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A NEW APPROACH FOR CULTURING LEMNA MINOR (DUCKWEED) AND STANDARDIZED METHOD FOR USING ATRAZINE AS A REFERENCE TOXICANT
Citation:
Lazorchak, J M., E. M. SuszcynskyMeister, T. A. Hughes, M E. Smith, AND T V. Reddy. A NEW APPROACH FOR CULTURING LEMNA MINOR (DUCKWEED) AND STANDARDIZED METHOD FOR USING ATRAZINE AS A REFERENCE TOXICANT. Presented at Society of Environmental Toxicology and Chemistry, Philadelphia, PA, November 12-14, 1999.
Description:
Lemna minor (Duckweed) is commonly used in aquatic toxicity investigations. Methods for culturing and testing with reference toxicants, such as atrazine, are somewhat variable among researchers. Our goal was to develop standardized methods of culturing and testing for use with L. minor. A two-step culturing system was developed to readily provide healthy L. minor plants with minimal algal growth for toxicity testing. The first step consisted of a flow-through mass holding culture with nutrients supplied from commercial fertilizer stakes. The second step involved taking two frond plants from the flow-through culture to start a smaller static renewal culture that used a modified algal nutrient medium. Plants from both the mass and static cultures were monitored monthly for chlorophyll a levels. Monthly chlorophyll a levels in mass cultures averaged 0.85 mg/g wet tissue weight. Static cultures averaged 1.0 mg/g wet tissue weight. Total frond production was monitored bi-weekly in the static cultures with frond doubling occurring every three to four days. Atrazine was developed as a new reference toxicant for use in evaluating the consistency of the culture method. A 0 .5 dilution series was used with a 100% dilution concentration of 500 ug/L atrazine. Preliminary results indicate a frond number NOEC of 25-50 ug/L. The percent frond increase IC25 range was 35-60 ug/L and IC50 range was 95-170 ug/L. Wet weight measurements resulted in an NOEC of 25-50 ug/L and an IC25 range of 45-70 ug/L.