Ref ID : 840
A.V. Nebeker; Evaluation of a Daphnia magna renewal life-cycle test method with silver and endosulfan. Water Research 16(5):739-744, 1981
Reprint
In File
Notes
Four contract and two U.S. Environmental Protection Agency laboratories participated in round-robin tests using Daphnia magna as the test animals. The purpose was to determine if methods set forth in the "Proposed Standard Practice for Conducting Renewal Life Cycle Tests with Daphnids" (ASTM Drafts 2 and 4 with modification) are adequate for routine laboratory testing. The six facilities were Hasskell Laboratory, DuPont. Co; WAPORA, Inc.; Analytical Bio Chemistory Laboratories, Inc.; SRI International; Environmental Research Laboratory-Corvallis (EPA); and Environmental Research Laboratory-Duluth (EPA). Silver and endosulfan were the toxicants used. The 48-hr acute test used for determining EC50 values and estimating initial concentrations for the chronic test has been used for many years with good results, and this round-robin confirmed its value. The renewal life-cycle test as proposed by American Society for Testing and Material (ASTM) was found to be potentially useful, but only three of the six laboratories completed the tests successfully, and they had many difficulties. Forty-eight hour EC50 values (no food) for silver were 48, 55 (high values due to hard water), 8.4, 14.9, 1.1, 0.6, 0.64, 0.66, 0.9, 1.03, and 2.9 ug-1. The 48-hr EC50 values for endosulfan were 390, 630, 720, 372, 328, 343, 271, 218, 282, 266, 158, 280, 740 (LC50) and 378 (LC50) ug-1. The 21-day EC50 values for silver were 2.9, 3.6 and 3.9; for endosulfan they were 170 and 130 ug-1. Chronic MATC values based on reproduction for silver were 10.5-21.2, 20-41, 1.6-4.1, 8.8-19.4, 3.4-8.0 and 2.7-3.9 ug-1. Chronic MATC values for endosulfan were 35-73, 75-154, 20-32 and 32-48 ug-1. Culture and feeding procedures and care of brood animals in cultures prior to testing were found to be weak links in the test procedure. If young animals used to start the test were not healthy, the test was not likely to succeed, primarily because of the problem of maintaining at least 80% survival of control animals. Excessive handling during transfer to new solutions (3 times a week for 4 weeks) directly damaged animals during pipetting and stressed brood-carrying adults. Feeding rates of 30 mg food/l test water depleted dissolved oxygen. Lower feeding rates and modification of rations, as by addition of vitamin enriched algae, were suggested. The preparation of fresh test solutions 3 times a week, with analyses to verify the concentrations, is time consuming, expensive, and presents many opportunities for error. The laboratories felt that the flow-through daphnid life-cycle test is more reliable for most test purposes and that EPA should recommend it is addition to the renewal test.