Juvenile and Adult Daphnia Magna Survival in Response to Hypoxia

Abstract

This study was undertaken to determine survival of juvenile and adult Daphnia magna under hypoxic conditions in comparison to its predators. Because D. magna perform diel vertical migration to avoid visually-oriented predators, they spend a significant portion of the day at depth where light and oxygen levels are low. In this series of experiments, Daphnia magna were exposed to low dissolved oxygen concentrations and assessed for survival. Juvenile D. magna were hypothesized to tolerate a lower dissolved oxygen concentration than adults because of their smaller size and presumed lower oxygen consumption. The dissolved oxygen concentration lethal to 50 percent of both juvenile and adult D. magna was found to be 0.47 mg/L, which is significantly lower than the minimum dissolved oxygen limits experienced by its predators.