Nanoplastics exposure modulate lipid and pigment compositions in diatoms

A review on algal biomass dewatering and recovery of microalgal-based valuable products with different membrane technologies

Efficient microalgae harvesting and dewatering are critical processes for a range of applications, including the production of raw materials, nutritional supplements, pharmaceuticals, sustainable biofuels, and wastewater treatment. The optimization of these processes poses significant challenges due to the need for high efficiency and sustainability while managing costs and energy consumption. This review comprehensively addresses these challenges by focusing on the development and application of various membrane filtration technologies specifically designed for the effective harvesting and dewatering of algal biomass. Membrane filtration has emerged as a predominant method due to its ability to handle large volumes of microalgae with relatively low energy requirements. This review systematically examines the different membrane-based technologies and their effectiveness in recovering valuable components from algal biomass, such as lipids, proteins, and carbohydrates. The discussion begins with an overview of the physical characteristics of microalgae and their cultivation conditions, which are critical for understanding how these factors influence the performance of membrane filtration processes. Key aspects such as the features of algal cells, the presence of algal organic matter, and transparent exopolymer particles are explored in detail. The review also delves into various strategies for improving membrane antifouling properties, which are essential for maintaining the efficiency and longevity of the filtration systems. In addition, the advantages and disadvantages of different membrane techniques are reviewed, highlighting their respective performance in separating microalgae and dewatering. Finally, the review offers insights into future research directions and technological advancements that could further enhance the efficiency and sustainability of microalgae processing. This comprehensive evaluation aims to provide a thorough understanding of current membrane technologies, their applications, and the ongoing developments necessary to overcome existing limitations and improve overall process performance.

Zooming in the plastisphere: the ecological interface for phytoplankton-plastic interactions in aquatic ecosystems

Phytoplankton is an essential resource in aquatic ecosystems, situated at the base of aquatic food webs. Plastic pollution can impact these organisms, potentially affecting the functioning of aquatic ecosystems. The interaction between plastics and phytoplankton is multifaceted: while microplastics can exert toxic effects on phytoplankton, plastics can also act as a substrate for colonisation. By reviewing the existing literature, this study aims to address pivotal questions concerning the intricate interplay among plastics and phytoplankton/phytobenthos and analyse impacts on fundamental ecosystem processes (e.g. primary production, nutrient cycling). This investigation spans both marine and freshwater ecosystems, examining diverse organisational levels from subcellular processes to entire ecosystems. The diverse chemical composition of plastics, along with their variable properties and role in forming the "plastisphere", underscores the complexity of their influences on aquatic environments. Morphological changes, alterations in metabolic processes, defence and stress responses, including homoaggregation and extracellular polysaccharide biosynthesis, represent adaptive strategies employed by phytoplankton to cope with plastic-induced stress. Plastics also serve as potential habitats for harmful algae and invasive species, thereby influencing biodiversity and environmental conditions. Processes affected by phytoplankton-plastic interaction can have cascading effects throughout the aquatic food web via altered bottom-up and top-down processes. This review emphasises that our understanding of how these multiple interactions compare in impact on natural processes is far from complete, and uncertainty persists regarding whether they drive significant alterations in ecological variables. A lack of comprehensive investigation poses a risk of overlooking fundamental aspects in addressing the environmental challenges associated with widespread plastic pollution.

Plant and algal lipidomes: Analysis, composition, and their societal significance

Plants and algae play a crucial role in the earth's ecosystems. Through photosynthesis they convert light energy into chemical energy, capture CO2 and produce oxygen and energy-rich organic compounds. Photosynthetic organisms are primary producers and synthesize the essential omega 3 and omega 6 fatty acids. They have also unique and highly diverse complex lipids, such as glycolipids, phospholipids, triglycerides, sphingolipids and phytosterols, with nutritional and health benefits. Plant and algal lipids are useful in food, feed, nutraceutical, cosmeceutical and pharmaceutical industries but also for green chemistry and bioenergy. The analysis of plant and algal lipidomes represents a significant challenge due to the intricate and diverse nature of their composition, as well as their plasticity under changing environmental conditions. Optimization of analytical tools is crucial for an in-depth exploration of the lipidome of plants and algae. This review highlights how lipidomics analytical tools can be used to establish a complete mapping of plant and algal lipidomes. Acquiring this knowledge will pave the way for the use of plants and algae as sources of tailored lipids for both industrial and environmental applications. This aligns with the main challenges for society, upholding the natural resources of our planet and respecting their limits.

Exploring polystyrene weathering behavior: From surface traits to micro(nano)plastics and additives release

Plastic weathering in the natural environment is a dynamic and complex process, where the release of microplastics, nanoplastics and additives poses potential threats to ecosystems. Understanding the release of different weathering products from plastics is crucial for predicting and assessing the environmental hazards of plastics. This study systematically explored these phenomena by exposing polystyrene (PS) to UV irradiation and mechanical agitation for different durations (1 day, 5 days, 10 days, 20 days). The degree of aging, yellowing, brittleness, and the abundance of carbonyl (CO) functional groups in PS were all gradually increasing over time. The weathering pattern of PS surfaces manifested as initial particle oxidation followed by later cracks or flakes formation. The release of products was positively correlated with the aging degree of plastics, as well as among the various released products. Laser infrared and Raman tests indicated that, for microplastics, the size range of 10-20 μm consistently dominated over time, while the primary size range of nanoplastics shifted towards smaller sizes. Additives and other soluble products were prone to release from weathering plastics, with 20 different chemicals detected after 20 d. The release of plastic additives was closely related to aging time, additive type, and quantity. This study contributes to our understanding of the weathering process of plastics, clarifies the release patterns of products over time, and the relationships among different products. It helps predict and assess the environmental pollution caused by plastics.

The interfacial interaction between typical microplastics and Pb2+ and their combined toxicity to Chlorella pyrenoidosa

Microplastics (MPs), a new type of pollutant, have attracted much attention worldwide. MPs are often complexed with other pollutants such as heavy metals, resulting in combined toxicity to organisms in the environment. Studies on the combined toxicity of MPs and heavy metals have usually focused on the marine, while on the freshwater are lacking. In order to understand the combined toxic effects of MPs and heavy metals in the freshwater, five typical MPs (PVC, PE, PP, PS, PET) were selected to investigate the adsorption characteristics of MPs to Pb2+ before and after the MPs aging by ultraviolet (UV) irradiation through static adsorption tests. The results showed that UV aging enhanced adsorption of Pb2+ by MPs. It is noteworthy that MPs-PET had the highest adsorption capacity for Pb2+, and the interaction between MPs-PET and Pb2+ was the strongest. We specifically selected MPs-PET to study its combined toxicity with Pb2+ to Chlorella pyrenoidosa. In the combined toxicity test, MPs-PET and Pb2+ had significant toxic effects on Chlorella pyrenoidosa in the individual exposure, and the toxicity of individual Pb2+ exposure was greater than that of individual MPs-PET exposure. In the combined exposure, when MPs-PET and Pb2+ without adsorption (MPs-PET/Pb2+), MPs-PET and Pb2+ had a synergistic effect, which would produce strong physical and chemical stress on Chlorella pyrenoidosa simultaneously, and the toxic effect was the most significant. After the adsorption of MPs-PET and Pb2+ (MPs-PET@Pb2+), the concentration and activity of Pb2+ decreased due to the adsorption and fixation of MPs-PET, and the chemical stress on Chlorella pyrenoidosa was reduced, but the physical stress of MPs-PET still existed and posed a serious threat to the survival of Chlorella pyrenoidosa. This study has provided a theoretical basis for further assessment of the potential environmental risks of MPs in combination with other pollutants such as heavy metals.

Impact of polystyrene microplastics on the growth and photosynthetic efficiency of diatom Chaetoceros neogracile

The increasing prevalence of microplastic pollution in aquatic environments has raised concerns about its impact on marine life. Among the different types of microplastics, polystyrene microplastics (PSMPs) are one of the most commonly detected in aquatic systems. Chaetoceros neogracile (diatom) is an essential part of the marine food web and plays a critical role in nutrient cycling. This study aimed to monitor the ecotoxicological impact of PSMPs on diatoms and observe enzymatic interactions through molecular docking simulations. Results showed that diatom growth decreased with increasing concentrations and exposure time to PSMPs, and the lowest photosynthetic efficiency (Fv/Fm) value was observed after 72 and 96 h of exposure to 200 mg L-1 of PSMPs. High concentrations of PSMPs led to a decrease in chlorophyll a content (up to 64.4%) and protein content (up to 35.5%). Molecular docking simulations revealed potential interactions between PSMPs and the extrinsic protein in photosystem II protein of diatoms, suggesting a strong affinity between the two. These findings indicate a detrimental effect of PSMPs on the growth and photosynthetic efficiency of diatoms and highlight the need for further research on the impact of microplastics on marine microbial processes.

Mediator subunit MED8 interacts with heat shock transcription factor HSF3 to promote fucoxanthin synthesis in the diatom Phaeodactylum tricornutum

Fucoxanthin, a natural carotenoid that has substantial pharmaceutical value due to its anticancer, antioxidant, antiobesity, and antidiabetic properties, is biosynthesized from glyceraldehyde-3-phosphate (G3P) via a series of enzymatic reactions. However, our understanding of the transcriptional mechanisms involved in fucoxanthin biosynthesis remains limited. Using reverse genetics, the med8 mutant was identified based on its phenotype of reduced fucoxanthin content, and the biological functions of MED8 in fucoxanthin synthesis were characterized using approaches such as gene expression, protein subcellular localization, protein-protein interaction and chromatin immunoprecipitation assay. Gene-editing mutants of MED8 exhibited decreased fucoxanthin content as well as reduced expression levels of six key genes involved in fucoxanthin synthesis, namely DXS, PSY1, ZDS-like, CRTISO5, ZEP1, and ZEP3, when compared to the wild-type (WT) strain. Furthermore, we showed that MED8 interacts with HSF3, and genetic analysis revealed their shared involvement in the genetic pathway governing fucoxanthin synthesis. Additionally, HSF3 was required for MED8 association with the promoters of the six fucoxanthin synthesis genes. In conclusion, MED8 and HSF3 are involved in fucoxanthin synthesis by modulating the expression of the fucoxanthin synthesis genes. Our results increase the understanding of the molecular regulation mechanisms underlying fucoxanthin synthesis in the diatom P. tricornutum.

Effects of polyethylene terephthalate microplastics on cell growth, intracellular products and oxidative stress of Scenedesmus sp

Polyethylene terephthalate (PET) has been widely utilized in the synthesis of textile materials and packaging of foods and beverages. In recent years, it has been commonly detected in the form of microplastics (MPs) in wastewater. However, the effects of PET MPs on microalgal intracellular products and their interrelationships have been poorly investigated. In this study, the microalgae Scenedesmus sp. Strain H-1 was exposed to PET MPs to explore their effects on the growth, intracellular products (such as lipids, carbohydrates, and proteins), and antioxidative defense systems of Scenedesmus sp. The results demonstrated that PET MPs significantly reduced Scenedesmus sp. cell growth, with a maximum inhibition rate of 38.25% in the 500 mg L-1 treatment group. PET MPs had negative effects on glucose and nitrate utilization rates and reduced intracellular carbohydrates, intracellular proteins, and photosynthetic pigments. Surprisingly, PET MPs reduced acetyl-CoA carboxylase activity but induced lipid accumulation in microalgae. In addition, PET MPs significantly decreased the essential linoleic acid concentration and increased the palmitic acid content, resulting in reduced biodiesel quality. PET MPs induced the production of reactive oxygen species and malondialdehyde as well as the activities of superoxide dismutase and catalase. The results of the PCA indicated that the response mechanism of Scenedesmus sp. to PET MPs exposure was synergistic. This study provides fundamental data on the impact of MPs on the intracellular products of microalgae.

The co-presence of polystyrene nanoplastics and ofloxacin demonstrates combined effects on the structure, assembly, and metabolic activities of marine microbial community

Nanoplastic is increasing in environments and can address toxic effects on various organisms. Particle size, concentration, and surface functionalization most influence nanoplastic toxicity. Besides, nanoplastic can adsorb other contaminants (e.g., antibiotics) to aggravate its adverse effects. The combined effects of nanoplastics and antibiotics on planktonic/benthic microbial communities, however, are still largely unknown. In this study, the combined effects of polystyrene nanoplastic and ofloxacin on the structure, assembly, and metabolic activities of marine microbial communities were investigated based on amplicon sequencing data. The results mainly demonstrate that: (1) nanoplastic and ofloxacin have greater impacts on prokaryotic communities than eukaryotic ones; (2) niche breadths of planktonic prokaryotes and benthic eukaryotes were shrank with both high nanoplastic and ofloxacin concentrations; (3) increased ofloxacin mainly reduces nodes/edges of co-occurrence networks, while nanoplastic centralizes network modularity; (4) increased nanoplastic under high ofloxacin concentration induces more differential prokaryotic pathways in planktonic communities, while benthic communities are less influenced. The present work indicates that co-presence of nanoplastics and ofloxacin has synergistic combined effects on community structure shifts, niche breadth shrinking, network simplifying, and differential prokaryotic pathways inducing in marine microbial communities, suggesting nanoplastics and its combined impacts with other pollutions should be paid with more concerns.

Rethinking the effects of micro/nanoplastics from the global environmental change and systematic perspective: An aquatic environmental system-based comprehensive assessment approach of micro/nanoplastic impacts

The study on micro/nanoplastic pollution should embrace complexity. Here, we aim to develop an aquatic environmental system-based comprehensive assessment approach of micro/nanoplastic impacts (ACAM) to evaluate the effects of micro/nanoplastics on aquatic ecosystems from the global environmental change (GEC) and systematic perspective. A case study for freshwater systems in Saskatchewan, Canada was conducted to evaluate the comprehensive effects of multiple GEC factors (polystyrene-nanoplastics (PS-NPs), N, P, salinity, dissolved organic matter (DOM), pH, hardness) on Asterococcus superbus based on ten ecologically relevant endpoints. It is found that at the cellular level, PS-NPs and N had an antagonistic interaction on microalgal growth in the Saskatchewan freshwater ecosystem; at the molecular level, the PS-NP-induced changes in lipid composition in microalgae were regulated by P, DOM, and pH. The significance ranking of factor effects suggested that instead of PS-NPs pollution, the fluctuations in pH level, DOM and N concentrations should be paid attention to first in Saskatchewan. Under the combined impact of PS-NPs and other GEC factors, microalgae at station 14 (Qu'Appelle River near highway 56) might have the minimum growth rate with [-0.048, 0.094] d-1 in Saskatchewan. These findings demonstrate the efficacy of the developed ACAM in a more comprehensive and context-specific assessment of MNP risks, providing new insight for the management of MNP pollution.

Toxicity of nanoplastics to aquatic organisms: Genotoxicity, cytotoxicity, individual level and beyond individual level

Due to the small size, high mobility and large surface area, nanoplastics (NPs) showed high potential risks to aquatic organisms. This paper reviews the toxicity of NPs to aquatic organism at various trophic levels including bacteria, plankton (algae), zooplankton, benthos, and nekton (fish). The effects at individual level caused by NPs were explained and proved by cytotoxicity and genotoxicity, and the toxicity of NPs beyond individual level was also illustrated. The toxicity of NPs is determined by the size, dosage, and surface property of NPs, as well as environmental factors, the presence of co-contaminants and the sensitivity of tested organisms. Furthermore, the joint effects of NPs with other commonly detected pollutants such as organic pollutants, metals, and nanoparticles etc. were summarized. In order to reflect the toxicity of NPs in the real natural environment, studies on toxicity assessment of NPs with the coexistence of various environmental factors and contaminants, particularly under the concentrations in natural environment are suggested.

PFOS Induces Lipometabolism Change, Immune Defense, and Endocrine Disorders in Black-Spotted Frogs: Application of Transcriptome Profiling

Amphibian population declines are closely linked to increasingly serious environmental pollution. Field investigations revealed that perfluorooctane sulfonic acid (PFOS) distribution was detected in 100% of amphibians. In the present study, global transcriptome sequencing was determined on black-spotted frogs to quantify transcript expression levels and the development of an adverse outcome pathway for PFOS. A total of 1441 differentially expressed genes were identified in the PFOS exposure for 21 d, with 645 being downregulated and 796 upregulated. The gene functions and pathways for lipid metabolism, endocrine system, and immune defense were enriched. An adverse outcome pathway has been proposed, including PPAR (peroxisome proliferator-activated receptors) as the molecular initiating events; followed by changes in lipid metabolism, endocrine system, and immune defense; with an end result of liver damage or even population decline. This research provides molecular insight into the toxicity of PFOS. More research about differentially expressed genes is warranted to further provide the underlying mechanism that is altered as a result of PFOS toxicity in organisms.

Enhanced triacyclglycerols and starch synthesis in Chlamydomonas stimulated by the engineered biodegradable nanoparticles

Microalgae are promising feedstock for renewable fuels. The accumulation of oils in microalgae can be enhanced by nanoparticle exposure. However, the nanoparticles employed in previous studies are mostly non-biodegradable, which hinders nanoparticles developing as promising approach for biofuel production. We recently reported the engineered resin nanoparticles (iBCA-NPs), which were found to be biodegradable in this study. When the cells of green microalga Chlamydomonas reinhardtii were exposed to the iBCA-NPs for 1 h, the cellular triacyclglycerols (TAG) and starch contents increased by 520% and 60% than that in the control. The TAG production improved by 1.8-fold compared to the control without compromised starch production. Additionally, the content of total fatty acids increased by 1.3-fold than that in control. Furthermore, we found that the iBCA-NPs addition resulted in increased cellular reactive oxygen species (ROS) content and upregulated the activities of antioxidant enzymes. The relative expressions of the key genes involved in TAG and starch biosynthesis were also upregulated. Overall, our results showed that short exposure of the iBCA-NPs dramatically enhances TAG and starch accumulation in Chlamydomonas, which probably resulted from prompt upregulated expression of the key genes in lipid and starch metabolic pathways that were triggered by over-accumulated ROS. This study reported a useful approach to enhance energy-rich reserve accumulation in microalgae. KEY POINTS: 1. The first attempt to increase oil and starch in microalgae by biodegradable NPs. 2. The biodegradability of iBCA-NPs by the BOD test was more than 50% after 28 days. 3. The iBCA-NPs induce more energy reserves than that of previously reported NPs.

Self-Assembled Nanoscale Manganese Oxides Enhance Carbon Capture by Diatoms

Continuous CO₂ emissions from human activities increase atmospheric CO₂ concentrations and affect global climate change. The carbon storage capacity of the ocean is 20-fold higher than that of the land, and diatoms contribute to approximately 40% of carbon capture in the ocean. Manganese (Mn) is a major driver of marine phytoplankton growth and the marine carbon pump. Here, we discovered self-assembled manganese oxides (MnO_x) for CO₂ fixation in a diatom-based biohybrid system. MnO_x shared key features (e.g., di-μ-oxo-bridged Mn-Mn) with the Mn₄CaO₅ cluster of the biological catalyst in photosystem II and promoted photosynthesis and carbon capture by diatoms/MnO_x. The CO₂ capture capacity of diatoms/MnO_x was 1.5-fold higher than that of diatoms alone. Diatoms/MnO_x easily allocated carbon into proteins and lipids instead of carbohydrates. Metabolomics showed that the contents of several metabolites (e.g., lysine and inositol) were positively associated with increased CO₂ capture. Diatoms/MnO_x upregulated six genes encoding photosynthesis core proteins and a key rate-limiting enzyme (Rubisco, ribulose 1,5-bisphosphate carboxylase-oxygenase) in the Calvin-Benson-Bassham carbon assimilation cycle, revealing the link between MnO_x and photosynthesis. These findings provide a route for offsetting anthropogenic CO₂ emissions and inspiration for self-assembled biohybrid systems for carbon capture by marine phytoplankton.

An overview of the effects of nanoplastics on marine organisms

The ubiquity and detrimental effects of plastics in the environment have become global environmental concerns over the past decade. Intensive anthropogenic activities, such as urbanisation, industrialisation and increasing population density, have resulted in increased plastic pollution in the environment. Recently, nanoplastics have received increased research attention and concern because of their potential adverse effects on marine organisms. However, the potential ecological issues associated with nanoplastics are not yet fully understood because of the insufficient and limited research conducted to date on baseline data, exposure and associated risks for marine organisms. This review highlights an understanding of the nature and characteristics of nanoplastics, as well as the occurrence of nanoplastics in the marine environment. In the future, the effects of nanoplastics on marine organisms may directly or indirectly influence human health. Thus, this review also highlights the effects of nanoplastics on marine organisms. An overview and insights into the occurrence of nanoplastics in marine environments and their potential effects on marine organisms will facilitate the preventative interventions and measures of nanoplastics pollution in the marine environment.

Nanoplastic-Induced Nanostructural, Nanomechanical, and Antioxidant Response of Marine Diatom Cylindrotheca closterium

The aim of this study was to examine the effect of positively charged (amine-modified) and negatively charged (carboxyl-modified) polystyrene nanoplastics (PS NPs) on the nanostructural, nanomechanical, and antioxidant responses of the marine diatom Cylindrotheca closterium. The results showed that both types of PS NPs, regardless of surface charge, significantly inhibited the growth of C. closterium during short-term exposure (3 and 4 days). However, longer exposure (14 days) to both PS NPs types did not significantly inhibit growth, which might be related to the detoxifying effect of the microalgal extracellular polymers (EPS) and the higher cell abundance per PS NPs concentration. The exposure of C. closterium to both types of PS NPs at concentrations above the corresponding concentrations that resulted in a 50% reduction of growth (EC50) demonstrated phytotoxic effects, mainly due to the excessive production of reactive oxygen species, resulting in increased oxidative damage to lipids and changes to antioxidant enzyme activities. Diatoms exposed to nanoplastics also showed a significant decrease in cell wall rigidity, which could make the cells more vulnerable. Atomic force microscopy images showed that positively charged PS NPs were mainly adsorbed on the cell surface, while both types of PS NPs were incorporated into the EPS that serves to protect the cells. Since microalgal EPS are an important food source for phytoplankton grazers and higher trophic levels, the incorporation of NPs into the EPS and interactions with the cell walls themselves may pose a major threat to marine microalgae and higher trophic levels and, consequently, to the health and stability of the marine ecosystem.

Generation of micro(nano)plastics and migration of plastic additives from Poly(vinyl chloride) in water under radiation-free ambient conditions

A batch experiment was conducted to observe the liberation of micro- and nano-sized plastic particles and plastic additive-originated organic compounds from poly(vinyl chloride) under radiation-free ambient conditions. The weathering of PVC films in deionized water resulted in isolated pockets of surface erosion. Additional ^●OH from Fenton reaction enhanced PVC degradation and caused cavity erosion. The detachment of plastic fragments from the PVC film surfaces was driven by autocatalyzed oxidative degradation. Over 90% of micro-sized plastic particles were <60 μm in length. The detached plastic fragments underwent intensified weathering, which involved strong dehydrochlorination and oxidative degradation. Further fragmentation of micro-sized particles into nano-sized particles was driven by oxidative degradation with complete dehydrochlorination being achieved following formation of nanoplastics. 20 organic compounds released from the PVC films into the solutions were identified. And some of them can be clearly linked to common plastic additives. In the presence of additional ^●OH, the coarser nanoplastic particles (>500 nm) tended to be rapidly disintegrated into finer plastic particles (<500 nm), while the finest fraction of nanoplastics (<100 nm) could be completely decomposed and disappeared from the filtrates. The micro(nano)plastics generated from the PVC weathering were highly irregular in shape.

Polystyrene nanoplastics and wastewater displayed antagonistic toxic effects due to the sorption of wastewater micropollutants

The knowledge about the interaction of nanoplastics with other aquatic pollutants and their combined effects on biota is very scarce. In this work, we studied the interaction between polystyrene nanoplastics (PS NPs) (30 nm) and the micropollutants in a biologically treated wastewater effluent (WW). The capacity of PS NPs to sorb micropollutants was studied as well as their single and combined toxicity towards three freshwater organisms: the recombinant bioluminescent cyanobacterium, Anabaena sp. PCC 7120 CPB4337; the duckweed, Spirodela polyrhiza and the cladoceran, Daphnia magna. The endpoints were the inhibition of bioluminescence, the growth inhibition of the aquatic plant and the immobilization of D. magna after 24, 72 and 48 h of exposure, respectively. Combination Index (CI)-isobologram method was used to quantify mixture toxicity and the nature of interactions. PS NPs sorbed a variety of chemicals present in WW as micropollutants in a range of tens of ng/L to μg/L. It was found that those pollutants with positive charge were the main ones retained onto PS NPs, which was attributed to the electrostatic interaction with the negatively charged PS NPs. Regarding the toxicological effects, single exposure to PS NPs affected the three tested organisms. However, single exposure to WW only had a negative impact on the cyanobacterium and S. polyrhiza with no observed toxicity to D. magna. Regarding PS NPs-WW combined exposure, a reduction of toxicity in comparison with single exposure was observed probably due to the sorption of micropollutants onto PS NPs, which resulted in lower bioavailability of the micropollutants. In addition, the formation of PS NPs-WW heteroaggregates was observed which could result in lower bioavailability of PS NPs and sorbed micropollutants, thus lowering toxicity. This study represents a near-realistic scenario approach to the potential sorption of wastewater pollutants onto nanoplastics that could alter the toxicological effect on the biota.

Polystyrene nanoplastics impair the photosynthetic capacities of Symbiodiniaceae and promote coral bleaching

Reef-building corals are increasingly threatened by global and regional stresses, which affect the stability of the coral-Symbiodiniaceae association. Among them, plastic pollution has been an ongoing and growing concern. Whereas several studies have highlighted the detrimental impact of microplastics (0.1 μm-5 mm) on corals and their symbiotic dinoflagellate algae, the physiological changes induced by nanoplastic (NP, <0.1 μm) pollution are still poorly known. Long-term experiments (4 weeks) were conducted to investigate the effects of ecologically relevant NP concentrations (0 to 0.5 mg/L of 20 nm polystyrene NPs) on two Symbiodiniaceae in culture [CCMP2467 or Clade A1 and pd44b or Clade F1]. The effects of 0.5 mg/L NPs were also evaluated on Clade A1 living in symbiosis with the coral Stylophora pistillata, to assess the in hospite effects of NPs on coral symbionts. The photosynthetic efficiency of photosystem II, the oxidative status of the Symbiodiniaceae and the coral host, as well as the host-symbiont stability were evaluated at the end of the experiment. Symbiodiniaceae in culture exhibited a significant decrease in the maximal electron transport rate (ETR_max) at NP concentrations as low as 0.005 mg/L, highlighting an impairment of the photosynthetic capacities of the dinoflagellates in presence of nanoplastics. Also, Clade A1 exhibited a significant decrease in its Total Antioxidant Capacity (TAC) and an increase in Lipid Peroxidation (LPO), which evidence oxidative stress and cellular damage. Interestingly, Clade A1 in hospite did not show any signs of oxidative stress, however, the coral host exhibited increased TAC and LPO. Additionally, exposure of S. pistillata to 0.5 mg/L NPs induced significant bleaching (loss of symbionts and photosynthetic pigments). Overall, NPs were detrimental for both the Symbiodiniaceae in culture and the host-symbiont association. In the future, the persistence of reef corals may be severely impacted by the cumulative effects of nanoplastic pollution along with global warming.

Cell size matters: Nano- and micro-plastics preferentially drive declines of large marine phytoplankton due to co-aggregation

Marine plastic pollution represents a key environmental concern. Whilst ecotoxicological data for plastic is increasingly available, its impact upon marine phytoplankton remains unclear. Owing to their predicted abundance in the marine environment and likely interactions with phytoplankton, here we focus on the smaller fraction of plastic particles (~50 nm and ~2 µm polystyrene spheres). Exposure of natural phytoplankton communities and laboratory cultures revealed that plastic exposure does not follow traditional trends in ecotoxicological research, since large phytoplankton appear particularly susceptible towards plastics exposure despite their lower surface-to-volume ratios. Cell declines appear driven by hetero-aggregation and co-sedimentation of cells with plastic particles, recorded visually and demonstrated using confocal microscopy. As a consequence, plastic exposure also caused disruption to photosynthetic functioning, as determined by both photosynthetic efficiency and high throughput proteomics. Negative effects upon phytoplankton are recorded at concentrations orders of magnitude above those estimated in the environment. Hence, it is likely that impacts of NPs and MPs are exacerbated at the high concentrations typically used in ecotoxicological research (i.e., mg L-1).

Polystyrene nanoplastics change the functional traits of biofilm communities in freshwater environment revealed by GeoChip 5.0

There is an increasing concern regarding the potential effects of nanoplastics (NPs) on freshwater ecosystems. Considering the functional values of biofilms in freshwater, knowledge on whether and to what extent NPs can influence the ecosystem processes of biofilms were still limited. Herein, the freshwater biofilms cultured in lab were exposed to 100 nm polystyrene NPs (PS-NPs) of different dosages (1 and 10 mg/L) for 14 days. Confocal laser scanning microscope observation indicated that biofilms were dominated by filamentous, and spiral algae species and the intensity of extracellular polymeric substances increased under PS-NPs exposure. GeoChip 5.0 analysis revealed that PS-NPs exposure triggered a significant increase in functional genes α diversity (p < 0.05) and altered biofilms' functional structure. Furthermore, the abundance of genes involved in the total carbon and nitrogen cycling were increased under PS-NPs exposure. The abundance of nitrogen fixation genes experienced the most pronounced increase (24.4%) under 1 mg/L PS-NPs treatment, consistent with the increase of ammonium in overlying water. Whereas antibiotic resistance genes and those related to photosynthetic pigments production were suppressed. These results provided direct evidence for PS-NPs' effects on the biofilm functions in terms of biogeochemical cycling, improving our understanding of the potentials of NPs on freshwater ecosystems.

Suborganismal responses of the aquatic midge Chironomus riparius to polyethylene microplastics

Freshwater riverbeds are a major repository of microplastics (MPs) from inland activities. Benthic macroinvertebrates that live in close contact with sediments seem to ingest a considerable amount of such plastic particles. The effects of MPs on life-history traits are relatively well-known, but the suborganismal mechanisms underlying such effects remain unclear. This study addressed the potential effects of low-density polyethylene (LDPE) MPs on Chironomus riparius larvae at cellular and molecular levels. Fourth instar C. riparius larvae were exposed to 0.025 and 2.5 g/kg LDPE of dry sediment (sizes: <32 and 32-45 μm; with irregular shape) under laboratory conditions for 48 h. These short-term exposures to environmental concentrations of LDPE MPs induced changes in the energy reserves (mostly by decreasing carbohydrates and increasing lipids), increased antioxidant and detoxification responses (tGSH, CAT, and GST), and induced increases in the activity of AChE (related to neurotransmission). In addition, at the gene level, exposure to MPs modified mRNA levels of InR, Dis, EcR, Dronc, Met (endocrine system), Def (immune system), PARP, ATM, NLK, and Decay (DNA repair), generating important alterations in the C. riparius development and response to unfavorable situations. This study provides new evidence of the effects of LDPE MPs at the suborganismal level, filling the gap in knowledge regarding the mechanisms underlying the toxicity of MPs and spotlighting gene expression analyses as early indicators of MP toxicity in C. riparius which were confirmed by Integrated biomarker response analyses highlighting the gene expression as sensible and useful endpoints for LPDE pollution in freshwaters. These results, coupled with previous investigations on responses at the organismal level, emphasizes the potential adverse effects of LDPE MPs on C. riparius, which may compromise freshwater benthic communities, considering its ecological role within these habitats.

Microplastics and nanoplastics in the environment: Macroscopic transport and effects on creatures

Industrial progress has brought us an important polymer material, i.e. plastic. Because of mass production and use, and improper management and disposal, plastic pollution has become one of the most pivotal environmental issues in the world today. However, the current researches on microplastics/nanoplastics are mainly focused on individual aquatic, terrestrial and atmospheric environments, ignoring the fact that the natural environment is a whole. In this regard, the transport of microplastics/nanoplastics among the three environment compartments, including reciprocal contributions and inherent connections, and the impact of microplastics/nanoplastics on organisms living in multiple environments are research problems that we pay special attention to. Furthermore, this paper comprehensively reviews the transport and distribution of microplastics/nanoplastics in individual compartments and the toxicity of organisms, either alone or in combination with other pollutants. The properties of microplastics/nanoplastics, environment condition and the growth habit of organisms are critical to the transport, distribution and toxicity of microplastics/nanoplastics. These knowledge gaps need to be addressed urgently to improve cognition of the degree of plastic pollution and enhance our ability to deal with pollution. Meanwhile, it is hoped that the paper can provide a relatively complete theoretical knowledge system and multiple "leads" for future innovative ideas in this field.

Amino-nanopolystyrene exposures of oyster (Crassostrea gigas) embryos induced no apparent intergenerational effects

Early life stages (ELS) of numerous marine invertebrates mustcope with man-made contaminants, including plastic debris, during their pelagic phase. Among the diversity of plastic particles, nano-sized debris, known as nanoplastics, can induce effects with severe outcomes in ELS of various biological models, including the Pacific oyster Crassostrea gigas. Here, we investigated the effects of a sub-lethal dose (0.1 µg mL^-1) of 50 nm polystyrene nanobeads (nano-PS) with amine functions on oyster embryos (24 h exposure) and we assessed consequences on larval and adult performances over two generations of oysters. Only a few effects were observed. Lipid analyses revealed that first-generation (G1) embryos exposed to nano-PS displayed a relative increase in cardiolipin content (+9.7%), suggesting a potential modification of mitochondrial functioning. G1-larvae issued from exposed embryos showed decreases in larval growth (-9%) and lipid storage (-20%). No effect was observed at the G1 adult stage in terms of growth, ecophysiological parameters (clearance and respiration rates, absorption efficiency), or reproductive outputs (gonadic development, gamete quality). Second generation (G2) larvae issued from control G1 displayed a significant growth reduction after G2 embryonic exposure to nano-PS (-24%) compared to control (as observed at the first generation), while no intergenerational effect was detected on G2 larvae issued from G1 exposed embryos. Overall, the present experimental study suggests a low incidence of a short embryonic exposure to nano-PS on oyster phenotypes along the entire life cycle until the next larval generation.

Nanoplastics impact on marine biota: A review

Emerging contaminants, such as nanoplastics, are gaining a vast interest within the scientific community. Most of the plastic debris found in the marine environment originates from land-based sources, and once in the marine environment, plastic can be degraded into smaller fragments. Nanoplastics are considered to fall within the definition of other nanoparticles (1-100 nm in size) and may be divided into primary or secondary nanoplastics. Primary nanoplastics are those that enter the environment in their original small size associated with specific applications and consumer products, whilst secondary nanoplastics are a consequence of macro/microplastic degradation. The formation of nanoplastics changes the physical-chemical characteristics of the particle, thus at a nanoscale, it is expected that the strength, conductivity, and reactivity of the nanoparticles will differ substantially from macro/micro-sized particles. To date, the toxicity nanoplastics may pursue on marine biota is still scarce. Herein, a review of the available data on the effects of different polymer types of nanoplastics specific to marine biota is accounted for.

Effects of nanoplastics on energy metabolism in the oriental river prawn (Macrobrachium nipponense)

Nanoplastics are common pollutants in aquatic environments and have attracted widespread research attention. However, few studies focus on the effects of nanoplastic exposure on energy metabolism in crustaceans. Accordingly, we exposed juvenile oriental river prawns (Macrobrachium nipponense) to different concentrations of 75-nm polystyrene nanoplastics (0, 5, 10, 20, and 40 mg/L) for 7, 14, 21, or 28 days. Thereafter, the effects of nanoplastic exposure on metabolite content, energy metabolism-related enzyme activity, and gene expression were evaluated. Our results showed that (1) with increasing nanoplastic concentration and exposure time, the survival rate decreased, while weight gain rate and molting number increased and then decreased; glycogen, triglyceride, and total cholesterol content all declined while lactic acid content increased with higher exposure to nanoplastic concentrations; (2) the activities of acetyl-CoA carboxylase (ACC), hexokinase (HK), carnitine palmitoyl transferase-1, pyruvate kinase (PK), lipase, and fatty acid synthase tended to decrease, while the activity of lactate dehydrogenase (LDH) increased. In particular, the activity of 6-phosphofructokinase exposed to 5 mg/L nanoplastics increased significantly (P < 0.05). (3) Expression of the metabolism-related genes 6-phosphate glucokinase (G-6-Pase), HK, PK, ACC, Acetyl-CoA-binding protein (ACBP), CPT-1, and fatty-acid-binding protein 10 (FABP 10) increased and then decreased, while expression of the LDH gene showed an upward trend. These results indicate that nanoplastics affect growth, enzyme activity, and the gene expression of energy metabolism in M. nipponense, and that high concentrations of nanoplastics have a negative impact on energy metabolism.

Exposure of microalgae Euglena gracilis to polystyrene microbeads and cadmium: Perspective from the physiological and transcriptional responses

Micro(nano)plastics (MPs/NPs) are already present as contaminants in the natural environment globally and have been shown to be difficult to degrade, resulting in the potential for ecological damage and public health concerns. However, the adverse effects of exposure to MPs/NPs by aquatic organisms, especially freshwater microalgae, remains unclear. In the present study, the growth, physiology and transcriptome of the freshwater microalgae Euglena gracilis were comprehensively analyzed following exposure to 1 mg/L of polystyrene (PS) microbeads (5 μm PS-MPs and 100 nm PS-NPs), 0.5 mg/L cadmium (Cd), or a mixture of PS microbeads and Cd for 96 h. Results showed that the toxicity of PS-MPs to microalgae was greater than PS-NPs, inducing increased growth inhibition, oxidative damage and decreased photosynthesis pigment concentrations. PS-MPs alone or in combination with Cd caused cavitation within microalgal cells, as well as increasing the number and volume of vacuoles. The combined exposure toxicity test showed that a combination of Cd + PS-NPs was more toxic than Cd + PS-MPs, which may be explained by the transcriptomic analysis results. Differentially expressed genes (DEGs) in the Cd + PS-NPs group were mainly enriched in metabolism-related pathways, suggesting that algal metabolism was hindered, resulting in aggravation of toxicity. The reduced toxicity induced by Cd + PS-MPs may indicate a response to resist external stress processes. In addition, no adsorption of 0.5 mg/L Cd to 1 mg/L PS microbeads was observed, suggesting that adsorption of MPs/NPs and Cd was not the key factor determining the combined toxicity effects in this study.