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Title: PESTICIDE IMPACTS ON GROWTH AND METABOLIC ACTIVITIES OF TWO PHOTOSYNTHETIC ALGAE

Author
item MOSTAFA, FADWA - USDA FAS OICD
item Helling, Charles

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 4/6/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Pesticides, while beneficial to agriculture, can also adversely impact nontarget organisms. This study focuses on developing toxicology data for two soil algae exposed to three pesticides. Aqueous suspensions of Chlorella kesslerei and Anabaena inaequalis were treated with lindane, methyl parathion (MP), and pentachlorophenol (PCP). Monitoring algal growth and selected metabolic activities, as a function of dose and time, assessed pesticide toxicity. Lindane and MP always inhibited growth, with Anabaena responding faster (hormogonia count); however after 96 h Chlorella was sharply inhibited (cell count). PCP at low concentrations stimulated growth in both organisms, an effect reversed at higher doses. As with lindane and MP, Anabaena seemed more sensitive to the pesticide. Fortyeight-hour EC50 values dropped sharply (10.3 mg/l) after lindane application to Chlorella; values for Anabaena were significant only after 96 h. Toxicity of MP to Chlorella did not significantly increase from 48- to 96-h after exposure. In contrast, EC50 values for Anabaena declined steadily throughout the incubation period. Lindane and MP arrested the biosynthesis of chlorophyll a in both organisms, whereas PCP at lower doses slightly increased pigment biosynthesis in Anabaena, followed by suppression at higher concentrations. The chlorophyll a/b ratio remained constant during lindane exposure; it decreased with MP and PCP as concentration and time increased. Carbohydrate content in both species decreased sharply in response to each pesticide, with MP having the least impact. The research provides the information needed to determine which chemicals pose problems, for which organisms, and at what exposure levels and duration.