Negative effects of microplastic exposure on growth and development of Crepidula onyx

Nanoplastic pollution changes the intestinal microbiome but not the morphology or behavior of a freshwater turtle

Humans produce 350 million metric tons of plastic waste per year, leading to microplastic pollution and widespread environmental contamination, particularly in aquatic environments. This subsequently impacts aquatic organisms in myriad ways, yet the vast majority of research is conducted in marine, rather than freshwater systems. In this study, we exposed eggs and hatchlings of the Chinese soft-shelled turtle (Pelodiscus sinensis) to 80-nm polystyrene nanoplastics (PS-NPs) and monitored the impacts on development, behavior and the gut microbiome. We demonstrate that 80-nm PS-NPs can penetrate the eggshell and move into developing embryos. This led to metabolic impairments, as evidenced by bradycardia (a decreased heart rate), which persisted until hatching. We found no evidence that nanoplastic exposure affected hatchling morphology, growth rates, or levels of boldness and exploration, yet we discuss some potential caveats here. Exposure to nanoplastics reduced the diversity and homogeneity of gut microbiota in P. sinensis, with the level of disruption correlating to the length of environmental exposure (during incubation only or post-hatching also). Thirteen core genera (with an initial abundance >1 %) shifted after nanoplastic treatment: pathogenic bacteria increased, beneficial probiotic bacteria decreased, and there was an increase in the proportion of negative correlations between bacterial genera. These changes could have profound impacts on the viability of turtles throughout their lives. Our study highlights the toxicity of environmental NPs to the embryonic development and survival of freshwater turtles. We provide insights about population trends of P. sinensis in the wild, and future directions for research.

Distribution and effects of microplastics as carriers of heavy metals in river surface sediments

There are few studies on microplastics (MPs) in urban river sediments compared to oceans, soils, and even rivers. In this study, the seasonal abundance of MPs, as well as their influencing factors on heavy metal adsorption in river sediments of the Ancient Canal of Zhenjiang City, China, were investigated for the first time. Through on-site sampling, microscopic observation, Raman spectroscopy, scanning electron microscopy, and high-temperature digestion, the abundance, shape, color, particle size, type, and surface characteristics of MPs in Ancient Canal sediments in different seasons, as well as the influencing factors of MPs as heavy metal carriers in different seasons, were analyzed. The results showed that the average abundance of MPs is 2049.09 ± 883.78 and 2216.36 ± 826.21 items kg-1 dry sediments in summer and winter, respectively, and different sites change significantly. In addition, particle sizes, types, colors, and shapes of MPs exhibited seasonal variations. Four MPs shapes were mainly observed: fibers, fragments, particles, and films. Among them, MPs in summer sediments are mainly fiber, and MPs in winter sediments are mainly particles. In the sediment in summer and winter, transparent MPs and small-size (<0.5 mm) MPs are the main ones, where the abundance of MPs decreased with increasing MPs size. The main MPs species are polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene (PE), with PP being the predominant MPs in the sediments in different seasons. Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) revealed that the surfaces of the MPs were characterized by rough, porous, cracked, and torn, with the attachment of various heavy metal elements, and all of the heavy metal elements accumulated to different degrees on the MPs. There was a significant positive correlation (p < 0.05) between the Mn content in the MPs and the Mn content in the sediments in winter, suggesting that the Mn in the MPs in winter may be derived from the sediments. In addition, the type, shape, size, and color of MPs affect the adsorption capacity of heavy metals. Most of the adsorption of MPs on Pb showed a significant negative correlation, and the adsorption of MPs on Cr, Zn, Cu, Cd, and Mn showed a significant positive correlation. MPs can be used as carriers of heavy metals, which will further enhance the hazards of living organisms and pose a potential threat to the safety of the urban river environment.

The Plasticene era: Current uncertainties in estimates of the hazards posed by tiny plastic particles on soils and terrestrial invertebrates

Plastics are ubiquitous in our daily life. Large quantities of plastics leak in the environment where they weather and fragment into micro- and nanoparticles. This potentially releases additives, but rarely leads to a complete mineralization, thus constitutes an environmental hazard. Plastic pollution in agricultural soils currently represents a major challenge: quantitative data of nanoplastics in soils as well as their effects on biodiversity and ecosystem functions need more attention. Plastic accumulation interferes with soil functions, including water dynamics, aeration, microbial activities, and nutrient cycling processes, thus impairing agricultural crop yield. Plastic debris directly affects living organisms but also acts as contaminant vectors in the soils, increasing the effects and the threats on biodiversity. Finally, the effects of plastics on terrestrial invertebrates, representing major taxa in abundance and diversity in the soil compartment, need urgently more investigation from the infra-individual to the ecosystem scales.

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.

Biodegradable microplastics: Uptake by and effects on the rockpool shrimp Palaemon elegans (Crustacea: Decapoda)

Ingestion of microplastics can lead to deleterious consequences for organisms, as documented by numerous laboratory studies. The current knowledge is based on a multitude of effect studies, conducted with conventional fossil-based and non-degradable plastics. However, there is a lack of information about the acceptance and the effects of novel bio-based and biodegradable plastics. Biodegradable plastics are considered an alternative to conventional plastics and are showing rapidly growing production rates. Biodegradable plastics can disperse into the environment in the same way as conventional plastics do, becoming available to marine organisms. This study aims to provide new insights into the uptake and effects of biodegradable microplastics on marine invertebrates. Rockpool shrimp, Palaemon elegans, were fed with algal flakes coated with polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV) and conventional low-density polyethylene (LDPE) microparticles. Live observations showed that all of the different types of microplastics were ingested. After dissection of the shrimp, less LDPE particles were found in the stomachs than PLA and PHBV particles. This indicates a longer retention time of biodegradable microplastics compared to conventional microplastics. Presumably, less LDPE particles were ingested or evacuated from the stomach, probably by regurgitation. The ingestion of microparticles of all types of plastics induced enzymatic activity of short-chain carboxylesterases in the midgut glands of the shrimp. However, only PLA induced enzymatic activity of medium-chain carboxylesterases. Palaemon elegans showed no oxidative stress response after ingestion of microparticles, irrespective of polymer type. From our results we conclude that biodegradable plastics might have different effects than conventional plastics. The longer retention times of biodegradable plastics might enhance exposure to leaching additives and other harmful substances. Our study provides new insights into how biodegradable plastics might affect aquatic fauna and indicate that the use of biodegradable plastics needs to be reconsidered to some extent.

Impact of anthropogenic activities on the abundance of microplastics in copepods sampled from the southeast coast of India

In recent year, the use of plastics has become inevitable due to its unique properties that allow for the production of durable and non-durable goods. Post use, plastics enter the waste stream and now can be found in all compartments of the biosphere as microplastics (MPs). This study presents the abundance of MPs in surface water and within copepods in the southwestern Bay of Bengal during dry (June 2022) and wet season (November 2022). The MPs in the surface water were found in all three regions [Chennai, Tuticorin and Nagapattinam (four locations in each region)] and maximum in wet season (53 particles/m3). Moreover, during dry season the mean ingestion of MPs by copepods in Chennai (0.103 ± 0.04 particles/individual), Tuticorin (0.11 ± 0.07 particles/individual) and Nagapattinam (0.036 ± 0.01 particles/individual) is high compared to the wet season. The maximum level of MPs found in both surface water and ingestion by copepods in Tuticorin and Chennai is subjective to the high maritime activities than Nagapattinam region. Whatever, the anthropogenic activities in the study region increase the bioavailability of MPs pollutant in the copepods and transported to higher trophic levels, endangering marine life and human health. Hence, further studies are needed to determine their potential impact on marine food chain in this alarming situation.

Can Microplastics Accumulate Toxic dye in Water? An adsorption-desorption Study under Different Experimental Conditions

The adsorption/desorption of Rhodamine B (RhB) on Polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC) microplastics (MPs) was investigated in this study. The results showed that RhB adsorption on the selected MPs was fast. The adsorption coefficients (Kd) of RhB were 2036 ± 129, 1557 ± 91, and 63 ± 8.5 L kg- 1 for PS, PP, and PVC, respectively. RhB adsorption on PS and PP increased with increasing temperature and decreasing ionic strength, whereas RhB adsorption on PVC showed a completely opposite trend. The binding strength of RhB on the three types of MPs was weak as demonstrated by the high total desorption percentage, which ranged from 79.59 ~ 89.39%. This study shows that PP and PS MPs can accumulate RhB in the aquatic environment and their potential combined toxic risks should be taken seriously.

The distribution and characterisation of microplastics in air, surface water and sediment within a major river system

Rivers are key pathways for the transfer of microplastics (MP) to marine environments. However, there are considerable uncertainties about the amount of microplastics transported by rivers to the ocean; this results in inaccuracies in our understanding of microplastic quantity and transport by freshwater systems. Additionally, it has been suggested that rivers may represent long-term sinks, with microplastics accumulating in sediment due to their high density or other biological, chemical, and physical factors. The atmosphere is also an important pathway by which airborne microplastics may enter aquatic habitats. Here, we compare for first time microplastics type and concentration in these key environmental mediums (air, water and sediment) along a major river (Ganges), from sea to source to understand 1) the abundance, 2) the spatial distribution, and 3) characteristics. Mean microplastic abundance settling from the atmosphere was 41.12 MP m2 day-1; while concentrations in sediment were 57.00 MP kg-1 and in water were 0.05 MP L-1. Across all sites and environmental mediums, rayon (synthetically altered cellulose) was the dominant polymer (54-82 %), followed by acrylic (6-23 %) and polyester (9-17 %). Fibres were the dominant shape (95-99 %) and blue was the most common colour (48-79 %). Across water and sediment environmental mediums, the number of microplastics per sample increased from the source of the Ganges to the sea. Additionally, higher population densities correlated with increased microplastic abundance for air and water samples. We suggest that clothing is likely to be the prominent source of microplastics to the river system, influenced by atmospheric deposition, wastewater and direct input (e.g. handwashing of clothes in the Ganges), especially in high density population areas. However, we suggest that subsequent microplastic release to the marine environment is strongly influenced by polymer type and shape, with a large proportion of denser microplastics settling in sediment prior to the river discharging to the ocean.

Combined effects of microfibers and polychlorinated biphenyls on the immune function of hemocytes in the mussel Mytilus coruscus

Numerous studies have shown that microplastics can interact with other pollutants in the environment to produce synergistic effects, leading to more serious impacts. To date, there is little consensus on the combined effects of microfibers (MFs) and polychlorinated biphenyls (PCBs, Aroclor 1254), two legacy and alarming environmental pollutants. There is an urgent need to assess the impact of combined exposures on bivalve immune defences. In this study, we assessed the immune response of the mussels (Mytilus coruscus) hemocyte to MFs and PCBs alone and in combination by using flow cytometry. M. coruscus were exposed to MFs (1000 pieces/L) and PCBs (PCBs) (100 ng/L and 1000 ng/L) alone or in combination for 14 consecutive days and recovered for 7 days. The hemocyte of M. coruscus was collected on day 7, 14 and 21. MF exposure alone had no effect on the hemocyte. The total hemocyte count (THC), esterase (EA), lysosomal contents (LC), mitochondrial number (MN) and mitochondrial membrane potential (MMP) of mussels showed a decreasing trend with increasing PCB concentrations, both individually and in combination; The decreases in EA, MN and MMP were associated with the induction of reactive oxygen species (ROS). Hemocyte mortality (HM) was associated with a decrease in THC. Combined exposure to MFs and PCBs would exacerbate the effects on hemocyte immunity. These new findings improve our understanding of the toxic effects of MFs and organic chemical pollutants, and demonstrate the potential mechanism of PCBs to bivalves through changes in hemolymph immunity-related indicators.

A critical review on the evaluation of toxicity and ecological risk assessment of plastics in the marine environment

The increasing production of plastics together with the insufficient waste management has led to massive pollution by plastic debris in the marine environment. Contrary to other known pollutants, plastic has the potential to induce three types of toxic effects: physical (e.g intestinal injuries), chemical (e.g leaching of toxic additives) and biological (e.g transfer of pathogenic microorganisms). This critical review questions our capability to give an effective ecological risk assessment, based on an ever-growing number of scientific articles in the last two decades acknowledging toxic effects at all levels of biological integration, from the molecular to the population level. Numerous biases in terms of concentration, size, shape, composition and microbial colonization revealed how toxicity and ecotoxicity tests are still not adapted to this peculiar pollutant. Suggestions to improve the relevance of plastic toxicity studies and standards are disclosed with a view to support future appropriate legislation.

The role of microbe-microplastic associations in marine Nematode feeding behaviors

Fauna across many taxa and trophic levels have been shown to consume microplastics (MPs) in experiments, providing evidence that supports field-based gut content assessments. Multiple explanations exist regarding why fauna consume MPs, one of which posits that microbial growth on MPs may facilitate faunal ingestion. However, laboratory assessments on the reasons why MPs are consumed remain limited. Here, we assessed if the presence of microbes on MPs altered marine nematode feeding behaviors across current and potential future concentrations of MPs in a local system. We used a microcosm experiment in which field-collected sediment was spiked with bacterially treated or untreated fluorescent plastic microbeads (1.0-5.0 μm) in concentrations of 102, 104, and 106 per microcosm, representing local and potential future concentrations of MPs. Ingestion by the dominant interstitial fauna was investigated after 0, 3, and 7 days using bright field microscopy. Nematodes were the only fauna across microcosms that consumed MPs, but this consumption was variable and there were no apparent trends across exposure time, bacterial treatment, or MP concentration. There were also no genera- or feeding-type-specific trends in the number of MPs consumed, though four of the top five nematode genera that consumed MPs were pollution-tolerant genera. Our study demonstrates that microbe-MP associations do not drive marine nematodes to eat MPs, especially at local field concentrations. While there were no trends across any of the nematode genera in our study, we recognize that unrealistic MP concentrations in other studies may provide alternative explanations for nematode consumption of MPs.

Polyester microplastic fibers induce mitochondrial damage, apoptosis and oxidative stress in Daphnia carinata, accompanied by changes in apoptotic and ferroptosis pathway

With the widespread utilization of plastic products, microplastics (MPs) have merged as a newfound environmental contaminant in the United States, and the bulk of these MPs in the environment manifest as fibrous structures. Concerns have also been voiced regarding the potential hazards posed by microplastic fibers (MFs). However, research examining the toxicity of MFs, particularly in relation to planktonic organisms, remains severely limited. Meanwhile, polyester fiber materials find extensive applications across diverse industries. As a result, this investigation delved into the toxicology of polyester microplastic fibers (PET-MFs) with a focus on their impact on Daphnia carinata (D. carinata), a freshwater crustacean. Newly hatched D. carinata were subjected to varying concentrations of PET-MFs (0, 50, and 500 MFs/mL) to scrutinize the accumulation of PET-MFs within these organisms and their resultant toxicity. The outcomes revealed that D. carinata was capable of ingesting PET-MFs, leading to diminished rates of survival and reproduction. These effects were accompanied by mitochondrial impairment, heightened mitochondrial count, apoptosis, escalated generation of reactive oxygen species, augmented activity of antioxidant enzymes, and distinct patterns of gene expression. Interestingly, when comparing the group exposed to 50 MFs/mL with the one exposed to 500 MFs/mL, it was observed that the former triggered a more pronounced degree of mitochondrial damage, apoptosis, and oxidative stress. This phenomenon could be attributed to the fact that brief exposure to 500 MFs/mL resulted in greater mortality, eliminating individuals with lower adaptability. Those that survived managed to regulate elevated in vivo reactive oxygen species levels through an increase in glutathione S-transferase content, thereby establishing an adaptive mechanism. Low concentrations did not induce direct mortality, yet PET-MFs continued to inflict harm within the organism. RNA-seq analysis unveiled significant alterations in 279 and 55 genes in the 50 MFs/mL and 500 MFs/mL exposure groups, respectively. Functional enrichment analysis of the 50 MFs/mL group indicated involvement of the apoptosis pathway and ferroptosis pathway in the toxic effects exerted by PET-MFs on D. carinata. This study imparts valuable insights into the toxicological ramifications of PET-MFs on D. carinata, underscoring their potential risks within aquatic ecosystems.

Bioaccumulation of polystyrene microplastics and changes in antioxidant and AChE pattern in a freshwater snail (Filopaludina bengalensis) from river Ganga

Microplastic pollution is a leading global problem affecting terrestrial and marine aquatic ecosystems. Due to the stagnant nature of microplastics, the toxic effect of microplastics is more pronounced to benthic organisms than the surface feeder. Hence, the present study effort was to study the microplastic bioaccumulation pattern and changes in the enzymatic and nonenzymatic antioxidant and AChE pattern of freshwater snail Filopaludina bengalensis, which were subjected to 0.5 ppm to 5 ppm levels of polystyrene microsphere (∼ 30 µm) for 27 days. The study showed that microplastics were easily accumulated in the test organism in a dose and time-dependent manner, amounting to 82 ± 6.02 particles /individuals at a 5 ppm dose on the 27th day. However, no mortality was observed at the test microplastic dosages. The enzymatic antioxidant profile (SOD and catalase) showed limited variability and remained stable with increased duration and microplastic dose. However, the nonenzymatic antioxidant profile showed distinct variability with the complete seizing of the DPPH activity on the 27th day at 5 ppm microplastic dose and a gradual decrease of ABTS and FRAP activity at all the dose ranges. Even the AChE activity decreased with higher exposure concentrations. The present study for the first time shows the direct impact of microplastics on a freshwater snail widely available in the Indian subcontinent, indicating the role of microplastic pollution will create havoc in the Ganga river eco-biosystem in the long run.

Microplastics, a Global Issue: Human Exposure through Environmental and Dietary Sources

Plastic production has grown dramatically over the years. Microplastics (MPs) are formed from the fragmentation of larger plastic debris by combining chemical, physical, and biological processes and can degrade further to form nanoplastics (NPs). Because of their size, MPs and NPs are bioavailable to many organisms and can reach humans through transport along the food chain. In addition to the risk from ingesting MPs themselves, there are risks associated with the substances they carry, such as pesticides, pathogenic microorganisms, and heavy metals, and with the additives added to plastics to improve their characteristics. In addition, bioaccumulation and biomagnification can cause a cumulative exposure effect for organisms at the top of the food chain and humans. Despite the growing scientific interest in this emerging contaminant, the potential adverse effects remain unclear. The aim of this review is to summarize the characteristics (size, shape, color, and properties) of MPs in the environment, the primary sources, and the transport pathways in various environmental compartments, and to shed more light on the ecological impact of MPs and the potential health effects on organisms and humans by identifying human exposure pathways.

Interactive effects of microplastics and benzo[a]pyrene on two species of marine invertebrates

This study aimed to evaluate B[a]P and low-density polyethylene microplastics (MPs) toxicty, alone and in mixture (0.03 to 30 μg L-1 of B[a]P; and 5, 50 and 500 mg L-1 for MPs). Five mg L-1 of MPs is considerably higher than commonly reported environmental concentrations, although it has been reported for marine environments. Individual (sea urchin embryo-larval development and mortality of mysids) and sub-individual responses (LPO and DNA damage in mysids) were assessed. The toxicity increased as the B[a]P concentration increased, and microplastics alone did not cause toxicity. B[a]P toxicity was not modified by the lowest concentration of MPs (5 mg L-1), but at higher MPs concentrations (50 and 500 mg L-1), the effects of B[a]P on sea urchin development and in biomarkers in mysids were diminished. Microplastics interacted with B[a]P in seawater, reducing its toxicity, probably due to adsorption of B[a]P to the surface of microplastics.

Effect of High-Density Polyethylene Microplastics on the Survival and Development of Eastern Oyster (Crassostrea virginica) Larvae

Microplastic (MP) pollution is a growing global concern-especially in estuarine areas that serve as natural habitats and nurseries for many marine organisms. One such marine organism is the Eastern oyster (Crassostrea virginica), which is a reef-forming keystone species in the Chesapeake Bay, the largest estuary in the United States. To understand the potential impacts of MP pollution on the estuary ecosystem, the effects of high-density polyethylene (HDPE) MPs on Eastern oyster larval survival and development were investigated. Three cohorts of larvae were exposed to HDPE MPs with a size of 10-90 µm at a 10 mg/L concentration, after 7 to 11 days of fertilization. After exposure, the number and size of oyster larvae were measured twice a week for approximately 2 weeks until larval settlement. The experiment found that there were no significant differences in the rate of survival between the control and MP-addition treatments. However, we noticed that larval development was significantly delayed with the MP treatment. The percentage of larvae that were ready to settle was 64% with the control treatment compared to 43.5% with the MP treatment. This delay in growth resulted in a delayed larval settlement, which could adversely affect the survival of the Eastern oyster due to the increased risk of predation. The current study demonstrates that MPs could be a risk to the ecology of estuaries, and plastic pollution management is needed for the preservation of these estuaries.

Exposure to polypropylene microplastics via diet and water induces oxidative stress in Cyprinus carpio

The occurrence of accumulation of microplastics in humans and wildlife has become a serious concern on a global scale, especially in the last decade. Although there are many studies on microplastics, their biological effects and toxicity on freshwater fish have not been fully revealed. In order to evaluate the potential toxic effects of PP (polypropylene) microplastics in freshwater fish, we performed 1-day, 2-day, 3-day, 4-day, 5-day, 6-day, and 7-day microplastic exposure to different concentrations of the microplastics through water and diet on Cyprinus carpio. Fish samples were divided into 3 groups; Group-A with different PP microplastic concentrations in their water (A_Low:1.0 g/L and A_High:2.5 g/L), Group-B with different PP microplastic concentrations in their diet (B_Low:100 mg/g and B_High:250 mg/g), and Group-C (Control group) free of PP microplastics in their diet and water. The results showed that although microplastics did not cause death in C. carpio, they caused oxidative stress in comparing the MP exposed groups to the control groups. When indices of oxidative stress of fish individuals in all treatment groups were compared with the control group, it was determined that MDA (malondialdehyde) and GSH (glutathione) levels increased, while TPC (total protein content) and CAT (catalase) levels decreased depending on the concentrations and exposure times. Significant differences were observed between the control and treatment groups in the indices of oxidative stress (P<0.05). This study provided basic toxicological data to elucidate and quantify the effects of PP microplastics on freshwater fish. In addition, this study is the first study to indicate that microplastic exposure of carp via diet and water causes oxidative stress in gill tissues and causes changes in CAT, MDA, GSH, and TPC levels. The findings also provide useful reference data for improving knowledge of the effects of microplastics on organisms in freshwater systems.

Microplastics as vectors of chemical contaminants and biological agents in freshwater ecosystems: Current knowledge status and future perspectives

Microplastics (MPs) are becoming ubiquitous, and their environmental fate is becoming an issue of concern. Our review aims to synthesize current knowledge status and provide future perspectives regarding the vector effect of MPs for chemical contaminants and biological agents. The evidence in the literature indicates that MPs are a vector for persistent organic pollutants (POPs), metals and pharmaceuticals. Concentrations of chemical contaminant in orders of six-fold higher on MPs surfaces than in the surrounding environmental waters have been reported. Chemical pollutants such as perfluoroalkyl substances (PAFSs), hexachlorocyclohexane (HCHs) and polycyclic aromatic hydrocarbons (PAHs), exhibiting polarities in the range of 3.3-9 are the commonest chemicals reported on MP surfaces. Regarding metals on MPs including chromium (Cr), lead (Pb), cobalt (Co), the presence of C-O and N-H in MPs promote a relatively high adsorption of these metals onto MP surfaces. Regarding pharmaceuticals, not much has been done, but a few studies indicate that commonly used drugs such as ibuprofen, ibuprofen, diclofenac, and naproxen have been associated with MPs. There is sufficient evidence supporting the claim that MPs can act as vectors for viruses, bacterial and antibiotic-resistant bacteria and genes, and MPs act to accelerate horizontal and vertical gene transfer. An area that deserves urgent attention is whether MPs can act as vectors for invertebrates and vertebrates, mainly non-native, invasive freshwater species. Despite the ecological significance of invasive biology, little research has been done in this regard. Overall, our review summarises the state of the current knowledge, identifies critical research gaps and provides perspectives for future research.

Resilient amphipods: Gammarid predatory behaviour is unaffected by microplastic exposure and deoxygenation

Microplastics are a ubiquitous and persistent form of pollution globally, with impacts cascading from the cellular to ecosystem level. However, there is a paucity in understanding interactions between microplastic pollution with other environmental stressors, and how these could affect ecological functions and services. Freshwater ecosystems are subject to microplastic input from anthropogenic activities (eg. wastewater), but are also simultaneously exposed to many other stressors, particularly reduced dissolved oxygen availability associated with climatic warming and pollutants, as well as biological invasions. Here, we employ the comparative functional response method (CFR; quantifying and comparing organism resource use as a function of resource density) to investigate the relative impact of different microplastic concentrations and oxygen regimes on predatory trophic interactions of a native and an invasive alien gammarid (Gammarus duebeni and Gammarus pulex). No significant effect on trophic interaction strengths was found from very high concentrations of microplastics (200 mp/L and 200,000 mp/L) or low oxygen (40 %) stressors on either species. Additionally, both gammarid species exhibited significant Type II functional responses, with attack rates and handling times not significantly affected by microplastics, oxygen or gammarid invasion status. Thus, both species showed resistance to the simultaneous effects of microplastics and deoxygenation in terms of feeding behaviour. Based on these findings, we suggest that the trophic function, in terms of predation rate, of Gammarus spp. may be sustained under acute bouts of microplastic pollution even in poorly‑oxygenated waters. This is the first study to investigate microplastic and deoxygenation interactions and to find no evidence for an interaction on a key invertebrate ecosystem service. We argue that our CFR methods can help understand and predict the future ecological ramifications of microplastics and other stressors across taxa and habitats.

Ingestion of polystyrene microparticles impairs survival and defecation in larvae of Polistes satan (Hymenoptera: Vespidae)

Microplastics (MPs) are widespread pollutants of emerging concern, and the risks associated with their ingestion have been reported in many organisms. Terrestrial environments can be contaminated with MPs, and terrestrial organisms, including arthropods, are predisposed to the risk of ingesting MPs. In the current study, the larvae of the paper wasp Polistes satan were fed two different doses (6 mg or 16 mg at once) of polystyrene MPs (1.43 mm maximum length), and the effects of these treatments on immature development and survival till adult emergence were studied. Ingestion of the two doses resulted in mortality due to impaired defecation prior to pupation. The survival of larvae that ingested 16 mg of MPs was significantly lower than that of the control. The ingestion of 16 mg of MPs also reduced the adult emergence (11.4%) in comparison to the control (44.4%). MPs were not transferred from the larvae to the adults that survived. These findings demonstrate that MP ingestion can be detrimental to P. satan, e.g. larval mortality can decrease colony productivity and thus the worker force, and that MPs can potentially affect natural enemies that occur in crops, such as predatory social wasps.

Microplastic intrusion into the zooplankton, the base of the marine food chain: Evidence from the Arabian Sea, Indian Ocean

Microplastics (MPs) are ubiquitous in the marine environment, yet information regarding their occurrence in the food web is limited. We investigated the concentration and composition of MPs in water and diverse zooplankton groups from the Arabian Sea basin. Forty-one zooplankton tows were collected with a bongo net (330 μm mesh) from the Arabian Sea in January 2019. MPs in the surface water varied between 0 and 0.055 particles/m³, with a relatively higher concentration (0.013 ± 0.002 particles/m³) in the central Arabian Sea. Though fibrous MPs were most abundant in the seawater (77.14 %), zooplankton prefers small fragments (55.3 %). The size of MPs was distinctly smaller (277.1 ± 46.74 μm) in zooplankton than that in seawater (864.32 ± 73.72 μm), and MPs bioaccumulation was observed in almost all the zooplankton functional groups. Polymer composition revealed polyamide, polyethylene, polypropylene, and PVC were abundant in water and zooplankton, suggesting that the textile, fishing, shipping, and packaging industries are significant sources. The prevailing northeasterly winds, strong West India Coastal Current, and conducive westward radiated Rossby wave during January 2019 have carried the microplastic contaminated water mass away from the coast, posing a threat to the open ocean ecosystems. These results demand further attention to investigate the state of plastic pollution in the Arabian Sea basin.

Presence of microplastic in the Patella caerulea from the northeastern Mediterranean Sea

This study reports first evidence of microplastic detection in the Patella caerulea collected from 5 different stations located in İskenderun Bay and Mersin Bay. A total of 160 P. caerulea specimens were examined and 40 of them contained MPs in their soft tissues. The number of microplastics extracted per sample varied from 0.20 ± 0.5 items/ind to 0.45 ± 0.7 items/ind depending on station. Fibers were predominant type of MPs and accounted for 75 % to 87.5 % of total extracted MPs, followed by fragments (12.5-25 %). Majority of MPs were 0.5-1 mm size and black in color. Fourier transform infrared spectroscopy (FTIR) showed that the extracted MPs were polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), high density polyethylene (HDPE). This study contributes to the knowledge of the transfer of microplastics to the marine food web and highlights the need for protective measurements.

Polystyrene microplastics exposure modulated the content and the profile of fatty acids in the Cladoceran Daphnia magna

A growing number of studies has shown that the exposure to microplastics (MPs) of different polymeric compositions can induce diverse adverse effects towards several aquatic species. The vast majority of such studies has been focused on the effects induced by the administration of MPs made by polystyrene (PS; hereafter PS-MPs). However, despite the increase in the knowledge on the potential toxicity of PS-MPs, there is a dearth of information concerning their role in affecting energy resources and/or their allocation. The present study aimed at exploring the impact of 21-days exposure to three concentrations (0.125, 1.25 and 12.5 μg mL^-1) of PS-MPs of different sizes (1 and 10 μm) on fatty acids (FAs) profile of the freshwater Cladoceran Daphnia magna. The exposure to the highest tested concentration of PS-MPs induced an overall decrease in D. magna total FAs content, independently of the particle size. Moreover, a change in the accumulation of essential FAs by the diet was noted, with an enhanced synthesis of monounsaturated FAs-rich storage lipids. However, a sort of adaptation to counteract the adverse effects and to re-establish the FAs homeostasis was observed in individuals treated with high PS-MPs concentration, independently of their size. These results indicate that the exposure to PS-MPs could alter the allocation or induce changes in FAs composition in D. magna, with potential long-term consequences on life-history traits of this zooplanktonic species.

Bioaccumulation and ecotoxicological impact of micro(nano)plastics in aquatic and land snails: Historical review, current research and emerging trends

Microplastics (MPs) and nanoplastics (NPs) are ubiquitous emerging pollutants in the environment. Although MPs/NPs' hazardous effects have been described at different trophic levels, little attention has been given to how they can affect gastropod communities. Thus, the current study aimed to summarize and critically address data available in the scientific literature about micro(nano)plastics' ecotoxicological impact on snails. The analyzed data has evidenced MP/NP bioaccumulation in 40 gastropod species collected in the field; 15 gastropod species were used to assess the potential toxicity of MPs/NPs. Asia accounted for the highest level of MPs/NPs bioaccumulated in gastropods; it was followed by the South American, European and Antarctic continents. MPs/NPs' toxicity depends on their composition, shape and size, as well as on differences in methodological approaches adopted by different studies. Results have shown that MPs/NPs induce several impairments - such as behavioral changes, developmental toxicity, dysbiosis, histopathological alterations, oxidative stress -, generate ecological impairments, as well as act as pollutant vector and increase chiral chemicals' toxicity. Research gaps and recommendations for future research were highlighted to help better understanding MPs/NPs' toxicity in gastropods, given the extremely important role played by them in studies focused on investigating how MPs/NPs can affect invertebrate communities living in terrestrial and aquatic environments.

Beyond the exposure phase: Microplastic depuration and experimental implications

Currently, most studies focus on the effect of microplastics (MPs) in the exposure phase, but pay limited attention to the depuration phase. Depuration is a promising practice to achieve safe aquaculture production, which is also helpful to understand the long-term impact of MPs. Therefore, investigating the post-exposure scenarios of MPs has great practical significance. In order to provide implications for future research, this work attempted to systematize the current findings and knowledge gaps regarding the depuration of MPs. More specifically, three methods, including direct fitting, one-compartment kinetic model and interval observation, for estimating the retention time of MPs to further determine the minimum depuration time were introduced, in which the one-compartment kinetic model could also be used to calculate the depuration rate constant and biological half-life of MPs. Moreover, the post-exposure effect of MPs generally presented three scenarios: incomplete reversal (legacy effect), return to control level (recovery) and stimulatory response (hormesis-like effect). In addition, the possible tissue translocation of MPs, the influence of food abundance and body shape on MPs egestion, and the potential interaction with environmental factors, have aroused great scientific concerns and need further exploration and clarification.

Single and combined toxicity assessment of primary or UV-aged microplastics and adsorbed organic pollutants on microalga Chlorella pyrenoidosa

Microplastics (MPs), an emerging pollutant, have been increasingly raising concern due to the potential impacts on aquatic organisms. Moreover, the environmental aged MPs always exhibit different environmental behavior and interaction effect with organic pollutants from virgin MPs. In this work, the single and combined toxicity impact on Chlorella pyrenoidosa, a symbiont representative, has been investigated between MPs (e.g., polyamide microplastic (PA6), 75 μm) and organic pollutants (e.g., sulfamethoxazole (SMX) and dicamba (DCB)). Growth inhibition, chlorophyll accumulation, superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT) were investigated with the primary or UV-aged PA6. Above 0.5 g/L PA6 (primary or UV-aged) inhibited cell growth and chlorophyll accumulation after 96 h cultivation as compared with the control. Besides, the inhibition impacts have enhanced as the UV-aging time extending in the single PA6 systems. The algae growth inhibition rate after 96 h cultivation in both the system i.e., single (PA6: 6.9%) and combined (PA6-SMX: 14.2%, PA6-DCB: 14.9%) was slightly lower than that of exposing in organic pollutants alone (SMX: 23.9%, DCB: 25.0%), while the chl. b concentration in 60 days UV-aged PA6 combined with SMX (1.19 mg/L) or DCB (1.40 mg/L) systems were higher than in single SMX (1.04 mg/L) or DCB (1.33 mg/L) system. In addition, there were several differences of the cellular oxidative stress in the combined system of SMX and DCB. Specially, it was not noticeable of three enzymatic activities for SMX exposing in the presence of primary or UV-aged PA6. While SOD, CAT, and MDA activities was obviously increasing after exposing in PA6 and DCB combined system, indicating the significant synergistic effect on algae cells damage. This research verified the remarkable combined toxicity between UV-aged MPs and organic pollutants on microalgae.

Time-dependent immune injury induced by short-term exposure to nanoplastics in the Sepia esculenta larvae

Marine organisms are threatened by various environmental contaminants, and nanoplastics (NPs) is one of the most concerned. Studied have shown that NPs has a certain impact on marine organisms, but the specific molecular mechanism is still unclear. At present, researches on the effect of NPs on marine life mostly focus on crustaceans, gastropods, and bivalves. In this study, cephalopod Sepia esculenta larvae were first used to investigate the potential immune response molecular mechanisms caused by PS-NPs (50 nm, 50 mg/L) short-term exposure (4 and 24 h). Through S. esculenta larvae transcriptome profile of gene expression analysis, 548 and 1990 genes showed differential expression at 4 and 24 h after NPs exposure, respectively. GO and KEGG enrichment analysis were performed to find immune related DEGs. Then, the interaction relationship between the immune related DEGs after NPs exposure was known through the constructed protein-protein interaction network. 20 hub genes were found on the base of KEGG pathway numbers involved and protein-protein interaction numbers. This research supply valuable genes for the study of cephalopod immune response caused by NPs, which can help us further uncover the molecular mechanisms of organism against NPs.

The dangerous transporters: A study of microplastic-associated bacteria passing through municipal wastewater treatment

Microplastics (MPs) provide a stable and protective habitat for diverse wastewater bacteria, including pathogenic and antibiotic-resistant species. Therefore, MPs may potentially transport these bacteria through wastewater treatment steps to the environment and far distances. This study investigated bacterial communities of MP-associated bacteria from different stages of municipal wastewater treatment processes to evaluate the potential negative effect of these biofilms on the environment. The results showed a high diversity of bacteria that were strongly attached to MPs. After all treatment steps, the core bacterial groups remained attached to MPs and escaped from the wastewater treatment plant with effluent water. Several pathogenic bacteria were identified in MP samples from all treatment steps, and most of them were found in effluent water. These data provide new insights into the possible impacts of wastewater-derived MPs on the environment. MP-associated biofilms were proved to be important sources of pathogens and antibiotic-resistant genes in natural waters.

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.

Microplastics alter multiple biological processes of marine benthic fauna

Marine sediments are a sink for microplastics, making seabed organisms particularly exposed. We used meta-analysis to reveal general patterns in a surge in experimental studies and to test for microplastic impact on biological processes including invertebrate feeding, survival and energetics. Using Hedge's effect size (g), which assesses the mean response of organisms exposed to microplastics compared to control groups, we found negative impacts (significant negative g values) across all life stages (overall effect size (g) = -0.57 95 % CI [-0.76, -0.38]), with embryos most strongly affected (g = -1.47 [-2.21, -0.74]). Six of seven biological process rates were negatively impacted by microplastic exposure, including development, reproduction, growth and feeding. Survival strongly decreased (g = -0.69 [-1.21, -0.17]), likely due to cumulative effects on other processes such as feeding and growth. Among feeding habits, omnivores and deposit feeders were most negatively impacted (g = -0.93 [-1.69, -0.16] and -0.92 [-1.53, -0.31], respectively). The study incorporated the first meta-analysis to contrast the effects of leachates, virgin, aged and contaminated particles. Exposure to leachates had by far the strongest negative effects (g = -0.93 [-1.35, -0.51]), showing studies of contaminants and leachates are critical to future research. Overall, our meta-analysis reveals stronger and more consistent negative impacts of microplastics on seabed invertebrates than recorded for other marine biota. Seabed invertebrates are numerous and diverse, and crucial to bottom-up processes, including nutrient remineralisation, bentho-pelagic coupling and energy transfer through the ocean food web. Marine sediments will store microplastics over long timescales. The reveal that microplastics impinge on multiple fundamental biological processes of seabed fauna implies plastic pollution could have significant and enduring effects on the functioning of the ocean.

Long-term exposure to microplastics induces intestinal function dysbiosis in rare minnow (Gobiocypris rarus)

Microplastics are ubiquitous in the natural environment, especially in waters, and their potential impact is also a key issue of concern. In this study, we used 1 µm, 1000 μg/L, polystyrene (PS-MPs) particles to analyze the effects after exposure for 14 and 28 days in rare minnow (Gobiocypris rarus). Results indicated that PS-MPs induce structural alterations in the intestinal tissue, including epithelial damage, villi damage and the inflammatory cell infiltration, while the changes were severer after exposure for 28 days. Polystyrene microplastics also significantly increased the activities of catalase (CAT, increased 142 % and 385 % in 14d and 28d), superoxide dismutase (SOD, increased 17.76 % and 23.43 % in the 14d and 28d) and the content of malondialdehyde (MDA, increased 14.5 % and 442 % in the 14d and 28d), glutathione (GSH, increased 146 % and 298 % in the 14d and 28d). The results not only showed the characterization of gut microbial communities in rare minnow, but also indicated that microbial diversity and composition were altered in gut of fish exposed to PS-MPs. In the control groups, Proteobacteria (31.36-54.54 %), Actinobacteriota (39.99-52.54 %), Fusobacteriota (1.43-1.78 %), Bacteriadota (0.31-0.57 %) were the four dominant bacterial phyla in the intestinal of rare minnow. After exposure to microplastics, In the gut microbiota, the proportion of Proteobacteria increased 9.27 % and 30 % with exposure time, while Actinobacteria decreased 37.89 % and significantly different after 28 days. In addition, metabolomic analysis suggested that exposure to PS-MPs induced alterations of metabolic profiles in rare minnow and differential metabolites were involved in energy metabolism, inflammatory responsible secretion, oxidative stress, nucleotide and its metabolomics. In conclusion, our findings suggest that long-term exposure to microplastics could induce intestinal inflammation, oxidative stress, microbiota dysbiosis and metabolic disorder in rare minnow, and the alterations and severity were exacerbated by prolonged exposure. This study has extended our cognition of the toxicity of polystyrene, and enriched theoretical data for exploring the toxicological mechanism of microplastics.

Microplastics impede larval urchin selective feeding

Microplastics are emergent threats to marine organisms as ingestion can cause a multitude of physiological problems. Suspension feeders, including marine invertebrate larvae, are particularly susceptible to ingesting microplastics due to similarities in physical appearance to algal cells. Larval feeding involves multiple stages: the capture and subsequent selection of particles followed by ingestion from the mouth to the stomach, digestion, and finally, egestion. Yet, little is known about which aspect of the feeding process is disrupted by microplastics. Here, we determine if prior exposure to microplastics alters the feeding behavior of the larval sea urchin Heliocidaris crassispina. We conducted two experiments: a food handling experiment studied larval survival, growth, and time required to fill and vacate the stomach; and a particle selection experiment analyzed changes in the ability of the larvae to selectively ingest algal cells over microplastics. In both experiments, larvae were pre-exposed to algae only (control), the addition of 10 μm polystyrene beads at 1 bead mL^-1 or 1000 beads mL^-1 until 3- or 7-days post-fertilization. Previous exposure to microplastics lengthened stomach filling time and impaired particle selection. While there was no significant change in survivorship and larval arm length, these sub-lethal impacts on larval feeding likely have more severe ramifications in vivo where food is limited, and thus, potentially threaten post-settlement success.

Toxic effects of pristine and aged polystyrene microplastics on selective and continuous larval culture of acorn barnacle Amphibalanus amphitrite

This study evaluates the toxicity of pristine (Unwashed) and aged, clean (Biofilm-) or fouled (Biofilm+), PS microspheres (3 µm,10 µm), using Washed particles as a reference material, on selective and continuous larval culture of Amphibalanus amphitrite. Exposure to 3 µm Unwashed and Biofilm+ particles for 24 h induced significant mortality (60 % and 57 % respectively) in stage II larvae. Stage II and VI nauplii showed greater uptake of 3 µm Biofilm- particles. Accumulative exposure to microplastics in continuous larval culture significantly affected the naupliar survival, particularly of stage III and IV. Cumulative mortality was > 70% after exposure to 3 µm Unwashed and 10 µm Biofilm+ particles. Unwashed particles with increasing concentration and aged particles with increasing size, delayed the development of nauplii to cyprids. Though,> 50% cyprids showed successful settlement however the highest concentration of 3 µm Biofilm+ microspheres inhibited the settlement and induced precocious metamorphosis in 9 % of the cyprids.

Microplastic ingestion in zooplankton from the Fram Strait in the Arctic

Some of the highest microplastic concentrations in marine environments have been reported from the Fram Strait in the Arctic. This region supports a diverse ecosystem dependent on high concentrations of zooplankton at the base of the food web. Zooplankton samples were collected during research cruises using Bongo and MOCNESS nets in the boreal summers of 2018 and 2019. Using FTIR scanning spectroscopy in combination with an automated polymer identification approach, we show that all five species of Arctic zooplankton investigated had ingested microplastics. Amphipod species, found in surface waters or closely associated with sea ice, had ingested significantly more microplastic per individual (Themisto libellula: 1.8, Themisto abyssorrum: 1, Apherusa glacialis: 1) than copepod species (Calanus hyperboreus: 0.21, Calanus glacialis/finmarchicus: 0.01). The majority of microplastics ingested were below 50 μm in size, all were fragments and several different polymer types were present. We quantified microplastics in water samples collected at six of the same stations as the Calanus using an underway sampling system (inlet at 6.5 m water depth). Fragments of several polymer types and anthropogenic cellulosic fibres were present, with an average concentration of 7 microplastic particles (MP) L^-1 (0-18.5 MP L^-1). In comparison to the water samples, those microplastics found ingested by zooplankton were significantly smaller, highlighting that the smaller-sized microplastics were being selected for by the zooplankton. High levels of microplastic ingestion in zooplankton have been associated with negative effects on growth, development, and fecundity. As Arctic zooplankton only have a short window of biological productivity, any negative effect could have broad consequences. As global plastic consumption continues to increase and climate change continues to reduce sea ice cover, releasing ice-bound microplastics and leaving ice free areas open to exploitation, the Arctic could be exposed to further plastic pollution which could place additional strain on this fragile ecosystem.

Acute and chronic ingestion of polyethylene (PE) microplastics has mild effects on honey bee health and cognition

The massive use of plastic has contributed to huge quantities of hazardous refuse at a global scale and represents one of the most prominent issues of the Anthropocene. Microplastics (MPs) have been detected in almost all environments and pose a potential threat to a variety of plant and animal species. Many studies have reported a variety of effects, from negligible to detrimental, of MPs to aquatic organisms. Conversely, much less is known about their effect on terrestrial biota, and particularly on animal behavior and cognition. We assessed the oral toxicity of polyethylene (PE) MPs at three different concentrations (0.5, 5, and 50 mg L^-1), and at different timescales (1 day and 7 days of exposure) and tested for their effects on survival, food intake, sucrose responsiveness, habituation to sucrose and appetitive olfactory learning and memory in the honey bee Apis mellifera. We found that workers were not completely unaffected by acute and prolonged ingestion of this polymer. A significant effect of PE on bee mortality was found for the highest concentration but not for lower ones. PE affected feeding behavior in a concentration-dependent manner, with bees consuming more food than controls when exposed to low concentration PE. Regarding our behavioral and cognitive experiments, the high concentration PE was found to affect only bees' ability to respond consistently to sucrose but not sucrose sensitivity, habituation to sucrose or learning and memory abilities, even for prolonged exposure to PE. While these last results may look somewhat encouraging, we discussed why caution is warranted before ruling out the possibility that PE particles at environmental concentrations are harmful to honey bees.

Cyto-Genotoxic Effect Causing Potential of Polystyrene Micro-Plastics in Terrestrial Plants

The polystyrene micro-plastics (Ps-MPs) is one of the leading pollutants found in both aquatic and terrestrial ecosystems. While most of the studies on the morphology and cyto-toxicity of MPs have been based on aquatic organisms, their effects on terrestrial plants are still scarcely known. The present study was an attempt to measure the effect of different sizes (80, 100, 200, 500, 1000, 2000, 4000, and 8000 nm) and concentrations (100 and 400 mg/L) of Ps-MPs on the root length and chromosomes of root tip cells of Allium cepa using A. cepa root chromosomal aberration assay. Large size Ps-MPs (4000 and 8000 nm) showed the highest reduction in A. cepa root length; however, the differences were not significant (at p ≤ 0.05), with respect to negative control (Milli-Q water). The mitotic index showed both significant size- and concentration-dependent decreases, being the lowest (12.06%) in 100 nm at 100 mg/L concentration, with respect to the control (25.05%). The chromosomal abnormality index (CAI) and nuclear abnormality index (NAI) showed significant decreases, with respect to negative control. In addition, the induction of micro-nucleated cells was also observed in Allium root tip cells, when treated with MPs of all sizes, which can predict direct DNA damage to the plant cells. Hence, we conclude that most of the MP sizes caused cyto-toxic and nuclear damage by adversely impacting the spindle formation and induction of micro-nucleated cells in Allium cepa root tip cells. To the best of our knowledge, this is the first study that showed the effect of considerable size range of Ps-MP sizes on the root length and cell division in plants.

Internalization, reduced growth, and behavioral effects following exposure to micro and nano tire particles in two estuarine indicator species

Synthetic rubber emissions from automobile tires are common in aquatic ecosystems. To assess potential impacts on exposed organisms, early life stages of the estuarine indicator species Inland Silverside (Menidia beryllina) and mysid shrimp (Americamysis bahia) were exposed to three tire particle (TP) concentrations at micro and nano size fractions (0.0038, 0.0378 and 3.778 mg/L in mass concentrations for micro size particles), and separately to leachate, across a 5-25 PSU salinity gradient. Following exposure, M. beryllina and A. bahia had significantly altered swimming behaviors, such as increased freezing, changes in positioning, and total distance moved, which could lead to an increased risk of predation and foraging challenges in the wild. Growth for both A. bahia and M. beryllina was reduced in a concentration-dependent manner when exposed to micro-TP, whereas M. beryllina also demonstrated reduced growth when exposed to nano-TP (except lowest concentration). TP internalization was dependent on the exposure salinity in both taxa. The presence of adverse effects in M. beryllina and A. bahia indicate that even at current environmental levels of tire-related pollution, which are expected to continue to increase, aquatic ecosystems may be experiencing negative impacts.

Can microplastics facilitate the emergence of infectious diseases?

Plastic pollution is a major environmental problem. Small plastic particles (called microplastics) have been reported to have pernicious effects on human and wildlife health, by altering physiological functions (e.g., immunity, metabolism) and interfering with commensal microorganisms. However, in addition to these direct toxic effects, we suggest that microplastic pollution might also exert deleterious effects, modifying (i) the exposure to pathogens (e.g., multi-drug resistant bacteria) and (ii) the dynamics of vector-borne diseases. Therefore, we argue that microplastics should be considered as a ubiquitous environmental hazard, potentially promoting the (re)emergence of infectious diseases. The implementation of multi- and interdisciplinary research projects are crucial to properly evaluate if microplastic pollution should be added to the current list of global health threats.

Complex Bilateral Interactions Determine the Fate of Polystyrene Micro- and Nanoplastics and Soil Protists: Implications from a Soil Amoeba

Nano- and microplastics have become a serious global concern, threatening our living environments. Previous studies have shown that many organisms, including bacteria, animals, and plants, can be affected by microplastics. However, little is known about one ecologically important group of soil organisms, the protists. In this study, we investigated how polystyrene micro- and nanoplastics interacted with a soil amoeba Dictyostelium discoideum. The results showed that environmental concentrations of nano- and microplastics could negatively affect the soil amoeba's fitness and development. D. discoideum ingested both nano- and microplastics through phagocytosis but packed and excreted them during slug migration, which also promoted their biodegradation. Fourier transform infrared spectroscopy analyses revealed the formation of new oxygen-containing functional groups and the sign of possible oxidation of polystyrene. Also, nano- and microplastic exposure disrupted the nutrient and energy metabolisms of D. discoideum and affected the expression of key genes (e.g., cf45-1, dcsA, aprA, dymB, and gefB) related to morphogenesis and phagocytosis. In conclusion, our results show that nano- and microplastics have complex bilateral interactions with the soil amoeba, affecting each other's fate in the soil environment. This study provides new insights into how soil protists interact with nano- and microplastics in the soil ecosystem.

Slipper snail tales: How Crepidula fornicata and Crepidula atrasolea became model molluscs

Despite the great abundance and diversity of molluscs, only a few have attained "model research organism" status. One of those species is the slipper snail Crepidula fornicata. Its embryos were first used for classical lineage tracing studies in the late 19th century, and over a 100 years later they were "re-discovered" by our labs and used for modern fate mapping, gene perturbation, in vivo imaging, transcriptomics, and the first application of CRISPR/Cas9-mediated genome editing among the Spiralia/Lophotrochozoa. Simultaneously, other labs made extensive examinations of taxonomy, phylogeny, ecology, life-history, mode of development, larval feeding behavior, and responses to the environment in members of the family Calyptraeidae, which includes the genus Crepidula. Recently, we developed tools, resources, and husbandry protocols for another, direct-developing species, Crepidula atrasolea. This species is an ideal "lab rat" among molluscs. Together these species will be valuable for probing the cellular and molecular mechanisms underlying molluscan biology and evolution.

Microplastics and Their Impact on Reproduction—Can we Learn From the C. elegans Model?

Biologically active environmental pollutants have significant impact on ecosystems, wildlife, and human health. Microplastic (MP) and nanoplastic (NP) particles are pollutants that are present in the terrestrial and aquatic ecosystems at virtually every level of the food chain. Moreover, recently, airborne microplastic particles have been shown to reach and potentially damage respiratory systems. Microplastics and nanoplastics have been shown to cause increased oxidative stress, inflammation, altered metabolism leading to cellular damage, which ultimately affects tissue and organismal homeostasis in numerous animal species and human cells. However, the full impact of these plastic particles on living organisms is not completely understood. The ability of MPs/NPs to carry contaminants, toxic chemicals, pesticides, and bioactive compounds, such as endocrine disrupting chemicals, present an additional risk to animal and human health. This review will discusses the current knowledge on pathways by which microplastic and nanoplastic particles impact reproduction and reproductive behaviors from the level of the whole organism down to plastics-induced cellular defects, while also identifying gaps in current knowledge regarding mechanisms of action. Furthermore, we suggest that the nematode Caenorhabditis elegans provides an advantageous high-throughput model system for determining the effect of plastic particles on animal reproduction, using reproductive behavioral end points and cellular readouts.

Effects of high-molecular-weight polyvinyl chloride on Xenopus laevis adults and embryos: the mRNA expression profiles of Myf5, Esr1, Bmp4, Pax6, and Hsp70 genes during early embryonic development

Microplastics and associated adverse effects have been on the global agenda in recent years. Because of its importance as a model organism for studies on developmental biology, Xenopus laevis has been chosen as the study animal in in vitro teratogenesis studies. FETAX test uses early-stage embryos of X. laevis to measure the potential of substances to cause mortality, malformation, and growth inhibition in developing embryos. The aim of this study was to examine the effects of high molecular weight polyvinyl chloride (HMW-PVC) on parental X. laevis frogs and their embryos using the FETAX test. To this purpose, a HMW-PVC dose of 1% of body weight/twice each week was provided to frogs by oral gavage throughout 6 weeks. After the procedure, oocytes and sperms of HMW-PVC-exposed frogs were fertilized and FETAX was applied to selected embryos. After the completion of a 96-h incubation period, tadpoles were examined, their live/dead status were determined, their lengths were measured, and their anomalies were photographed. Besides, excised organs of the parental frogs were referred to histopathology examination. On the other hand, the mRNA expression levels of Hsp70, Myf5, Bmp4, Pax6, and Esr1 genes were determined by applying real-time quantitative PCR method to cDNA which was synthesized from the total RNA of embryos. The results showed that treatment with HMW-PVC dose of 1% of body weight/twice each week caused malformations and decreased viability. Hsp70 and Pax6 gene expression levels significantly decreased in all assay groups, as compared with controls. Lung and intestine tissues showed normal appearance in histopatological examination. Further research is required to explain the whole effects of HMW-PVC exposure on X. laevis embryos.

Effects of microplastics on the feeding rates of larvae of a coastal fish: direct consumption, trophic transfer, and effects on growth and survival

Microplastics are now found throughout the world's oceans, and although many organisms ingest microplastics, less is known about how plastics in seawater may affect key processes such as feeding rate, growth, and survival. We used a series of laboratory experiments to test whether microplastics in seawater affected the feeding rates of larvae of the California Grunion, Leuresthes tenuis. In addition, we tested whether trophic transfer of microplastics from zooplankton to larval fish can occur and affect growth and survival of fish. We measured feeding rates of grunion larvae at various concentrations of 75-90 µm and 125-250 µm polyethylene microplastics and under both still water and turbulent conditions. In these experiments, exposure to microplastics had modest effects on feeding rates, though responses may be somewhat complex. Low concentrations of microplastics increased feeding rates compared to the control, but at higher concentrations, feeding rates were indistinguishable from those in the control group, though effects were small compared to natural variation in feeding rates among individual fish. Experiments to test for trophic transfer of microplastics revealed that grunion larvae that were fed brine shrimp exposed to high concentrations of microplastics had lower growth rates and elevated mortality rates. Overall, our results suggest that the direct effects of microplastics on feeding rates of California Grunion during the early larval phase are minor, while the trophic transfer of microplastics from zooplankton to larval fish may have significant effects on their growth and survival.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00227-021-04010-x.

Effects of nanoplastics on microalgae and their trophic transfer along the food chain: recent advances and perspectives

Nanoplastics (NPs) have drawn increasing attention in recent years due to their potential threats to aquatic ecosystems. Microalgae are primary producers, which play important roles in the normal functioning of ecosystems. According to the source of production and laboratory experiments, both NPs and microalgae are likely to be widely found in various water environments, so they have a great chance of interacting with each other. Although tremendous efforts have been made to explore these potential interactions, a timely and critical review is still missing. In this paper, the effects of NPs on microalgae and their trophic transfer along the food chain are summarized. The toxic impact of NPs on microalgae is tightly associated with the concentrations, sizes and surface charge of NPs, as well as the microalgal species. In addition, NPs could also interact with many other contaminants, thus leading to combined effects on microalgae. NP exposure might block substance and energy exchange between microalgae and their surrounding environment, lead to a shading effect on microalgae, promote the production of reactive oxygen species (ROS) or induce direct physical damage on microalgae, thereby inhibiting the growth of microalgae. Moreover, NPs could also be trophically transferred along the food chain through microalgae and subsequently affect the species at a higher trophic level. Yet importantly, current understanding of the interactions between NPs and microalgae is still quite limited, and needs to be further studied.

Dangerous microplastics in topshells and anemones along the north coast of Spain

While levels of microplastics and other pollutants keep increasing in all coastal habitats, seafood is being eaten all over the world. In this research, three edible species were sampled from six points along the central north coast of Spain: Actinia equina anemones and Phorcus lineatus and Steromphala umbilicaris topshells (N = 100). Putative microplastics (N = 2157) were identified, counted, and many analyzed through FT-IR spectroscopy. Herbivorous topshells contained significantly more microplastics than carnivorous anemones. The most common particles were fibers, with transparent, blue and black as most prominent colours. Plastics included PE, polyester, PET, PP, nylon, PS, PVB and acrylic fibers. The sampled items contained several harmful compounds, including PTTC of which even one particle could be fatal if inhaled. This highlights the urgent need for studies regarding the safety of seafood.

Microplastics pollution in the intertidal limpet, Nacella magellanica, from Beagle Channel (Argentina)

Microplastics (MPs) have been identified in diverse marine invertebrates; however, there are few studies on limpets. This study aimed to evaluate and compare the presence of MPs in Nacella magellanica among sites of the Beagle Channel with different degree of anthropogenic influence. Intertidal limpets were sampled in three sites: Ushuaia Bay (UB) (inside Ushuaia city), a site with high anthropogenic influence owing to population growth, and fisheries, industrial and port activities; Ensenada Zaratiegui (EZ) and Playa Larga (PL) (west and east of Ushuaia city, respectively), both sites with a certain degree of environmental protection and low anthropogenic influence. MPs were isolated from the whole soft tissue of individuals by oxidative digestions with H₂O₂ (30%; 1:10 w/v). MPs occurrence was 100% in organisms from UB and EZ, whereas 90% in PL. Limpets from UB showed 10 ± 6.69 MPs/ind and 2.22 ± 0.78 MPs/g ww, while in PL and EZ there were 2.90 ± 2.02 MPs/ind and 0.96 ± 0.94 MPs/g ww; and 5.60 ± 2.59 MPs/ind and 2.41 ± 1.47 MPs/g ww, respectively. Fibres were the most abundant MPs type, followed by fragments and films. Fibres and films were identified as semi-synthetic cellulose and, although the polymer matrix of fragments was masked by copper phthalocyanine, one of them could be identified as polystyrene. As expected, the highest abundance of MPs was found in UB. However, a lower abundance of particles was detected in PL (downstream of UB) than in EZ (upstream of UB). This could be due to the influence of both the main current of the Beagle Channel and fluvial discharges, reducing the buoyancy of MPs. More studies are needed to understand the contribution of regional and local features to the accumulation of MPs in these environments and their interaction with the biota.

Evidence of deleterious effects of microplastics from aquaculture materials on pediveliger larva settlement and oyster spat growth of Pacific oyster, Crassostrea gigas

Plastic is currently used in aquaculture as a material for settlement and magnification of oyster spats. Plastic weathering and fragmentation under natural conditions can lead to the production of micro and nanoparticles and additive leakage, with potential toxic effects on marine life. This study investigates the effects of the exposure to microplastic (MPs) cocktail derived from aged aquaculture material on oyster pediveliger larvae (Crassostrea gigas). The cocktail was made of high-density polyethylene (HDPE), polypropylene (PP) and polyvinyl chloride (PVC). The concentrations tested were 0, 0.1, and 10 mg MP·L^-1. During the 7-day fixation phase, pediveliger larvae (17 days) were exposed to the MP cocktail in laboratory-controlled conditions. After exposure, the success of settlement was significantly lower for larvae exposed to 10 mg MP·L^-1 (49 ± 0.9%) compared to control ones (61.8 ± 1.6%). No malformations or metamorphosis abnormalities were observed. Growth of pediveliger and spat stages was monitored up to 11 months. During the first twenty-eight days of development, spat growth was significantly lower for the two MPs exposure conditions (0.1 and 10 mg MP·L^-1; respectively -51.8% and -44.4%) compared to control group. Subsequently, the previously exposed oysters grew faster than the control condition, resulting in a significantly greater growth (0.1 and 10 mg MP·L^-1: +18.3% and +19.7%) than the control group at the end of follow-up. The nearly one-year follow-up highlighted the potential effects of MPs from aquaculture on larvae and spat of C. gigas.

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.