Plastic Leachates Research Articles

Determination of extractable pollutants from microplastics to vegetables: Accumulation and incorporation into the food chain

The presence and impacts of microplastics (MPs) are being extensively researched and reviewed, especially in the marine environment. However, mobility, transportation routes, and accumulation of leaching compounds such as additives in plastic waste including MPs are scarcely studied. Information regarding ecotoxicity and leachability of compounds related to MPs contamination in the environment is limited. Current work presents the levels of leachates from plastic materials in edible-root and non-edible root vegetables. Samples were analyzed by static headspace and gas chromatography-mass spectrometry (SHS-GC-MS) and the presence of 93 putative compounds was accurately monitored in the samples by the usage of Mass Spectrometry-Data Independent Analysis software. The application of chemometrics to the SHS-GC-MS dataset allowed differentiation between the levels of plastic related compounds in edible root and non-edible root vegetables, the former showing a higher content of plastic leachates. For SHS sampling, 3 g of the sample were incubated at 130 °C for 35 min in the HS vial and toluene and naphthalene were added as internal standards for quantification purposes. The developed SHS-GC-MS methodology is straightforward, reliable, and robust and allowed the quantification of sixteen plastic associated compounds in the samples studied in a range from 0.14 to 28800 ng g−1 corresponding to 2,4-di-tert-butylphenol and p,α-dimethylstyrene, respectively. Several of the quantified compounds pointed out to potential contamination of polystyrene and/or polyvinyl chloride MPs.

The unusual suspects: Screening for persistent, mobile, and toxic plastic additives in plastic leachates

Plastic additives are a diverse group of chemical compounds added to plastic products to give them their unique physical-chemical properties. Persistent, mobile, and toxic (PMT) plastic additives are a highly polar, environmentally stable sub-group of plastic additives with a variety of uses in plastic products. Due to their mobility into water, they can pose a significant long-term risk to the aquatic environment. Despite the potential threat, PMT plastic additives remain largely unregulated and under-studied. Notably, there is a need for dedicated analytical methodology and leaching studies to determine their potential emission from plastic products. Here we present an optimized leaching protocol and novel instrumental analysis method for the screening of 124 PMT plastic additives registered for use in Canada using high performance liquid chromatography with quantitative time-of-flight mass spectrometry (HPLC-QToF-MS). The analytical method covered a log Kow/Dow range between 0.21 and 6.02, which covered 72% of the PMT plastic additives used in Canada. A total of 52 PMT plastic additive suspects were leached in the optimization experiments, 44 of which were unique based on accurate mass and retention time. The conditions that resulted in the greatest numbers of PMT plastic additives leached were lake water, UV light exposure, and a timeframe of approximately 30 days. The analytical and leaching methods presented here offer new tools to study PMT plastic additives and assess their leaching in an environmentally relevant matrix, which can inform monitoring, threat assessment, and regulatory efforts moving forward.

The toxicity of microplastics and their leachates to embryonic development of the sea cucumber Apostichopus japonicus

Microplastic pollution has been widely detected across the global ocean, posing a major threat to a wide variety of marine biota. To date, the deleterious impacts of microplastics have predominantly been linked to their direct exposure, while the potential risks posed by the leachates emanating from microplastics have received comparatively less attention. Here, the toxicity of virgin plasticized polyvinyl chloride (PVC) microspheres and their leachates were evaluated on the embryo-larval development of sea cucumber Apostichopus japonicus using an in-vitro assay. Results showed that a significant toxic effect of both PVC microspheres and their leachates on the embryo development and larval growth of sea cucumbers follows a dose-dependent and time-dependent pattern. Nonetheless, the toxicity of PVC leachates surpasses that of the microspheres themselves. Abnormal developmental phenotypes, such as aberrant gastrulation, misaligned mesenchymal cells, and delayed arm development, were also observed in embryos and larvae treated with PVC. Further chemical analyses of PVC microspheres and leachates revealed the existence of five distinct phthalate esters (PAEs), with DIBP (diisobutyl phthalate) and DBP (dibutyl phthalate) exhibiting higher concentrations in the PVC leachates. This finding suggests that the elevated toxicity of plastic leachate may be attributed to the leaching of phthalate additives from the plastic particles.

Endocrine disruptor responses in the embryos of marine medaka (Oryzias melastigma) after exposure to aged plastic leachates

The issue of the additives leached from plastics has attracted widespread attention. More crucially, endocrine disruptor status for several leached additives has been established. However, little is known about the overall endocrine disrupting effects of aged plastic leachates. Therefore, the transcriptional responses of endocrine-related genes were assessed in the embryos of marine medaka (Oryzias melastigma), which were exposed to the leachates from aged plastics that were immersed into the simulated seawater (SW) or fish digest (FD). The results revealed that there was a great difference between the SW and FD leachates in the transcripts of endocrine-related genes. With the exception of cyp1a, all target genes had their transcripts potentially down-regulated by the FD leachates. Chgl (a biomarker for estrogens), pparβ (related to lipid metabolism), and cyp19a (related to sexual differentiation and reproduction) transcripts tended to be repressed by the SW leachates, while pparα, pparγ and cyp1a (mediating metabolism of xenobiotics) transcripts were stimulated. In addition, a redundancy analysis was carried out to determine the relationship between the leached additives and the transcriptional changes. However, the additives only partially explained the variation in the transcripts of endocrine-related genes (24.8%), indicating that other leached additives may have an impact on target gene transcription. This study provided molecular evidence of the aged plastic leachates’ endocrine disrupting effects. Exploring the primary factors that affect the transcriptional alterations would require more research.

Macro- and microplastic leachates show a slightly toxic effect on seed germination of cotton

Utilizing degradable mulching film effectively decreases the accumulation of plastic residuals in agriculture fields and their impacts on plant growth. However, the chemical risks to plants raised by leached substances from different microplastics are still unknown. This work determined the characteristics of macro- and microplastic leachates from different degradation (PE, PO, and Bio) and size (1 × 1 cm, 450–600 μm and <355 μm), as well as their impact on the germination of two varieties of cotton seeds. Our study revealed that degradable characteristics of macro-plastic significantly affect its leachates. Leachates of Bio gained higher dissolved organic carbon (DOC) concentration, aromatic, and values of slope ratios (SR) compared with PO and PE. The particle size of Bio macro- and microplastics also influences indicators such as SR, E250/E365, E253/E203, and Fmax value; however, fluctuations of those indicators were significantly lower than that induced by different degradable traits. Leachates of PE, PO, and Bio seem to have little impact on the germination of two varieties of cotton seeds, only mean germination time (MGT) and shoot height were slightly different among each treatment. A slight fluctuation of enzyme activities also indicates that plastic leachate did not generate excessive oxidative stress in cotton during germination. Leachates of macro- and microplastic under the tested concentration exhibited a slight toxic impact on cotton, which has high-stress tolerance. Thus, further studies should concentrate on the effects of plastic leachate on sensitive plants.

Size-dependent response of the mussel collective behaviour to plastic leachates and predator cues

Both individual and collective anti-predator behaviours are essential for the survival of many species. This is particularly true for ecosystem engineers such as intertidal mussels, which through their collective behaviour create novel habitats for a range of organisms and biodiversity hotspots. However, contaminants may disrupt these behaviours and consequently indirectly affect exposure to predation risk at the population level. Among these, plastic litter is a major and ubiquitous contaminant of the marine environment. Here, we assessed the impact of microplastic (MP) leachates of the most produced plastic polymer, polypropylene (PlasticsEurope, 2022), at a high but locally relevant concentration (i.e. ca. 12 g L−1) on the collective behaviours and anti-predator responses of both small and large Mytilus edulis mussels. Indeed, in contrast to large mussels, small ones reacted to MP leachates, showing a taxis towards conspecifics and stronger aggregations. All mussels reacted to the chemical cues of the predatory crab, Hemigrapsus sanguineus, but with two different collective anti-predator behaviours. Small mussels only showed a taxis towards conspecifics when exposed to predator cues. This response was also found in large ones with a tendency to form more strongly bound aggregations and a considerable reduced activity, i.e. they significantly delayed their time to start to form aggregations and decreased their gross distance. These anti-predator behaviours were respectively inhibited and impaired in small and large mussels by MP leachates. The observed collective behavioural changes may reduce individual fitness by enhancing predation risk, particularly in small mussels that are the crab H. sanguineus's favourite preys. Given the key role of mussels as ecosystem engineers, our observations suggest that plastic pollution may have implication on M. edulis at the species level, but also enhancing a cascading effect towards a higher level of organisation such as population, community and ultimately structure and function of intertidal ecosystem.

A new concept for the ecotoxicological assessment of plastics under consideration of aging processes

AbstractMicroplastics are widely distributed in aquatic and terrestrial environments, but up to now less is known about (eco)toxicological impacts under realistic conditions. Research so far has focused mainly on impacts on organisms by fresh, single‐origin plastic fragments or beads. However, plastics found in the environment are complex in composition, this means different polymer types and sources, with and without additives and in all stages of age, and therefore, in a more or less advanced stage of degradation. For oxidized degradation products that might be released from plastic materials during aging, there is a lack of information on potentially adverse effects on aquatic biota. The latter is of particular interest as oxidized degradation products might become more water soluble due to higher polarity and are more bioavailable, therefore. The present study focused on plastic leachates of polystyrene (PS) and polylactic acid (PLA), which were derived from alternating stress by hydrolysis and ultraviolet (UV) radiation—representing a realistic scenario in the environment. Test specimens of PS, PLA, or a PLA/PS layer (each 50%) were alternately exposed to UV radiation for 5 days followed by hydrolysis for 2 days, for several weeks alternating. Ecotoxicological effects of the storage water (artificial freshwater) of the test specimens and additionally, in a second experimental setup, the effects of five potential polymer degradation products were detected by 72 h algae growth inhibition tests with Desmodesmus subspicatus. Results clearly indicate inhibitory effects on algae growth by contaminants in the storage water of stressed plastics with increasing growth inhibition of proceeding hydrolysis and UV stress times. Different polymers caused variable inhibitions of algae growth with stronger inhibitions by PS and less effects by PLA and the mixed layer of both. Moreover, not microplastic particles but the resulting dissolved degradation products after aging caused the ecotoxicological effects—with strong effects by the oxidized degradation products. The existing data highlight the relevance of plastic aging as a framework for microplastic ecotoxicity evaluation and allow a proof of concept.

A protocol for lixiviation of micronized plastics for aquatic toxicity testing

Plastics contain various types and amounts of additives that can leach into the water column when entering aquatic ecosystems. Some leached plastic additives are hazardous to marine biota at environmentally relevant concentrations. Disparate methodological approaches have been adopted for toxicity testing of plastic leachates, making comparison difficult. Here we propose a protocol to standardize the methodology to obtain leachates from microplastics (MPs) for aquatic toxicity testing. Literature reviewing and toxicity tests using marine model organisms and different types of MPs were conducted to define the main methodological aspects of the protocol. Acute exposure to leachates from the studied plastics caused negative effects on the early life stages of sea urchins and marine bacteria. We provide recommendations of key factors influencing lixiviation of MPs , such as particle size (<250 μm), solid-to-liquid ratio (1–10 g/L), mixing conditions (1–60 rpm), and lixiviation time (72 h). The proposed methodology was successful to determine the toxicity of leachates from different micronized plastics on marine biota. Our recommendations balance sensitivity, feasibility and environmental relevance, and their use would help ensure comparability amongst studies for a better assessment of the toxicity of plastic leachates on aquatic biota.

Plastic leachate exposure drives antibiotic resistance and virulence in marine bacterial communities

Plastic pollution is a serious global problem, with more than 12 million tonnes of plastic waste entering the oceans every year. Plastic debris can have considerable impacts on microbial community structure and functions in marine environments, and has been associated with an enrichment in pathogenic bacteria and antimicrobial resistance (AMR) genes. However, our understanding of these impacts is largely restricted to microbial assemblages on plastic surfaces. It is therefore unclear whether these effects are driven by the surface properties of plastics, providing an additional niche for certain microbes residing in biofilms, and/or chemicals leached from plastics, the effects of which could extend to surrounding planktonic bacteria. Here, we examine the effects of polyvinyl chloride (PVC) plastic leachate exposure on the relative abundance of genes associated with bacterial pathogenicity and AMR within a seawater microcosm community. We show that PVC leachate, in the absence of plastic surfaces, drives an enrichment in AMR and virulence genes. In particular, leachate exposure significantly enriches AMR genes that confer multidrug, aminoglycoside and peptide antibiotic resistance. Additionally, enrichment of genes involved in the extracellular secretion of virulence proteins was observed among pathogens of marine organisms. This study provides the first evidence that chemicals leached from plastic particles alone can enrich genes related to microbial pathogenesis within a bacterial community, expanding our knowledge of the environmental impacts of plastic pollution with potential consequences for human and ecosystem health.

Insight into chemical features of migrated additives from plastics and associated risks to estuarine ecosystem

Distinct hydrodynamic conditions created a hotspot of plastic and associated additive pollution within estuaries, which is of considerable scientific interest. However, the effects of specific estuarine weathering (severe mechanical wear, constant turbulence, and strong ultraviolet radiation) on migration of additives remain unclear. Therefore, we investigated the release of migrated plastic additives (MPAs) from three representative plastics, namely floating foam, fishing nets, and packaging bags, under simulated estuarine conditions. Sixty-seven MPAs leached out under the wave scenario, greater than those under the ultraviolet radiation (62) and shoal (40) scenarios. We detected forty MPAs in the plastic bag leachates, whereas fewer MPAs were released from the foam and nets. Several MPAs were peculiar to specific plastics, e.g., antistatic and curing agents in the bag and foam leachates, respectively. Particularly, a suite of nonionic surfactants, octylphenol polyethoxylates (OPEOn), exhibited outstanding responses in the packaging bag leachates and had elevated toxic potential. OPEOn significantly inhibited the hatching of zebrafish and caused cardiovascular system disorder and morphological distortions even at environmentally relevant concentrations as in estuaries. Collectively, the leaching of MPAs was significantly enhanced by wave actions, and the plastic leachates, particularly those of plastic bags, can cause detrimental risks to the estuarine ecosystem.

A comparative study on endocrine disrupting effects of leachates from virgin and aged plastics under simulated media in marine medaka larvae (Oryzias melastigma)

Marine plastic pollution has garnered substantial attention, but the potential endocrine disrupting effects of plastic leachates in marine organisms remain unclear. In this study, the larvae of marine medaka (Oryzias melastigma) were exposed to the leachates from virgin and aged plastics soaked in simulated seawater and fish digest for 3 days. The concentrations of vitellogenin (VTG), estradiol (E2), and 11-ketotestosterone (11-KT), as well as the transcripts of endocrine-related genes were measured in the larvae. The results revealed that endogenous E2 was more sensitive to plastic leachates than VTG and 11-KT, which was significantly affected by 26.7 % of all plastic leachates. Among all genes, estrogen receptor α was impacted mostly, being up-regulated by 53.3 % of leachates from aged plastics. The comparative results demonstrated that the leachates from plastics with different statuses caused a greater difference than those from plastics in different simulated media, and the leachates from aged plastics resulted in higher endocrine disrupting effects than those from virgin plastics. In addition, seven leached additives (plasticizers and flame retardants) could explain 25.6 % of the hormonal effects using redundancy analysis, indicating that other additives in the plastic leachates can also play important roles in regulating the endocrine system of O. melastigma larvae.

Gross Negligence: Impacts of Microplastics and Plastic Leachates on Phytoplankton Community and Ecosystem Dynamics.

Plastic debris is an established environmental menace affecting aquatic systems globally. Recently, microplastics (MP) and plastic leachates (PL) have been detected in vital human organs, the vascular system, and in vitro animal studies positing severe health hazards. MP and PL have been found in every conceivable aquatic ecosystem─from open oceans and deep sea floors to supposedly pristine glacier lakes and snow covered mountain catchment sites. Many studies have documented the MP and PL impacts on a variety of aquatic organisms, whereby some exclusively focus on aquatic microorganisms. Yet, the specific MP and PL impacts on primary producers have not been systematically analyzed. Therefore, this review focuses on the threats posed by MP, PL, and associated chemicals on phytoplankton, their comprehensive impacts at organismal, community, and ecosystem scales, and their endogenous amelioration. Studies on MP- and PL-impacted individual phytoplankton species reveal the production of reactive oxygen species, lipid peroxidation, physical damage of thylakoids, and other physiological and metabolic changes, followed by homo- and heteroaggregations, ultimately eventuating in decreased photosynthesis and primary productivity. Likewise, analyses of the microbial community in the plastisphere show a radically different profile compared to the surrounding planktonic diversity. The plastisphere also enriches multidrug-resistant bacteria, cyanotoxins, and pollutants, accelerating microbial succession, changing the microbiome, and thus, affecting phytoplankton diversity and evolution. These impacts on cellular and community scales manifest in changed ecosystem dynamics with widespread bottom-up and top-down effects on aquatic biodiversity and food web interactions. These adverse effects─through altered nutrient cycling─have "knock-on" impacts on biogeochemical cycles and greenhouse gases. Consequently, these impacts affect provisioning and regulating ecosystem services. Our citation network analyses (CNA) further demonstrate dire effects of MP and PL on all trophic levels, thereby unsettling ecosystem stability and services. CNA points to several emerging nodes indicating combined toxicity of MP, PL, and their associated hazards on phytoplankton. Taken together, our study shows that ecotoxicity of plastic particles and their leachates have placed primary producers and some aquatic ecosystems in peril.

Photosynthetic, Molecular and Ultrastructural Characterization of Toxic Effects of Zinc in Caulerpa racemosa Indicate Promising Bioremediation Potentiality.

Caulerpaceae are unconventional green algae composed of multinucleated, single siphonous cells. The species of Caulerpa are acquiring major scientific interest for both their invasion in the Mediterranean ecological niche and for the production of valuable natural metabolites. Furthermore, the abilities of Caulerpa spp. in the biorecovery of polluted waters were recently investigated. Among heavy metal contaminants in marine systems, zinc (Zn) is considered a critical pollutant, progressively accumulating from plastic leachates. In this study, the responses of Caulerpa racemosa to different levels (5-10 mg L-1) of Zn were studied for 14 days under laboratory-controlled conditions. Effects of Zn were monitored by measuring the growth rate, photosynthetic efficiency and gene expression. Moreover, the ability of Caulerpa to remove Zn from seawater was monitored. Zn induced detrimental effects by decreasing the relative growth rate (RGR) and maximal PSII photochemical efficiency (Fv/Fm). Moreover, C. racemosa, grown in contaminated seawater, reduced the levels of Zn to a final concentration of 1.026 and 1.932 mg L-1 after 14 days, thus demonstrating efficient uptake. Therefore, our results characterized the effects of zinc on C. racemosa and the possible role of this alga as being effective in the bioremediation of marine seawater.

Plastic leachates impair picophytoplankton and dramatically reshape the marine microbiome

BackgroundEach year, approximately 9.5 million metric tons of plastic waste enter the ocean with the potential to adversely impact all trophic levels. Until now, our understanding of the impact of plastic pollution on marine microorganisms has been largely restricted to the microbial assemblages that colonize plastic particles. However, plastic debris also leaches considerable amounts of chemical additives into the water, and this has the potential to impact key groups of planktonic marine microbes, not just those organisms attached to plastic surfaces.ResultsTo investigate this, we explored the population and genetic level responses of a marine microbial community following exposure to leachate from a common plastic (polyvinyl chloride) or zinc, a specific plastic additive. Both the full mix of substances leached from polyvinyl chloride (PVC) and zinc alone had profound impacts on the taxonomic and functional diversity of our natural planktonic community. Microbial primary producers, both prokaryotic and eukaryotic, which comprise the base of the marine food web, were strongly impaired by exposure to plastic leachates, showing significant declines in photosynthetic efficiency, diversity, and abundance. Key heterotrophic taxa, such as SAR11, which are the most abundant planktonic organisms in the ocean, also exhibited significant declines in relative abundance when exposed to higher levels of PVC leachate. In contrast, many copiotrophic bacteria, including members of the Alteromonadales, dramatically increased in relative abundance under both exposure treatments. Moreover, functional gene and genome analyses, derived from metagenomes, revealed that PVC leachate exposure selects for fast-adapting, motile organisms, along with enrichment in genes usually associated with pathogenicity and an increased capacity to metabolize organic compounds leached from PVC.ConclusionsThis study shows that substances leached from plastics can restructure marine microbial communities with the potential for significant impacts on trophodynamics and biogeochemical cycling. These findings substantially expand our understanding of the ways by which plastic pollution impact life in our oceans, knowledge which is particularly important given that the burden of plastic pollution in the marine environment is predicted to continue to rise.DubVoHjQQ1D-hWwEoHQrx7Video

A holistic assessment of the sources, prevalence, and distribution of bisphenol A and analogues in water, sediments, biota and plastic litter of the Ebro Delta (Spain)

Bisphenol A (BPA) is one of the main ubiquitous compounds released from plastics in the environment. This compound, considered an endocrine disruptor, poses a risk to aquatic wildlife and human population, being included in multiple environmental monitoring programmes. Following the regulations restricting BPA use in the last years, BPA-like chemicals have been produced and used as BPA substitutes. However, they are not commonly included in monitoring programs yet and their presence is thus misrepresented, despite showing similar endocrine disrupting potential. In this work, an analytical method for analysing bisphenol A and five of its analogues (Bisphenol S, B, F, AF and Tetrabromobisphenol A) is described, validated for water (riverine, sea and wastewater), sediment, and biota (fish and biofilm) and applied to monitor their presence in the Ebro River Delta (NE Spain). In addition, plastic litter was also collected to evaluate their role as potential source of bisphenols. All compounds except BPF were detected in the analysed samples. Wastewater treatment plants (WWTPs) were discarded as major sources of BPs into the natural aquatic environment, as no BPs were detected in treated effluents. Indeed, the high levels of BPs in the natural environment could be related with direct discharge of raw wastewater from small rural population nucleus. The analysis of riverine plastic leachates yielded 4 out of the 6 BPs analysed, strengthening the hypothesis that plastic debris are also a source of BPs in the natural environment. Whereas Bisphenol S and BPA were detected in water and, to a limited extent, in biota, less polar analogues (mainly BPAF and TBBPA) were not found in any of the water samples. Instead, these hydrophobic BPs were found in fish tissues and biofilm, pointing out plastics and microplastics as their possible vectors. Finally, biofilm demonstrated its potential as sentinel of chemical contamination in freshwater environment.

Plastic pollution fosters more microbial growth in lakes than natural organic matter

Plastic debris widely pollutes freshwaters. Abiotic and biotic degradation of plastics releases carbon-based substrates that are available for heterotrophic growth, but little is known about how these novel organic compounds influence microbial metabolism. Here we found leachate from plastic shopping bags was chemically distinct and more bioavailable than natural organic matter from 29 Scandinavian lakes. Consequently, plastic leachate increased bacterial biomass acquisition by 2.29-times when added at an environmentally-relevant concentration to lake surface waters. These results were not solely attributable to the amount of dissolved organic carbon provided by the leachate. Bacterial growth was 1.72-times more efficient with plastic leachate because the added carbon was more accessible than natural organic matter. These effects varied with both the availability of alternate, especially labile, carbon sources and bacterial diversity. Together, our results suggest that plastic pollution may stimulate aquatic food webs and highlight where pollution mitigation strategies could be most effective.

Microplastic leachates disrupt the chemotactic and chemokinetic behaviours of an ecosystem engineer (Mytilus edulis)

The massive contamination of the environment by plastics is an increasing global scientific and societal concern. Knowing whether and how these pollutants affect the behaviour of keystone species is essential to identify environmental risks effectively. Here, we focus on the effect of plastic leachates on the behavioural response of the common blue mussel Mytilus edulis, an ecosystem engineer responsible for the creation of biogenic structures that modify the environment and provide numerous ecosystem functions and services. Specifically, we assess the effect of virgin polypropylene beads on mussels’ chemotactic (i.e. a directional movement in response to a chemical stimulus) and chemokinetic (i.e. a non-directional change in movement properties such as speed, distance travelled or turning frequency in response to a chemical stimulus) responses to different chemical cues (i.e. conspecifics, injured conspecifics and a predator, the crab Hemigrapsus sanguineus). In the presence of predator cues, individual mussels reduced both their gross distance and speed, changes interpreted here as an avoidance behaviour. When exposed to polypropylene leachates, mussels moved less compared to control conditions, regardless of the cues tested. Additionally, in presence of crab cues with plastic leachates, mussels significantly changed the direction of movement suggesting a leachate-induced loss of their negative chemotaxis response. Taken together, our results indicate that the behavioural response of M. edulis is cue-specific and that its anti-predator behaviour as well as its mobility are impaired when exposed to microplastic leachates, potentially affecting the functioning of the ecosystem that the species supports.

Seeping plastics: Potentially harmful molecular fragments leaching out from microplastics during accelerated ageing in seawater

Microplastics are the particulate plastic debris found almost everywhere as environmental contaminants. They are not chemically stable persistent pollutants, but reactive materials. In fact, synthetic polymers exposed to the environment undergo chemical and physical degradation processes which lead not only to mechanical but also molecular fragmentation, releasing compounds that are potentially harmful for the environment and human health. We carried out accelerated photo-oxidative ageing of four reference microplastics (low- and high-density polyethylene, polypropylene, and polystyrene) directly in artificial seawater. We then made a characterization at the molecular level along with a quantification of the chemical species leached into water. Gas chromatography/mass spectrometry analyses performed after selective extraction and derivatization enabled us to identify more than 60 different compounds. Analysis of the leachates from the three polyolefins revealed that the main degradation products were mono- and dicarboxylic acids, along with linear and branched hydroxy acids. The highest amount of leached degradation species was observed for polystyrene, with benzoic acid and phenol derivatives as the most abundant, along with oligomeric styrene derivatives. The results from reference microplastics were then compared with those obtained by analyzing leachates in artificial seawater from aged plastic debris collected in a natural environment. The differences observed between the reference and the environmental plastic leachates mainly concerned the relative abundances of the chemical species detected, with the environmental samples showing higher amounts of dicarboxylic acids and oxidized species.

Structure and activity of marine bacterial communities responding to plastic leachates

Plastic in the ocean releases organic compounds that are able to enter the marine dissolved organic carbon pool and be utilized by heterotrophic bacteria. However, no information is known about which groups of bacteria are able to grow and degrade plastic leachates. Here we characterized a marine bacterial community from the NW Mediterranean Sea growing on plastic leachates and quantified its total activity. We used two petro-based plastics, low density polyethylene (LDPE) and polystyrene, and one biodegradable plastic, polylactic acid (PLA), to generate leachates under irradiated (UV–Vis) and non-irradiated conditions. Then we incubated them with a natural bacterial inoculum and determined the single-cell activity and associated taxonomy of the bacterial groups, using a combination of Catalyzed Reporter Deposition-Fluorescence In Situ Hybridization (CARDFISH) and BioOrthogonal Non-Canonical Amino acid Tagging (BONCAT). The community growing in the leachates was mainly composed of Alteromonas (Gammaproteobacteria), followed by Roseobacter (Alphaproteobacteria) and unclassified Gammaproteobacteria. Overall, marine bacteria in the irradiated treatments showed higher total activity compared to the non-irradiated ones, with the community growing on LDPE's leachates presenting the highest values. The biodegradable PLA leachates presented lower activity than those from petro-based plastics but similar bacterial composition, suggesting that it is possible that PLA could last in the ocean as much as petro-based plastics do. The results from this study show the impact of marine plastic debris in the marine microbial community and the marine carbon cycle.

Aged Plastic Leaching of Dissolved Organic Matter Is Two Orders of Magnitude Higher Than Virgin Plastic Leading to a Strong Uplift in Marine Microbial Activity

Plastic debris reaching the ocean is exponentially increasing in parallel with plastic production. Once into seawater, plastic starts to leach organic compounds that are presumably additives and plastic oligomers, and that process is enhanced by solar radiation. From previous studies with virgin plastic, it has been estimated that up to 23,600 metric tons of dissolved organic carbon (DOC) can be released into seawater every year from all the plastic entering the ocean. However, most plastic found in the ocean has been aged through weathering and sunlight radiation, which could result in enhanced leaching. Despite this, dissolved organic matter (DOM) leaching from aged plastic and the effect on microbial communities and their activity has never been explored. Here we studied DOM leaching by aged plastic collected from a sand beach and how it compares with that from virgin plastic. After characterizing the DOM leached from plastic through fluorescence techniques, we also explored the bioavailability of the DOM leached and its fluorescent fraction through biodegradation experiments. Finally, we determined single cell activities of the prokaryotic community growing on the plastic leachates. We found that the release of DOC by aged plastic was two order of magnitude higher than that leached by virgin new plastic. Extrapolating that into the ocean and assuming that most of the plastic arriving there is not new, we estimated that up to 57,000 metric tons of DOC can be released by plastic debris every year. A fraction of the DOM released by plastic was fluorescent (FDOM), especially in the protein-like region, and bioavailable to microbial uptake, as it is also shown by the increase in the single cell activities of the bacteria growing on the leachates. Since most plastics in the ocean have been exposed to sunlight radiation provoking aging, our results unveil that the amount of carbon released by plastics is much higher than hitherto recognized, and thus will have a stronger impact in the oceanic carbon cycle and in marine ecosystems.