) laboratory. 10 mL of 4 M NaOH or 4 M KOH was added to 500 mL of the collected water sample, and the mixture was thoroughly agitated before being left to stand at room temperature (rt) for 24 hours (h) to facilitate organic matter digestion. Thereafter, 30% (w/v) aqueous hydrogen peroxide (H2O2) was added to the mixture, which was again stirred thoroughly and maintained at room temperature for an additional 24 h to ensure complete oxidation of remaining organic residues. The sample was filtered using a cellulose nitrate membrane filter (Sartorius 11406-47-CAN, 47 mm, white with black grids) with a pore size of 0.45 μm, mounted on a vacuum filtration assembly. After filtration, the filter paper with the filtered residue was placed in a glass Petri dish and allowed to dry at room temperature for 2 h. After drying, the filter was visually inspected and examined under a microscope (Nikon Digital sight DS- Fi2) to count and record the number of plastic particles falling within the specified size range >500–5000 μm. In this study, analysis was restricted to particles >500 µm to ensure reliable visual identification and robust FTIR polymer confirmation across all samples. IR analyses were carried out using a Shimadzu IRXross Fourier Transform infrared (FTIR) spectrophotometer mounted with Survey IRTM (CZETIK). The identification of MP polymers was performed using the built-in FTIR polymer library and cross-referenced with the NIST polymer database as referenced in Plastic Marine Debris Polymers in the Hawaiian Islands: Beach, Sea Surface, and Seafloor (). These libraries provided reliable matches for comparing the sample spectra with known polymer types (Supplementary Figures 3.1, 3.2). Minimum values of 0.6–0.7 (60–70%) were considered acceptable spectral matches for polymer identification (Morgado et al., 2021). The chemical nature of 20% of the observed MPs could be determined by FTIR in this study.
2.3 Quality assurance/quality control
The laboratory work was carried out within a clean, designated laboratory space. At all points in time, researchers were wearing laboratory coats and gloves to minimize contamination of the workplace. Filter papers were scrutinized for contaminants under the microscope before use to ascertain the absence of MPs before experimentation. In addition, blanks were run that used 4M aq. KOH and 4M aq. NaOH. Data analysis of microplastic (MP) abundance and distribution was conducted using Excel® to evaluate spatial variability across all sampling sites.
2.4 Statistical data analysis
To evaluate spatial variability in microplastic concentrations among regions. The Kruskal–Wallis test (Kruskal and Wallis, 1952) was used to evaluate differences among the six study regions. Effect size was estimated using epsilon-squared (ϵ²) following Tomczak and Tomczak (2014), where ϵ² = (H − k + 1)/(N − k). Spearman’s rank correlation (Spearman, 1904) was applied to assess monotonic trends in microplastic concentrations along the Spain–Abu Dhabi transect. In addition, the Pollution Load Index (PLI) was calculated to evaluate the extent of microplastic contamination and regional variability.
3 Results and discussion
3.1 Overall distribution of microplastics from Spain to Abu Dhabi
A total of 100 surface water samples were collected during the voyage of Jaywun research vessel from Spain to Abu Dhabi between Nov. 25th and Dec. 20th, 2022. The survey covered six major regions, the latter five situated within the MENA region: the North Atlantic (off the Spanish and Portuguese coasts), the Mediterranean Sea, the Red Sea, the Arabian Sea, Strait of Hormuz and UAE waters in both the Arabian Sea and the Arabian Gulf. Microplastic (MP) concentrations (>500–5000 µm) varied considerably across the six marine regions (Figure 2). Concentrations ranged from a minimum of 4 MPs L−1 recorded in the Mediterranean Sea (MP-16) to a maximum of 290 MPs L−1 at the Western entrance to the Strait of Gibraltar (MP-5). The Arabian Sea (56.0 ± 31.6 MPs L−1) recorded the highest mean abundance, followed by UAE waters in the Arabian Gulf (30.6 ± 21.4 MPs L−1), with notable hotspots near major ports and more heavily trafficked shipping routes, the North Atlantic (27.0 ± 13.5 MPs L−1), and the Red Sea (26.8 ± 10.4 MPs L−1), while the Mediterranean Sea showed the lowest average concentration of 15.5 ± 9.6 MPs L−1 (Table 1). It must be noted that in the North Atlantic the sites were on the average 70,0 km from the nearest shoreline, in the Mediterranean 118,0 km, in the Red Sea 55,5 km, in the Arabian Sea along the Yemeni and Omani coast 69,7 km, and in UAE waters 31,4 km.
Figure 2
Table 1
| Sampling areas | Minimum (MPs L−1) | Maximum (MPs L−1) | Average (MPs L−1) |
|---|---|---|---|
| North Atlantic (West Europe) | 12 | 42 | 27.0 ± 13.5 |
| Mediterranean Sea | 4 | 38 | 15.5 ± 9.6 |
| Red Sea | 8 | 40 | 24.5 ± 11.0 |
| Arabian Sea | 10 | 116 | 56.0 ± 31.6 |
| UAE waters in the Arabian Gulf | 10 | 106 | 30.6 ± 21.4 |
Minimum, maximum and average number (± STD) of MPs in the open water bodies assessed.
In general, narrow connections between water bodies such as the Strait of Hormuz (34.4 ± 24.2 MPs L−1), the Bab el-Mandeb Strait (36 MPs L−1), and the Suez Canal (31.3 ± 10.1 MPs L−1) exhibited higher MP concentrations. The highest MP concentration was found at the Western entrance to the Strait of Gibraltar (290 MPs L−1). The greatest diversity of polymers was recorded at site MP-21, located at the outlet of the Suez Canal on the side of the Red Sea, highlighting the influence of busy marine corridors on the heterogeneity of plastic pollution. Overall, 3,469 MPs were detected across all sites, reflecting strong spatial variability influenced by anthropogenic activities and hydrodynamic transport. The polymer composition of MPs showed a diverse range of plastic types across all sampled regions (Figure 3). Polyester (PES) in general and the specific polyester polyethylene terephthalate (PET) were the most dominant, accounting for 30% and 29% of total polymers, respectively. PES primarily originates from synthetic textiles and fabrics, accounting for approximately 78% of global synthetic fiber production (), while PET is a thermoplast that is also predominantly used in synthetic fibers, but is also used in containers for liquids and foods. It has a density ranging from 1.35 to 1.40 g/cm³ and thus is denser than seawater with 1.025 g/cm³ (Zhang et al., 2020; Li et al., 2025). Other polymers included polyamide-66 (PA6/66, 17%), acrylonitrile butadiene styrene (ABS, 9%), and smaller proportions of cellulose acetate (CA, 3%), polystyrene (PS, 3%), polypropylene (PP, 1%), polyethylene (PE, 2%), crumb rubber (CR, 4%), and polyvinyl chloride (PVC, 2%). PS is used in food packaging and transport containers (styrofoam®), accounting for approximately 31% of plastics in Asian surface waters and showing a high prevalence in the Indian Ocean, where it is widely dispersed throughout marine environments (). Polyamide (PA, Nylon) originates mainly from fishing gear, nets, and industrial ropes. This polymer contributes approximately 10% of global marine debris, with an estimated 600,000 tonnes of fishing nets discarded into the ocean annually (Zheng et al., 2024). CA is used in cigarette filters. This bio-based polymer degrades slowly and can persist in the marine environment for up to 10 years, breaking down primarily through UV radiation, wave action, and physical abrasion (Mazzotta et al., 2022; Serbruyns et al., 2024). ABS is used in automotive parts, electronics, and 3D printing. It is a common industrial thermoplastic composed of 15–35% acrylonitrile, 5–30% butadiene, and 40–60% styrene. It poses persistent environmental and health concerns due to its durability and is known to emit micro- and nanoplastics during manufacture and use (; ). Polypropylene (PP) and polyethylene (PE) are low-density, buoyant polymers, allowing them to float and disperse widely across marine systems through ocean currents (Pilapitiya and Ratnayake, 2024; Gunawardhana et al., 2024). PVC, the third most widely used polymer in Europe, is the least stable among high-volume plastics due to its high sensitivity to UV radiation, making photo-degradation particularly significant. The commercial PVC products typically consist of the polymer resin blended with various additives ().
Figure 3
3.2 Distribution of MPs in the North Atlantic, off the coasts of Spain and Portugal and near the Strait of Gibraltar
In the North Atlantic, off the coasts of Spain and Portugal, four sites, MP-1 to MP-4 (Figure 4), one of them within the Ria Vigo Bay (MP-1), were sampled between Nov. 25th and Nov. 27th, 2022. Microplastic (MP) concentrations within the >500–5000 µm size range showed considerable variation (Tables 1, 2), ranging from 12 MPs L−1 at MP-2 to a peak of 42 MPs L−1 at MP-4, with an average of 27.0 (± 13.5) MPs L−1. 290 MPs L−1 were recorded at MP-5, a sampling point just at the entrance of the Strait of Gibraltar. This hotspot likely reflects localized inputs from anthropogenic activities, atmospheric deposition, and hydrodynamic accumulation processes. Through the Strait of Gibraltar, the North Atlantic receives dense, warm, and saline waters originating from the Mediterranean outflow (). As noted by Palmieri et al. (2024) in their investigation of MP contamination in the Strait of Gibraltar, there are strong and variable currents in the strait that play a major role in microplastic transport and accumulation. Between 300 to 400 ships travel the Strait of Gibraltar daily, with about 90,000 commercial ships annually making the journey. In addition, there is a major refinery on the Spanish side, among other industries.
Figure 4
Table 2
| Sampling areas | Minimum (MPs L−1) | Maximum (MPs L−1) | Average (MPs L−1) |
|---|---|---|---|
| Strait of Gibraltar | 290 | 290 | 290 |
| Suez Canal | 22 | 42 | 31.3 ± 10.1 |
| Bab el-Mandeb Strait | 36 | 36 | 36 |
| Strait of Hormuz | 6 | 108 | 34.4 ± 24.2 |
Minimum, maximum and average number (± STD) of MPs at marine choke points assessed in this study.
MP presence and distribution in Ria de Vigo have been investigated previously and have been found to be driven by the output of wastewater treatment plants (Sousa et al., 2021). Previous studies from the further reaches of the North Atlantic have reported substantially lower concentrations, averaging 1 item/m³ (; ), indicating that the levels observed in this study closer to coastline are considerably higher. It has been shown in other areas of the world that MP concentrations in water (Zhang et al., 2025) and sediments (Marques Mendes et al., 2021) near estuaries and sources on land are often much higher than those in the open sea. Additionally, the different MP concentrations may reflect the different sampling techniques used (also, see below).
In our study, polymer analysis identified four main polymer types for sites 1-5: cellulose acetate (CA), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET), and an acrylonitrile butadiene styrene–styrene copolymer. As shown in (Figure 4), ABS was the most dominant polymer (60%), followed by CA (20%) and PET (20%). This composition reflects diverse sources of plastic contamination, indicating that both land-based discharges and maritime activities contribute to the presence and variability of microplastics in these waters.
3.3 Distribution of MPs in the Mediterranean Sea
A number of reviews have looked at MP contamination in the Mediterranean Sea (Suaria et al., 2016; Sharma et al., 2021; Terzi et al., 2024). The Mediterranean region is heavily reliant on the maritime sector, and these waters serve as major international shipping routes for container freight and for oil and chemical tankers, thereby exposing the Mediterranean Sea to considerable marine pollution (International Maritime Organization (IMO), 2025). Floating plastic debris in the Mediterranean Sea has already been investigated scientifically in 1980 (Morris, 1980). Different models have been forwarded that reflect the input and distribution of MP in the Mediterranean Sea (Kaandorp et al., 2020; ). MP concentration was found to be particularly high near shipping lanes, mussel farms, the entry of large rivers (Schmidt et al., 2018; Simon-Sánchez et al., 2019) and near large cities (Pasquini et al., 2016), for instance along the south-east French Mediterranean coast (Galgani et al., 2000).
During the survey, 13 sites (MP-6 to MP-18) were sampled across the Mediterranean Sea between Nov. 28th and Dec. 6th, 2022 (Figure 5). Sampling covered regions just off the Strait of Gibraltar, off the coasts of Algeria, Tunisia, and Malta, reaching the eastern end of the Mediterranean Sea at the Suez Canal. MP concentrations within the >500–5000 µm size range varied (Table 1) from 4 MPs L−1 (MP-16) to 38 MPs L−1 (MP-17), with an average of 15.5 ± 9.6 MPs L−1, indicating moderate variability. Compared to other regions, the Mediterranean Sea showed lower MP concentrations, although higher levels were detected near Tunis (MP-8, 34 MPs L−1) and near to the Suez Canal (MP-17, 38 MPs L−1), areas (Table 2) influenced by dense shipping and anchorage activities. Tsiaras et al., 2022 documented that previous studies have reported highly variable MP abundances across different parts of the Mediterranean Sea. Wakkaf et al., 2020 documented 453 ± 335 particles/m³ in the southern Mediterranean, while reported 858,029 ± 4,082,964 particles/km² in the western Mediterranean. In contrast, Adamopoulou et al., 2021 observed much lower levels of 0.26 ± 0.36 particles/m³ in the eastern Mediterranean. Compared to these findings, our study recorded an average of 15.5 ± 9.6 MPs L−1, highlighting both methodological differences and the spatial variability of MP pollution within the basin. Polymer analysis of the Mediterranean Sea samples revealed a clear dominance of polyethylene terephthalate (PET), which accounted for 64% of all identified polymers (Figure 5). This predominance reflects significant inputs from packaging materials, textiles, and consumer plastics. Polyamide-6 (PA6), mainly originating from fishing gear and synthetic fibers, contributed 18%, while both crumb rubber (CR) and polyethylene (PE) each made up 9%, indicating sources such as tire wear particles and plastic films. Comparable findings have been reported in earlier studies, where PE and polyamides as well as PET have been noted as the dominant MPs. Thus, while in the Eastern Mediterranean (Turkey), PE was identified as the most dominant polymer, accounting for over 59% (Gedik et al., 2022), in the Mediterranean Sea off Egypt, PET was found to be the usual polymer type (Sayed et al., 2021). Also, in a review of MPs in the Mediterranean Sea, it was found that PET dominated the water column across many locations (Terzi et al., 2024).
Figure 5
3.4 Distribution of MPs in the Red Sea
The Red Sea is a narrow, elongated body of water stretching south eastward from Suez, Egypt, for approximately 1,930 km to the Bab el-Mandeb Strait, which connects it to the Gulf of Aden and subsequently to the Arabian Sea. It spans a maximum width of about 306 km, reaches a depth of 3,040 m, and covers an area of roughly 450,000 km² (Schreiber and Ryan, 2025). The Red Sea is characterized by some of the world’s warmest and most saline waters. Linked to the Mediterranean Sea via the Suez Canal, it serves as one of the busiest maritime routes globally, facilitating major trade and shipping between Europe and Asia (Schreiber and Ryan, 2025).
3 samplings were conducted within the area of the Suez Canal (MP-19 to MP-21). Here, increased MP concentration (31.3 ± 10.1 MPs L−1) was found as compared to the water bodies it connects, the Mediterranean and the Red Sea. During the expedition, 8 sites (MP-22 to MP-29) were sampled across the Red Sea (Figure 6) between Dec. 6th and Dec. 12th, 2022. The transect began at the Southern entrance of the Suez Canal and extended southward to the end of the Red Sea, providing a comprehensive overview of MP distribution along this key maritime corridor. MP concentrations within the range of >500–5000 µm (Table 1) varied from 8 MPs L−1 (MP-24) to 40 MPs L−1 (MP-23), with an average of 24.5 ± 11.0 MPs L−1 across all samples. Higher concentrations were recorded at MP-23 (40 MPs L−1), located near the Suez Canal, where dense ship traffic, anchorage zones, and restricted water circulation promote localized accumulation. The Gulf of Suez, one of the world’s busiest shipping routes with over 18,000 commercial vessels annually, also supports oil and mining operations, contributing significantly to plastic inputs in the region (Taher et al., 2023). Previous studies across the Red Sea and the Gulfs of Suez and Aqaba identified most particles as secondary microplastic fragments, primarily originating from maritime operations, cargo transport, and recreational activities (). Lower MP concentrations were observed at MP-24 (8 MPs L−1) and MP-26 (10 MPs L−1), corresponding to areas with reduced human and industrial influence.
Figure 6
Analysis of the polymers found in the Suez Canal and Red Sea (Figure 6) revealed a clear dominance of polyethylene terephthalate (PET), accounting for 58% of the total identified polymers. Polyvinyl chloride (PVC) followed at 18%, likely originating from construction and industrial activities, while polystyrene (PS) contributed 8%. Both polyamide-6 (PA6) and polyethylene (PE) represented 8% each, reflecting inputs from fishing gear, textiles, and plastic films. Overall, the results highlight PET as the predominant polymer in the Red Sea. In comparison, Marti et al. (2017) reported polyethylene (PE) and polypropylene (PP) as dominant polymers along the Arabian coast of Saudi Arabia, while Sayed et al. (2021) identified rayon and PET as major polymer along other stretches of the Red Sea coast.
3.5 Distribution of MPs in the Arabian Sea
The Arabian Sea, a northwestern extension of the Indian Ocean, covers approximately 3,862,000 km² and serves as a major maritime route connecting Europe and India. It is bordered by the Horn of Africa and the Arabian Peninsula to the west, Iran and Pakistan to the north, India to the east, and the Indian Ocean to the south (Verlaan and Aleem, 2025). The sea connects to the Persian Gulf via the Gulf of Oman and the Strait of Hormuz, and to the Red Sea through the Gulf of Aden and the Bab el-Mandeb Strait. With an average depth of 2,734 m, the Arabian Sea is characterized by a monsoon-driven climate that significantly influences its oceanographic circulation and ecosystem dynamics (Verlaan and Aleem, 2025). During the expedition, twelve sites (MP-31 to MP-42) were sampled across the Arabian Sea between Dec. 13th and Dec. 18th, 2022 (Figure 7). The sampling transects encompassed key regions, including the Gulf of Aden and the Gulf of Oman, representing an important transitional zone connecting the Arabian Sea with both the Red Sea and the wider Indian Ocean.
Figure 7
MP concentrations within the >500–5000 µm size range (Table 1) varied notably, from 10 MPs L−1 (MP-31) to a maximum of 116 MPs L−1 (MP-41), with an average concentration of 56.0 ± 31.6 MPs L−1. Several sites, including MP-34 (72 MPs L−1), MP-39 (96 MPs L−1), and MP-42 (74 MPs L−1), exhibited higher concentrations, indicating localized accumulation zones. The highest values were observed along the coast of Oman, a region influenced by strong currents and intense maritime activities. From models looking at seasonal currents and MP buoyancy, it is predicted that a significant portion of MPs found along the Omani and Yemeni coastlines likely originates from countries such as India and Sri Lanka (Van Der Mheen et al., 2020). A hydrodynamic model combined with CYGNSS satellite data by Sobhani et al. (2024) demonstrates that tides, winds, and density-driven currents are main factors in the MP transport in the Arabian Sea and the Gulf of Oman, with particle concentrations estimated from ocean surface roughness. Their model showed that the highest accumulation in the northeast Arabian Sea would be expected during early winter (December–January), with higher levels also along Oman’s northern coast and the Strait of Hormuz. Concentrations varied seasonally, decreasing from spring to autumn under the influence of wind speed and sea surface currents. The timing of our sampling in December aligns with these patterns, supporting the observed wintertime increase in MP abundance across the Arabian Sea.
Polymer analysis in our study revealed (Figure 7) a dominance of polyamides PA66 (43%), followed by polyethylene terephthalate (PET) representing 29% of the total. Other polymers, including ABS, polyester (PES), PVC, and PP, each contributing 7%. A study by Rigi et al. (2023) reported PP as the dominant polymer in intertidal sediments along the Oman Sea. This contrast may be attributed to differences in sample type, as their results were based on sediment samples, while our study focused on water samples.
3.6 Distribution of MPs in the Strait of Hormuz
The Strait of Hormuz forms a geographically and environmentally isolating bottleneck at the entrance to the Arabian Gulf, allowing only a restricted water exchange between the Arabian Gulf and the Indian Ocean through a narrow, 52 km-wide opening (). The Strait of Hormuz serves as a key maritime corridor for the transport of oil and natural gas (Wang and Lu, 2015; Ghaderi, 2025), and this region holds a vital significance for the global energy trade (Wang et al., 2023; Ghaderi, 2025), where the waterway serves more than 90% of the Gulf’s oil exports and approximately 40% of the global oil supply (; ; Ghaderi, 2025). Its depth varies from about 40 m along the Iranian coast in the north to nearly 200 m near the Musandam coast in the south.
During the voyage, MP sampling in the Strait of Hormuz was conducted on Dec. 19th, 2022, off both the Omani and Iranian coasts. A total of 24 sites were sampled along the transect, with stations located at approximately one-hour intervals along the route.
MP concentrations (>500–5000 µm) in the Strait of Hormuz showed substantial variations across the 24 sampled sites (MP-43 to MP-66). Concentrations ranged from a minimum of 6 MPs L−1 (MP-52) to a maximum of 108 MPs L−1 (MP-43) near the Arabian Sea, with an average of 34.4 ± 24.2 MPs L−1 (Table 2). The dataset shows that the majority of stations recorded concentrations exceeding 15 MPs L−1, indicating a generally higher level of microplastic presence throughout the transect. This pattern suggests that MPs are not limited to isolated hotspots but are rather widely dispersed. A previous study of beaches in Suru on the Strait of Hormuz reported a MP abundance of 14 ± 4 particles/kg (Naji et al., 2017). Similarly, a study from Iran documented a MP density of 9.28 ± 2.1 items/km² along the Arabian Gulf coastline (). However, these two studies were conducted close to the shore, whereas the current sampling was carried out in international waters along one of the world’s major shipping routes. reported that up to 80% of MPs in the surface waters of shipping lanes originate from antifouling paints used on ships’ hulls to prevent the attachment of barnacles and other organisms. The study further noted that higher concentrations of coating-related particles near shipping routes can be observed as “ship-related skid marks,” similar to the wear-and-tear debris generated by vehicle tyres (). Notably high concentrations were observed at the majority of sites, with over 85% recording values exceeding 15 MPs L−1, such as MP-44 (80 MPs L−1), MP-45 (55 MPs L−1), MP-53 (66 MPs L−1), MP-55 (52 MPs L−1), and MP-60 (50 MPs L−1), indicating a widespread MP presence across the transect, at sites likely affected by intense vessel traffic, localized current convergence (Figure 8) and dynamic water exchange in the Strait of Hormuz.
Figure 8
Polymer composition analysis revealed (Figure 8) that polyethylene terephthalate (PET) dominated the identified particles, representing 36% of the total polymer types, followed by polyester (PES) at 24%, acrylonitrile butadiene styrene (ABS) and polyamide-66 (PA66) at each 12%. Smaller fractions of cellulose acetate (CA) 8%, crumb rubber (CR), and polyvinyl chloride (PVC) at each 4% make up most of the remainder. Collectively, PET and PES recorded 60% of the identified polymers, suggesting that could be from synthetic fibers and textile related sources. PES primarily originates from synthetic textiles, while PET is widely used in both synthetic fibers and food packaging (; Zhang et al., 2020; Li et al., 2025). Similarly Naji et al., 2017 reported polyethylene (PE), nylon, and PET (polyethylene terephthalate) were the commonly recovered polymers along the beaches of the Strait of Hormuz.
3.7 Distribution of MPs in UAE waters
The United Arab Emirates (UAE) has a total land area of approximately 83,000 km² and shares maritime borders with the Islamic Republic of Iran to the north and Qatar to the west. It is composed of seven coastal emirates including Abu Dhabi along the Arabian Gulf (Subraelu et al., 2022). Abu Dhabi’s territorial waters are located in the southeastern part of the Arabian Gulf, with the emirate’s coastline extending for about 700 km, and is fringed by nearly 200 islands (). Water circulation in the Arabian Gulf (Figure 9) is primarily driven by a dynamic interaction of surface inflows and deep outflows across the Strait of Hormuz. Surface water enters the Gulf from the Oman Sea, flowing along the Iranian coast, and exits through deeper layers from the Arabian Gulf into the Oman Sea (). Altogether, the Arabian Gulf can be seen as a semi-closed evaporative basin. Along the UAE coast, including Abu Dhabi, coastal currents flow toward the Strait of Hormuz and curve around the Musandam Peninsula into the Gulf of Oman (Purnama and Al Barwani, 2006). These hydrodynamic processes not only play a critical role in nutrient transport and ecosystem dynamics but also in pollutant dispersion in Abu Dhabi’s marine environment.
Figure 9
During the expedition, MP sampling in UAE waters was conducted between Dec. 19th and 20th, 2022, covering transects off the Ras Al Khaimah, Umm Al Quwain, Sharjah, Dubai, and Abu Dhabi coasts (Figure 10). A total of 34 sites (MP-67 to MP-100) were sampled, representing the most intensive sampling segment of the voyage. The stations were spaced at 15-minute intervals within Abu Dhabi waters to capture fine-scale spatial variation. This high-resolution approach provided a detailed understanding of MP distribution in Abu Dhabi waters relative to international seas.
Figure 10
MP concentrations (>500–5000 µm) in UAE waters demonstrated moderate to high spatial variability across the 34 sampled sites (MP-67 to MP-100). Concentrations ranged (Table 1) from a minimum of 10 MPs L−1 (MP-71) to a maximum of 106 MPs L−1 (MP-88) in Abu Dhabi, with an average of 30.6 ± 21.4 MPs L−1 which is higher than the study by which reported average concentrations of MPs in Abu Dhabi marine water samples ranging from 4.5 to 12 MPs L−1. Furthermore, these concentrations were higher than those reported along the Dubai coast (5.30-7.85 items/L; ). Unlike the studies of Ali et al. and which focused on nearshore environments, the present sampling was conducted both in deep sea as well as in coastal waters, encompassing major shipping routes. Higher concentrations were particularly recorded at MP-72 (88 MPs L−1), MP-94 (86 MPs L−1), MP-80 (44 MPs L−1), MP-86 (40 MPs L−1) and MP-89 (32 MPs L−1), and reflecting localized hotspots and marine traffic zones. According to Lebreton et al. (2017), the Arabian Gulf, being a semi-enclosed basin connected to the open ocean solely through the Strait of Hormuz, experiences restricted water exchange and minimal influence from Indian Ocean currents that could transport external MPs. Therefore, the occurrence of MPs in this region is primarily linked to local inputs, including riverine discharge from the Shatt al-Arab and Iranian river systems, along with waste emissions from densely populated coastal cities (Lebreton et al., 2017; Pu et al., 2024). Supporting this, satellite-based modelling using Sentinel-2 imagery (bands B5 and B9) identified MP accumulation hotspots near Jebel Ali Port and major recreational beaches, aligning with the west-to-east circulation patterns reported by . This further reflects that the presence of MPs in UAE waters is largely influenced by land-based and marine anthropogenic activities, including inputs from ports, shipping operations, industrial discharges, recreational activities, and localized current-driven redistribution, all of which collectively contribute to the observed spatial accumulation patterns.
The polymer composition analysis revealed (Figure 10) that polyester (PES) was the dominant polymer type, constituting approximately 59% of the total identified microplastic particles and it was recorded from 20 sites. This high proportion indicates a strong influence from synthetic textiles, fishing nets, and industrial fibers commonly associated with polyester-based materials, PES being the most important component of synthetic fibers, globally (). Polyamide-66 (PA66) was the second most prevalent polymer recorded from 7 sites, contributing 21%, likely derived from nylon ropes, nets, and other marine or industrial sources. Smaller fractions of acrylonitrile butadiene styrene (ABS), crumb rubber (CR), and polystyrene (PS) were recorded, each at 6%, suggesting localized inputs from packaging materials, consumer plastics, and rubber components. Minor occurrences of a polyethylene terephthalate (PET) were detected, each representing 3% of the total. Overall, the predominance of polyester and polyamide polymers in the MPs indicates that synthetic fiber, fishing gear, consumer products, oilfield-related activities, and packaging waste are the major contributors to contamination in this region. reported that in Abu Dhabi waters the dominant polymers identified in both water and sediment were acrylonitrile-butadiene-styrene (ABS), nylon 6,6 (PA66), cellulose acetate (CA), and polyethylene terephthalate (PET). A study from the eastern coastline of Saudi Arabia sediment samples recorded PET as the major polymer ().
A limitation of the present study is that sampling was conducted during a single expedition between November and December 2022, representing a temporal snapshot of MP distribution across the surveyed regions. MP concentrations in marine environments may reveal seasonal variability due to changes in hydrodynamic conditions, including ocean currents, wind patterns, storm events, precipitation, and variations in anthropogenic activities. Consequently, the concentrations reported in this study may not fully represent year-round conditions. Nevertheless, the study provides an insight into MP abundance and distribution across major international shipping routes and marine regions extending from Europe to the Arabian Gulf. Future studies incorporating multi-seasonal or long-term monitoring would provide a more comprehensive understanding of temporal variations in MP abundance, transport, and accumulation patterns across international waters.
The current analysis focuses on MPs within the size range of >500–5000 µm; therefore, smaller MPs were not assessed. Although FTIR was used for polymer identification, highly weathered particles may be more difficult to characterize accurately. In addition, environmental factors such as ocean currents, wind patterns, and other hydrodynamic processes were not directly measured and may have influenced the observed distribution of microplastics. Despite these limitations, the study provides an important baseline assessment and comparison of MP abundance and polymer composition across UAE waters with international waters from Europe to the Arabian Gulf.
4 Pollution load index
To evaluate the extent of microplastic (MP) contamination in surface waters from 100 sites in this study, an integrated Pollution Load Index (PLI) was computed following the method proposed by Tomlinson et al. (1980) and utilized for evaluation of MP pollution in Indian sediments by Ranjani et al. (2021). The contamination factor (CF) for each site was first calculated using Equation (1), where Ci is the microplastic concentration at the site and Cb is the background concentration (Ranjani et al., 2021). The PLI at each site was determined based on the ratio of the microplastic concentration at the site (Ci) and what is seen as the background concentration Cb (see below). The PLI value is calculated according to Equation 2 (Ranjani et al., 2022).
where CF of the MP is the quotient of the MP concentration at each location (Ci) and the background MP concentration (Cb). The lowest concentration of MP value detected in the water sample in this study was considered as a background value.
The calculated Pollution Load Index (PLI) values for all sampling sites ranged from a minimum of 1.00 at MP-16 to a maximum of 8.51 at MP-5, with an average value of 2.85 ± 1.9 across all regions. Based on the hazard classification, all sites fall within Hazard Level I (PLI< 10) (Table 3; Figure 11). As at a number of sites the hazard category of PLI is nearing the value of II and as still too little is known on the detrimental effects of MPs in the environment, continuous meticulous monitoring is recommended to track potential increases in contamination due to growing maritime activities and coastal developments.
Table 3
| PLI | Hazard Category |
|---|---|
| <10 | I |
| >10-20 | II |
| 20-30 | III |
| >30 | IV |
Hazard level criteria for MP pollution (Ranjani et al., 2021).
Figure 11
5 Kruskal–wallis test
To evaluate regional differences in microplastic concentrations, a Kruskal–Wallis (Kruskal and Wallis, 1952) test was performed due to the non-normal distribution of the data. This non-parametric test allows comparison among multiple independent groups without assuming normality. Effect size was estimated using epsilon-squared (Tomczak and Tomczak, 2014). The Kruskal–Wallis statistic was calculated based on ranked data. Effect size (ϵ²) was determined using the formula (H − k + 1)/(N − k), which quantifies the proportion of variation explained by the regions.
Where:
N = total number of observations, k = number of groups (regions), ni = number of observations in group i, Ri = sum of ranks for group i.
Epsilon-squared (Effect Size):
Where:
H = Kruskal–Wallis statistic, k = number of groups, N = total sample size.
The results demonstrated significant variation, with a test statistic (H) of 20.93, degrees of freedom (df) equal to 5, and a p-value less than 0.001. This indicates that microplastic levels differ meaningfully between the sampled regions. Furthermore, the effect size (ϵ² = 0.17) suggests a moderate influence of region on the distribution of microplastics. The boxplot also shows (Figure 12) the non-normal, skewed distributions and highlights regional differences, which support the findings from the Kruskal–Wallis test.
Figure 12
5.1 Spearman rank correlation
The relationship between MP concentration and sampling order along the Spain–Abu Dhabi transect revealed no statistically significant association. The correlation coefficient (ρ = 0.033) and p-value (p = 0.743) indicate (Figure 13) that there is no consistent spatial trend in microplastic concentration along the route.
Figure 13
6 MP concentrations in comparison
There has been a lot of discussion about sampling methods and MP detection in the marine environment. A recent investigation showed that trawl net studies could be undersampling particle density by approximately three orders of magnitude (). As commented on by , lower amounts of plastic in surface trawl samples are observed than models by and have predicted, leading to the possibility that particles smaller than 4.75 mm had been displaced from the ocean’s surface. Later, Reisser et al. (2015) and Kooi et al. (2017) demonstrated that some of this “missing” plastic could actually be located just below the depth typically sampled by surface trawls. On the other hand, grab sampling is highly prone to air contamination, although the authors took precautions to prevent this.
The current data can be compared with citizens’ sampling data analyzed and collated by , utilizing the 1L grab sampling method also used in the present paper. reported an average MP concentration of 17.9 MPs L−1 (n = 685) across global open ocean waters, including 13.4 MPs L−1 for the Atlantic Ocean overall. In contrast, the present study found about double the concentrations, with an average of 34.7 MPs L−1 across all the sampled water bodies and 27.0 MPs L−1 in the North Atlantic Ocean. This discrepancy may be explained by differences in the sampling locations, as much of the dataset from was collected away from major shipping routes, whereas the sites examined in this study were all located on or very near to shipping lanes, potentially contributing to elevated MP levels.
7 Conclusion
This study presents the first transboundary assessment of microplastic (MP) pollution from Spain to Abu Dhabi, covering six major marine regions: the North Atlantic, Mediterranean Sea, Red Sea, Arabian Sea, Strait of Hormuz and UAE waters. The results reveal clear spatial variability in MP abundance, with concentrations ranging from 4 to 290 MPs L−1 and an overall mean of 34.7 ± 29.0 MPs L−1. The highest microplastic levels were observed in the the Arabian Sea (56.0 ± 31.6 MPs L−1) and the Strait of Hormuz (34.4 ± 24.2 MPs L−1), while lower levels occurred in the Mediterranean (15.5 ± 9.6 MPs L−1), the North Atlantic Ocean (27.0 ± 13.5 MPs L−1) and the Red Sea (24.5 ± 11.0 MPs L−1). Moderate contamination (30.6 ± 21.4 MPs L−1) was detected in UAE waters, particularly near major shipping routes and ports. These findings underscore the influence of hydrodynamic conditions, maritime transport, and regional anthropogenic activities on MP distribution across interconnected marine systems. Polymer analysis identified polyester (PES) and polyethylene terephthalate (PET) as dominant types (>57%), reflecting major contributions from synthetic textiles and packaging materials. Polyamides (PA6/66), acrylonitrile butadiene styrene (ABS), and cellulose acetate (CA) were also present, indicating additional inputs from fishing gear, industrial plastics, and bio-based materials. The Pollution Load Index (PLI) values (1.00–8.51; mean 2.85 ± 1.9) placed all regions at Hazard Level I (PLI< 10), but some nearing Hazard Level II. Statistical analysis using the Kruskal–Wallis test further confirmed significant regional differences in microplastic concentrations (H = 20.93, df = 5, p< 0.001), supporting the observed spatial variability across the study regions. This pattern was also reflected in the boxplot analysis, which highlighted regional differences in microplastic concentrations. Spearman correlation showed no significant trend along the transect (ρ = 0.033, p = 0.743), suggesting localized hotspots rather than a continuous spatial gradient. This study establishes an important baseline for understanding transboundary microplastic transport and provides a reference for future monitoring and management of marine plastic pollution in the UAE and broader regional waters. Future studies should focus on long-term and multi-seasonal monitoring to better understand MP transport and temporal variability. Advanced analytical techniques such as automated FTIR imaging, Raman spectroscopy, and machine learning may further improve polymer identification. In addition, studies on the ecological impacts of MPs on marine organisms and ecosystems are needed to support effective management strategies.
Statements
Data availability statement
The original contributions presented in the study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.
Author contributions
AA: Data curation, Formal analysis, Investigation, Methodology, Project administration, Supervision, Writing – original draft, Writing – review & editing. RT: Data curation, Formal analysis, Writing – original draft, Writing – review & editing. HA: Data curation, Formal analysis, Investigation, Methodology, Project administration, Supervision, Writing – review & editing. TT: Conceptualization, Formal analysis, Investigation, Methodology, Supervision, Validation, Writing – review & editing. AS: Formal analysis, Methodology, Software, Writing – review & editing.
Funding
The author(s) declared that financial support was not received for this work and/or its publication.
Acknowledgments
This study is part of the Marine Water Quality Monitoring Programme. The authors extend their sincere gratitude to the management of the Environment Agency, Abu Dhabi, for their unwavering support and encouragement. Special thanks go to the Executive Director, Faisal Ali Al Hammadi, from the Environmental Quality Sector (EQS), and the Environmental Information, Science & Outreach Management (EISOM) section of EAD for their assistance in developing the map and reviewing this manuscript. Additionally, we are grateful to the Abu Dhabi Quality and Conformity Council (ADQCC) for their analysis of the microplastic samples, which was critical to the study.
Conflict of interest
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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Supplementary material
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmars.2026.1856396/full#supplementary-material
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Summary
Keywords
Jaywun research vessel, microplastics, pollution load index (PLI), transboundary assessment, UAE waters
Citation
Al Hashmi AH, Thankamony R, Al Hammadi HA, Thiemann T and Siddiqui A (2026) First expedition Jaywun research vessel: assessment of microplastics from international waters, Spain to Abu Dhabi, U.A.E. Front. Mar. Sci. 13:1856396. doi: 10.3389/fmars.2026.1856396
Received
15 April 2026
Revised
08 June 2026
Accepted
29 June 2026
Published
21 July 2026
Volume
13 - 2026
Edited by
Gajalakshmi S, Pondicherry University, India
Reviewed by
Mircea Nicusor Nicoara, Alexandru Ioan Cuza University, Romania
Driss Azdem, Mohammed V University, Morocco
Updates
Copyright
© 2026 Al Hashmi, Thankamony, Al Hammadi, Thiemann and Siddiqui.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Abdulsalam Husain Al Hashmi, 960711104@uaeu.ac.ae; a.alhashmi@ead.gov.ae
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