Toxicity of nanoplastics during the embryogenesis of the ascidian Ciona robusta (Phylum Chordata)

Abstract

Nanoplastics are considered contaminants of emerging concern at the global scale. The recent evidence of their occurrence in seawater from the Mediterranean Sea calls for a thorough evaluation of their impact on marine life and in particular on vulnerable life stages such as planktonic embryos. Here, we investigated the impact of increasing nominal concentrations of 50 nm amino-modified (PS-NH₂) and 60 nm carboxy-modified (PS-COOH) polystyrene nanoparticles (PS NPs) on the embryonic development of the ascidian Ciona robusta (phylum Chordata), a common benthic invertebrate living in Mediterranean coastal areas with the peculiarity of being an early chordate developmental model. A strong agglomeration of PS-COOH (approx. 1 µm) was observed in natural sea water (NSW) already at time 0, while PS-NH₂ resulted still monodispersed (approx. 130 nm) but largely aggregated after 22 h with a microscale dimension similar to those negatively charged. However, their effect on C. robusta embryos development largely differed at 22 h: PS-COOH did not affect larvae phenotypes nor their development, while PS-NH₂ caused a dose-dependent effect (EC₅₀ (22 h) of 7.52 μg mL⁻¹) with various degrees of phenotype malformations (from mild to severe) and impairment of larval swimming. Embryos (up to 30%) exposed to 15 µg mL⁻¹PS-NH₂ resulted not developed and the majority was unable to hatch. Calculated PS-NH₂ EC₅₀ resulted higher than those available for other marine invertebrate species, suggesting a protective role of the egg envelopes surrounding C. robusta embryos toward nanoplastics exposure.

Keywords:

• Polystyrene nanoparticles
• reactive oxygen species
• surface charge
• phenotype
• embryotoxicity

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Acknowledgements

This study was performed in the framework of the PhD project entitled ‘Ciona robusta (formerly Ciona intestinalis type A) as model system for ecotoxicologcal studies’ co-funded by the University of Siena (Italy) and the Zoological Station Anton Dohrn of Naples. PhD student Maria Concetta Eliso, PhD School in Geological, Environmental and Polar sciences and technologies, Department of Physical, Earth and Environmental Sciences, University of Siena (Italy). DLS and EM analyses performed with the support of the Department of Biotechnologies, Chemistry and Pharmacy of the University of Siena (Italy). We thank the BIOINforMA group of the Zoological Station Anton Dohrn of Naples for the preliminary analyses of the RNA-seq.

Disclosure statement

No potential conflict of interest was reported by the author(s).