Abstract: As triclosan (TCS) is detected continuously in water samples recently, more and more attentions focus on its toxic effects in aquatic ecosystems. Toxicology experiment methods were used to investigate the ecotoxicological effects of low concentration TCS on Hydrilla verticillata, a typical submerged plant, during a longterm exposure time. The results showed that TCS was detected in H. verticillata with the exposure of 0.05-0.5 mg·L^-1 TCS in 28 d. The highest concentration of TCS in H.verticillata was detected in the 0.1 mg·L^-1 TCS treatment. Compared with that in the control, foliar chlorophyll content of H. verticillatashowed a trend of inhibitionpromotioninhibition during the whole exposure period, while the chlorophyll content of stems was significantly inhibited at the early stage and increased gradually at the end of exposure stage. The content of soluble protein in the leaves showed a promotioninhibitionpromotion trend, while that in stems showed a trend of promotion and then inhibition. The antioxidant defense system of H. verticillata was disturbed by TCS, with the destructive effect of TCS on the antioxidant enzymes in leaves and stems of plants being significantly different. Our results provide toxicological data and theoretical basis for effective assessment of the ecological risk of TCS in water environment.

Key words: Larix olgensis, environmental factor, photosynthetic indicator, spatial heterogeneity.