In situ correlation between microplastic and suspended particulate matter concentrations in river-estuary systems support proxies for satellite-derived estimates of microplastic flux

Rivers are key pathways for transporting microplastics from land to the oceans, yet microplastic flux estimates remain uncertain. Remote sensing allows repeated broad-scale measurements and can be used to extrapolate limited in situ observations. This study investigated the relationship between suspended particulate matter (SPM), a satellite-observable water quality parameter, and microplastic concentration in a partially mixed estuary (Tamar, UK). Microplastic concentrations ranged from 0.04 to 0.99 microplastics/m3, decreasing downstream. A significant correlation was found between SPM and microplastic concentration over two seasons. This relationship was used to compute a multiyear timeseries of proxy microplastic concentration from satellite imagery and produce estimates of annual proxy microplastic flux. This approach could be applied to investigate microplastic flux in other major rivers worldwide where such a relationship between microplastics and SPM exists. To apply this workflow elsewhere, the establishment of local SPM-to-microplastic relationships from in situ observations and local validation of remote sensing SPM algorithms are essential.

Insight into the marine microplastic abundance and distribution in ship cooling systems

Microplastics (MPs) are becoming widely recognized as one of many global environmental issues. Although recently, it has been suggested that marine plastics may affect a ship's operation, the presence of MPs in a ship's cooling system has not received significant attention. In this study, samples of 40 L each were taken from each of the five main pipes (sea chest (SC), ejector pump (EP), main engine jacket freshwater pump (MJFP), main engine jacket freshwater cooler (MJFC), and expansion tank (ET)) in each season (February, May, July, October 2021) to identify and characterize MPs in the five main pipes of the ship cooling system from the training ship Hanbada, Korea Maritime and Ocean University. As a result of FTIR analysis, the total MP abundance was 24,100 particles/m³ in the cooling system of the ship. MP concentrations were observed to be higher (p < 0.05) in winter and spring (dry season: 1578 ± 604 particles/m³) than in summer and autumn (wet season: 990 ± 390 particles/m³). In addition, the MP concentration in the seawater cooling system (SCS) (1509 ± 553 particle/m³) was slightly higher (p > 0.05) than that in the freshwater cooling system (FCS) (1093 ± 546 particles/m³). Compared to previous studies, it was confirmed that the quantitative amount of MPs on board was similar to or slightly less than the concentration of MPs investigated along the coast of Korea (1736 particles/m³). To identify the chemical composition of MPs, an optical microscope and FTIR analysis was carried out, and PE (polyethylene), PP (polypropylene), and PET (polyethylene terephthalate) were identified as major chemicals in all samples. MPs in the form of fibers and fragments accounted for approximately 95% of the total. This study provided evidence of MP contamination in the main pipe in the cooling system of the ship. These findings confirm that marine MPs existing in seawater may have flowed into the ship's cooling system, and it is necessary to understand the effect of marine MPs on the ship's engine and cooling system through continuous monitoring.

Determining the distribution and accumulation patterns of floating litter in the Baltic Sea using modelling tools

Marine plastic floating on the sea surface is an extensive environmental problem. The present study investigated the transport patterns of marine litter and areas of its accumulation in the Baltic Sea by using a hydrodynamic model coupled with a particle-tracking model. We also studied the extent of marine litter from the main polluting rivers. Mapping of marine plastic debris distribution in 2017-2018 revealed that the largest plastic accumulation area is between latitude 59° N and 61° N, which includes the Northern Baltic Proper, Archipelago Sea, and the Gulf of Finland. The floating plastic spreads from the largest plastic pollution sites River Vistula, Oder and Neman to the waters of all the countries around the Baltic Sea.

Willingness to pay for cleaning up beach litter: A meta-analysis

At the global level, the UN 2030 Agenda for Sustainable Development Goal 14 calls for action to significantly reduce marine litter pollution by 2025. To understand the non-market benefits of removing marine litter, researchers have conducted numerous studies on Willingness to Pay (WTP) for reductions in beach litter. This paper estimates the overall effect size of WTP for a worldwide dataset of 63 primary studies over 22 years by applying a meta-regression technique to assess the variability in WTP estimates. The results show an annual mean effect size of $US0.71 (or $US35.29) per person for a 1 % (for a corresponding 50 %) reduction in all types of beach litter. The observed heterogeneity is associated with WTP elicitation methods, beach attributes, geographic locations, and per-capita income. This study yields valuable information for policy makers to develop cost-effective policies and recommends standardised measurements to benchmark changes in marine litter pollution.

A new look at the potential role of marine plastic debris as a global vector of toxic benthic algae

Marine plastic debris provides a significant surface area for potential colonization by planktonic and benthic harmful microalgae and for the adsorption of their toxins. Furthermore, floating plastics may substantially expand the substrate area available for benthic algae in the ocean, intensifying the transfer of potent toxins through pelagic food webs. In this study, we quantify the available surface area of micro- and macroplastics in different oceanic regions and assess the potential role of floating plastics as vectors for the transfer of toxins from three widespread benthic dinoflagellates, Gambierdiscus spp., Ostreopsis cf. ovata and Prorocentrum lima. To avoid bias associated to the occurrence of benthic algae in deep waters, we selected only records from 0 to 100 m depths. We estimate that 26.8 × 10¹⁰ cm² of plastic surface area is potentially available in surface waters of the global ocean, mostly in the size range of large microplastics (1.01-4.75 mm). Based on the distribution of floating plastics and the habitat suitability of the selected microalgal species, the plastic relative colonization risks will be greater in the Mediterranean Sea and in the subtropical and temperate western margins of the oceans, such as the North American and Asian eastern coasts and, to a lesser extent, southern Brazil and Australia. In places where the colonization of O. cf. ovata cells on floating plastic debris has been properly quantified, such as the Mediterranean and southern Brazil, we estimate a colonization potential of up to 2 × 10⁶ cells km^-2 of ocean surface during the regular occurrence period and up to 1.7 × 10⁸ cells km^-2 during massive blooms of this species. As plastic pollution and harmful benthic algal blooms have both increased substantially over the past decades, we suggest that their interactive effects can become a major and novel threat to marine ecosystems and human health.

Heterogeneous weathering of polypropylene in the marine environment

Polypropylene (PP) inkjet cartridges spilled during January 2014 in the northwest Atlantic Ocean from a container ship and subsequently retrieved from beaches around Europe and the Azores along with a matching reference cartridge that had not been exposed to the environment were physically and chemically characterized. Compared with the reference, the cartridges retrieved from the marine environment exhibited considerable cracking-fracturing, discoloration, surface roughness, loss of gloss and staining. Infrared analysis revealed that weathering was highly heterogeneous, with the carbonyl index ranging from <0.1 to >0.9 over areas of sub-mm-dimensions. The high degree of weathering was partly attributed to the presence, quality, and distribution of the titanium dioxide pigment, TiO₂. Thus, in the absence of sufficient protection by encapsulation or addition of antioxidants, the ultraviolet light-absorbing pigment promoted the formation of free radicals and photocatalytic oxidation. The results of this study show that consumer plastics containing TiO₂ for coloration or tinting purposes, when not designed for exterior use (in the absence of encapsulation or antioxidants), may experience accelerated weathering in the marine environment, and that estimates of plastic persistence should factor in the role of additives that promote photoactivity.

An assessment of floating marine debris within the breakwaters of the University of the South Pacific, Marine Studies Campus at Laucala Bay

Contributions of Pacific Islands countries to marine plastic debris are disproportionate to the effects on people's connections to the ocean. Plastic waste management initiatives face challenges in containing waste and consequently plastics plague coastal environments. The Seabin, a floating trash skimmer, presents a novel and replicable approach to collecting and cataloguing marine plastics. The objectives of the study were to conduct an audit of marine plastic debris within the breakwaters of the University of the South Pacific, Marine Campus at Laucala Bay while simultaneously gauging the effectiveness of the Seabin and providing recommendations to enhance its utility. Inorganic debris was comprised entirely of plastics while the majority of debris collected was organic. This study provides the first assessment of floating marine plastic debris in an inshore environment of a Pacific Island country. Plastic debris assessments have the potential to inform policy and pivot management efforts to mitigate plastic waste pollution.

Potential sources of marine plastic from survey beaches in the Arctic and Northeast Atlantic

Plastic litter is accumulating on pristine northern European beaches, including the European Arctic, and questions remain about the exact origins and sources. Here we investigate plausible fishery and consumer-related sources of beach littering, using a combination of information from expert stakeholder discussions, litter observations and a quantitative tool - a drift model - for forecasting and backtracking likely pathways of pollution. The numerical experiments were co-designed together with practice experts. The drift model itself was forced by operational ocean current, wave and weather forecasts. The model results were compared to a database of marine litter on beaches, collected every year according to the standardized monitoring program of the Oslo/Paris Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR). By comparing the heterogeneous beach observations to the model simulations, we are able to highlight probable sources. Two types of plastic are considered in the simulations: floating plastic litter and submerged, buoyant microplastics. We find that the model simulations are plausible in terms of the potential sources and the observed plastic litter. Our analysis results in identifiable sources of plastic waste found on each beach, providing a basis for stakeholder actions.

Examining the dependence of macroplastic fragmentation on coastal processes (Chesapeake Bay, Maryland)

Plastic debris in the coastal environment is subject to complex and poorly characterized weathering processes. To better understand how key environmental factors affect plastic degradation in a coastal zone, we conducted an in situ experiment. We deployed strips of high density polyethylene (HDPE) and polystyrene (PS) in paired coastal areas of contrasting conditions (hydrodynamic activity: erosional or depositional; water depths: subtidal or intertidal). Strips were collected after environmental exposures at 4, 8, and 43 weeks and analyzed for change in mass, algal biofilm growth, and imaged by petrographic and electron microscopy (SEM-EDS). Significant surface erosion was evident on both polymers, and was more rapid and more extensive with PS. Degradation of PS was responsive to intensity of hydrodynamic activity, and was greater at intertidal depths, highlighting the critical role played by photo-oxidation in the coastal zone, and suggesting that algal biofilms may slow degradation by playing a photo-protective role.

Polycyclic aromatic hydrocarbon sorption and bacterial community composition of biodegradable and conventional plastics incubated in coastal sediments

Resistant to degradation, plastic litter poses a long-term threat to marine ecosystems. Biodegradable materials have been developed to replace conventional plastics, but little is known of their impacts and degradation in marine environments. A 14-week laboratory experiment was conducted to investigate the sorption of polycyclic aromatic hydrocarbons (PAHs) to conventional (polystyrene PS and polyamide PA) and bio-based, biodegradable plastic films (cellulose acetate CA and poly-L-lactic acid PLLA), and to examine the composition of bacterial communities colonizing these materials. Mesoplastics (1 cm²) of these materials were incubated in sediment and seawater collected from two sites in the Gulf of Finland, on the coast of the highly urbanized area of Helsinki, Finland. PS sorbed more PAHs than did the other plastic types at both sites, and the concentration of PAHs was consistently and considerably smaller in plastics than in the sediment. In general, the plastic bacterial biofilms resembled those in the surrounding media (water and/or sediment). However, in the sediment incubations, the community composition on CA diverged from that of the other three plastic types and was enriched with Bacteroidia and potentially cellulolytic Spirochaetia at both sites. The results indicate that certain biodegradable plastics, such as CA, may harbour potential bioplastic-degrading communities and that PAH sorption capacity varies between polymer types. Since biodegradable plastics are presented as replacements for conventional plastics in applications with risk of ending up in the marine environment, the results highlight the need to carefully examine the environmental behaviour of each biodegradable plastic type before they are extensively introduced to the market.

Microplastics in three typical benthic species from the Arctic: Occurrence, characteristics, sources, and environmental implications

Microplastics (MPs) in the Arctic have raised increasing concern, but knowledge on MP contamination in benthic organisms from Arctic shelf regions, e.g., the Chukchi Sea is still limited. Therefore, the present study investigated the occurrence, characteristics, sources, and environmental implications of MPs in the three most common benthic species, namely sea anemone (Actiniidae und.), deposit-feeding starfish (Ctenodiscus crispatus), and snow crab (Chionoecetes opilio), from the Chukchi Sea. The abundances of MPs in the three benthic species were significantly greater than those from the Bering Sea, but lower than those from other regions globally. The top three compositions of MPs in the three species were polyester, nylon, and polyethylene terephthalate. The detection limit for MP size in the present study was 0.03 mm and the mean size of MP in the three species was 0.89 ± 0.06 mm. The surfaces of MPs found in the starfish and crabs were covered with many attachments, cracks, and hollows, while the surfaces of MPs found in the sea anemones were smooth, which was likely a consequence of different feeding behaviors. There was a significantly positive correlation between the abundances of MPs and other anthropogenic substances. The mean MP abundances in the sea anemones ranged from 0.2 items/individual to 1.7 items/individual, which was significantly higher than that in the deposit-feeding starfish (0.1-1.4 items/individual) and snow crabs (0.0-0.6 items/individual). Sea anemones inhabiting lower latitudes ingested relatively higher levels of MPs than those inhabiting higher latitudes. The MP abundances in the sea anemones are significantly and positively correlated with the seasonal reduced ratio of sea ice coverage from August to September. Our findings indicate that sea anemones could function as a bioindicator of MP pollution, and that the MPs in the benthos from the Chukchi Sea might originate from the melting sea ice, fishery activities and ocean currents.

A review of the treatment options for marine plastic waste in South Africa

Marine plastic is a major worldwide challenge, for which many solutions are being proposed. However, most of the solutions focus on the prevention and collection of the plastic, with little emphasis on the development of waste treatment options. This review seeks to propose areas where further studies could assist to close gaps in knowledge. Some identified gaps include a poor understanding of the quantities and composition of marine plastics, a lack of information about existing marine plastic treatment technologies, and the environmental impact of the available options. To better understand the capabilities of the current South African plastics recycling industry, data from the South African Waste Information Centre (SAWIC) are reported and discussed. While there is a lack of technology development for the treatment of marine plastic globally, the intention of this review is to drive research in this area by creating awareness and encouraging implementation of possible treatment technologies.

A diagnostic approach with onshore-offshore advection-diffusion equations for buoyant plastics

A model is proposed for the beach process of buoyant marine plastics, specifically its beaching and backwashing, by introducing beaching and backwashing diffusion coefficients and the onshore-offshore advection-diffusion equations of plastics for the upper layers in the beach and adjacent coastal sea. The backwashing diffusion coefficient was estimated from the average residence time of the beached plastics and the beach width, and then the beaching diffusion coefficient was estimated from the flux-balance assumption between the beaching and backwashing fluxes. Finite difference calculations in the staggered-grid system demonstrated that the amount of beached plastics responds as predicted by the linear system analysis when the beach had an exponential decay type of unit impulse response regardless of the ratio between the residence time and the period of beaching flux fluctuation from the nearshore. The condition in which the flux balance assumption holds was also discussed.

Leaching of flame-retardants from polystyrene debris: Bioaccumulation and potential effects on coral

Marine plastic debris can act as a reservoir of chemical additives that can pose a potential threat to sensitive ecosystems such as coral reefs. A survey of foam macrodebris collected on beaches indeed revealed high concentrations of hexabromocyclododecanes (ΣHBCDD) in polystyrene (PS) samples (up to 1940 μg g^-1). Results also showed that PS fragments can still leach over 150 ng g^-1 d^-1 of ΣHBCDD (primarily as the α-isomer) for relatively long durations, and that these additives are readily bioaccumulated and well-retained by corals. Despite significant HBCDD bioaccumulation in coral tissue, short-term exposure to HBCDD or PS leachate had no considerable effect on coral photosynthetic activity, symbiont concentration and chlorophyll content. Exposure to the PS leachate did however cause consistent polyp retraction in nubbins over the 5-day exposure. This response was not observed in animals exposed to HBCDD alone, suggesting that another constituent of the leachate stressed corals.

Recycled electronic plastic and marine litter

Black consumer plastics are often contaminated with hazardous chemicals because of technological constraints on sorting dark plastic during recycling of municipal waste coupled with the convenience of waste electrical and electronic equipment (WEEE) as a secondary source of black plastic. In this study, samples of beached plastic litter (n = 524) from southwest England were categorised according to origin, appearance and colour (black versus non-black) before being analysed by x-ray fluorescence (XRF) spectrometry for elements that are characteristic of EEE. The small number of items of WEEE retrieved (n = 36) were largely restricted to wiring insulation and constructed of lead-stabilised polyvinyl chloride (PVC). Among the remaining samples, Br, Cd, Cr and Pb were commonly detected in all categories of black plastics (n = 264) with maximum concentrations of 43,400 mg kg^-1, 2080 mg kg^-1, 662 mg kg^-1 and 23,800 mg kg^-1, respectively. Moreover, concentrations of Br were significantly correlated with concentrations of the flame retardant synergist, Sb (n = 22), and 35 samples were potentially non-compliant with regard to limits defined by the Restriction of Hazardous Substances Directive. For plastics of other colours (n = 224), Br and Pb were detected in fewer samples and Br was co-associated with Sb in only two cases, with occasional high concentrations Cd, Cr and Pb largely attributed to the historical use of cadmium sulphide and lead chromate pigments. An avian physiologically-based extraction test applied to selected samples cut to mm-dimensions revealed bioaccessibilities ranging from <0.1% for Cr in a green fragment to about 2.4% (or about 580 mg kg^-1) for Pb in black PVC. The recycling of WEEE into consumer, industrial and marine (e.g. fishing) plastics that are mainly coloured black appears to be an important vehicle for the introduction of hazardous chemicals into the environment and a source of their exposure to wildlife.

Determining suitable fish to monitor plastic ingestion trends in the Mediterranean Sea

The presence of marine litter is a complex, yet persistent, threat to the health and biodiversity of the marine environment, and plastic is the most abundant, and ubiquitous type of marine litter. To monitor the level of plastic waste in an area, and the prospect of it entering the food chain, bioindicator species are used extensively throughout Northern European Seas, however due to their distribution ranges many are not applicable to the Mediterranean Sea. Guidance published for the Marine Strategy Framework Directive suggests that the contents of fish stomachs may be analyzed to determine trends of marine plastic ingestion. In order to equate transnational trends in marine plastic ingestion, the use of standardized fish species that widely occur throughout the basin is favoured, however for the Mediterranean Sea, specific species are not listed. Here we propose a methodology to assess how effective Mediterranean fish species, that are known to have ingested marine plastic, are as bioindicators. A new Bioindicator Index (BI) was established by incorporating several parameters considered important for bioindicators. These parameters included species distribution throughout the Mediterranean basin, several life history traits, the commercial value of each species, and the occurrence of marine litter in their gut contents. By collecting existing data for Mediterranean fish, ranked scores were assigned to each trait and an average value (BI value) was calculated for each species. Based on their habitat preferences, Engraulis encrasicolus (pelagic), Boops boops (benthopelagic), three species of Myctophidae (Hygophum benoiti, Myctophum punctatum and Electrona risso) (mesopelagic), Mullus barbatus barbartus (demersal) and Chelidonichthys lucerna (benthic), were identified as currently, the most suitable fish for monitoring the ingestion of marine plastics throughout the Mediterranean basin. The use of standardized indicator species will ensure coherence in the reporting of marine litter ingestion trends throughout the Mediterranean Sea.

Prevention through policy: Urban macroplastic leakages to the marine environment during extreme rainfall events

The leakage of large plastic litter (macroplastics) into the ocean is a major environmental problem. A significant fraction of this leakage originates from coastal cities, particularly during extreme rainfall events. As coastal cities continue to grow, finding ways to reduce this macroplastic leakage is extremely pertinent. Here, we explore why and how coastal cities can reduce macroplastic leakages during extreme rainfall events. Using nine global cities as a basis, we establish that while cities actively create policies that reduce plastic leakages, more needs to be done. Nonetheless, these policies are economically, socially and environmentally cobeneficial to the city environment. While the lack of political engagement and economic concerns limit these policies, lacking social motivation and engagement is the largest limitation towards implementing policy. We recommend cities to incentivize citizen and municipal engagement with responsible usage of plastics, cleaning the environment and preparing for future extreme rainfall events.

Ubiquity of microplastics in coastal seafloor sediments

Microplastic pollutants occur in marine environments globally, however estimates of seafloor concentrations are rare. Here we apply a novel method to quantify size-graded (0.038-4.0mm diam.) concentrations of plastics in marine sediments from 42 coastal and estuarine sites spanning pollution gradients across south-eastern Australia. Acid digestion/density separation revealed 9552 individual microplastics from 2.84l of sediment across all samples; equating to a regional average of 3.4 microplastics·ml^-1 sediment. Microplastics occurred as filaments (84% of total) and particle forms (16% of total). Positive correlations between microplastic filaments and wave exposure, and microplastic particles with finer sediments, indicate hydrological/sediment-matrix properties are important for deposition/retention. Contrary to expectations, positive relationships were not evident between microplastics and other pollutants (heavy metals/sewage), nor were negative relationships with neighbouring reef biota detected. Rather, microplastics were ubiquitous across sampling sites. Positive associations with some faunal-elements (i.e. invertebrate species richness) nevertheless suggest high potential for microplastic ingestion.

Heavy metals, metalloids and other hazardous elements in marine plastic litter

Plastics, foams and ropes collected from beaches in SW England have been analysed for As, Ba, Br, Cd, Cl, Cr, Cu, Hg, Ni, Pb, Sb, Se, Sn and Zn by field-portable-x-ray fluorescence spectrometry. High concentrations of Cl in foams that were not PVC-based were attributed to the presence of chlorinated flame retardants. Likewise, high concentrations of Br among both foams and plastics were attributed to the presence of brominated flame retardants. Regarding heavy metals and metalloids, Cd and Pb were of greatest concern from an environmental perspective. Lead was encountered in plastics, foams and ropes and up to concentrations of 17,500μgg(-1) due to its historical use in stabilisers, colourants and catalysts in the plastics industry. Detectable Cd was restricted to plastics, where its concentration often exceeded 1000μgg(-1); its occurrence is attributed to the use of both Cd-based stabilisers and colourants in a variety of products.

Plastic debris and policy: Using current scientific understanding to invoke positive change

Captain Charles Moore introduced the world to the "Great Pacific Garbage Patch" in the mid-1990s, and images of plastic debris in the oceans began to sweep the media. Since then, there has been increasing interest from scientists, the public, and policy makers regarding plastic debris in the environment. Today, there remains no doubt that plastic debris contaminates aquatic (marine and freshwater) habitats and animals globally. The growing scientific evidence demonstrates widespread contamination from plastic debris, and researchers are beginning to understand the sources, fate, and effects of the material. As new scientific understanding breeds new questions, scientists are working to fill data gaps regarding the fate and effects of plastic debris and the mechanisms that drive these processes. In parallel, policy makers are working to mitigate this contamination. The authors focus on what is known about plastic debris that is relevant to policy by reviewing some of the weight of evidence regarding contamination, fate, and effects of the material. Moreover, they highlight some examples of how science has already been used to inform policy change and mitigation and discuss opportunities for future linkages between science and policy to continue the relationship and contribute to effective solutions for plastic debris. Environ Toxicol Chem 2016;35:1617-1626. © 2016 SETAC.

Microplastics as vectors for bioaccumulation of hydrophobic organic chemicals in the marine environment: A state-of-the-science review

A state-of-the-science review was conducted to examine the potential for microplastics to sorb hydrophobic organic chemicals (HOCs) from the marine environment, for aquatic organisms to take up these HOCs from the microplastics, and for this exposure to result in adverse effects to ecological and human health. Despite concentrations of HOCs associated with microplastics that can be orders of magnitude greater than surrounding seawater, the relative importance of microplastics as a route of exposure is difficult to quantify because aquatic organisms are typically exposed to HOCs from various compartments, including water, sediment, and food. Results of laboratory experiments and modeling studies indicate that HOCs can partition from microplastics to organisms or from organisms to microplastics, depending on experimental conditions. Very little information is available to evaluate ecological or human health effects from this exposure. Most of the available studies measured biomarkers that are more indicative of exposure than effects, and no studies showed effects to ecologically relevant endpoints. Therefore, evidence is weak to support the occurrence of ecologically significant adverse effects on aquatic life as a result of exposure to HOCs sorbed to microplastics or to wildlife populations and humans from secondary exposure via the food chain. More data are needed to fully understand the relative importance of exposure to HOCs from microplastics compared with other exposure pathways. Environ Toxicol Chem 2016;35:1667-1676. © 2016 SETAC.

From macroplastic to microplastic: Degradation of high-density polyethylene, polypropylene, and polystyrene in a salt marsh habitat

As part of the degradation process, it is believed that most plastic debris becomes brittle over time, fragmenting into progressively smaller particles. The smallest of these particles, known as microplastics, have been receiving increased attention because of the hazards they present to wildlife. To understand the process of plastic degradation in an intertidal salt marsh habitat, strips (15.2 cm × 2.5 cm) of high-density polyethylene, polypropylene, and extruded polystyrene were field-deployed in June 2014 and monitored for biological succession, weight, surface area, ultraviolet (UV) transmittance, and fragmentation. Subsets of strips were collected after 4 wk, 8 wk, 16 wk, and 32 wk. After 4 wk, biofilm had developed on all 3 polymers with evidence of grazing periwinkles (Littoraria irrorata). The accreting biofilm resulted in an increased weight of the polypropylene and polystyrene strips at 32 wk by 33.5% and 167.0%, respectively, with a concomitant decrease in UV transmittance by approximately 99%. Beginning at 8 wk, microplastic fragments and fibers were produced from strips of all 3 polymers, and scanning electron microscopy revealed surface erosion of the strips characterized by extensive cracking and pitting. The results suggest that the degradation of plastic debris proceeds relatively quickly in salt marshes and that surface delamination is the primary mechanism by which microplastic particles are produced in the early stages of degradation. Environ Toxicol Chem 2016;35:1632-1640. © 2016 SETAC.