Combined toxicity of micro/nano scale polystyrene plastics and ciprofloxacin to Corbicula fluminea in freshwater sediments

Abstract

Plastic pollution has become a global environmental threat, and its potential to affect the bioavailability and toxicity of pharmaceuticals to aquatic organism are of growing concern. However, little is known regarding the combined toxicity of micro/nano-plastics and pharmaceuticals to benthic organisms in sediments. Thus, we employed a freshwater benthic bivalve, Corbicula fluminea (C. fluminea), to investigate the individual and co-toxicity of model plastics, microscopic fluorescent polystyrene (PS) (PS nano-plastic (PS-NP) and PS micro-plastic (PS-MP), 80 nm and 6 μm, respectively) and the common antibiotic ciprofloxacin (CIP) in formulated sediments. Our results suggest that oxidative damage and neurotoxicity were confirmed to occur in C. fluminea in all the treatments. The oxidative damage in the digestive glands reduced the clam ability to scavenge free radicals, causing severe tissue damage to the digestive glands of C. fluminea. Filtration rates of C. fluminea were significantly decreased in a concentration-dependent manner across all the treatments, which might be due to the inhibition of acetylcholinesterase activities. Interactions between CIP and micro/nano-plastic were observed, whereby the presence of PS decreased the toxicity of CIP in the digestive glands but aggravated the C. fluminea siphoning inhibition rate in the nano-plastic co-treatments group; in addition, the CIP toxicity to C. fluminea decreased because that the concentration of free dissolved CIP was lowered by micro/nano-PS. Taken together, the current study could contribute greatly to evaluating the ecological risk of CIP and PS in aquatic environments and sheds light on potential issues of food safety caused by both emerging pollutants.

Keywords: Ciprofloxacin; Corbicula fluminea; Polystyrene microplastic; Sediment; Toxicity.