Effects of suspended solids on the bioavailability of chlordane to Daphnia magna

D. magna were exposed to technical grade chlordane in water containing 0, 100, 500 or 750 mg suspended solids per litre. The suspended solids were montmorillonite clay and Roselawn Pond sediments with organic carbon contents of 0 and 1.7 per cent respectively. The initial chlordane concentration (0.1-0.2 mg per litre) caused 80 per cent daphnid mortality after 48 h exposure in the absence of suspended solids. In the presence of suspended solids, daphnid mortality was significantly reduced, reflecting decreases in the percentage of aqueous chlordane. Results suggested that threshold suspended solid concentrations of 200 mg per litre (pond sediment) and 300 mg per litre (montmorillonite clay) were required to affect the bioavailability of chlordane to D. magna.