Distribution and translocation of micro- and nanoplastics in fish.

Microplastics (MPs) and nanoplastics (NPs) are regarded as emerging particulate contaminants. Here, we first summarize the distribution of plastic particles in fish. Field investigations verify the presence of various kinds of fibrous, spherical, and fragmentary MPs in fish gastrointestinal tract and gills, and specifically in muscle and liver. Laboratory works demonstrate that NPs even penetrate into blood vessels of fish and pass onto next generations. Second, we systematically discuss the translocation ability of MPs and NPs in fish. MPs can enter early-developing fish through adherence, and enter adult fish internal organs by intestine absorption or epidermis infiltration. NPs can not only penetrate into fish embryo blastopores, but also reach adult fish internal organs through blood circulation. Third, the cellular basis for translocation of plastic particles, NPs in particular, into cells are critically reviewed. Endocytosis and paracellular penetration are two main pathways for them to enter cells and intercellular space, respectively. Finally, we compare the chemical and physical properties among various particular pollutants (MPs, NPs, settleable particulate matters, and manufactured nanomaterials) and their translocation processes at different biological levels. In future studies, it is urgent to break through the bottleneck techniques for NPs quantification in field environmental matrix and organisms, re-confirm the existence of MPs and NPs in field organisms, and develop more detailed translocating mechanisms of MPs and NPs by applying cutting-edge tracking techniques.

Fish Ingest Microplastics Unintentionally.

Microplastics (size of plastic debris <5 mm) occur in various environments worldwide these days and cause detrimental effects on biota. However, the behavioral responses of fish to microplastics in feeding processes are not well understood. In the present study, juveniles from four fish species and two common shapes of microplastics were used to explore fish feeding responses. We found swallowing-feeding fish ingested more pellets than filtering- and sucking-feeding fish. With high-definition and high-speed observational experiments, we found that all species did not actively capture microfibers; instead, they passively sucked in microfibers while breathing. Surprisingly, fish showed a rejective behavior, which was spontaneously coughing up microfibers mixed with mucus. Nevertheless, some of the microfibers were still found in the gastrointestinal tracts and gills of fish, while abundances of ingested microfibers were increased in the presence of food. Our findings reveal a common phenomenon that fish ingest microplastics inadvertently rather than intentionally. We also provide insights into the pathways via which microplastics enter fish and potential strategies to assess future ecological risk and food safety related to microplastics.

Swimming behavior affects ingestion of microplastics by fish.

Microplastics (< 5 mm) are widely found in organisms and have the potential harm to ecosystems. Despite their widespread prevalence in environments, there is high individual varation in the abundance of microplastics found in individuals of the same species. In the present study, juvenile cichlid fish (Chindongo demasoni) were chosen to determine the ingestion personality for microplastics in the laboratory. The visible implant fluorescent tags were used for individual recognition. The fish were fed with microplastic fiber, pellet, and food for comparison. Our results showed that the observation of the behaviors of fish could be successfully matched with subsequent measurements for each individual through the tag method in microplastic research. The difference in the abundance of fiber (0-27 items/ind.) among fish individuals was also observed in our study. Meanwhile, the abundance of fiber showed a positive correlation with the average speed and covered area of fish, which indicates the degree of activity of fish. Moreover, fish with higher speed or a front position had higher capturing times for pellet. Our results suggest that the swimming behaviors of fish affect their ingestion of microplastics, and active fish had a higher likelihood of ingesting microplastics, which might be one of the reasons for the common phenomena, i.e., great individual differences observed in microplastic studies.

Process-oriented impacts of microplastic fibers on behavior and histology of fish.

Microplastic pollution has raised global concern for its hazards to biota. To determine the direct impact of microplastics during their contact with fish, we exposed goldfish (Carassius auratus) to 100 and 1000 items/L waterborne microplastic fibers in the short- and long-term. In the presence of 1000 items/L of microplastic fibers, the coughing behavior of fish increased significantly after 2 h of exposure. Predatory behaviors decreased significantly by 53.0% after 45 d of exposure, and the reduction in daily food intake was negatively related to exposure duration in the 1000 items/L group. In addition, microplastic fibers stimulated dynamic mucus secretion across different fish tissues during the different processes evaluated in this study, with 30.0% and 62.9% overall increases in the secretory capacity of mucus cells in the 100 and 1000 items/L groups, respectively. These behavioral and histological alterations were derived from the ventilation, feeding, and swimming processes of goldfish. We regarded these changes as process-oriented impacts, suggesting the effects of microplastics on fish and how fish cope with microplastics.

Microfiber fallout during dining and potential human intake.

The pervasiveness of microfibers, including fibrous microplastics indoors and outdoors, has drawn attention. However, some places such as the dining environment that are closely related to human diet and health have been neglected. Here, we characterized short-term microfiber fallout in different dining spots and conducted long-term monitoring in a college cafeteria. The results showed that the microfiber abundance of restaurants during the peak hour of dinnertime (75 ± 19 MFs/plate/meal) was approximately two times that of households (36 ± 23 MFs/plate/meal). The high microfiber abundance was positively correlated with strong human activities (i.e., sitting rate of people) in restaurants, which was verified by the kinetics data of the cafeteria (R2 =0.871, p = 0.000). Cotton (63%), polyester (17%), and rayon (14%) were the top three detected microfibers via µ-FTIR, and cloth friction can aggravate fiber shedding significantly. Moreover, high hairiness and short staple yarn style were likely to increase the formation of microfibers. Additionally, room structure can obviously influence microfiber abundance that households without separate dining rooms showed three times higher microfiber abundance (66 MFs/plate/meal) than those (21 MFs/plate/meal) with separate dining rooms, because partition walls were verified to effectively reduce fiber transport. Collectively, microfiber fallout during dining deserves our great attention, which may induce human intake of 63-232 MFs/person/d.