Project

Fate and effects of nano- and microplastic in the aquatic environment

Goal: The amount of nano- and microplastics in the freshwater and marine aquatic environment rises due to the industrial production of plastic and the degradation of macroplastic into small particles. Many studies regarding ecological effects of plastics in the aquatic environment focus on macro plastic and address effects on fish or birds. The uptake of microplastic by lugworms, mussels, amphipods, barnacles, sea cucumbers and fish has been described, but information about negative biological effects of microplastic is limited. Aside from biological effects, microplastics are hypothesised to act as a carrier for persistent organic pollutants (POPs) in aquatic food webs. Little is known about the fate and effects of nano- and microplastic in rivers and seas, while there are lots of speculations about possible effects. Therefore, this project aims to systematically investigate nano- and microplastic pollution of aquatic systems, bioaccumulation of plastic and associated chemicals by aquatic organisms, development of models for bioaccumulation of plastic and plastic associated POPs, effects of plastic ingestion and assessment of risks of foodweb transfer of accumulated plastic towards higher tropic levels. Focus is on rivers, lakes, oceans and on seas close to densely inhabited regions, such as the Rhine, Meuse, North Sea and the Wadden Sea.

Date: 1 September 2012 - 1 September 2025

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Albert Koelmans
added a research item
In Europe, policy frameworks demand the monitoring of microplastics in marine sediments. Here we provide a monitoring and data analysis method for microplastic particles designed to be used in the context of Marine Strategy Framework Directive (MSFD) and OSPAR policy frameworks. Microplastics were analysed in marine sediments at four different locations in Dutch coastal and transitional waters using replicate sampling to investigate micro-spatial variation. Particle size distribution followed a power law with slope 3.76. Thirteen polymers were identified, with their composition varying between sediments near densely populated West coast areas versus the more rural Wadden Sea area. We quantify differences in the micro-spatial variation of microplastic concentrations between locations using the relative standard error of the mean (RSEM). This metric provides an opportunity to optimize the sensitivity of trend detection in microplastic monitoring networks by selecting locations with relatively low micro-spatial variation. We provide a method to optimize the number of replicate samples for a given location using its relationship with the RSEM. Two replicate samples appear to be cost-effective for relatively homogenous locations, whereas more heterogenous locations require four replicates.
Albert Koelmans
added a research item
Current methods of characterizing plastic debris use arbitrary, predetermined categorizations and assume that the properties of particles are independent. Here we introduce Gaussian mixture models (GMM), a technique suitable for describing non-normal multivariate distributions, as a method to identify mutually exclusive subsets of floating macroplastic and microplastic particles (latent class analysis) based on statistically defensible categories. Length, width, height and polymer type of 6,942 particles and items from the Atlantic Ocean were measured using infrared spectroscopy and image analysis. GMM revealed six underlying normal distributions based on length and width; two within each of the lines, films, and fragments categories. These classes differed significantly in polymer types. The results further showed that smaller films and fragments had a higher correlation between length and width, indicating that they were about the same size in two dimensions. In contrast, larger films and fragments showed low correlations of height with length and width. This demonstrates that larger particles show greater variability in shape and thus plastic fragmentation is associated with particle rounding. These results offer important opportunities for refinement of risk assessment and for modeling the fragmentation and distribution of plastic in the ocean. They further illustrate that GMM is a useful method to map ocean plastics, with advantages over approaches that use arbitrary categorizations and assume size independence or normal distributions.
Albert Koelmans
added a research item
There is an urgent need for data on microplastics (MPs) in uptake media relevant to humans. Here we apply Laser Direct Infra-Red (LDIR) spectroscopy for the rapid analysis of MP>10 µm in clean matrices such as bottled drinking water and (deposited) air samples, using strict QA/QC criteria. Nine water bottles of three different brands were found to contain on average 96 particles/L (range 7 to 364, median 44 particles/L) with polymer abundances in the order polyethylene terephthalate and/or polyurethane > polyamide > polyvinylchloride. Further, for laboratory and household rooms, MP deposition rates were measured, ranging from 0 to 573 particles m-2h-1. For household deposition samples, these rates translated to 7 MP (range 0 – 16) consumed in an average meal. Polyethylene terephthalate and/or polyurethane > polyamide > polypropylene were the most abundant polymers. We find a statistically significant positive relationship between the total surface area of textile per unit of room volume (m2/m3) and the deposition of MP. Power law distributions for particle width, height, area, volume and mass were constructed for both sample types, with slopes ranging from 1.9 to 3.8. LDIR appears to be a relatively fast MP measurement method, with MP recovery during sample preparation as a potential improvement point.
Albert Koelmans
added a research item
Microplastic particles are ubiquitous in the environment, from the air we breathe to the food we eat. The key question with respect to these particles is to what extent they cause risks for the environment and human health. There is no risk assessment framework that takes into account the multidimensionality of microplastic particles against the background of numerous natural particles, which together encompass an infinite combination of sizes, shapes, densities and chemical signatures. We review the current tenets in defining microplastic characteristics and effects, emphasizing advances in the analysis of the diversity of microplastic particles. We summarize the unique characteristics of microplastic compared with those of other environmental particles, the main mechanisms of microplastic particle effects and the relevant dose metrics for these effects. To characterize risks consistently, we propose how exposure and effect thresholds can be aligned and quantified using probability density functions describing microplastic particle diversity. Microplastic is a complex contaminant causing great concern in society. This Review examines the properties of microplastic particles compared with natural particles in the environment and discusses methods of assessing the risks to humans and the environment.
Albert Koelmans
added a research item
Understanding the multidimensionality of microplastics is essential for a realistic assessment of the risks these particles pose to the environment and human health. Here, we capture size, shape, area, polymer, volume and mass characteristics of >60 000 individual microplastic particles as continuous distributions. Particles originate from samples taken from different aquatic compartments, including surface water and sediments from the marine and freshwater environment, waste water effluents, and freshwater organisms. Data were obtained using state-of-the-art FTIR- imaging, using the same automated imaging post-processing software. We introduce a workflow with two quality criteria that assure minimum data quality loss due to volumetric and filter area subsampling. We find that probability density functions (PDFs) for particle length follow power law distributions, with median slopes ranging from 2.2 for marine surface water to 3.1 for biota samples, and that these slopes were compartment-specific. Polymer-specific PDFs for particle length demonstrated significant differences in slopes among polymers, hinting at polymer specific sources, removal or fragmentation processes. Furthermore, we provide PDFs for particle width, width to length ratio, area, specific surface area, volume and mass distributions and propose how these can represent the full diversity of toxicologically relevant dose metrics required for the assessment of microplastic risks.
Albert Koelmans
added a research item
A tube-feeding model for administering microplastic (MP, Ø = 30 μm) spheres to fish larvae was employed to quantify the uptake of hydrophobic organic contaminants (HOCs) into the larval body through a single administration of MP. Polychlorinated biphenyl-153 (PCB-153) was used as a representative HOC that can be sorbed to MP in the sea. Atlantic herring (Clupea harengus) larvae (34–51 days post-hatching) were selected as the animal model. The herring larvae were tube-fed a single load of up to 200 polystyrene or polyethylene MP spheres spiked with ¹⁴C-labelled PCB-153, and the control larvae were tube-fed an isotonic solution without MP. At the time of sampling (24 h post feeding), some larvae had evacuated all MP spheres from the gut, while others still had MP remaining in the gut. In larvae with a significant number of MP spheres still present in the gut, whole-body scintillation counting (including the MP in the gut lumen) showed elevated levels of the tracer compared to those in the control fish larvae. For larvae in which all or almost all MP had been evacuated by the time of sampling, the tracer levels of the whole body were not significantly different compared to those for the control fish larvae. These data indicate that there was no significant transfer of PCB-153 from contaminated MP into fish larvae within a gut-transit time of <24 h. This study suggests that the vector role of MP in HOC uptake and absorption may be minor compared to that of other HOC uptake pathways.
Albert Koelmans
added a research item
Microplastic contamination is attracting increasing attention worldwide. In this study, the patterns of microplastic contamination in surface water and sediment from 58 sites, and living fish from 31 sites were investigated in a semi-closed bay (Laizhou Bay, China). Microplastics in Laizhou Bay were pervasively distributed, particularly in the form of fibers. Microplastic abundance exhibited no significant differences among regions in either surface waters or sediments, indicating multiple sources of microplastics pollution in the bay. Spatial hotspot (Getis-Ord Gi*) analysis demonstrated that microplastic pollution was mainly concentrated in the Laizhou-Weifang area, which in turn was mainly affected by ocean current dynamics. Although the spatial distribution of microplastics in sediments was different from surface water, it was also affected by geology, hydrogeology, and anthropogenic activities. The most common polymer in the surface waters was polyethylene terephthalate (PET), while cellophane (CP) was the most frequently observed polymer in sediment, suggesting different sinking behaviors of these microplastics. The proportion of low-density microplastics (PE and PP) in surface water was approximately 19.9%, but these microplastics accounted for only approximately 1.7% in the sediment, suggesting that low-density microplastic particles preferentially migrate to open sea. There were significant differences in shape, size and polymer type of the microplastics among surface water, sediment and biota (p < 0.05). Cluster analysis suggested that the Gudong, Yellow River Estuary and Laizhou-Weifang regions are three sources of microplastics, which might originate from river input, plastic recycling and marine raft aquaculture. Furthermore, microplastic particle diversity was greater in sediment at offshore sites, suggesting that these sites receive microplastics from multiple sources. Our results characterize the microplastic pollution pattern, clarify the possible transfer mechanisms between different environmental media, and will provide important information for risk evaluation and pollution control in this area.
Albert Koelmans
added a research item
Microplastics (MPs) are considered an emerging issue as environmental pollutants and a potential health threat. This review will focus on recently published data on concentrations in food, possible effects, and monitoring methods. Some data are available on concentrations in seafood (fish, bivalves, and shrimps), water, sugar, salt, and honey, but are lacking for other foods. Bottled water is a considerable source with numbers varying between 2600 and 6300 MPs per liter. Particle size distributions have revealed an abundance of particles smaller than 25 µm, which are considered to have the highest probability to pass the intestinal border and to enter the systemic circulation of mammals. Some studies with mice and zebrafish with short- or medium-term exposure (up to 42 days) have revealed diverse results with respect to both the type and extent of effects. Most notable modifications have been observed in gut microbiota, lipid metabolism, and oxidative stress. The principal elements of MP monitoring in food are sample preparation, detection, and identification. Identified data gaps include a lack of occurrence data in plant- and animal-derived food, a need for more data on possible effects of different types of microplastics, a lack of in silico models, a lack of harmonized monitoring methods, and a further development of quality assurance.
Albert Koelmans
added a research item
Because of their diverse sizes, shapes and densities, environmental microplastics are often perceived as complex. Many studies struggle with this complexity, and either address only a part of this diversity, or present data using discrete classifications for sizes, shapes and densities. We argue that such classifications will never be fully satisfactory, as any definition using classes does not capture the essentially continuous nature of environmental microplastic. Therefore, we propose to simplify microplastics by fully defining them through a 3D probability distribution, with size, shape and density as dimensions. Besides introducing the concept, we parameterize these probability distributions, using empirical data. This parameterization results in an approximate yet realistic representation of ‘true’ environmental microplastic. This approach to simplify microplastic could be applicable to exposure measurements, effect studies and fate modelling. Furthermore, it allows for easy comparison between studies, irrespective of sampling or laboratory setup. We demonstrate how the 3D probability distribution of environmental versus ingested microplastic can be helpful in understanding bioavailability of and exposure to microplastic. We argue that the concept of simplified microplastic will also be helpful in probabilistic risk modelling, which would greatly enhance the understanding of the risk that microplastics pose to the environment.
Albert Koelmans
added 2 research items
The role of plastic as a vector for bioaccumulation of toxic chemicals is central to the risk assessment of microplastic for human health and the environment. However, transfer kinetics of sorbed contaminants from ingested microplastics are poorly understood. We develop and parameterise a chemical exchange model on microplastics in a gut fluid mimic of aquatic biota, and also included food to provide a better representation of contaminant dynamics when plastic and food are ingested, as would occur in nature. The transfer kinetics of 14 polychlorinated biphenyls (PCBs) were measured in gut fluid mimic systems under three environmentally relevant exposure scenarios of plastic ingestion by organisms, for low-density polyethylene (LDPE) and polyvinyl chloride (PVC), and were evaluated with the model. Chemical transfer was demonstrated to be biphasic and fully reversible, with fast exchange within hours followed by a slow transfer lasting for weeks to months. In clean gut systems, the bioavailability of plastic-associated PCBs for lugworms and cod ranged from 14-42% and 45-83% respectively. However, in contaminated gut systems, clean microplastic was capable of rapidly extracting (‘cleaning’) PCBs from food inside the gut, thus demonstrating that the effect of microplastic is context dependent. Therefore, chemical contamination and cleaning are likely to occur simultaneously due to the ingestion of microplastic.
Marine plastic pollution has become a prominent environmental issue in the recent years. Plastic ingestion is of special concern, as its magnitude and consequences for marine organisms and potentially humans are still largely unknown. We reviewed 93 papers on plastic ingestion by wild marine fish published since 1972. Plastic ingestion was detected in 323 (65%) of 494 examined fish species, and in 262 (67%) of 391 examined commercial fish species. These proportions are likely greater, as a detailed analysis of the sampling effort and analytical methods used in the reviewed studies suggests an underestimation of plastic ingestion in some assessments. A significant positive relationship (R = + 0.845, p = 0.004) was found between the sample size up to N = 10 and the detection of plastic ingestion. We also found significant differences in detection and frequency of occurrence (FO, %) of plastic ingestion among the three main types of analytical methods: naked-eye, microscopic analysis and chemical digestion. The chemical digestion method, which is also the most robust laboratory method, had the greatest detection (86%) and the highest FO (37.6 ± 0.6%). To avoid the underestimation of plastic ingestion in future work, we provided recommendations for sample sizes and laboratory analysis.
Albert Koelmans
added a research item
The ability to synthesize metal-doped nanoplastic opens windows to accurately assess the potential environmental hazards that nanoplastic poses.
Albert Koelmans
added a research item
Assessing global water quality issues requires a multi-pollutant modelling approach. We discuss scientific challenges and future directions for such modeling. Multi-pollutant river models need to integrate information on sources of pollutants such as plastic debris, nutrients, chemicals, pathogens, their effects and possible solutions. In this paper, we first explain what we consider multi-pollutant modelling. Second, we discuss scientific challenges in multi-pollutant modelling relating to consistent model inputs, modelling approaches and model evaluation. Next, we illustrate the potential of global multi-pollutant modelling for hotspot analyses. We show hotspots of river pollution with microplastics, nutrients, triclosan and Cryptosporidium in many sub-basins of Europe, North America and South Asia. Finally, we reflect on future directions for multi-pollutant modelling, and for linking model results to policy-making.
Albert Koelmans
added 2 research items
Diverse effects of nano- and microplastic (NMP) have been demonstrated in the laboratory. We provide a broad review of current knowledge on occurrence, measurement, modeling approaches, fate, exposure, effects, and effect thresholds as regard to microplastics in the aquatic environment. Using this information, we perform a ‘proof of concept’ risk assessment for NMP, accounting for the diversity of the material. New data is included showing how bioturbation affects exposure, and exposure is evaluated based on literature data and model analyses. We review exposure and effect data and provide a worst case risk characterization, by comparing HC5 effect thresholds from ‘all inclusive’ Species Sensitivity Distributions (SSDs) with the highest environmental concentrations reported. HC5 values show wide confidence intervals yet suggest that sensitive aquatic organisms in near-shore surface waters might be at risk.
Albert Koelmans
added 2 research items
We present a generic theoretical model (MICROWEB) that simulates the transfer of microplastics and hydrophobic organic chemicals (HOC) in food webs. We implemented the model for an Arctic case comprised of nine species including Atlantic cod, with polar bear as top predator. We used the model to examine the effect of plastic ingestion on trophic transfer of microplastics and persistent HOCs (PCBs) and metabolizable HOCs (PAHs), spanning a wide range of hydrophobicities. In a scenario where HOCs in plastic and water are at equilibrium, PCBs biomagnify less when more microplastic is ingested, because PCBs biomagnify less well from ingested plastic than from regular food. In contrast, PAH biomagnify more when more microplastic is ingested, because plastic reduces the fraction of PAH available for metabolisation. We also explore non-equilibrium scenarios representative of additives that are leaching out, as well as sorbing HOCs, quantitatively showing how the above trends are strengthened and weakened, respectively. The observed patterns were not very sensitive to modifications in the structure of the food web. The model can be used as a tool to assess prospective risks of exposure to microplastics and complex HOC mixtures for any food web, including those with relevance for human health.
Albert Koelmans
added 2 research items
We performed an environmental risk assessment for microplastics (< 5 mm) in the marine environment by estimating the order of magnitude of the past, present and future concentrations based on global plastic production data. In 2100, from 9.6 to 48.8 particles m-3 are predicted to float around in the ocean, which is a 50-fold increase compared to the present-day concentrations. From a meta-analysis with effect data available in literature, we derived a safe concentration of 6650 buoyant particles m-3 below which adverse effects are not likely to occur. Our risk assessment (excluding the potential role of microplastics as chemical vectors) suggests that on average, no direct effects of free-floating microplastics in the marine environment are to be expected up to the year 2100. Yet, even today, the safe concentration can be exceeded in sites that are heavily polluted with buoyant microplastics. In the marine benthic compartment between 32 and 144 particles kg-1 dry sediment are predicted to be present in the beach deposition zone. Despite the scarcity of effect data, we expect adverse ecological effects along the coast as of the second half of the 21st century. From then ambient concentrations will start to outrange the safe concentration of sedimented microplastics (i.e. 540 particles kg-1 sediment). Additional ecotoxicological research in which marine species are chronically exposed to realistic environmental microplastic concentration series are urgently needed to verify our findings.
Data on ingestion of microplastics by marine biota are quintessential for monitoring and risk assessment of microplastics in the environment. Current studies, however, portray a wide spread in results on the occurrence of microplastic ingestion, highlighting a lack of comparability of results which might be attributed to a lack of standardisation of methods. We critically review and evaluate recent microplastic ingestion studies in aquatic biota, propose a quality assessment method for such studies, and apply the assessment method to the reviewed studies. The quality assessment method uses ten criteria: Sampling method and strategy, Sample size, Sample processing and storage, Laboratory preparation, Clean air conditions, Negative controls, Positive controls, Target component, Sample (pre-)treatment, and Polymer identification. The results of this quality assessment show a dire need for stricter quality assurance in microplastic ingestion studies. On average studies score 8.0 out of 20 points for ‘completeness of information’, and ‘zero’ for ‘reliability’. Alongside the assessment method, a standardised protocol for detecting microplastic in biota samples incorporating these criteria is provided.
Albert Koelmans
added a research item
Albert Koelmans
added 2 research items
Quantifying the transport of plastic debris from river to sea is crucial for assessing the risks of plastic debris to human health and the environment. We present a global modelling approach to analyse the composition and quantity of point-source microplastic fluxes from European rivers to the sea. The model accounts for different types and sources of microplastics entering river systems via point sources. We combine information on these sources with information on sewage management and plastic retention during river transport for the largest European rivers. Sources of microplastics include personal care products, laundry, household dust and tyre and road wear particles (TRWP). Most of the modelled microplastics exported by rivers to seas are synthetic polymers from TRWP (42%) and plastic-based textiles abraded during laundry (29%). Smaller sources are synthetic polymers and plastic fibres in household dust (19%) and microbeads in personal care products (10%). Microplastic export differs largely among European rivers, as a result of differences in socio-economic development and technological status of sewage treatment facilities. About two-thirds of the microplastics modelled in this study flow into the Mediterranean and Black Sea. This can be explained by the relatively low microplastic removal efficiency of sewage treatment plants in the river basins draining into these two seas. Sewage treatment is generally more efficient in river basins draining into the North Sea, the Baltic Sea and the Atlantic Ocean. We use our model to explore future trends up to the year 2050. Our scenarios indicate that in the future river export of microplastics may increase in some river basins, but decrease in others. Remarkably, for many basins we calculate a reduction in river export of microplastics from point-sources, mainly due to an anticipated improvement in sewage treatment.
Here we report concentrations of pollutants in floating plastics from the North Pacific accumulation zone (NPAC). We compared chemical concentrations in plastics of different types and sizes, assessed ocean plastic potential risks using sediment quality criteria, and discussed the implications of our findings for bioaccumulation. Our results suggest that at least a fraction of the NPAC plastics is not in equilibrium with the surrounding seawater. For instance, ‘hard plastic’ samples had significantly higher PBDE concentrations than ‘nets and ropes’ samples, and 29% of them had PBDE composition similar to a widely used flame-retardant mixture. Our findings indicate that NPAC plastics may pose a chemical risk to organisms as 84% of the samples had at least one chemical exceeding sediment threshold effect levels. Furthermore, our surface trawls collected more plastic than biomass (180 times on average), indicating that some NPAC organisms feeding upon floating particles may have plastic as a major component of their diets. If gradients for pollutant transfer from NPAC plastic to predators exist (as indicated by our fugacity ratio calculations), plastics may play a role in transferring chemicals to certain marine organisms.
Albert Koelmans
added 2 research items
Understanding the global mass inventory is one of the main challenges in present research on plastic marine debris. Especially the fragmentation and vertical transport processes of oceanic plastic are poorly understood. However, whereas fragmentation rates are unknown, information on plastic emissions, concentrations of plastics in the ocean surface layer (OSL) and fragmentation mechanisms is available. Here, we apply a systems engineering analytical approach and propose a tentative 'whole ocean' mass balance model that combines emission data, surface area-normalized plastic fragmentation rates, estimated concentrations in the OSL, and removal from the OSL by sinking. We simulate known plastic abundances in the OSL and calculate an average whole ocean apparent surface area-normalized plastic fragmentation rate constant, given representative radii for macroplastic and microplastic. Simulations show that 99.8% of the plastic that had entered the ocean since 1950 had settled below the OSL by 2016, with an additional 9.4 million tons settling per year. In 2016, the model predicts that of the 0.309 million tons in the OSL, an estimated 83.7% was macroplastic, 13.8% microplastic, and 2.5% was < 0.335 mm 'nanoplastic'. A zero future emission simulation shows that almost all plastic in the OSL would be removed within three years, implying a fast response time of surface plastic abundance to changes in inputs. The model complements current spatially explicit models, points to future experiments that would inform critical model parameters, and allows for further validation when more experimental and field data become available.
Researcher and media alarms have caused plastic debris to be perceived as a major threat to humans and animals. However, although the waste of plastic in the environment is clearly undesirable for aesthetic and economic reasons, the actual environmental risks of different plastics and their associated chemicals remain largely unknown. Here we show how a systematic assessment of adverse outcome pathways based on ecologically relevant metrics for exposure and effect can bring risk assessment within reach. Results of such an assessment will help to respond to the current public worry in a balanced way and allow policy makers to take measures for scientifically sound reasons.
Albert Koelmans
added a project reference
Albert Koelmans
added a research item
Microplastics (<5 mm) are ubiquitous in the marine environment and are ingested by zooplankton with possible negative effects on survival, feeding, and fecundity. The majority of laboratory studies has used new and pristine microplastics to test their impacts, while aging processes such as weathering and biofouling alter the characteristics of plastic particles in the marine environment. We investigated zooplankton ingestion of polystyrene beads (15 and 30 μm) and fragments (≤30 μm), and tested the hypothesis that microplastics previously exposed to marine conditions (aged) are ingested at higher rates than pristine microplastics. Polystyrene beads were aged by soaking in natural local seawater for three weeks. Three zooplankton taxa ingested microplastics, excluding the copepod Pseudocalanus spp., but the proportions of individuals ingesting plastic and the number of particles ingested were taxon and life stage specific and dependent on plastic size. All stages of Calanus finmarchicus ingested polystyrene fragments. Aged microbeads were preferred over pristine ones by females of Acartia longiremis as well as juvenile copepodites CV and adults of Calanus finmarchicus. The preference for aged microplastics may be attributed to the formation of a biofilm. Such a coating, made up of natural microbes, may contain similar prey as the copepods feed on in the water column and secrete chemical exudates that aid chemodetection and thus increase the attractiveness of the particles as food items. Much of the ingested plastic was, however, egested within a short time period (2-4 h) and the survival of adult Calanus females was not affected in an 11-day exposure. Negative effects of microplastics ingestion were thus limited. Our findings emphasize, however, that aging plays an important role in the transformation of microplastics at sea and ingestion by grazers, and should thus be considered in future microplastics ingestion studies and estimates of microplastics transfer into the marine food web.
Albert Koelmans
added a research item
Recent studies suggest size-selective removal of small plastic particles from the ocean surface, an observation that remains unexplained. We studied one of the hypotheses regarding this size-selective removal: the formation of a biofilm on the microplastics (biofouling). We developed the first theoretical model that is capable of simulating the effect of biofouling on the fate of microplastic. The model is based on settling, biofilm growth and ocean depth profiles for light, water density, temperature, salinity and viscosity. Using realistic parameters, the model simulates the vertical transport of small microplastic particles over time, and predicts that the particles either float, sink to the ocean floor, or oscillate vertically, depending on the size and density of the particle. The predicted size-dependent vertical movement of microplastic particles results in a maximum concentration at intermediate depths. Consequently, relatively low abundances of small particles are predicted at the ocean surface, while at the same time these small particles may never reach the ocean floor. Our results hint at the fate of ‘lost’ plastic in the ocean, and provide a start for predicting risks of exposure to microplastics for potentially vulnerable species living at these depths. Ups and downs in the ocean: Effects of biofouling on the vertical transport of microplastics. Available from: https://www.researchgate.net/publication/317596309_Ups_and_downs_in_the_ocean_Effects_of_biofouling_on_the_vertical_transport_of_microplastics [accessed Jun 19, 2017].
Albert Koelmans
added a project goal
The amount of nano- and microplastics in the freshwater and marine aquatic environment rises due to the industrial production of plastic and the degradation of macroplastic into small particles. Many studies regarding ecological effects of plastics in the aquatic environment focus on macro plastic and address effects on fish or birds. The uptake of microplastic by lugworms, mussels, amphipods, barnacles, sea cucumbers and fish has been described, but information about negative biological effects of microplastic is limited. Aside from biological effects, microplastics are hypothesised to act as a carrier for persistent organic pollutants (POPs) in aquatic food webs. Little is known about the fate and effects of nano- and microplastic in rivers and seas, while there are lots of speculations about possible effects. Therefore, this project aims to systematically investigate nano- and microplastic pollution of aquatic systems, bioaccumulation of plastic and associated chemicals by aquatic organisms, development of models for bioaccumulation of plastic and plastic associated POPs, effects of plastic ingestion and assessment of risks of foodweb transfer of accumulated plastic towards higher tropic levels. Focus is on rivers, lakes, oceans and on seas close to densely inhabited regions, such as the Rhine, Meuse, North Sea and the Wadden Sea.