The Hormesis Of Organophosphorus Pesticides On Two Red Tide Microalgae

Setting up 6 different mass concentrations 0,0.001,0.01,0.1,1 and 10 mg·L-1 of Glyphosate-isopropylammonium and DDVP, the growth rate, content of pigment, content of protein, activities of two antioxidant enzymes (SOD, CAT) and contents of inorganic P and N of red-tide species Phaeocystis globosa and Heterosigma akashiwo were measured in order to reveal the hormesis effect of organophosphorus pesticide in marine microalgae, and understand the laws of homesis induced by organophosphorus pesticides. The results showed:(1) Glyphosate-isopropylammonium and DDVP in low concentrations stimulated the growth of Phaeocystis globosa and Heterosigma akashiwo, while the growth of marine microalgae were restrained to different degrees under high concentrations of organophosphorus pesticides. There were significant concentrations and timing differences in the hormesis induced by organophosphorus pesticides in microalgae. Heterosigma akashiwo is more sensitive to two kinds of organophosphorus pesticides, and Phaeocystis globosa was tolerance stronger to organophosphorus pesticides. (2) Organophosphorus pesticides had significant impact on the content of chlorophyll-a. The variation trend of chlorophyll-a was consistent with the growth of microalgae, which showed inductive effect in low concentrations (<1 mg·L-1) while reduced the content of chlorophyll-a in high concentrations. (3) Antioxidant enzyme of Phaeocystis globosa and Heterosigma akashiwo were significantly affected by organophosphorus pesticides. Organophosphorus pesticides in low concentrations stimulated the SOD and CAT activities, while in high concentrations restrained the activities. Meanwhile, SOD activity decreased with the increasing concentration of pesticides. The highest CAT activity of Phaeocystis globosa was in the concentration of 0.001 mg·L-1 while Heterosigma akashiwo was in 0.1 mg·L-1. Under the treatments of DDVP, SOD and CAT activities of two kinds of microalgae showed hormesis effect in 24 hours, to 48 hours, the enzyme activities recovered at higher concentrations (≥1 mg·L-1). Antioxidant enzyme of Phaeocystis globosa and Heterosigma akashiwo were tolerance stronger to DDVP, and SOD was more sensitive to contamination. (4) Low concentrations of Glyphosate-isopropylammonium and DDVP accelerated the absorption of inorganic P and N. Meanwhile, there were higher inorganic P and N contents in the culture medium under higher concentrations of Glyphosate-isopropylammonium.