Ecotoxicity of seawater in and out dockyards

Seawater pollution around dockyards was assessed by two kinds of standard bioassay and chemical analysis targeting new antifouling compounds. Seawater samples were collected at thirteen sites in and out dockyards in 2003. Ecotoxicity of the samples without concentration was assessed using marine microalgae Skeletonama costatum and marine crustacean Artemia salina. All the samples had no significant effects on crustacean. Four samples collected in the dock before and after repair practice with sandblast had severe toxic effects on algal growth with low 72-hour EC50s. Chemical analysis showed the toxic seawater contained three antifouling compounds such as Diuron, Irgarol 1051, and Irgarol´s metabolite M1. The concentrations in the seawater were ranging 51-85 mug/L for Diuron, 2.4-25 mug/L for Irgarol, and 1.4-19 mug/L for M1. It was speculated that both Diuron and Irgarol were responsible for the toxicity of seawater according to the relationship between the residue concentrations and the EC50s obtained from algal bioassay. The experimental results clearly indicated that the state-of-the-art practice at dockyard could discharge contaminants to marine environment around the dockyards. It is needed to minimize toxic discharge from dockyards