Comparison of four chronic toxicity tests using algae, bacteria, and invertebrates assessed with sixteen chemicals

The performances of four chronic toxicity tests, comprising the Daphnia magna 21-day (d) (crustacean), Brachionus calyciflorus 2-d (rotifer), Pseudokirchneriella subcapitata 72-h (green algae), and the Microtox chronic 22-h (bacteria) tests, mere compared. Sixteen chemicals with toxicity covering 6 orders of magnitude mere studied. Very high correlations were found between the NOEC/EC10 Pseudokirchneriella 72-h, NOEC/EC10 Brachionus 2-d, and the NOEC Daphnia 21-d tests. The toxicological response of rotifers and microalgae were within the same order of magnitude as the response of Daphnia in 80% of cases (13/16 chemicals). The Microtox chronic test also anticipated the overall results of the Daphnia 21-d test, but the prediction was rather imprecise, compared with microalgae and rotifers, The test measuring the algal growth inhibition of P. subcapitata after 72 h was the most sensitive bioassay. Toxicity on microalgae after 72 h could be estimated after 5 h by measuring either the direct fluorescence of either photosynthetic pigments or fluorescein diacetate in 56 and 43% of cases, respectively. The median value of the ratio between EC10 and EC50 was 3.75, 2, and 1.5 with the algae, the rotifers, and the bacteria, respectively. (C) 2000 Academic Press.