In this session, we will explore the current state of knowledge and ongoing research on litter and macro-, micro-, and nanoplastics in estuarine and marine systems. The session will cover a wide range of topics, including:
• Recent findings on plastic distribution and accumulation in estuaries, shorelines, nearshore and open waters, nearshore and deep seafloor environments.
• Source-to-sink investigations, considering quantities and distribution across estuarine and marine environmental matrices (water, sediment and biota) and compartments (coastline, surface water, water column and seabed),
• Transport and accumulation/dispersal processes influenced by ocean currents, tides, waves and gyres.
• The role of extreme weather events, such as storms and floods, in redistributing plastic debris in estuarine and marine environments
• Impacts on biota, their structure and on different habitats from estuary and coastline to open waters, including seabed.
• Modelling approaches for local, regional, and global estimations of marine plastic accumulation and/or release to ocean basins, their impacts, and assessing the effectiveness of prevention and mitigation measures.
• Legislative and regulatory efforts, including international monitoring programs and measures aimed at reducing marine plastic pollution.
Orals: Fri, 8 May, 14:00–15:45 | Room 1.34
Plastic transport and storage dynamics in estuaries have important implications for environmental risk in these systems and also modulate the transfer from terrestrial to oceanic spheres. Here we synthesize fieldwork, theory, and experiments with numerical modeling to elucidate the source, transport, and fate of microplastics in an urban estuary in southern California. Riverine concentration-discharge models based on streamflow sampling are used to estimate microplastic flux at the two major riverine inputs to the estuary. Utilizing the Delft-3D hydrodynamic model coupled with particle tracking, microplastic transport is simulated for a dry and wet Water Year (October - September). Subtidal sediments collected from the estuary support modeled results of microplastic accumulation rates in bed layer sediments. Intertidal sediment cores collected within high and low areas of the saltmarsh and dated using fallout radionuclide analysis revealed the present and historical influence of stormflow event-driven suspended sediment (and microplastic) mobilization as well as the effect of dredging-based sediment management on microplastic accretion. Additionally, we investigate the importance of tides (i.e., bi-directional flow, phase, and range) and stormflow peak discharge on determining particle transport distance, flushing, and areas of peak accumulation. Local hydrodynamics and particle characteristics are also examined to contextualize observations of spatial partitioning of microplastic types. Finally results of this study are considered to inform future microplastic and sediment management in watersheds and estuaries.
How to cite: Gray, A., Murphy-Hagan, C., Brand, M., and Hapich, H.: Microplastic transport and fate in an Urban Estuary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22100, https://doi.org/10.5194/egusphere-egu26-22100, 2026.
Coastal zones are recognised sinks for plastic debris, although studying the transport and dispersion of plastic debris in nearshore waters remains challenging. The understanding of coastal processes and how these can be applied to numerical modelling studies is not yet fully mature. Most Lagrangian numerical modelling studies of plastic debris transport to date have been conducted at the basin or sub-basin level, typically using low-resolution hydrodynamic data (>2.5 km). These resolutions are generally sufficient at larger scales, but at smaller scales they create uncertainties regarding mainly the beaching of particles on the coastline and poor resolution of coastal structures or complex geometries.
The LOCATE numerical model addresses these constraints by incorporating high-resolution hydrodynamic data in nested grid configurations, focusing on areas of high interest. Specifically, this has been applied to the Barcelona coastline, where the LOCATE model used a coupled current-wave dispersion module with a three-way nested grid for current data, of 2.5 km resolution from CMEMS within the study domain, a 350 m high-resolution grid from the Spanish Port Authority (Puertos del Estado) covering the Barcelona metropolitan area, and a 70 m resolution grid covering the Port and the urban coastline. The use of high-resolution hydrodynamic data with the LOCATE model was validated using drifter data. Complex geometric structures were resolved, demonstrating that particles had residence times over 18 times longer within the Port when using high-resolution data compared to only using low-resolution data. Furthermore, a beaching module that calculated the real-time distance of a particle to the shoreline was developed using high-resolution shoreline data. This provided much more realistic beaching patterns, compared to determining particle beaching using its advected velocity, as well as shoreline continuity between the different resolutions in the hydrodynamic data.
These adaptations alone, however, do not address coastline or beach processes not included even in the highest-resolution hydrodynamic data. For this, a probabilistic framework was assumed, where a beaching timescale of 26.35 h was determined using a sensitivity analysis for backtracking simulations initiated in nearshore environments where particles could only cross the land-water boundary at known discharge sources. A further condition based on a minimum particle trajectory distance was also introduced to avoid artefacts. This final probabilistic configuration allowed for particle advection near the shoreline with more realistic trajectories within complex shorelines, considering stochastic elements of particle transport at localised scales. These parameterisations highlight the adaptations required to coastal and nearshore Lagrangian numerical modelling and serve as an area of future research which may be transposed to other locations.
Acknowledgements
This study was carried out within the TRAP project (Participatory Strategies for the Management of Plastic Pollution on the Transboundary Coast), which was 65% co-financed by the European Union through the Interreg VI-A Spain-France-Andorra Programme (POCTEFA 2021-2027). The objective of POCTEFA is to strengthen the economic and social integration of the Spain-France-Andorra border region
How to cite: Hernandez, I., Castro-Rosero, L. M., Liste, M., Espino, M., and Alsina, J. M.: Dispersion of floating marine litter: Lagrangian numerical simulations at coastal scales, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14025, https://doi.org/10.5194/egusphere-egu26-14025, 2026.
It is assumed that the eventual sink of global microplastic pollution is the deep sea. The primary vector for sediment and particulate pollutants to the deep sea are gravity currents down canyons along the coastline and at the shelf edge, and it has become recognised that these trap and transport microplastics. In order to quantify the potential storage within these marine environments, we develop a reduced complexity model of the transport of microplastic within turbidity currents. We find that the relatively simple model can produce turbidity currents similar to that observed within the Whittard Canyon, offshore Ireland. Based on this model we map the fate of microplastic within the canyon. Under most scenarios, the model implies that small microplastics, fibres and fragments, will be transported into the canyon with little material leaving the canyon. Our best fitting model would suggest that only 15% of the source microplastic will bypass the canyon and be exported to the deep ocean floor. Marine canyons might therefore be a major sink of microplastic pollution, and act as a sponge between the anthropogenic source and the abyssal plane. This could have severe impacts on the ecosystems within these environments.
How to cite: Armitage, J., Teles, V., and Rohais, S.: Submarine canyons as microplastic reservoirs: insight from a reduced complexity model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3560, https://doi.org/10.5194/egusphere-egu26-3560, 2026.
Marine plastic debris that is discarded into the ocean and eventually beaches is an acute problem for small island nations such as the Seychelles. To address this problem and enable anticipatory action, the sources of marine plastic debris need to be identified. Recent observations suggest that not all of the debris that arrives at the Seychelles is from terrestrial input. However, there is currently a lack of quantitative attribution of maritime debris sources.
Therefore, we investigate the potential shipping and fishing vessel plastic debris sources in the southwestern Indian Ocean that beach at the Seychelles. We use a 2D Lagrangian particle-tracking model, based on OceanParcels, with particles that are advected by currents from a 1/50° (~2 km) regional ocean model. We combine this with satellite-tracked fishing and shipping data to inform particle starting locations and weightings. This model resolution allows us to resolve island to sub-island accumulation patterns.
Spatially, model results suggest that debris beaching at the Seychelles from shipping vessels is concentrated along a limited number of high-activity shipping routes. The port destinations of these routes are consistent with the origin of plastic bottles inferred from labels in a previous study. Model results also show that 50-66% of fishing debris that beaches at the Seychelles is discarded within its own exclusive economic zone, depending on the island group.
Temporally, the season during which debris is discarded strongly impacts the likelihood of beaching. This seasonal profile varies in amplitude and phase between islands due to wind-driven surface current changes. Additionally, we find debris beaching patterns can vary substantially between islands and on a sub-island scale. This highlights the importance of higher-resolution models for investigating plastic accumulation at kilometre-scale islands. We also assess the model against observations including bottle drifters and seasonal accumulation data at the Aldabra Atoll, the latter of which is consistent with sub-island scale accumulation seasonality from the model.
Given that most marine debris originates from a few major shipping routes and from within the Seychelles exclusive economic zone, we suggest targeted enforcement of MARPOL Annex V could tackle the source of the issue.
How to cite: Albinski, A., Savage, J., Burt, A., Vogt-Vincent, N., and Johnson, H.: Shipping and fisheries are major sources of plastic pollution for the Seychelles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20648, https://doi.org/10.5194/egusphere-egu26-20648, 2026.
Based on our modeling, more than 10 million tonnes of plastic have entered the oceans, yet their ultimate fate and long-term impacts remain uncertain. We developed a multimedia model constrained by observations from beaches, seawaters, and seabeds to reconstruct the size (≥>0.2 mm), source, age, and storage of marine plastics since 1950. We find that beaches are the primary mass reservoir, while most particles remain suspended in the water column or sink toward the deep ocean. Continental emissions primarily contaminate nearby regions, whereas maritime sources disperse particles widely across ocean basins. Global mean ages of plastics range from 14 (10–16) years at the surface to 26 (20–32) years on beaches and 38 (35–42) years on seabeds on a mass-weighted basis, and are generally higher when weighted by particle numbers, highlighting the enduring legacy of historical plastic emissions. Persistent fragmentation of older plastics, combined with accelerating new inputs, produces a numerical dominance of small plastic fragments (<1 mm) despite their negligible contributions to total mass (<5%). These findings establish a quantitative framework for the ocean plastic cycle, facilitating the quantification of its ecological and climatic impacts. This underscores the urgent necessity for proactive measures to mitigate the environmental and socio-economic repercussions.
How to cite: Wang, X., Wu, P., Pang, Q., Zhang, Z., Peng, D., Xu, R., Wang, X., Xu, X., Zeng, E. Y., Cózar, A., Schartup, A. T., Lei, L., and Zhang, Y.: Plastics long shadow: legacy and fate of plastic pollution in the oceans, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4170, https://doi.org/10.5194/egusphere-egu26-4170, 2026.
The amount of plastic pollution in the environment has increased exponentially since its mass production began in the 1950s. As the vast majority of plastic cannot biodegrade, it instead slowly fragments through mechanical and chemical processes, producing microplastics (MPs; <5 mm) that are now found across the globe. Growing concern exists regarding the potential impacts of MPs on ecosystems. While considerable research has investigated MP pollution in aquatic and coastal environments, the quantity, distribution, and historical accumulation of MPs in UK salt marshes remain largely unknown.
Salt marshes are coastal wetlands with a unique range of flora and fauna, providing coastal protection and critical ecosystem services. However, they may also act as long-term sinks for MPs. Studies of MPs in salt marsh sediments are scarce, and very few have incorporated sediment dating using short-lived radioisotopes (210Pb, 137Cs, 241Am) to establish a history of plastic pollution.
In this study, sediment cores from four UK salt marshes (Welwick in the Humber Estuary, Lindisfarne on the Northumberland coast, Skinflats in the Firth of Forth, and Caerlaverock in the Solway Estuary) were collected and dated using 210Pb, 137Cs, and 241Am, with chronologies constructed using the Bayesian Plum model. MPs were extracted from the cores and identified, providing insights into the types, quantities, and temporal trends of plastics in UK salt marshes. At Welwick, an additional core was collected from an area with visible surface plastic to investigate the relationship between surface and subsurface MP accumulation. Welwick Saltmarsh was selected due to its location along the River Humber, a region known for high levels of plastic pollution.
To extract MPs, organic matter in the sediment cores was digested using 30% H₂O₂ in an ice bath, minimising polymer degradation compared to heated methods. MPs were extracted via density separation with 1.5 g/cm3 LST FastFloat and subsequently identified using Nile Red staining, fluorescence microscopy, and Raman spectroscopy.
The cores were found to contain sparse particles and fibres of polystyrene, polyethylene, polyethylene terephthalate and styrene-butadiene rubber. The core collected from Skinflats contained the greatest concentration of MPs (12 MPs), including a styrene-butadiene rubber particle likely derived from tyre wear associated with the nearby major road, whereas the remaining three cores contained only 2–3 MPs each. The oldest MPs found date from the 1950s. Overall, concentrations of MPs were surprisingly low.
This research is the first to examine historical microplastic pollution using dated sediment cores from multiple UK salt marshes across different estuarine systems. Although microplastics in soils can alter microbial communities and plant growth, the low concentrations observed here suggest minimal implications for salt marsh ecosystem functioning, including carbon sequestration processes and the success of habitat restoration or realignment efforts.
How to cite: Gilbert, A., Gehrels, W., Hodson, M., Kroger, R., and Blake, W.: A History of Microplastic Pollution in UK Salt Marshes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19187, https://doi.org/10.5194/egusphere-egu26-19187, 2026.
Plastic pollution is a critical global challenge, with annual production surpassing 400 million tonnes and only a small fraction properly managed. The remainder accumulates in terrestrial and aquatic environments, with rivers acting as major conduits to the ocean. Causing ecological, social and economic impacts that affect the fulfilment of the Sustainable Development Goals (SDGs). Estuaries, located at the land–sea interface, represent key zones for intercepting this flux. In order to address this environmental problem, given the strategic location of estuaries, this study assesses the potential of tidal marshes to retain meso- and macroplastic debris in shallow estuaries.
A multi-scale approach was implemented, combining controlled hydraulic flume experiments, field campaign, and GIS-based spatial modelling in the Santoña Marshes (northern Spain). Laboratory tests quantified plastic entrapment by salt-marsh vegetation (Juncus maritimus, Halimione portulacoides and Spartina maritima) under variable hydrodynamic condition representative of tidal flows varying water levels, flow rates and wind speeds, and the most common plastic materials found in salt marshes. Field surveys tracked floating buoys simulating plastics, under natural conditions, providing qualitative evidence of retention pathways. Geospatial analysis integrated one-year tidal flooding probabilities with vegetation distribution, local bathymetry, plant height, tidal patterns and laboratory entrapment results to estimate the probability of plastic reaching vegetated areas and its potential retention over a year, identifying possible accumulation hotspots.
Results indicate high entrapment efficiency under controlled conditions (≈90% per species), supported by field observations. Spatial modelling revealed significant variability across the entire marsh. Quantitative values for vegetation trapping potential were obtained with a resolution of 10 m. These results were visualised by classifying the area into categories of high, medium and low potential retention. Zones with high potential retention are associated with longer flooding durations throughout the year, which increase the likelihood of plastics reaching vegetated areas. These zones often coincide with the presence of secondary channels and dense vegetation, which slow water flow and enhance plastic trapping. Conversely, areas with low potential retention are typically located near the coastline, where flooding occurs for shorter periods, limiting the time available for plastics to interact with vegetation.
This work delivers species-specific, quantitative evidence of plastic trapping in estuarine environments, offering critical insights for management strategies and informing numerical models aimed at mitigating plastic pollution at the land–sea interface.
How to cite: Pérez García, L., Núñez, P., Sánchez, M., Bárcena, J. F., Abascal, A. J., and García, A.: Assessing the Potential Entrapment of Meso- and Macroplastic Debris by Tidal Marshes in Shallow Estuaries, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7795, https://doi.org/10.5194/egusphere-egu26-7795, 2026.
Coastal dunes worldwide trap marine plastics within psammophilous vegetation. Such processes may impact dune formation by altering sediment dynamics and affecting plant health. This study aims to assess whether plastics act as active geomorphic agents and explores how strategic vegetation management could transform this challenge into Nature-Based Solutions (NBS) for coastal regions at risk from plastic pollution.
We aim to develop a comprehensive UAV-based framework to evaluate interactions among plastic, vegetation, and geomorphology in dune systems. High-resolution surveys produce orthomosaics and DSMs, enabling us to map plastic distribution alongside traditional dune features such as scarp development, sediment retention volume, surface roughness, and gradients of vegetation health.
The analysis is guided by three research perspectives:
- Plastic entrapment dynamics by dune-building species
- Vegetation response to debris accumulation
- Geomorphic feedbacks influencing dune profile evolution
By establishing quantitative links between plastic accumulation and measurable geomorphic change, this study aims to identify critical thresholds where pollution may transform protective dunes into erosion-prone features. Marine plastics are regarded as a quantifiable factor influencing dune evolution, providing insights for vegetation-based strategies to maintain coastal stability.
Keywords: marine plastics, coastal geomorphology, UAV remote sensing, Nature-Based Solutions, dune evolution
How to cite: Corbau, C., Pignoni, E., Lazarou, A., Coltorti, M., and Simeoni, U.: Marine plastics as geomorphic agents in coastal dune systems: UAV framework and nature-based solutions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10462, https://doi.org/10.5194/egusphere-egu26-10462, 2026.
Since the 1950s, the increase in plastic production has led to widespread mismanagement and substantial discharges of plastic waste into the marine environment. Once released, (micro-)plastics can drift, remain buoyant, sink, strand on coastlines, be ingested, or fragment into smaller particles. Understanding the marine life cycle of large (L-MP, 5mm–300µm) and small (S-MP, 300-1µm) microplastics is therefore a major challenge, particularly regarding the “missing plastic” paradox, highlighting the imbalance between plastic inputs and surface observations in the ocean1. Recent studies2,3 show that a proportion of MP is distributed throughout the water column, where it can aggregate with organic matter, marine snow, and microbial and phytoplanktonic organisms, ultimately settling to the sea floor. This project investigates MP fate in the marine environment, and the roles of MP type, shape, and environmental conditions in their sedimentation in the Calanques National Park (CNP) and Marseille Bay, a highly urbanized coastal area under strong anthropogenic pressure.
Two field campaigns were conducted in March and September 2025 in Marseille Bay and the CNP. Subsurface waters were sampled using in situ pumping, while surface waters were collected using manta trawls. In addition, anchored particle interceptor traps (PIT) were deployed for one month in Marseille Bay. Microplastics from water and PIT samples were extracted following adapted protocols for L-MP4, with adjustments to recover S-MP (>32µm) and to characterize them using micro-infrared spectroscopy5. Complementary geochemical (POC, PON) and biological (chlorophyll a, TEP) analyses were performed on PIT samples.
The campaigns provide robust estimates of subsurface L- and S-MP concentrations, showing a size-dependent shape and abundance distributions, with MP concentrations decreasing and fiber abundances increasing as size increases. Samples of manta and pump collected from the same location reveal differences in the abundance and polymer composition of L-MPs in surface and subsurface waters. PIT deployment provides the first MP sedimentation fluxes for this area, which are put in perspective with hydrodynamic, geochemical, and biological parameters to elucidate the role of aggregation in MP vertical transport. Overall, these findings highlight the importance of S-MP contribution (<300µm) in the diagnosis of MP pollution and provide the first estimates of MP vertical fluxes in Marseille Bay.
References
1Isobe, A. & Iwasaki, S. The fate of missing ocean plastics: Are they just a marine environmental problem? Sci. Total Environ. 825, 153935 (2022).
2Rowlands, E. et al. Vertical flux of microplastic, a case study in the Southern Ocean, South Georgia. Mar. Pollut. Bull. 193, 115117 (2023).
3Galgani, L. et al. Hitchhiking into the Deep: How Microplastic Particles are Exported through the Biological Carbon Pump in the North Atlantic Ocean. Environ. Sci. Technol. 56, 15638–15649 (2022).
4Alcaïno, A. et al. Influence of the Rhone River intrusion on microplastic distribution in the Bay of Marseille. Reg. Stud. Mar. Sci. 73, 103457 (2024).
5Nguyen, T. T. et al. Spatial and seasonal abundance and characteristics of microplastics along the Red River to the Gulf of Tonkin, Vietnam. Sci. Total Environ. 957, 177778 (2024).
How to cite: Surmont, A., Vidal, L., Labille, J., Licari, L., Wong-Wah-Chung, P., and Lebarillier, S.: Distribution and Vertical Fluxes of large and small microplastics (MP) in the Calanques National Park (CNP) and Marseille Bay , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6645, https://doi.org/10.5194/egusphere-egu26-6645, 2026.
Marine plastic pollution research has traditionally focused on the abundance and impacts in surface waters, resulting in substantial knowledge gaps regarding their vertical distribution and ultimate fate. This study addresses these limitations by providing a comprehensive assessment of plastic transport dynamics across multiple compartments. Plastic concentrations and composition (shape, size, and polymer type) were quantified from the sea surface to the sediment using high-resolution sampling instruments.
Our results demonstrate an exponential decrease in plastic abundance with depth, while revealing particle retention within the mixed layer, immediately above the pycnocline. Notably, sediments constitute the dominant sink, containing the vast majority of the plastic load (98% of the total measured abundance). Furthermore, sediments accumulated the highest-density polymers and smallest particle sizes, suggesting that density-driven sedimentation and fragmentation processes play a key role in vertical transport.
These findings highlight the importance of understanding vertical transport processes as a critical step in identifying the ultimate sinks of plastic and assessing its potential long-term environmental impacts, thereby supporting the development of more effective mitigation strategies.
How to cite: Quintana, R., Manzano-Medina, S., Pérez-López, L., Oyón-Sanz, A., González-Gordillo, J. I., Marti, E., and Morales-Caselles, C.: Beyond the Surface: Vertical Distribution of Plastics in Coastal Areas of the Gulf of Cádiz, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14036, https://doi.org/10.5194/egusphere-egu26-14036, 2026.
Posters on site: Thu, 7 May, 10:45–12:30 | Hall X4
Plastic pollution in the marine environment has become a global issue with severe ecological, economic, and social consequences. Oceanic islands are particularly vulnerable, as they combine unique ecosystems with exposure to multiple pathways of plastic leakage, including maritime traffic, fisheries, tourism and hydrodynamic transport. In this study, numerical modelling and field observations are combined to investigate the transport pathways, seasonal variability and accumulation patterns of floating plastic debris in the Canary Islands, with particular focus on Tenerife. Developed within the scope of the PLAST4H2 project (EAPA_0018/2022), funded by the Interreg Programme of the European Union, this work addresses the need for regionally resolved assessments of marine litter dynamics in complex insular systems.
The field data analysed comprises 25 beach cleanup campaigns conducted in Tenerife between 2024 and 2025, providing insights into the composition and spatial variability of coastal plastic pollution. Simulations were performed using the MOHID-Lagrangian model, forced by high-resolution three-dimensional metocean data from the Copernicus Marine Service. A model sensitivity analysis was conducted to assess the influence of particle properties and hydrodynamic resolution in the simulated results, alongside an assessment of seasonal variability in transport and accumulation patterns.
The sensitivity analysis reveals that variations in particle morphology exert a negligible effect on horizontal transport dynamics, whereas hydrodynamic resolution significantly influences result accuracy. The seasonal simulations show pronounced contrasts across the archipelago: winter conditions promote enhanced mixing and widespread nearshore retention, favouring the persistence of locally sourced debris, while summer circulation dominated by the Canary Current and mesoscale recirculation drives more focused accumulation along Tenerife’s eastern coast.
These findings identify persistent accumulation hotspots on Tenerife’s eastern and southwestern shores and emphasise the interplay between regional advection and local recirculation in shaping debris accumulation patterns. This work advances understanding of marine plastic transport in insular environments and provides a transferable framework for future monitoring and mitigation strategies.
How to cite: Querido, C., Pinto, L., Neves, R., and de la Moneda, A.: Lagrangian Modelling of Plastic Transport and Accumulation around Tenerife Island, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4001, https://doi.org/10.5194/egusphere-egu26-4001, 2026.
Concern about the problem of marine debris has grown in recent years, as it is now known to be a large-scale problem affecting everything from coastal environments to the open sea [1]. Therefore, understanding how these pollutants move and are transported is key to developing containment and prevention policies but also management strategies. Due to its specific location, Ireland poses a challenge in terms of transport, as it has complex circulation patterns that interact with multiple land inputs. That is why numerical modelling is a valuable tool for assessing the transport and fate of marine debris at different spatial scales.
In this study, a Lagrangian modeling approach is applied to the Irish Sea to estimate marine litter concentrations in both coastal areas and offshore waters. Rivers are assumed to be the main terrestrial sources of waste, with contributions from the main Irish rivers estimated and weighted according to demographic and socioeconomic factors, such as population size and a deprivation index associated with each river basin. The aim is to obtain a more realistic view of anthropogenic pressure on the marine environment.
Particle tracking simulations were performed using the Lagrangian MOHID model [2], a powerful tool for simulating the transport and dispersion of passive tracers in the marine environment. In this case, 3D simulations of the trajectories of virtual particles representing marine debris will be taken into account. This approach allows for the identification of both accumulation and barrier zones, providing solid support for empirical data-based marine debris management and mitigation strategies.
[1] Rangel-Buitrago, N., Williams, A., Costa, M. F., & de Jonge, V. (2020). Curbing the inexorable rising in marine litter: An overview. Ocean & Coastal Management, 188, 105133.
[2] Cloux, S., Allen-Perkins, S., de Pablo, H., Garaboa-Paz, D., Montero, P., & Muñuzuri, V. P. (2022). Validation of a Lagrangian model for large-scale macroplastic tracer transport using mussel-peg in NW Spain (Ría de Arousa). Science of the Total Environment, 822, 153338.
How to cite: Cloux González, S. and Dabrowski, T.: Modeling Coastal and Offshore Marine Litter Accumulation in the Irish Seas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7072, https://doi.org/10.5194/egusphere-egu26-7072, 2026.
The transport of microplastics (MPs) from rivers to the ocean remains poorly constrained, highlighting the need for quantitative evaluation of the MPs budget in estuarine environments. This study quantitatively evaluated MPs transport in an estuary using field observations and numerical simulations, focusing on vertical distribution, mass flux, and salt-wedge processes. MPs in estuarine environments were found to accumulate vertically and be re-transported by tidal forcing, resulting in seaward export over a single tidal cycle.
Field observations were conducted in the estuarine reach of the Oita River during one tidal cycle, with five sampling campaigns from high tide through low tide to the subsequent high tide. Water samples were collected at 50 cm vertical intervals from the surface to near the riverbed, and flow velocities were measured simultaneously.
The results showed that vertical MPs mass fluxes consistently followed a depth-dependent pattern of bottom > mid-depth > surface during both neap and spring tides, indicating persistent bottom-dominated transport. Spatiotemporal integration of MPs mass fluxes yielded a net seaward transport of +1.22 × 10³ mg/m over one tidal cycle, quantitatively demonstrating MPs export from land to the coastal ocean. This net export resulted from dominant land-to-sea transport during ebb tide, driven by upstream MPs fluxes and resuspension from the bottom layer, exceeding landward transport during flood tide.
Numerical simulations reproduced MPs accumulation near the halocline formed during ebb tide and subsequent seaward transport by bottom currents, consistent with the observed positive net flux. These results demonstrate that estuarine MPs transport is asymmetrically controlled by tidal flow and salinity stratification, with the halocline playing a key role in MPs accumulation and seaward export.
How to cite: Iga, Y. and Kataoka, T.: Quantitative tidal control of spatiotemporal microplastics variability in an estuary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15368, https://doi.org/10.5194/egusphere-egu26-15368, 2026.
Marine debris has become a critical global environmental issue, and river mouths are one of the primary pathways through which land-based waste enters the oceans. Therefore, accurate quantification of marine debris at river mouths is essential for coastal management and marine-conservation-related policymaking. However, existing survey-based approaches largely rely on manual visual inspection, which is not only time-consuming but also subject to human bias; thus, these approaches cannot be used to effectively assess marine debris coverage across large areas. Some studies have applied artificial-intelligence-based image recognition techniques to assess marine debris coverage, but most of these studies have focused on debris classification rather than quantitative estimation of debris coverage. To address these limitations, the present study developed an efficient and accurate method for estimating the debris coverage at river mouths, thereby improving upon the subjectivity and inefficiency inherent in traditional visual survey methods. Image data from two sources were used in this study: (1) images captured under various simulated scenarios by high-resolution cameras and (2) high-resolution aerial images acquired by unmanned aerial vehicles (UAVs) at river mouths. Following image acquisition, an artificial-intelligence-based image analysis system was employed to perform preprocessing procedures on the images—including noise reduction, grayscale conversion, binarization, and edge detection—to quantify the proportion of the debris-covered area within each image. To validate the reliability of the image-based estimates, this study adopted an aerial grid method as a reference benchmark. Aerial grids were overlaid on images of the examined areas, and the proportion of debris within each grid cell was manually calculated to determine the actual debris coverage. The accuracy of the proposed methodology was evaluated by comparing its results with those derived using the aerial grid method, and potential sources of error were examined. The results indicated that integration of UAV aerial imaging, image processing techniques, and coverage quantification methods enables the feasible and accurate estimation of the debris coverage at river mouths. The proposed approach can assist governmental agencies and nongovernmental organizations in the evidence-based planning of marine debris monitoring programs, marine debris cleanup efforts, and relevant conservation policies.
How to cite: Yang, H.-C. and Chen, Y.-C.: High-Efficiency Method for Estimating Waste Coverage at River Mouths, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2037, https://doi.org/10.5194/egusphere-egu26-2037, 2026.
Microplastics (MPs) are an emerging concern in marine environments due to their widespread distribution, ingestion by marine organisms, and role as sources and carriers of hazardous chemicals. This study examined MP levels, spatial distribution, and contamination characteristics in surface waters of the eastern offshore region of South Korea (East Sea). Traditional grab sampling provides limited spatial coverage and may not sufficiently capture large-scale MP patterns. To address this drawback, we utilized a custom-designed Surface Water Underway Sampler (SWUS), which enables continuous collection of surface waters, including the air–sea interface layer, from a fast-moving vessel. In this study, seawater samples (>20㎛) were collected along 15 transect lines in East Sea using the SWUS aboard the R/V Onnuri in April 2023. MPs were detected in all surface water samples collected across the East Sea, with concentrations ranging from 14.8-315.5 n/m³ (mean: 90.0 ± 79.5 n/m³). Notably, 79% of the MPs were smaller than 200 μm. Fragment-type MPs were the most dominant shape (74.8%), followed by fibers (24.8%) and films (0.4%). The predominant polymer types were polyester/polyethylene terephthalate (PES/PET, 29.3%), polypropylene (PP, 28.9%), and alkyd (10.5%), followed by polyethylene vinyl acetate (PEVA, 6.1%), polyamide (PA, 5.9%), and polyethylene (PE, 4.5%). Overall, high-density polymers (> 1 g/cm³) accounted for 58.7% of the total, indicating a relatively higher proportion compared to low-density polymers such as PP, PE, and PEVA. Higher MP abundance was observed in the central regions of the East Sea despite the lower human activity and industrial facilities, suggesting that physical oceanographic processes may play an important role in the transport and distribution of MPs in the region. To our knowledge, this is the first study to examine the distribution of microplastics (>20 µm) in surface waters of the East Sea using the SWUS. This method enhances the representativeness of MP data and provides new insights into large-scale variability in surface MP concentrations. Our findings demonstrate the utility of SWUS as an effective tool for high-resolution, spatially extensive monitoring of microplastics in marine environments.
How to cite: Han, G. M., Ha, S. Y., Cho, Y., Jang, M., and Hong, S. H.: Application of a Continuous Underway Sampling Device for Microplastic Assessment in Surface Offshore Waters of South Korea (East Sea), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8465, https://doi.org/10.5194/egusphere-egu26-8465, 2026.
Coastal estuaries are recognized as hotspots for both microplastics (MPs) and harmful algal blooms (HABs); however, the role of dinoflagellates in facilitating MP sinking remains poorly understood. In this study, we investigated aggregate formation between dinoflagellate Prorocentrum minimum and polyethylene (PE; densities of 1.0 and 1.4 g cm⁻³, particle size 10–20 µm) and polypropylene (PP; density 0.91 g cm⁻³, particle size 45–75 µm) using roller–shaker incubations. Phytoplankton growth, aggregate morphology, sinking velocity, and aggregate stability were evaluated through microscopic observations and statistical analyses. Growth of P. minimum was not inhibited by MP exposure; notably, PE treatments exhibited significantly higher biomass than the control during both the exponential and stationary phases (p < 0.05). Aggregates first appeared on Day 10 and progressively incorporated MPs and fragmented thecal plates. The sinking ratio of PE1.0 particles increased steadily, reaching approximately 22% (R² = 0.96, p < 0.05), whereas PP particles exhibited negligible sedimentation (<1%). Sinking velocities increased from 0.38 mm s⁻¹ on Day 10 to 0.76 mm s⁻¹ on Day 16 (p < 0.05), but subsequently declined to 0.66 mm s⁻¹ by Day 31 despite continued increases in aggregate size. This deviation from Stokes’ law was attributed to the accumulation of low-density cellulose thecal plates, which reduced aggregate density and structural cohesion. Principal component analysis (PCA) showed that PC1 explained 53.9% of the variance and was positively associated with aggregate area and sinking velocity, whereas PC2 accounted for 22.9% of the variance and indicated a negative influence of thecal plate abundance on sinking velocity. Long-term incubations conducted under cold and dark conditions (>70 days) revealed no evidence of aggregate resuspension. Collectively, these results demonstrate that thecate morphology constrains MP export efficiency relative to extracellular polymeric substance (EPS)-rich raphidophytes. Nevertheless, scaling our experimental results suggests that Prorocentrum blooms may export on the order of 10¹⁰ MP particles annually, underscoring the importance of species-specific traits as key regulators of MP vertical transport and ultimate fate in coastal ecosystems.
How to cite: Baek, S., Sudusinghe, K. D., Lim, Y. K., and Hong, S. H.: Microplastic aggregation and sinking mediated by the harmful dinoflagellate Prorocentrum minimum under simulated marine conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8762, https://doi.org/10.5194/egusphere-egu26-8762, 2026.
Previous investigations along Colombia’s central Caribbean coast have documented microplastic (MP) pollution in terms of typology, abundance, and spatial distribution. However, the influence of sediment granulometry and associated statistical parameters (mean, median, sorting, skewness, and kurtosis) on MP occurrence remains poorly understood. This study addresses this gap through an integrated assessment conducted at 15 coastal sites along the central Caribbean coast of Colombia. Sediment samples were collected and analyzed to determine granulometric characteristics and to quantify MP abundance, shapes, and potential impacts, enabling evaluation of their relationships. Grain-size distributions were broadly homogeneous among the surveyed beaches, with dominance of sand, slightly gravelly sand, and slightly gravelly muddy sand. Sorting conditions were primarily moderately well sorted (60%), followed by moderately sorted (20%), well sorted (13%), and very well sorted sediments (7%). Microplastic densities ranged from 160 to 1,120 MPs kg⁻¹, values comparable to those reported for beaches and coastal embayments worldwide. Fibres were the dominant MP typology, representing 86.8% of the total items recorded. Multiple linear regression analysis indicated that approximately 30% of the variability in MP occurrence could be explained by the sediment statistical parameters considered, with sorting emerging as the most influential variable, accounting for ~11% of the explained variance (r² = 0.27; F = 0.67). These findings highlight the role of sedimentary processes in modulating microplastic accumulation on sandy beaches. To manage the MP issue, reducing the current elevated plastic inputs into the environment is necessary/mandatory. Approaches to reach this goal must be focused on the entire plastic life cycle (extraction, design, production, use, disposal, recovery, recycling).
How to cite: Rangel-Buitrago, N.: Microplastic Occurrence in Relation to Sediment Granulometry Along the Central Caribbean Coast of Colombia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13357, https://doi.org/10.5194/egusphere-egu26-13357, 2026.
The fragmentation of plastics in the marine environment represents one of the most persistent and complex challenges in contemporary environmental science. Over the past decade, a limited number of laboratory experiments and numerical modeling have shown that plastics do not fragment into uniform debris but instead undergo a cascade of fragmentation processes that govern particle size distributions, transport behavior, and ecological impacts. However, real-world examples of plastic fragmentation remain rare, despite being essential for calibrating and validating generic numerical models. There is therefore a strong need for data derived from natural systems, ideally based on large and statistically representative datasets.
In Normandy, France, the Dollemard coastal landfill provides a unique opportunity to address this issue through the study of a traceable anthropogenic marker: VALSTAR brand beer bottle caps. Manufactured from polyethylene, these caps were deposited in very large quantities from the 1960s to the 1990s. Due to ongoing coastal erosion, they continue to be released and are now found in significant numbers within the adjacent marine environment.
The surfaces of these bottle caps exhibit advanced degradation, with numerous microplastics still attached to the remaining material. Systematic microscopic photographs of the degraded surfaces were acquired and automatically analyzed to quantify the number, size, and shape parameters of the attached microplastics. In parallel, a surface degradation index was established for the upper face of each cap, combined with a weighting method to estimate mass balance. From a total collection of 787 recovered caps, a representative subset of 107 was analyzed in detail. In addition, a single bottle cap was artificially aged in a UV chamber under controlled conditions to better isolate and characterize the role of UV radiation in the fragmentation process.
The results demonstrate the coexistence of two fragmentation mechanisms: surface ablation and macro-fragmentation. Macro-fragmentation remains a secondary process, accounting for only 16% of the cases observed in the total dataset. UV-induced degradation does not appear to govern fragmentation at the scale of the smallest microplastics (µm range). Instead, it influences the particle size distribution of larger microplastics in the millimeter range. Thus, a clear bimodal size distribution is observed in the dataset, with a dominant population centered around an equivalent diameter of approximately 45 µm, and a secondary population of larger fragments, ranging from 0.8 to 0.9 mm. Comparing pristine caps, caps recovered in situ from landfills, and caps from marine settings allows a first-order estimation of fragmentation kinetics over the past 40 years. This comparison suggests an average mass loss of approximately 3.9% for the caps in the studied collection.
How to cite: Rohais, S., Roujolle, R., Vaireaux, J., Lieunard, V., Bailleul, J., Tallec, K., Baby, M. G., and Romero-Sarmiento, M.-F.: Valstar Beer Bottle Caps as Anthropocene Fossils constraining Plastic Fragmentation in the Marine Environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9867, https://doi.org/10.5194/egusphere-egu26-9867, 2026.
The MISP project (MIsure Sperimentali nei corsi d’acqua del Distretto delle Alpi Orientali per la cattura dei rifiuti e delle Plastiche galleggianti – Experimental measures in Eastern Alps District waterways for the capture of floating waste and plastics) aims to improve knowledge of waste and plastic pollution and to reduce floating waste in the Venice Lagoon and in selected rivers flowing into it, consequently limiting the arrival of floating garbage in the north part of the Adriatic Sea.
The project is financed by the Italian Ministry of the Environment and Energy Security under Law No. 60/2022 (“SalvaMare” Law) and is coordinated by the Eastern Alps District – River basin Authority (Autorità di Bacino Distrettuale delle Alpi Orientali).
MISP project, for the purpose of reduce plastic pollution, includes two main experimental measures, which are: positioning of three floating waste capture barriers in three different rivers of the catchment draining into the Venice Lagoon, and the construction and operation of a prototype boat equipped with technology for capturing floating waste in the Venice Lagoon.
The Venice Lagoon is an extremely valuable and complex environment from both a naturalistic and cultural perspective. Together with the city of Venice, the lagoon is part of the UNESCO World Heritage Site and is included in the Natura 2000 network. This particular aquatic environment is affected by multiple anthropogenic pressures, among which plastic waste pollution is one of the most critical. Increasing knowledge of the quantity, distribution and movement of floating plastic waste is essential for planning effective mitigation actions.
A core component of the MISP project is a tracking activity aimed at studying floating plastic pathways within the Venice Lagoon and identifying accumulation areas that will be important for the boat operation. During 2025 and early 2026, about 170 GPS trackers have been deployed at different locations in the lagoon and at selected river mouths. The trackers are designed to simulate the floating plastic waste targeted by the project and consist of floating plastic jars containing a GPS device. Each tracker can transmit its position every 18 hours, and the collected data are visualized and analysed through a WebGIS platform that reconstructs trajectories and supports spatial analysis.
Data analysis through the WebGIS will provide various results, such as: waste transport dynamics and accumulation patterns in the study area, average distance travelled by floating waste, environmental conditions that influence the movement or retention of floating litter (e.g. wind, tides, storms, shoreline vegetation, and lagoon hydrodynamics).
All these results will enable a more efficient waste collection with the project boat and a future sharing of them with local stakeholders will be useful for other waste collection initiatives in the project area.
How to cite: Pasini, S., Poletto, G., Manghi, M., and Braidot, A.: MISP, a project to better understand and reduce plastic pollution in the Venice Lagoon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19115, https://doi.org/10.5194/egusphere-egu26-19115, 2026.
