HP3 Freshwater Bivalve Ecotoxicology
Ballroom G, Level 4
2:10 PM - 5:30 PM, Thursday, 13 November 2003
Chair: Cox, Stephen ,
Co-chair: Van Hassel, John ,
(587) Effect of algal density and dissolved selenium concentration on a freshwater bivalve′s ventilation activity.
Fournier, E.1, Adam, C.1, Massabuau, J.C.2, Garnier-Laplace, J.1, 1 Inst. of Radioprotection and Nuclear Safety (IRSN), Saint Paul Lez Durance, France2 LEESA-UMR5805, Arcachon, France
ABSTRACT- In filter feeders, the ventilation activity is a primary limiting step that controls the water flow pattern and the delivery of contaminants into the mantle and branchial cavities. A number of different parameters such as algal food density or dissolved oxygen concentration can influence the ventilation and hence the bioaccumulation potential of the contaminant. Selenium is essential for living organisms at low concentrations, but may be toxic at higher levels. In oxic freshwaters it exists predominantly in the +6 and +4 oxidation states as selenate (SeO42-) and selenite (SeO32-) respectively, whereas in the biota it is found as Se(-2) in selenoproteins or as elemental selenium. A series of experiments were performed to characterize the ventilation activity of Corbicula fluminea, measured by algal clearance rates, for different conditions of both algal cell densities and dissolved Se concentrations. All experiments were performed after acclimatizing the organisms during a 6-day period to the synthetic water composition, at a regulated algal density of 3-4x105 cells/mL. Initial experiments were performed without selenium contamination to investigate the changes in ventilation activity for a range of algal concentrations (105 - 106 cells/mL). Low algal concentrations induced a strong ventilation stimulus. Experiments exposing the organisms to selenium contamination of up to 500 
g/L for each of the oxidation states (+6, +4, -2), following the same experimental protocol were performed. These experiments were carried out at each of two different algal concentrations, selected to provide contrasting ventilation behaviors. The effects of selenium contaminations on the ventilation activity were studied. The accumulation of selenium by the organisms was also investigated at an organ level for the different exposure conditions. From this set of experiments a limited number of conditions will be selected to provide highly contrasting ventilation flow rates and selenium bioaccumulation levels, in order to study the effect of long term exposures, in particular on the antioxidative status of the organisms.
Key words: Ventilation, Bivalve, Feeding, Selenium