PARENT SESSION
WP5 Metal Availability
3:00 PM to 6:30 PM, Wednesday, 09 May 2001
Session Chair: C. Janssen, B. Stubblefield
Room 5

(393) Copper toxicity for Daphnia magna, Raphidocelis subcapitata and local crustaceans in six European surface waters.

Heijerick, Dagobert¹, Bossuyt, Bart¹, Janssen, Colin¹, ¹

ABSTRACT- A number of ecological issues are not or inadequately addressed in presently used procedures to assess the risks of metals to aquatic environments. Main issues which are not taken into account are: 1) background concentrations of essential metals like copper affect the sensitivity of resident communities, and 2) laboratory toxicity test results may not reflect field population and community responses due to differences in metal bioavailability and sensitivity in different regions. In this study, six pristine surface waters from different European regions were collected, physico-chemically characterised, spiked with copper and used in acute and chronic toxicity assays with the waterflea Daphnia magna, the green algae Raphidocelis subcapitata and in situ collected crustaceans (mainly daphnids). Surface waters were collected in Sweden, Wales, England, The Netherlands and Belgium. Observed data were compared with toxicity predictions based on recently developed mechanistic models (Biotic Ligand Model, BLM). Observed 48h-EC₅₀s for D. magna ranged from 40 to 680 g/L total copper, and were between a factor 2 to 27 higher than reported and observed 48h-EC₅₀s in standard artificial test medium (EEG-medium, 48h-EC₅₀: 25 g/L). Similar results were obtained with the green algae R. subcapitata with observed values up to a factor 10 higher than reported and observed 72h-EbC₅₀s in standard artificial medium (ISO-medium, 72h-EbC₅₀: 20-30 g/L). Predictions with the BLMs, based on the physico-chemistry of the media (and hence the metal speciation, bioavailability and competition of metals for the biotic ligand), however, were within a factor 2 of the observed effect-concentrations. The results of this study demonstrate 1) that factors affecting metal bioavailablity and speciation should be incorporated in regulatory systems, and 2) the potential application of bioavailability models such as the BLMs in scientifically-based risk assessment procedures of metals in general and copper in particular.

Key words: copper toxicity, Daphnia magna, Raphidocelis subcapitata, surface waters