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Title: IMPACT OF FOUR PESTICIDES ON THE GROWTH AND METABOLIC ACTIVITIES OF TWO PHOTOSYNTHETIC ALGAE.

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

Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2002
Publication Date: 1/30/2002
Citation: N/A

Interpretive Summary: Pesticide environmental risk assessment is an essential element in the continuing evaluation of agrichemical use. A significant consideration is whether the chemical(s) adversely affect beneficial soil or aquatic organisms. In this research, two types of soil-isolated algae (Chlorella and Anabaena), were exposed to four pesticides [lindane, pentachlorophenol (PCP), isoproturon, and methyl parathion], in water solution. The method allowed determination of three key indicators of pesticide impact: growth, chlorophyll biosynthesis, and carbohydrate production. Insecticide methyl parathion had little effect on the algae, at environmentally relevant concentrations, but lindane and isoproturon each were toxic to Chlorella, and PCP, to Anabaena. Standardized EC50 values, developed in this work, can be used to compare toxicities here with those developed for other chemicals and/or microorganisms. This will benefit environmental regulation agencies or others involved in risk assessment.

Technical Abstract: The acute toxicity was determined for soil algae Chlorella kesslerei and Anabaena inaequalis, exposed to pesticides lindane, pentachlorophenol (PCP), isoproturon (IPU), and methyl parathion (MP). Toxicity markers included growth inhibition, chlorophyll biosynthesis, and total carbohydrate content, as a function of dose and time. Concentration response functions (EC50) were estimated by probit data transformation and weighted linear regression analyses. Lindane=s toxicity to Chlorella increased sharply with time (EC50 was 7490, 10.3, 0.09 mg/L; 24, 48, 72 h), but remained nearly constant through 72 h with Anabaena (8.7-6.7 mg/L; 24-72 h). PCP at low concentrations stimulated algal growth and chlorophyll a production, an effect reversed at higher doses. Anabaena was less tolerant of PCP and MP than was Chlorella. 96-h static EC50 values for Chlorella were: 0.003, 34, 0.05, and 291 mg/L for lindane, PCP, isoproturon, and MP, respectively; for Anabaena, these were 4.2, 0.13, 0.21, and 19 mg/L. Carbohydrate production responses resembled those of cell density (growth) and chlorophyll biosynthesis, with MP having the lowest adverse impact. Overall relative toxicity among the tested pesticides was: for Chlorella, lindane greater than IPU much greater than PCP much greater than MP; and for Anabaena, PCP greater than IPU greater than lindane greater than MP. The results confirm that toxicants such as these pesticides may affect individual (though related) species to significantly different degrees.