Quantitative investigation of the mechanisms of microplastics and nanoplastics toward zebrafish larvae locomotor activity

This study investigated the direct and indirect toxic effects of microplastics and nanoplastics toward zebrafish (Danio rerio) larvae locomotor activity. Results showed that microplastics alone exhibited no significant effects except for the upregulated zfrho visual gene expression; whereas nanoplastics inhibited the larval locomotion by 22% during the last darkness period, and significantly reduced larvae body length by 6%, inhibited the acetylcholinesterase activity by 40%, and upregulated gfap, α1-tubulin, zfrho and zfblue gene expression significantly. When co-exposed with 2 μg/L 17 α-ethynylestradiol (EE2), microplastics led to alleviation on EE2’s inhibition effect on locomotion, which was probably due to the decreased freely dissolved EE2 concentration. However, though nanoplastics showed stronger adsorption ability for EE2, the hypoactivity phenomenon still existed in the nanoplastics co-exposure group. Moreover, when co-exposed with a higher concentration of EE2 (20 μg/L), both plastics showed an enhanced effect on the hypoactivity. Principal component analysis was performed to reduce data dimensions and four principal components were reconstituted in terms of oxidative stress, body length, nervous and visual system related genes explaining 84% of total variance. Furthermore, oxidative damage and body length reduction were evaluated to be main reasons for the hypoactivity. Therefore, nanoplastics alone suppressed zebrafish larvae locomotor activity and both plastic particles can change the larvae swimming behavior when co-exposed with EE2. This study provides new insights into plastic particles’ effects on zebrafish larvae, improving the understanding of their environmental risks to the aquatic environment.

Qiqing Chen, Michael Gundlach, Shouye Yang and al., Science of The Total Environment, Volumes 584–585, 15 April 2017, Pages 1022–1031

The article

Microplastic ingestion in fish larvae in the western English Channel

Microplastics have been documented in marine environments worldwide, where they pose a potential risk to biota. Environmental interactions between microplastics and lower trophic organisms are poorly understood. Coastal shelf seas are rich in productivity but also experience high levels of microplastic pollution. In these habitats, fish have an important ecological and economic role. In their early life stages, planktonic fish larvae are vulnerable to pollution, environmental stress and predation. Here we assess the occurrence of microplastic ingestion in wild fish larvae. Fish larvae and water samples were taken across three sites (10, 19 and 35 km from shore) in the western English Channel from April to June 2016. We identified 2.9% of fish larvae (n = 347) had ingested microplastics, of which 66% were blue fibres; ingested microfibers closely resembled those identified within water samples. With distance from the coast, larval fish density increased significantly (P < 0.05), while waterborne microplastic concentrations (P < 0.01) and incidence of ingestion decreased. This study provides baseline ecological data illustrating the correlation between waterborne microplastics and the incidence of ingestion in fish larvae.

Madeleine Steer, Matthew Cole, Richard C. Thompson, Penelope K. Lindeque, Environmental Pollution, Volume 226, July 2017, Pages 250–259

The article

Environmentally relevant concentrations of microplastic particles influence larval fish ecology

The widespread occurrence and accumulation of plastic waste in the environment have become a growing global concern over the past decade. Although some marine organisms have been shown to ingest plastic, few studies have investigated the ecological effects of plastic waste on animals. Here we show that exposure to environmentally relevant concentrations of microplastic polystyrene particles (90 micrometers) inhibits hatching, decreases growth rates, and alters feeding preferences and innate behaviors of European perch (Perca fluviatilis) larvae. Furthermore, individuals exposed to microplastics do not respond to olfactory threat cues, which greatly increases predator-induced mortality rates. Our results demonstrate that microplastic particles operate both chemically and physically on larval fish performance and development.

Oona M. Lönnstedt, Peter Eklöv, Science, vol. 352 (6290), p. 1213-1216, June 2016

The article

Assessing the impact of exposure to microplastics in fish

(…) Collectively, these experiments demonstrate that fish will actively take up microplastics from the water column, as well as ingesting them via their diet. Although ingestion of the micron-sized plastics does not appear to adversely impact the survival or health of adult fish, at least in the short term, there is evidence to support negative changes in the body condition of larval fish. Furthermore, there was evidence that MPs have the potential to partition an organic pollutant and act as a vector to transport this chemical into the food chain. These results highlight the need for longer-term studies that can more fully evaluate the environmental impacts of plastic ingestion for aquatic organisms.

Environment Agency UK, T. Katzenberger and K.Thorpe, March 2015

The report