Temporal Changes in the Toxicity of Pentachlorophenol to Chlorella pyrenidosa Algae

Abstract

The toxicity of pentachlorophenol (PCP) on Chlorella pyrenidosa algae was investigated with specific attention given to possible variation of toxic effects with time. A concentration‐effect relationship was observed in which there was significant inhibition of PCP on cell density and chlorophyll A content. The inhibition rate of PCP on cell density was dependent on exposure time. The IC₅₀ values after exposure times of 2, 4 and 6 days for cell growth were 4.18 ± 0.49, 3.49 ± 0.40 and 3.30 ± 0.26 mg/L, respectively. There was also inhibition of chlorophyll A production, which appeared to increase marginally with exposure time for a given concentration of PCP. The corresponding IC₅₀values on day 2, 4 and 6 were 2.30 ± 0.12, 2.63 ± 0.38 and 3.30 ± 0.34 mg/L, respectively. The effect of PCP on nitrate reductase (NR), was first stimulation followed by an inhibition phase. It is postulated that the observed temporal changes in the activity of nitrate reductase (NR) may occur through the addition or loss of phosphorus in the NR protein.

Keywords:

• Toxicity
• Pentachlorophenol
• Algae
• Temporal changes
• Chlorella pyrenidosa

Acknowledgments

The authors are indebted to Dr. Binglan Yu for her kind help. This study was supported by the National Natural Science foundation of China (grant no. 29777010).