Toxicity of microplastics and copper, alone or combined, in blackspot seabream (Pagellus bogaraveo) larvae

Microplastics and copper impacts on feeding, oxidative stress, antioxidant enzyme activity, and dimethylated sulfur compounds production in Manila clam Ruditapes philippinarum

Microplastics (MPs) are widespread ocean pollutants and many studies have explored their effects. However, research on MPs combined impact with copper (Cu) on dimethylated sulfur compound production is limited. Dimethyl sulfide (DMS) is an important biogenic sulfur compound related to global temperatures. This study examined the ecotoxicological effects of polyamide 6 MPs and Cu on dimethylsulfoniopropionate (DMSP), DMS, and dimethyl sulfoxide (DMSO) production in Manila clams (Ruditapes philippinarum). Our findings showed that MPs and Cu increased oxidative stress, indicated by higher superoxide anion radical production and malondialdehyde levels while decreasing glutathione contents and increasing superoxide dismutase activities. Additionally, MPs and Cu exposure reduced DMS and dissolved DMSO (DMSOd) concentrations due to decreased grazing. These results contribute to a better understanding of the ecotoxicological effects of MPs/Cu on bivalves and their roles in the organic sulfur cycle, suggesting a need for further research on long-term impacts on them.

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

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

Microplastics from face masks: Unraveling combined toxicity with environmental hazards and their impacts on food safety

Microplastics (MPs) refer to tiny plastic particles, typically smaller than 5 mm in size. Due to increased mask usage during COVID-19, improper disposal has led to masks entering the environment and releasing MPs into the surroundings. MPs can absorb environmental hazards and transfer them to humans and animals via the food chain, yet their impacts on food safety and human health are largely neglected. This review summarizes the release process of MPs from face masks, influencing factors, and impacts on food safety. Highlights are given to the prevalence of MPs and their combined toxicities with other environmental hazards. Control strategies are also explored. The release of MPs from face masks is affected by environmental factors like pH, UV light, temperature, ionic strength, and weathering. Due to the chemical active surface and large surface area, MPs can act as vectors for heavy metals, toxins, pesticides, antibiotics and antibiotic resistance genes, and foodborne pathogens through different mechanisms, such as electrostatic interaction, precipitation, and bioaccumulation. After being adsorbed by MPs, the toxicity of these environmental hazards, such as oxidative stress, cell apoptosis, and disruption of metabolic energy levels, can be magnified. However, there is a lack of comprehensive research on both the combined toxicities of MPs and environmental hazards, as well as their corresponding control strategies. Future research should prioritize understanding the interaction of MPs with other hazards in the food chain, their combined toxicity, and integrating MPs detection and degradation methods with other hazards.

Toxic effects of microplastic and nanoplastic on the reproduction of teleost fish in aquatic environments

Microplastics and nanoplastics are widely present in aquatic environments and attract significant scholarly attention due to their toxicity, persistence, and ability to cross biological barriers, which pose substantial risks to various fish species. Microplastics and nanoplastics can enter fish through their digestive tract, gills and skin, causing oxidative damage to the body and adversely affecting their reproductive system. Given that fish constitute a crucial source of high-quality protein for humans, it is necessary to study the impact of microplastics on fish reproduction in order to assess the impact of pollutants on ecology, biodiversity conservation, environmental sustainability, and endocrine disruption. This review explores the reproductive consequences of microplastics and nanoplastics in fish, examining aspects such as fecundity, abnormal offspring, circadian rhythm, gonad index, spermatocyte development, oocyte development, sperm quality, ovarian development, and changes at the molecular and cellular level. These investigations hold significant importance in environmental toxicology.

Microbial strategies for effective microplastics biodegradation: Insights and innovations in environmental remediation

Microplastics (MPs), diminutive yet ubiquitous fragments arising from the degradation of plastic waste, pervade environmental matrices, posing substantial risks to ecological systems and trophic dynamics. This review meticulously examines the origins, distribution, and biological impacts of MPs, with an incisive focus on elucidating the molecular and cellular mechanisms underpinning their toxicity. We highlight the indispensable role of microbial consortia and enzymatic pathways in the oxidative degradation of MPs, offering insights into enhanced biodegradation processes facilitated by innovative pretreatment methodologies. Central to our discourse is the interplay between MPs and biota, emphasizing the detoxification capabilities of microbial metabolisms and enzymatic functions in ameliorating MPs' deleterious effects. Additionally, we address the practical implementations of MP biodegradation in environmental remediation, advocating for intensified research to unravel the complex biodegradation pathways and to forge effective strategies for the expeditious elimination of MPs from diverse ecosystems. This review not only articulates the pervasive challenges posed by MPs but also positions microbial strategies at the forefront of remedial interventions, thereby paving the way for groundbreaking advancements in environmental conservation.

Combined toxicity of microplastics and copper on Goniopora columns

As microplastics (MP) become ubiquitous, their interactions with heavy metals threatens the coral ecosystem. This study aimed to assess the combined toxicity of MP and copper (Cu) in the environment of coral. Goniopora columna was exposed to polyethylene microplastics (PE-MP) combined with Cu2+ at 10, 20, 50, 100, and 300 μg/L for 7 days. Polyp length and adaptability were recorded daily, and coral samples were collected at 1, 3, 5, and 7 days to analyse zooxanthellae density and antioxidant activity. Tissue observations and the analysis of MP and Cu2+ accumulation were conducted on the 7th day. After 1 day of exposure, PE-MP combined with different concentrations of Cu2+ significantly decreased polyp length and adaptability compared with PE-MP alone. Simultaneously, a significant increase in malondialdehyde (MDA) content, lead to coral oxidative stress, which was a combined effect with PE-MP. After 3 days of exposure, PE-MP combined with Cu2+ at >50 μg/L significantly reduced zooxanthellae density, damaging the coral's symbiotic relationship. In antioxidant enzyme activity, superoxide dismutase (SOD) activity decreased significantly after 1 day of exposure. After 3 days of exposure, glutathione peroxidase (GPx) activity significantly increased with Cu2+ at >20 μg/L. After 5 days of exposure, PE-MP combined with different concentrations of Cu2+ significantly reduced catalase (CAT), glutathione (GSH), and glutathione transferase (GST) activity, disrupting the antioxidant enzyme system, and acting antagonistically to PE-MP alone. Tissue observations revealed that the PE-MP combined with Cu2+ at >50 μg/L caused severe mesenteric atrophy, vacuolar, and Cu2+ accumulation in the coral mesenteric compared with PE-MP alone. The results suggest that combined exposure of PE-MP and copper leads to more severe oxidative stress, disruption antioxidant enzyme system, tissue damage, and Cu2+ accumulation, resulting in a significant maladaptation of corals to the environment.

Insight into microplastics in the aquatic ecosystem: Properties, sources, threats and mitigation strategies

Globally recognized as emergent contaminants, microplastics (MPs) are prevalent in aquaculture habitats and subject to intense management. Aquaculture systems are at risk of microplastic contamination due to various channels, which worsens the worldwide microplastic pollution problem. Organic contaminants in the environment can be absorbed by and interact with microplastic, increasing their toxicity and making treatment more challenging. There are two primary sources of microplastics: (1) the direct release of primary microplastics and (2) the fragmentation of plastic materials resulting in secondary microplastics. Freshwater, atmospheric and marine environments are also responsible for the successful migration of microplastics. Until now, microplastic pollution and its effects on aquaculture habitats remain insufficient. This article aims to provide a comprehensive review of the impact of microplastics on aquatic ecosystems. It highlights the sources and distribution of microplastics, their physical and chemical properties, and the potential ecological consequences they pose to marine and freshwater environments. The paper also examines the current scientific knowledge on the mechanisms by which microplastics affect aquatic organisms and ecosystems. By synthesizing existing research, this review underscores the urgent need for effective mitigation strategies and further investigation to safeguard the health and sustainability of aquatic ecosystems.

Impacts of exposure to nanopolystyrene and/or chrysene at ambient concentrations on neurotoxicity in Siniperca chuatsi

Health risks caused by widespread environmental pollutants such as nanopolystyrene (NP) and chrysene (CHR) in aquatic ecosystems have aroused considerable concern. The present study established juvenile Mandarin fish (Siniperca chuatsi) models of NP and/or CHR exposure at ambient concentrations for 21 days to systematically investigate the underlying neurotoxicity mechanisms. The results showed that single and combined exposure to NP and CHR not only reduced the density of small neuronal cells in the grey matter layer of the optic tectum, but also induced brain oxidative stress according to physiological parameters including CAT, GSH-Px, SOD, T-AOC, and MDA. The co-exposure alleviated the histopathological damage, compared to NP and CHR single exposure group. These results indicate that NP and/or CHR causes neurotoxicity in S. chuatsi, in accordance with decreased acetylcholinesterase activity and altered expression of several marker genes of nervous system functions and development including c-fos, shha, elavl3, and mbpa. Transcriptomics analysis was performed to further investigate the potential molecular mechanisms of neurotoxicity. We propose that single NP and co-exposure induced oxidative stress activates MMP, which degrades tight junction proteins according to decreased expression of claudin, JAM, caveolin and TJP, ultimately damaging the integrity of the blood-brain barrier in S. chuatsi. Remarkably, the co-exposure exacerbated the blood-brain barrier disruption. More importantly, single NP and co-exposure induced neuronal apoptosis mainly activates the expression of apoptosis-related genes through the death receptor apoptosis pathway, while CHR acted through both death receptor apoptosis and endoplasmic reticulum apoptosis pathways. Additionally, subchronic CHR exposure caused neuroinflammation, supported by activation of TNF/NF-κB and JAK-STAT signaling pathways via targeting-related genes, while the co-exposure greatly alleviated the neuroinflammation. Collectively, our findings illuminate the underlying neurotoxicity molecular mechanisms of NP and/or CHR exposure on aquatic organisms.

Toxicity of co-exposure of microplastics and lead in African catfish (Clarias gariepinus)

Microplastics (MPs) are an emerging threat to freshwater ecosystems with several ecotoxicological ramifications for fish. Microplastics (MPs) can adsorb heavy metals on their surfaces and increase their availability to aquatic organisms. The combined impact of lead and microplastics on fish has only been studied seldom utilizing a variety of markers. The present study aimed to evaluate the hematological, biochemical, and inflammatory signals (cytokines), as well as antioxidant enzymes in African catfish (Clarias gariepinus) exposed to lead (Pb) and MPs individually and combined for 15 days (acute toxicity experiment). The fish were split into four groups, the first of which was the control group. The second group received exposure to 1 mg/L of lead nitrate [Pb(NO3)2]. The third group was given 100 mg/L of MPs. A solution containing 100 mg/L of MPs and 1 mg/L of lead nitrate [Pb(NO3)2] was administered to the fourth group (the combination group). According to the findings, when MPs and Pb were combined for 15 days, the red blood cells (RBCs), thrombocytes, and lymphocytes were significantly reduced in comparison to the control fish. When compared to the control fish, the fish exposed to MPs and Pb alone or together showed a significant rise in blood interleukin-1β (IL-1β) and interleukin-6 (IL-6) cytokines. Both MPs and Pb exposure in catfish resulted in significant changes in the plasma electrolytes. The fish treated with MPs and Pb individually or in combination showed significant reduction in superoxide dismutase (SOD) and total antioxidant capacity (TAC) levels compared to the control group. The fish exposed to the combined action of MPs and Pb showed a considerable modification in all biochemical markers. The difference in the mean concentration of Pb (mg/L) between the fish exposed to Pb alone and the fish subjected to Pb and MPs combination was not statistically significant. In conclusion, according to this investigation, exposure to Pb caused an insignificant increase in Pb accumulation when MPs were present. However, co-exposure may result in anemia, cellular harm, extremely high levels of oxidative stress, and an inflammatory reaction.

The Combined Effect of Copper Nanoparticles and Microplastics on Transcripts Involved in Oxidative Stress Pathway in Rainbow Trout (Oncorhynchus Mykiss) Hepatocytes

Copper nanoparticles (CuNPs) and microplastics (MPs) are two emerging contaminants of freshwater systems. Despite their co-occurrence in many water bodies, the combined effects of CuNPs and MPs on aquatic organisms are not well-investigated. In this study, primary cultures of rainbow trout hepatocytes were exposed to dissolved Cu, CuNPs, MPs, or a combination of MPs and CuNPs for 48 h, and the transcript abundances of oxidative stress-related genes were investigated. Exposure to CuNPs or dissolved Cu resulted in a significant increase in the transcript abundances of two antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD). Exposure to CuNPs also led to an upregulation in the expression of Na+/K+ ATPase alpha 1 subunit (ATP1A1). Microplastics alone or in combination with CuNPs did not have a significant effect on abundances of the target gene transcripts. Overall, our findings suggested acute exposure to CuNPs or dissolved ions may induce oxidative stress in hepatocytes, and the Cu-induced effect on target gene transcripts was not associated with MPs.

Physiological effects and molecular response in the marine rotifer Brachionus plicatilis after combined exposure to nanoplastics and copper

Because nanoplastics (NPs) can transport pollutants, the absorption of surrounding pollutants into NPs and their effects are important environmental issues. This study shows a combined effect of high concentrations of NPs and copper (Cu) in the marine rotifer Brachionus plicatilis. Co-exposure decreased the growth rate, reproduction, and lifespan. The highest level of NP ingestion was detected in the co-treated group, but the Cu concentration was higher in the Cu single-exposure group. ERK activation played a key role in the downstream cell signaling pathway activated by the interaction of NPs and Cu. The increased sensitivity of B. plicatilis to Cu could be due to the impairment of MXR function caused by a high concentration of NPs, which supports our in vivo experiment results. Our results show that exposure to NPs could induce the dysfunction of several critical molecular responses, weakening resistance to Cu and thereby increasing its physiological toxicity in B. plicatilis.

Microplastics in aquatic environments: A comprehensive review of toxicity, removal, and remediation strategies

The occurrence of microplastics (MPs) in aquatic environments has been a global concern because they are toxic and persistent and may serve as a vector for many legacies and emerging pollutants. MPs are discharged to aquatic environments from different sources, especially from wastewater plants (WWPs), causing severe impacts on aquatic organisms. This study mainly aims to review the Toxicity of MPs along with plastic additives in aquatic organisms at various trophic compartments and available remediation methods/strategies for MPs in aquatic environments. Occurrences of oxidative stress, neurotoxicity, and alterations in enzyme activity, growth, and feeding performance were identical in fish due to MPs toxicity. On the other hand, growth inhibition and ROS formation were observed in most of the microalgae species. In zooplankton, potential impacts were acceleration of premature molting, growth retardation, mortality increase, feeding behaviour, lipid accumulation, and decreased reproduction activity. MPs togather with additive contaminants could also exert some toxicological impacts on polychaete, including neurotoxicity, destabilization of the cytoskeleton, reduced feeding rate, growth, survivability and burrowing ability, weight loss, and high rate of mRNA transcription. Among different chemical and biological treatments for MPs, high removal rates have been reported for coagulation and filtration (>86.5 %), electrocoagulation (>90 %), advanced oxidation process (AOPs) (30 % to 95 %), primary sedimentation/Grit chamber (16.5 % to 58.84 %), adsorption removal technique (>95 %), magnetic filtration (78 % to 93 %), oil film extraction (>95 %), and density separation (95 % to 100 %). However, desirable extraction methods are required for large-scale research in MPs removal from aquatic environments.

Factors Affecting the Adsorption of Heavy Metals by Microplastics and Their Toxic Effects on Fish

Fish not only constitute an important trophic level in aquatic ecosystems but also serve as an important source of protein for human beings. The health of fish is related to the sustained and healthy development of their entire aquatic ecosystem. Due to the widespread use, mass production, high disposal frequency, and degradation resistance of plastics, these pollutants are released into aquatic environments on a large scale. They have become one of the fastest growing pollutants and have a substantial toxic effect on fish. Microplastics have intrinsic toxicity and can absorb heavy metals discharged into water. The adsorption of heavy metals onto microplastics in aquatic environments is affected by many factors and serves as a convenient way for heavy metals to migrate from the environment to organisms. Fish are exposed to both microplastics and heavy metals. In this paper, the toxic effects of heavy metal adsorption by microplastics on fish are reviewed, and the focus is on the toxic effects at the individual (survival, feeding activity and swimming, energy reserves and respiration, intestinal microorganisms, development and growth, and reproduction), cellular (cytotoxicity, oxidative damage, inflammatory response, neurotoxicity, and metabolism) and molecular (gene expression) levels. This facilitates an assessment of the pollutants' impact on ecotoxicity and contributes to the regulation of these pollutants in the environment.

Effects of microplastics on the toxicity of co-existing pollutants to fish: A meta-analysis

Aquatic ecosystems are among the main destination for microplastics (MPs) in the environment. MPs that enter aquatic ecosystems can contribute to pollution together with other co-existing pollutants. However, whether such pollution results in higher or lower toxicity to fish than that caused by co-existing pollutants alone remains controversial. This study aimed at closing this research gap based on 1380 biological endpoints under the background of environmental MP concentrations collected from 55 laboratory studies. Overall, MPs in co-existing pollutant solutions significantly increased the toxicity to fish. Specifically, MPs elevated negative effects on the immune system, metabolism, and oxidative damage. Subgroup analysis indicated that changes in toxicity were related to fish life stage and MP size, but not to co-existing pollutant or MP type. Meta-regression analysis indicated that changes in toxicity were not related to the logarithm of the octanol-water partition coefficient (logKow) or exposure time. Finally, the differences between laboratory research and the actual aquatic environment were discussed from four aspects: MPs, co-existing pollutants, environmental factors, and experimental objects. Our study provides a basis for further understanding the potential impact of MPs on aquatic organisms from a combined pollution perspective. Moreover, our results can provide a reference for the conservation and management of aquatic ecosystems.

Polystyrene microparticles can affect the health status of freshwater fish - Threat of oral microplastics intake

Plastic waste pollution is considered one of the biggest problems facing our planet. The production and use of these materials has led to huge amounts of plastic waste entering the aquatic environment and affecting aquatic life. In our experiment, the effect of polystyrene microparticles (PS-MPs; 52.5 ± 11.5 μm) on individual juvenile rainbow trout (Oncorhynchus mykiss) was tested at three different dietary concentrations of 0.5, 2 and 5 % for six weeks. At the end of the experiment, various health parameters of exposed organisms were compared with the control group. The haematological profile revealed an immune response by a decrease in lymphocyte count with a concurrent increase in the number of neutrophil segments at the highest concentration of PS-MPs (5 %). Biochemical analysis showed significant reductions in plasma ammonia in all tested groups, which may be related to liver and gill damage, as determined by histopathological examination and analysis of inflammatory cytokines expression. In addition, liver damage can also cause a significant decrease in the plasma protein ceruloplasmin, which is synthesized in the liver. PS-MPs disrupted the antioxidant balance in the caudal kidney, gill and liver, with significant changes observed only at the highest concentration. In summary, PS-MPs negatively affect the health status of freshwater fish and represent a huge burden on aquatic ecosystems.

Interactions of microplastics with organic, inorganic and bio-pollutants and the ecotoxicological effects on terrestrial and aquatic organisms

As emerging contaminants, microplastics (MPs) have attracted global attention. They are a potential risk to organisms, ecosystems and human health. MPs are characterized by small particle sizes, weak photodegradability, and are good environmental carriers. They can physically adsorb or chemically react with organic, inorganic and bio-pollutants to generate complex binary pollutants or change the environmental behaviors of these pollutants. We systematically reviewed the following aspects of MPs: (i) Adsorption of heavy metals and organic pollutants by MPs and the key environmental factors affecting adsorption behaviors; (ii) Enrichment and release of antibiotic resistance genes (ARGs) on MPs and the effects of MPs on ARG migration in the environment; (iii) Formation of "plastisphere" and interactions between MPs and microorganisms; (iv) Ecotoxicological effects of MPs and their co-exposures with other pollutants. Finally, scientific knowledge gaps and future research areas on MPs are summarized, including standardization of study methodologies, ecological effects and human health risks of MPs and their combination with other pollutants.