Since most environmental pollutants are thought to finally accumulate in the ocean, it is important to develop a quick and convenient assay system for seawater pollution. In this study, we tested the possibility of using flagellar regeneration in a marine unicellular organism,
Dunaliella sp., as an endpoint of bioassay.
Dunaliella sp. has two flagella of equal length and swims by beating its flagella. When the flagella are amputated by mechanical treatment, they rapidly regenerate to their original lengths in 6-8 hr. We examined the effects of five pollutants {Cu
2+, Cd
2+, linear alkyl benzene sulfonate (LAS), 4-nonylphenol (NP), and bisphenol A (BPA)} on flagellar regeneration. Each chemical exhibited a characteristic inhibition pattern, with the inhibitory effect being stronger in the order of NP>Cu
2+>LAS>BPA>Cd
2+. The EC50 value of Cu
2+ was 4-8 times lower than the effluent standard value in Japan. Flagellar regeneration occurred normally in 20-100% artificial seawater, showing that this endpoint can be used even in brackish water. We therefore collected coastal seawater samples in Toyama Bay and examined their effects on flagellar regeneration. Results showed that the seawater samples collected from some fishing ports and a coastal area inhibited flagellar regeneration, and flagella regrew only to 77-87% of the control length. Thus, the flagellar regeneration assay using
Dunaliella sp. appears sensitive and can be a useful method for assessing seawater pollution.
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