EVALUATION OF A HIGH-HARDNESS COMBO MEDIUM AND FROZEN ALGAE FOR DAPHNIA-MAGNA

A new high-hardness (H-H) COMBO medium for long-term culturing and bio assay testing of Daphnia magna was evaluated in 21-day survival, growt h, and reproduction studies. The COMBO medium originally designed for softwater daphnid species (i.e., D. pulicaria) was modified for the ha rdwater species D. magna. This medium also allowed continuous culturin g of a green algal food source for daphnids, Ankistrodesmus falcatus. After 12 generations of culturing in H-H COMBO medium, the mean fecund ity was 128+/-12 (coefficient of variation=9.4%). No significant obser vations of dead young, aborted eggs, or reduced antennas were made dur ing the 6 months of continuous culturing. The no-observable-effect con centration (NOEC) for a reference toxicant standard, 3,4-dichloroanili ne (3,4-DCA), was 8.3 mu g/liter, which is similar to published values . These studies demonstrate that H-H COMBO is an acceptable medium for use for culturing and bioassay testing with D., magna Additional expe riments using frozen aliquots of A. falcatus were conducted. Although mean fecundity (64+/-7) and adult length were significantly decreased from the values for daphnids fed fresh algae, the NOEC for 3,4-DCA was >25 mu g/liter. The use of this alternative food source in bioassay t esting appears promising, but further optimization of feeding rates is warranted. (C) 1998 Academic Press.