Screening study of four environmentally relevant microplastic pollutants: Uptake and effects on Daphnia magna and Artemia franciscana

The comparative toxicity of biobased, modified biobased, biodegradable, and petrochemical-based microplastics on the brackish water flea Diaphanosoma celebensis

The escalating production and improper disposal of petrochemical-based plastics have led to a global pollution issue with microplastics (MPs), which pose a significant ecological threat. Biobased and biodegradable plastics are believed to mitigate plastic pollution. However, their environmental fate and toxicity remain poorly understood. This study compares the in vivo effects of different types of MPs, poly(butylene adipate-co-terephthalate) as a biodegradable plastic, polylactic acid (PLA) as a biobased plastic, β-cyclodextrin-grafted PLA as a modified biobased plastic, and low density polyethylene as the reference petrochemical-based plastic, on the key aquatic primary consumer Diaphanosoma celebensis. Exposure to MPs resulted in significant reproductive decline, with comparable effects observed irrespective of MP type or concentration. Exposure to MPs induced distinct responses in redox stress, with transcriptional profiling revealing differential gene expression patterns that indicate varied cellular responses to different types of MPs. ATP-binding cassette transporter activity assays demonstrated altered efflux activity, mainly in response to modified biobased and biodegradable MPs. Overall, this study highlights the comparable in vivo and in vitro effects of biobased, biodegradable, and petrochemical-based MPs on aquatic primary consumers, highlighting their potential ecological implications.

Confocal Surface-Enhanced Raman Imaging of the Intestinal Barrier Crossing Behavior of Model Nanoplastics in Daphnia Magna

Nanoplastics (nP) pose hazards to aquatic animals once they are ingested. Significant knowledge gaps exist regarding the nP translocation across the animal intestine, which is the first barrier between the ingested nP and the animal body. We examined the intestinal barrier crossing behavior of nP in an aquatic animal model (Daphnia magna) and determined the translocation mechanism with the help of model "core-shell" polystyrene nanoplastics (nPS) and confocal surface-enhanced Raman spectroscopy (SERS). The Raman reporter (4-mercaptobenzoic acid)-tagged gold "core" of the model nPS enables sensitive and reliable particle imaging by confocal SERS. This method detected SERS signals of model nPS concentration as low as 4.1 × 109 particles/L (equivalent to 0.27 μg/L PS "shell" concentration). The translocation was observed with the help of multilayer stacked Raman maps of SERS signals of the model nPS. With a higher concentration or longer exposure time of the model nPS, uptake and translocation of the plastic particles increased. In addition, we demonstrated that clathrin-dependent endocytosis and macropinocytosis were two major mechanisms underlying the translocation. This study contributes to a mechanistic understanding of nP translocation by using the pioneering model nPS and an analytical toolkit, which undergird further investigations into nP behavior and health effects in aquatic species.

Multi-level toxicity assessment of polylactic acid (PLA) microplastics on the cladoceran Daphnia magna

The accumulation of plastics waste in the environment has raised a worrisome concern, moving the society to seek out for sustainable solutions, such as the transition from the use of fossil-based, conventional plastics to bioplastics (BPs). However, once in the environment bioplastics have the same probability to accumulate and experience weathering processes than conventional plastics, leading to the formation of microplastics (MPs). However, to date the information on the potential toxicity of MPs originated from the weathering of bioplastics is limited. Thus, this study aimed at investigating the adverse effects induced by the exposure to MPs made of a bioplastic polymer, the polylactic acid (PLA), towards the freshwater cladoceran Daphnia magna. Organisms were exposed for 21 days to three concentrations (0.125 µg/mL, 1.25 µg/mL and 12.5 µg/mL) of PLA microplastics (hereafter PLA-MPs). A multi-level approach was performed to investigate the potential effects through the biological hierarchy, starting from the sub-individual up to the individual level. At the sub-individual level, changes in the oxidative status (i.e., the amount of reactive oxygen species and the activity of antioxidant and detoxifying enzymes) and oxidative damage (i.e., lipid peroxidation) were explored. Moreover, the total caloric content as well as the content of protein, carbohydrate and lipid content assess were used to investigate the effects on energy reserves. At individual level the changes in swimming activity (i.e., distance moved and swimming speed) were assessed. Our results showed that the exposure to PLA-MPs induced a slight modulation in the oxidative status and energy reserves, leading to an increase in swimming behavior of treated individuals compared to control conspecifics. These results suggest that the exposure to MPs made of a bioplastic polymer can induce adverse effects similar to those caused by conventional polymers.

Toxicity effects and mechanism of micro/nanoplastics and loaded conventional pollutants on zooplankton: An overview

Micro/nanoplastics in aquatic environments is a noteworthy environmental problem. Zooplankton, an important biological group in aquatic ecosystems, readily absorb micro/nanoplastics and produce a range of toxic endpoints due to their small size. This review summarises relevant studies on the effects of micro/nanoplastics on zooplankton, including combined effects with conventional pollutants. Frequently reported adverse effects include acute/chronic lethal effects, oxidative stress, gene expression, energetic homeostasis, and growth and reproduction. Obstruction by plastic entanglement and blockage is the physical mechanism. Genotoxicity and cytotoxicity are molecular mechanisms. Properties of micro/nanoplastics, octanol/water partition coefficients of conventional pollutants, species and intestinal environments are important factors influencing single and combined toxicity. Selecting a wider range of micro/nanoplastics, focusing on the aging process and conducting field studies, adopting diversified zooplankton models, and further advancing the study of mechanisms are the outstanding prospects for deeper understanding of impacts of micro/nanoplastics on aquatic ecosystem.

Do weathered microplastics impact the planktonic community? A mesocosm approach in the Baltic Sea

Microplastics (MPs) are ubiquitous pollutants of increasing concern in aquatic systems. However, little is still known about the impacts of weathered MPs on plankton at the community level after long-term exposure. In this study, we investigated the effects of weathered MPs on the structure and dynamics of a Baltic Sea planktonic community during ca. 5 weeks of exposure using a mesocosm approach (2 m3) mimicking natural conditions. MPs were obtained from micronized commercial materials of polyvinyl chloride, polypropylene, polystyrene, and polyamide (nylon) previously weathered by thermal ageing and sunlight exposure. The planktonic community was exposed to 2 μg L-1 and 2 mg L-1 of MPs corresponding to measured particle concentrations (10-120 μm) of 680 MPs L-1 and 680 MPs mL-1, respectively. The abundance and composition of all size classes and groups of plankton and chlorophyll concentrations were periodically analyzed throughout the experiment. The population dynamics of the studied groups showed some variations between treatments, with negative and positive effects of MPs exhibited depending on the group and exposure time. The abundance of heterotrophic bacteria, pico- and nanophytoplankton, cryptophytes, and ciliates was lower in the treatment with the higher MP concentration than in the control at the last weeks of the exposure. The chlorophyll concentration and the abundances of heterotrophic nanoflagellates, Astromoeba, dinoflagellate, diatom, and metazooplankton were not negatively affected by the exposure to MPs and, in some cases, some groups showed even higher abundances in the MP treatments. Despite these tendencies, statistical analyses indicate that in most cases there were no statistically significant differences between treatments over the exposure period, even at very high exposure concentrations. Our results show that weathered MPs of the studied conventional plastic materials have minimal or negligible impact on planktonic communities after long-term exposure to environmentally relevant concentrations.

Warming temperatures exacerbate effects of microplastics in a widespread zooplankton species

The emergence of microplastics as a global contaminant of concern has coincided with climate change induced temperature warming in aquatic ecosystems. Warmer temperatures have been previously demonstrated to increase the toxicity of certain contaminants, but it is currently unclear if microplastics are similarly affected by temperature. As aquatic organisms simultaneously face microplastic pollution and both increasing and variable temperatures, understanding how temperature affects microplastic toxicity is pertinent in this era of human-induced global change. In this study, we investigate the effects of environmentally relevant microplastic exposure to Daphnia pulex survival, reproduction, and growth at three different temperatures. To simulate an environmentally relevant exposure scenario, we created microplastics with physicochemical characteristics often detected in nature, and exposed organisms to concentrations close to values reported in inland waters and 1-2 orders of magnitude higher. The three temperatures tested in this experiment included 12 °C, 20 °C, and 24 °C, to simulate cool/springtime, current, and warming scenarios. We found the highest concentration of microplastics significantly impacted survival and total offspring compared to the control at 20 °C and 24 °C, but not at 12 °C. The adverse effect of high microplastic concentrations on total offspring at warmer temperatures was driven by the high mortality of the juveniles. We observed no effect of microplastics on time to first reproduction or average growth rate at any temperature. Warmer temperatures exacerbated microplastic toxicity, although only for concentrations of microplastics not currently observed in nature, but these concentrations are possible in pollution hotspots, through pulses pollution events or future worsening environmental contamination. The results of our study illustrate the continued need to further investigate climate change related co-stressors such as warming temperatures in microplastic and pollution ecology, through environmentally realistic exposure scenarios.

Ingestion and depuration of polyester microfibers by Crassostrea gasar (Adanson, 1757)

The study aimed to obtain environmentally relevant microfibers (MFs) from polyester fabric and assess their impact on the oyster Crassostrea gasar. MFs were obtained by grinding the fabric, and their accumulation in oysters gills and digestive glands was analyzed after exposure to 0.5 mg/L for 2 and 24 h. Additionally, a 48 h depuration was conducted on the oysters exposed for 24 h. Sublethal effects were assessed in oysters exposed for 24 h and depurated for 48 h, using biomarkers like Catalase (CAT), Glutathione S-transferase (GST), and Glutathione Peroxidase (GPx), along with histological analyses. Polyester fabric grinding produced significant MFs (average length: 570 μm) with degraded surface and increased malleability. Oysters showed increased MF accumulation in digestive glands post-exposure, with no impact on antioxidant enzymes. Depuration decreased MFs accumulation. Histological analysis revealed accumulation in the stomach and brown cells, possibly indicating inflammation. This raises concerns about MFs bioaccumulation in marine organisms, impacting the food chain and safety.

Effect of polystyrene nanoplastics exposure on gene expression and pathogenesis of zoonotic pathogen, Edwardsiella piscicida

A surge in the number of anthropogenic pollutants has been caused by increasing industrial activities. Nanoplastics are spotlighted as a new aquatic pollutant that are a threat to microbes and larger organisms. Our previous study showed that the subinhibitory concentrations of aquatic pollutants such as phenol and formalin act as signaling molecules and modulate global gene expression and metabolism. In this study, we aimed to investigate the impact of a new type of anthropogenic contaminant, polystyrene (PS) nanoplastics, on the expression of key virulence factors in zoonotic pathogen Edwardsiella piscicida and the assessment of potential changes in the susceptibility of zebrafish as a model host. The TEM data indicated a noticeable change in the cell membrane indicating that PS particles were possibly entering the bacterial cells. Transcriptome analyses performed to identify the differentially expressed genes upon PS exposure revealed that the genes involved in major virulence factor type VI secretion system (T6SS) were down-regulated. However, the expression of T6SS-related genes was recovered from the PS adapted E. piscicida when nanoplastics are free. This demonstrated the hypervirulence of pathogen in infection assays with both cell lines and in vivo zebrafish model. Therefore, this study provides experimental evidence elucidating the direct regulatory impact of nanoplastics influx into aquatic ecosystems on fish pathogenic bacteria, notably influencing the expression of virulence factors.

Microplastic ingestion in aquatic and soil biota: A comprehensive review of laboratory studies on edible size and intake pattern

Microplastic contamination is ubiquitous and can be transferred through the food chain to humans. However, studies on microplastic size have mainly focused on large animals with a body length >20 mm. To address this gap, we conducted a comprehensive review of 169 laboratory studies to determine the edible size of microplastics for macrofauna and flora in aquatic and soil biota. Our findings indicate that microplastics with a size of <300 μm and 1 μm, respectively, are edible for these organisms, which are positioned at the base of the food chain. We also analyzed intake and depuration patterns and identified factors affecting microplastic ingestion. Our study fills an important knowledge gap by identifying the range of microplastic sizes that can enter the food chain and be transferred to humans. The study findings have strong implications for the ecological risk assessment of microplastics and suggest a starting point for mitigating this threat.

Trophic transfer and their impact of microplastics on estuarine food chain model

Microplastic contamination in marine ecosystems, and its negative effects through trophic transfer among marine organisms, remains a growing concern. Our study investigates the trophic transfer and individual impacts of polystyrene microplastics (MPs) in an estuarine food chain model, comprising Artemia salina as primary organism, Litopenaeus vanamei as secondary organism, and Oreochromis niloticus as tertiary organism. A. salina were exposed to 1 µm polystyrene microplastics (106 particles/ml), further it was fed to L.vannamei, which, in turn, were fed to O.niloticus. MPs transfer was studied over 24 and 48 h. Fluorescence microscopy confirmed MPs presence in the gut and fecal matter of all the test organisms. Histopathology revealed MPs in the gut epithelium, but did not translocate to other tissues of the test species. MPs exposed A.salina had a bioconcentration factor of 0.0029 ± 0.0008 (24 h) and 0.0000941 ± 0.0000721 (48 h). Whereas, the bioaccumulation factor values for L. vanamei were 0.00012143 ± 0.000009 (24 h) and 0.0025899 ± 0.0024101 (48 h), and for O.niloticus were 0.154992 ± 0.007695 (24 h) and 0.00972577 ± 0.00589923 (48 h). Despite low MPs transfer among trophic levels, the induced stress was evident through biochemical responses in all the test species. This implies the potential risk of MPs ultimately reaching humans via the food chain.

No Effect of Realistic Concentrations of Polyester Microplastic Fibers on Freshwater Zooplankton Communities

Zooplankton are a conduit of energy from autotrophic phytoplankton to higher trophic levels, and they can be a primary point of entry of microplastics into the aquatic food chain. Investigating how zooplankton communities are affected by microplastic pollution is thus a key step toward understanding ecosystem-level effects of these global and ubiquitous contaminants. Although the number of studies investigating the biological effects of microplastics has grown exponentially in the last decade, the majority have used controlled laboratory experiments to quantify the impacts of microplastics on individual species. Given that all organisms live in multispecies communities in nature, we used an outdoor 1130-L mesocosm experiment to investigate the effects of microplastic exposure on natural assemblages of zooplankton. We endeavored to simulate an environmentally relevant exposure scenario by manually creating approximately 270 000 0.015 × 1- to 1.5-mm polyester fibers and inoculating mesocosms with zero, low (10 particles/L), and high (50 particles/L) concentrations. We recorded zooplankton abundance and community composition three times throughout the 12-week study. We found no effect of microplastics on zooplankton abundance, Shannon diversity, or Pielou's evenness. Nonmetric multidimensional scaling plots also revealed no effects of microplastics on zooplankton community composition. Our study provides a necessary and realistic baseline on which future studies can build. Because numerous other stressors faced by zooplankton (e.g., food limitation, eutrophication, warming temperatures, pesticides) are likely to exacerbate the effects of microplastics, we caution against concluding that polyester microfibers will always have no effect on zooplankton communities. Instead, we encourage future studies to investigate the triple threats of habitat degradation, climate warming, and microplastic pollution on zooplankton community health. Environ Toxicol Chem 2024;43:418-428. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Influence of synthetic and natural microfibers on the growth, substance exchange, energy accumulation, and oxidative stress of field-collected microalgae compared with microplastic fragment

Synthetic microfibers (MFs), which are Microplastics (MPs), have not received attention commensurate with their abundance in the environment. Currently, limited studies on MFs have focused on their effects on marine organisms. It is therefore necessary to conduct exposure experiments of MFs on freshwater organisms to provide reference data for the ecological risk assessment of MFs. As a primary producer in freshwater ecosystems, microalgae have an ecological niche that is highly overlapping with that of MFs. In this study, we examined the effects of MFs on the growth of Chlorella and indicators of oxidative stress to examine their potential risk on the microalgae population. The results showed that inhibition rate of microalgae increased with MF concentration in the range of 0.01-100 mg/L. Compared with natural fibers such as cotton and wool, PET and PP fibers showed significant growth inhibition, but less so when in fragment form with the same material and concentration. PP and PET particles, whether fibers or fragments, increased the total antioxidant capacity of microalgal cells and caused oxidative damage. To determine the influence of MFs on the interaction of cells in the environment, the exchanged substances and accumulated energy of microalgae cells were also detected. The results indicated that PP and PET fibers, as well as fragments, increased the diameter and membrane permeability of microalgae cell, thus interfering with the cell division and substance exchange processes. PET fibers and fragments showed different interactions at the level of individual cells and populations. This suggests that the evaluation of MPs should consider examinations from cells to population and even community levels in the future.

Microplastics affect interspecific interactions between cladoceran species in the absence and presence of predators by triggering asymmetric individual responses

Although many studies have reported the negative effects of microplastics on aquatic organisms, most research is focused on individual scales. Individual studies highlight harm mechanisms, but understanding broader ecological effects necessitates evidence from multiscale perspectives, particularly those based on interspecific interactions. Therefore, in this study, we investigated the impacts of different microplastic concentrations (0, 0.4, 2, and 10 mg/L) on individual characteristics (physiology, behavior, and grazing rate) and population dynamics of two cladoceran species Daphnia magna and Scapholeberis kingi, and their interrelationships within communities in the absence and presence of predators (larvae of Agriocnemis pygmaea). We used 32-38 μm polyethylene microplastics; these particles were detected in the guts of D. magna, especially at higher concentrations, but were not found in S. kingi. Consequently, with increasing microplastic concentrations, the grazing and reproductive capacity of D. magna diminished, weakening their dominance in the coexistence system without damselfly larvae. Additionally, as microplastic concentration increased, D. magna faced greater oxidative damage and a reduction in mobility, making this species more susceptible to predation by damselfly larvae and less dominant in the predator-inhabited coexistence system. This study reveals the mechanism by which asymmetric impacts of microplastics on individual traits altered interspecific competition between zooplankton species, thereby illuminating the role of microplastics in altering zooplankton communities.

Freshwater Lacustrine Zooplankton and Microplastic: An Issue to Be Still Explored

Lakes are essentially interlinked to humans as they provide water for drinking, agriculture, industrial and domestic purposes. The upsurge of plastic usage, its persistence, and potential detrimental effects on organisms cause impacts on the trophic food web of freshwater ecosystems; this issue, however, still needs to be explored. Zooplankton worldwide is commonly studied as an indicator of environmental risk in aquatic ecosystems for several pollutants. The aim of the review is to link the existing knowledge of microplastic pollution in zooplankton to assess the potential risks linked to these organisms which are at the first level of the lacustrine trophic web. A database search was conducted through the main databases to gather the relevant literature over the course of time. The sensitivity of zooplankton organisms is evident from laboratory studies, whereas several knowledge gaps exist in the understanding of mechanisms causing toxicity. This review also highlights insufficient data on field studies hampering the understanding of the pollution extent in lakes, as well as unclear trends on ecosystem-level cascading effects of microplastics (MPs) and mechanisms of toxicity (especially in combination with other pollutants). Therefore, this review provides insight into understanding the overlooked issues of microplastic in lake ecosystems to gain an accurate ecological risk assessment.

Natural infochemical DMSP stimulates the transfer of microplastics from freshwater zooplankton to fish: An olfactory trap

Natural infochemicals may largely affect the trophic transfer of microplastics (MPs) in ecosystems but such infochemical effect and mechanisms are poorly understood. Here, a daphnids-zebrafish freshwater microcosm was designed to elucidate whether and how an algae-derived infochemical, dimethylsulfoniopropionate (DMSP), affects the ingestion and transfer of MPs. Daphnids fast accumulated DMSP and MPs from water, and DMSP in daphnids was mainly enriched from the DMSP in water but not from MPs. DMSP did not change the MP ingestion by daphnids. A low concentration of DMSP (0.5 nM) increased predation of daphnids by zebrafish, while high concentrations of DMSP (50, 100 and 200 nM) did not increase predation rates. The concentration of DMSP in daphnids and the MP predation by zebrafish showed a unimodal relationship. The predation for MP by zebrafish in the 0.5 and 5 nM DMSP treatments was 1.89 and 1.56 times that of the control, respectively. The concentrations of DMSP in freshwater samples were lower than 50 nM. This suggests DMSP at environmentally relevant concentrations may promote the trophic transfer of MPs in freshwater ecosystems via olfactory traps.

Theoretical and experimental investigation on rapid and efficient adsorption characteristics of microplastics by magnetic sponge carbon

Microplastic pollution control has always been a thorny problem all over the world. Magnetic porous carbon materials have shown a good development prospect in microplastic adsorption due to their excellent adsorption performance and easy magnetic separation from water. However, the adsorption capacity and rate of magnetic porous carbon on microplastics are still not high, and the adsorption mechanism is not fully revealed, which hinders its further development. In this study, magnetic sponge carbon was prepared using glucosamine hydrochloride as the carbon source, melamine as the foaming agent, iron nitrate and cobalt nitrate as the magnetizing agents. Among them, Fe-doped magnetic sponge carbon (FeMSC) exhibited excellent adsorption performance for microplastics due to its sponge-like morphology (fluffy), strong magnetic properties (42 emu/g) and high Fe-loading (8.37 Atomic%). FeMSC could adsorb to saturation within 10 min, and the adsorption capacity of polystyrene (PS) reached as high as 369.07 mg/g in 200 mg/L microplastic solution, which was almost the fastest adsorption rate and highest adsorption capacity reported so far in the same condition. The performance of the material against external interference was also tested. FeMSC performed well in a wide pH range and different water quality, except in the strong alkaline condition. This is because the surface of microplastics and adsorbents will have many negative charges under strong alkalinity, significantly weakening the adsorption. Furthermore, theoretical calculations were innovatively used to reveal the adsorption mechanism at the molecular level. It was found that Fe-doping could form chemisorption between PS and the adsorbent, thereby significantly increasing the adsorption energy between the adsorbent and PS. The magnetic sponge carbon prepared in this study has excellent adsorption performance for microplastics and can be easily separated from water, which is a promising microplastic adsorbent.

Size-selective microplastic uptake by freshwater organisms: Fish, mussel, and zooplankton

Microplastics, as an emergent pollutant, have garnered substantial attention within aquatic environments, yet a significant knowledge gap persists regarding the interplay of organism size and pollution impacts on microplastic uptake in freshwater ecosystems. The main aim of the current study is to assess the microplastic ingestion by aquatic organisms across diverse trophic levels. To achieve this objective, zooplankton, mussels (Anodonta anatina), and fish (Carassius gibelio) were collected from the highly polluted Susurluk River Basin in Türkiye. The size distribution encompassed 160.8 ± 56.9 μm for the prevailing zooplankton, 6.9 ± 2.2 cm for mussel, and 20.4 ± 3.1 cm for fish, respectively. While no microplastic ingestion was observed among zooplankton, the finding highlights the influence of body-size and pollution on microplastic ingestion. In contrast, A. anatina and C. gibelio contained 617 and 792 microplastic particles, respectively. Predominantly, fibers emerged as the most prevalent microplastic type across trophic levels (except zooplankton) followed by films. Notably, only fish exhibited fragments within their gastrointestinal tract. A substantial correlation emerged between microplastic abundance and mussel size and weight, but no such correlation manifested for fish. The study also revealed a positive link between microplastic count and turbidity (phosphate and high Chl a level), impacting mussel ingestion capacity due to the variability in the food availability and potential shifts in feeding preferences. Conversely, no distinct pattern emerged for fish concerning water quality parameters and ingested microplastics. Consequently, our study underscores diverse microplastic uptake patterns in freshwater ecosystems, with a predominant frequency of microplastics falling with the 0.3 mm-3.0 mm range, emphasizing the significance of size-selective uptake by organisms.

Sublethal Effects of Polystyrene Nanoplastics on the Embryonic Development of Artemia salina (Linnaeus, 1758)

Currents, wave motion, solar radiation, and abrasion are mechanisms responsible for the degradation of large plastic artifacts and contribute to the dispersion of micro and nanoplastics into aquatic ecosystems, which are, currently, the most dangerous threats due to their invisibility and persistence. The present work evaluated the possible lethal and sublethal effects of amino-modified polystyrene nanoplastics (nPS-NH2) with diameters of 50 nm and 100 nm on Artemia salina (A. salina), an organism at the base of the trophic chain of the aquatic system, using a widely used model for the analysis of embryotoxicity from environmental pollutants. For this purpose, after evaluating the biodistribution of nanoplastics in the body of the tested animals, several endpoints such as anomalies, apoptosis, and ROS production were assessed. In addition, particular attention was dedicated to evaluating the correlation between toxicity and the particle size tested. The results reported that, despite the absence of a lethal impact, several sublethal effects involving gut and body size malformations, as well as the enhancement of apoptosis and oxidative stress in relation to an increase in tested concentration and a decrease in nanoparticle size.

Acute toxicity of tire wear particles and leachate to Daphnia magna

Tire wear particles (TWP) are a new pollutant widely present in the environment, and have been identified as microplastics (MPs), which are receiving increasing attention due to their toxic effects on aquatic organisms. In this study, D. magna was used as test organism, and the leachate from TWP was prepared by hot water extraction for 30 (30-E) and 120 min (120-E). The acute toxic effects of particles and leachate on D. magna were studied under different exposure concentrations. The results showed that zinc and pyrene were the highest detected contaminants in the leachate. The 48 h-LC50 values for particles and leachate were determined to be 56.99, 461.30 (30-E), and 153.00 mg/L (120-E), respectively. Following a 48 h exposure period, the immobilization of D. magna exposed to the particles and their leachate were increased with the concentration increase. The physical damage of the gut was found to be a possible mechanism for particle-induced biotoxicity. The compounds leached from TWP were responsible for the acute toxicity of leachate. Particles usually demonstrated a greater degree of toxicity in comparison to their leachate, especially at environmentally relevant concentrations. Exposure to particles and leachate resulted in the inhibition of swimming speed, swimming acceleration, filtration rate, and ingestion rate in D. magna. Furthermore, thoracic limb activity was observed to be inhibited. The heart rate of D. magna was significantly increased by the presence of particles at a concentration of 200 mg/L and leachate at concentrations of 400 and 800 mg/L (120-E). The observed alterations in behavior and physiological endpoints may be related to oxidative stress and neurotoxicity in the organism. Reduced superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) activities indicated that D. magna may suffer from excessive oxidative stress, whereas the increase of acetylcholinesterase (AChE) activity may serve as a biomarker of susceptibility to evaluate the environmental risks of TWP and corresponding leachates as potential aquatic pollutants.. Therefore, a more comprehensive risk assessment of TWP in the environment is necessary.

Adsorption behavior of triclosan on microplastics and their combined acute toxicity to D. magna

Microplastics (MP) have been recently identified as emerging water contaminants in worldwide. Owing to its physicochemical properties, MP have been considered as a vector of other micropollutants and may affect their fate and ecological toxicity in the water environment. In this study, triclosan (TCS), which is a widely-used bactericide, and three frequently found types of MP (PS-MP, PE-MP, and PP-MP) were investigated. The adsorption behavior of TCS on MP was investigated by the effect of reaction time, initial concentration of TCS, and other water chemistry factors. Elovich model and Temkin model are the most fitted well with kinetics and adsorption isotherms, respectively. The maximum TCS adsorption capacities were calculated for PS-MP (9.36 mg/g), PP-MP (8.23 mg/g), and PE-MP (6.47 mg/g). PS-MP had higher affinity to TCS owing to hydrophobic and π-π interaction. The TCS adsorption on PS-MP was inhibited by decreasing concentrations of cations, and increasing concentration of anion, pH, and NOM concentration. At pH 10, only 0.22 mg/g of adsorption capacity was obtained because of the isoelectric point (3.75) of PS-MP and pKa (7.9) of TCS. And almost no TCS adsorption occurred at NOM concentration of 11.8 mg/L. Only PS-MP had no acute toxic effect on D. magna, whereas TCS showed acute toxicity (EC_50,24h of TCS = 0.36 ± 0.4 mg/L). Although survival rate increased when TCS with PS-MP due to lower the TCS concentration in solution via adsorption, PS-MP was observed in intestine and body surface of D. magna. Our findings can contribute to understanding the combined potential effects of MP fragment and TCS to aquatic biota.

The genus Artemia, the nanoplastics, the microplastics, and their toxic effects: a review

Plastic pollution is a threat to the marine environment, the destination of mismanaged plastic. Due to reduced size, microplastics and nanoplastics (MNPs) can interact with a wide range of organisms. Non-selective filter feeder zooplanktonic microcrustaceans are potential targets for MNP accumulation. Zooplankton is a key group for the food web, linking primary producers to secondary consumers. The genus Artemia has been widely used to investigate the effects of plastic particles on the biota. The present work critically reviewed the ecotoxicological studies about plastic particles and Artemia, pointing out methodological aspects and effects caused by MNPs, highlighting their importance and limitations, and suggesting directions for future research. We analyzed twenty-one parameters into four categories: characteristics of plastic particles, general particularities of brine shrimp, methodologies of the cultures, and toxicological parameters. The principal gaps in the area are the lack of methodological standardization regarding the physicochemical parameters of the particles, the biology of the animals, and culture conditions. Even though few studies performed realistic exposure scenarios, results indicate MNPs as potential harmful contaminants to microcrustaceans. The main effects reported were particle ingestion and accumulation followed by reduced brine shrimp survival/mobility. The present review poses Artemia as suitable animals for investigations concerning the risks of MNP exposure at the individual level and to the ecosystems, although protocol standardization is still needed.

Seasonal variation and spatial distribution of microplastic pellets and their associated contaminants along the central east coast of India

Microplastic pellets (MPPs) are one of the significant sources of plastic pollution on shorelines worldwide. In this study, for the first time, we have examined the occurrence of MPPs and their spatial and seasonal distributions, adsorbed contaminants, polymer composition, and ecological risks at eight renowned beaches of Andhra Pradesh, central east coast of India. A total of 3950 MPPs were collected from eight beaches along the central east coast of India during October 2020, representing pre-northeast monsoon (pNEM), and during January 2021, representing the northeast monsoon (NEM). The abundance of MPPs was higher during the NEM than those found in the pNEM. ATR-FTIR and SEM analyses were conducted to characterize the polymer types and weathering patterns of MPPs. Energy-Dispersive X-ray spectrometer (EDS) results show the MPP adsorbance of heavy metals such as Ni, Cr, Cu, Pb, and Zn. The degree of contamination and polymer hazard risks of MPPs were assessed using the pollution load index (PLI) and polymer hazard index (PHI). The conducive wind and currents during the NEM lead to higher MPP abundance than during the pNEM. However, the spatial variations of MPPs showed significant differences among the beaches. This study revealed that the presence of MPPs on the beaches along the central east coast of India might pose a considerable polymer hazard risk to the ecosystem. The substantial surface weathering features of MPPs would lead to more toxic nanoplastics in the future.

Sources, distribution, and environmental effects of microplastics: a systematic review

Microplastics (MPs) are receiving increasing attention from researchers. They are environmental pollutants that do not degrade easily, are retained for prolonged periods in environmental media such as water and sediments, and are known to accumulate in aquatic organisms. The aim of this review is to show and discuss the transport and effects of microplastics in the environment. We systematically and critically review 91 articles in the field of sources, distribution, and environmental behavior of microplastics. We conclude that the spread of plastic pollution is related to a myriad of processes and that both primary and secondary MPs are prevalent in the environment. Rivers have been indicated as major pathways for the transport of MPs from terrestrial areas into the ocean, and atmospheric circulation may be an important avenue for transporting MPs between environmental compartments. Additionally, the vector effect of MPs can change the original environmental behavior of other pollutants, leading to severe compound toxicity. Further in-depth studies on the distribution and chemical and biological interactions of MPs are highly suggested to improve our understanding of how MPs behave in the environment.

Presence, variation, and potential ecological impact of microplastics in the largest shallow lake of Central Europe

The presence of microplastics (MPs) in the global ecosystem has generated a rapidly growing concern worldwide. Although their presence in the marine environment has been well-studied, much less data are available on their abundance in freshwaters. MPs alone and in combination with different chemicals has been shown to cause acute and chronic effects on algae and aquatic invertebrate and vertebrate species at different biological levels. However, the combined ecotoxicological effects of MPs with different chemicals on aquatic organisms are still understudied in many species and the reported data are often controversial. In the present study, we investigated, for the first time, the presence of MPs in Lake Balaton, which is the largest shallow lake of Central Europe and an important summer holiday destination. Moreover, we exposed neonates of the well-established ecotoxicological model organism Daphnia magna to different MPs (polystyrene [3 μm] or polyethylene [≤ 100 μm]) alone and in combination with three progestogen compounds (progesterone, drospirenone, levonorgestrel) at an environmentally relevant concentration (10 ng L^-1) for 21 days. The presence of 7 polymer types of MPs in the size range of 50-100 μm was detected in Lake Balaton. Similarly to the global trends, polypropylene and polyethylene MPs were the most common types of polymer. The calculated polymer-independent average particle number was 5.5 particles m^-3 (size range: 50 μm - 100 μm) which represents the values detected in other European lakes. Our ecotoxicological experiments confirmed that MPs and progestogens can affect D. magna at the behavioral (body size and reproduction) and biochemical (detoxification-related enzyme activity) levels. The joint effects were negligible. The presence of MPs may lead to reduced fitness in the aquatic biota in freshwaters such as Lake Balaton, however, the potential threat of MPs as vectors for progestogens may be limited.

Polymer Chemical Identity as a Key Factor in Microplastic-Insecticide Antagonistic Effects during Embryogenesis of Sea Urchin Arbacia lixula

As a proxy for pollutants that may be simultaneously present in urban wastewater streams, the effects of two microplastics-polystyrene (PS; 10, 80 and 230 μm diameter) and polymethylmethacrylate (PMMA; 10 and 50 μm diameter)-on fertilisation and embryogenesis in the sea urchin Arbacia lixula with co-exposure to the pyrethroid insecticide cypermethrin were investigated. Synergistic or additive effects were not seen for plastic microparticles (50 mg L^-1) in combination with cypermethrin (10 and 1000 μg L^-1) based on evaluation of skeletal abnormalities or arrested development and death of significant numbers of larvae during the embryotoxicity assay. This behaviour was also apparent for male gametes pretreated with PS and PMMA microplastics and cypermethrin, where a reduction in sperm fertilisation ability was not evidenced. However, a modest reduction in the quality of the offspring was noted, suggesting that there may be some transmissible damage to the zygotes. PMMA microparticles were more readily taken up than PS microparticles, which could suggest surface chemical identity as potentially modulating the affinity of larvae for specific plastics. In contrast, significantly reduced toxicity was noted for the combination of PMMA microparticles and cypermethrin (100 μg L^-1), and may be related to less ready desorption of the pyrethroid than PS, as well as cypermethrin activating mechanisms that result in reduced feeding and hence decreased ingestion of microparticles.

Ecotoxicology of microplastics in Daphnia: A review focusing on microplastic properties and multiscale attributes of Daphnia

The ubiquitous presence of microplastics in aquatic environments is considered a global threat to aquatic organisms. Species of the genus Daphnia provide an important link between aquatic primary producers and consumers of higher trophic levels; furthermore, these organisms exhibit high sensitivity to various environmental pollutants. Hence, the biological effects of microplastics on Daphnia species are well documented. This paper reviews the latest research regarding the ecotoxicological effects of microplastics on Daphnia, including the: 1) responses of individual, population, and community attributes of Daphnia to microplastics; 2) influence of the physical and chemical properties of microplastics; and 3) joint toxicity of microplastics and other pollutants on responses of Daphnia. Our literature review found that the published literature does not provide sufficient evidence to reveal the risks of microplastics at the population and community levels. Furthermore, we emphasized that high-level analysis has more general implications for understanding how individual-level research can reveal the ecological hazards of microplastics on Daphnia. Based on this review, we suggest avenues for future research, including microplastic toxicology studies based on both omics-based and community-level methods, especially the latter.

Ingestion and impacts of water-borne polypropylene microplastics on Daphnia similis

Polypropylene microplastics are the leading contaminant in aquatic environments, although research on their toxicity remains scarce. The proposed research focuses on the harmful consequences of acute exposure to polypropylene microplastics in Daphnia similis. This work converts widely available polypropylene bags into microplastics using xylene. FTIR findings demonstrated the lack of xylene residue in the produced polypropylene microplastic particles, which were spherical and ranged in size from 11.86 to 44.62 µm (FE-SEM). The results indicate that acute exposure to polypropylene microplastics causes immobility in D. similis. Ingestion of microplastics enhances the generation of reactive oxygen species (ROS), as shown by biochemical studies. Due to the production of free radicals in D. similis, the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) and a non-antioxidant enzyme of reduced glutathione (GSH) and also oxidative stress effects in lipid (lipid peroxidation - LPO), protein (carbonyl protein - CP) were increased. Additionally, the amount of the neurotransmitter enzyme acetylcholinesterase (AChE) activity was decreased. These findings indicate that the accumulation of polypropylene microplastics in the bodies of filter-feeding organisms should aggravate toxicity in the freshwater environment.

The effect of microplastics on the interspecific competition of Daphnia

Microplastic pollution is currently one of the most intensely studied ecological issues. Numerous studies have estimated the distribution and concentration of microplastics in various environments and determine how they affect their inhabitants. Much less effort has been place on assessing the possible effects of microplastics on interactions between organisms, including interspecific competition. Our aim was to test the hypothesis that the presence of microplastics affects the proportion of individuals of coexisting species and the elimination rate of the inferior competitor. The hypothesis was tested in competitive experiments done in the absence and presence of spherical non-biodegradable polystyrene and polyethylene and biodegradable polyhydroxybutyrate in environmentally relevant densities. In each of the experiments, we used three different pairs of closely related planktonic species of the genus Daphnia composed of the superior and inferior competitor: D. pulex and D. magna, D. magna and D. galeata, D. pulex and D. galeata. The results support our hypothesis and demonstrate each microplastic type had a different effect on the density of the competing species. The presence of polystyrene and polyethylene lowered the density of the superior competitor in each of the three pairs, at least partially due to a reduction in the number of gravid females, but not their fecundity. The presence of the polyhydroxybutyrate, in turn, increased the population density of D. magna in the variants with each of the two remaining species. Moreover, the presence of microplastics affected the elimination rate of the inferior competitor, i.e. polystyrene expedited the exclusion of D. magna by D. pulex, and polyhydroxybutyrate hampered the exclusion of D. magna by D. pulex. Our results suggest that long-term exposure to environmentally relevant densities of both non-biodegradable and biodegradable microplastics may affect the relative abundance of co-occurring species in zooplankton communities, and thus the functioning of aquatic ecosystems.

The Response of Duckweed Lemna minor to Microplastics and Its Potential Use as a Bioindicator of Microplastic Pollution

Biomonitoring has become an indispensable tool for detecting various environmental pollutants, but microplastics have been greatly neglected in this context. They are currently monitored using multistep physico-chemical methods that are time-consuming and expensive, making the search for new monitoring options of great interest. In this context, the aim of this study was to investigate the possibility of using an aquatic macrophyte as a bioindicator of microplastic pollution in freshwaters. Therefore, the effects and adhesion of three types of microplastics (polyethylene microbeads, tire wear particles, and polyethylene terephthalate fibers) and two types of natural particles (wood dust and cellulose particles) to duckweed Lemna minor were investigated. The results showed that fibers and natural particles had no effect on the specific growth rate, chlorophyll a content, and root length of duckweed, while a significant reduction in the latter was observed when duckweed was exposed to microbeads and tire wear particles. The percentage of adhered particles was ten times higher for polyethylene microbeads than for other microplastics and natural particles, suggesting that the adhesion of polyethylene microbeads to duckweed is specific. Because the majority of microplastics in freshwaters are made of polyethylene, the use of duckweed for their biomonitoring could provide important information on microplastic pollution in freshwaters.

Enhanced settling of microplastics after biofilm development: A laboratory column study mimicking wastewater clarifiers

The settling of microplastics (MPs) is crucial for their removal from municipal wastewater treatment plants (WWTPs) and sedimentation in static waterbodies, where they can accumulate in bottom sediments. Biofilm formation on MPs enhances their aggregation with other particles, thereby changing their density and size and altering their settling rates. However, only a few studies have investigated the settling of MPs of different sizes and materials. Specifically, the settling of small-sized MPs (<150 μm) has been poorly documented. In this study, cylindrical and fragmented particles of four polymer types (high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET)) were used to investigate the settling or floating of reference MPs (20-130 μm) in a custom-made column that simulated a primary sedimentation tank in a typical WWTP before and after incubation in wastewater influent. The settling velocity of the reference MP particles was strongly influenced by the particle size and density. The settled fractions of all the cylindrical reference MPs increased significantly (up to 5 times) due to biofilm formation at overflow velocities of 0.15, 0.26, and 0.40 mm s^-1. This was observed even for HDPE and PP (density <1 g cm^-3) after biofilm formation. The fragmented reference MPs showed complex and rather unpredictable behavior, possibly due to their irregular shape. Generally, the settling of pristine PS and PET in the laboratory tests was consistent with the theoretical predictions obtained using Stokes' law. The experimental findings of this study can be used to develop models that predict the removal efficiencies of MPs in WWTPs and to estimate the sinking of MPs to bottom sediments of static waterbodies.

Plastics in scene: A review of the effect of plastics in aquatic crustaceans

Plastic pollution in aquatic environments is present in all compartments from surface water to benthic sediment, becoming a topic of emerging concern due to the internalization, retention time, and its effects on aquatic biota. Crustacea with nearly 70,000 species, broad distribution and different roles in the trophic webs is a significant target of the increasing plastic pollution. At least 98 publications in the last 10 years report the impact of plastics in crustaceans, all suggesting that this taxon is at high risk for ecosystem disadvantage by plastic contamination loads. This review compiles the current knowledge on physiological effects (endpoints) by plastic contamination analyzed in crustaceans in the last 10 years, highlighting their use as model species for ecotoxicological tests, sentinels species and bioindicators. Plastic contamination analyzed in this review includes macroplastic, microplastic, and nanoplastic, in a wide variety of types. The studies were focused on 38 marine species with an economic interest in fisheries and aquaculture; 14 freshwater with a higher frequency in standard test species and 4 estuarial and 3 mangrove species with ecological interest. The publications reviewed were divided into studies describing plastic presence in crustaceans without reporting toxic effects and those with analysis of plastic toxicity. Publications describing the plastic presence in the organisms show that the ingestion in individual effects and food-web transfer in ecological effects were the most frequent endpoints. The publications that analyzed plastic toxicity through survival, nutrition-metabolism-assimilation, and reproduction in individual effects, and bioaccumulation in ecological effects were the most frequent endpoints. This review gathers the available information on the use of crustaceans as model species in environmental impact for toxicity screening and hazard assessment. Besides, identifying knowledge gaps will let us propose some future directions in research and the effects on target fisheries species which involves a possible effect on human health.

Acute and multigenerational effects of petroleum- and cellulose-based microfibers on growth and photosynthetic capacity of Lemna minor

Comparative toxicological assessment studies on the effects of petroleum- and cellulose-based microfibers on aquatic plants are limited. Therefore, we evaluated the acute and 10-generational toxicological effects of two types of petroleum- and cellulose-based microfibers on the duckweed Lemna minor. Plant growth and photosynthesis parameters were monitored as bioindicators. The multigenerational test revealed the following ranking of the microfibers according to the severity of their effects on L. minor: polypropylene > lyocell > viscose > polyethylene terephthalate. The acute tests revealed a significant increase in the energy required to initiate photosynthesis, although the growth of L. minor was not adversely affected by any microfiber. Both petroleum- and cellulose-based microfibers induced adverse effects on the growth and photosynthesis of L. minor in multigenerational tests. The results of the generational tests contribute to the understanding of the long-term adverse effects of microfibers on aquatic plants.

The first plastic produced, but the latest studied in microplastics research: The assessment of leaching, ecotoxicity and bioadhesion of Bakelite microplastics

Bakelite, the first synthetic plastic, is a rather unexplored material in the field of ecotoxicology, despite its long production and use. The aim of this study was to investigate the ecotoxicity of Bakelite microplastics (before and after leaching) and its leachates on four aquatic organisms: the crustacean Daphnia magna, the plant Lemna minor, the bacterium Allivibrio fischeri and the alga Pseudokirchneriella subcapitata. Bakelite microplastics before and after leaching and leachates affected all organisms, but to varying degrees. Leachates showed increased ecotoxicity to Daphnia magna, while Pseudokirchneriella subcapitata was more affected by particles. For Lemna minor and Allivibrio fischeri, the effects of particles before leaching and leachate were comparable, while the negative effect of particles after leaching was minimal or not present. All leachates were analysed, and phenol and phenol-like compounds were the predominant organics found. In addition, bioadhesion of Bakelite microplastics to the surface of Daphnia magna and Lemna minor was confirmed, but the particles were mainly weakly adhered. Results of this study suggest that, in addition to the recently studied microplastics from consumer products (e.g. from polyethylene and polystyrene), microplastics from industrial plastics such as Bakelite may be of increasing concern, primarily due to leaching of toxic chemicals.

Toxicity evaluation of polypropylene microplastic on marine microcrustacean Artemia salina: An analysis of implications and vulnerability

Polypropylene microplastic particles are one of the predominant pollutants in marine ecosystems and their toxic effects are unknown in aquatic biota. The study aims to prepare the spherical shaped polypropylene microplastics (size range 11.86 μm-44.62 μm) and assess their toxic effects (1, 25, 50, 75 and 100 μg/mL) in various life stages (nauplii, metanauplii and juvenile) of marine microcrustacean Artemia salina within 48 h. In addition, microplastics ingestion by Artemia nauplii was proved by FTIR analysis. The results revealed, microplastics accumulation in their tract leads to change in their homeostasis, as followed increase in the oxidative burst causes mortality in nauplii (LC₅₀ 40.947 μg/mL) and meta nauplii (LC₅₀ 51.954 μg/mL). In juvenile, swimming behaviour was changed. Moreover, microplastic consumption disturbs the antioxidant biomarkers such as superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), glutathione -S- Transferase (GST) and reduces the neurotransmitter enzyme acetylcholinesterase (AChE) activity. In addition, histology of juvenile Artemia showed damage in epithelial cells. This study indicates that exposure to polypropylene microplastics is more harmful to zooplanktonic organisms of the marine ecosystem.

Virgin and UV-weathered polyamide microplastics posed no effect on the survival and reproduction of Daphnia magna

Although evidence suggests that microplastic (MP) particles pose a risk to organisms, the effects of virgin and weathered MP should be evaluated separately as their effects may be different. In this work, we provide new information on the toxic potential of virgin and UV-weathered polyamide, one of the commonly used plastics worldwide. Polyamide MP particles were subjected to UV-weathering in wet conditions over 26 days in a customized irradiation chamber equipped with UV-C light tubes (15 W each, max. wavelength 254 nm). The toxicity of virgin and UV-weathered polyamide MP (< 180 µm in one dimension, 100 and 300 mg L^-1) was evaluated by studying Daphnia magna reproduction in natural lake water spiked with MP, following the 21-day OECD 211 test guideline. In parallel, a nonionic surfactant Tween 20 (7 mg L^-1) was added to the test medium to improve the suspendability of the MP. The results of the tests showed no adverse effects of either virgin or UV-weathered polyamide MP on the reproduction of D. magna. In addition, presence of Tween 20 in the test medium had no effects on the test results. These results bring a new perspective on the potential long-term impact of polyamide particles on aquatic organisms, especially considering that the polyamide has received marginal attention in the ecotoxicological research. However, standard test endpoints (survival and reproduction) may still miss long-term adverse effects of insoluble e.g., plastic particles and additional studies may be necessary.

Simultaneous Quantification of Bisphenol-A and 4-Tert-Octylphenol in the Live Aquaculture Feed Artemia franciscana and in Its Culture Medium Using HPLC-DAD

Aquaculture, a mass supplier of seafood, relies on plastic materials that may contain the endocrine disruptors bisphenol-A (BPA) and tert-octylphenol (t-OCT). These pollutants present toxicity to Artemia, the live aquaculture feed, and are transferred through it to the larval stages of the cultured organisms. The purpose of this work is the development and validation of an analytical method to determine BPA and t-OCT in Artemia and their culture medium, using n-octylphenol as the internal standard. Extraction of the samples was performed with H₂O/TFA (0.08%)–methanol (3:1), followed by SPE. Analysis was performed in a Nucleosil column with mobile phases A (95:5, v/v, 0.1% TFA in H₂O:CH₃CN) and B (5:95, v/v, 0.08% TFA in H₂O:CH₃CN). Calibration curves were constructed in the range of concentrations expected following a 24 h administration of BPA (10 μg/mL) or t-OCT (0.5 μg/mL), below their respective LC₅₀. At the end of exposure to the pollutants, their total levels appeared reduced by about 32% for BPA and 35% for t-OCT, and this reduction could not be accounted for by photodegradation (9–19%). The developed method was validated in terms of linearity, accuracy, and precision, demonstrating the uptake of BPA and t-OCT in Artemia.

Impacts to Larval Fathead Minnows Vary between Preconsumer and Environmental Microplastics

Microplastics are a complex suite of contaminants varying in size, shape, polymer, and associated chemicals and are sometimes referred to as a "multiple stressor." Still, the majority of studies testing hypotheses about their effects use commercially bought microplastics of a uniform size, shape, and type. We investigated the effects of polyethylene and polypropylene microplastics purchased as preproduction pellets (referred to as "preconsumer") and a mixture of polyethylene and polypropylene collected from the environment (environmental microplastic). Embryo-stage fathead minnows were exposed to either the physical plastic particles and their leachates or the chemical leachates alone at an environmentally relevant (280 particles/L) or high (2800 particles/L) concentration for 14 d. The effects of microplastics differed by polymer type and presence of environmental contaminants, and effects can be driven by the physical particles and/or the chemical leachates alone. Larvae exposed to preconsumer polyethylene experienced a decrease in survival, length, and weight, whereas preconsumer polypropylene caused an increase in weight. Environmental microplastics caused a more drastic increase in length and weight and almost 6 times more deformities as the preconsumer microplastics. Although preconsumer microplastics caused effects only when organisms were exposed to both the particles and the chemical leachates, the environmental microplastics caused effects when organisms were exposed to the chemical leachates alone, suggesting that the mechanism of effects are context-dependent. The present study provides further support for treating microplastics as a multiple stressor and suggests that testing for effects with pristine microplastics may underestimate the true effects of microplastics in the environment. Environ Toxicol Chem 2022;41:858-868. © 2021 SETAC.

Microplastic Fibers Increase Sublethal Effects of AgNP and AgNO3 in Daphnia magna by Changing Cellular Energy Allocation

The effects of combined exposure to microplastics and contaminants are still not completely understood. To fill this gap, we assessed the effects of polyethylene terephthalate microplastic fibers (100 mg/L; 360 µm average length) on the toxicity of silver nanoparticles (AgNPs; 32 nm) and silver nitrate (AgNO₃ ; 0.1-10 µg Ag/L) to Daphnia magna. Acute immobilization (median effect concentration [EC50]) and cellular energy allocation (CEA; ratio between available energy and energy consumption) were determined in neonates (<24 h old) and juveniles (7 d old), respectively. The 48-h EC50 for AgNP and AgNO₃ (2.6 and 0.67 µg Ag/L, respectively) was not affected by the presence of microplastic fibers (2.2 and 0.85 µg Ag/L, respectively). No decrease in the available energy was observed: lipid, carbohydrate, and protein contents were unaffected. However, a significant increase in energy consumption was observed in animals exposed to AgNO₃ (250% compared with control) and to the combination of microplastic fibers with AgNP (170%) and AgNO₃ (260%). The exposure to microplastic fibers alone or in combination with both Ag forms decreased the CEA (values were 55-75% of control values). Our results show that after short-term exposure (48 h), microplastic fibers increased Ag toxicity at a subcellular level (i.e., CEA), but not at the individual level (i.e., immobilization). These results highlight the importance of combining different levels of biological organization to fully assess the ecotoxicological effects of plastics in association with environmental contaminants. Environ Toxicol Chem 2022;41:896-904. © 2021 SETAC.

The contamination of microplastics in China's aquatic environment: Occurrence, detection and implications for ecological risk

The widespread occurrence of microplastics in aquatic ecosystems that resulted in environmental contamination has attracted worldwide attention. Microplastics pose a potential threat to the growth and health of aquatic organisms, thereby affecting the function of the ecosystems. As one of the top ten countries producing and consuming plastic products globally, China's aquatic ecosystems have been profoundly affected by microplastics. In this review, we have summarized the microplastics contamination in three typical water environments (marine environment, freshwater environment, and wastewater treatment plants) in China, elaborated on the adverse impacts of microplastics on the ecological environment, and evaluated the potential ecological risks exposed to the ecosystem. In addition, the progress of microplastics extraction methods, as the important basis of microplastics related research, in aquatic ecosystems was introduced, especially the difference between the extraction of microplastics from wastewater and sludge samples. At present, most of the research on microplastics focuses on "one point", such as a certain river or wastewater treatment plant. Research on the mitigation and transfer of microplastics among different connected water environments is still lacking. Also, the microscale ecotoxicity caused by microplastics is poorly understood. In the end, we proposed suggestions and perspectives for future research regarding microplastics in the aquatic ecosystems in China.

Microplastic pollution in wild populations of decapod crustaceans: A review

Along with the increasing amount of plastic production and waste disposal, the presence of microplastics has been confirmed in all compartments of ecosystems. The microplastics in biota is of particular concern due to the potential eco-risks associated with long term exposure and the potential for transportation along food webs. Decapoda represents a diverse taxonomic group within the subphylum Crustacea, and some of which are highly valued in fishery and biological production. The interaction between microplastic pollution and wild populations of decapod crustaceans have been documented less than fish or bivalves but are critical to understand the fates of microplastics in marine eco-systems and enrich the baselines for consumption analyses. Our review systematically summarizes the occurrence, abundance and characteristics of microplastics detected in edible and non-edible sections of decapod crustaceans from field observations. Sub-groups between crabs and shrimps were also included for comparison. The occurrence of microplastics in the edible sections were less than those in non-edible sections, and there are differences between crabs and shrimps. Fibrous microplastics and items with a size category less than 1 mm were dominant pollutants across all available literature. The methodology selection, biological features and uptake pathways play roles in the microplastic body burden in Decapoda. Our work enriches the understanding of microplastic pollution in wild populations of decapod crustaceans but their contribution to the human exposure to microplastics needs to be addressed with more accurate measurements.

Critical review of environmental impacts of microfibers in different environmental matrices

Microfibers, as globally emerging environmental pollutants, have received increasing attention over recent years. In ecosystems, natural textile microfibers are the predominant fibers. The inadvertent ingestion of microplastics by organisms in an ecosystem provides a channel for microfibers to enter biological webs. Based on existing research on microfibers, this review summarizes the potential adverse impacts of microfibers on organisms living in marine, freshwater, and soil ecosystems, and provides a brief introduction to the source of microfibers, as well as the related current status and future challenges. Although previous studies have recorded the adverse effects of microfibers on ecosystems, there remains a lack of evidence on the toxic effects of microfibers on the primary producer level in food chains (e.g., phytoplankton). This is essential, as the long-term effects of microfiber toxicity on different ecosystems ultimately affect human health. The analysis of microfiber toxicity paves the way for the field of environmental research and provides future perspectives for researchers in the fields of ecotoxicology and microplastics.

Effect of short-term exposure to fluorescent red polymer microspheres on Artemia franciscana nauplii and juveniles

Microplastics (MPs) are ubiquitously present in the world's seas with unknown potential toxic effects on aquatic ecosystems. The aim of this study was to evaluate biochemical responses caused by 1-5 μm diameter plastic fluorescent red polymer microspheres (FRM), under short-term exposure of nauplii and juveniles of Artemia franciscana, using a set of biomarkers involved in important physiological processes such as biotransformation, neuronal transmission and oxidative stress. Two FRM concentrations (0.4 and 1.6 mg mL^-1) present in the water at ecologically relevant concentrations were used to study their toxicity. No significant differences were found in growth, survival and feeding behaviour of nauplii, after 2 days of exposure to both FRM concentrations. However, in juveniles, survival decreased after 5 days of exposure to FRM1.6; but no significant differences were found in either growth or feeding behaviour. It was observed that nauplii and juveniles, under short-term exposure, had the ability to ingest and egest FRM particles, although their accumulation was higher in nauplii than in juveniles, maybe related with the capacity of the latter to empty their gut content faster, in the presence of food. Regarding biomarkers responses in nauplii, all enzymatic activities increased significantly, after short-term exposure to the higher FRM concentration tested (FRM1.6), which could be related with detoxifying MPs-triggered oxidative stress. In juveniles, the inhibition of ChE and the decrease in the activity of antioxidant enzymes, after 5 days of exposure to FRM1.6, might indicate a neurotoxic effect and oxidative damage induced by FRM. This study provides further evidences that accumulation of MPs in the gut by nauplii and juveniles of A. franciscana can induce negative effects on important physiological processes with influence on their health, highlighting the general concern about the negative effects of MPs pollution on aquatic species, as well as the need to understand the mechanism of MPs toxicity and its possible impacts on environmental safety. Graphical abstract.

The first comprehensive study evaluating the ecotoxicity and biodegradability of water-soluble polymers used in personal care products and cosmetics

Water-soluble polymers (WSPs) are organic materials that have been used for decades in various applications as part of paints, coatings, adhesives, washing agents, pharmaceuticals, personal care products and cosmetics. However, their ecotoxicity, biodegradability, and overall impact on the environment are still unknown. In this study four polyacrylic acid- based WSPs (three in the solid state and one in the liquid state), which are widely used in cosmetic industry, were tested in terms of their ecotoxicity and biodegradability. The ecotoxicity tests were performed using aquatic plant Lemna minor, microalga Pseudokirchneriella subcapitata, crustacean Daphnia magna, bacterium Allivibrio fischeri, and a mixed bacterial culture of activated sludge (with heterotrophic and nitrifying microorganisms tested separately). All four WSPs had low or moderate effects on the tested organisms at several endpoints. However, the liquid WSP had a specific toxic effect on the bioluminescence of Allivibrio fischeri and the oxygen consumption of nitrifying microorganisms - 100 mg/L caused 73% and 88% inhibition, respectively. Therefore, some WSPs capable of inhibiting nitrifying microorganisms could have implications for the nitrification process in wastewater treatment plants and aquatic ecosystems, despite 100 mg/L being a high tested concentration and probably difficult to reach in wastewater. All investigated WSPs were not biodegradable; therefore, their persistence in the environment could be expected.

Effects of synthetic and natural microfibers on Daphnia magna-Are they dependent on microfiber type?

Microfibers, which are sourced from textiles and some products from the fishery industry, are the biggest contributors to microplastic pollution in aquatic ecosystems. In addition to these synthetic microfibers, naturally derived microfibers can also be found in aquatic environments. However, there are limited studies on the ecotoxicity of natural microfibers. To shed light on this topic, this study assessed and compared the toxicity of natural and synthetic microfibers on Daphnia magna, using lyocell, polyester (PET) and polypropylene (PP) microfibers. To evaluate the adverse effect of microfibers on D. magna, after effects including depuration, food intake, growth, mortality, and immobilization rate were continually observed for up to 96 h after the initial 48 h of exposure to the microfibers. Immobilization rate decreased in the following order: PP, PET, and lyocell. However, the depuration of microfibers in the lyocell and PET treatment groups was similar, with higher mortality rates than in the PP treatment group. Furthermore, despite the high rates of food intake following exposure, the lyocell and PET exposed groups exhibited growth inhibition during the same period. This growth inhibition corresponded with, and was likely due to, reductions in the length of gut microvilli, probably an expression of gut damage, which is believed to have reduced nutrient absorption in the affected individuals. Based on the results of this study, it was confirmed that even natural microfibers, and not just synthetic microfibers, can have adverse effects on aquatic organisms. This study confirmed not only the toxicity of microfibers, but also the consequences of their after effects. These results could be the basis for future research on the after effects of microplastics on aquatic organisms and provide directions for further microplastic ecotoxicity studies.

Influence of Microplastics on the Growth and the Intestinal Microbiota Composition of Brine Shrimp

Microplastics (MPs) are ubiquitous in the aquatic environment and can be frequently ingested by zooplankton, leading to various effects. Brine shrimp (Artemia parthenogenetica) has an important role in the energy flow through trophic levels in different seawater systems. In this work, the influence of polyethylene (PE) and polystyrene (PS) MPs on the growth of brine shrimp and corresponding changes of gut microbiota were investigated. Our results showed that the MPs remarkably reduced the growth rate of brine shrimp, and the two types of MPs have different impacts. The average body length of brine shrimps was reduced by 17.92 and 14.95% in the PE group and PS group, respectively. MPs are mainly found in the intestine, and their exposure evidently affects the gut microbiota. By using 16S rRNA gene high-throughput sequencing, 32 phyla of bacteria were detected in the intestine, and the microbiome consisted mainly of Proteobacteria, Firmicutes, and Actinobacteria. MPs’ exposure significantly increased the gut microbial diversity. For the PE group, the proportion of Actinobacteria and Bacteroidetes increased by 45.26 and 2.73%, respectively. For the PS group, it was 54.95 and 1.27%, respectively. According to the analysis on genus level, the proportions of Ponticoccus, Seohaeicola, Polycyclovorans, and Methylophaga decreased by 46.38, 1.24, 1.07, and 2.66%, respectively, for the PE group and 57.87, 1.43, 0.88, and 2.24%, respectively, for the PS group. In contrast, the proportions of Stappia, Microbacterium, and Dietzia increased by 1.12, 23.27, and 11.59%, respectively, for the PE group, and 1.09, 3.79, and 42.96%, respectively, for the PS group. These experimental results demonstrated that the ingestion of MPs by brine shrimp can alter the composition of the gut microbiota and lead to a slow growth rate. This study provides preliminary data support for understanding the biotoxicity of MPs to invertebrate zooplankton and is conducive to the further risk assessment of MP exposure.

Determination of nano and microplastic particles in hypersaline lakes by multiple methods

Microplastics and nanoplastics have a range of impacts on the aquatic environment and present major challenges to their mitigation and management. Their transport and fate depend on their composition, form, and the characteristics of the receiving environment. We explore the spatial and temporal dynamics of plastic particles in the world's second-largest hypersaline lake, combining information from microscopic, thermal gravimetric, and fractional methods. Studies on microplastic and nanoplastic pollution in these important environments are scarce, and there is limited understanding of their dynamics and fate. Our results for Urmia Lake (Iran) in 2016 and 2019 show a discrepancy in the composition and quantity of microplastics measured in river tributaries to the lake and the lake itself, suggesting an active microplastic sink. Potential sink mechanisms in hypersaline lakes are explored. The present study indicates that microplastics have different transport mechanisms and fate in these extreme environments, compared to lake and ocean environments.

Micro/nanoplastics effects on organisms: A review focusing on 'dose'

Microplastics have become predominant contaminants, attracting much political and scientific attention. Despite the massively-increasing research on microplastics effects on organisms, the debate of whether environmental concentrations pose hazard and risk continues. This study critically reviews published literatures of microplastics effects on organisms within the context of "dose". It provides substantial evidence of the common occurrence of threshold and hormesis dose responses of numerous aquatic and terrestrial organisms to microplastics. This finding along with accumulated evidence indicating the capacity of organisms for recovery suggests that the linear-no-threshold model is biologically irrelevant and should not serve as a default model for assessing the microplastics risks. The published literature does not provide sufficient evidence supporting the general conclusion that environmental doses of microplastics cause adverse effects on individual organisms. Instead, doses that are smaller than the dose of toxicological threshold and more likely to occur in the environment may even induce positive effects, although the ecological implications of these responses remain unknown. This study also shows that low doses of microplastics can reduce whereas high doses can increase the negative effects of other pollutants. The mechanisms explaining these findings are discussed, providing a novel perspective for evaluating the risks of microplastics in the environment.

Microplastics and plankton: Knowledge from laboratory and field studies to distinguish contamination from pollution

Due to their ubiquitous presence, size and characteristics as ability to adsorb pollutants, microplastics are hypothesized as causing a major impact on smaller organisms, such as plankton. Despite this, there is a need to determine whether these impacts just relate to the environmental presence of the materials or their effects on biological processes. Therefore, we aimed to 1) review current research on plankton and microplastics; 2) compare field and laboratory experimental findings, and 3) identify knowledge gaps. The systematic review showed that 70% of the 147 relevant scientific publications were from laboratory studies and microplastics interactions with plankton were recorded in 88 taxa. Field study publications were relatively scarce and the characteristics of microplastics collected in the field were very different from those used in laboratory experiments thereby limiting the comparison between studies. Our systematic review highlighted knowledge gaps in: 1) the number of field studies; 2) the non-comparability between laboratory and field conditions, and 3) the low diversity of plankton species studied. Furthermore, this review indicated that while there are many studies on contamination by microplastics, the effects of this contamination (i.e., pollution per se) have been less well-studied, especially in the field at population, community, and ecosystem levels.

Resolving the effects of environmental micro- and nanoplastics exposure in biota: A knowledge gap analysis

The pervasive spread of microplastics (MPs) and nanoplastics (NPs) has raised significant concerns on their toxicity in both aquatic and terrestrial environments. These polymer-based materials have implications for plants, wildlife and human health, threatening food chain integrity and ultimate ecosystem resilience. An extensive - and growing - body of literature is available on MP- and NP-associated effects, including in a number of aquatic biota, with as yet limited reports in terrestrial environments. Effects range from no detectable, or very low level, biological effects to more severe outcomes such as (but not limited to) increased mortality rates, altered immune and inflammatory responses, oxidative stress, genetic damage and dysmetabolic changes. A well-established exposure route to MPs and NPs involves ingestion with subsequent incorporation into tissues. MP and NP exposures have also been found to lead to genetic damage, including effects related to mitotic anomalies, or to transmissible damage from sperm cells to their offspring, especially in echinoderms. Effects on the proteome, transcriptome and metabolome warrant ad hoc investigations as these integrated "omics" workflows could provide greater insight into molecular pathways of effect. Given their different physical structures, chemical identity and presumably different modes of action, exposure to different types of MPs and NPs may result in different biological effects in biota, thus comparative investigations of different MPs and NPs are required to ascertain the respective effects. Furthermore, research on MP and NP should also consider their ability to act as vectors for other toxicants, and possible outcomes of exposure may even include effects at the community level, thus requiring investigations in mesocosm models.