Evaluation of a 14-day static renewal toxicity test with Daphnia magna straus.

Two replicate 14-day static renewal chronic toxicity tests were conducted with Daphnia magna Straus for each of three test chemicals (boric acid, aniline, and 2,4-dichlorophenol). These tests were conducted at 24 +/- 2 degrees C. The objective of this study was the comparison of the 14-day test results with chronic values derived for the same chemicals from 21-day studies (20 degrees C). It was hypothesized that the comparison of the chronic data resulting from the two test regimes would support the shortening of the standard 21-day exposure period and reduce the cost of these labor intensive studies. The results of this study are as follows: 1. The 14-day test met the 21-day chronic test acceptability criteria in terms of control data associated with the mean number of broods/adult, mean total young/adult, mean brood size and survival. 2. A comparison of the results shows the similarity of the chronic values generated from the 14 and 21-day tests. In all cases, the chemical specific chronic values were within a factor of 2. The chronic values for 2,4-dichlorophenol generated from the two test regimens were virtually identical (i.e., 14-day--1.1 and 1.2 mg/L; 21-day--1.1 mg/L). 3. The comparison of the chronic values resulting from the 14 and 21-day tests supports the use of the 14-day exposure period. A shorter exposure period will help reduce the cost of these labor intensive studies without compromising their scientific integrity.