Effect and mechanism of microplastics exposure against microalgae: Photosynthesis and oxidative stress

Effects of polystyrene microplastics on growth, physiological traits of Microcystis aeruginosa and microcystin production and release

With the increasing pollution from microplastics (MPs) in freshwater ecosystems, the effects of MPs on microalgae warrant further investigation. In our research, we examined how polystyrene microplastics (PS-MPs) with various particle sizes and concentrations affect the growth and physiology of Microcystis aeruginosa at different initial algal densities. The results showed that PS-MPs inhibited M. aeruginosa growth at low initial algal densities, with the highest inhibition rate (62.59 %) observed at 0.1 μm, 1 mg/L PS-MPs. Effects on photosynthesis were correlated with changes in initial algal density, and PS-MPs caused notable disturbances to the antioxidant defense system of M. aeruginosa. Compared to medium-sized PS-MPs (1 μm), PS-MPs with smaller (0.1 μm) or larger particle sizes (5 μm) caused greater growth inhibition and more pronounced changes in photosynthesis and oxidative damage. At low initial algal densities, PS-MPs addition led to a substantial rise in the intracellular levels of microcystin-LR (MC-LR), with a 150 % increase over the control at 0.1 μm, 1 mg/L PS-MPs. However, at high initial algal densities, apoptosis rates rose, leading to greater MC-LR release. This research offers a foundation for assessing the impact of PS-MPs on algal growth, as well as the production and release of MC-LR, contributing to the evaluation of MPs' risks to aquatic ecosystems.

Responses of different species of marine microalgae and their community to gear-derived microplastics

The impact of gear-derived microplastics (MPs) on microalgal community stability is unknown. In this work, three types of gear-derived MPs were obtained from floats, pallets, and tires. After exposure to individual microalgal species (Phaeodactylum tricornutum, Chaetoceros curvisetus, Chlorella vulgaris, Isochrysis galbana), small-sized MPs (22 μm) exhibited stronger toxicity than large-sized MPs (135 μm), and the toxicity was MPs concentration independent. The three MPs (1 mg/L) significantly inhibited the growth of P. trichodinium, C. curvisetus and I. galbana. P. tricornutum was the most sensitive species, and the MPs decreased its chl a content, increased ROS level and reduced membrane integrity. Strong heteroaggregation with MPs is a cause of the observed toxicity. Furthermore, algal community was constructed using these four algal species, and P. tricornutum became the dominant species after community stability. After 96-h exposure to small-sized MPs at all the tested concentrations, the proportion of P. tricornutum highly decreased, thus increasing community stability and diversity maintenance. Photo-aging (20 days) further decreased algal number in the community from 16.54 % (original MPs) to 25.12 % (photo-aged MPs), while the Shannon diversity index increased from 0.93 to 0.99. The introduction of harmful algae (Alexandrium tamarense) decreased total algal number in algal community by 45.10 %, and led to the replacement of dominant species to C. vulgaris. Interestingly, algal number after the exposure of MPs and aged MPs recovered by 7.59 % and 14.71 %, respectively. This work provides useful information on the risk of gear-derived MPs to microalgal community in marine environments (especially mariculture areas).

Molecular mechanisms by which polyethylene terephthalate (PET) microplastic and PET leachate promote the growth of benthic cyanobacteria

Toxic blooms of benthic cyanobacteria greatly threaten freshwater ecological health and drinking water safety. Meanwhile, microplastic pollution is becoming increasingly severe and microplastics accumulate in large quantities at the bottom of lakes and rivers, widely coexisting with algae. However, impacts of microplastics on benthic cyanobacteria are still unknown. This study investigated effects of microplastic polyethylene terephthalate (PET) - which is commonly found at the bottom of lakes and rivers - and its leachate at environmentally relevant concentration (0.3 mg/L) and high exposure concentration (3.0 mg/L) on typical benthic cyanobacteria (Oscillatoria sp. and Pseudanabaena sp.), and clarified the related molecular mechanisms through transcriptomic analysis. Results show that PET or PET leachate (PET-L) can promote benthic cyanobacterial growth and promotive effect of PET-L is more obvious than that of PET system. Promotion effect of PET or PET-L is more significant at environmentally relevant concentration (39-63 % increase compared with the control) compared with high exposure concentration (21-58 % increase compared with the control). In the presence of PET or PET-L, due to an increase in the number of cyanobacterial cells, concentrations of harmful metabolites (cylindrospermopsin, geosmin, and 2-methylisoborneol) in water also increased. Although PET particles may not be conducive to benthic cyanobacterial growth due to shading effect and mechanical damage, photosynthetic efficiency of algae was improved and dysregulated genes related to photosynthesis and extracellular transport of glycolipid were upregulated according to transcriptome analysis. Moreover, PET decomposition components, such as terephthalic acid and ethylene glycol, may be able to serve as carbon sources for cyanobacterial growth. Upregulation of genes associated with glycolysis, oxidative phosphorylation, and translation revealed that PET can promote the growth of benthic cyanobacteria. This study has important value in evaluating the impact of benthic cyanobacteria on aquatic ecological health and drinking water safety with the coexistence of microplastics.

Interactions between the co-contamination system of oxcarbazepine-polypropylene microplastics and Chlorella sp. FACHB-9: Toxic effects and biodegradation

The co-contamination of microplastics and pharmaceutical pollutants has attracted increasing attention. However, studies on the joint toxicity of pollutants on organisms in aquatic ecosystems are still lacking. This study aimed to investigate the joint toxicity of oxcarbazepine (OXC, 30 mg/L) and polypropylene microplastics (PP-MPs, 500 mg/L and particle size of 180 μm) microplastics on microalgae (Chlorella sp. FACHB-9) and the biodegradation of OXC by strain FACHB-9. Compared to the single OXC exposure, the cell density of microalgae was decreased by 38.93% in OXC/PP-MPs co-contamination system, with enhanced oxidative stress and decreased photosynthetic efficiency. Transcriptomic analyses indicated that photosynthetic pathways and TCA cycle pathways were significantly inhibited, while DNA damage repair pathways were up regulated in microalgae co-exposed to OXC and PP-MPs. Moreover, strain FACHB-9 showed a remarkable degradation effect (91.61% and 86.27%) on OXC in single and mixture group, respectively. These findings significantly expanded the existing knowledge on the joint toxicity of pollutants on microalgae, indicating prospective promise of microalgae for the bioremediation of polluted aquatic environments.

Uptake, growth, and oxidative stress responses of Rhizophora mucronata (Poir. in Lam.) propagules exposed to high-density polyethylene microplastics

The plastic revolution's contribution to global pollution gives rise to microplastics (MPs), bearing a toll on the marine environment. Knowledge of mangrove exposure to MPs causing adverse effects has yet to be elucidated. Hence, the physiological responses of R. mucronata propagules exposed to ubiquitous High-Density Polyethylene Microplastics (HDPE-MPs) were investigated. The set-up consists of a control (0 mg/L) and an environmentally relevant treatment group (32.65 mg/L), acclimatized and exposed for three months. Scanning Electron Microscopy (SEM) shows agglomeration of HDPE-MPs on root surfaces and translocation to the shoot system of smaller MPs (< 50 μm). Attenuated Total Reflectance Fourier Transform-Infrared Spectroscopy (ATR FT-IR) confirmed uptake in the roots. Root length, count, plant height, foliar area, and oxidative stress biomarkers (carbonyl protein and total chlorophyll) all show significant differences (p < 0.05). Indeed, plastic pollution has detrimental effects on mangroves that may consequently affect mangrove forest diversity and productivity.

Divergent responses of microalgal-bacterial granular sludge to two typical microplastics polystyrene and polybutylene succinate during the treatment of sulfamethoxazole-containing wastewater

This study evaluated the mechanisms by which biodegradable microplastics (polystyrene, PS MPs) and non-biodegradable microplastics (polybutylene succinate, PBS MPs), affect the performance of microalgal-bacterial granular sludge in sulfamethoxazole (SMX)-containing wastewater. Macroscopically, microalgal-bacterial granular sludge adapted to PS MPs more significantly and rapidly than PBS MPs. PS MPs slightly inhibited the removal of chemical oxygen demand (COD) and NH4+-N, with the average removal rate reduced by 4.54% and 3.65%, respectively. Nonetheless, PBS MPs facilitated the degradation of SMX with the main pathway being the breakage of N-S bonds. At the microscopic level, the inhibition of Proteobacteria and Cyanobacteria abundance by PS MPs emerged as a significant factor affecting the performance of granular sludge. Conversely, the enrichment of Desulfobacterota promoted by PBS MPs favorably impacted the removal and degradation of pollutants. Overall, PBS MPs showed better environmental compatibility and lower ecotoxicity for microalgal-bacterial granular sludge treatment of antibiotic-containing wastewater.

Impact of microplastics on plant physiology: A meta-analysis of dose, particle size, and crop type interactions in agricultural ecosystems

The increasing prevalence of plastic pollution has led to widespread environmental concerns, particularly with microplastics (MPs) that persist in various ecosystems. As MPs accumulate in terrestrial environments, their potential impact on plant health and agricultural productivity has become a growing area of focus. This study presents a comprehensive meta-analysis evaluating the effects of MPs on plant physiological and biochemical parameters, synthesizing data from 37 studies comprising 2886 observations. Our findings indicate that MPs significantly decrease plant biomass by 13 % (95 % CI: 7-19 %) and chlorophyll content by 28 % (95 % CI: 23-34 %), impairing crop growth and quality. Notably, higher doses and smaller MP particle sizes exert more pronounced inhibitory effects, particularly on root activity and biomass, while larger MPs predominantly damage plant roots. Furthermore, MPs were found to significantly increase oxidative stress in plants, evidenced by a 20 % rise in oxidative damage (95 % CI: 15-25 %) and a 14 % increase in antioxidant capacity (95 % CI: 8-19 %). This study highlights intricate interactions between MP type, particle size, dose, and plant species, with particle size having a greater impact than dose. This study emphasizes the importance of accounting for crop diversity and environmental factors to fully elucidate the potential risks posed by MP pollution to agricultural ecosystems.

Evaluating physiological responses of microalgae towards environmentally coexisting microplastics: A meta-analysis

Microplastics (MPs) are abundantly present in aquatic environments, where the phytoplankton-microalgae, are now inevitably bound to a long-term coexistence with them. While numerous studies have focused on the toxicological effects of high-concentration MPs exposure, there remains controversy over whether and how MPs affect microalgae at environmentally relevant concentrations. This study aims to draw conclusions that narrow the gap from 52 studies with varying results. Overall, MPs can inhibit growth and photosynthesis, induce oxidative damage, from which microalgae can recover after an appropriate period. Cyanobacteria exhibit greater vulnerability than chlorophyta. The relative size of MPs to algal cells potentially governs their coexistence behavior, thereby altering the mechanisms of impact. Pristine MPs may increase the production of extracellular polymeric substances (EPS) and microcystins (MCs), while aged MPs have the opposite effect. Additionally, relevant factors are systematically discussed, offering insights for future research.

Polystyrene microplastics enhanced the photo-degradation and -ammonification of algae-derived dissolved organic matters

Algae-derived organic matter (ADOM) is a key source of chromophoric dissolved organic matter (CDOM) in natural waters. When exposed to solar irradiation, ADOM undergoes gradual degradation and transformation. The escalating presence of microplastics (MPs) can act as a novel type of environmental photosensitizer, however its impacts on ADOM photodegradation remains largely unexplored. Thus, in this study, ADOM were extracted from four common algal species (Microcystis aeruginosa, Synechococcus sp., Chlorella pyrenoidosa and Scenedesmus obliquus) and exposed to UV irradiation with or without polystyrene (PS) MPs, namely ADOM+PS groups and ADOM groups, respectively. The results indicated that a more rapid degradation of amino acid-like substances (∼38 % vs. ∼22 %) and more ammonia products (1.86 vs. 1.21 mg L-1) were observed in the ADOM+PS groups compared to the ADOM groups after a five-day exposure. This enhanced photodegradation might be attributed to the production of environmentally persistent free radicals and reactive species during the photoaging of PS. Furthermore, PS-derived high electron transfer belt activity of ADOM led to the production of highly aromatic and humified products. These humic-like products could potentially accelerate the degradation of amino acid-like compounds by exciting the generation of excited triplet CDOM. This study underscores the role of MPs as environmental photosensitizers in promoting ADOM degradation and ammonia generation, providing insights on the transformation of ADOM mediated by emerging pollutants and its impact on aquatic carbon and nitrogen cycles.

Tire microplastic particles and warming inhibit physiological functions of the toxic microalga Alexandrium pacificum

Previous studies have confirmed that the tire microplastic particles (TMPs) have a variety of toxic biological effects. However, the potential toxic mechanisms of TMPs remain to be elucidated, especially in the interaction between particle behavior and seawater warming. In this study, we investigated the effects of three different concentrations of TMPs suspensions (0 mg/L, 1 mg/L, and 500 mg/L) on Alexandrium pacificum in both the presence and absence of warming. Our results revealed significant differences in toxicity among different concentrations of TMPs towards A. pacificum, i.e., low concentrations promoting but high concentrations inhibiting, furthermore, warming exacerbated these toxicological responses. Specifically, under elevated temperature, high concentrations TMPs could inhibit photosynthetic pigment and chlorophyll fluorescence parameter, as well as the nutrient absorption, and induced oxidative stress. Furthermore, TMPs could adsorb onto microalgae surfaces and thus, forming heterogeneous aggregates through agglomeration with extracellular secretions. This is strongly correlated with biomarker response. Overall, these findings highlight the influence of warming on the toxicity of TMPs and provide valuable data for risk assessment.

Interconnected impacts of water resource management and climate change on microplastic pollution and riverine biocoenosis: A review by freshwater ecologists

The relationship between river hydrology and microplastic (MP) pollution is complex: increased discharge does not always mobilize more MPs, but floods can effectively flush out MPs from river catchments. Climate change and water resource management further influence MP pollution and its fate by altering river hydro-sedimentary regimes. This review investigates the interconnected impacts of these factors from a comprehensive perspective, focusing on how they affect MP concentration in freshwater ecosystems, particularly in regulated rivers and associated reservoirs. Our review reveals a scarcity of studies that jointly analyze the interrelated issues of MP pollution, water resource management, and climate change. Key findings indicate that variations in river discharge significantly influence MP mobilization, mainly depending on catchment land use, channel morphology, position within the catchment, and MP characteristics. Reservoirs function as both sinks and sources of MPs, underscoring their complex role in MP dynamics and the need for sustainable sediment management strategies. The increasing frequency of extreme weather events, driven by climate change, along with prolonged droughts intensified by water management practices, exacerbates MP pollution. These changes contribute to the local concentration of MPs, posing direct physical threats to aquatic organisms, particularly benthic species, through pollution and habitat alterations. Current policies on plastic pollution, water resources and climate change are underdeveloped, as these topics have been treated separately so far. In conclusion, this review provides perspectives on future research and policy directions to address challenges posed by MPs and to preserve rivers against multiple stressors.

Meta-analysis of the effects of microplastic on fish: Insights into growth, survival, reproduction, oxidative stress, and gut microbiota diversity

Aquatic ecosystems are primary repositories for microplastics (MPs), which pose significant risks to aquatic organisms. This study addresses the gap in understanding the effects of MPs pollution by analyzing 3,757 biological endpoints from 85 laboratory studies. Overall, our results indicate that MPs exposure significantly inhibits fish growth, survival, and reproductive ability, and increases oxidative damage, specifically, MPs exposure leads to elevated levels of malondialdehyde. However, MPs do not have a significant impact on the diversity of fish gut microbiota. Subgroup and correlation analyses indicate that the extent of various toxic effects is influenced by multiple factors, including MPs' type, exposure pathway, size, concentration, as well as the aquatic environment or life stage of the fish. In addition, the regression analysis revealed a relationship between the magnitude of toxic effects and the size, concentration, or duration of MPs exposure. This study provides useful information for understanding the potential impacts of MPs on aquatic organisms and offers new insights for the protection and management of aquatic ecosystems.

Degradation of Polymer Materials in the Environment and Its Impact on the Health of Experimental Animals: A Review

The extensive use of polymeric materials has resulted in significant environmental pollution, prompting the need for a deeper understanding of their degradation processes and impacts. This review provides a comprehensive analysis of the degradation of polymeric materials in the environment and their impact on the health of experimental animals. It identifies common polymers, delineates their degradation pathways, and describes the resulting products under different environmental conditions. The review covers physical, chemical, and biological degradation mechanisms, highlighting the complex interplay of factors influencing these processes. Furthermore, it examines the health implications of degradation products, using experimental animals as proxies for assessing potential risks to human health. By synthesizing current research, the review focuses on studies related to small organisms (primarily rodents and invertebrates, supplemented by fish and mollusks) to explore the effects of polymer materials on living organisms and underscores the urgency of developing and implementing effective polymer waste management strategies. These strategies are crucial for mitigating the adverse environmental and health impacts of polymer degradation, thus promoting a more sustainable interaction between human activities and the natural environment.

First insight of the intergenerational effects of tri-n-butyl phosphate and polystyrene microplastics to Daphnia magna

As an emerging organic pollutant, tributyl phosphate (TnBP) can be easily adsorbed by microplastics, resulting in compound toxic effects. In the present work, the effects of polystyrene microplastics (PS-MPs) and TnBP on the survival, growth, reproduction and oxidative stress of Daphnia magna (D. magna) have been evaluated through multigenerational test. Compared with the alone exposure groups, the somatic growth rate and the expression values of growth related genes rpa1, mre11, rnha, and rfc3_5 in the F1 generation of the combined exposure groups were significantly lower (p < 0.05), indicating synergistic effect of PS-MPs and TnBP on the growth toxicity and transgenerational effects. In addition, compared with the PS-MPs groups, significantly lower average number of offspring and expression values of reproduction related genes ccnb, mcm2, sgrap, and ptch1 were observed in the combined exposure group and TnBP group (p < 0.05), indicating TnBP might be the major factor causing reproductive toxicity to D. magna. Although PS-MPs and TnBP alone or in combination also had toxic impacts on the growth, survival and reproduction of D. magna in generations F0 and F2, the effects were less than F1 generation. Regarding oxidative stress, the activity of SOD, CAT and GSH-Px and MDA content in the generations F0 and F1 of combined exposure groups were higher than the TnBP group but lower than the PS-MPs groups, suggesting that PS-MPs might be the dominant cause of the oxidative damage in D. magna and the presence of TnBP would alleviate oxidative stress by reducing the bioaccumulation of PS-MPs. The present work will provide a theoretical basis for further understanding of the toxic effects and ecological risks of combined TnBP and microplastic pollution on aquatic organisms.

Unveiling the impacts of microplastics on cadmium transfer in the soil-plant-human system: A review

The co-contamination of soils by microplastics (MPs) and cadmium (Cd), one of the most perilous heavy metals, is emerging as a significant global concern, posing risks to plant productivity and human health. However, there remains a gap in the literature concerning comprehensive evaluations of the combined effects of MPs and Cd on soil-plant-human systems. This review examines the interactions and co-impacts of MPs and Cd in soil-plant-human systems, elucidating their mechanisms and synergistic effects on plant development and health risks. We also review the origins and contamination levels of MPs and Cd, revealing that sewage, atmospheric deposition, and biosolid applications are contributors to the contamination of soil with MPs and Cd. Our meta-analysis demonstrates that MPs significantly (p<0.05) increase the bioavailability of soil Cd and the accumulation of Cd in plant shoots by 6.9 and 9.3 %, respectively. The MPs facilitate Cd desorption from soils through direct adsorption via surface complexation and physical adsorption, as well as indirectly by modifying soil physicochemical properties, such as pH and dissolved organic carbon, and altering soil microbial diversity. These interactions augment the bioavailability of Cd, along with MPs, adversely affect plant growth and its physiological functions. Moreover, the ingestion of MPs and Cd through the food chain significantly enhances the bioaccessibility of Cd and exacerbates histopathological alterations in human tissues, thereby amplifying the associated health risks. This review provides insights into the coexistence of MPs and Cd and their synergistic effects on soil-plant-human systems, emphasizing the need for further research in this critical subject area.

Preferential adsorption of medium molecular weight proteins in extracellular polymeric substance alleviates toxicity of small-sized microplastics to Skeletonema costatum

Extracellular polymeric substances (EPS) secreted by organisms tend to encapsulate microplastics (MPs), forming an EPS-corona that affects the fate of MPs in marine ecosystems. However, the impact of the EPS-corona on the biotoxicity of MPs to marine organisms remains poorly understood. Herein, the effect of the EPS-corona on the toxicity of polystyrene (PS) MPs of different sizes (0.1 and 1 µm) to Skeletonema costatum (S. costatum) was investigated. The preferential adsorption of medium molecule weight (∼55 kDa) proteins onto PS MPs mainly contributed to the EPS-corona formation, decreasing the surface charge negativity of small-sized PS MPs (0.1 µm) by 72.4 %. Nitrogen (N) and oxygen (O) moieties in polysaccharides and proteins were identified as the preferential adsorption sites in the EPS-PS MPs interaction. Density functional theory (DFT) calculations confirmed the nuclear magnetic resonance spectroscopy (NMR) results, revealing that the binding mode between EPS and PS MPs was mainly hydrogen bonding. In addition, EPS-corona increased the cell density of S. costatum by 35.5-36.0 % when exposed to small-sized PS MPs (0.1 µm, 25-50 mg/L). These findings provide new insights into how EPS-corona affects the environmental fate and ecological risks associated with micro- and nano-sized plastics in marine ecosystems.

Multi-omics analyses reveal the responses of wheat (Triticum aestivum L.) and rhizosphere bacterial community to nano(micro)plastics stress

The pervasive existence of nanoplastics (NPs) and microplastics (MPs) in soil has become a worldwide environmental concern. N/MPs exist in the environment in a variety of forms, sizes, and concentrations, while multi-omics studies on the comprehensive impact of N/MPs with different properties (e.g. type and size) on plants remain limited. Therefore, this study utilized multi-omics analysis methods to investigate the effects of three common polymers [polyethylene-NPs (PE-NPs, 50 nm), PE-MPs (PE-MPs, 10 μm), and polystyrene-MPs (PS-MPs, 10 μm)] on the growth and stress response of wheat, as well as the rhizosphere microbial community at two concentrations (0.05 and 0.5 g/kg). PS and PE exhibited different effects for the same particle size and concentration. PE-NPs had the most severe stress effects, resulting in reduced rhizosphere bacteria diversity, plant biomass, and antioxidant enzyme activity while increasing beneficial bacteria richness. N/MPs altered the expression of nitrogen-, phosphorus-, and sulfur-related functional genes in rhizosphere bacteria, thereby affecting photosynthesis, as well as metabolite and gene levels in wheat leaves. Partial least squares pathway models (PLSPMs) indicated that concentration, size, and type play important roles in the impact of N/MPs on the plant ecological environment, which could have essential implications for assessing the environmental risk of N/MPs.

Impacts of microplastic and seawater acidification on unicellular red algae: Growth response, photosynthesis, antioxidant enzymes, and extracellular polymer substances

Microplastics (MPs) pollution and seawater acidification have increasingly become huge threats to the ocean ecosystem. Their impacts on microalgae are of great importance, since microalgae are the main primary producers and play a critical role in marine ecosystems. However, the impact of microplastics and acidification on unicellular red algae, which have a unique phycobiliprotein antenna system, remains unclear. Therefore, the impacts of polystyrene-MPs alone and the combined effects of MPs and seawater acidification on the typical unicellular marine red algae Porphyridium purpureum were investigated in the current study. The result showed that, under normal seawater condition, microalgae densities were increased by 17.75-41.67 % compared to the control when microalgae were exposed to small-sized MPs (0.1 μm) at concentrations of 5-100 mg L-1. In addition, the photosystem II and antioxidant enzyme system were not subjected to negative effects. The large-sized MPs (1 μm) boosted microalgae growth at a low concentration of MPs (5 mg L-1). However, it was observed that microalgae growth was significantly inhibited when MPs concentration increased up to 50 and 100 mg L-1, accompanied by the remarkably reduced Fv/Fm value and the elevated levels of SOD, CAT enzymes, phycoerythrin (PE), and extracellular polysaccharide (EPS). Compared to the normal seawater condition, microalgae densities were enhanced by 52.11-332.56 % under seawater acidification, depending on MPs sizes and concentrations, due to the formed CO2-enrichment condition and appropriate pH range. PE content in microalgal cells was significantly enhanced, but SOD and CAT activities as well as EPS content markedly decreased under acidification conditions. Overall, the impacts of seawater acidification were more pronounced than MPs impacts on microalgae growth and physiological responses. These findings will contribute to a substantial understanding of the effects of MPs on marine unicellular red microalgae, especially in future seawater acidification scenarios.

Tracing the entry process of submicrometre plastics in soybean sprouts by leaf-derived fluorescent carbon dots

As a global emerging contaminant, microplastics (MPs) in water or soil can accumulate in vegetables, making them easily ingested through the diet. With excellent and tunable optical properties, carbon dots (CDs) are highly advantageous for tracing the entry process of MPs. Originally, long-wavelength CDs were synthesized from leaf-derived extracts, and fluorescent submicrometer plastics (CDs-MPs) with clean surfaces and concentrated particle sizes were obtained by soap-free microemulsion polymerization. The concentration of CDs-MPs exhibits a significant linear relationship with long-wavelength fluorescence intensity (λEx/λEm: 415/676 nm). Soybean sprouts (SBS), as an important type of food, are susceptible to contamination of MPs due to their soft epidermis and rapidly growing biomass. The results showed that CDs-MPs could be embedded into the cortex of SBS and enter the plant with cell division and elongation, leading to an increase in pore size on the cell wall surface. After entering the root system, CDs-MPs will pass through the Casparian strip and migrate in the vessels. Then, CDs-MPs enter the leaves through vascular bundles, and the distribution and size of epicuticular wax on leaves have changed. Furthermore, SBS showed resistant growth and increased levels of oxidative response when exposed to MPs/CDs-MPs. It is the first study to demonstrate the application of leaf-derived CDs in the prevention of MPs pollution by revealing the migration behavior of submicrometre plastics in SBS.

Global analysis of the adverse effects of micro- and nanoplastics on intestinal health and microbiota of fish

The wide occurrence of micro- and nanoplastics (MPs/NPs) within aquatic ecosystems has raised increasing concerns regarding their potential effects on aquatic organisms. However, the effects of MPs/NPs on intestinal health and microbiota of fish remain controversial, and there is a lack of comprehensive understanding regarding how the impact of MPs/NPs is influenced by MPs/NPs characteristics and experimental designs. Here, we conducted a global analysis to synthesize the effects of MPs/NPs on 47 variables associated with fish intestinal health and microbiota from 118 studies. We found that MPs/NPs generally exerted obvious adverse effects on intestinal histological structure, permeability, digestive function, immune and oxidative-antioxidative systems. By contrast, MPs/NPs showed slight effects on intestinal microbial variables. Further, we observed that the responses of intestinal variables to MPs/NPs were significantly regulated by MPs/NPs characteristics and experimental designs. For instance, polyvinyl chloride plastics showed higher toxicity to fish gut than polyethylene and polystyrene did. Additionally, larval fish appeared to be more sensitive to MPs/NPs than juvenile fish. Collectively, this study highlights the potential impacts of MPs/NPs on intestinal health and microbiota of fish, and underscores the determinant role of MPs/NPs characteristics and experimental designs in MPs/NPs toxicity.

Tracking the micro- and nanoplastics in the terrestrial-freshwater food webs. Bivalves as sentinel species

Micro- (MPs) and nanoplastics (NPs) are currently ubiquitous in the ecosystems, and freshwater biota is still insufficiently studied to understand the global fate, transport paths, and consequences of their presence. Thus, in this study, we investigated the role of bivalves and a trophic transfer of MPs and NPs in an experimental food chain. The food chain consisted of terrestrial non-selective detritivore Dendrobaena (Eisenia) sp., freshwater benthic filter feeder Unio tumidus, and freshwater benthic detritivore-collectors Asellus aquaticus or Gammarus sp. Animals were exposed to different fluorescently labeled micro- and nanoplastics (PMMA 20 μm, nanoPS 15-18 nm, and 100 nm, PS 1 μm and 20 μm, PE from cosmetics) as well as to the faeces of animals exposed to plastics to assess their influence on the environmental transportation, availability to biota, and bioaccumulation of supplied particles. Damaged and intact fluorescent particles were observed in the faeces of terrestrial detritivores and in the droppings of aquatic filter feeders, respectively. They were also present in the guts of bivalves and of crustaceans which were fed with bivalve droppings. Bivalves (Unio tumidus, and additionally Unio pictorum, and Sphaerium corneum) produced droppings containing micro- and nanoparticles filtered from suspension and deposited them onto the tank bottom, making them available for broader feeding guilds of animals (e.g. collectors, like crustaceans). Finally, the natural ageing of PS and its morphological changes, leakage of the fluorescent labelling, and agglomeration of particles were demonstrated. That supports our hypothesis of the crucial role of the characterization of physical and chemical materials in adequately understanding the mechanisms of their interaction with biota. Microscopical methods (confocal, fluorescent, scanning electron) and Raman and FT-IR spectroscopy were used to track the particles' passage in a food web and monitor structural changes of the MPs' and NPs' surface.