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

(389) Relative contribution of water, sediment and food as cadmium and zinc sources to a freshwater fish the gudgeon (Gobio gobio): modelling of metal accumulation.

Bervoets, Lieven¹, Van Campenhout, Karen¹, Blust, Ronny¹, ¹

ABSTRACT- Generally, the uptake and accumulation of metals can not be satisfactorily predicted on the basis of the total concentrations in the environment. Usually somewhat better results are obtained by relating metal uptake to the activity of the free metal ion in the exposure water. Although this free ion activity model has been applied successfully under laboratory conditions, it does not necessarily work under natural exposure conditions. In nature aquatic organisms are not only exposed to metals via the water but also via food and eventually via the sediment. Even under these complex exposure conditions the existence of a relationship between metal ion activity in the water and accumulated metal levels does not prove that the organisms take up metals from the water phase. Indeed such a relationship might also be the result of a food chain effect in which only the organisms at the bottom of the chain are exclusively exposed to the metals via the water phase. In this study the relative importance of water, food and sediment as sources of an essential (Zn) and a non-essential (Cd) metal to the freshwater fish Gobio gobio was investigated. As food we used larvae of the non biting midge Chironomus riparius. As sediment a reference sediment from an unpolluted river was used. Sediments were spiked with both metals up to concentrations that are found in polluted rivers. Midge larvae were loaded with metals via exposure to water and loss from food and sediment to the water compartment was measured. Four experiments were conducted. In three separate treatments gudgeon were exposed to either water, food, or sediment alone, whereas in the fourth experiment the fish were exposed to water food and sediment simultaneously. From the separate experiments uptake and elimination rate constants were calculated and used to construct a three-compartment accumulation model. Subsequently, it was tested if this model could predict the accumulation of the metals in the combined experiment.

Key words: bioavailability, metal, exposure route, gudgeon