Plastic litter is a part of the carbon cycle in an urban river: Microplastic and macroplastic accumulate with organic matter in floating debris rafts.

Watershed models of plastic export from rivers to oceans have large uncertainties, and improvements require direct measurements of riverine macroplastic (>5 mm) and microplastic (<5 mm). Also, plastic represents allochthonous carbon inputs to rivers but is rarely measured as carbon mass. We quantified plastic and organic matter within floating debris rafts and open water in an urban river. Macroplastics only occurred in debris rafts. Microplastics had higher concentrations in debris rafts relative to open water. Across sites, organic matter was positively correlated with microplastics and macroplastics. Last, carbon in plastic was 40% of the carbon mass in coarse particulate organic matter in debris rafts. Floating plastic litter accumulates with particulate organic matter in debris rafts. Plastic is an overlooked and ecological meaningful component of carbon standing stocks in urban rivers. Results will inform improved carbon budget calculation in rivers and watershed models of plastic export. PRACTITIONER POINTS: Plastic particles floating on the surface of an urban river accumulate in debris rafts compared to open water in terms of count and mass. Abundance and composition of plastic particles in debris rafts were distinct from those in open water areas. Plastic litter as units of carbon mass was in the same order of magnitude as carbon mass in course particulate organic matter. Plastic litter moves in similar ways to naturally occurring organic particles and should be measured as a part of the riverine carbon cycle.

Reduction scenarios of plastic waste emission guided by the probability distribution model to avoid additional ocean plastic pollution by 2050s.

Marine plastic pollution is progressing worldwide and will become increasingly serious if plastic waste emissions continue at the current rate or increase with economic growth. Here, we report a particle tracking-based probability distribution model for predicting the abundances of marine macroplastics and microplastics, which undergo generation, transport, and removal processes in the world's upper ocean, under various scenarios of future land-to-sea plastic waste emissions. To achieve the Osaka Blue Ocean Vision, which aims to reduce additional pollution by marine plastic litter to zero by 2050, plastic waste emission in ∼2035 should be reduced by at least 32 % relative to 2019. It is necessary to take stringent measures such as 'system change scenario' or 'improve waste management scenario' proposed in previous studies to reduce the marine plastic pollution by 2050.

The retention of plastic particles by macrophytes in the Amazon River, Brazil.

This study evaluated the presence of plastics and microplastics in macrophytes in an urbanized sector of the Amazon River. A total of 77 quadrats in 23 macrophyte banks were sampled during the dry (September 2020) and rainy (June 2021) season. Five species were identified: Paspalum repens, Pontederia rotundifolia, Pistia stratiotes, Salvinia auriculata and Limnobium laevigatum, with P. repens being dominant during the dry season (47.54%) and P. rotundifolia during the rainy season (78.96%). Most of the plastic particles accumulated in Paspalum repens (49.3%) and P. rotundifolia (32.4%), likely due to their morphological structure and volume. The dry season showed a higher accumulation of plastic particles than the rainy season. Microplastics were found in most samples, during both the dry (75.98%) and rainy seasons (74.03%). The upstream macrophyte banks retained more plastic particles compared to the downstream banks. A moderate positive correlation was observed between the presence of plastic particles and macrophyte biomass, and a weak positive correlation between the occurrence of microplastics and mesoplastics. White and blue fragments, ranging from 1 to 5 mm were the most common microplastics found in the macrophyte banks. Green fragments and green and blue fibers were identified as polypropylene, blue and red fragments as polyethylene, and white fragments as polystyrene. Therefore, the results of this study highlight the first evidence of the retention of plastic particles in macrophytes of the Amazon and highlight a significant risk due to the harmful effects that this type of plastic can cause to the fauna and flora of aquatic ecosystems.

River plastic transport and storage budget.

Rivers are one of the main conduits that deliver plastic from land into the sea, and also act as reservoirs for plastic retention. Yet, our understanding of the extent of river exposure to plastic pollution remains limited. In particular, there has been no comprehensive quantification of the contributions from different river compartments, such as the water surface, water column, riverbank and floodplain to the overall river plastic transport and storage. This study aims to provide an initial quantification of these contributions. We first identified the main relevant transport processes for each river compartment considered. We then estimated the transport and storage terms, by harmonizing available observations on surface, suspended and floodplain plastic. We applied our approach to two river sections in The Netherlands, with a focus on macroplastics (≥2.5 cm). Our analysis revealed that for the studied river sections, suspended plastics account for over 96% of item transport within the river channel, while their relative contribution to mass transport is only 30%-37% (depending on the river section considered). Surface plastics predominantly consisted of heavier items (mean mass: 7.1 g/#), whereas suspended plastics were dominated by lighter fragments (mean mass: 0.1 g/#). Additionally, the majority (98%) of plastic mass was stored within the floodplains, with the river channel accounting for only 2% of the total storage. Our study developed a harmonized approach for quantifying plastic transport and storage across different river compartments, providing a replicable methodology applicable to different regions. Our findings emphasize the importance of systematic monitoring programs across river compartments for comprehensive insights into riverine plastic pollution.

A review of plastic debris in the South American Atlantic Ocean coast - Distribution, characteristics, policies and legal aspects.

The presence of plastics in the oceans has already become a pervasive phenomenon. Marine pollution by plastics surpasses the status of an emerging threat to become a well-established environmental problem, boosting research on this topic. However, despite many studies on the main seas and oceans, it is necessary to compile information on the South American Atlantic Ocean Coast to identify the lack of research and expand knowledge on marine plastic pollution in this region. Accordingly, this paper conducted an in-depth review of monitoring methods, sampling, and identification of macroplastics and microplastics (MPs) in water, sediments, and biota, including information on legal requirements from different countries as well as non-governmental initiatives. Brazil was the country with the highest number of published papers, followed by Argentina. MPs accounted for 75 % of the papers selected, with blue microfibers being the most common morphology, whereas PE and PP were the most abundant polymers. Also, a lack of standardization in the methodologies used was identified; however, the sites with the highest concentrations of MPs were the Bahía Blanca Estuary (Argentina), Guanabara Bay (Brazil), and Todos os Santos Bay (Brazil), regardless of the method applied. Regarding legislation, Uruguay and Argentina have the most advanced policies in the region against marine plastic pollution due to their emphasis on the life cycle and the national ban on certain single-use plastics. Therefore, considering its content, this expert review can be useful to assist researchers dealing with plastic pollution along the South American Atlantic Ocean Coast.

Water hyacinths retain river plastics.

Rivers represent one of the main conduits for the delivery of plastics to the sea, while also functioning as reservoirs for plastic retention. In tropical regions, rivers are exposed to both high levels of plastic pollution and invasion of water hyacinths. This aquatic plant forms dense patches at the river surface that drift due to winds and currents. Recent work suggests that water hyacinths play a crucial role in influencing plastic transport, by efficiently trapping the majority of surface plastic within their patches. However, a comprehensive understanding of the interaction between water hyacinths and plastics is still lacking. We hypothesize that the properties relevant to plastic transport change due to their trapping in water hyacinth patches. In particular, the length scale, defined as the characteristic size of the transported material, is a key property in understanding how materials move within rivers. Here, we show that water hyacinth patches trap on average 54%-77% of all observed surface plastics at the measurement site (Saigon river, Vietnam). Both temporally and spatially, we found that plastic and water hyacinth presence co-occur. The formation of plastic-plant aggregates carries significant implications for both clean-up and monitoring purposes, as these aggregates can be detected from space and need to be jointly removed. In addition, the length scale of trapped plastics (∼4.0 m) was found to be forty times larger than that of open water plastics (∼0.1 m). The implications of this increased length scale for plastic transport dynamics are yet to be fully understood, calling for further investigation into travel distances and trajectories. The effects of plastic trapping likely extend to other key properties of plastic-plant aggregates, such as effective buoyancy and mass. Given the prevalence of plant invasion and plastic pollution in rivers worldwide, this research offers valuable insights into the complex environmental challenges faced by numerous rivers.

Chemical analysis of marine microdebris pollution in macroalgae from the coastal areas of Argentina.

Marine microdebris (MDs, <5 mm) and mesodebris (MesDs, 5-25 mm), consist of various components, including microplastics (MPs), antifouling or anticorrosive paint particles (APPs), and metallic particles (Mmps), among others. The accumulation of these anthropogenic particles in macroalgae could have significant implications within coastal ecosystems because of the role of macroalgae as primary producers and their subsequent transfer within the trophic chain. Therefore, the objectives of this study were to determine the abundance of MDs and MesDs pollution in different species of macroalgae (P. morrowii, C. rubrum, Ulva spp., and B. minima) and in surface waters from the Southwest Atlantic coast of Argentina to evaluate the ecological damage. MDs and MesDs were chemically characterized using µ-FTIR and SEM/EDX to identify, and assess their environmental impact based on their composition and degree of pollution by MPs, calculating the Polymer Hazard Index (PHI). The prevalence of MDs was higher in foliose species, followed by filamentous and tubular ones, ranging from 0 to 1.22 items/g w.w. for MPs and 0 to 0.85 items/g w.w. for APPs. It was found that macroalgae accumulate a higher proportion of high-density polymers like PAN and PES, as well as APPs based on alkyd, PMMA, and PE resins, whereas a predominance of CE was observed in surrounding waters. Potentially toxic elements, such as Cr, Cu, and Ti, were detected in APPs and MPs, along with the presence of epiplastic communities on the surface of APPs. According to PHI, the presence of high hazard score polymers, such as PAN and PA, increased the overall risk of MP pollution in macroalgae compared to surrounding waters. This study provided a baseline for MDs and MesDs abundance in macroalgae as well as understanding the environmental impact of this debris and their bioaccumulation in the primary link of the coastal trophic chain.

The processes and transport fluxes of land-based macroplastics and microplastics entering the ocean via rivers.

Approximately 80% of marine plastic waste originates from land-based sources and enters oceans through rivers. Hence, to create effective regulations, it is crucial to thoroughly examine the processes by which land-based plastic waste flows into marine environments. To this end, this review covers the complete journey of macro- and microplastics from their initial input into rivers to their ultimate release into oceans. Here, we also discuss the primary influencing factors and current popular research topics. Additionally, the principles, applicability, accuracy, uncertainty, and potential improvement of the standard methods used for flux estimation at each stage are outlined. Emission estimates of land-based macro- and microplastics are typically assessed using the emission factor approach, coefficient accounting approach, or material flow analysis. Accurately estimating mismanaged plastic waste is crucial for reducing uncertainty in the macroplastic emission inventory. In our review of the processes by which land-originating plastics enter rivers, we categorized them into two major types: point-source and diffuse-source pollution. Land surface hydrological models simulate transport from diffuse sources to rivers, necessitating further research. Riverine (micro)plastic flux to the ocean is often estimated using monitoring statistics and watershed hydrological models at the watershed scale; however, standardized monitoring methods have not yet been established. At the global scale, algorithms based on river datasets are often used, which require further improvements in river data selection and microplastic number-mass conversion factors. Furthermore, the article summarizes the accuracy and sources of uncertainty of various methods. Future research efforts should focus on quantifying and mitigating uncertainties in resultant projections. Overall, this review deepens our understanding of the processes by which land-based plastic waste enters the ocean and helps scholars efficiently select or improve relevant methods when studying land-ocean transport fluxes.

Spatial accumulation of flood-driven riverside litter in two Northern Atlantic Rivers.

The escalation of litter accumulation in aquatic environments is recognized as an emerging global concern. Although rivers represent the main conduits for land-based waste into the oceans, the spatial dynamics of litter accumulation in these systems remain poorly investigated, especially after hydro-climatic extreme events. Floods have been identified as major drivers of litter mobilization, including macroplastics, within rivers. However, predicting flood-induced litter accumulation along riverbanks is complex due to the cumulative interplay of multiple environmental (geomorphological and riparian) and anthropogenic factors. Using empirical data collected from 14 stream reaches in two Northern Atlantic rivers in Portugal, our study evaluates which factors, among geomorphological, riparian, and anthropogenic descriptors, best drive riverside litter accumulation after floods. Taking into account the longitudinal gradient and the spatial heterogeneity of the studied reaches, our study enhances how the accumulation and characteristics (type, size) of riverside litter vary across a rural-urban continuum. Our model reveals that the combination of the human population density and the stream slope at river reach showed the highest explanatory power for the accumulation of riverside litter. Our findings indicate that litter tends to be retained close to the source, even under flood conditions. We also found that the structure of riparian vegetation showed low explanatory power for litter accumulation. However, riparian trapping could be influenced by litter input (density and type) which varies with anthropogenic activities. This work highlights the importance of gathering field data to identify critical areas of riverside litter accumulation within river basins. Our findings can further support environmental managers in designing and implementing effective cleanup campaigns and implementing plastic recovery strategies at specific areas. Nevertheless, it is crucial to enhance coordinated efforts across the entire value chain to reduce plastic pollution, promote innovative approaches for plastic litter valorization, and establish effective prevention pathways.

Litter traps: A comparison of four marine habitats as sinks for anthropogenic marine macro-litter in Singapore.

The potential for marine litter being trapped in biodiverse marine habitats such as mangrove forests, seagrass meadows and coral reefs is poorly understood. This study presents the first comprehensive investigation on the status of macro-litter across four marine habitats in Singapore during the two monsoonal seasons. Overall, litter density did not vary considerably between the southwest and the northeast monsoon. The litter density in terms of count was generally lower in seagrass meadows and coral reefs compared to mangroves and beaches. Plastic was the major type of litter found across most habitat types. Notably, many fishing-related items were found on coral reefs, while drinking straws were abundant at the mangrove strandlines during the southwest monsoon. Foam fragments and cigarette butts were common at the beach strandlines. These results suggest that mangroves among other habitats examined here should be prioritised for clean-up efforts in order to restore these critical coastal habitats.

Comparison of macroplastics dynamic across a tidal-dominated coastal habitat seascape including seagrasses, salt marshes, rocky bottoms and soft sediments.

Coastal environments are usually composed by heterogeneous coastal-seascape, which can modify macroplastics accumulation dynamic. We evaluated seasonally the litter trapped on tidal-dominated habitats including two seagrass species, salt marsh, sandy beach, bare sediment and rocky bottom. Vegetated habitats showed the highest plastic accumulation in autumn-winter seasons, especially in medium-lower tidal-elevation zones. Seagrasses accumulated most of the degraded macroplastics, whereas averaged smaller sizes of litter were found in the salt marsh. The trapping ability of macrophytes was related to aboveground-biomass properties (i.e., height, width or flexibility) rather than shoot-density. Sandy beaches exhibited the highest plastics accumulation matching with the touristic-peak in the area, whereas rocky bottom was an important sink for macroplastics. This study provides authorities with comprehensible information to address the marine plastic litter problem taking into account the habitat-connectivity, the litter trap-ability of macrophytes and the tidal-elevation influence in order to improve future actions to deal with plastic pollution.

Macrolitter and mesolitter in the Thames Estuary: A temporal litter assessment and brand audit of submerged and riverbed debris.

Macroplastic is a growing concern for marine environments with estuaries providing a major pathway for pollution from land-based sources to the sea. In the Thames Estuary, plastic was abundant floating below the surface and on the riverbed, with an average catch per unit effort of 0.57 ± 0.42 and 2.75 ± 2.44 item per minute respectively. Whilst the abundance of litter differed between midwater and benthic zones, the types of products recovered did not. These were identified through visual examination and use of a unique citizen science engagement protocol, allowing for the item age, brand and countries of origin to be established. The majority of litter from the present study (n = 1335) was packaging (40%), some of which was over 30-years old and may have originated from landfill run off. Also abundant was sewage-related debris, the inputs of which was related to heavy or prolonged rainfall. Peaks in this material were recorded in September 2020 following the greatest volume of rain recorded in a single day and in June 2019 after the longest period of continuous rainfall. The Covid-19 pandemic did not influence the abundance or diversity of plastic recovered between December 2018 and September 2020. The durability of plastic ensures it has high potential for harm through entanglement, deoxygenation of sediment and ingestion. The retention in the environment also increases opportunities to fragment into micro- or nanoplastics and, therefore, it is important to monitor plastics at both a macro- and micro-scale.

Accumulation and exposure classifications of plastics in the different coastal habitats in the western Philippine archipelago.

Studies consistently ranked the Philippines as one of the top contributors of plastic wastes leaking into the ocean. However, most of these were based on probabilities and estimates due to lack of comprehensive ground-truth data, resulting also in the limited understanding of the contributing factors and drivers of local pollution. This makes it challenging to develop science-driven and locally-contextualized policies and interventions to mitigate the problem. Here, 56 sites from different coastal habitats in the western Philippine archipelago were surveyed for macroplastics standing stock, representing geographic regions with varying demography and economic activities. Clustering of sites revealed three potential influencing factors to plastic accumulation: population density, wind and oceanic transport, and habitat type. Notably, the amount and types of dominant plastics per geographic region varied significantly. Single-use plastics (food packaging and sachets) were the most abundant in sites adjacent to densely populated and highly urbanized areas (Manila Bay and eastern Palawan), while fishing-related materials dominated in less populated and fishing-dominated communities (western Palawan and Bolinao), suggesting the local industries significantly contributing to the mismanaged plastics in the surveyed sites. Meanwhile, isolated areas such as islands were characterized by the abundance of buoyant materials (drinking bottles and hygiene product containers), emphasizing the role of oceanic transport and strong connectivity in the oceans. Exposure assessment also identified single-use and fishing-related plastics to be of "high exposure (Type 4)" due to their high abundance and high occurrence. These increase their chances of encountering and interacting with organisms and habitats, thus, resulting into more potential harm. This study is the first comprehensive work done in western Philippines, and results will help contextualize local pollution, facilitating more effective management and policymaking.

Polymer Characterization of Submerged Plastic Litter from Lake Tahoe, United States.

Monitoring plastic litter in the environment is critical to understanding the amount, sources, transport, fate, and environmental impact of this pollutant. However, few studies have monitored plastic litter on lakebeds which are potentially important environments for determining the fate and transport of plastic litter in freshwater basins. In this study, a self-contained underwater breathing apparatus was used for litter collection at the lakebed along five transects in Lake Tahoe, United States. Litter was brought to the surface and characterized by litter type. Plastic litter was subsampled, and polymer composition was determined using attenuated total reflection Fourier transform infrared spectroscopy. The average plastic litter from the lakebed for the five dive transects was 83 ± 49 items per kilometer. The top plastic litter categories were other plastic litter (plastic litter that did not fall in another category), followed by food containers, bottles <2 L, plastic bags, and toys. These results are in line with prior studies on submerged litter, and intervention approaches or ongoing education are needed. The six polymers most frequently detected in the subsamples were polyvinyl chloride, polystyrene/expanded polystyrene, polyethylene terephthalate/polyester, polyethylene, polypropylene, and polyamide. These observations reflect global plastic production and microplastic studies from lake surface water and sediments. We found that some litter subcategories were primarily comprised of a single polymer type, therefore, in studies where the polymer type cannot be measured but litter is categorized, these results could provide an estimate of the total polymer composition for select litter categories.

Towards continuous mass and size distributions for beach plastic litter: Spatiotemporal analyses of abundance and composition.

Beaches are known as hotspots for the accumulation of plastic debris and are widely used for monitoring marine litter on a global scale. However, there is a significant knowledge gap regarding temporal trends in marine plastic pollution. Moreover, existing studies on beach plastics and popular monitoring protocols only provide count data. Consequently, it is not possible to monitor marine litter based on weights, which hampers the further application of beach plastic data. To address these gaps, we conducted an analysis of spatial and temporal trends in plastic abundance and composition using OSPAR beach litter monitoring data from 2001 to 2020. We established size and weight ranges for 75 (macro-)plastic categories to estimate the total plastic weight, enabling us to investigate plastic compositions. While the amount of plastic litter exhibits significant spatial variation, most individual beaches displayed notable temporal trends. The spatial variation in composition is primarily attributed to differences in total plastic abundance. We describe the compositions of beach plastics using generic probability density functions (PDFs) for item size and weight. Our trend analysis, method for estimating plastic weight from count data, and PDFs for beached plastic debris represent novel contributions to the field of plastic pollution science.

Comparison of microbial colonization between natural and plastic substrata in a polluted watershed.

Plastic pollution represents a threat for biological communities and the ecological functions they provide in river ecosystems. In this study, we compared the microbial colonization of two plastics (biodegradable and non-biodegradable) and three natural substrata (leaves, sediment, and rocks) in two study sites of an urbanized watershed differing in their plastic-contamination degree (upstream and downstream). The density and diversity of bacterial, fungal, and algal communities, as well as the extracellular enzymatic activities ß-glucosidase (GLU), N-acetyl-glucosaminidase (NAG), and phosphatase (PHO), were analysed in each substrata and site over a 4-week colonization experiment. Results showed higher microbial densities and enzymatic activities in leaves and sediment compared to plastics and rocks, probably due to the greater availability of organic carbon and nutrients in the former substrata. However, the microbial colonization of the two plastics was only different in the downstream site, where bacterial density and enzymatic activities were higher in the biodegradable plastic compared to the non-biodegradable plastic. Accordingly, the presence of biodegradable plastics would enhance the heterotrophic metabolism in plastic-polluted rivers.

A multi-criteria assessment of the implementation of innovative technologies to achieve different levels of microplastics and macroplastics reduction.

This paper proposes and applies a multicriteria decision analysis framework tailored to assess measures for reducing the concentration of microplastics and macroplastics in seas, by implementing ground-breaking clean-up technologies and addressing different types of pollutant sources. Environmental, socio-economic and financial impacts are considered to provide a ranking of these measures for better-informed decision making. The data required to evaluate the performance of the technologies in different locations and scales are analyzed to understand the consequences of the different measures in terms of plastic pathways and sites, and the amounts accumulated, using innovative simulation models. The framework is applied to the Mediterranean Sea, providing insights for designing measures to respond to the challenges of cleaning seas and fulfill the EU marine strategy. The results for the best ranked alternatives show that dealing with microplastics is much more expensive (by one order of magnitude) than dealing with macroplastics.

Macro- and microplastics as complex threats to coral reef ecosystems.

The impacts of macroplastics (macro-), microplastics (MPs, <5mm), and nanoplastics (NPs, <100 nm) on corals and their complex reef ecosystems are receiving increased attention and visibility. MPs represent a major, contemporary, sustainability challenge with known and unknown effects on the ocean, and coral reef ecosystems worldwide. However, the fate and transport processes of macro-, MPs, and NPs and their direct and indirect impacts on coral reef ecosystems remains poorly understood. In this study, we verify and briefly summarize MPs distribution and pollution patterns in coral reefs from various geographical regions and discuss potential risks. The main interaction mechanisms show that MPs may substantially affect coral feeding performance, proper skeletal formation, and overall nutrition and, thus, there is an urgent need to address this rapidly growing environmental problem. From a management perspective, macro-, MPs, and NPs should, ideally, all be included in environmental monitoring frameworks, as possible, to aid in identifying those geographical areas that are most heavily impacted and to support future prioritization of conservation efforts. The potential solutions to the macro-, MP, and NP pollution problem include raising public awareness of plastic pollution, developing robust, environmental, conservation efforts, promoting a circular economy, and propelling industry-supported technological innovations to reduce plastic use and consumption. Global actions to curb plastic inputs, and releases of macro-, MP, and NP particles, and their associated chemicals, to the environment are desperately needed to secure the overall health of coral reef ecosystems and their inhabitants. Global scale horizon scans, gap analyses, and other future actions are necessary to gain and increase momentum to properly address this massive environmental problem and are in good accordance with several relevant UN sustainable development goals to sustain planetary health.

Harmful algae and pathogens on plastics in three mediterranean coastal lagoons.

Plastic is now a pervasive pollutant in all marine ecosystems. The microplastics and macroplastic debris were studied in three French Mediterranean coastal lagoons (Prevost, Biguglia and Diana lagoons), displaying different environmental characteristics. In addition, biofilm samples were analyzed over the seasons to quantify and identify microalgae communities colonizing macroplastics, and determine potentially harmful microorganisms. Results indicate low but highly variable concentrations of microplastics, in relation to the period and location of sampling. Micro-Raman spectroscopy analyses revealed that the majority of macroplastic debris corresponded to polyethylene (PE) and low-density polyethylene (LDPE), and to a far lesser extent to polypropylene (PP). The observations by Scanning Electron Microscopy of microalgae communities colonizing macroplastic debris demonstrated differences depending on the seasons, with higher amounts in spring and summer, but without any variation between lagoons and polymers. Among the Diatomophyceae, the most dominant genera were Amphora spp., Cocconeis spp., and Navicula spp.. Cyanobacteria and Dinophyceae such as Prorocentrum cordatum, a potentially toxic species, were also found sporadically. The use of Primer specific DNA amplification tools enabled us to detect potentially harmful microorganisms colonizing plastics, such as Alexandrium minutum or Vibrio spp. An additional in situ experiment performed over one year revealed an increase in the diversity of colonizing microalgae in relation to the duration of immersion for the three tested polymers PE, LDPE and polyethylene terephthalates (PET). Vibrio settled durably after two weeks of immersion, whatever the polymer. This study confirms that Mediterranean coastal lagoons are vulnerable to the presence of macroplastic debris that may passively host and transport various species, including some potentially harmful algal and bacterial microorganisms.