Is the Chemical Toxicity of Robot In-Water Cleaning wastewater? ; Focusing on fish developmental toxicity

Abstract

The biological settlement of marine organisms on the vessels is a major issue for shipping worldwide, causing problems in vessels or marine structure. To prevent biofouling, antifouling paints have been used to surface of vessels or marine structure. Chemical contaminants can be discharged by hull cleaning processes, including dry-dock cleaning or in-water cleaning process, all of which produce readily transportable contaminants into the marine environment, where they are referred to as ‘hotspots’ of contamination in coastal areas. However, many countries have not yet established effective evaluation methods for disposal of waste mixtures or management guidelines for area of cleaning. To clarify the potential toxic effects of remotely operated vehicles (ROV) in-water cleaning wastewater, we investigated the developmental toxicity on embryonic flounder, which is an organism sensitive to chemical contamination. The composition of metal was dominated by Iron, Zinc and Copper. In the organic biocide composition, CuPT and ZnPT was the most abundant biocide in ROV A and ROV B cleaning wastewater. The wastewater from two in-water robot cleaning wastewater produced a largely overlapping suite of developmental malformations including pericardial edema, spinal curvature, and tail fin defects. In the analyses of differential gene expression profiles (fold change of genes with a cutoff ＜ 0.05) as assessed using high-throughput RNA sequencing, genes associated with muscle development were significantly changed commonly. Gene ontology of embryos exposed to ROV A wastewater highly enriched the nervous system development and cell development, while cell signaling and transport showed in embryos exposed to ROV B wastewater. We analyzed the gene regulatory network for significant GO terms related genes in ROV A and ROV B and revealed key genes in each pathways. Our results can be provided to understand the impacts on non-target coastal organisms from hull cleaning wastewater contamination.