Joint toxicity of microplastics with triclosan to marine microalgae Skeletonema costatum

Antagonistic effects of polystyrene microplastics and tetracycline on Chlorella pyrenoidosa as revealed by infrared spectroscopy coupled with multivariate analysis

Microplastics and antibiotics are typical emerging contaminants in the environment, posing considerable risks to the ecosystem and human health. Previous studies have reported synergistic or antagonistic effects in the presence of both microplastics and antibiotics, destructing cell membrane, inhibiting photosynthetic capability, and inducing antioxidant enzyme activity. However, there is still lack of comprehensive understanding of the mechanisms. This study applied infrared biospectroscopy and multivariate analysis to explore the physiological and biochemical toxicity of polystyrene microplastics and tetracycline co-exposure on Chlorella pyrenoidosa. Either tetracycline or polystyrene microplastics alone posed toxicities on C. pyrenoidosa, mainly due to changes in photosynthetic content, cell membrane permeability, MDA content and antioxidant enzyme activity. Co-exposure of tetracycline and polystyrene microplastics exhibited an antagonistic effect. Infrared spectroscopy coupled with multivariate analysis isolated the discriminating biomarkers representing different toxicity mechanisms, successfully explaining the mechanism of antagonism as reducing ROS production, regulating antioxidant enzyme activity, stabilizing cell membrane, and interfering with signaling and protein synthesis. A random forest model was developed and satisfactorily recognized the toxicity of individual toxins (accuracy of 98.75 %, sensitivity of 99.22 % and specificity of 99.65 %). It also rapidly apportioned toxicity origin and evidenced that tetracycline contributed to the majority of binary toxicities. This study provided scientific guidance and a theoretical basis for assessing and apportioning the binary toxicities of emerging contaminants.

The potential of microplastics acting as vector for triclosan in aquatic environments

There is increased evidence of the co-occurrence of microplastics (MPs) with other co-pollutants in surface water globally, leading to ecological and environmental concerns. The risks and toxicity of co-occurring pollutants largely depend on the mechanisms controlling the activation of their various sources, their fate and transport in different environmental media. Due to their size-specific surface area, MPs in the environment can have a strong affinity for interactions with hydrophobic compounds and have a high sorption capacity for various emerging contaminants (ECs). ECs like the antibacterial and antifungal agent such as Triclosan (TCS) are persistent in the environment. Moreover, TCS in aquatic environments has a low solubility, and high octanol-water partitioning co-efficient which raises the possibility of TCS to interact with other environmental pollutants such as MPs. The interactions of TCS with MPs in the environment are controlled by a range of mechanism such as hydrogen bonding, hydrophobic interactions, π-π interactions as well as electrostatic interactions. The interacting behaviour of these driving forces needs to be fully understood to determine how the co-occurrence of TCS and MPs may lead to adverse effects on the biological functioning of aquatic ecosystems. Hence, here we conduct a systematic review of the current state-of-the-art and synthesize the available knowledge of how MPs can act as vectors for TCS in aquatic environments. This review reveals MP and TCS interactions in aquatic ecosystems, their individual and collective fate, and toxicological impacts on aquatic organisms, evidencing that MPs can act as potential vectors for transporting TCS across different trophic levels. This review also reveals critical limitations in the research of the combined toxicity and interactions of co-occurring MPs and TCS. Based on the rigorous review of the current knowledge base, we propose that multifactorious investigations along with long-terms monitoring are crucial to fully understand the impacts of co-occurring MPs and TCS in aquatic systems to underline future mitigation policies and management plans.

Co-exposure to triclosan and polystyrene nanoplastics on neurodevelopmental toxicity and gut microbiota dysbiosis in zebrafish (Danio rerio)

Triclosan (TCS) and nanoplastics (NPs) are emerging environmental pollutants frequently found in human-related samples. While prior research has investigated TCS's neuro and enterotoxicity, the combined effects of TCS and NPs remain unclear. The polystyrene nanoplastics (PS-NPs, 100 nm) were characterized by scanning electron microscopy (SEM) and nanoparticle tracking analysis, and the interaction and physical properties of polystyrene nanoplastic and TCS under co-exposure were characterized by Fourier transform infrared spectroscopy and SEM. We conducted acute exposure (6 hpf-5 dpf) and chronic exposure (6 hpf-90 dpf) experiments on zebrafish larvae, that is, co-exposure to TCS (250 μg/L) and PS-NPs (100 μg/L, 1000 μg/L). The distribution characteristics of PS-NPs and TCS+PS-NPs in vivo were studied using fluorescent PS-NPs. In addition, the results were evaluated by histopathology, behavioral tests, 16S rDNA sequencing and comparative toxicogenomic database analysis (CTD). In the co-exposure to TCS and PS-NPs, TCS did not alter the distribution characteristics of PS-NPs in zebrafish larvae. The co-exposure exacerbated neurodevelopmental inhibition, leading to neurodevelopmental abnormalities in zebrafish larvae, including developmental malformations, reduced spontaneous motor activity. Additionally, significant behavioral abnormalities were observed in adult zebrafish, such as reduced motor activity and delayed responses. Analysis of the CTD database suggested that the oxidative stress response pathway might mediate the neurotoxicity and gut microbiota dysbiosis caused by TCS+PS-NPs, with a focus on changes in neurodevelopmental genes (syn2a, ngn1, gap-43). Chronic co-exposure resulted in dysbiosis and decreased diversity of the gut microbiota in adult zebrafish, as well as various histopathological damages, such as partial shedding of intestinal villi and thinning of the intestinal wall. In general, the co-exposure of TCS and PS-NPs exacerbates the oxidative stress response and further induces neurodevelopmental toxicity and intestinal microbiota dysregulation. The assessment of the complex interaction between the two reveals the environmental risks of emerging pollutants and nanoplastics coexisting.

Biofilm-mediated mass transfer of sorbed benzo[a]pyrene from polyethylene to seawater

Plastic waste, including microplastics (MPs), often serves as a carrier for hydrophobic organic contaminants (HOCs) and additives in aquatic environments. However, little is known about the fate of contaminants in plastics, especially under the influence of biofilm in field conditions. In this study, polyethylene (PE) was pre-sorbed with varying concentrations of benzo[a]pyrene (BaP), a non-polar contaminant, and deployed in situ to study desorption kinetics under natural biofilm colonization. Based on the desorption kinetics of BaP from PE, a mass transfer model was developed to describe the desorption of non-polar contaminants from PE under the influence of biofilm formation. This study proved that biofilm, acting as an intermediary between plastics and the aquatic environment, did not serve as a sink for plastic-sorbed BaP, but accelerated the desorption process of BaP by reducing the partition coefficient between the plastic and the boundary layer. Furthermore, based on our developed model (IABL-ODD), the effects of biofilm on the fate of other non-polar and weakly polar contaminants in PE were predicted. This study highlights the influence of biofilm on the desorption of hydrophobic contaminants from plastics in field conditions and also informs future work on more relevant processes such as additive leaching.

Toxicity of microplastics and nanoplastics to benthic Sargassum horneri: The role of nitrogen availability in modulating stress responses

Over the past few decades, the accumulation of micro- and nanoplastics (MNPs) have identified as enduring contaminants, posing significant risks to aquatic organisms. However, the interplay of MNPs and environmental stressors (e.g. nutrient etc.) is not well understood. In this study, Sargassum horneri, a typical benthic macroalgae, was cultured with two sizes of plastic particles (MPs (5 μm), NPs (0.05 μm) and nitrogen concentrations (LN (30 μM), HN (120 μM)) for 20 days to investigate the interactive effects between MNPs and nitrogen levels by measuring different physiological and biochemical parameters. The results demonstrated that both MPs and NPs decrease growth rate, non-photochemical quenching (NPQ), and catalase (CAT) activity, but increased the chlorophyll a and c, carotenoid, and soluble protein contents at low nitrogen level. Notably, the inhibitory effect on growth rate was more pronounced in the NPs conditions. Compared to low nitrogen groups, high nitrogen concentration increased the growth rate, NPQ, the ratio of carotenoids to chlorophyll a, the energy absorbed by each reaction center (ABS/RC), the energy dissipated by each reaction center (DI0/RC), superoxide dismutase (SOD), and CAT levels at same MPs or NPs treatment, respectively. Meanwhile, there was no significant difference among different sizes of plastic particle treatment groups in high nitrogen conditions. These results imply that NPs may exhibit potentially greater detrimental effects than MPs, when the algae were cultured under low nitrogen conditions. However, increased nitrogen availability appears to alleviate the toxic effects of MNPs by enhancing the algal photoprotective and antioxidant capacities. These findings highlight the potential for nutrient enrichment to mitigate the toxic impacts of micro- and nanoplastics on benthic macroalgae, providing valuable insights into future ecosystem response to increasing MNPs pollution in nutrient-variable coastal environments.

Microplastics in Agricultural Soils: Sources, Fate, and Interactions with Other Contaminants

Microplastics (MPs) are recognized as emerging soil contaminants. However, the potential risks of MPs to agroecosystems have not been fully revealed, especially the compound toxic effects of MPs with co-existing organic or inorganic pollutants (OPs/IPs) in agricultural fields. In this study, we quantified the contributions of different agronomic practices to the sources of MPs in soil and highlighted the important influences of long-term tillage and fertilization on the migration and aging of MPs in agricultural fields. In addition, the antagonistic and synergistic interactions between MPs and OPs/IPs in soil were explored. We emphasized that the degree of adsorption of MPs and soil particles to OPs/IPs is a key determinant of the co-toxicity of those contaminants in soil. Finally, several directions for future research are proposed, and these knowledge gaps provide an important basis for understanding the contamination process of MPs in agricultural soils.

Polyethylene microplastics decrease the bioaccumulation and toxicity of picoxystrobin and azoxystrobin to microalgae Scenedesmus obliquus

Fungicide residues can interact with microplastics (MPs) in the aquatic environment leading to mixed toxicity on phytoplankton. The investigation of biological effects obtained from combined fungicide and MPs is essential for proper evaluation of the ecological risks. Until now, the mechanisms that how polyethylene (PE) MPs altered the toxicity of picoxystrobin and azoxystrobin on microalgae Scenedesmus obliquus was unknown. Here, the impacts of PE-MPs on freely dissolved concentrations (Cfree) of the 2 fungicides and their toxicity to microalgae growth were assessed after 96 h exposure. We found that the presence of PE-MPs reduced the bioaccumulation of picoxystrobin and azoxystrobin in microalgae through decreasing the fungicide Cfree. Furthermore, inhibition effects on microalgae growth and chlorophyll generation was alleviated significantly in the combination of fungicide and PE-MPs compared with the fungicide alone. Specifically, 400 mg/L of 25 μm PE induced more profound influences than other treatments in terms of decreasing Cfree, promoting growth rate, and increasing chlorophyll content that might be attributed to its higher adsorption capacity for the fungicides. Our results demonstrated the antagonism between the fungicides and PE-MPs, clarifying that PE-MPs functioned in lowering the bioavailability and acte toxicity of the 2 strobilurin fungcides to microalgae via physical adsorption especially under the small size and high level of PE-MPs. This study provides evidences that the existence of MPs is capable of influencing the toxicological behavior of fungicides in the environment, and can be a starting point for more sophisticated mechanism investigation of joint toxicity for fungicides and MPs.

Fabrication of chitosan-modified magnetic durian shell biochar for removal of the microplastics

Microplastics (MPs) are an emerging threat to terrestrial ecosystems and have attracted global attention. In this study, durian shell was used as biochar raw material to provide magnetism, and then it was modified with chitosan to make chitosan-modified magnetic biochar (CMBC). The prepared CMBC was used to simulate the adsorption of MPs in sewage. Experimental results showed that the amount of CMBC was 0.1 g, pH was 10, the concentration of 160 mg/L had the optimal adsorption effect, the adsorption rate reached up to 97.22 %, and the adsorption capacity was 15.56 mg/g. According to the adsorption kinetic analysis, the adsorption process conformed to be the Freundlich model. The removal rate of MPs still remained at 76.41 % when CMBC, a green environmentally friendly adsorption material, was recycled for five times. This research broadens the understanding for the evaluation of magnetic biochar effectiveness in the adsorption of MPs pollution.

Spotlight on the long-term effects of micro/nanoplastics exposure on Spirulina platensis: Algal cells, extracellular polymeric substances, and phycocyanin

Spirulina platensis (SP) provides humans with proteins and natural pigments. The effects of micro/nanoplastics (MNPs) on SP are of great interest. We focused on the effects of high concentrations (100-300 mg/L) of polystyrene MNPs on SP for 50 days. MNPs caused growth retardation, a decrease in peak concentration of algal cells, the emergence of surface cracks and pores, and stimulated the secretion of extracellular polymeric substances that promoted heterogeneous aggregation of SP. During the first 35 days, there were significant differences between the exposure groups in the phycocyanin concentration, yield and purity and the ratio of phycocyanin to phycobiliprotein, with the higher MNPs concentration resulting in lower values, whereas on day 50 there were no statistically significant differences in any of these metrics between the control or exposure groups. This study enriches the knowledge about the long-term effects of MNPs on SP for microalgae culture and food industry.

Interactive toxicity effects of metronidazole, diclofenac, ibuprofen, and differently functionalized nanoplastics on marine algae Chlorella sp

Pharmaceutical products (PPs) and nanoplastics (NPs) are prominent emerging contaminants that pose serious threats to marine ecosystems. The present study aimed to investigate both pristine and combined toxicity of PPs (metronidazole, diclofenac, and ibuprofen) and polystyrene nanoplastics (PSNPs) with amine (NH2-PSNPs) and carboxyl (COOH-PSNPs) surface functionalization on marine microalgae Chlorella variabilis. Toxicity assessment included the evaluation of growth inhibition, total reactive oxygen species production, malondialdehyde content, antioxidant activity, and photosynthetic activity. Furthermore, changes in the surface functional groups of the algae after exposure to contaminants were examined. The correlation among the toxicity endpoints was assessed using Pearson correlation and cluster heatmap analysis. Zeta potential analysis and hydrodynamic size measurements revealed that the PSNPs became unstable in the presence of PPs. This instability facilitated the aggregation and rapid settlement of PSNPs, consequently impeding their direct interaction with algal cells. Growth inhibition results indicated that Chlorella variabilis exhibited minimal growth inhibition when exposed to pristine PPs (1 mg L-1), whereas PSNPs (1 mg L-1) caused substantial growth inhibition. Notably, the combined toxicity of PSNPs and PPs was lower compared to pristine PSNPs. The independent action model revealed that the combination of PPs and PSNPs showed an antagonistic mode of interaction. The potential reasons for the decreased toxicity observed in the mixture of PSNPs and PPs compared to pristine PSNPs can be attributed to diminished oxidative stress and enhanced photosynthetic activity. These findings provide valuable insights into the role of PPs in modulating the toxicity of PSNPs towards microalgae.

Less toxic combined microplastics exposure towards attached Chlorella sorokiniana in the presence of sulfamethoxazole while massive microalgal nitrous oxide emission under multiple stresses

Microalgae-based wastewater treatment could realize simultaneous nutrients recovery and CO2 sequestration. However, impacts of environmental microplastics (MPs) and antibiotic co-exposure on microalgal growth, nutrients removal, intracellular nitric oxide (NO) accumulation and subsequent nitrous oxide (N2O) emission are unclarified, which could greatly offset the CO2 sequestration benefit. To reveal the potential impacts of environmental concentrations of MPs and antibiotic co-exposure on microalgal greenhouse gas mitigation, this study investigated the effects of representative MPs (PE, PVC, PA), antibiotic sulfamethoxazole (SMX), and nitrite (NO2--N) in various combinations on attached Chlorella sorokiniana growth, nutrients removal, anti-oxidative responses, and N2O emission originated from intracellular NO build-up. Microalgal biofilm growth was more inhibited under 10 μg/L MPs than 100 μg/L SMX, and MPs+SMX co-exposure displayed toxicity antagonism while MPs+MPs co-exposure caused toxicity synergism (up to 66 % growth inhibition). Extracellular polysaccharides content correlated well with microalgal biofilm density under various stresses, while SMX involved stresses displayed chlorophyll a content reduction. Microalgal assimilation and MPs adsorption contributed to nutrients removal, and phosphorus removal displayed less variance among different stresses (residual phosphorus <0.5 mg/L) than nitrogen. Intracellular NO conversion to N2O almost doubled during the co-exposure processes, and N2O emission under NO2--N + PE+PVC co-exposure could offset the contribution of microalgal CO2 sequestration by as high as 176.2 %. Results of this study appealed for urgent concern regarding environmental MPs and antibiotic co-exposure on primary producers' growth characteristics and their greenhouse gas mitigation properties.

Adsorption of emerging pollutants utilizing chitosan derivatives: Recent advances and future perspective

Globalization resulted in technological advancement, and urban population growth. Consequently, pollution emerged as an imminent risk to the survival of all species on Earth. Consequently, on a worldwide basis, sustainability become a major issue for legislators. Inconsistent impacts on both human and animal growth and wellness triggered health issues associated with water contamination through the chronic toxicants. Micropollutants' pollution prompted severe concerns due to their malignant, indestructible, and accumulative properties. The elimination of these toxins from industrial processes has become one of the most significant ecological challenges. A variety of both organic and simulated sorbents are available, and each of these have unique benefits. In the recent years, chitosan and its composite materials have been attempted and have been proven to be applicable for the resolution of many challenging issues related to water pollution. Among various notable benefits of adsorption processes, economic viability, ease of access, and adherence to environmental regulations are notable. Considering the above-mentioned issues, the article targets the assessment of chitosan and its composite materials for relevant environmental applications. Accordingly, the article aims to examine the performance, advantages, and disadvantages of chitosan as an adsorbent.

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.

Evaluating Toxic Interactions of Polystyrene Microplastics with Hazardous and Noxious Substances Using the Early Life Stages of the Marine Bivalve Crassostrea gigas

Plastics pose a significant threat to marine ecosystems, owing to their slow biodegradability. Microplastics (MPs), in particular, affect marine life and maricultural organisms and can enter the food chain via ingestion by marine organisms, leading to bioaccumulation in predators, including humans. This study assessed the toxic interactions between polystyrene microplastic particles (PSMPs) and cadmium (Cd) and phenanthrene (Phe) using marine bivalves. While PSMPs were non-toxic to Pacific oysters (Crassostrea gigas), the toxicity of Cd and Phe was concentration-dependent. In most conditions, PSMPs reduced the toxicity of Cd and Phe, but in simultaneous exposure, they acted as Cd messengers, altering the toxicity during the adult stage. This study confirms that PSMPs can interact with coastal environmental pollutants, thereby accelerating biotoxicity and posing a significant threat to marine wildlife, mariculture, and human health. It also highlights the need to assess MP toxicity in coastal environments and their interactions with pollutants.

Plastics aplenty in paddy lands: incidence of microplastics in Indian rice fields and ecotoxicity on paddy field phytoplankton

Occurrence of microplastics (MP) in natural paddy fields and its impact are less studied. This study reports the abundance of MP in two paddy fields of Kerala, India, cultivating rice crops, 'Pokkali' and 'Uma' crops, which are vital to Kerala's food security and climate resilience. Fourier transform infrared spectroscopy (FTIR) analyses confirmed the presence of polyethylene (PE) and polypropylene (PP) fragments as major MP in the surface water of paddy fields during vegetative (transplantation) and ripening (near harvesting) phases. MP density in the vegetative phase of 'Pokkali' (1370 ± 468.51 fragments/m3) and 'Uma' (1110 ± 304.96 fragments/m3) was thrice more than the ripening phase concentrations (400 ± 196.85 and 370 ± 57.00 fragments/m3, respectively). Subsequently, ecotoxicity of MP and plastic leachates (PL) on phytoplankton that are naturally found in rice fields was examined. Microalga, Chlorococcum sp., and cyanobacterium, Synechococcus sp., were grown in modified BG11 and BG11 media, respectively, and tested with paddy field concentrations for PE-MP and PE-PL. MP bestowed a significant hormetic effect on the specific growth rate of the microalga (121% of the control) whereas the cyanobacterial growth was negatively impacted (70% of the control). Both phytoplankton exhibited a similar response when exposed to PL, but results were neither dose-dependent nor significant. Further, increased catalase activity and compromised superoxide dismutase machinery in the cyanobacterium corroborated the toxic impact on growth (p ≤ 0.05), which indicates reactive oxygen species (ROS) generation in MP-treated groups. ROS generation indicates oxidative stress following MP exposure in the studied phytoplankton perhaps through surface contact or by leaching of toxic intermediates into the medium. The distinctive responses of paddy field phytoplankton to MP and PL stress suggest that MP pollution may enrich certain resilient species over others leading to a possible change in phytoplankton community structure. Pollution load indices suggest that even environmental concentrations of MP and PL may affect the rice productivity as paddy field phytoplankton play a significant role in sustaining and enhancing crop health. Therefore, the presence of MP at alarming concentrations in the paddy fields signifies the emergence of a global environmental and food security concern.

Microplastic and nanoplastic pollution: Assessing translocation, impact, and mitigation strategies in marine ecosystems

The widespread presence of plastic debris in marine ecosystems was first highlighted as a serious concern in the United Nations Convention on the Law of the Sea (UNCLOS) and the 1972 London Convention. This realization identified plastic pollution as one of the major global environmental issues. Majorities of plastic debris are neither recycled nor incinerated, as a result, it eventually makes its way into lakes, rivers, and oceans. Analysis of water and sediment worldwide indicates that microplastics and nanoplastic are ubiquitous in soils, freshwater, and marine ecosystems. Microplastic and nanoplastics are distributed throughout marine environments via processes such as biofouling and chemical leaching, contaminating both pelagic and benthic species. Despite growing recognition of the hazards posed by microplastics and nanoplastics, regulatory efforts remain hampered by limited understanding of their broader ecological impacts, particularly how diverse factors translate into population declines and ecosystem disruptions. This review examines the pathways of microplastic and nanoplastic pollution, their interactions with other environmental stressors such as climate change and chemical pollution, and their effects on marine food webs. The review highlights the urgent need for further research into the behavior and fate of nanoplastics, which are the degradation product of microplastics, owing to their nano size they pose additional risks, unique properties, and potential for widespread ecological impacts. Studies have demonstrated that smaller microplastics and nanoplastics, particularly nanoplastics, are more toxic than larger microplastics. Additionally, microplastics and nanoplastics serve as vectors for contaminants such as heavy metals, exacerbating their toxicity. They also translocate through marine food chains, posing potential health risks. While evidence of their impact continues to grow, the chronic toxicity of microplastics and nanoplastics remains poorly understood, emphasizing the need for further research, particularly at the cellular level, to fully understand their effects on marine ecosystems and human health. This review also concludes with a call for standardized measurement methods, effective mitigation strategies, and enhanced international cooperation to combat this escalating threat. Future research should prioritize the complex interactions between microplastics and nanoplastics, other pollutants, and marine ecosystems, with the ultimate goal of developing holistic approaches to manage and mitigate the impact of plastic pollution. PRACTITIONER POINTS: Microplastic/nanoplastic translocate through marine food webs, affecting species and human health. Nanoplastics are more toxic than microplastics, exacerbating environmental risks. Nanoplastic aggregation influences their distribution and ecological interactions. Future research should focus on nanoplastic behavior, transport, and toxicity.

Impact of microplastics on aquatic flora: Recent status, mechanisms of their toxicity and bioremediation strategies

The accumulation of microplastics (MPs) in aquatic environments has occurred pervasively. The MPs affect almost all the aquatic plants including the aquatic microorganisms, ultimately disturbing the food chain. Aquatic flora attracts MPs due to the formation of several chemical bonds and interactions, including hydrogen bonds, electrostatic, hydrophobic, and van der Waals. Consequently, they hinder plant growth when adsorbed to the plant surfaces. Moreover, the major metabolic processes, including photosynthesis, reproduction, and nutrient uptake, get affected due to the pore-filling of plant tissues and the blockage of sunlight. Subsequently, prolonged exposure to MPs inflicts excessive generation of reactive oxygen species (ROS), ultimately accelerating programmed cell death. However, it has been realized that bioremediation techniques, including phytoremediation, can effectively mitigate MPs pollution by adsorbing or accumulating MPs by 25-80% at the laboratory scale. In this connection, several microorganisms are vital in deteriorating MPs due to their ability to form biofilm over the MPs' surface. Additionally, the secretion of extracellular enzymes such as styrene monooxygenase, styrene oxide isomerase, phenylacetaldehyde dehydrogenase, PETase, etc., facilitates the degradation of MPs. Moreover, the inherent ability of plants to adsorb and accumulate MPs can be utilized to manage the MPs in aquatic ecosystems. However, there is a dearth of literature and comprehensive reviews highlighting the potential of bioremediation strategies. Therefore, apart from addressing the impact of MPs on aquatic flora, this article attempts to elucidate the physical and chemical basis of plant-plastic interaction and the potential strategies aquatic flora including microorganisms employ to mitigate plastic pollution.

Microplastic-enhanced chromium toxicity in Scenedesmus obliquus: Synergistic effects on algal growth and biochemical responses

This study explores the combined toxicity of microplastics (MPs) and chromium (Cr6 +) on the freshwater green algae Scenedesmus obliquus. As emerging contaminants in aquatic ecosystems, MPs have been shown to intensify the toxicity of Cr6+, leading to a more significant impact on algal growth and biochemical responses than either stressor alone. A 30-day experimental simulation revealed that co-exposure to Cr6+ and 5 µm diameter polystyrene MPs resulted in significantly enhanced toxicity compared to individual exposures, characterized by a notable decrease in algal growth, diminished photosynthetic pigments, and protein content, alongside oxidative system damage. 100 nm MPs exhibited a distinct toxicity profile, with more pronounced effects when not combined with Cr6+, suggesting size-dependent interactions with algal cells. Transcriptomic analysis illuminated the complex regulatory mechanisms, indicating that toxicity primarily modulates metabolic pathways essential for photosynthesis, oxidative phosphorylation, the TCA cycle, and ribosome function in Scenedesmus obliquus. This study not only delineates the distinct toxicity effects of single and combined exposure systems but also emphasizes the need for a deeper understanding of the role of MPs in environmental pollution and their potential to modulate the toxicity of heavy metals in aquatic ecosystems.

Microplastics in aquatic ecosystems: Detection, source tracing, and sustainable management strategies

Microplastics (MPs) are emerging contaminants characterized by persistence, cross-media transport, and complex pollutant interactions, posing serious ecotoxicological risks to ecosystems and human health. Effective MPs management requires multi-faced, long-term, strategies involving targeted sampling, quantitative detection, and comprehensive risk assessments, all of which entail significant resource investment. Despite advancements in remediation technologies, a holistic governance framework integrating these innovations remains underdeveloped. This review synthesizes current knowledge on MPs, elaborating on their diverse morphologies, degradation pathways, and their role as vectors for toxic substances. State-of-the-art extraction techniques are evaluated in this article, including micropore adsorption using nanocomposites, alongside the incorporation of advanced analytical tools such as spectroscopic methods, electron microscopy, and bioinformatics to augment environmental forensics. This review also underscores the necessity of formulating robust global policies to regulate MPs pollution and discusses the potential of biodegradation and thermal degradation as sustainable solutions for MPs removal. By promoting an interdisciplinary approach, this review advocates for a coordinated global response, integrating environmental science, policy frameworks, and waste management strategies to mitigate the escalating impact of MPs on ecosystems and human well-being.

Microplastic pollution in aquatic ecosystems: impacts on diatom communities

In recent years, heightened concern has emerged regarding the pervasive presence of microplastics in the environment, particularly in aquatic ecosystems. This concern has prompted extensive scientific inquiry into microplastics' ecological and physiological implications, including threats to biodiversity. The robust adsorption capacity of microplastic surfaces facilitates their widespread distribution throughout aquatic ecosystems, acting also as carriers of organic pollutants. However, to comprehensively understand the broader implications of this pollution, a thorough examination of the origins, composition, and widespread distribution of microplastics within aquatic biotopes is imperative. Diatoms, unicellular photosynthetic organisms, play a pivotal role in aquatic ecosystems as primary producers, forming the base of the aquatic food web. Investigating the relationship between microplastics and diatoms, leveraging methodological advancements, holds promise in unraveling the intricate action mechanisms underlying their interactions. Such inquiry sheds light on the physiological responses elicited and provides crucial insights into the ecological dynamics within aquatic environments. This study explores the understanding of microplastic-diatom interactions, focusing on how microplastic types, sizes, and concentrations influence diatoms. Ultimately, the current study strongly advocates for transdisciplinary collaborations, such as partnerships between ecologists, materials scientists, and policymakers, as the complexity of microplastic pollution demands collective efforts to address this critical and alarming environmental issue.

Phenotypic and Gene Expression Alterations in Aquatic Organisms Exposed to Microplastics

The use of plastics, valued for its affordability, durability, and convenience, has grown significantly with the advancement of industry. Paradoxically, these very properties of plastics have also led to significant environmental challenges. Plastics are highly resistant to decomposition, resulting in their accumulation on land, where they eventually enter aquatic environments, due to natural processes or human activities. Among these plastics, microplastics, which are tiny plastic particles, are particularly concerning when they enter aquatic ecosystems, including rivers and seas. Their small size makes them easily ingestible by aquatic organisms, either by mistake or through natural feeding behaviors, which poses serious risks. Moreover, microplastics readily adsorb other pollutants present in aquatic environments, creating pollutant complexes that can have a synergistic impact, magnifying their harmful effects compared to microplastics or pollutants acting alone. As a result, extensive research has focused on understanding the effects of microplastics on aquatic organisms. Numerous studies have demonstrated that aquatic organisms exposed to microplastics, either alone or in combination with other pollutants, exhibit abnormal hatching, development, and growth. Additionally, many genes, particularly those associated with the antioxidant system, display abnormal expression patterns in these conditions. In this review, we examine these impacts, by discussing specific studies that explore changes in phenotype and gene expression in aquatic organisms exposed to microplastics, both independently and in combination with adsorbed pollutants.

Effects of microplastics and salt single or combined stresses on growth and physiological responses of maize seedlings

Plastic film (mulch film) is widely used in saline and alkaline soils because it can effectively reduce salt stress damage. However, it results in the accumulation of microplastics (MPs) in the soil, which pose a threat to crop growth and production. This study investigates the effects of 50 mg l-1 MPs and 100 mM sodium chloride (NaCl), individually or in combination, on the growth and physiological characteristics of maize (Zea mays) seedlings. The results demonstrated that compared to the control, MPs and NaCl single or combined stress reduced seedling biomass and water content, and the combined stress was more serious. Stress significantly reduced N and K contents in leaves, and Na content under combined stress was lower than under single NaCl stress. Compared to single stress, the combined stress further enhanced oxidative damage by increasing H2O2 and MDA content, a disrupted chloroplast structure, and reduced chlorophyll content, ultimately leading to a decline in chlorophyll fluorescence parameters and photosynthetic efficiency. Single MPs or NaCl stress led to the accumulation of proline, soluble proteins, and soluble sugars, while the combined stresses further increased the content of these osmotic substances in plants. Moreover, single or combined stress increased the activity of CAT, POD, SOD and the content of AsA and GsH. Collectively, NaCl and MPs single or combined stress exert notable toxic effects on maize seedling growth. Although the combined stress inhibited seedling growth more than the single stress, the combined stress of MPs and NaCl showed antagonistic effects. These findings underscore the importance of assessing the ecological risks posed by the combined effects of MPs and salt stresses on maize plants.

Microplastics as an Emerging Potential Threat: Toxicity, Life Cycle Assessment, and Management

The pervasiveness of microplastics (MPs) in terrestrial and aquatic ecosystems has become a significant environmental concern in recent years. Because of their slow rate of disposal, MPs are ubiquitous in the environment. As a consequence of indiscriminate use, landfill deposits, and inadequate recycling methods, MP production and environmental accumulation are expanding at an alarming rate, resulting in a range of economic, social, and environmental repercussions. Aquatic organisms, including fish and various crustaceans, consume MPs, which are ultimately consumed by humans at the tertiary level of the food chain. Blocking the digestive tracts, disrupting digestive behavior, and ultimately reducing the reproductive growth of entire living organisms are all consequences of this phenomenon. In order to assess the potential environmental impacts and the resources required for the life of a plastic product, the importance of life cycle assessment (LCA) and circularity is underscored. MPs-related ecosystem degradation has not yet been adequately incorporated into LCA, a tool for evaluating the environmental performance of product and technology life cycles. It is a technique that is designed to quantify the environmental effects of a product from its inception to its demise, and it is frequently employed in the context of plastics. The control of MPs is necessary due to the growing concern that MPs pose as a newly emergent potential threat. This is due to the consequences of their use. This paper provides a critical analysis of the formation, distribution, and methods used for detecting MPs. The effects of MPs on ecosystems and human health are also discussed, which posed a great challenge to conduct an LCA related to MPs. The socio-economic impacts of MPs and their management are also discussed. This paper paves the way for understanding the ecotoxicological impacts of the emerging MP threat and their associated issues to LCA and limits the environmental impact of plastic.

Perfluorobutanoic acid weakens the heterogeneous aggregation of microplastics and microalgae: Perspective from physicochemical properties, extracellular polymeric substances secretion and DLVO theory

Microplastics (MPs) and per- and poly-fluoroalkyl substances extensively coexist in aquatic environments and potentially endanger organisms. Microalgae may decrease the effective concentration of pollutants via hetero-aggregation with MPs and adsorption of emerging contaminants. However, the potential influence of coexistent pollutants on hetero-aggregation of MPs and microalgae remains unknown. This study investigated the hetero-aggregation process involving different sizes of polystyrene (PS, 3.0 and 50.0 μm) with Chlorella sorokiniana (C. sorokiniana) in the presence or absence of perfluorobutanoic acid (PFBA) along settling experiments, scanning electron microscope, and Derjaguin-Landau-Verwey-Overbeek (DLVO) model. We found that the hetero-aggregation between C. sorokiniana and 3 μm PS was more pronounced than with 50 μm PS, while PFBA inhibited this process. ΔOD1 values (reflected hetero-aggregation level) for 3PS-cells and 50PS-cells were 0.189 and 0.087, respectively, and PFBA decreased these values to 0.134 and 0.033. Furthermore, extracellular polymeric substances, known as inducer of hetero-aggregation, increased by 14.33% when exposed to 3 μm PS alone, whereas the co-exposure group showed a decrease of 4.52% compared to 3PS-cells group. PFBA also significantly decreased the protein/polysaccharide ratios in both MPs sizes, reducing hetero-aggregation. DLVO theory revealed that microalgae lowered the energy barrier significantly, while PFBA elevated it, indicating that hetero-aggregation was inhibited by PFBA. This study provides new perspectives for pollutant removal and toxicity variation in aquatic environments.

Sandstorms contribute to the atmospheric microplastic pollution: Transport and accumulation from degraded lands to a megacity

Surface dust from degraded lands is a major global aerosol source, mobilized by meteorological events like sandstorms. Microplastics (MPs) in dust can be enriched in the atmosphere and transported over long distances to sensitive regions during sandstorms. This study was conducted in a megacity frequently impacted by sandstorms in spring, exploring the influx, characteristics, enrichment mechanism, and transport pathway of sandstorm-derived MPs. The deposition rate of these MPs reached 1823.65 ± 892.53 items·m-2·d-1, predominantly consisting of low-density polymers and those mainly used in synthetic fiber, with an average size of 60.75 µm. Compared to MPs in annual atmospheric deposition, these MPs were smaller and contained a higher proportion of potentially harmful polymers. These factors could increase exposure risks for residents from sandstorm-derived MPs, along with distinct meteorological and ecological effects. Backward trajectory analysis suggested the observed sandstorms originated from the Mongolian Plateau, over 1000 km away. Comparisons of MPs from surface-collected dust on the Mongolian Plateau with sandstorms-delivered MPs revealed the transport was determined by MP shape, size, and density. This study highlights the critical role of sandstorms in the MP atmospheric cycling, emphasizing the extensive impacts of MPs and the need for coordinated mitigation efforts across regions.

Unraveling the toxicity mechanisms of nanoplastics with various surface modifications on Skeletonema costatum: Cellular and molecular perspectives

Nanoplastics are ubiquitous in marine environments, exhibiting high bioavailability and potential toxicity to marine organisms. However, the impacts of nanoplastics with various surface modifications on marine microalgae remain largely unexplored. This study explored the toxicity mechanisms of two nanoplastic types-polystyrene (PS) and polymethyl methacrylate (PMMA)-with distinct surface modifications on Skeletonema costatum at cellular and molecular levels. Results showed that nanoplastics significantly impaired the growth of microalgae, particularly PS-NH2, which caused the most pronounced growth inhibition, reaching 56.99 % after a 96-h exposure at 50 mg/L. Transcriptomic profiling revealed that nanoplastics disrupted the expression of genes predominantly involved in ribosome biogenesis, aminoacyl-tRNA biosynthesis, amino acid metabolism, and carbohydrate metabolism pathways. The integrated biochemical and transcriptomic evidence highlighted that PS-NH2 nanoplastics had the most adverse impact on microalgae, affecting fundamental pathways such as ribosome biogenesis, energy metabolism, photosynthesis, and oxidative stress. Our findings underscore the influence of surface-modified nanoplastics on algal growth and contribute new understanding to the toxicity mechanisms of these nanoplastics in marine microalgae, offering critical information for assessing the risks of emerging pollutants.

Impacts of atmospheric particulate matter deposition on phytoplankton: A review

In many rapidly urbanizing and industrializing countries, atmospheric pollution causes severe environmental problems and compromises the health of humans and ecosystems. Atmospheric emissions, which encompass gases and particulate matter, can be transported back to the earth's surface through atmospheric deposition. Atmospheric deposition supplies chemical species that can serve as nutrients and/or toxins to aquatic ecosystems, resulting in wide-ranging responses of aquatic organisms. Among the aquatic organisms, phytoplankton is the basis of the aquatic food web and is a key player in global primary production. Atmospheric deposition alters nutrient availability and thus influences phytoplankton species abundance and composition. This review provides a comprehensive overview of the physiological responses of phytoplankton resulting from the atmospheric deposition of trace metals, nitrogen-containing compounds, phosphorus-containing compounds, and sulfur-containing compounds in particulate matter into aquatic ecosystems. Knowledge gaps and critical areas for future studies are also discussed.

The role of algae in regulating the fate of microplastics: A review for processes, mechanisms, and influencing factors

As an important emerging pollutant, the fate of microplastics (MPs) in ecosystems is of growing global concern. In addition to hydrodynamics and animals, algae can also affect the transport of MPs in aquatic environments, which could potentially remove MPs from the water column. Although researchers have conducted many studies on the sink of MPs regulated by algae in both marine and freshwater environments, there is still a lack of comprehensive understanding coupled with the increasingly scattered study contents and findings. This review aims to provide a systematic discussion of the processes, mechanisms, and influencing factors, which are coupled with the sink of MPs changes by algae. The main processes identified include retention, flocculation, deposition, and degradation. The retention of MPs is achieved by adhesion of MPs to algae or embedment/encrustation of MPs within the epibiont matrix of algae, thereby preventing MPs from migrating with water currents. The extracellular polymeric substances (EPS) and enzymes produced by algal metabolic activities can lead not only to the formation of aggregates containing MPs but also to the biodegradation of MPs. The processes that algae alter the fate of MPs in aquatic environments are very complex and can be influenced by various factors such as algal attributes, microplastic characteristics and environmental conditions. This review provides insights into recent advances in the fate of aquatic MPs and highlights the need for further research on MPs-algae interactions, potentially shortening the knowledge gap in the sink of MPs in aquatic ecosystems.

Size-dependent influences of nano- and micro-plastics exposure on feeding, antioxidant systems, and organic sulfur compounds in ciliate Uronema marinum

Protozoa play a pivotal role in the microbial cycle, and ciliated protozoan grazing habits are associated with dimethyl sulfide (DMS) cycle. Many studies have explored the impacts of nanoplastics (NPs) and microplastics (MPs) on ecotoxicological effects of ciliates. However, limited research exists on NPs and MPs influences on the production of organic sulfur compounds. The impact of NPs and MPs on the production of dimethyl sulfoxide (DMSO) and carbonyl sulfide (COS) remains unclear. Therefore, we examined the impacts of three concentrations (1 × 105, 5 × 105, and 1 × 106 items/mL) of polystyrene (PS) NPs (50 nm) and MPs (1 and 5 μm) on the ecotoxicology and DMS/dimethylsulfoniopropionate (DMSP)/DMSO/COS production in the ciliate Uronema marinum. NPs and MPs exposure were found to reduce the abundance, growth rate, volume, and biomass of U. marinum. Additionally, NPs and MPs increased the superoxide anion radical (O2˙─) production rates and malondialdehyde (MDA) contents (24 h), leading to a decline in glutathione (GSH) content and an ascend in superoxide dismutase (SOD) activity to mitigate the effects of reactive oxygen species (ROS). Exposure to PS NPs and MPs decreased the ingestion rates of algae by 7.5-14.4%, resulting in decreases in DMS production by 56.8-85.4%, with no significant impact on DMSO production. The results suggest a distinct pathway for the production of DMSO or COS compared to DMS. These findings help us to understand the NPs and MPs impacts on the marine ecosystem and organic sulfur compound yield, potentially influencing the global climate.

Effects of polystyrene microplastics on the extracellular and intracellular dissolved organic matter released by Skeletonema costatum using a novel in situ method

Microplastics (MPs) affect the physicochemical algal-dissolved organic matter properties, indirectly influencing the environmental behavior of contaminants including persistent organic pollutants and heavy metals. Limited research is available on the roles played by intracellular- and extracellular-dissolved organic matter (I-DOM and E-DOM) in the processes that affect the environmental behavior of contaminants. Furthermore, the effects of MPs on the production of I-DOM and E-DOM, as well as their environmental behaviors, remain uncertain. A critical issue lies in the challenge of quantitatively identifying I-DOM and E-DOM in situ. In this work, a new fluorescence ratio method was developed and applied to in situ examine the impacts of polystyrene (PS) MPs (50, 500 nm, and 5 μm) on the I-DOM and E-DOM released by Skeletonema costatum (S. costatum). The experimental results indicated that the detection limits were 0.06 mg L-1, with the respective minimum detectable proportions being 2% for both E-DOM and I-DOM. The suppressive effects of 10-50 mg L-1 of 50 and 500 nm PS MPs on the cell proliferation of S. costatum and the E-DOM secretion were most pronounced on day 6. And the rates of suppression of E-DOM secretion were 10.1%-18.2% and 4.2%-13.9%, respectively. The exposure of algal cells to 50 mg L-1 of 50 and 500 nm PS MPs led to cell rupture and the leakage of I-DOM on day 6. This suggests that the developed method in the laboratory could offer a promising approach for studying the generation of E-DOM and I-DOM in situ, as well as their environmental behaviors affected by MPs.

In Vitro and In Vivo Genotoxicity of Polystyrene Microplastics: Evaluation of a Possible Synergistic Action with Bisphenol A

The ubiquitous presence of plastics represents a global threat for all ecosystems and human health. In this study, we evaluated, in vitro and in vivo, the genotoxic potential of different concentrations of polystyrene microplastics (PS-MPs) and their possible synergistic interactions with bisphenol-A (BPA). For the in vitro and the in vivo assays, we used human lymphocytes and hemocytes from Lymnaea stagnalis, respectively. The genomic damage was evaluated by the micronucleus assay, and differences in eggs laid and growth of L. stagnalis were also evaluated. In human lymphocytes, PS-MPs alone at the concentration of 200 μg/mL and in association with BPA 0.100 µg/mL significantly increased the frequencies of micronuclei and nuclear buds, indicating a possible in vitro genotoxic additive action of these two compounds. Vice versa, PS-MPs did not result in genotoxicity in hemocytes. Our results indicated that PS-MPs have genotoxic properties only in vitro and at a concentration of 200 µg/mL; moreover, this compound could intensify the genomic damage when tested with BPA, indicating possible cumulative effects. Finally, PS significantly reduced the growth and the number of laid eggs in L. stagnalis.

Combined effects of microplastics and pharmaceutical and personal care products on algae: A critical review

Microplastics (MPs) and pharmaceuticals and personal care products (PPCPs) are ubiquitous in aquatic environments. Algae play an important role in aquatic environments. Thus, it is important to study the response of algae to combined exposure of MPs and PPCPs. Here, we review the effects of MPs and PPCPs on algae. First, the individual effects of MPs and PPCPs on algae were summarized. Second, the combined effects of MPs and PPCPs on algae were systematically analyzed. (1) Antagonism: ① when the MPs are too large to enter the algal cells, the adsorption of PPCPs onto MPs results in decreased the contact of MPs and PPCPs with algae; ② PPCPs and MPs have opposing actions on the same biological target; ③ MPs increase the activity of metabolic enzymes in algae, thus promoting the PPCP degradation. (2) Synergy: ① when the MPs are small enough to enter algal cells, the adsorption of PPCPs on MPs promotes the entry of PPCPs; ② when MPs are negatively charged, the adsorption of positively charged PPCPs by MPs decreases the electrostatic repulsion, increasing the interaction between algae and MPs; ③ complementary modes of action between MPs and PPCPs show combined effects on the same biological target. Third, the relative importance of the factors that impact the combined effects are evaluated using the random forest model decreased in the following order: PPCP types > algal species > MP size > MP concentration > MP types > exposure time. Finally, future directions for the combined effects of MPs and PPCPs are proposed, which will facilitate a better understanding of the environmental fate and risks of both MPs and PPCPs.

Microplastics enhanced the allelopathy of pyrogallol on toxic Microcystis with additional risks: Microcystins release and greenhouse gases emissions

Cyanobacteria blooms (CBs) caused by eutrophication pose a global concern, especially Microcystis aeruginosa (M. aeruginosa), which could release harmful microcystins (MCs). The impact of microplastics (MPs) on allelopathy in freshwater environments is not well understood. This study examined the joint effect of adding polystyrene (PS-MPs) as representative MPs and two concentrations (2 and 8 mg/L) of pyrogallol (PYR) on the allelopathy of M. aeruginosa. The results showed that the addition of PS-MPs intensified the inhibitory effect of 8 mg/L PYR on the growth and photosynthesis of M. aeruginosa. After a 7-day incubation period, the cell density decreased to 69.7 %, and the chl-a content decreased to 48 % compared to the condition without PS-MPs (p < 0.05). Although the growth and photosynthesis of toxic Microcystis decreased with the addition of PS-MPs, the addition of PS-MPs significantly resulted in a 3.49-fold increase in intracellular MCs and a 1.10-fold increase in extracellular MCs (p < 0.05). Additionally, the emission rates of greenhouse gases (GHGs) (carbon dioxide, nitrous oxide and methane) increased by 2.66, 2.23 and 2.17-fold, respectively (p < 0.05). In addition, transcriptomic analysis showed that the addition of PS-MPs led to the dysregulation of gene expression related to DNA synthesis, membrane function, enzyme activity, stimulus detection, MCs release and GHGs emissions in M. aeruginosa. PYR and PS-MPs triggered ROS-induced membrane damage and disrupted photosynthesis in algae, leading to increased MCs and GHG emissions. PS-MPs accumulation exacerbated this issue by impeding light absorption and membrane function, further heightening the release of MCs and GHGs emissions. Therefore, PS-MPs exhibited a synergistic effect with PYR in inhibiting the growth and photosynthesis of M. aeruginosa, resulting in additional risks such as MCs release and GHGs emissions. These results provide valuable insights for the ecological risk assessment and control of algae bloom in freshwater ecosystems.

Alleviating effects of microplastics together with tetracycline hydrochloride on the physiological stress of Closterium sp

Microplastics have significant influence on both freshwater cyanobacteria and marine microalgae, especially under co-exposure with other pollutants such as heavy metals, antibiotics, and pharmaceuticals. In the present study, combined effects of microplastics (polyethylene terephthalate (PET) or polybutylene terephthalate (PBT)) and tetracycline hydrochloride (TCH) on the microalgae Closterium sp. were studied to evaluate their acute toxicity, and the cell density, total chlorophyll concentration, photosynthetic activity, antioxidant system, and subcellular structure of Closterium sp. under different treatments were used to explain the physiological stress mechanism of the combined effects. The results indicate that both the single and combined treatments have inhibition effects on the cell growth and photosynthetic activity, with inhibition efficiencies (in terms of cell density) of 5.0%, 9.2%, 66.7%, 55.1%, and 59.8% for PET (100 mg L-1), PBT (100 mg L-1), TCH (10 mg L-1), PET/TCH (PET 100 mg L-1 and TCH 10 mg L-1), and PBT/TCH (PBT 100 mg L-1 and TCH 10 mg L-1), respectively, and relative electron-transport rates (rETRs) of 7.3%, 12.7%, 66.8%, 54.0%, and 59.9%, respectively, for each treatment compared with the control on the 7th day. Moreover, both PET and PBT have positive effects in alleviating TCH toxicity toward Closterium sp., and at the same time, the malondialdehyde level (MDA), superoxide dismutase (SOD) activity, and catalase (CAT) activity induced by the combined treatments were much higher than those from the single microplastic treatments but lower than those from TCH treatment after 7 days. It was demonstrated that TCH causes a much more serious oxidative stress than PET/TCH and PBT/TCH, and the lower oxidative stress of the PET/TCH and PBT/TCH groups could be attributed to the adsorption of TCH to PET or PBT. This work improves the understanding of the combined toxicity effects of microplastics and TCH on Closterium sp.

Amide groups within polystyrene accelerates tetracycline removal in a continuous advanced microalgal treatment system

Livestock effluents are challenging to be treated owing that antibiotics and microplastics are untargeted for most biological technologies. As far, microalgal wastewater treatment is recognized as an effective technique for dealing with. In this study, a continuous-flow system was conducted over 45 days to evaluate the effectiveness of Chlamydomonas sp. JSC4 in removing tetracycline (TCH) under the influence of polystyrene (PS). It shows that PS significantly enhanced the dissipation efficiency of TCH from livestock effluents, and 9.83 % TCH removal was increased under 5 mg/L of both TCH and PS exposure. Meanwhile, higher microalgal bioactivity was a significant factor in achieving desirable pollutants removal efficiency, as 87.14 % microalgal biomass was improved owing to reduction of oxidative stress and augmentation of photosynthesis. Importantly, the pivotal active sites, NH2 and CO, were rapidly covered via π-π interactions and hydrogen bonds during adsorption process between TCH and PS, accounting for mitigation of TCH-PS complexes toxicity and improvement of microalgal ribosome metabolism. Additionally, co-exposure to TCH and PS resulted in maximum lipids (0.57 g/L) and energy (20.79 kJ/L) production, further encouraging a fantastic vision for the tertiary process of livestock effluents via advanced microalgal treatment.

Release kinetic study of microplastics from N95 face masks and consequent effects on freshwater alga Scenedesmus obliquus

The uncontrolled disposal of N95 face masks, widely used during the recent COVID-19 pandemic can release significant amounts of microplastics and other additives into aquatic bodies. This study aimed to: (i) to quantify and analyze the released microplastics and heavy metals from N95 face masks weathered for various time periods (24, 48, 72, 96, 120, and 144 h) and (ii) to assess the cytotoxicity potential of the leachates on a model organism, freshwater alga Scenedesmus obliquus. The mask leachates contained microplastics, polypropylene in different shapes and sizes, and heavy metals like Cu, Cd, and Zn. The leachates significantly reduced cell viability and increased reactive oxygen species (ROS) generation, antioxidant enzyme activity, and membrane damage. The effects were also accompanied by a significant drop in the photosynthetic yield. All of the examined parameters indicated a dose-response relationship, with longer leaching periods resulting in higher microplastic concentrations. Mask leachates severely damaged the structural integrity of the algal cells, as seen in scanning electron microscopy images. The findings of our study confirm that the releases from disposable N95 face masks pose a severe threat to freshwater microalgae, and the cascading effects would harm the aquatic ecosystems.

Insights into the response mechanisms of Tetradesmus obliquus to aged polylactic acid and tetracycline exposure via transcriptome analysis and physiological evaluations

Microplastics (MPs) and antibiotics, identified as emerging pollutants, are extensively prevalent in aquatic environments and display prolonged durability. Unlike conventional plastics, biodegradable plastics are more susceptible to decomposition in the environment, resulting in the generation of microplastics and posing potential risks to the aquatic ecosystems. In this study, we assessed growth inhibition, chlorophyll a content, malondialdehyde content (MDA), and antioxidant enzyme activities. These measurements were integrated with transcriptome analysis to explore the response mechanisms of virgin and aged polylactic acid (vPLA and aPLA) and tetracycline (TC) following 14-day exposure to Tetradesmus obliquus, either individually or in combination. The findings indicated that exposure to vPLA did not significantly impact the growth of T. obliquus. Conversely, aPLA demonstrated growth-promoting effects on T. obliquus, particularly in the latter incubation stages. Moreover, a 14-day exposure significantly increased the chlorophyll a content and the activities of superoxide dismutase (SOD), catalase glutathione (CAT) and glutathione S-transferase (GST) within the algal cells. Apart from 1 mg L-1, the TC concentrations of 2.5, 5.0, and 10 mg L-1 exhibited significant toxic effects on T. obliquus, including growth inhibition, decreased chlorophyll a content, elevated activities of SOD, CAT, and GST, and increased MDA levels. Exposure to a combination of 300 mg L-1 aPLA and 5.0 mg L-1 TC, compared to solely 5 mg L-1 TC, demonstrated a notable reduction in TC toxicity to T. obliquus in the presence of aPLA. This was indicated by elevated algal cell density and chlorophyll a content, as well as a decrease in MDA content. Transcriptome analysis indicated an enrichment of differentially expressed genes (DEGs) in pathways linked to porphyrin metabolism, photosynthesis, carbon fixation, and metabolism within the aPLA + TC combined exposure. The study aid in expanding our knowledge of the potential ecological risks posed by biodegradable plastics and accompanying pollutants in aquatic environments.

A study on the effect of fluorescently stained micro(nano)plastics on the full life history of Skeletonema costatum

As a new type of environmental pollutant, micro(nano)plastics have become a research hotspot in recent years, and their effects on the full life history of marine microalgae have not been studied. To investigate the effects of micro(nano)plastics on the growth, photosynthesis, physiological morphology and interaction of microalgae during the full life cycle, we selected fluorescently stained polystyrene (PS) plastic microbeads as the target pollutant. By sampling and testing the growth rate, photosynthesis and physiological morphology parameters of algal species, the influence of different concentrations of PS (10, 50 and 100 mg/L) and different particle sizes (0.1, 0.5 and 1 μm) on the full life history of Skeletonema costatum (S. costatum) was investigated. The results showed that after adding PS (particle sizes of 0.5 and 1 μm), the response of S. costatum showed a dual character, while adding the same kind of microplastics (MPs) with a particle size of 0.1 μm inhibited S. costatum throughout the full life cycle. Compared with previous studies, short-term experimental data may overestimate the true ecological risks of MPs. In addition, 0.1 μm fluorescent-stained MPs obviously accumulated around the microalgae, indicating that MPs mainly adhered to the surface of algal cells and may enter the food chain by direct or indirect ways, which can cause negative effects on the aquatic ecosystem. This study supports a more accurate assessment of the true risk of MPs to marine aquatic ecosystems.

Physiological and transcriptome level responses of Microcystis aeruginosa and M. viridis to environmental concentrations of triclosan

The toxicity of triclosan (TCS) to various aquatic organisms has been demonstrated at environmental concentrations. However, the effects and mechanisms of TCS on toxic cyanobacteria remains largely unexplored. This study investigated the physiological and molecular variations in two representative toxic Microcystis species (M. aeruginosa and M. viridis) under exposure to TCS for 12 d. Our findings demonstrated that the median effective concentration (EC50) of TCS for both Microcystis species were close to the levels detected in the environment (M. aeruginosa: 9.62 μg L-1; M. viridis: 27.56 μg L-1). An increased level of reactive oxygen species (ROS) was observed in Microcystis, resulting in oxidative damage when exposed to TCS at concentrations ranging from 10 μg L-1 to 50 μg L-1. The photosynthetic activity of Microcystis had a certain degree of recovery capability at low concentrations of TCS. Compared to M. aeruginosa, the higher recovery capability of the photosynthetic system in M. viridis would be mainly attributed to the increased ability for PSII repair and phycobilisome synthesis. Additionally, the synthesis of microcystins in the two species and the release rate in M. viridis significantly increased under 10-50 μg L-1 TCS. At the molecular level, exposure to TCS at EC50 for 12 d induced the dysregulation of genes associated with photosynthesis and antioxidant system. The upregulation of genes associated with microcystin synthesis and nitrogen metabolism further increased the potential risk of microcystin release. Our results revealed the aquatic toxicity and secondary ecological risks of TCS at environmental concentrations, and provided theoretical data with practical reference value for TCS monitoring.

General performance, kinetic modification, and key regulating factor recognition of microalgae-based sulfonamide removal

Sulfonamides have been widely detected in water treatment plants. Advanced wastewater treatment for sulfonamide removal based on microalgal cultivation can reduce the ecological risk after discharge, achieve carbon fixation, and simultaneously recover bioresource. However, the general removal performance, key factors and their impacts, degradation kinetics, and potential coupling technologies have not been systematically summarized. To guide the construction and enhance the efficient performance of the purification system, this study summarizes the quantified characteristics of sulfonamide removal based on more than 100 groups of data from the literature. The biodegradation potential of sulfonamides from different subclasses and their toxicity to microalgae were statistically analyzed; therefore, a preferred option for further application was proposed. The mechanisms by which the properties of both sulfonamides and microalgae affect sulfonamide removal were comprehensively summarized. Thereafter, multiple principles for choosing optimal microalgae were proposed from the perspective of engineering applications. Considering the microalgal density and growth status, a modified antibiotic removal kinetic model was proposed with significant physical meaning, thereby resulting in an optimal fit. Based on the mechanism and regulating effect of key factors on sulfonamide removal, sensitive and feasible factors (e.g., water quality regulation, other than initial algal density) and system coupling were screened to guide engineering applications. Finally, we suggested studying the long-term removal performance of antibiotics at environmentally relevant concentrations and toxicity interactions for further research.

Insights into the synergistic toxicity mechanisms caused by nano- and microplastics with triclosan using a dose-dependent functional genomics approach in Saccharomyces cerevisiae

The emergence of polystyrene (PS) nano- and microplastics (NMPs) and triclosan (TCS) as environmental contaminants has raised concerns about their combined toxicities to organisms, but the complex toxicity arising from their interactions and the underlying molecular mechanisms remain obscure to us. In this study, we comprehensively detected the combined toxicity of PS-NMPs and TCS via the dose-dependent yeast functional genomics profiling. Firstly, our findings demonstrated that the combined exposure to PS-NMPs and TCS elicited a synergistic toxic effect in which the toxicity depended on the size of the PS-NMPs. Secondly, we found that TCS exposure, either alone or in combination with PS-NMPs, influenced lipid biosynthetic processes and ATP export pathways, while the unique responsive genes triggered by combined exposure to TCS and PS-NMPs are significantly enriched in mitochondrial translation, ribosomal small subunit assembly, and tRNA wobble uridine modification. Thirdly, our results demonstrated that point of departure (POD) at the pathway level was positively correlated with IC50, and POD was a more sensitive predictor of toxicity than the apical toxicity endpoints. More importantly, our findings suggested that the combined exposure of PS-NMPs in a size-dependent manner not only alleviated the harmful effects of TCS on glycerophospholipid metabolism, but also exacerbated its negative impact on oxidative phosphorylation. Collectively, our study not only provides new insights into the intricate molecular mechanisms that control the combined toxicity of PS-NMPs and TCS, but also confirms the effectiveness of the dose-dependent functional genomics approach in elucidating the molecular mechanisms of the combined toxicity of pollutants.

Micro/nano-plastics and microalgae in aquatic environment: Influence factor, interaction, and molecular mechanisms

Micro/nano-plastics, as emerging persistent pollutant, are frequently detected in aquatic environments together with other environmental pollutants. Microalgae are the major primary producers and bear an important responsibility for maintaining the balance of aquatic ecosystems. Numerous studies have been conducted on the influence of micro/nano-plastics on the growth, photosynthesis, oxidative stress, gene expression and metabolites of microalgae in laboratory studies. However, it is difficult to comprehensively evaluate the toxic effects of micro/nano-plastics on microalgae due to different experimental designs. Moreover, there is a lack of effective analysis of the aforementioned multi-omics data and reports on shared biological patterns. Therefore, the purpose of this review is to compare the acute, chronic, pulsed, and combined effect of micro/nano-plastics on microalgae and explore hidden rules in the molecular mechanisms of the interaction between them. Results showed that the effect of micro/nano-plastics on microalgae was related to exposure mode, exposure duration, exposure size, concentration, and type of micro/nano-plastics. Meanwhile, the phenomenon of poisoning and detoxification between micro/nano-plastics and microalgae was found. The inhibitory mechanism of micro/nano-plastics on algal growth was due to the micro/nano-plastics affected the photosynthesis, oxidative phosphorylation, and ribosome pathways of algal cells. This brought the disruption of the functions of chloroplasts, mitochondria, and ribosome, as well as impacted on energy metabolism and translation pathways, eventually leading to impairment of cell function. Besides, algae resisted this inhibitory effect by regulating the alanine, aspartate, and glutamate metabolism and purine metabolism pathways, thereby increasing the chlorophyll synthesis, inhibiting the increase of reactive oxygen species, delaying the process of lipid peroxidation, balancing the osmotic pressure of cell membrane.

Microplastics supply contaminants in food chain: non-negligible threat to health safety

The occurrence of microplastics (MPs) and organic pollutants (OPs) residues is commonly observed in diverse environmental settings, where their interactions can potentially alter the behavior, availability, and toxicity of OPs, thereby posing risks to ecosystems. Herein, we particularly emphasize the potential for bioaccumulation and the biomagnification effect of MPs in the presence of OPs within the food chain. Despite the ongoing influx of novel information, there exists a dearth of data concerning the destiny and consequences of MPs in the context of food pollution. Further endeavors are imperative to unravel the destiny and repercussions of MPs/OPs within food ecosystems and processing procedures, aiming to gain a deeper understanding of the joint effect on human health and food quality. Nevertheless, the adsorption and desorption behavior of coexisting pollutants can be significantly influenced by MPs forming biofilms within real-world environments, including temperature, pH, and food constituents. A considerable portion of MPs tend to accumulate in the epidermis of vegetables and fruits, thus necessitating further research to comprehend the potential ramifications of MPs on the infiltration behavior of OPs on agricultural product surfaces.

Meta-analysis for systematic review of global micro/nano-plastics contamination versus various freshwater microalgae: Toxicological effect patterns, taxon-specific response, and potential eco-risks

Micro/nano-plastics (MNPs), as emerging persistent pollutants, are threatening freshwater ecosystems worldwide. Microalgae are important primary producers at the base of trophic level and susceptible to MNPs contamination, possibly resulting in further contamination in higher trophic levels and water quality. This study conducted a systematic review of 1071 observations from 63 publications, utilizing meta-analysis and subgroup analysis to investigate the toxicological effect patterns of MNPs parameters (size, concentration, and type) on microalgae. We also explored the potential eco-risks of certain specific MNPs parameters and subtle variations in the response of various microalgae taxa to MNPs. Results suggested that microplastics significantly inhibited microalgal photosynthesis, while nano-plastics induced more severe cell membrane damage and promoted toxin-release. Within a certain range of concentrations (0∼50 mg/L), rising MNPs concentration progressively inhibited microalgal growth and chlorophyll-a content, and progressively enhanced toxin-release. Among MNPs types, polyamide caused higher growth inhibition and more severe lipid peroxidation, and polystyrene induced more toxin-release, whereas polyethylene terephthalate and polymethyl methacrylate posed minimal effects on microalgae. Moreover, Bacillariophyta growth was inhibited most significantly, while Chlorophyta displayed strong tolerance and Cyanophyta possessed strong adaptive and exceptional resilience. Particularly, Komvophoron, Microcystis, Nostoc, Scenedesmus, and Gomphonema were more tolerant and might dominate freshwater microalgal communities under MNPs contamination. These results are crucial for acquiring the fate of freshwater microalgae under various MNPs contamination, identifying dominant microalgae, and reasonably assessing and managing involved eco-risks.

Comparative analysis of the effects of microplastics and nitrogen on maize and wheat: Growth, redox homeostasis, photosynthesis, and AsA-GSH cycle

Microplastics (MPs) pose a significant threat to the function of agro-ecosystems. At present, research on MPs has mainly focused on the effects of different concentrations or types of MPs on a crop, while ignoring other environmental factors. In agricultural production, the application of nitrogen (N) fertilizer is an important means to maintain the high yield of crops. The effects of MPs and N on growth parameters, photosynthetic system, active oxygen metabolism, nutrient content, and ascorbate-glutathione (AsA-GSH) cycle of maize and wheat were studied in order to explicit whether N addition could effectively alleviate the effects of MPs on maize and wheat. The results showed that MPs inhibited the plant height of both maize and wheat, and MPs effects on physiological traits of maize were more severe than those of wheat, reflecting in reactive oxygen metabolism and restriction of photosynthetic capacity. Under the condition of N supply, AsA-GSH cycle of two plants has different response strategies to MPs: Maize promoted enzyme activity and co-accumulation of AsA and GSH, while wheat tended to consume AsA and accumulate GSH. N application induced slight oxidative stress on maize, which was manifested as an increase in hydrogen peroxide and malonaldehyde contents, and activities of polyphenol oxidase and peroxidase. The antioxidant capacity of maize treated with the combination of MPs + N was better than that treated with N or MPs alone. N could effectively alleviate the adverse effects of MPs on wheat by improving the antioxidant capacity.

Role of UV radiation and oxidation on polyethylene micro- and nanoplastics: impacts on cadmium sorption, bioaccumulation, and toxicity in fish intestinal cells

This study investigated the role of ultraviolet (UV) radiation and oxidation in high-density polyethylene microplastics (2-15 μm) and nanoplastics (0.2-9.9 μm) (NMPs) on particle chemistry, morphology, and reactivity with cadmium (Cd). Additionally, toxicity of NMPs alone and with Cd was evaluated using RTgutGC cells, a model of the rainbow trout (Oncorhynchus mykiss) intestine. The role on NMPs on Cd bioaccumulation in RTgutGC cells was also evaluated. Dynamic light scattering indicated that after UV radiation NPs agglomerated size increased from 0.8 to 28 µm, and to 8 µm when Cd was added. Oxidized MPs agglomerated size increased from 11 and 7 to 46 and 27 µm in non-UV- and UV-aged oxidized MPs when adding Cd, respectively. Cd-coated particles exhibited generally significantly higher zeta potential than non-Cd-coated particles, while attenuated total reflectance-Fourier transform infrared spectroscopy showed that the functional chemistry of the particles was oxidized and modified after being exposed to UV radiation. Presence of NMPs resulted in a significant decrease in Cd bioaccumulation in RTgutGC cells (100.5-87.9 ng Cd/mg protein) compared to Cd alone (138.1 ng Cd/mg protein), although this was not quite significant for co-exposures with UV-aged NPs (105.7 ng Cd/mg protein). No toxicity was observed in RTgutGC cells exposed to NMPs alone for 24 h. Moreover, co-exposures with Cd indicated that NMPs reduce the toxicity of Cd. Altogether these results show that UV aging enhances NMP surface reactivity, increasing Cd absorption in solution, which resulted in a reduction in Cd bioavailability and toxicity.

Comparative impact of pristine and aged microplastics with triclosan on lipid metabolism in larval zebrafish: Unveiling the regulatory role of miR-217

The prevalence of microplastics (MPs), especially aged particles, interacting with contaminants like triclosan (TCS), raises concerns about their toxicological effects on aquatic life. This study focused on the impact of aged polyamide (APA) MPs and TCS on zebrafish lipid metabolism. APA MPs, with rougher surfaces and lower hydrophobicity, exhibited reduced TCS adsorption than unaged polyamide (PA) MPs. Co-exposure to PA/APA MPs and TCS resulted in higher TCS accumulation in zebrafish larvae, notably more with PA than APA. Larvae exposed to PA + TCS exhibited greater oxidative stress, disrupted lipid metabolism, and altered insulin pathway genes than those exposed to TCS. However, these negative effects were lessened in the APA + TCS group. Through miRNA-seq and miR-217 microinjection, it was revealed that PA + TCS co-exposure upregulated miR-217, linked to lipid metabolic disorders in zebrafish. Moreover, molecular docking showed stable interactions formed between PA, TCS, and the insulin signaling protein Pik3r2. This study demonstrated that PA and TCS co-exposure significantly inhibited the insulin signaling in zebrafish, triggering lipid metabolism dysregulation mediated by miR-217 upregulation, while APA and TCS co-exposure alleviated these disruptions. This research underscored the ecological and toxicological risks of aged MPs and pollutants in aquatic environments, providing crucial insights into the wider implications of MPs pollution.

Effects of micro- and nano-plastics on growth, antioxidant system, DMS, and DMSP production in Emiliania huxleyi

Due to the potential impacts of microplastics (MPs) and nanoplastics (NPs) on algal growth and thereby affect the climate-relevant substances, dimethylsulfoniopropionate (DMSP) and dimethyl sulfide (DMS), we studied the polystyrene (PS) MPs and NPs of 1 μm and 80 nm impacts on the growth, chlorophyll content, reactive oxygen species (ROS), antioxidant enzyme activity, and DMS/DMSP production in Emiliania huxleyi. E. huxleyi is a prominent oceanic alga that plays a key role in DMS and DMSP production. The results revealed that high concentrations of MPs and NPs inhibited the growth, carotenoid (Car), and Chl a concentrations of E. huxleyi. However, short-time exposure to low concentrations of PS MPs and NPs stimulated the growth of E. huxleyi. Furthermore, high concentrations of MPs and NPs resulted in an increase in the superoxide anion radical (O2.-) production rate and a decrease in the malondialdehyde (MDA) content compared with the low concentrations. Exposure to MPs and NPs at 5 mg L-1 induced superoxide dismutase (SOD) activity as a response to scavenging ROS. High concentrations of MPs and NPs significantly inhibited the production of DMSP and DMS. The findings of this study support the potential ecotoxicological impacts of MPs and NPs on algal growth, antioxidant system, and dimethylated sulfur compounds production, which maybe potentially impact the global climate.

Mechanism of microplastics effects on the purification of heavy metals in piggery effluents by microalgae

Microalgae is an effective bioremediation technique employed for treating piggery effluent. However, there is insufficient study on how the presence of microplastics (MPs) in wastewater affects the ability of microalgae to remove heavy metals from piggery effluent. This study aims to investigate the influence of two prevalent heavy metals found in piggery wastewater, Cu2+ (2 mg/L) and Zn2+ (2 mg/L), on their removal by microalgae (Desmodesmus sp. CHX1) in the presence of four types of MPs: polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene terephthalate (PET). The results revealed that smaller particle size MPs promoted chlorophyll accumulation, while larger particles inhibits it. Additionally, higher concentrations of MPs promoted chlorophyll accumulation, while lower concentrations inhibited it. As for heavy metals, the presence of microplastics reduced the removal efficiency of Cu2+ and Zn2+ by Desmodesmus sp. CHX1. The highest inhibition of Cu2+ was 30%, 10%, 19%, and 16% of the control (CK), and the inhibition of Zn2+ was 7%, 4%, 4%, and 13%, respectively, under the treatments of PE, PVC, PP and PET MPs. Furthermore, Desmodesmus sp. CHX1 can secrete more extracellular polymeric substances (EPS) and form heterogeneous aggregates with MPs to counteract their pressure. These findings elucidate the impact of MPs on microalgae in bioremediation settings and offer useful insights into the complex relationships between microalgae, MPs, and heavy metals in the environment.

Phthalocyanine blue leaching and exposure effects on Microcystis aeruginosa (cyanobacteria) of photoaged microplastics

Light-stabilizing additives may contribute to the overall pollution load of microplastics (MPs) and potentially enter the food chain, severely threatening aquatic life and human health. This study investigated the variation between polystyrene (PS) MPs and phthalocyanine blue (CuPC)-containing MPs before and after photoaging, as well as their effects on Microcystis aeruginosa. The presence of PS-MPs increased cell mortality, antioxidant enzyme activity, and the variation in extracellular components, while the presence of CuPC exacerbated these variations. CuPC-containing MPs caused different increasing trends in superoxide dismutase and malondialdehyde activities due to electron transfer across the membrane. Transcriptomic analysis revealed that the MPs and CuPC affected various cellular processes, with the greatest impact being on cell membranes. Compared with MPs, CuPC negatively affected ribosome and polysaccharide formation. These findings provide insights into the molecular mechanisms underlying the cellular response to MPs and their associated light-stabilizer pollution and imply the necessity for mitigating the pollution of both MPs and light-stabilizers.