Effects Of Polyethylene Microplastics Research Articles

Disruption of microbiota induced by polyethylene microplastics alters defense response of earthworms Eisenia fetida

Microplastics, recognized as some of the most pervasive and enduring pollutants, have emerged as a potential threat to environmental eco-health. While much is known about the effects of microplastics on soil microorganisms, our understanding of how they interact with terrestrial organisms and the underlying mechanisms remains limited. In this study, the effects of polyethylene microplastics at a concentration of 0.5 % (w/w) on the antioxidant enzymes, gut microbiota of Eisenia fetida and the soil microbiota on days 1, 3, 7, 15, and 30 were investigated. The results indicated that exposure to microplastics slightly increased the activities of superoxide dismutase (1.22-fold on day 3, 1.12-fold on day 7) and catalase (1.10-fold on day 3, 1.09-fold on day 7) in E. fetida, while exposure markedly decreased peroxidase activity (1.33- to 1.79-fold) throughout the whole period. Both the soil microbiota and the gut microbiota of E. fetida in terms of diversity and composition were significantly affected by the microplastic amendment, and their structure tended to be similar throughout the exposure time. The family Nocardiaceae was significantly enriched in both the soil and E. fetida gut biota with microplastic exposure. Our results demonstrated that the antioxidant enzyme response of E. fetida was closely related to both the microbiota, although this relationship with the gut microbiota may have been weakened by microplastic exposure. Overall, this study furnishes new perspectives on the ecotoxicity of microplastics, revealing significant implications for the vitality of soil-dwelling organisms and the overarching health of terrestrial ecosystems.

Different effects of polyethylene microplastics on bioaccumulation of three fungicides in maize (Zea mays L.)

Despite the ubiquity of microplastics (MPs) and pesticides in agricultural soils, the effects of MPs on the behavior and bioavailability of pesticides in soil–plant systems remain largely unknown. This study comparatively investigated the adsorption and dissipation of three commonly used fungicides (metalaxyl, azoxystrobin and tebuconazole) in soil as well as their accumulation and distribution in maize Zea mays L. with and without the amendment of polyethylene MPs (PE-MPs). The results showed that the adsorption of the fungicides to both MPs and soil was strongly dependent on their octanol/water partition coefficients (logKow). The addition of 5% PE-MPs significantly increased the adsorption of the hydrophobic fungicides azoxystrobin and tebuconazole to soil due to their greater adsorption affinity to PE-MPs than to soil, while the effect was negligible in the case of the hydrophilic fungicide metalaxyl. The enhanced adsorption of azoxystrobin and tebuconazole to soil with the amendment of PE-MPs decreased their bioavailable fractions in soil, especially the concentration in in situ pore water, resulting in prolonged persistence in soil and reduced accumulation in maize plants. PE-MPs caused a greater reduction in the dissipation and bioaccumulation of tebuconazole than azoxystrobin, presumably because PE-MPs were more effective in promoting the adsorption of tebuconazole (with a higher logKow) in soil. Comparatively, PE-MPs had little effect on the dissipation and bioaccumulation of metalaxyl since its bioavailability was almost unaffected. Our work provides effective information for the risk assessment of co-contamination of MPs and pesticides.

Effects of polyethylene microplastics with different particle sizes and concentrations on the community structure and function of periphytic biofilms

The widespread use of microplastics (MPs) inevitably lead to their release into aquatic environment, where they are likely to encounter the periphytic biofilms, leading to changes in microbial community structure and function. However studies on the toxicity of MPs with different particle sizes and concentrations to biofilms are still lacking. Here, the effects of polyethylene (PE) MPs with three sizes (10, 40 and 120 µm) and two concentrations (2 and 20 mg/L) on biofilm communities were investigated in microcosms over a 28-day incubation period. High-throughput sequencing showed that the alpha and beta diversity of biofilm community were significantly altered by MPs, depending on their size and concentration. Typically, larger particle sizes and higher concentrations resulted in more significant changes in biofilm community structure, indicating a stronger shading effect of larger particles. Compared to the controls, 120 µm MPs treatments significantly reduced the Chao1 and Shannon index of biofilm community regardless of the concentration, while 40 µm MPs reduced the Shannon index only at high concentrations. Moreover, MPs resulted in the changes in the abundances of bacterial communities, with the abundance of Cyanobacteria increasing significantly while that of Proteobacteria and Bacteroidetes decreasing in all treatments. Interestingly, functional analysis by FAPROTAX suggested that a decrease in the abundance of chemoheterotrophy genes and an increase in photoautotrophic- and nitrification-associated genes were observed after exposure to MPs, leading to potential changes of the carbon and nitrogen metabolism of biofilms. These results highlighted that MPs exposure had negative impacts on microbial community structure and function, which in turn affects microbial-mediated processes.

Effects of Polyethylene Microplastics on Growth and Halocarbon Release of Marine Microalgae

Volatile halocarbons (VHCs) are important trace greenhouse gases and ozone-destroying substances and play an important role in global climate change. As an important producer of VHCs, the release of VHCs by marine microalgae is affected by marine environmental factors. Microplastics are an important pollutant in the ocean; however, there are few studies on VHCs release from marine microalgae under the influence of microplastics. This study aimed to explore the effects of different concentrations of polyethylene (PE) microplastics on the growth, photosynthesis, oxidative stress, and release of VHCs by diatoms and dinoflagellates by measuring the density of algae, maximum photoquantum efficiency (Fv/Fm), reactive oxygen species (ROS), and concentration of VHCs. The results revealed that PE microplastics mainly inhibited the growth of Nitzschia closterium f. minutissima and promoted the growth of Prorocentrum donghaiense. The addition of 50 μm PE microplastics had a shielding effect on the growth of the two microalgae, resulting in the inhibition of Fv/Fm of two kinds of microalgae, and the inhibition effect of PE microplastics on P. donghaiense was more significant. Compared with that in the control group, PE microplastic stress stimulated the increase in ROS production in algal cells, which caused an oxidative stress response in these microalgae, thereby promoting the release of three types of volatile brominated halocarbons.

Effects of polyethylene microplastics on properties, enzyme activities, and the succession of microbial community in Mollisol: At the aggregate level

Soil, as a heterogeneous body, is composed of different-sized aggregates. There is limited data available on the potential role of microplastics (MPs) in microbial properties at the soil aggregate level. In this study, changes in microbial construction and diversity in farmland bulk soil and aggregates induced by polyethylene MPs (PE-MPs) were investigated at a dose of 0.5% (w/w) through 16s rDNA sequencing and enzyme activity measurements of different particle size aggregates in incubated soil. The presence of low-dose PE-MPs increased the proportion of >1 mm soil aggregates fraction, and decreased soil available nitrogen and available phosphorus in bulk soils. Furthermore, low-dose PE-MPs increased bacterial richness and diversity in 1–0.5 and < 0.25 mm fractions and decreased operational taxonomic unit, abundance-based coverage estimator, and Chao1 indices in bulk soil and >1 mm fractions. The levels of predicted functional genes taking part in the biodegradation and metabolism of exogenous substances also increased. At the phylum level, PE-MPs changed the proportion of Proteobacteria and Actinobacteria. The variations in soil aggregate properties were significantly correlated with the bacterial communities’ composition and diversity. This study deepens our perception of the soil microenvironment, microbial community composition, and diversity in response to PE-MPs.

The effects of polyethylene microplastics on the growth, reproduction, metabolic enzymes, and metabolomics of earthworms Eisenia fetida

The existing data regarding the effects of polyethylene (PE) microplastics (MPs) smaller than 5 mm in size on earthworms are insufficient to fully comprehend their toxicity. In this study, earthworms Eisenia fetida were exposed to artificially added PE at a concentration ranging from 0.05 to 20 g/kg soil (0.005%−2%) for 60 days to determine the concentration range causing negative effects on earthworms and to uncover the potential toxic mechanisms. The individual growth, reproduction, and metabolic enzyme activities, including phase I enzymes (cytochrome P450 [CYP] 1A2, 2B6, 2C9, and 3A4), and phase II metabolic enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione sulfotransferase (GST)), and metabolomics were measured. The observed variations in responses of multiple cross-scale endpoints indicated that individual indices are less responsive to PE MPs than metabolic enzymes or metabolomics. Despite the absence of significant alterations in growth inhibition based on body weight, PE MPs at concentrations equal to or exceeding 2.5 g/kg were found to exert a toxic effect on earthworms, which was evidenced by significant changes in metabolic enzyme activities (CYP1A2, 2B6, 2C9, and 3A4, SOD, CAT, and GST) and important small molecule metabolites screened based on metabolomics, likely due to the bioaccumulation of PE. The toxicity of PE MPs to earthworms is inferred to be associated with neurotoxicity, oxidative damage, decreased detoxification capacity, energy metabolism imbalance, and impaired amino acid and purine metabolism due to bioaccumulation. The findings of this study will enhance our understanding of the molecular toxicity mechanisms of PE MPs and contribute to a more accurate assessment of the ecological risks posed by PE MPs in soil.

The original polyethylene microplastics inhibit the growth of sweet potatoes and increase the safety risk of cadmium.

Microplastics (MPs) and heavy metals (HMs) co-exist in sweet potato fields of China. As the main component of agricultural field mulch and one of the most polluting and harmful HMs, the effects of polyethylene microplastics (PE MPs) and cadmium (Cd) on sweet potato and soil environment are remains unclear. Here, pot and hydroponic experiments are used to explore the effects of original and weathered PE MPs on growth and Cd uptake of sweet potatoes. The results of pot experiments reveal that compared with the control (0%), 5% of weathered PE MPs can significantly increase soil electrical conductivity (EC); both 5% of the original PE MPs and weathered PE MPs can significantly reduce the concentration of Olsen phosphorus (P) and Olsen potassium (K) in soil, inhibit plant growth, but significantly increase Cd accumulation and glutathione (GSH) level in tissues of sweet potatoes, and also induce membrane lipid peroxidation. In addition, compared to 5% weathered PE MPs, 5% original PE MPs significantly reduce soil EC, growth and peroxidase level of sweet potatoes, but significantly increase Cd concentration in leaves and stems. The results of hydroponic experiment show that original PE MPs significantly increase the P, K, and Cd adsorption compared with weathered PE MPs, and Cd increases the original PE MPs accumulation in the root cortex but decrease PE MPs accumulation in shoots. To sum up, our study investigates the differences and reasons of the effects of original and weathered PE MPs on growth and Cd absorption of sweet potatoes.

Effects of Polyethylene Microplastics and Phenanthrene on Soil Properties, Enzyme Activities and Bacterial Communities

Microplastics (MPs) or polycyclic aromatic hydrocarbons (PAHs) pollution has received increasing concern due to their ubiquitous distribution and potential risks in soils. However, nothing is known about the influences of PAHs-MPs combined pollution on soil ecosystems. To address the knowledge gap, a 1-year soil microcosm experiment was conducted to systematically investigate the single and combined effect of polyethylene (PE) /phenanthrene (PHE) on soil chemical properties, enzymatic activities and bacterial communities (i.e., diversity, composition and function). Results showed that PE and PHE-PE significantly decreased soil pH. The available phosphorus (AP) and neutral phosphatase activity were not considerably changed by PHE, PE and PHE-PE. Significant enhancement of dehydrogenase activity in a PHE-PE amended system might be due to the degradation of PHE by indigenous bacteria (i.e., Sphingomonas, Sphingobium), and PE could enhance this stimulative effect. PHE and PHE-PE led to a slight increase in soil organic matter (SOM) and fluorescein diacetate hydrolase (FDAse) activity but a decrease in available nitrogen (AN) and urease activity. PE significantly enhanced the functions of nitrogen cycle and metabolism, reducing SOM/AN contents but increasing urease/FDAse activities. There were insignificant impacts on overall community diversity and composition in treated samples, although some bacterial genera were significantly stimulated or attenuated with treatments. In conclusion, the addition of PHE and PE influenced the soil chemical properties, enzymatic activities and bacterial community diversity/composition to some extent. The significantly positive effect of PE on the nitrogen cycle and on metabolic function might lead to the conspicuous alterations in SOM/AN contents and urease/FDAse activities. This study may provide new basic information for understanding the ecological risk of PAHs-MPs combined pollution in soils.

Insight into effects of polyethylene microplastics in anaerobic digestion systems of waste activated sludge: Interactions of digestion performance, microbial communities and antibiotic resistance genes

The environmental risks of microplastics (MPs) have raised an increasing concern. However, the effects of MPs in anaerobic digestion (AD) systems of waste activated sludge (WAS), especially on the fate of antibiotic resistance genes (ARGs), have not been clearly understood. Herein, the variation and interaction of digestion performance, microbial communities and ARGs during AD process of WAS in the presence of polyethylene (PE) MPs with two sizes, PE MPs-180μm and PE MPs-1mm, were investigated. The results showed that the presence of PE MPs, especially PE MPs-1mm, led to the increased hydrolysis of soluble polysaccharides and proteins and the accumulation of volatile fatty acids. The methane production decreased by 6.1% and 13.8% in the presence of PE MPs-180μm and PE MPs-1mm, respectively. Together with this process, hydrolytic bacteria and acidogens were enriched, and methanogens participating in acetoclastic methanogenesis were reduced. Meanwhile, ARGs were enriched obviously by the presence of PE MPs, the abundances of which in PE MPs-180μm and PE MPs-1mm groups were 1.2–3.0 times and 1.5–4.0 times higher than that in the control by the end of AD. That was associated with different co-occurrence patterns between ARGs and bacterial taxa and the enrichment of ARG-hosting bacteria caused by the presence of PE MPs. Together these results suggested the adverse effects of PE MPs on performance and ARGs removal during AD process of WAS through inducing the changes of microbial populations.

Effects of polyethylene and polylactic acid microplastics on plant growth and bacterial community in the soil

Microplastics (MPs), especially biodegradable MPs (BMPs) have attracted increasing attention in recent years. However, the effects of MPs with different biodegradability on the soil-plant systems are not well explored. In this study, the effects of polyethylene MPs (PEMPs) and polylactic acid MPs (PLAMPs) on physio-biochemical performance and metabolomic profile of soybean (Glycine max), as well as the bacterial communities in soil were investigated. Our results showed that PEMPs had no noticeable toxicity on the plant growth, while 0.1% PLAMPs significantly decreased the root length by 27.53% when compared with the control. The peroxidase (POD) activity was reduced and catalase (CAT) activity was increased by MPs in plant leaves. The metabolomics study suggested that the significantly affected metabolic pathway is amino acid metabolism. Additionally, Shannon and Simpson indices of rhizosphere soil were changed only under 0.1% PLAMPs. The key bacteria involved in the dinitrogen fixation were also altered. This study provides a novel insight into the potential effects of MPs with different biodegradability on soil-plant systems and highlights that BMPs might have stronger negative effects for terrestrial ecosystem, which needs to be further explored in future research.

Effects of polyethylene microplastics on cell membranes: A combined study of experiments and molecular dynamics simulations

Microplastics (MPs), widely distributed within the environment, can be ingested by humans easily and cause various biological reactions such as oxidative stress, immune response and membrane damage, ultimately representing a threat to health. Cell membranes work as first barrier for MPs entering the cell and playing biological effects. For now, the researches on interactions of MPs on cell membranes lack an in-depth and effective theoretical model to understand molecular details and physicochemical behaviors. In present study, observations of calcein leakage established polyethylene plastic nanoparticles (PE PNPs), especially of high concentrations, harming cell membrane integrity. SYTOX green and lactate dehydrogenase (LDH) assays supported the evidence that the exposure of cells to PE PNPs caused significant cell membrane damage in dose-response. Molecular dynamics (MD) simulations were further applied to determine the effects of PE on the properties of dipalmitoyl phosphatidylcholine (DPPC) bilayer. PE permeated into lipid membranes easily resulting in significant variations in DPPC bilayer with lower density, fluidity changes and membrane thickening. Besides, PE aggregates bound were more likely to cause pore formation and serious damage to the DPPC bilayer. The interaction mechanisms between MPS and cell membrane were explored which provided valuable insights into membrane effect of MPs.

Effect of Polyethylene (LDPE) Microplastic on Remediation of Cadmium Contaminated Soil by &amp;lt;i&amp;gt;Solanum nigrum&amp;lt;/i&amp;gt; L.

Solanum nigrum L. has a delightful prospect as a hyperaccumulation plant for cadmium pollution remediation, and microplastic is a new type of pollution that has received wide attention. In this study, the effects of polyethylene microplastics (LDPE) (0.135, 0.27, 0.81 and 1.35 mg·kg-1) and cadmium (20 mg·kg-1) on the growth indexes and soil physical and chemical properties of Solanum nigrum L. were investigated in a 17-day microcosm experiment. The results showed that single LDPE contamination showed a trend of low concentration promotion and medium-high concentration inhibited the growth index of Solanum nigrum L. and soil physicochemical index, and single Cd contamination was more stressful to plants than single LDPE contamination, while low concentration of LDPE could reduce the effect of Cd on soil physical and chemical properties and promote plant growth and uptake of soil nutrients. These findings suggest that high concentrations of microplastics can inhibit the growth of Solanum nigrum L. alone or in combination with Cd, rather than reducing the toxicity of Cd.

Effects of polyethylene microplastics on the growth of Arabidopsis thaliana &amp;amp; Phaseolus vulgaris and their soil

As the amount of manufactured goods in the world increases, their disposal methods also come into question with many plastic products ending up in both the ocean and on land. These plastics can break down, creating microplastics that can persist for long time periods. While extensive research has been done on the effects of microplastics on marine ecosystems, less is known about the effects of different concentrations of microplastics in terrestrial ecosystems. Our study used the plants Arabidopsis thaliana and Phaseolus vulgaris to explore the effects of microplastics on plant growth and soil quality. We hypothesized that an increase in the concentration of microplastics would result in shorter plant height and root length, as well as a reduced water holding capacity (WHC) of the soil. We found that the majority of the results were not statistically significant, except for the soil’s WHC for P. vulgaris, where the 0.5 μg/L treatment was lower than the control. These findings can serve as a guide for future studies that can further explore the effect of microplastics on terrestrial ecosystems.

Effects of polyethylene microplastics on the microbiome and metabolism in larval zebrafish

Various microplastics (MPs) are found in the environment and organisms. MP residues in organisms can affect health; however, their impacts on metabolism in aquatic organisms remain unclear. In this study, zebrafish embryos were exposed to polyethylene MPs with sizes ranging from 1 to 4 μm at concentrations of 0, 10, 100, and 1000 μg/L for 7 days. Through qPCR technology, the results indicated that zebrafish exposed to polyethylene MPs exhibited significant change in microbes of the phyla Firmicutes, Bacteroidetes, Proteobacteria, and Verrucomicrobia, etc. Moreover, 16S RNA gene sequencing revealed that there was a significant difference in alpha diversity between the control and 1000 μg/L MP-treated groups. At the genus level, the abundance of Aeromonas, Shewanella, Microbacterium, Nevskia and Methyloversatilis have increased remarkably. Conversely, the abundance of Pseudomonas, Ralstonia and Stenotrophomonas were significant reduction after MPs exposure. In addition, the levels of TG (triglyceride), TCHO (total cholesterol), NEFA (nonesterified fatty acid), TBA (total bile acid), GLU (glucose) and pyruvic acid significantly changed in MP-treated larval zebrafish, indicating that their metabolism was disturbed by MPs. Transcriptional levels of glucose and lipid metabolism-related genes showed a decreasing trend. Furthermore, LC/MS-based nontargeted metabolomics analysis demonstrated that a total of 59 phospholipid-related substances exhibited significant changes in larval fish treated with 1000 μg/L MPs. The mRNA levels of phospholipid metabolism-related genes were also obviously changed. Pearson correlation analysis indicated that the abundance of Aeromonas, Shewanella and Chitinibacter bacteria showed a negative correlation with most phospholipids, while Nevskia, Parvibacter and Lysobacter showed a positive correlation with most phospholipids. Based on these results, it is suggested that 1–4 μm PE-MPs could impact the microbiome and metabolism of larval zebrafish. All of these results indicated that the health risk of MPs cannot be ignored.

Effects of environmentally relevant levels of polyethylene microplastic on Mytilus galloprovincialis (Mollusca: Bivalvia): filtration rate and oxidative stress.

The objective of the present study was to evaluate the potential toxic effects of polyethylene microplastics (PE-MPs) (40-48 μm) on the Mediterranean mussel Mytilus galloprovincialis in controlled laboratory conditions. The exposure was carried out for 14 days with three environmentally relevant PE-MPs concentrations of 1, 10, and 100 and a high concentration of 1000 μg/L. Effects of PE-MPs were assessed by evaluating the filtration rate (FR) after 7 and 14 days of exposure and by analyzing biochemical biomarkers of oxidative stress (catalase - CAT, glutathione S-transferase - GST, and the levels of lipid peroxidation - LPO) in the M. galloprovincialis digestive gland after 14 days of exposure. Results showed that M. galloprovincialis does not accumulate PE-MPs of 40-48 μm size in its whole tissues. The filtration rate was significantly reduced with the increase of PE-MPs concentrations. The biochemical biomarkers indicated that PE-MPs induced oxidative damage (LPO) at low concentrations (1 and 10 μg/L) with a significant reduction in females of 1000 μg/L treated group and inactivate antioxidative system (CAT and GST) in the digestive gland of both sexes at high concentrations (100 and 1000 μg/L). This study demonstrates that PE-MPs have biological effects on M. galloprovincialis at environmentally relevant concentrations thus brings new insights on the potential impacts of PE-MPs in marine bivalves.

Effects of polyethylene microplastics on the fate of antibiotic resistance genes and microbial communities in anaerobic digestion of dairy wastes

Microplastics (MPs) have been confirmed to affect the digestion performance of the anaerobic digestion (AD) and to influence the occurrence of antibiotic resistance genes (ARGs) in the environment. In this study, the effects of polyethylene (PE) MPs on digestion performance and the fate of ARGs and microbial communities in thermophilic AD (55 °C) and hyperthermophilic AD (65 °C) of dairy wastes were investigated. The results showed that the effects of PE MPs were similar at different temperatures. At 55 °C and 65 °C, the presence of PE MPs improved methane production by 8.4% and 41.2% and enhanced COD removal rates to 52.8% and 52.4%, respectively, mainly by increasing the abundances of microorganisms involved in hydrolysis, acidogenesis and acid utilization (e.g. Clostridium , Dechloromonas and Caldicoprobacter ). PE MPs significantly increased the fold changes in the abundances of tet C, tet G and tet W from 0.71 to 12.63 to 1.15–28.62. According to redundancy analysis and correlation analysis, free ammonia contributed the most (51% of the total variation) to the changes in host bacteria, which probably changed the fate of ARGs in different AD system. This study indicated the discharge of PE MPs presents a novel challenge in reducing the risks of ARG transmission. • The effects of polyethylene microplastics on anaerobic digestion were investigated. • Polyethylene efficiently increased the methane production and COD removal rate. • Polyethylene significantly increased the abundances of tet C, tet G and tet W. • Polyethylene shifted the microbial communities involving gas production.

LDPE microplastic films alter microbial community composition and enzymatic activities in soil

Concerns regarding microplastic contamination have spread from aquatic environments to terrestrial systems with a growing number of studies have been reported. Notwithstanding, the potential effects on soil ecosystems remain largely unexplored. In this study, the effects of polyethylene microplastics on soil enzymatic activities and the bacterial community were evaluated, and the microbiota colonizing on microplastics were also investigated. Microplastic amendment (2000 fragments per kg soil) significantly increased the urease and catalase activities in soil after 15 days, and no discernible alteration of invertase activities was detected. Results from high-throughput sequencing of 16S rRNA revealed that the alpha diversities (richness, evenness, and diversity) of the microbiota in soil were not obviously changed by the PE amendment, whereas the diversity indexes of microbiota on plastic fragments were significantly lower than those in the control and amended soils. Different taxonomic composition was observed in between the control and amended soils after 90 days of incubation. Bacterial assemblages with distinct community structure colonized the PE microplastics. Additionally, several taxa including plastic-degrading bacteria and pathogens were more abundant on microplastics. Simultaneously, the predicted functional profiles showed that the pathways of amino acid metabolism and xenobiotics biodegradation and metabolism were higher on the microplastics. These results indicated that microplastics in soil, compared with those in aquatic environments, can also act as a distinct microbial habitat, potentially altering the ecological functions of soil ecosystems.

Effects of polyethylene microplastics on the acute toxicity of a synthetic pyrethroid to midge larvae (Chironomus tepperi) in synthetic and river water

Microplastics are ubiquitous pollutants in the aquatic environment. However, our understanding of the interaction of chemicals, particularly synthetic pyrethroids, with microplastics and the potential toxic effects of sorbed contaminants on aquatic organisms under realistic conditions is still extremely limited. In this study, we examined whether the presence of polyethylene (PE) microplastics can affect the acute toxicity of the synthetic pyrethroid bifenthrin to an invertebrate Chironomus tepperi in both synthetic and river water. Bifenthrin alone was, as expected, acutely toxic to exposed larvae (LC50 of 0.5 μg/L after 48 h exposure). The addition of microplastics to synthetic water significantly reduced the toxicity of bifenthrin (apparent LC50 = 1.3 μg/L), most likely because sorption of bifenthrin to microplastics reduced its bioavailability to the exposed larvae. A sorption capacity experiment showed that >92% of bifenthrin was sorbed to microplastics. In river water containing 9.6 mg/L organic carbon, bifenthrin alone was less toxic (LC50 = 1.3 μg/L) than in synthetic water. Strikingly, the addition of microplastics to river water did not mitigate bifenthrin toxicity (apparent LC50 = 1.4 μg/L), most likely due to greater interaction of bifenthrin with organic carbon than with microplastics. While PE microplastics reduced the negative effects of bifenthrin in synthetic water, the presence of organic carbon in river water without microplastics also reduced toxicity. This suggests that while sorption of contaminants to microplastics does occur, it may not be as relevant under environmentally realistic conditions with mg/L concentrations of organic matter.

Effects of polyethylene microplastics on the gut microbial community, reproduction and avoidance behaviors of the soil springtail, Folsomia candida

Microplastics (MPs) are an emerging contaminant and are confirmed to be ubiquitous in the environment. Adverse effects of MPs on aquatic organisms have been widely studied, whereas little research has focused on soil invertebrates. We exposed the soil springtail Folsomia candida to artificial soils contaminated with polyethylene MPs (<500 μm) for 28 d to explore the effects of MPs on avoidance, reproduction, and gut microbiota. Springtails exhibited avoidance behaviors at 0.5% and 1% MPs (w/w in dry soil), and the avoidance rate was 59% and 69%, respectively. Reproduction was inhibited when the concentration of MPs reached 0.1% and was reduced by 70.2% at the highest concentration of 1% MPs compared to control. The half-maximal effective concentration (EC50) value based on reproduction for F. candida was 0.29% MPs. At concentrations of 0.5% dry weight in the soil, MPs significantly altered the microbial community and decreased bacterial diversity in the springtail gut. Specifically, the relative abundance of Wolbachia significantly decreased while the relative abundance of Bradyrhizobiaceae, Ensifer and Stenotrophomonas significantly increased. Our results demonstrated that MPs exerted a significant toxic effect on springtails and can change their gut microbial community. This can provide useful information for risk assessment of MPs in terrestrial ecosystems.