IMPACT OF POLYETHYLENE MICROSPHERES FEEDING ON SEABASS LARVAE DEVELOPMENT

Microplastics including polyethylene (PE) microbeads are present in marine habitats worldwide and may be ingested by fish larvae, with unknown consequences for their health and future life. Within the framework of the MICRO project (INTERREG IVA 2 Seas Programme), the purpose of the present work was to evaluate the effect of per os administration of PE microbeads on European seabass () larvae development. Larvae were fed from day 8 post-hatching (dph) until 26 dph with an inert diet including 0, 103, 104 and 105 fluorescent microbeads (mix of 10-45 μm) per gram. From 27 to 35 dph, larvae were fed a diet devoid of microplastics. PE beads ingestion was followed in the larvae using
fluorescent microscopic analysis and samplings were performed to investigate their impact on different ontogenetic processes by gene expression analysis.
Ingestion of PE had no effect on mortality but induced a significant decrease (25%) in growth rate. PE microbeads were detected using histological techniques in the gastrointestinal tracts of larvae as long as fish were fed on a diet incorporating microplastic (i.e 26 dph). Any fluorescent beads were found in the larvae 4 days after the end of exposure suggesting that PE microbeads were totally flushed through faeces. Molecular analyses reveal that expression of IGF1 and osteocalcin genes tended to be reduced in fish exposed to PE. This down-regulation of genes involved in fish growth and ossification can be related to the decrease of growth rate observed in these groups.
Altogether, these findings are important in understanding the environmental impact of microplastics present in marine environment on the development of marine fish larvae and, more generally, the possible consequences on the population biology of marine fish species.