Department Chair

Dr. Gregory Wadsworth, Associate Professor and Chair of Biology

Date of Award


Access Control

Open Access

Degree Name

Biology, M.A.


Biology Department


Dr. Alicia Perez- Fuentetaja, Associate Professor of Biology

Department Home page

First Reader

Dr. Howard Riessen, Professor of Biology

Second Reader

Dr. Randal Snyder, Professor of Biology


Many physiological processes of Daphnia are negatively affected at low calcium concentrations. The concentration of calcium within lake water influences how Daphnia populations will survive and reproduce in natural environments. An experiment was designed to test the effects of calcium concentration and food level on the growth and reproduction of a Daphnia hybrid. Daphnia pulex x Daphnia pulicaria were reared in a soft water medium at three calcium concentrations (2.5mg/L, 1.0mg/L, 0.50mg/L) and high and low food levels (5.6 x 105 and 5.6 x 104 cells of the algae Ankistrodesmus sp.) in a 2 x 3 factorial design. The experiment results show that at low calcium concentrations (< 1.0 mg/L), survival, reproduction, intrinsic rate of natural population increase “r”, time until first reproduction, molting and length of adult individuals and neonates were all negatively affected. Some of the physiological mechanisms exhibited interacting effects between calcium concentration and food level. In the case of the lipids accumulated and ovary condition of an individual, food was more important than calcium concentration. This experiment offers insight into how daphniids in natural settings are responding to the multiple stressors that they are already facing in many freshwater lakes.