PARENT SESSION

PM03 Metals in the Environment: Dietary Concerns in Aquatic Systems
Exhibit Hall
8:00 AM - Monday, 10 November 2003

(PM063) Algal assimilation of cadmium lowers bioavailability to Ceriodaphnia dubia.

Metzler, David¹, Allen, Herbert¹, Kim, Sang², Cha, Daniel¹, ¹ University of Delaware, Newark, Delaware, USA² Kwangju Institute of Science and Technology, Kwangju, Korea

ABSTRACT- Continuous supplies of Selenastrum capricornutum were produced in chemostats having a 3-day hydraulic retention time. Cadmium was added and the algal suspensions were continuously introduced to flow-though bioassay chambers containing Ceriodaphnia dubia. Reproduction of ceriodaphnia was determined during the 7-day chronic toxicity test. Cadmium was added to provide two different treatments. Cadmium was added directly to the algal chemostats (assimilated treatment). The algal suspension introduced to the bioassay chambers contained Cd in three forms: soluble, adsorbed onto the algae, and assimilated into the algae. In the second treatment Cd was added to the suspension of algae between the chemostat and the bioassay chamber (assimilated treatment). Cadmium was present only in two forms: soluble and adsorbed onto the algae. The response (EC₅₀) to soluble + adsorbed Cd (0.38 ± 0.21 g/L) is greater than that for soluble + adsorbed + assimilated Cd (0.85 ± 0.1 g/L). This indicates that food-borne Cd is less toxic than soluble Cd. The EC₅₀ is increased by assimilation of Cd into the food.

Key words: cadmium, dietary metals, Ceriodaphnia dubia, Selenastrum capricornutum