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

Predator traits influence uptake and trophic transfer of nanoplastics in aquatic systems-a mechanistic study

Predicting the response of aquatic species to environmental contaminants is challenging, in part because of the diverse biological traits within communities that influence their uptake and transfer of contaminants. Nanoplastics are a contaminant of growing concern, and previous research has documented their uptake and transfer in aquatic food webs. Employing an established method of nanoplastic tracking using metal-doped plastics, we studied the influence of biological traits on the uptake of nanoplastic from water and diet in freshwater predators through two exposure assays. We focused on backswimmers (Anisops wakefieldi) and damselfly larvae (Xanthocnemis zealandica) - two freshwater macroinvertebrates with contrasting physiological and morphological traits related to feeding and respiration strategies. Our findings reveal striking differences in nanoplastic transfer dynamics: damselfly larvae accumulated nanoplastics from water and diet and then efficiently eliminated 92% of nanoplastic after five days of depuration. In contrast, backswimmers did not accumulate nanoplastic from either source. Differences in nanoplastic transfer dynamics may be explained by the contrasting physiological and morphological traits of these organisms. Overall, our results highlight the importance and potential of considering biological traits in predicting transfer of nanoplastics through aquatic food webs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43591-024-00096-4.

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

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

Effects of dissolved organic matter on the environmental behavior and toxicity of metal nanomaterials: A review

Metal nanomaterials (MNMs) have been released into the environment during their usage in various products, and their environmental behaviors directly impact their toxicity. Numerous environmental factors potentially affect the behaviors and toxicity of MNMs with dissolved organic matter (DOM) playing the most essential role. Abundant facts showing contradictory results about the effects of DOM on MNMs, herein the occurrence of DOM on the environmental process change of MNMs such as dissolution, dispersion, aggregation, and surface transformation were summarized. We also reviewed the effects of MNMs on organisms and their mechanisms in the environment such as acute toxicity, oxidative stress, oxidative damage, growth inhibition, photosynthesis, reproductive toxicity, and malformation. The presence of DOM had the potential to reduce or enhance the toxicity of MNMs by altering the reactive oxygen species (ROS) generation, dissolution, stability, and electrostatic repulsion of MNMs. Furthermore, we summarized the factors that affected different toxicity including specific organisms, DOM concentration, DOM types, light conditions, detection time, and production methods of MNMs. However, the more detailed mechanism of interaction between DOM and MNMs needs further investigation.

Ecotoxicity and trophic transfer of metallic nanomaterials in aquatic ecosystems

Metallic nanomaterials (MNMs) possess unique properties that have led to their widespread application in fields such as electronics and medicine. However, concerns about their interactions with environmental factors and potential toxicity to aquatic life have emerged. There is growing evidence suggesting MNMs can have detrimental effects on aquatic ecosystems, and are potential for bioaccumulation and biomagnification in the food chain, posing risks to higher trophic levels and potentially humans. While many studies have focused on the general ecotoxicity of MNMs, fewer have delved into their trophic transfer within aquatic food chains. This review highlights the ecotoxicological effects of MNMs on aquatic systems via waterborne exposure or dietary exposure, emphasizing their accumulation and transformation across the food web. Biomagnification factor (BMF), the ratio of the contaminant concentration in predator to that in prey, was used to evaluate the biomagnification due to the complex nature of aquatic food chains. However, most current studies have BMF values of less than 1 indicating no biomagnification. Factors influencing MNM toxicity in aquatic environments include nanomaterial properties, ion variations, light, dissolved oxygen, and pH. The multifaceted interactions of these variables with MNM toxicity remain to be fully elucidated. We conclude with recommendations for future research directions to mitigate the adverse effects of MNMs in aquatic ecosystems and advocate for a cautious approach to the production and application of MNMs.

Direct and gut microbiota-mediated toxicities of environmental antibiotics to fish and aquatic invertebrates

The accumulation of antibiotics in the environment has ecological impacts that have received less attention than the human health risks of antibiotics, although the effects could be far-reaching. This review discusses the effects of antibiotics on the health of fish and zooplankton, manifesting in direct or dysbiosis-mediated physiological impairment. Acute effects of antibiotics in these organism groups are usually induced at high concentrations (LC₅₀ at ∼100-1000 mg/L) that are not commonly present in aquatic environments. However, when exposed to sub-lethal, environmentally relevant levels of antibiotics (ng/L-μg/L) disruption of physiological homeostasis, development, and fecundity can occur. Antibiotics at similar or lower concentrations can induce dysbiosis of gut microbiota which can affect the health of fish and invertebrates. We show that the data about molecular-level effects of antibiotics at low exposure concentrations are limited, hindering environmental risk assessment and species sensitivity analysis. Fish and crustaceans (Daphnia sp.) were the two groups of aquatic organisms used most often for antibiotic toxicity testing, including microbiota analysis. While low levels of antibiotics impact the composition and function of gut microbiota in aquatic organisms, the correlation and causality of these changes to host physiology are not straightforward. In some cases, negative or lack of correlation have occurred, and, unexpectedly, gut microbial diversity has been unaffected or increased upon exposure to environmental levels of antibiotics. Efforts to incorporate functional analyses of gut microbiota are beginning to provide valuable mechanistic information, but more data is needed for ecological risk assessment of antibiotics.

Progress on the Effects of Microplastics on Aquatic Crustaceans: A Review

It is impossible to overlook the effects of microplastics on aquatic life as they continuously accumulate in aquatic environments. Aquatic crustaceans, as both predator and prey, play an important role in the food web and energy transmission. It is of great practical significance to pay attention to the toxic effects of microplastics on aquatic crustaceans. This review finds that most studies have shown that microplastics negatively affect the life history, behaviors and physiological functions of aquatic crustaceans under experimental conditions. The effects of microplastics of different sizes, shapes or types on aquatic crustaceans are different. Generally, smaller microplastics have more negative effects on aquatic crustaceans. Irregular microplastics have more negative effects on aquatic crustaceans than regular microplastics. When microplastics co-exist with other contaminants, they have a greater negative impact on aquatic crustaceans than single contaminants. This review contributes to rapidly understanding the effects of microplastics on aquatic crustaceans, providing a basic framework for the ecological threat of microplastics to aquatic crustaceans.

Microplastics enhance the toxicity and phototoxicity of UV filter avobenzone on Daphnia magna

Microplastics (MPs) and ultraviolet (UV) filters cause pollution in aquatic ecosystems. Moreover, regulations on the use and discharge of UV filters in personal care products are lacking. Therefore, the combined toxicity of MPs (virgin polystyrene (PS) spheres; size: 200 nm) and avobenzone (AVO; a UV filter) on Daphnia magna were assessed. The exposure groups were AVO, AVO + UV irradiation for 6 h [AVO (UV)], AVO with MPs (Mix), and AVO with MPs + UV irradiation for 6 h [Mix (UV)]. The daphnids were exposed to these treatments for 48 h and observed for an additional 6 h. Energy reserves of all treated groups increased compared to that of the control group. Growth in the Mix group was inhibited despite a high food uptake, and food uptake and growth inhibition were validated in the Mix (UV) group. Additionally, the food uptake of the AVO (UV) and Mix (UV) groups decreased during the recovery period, possibly owing to a decrease in the normal feeding ability resulting from an increase in abnormality. These results indicate that the combined toxicity of MPs+AVO can be exacerbated under natural conditions; the complex toxicity should be considered when assessing aquatic environment pollution.

Joint effects of microplastics and ZnO nanoparticles on the life history parameters of rotifers and the ability of rotifers to eliminate harmful phaeocystis

The rising concentration of microplastics and nanoparticles coexisting simultaneously in marine may bring joint harm to zooplankton. Rotifer is an important functional group of marine zooplankton, which plays an important role in the energy flow of marine ecosystem. To evaluate the comprehensive effects of nano-sized microplastics and metal oxide nanoparticles on life history parameters of rotifers and population dynamics of rotifers during eliminating harmful algae Phaeocystis, we exposed rotifers Brachionus plicatilis to the multiple combinations of different concentrations of nanoplastics and ZnO nanoparticles. Results showed that rotifer maturation time was prolonged and the total offspring was decreased significantly with rising ZnO nanoparticles and microplastics concentrations, and microplastics and ZnO nanoparticles had significant interaction, which brought more serious joint deleterious effects on survival, development, and reproduction. At the population level, ZnO nanoparticles exacerbated the delayed effect of microplastics on the elimination of Phaeocystis by rotifers, although eventually rotifers also completely eliminated Phaeocystis in the closed system. This study provided new insights into revealing the comprehensive impact of microplastics and ZnO nanoparticles on zooplankton not only from the perspective of life history parameters of rotifers but also from the perspective of population dynamics of rotifers controlling harmful algae, which is of great significance to understand the impact of mixed pollutants on marine ecosystem.

Trojan horse in the intestine: A review on the biotoxicity of microplastics combined environmental contaminants

With the reported ability of microplastics (MPs) to act as "Trojan horses" carrying other environmental contaminants, the focus of researches has shifted from their ubiquitous occurrence to interactive toxicity. In this review, we provided the latest knowledge on the processes and mechanisms of interaction between MPs and co-contaminants (heavy metals, persistent organic pollutants, pathogens, nanomaterials and other contaminants) and discussed the influencing factors (environmental conditions and characteristics of polymer and contaminants) that affect the adsorption/desorption process. In addition, the bio-toxicological outcomes of mixtures are elaborated based on the damaging effects on the intestinal barrier. Our review showed that the interaction processes and toxicological outcomes of mixture are complex and variable, and the intestinal barrier should receive more attention as the first line of defensing against MPs and environmental contaminants invasion. Moreover, we pointed out several knowledge gaps in this new research area and suggested directions for future studies in order to understand the multiple factors involved, such as epidemiological assessment, nanoplastics, mechanisms for toxic alteration and the fate of mixtures after desorption.