METIER (MODULAR ECOTOXICITY TESTS INCORPORATING ECOLOGICAL RELEVANCE).2. ECOTOXICITY OF POORLY WATER-SOLUBLE COMPOUNDS - CONCENTRATION VERSUS DOSE

A significant binding of a toxicant to algal cells would reduce effect ive toxicant concentration, bringing changes in NOEC (non-observed eff ect concentration) values. Furthermore, if the algal cells are ingeste d, this may increase the significance of feeding as a route of contami nant uptake. Therefore, particularly when dealing with poorly water-so luble compounds, the amount of food ingested could become a relevant e cotoxicological parameter to be assessed. The OECD guideline for the ' 'Daphnia, reproduction test'' indicates that the concentration of test substances must remain within 20% of the nominal concentration. The a im of this work was to look for any change in a compound concentration due to the presence of algae (the food of Daphnia magna). During the 48-h interval between medium renewal in chronic tests with D. magna, t here is a loss of the effective 3,4-dichloroaniline concentration whic h is greater with increasing algae densities and decreasing nominal co ncentrations.