Effect of Food and Light on the Sensitivity of Copper and Zinc to Freshwater Benthic Ostracod Heterocypris incongruens

Abstract

Freshwater green algae Scenedesmus acutus and ostracod Heterocypris incongruens were used to evaluate sediment toxicity. They were exposed to a series of copper and zinc concentrations for 6 days. Effects of different food (algae and TetraMin^®) and modifications of photoperiod in the toxicity test were also determined. TetraMin^® met the validity criteria, though it cannot be a complete substitute of algal food in the toxicity test. Modification of photoperiod has significant influenced on the ostracod toxicity test. The median lethal concentrations (LC50) of copper when fed with TetraMin^® were 270 μgCu/L and 571 μgCu/L under 24-h dark and light/dark conditions, respectively. Almost no significant effect on ostracod sensitivity to zinc when exposed under light (470 to 423 μgZn/L). On the other hand, light condition has similar effects on ostracod sensitivity to copper and zinc when fed with S. acutus. The preliminary results of the ostracod toxicity tests seem to show complex phenomena of multi exposure pathways and further investigation of the interrelationship between ostracod and food organisms is necessary.