Effects of chemical stress on the population dynamics of Daphnia magna: a comparison of two test procedures.
Ten substances were tested to compare two methods that can be used in chronic toxicity studies with the Cladoceran Daphnia magna. In semistatic experiments with cohorts (life-table studies) survival appeared to be a dominant factor in exponential population growth. Specific inhibition of reproduction as a result of toxic stress was observed only in tests with bromide and 2,4-dichloroaniline. For some substances (cadmium, bichromate, metavanadate, and bromide) individual growth (carapace length) was found to be a sensitive parameter. In intermittent-flow experiments with small expanding populations the yield (carrying capacity) proved to be a highly sensitive parameter, probably owing to the fact that in these tests populations grow logistically, i.e., become additionally stressed by food limitation. Chemically induced reductions in food ingestion and conversion efficiency may thus become very predominant. In view of the place of these crustaceans in the food web such reductions in the carrying capacity would seem to be of great ecotoxicological importance.
Laboratory for Ecotoxicology, Institute for Inland Water Management and Waste Water Treatment, Ministry of Transport and Public Works, Lelystad, The Netherlands.
C J
CJ
van Leeuwen
G
G
Niebeek
M
M
Rijkeboer
D000814:Aniline Compounds; D000818:Animals; D001965:Bromides / Q000633:toxicity; D003621:Daphnia / Q000502:physiology*; D007928:Lethal Dose 50; D011192:Potassium Dichromate / Q000633:toxicity; D012098:Reproduction / Q000187:drug effects; D013464:Sulfuric Acids / Q000633:toxicity; D014873:Water Pollutants / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D000814:Aniline Compounds; D001965:Bromides; D013464:Sulfuric Acids; D014873:Water Pollutants; D014874:Water Pollutants, Chemical; C054619:2,4-dichloroaniline; D011192:Potassium Dichromate