Mediterranean Microplastics: The Levantine Basin Has Become the Sea’s Plastic Sink

Mediterranean microplastics are not evenly spread: surface currents push them eastwards, where they accumulate in the southeastern corner of the basin, off the Levantine coast. This is the finding of the first basin-scale assessment, published in the journal Environmental Pollution, which combined data from 108 field studies with a current model tracking nearly 580,000 particles. The research also produced a surprising result: water and fish are not most contaminated in the same places.

Researchers from the University of Girona (UdG) and the Institute of Marine Sciences in Barcelona (ICM-CSIC), working with French (LOCEAN-IPSL) and German (GEOMAR) co-authors, approached the question from two directions. First, they systematically screened the literature published between 2012 and 2026 and harmonised microplastics data for surface waters and fish into common units. Second, they used a computer model to follow where currents carry particles released at the sea surface over a four-year period.

In short: Mediterranean microplastics are most concentrated in the southeastern Levantine region, where a single cubic metre of seawater can hold up to 324 particles. Fish contamination, however, peaks elsewhere – including the Alboran Sea, off Algeria and in the Northern Adriatic – meaning a water sample alone does not predict how much plastic fish ingest.

Why the Mediterranean is a special case

The Mediterranean is one of the world’s plastic pollution hotspots: according to the literature, microplastic concentrations here can be up to four times the global average. The semi-enclosed basin renews its water slowly, its coastline is densely populated, and an estimated 229,000 tonnes of plastic enter it every year – 70 percent of which is attributed to just three countries: Egypt, Turkey and Italy. Beyond land-based sources, coastal cities, tourism, fishing and rivers – especially during flash floods – add significant loads.

The region’s geography amplifies the effect. Continental shelves are narrow, so open-sea currents reach coastal waters directly and move material quickly between the coast and the deep basins. Atlantic water entering through the Strait of Gibraltar flows eastward along the North African coast before breaking into a series of gyres and jets. This “conveyor belt” decides where plastic from land ultimately ends up.

From nearly 600 papers to 108 usable studies

The researchers identified 591 articles in Web of Science and Scopus. After a three-stage screening against 11 criteria, 108 studies remained: 53 reported fish data only, 47 water data only, and 8 both. Water results were converted to items per cubic metre and fish results to items per individual, and every value was assigned to one of the Mediterranean fisheries Geographical Sub-Areas (GSAs). This made the entire basin comparable for the first time.

Mapping Mediterranean microplastics: the Levant leads

Across the whole basin, the mean surface-water microplastic concentration was 2.12 items/m³, but with a very large spread (±10.52), showing how patchy the pollution is. The three most contaminated sub-areas were:

• Levant (GSA 27): a mean of 6.79 items/m³ – also home to the highest single value recorded in the basin, 324.10 items/m³;
• Sardinia West (GSA 11.1): 3.18 items/m³;
• Cyprus Island (GSA 25): 2.96 items/m³.

In all other sub-areas, the mean stayed at or below 2.75 items/m³. The western basin generally showed lower values despite dense urbanisation and riverine inputs. The authors attribute this to more energetic circulation, including the Northern Current and eddies in the Algerian Basin, which disperse particles towards the open sea.

Plastic found in the guts of ninety fish species

For fish, 387 values were compiled, and microplastic ingestion was confirmed in 90 species plus three further taxa identified at genus level. The overall mean was 3.99 items per individual. The highest averages came from the southern parts of the basin:

• Southern Alboran Sea (GSA 3): 13.2 items/individual;
• Algeria (GSA 4): 12.0 items/individual;
• South Levant, Egypt (GSA 26): 8.39 items/individual.

Other sub-areas above the mean included the Northern Adriatic (GSA 17), the Ligurian and North Tyrrhenian Sea, the Gulf of Hammamet, Sardinia East and the Western Ionian. The highest single value, 57.5 items, was recorded in a golden grey mullet (Chelon auratus) from the Ligurian Sea. Greater amberjack (Seriola dumerili), gilthead seabream (Sparus aurata) and three Chelon species also stood out, each averaging more than 10 items per individual. The species found with microplastics in the most sub-areas were the European pilchard (Sardina pilchardus, 13 GSAs), bogue (Boops boops) and red mullet (Mullus barbatus, 12 GSAs each).

An important caveat is that the items-per-individual metric ignores fish size, because most studies did not report body weights. The values should therefore be read as a coarse indicator of burden, not as a precise weight-normalised concentration.

Polluted water does not mean polluted fish

Perhaps the study’s most important finding is that contamination in water and in fish is spatially decoupled. Waters off the Levant, Sardinia West and Cyprus are among the most polluted, yet fish there carry comparatively lower loads. In the Alboran Sea, off Algeria or in the Northern Adriatic, by contrast, fish burdens are high despite moderate water concentrations.

The authors suggest several reasons. Fish move, their feeding habits differ, and they can take up microplastics not only directly but also through the food web and from the seabed. Fish samples also capture a single moment, whereas water contamination is shaped by long-term circulation. The lesson: fish contamination is an integrated signal from the whole basin, not a mirror of local water quality. This is why the researchers call for harmonised monitoring of indicator species – above all Boops boops and Mullus barbatus – which occur across most of the basin, are easy to sample, and cover both open-water and near-bottom habitats.

What the particle-tracking model reveals

To interpret the observations, the researchers used the open-source OpenDrift model, driven by Copernicus Marine current data for 2006–2020. They released 579,960 virtual particles at the sea surface across the whole basin (excluding the Marmara, Black and Azov Seas) and followed them for four years. This is what the model showed about the journey of Mediterranean microplastics:

• Eastward accumulation: after three years, particles had gathered in the southern sub-areas of the eastern basin. In the Levant, particle numbers rose to more than ten times their initial level. In the western basin, only the Ligurian and North Tyrrhenian Sea received slightly more particles than were originally released there.
• Beaching: 58.5 percent of particles reached a coastline at least once during the four years. For particles from the most contaminated sub-areas, the average was 75.3 percent, rising above 85 percent for Cyprus, the Levant and Egypt. First beaching typically occurred about one year after release.
• Strong links in the east: 66.6 percent of particles from the North Levant (southern Turkey), 60.1 percent from the Egyptian coast, 59.7 percent from Crete and 54.9 percent from Cyprus reached the Levant or South Levant. Particles remaining within the Levant itself accounted for 67.1 percent – the strongest connection in the model.
• Retention: the fate of particles reaching contaminated zones varied, but overall retention dominated. The South Levant retained 88 percent and the Levant 93 percent of incoming particles.
• Long journeys: a small share (below 1 percent) of particles entering from the Atlantic reached the Levant, the easternmost point of the basin, within four years.

Water-contamination hotspots were more strongly connected to each other (33.4 percent on average) than to fish-contamination hotspots (21.2 percent). A seasonal difference also emerged: particles released in November and December were more likely (above 25 percent) to reach fish-contamination hotspots.

Limitations of the study

The authors stress that the results need careful interpretation. Of the studies reviewed, 84 percent focused on coastal waters, and many sub-areas were covered by only one or two studies – or none at all – especially along the southern and eastern shores. Two-thirds of the samples were taken with 300–335 micrometre mesh nets, which earlier comparisons suggest may capture around 2.5 times fewer particles than a 100 micrometre net, meaning true Mediterranean microplastics concentrations may be higher.

The model also involves simplifications: it does not account for direct wind and wave drift, or for polymer type, density, fragmentation and biofouling. The results therefore show typical long-term circulation tendencies rather than precise reconstructions of individual pollution events.

What this means for waste management

The study’s key message is that Mediterranean microplastics do not stay where they enter the sea. Particles escaping off one country’s coast may appear years later on another country’s beach or in its fish. This cross-border responsibility is clearly visible in Alanya, Turkey, where local microplastic pollution is threatening tourism and experts are calling for stricter controls on recycling facilities. The wider context – including evidence of contamination linked to irregular discharges from some recycling plants – is covered in our analysis of Turkey’s role as Europe’s plastic waste terminus.

According to the authors, the next step is to identify sources precisely – separating the shares of urban waste, rivers, fishing and aquaculture, and shipping – because targeted action can only be built on that basis. The options for tackling pollution at source are already known: a Swiss case study showed that effective waste management significantly reduces plastic emissions, with synthetic textiles consistently among the largest sources of microplastics.

On the regulatory side, the researchers call for harmonised monitoring: the same net and filter sizes, common units, routine polymer identification (FTIR or Raman spectroscopy) and reporting of fish body weights. This would align with Descriptor 10 on marine litter under the EU Marine Strategy Framework Directive (MSFD) and with the UNEP/MAP framework for regional cooperation.

For Central European readers there is a tangible takeaway too: the Northern Adriatic, a summer destination for tens of thousands of Hungarians, ranks among the critical areas based on fish contamination, and according to the model nearly a fifth of the particles arriving there never left the area during the whole simulation. The cleanliness of the sea does not depend on coastal states alone – any plastic not captured at source is likely to end up in the sea sooner or later.

Frequently asked questions about Mediterranean microplastics

How much microplastic is in Mediterranean surface waters?

The mean surface-water microplastic concentration across the whole Mediterranean is 2.12 items per cubic metre. The pollution is very patchy, however: the Levant averages 6.79 items/m³ and also recorded the highest single value, 324.10 items per cubic metre. The western basin generally shows lower concentrations because stronger currents disperse particles towards the open sea.

Why do microplastics accumulate in the eastern Mediterranean?

Mainly because of ocean currents. Surface water entering from the Atlantic flows eastward, and the eastern basin renews its water slowly, so particles become trapped there. In the model, particle numbers in the Levant rose to more than ten times their initial level after three years, and 93 percent of incoming particles were retained in the area.

Are fish most contaminated where the water is most polluted?

No, the study found that water and fish contamination are spatially decoupled. Waters off the Levant, Sardinia West and Cyprus are among the most polluted, yet fish there carry lower loads. In the Alboran Sea, off Algeria and in the Northern Adriatic, fish burdens are high despite moderate water levels, because fish move and also take up particles through the food web.

Which fish species were found with microplastics in the Mediterranean?

The study confirmed microplastic ingestion in 90 fish species and three further taxa identified at genus level. The species found in the most sub-areas were the European pilchard, the bogue (Boops boops) and the red mullet. Particularly high averages, above 10 items per individual, were found in greater amberjack, gilthead seabream and three Chelon species.

How reliable are the study’s results?

The results show typical tendencies rather than precise measurements for every area. Of the studies reviewed, 84 percent focused on coastal waters, several sub-areas had little or no data, and the widely used 300–335 micrometre nets capture fewer particles than finer meshes. The model also left out wind and wave drift, so actual contamination may be higher.

🔗 Official sources and references: 👉

• Scientific publication (Environmental Pollution, Volume 406, 2026, open access): 👉 Garcia-Garin, O., Artana, C., Minsart, J., Clavel-Henry, M.: Systematic review of microplastic concentrations in water and fish: Modelling distribution patterns and transport dynamics across the Mediterranean Sea – DOI: 10.1016/j.envpol.2026.128690
• Open dataset (Zenodo): 👉 Microplastic concentrations in water samples and ingested by fish from peer-reviewed studies in the Mediterranean Sea

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