Effects of the coastal sediment extracts containing persistent organic pollutants (POPs) on embryonic flounder

Abstract

Sediment is a long term storage for pollutants and a secondary source of contamination for aquatic species. The toxic effects of complex mixtures of pollutants accumulated in sediments are poorly documented. To highlight the different factors influencing sediment toxicity, we identified and analyzed the developmental toxicity level on three contrasted sediments including different contaminant sources. Sediment toxicity was evaluated using the olive flounder embryo-larval assay with exposure to sediment extracts (SE). Chemical analyses revealed difference in contamination profile among three sediments. Mainly impacted by pesticide elements in sediment from Jinhae bay(SEJ), but polycyclic aromatic hydrocarbons in sediment from Young-il bay(SEY). Occurrence percentage of pericardial edema was higher in embryonic flounder exposed to SC from Young-il Bay. Consistent with the malformation toxicity, the expression level of genes related to heart formation including the Nkx 2.5 and robo 1 was greater in embryonic flounder exposed to SEY. In analyses of differential gene expression (DEG) profiles (fold change of genes with a cutoff P < 0.05), by high-throughput sequencing (RNA-seq), embryos exposed to SEJ showed changes related to nervous system development. Genes related to immune system were down-regulated in embryos exposed to SEY. Embryos exposed to SEJ and SEY showed significantly up-regulated gens including the cytochrome P4501A1. These results show the necessity of combining chemical analysis of sediment with embryonic toxicity assessment to accurately evaluate the environmental risks associated with sediment contamination.