Estimating the Potential Toxic Effects on Copepod (Tigriopus japonicus) by Exposing the By-Product After Biofouling Removal from Underwater Hull Cleaning Robot

Abstract

Recently, the mechanical underwater robot was developed to remove fouling by attaching, brushing, and suctioning (SLM Global ©). By the way, by-product after biofouling removal (BPBR) is produced during operation of underwater robot. This BPBR may contain various debris and antifouling compounds that have been previously painted and is suspected to continually release the toxic chemicals. Thus, purpose of this study is to estimate the toxicity of the BPBR and how much the filtering of the underwater robot removing system can reduce the toxicity risk. For this, we exposed the filtered BPBR and the non-filtered BPBR to first and second generation of copepod and investigated acute and chronic toxicity. Additionally, transcriptomic analysis was performed to investigate the toxic effects at the genetic level through mRNA. In acute toxicity, mortality was much higher in non-filtered BPBR exposure. Chronic exposure to non-filtered BPBR induced the developmental retardation in Tigriopus japonicus. Transcriptomic analysis using DEGs between non-filtered BPBR exposed and the control groups (B05/Control) showed that non-filtered BPBR has a potential to induce genotoxicity. However, although the non-filtered BPBR induced higher toxicity at much lower dose, filtered BPBR also induced mortality and developmental delay. In addition, although the number of identified DEGs between filtered BPBR exposed and control group was relatively small and a reasonable network and pathways could not be established, the expression patterns of common DEGs with B05/Control were similar. Therefore, these results suggest that if BPBR is not filtered during the process of the underwater robot removing system, there is a possibility of causing toxicity such as mortality, developmental retardation, and genotoxicity. In addition, results also suggest that the potential risk can be reduced through filtering, but the necessity of more delicate and precision methods to remove toxicants effects even after filtering through the further functional studies.