Acute toxicities of trace metals and common xenobiotics to the marine copepod Tigriopus japonicus: Evaluation of its use as a benchmark species for routine ecotoxicity tests in Western Pacific coastal regions

Marine copepods have recently been recognized as important organisms in ecotoxicity testing for regulatory purposes. The harpacticoid copepod Tigriopus japonicus has a wide geographical distribution along the coast in the Western Pacific including Japan, South Korea, Taiwan, and Hong Kong. This study evaluated the acute toxicity sensitivity profile of Tigriopus japonicus against 12 common toxic substances including six endocrine disrupting chemicals (EDCs), three biocides and three trace metals. Through standard acute toxicity test procedures, toxicity endpoints LC₅₀, LC₁₀, and no observed effect concentration (NOEC) of each chemical were obtained. Although T. japonicus depicted different sensitivities towards different chemicals, a dose-response relationship was consistent in all cases. T. japonicus was particularly sensitive to most of the EDCs, but relatively less sensitive to molinate (a thiocarbate herbicide). Across all tested chemicals, tributyltin (TBT) was the most toxic to the copepod with the LC₅₀, LC ₁₀, and NOEC of 0.05, 0.03, and 0.02 mg/L, respectively. A comparison made with available data on acute toxicities of these chemicals to other marine copepod species revealed that T. japonicus is generally more sensitive to EDCs and in particular to TBT. We, therefore, strongly advocate that T. japonicus shall be adopted as a benchmark marine species for routine ecotoxicity testing and ecotoxicological studies in Western Pacific coasts.