EFFECTS OF WATERBORNE IRON ON GROWTH, REPRODUCTION, SURVIVAL AND HEMOGLOBIN IN DAPHNIA-MAGNA

Effects of waterborne iron (FeCl3 .times. 6 H2O) on growth, reproduction, survival and Hb content in D. magna were studied from subnormal to toxic concentrations in hard reconstituted water. Low concentrations of Fe stimulated reproduction and Hb synthesis after chronic exposure for 21 days. Maximum reproduction occurred between 0.1 and 1 .mu.g Fe 1-1. Juvenile growth was not stimulated by Fe but was slightly inhibited between 1 and 8 .mu.g Fe 1-1 and above 128 .mu.g Fe 1-1. A slight inhibition of growth persisted for 21 days. Total Hb content was above the control with no waterborne Fe at all but one concentration (512 .mu.g Fe 1-1). The highest value (3.8 .times. control value) was found at 2.mu.g Fe 1-1. Hb content decreased between 64 and 512 .mu.g Fe 1-1 and increased at higher concentrations. The decrease coincided with an inhibited reproduction. The increase was found in non-reproductive survivors. A comparison with a previous study in D. magna suggests that ambient conditions (hardness and pH) and aging of the water are important for the effects of waterborne iron. At a hardness of 250 mg 1-1 as CaCO3 and a pH range of 7.0-8.0, the ZEP (zero equivalent point) for reproduction was 158 .mu.g Fe 1-1. Continuous exposure to higher concentrations is expected to lead to extinction of a D. magna population.